Notes
Chapter - 3 Electrical Utilities 3.1
Electrical Motors
Electric motors convert electrical energy into mechanical energy. There are basically 3 types of motors: 1. 2. 3.
AC Induction Motors AC Synchronous Motors DC Motors
The detailed classification of electric motors is given below : Electric Motors A.C. Motors
D.C. Motors Brushless D.C
Brush D.C
Shunt Wound Separately Excited
Series wound Compound wound
Single Phase Three phase/polyphase Shaded pole
Induction
Reluctance Split Phase
Squirrel cage
Linear Induction Synchromous
Slip ring Synchronous
Electric motors are inherently very efficient. Their efficiencies vary from 85% to 95% for motors of sizes ranging from 10 HP to 500 HP. It is still possible to improve the efficiency of these motors by 1 to 4% by improving the design of motor . 3.1.1
Power Consumption in Motors
a)
Efficiency and Power Factor
The power consumed by a 3-phase AC motor is given by Power Input =
3 x Voltage x Current x Power Factor
If the voltage is in Volts and the current in Amperes, the power will be in Watts (w). The power in Watts divided by 1000 is kilowatts (kW). The power input to the motor varies with the output shaft load. Electrical Power input (kW) =
Mechanical Shaft Output x 100 Motor Efficiency (%)
Electrical Power input (KVA) =
Power Input (kW) x 100 Power Factor
Variations of motor efficiency and power factor with load are shown in Fig. 3.1 Torque speed and current speed characteristics of different types of rotors are shown in Fig.3.2. The load vs full load current is shown in Fig. 3.3. The following may be noted from these curves. 75
3. 4. 5. 6.
% Efficiency & Power Factor
7.
%
100
1.0
90
0.9
80
0.8
70
0.7
60
0.6
50
0.5
40
0.4
30
0.3
20
0.2
10
0.1
100 90
SMALL MOTOR (BELOW 25 HP)
80 % Full Load Current
2.
The motor efficiency remains almost constant upto 50% load. Below 50% load, the efficiency drops significantly till it reaches zero at 0% load. At a particular operating voltage and shaft load, the motor efficiency is fixed by design, it cannot be changed externally. The power factor reduces with load. At no load the p.f. is in the range of 0.05 to 0.2 depending on size of the motor. At no load, the power consumption is only about 5% or so, just sufficient to supply the iron loss, friction and windage losses. The no load current is however of the order of 30% to 50% of full load current. This amount of magnetizing current is required because of air gap in the motor. The starting torque is 100% to 200%, the maximum torque is 200% to 300% of rated torque. The starting current remains at a high value of more than 500% of rated current upto 75% to 80% speed and then drops sharply.
70 60
LARGE MOTOR (25 HP & ABOVE)
50 40 30 20 25
75
50
100
% Load (Shaft Power)
Fig 3.3 : Current v/s Load 3.1.2
pf
1.
Importance of Motor Running Cost-Life Cycle Costs
Motors can run without problems for 20 years or more with good protection and routine maintenance. However, if they are running inefficiently, it is worthwhile replacing them as running costs are much more than first costs. Motors can be considered as consumable items and not capital items, considering the current energy prices. The importance of running cost can be seen from Table 3.1. The following points may be noted: Table 3.1 : Importance of Motor Running Cost
0 0
25
50
75
100
% Load j
Efficiency
7.5
Motor Rating (kW)
+ Power Factor
Low Efficiency
Fig 3.1 : Load vs Efficiency & Power Factor.
37
High Efficiency
Low Efficiency
High Efficiency
Efficiency
0.86
0.88
0.92
0.93
Power Input (kW)
8.72
8.52
40.22
39.78
Running Hours
6000
6000
Energy Input (kWh)
52320
51120
6000 241320
6000 238680
Running Cost
209280
204480
965280
954720
Running Cost (Rs.) for 10 years
2092800
2044800
9652800
9547200
First Cost (Rs.) First Cost as % of Running cost for 10 years
12000
12000
70000
70000
0.57
0.59
0.72
0.73
(Rs.) per Annum (@Rs. 4.00/ kWh)
1.
2. Fig 3.2 : Performance with Tee Bar, Deep Bar, Trapezoidal and Double Cage Rotors 76
Even a small motor of 7.5 kW consumes, at full load, electricity worth Rs. 20 lakh in 10 years. Similarly, a 37 kW motor consumes about Rs. 1 crore worth of electricity in 10 years. The first cost is only around 1% of the running cost for 10 years, hence running costs are predominant in life cycle costing.
77
3. 4.
Even a small difference in efficiency can make a significant difference in running cost. When economically justified, motors may be replaced, even if these have been recently installed.
3.1.3
1. 2. 3. 4. 5. 6. 7. 8. 9.
Energy Saving Opportunities in Motors
The main energy saving opportunities in motors can be summarized as follows: a) b) c) d) e) f) g) h)
Stopping idle or redundant running of motors. Matching motor with the driven load (sizing of motors) Operation of under-loaded Delta connected motor in Star connection. Soft starters with Energy Saving Features. Use of Variable Frequency Drives (VFDs) Improving drive transmission efficiency Use of high efficiency motors Improvement in motor drive systems
Current (star) Current (Delta) Power factor (star) Power factor (Delta) Efficiency (star) Efficiency (Delta) Speed (star) Speed (Delta) Change overline
Oversized Motors lead to the following problems: 1. 2. 3. 4. 5. 6. 7. 8.
Fig. 3.4 : Motor Performance in Delta and Star Connections
Higher investment cost due to larger size. Higher running cost due to decrease in efficiency. Higher maximum demand due to poor power factor. Higher cable losses and demand charges. Higher switchgear cost. Higher space requirement. Higher installation cost. Higher rewinding cost (in case of motor burnout)
Table 3.2 Shows the effects of oversized motors on the energy bill and investment
Table - 3.2 : Increased Costs due to Oversized Motors Motor Rating (kW)
15
30
55
Motor Load Requirement (kW) Motor Efficiency % Input Power (kW) Input Energy (kWh) (for 6000 hrs/ annum) Motor Power Factor Input KVA Energy Difference (kWh) Increase in Running Cost (Rs.) Investment (Rs.) Increase in Investment (Rs.)
15 89 16.85 101100
15 89 16.85 101100
15 84 17.85 107100
0.89 18.93 25000 -
0.75 22.44 55000
0.50 35.70 6000 24000 95000
30000
70000
The following suggestions are made : 1. If a motor is oversized and continuously loaded below 30% of its rated shaft load, the motor can be permanently connected in Star. 2. If the motor is normally loaded below 30% but has a high starting torque requirement, then the motor can be started with a suitable starter and, after overcoming the starting inertia, be automatically switched from Delta to Star, using timer control or current sensing. If the load is below 30% most of the time, but if the load exceeds 50% sometimes, automatic Star-Delta changeover Switches (based on current or load sensing) can be used. But, if the changeover is very frequent the contactors would get worn out and the savings achieved may get neutralised by the cost of frequent contactor replacements. 3. If the motor is nearly always operating above 30% of the rated load and sometimes runs below 30% load, a careful analysis is required before installing any arrangement for operation in star connection at light loads. Case Study 1: ‘Delta' to 'Star' connection in Vegetable Oil Works Brief A 25 hp/18.5 kW motor was driving a cooling water circulation pump. The motor was 30% loaded. It was decided to connect the delta connected motor in star. The electrical measurement before & after connection of motor from 'delta' to 'star' is given below: Parameters
Voltage (V) Current (A) Power Factor Power Input (kW) Speed (rpm)
78
79
Before Implementation (Delta) 415 18.5 0.5 6.72 1469
After Implementation (Star) 415 9.5 0.87 5.96 1454
Saving / Improvement 9.0 0.37 0.76
Energy Saving
Energy Saving
Energy Savings Annual Saving Investment Payback Period
: : : :
0.76 kW i.e. 11.3% 6080 kWh Rs.5000 10 months
Annual savings Annual saving Investment Payback period
: : : :
1,16,000 kWh Rs. 0.47 Million Rs. 0.5 Million 13 months
Case Study 2: Use of Soft Starter to Facilitate Large Motor Starting with Power Supply from Captive D.G. Set
Case Study 4: High Efficiency Gear in Place of Low Efficiency Gear (for a Reactor with Worm Gear )
Brief
Energy Saving
Measurements made in a continuous chemical process plant, where a soft starter was introduced to reduce the starting kick when the motor is started on D.G. set, are high-lighted below : : 250 hp Air Compressor : 250 hp, 415 V, 3-Phase, 1500 rpm, 313 A
Application Motor Details Starting Using Star/Delta Starter Initial Starting kick Maximum Starting Current Continuous Current
: 1800 A for 2 Sec. (Direct) : 480 A (star) / 536 A (delta) : 278 A
: Current Limit - 200% ; Ramp Time - 30 seconds : 685 A which Reduces to 155 A in 30 seconds
Low efficiency gear
Worm gear
Saving/Improvement
Motor Rating (kW)
7.5
3.75
3.75
Actual Motor
3.75 3.75
3.0 3.0
0.75 0.75
Input (kW) Case Study 5:
Starting With Soft Starter : Settings Starting Current Kick
Parameter
Use of High Efficiency Motors in a Textile Plant
Brief The Ring Frame motor rating was 40 kW. A standard efficiency motor was compared with an energy efficient motor as given in table below: Energy Saving Standard Motor vs EE Motor
Benefits : Starting current kick reduced by about 60%. Any dip in voltage at the main busbar of DG Set is reduced. The expenditure on maintenance of the motor and the attached mechanical load is also reduced.
Description
Case Study 3 : VFD for Cooling Tower Pump in a Chemical Plant
Motor rating, kW
40
40
Efficiency %
92
94.5
96.22
92.54
44
44.5
2.187
2.080
Annual electricity saving, kWh
-
9564
Pay back period on extra cost of EE motor, months
-
5
Brief
Energy consumed, kWh/doff This is a case study from a chemical plant manufacturing resins, used for manufacturing paints. A cooling tower with a 125 HP pump was used for process cooling applications. In the existing system, flow variation was through closing/opening valves at the end use points. Also, in the existing system, the return water line of the cooling tower was throttled to control the flow. After installation of an inverter to control the motor speed, this valve was fully opened, thus eliminating the throttling losses.
Weight of yarn per doff Specific energy consumption, kWh/kg yarn
Motor Rating : 125 hp, 415 V, 170A, 2975 rpm.
Valve position 20% open
Power consumption 53.5 kW
Fully open
40 kW
Power Saving
13.5 kW 80
81
Standard Energy Efficient (Low Eff) Motor (EE) Motor
Table shows comparative data of super efficient motors developed by one manufacturer.
Energy Efficiency Estimates for Emerging Motor Technologies Table 3.3 : Energy Efficiency Estimates for Emerging Motor Technologies
Super Efficient Motor
Output Frame Size Supply System RPM Efficiency Fan Ambient Taking annual running hours Input kW at full load Input kW difference Unit Rate (Rs/kWh.) Annual Savings Net Unit Price (Rs.) Price difference Payback
3.1.4
Standard Motor
Super Efficient Motor
15 kW 160 L 415 V +_ 6%; 50 Hz V +_ 3% 1445 89% Plastic 40° C 7165 16.85
15 kW 160 L 415 V +_ 10%; 50 Hz V +_ 5% 1475 93% C.I 50° C 7165 16.13 0.72 4 20,635 32200 10,260 19 months
21940 -
Energy Savings (%)
Notes
New Motors Superconductor
2 to 10
Higher efficiencies at partial load
Copper Rotor
1 to 3
5% has been reported
Switched Reluctance
3
Permanent Magnet
5 to 10
Written Pole
3 to 4
Controls MagnaDrive
Up to 60
Savings are great compared to non- ASDs. Compared to ASDs (Ajustable speed drive )energy savings will be less.
PAYBACK drive
Up to 60
Savings are great compared to non -ASDs. Compared to ASDs energy savings will be less.
Advanced ASDs
2
Savings are compared to conventional ASDs
Emerging New Motor Systems
Emerging motor system improvements can be categorized into the following three areas of development opportunities: 1.
Technology
Upgrades to the motors themselves, for example: (Source : LBNL :Energy Efficient Techologies for Industries)
• • • • • •
super conductive motors permanent magnet motors copper rotor motors switched reluctance (SR) drives written pole motors very low loss magnetic steels
3.2
2. System design optimization and management, such as: • • •
end use efficiency improvements use of premium lubricants advanced system design and management tools
3. Controls on existing systems, for example: • • •
3.1.5
multi-master controls on compressors sensor based controls advanced adjustable speed drives with improvements like regenerative braking, active power factor correction, better torque/speed control.
Electric Furnaces
Electricity is a very clean but costly fuel for heating and melting applications. There are number of advantages in electricity use like improved product quality due to absence of fuel impurities, excellent power control, clean environment (pollution is transferred to central power station) and high efficiency at end use point. But since conversion efficiency of fuel to electricity is only 35% at the power station, the overall efficiency from fuel to end use heating is likely to be 15 to 25%. Hence keeping the overall energy scenario in view, electricity should be used for only special heating applications. Fuel should be used directly to the extent possible. For many conventional heating applications like billet heating and heat treatment, alternate fuels, especially natural gas where available, must be considered. Many companies have changed over from electric heating to heating by other fuels to reduce costs.(However for Induction and Arc Furnances no alternatives are presently available ) Table 3.4 gives the inter-fuel substitution.
Potential Energy Savings
Primary specific electrical energy savings for particular motor applications are summarized in Table 3.3. 82
83
Table - 3.4 : Interfuel Substitution : Cost of Alternative Fuels Energy Source
Cost
Heat Value
Coal Oil Natural Gas Electricity
Rs. 2000/MT Rs. 20/Kg Rs. 8/Nm3 Rs. 4.50/kWh
4000 kCal/Kg. 10000 kCal/Kg. 9000 kCal/Nm3 860 kCal/kWh
Energy Balance
Cost Per 1000 kCal Rs. 0.50 Rs. 2.00 Rs. 0.88 Rs. 5.23
Electricity is used in arc furnaces, induction furnaces, heat treatment furnaces, billet heaters, ovens, infrared heaters, etc. Case Study 6 : Replacement of Electric Oven by Gas Fired Oven in an Engineering Industry
Energy Percentage (kWh/tonne) (%)
Input Energy
660
100
Useful Heat
380
58.5
2
Coil I R
130
20
Radiation Losses
97.5
15
Conduction Losses
34
5.2
Other Unaccounted
18.5
1.3
Table-3.6 : Heat Balance of a Heat Treatment Furnaces (Bell Type)
Brief
Energy Input
822.75 kWh
Heat In Charge
167.00 kWh
Surface Heat Losses Energy
Electrical Oven
LPG Fired Oven
Existing Oven : 18 kW Rating
Cost of Electricity / hr : 0.11 kW X Rs. 5.00 = Rs. 0.55 (For Auxillaries)
Cost of Electricity/hr : 18 kW x Rs. 5= Rs. 90 Cost of LPG/hr : 1.55 Kg x Rs. 25 = Rs. 38.75 Total Running Cost/hr : Rs. 90.00
Total Running Cost / hr = Rs. 39.30
Savings per Hour
= 90.00 - 39.30 = Rs. 50.70 (56%)
Annual Savings:
= Rs. 50.70 x 24 hours x 25 Days x 12 Rs. 63,000
Payback Period
3 Months
204.00 kWh
Outer Bell
136.10 kWh
Inertia Loss
250.90 kWh
Inner Bell Inertia Loss
44.50 kWh
Unaccounted Loss
20.25 kWh
Table-3.7 : Heat Balance in the Arc Furnace kWh/Liquid Metal Tonne Steel Plant 1: 170 T Furnace
Steel Plant 2 : 30 T Furnace
Energy Input
= Rs. 3,65,040 Cost of LPG Fired Oven
Soaking Heating
Electrical Energy
426
682
Carbon Combustion
126
126
Other Chemical Reactions
70
70
Combustion of Graphite Electrodes
48
64
Total Energy Output
670
942
(exothermic)
3.2.1 Heat Balance and Energy Saving Opportunities In order to estimate the efficiency of furnaces and also to identify major losses, a heat balance is useful. A heat balance gives information on the energy input, useful energy and major losses. Table -3.5 : Energy Balance of Coreless Induction Furnaces Material Crucible Capacity Production Capacity Power Volt
: : : : :
Grey Iron 3200 Kg 1600 kg/hr. 733 kW 968 volts
Useful Heat in Liquid Metal
392
426
Exhaust Gases
104
120
Sensible Heat in Slag
57
76
Electrical Losses
47
60
-
170
Conduction, Radiation
40
60 12
Losses During Operation
84
Heat Losses ---Electrodes
12
Unaccounted Losses
18
18
Total
670
942
85
Table - 3.8 : Energy Balance of a Continuous furnace (Heat treatment furnace conveyor system) Energy Balance
Energy (kWh)
Percentage
Total Energy Input per hour
37.4
100
Losses Through Insulation
3.8
10
Losses in Cooling Zone
5
13.0
Losses Due to Conveyor
8.6
23
Useful Heat
10
27
Unaccounted Losses*
10
27
Energy Saving Annual energy saving Investment Payback period
: 30,000 kWh : Rs.61,000/: 13 months
3.2.2 Energy Savings by Operational Features
a) Reduction of internal volume of the oven to match the basket size. b) Proper sealing of the door to reduce the heat loss. c) Repair of the rear wall of the oven, which had developed cracks, to reduce heat loss. d) Reduction of weight of basket from 30 kg to 10 Kg. e) Use of ceramic fibre insulation in place of fire bricks to reduce starting time and reduce thermal inertia.
a) Operate at full power and capacity as far as possible to get as high a utilization rate as possible. Poor capacity utilization of electric furnaces cause a large wastage of energy. Holding periods can be kept to a minimum. Separate holding furnaces can sometimes be useful. b) Minimise tapping time and frequency to reduce radiation losses and to reduce operation at low power levels. c) Charging system should be such that charging time and frequency are minimised. Possibility of charge compacting and preheating can be explored. d) Molten metal handling and transfer system including ladles can be designed in such a fashion that transfer time and loss in temperature are minimised. Ladle preheating system lead to savings. Well insulated ladles are also necessary. e) Opening of furnace lids, slagging door etc. must be minimised. f) For heat treatment furnaces, production can be so planned that once a furnace is started, it can be utilised continuously, otherwise a lot of energy is wasted in heating the furnace itself. Capacity utilisation is also very important. g) For many heat treatment applications, it may be worthwhile collecting jobs so that full capacity utilisation is achieved. h) Weight of jigs and fixtures for heat treatments should be minimised. i) Surface temperature may be kept at 45oC to 60oC for heat treatment furnaces to reduce radiation losses. j) Process parameters, like heat treatment cycle time and temperatures, have to be checked.
It was decided to replace the 28 kW oven with a smaller 12 kW oven. The important difference between the old oven and the new oven are highlighted in Table below.
Case Study 8 : Electrical Energy Conservation in a Foundry through operational improvement .
* Mostly due to convective heat loss due to cold air ingress Case Study 7 : Replacement of an Inefficient, Oversized Oven Brief In a fuse gear industry, the major energy consuming equipment was an oven used for drying ink on ceramic parts and softening of brass components. During the energy audit, some measures suggested to reduce the energy consumption were;
Comparison of Performance of Old and New Ovens
Brief The plant is equipped to produce about 350 tonnes of Malleable Iron and S.G. Iron Castings per month. Steel scrap is melted in two 4 tonne / 1150 KVA mains frequency furnaces. The product mix consists of a large number of relatively low and medium weight castings. Moulds are made on automatic moulding machines (Pneumatic). The castings are shot blasted, annealed in electric furnaces (600 kW). Fettling and grinding also uses pneumatic tools. These are fed by two compressors of 93 kW each, working one at a time. The present production level is around 220 Tonnes / month. Energy consumption is about 700,000 kWh/month with a maximum demand of around 2700 kVA. Approximate percent consumption of major equipments are given in the Table below.
86
87
% Distribution Among Major Loads On A Typical Day
% of Total load
Total load 100
Melting Furnaces 60
Annealing furnaces 17.14
Compressors 11.48
Sand Plant 2.55
Other Loads 6.52
Case Study 10: Modification Annealing Ovens in a cable manufacturing industry Lighting 2.28
Energy saving was achieved through operational improvement like compacting the scrap and loading it with crane, closing the furnace lid, shutting off the ventilation fans for capacitor cooling during favorable ambient conditions etc. Energy Saving
Brief A cable manufacturing industry, has several annealing ovens, which account for a significant portion of the electricity consumption. A 317 kW oven is used for annealing aluminum conductor in large drums. The oven was large for the jobs being handled. It was redesigned for the job, cutting ceiling height and the insulation was changed to ceramic fibre. The observations are as follows : Parameters
Parameter
Saving/Improvement
Before
After
Implementation
Before
After
Implementation
Implementation
SEC (kWh / T)
900
700
( - ) 200
Charging time (hrs.)
10
4
(-)6
Production
Annual Saving (kWh)
-
-
( - ) 1,22,070
(Charges per day)
Radiation loss (kWh/day)
500
-
( - ) 1,00,000
Ventilator fan for
15
NIL
Energy Consumption (kWh)
Savings/Improvement
Implementation
1930
500
( - ) 1430
8.5
3.5
( - ) 5.0
3.0
5.0
(+ ) 2.0
Time needed (hrs.) (5 Tonne charge)
( - ) 30,000 kWh/annum
Energy saving
capacitors (HP)
Case Study 9: Replacement of inefficient arc furnace with induction furnace
Annual Savings Investment Payback period
: Rs. 1.2 Million : Rs. 0.25 Million : 3 months
Brief
3.3 Compressed Air System
Background : A leading automobile components casting foundry had two indirect arc furnaces of capacity 30kg and 80kg respectively. These furnaces were used for producing specialized automobile components. Smaller capacities of the existing furnace meant the number of melting batches was high and correspondingly the fixed heat loss component was very high.
Compressed air is one of the most expensive utilities in manufacturing facilities. First used more than a century ago in pneumatic drills for mining, compressed air has now become an indispensable and a productivity improvement tool for a number of applications ranging from air powered hand held tools to advanced pneumatic robotics. Cost of energy in the compressed air is at least 5 times that of electricity. The energy content in compressed air is further reduced by pressure drop in distribution systems, leakage etc. as shown in fig.3.5. Hence it is important to manage generation, distribution and utilisation of compressed air from energy efficiency viewpoint.
These inefficient arc furnaces were replaced with one medium frequency (3000 Hz) induction furnace of capacity 125 kW, having two pots 50 kg and 100 kg respectively. The 50-kg pot is rated at 90 kW while for the 100-kg pot rating is 125 kW. Energy Saving : Particulars
Monthly energy consumption Metal tapped per month No of heats per month Specific energy consumption per Mt. Annual energy consumption Cost of energy Annual energy savings Annual cost savings Investment incurred Payback period
Units
Before implementation (Indirect arc Furnaces)
After impleme ntation
Improve ment
% Improve ment
8267
12447
60
kWh
30 kg IAF 14434
80 kg IAF 6280
Total / avg. 20714
Kg No kWh
13970 438 968
2100 27 2990
16070 465 1085
13974 330 592
-2096 -135 494
-13 -29 60
kWh
173208
75360
248568
99204
-149364
-60
Rs kWh Rs Rs Years
621816
270542
892359
-536217
-60
356142 149364 536217 1000000 1.86 2
Fig . 3.5 : Energy Flow Diagram
88
89
3.3.1 Analysis of Compressed Air System 3.3.1.1 Data Collection As a first step towards managing energy use in compressed air system, the following information should be collected. This exercise if done systematically can be extremely useful for identifying energy saving potential. 1) Specifications of each compressor such as capacity, pressure, motor ratings etc. 2) Loading and unloading pressure setting of each compressor 3) How many compressor normally operate and whether any shift-wise or daily variation in number of compressors operated 4) Collect data on end- use of compressed air in the plant, such as : Pressure, flow, end use, dryers, regulators, etc. 5) Pipe size and its layout
The pump-up test described above gives only an estimate of the compressor capacity and cannot be considered as very accurate. It is only a simple practical method under site conditions with minimal instrumentation. A more scientific method of conducting the pump-up test with proper installed instrumentation is available in IS:5456-1985. The power consumption can be measured with portable power meter or energy meter and the specific power consumption (kW/100cfm) can be calculated. Some of the common causes of higher Specific Power Consumption are: -
Poor inter-cooler performance. Malfunctioning of discharge and/or suction valves. Worn out piston rings. Choked suction side filters.
Case study 11 : Installing Refrigeration dryers in Compressed Air system
3.3.1.2 Analysis Of Equipment and System Performance The following actions need to be taken to estimate the compressed air system parameters: a) Estimation of capacity of each compressor b) Measurement of power input to the compressor at full load and part load conditions c) Estimation of total compressed air leakage in the plant and section-wise leakage estimation if possible d) Conduct a survey of compressed air leakage points by soap solution method or by using ultrasonic leakage detector. e) Estimate pressure drops in headers. f) Loading & unloading pressures and loading and unloading time of compressors . 3.3.1.3 Estimation of Capacity of Compressors The ideal method of estimating air compressor capacity is to use flow meters. In the absence of flow meters, the capacity can be estimated on site by the Pump-Up test. The compressor capacity can then be estimated by using the following formula: (P2 - P1) x Vr x Tc Pa t Where,
Brief It is recommended to replace absorption type air dryer with refrigeration type dryer as absorption dryer uses 10% - 15% purge air for re-generation of desicant . Energy Saving Saving Obtained by installing Refrigeration Dryer in Compressor Parameter Actual load (kW) Total running hours / year Annual Energy consumption (kWh)
Annual savings (Rs.) Investment (Rs.) Payback period (years)
Before Implementation 16.6 1800
After Implementation 14.11 1800
Saving / Improvement 2.49 -
29880
25398
4482
-
-
15780 94000 6
Case Study 12 : Installation of automatic drain traps in compressed air network Brief
Q=
Q = Capacity of the air compressor, Nm3/min P1 = Initial pressure, (kg/cm2 a ) P2 = Final pressure, (kg/cm2 a ) Pa = Atmospheric pressure (kg/cm2 a ) Vr = Receiver volume, m3(including piping from compressor to receiver and up to receiver outlet valve and also oil separator volume for screw compressors) t = time taken to raise the pressure from P1 to P2, minutes Tc= Temperature correction factor (= Tr/Ta) Tr = Air temperature in receiver, °K (i.e. °C + 273 ) Ta = Ambient temperature, °K (i.e. °C + 273 )
90
In an engineering unit, moisture traps were found stuck up in either open or closed condition thus making a loss of compressed air continuously or corroding of pipeline and other networking devices. On rectifying the faults, savings were as under: Energy Saving Particulars Annual total energy savings, kWh Annual Cost savings, Rs. (million) Cost of implementation Rs. (million) Simple payback period (months)
91
Actual energy savings 84,000 0.42 0.10 3
Case Study 13 : Improving the performance of 500 cfm reciprocating compressor Brief In an engineering company, plant was having 3 nos - air compressors of IR make. All the three compressors were run continuously totaling to air requirement of 980 cfm. While the performance of 2 nos air compressors of 240 CFM each was found satisfactory, the 3rd compressor of 500 cfm was performing sub standard. The volumetric efficiency was only 87 % and the power consumption was more (20 kW/100 cfm) as against 19.4 kW/100 cfm. Efficiency of the compressor 3 had gone down. By improving the performance of this compressor, one compressor of 240 cfm was totally stopped. After maintenance the savings effected were as under:
Leakage tests can be done separately for each section of the plant by isolating the supply to compressed air to the remaining sections of the plant during the leakage test. Case Study 14 : Cost of compressed air leakage from holes at different pressures
Actual energy savings 74,000 0.340 0.100 4
QxT T+ t
Where, Q = Compressor capacity, in m3/min (as estimated from the pump-up test) T = Time on load ,min t = Time on unload, min Leakage points can be identified from audible sound. For small leakage, ultrasonic leakage detectors can be used. Soap solution can also be used to detect small leakage in accessible lines. The following points can help reduce compressed air leakage: a) b) c) d) e) f) g)
Reduce the line pressure to the minimum acceptable. Selection of good quality pipe fittings. Provide welded joints in place of threaded joints. Sealing of unused branch lines or tappings. Provide ball valves (for isolation) at the main branches at accessible points. Install flow meters on major lines. Avoid installation of underground pipelines to avoid corrosion & leakage.
92
0.211
0.0207
744
1/32
0.845
0.083
2981
Cost of Wastage, Rs. (for 8000 hrs/year) @ Rs. 4.50/kWh
3.38
0.331
11925
1/8
13.5
1.323
47628
1/4
54.1
5.3
190865
1/64
0.406
0.069
2485
1/32
1.62
0.275
9915
1/16
6.49
1/8
26
4.42
159120
1/4
104
17.68
636480
At 7 bar (100 psig) pressure
Leakage of compressed air is a major reason for the poor overall efficiency of compressed air systems. It may be noted that, at 7 bar (100 psig), about 100 cfm air leakage is equivalent to a power loss of 17 kW i.e. about Rs. 0.62 million per annum.
Air Leakage in m3/min, q =
1/64
1/16
3.3.1.4 Estimation Of Air Leakage Level
The leakage level can be estimated by observing the average compressor loading and unloading time, when there is no legitimate use of compressed air on the shop floor.
Power Wasted kW
At 3 bar (45 psig) pressure
Energy Saving Particulars Annual total energy savings, kWh Annual Cost savings, Rs. (million) Cost of implementation Rs. (million) Simple payback period (months)
Air Leakage Scfm
Orifice Diameter (in inches)
1.10
39719
Estimation of Pressure Drop The pressure loss from the air compressors to the end-use points may be kept at as low a level as possible, i.e., below 0.3 to 0.5 bar. The air compressors should be located close to the equipment requiring large quantum of air for reducing pressure drops. If the end-uses are spread over a large area, a ring main header can help reduce pressure drop. The pressure drop in pipelines is approximately proportional to the square of the air velocity. The pressure loss can also be calculated for straight pipe lines by the following formula Pressure drop (in bars) = 7.5 x 10 4 x Q1.85 x L d5 x p where, Q = Air flow in m3 /min. (Free air) L = Length of pipeline (m) d = Inside diameter of pipe, mm p = Initial pressure, bar (absolute) Case Study 15 : Pressure drop calculation for a 3" header and a 4" header for a flow of 100 scfm and a pressure of 7 bar, based on the above equation
93
Brief
3.3.2 Identifying Energy Saving Opportunities Description
Units
Inlet pressure
bar, abs
7
7
It is very important to have a systematic approach for saving energy in compressed air system. The fundamentals of this approach are basically:
Air flow
scfm
100
100
1.
Length of pipe
meter
100
100
Pipe inside dia. mm
75
100
Pressure drop
bar
2.1
0.5
psi
30.9
7.3
3" Header
4" Header
Normally, the velocity of compressed air should not be allowed to exceed 6 m/s. Pipe fittings like valves, elbows & no. of bends etc. also contribute to additional pressure losses. Case Study 16 : Pressure Drop (in bar) In different Pipe sizes of 100 ft. Length Brief
Nominal FAD, cfm pipe size (Free Air (in inches) Delivery)
Line Pressure, psig 40
50
75
100
125
150
1
10
4.39
3.70
2.68
2.09
1.72
1.46
2 3 4
20 50 100
0.54 0.43 0.41
0.46 0.36 0.34
0.33 0.26 0.25
0.26 0.20 0.19
0.21 0.17 0.16
0.18 0.14 0.14
6
200
0.24
0.21
0.19
0.16
0.14
0.11
Manage end use of air. This includes proper understanding of end use requirement, often termed as the ultimate goal to be achieved. 2. Match the system with the end use requirement in the most efficient way. 3. Improve the efficiency of compressors and related equipments through maintenace. 4. Scouring (moisture removal) by compressed air can be replaced by high pressure blowers. The energy saving can be 80%. 5. Material conveying applications can be replaced by blower systems or preferably by a combination of belt/screw conveyers and bucket elevators. 6. For applications like blowing of components, use of compressed air amplifiers, blowers or gravity-based systems may be possible. 7. Use of compressed air for cleaning should be discouraged. 8. Replacement of pneumatically operated air cylinders by hydraulic power packs can be considered. 9. Use of compressed air for personal comfort cooling can cause grievous injuries and is extremely wasteful. If a ¼" hose pipe is kept open at a 7 bar compressed air line for personal cooling for at least 1000 hours/annum, it can cost about Rs. 1.0 lakh/annum. Operating cost of a 1.5 TR window air conditioner for the same period would be only about Rs. 12,000/- per annum. 10. Use vacuum systems in place of venturi system. 11. Mechanical stirrers, conveyers, and low-pressure air may mix materials far more economically than high-pressure compressed air. 12. Air conditioning systems can cool cabinets more economically than vortex tubes that cool by venting expensive high pressure air. Case Study 18 :
Installation of VSD on a compressor to avoid the compressed air blow-off in the system
Brief Case Study 1 7 : Reduction in pressure drop in the compressed air. Brief A leading bulk drug company has three reciprocating compressors having the capacity of 280 cfm and the corresponding power consumption was 58 kW at 7.5 kg/cm2. The actual air requirement at user end was only 6.0 kg/cm2. The pressure drop in the system was taking place of the order of 1.5 kg/cm2. On analysis, it was found that high pressure drop in the system was due to under sizing of the piping. The existing(2") piping was replaced by suitable sized piping (3"). Overall saving in energy was as under:
Energy Saving Particulars
Actual energy savings 3
Energy Saving Particulars Annual total energy savings, kWh Annual Cost savings, Rs. (million) Cost of implementation Rs. (million) Payback period (years)
The chemical plant has five process fermentors, where the compressed air is used as raw material and as well as for the agitation. Five large compressors in use were of reciprocating, single stage, double acting, horizontal, non-lubricated type having the capacity of 4000 m3/hr, rated pressure 1.5 kg/cm2, rated motor 200 kW. In view of the variations in the load and the energy lost due to bleed off, variable speed drive was installed to adjust the speed based on requirement.
Actual energy savings 35,000 0.123 0.25 2 94
Average bleed air quantity(m /hr)
1320
Annual total energy savings, million kWh
0.580
Annual Cost savings, Rs. (million)
1.52
Cost of implementation Rs. (million)
2.0
Payback period (months)
16
95
Case Study 19 :
Energy saving in compressed air system by eliminating artificial demand
Case Study 21 : Monitoring of air consumption using hour meter installed at compressor motor and reduction of air leakages
Brief
Brief
In a manufacturing industry, compressed air is the major utility used in many applications. The industry has 2 centrifugal compressors of 3000 cfm each and 3 reciprocating compressors of 1000 cfm each. 1 centrifugal compressor and 2 reciprocating compressors are always running totaling to 5000 cfm. It was observed that there was a fluctuation of pressure from 98 psi to 67 psi. Two intermediate control stations each of 4500 cfm have been installed which reduced the fluctuation of pressure from 31 psi to 2 psi. Energy saving potential was as under:
In a paper and pulp industry, for supplying instrument air, two compressors working at 10 kg/cm2 and 1 m3 per minute were running. The air leakage in the system increased and the air compressors started running for more than 20 hrs a day to meet the requirement. Upon installation of the hour meters, it became easy to monitor the running hours of compressors and also estimate the air consumption as well as leakages .The leakages were arrested and also a reduction in total running hrs of compressors was achieved . Savings effected were as under: Energy Saving
Energy Saving Particulars Particulars Actual energy savings Annual total energy savings, million kWh 0.873 Annual Cost savings, Rs. (million) 2.9 Cost of implementation Rs. (million)
2.0
Payback period (months)
9
Case Study No. 20 : Saving due to pressure optimization
Actual energy savings
Annual total energy savings, kWh
75,000
Annual savings, Rs. (million)
0.3
Cost of implementation Rs.
2,000
Payback period (months)
<1
Case Study 22 : Arresting of air leakages in an automobile unit
Brief
Brief
In an automobile plant, it was reported that the maximum air pressure requirement at machine end is 6.5-7.0 kg/cm2 but plant is maintaining 7.0- 8.5 kg/cm2. Generating higher pressure than required is a loss of power i.e roughly 4% loss in maintaining 1 kg/cm2 higher pressure. The details of losses are as follows: Energy Saving Pressure requirement : 6.5-7.0 kg/cm2 Pressure maintained : 7.0-8.5 kg/cm2 Rated Compressor power : 75 kW for 458 cfm compressor Rated Avg. compressor power : 65 kW ( ON and OFF load) Avg. compressor power (ON and OFF load) after reduction in pressure by 1 kg / cm2 : 62.4 kW Particulars Annual total energy savings,kWh Annual Cost Savings, Rs. Cost of Implementation Payback Period
Actual energy savings 10,000 61,000 Nil Immediate
96
A leading automobile unit, which produces 2 wheelers, has seven large compressors with a rated output of 7500 cfm. Compressors consume about 60 lakh units annually (i.e about 12 % of total power consumption). The compressed air is mainly used in pneumatic tools, instruments, control valves. During the recently concluded energy audit, it was observed that the leakage in the system was 1400 cfm, which was about 20% total air consumption. After arresting the leakages, the savings to the company were as under: Energy Saving Particulars
Actual energy savings
Annual total energy savings, kWh
0.864
Annual Cost savings, Rs. (million)
3.0
Cost of implementation Rs. (million)
0.2
Payback period (month)
1
97
3.4
Pumps, Blowers, Fans & Variable Speed Drives
Pumping of water and blowing of air are very basic needs. This can be done by either positive displacement systems like reciprocating pumps, gear pumps, roots blowers etc. or by the centrifugal pumps and blowers. Centrifugal devices do not use a rubbing barrier as in positive displacement equipments but depend upon the kinetic energy imparted to water or air due to rotating motion. They are used in majority of applications needing FLOW due to their inherent reliability, ruggedness and reasonably good efficiency. Basic energy is proportional to the product of FLOW and TOTAL PRESSURE HEAD. The head is mainly friction head and static head. The static head is a function of choice of location and inherent system design while the friction head varies inversely with fifth power of pipe diameter and other flow passages as also to the square of FLOW. The friction based energy is thus decided by CUBE OF FLOW. The equations relating rotodynamic pump performance parameters of flow, head and power absorbed, to speed are known as the Affinity Laws and are as follows: Q N H N2 3 P N Where: Q = Flow rate H = Head P = Power absorbed N = Rotating speed Efficiency is essentially independent of speed Flow: Flow is proportional to the speed
The operation of fan is similar. There is no static head. The head in the heat exchanger is small compared to head lost in ducts, bends and dampers. In addition to the elegant universally applicable variable speed method of capacity control, we can use variable pitch designs and inlet guide vane control for fans. 3.4.1 Energy Saving in Pumps Basically, for an ideal system with given piping, the open valve system characteristics should cut the pump curve at BEP flow (Best Efficiency Point Flow). But this is rarely possible. Hence, a practical system suffers in varying degrees by : 1. 2. 3. 4. 5.
6.
7. 8. 9.
Loss due to drop in efficiency of the pump for off duty point operation. Loss in throttling valve to some extent. Piping size of historical value and layout which can be changed. A pump of old design which has room for improvement. An old heat exchanger, where the design emphasis may be on lesser material content (low first cost) and smaller space giving relatively higher drop for same function. It is very important to realise that the effects of flow may be proportional to first power of Q (heat exchangers have even Q0.8), so that reduction in flow by even marginal percentage brings about considerable energy savings. An unquestioned Static Head can be altered in some cases by re-layout and other innovative changes. Very large drop (relative) in throttling valve which can be minimised or eliminated. There is a fair chance of improving new working point pump efficiency to increase savings.
The methods for saving energy by altering the pump characteristic are briefly as under :
H1/H2 = (N1²) / (N2²)
1. 2. 3. 4. 5. 6.
Power (kW): Power is proportional to the cube of speed
Case Study 23 : Eliminating Throttling Losses by Use of Variable Speed Drive
kW1 / kW2 = (N1³) / (N2³)
Brief
Optimizing the energy efficiency of a pumping system needs attention, action and investments to use the highest possible pump efficiency, to use the pump around its Best Efficiency Point (BEP) which is at a unique flow, to minimize pipe and exchanger losses, minimize/eliminate use of valves and select Minimum Needed Flow under ALL operating conditions. This may call for variable flow systems in many cases to suit operation or to SAVE energy. Changing flow will need retuning the system for optimization.
Figure below shows a system with an unthrottled flow of 12000 lpm and a variation upto 6000 lpm. The pump efficiency figures are shown on the head-flow curve. The best efficiency of 85% is at 12000 lpm which is lowered to 69% at 6000 lpm. Static head is 10 metres. The throttled operation parameter are shown in the Table below.
Q1 / Q2 = N1 / N2 Head: Head is proportional to the square of speed
By trimming the impeller i.e. reduction in impeller diameter. By changing the impeller to get a different characteristic. By a change of blade angle in axial flow type if that feature exists/or installed. By changing the pump if the change is drastic/also for more efficiency. By change of Speed - Most elegant and universally applicable method. By stopping of pump, if parallel operation is properly planned.
Incorporating efficient pump and method of flow capacity control at the design stage or as a retrofit by using variable speed, trimming of impellers, variable pitch designs (axial flow), changing impellers and change of pumps along with minimal flow concept and better (bigger) heat exchangers, summarises the total concept of energy saving measures. 98
99
Case Study 24 : Modification of Pumps at a Fertilizer Plant : Brief An in-house energy audit by Technical Services department revealed mismatches due to insufficient data at design stage or extra safety margins. A large number of impellers were trimmed. In the Ammonia plant, 6 numbers of cooling water pumps of 960 kW motors were being operated to maintain cooling water pressure at 5 Kg/Sq. cm. Gauge. After the system study, it was decided to operate at lower head and higher flow. One heat exchanger at a height was served with a booster pump. This measure saved 500 kW. Table below summarises different saving measures resulting in a saving of 774.4 kW. Energy Saving Modification on Pumps at a Fertilizer Plant Description Power
Throttling Losses and Savings By Use of Variable Speed Pump Performance With Throttling Control Flow lpm System Pressure (m) Pump Pressure (m) Pump Efficiency (%) Pump Input (kW) Motor Load (%) F.L Motor Efficiency (%) Motor Input (kW) Starter Efficiency (%) Input (kW)
12000 23.50 23.20 86.00 53.58 97.41 90.00 59.53 99.80 59.65
9000 17.93 27.50 79.50 50.87 92.49 89.60 56.77 99.80 56.88
6000 13.35 29.50 69.00 41.92 76.20 89.00 47.10 99.80 47.20
Original Data
After Modification
Flow
Dia
Cons.
Head
Flow
Dia
Cons.
Head
Saving
M3/hr
Mm
kW
M
M3/hr
Mm
kW
M
kW
Condensate
150
321
159
220
150
291
130
180
29
Hot Condensate
150
346
83
175
150
320
70.2
150
12.8
C/X - 102 Conds.
82.1
258
57
155.3
82.1
202
35
146
22
C/X - 701 Conds.
60.2
250
45
158
60.2
203
27
95
18
C/X - 101 Conds.
102
280
63
158
102
NA
38
95
20.2
D.M. Transfer
125
306
60
128
125
294
55.4
118
20.5
Treated Ammonia Conds. 186
350
125
102.6
186
320
104.5
86
20.5
Treated Amm. Conds.
350
125
102.6
186
320
104.5
86
20.5
186
Additionally 1. 2.
Energy Saving The same system was equipped with an inverter with 97.5%, efficiency changing to 89.5% at reduced load (See Table below).
Ammonia CW pump was totally stopped saving 500 kW . One G.S.W. pump was stopped due to inter-connection of C.W and G.S.W, thereby saving 80 kW.
Case study 25 :
Pump Performance With Variable Speed
Replacing the inefficient pumps with energy efficient pumps matching the characteristics with the others connected in parallel
Brief Flow lpm System / Pump Pressure (m) Pump Efficiecny (%) Pump Input (KW) Motor RPM Motor Load % F.L. Motor Efficiency (%) Motor Input (kW) Controller Efficiency % Input (kW) Savings Inputs (kW) % Saving (Throttled - Input)
12000 23.50 86.00 53.58 1450 97.40 93.70 57.18 97 58.95 0.70 1.12
9000 17.93 85.50 31.02 1210 56.40 93.60 33.14 94 35.25 21.63 38.03
6000 13.35 78.00 16.78 1000 30.50 90.00 18.64 89.50 20.83 26.37 55.80
100
In one of the Jal Board boosting stations, there were 6 nos pumps-3 of 125 HP and other 3 of 100 HP pumps. While the 125 HP pumps were giving their efficiency near to the rated efficiency of 58 %, the 100 HP pumps were giving efficiency in the range of 13% to 19 %. The efficiency had gone down as these were run in parallel with 125 HPpumps, which were having different characteristics. Further, the head generated by these pumps was much higher than required as the flow was being throttled. Energy Saving Replacement of 100 HP pump by energy efficient pump with VFD Energy saving Annual saving Investment Payback period 101
: : : :
0.185 Million kWhr 0.74 Million 1.2 MIllion 20 months
Case study No. 26 : Use of one high capacity pump in place of 4 nos of small capacity chilled water pumps Brief No. of Pumps in parallel Capacity of pumps Valve throttled New pumps (1 no.)
: 4 (20 HP each) : 20.5 lps, 43.75m : 60%-80% : 50 HP
Instead of 4 nos. of Pumps, one big pump of 50 HP motor and energy efficient pump was installed. Savings effected were as follows: Energy Saving Annual energy saving Annual cost saving Investment in modification Simple payback 3.4.2
: 0.123 Million kWhr : Rs 0.637 Million : Rs 0.370 Million : 7 months
System Operation and Energy Saving Methods for Blowers/Fans :
Fig. 3.6 shows a fan performance curve for flow reduction from 0.66 per unit to 0.50 per unit. The system head characteristic does not have static head in the case of blowers and fans. The system resistance consists of dampers, ducts with bends etc. and diffusers or such other equipments. The system curve follows the expression KQ2 which is a parabola starting from origin.
3.
By Inlet guide vane - Introduces prerotation to add tangential velocity at inlet to improve entry conditions with reduced flow. Better compared to dampers. Changing to better suited blower/fan. By changing blade angle in axial flow fans if applicable. By changing the speed, which is applicable to all blowers/fans. By stopping redundant fans/blowers. Improved design FRP fans for cooling towers have given 10% to 30% savings.
4. 5. 6. 7. 8.
Case study 27 : Replacement of Inefficient fans Brief The test results for the individual fans show that there is mismatch between fan selection and the exact requirements and the operating static pressure of these fans is between 13% and 60% of the rated pressure and the flow of fans is between 90% and 150% of the rated flow. This mismatch has resulted in low operating efficiency of the fan system. It is suggested to replace the low efficiency fans with high efficiency fans. Sl. No. 1 2 3 4 5 6 7 8
Fan Name
% of Flow
Cooler fan A Cooler fan B Cooler fan C Air fan Reverse fan Mill fan Cement fan ESP fan
89.78 127.36 86.74 119.32 99.65 35.03 19.41 30.99
% of Static Pressure 55.65 45.84 59.09 27.99 27.00 39.08 13.43 13.54
Static Efficiency 55.00 65.10 58.84 36 .88 16.93 18.70 4.19 9.97
Energy Saving Calculation for kVA Savings by Changing the Fan Motor (OnlyCooler Fan-1 is taken for example) Parameter Power consumption (kW) Power factor Annual saving (Rs.)
Before Implementation 108
After Implementation 78
Saving/ Improvement ( - ) 30
0.80 -
0.85 -
( + ) 0.05 ( + ) 4,92,480
Fig 3.6 : Fan Performance with Variable Speed Operation All the points listed under pumps are applicable to blowers/ fans. The loss in damper at reduced flow is shown in Fig. 3.6 by shaded areas. Due to absence of static head, a larger proportion of energy is dissipated in dampers. Capacity control saving methods are listed below alongwith energy related comments: 1. 2.
By outlet damper - Reduces energy use but relatively large damper loss. By inlet damper - Reduced suction reduces effective density to give reduced head/flow. Better compared to outlet damper. 102
* The impeller power for the new fan is calculated by taking 10% margin in present flow. 15% margin in present static pressure and 90% fan efficiency for cooler than (for other fans - 75% fan efficiency) Total energy saving for all the fans in above table (kWh/t clinker) : 1.037 Annual saving : Rs.2.2 Million Investment : Rs.2.4 Million Payback period : 13 months
103
Case Study 28: Speed Reduction of Vacuum Blowers and Agitators in Pulp & Paper Industry Brief (a) Some of the vacuum blowers of PM 1 were being operated with dampers closed to a greater degree. The blowers are belt driven. The pulley sizes are changed to reduce the speed of the fans. (b) Speed reduction was carried out on new bleached high density tower agitator. (c) The plant personnel decided to operate the blower at 2100 rpm and keep the damper fully open. After implementation, the power consumption was measured to be 17.4 kW. Energy Saving (a) Annual Saving Investment Payback period
: Rs. 0.12 Million : Rs. 0.1 Million : 10 months
(b) Annual Saving Investment Payback period
: Rs.93000 : Rs.15000 : 2 months
(c) Energy Saving Annual energy saving Annual saving Investment Payback period
: : : : :
Energy saving Average running kW of ID fan with VFC Average running kW of ID fan with VFD Energy saved/day (42 x 24 hours) Annual saving Investment Payback period
: : : : : :
55 kW 13 kW 1008 kWh Rs. 0.647 Million Rs. 1.2 Million 2 years
Case Study 31: Installation of Variable Frequency Drive for Control of ID Fans in place of Inlet Damper Control in Pulp & Paper Industry Brief 50 tph AFBC boiler was provided with 2 nos. ID fans. The furnace draft was being controlled by varying the inlet damper position of ID fans. Each ID fan is driven by 90 kW motor, 750 rpm. The normal damper opening when boiler was at full load awas 55%. It was decided to install 2 nos. 90 kW VFDs for fan control. Energy Saving
16 kWh 96000 kWh Rs. 0.48 Million Nil Immediate
Power consumption before VFD Power consumption after VFD Annual Saving Investment Payback period
: : : : :
84 kW (each motor) 58 kW (each motor) Rs. 0.75 Million Rs. 1.1 Million 18 months
Case Study No. 32 : VFD in Pump in Paper Plant
Case study 29 : Interconnection of Blowers in the plant
Brief
Brief
Industry Application Motor Rating
: : :
Previous System
:
Problem Observed
:
1. Excess Water drained & hence wastage of water 2. Energy loss due to drain control 3. Mechanical wear & tear
Present System
:
Water outlet controlled by varying the speed of AC motor using V.F.D.
There are 7 nos. of 3000 cfm (6" head) blower for machine exhaust. It is suggested to inter-connect the blower with damper so that minimum number of blowers can be run common to all machines and can also be run independently if required. Energy Saving Annual saving Investment Payback period
: Rs. 1,62,940 : Rs. 25000 : 2 months
Paper Pump (Water Suction) 3 Phase AC Induction Motor Rating : 130 HP - Volt : 415 V Current : 160 A - RPM : 1440 Motor was run through Star-Delta Starter
Case Study 30 : Replacement of Variable Speed Fluid Coupling (VFC) with Variable Frequency Drive (VFD) in Pulp & Paper industry Brief The variable fluid coupling was replaced with a variable frequency drive for I.D. fan of soda recovery boiler, for furnace draft control. The fan was operating around 740 rpm, whereas motor speed was 970 rpm. Recognizing the efficieny difference between VFC and VFD, VFD was installed to replace VFC.
104
Previous System Present System
105
Freq (Hz) 50 25 to 40
Amp.
kW
100 40 to 50
60 40
Water m3 / hr. 130 130
Drain Valve 50 to 70 open 100% (Average)
Energy Saving Actual capacity of 100 kW motor Actual requirement for process Without drive power consumption With AC Drive power consumption Energy Saving Annual Saving Investment Payback period
Option (a) : : : : : : : :
500 m3/hr 130 m3/hr 60 kW 40 kW 480 kWh/day Rs 0.65 Million Rs 0.325 Million 5 months
3.4.3 Sample Calculations A)
An industrial fan with measured flow rate of 90 m3/s has 80 mm WC static pressure developed across it. The motor power drawn is 120 kW and motor efficiency of 86%. We first find out the fan static efficiency. For the above fan, the bagfilter in the system was replaced with ESP (Electrostatic Precipitator). The pressure drop across the bagfilter was 65 mm WC. With ESP, pressure drop was 20 mmWC. Flow rate increased by 20%. The original flow can be obtained by two options:
a)
Impeller trimming
b) Reduced RPM with pulley diameter change
New Flow rate, Q2
= 90 x 1.2 = 108 m3/hr Pressure developed across fan, H2 = 80-(65-20) = 35 mm WC New fan static efficiency = 68 -5 = 63% For flow Q1 = 90 m3/s, H1 =?, Q2 = 108 m3/s and H2= 35 mm WC (Q2/ Q1)2 = (H2/H1) (108/90)2 = (35/H1) H1 = (90/108)2 x35 = 24 mm ) Power developed at fan shaft = 90 x 24 102 x 0.63 = 33.61 kW New impeller diameter (D2) Considering the fan law (D1 / D2) = (Q1/Q2) = (N1/N2) D1 = 70 mm, Q1=108, Q2 = 90, D2 = 58 mm, N1= 850 RPM New impeller diameter, D2 = 58 mm New RPM = 90/108 x 850 = 708 RPM Option (b)
For option (a), if original impeller size were 70 mm in diameter, what would be the new impeller diameter if efficiency drops by 5%? For option (b), what would be the required reduction in RPM if fan was originally running at 850 RPM and efficiency at reduced RPM is expected to be 66%? We finally find out the differential energy savings between the two options at 8760 hours/annum and at Rs.4 / unit. Motor power drawn Power input at fan shaft (BHP)
= 120 kW = 120 x 0.86 = 103.2 kW Flow, Q1 = 90 m3/s Pressure developed across fan, H1 = 80 mm Original impeller diameter (D1) = 70 mm Original RPM = 850 RPM Fan static efficiency = Flow x Pressure developed across fan x100 102 x Power developed at fan shaft = 90 x 80 x 100 102 x 103.2 = 68 %
106
Efficiency at reduced RPM Power developed at fan shaft Differential power savings
= 66% = 90 x 24 102 x 0.66 = 32.08 kW = 1.53 / 0.86 x 8760 hours/annum x Rs.4 / kWh = Rs. 62340
B) A centrifugal pump pumping water operates at 35 m3/hr and at 1440 RPM. The pump operating efficiency is 68% and motor efficiency is 90%. The discharge pressure gauge shows 4.4 kg/cm2. The suction is 2m below the pump centerline. If the speed of the pump is reduced by 50 % estimate the new flow, head and power Flow = 35 m3/hr Head developed by the pump = 44 - (-2) = 46 m Hydraulic Power = Q (m3/s) x Total head, hd - hs (m) x (kg/m3) x g (m2/s)/1000 Power drawn by the motor = (35/3600) x 46 x 1000 x 9.81 1000 x 0.68 x 0.9 (i.e. efficiency of pump & motor) = 7.2 kW Flow at 50 % speed Q2 : 35 / Q2 = 1440/720 Q2 = 17.5 m3/hr Head at 50 % speed H2 : 46 / H2 = (1440/720)2 H2 = 11.5 m Power at 50 % speed P2 : 7.2/kW2 = 14403 / 7203 P2 = 0.9 kW
107
3.5 Refrigeration & Air Conditioning System Refrigeration systems are used for process cooling by chilled water or brine, ice plants, cold storage, freeze drying, air-conditioning systems etc. The refrigerant temperatures for process cooling applications may range from 15°C to as low as 70°C. Comfort air-conditioning requires refrigerant temperatures in the range of 0°C to 5°C. Air-conditioning generally implies cooling of room air to about 24°C and relative humidity of 50%-55%. In some applications, air-conditioning involves humidification of air up to 70%80% relative humidity (as in textile industry) or dehumidification of air to less than 20% (e.g.in some pharmaceutical industries, rooms housing sophisticated electronic equipment, storage rooms for hygroscopic materials etc.).
The other commonly used and easily understood figure of merit is Specific Power Consumption = Power Consumption (kW) Refrigeration effect (TR) A lower value of Specific Power Consumption implies that the system has better efficiency. 3.5.1.1 Specific Energy Consumption in Refrigeration andAir-conditioning Systems Table 3.9 shows the figures of merit for Vapour Compression systems using reciprocating and centrifugal compressors. Table 3.10 shows the figures of merit for steam heated and also direct natural gas / LDO fired absorption chillers; here, in addition to COP and EER, the specific steam consumption in kg/hr/TR is mentioned. Table 3.9 : COP, EER & Specific Power for Vapour Compression Systems (for chilled water at 8oC with water cooled condensers) Capacity TR
There are types of refrigeration system : a) Vapour Compression System b) Vapour Absorption System
Power kW
COP
EER Btu/hr/W Specific Power kW/TR
Open Type Reciprocating Compressors
Vapour compression machines are used extensively for refrigeration. This system requires motive power to drive a compressor, which is supplied by an electric motor or engine. With increasing electricity prices, there is renewed interest in Absorption Refrigeration machines, wherein heat is used for cooling. Users having waste heat or economical heat energy sources are using the absorption chillers.
10.78
6.62
5.75
19.7
0.61
32.20
21.38
5.32
18.2
0.66
48.30
32.06
5.32
18.2
0.66
64.40
42.75
5.32
18.2
0.66
Semi-hermetic Reciprocating Compressors 9.26
7.00
4.62
15.8
0.76
13.90
12.10
4.03
13.8
0.87
42.00
34.50
4.28
14.6
0.82
6.00
20.5
0.59
2.9 to 2.3
7.8 to 10
1.2 to 1.5
Open Type Centrifugal Compressors 563.67
3.5.1 Energy Consumption in Refrigeration Systems
329.94
Window Air-conditioners & Split Units
The cooling effect of refrigeration systems is generally quantified in tonnes of refrigeration. 1 Tonne of Refrigeration (TR)
1.8 to 2.3
Note : The above data is based only on the compressor power consumption, auxiliary power for pumps, fans etc. is excluded.
= 3023 kcal/hr = 3.51 kWthermal = 12000 Btu/hr
The commonly used figures of merit for comparison of refrigeration systems are Coefficient of Performance (COP), Energy Efficiency Ratio (EER) and Specific Power Consumption (kW/TR). The definition of these terms are given below. If both refrigeration effect and the work done by the compressor (or the input power) are taken in the same units (TR or kcal/hr or kW or Btu/hr), the ratio is COP = Refrigeration Effect Work done If the refrigeration effect is quantified in Btu/hr and the work done is in Watts, the ratio is EER
1.5
= Refrigeration Effect (Btu/hr) Work done (Watts)
Higher COP or EER indicates better efficiency.
108
Table 3.10 : COP, EER & Specific Power for Vapour absorption Systems (for chilled water at 8oC with water cooled condensers)
Capacity TR
Steam pressure Steam cons. kg/cm2 K=Kg/hr.
Single Effect Chiller (Steam heated) 3.0 2101.0 240 Double Effect Chiller (Steam heated) 100 8.0 490.2 155 8.0 736.5 270 8.5 1284.0 500 8.0 2296.0 Double Effect Chiller (Direct fired) 3 78 27.3 m /hr natural gas 150 54.6 lit/hr LDO 109
COP
EER Btu/hr/W
Specific steam cons. Kg/hr/TR
0.61
2.10
8.75
1.10 1.13 1.13 1.17
3.76 3.86 3.86 4.00
4.90 4.75 4.76 4.59
0.96
3.28
0.96
3.27
0.35 m3/hr/TR 0.36 lit/hr/TR
Comments :
(b)
a)
The approximate thumb rule is that for every 1oC higher temperature in the evaporator, the specific power consumption will decrease by about 2% to 3%.
Well designed and well maintained vapour compression systems, using reciprocating compressors, for chilled water at about 8°C have COP of 4 to 5.8, EER in the range of 14 to 20 Btu/hr/W and Specific Power Consumption in the range of 0.61 to 0.87 kW/TR. It may be noted that Open-type compressors are more efficient than semi-hermetic compressors.
Operate at Higher Temperature
(c )
Accurate Measurement and Control of Temperature
b) Centrifugal compressors, which are generally used for cooling loads about 150 TR, can have COP of about 6, EER greater than 20 and Specific Power Consumption of 0.59 kW/TR.
When the refrigeration system's cooling capacity is significantly more than the actual cooling load, expansion valve control based on superheat sensing often leads to supercooling, resulting in an energy penalty due to unnecessarily lower temperature and also lower COP at lower temperatures.
c)
(d) Reduce Air-conditioning Volume and Shift Unnecessary Heat Loads
Double Effect Absorption chillers at about 8°C have COP in the range of 1 to 1.2, EER in the range of 3.3 to 4 Btu/hr/W. The Specific Steam Consumption of double effect machines is in the range of 4.5 to 5.25 kg/hr/TR, at a steam pressure of 8 to 8.5 bar. The specific fuel consumption figures of directly fired double effect chillers are 0.35m3/hr/TR (natural gas) and 0.36 lit/hr/TR (LDO). In comparison with compression system, it can still save energy cost if waste heat or any other cheaper alternative fuel is available.
• • • • (e)
3.5.2 Energy Saving Opportunities (a)
Avoid Refrigeration & Air-conditioning to the Extent Possible • •
Minimise Heat Ingress • • • • • • • • • •
The system efficiency of both vapour compression and absorption systems is critically dependent on the performance of the heat exchangers i.e. evaporator, condenser and cooling tower. Any deterioration in these equipment leads to huge energy penalties.
Use Evaporative Cooling for Comfort Cooling in Dry Areas : Use Cooling Tower Water at Higher Flows for Process Cooling : (f)
Table 3.11 : Effect of Evaporator and Condenser Temperatures on Refrigeration Machine Performance Evaporator Temperature o C +5
0
-5
Condens er Temperature o C
Capacity +35 151 94
+40 143 102.7
+45 135 110.6
+50 127 117.8
Sp.Power (kW/TR)
0.62
0.72
0.82
0.93
Capacity (TR)
129
118
111
104
Power cons. (kW)
90
96.8
103
108.9
Sp.Power (kW/TR) Capacity (TR) Power cons. (kW)
0.70 103 84.2
0.82 96 89.6
0.93 90 94.7
1.05 84 99.4
Sp.Power (kW/TR)
0.82
0.93
1.05
1.19
110
Check and Maintain Thermal Insulation Insulate Pipe Fittings & Flanges Use Landscaping to the Reduce Solar Heat Load Reduce Excessive Window Area Use Low Emissivity (Sun Control) Films Use Low Conductivity Window Frames Provide Insulation on Sun-Facing Roofs and Walls. Provide Evaporative Roof Cooling Use Doors, Air-Curtains, PVC Strip Curtains Use High Speed Doors for Cold Storage Using Favourable Ambient Conditions
• • •
Capacity (TR) Power cons. (kW)
Unnecessary heat loads may be kept outside air-conditioned spaces. Use False Ceilings Use Small "Power Panel" Coolers Use Pre-Fabricated, Modular Cold Storage Units
Use Cooling Tower Water Directly for Cooling in Winter Design New Air-conditioning Systems with Facility for 100% fresh air during winter Use Ground Source Heat Pumps
(g) Use Evaporators and Condensers with Higher Heat Transfer Efficacy •
•
• •
Use Heat Exchangers with Larger Surface Area 1°C higher temperature in the evaporator or 1°C lower temperature in the condenser can reduce the specific power consumption by 2 to 3%. Use Plate Heat Exchangers for Process and Refrigeration Machine Condenser Cooling Plate heat exchangers have a temperature approach of 1oC to 5oC instead of around 5oC to 10oC for shell and tube heat exchangers. Avoid the Use of Air Cooled Condensers for large cooling loads . Use evaporative Pre-coolers for Air-cooled Condensers
111
Case Study 33 : Replacement of Existing Evaporator with a New Evaporator with Better Heat Transfer Efficacy
The methods used for air purging are : •
Brief • After achieving the saving by reduction in speed of compressors, a decision was taken to replace the existing "Ammonia Evaporator Coil in Tank" with "Shell & Tube Heat Exchanger". The comparative measurements are as follows. Parameter Power consumption (kW) Operating hrs./day Energy Consumption (kWh/day)
Before Implmentation 39.9 10 323
After Implementation 32.3 6.7 267
Saving / Improvement 7.6 3.3 56
Brief : : : :
18371 kWh Rs. 82670 Rs. 0.12 Million 1.5 years
3.5.2.1 Energy Saving Opportunities in Normal Operation • •
• •
Use Building Thermal Inertia Put HVAC Window Air Conditioners and Split Units on Timer or Occupancy Sensing Control Interlock Fan Coil Units in Hotels with Door Lock or Master Switch Improve Utilisation Of Outside Air. Maintain Correct Anti-freeze Concentration Install a Control System to Co-ordinate Multiple Chillers. Permit Lower Condenser Pressures during Favourable Ambient Conditions. Optimise Water/Brine/Air Flow Rates Defrosting : The most widely used methods for defrosting are:
• •
1. Shutting down the compressor, keeping the fan running and allowing the space heat to melt the frost. 2. Using out side warm air to melt the frost after isolating the coil from the cold room. 3. Using electric resistance heaters in thermal contact with the coil. 4. Bypass the condenser and let the hot gas into the evaporator to melt the frost. 5. Spray water on the coils to melt the frost. Match the Refrigeration System Capacity to the Actual Requirement Monitor Performance of Refrigeration Machines
• • • • •
3.5.2.2 Maintenance to Ensure Energy Efficient Operation • • • •
Purging of non-condensibles plays an important role in maintaining the efficiency of refrigeration machines. Case Study 34 : Modification in Chilled Water Pumping System
Energy Saving Annual savings Annual savings Investment Payback period
•
Direct venting of the air-refrigerant mixture, which is a primitive manual technique. A small compressor draws a sample of the refrigerant gas and compresses the mixture, condensing as much as possible of the refrigerant, and vents the vapour mixture that is now rich in non-condensibles. A low temperature evaporator, in-built in the system, condenses most of the refrigerant from the refrigerant-air mixture drawn from the condensor or receive and vents the non-condensibles. This method does not require a separate compressor and is used widely.
Clean Fouled Heat Exchangers Specify Appropriate Fouling Factors for Condensers Do Not Overcharge Oil Purging the Condenser of Air
112
The chilled water system had primary (chiller side) and secondary (process side) pumps with a hot well and cold well arrangement. Since the chilled water requirement for the plant was reasonably steady, it was decided to eliminate the primary pump and connect the warm chilled water from the secondary side directly to the chiller, bypassing the hot well. In view of the increased pressure requirement, a new, efficient pump of appropriate head requirement was recommended. The power consumption scenario before and after this change is as follows: Energy Saving Parameter Operating hrs. of primary pump (hrs.) Energy consumption (kWh/day) Operating hrs. of secondary pump (hrs.) Energy consumption (kWh/day) Total power consumption (kWh/day)
Before Implementation 10
After Implementation NIL
Saving / Improvement -
85 24
NIL 24
-
271 356
139 139
132 217
Case study 35 : Replacement of inefficient condensers of central AC plant of administrative building of a corporate house Brief In the administrative building, there are two compressors installed by a company. Each compressor is of 60 TR rating as per normal perception of the operating staff. Originally there were two 10 HP pumps for circulation of condenser cooling water and the cooling was achieved by spray nozzles. Subsequently an induced draft cooling tower was installed for condenser water cooling. Further one 15 HP pump was put in parallel to existing 10 HP pumps because of poor cooling and high discharge problem, it was thought that the water supply was inadequate. There are two independent DX coils (Air Handling Units). 113
During the study the pressures, temperatures & water flow in the cooling water circuit were measured. It was observed that there was a high discharge pressure and low suction pressure due to heavy scaling in condenser.
-
Consequent upon study, the condensers were replaced. Valves were replaced with butterfly valves and cooling coils were cleaned. Filters of AHU units were also replaced.
-
Energy Saving Annual energy saving Annual Saving Investment Payback period
: : : :
21275 kWh Rs. 75,000 Rs. 0.16 Million 2 years
Case study 36 : Savings due to stopping bypass through idle pumps and idle condensers. Brief In an automobile plant, condenser water was flowing through the idle pumps and the idle condensers resulting in loss of head as the valves had broken down and were passing. By stopping by-pass though idle pumps and idle condensers the energy savings was as follows : Energy Saving Annual Energy Saving Annual Saving Investment Payback 3.5.3
: : : :
-
Periodically clean plugged cooling tower distribution nozzles. Install new nozzles to obtain a more uniform water pattern. Replace splash bars with self-extinguishing PVC cellular film fill. On old counterflow cooling towers, replace old spray type nozzles with new square spray ABS practically non-clogging nozzles. Replace slat type drift eliminators with low pressure drop, self extinguishing, PVC cellular units. Follow manufacturer's recommended clearances around cooling towers and relocate or modify structures that interfere with the air intake or exhaust. Optimize cooling tower fan blade angle on a seasonal and/or load basis. Correct excessive and/or uneven fan blade tip clearance and poor fan balance. Use a velocity pressure recovery fan ring. Consider on-line water treatment. Restrict flows through large loads to design values. Shut off loads that are not in service. Take blow down water from return water header. Optimise blowdown flow rate. Send blowdown water to other uses or to the cheapest sewer to reduce effluent treatment load. Install interlocks to prevent fan operation when there is no water flow. Replace ordinary Aluminium fans by more energy efficient aerodynamically designed FRP fans (Fibre Reinforced Plastic).
Case study 37 : Replacement of existing metal (aluminum alloy) blades by FRP blades for cooling towers.
2760 kVAh Rs.979800 Nil Immediate
Brief The cooling tower specification is given below:
Cooling Towers
In many plants, after the cooling tower has been in service for a few years, the need for improving its performance is felt. This may be due to: a) Deterioration of efficiency of the cooling tower, b) Deterioration in the efficiency of the heat exchangers (coolers, condensers etc.) at the end-use side, c) Additional heat rejection due addition of equipment, plant capacity etc. Two parameters, which are useful for determining the performance of cooling towers, are the Temperature Range and Temperature Approach.
Sl. No. 1.
Location Cooling Plant Cooling tower
Specification Capacity 200 TR
Fan M otor Rated Power (kW)
Actual Power kW
11.5
5.93
Replace the aluminum blades by new energy efficient FRP blades. By using FRP blades there will be a minimum saving of 10% in the energy. Savings obtained by conversion of aluminium blades to FRP blades. Energy Saving
3.5.3.1 General Tips to Save Energy in Cooling Towers -
-
Control cooling tower fans based on leaving water temperatures. Control the optimum temperature as determined from cooling tower and chiller performance data. Use two-speed or variable speed drives for cooling tower fan control if the fans are few. Stage the cooling tower fans with on-off control if there are many. Turn off unnecessary cooling tower fans when loads are reduced. Cover hot water basins to minimize algae growth that contributes to fouling. Balance flow to cooling tower hot water basins. 114
Actual power on cooling tower fan motor : 5.93 kW Percentage of power savings by conversion to FRP blades : 10% Working hrs/ day : 24 Working days/ year : 355 Tariff (Rs./unit) : Rs. 3.53 Annual saving : 5.93 x 0.10 x 24 x 355 = 5,052,36 kWh Annual saving @ of Rs 3.53/kWh : Rs.17,834 Investment : Rs.10,000 Payback period : 7 months
115
Case study 38 : Installation of automatic temperature controller in the cooling tower systems. Brief 0
Install automatic temperature controller for cooling towers (28-30 C). The controller switches off the fan when the cold well temperature goes below the set temperature and switches on when temperature goes above the set temperature (2830 0C). Energy Saving Parameter Annual Power Consupmtion (kWh)
Before Implementation 114423
After Implementation 80096
Annual Saving Investment Payback period 3.6
Saving/ Improvement % 30%
: Rs.137300 : Rs.50000 : 5 months
3.6.2.1 Variation of losses during operation The losses vary during the operation of a transformer due to loading, voltage changes, harmonics and operating temperature. Case Study 39: Parallel operation of transformers in a Tea Industry Brief Energy Audit for Tea Factories making C.T.C. Tea, was conducted. Power is received at 22 kV and 11 kV by separate lines. This is stepped down by two 500 kVA Transfromer 22 kV/433V which feeds segregated loads. The typical loss figures for 500 kVA transformers are 1660 W for no load and 6900W as load losses for 100% load. It was recommended to parallel both transformers for a total 500 kVA load on secondary side. Also, cut off one transformer from H.V. side in lean season and holidays when the load is 5% to below 25%. Calculations
Energy Savings in Transformers
Transformer is the most efficient equipment in an electrical system. Distribution transformers are very efficient, with efficiencies of 97% or above. It is estimated that transformer losses in power distribution networks can exceed 3% of the total electrical power generated. In India, for an annual electricity consumption of about 500 billion kWh, this would come to around 15 billion kWh. 3.6.1
3.6.2 Transformer Operation
Losses in Transformers
Transformer losses consist of two parts: No-load loss and Load loss 1. No-load loss (also called core/iron loss) is the power consumed to sustain the magnetic field in the transformer's steel core. Core loss occurs whenever the transformer is energized; core loss does not vary with load. Core losses are caused by two factors: hysteresis and eddy current losses. Hysteresis loss is that energy lost by reversing the magnetic field in the core as the magnetizing AC rises and falls and reverses direction. Eddy current loss is a result of induced currents circulating in the core. 2. Load loss (also called copper loss) is associated with full-load current flow in the transformer windings. Copper loss is power lost in the primary and secondary windings of a transformer due to the ohmic resistance of the windings. Copper loss varies with the square of the load current. (P = I²R) For a given transformer, the manufacturer can supply values for no-load loss, PNOLOAD, and load loss, PLOAD. The total transformer loss, PTOTAL, At any load level can then be calculated from: PTOTAL = PNO-LOAD + (%Load/100)² x PLOAD
For total load of 500 kVA, there are three options. a) Only one transformer takes full 500 kVA Load. Losses = 1 . 66 ( No L oad) + ( 500 /500 ) 2 x 6 . 9 k W ( l oad l osses )=8.56 kW b)One transformer takes segregated 300 kVA while second takes 200 kVA segregated load. Losses = 1 . 66 + ( 300 /500 )2 x 6 . 9 + 1 . 66 + ( 200 /500 ) 2 x 6 . 9 k W=6.90 kW c) Both are paralleled to take 250 kVA each. Losses = 2 (1.66 + (250/500)2 x 6.9) kW= 6 .77 kW. Thus on major load, the losses are minimum by paralleling both transformers. Operation at part load during lean season : a) Two paralleled transformers Losses = 2 { 1 . 66 + ( 0 . 25 /2 ) 2 x 6 . 9 } = 3 . 54 k W at 25 % load Losses = 2 { ( 1 . 66 ) + ( 0 . 05 /2 ) 2 x 6 . 9 } = 3 . 33 k W at 5 % load b) Only one transformer is energized Losses = 1 . 66 x ( 0 . 25 ) 2 x 6 . 9 = 2 . 09 k W at 25 % load Losses = 1 . 66 x ( 0 . 05 ) 2 x 6 . 9 = 1 . 68 k W at 5 % load Thus losses are minimum at low loads using only one transformer .
Where transformer loading is known, the actual transformers loss at given load can be computed as: 2
kVA Load = No load loss + Rated kVA x (full load loss)
116
The tariff was kVA of M. D. x R s . 60 + R s . 0 . 89 x k Wh + R s . 150 meter rent. The total annual consumption for the factory was 1.85 Million kWh per year and the electricity bill was Rs 2.04 Million giving Rs 1.10/kWh as average cost.
117
Saving in load losses =
Energy saving
[( pf1 ) - 1 ] 2
Annual energy saving Annual saving Investment Payback period
(Per unit loading as per kW) 2 x Load losses at full load x
: 1000 kWh : Rs.10000 : Nil : Immediate
Thus, if p.f. is 0.8 and it is improved to unity, the saving will be 56.25% . Case study 40 : Reallocation of the load of transformer
3.6.2.2 Energy Saving by optimum -utilisation of transformers
Brief
Table 3.12 summarises the variation in losses and efficiency for a 1000 kVA transformer and also shows the difference in losses by using a 1600 kVA transformer for the same. The 1000 kVA transformer has a no load loss of 1700 watts and load loss of 10500 Watts at 100% load. The corresponding figures for 1600 kVA transformer are 2600 Watts and 17000 Watts respectively. Loading is by linear loads. Temparatures assumed equal.
Presently there are 3 numbers of transformers in a plant. From the data given it can be seen that Transformer No.3 i.e. 1250 kVA transformer is loaded only 28.70% i.e. 359 kVA against 1250 kVA. It is recommended to shift the load to a lower capacity transformer of 750 kVA which is lying idle.
Transformer
Table 3.12 : Comparison of transformer losses TRANSFORMER-1 1000 kVA, No load losses = 1700 W Per unit
TRANSFORMER-2 1600 kVA. No load losses = 2600 W
Difference in losses, W
1 2 3 4
Rated kVA 2000 2000 1250 750
Voltage
Current
Loading kVA
440 440 440 440
1200 1280 471 -
914.94 953.29 358.87 -
Loading % 45.72 47.66 28.70 Idle
Savings obtained by reallocating transformer No.3 load to idle transformer:
Load
Load losses
Total losses
Output kW
Efficiency %
Load losses, W
Total losses, W
0.1
105
1805
100
98.23
60
2660
861
0.2
420
2120
200
98.9 5
265
2865
745
0.4
1680
3380
400
99.16
1062
3662
282
0.6
3780
5480
600
99.09
2390
4990
-490
0.8
6720
8420
800
98.96
4250
6850
-1570
1.0
10500
12200
1000
98.18
6640
9240
-2960
Calculations
The efficiency of 1000 kVA transformer is maximum at about 40% load. Using a 1600 kVA transformer causes under loading for 1000 kW load. The last column show the extra power loss due to oversized transformer. As expected, at light loads, there is extra loss due to dominance of no load losses. Beyond 50% load, there is saving which is 2.96 kW at 1000 kW load. The saving by using a 1600 kVA transformer in place of a 1000 kVA transformer at 1000 kW load for 8760 hours/annum is 25930 kWh/year @ Rs .5.0/kWh, this is worth Rs 0.129 Million. The extra first cost would be around Rs 1.5 Million. Hence deliberate oversizing is not economically viable. 3.6.2.3 Reduction of losses due to improvement of power factor Transformer load losses vary as square of current. Industrial power factor vary from 0.6 to 0.8. Thus the loads tend to draw 60% to 25% excess current due to poor power factor. For the same kW load, current drawn is proporational to kW/pf. If p.f. is improved to unity at load end or transformer secondary, the saving in load losses is as under. 118
Transformer Loading:
Existing average load Existing transformer No.3 rating Percentage loading of TR : 3 Recommended Transformer rating with respect to average load Copper loss for existing 1250 kVA transformer
= 358.87 kVA = 1250 kVA = 28.70% = 750 kVA
= (0.2870)2 x 6 x 24 x 330 = 3914 kWh = 0.59 kW (where 6 kW = full load copper loss of existing 1250 kVA transformer-considering 330 days 24 hrs operation in a year) Iron loss for 1250 kVA transformer = 2.5 x 24 x 365 = 21900 kW (Where 2.5 kW = iron loss for1250 kVA transformer) Total loss for 1250 kVA transformer
= 21900 + 3914 kWh = 25814 kWh
On replacement of 1250 kVA transformer with 750 kVA transformer, the average loading of 750 kVA transformer will be = 359 = 47.85% 750 Copper loss for 750 kVA transformer =(0.4785)2 x 4 x 330 x 24 = 7255 kWh (where 4 kW = full load copper loss of 750 kVA transformer-considering operating hours – 24 for 330 days) Iron loss for 750 kVA transformer
= 1.95 x 365 x 24 = 17082 kWh (where 1.95 kW = iron loss for 750 kVA transformer) Total losses for 750 kVA transformer 119
= 7255 + 17082 = 24337 kWh
Monetary saving Investement Payback period
Energy Saving Savings in kWh Annual Savings @ Rs.4.20 per kWh Case study 41:
= 25814 – 24337 = 1477 kWh =1477 x 4.20 = Rs. 6203
Operating the two transformers in parallel to reduce transformer losses.
Brief
3.7
Energy Savings in Lighting
Lighting energy consumption contributes to 20 to 45% in commercial buildings and about 3 to 10% in industrial plants. Most industrial and commercial energy users are aware of energy savings in lighting systems. Significant energy savings can be realized with a minimal investment of capital and common sense.
Power is received from the electricity board and 3 nos. of 10000 kVA, 33kV/ 433 volts transformer are installed for stepping it down to 433 volts for plants distribution. Each transformer feeds its own P.C.C. and facility is available to run the transformer in parallel. Now the transformers are run independently and the loads in them are not balanced. The load on the T.R. 2 and 3, which were in service, was monitored for 24 hrs. These transformers have their maximum efficiency at 25 to 50% of loading. As per monitoring, transformer 3 is loaded around 50% and transformer 2 is loaded at less than 25% of their respective rated capacities both operating outside their maximum efficiency ranges. These transformers were run in parallel.
Total losses before parallel operation Total losses after parallel operation Energy saving by parallel operation Monetary saving/yr. Operation Load on each transformer in day time Load on each transformer in night time Investment Payback period
Table 3.13 : Recommended lighting levels
Illuminance Examples of Area of Activity level (lux) General Lighting for rooms and areas used either infrequently and/or casual or simple visual tasks
General lighting for interiors
Energy Saving : : : : : : : : :
: Rs.52,000 : Nil : Immediate
75.2 kW 64.5 kW 4035 kWh Rs.14,204 24. x 365 hrs 66% - 77% 15% - 20% Nil Immediate
20
Minimum service illuminance in exterior circulating areas, outdoor stores , stockyards
50 70
Exterior walkWays & platforms. Boiler house.
100
Transformer yards, furnace rooms etc.
150
Circulation areas in industry, stores and stock rooms. Minimum service illuminance on the task.
200 300
Medium bench & machine work, general process in chemical and food industries, casual reading and filing activities.
450
Hangers, inspection, drawing offices, fine bench and machine assembly, colour work, critical drawing tasks.
1500
Very fine bench and machine work, instrument & small precision mechanism assembly; electronic components, gauging & inspection of small intricate parts (may be partly provided by local task lighting)
3000
Minutely detailed and precise work, e.g. Very small parts of instruments, watch making, engraving.
Case study 42 : Power saving by optimizing transformer operation in large Government building Brief
Additional localised lighting for visually exacting tasks
One transformer is dedicated to one separate annexe building, the other 4 nos are connected in the configuration of 2 each on east and west wing of the buildings. Switching off one transformer each on west and east wing load during weekly off days and transferring the load on the other transformers in line shall save the the no-load losses of the transformer & the maximum efficiceny of the other 2 transformers can be attained by loading at 40-50 % load.
(Source : CIE, IES) Indian standards IS 3646 & SP-32 describes the illuminance requirements at various work environments in detail.
Energy Saving
3.7.1.1 Use Natural Day Lighting
Energy Saving per hour Total energy saving
: 2kW : 13,000 kWh 120
3.7.1 Energy Saving Opportunities
The utility of using natural day lighting instead of electric lighting during the day is well known, but is being increasingly ignored especially in modern air121
conditioned office spaces and commercial establishments like hotels, shopping plazas etc. Industrial plants generally use daylight in some fashion, but improperly designed day lighting systems can result in complaints from personnel or supplementary use of electric lights during daytime. Light pipe: This is a reflective tube that brings clean light from the sky into a room, no need for lighting or incandescent bulbs. These are aluminium tubes having silver lining inside. One 13" light pipe can illuminate about 250 sq.ft of floor area with an illuminance of 200 lux. A 9" dia pipe can give the same iilluminance over a 100 sq.ft area. A 4 ft length of light pipe of the above size provides a daytime average of 750 watts worth of light in June, 250 watts in December. If the pipe length increases to 20 ft, 50% of the light reaches the surface. These are expensive, costing between 150 to 250 dollars and is one of the emerging technologies in day lighting. Case study 43 : Installation of solar energy systems in canteen/guest houses Brief Solar water heaters in canteen were installed in place of electric heaters. By installing these heaters, at least 8 months in an year, solar energy could be used. Existing heaters were retained for supplementing these units in case of bad weather or rainy season. Energy Saving Annual saving Annual saving Investment Payback period
: 0.216 Million kWh : Rs. 0.68 Million : Rs. 0.45 Million : 8 months
3.7.1.2 De-lamping to reduce excess lighting De-lamping is an effective method to reduce lighting energy consumption. In some industries, reducing the mounting height of lamps, providing efficient luminaires and then de-lamping has ensured that the illuminance is hardly affected. De-lamping at empty spaces where active work is not being performed is also a useful concept.
Table 3.14 :Information on Commonly Used Lamps Lamp Type
3.7.1.4 Selection of High Efficiency Lamps and Luminaires Details of common types of lamps are summarised in table 3.14 below. From this list, it is possible to identify energy saving potential for lamps by replacing with more efficient types.
Color Lamp Rendering Life(hrs) Index
8 to 17
100
1000
Tungsten Halogen (Single ended)
75,100,150,500,1000,2000 (no ballast)
13 to 25
100
2000
Tungsten Halogen (Double ended)
200,300,500,750,1000,1500, 2000 (no ballast)
16 to 23
100
2000
Fluorescent Tube lights (Argon filled)
20,40,65 (32,51,79)
31 to 58
67 to 77
5000
Fluorescent Tube lights (Kryptonne filled)
18,36,58 (29,46,70)
38 to 64
67 to 77
5000
Compact Fluorescent Lamps (CFLs) (without prismatic envelope) Compact Fluorescent Lamps (CFLs) (with prismatic envelope)
5, 7, 9,11,18,24,36 (8,12,13,15,28,32,45)
26 to 64
85
8000
9,13,18,25 (9,13,18,25) i.e. rating is inclusive of ballast consumption
48 to 50
85
8000
Mercury Blended Lamps
160 (internal ballast, rating is inclusive of ballast consumption)
18
50
5000
High Pressure Mercury Vapour (HPMV)
38 to 53
45
5000
Metal Halide Lamps (Single ended)
80,125,250,400,1000,2000 (93,137,271,424,1040,2085 ) 250,400,1000,2000 (268,427,1040,2105)
51 to 79
70
8000
Metal Halide Lamps (Double ended)
70,150,250 (81,170,276)
62 to 72
70
8000
High Pressure Sodium Vapour Lamps (HPSV)
70,150,250,400,1000 (81,170,276,431,1060)
69 to 108
25 to 60
>12000
Low Pressure Sodium Vapour Lamps (LPSV)
35,55,135 (48,68,159)
90 to 133
Source : Best Practice Manual-Lighting : MEDA
122
Efficacy (including ballast losses, where applicable) Lumens/Watt
General Lighting Service 15,25,40,60,75,100,150,200, (GLS) (Incandescent bulbs) 300,500 (no ballast)
3.7.1.3 Task Lighting Task Lighting implies providing the required good illuminance only in the actual small area where the task is being performed, while the general illuminance of the shop floor or office is kept at a lower level; e.g. Machine mounted lamps or table lamps.
Lamp Rating in Watts (Total Power including ballast losses in Watts)
123
--
>12000
Table- 3.15 Summarises the replacement possibilities with the potential savings. Table 3.15: Savings by Use of More Efficient Lamps
Case study 46 : Conversion of High pressure mercury vapour lamp and Halogen lamp with High pressure sodium vapour lamp. Brief
Lamp type
Power saving
Sector Existing Domestic/Commercial Industry
Industry/Commercial
GLS GLS GLS TL HPMV HPMV
Replace by
100 W *CFL 25 W 13 W *CFL 9W 200 W Blended 160 W 40 W TLD 36 W 250 W HPSV 150 W 400 W HPSV 250 W
Watts
%
75 4 40 4 100 150
75 31 20 10 37 35
Energy Saving Annual saving Investment Payback period
* Wattages of CFL includes energy consumption in ballasts.
(Source : Website of Bureau of Energy Efficiency)
Case study 44:
High pressure mercury vapour lamp of 250W & 400W capacity, halogen lamp of 500 W were used for street lighting in a manufacturing plant. 250W and 400W High pressure mercury vapour lamp used for street lighting could be replaced with 70W & 150W High pressure sodium vapour lamp respectively. 500W Halogen lamps used for street lighting and outside the factory could be replaced with 70W Highpressure sodium vapour lamp.
Replacement of Incandescent lamps and blended mercury vapor lamps by compact fluorescent lamps (CFL)
: Rs.97,700/: Rs.20,000 : 3 months
Case study 47 : Replacement of filament type indicating lamps by LED type indicating lamps, assuming 0.8 as load factor:
Brief The lighting conversion efficiency of the incandescent lamp is 13.8 lumens per watt which is very low. Blended mercury vapor lamps of 160 W installed had much higher luminous intensity than required. Blended lamps were very inefficient and the lighting conversion efficiency was only 18 lumens per watt. Replaced incandescent and blended type mercury vapor lamps with CFL. Energy Saving Annual energy saving Investment Payback period
: Rs. 2.07 Million : Rs. 1.24 Million : 8 months
Case study 45 : Utilization of natural light by installing translucent sheets for roofs in plant. Brief Fluorescent lamps were used to illuminate 100 rooms even during daytime, since natural lighting was not sufficient. Plant had already installed translucent sheets in many offices and wanted to install in other offices in a phased manner. Installed translucent sheets in the roofs to utilize natural lighting. After installing translucent sheets, lamps could be switched off for 8 hrs a day. Energy Saving Annual Saving Investment Payback period
Brief In a refractory manufacturing unit, there were 150 nos of 10 W filament type lamps for indication purpose. These used to be glowing for 24 hrs for all the days of the year. It was consuming 1.2 kW. The total energy consumed was 10512 units on yearly basis. During the energy audit, it was decided that these can be replaced by LED type lamps consuming only 1 w power. After replacement by 10 nos of 1 W LED lamps, the total consumption became of 1051 units per year. The saving annually was observed of 9461 units, resulting in monetary saving of Rs 0.43 lakh per year (Rate of Rs 4.50 per unit). Energy Saving Annual Saving Investment Payback period
3.7.1.5 Reduction of Lighting Feeder Voltage Fig. 3.7 shows the effect of variation of voltage on light output and power consumption for fluorescent tube lights. Similar variations are observed on other gas discharge lamps like mercury vapour lamps, metal halide lamps and sodium vapour lamps. Table-3.16 summarises the effects. Hence reduction in lighting feeder voltage can save energy, provided the drop in light output is acceptable.
: Rs.21,500 : Rs.20000 : 11 months
124
: Rs.43,000/: Rs.15000/: 4 months
125
Case Study 48 : Use of lighting voltage controller to reduce lighting energy consumption Brief A paper manufacturing plant has a connected lighting load of nearly 370 kW. This consists of fluorescent fittings, HPSV,HPMV & CFL lamps for plant, office and area lighting. The lighting load is fed from 3.3 kV bus by 4 nos. of LT transformers. These transformers have lighting loads apart from other loads. Each transformer is connected to a Lighting circuit Distribution box. The total actual load varies between 300 to 350 kW during night. Meters are fitted at each DB to measure power consumption. The voltage levels at lighting DBs vary between 225 & 240 V. Lighting loads consume less power at lower voltages. The installation of lighting voltage controllers, of different kVA, on each DB brought down the lighting consumption by 20%. The output voltages were set at 210 V. Energy Saving
Fig 3.7: Effect of Voltage Variation on Fluorescent Tube light Parameters Table 3.16 : Variation in Light Output and Power Consumption Particulars Fluorescent lamps Light output Power input HPMV lamps Light output Power input Mercury Blended lamps Light output Power input Metal Halide lamps Light output Power input HPSV lamps Light output Power input LPSV lamps Light output Power input
10% lower voltage
10% higher voltage
Decreases by 9 % Decreases by 15 %
Increases by 8 % Increases by 8 %
Decreases by 20 % Decreases by 16 %
Increases by 20 % Increases by 17 %
Decreases by 24 % Decreases by 20 %
Increases by 30 % Increases by 20 %
Decreases by 30 % Decreases by 20 %
Increases by 30 % Increases by 20 %
Decreases by 28 % Decreases by 20 %
Increases by 30 % Increases by 26 %
Decreases by 4 % Decreases by 8 %
Decreases by 2 % Increases by 3 %
(Source : Website of Bureau of Energy Efficiency)
No. of DB lighting circuits Total Power consumption
: 4 : 338 kW
After installation Total Power consumption Annual Total energy savings Annual Cost savings Cost of Implementation Simple payback period
: 275 kW : 0.245 Million kWh : Rs. 0.49 Million : Rs. 1.24 Million : 2 .5 years
Case study 49 : Installation of Automatic Voltage Regulator (Energy Saver) in Lighting Circuit. Brief The lighting to the plant was provided mainly by discharge lamps like blended mercury vapour lamps, sodium vapour lamps and fluorescent lamps. In discharge lamps, the light output is roughly proportional to the input voltage. A reduction in voltage of about 5% does not cause a proportional reduction in light output. The light output is reduced marginally by 2%, but there is a substantial reduction of about 10% in power consumption. Similarly, a higher voltage does not give proportionally higher light output, but the power consumed is substantially high. The lighting & other electrical loads were segregated into different circuits and energy saver was connected to the lighting load only. The total lighting load worked out to 900 kW. Nearly 25% of lighting energy consumed could be saved by installing Energy Saver. Energy Saving Annual Energy saving Annual Saving Investment Payback period
126
127
: : : :
7,68,960 kWh (considering 10% saving) Rs 3.5 Million Rs 3.2 Million 11 months
3.7.1.6 Electronic Ballasts Conventional electromagnetic ballasts (chokes) are used to provide higher voltage to start the tube light and subsequently limit the current during normal operation. Table-3.17 shows the approximate savings by use of electronic ballasts. Table - 3.17 : Savings by use of Electronic Ballasts
Type of Lamp
Twilight switches can be used to switch the lighting depending on the availability of daylight. Care should be taken to ensure that the sensor is installed in a place, which is free from shadows, light beams of vehicles and interference from birds. Dimmers can also be used in association with photocontrol; however, electronic dimmers normally available in India are suitable only for dimming incandescent lamps. Dimming of fluorescent tube lights is possible, if these are operated with electronic ballasts; these can be dimmed using motorised autotransformers or electronic dimmers (suitable for dimming fluorescent lamps; presently, these have to be imported).
With Conventional Electromagnetic Ballast
With Electronic Ballast
Power Savings, Watts
Infrared and Ultrasonic occupancy sensors can be used to control lighting in cabins as well as in large offices. Simple infrared occupancy sensors are now available in India. However ultrasonic occupancy sensors have to be imported.
53 81
42
11
75
6
In developed countries, the concept of tube light fixtures with in-built electronic ballast, photo-controlled dimmer and occupancy sensor is being promoted as a package.
40 W Tubelight 70 W HPSV
(Source : Website of Bureau of Energy Efficiency)
3.7.1.9 Exterior Lighting Control
Electronic ballasts have also been developed for 20W and 65W fluorescent tube lights, 9W & 11W CFLs, 35W LPSV lamps and 70W HPSV lamps. These are now commercially available.
Use a lighting control panel with time clock and photocell to control exterior lighting to turn on at dusk and off at dawn and turn non-security lighting off earlier in the evening for energy savings.
Case Study 50:
Case study
Use of Electronic Ballasts at Electrical Switchgear Manufacturing Plant
Brief No. of electronic blasts Hours/annum operation
Brief : 24000 : 2400
Energy Saving Annual Energy Saving through electronic ballast Annual additional saving due to reduced heat load on air-conditiong (kWh) Total annual energy saving Annual saving Investment Payback period
51 : Installing Photo Electric Controls in identified areas to control artificial lighting
: 8,83,200 kWh : 1,39,100 : : : :
10,22,300 kWh Rs 6.29 Million Rs 3.6 Million 7 months
3.7.1.7 Low Loss Electromagnetic Chokes for Tube Lights
The lighting in the plant was mainly provided by fluorescent lamps. The shop areas were provided with north light in the roof which provided good lighting in the shop floor during day time when sky was clear. Apart from this, the machines were also provided with work lights. In spite of all these provisions the shop artificial lights were always switched on. Segregated lighting and fan circuits provided distribution boards exclusively for lighting. Installed photo electric switches to switch off light in identified areas. Energy Saving Annual Energy saving Annual saving Investment Payback period
: : : :
43,800 kWh Rs.1,57,000/Rs.80,000/6 months
The loss in standard electromagnetic choke of a tube light is likely to be 10 to 15 Watts. Use of low loss electromagnetic chokes can save about 8 to 10 Watts per tube light. The saving is due to the use of more copper and low loss steel laminations in the choke, leading to lower losses.
Case study 52 : Providing Day Light Switches to control lamps in identified areas.
3.7.1.8 Timers, Twilight Switches & Occupancy Sensors
Brief
Automatic control for switching off unnecessary lights can lead to good energy savings. Simple timers or programmable timers can be used for this purpose.
The process area of the plant was provided with enough lighting by means of Fluorescent Lamps. Fluorescent lamps were ON throughout the day. It was observed that translucent sheets were not provided in the roof.
The timings may have to change, once in about two months, depending upon the season. Use of timers is a very reliable method of control. 128
129
Installed Day Light Switches to switch off lamps and provided translucent sheets in the roof to get natural light in daytime.
Energy Saving Annual Energy Saving Annual Saving Investment Payback period
Energy Saving Annual Energy Saving Annual saving Investment Payback Period Case Study 53:
: : : :
2,74,176 kWh Rs.11,67,990 Rs.68000/1 months
Street lighting modifications at Municipal Corporation
Brief Conventionally, streetlight planning in a Municipal Corporation was not systematic - it was normally quantity based and not lighting design based. Photometric & Installation terms were totally ignored and the Selection criteria for Lamps & Luminaires ignored. The corporation realized the need for uniform & required level of illumination with increased energy efficiency. As a part of this innovation, they decided to develop street lighting on new roads in a scientific and systematic manner by implementing "Code of practice for lighting of Public thoroughfares IS 1944 (Part I & II), 1970". During different seasons street light ON / OFF timings are changed. •
The ON time varies from 6:00 pm during winters to 7:45 pm during summers.
•
The OFF time varies from 7:15 am during winters to 5:30 am during summers.
•
It is necessary to fix ON / OFF timings for the entire year according to sunset and sunrise timings.
•
For this purpose annual programmable time switches are preferable rather than the conventional manual ones to switch ON & OFF exactly at the required timings throughout the year.
Pole height (m) Meters Mounting height Span between Poles Over hang (m) Meters Angle of Tilt (degrees) Wattage of Luminaries No. of poles No. of HPSV lamps Cost of Installations (Rs.) Annual Electrical Consumption (kWh) Average Illumination
Before Implementation 8.5 to 10 7 to 8 30 1.5 to 3 15 250 33 66 7,57,100 74,500 Less than10 Lux
After Implementation 8.5 to 10 10 42 0.9 to 1.25 5o-10 o 250 22 (33% reduction) 44 5,90,000 (22% saving) 50,100 (32.75% saving) 30 Lux with 40% uniformity 130
24400 kWh Rs.167100 Rs. 240 Million for 21 major roads 54 months
3.7.1.10 T5 Fluorescent Tube Light The Fluorescent tube lights in use presently in India are of the T12 (40w) and T8 (36W). T12 implies that the tube diameter is 12/8" (33.8mm), T8 implies diameter of 8/8" (26mm) and T5 implies diameter of 5/8" (16mm). This means that the T5 lamp is slimmer than the 36W slim tube light. The advantage of the T5 lamps is that due to its small diameter, luminaire efficiencies can be improved by about 5%. However, these lamps are about 50mm shorter in length than T12 and T8 lamps, which implies that the existing luminaires cannot be used. In addition, T5 lamp can be operated only with electronic ballast. Case Study 54 : Use of T5 fluorescent lamps in Pharmaceutical industry Brief Prior to the installation of T5 lamps, the administration, Clean room and R&D areas of the plant were using T8 (36W) lamps. There were about 1500 lamps altogether. The lamps were having electromagnetic ballasts which consume about 12 watts/lamp. After consultations with the manufacturer of T5 tube lights, a deferred payment scheme was evolved where in the cost of the lamp will be repaid in 12 months. Warranty was also given for 12 months, during which if a lamp fails, free replacement is ensured. The price of one T5 lamp was Rs 875/-. Energy Saving Power consumption of 36w T/L Power consumption of 28 w T5 T/L Energy saving per T/L Annual energy saving Annual savings Investment Payback period
Almost 5 to 10% savings are achieved by using annual programmable time switch. Parameter
: : : :
: : : : : : :
48 W 29 W 19 W 0.13 Million kWh Rs 0.6 Million Rs. 1.2 Million 2 years
3.7.1.11 Lighting Maintenance Maintenance is vital to lighting efficiency. Light levels decrease over time because of aging lamps and dirt on fixtures, lamps and room surfaces. Together, these factors can reduce total illumination by 50 percent or more, while lights continue drawing full power. The following basic maintenance suggestions can help prevent this. • • • •
Clean fixtures, lamps and lenses every 6 to 24 months by wiping off the dust. Replace lenses if they appear yellow. Clean or repaint small rooms every year and larger rooms every 2 to 3 years. Consider group re-lamping.
131
3.8
Energy saving can be achieved in homes and our day-to-day life by adopting the following simple measures.
Towards Energy Efficient Homes
Home uses of energy constitute the following: • • • • •
3.8.2
For cooking (LPG, kerosene, electricity, biogas, biomass) For lighting (electricity, kerosene, biogas) For heating (electricity, kerosene, coal, biomass) For cooling (electricity, use of home gadgets) For transportation (petrol, diesel, electricity)
3.8.1
• •
Electricity
Consumption level of some of the commonly used household electrical appliances is given in the following table-3.18. Table 3.18 : Electricity Consumption of Electrical Appliances Appliances Instant Geyser Immersion Rod Air Conditioner Air Cooler Fan Refrigerator Electric Kettle Hot plate Oven Toaster Iron Incandescent Lamp Fluorescent Lamp Slim Tube Compact Fluorescent Lamp TV Vacuum Cleaner Desktop Cleaner
Capacity 3000 Watt 1000 Watt 1500 – 2500 Watt 170 Watt 60 Watt 200/300/500 Watt 1000 – 2000 Watt 1000 – 1500 Watt 1000 Watt 800 Watt 750 Watt 100/ 60/ 40 Watt 40/ 20 Watt 36 Watt 7/ 9/ 11/ 13 Watt 180 Watt 800 Watt 120 Watt
Consumption 3 units/ hour 1 unit/ hour 8.5 – 14.5 units/ day 1.7 units/ day 0.6 unit/ day 2/3/5 unit/ day 1 – 2 units/ hour 1 – 1.5 units/ hour 1 unit/ hour 0.8 unit/ hour 0.65 – 0.75 unit/ hour 0.5/ 0.3/ 0.2 unit/ day 0.28/ 0.15 unit /day 0.26 unit/day 0.06-0.09 unit/ day 0.2 unit/ hour 0.8 unit/ hour 0.13 unit/ hour
The following appliances typically can be attributed as electricity guzzlers: • • • • • • •
Air conditioner Electric Water heater Refrigerator Washing machine Television Incandescent lamp Computer
• • • • •
Use natural lighting during the day. Replace incandescent lamps with a CFL. Payback period of CFL assuming its cost as Rs. 110/- is less than 6 months. Switch off the light when not in use. Use 28W tubelight in place of 40W tubelight. Replace the conventional choke with electronic blast. Use electronic regulators for energy saving. Lubricate the fans regularly.
3.8.3 • • • • • • •
• • •
Rational use of energy does not mean that we sacrifice the need for comfortable existence. Rational use of energy strictly means to use the available energy more efficiently and avoid wastage of energy when a particular appliance is not in use. Energy saving potential in a typical house is 20%-25%. If the electricity bill is Rs. 2000/- p.m., one saves about Rs. 400/- p.m. by proper use of electrical appliances. 132
• •
Washing Machine
Using the machine at full load, the water consumption remains the same irrespective of load of clothes. Switch on the washing machine after loading. Put off the machine from the main switch after use. Same about 15%-20% of power by setting thermostat to 500C.
3.8.7
Rational Use of Energy
Refrigerator
Use stabilizer with refrigerator & set the voltage to 220 volt. Check the gaskit to avoid ingress of heat from outside. Avoid frequent opening of refrigerator door. Do not place the refrigerator in kitchen or congested area. Regular defrosting to avoid ice accumulation in the freezer. Cool the food before putting it in the refrigerator. Purchase 'Star' rated Energy Efficient Refrigerators only.
3.8.6 •
Electric Water Heater
Change of heating element every 5 to 6 years. Set the thermostat at 50 0C to save power. Put on the water heater only 15 minutes before use.
3.8.5 • • • • • • •
Air-conditioner
Use stabilizer with air conditioner & act the voltage to 220 V. Clean the filters, condenser coils and thermostat at regular intervals. Avoid frequent opening of doors and windows. Avoid direct sunlight in the air conditioned space. Installation of reed screens in air-conditioners. Save Re. 1/- per hour by setting the room temperature to 250C. Purchase 'Star' rated energy efficient Air Conditioners only.
3.8.4 • • •
Lighting & Fans
Television
Switch off the TV from the main switch and not through remote control. Don't leave TV on stand-by mode as it consumes around 80 watts of power even when not being viewed.
133
3.8.8 Computers • •
D. Air Conditioning System: 1. Effectiveness of existing Units is only 64% and 8,10,000 kWh specific power consumption is high 2. Cooling water and chilled 1,20,000 kWh water is flowing in idle Units.
Switch on the computer when required to be used . Don't leave the computer in stand-by mode when not in use as in stand-by mode, it consumes 60 watts of power (monitor plus CPU) while no useful work is being done.
3.9
Energy Audit Study Conducted by PCRA
Case Study 55 : Energy Audit of a Bank's Head Quarter building in New Delhi Brief
Review of Electricity Bills, Contract Demand & Power Factor Study of DG Set Study of Motor Loading Study of Illumination Study of Air Conditioning System
Energy Savings Sl Equipment / No. Observation Reason
Expected Savings Expected Savings per annum per annum (kWh/kVAh, kL) (Rs in lakh)
Expected Investment (Rs in Lakh)
Payback Period
Action Required
Power Factor is poor and is sometimes leading
B. DG Set: 1. Specific Power Generation of DG sets very low. C. Illumination: 1.
2.
Use of energy efficient lights Use of 28 W, T5 tube lights
1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13.
A. Load Management: 1.
5.88
Nil
-Keep the idle Units isolated Immediate by closing the appropriate valves.
References
Punjab National Bank- with its beginning in April, 1895 at Lahore- is at present one of the foremost banks in India with a network of 4500 offices, serving more than 3.7 crore customers and having a business turn over exceeding Rs 1,94,000 crores. The focus areas during the Energy Audit were: 1.1 1.2 1.3 1.4 1.5
-Install Screw Chillers of 39.69 75.00 23 months total 600 TR capacity
4,23,420 kVAh
12 kL of HSD
11,497 kWh
2,26,000 kWh
20.75
3.96
0.56
11.07
4.00
Minimal
0.14
16.00
3 months -Monitor and Maintain Power Factor. - Connect capacitors through APFC (Automatic Power Factor Controller - Install capacitors of 800 kVAR. -The engine needs service. Consult the dealer or Immediate manufacturer - Replacing existing incandescent and 3 months halogen lamps with CFLs
18 months
Replacing existing 2000 nos. of tube lights with 28 W T/L having electronic chokes.
14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28.
134
Designing with Light- A lighting Handbook - Anil Walia-International Lighting Academy Handbook of Functional requirements on Industrial Buildings-SP-32- Bureau of Indian Standards Energy Savings in Electric Motors : PCRA Energy Savings in Electric Furnaces : PCRA Energy Savings in Compressed Air System : PCRA Energy Savings in Pumps, Fans & Variable Speed Drives : PCRA Energy Savings in Refrigeration & Air Conditioning System : PCRA Energy Audit Reports of PCRA IS : 325 - "Three Phase Induction Motors - Specifications" IEC: 60034 (1to 18) - Rotating Electrical Machines IS : 4722 - Rotating Electrical Machines IS: 8789 - Values of Performance characterstics for Three-Phase Induction Motors IS : 12615 - Induction Motors :Energy Efficient Three-Phase squiral cagespeficiation IS : 13555 - Guide for selection & Application of Three-phase A.C. Induction Motors for different types of driven equipment. NEMA MG-1 : National Electrical Mnaufacturers Association, USA EEMA -19 : Energy Efficeint Indution Motors - Three phase - squiral cage Preformance, Selection & Application of Large A.C. Motors by Devki Energy Consultancy Pvt. Ltd., Vodadora Induction Machines by P.L. Alger Electrical Machies by M. Mostenko 'Industrial Furances' (Book), E.I. Kazantsev, Mir Publishers, Moscow. 'Handbook of Electrical Heating for Industry': C.James Erickson, IEEE Press The Institute of Electrical and Electronics Engineers Inc., (IEEE), New York 'Efficient Use and Management of Electricity in Industry' Devki Energy Consultancy Pvt. Ltd, Vadodara. 'Energy Audit Manual' (Series No.1) - 'Steel Foundary', National Productivity Council, New Delhi. 'BCIRA' Publication - UK 'Industrial Furnaces' W.Trinks - M.H. Mawhinney - John Wiley 'Induction Heating Handbook' John Davies & Peter Simpson - Mcgraw Hill Compressed Air System - A Guidebook on Energy and Cost Saving, E.M. Talbott, The Fairmont Press Inc., Zilburn, USA. Compressors-Selection & Sizing, Boyce & Brown, Gulf Publishing Co., Houstonne, USA
135
29. 'Pump Hand Book'-I.J. Karassik, WC Krutzsch, W.H. Fraser, J.P. Messina, McGraw Hill International. 30. 'Analysis of Water Distribution Systems'- T.M. Walski CBS Publishers, Delhi. 31. Refrigeration and Air Conditioning' - W.F. Stoecker and J.W. Jones - Tata McGraw Hill. 32. 'Technology Menu for Efficient Energy Use'-National Productivity Council, India and Centre for Energy and Enviornmental- Studies of Princetonne University. 33. 'Good Practice Guide No. 2' - Energy Efficiency Office, Deptt. of Energy, U.K. 34. 'Energy Saving, with Adjustable Frequency Drive'- Allen Bradley Publication. 35. Saving Electricity in Utiltiy Systems of Industrial Plants, Devki Energy Consultacny Pvt. Ltd., Vadodara. 36. Industrial Refrigeration Handbook, Wilber F. Stoeker, McGraw Hill . 37. Refrigeration and Air conditioning, M. Prasad, New Age International (P) Ltd. 38. ASHRAE Handbooks, ASHRAE, Atlanta, Georgia, USA. 39. Cooling Tower Technology- Maintenance, Upgrading and Rebuilding, Robert Burger, The Fairmont Press Inc., Georgia, USA 40. Low-E Glazing Design Guide, Timothy E. Johnson, Butterworth Architecture. 41. Best Practice Manual - Electric Motors Transformers, Lighting : MEDA. 42. Energy Efficient Technologies for Industries, LBNL ,USA. 43. Bureau of Energy Efficiency-Course Material for Energy Manager/Auditor. 44. Websites/Product Information CDs of the following manufacturers: 1. www.energymanagertraining.com 2. Cromptonne Greaves Lighting Division 3. Bajaj Electricals 4. GE lighting, USA 5. Watt Stopper Inc, USA 6. Vergola India Ltd 7. Lighting reasearch centre, USA
Section 3 Energy Conservation in the Hydrocarbon sector Ø Chapter - 4 Ø Chapter - 5 Ø Chapter - 6 Ø Chapter - 7
136
Refining Sector Exploration & Production LPG Bottling Plants Marketing Terminals/ Depots
Chapter - 4 Refining Sector 4.1
Introduction
The downstream oil sector is an extremely important part of the supply chain. Growing demand for oil products clearly means that there will be a rising volume of crude oil that needs to be refined. Moreover, the oil products demand structure will change, with the expected continued move towards lighter distillates. At the same time, driven by environmental concerns, products specifications shall be moving towards significantly cleaner products that will necessitate substantial reduction in sulphur content as well as improvements in other quality parameters. To meet these challenges, the downstream sector will require significant investments to ensure that sufficient distillation capacity is in place, supported by adequate conversion and desulphurisation, as well as other secondary processes and facilities. Refining capacity additions have fluctuated considerably through cycles of both excess and tight capacity. In the 1970s and 1980s, the refining industry experienced periods of rapid expansion fuelled by rising demand and anticipated sustained growth. Global capacity peaked at 82 million barrels per day (mb/d) in 1981 and declined to 73-74 mb/d by the late 1980s. The 1990s and early part of this century were more balanced with regard to capacity and demand, until the consumption surge of refined products in 2004 and 2005 that created a much tighter situation in the refining sector. Regionally, the Middle East, India and China are the focus for major refining capacity expansions over the rest of this decade, accounting together for almost 8 mb/d of announced projects. 4.2
Refining sector in India
Having achieved the capacity additions targets of 34 MTPA of the 10th Plan (Period 2002-07), the installed capacity at the end of 11th Plan (2007-08 to 2011-2012) has been pegged at around 241 MTPA (Table 4.1). Among the refineries expected to come up during the 11th Plan, the most significant is the export oriented 29 MTPA RPL refinery at Jamnagar. Table- 4.1 Cumulative refining capacity and capacity additions during Eleventh Plan (by year) (MT) 2010 2011 2012 1 April 2007 2008 2009 Refining 148.97 158.70 194.70 210.21 225.88 240.96 Capacity Capacity addition
139
9.73
36.00
15.51
15.67 15.08
As on April, 2008, India with 19 refineries had a total installed refinery capacity of 149 MTPA. Of this, 105.5 MTPA capacity was in the public sector and the rest in private sector. (Table - 4.2) Table - 4.2 Refinery
Public sector Indian Oil Corporation Limited (IOCL) Guwahati Barauni Koyali Haldia Mathura Digboi Panipat BRPL, Bongaigaon CPCL, Manali CPCL, Narimanam Total (IOCL) Hinudstan Petroleum Corporation Limited(HPCL) Mumbai Visakhapatnam
State
Capacity MTA
Throughput (MT)
Capacity Utilization (%)
Assam Bihar Gujarat West Bengal Uttar Pradesh Assam Haryana
1.00 6.00 13.70 6.00 8.00 0.65 12.00
0.92 5.64 13.71 5.72 8.03 0.56 12.82
92.00 94.00 100.07 95.33 100.38 86.15 106.83
Assam Tamil Nadu Tamil Nadu
2.35 9.50 1.00 60.20
2.01 9.80 0.46 59.67
85.53 103.16 46.00 99.12
5.50 7.50
7.35 9.41
133.64 125.47
13.00
16.76
128.92
Maharashtra Andhra Pradesh
Total (HPCL)
4.3
Oil Trade
With indigenous production stagnating at around 30 MT per annum during the last five years and the increase in demand being met through increased imports, India's self-sufficiency in petroleum products has decreased from 29.4% in 2003-04 to 25.5% in 2007-08. India imported 121.7 MT of crude and 22.7MT of petroleum products at a value of Rs. 3,50,270 Crore. As per Hydro-carbon vision 2025, almost 90% of India's crude demand shall have to be met through imports, India's net oil import is projected to increase to 3 mb/day in 2015 and 6 mb/day in 2030 while product exports are expected to reach nearly 1.6 mb/day. The total production of petroleum products in India during 2007-08 was 149.90 MT, against domestic consumption of 129.24 MT. Since the year 2001-02, with excess production vis-à-vis in-house consumption, India became net exporter of petroleum products (Figure-4.1). In the year 2007-08, India's total export of petroleum products was 39.33 MT resulting in export earnings of Rs.1,07,603 crore (Figure-4.2). The export of petroleum products during the year were dominated by diesel (14.3 MT), followed by naphtha (9.3 MT), petrol (4.2 MT), and Fuel Oil (4.72 MT). Foreign exchange earnings from petroleum products export during the year 2007-08 constituted around 15% of the country's total export earnings, which is more than any other sector i.e. minerals, textiles or gems & jewellery etc. It is projected that by 2015, India's net product export shall reach nearly 1.6 Mb per day. Figure -4.1 Demand- supply position of petroleum products since 2001-02
160 Oil & Natural Gas Corporation (ONGC) Tatipaka MRPL, Mangalore Total (ONGC) Bharat Petroleum Corporation Limited (BPCL) BPCL, Mumbai KRL, Kochib NRL, Numaligarh Total (BPCL) Total (public sector) Private sector RIL, Jamnagar Essar Oil, Vadinar Total (private sector) Grand total
140 Tamil Nadu Karnataka
0.08 9.69 9.77
0.06 12.53 12.59
75.00 129.31 128.86
120 100 80 60
Maharashtra Kerala Assam
Gujarat Gujarat All India
12.00 7.50 3.00 22.5 105.47
12.74 8.17 2.57 23.48 112.50
106.17 108.93 85.67 104.36 106.67
33.00 10.50 43.50 148.97
31.80 6.50 38.30 150.80
96.36 61.90 88.05 101.22
The complexity of the refining sector has increased markedly since the end of the 1990s due to capacity additions and expansion of cracking units. Between 1997 and 2006, Vis breaker capacity increased from 65 to 130 kb per day, Coking capacity from 30 to 250 kb per day, Catalytic cracking capacity from 150 to 470 kb per day and Catalytic Hydro Cracking Capacity from 25 to 310 kb per day. Distillation capacity is projected to be almost doubled by 2014 to 5.2 Mb per day as a result of capacity expansion and commissioning of New Greenfields Refineries.
140
40 20 0
2
1 00
/0
2 2
2 00
/0
3 2
3 00
/0
4 2
4 00
Demand Source : PPAC (2007) and MOP&NG (2006)
141
/0
5 2
5 00
/0
6 2
6 00
/0
7
Supply
2
7 00
/0
8
Figure -4.2 Earnings from export of petroleum products 120
Value in Rs. Lakh Lakhs
100
Energy is consumed in refineries as: •
Direct fuel in heaters/ boilers/ GTGs
•
Indirect fuel to raise steam
80 60 40
•
To generate power through STGs
•
To meet process requirement
20 0 2001/02
2002/03
2003/04
2004/05
2005/06
2006/07
•
Steam & power for process equipments drive, utilities, illumination etc.
•
Cooling water circulation
2007/08
Source : PPAC (2007)
4.4.1
4.4 Energy Consumption in Refining Industry Petroleum refining industry in India is one of the major energy users, consuming around 7.5% of the total energy consumed by the industrial sector. Energy use in a refinery varies due to changes in the type of crude processed, the product mix, the complexity of refinery as well as the sulfur content requirement of the final products. Furthermore, operational factors like capacity utilization, maintenance practices, as well as the age of the equipment affect energy use in a refinery. The major energy consuming processes in a refinery are crude distillation, followed by the hydrotreater, reforming, and vacuum distillation. This is followed by a number of processes consuming a somewhat similar amount of energy, i.e., thermal cracking, catalytic cracking, hydrocracking, alkylate and isomer production. Total energy consumption in Indian refineries during the year 2007-08, was about 316 Trillion Btu or about 2.1 Trillion Btu per million tonne of crude oil throughput. During the five years period, between 2002-03 and 2006-07, while the refinery throughput rose by 28%, the corresponding increase in energy demand shotup by nearly 52%. This increase in energy consumption was due in part to the refinery capacity expansion but mainly it was due to the addition of energy intensive secondary processing units to improve fuel quality to meet Euro III & Euro IV norms for transport fuels and also to reduce the bottom of the barrel by producing value added products. However, the energy consumption per million tonne of crude throughput has reduced marginally in the year 2007-08, due to energy efficiency improvement programmes aggressively taken up by various refinery units (Table - 4.3). Table - 4.3: Energy Consumption in Indian Refineries Year
2002-03 2003-04 2004-05 2005-06 2006-07 2007-08
Throughput Total Energy Consumption % change (MT) Consumed per tonne of over the (TBtu) throughput previous (TBtu/MT) year 110.582 202.558 1.832 118.680 239.204 2.016 +10.04 124.304 251.437 2.023 + 0.35 126.986 274.113 2.159 + 6.70 141.463 308.002 2.177 + 0.83 150.806 316.506 2.099 - 3.60
Source: CHT 142
Specific energy consumption in Indian refineries
Amongst the 19 refineries in Public and Private Sector, Reliance refinery is India's most energy efficient in terms of the Energy Intensity Index*. Reliance ranks in the top 5% of worldwide refineries, with an EII of 64 in 2002, and it ranked highest of all participating refineries in the Shell Benchmark of energy and loss performance. Table - 4.4 shows the performance of PSU, Indian refineries in terms of their MBN rating (excluding the Reliance refinery, which does not report an MBN index). However, energy consumption per unit of input, is a misleading indicator of the energy performance of refineries as it does not account for differences in complexities, output slates or type of crude processed. A simple topping unit, for example, will always have a lower specific energy consumption than a complex refinery- sometimes one-fourth as much- but may not be able to produce blended gasoline or to remove sulfur from final products. In India, the energy performance of refineries is expressed in terms of specific energy consumption, measured as 1000 BTUs per barrel per Energy Factor (MBTU/Bbl/NRGF). This unit, commonly referred to as MBN, was developed by the Centre for High Technology (sponsored by the Ministry of Petroleum & Natural Gas) to provide a comparable basis to compare energy performance of refineries of different configurations by accounting for the throughput of secondary units. 4.4.2
Secondary Processing Units in Indian Refineries
Comparing the ratio of primary upgrading capacity to crude distillation i.e. cracking to distillation ratio, Indian refineries are relatively simple. Most large refineries in India have a cracking to distillation ratio of less than 40%, the only exceptions being the Reliance Refinery (59%) and Panipat Refinery (55%), that meet the average of the US Refinery Industry (56%). Higher cracking to distillation ratio facilitate refineries the flexibility to process lighter to very heavy crudes. 4.4.3
Refinery fuel use and losses
As can be seen from Table-4.5, aggregate refinery fuel use and losses have increased over the years as refinery throughput has expanded and new upgrading units have been brought on line. To process less expensive, heavy and higher sulphur crude to meet the domestic demand pattern, it would be necessary to expand the secondary cracking facilities of less complex refineries. *
The Solomon's EII is a unit-by-unit bench marking methodology that adjusts the unit consumption energy coefficients for process units based on feedstock or operational parameters. 143
Table 4.4
Energy Performance of Indian Refineries (1000BTU/Bbl/NRGF)
Refinery
2003-04 2004-05 2005-06 2006-07 2007-08
2003-04
2004-05
2005-06
2006-07
2007-08
118680
124304
126986
141463
150806
5362
5578.4
5532
6359
6743
Naphtha
11046
14219.6
14493
16730
16470
Motor Gasoline
11211
11057.5
8308
12423
14129
4393
2007.9
4091
41532
3154
244
226.5
212
187
186
Aviation Turbine Fuel (Jet Kerosene) Kerosene
4302
5197.2
6219
7850
8915
9948
9042.8
8862
8477
7867
Light Diesel Oil
1628
1385.2
944
803
713
40664
53666
58467
IOCL-Guwahati
104.79
81.68
77.67
77.21
77.44
IOCL-Barauni IOCL-Gujarat
77.69 69.89
74.07 78.86
71.91 75.00
72.95 73.03
69.34 68.52
IOCL-Haldia
87.87
80.35
76.42
71.13
69.33
IOCL-Mathura
75.37
76.42
69.19
66.8
67.08
LPG
151.16
98.83
92.37
92.49
92.06
IOCL-Panipat HPCL-Mumbai
69.19 91.18
68.81 95.29
66.76 94.62
68.07 90.41
61.31 92.26
HPCL-Visakh
99.85
99.39
94.39
87.56
86.83
BPCL-Mumbai BPCL-Kochi
94.46 92.00
95.98 94.80
78.19 95.50
70.47 93.06
70.48 87.25
Middle Distillates
CPCL-Manali
97.66
84.86
77.17
73.75
73.55
139.81 93.39
154.21 94.26
167.29 92.47
130.57 91.39
138.85 90.64
81.39 66.69 81.85
72.22 65.07 81.09
70.53 65.27 76.43
71.2 63.5 73.55
66.15 61.55 70.73
IOCL-Digboi
CPCL-CBR BRPL NRL MRPL Industry average Source : CHT
4.5
Table- 4.5 Refinery Throughput and Output (1000 tonnes per year)
Energy Efficiency opportunities in Petroleum Refineries
A large variety of opportunities exist within petroleum refineries to reduce energy consumption while maintaining or enhancing the productivity of the plant. Studies by several companies in the petroleum refining industry have demonstrated the existence of a substantial potential for energy efficiency improvement in almost all facilities. Competitive benchmarking data indicate that most petroleum refineries can economically improve energy efficiency by 10-20%. Major areas for energy efficiency improvement are utilities (30%), fired heaters (10%), process optimization (15%), heat exchangers (15%), motor and motor applications (10%), and other areas (10%). Of these areas, optimization of utilities, heat exchangers, and fired heaters offer the most low investment opportunities, while other opportunities may require higher investments. Energy efficiency in refining sector can be divided into three broad categories i.e. •
Process specific
•
Utilities related
•
Generic
Throughput Light Distillates
Others MTO
High Speed Diesel
43129
Others
486
525.2
1649
626
891
Heavy Distillates Lubricants
666
645.8
676
967
855
13355 2739
14814.5 3159.9
14118 3182
15524 3791
15957 4124
50 3379 1304
56.1 3346.9 373.7
54 3575 1224
62 3838 1761
66 4450 2772
113244 118444.9
119911
136074
145793
10069
11691
12274
Fuel Oil Petroleum Coke Paraffin Wax Bitumen Others Total products
* Gross Refinery Fuel &
8894
9312.9
Loss * This includes external fuels used such as natural gas etc.
144
145
Table 4.6 provides access keys by process and utility system to the description of the energy efficiency opportunities. For individual refineries, actual payback period and energy savings for the measures will vary, depending on plant configuration and size, plant location, and plant operating characteristics.
Desalting CDU VDU Hydrotreater Cat. Reformer FCC Hydrocracker Coker Visbreaker Alkylation Hydrogen Utilities
X X X X X X X X X X X X X X
X X X X X X X X X X X X X X X X X X X X X X X
X X X X X X X X X X X X
X X X X X X X X X X X
X X X X X X X X X X X
X X X X X X X X X X X X X X X X X X X X X X X X X X
O th e r O p p o r t u n itie s
Process
E n e rg y m a n a g e m e n t C o g e n e r a t io n G a s E x p a n s io n T u r b in e s H ig h T e m p e r a t u r e C o g e n e r a tio n G a s ific a t io n F la r e G a s R e c o v e r y P o w e r R e c o v e ry B o ile r s S te a m D is tr ib u tio n P r o c e s s In te g r a tio n P ro c e s s H e a te rs D is tilla tio n H yd ro g en M an ag em e n t M o to rs L ig h tin g
Table 4.6 Energy Efficiency opportunities in petroleum refineries. For each major process in the refinery (in rows) the applicable categories of energy efficiency measures are given (in columns).
•
4.5.1
Desalting
The principle of desalting is to wash the crude oil or heavy residues with water at high temperature and pressure to dissolve, separate and remove the salts and solids. Crude oil may contain varying quantities of inorganic compounds such as water soluble salts, sand, silt, rust particles and other solids, together characterized as bottoms sediment. The salt in the crude is primarily in the form of dissolved or suspended salt crystals in water emulsified with the crude. These impurities, especially salts, could lead to fouling and corrosion of heat exchangers (crude preheaters) and especially the crude distillation unit overhead system. Salts are detrimental to the activity of many of the catalysts used in the downstream conversion processes and sodium salts stimulates coke formation in furnaces. The water phase from the overheads crude distillation unit and other used water streams are normally fed to the desalter as washwater. Efforts are made in the industry to minimize water content of the crude to less than 0.3% and bottoms sediments to less then 0.015%. The concentration of inorganic impurities in the cleaned stream are highly dependent on the design and operation of the desalter as well as the crude source. The quantity of inorganic impurities in the crude oil depends very much on the crude origin and the crude handling during transportation. The water used in crude desalting is often untreated or partially treated water from other refining process. Table 4.7 shows the typical operating conditions and water consumptions in the desalters, depending on the type of crude oil used. Table- 4.7 Operating conditions and water consumption in the Desalters
Crude oil density kg/m3 (at 150°C) <825 825-875 >875
X X X
Water Wash % v/v 3-4 4-7 7 - 10
Temp (°C) 115 - 125 125 - 140 140 - 150
Good Desalting Practices I
X
Note : "X" indicates that relevant energy efficiency measures are possible in these areas. Lighting and boilers, used throughout refineries, are all included under Utilities.
ii • • •
146
PROCESS SPECIFIC
Multistage Desalters and the combined use of AC and DC fields: Multistage desalters and the combined use of AC and DC fields provide high desalting efficiencies resulting in substantial energy savings. Two-stage or even three-stage desalting is used either (if) the crude oil salt content is higher than 0.02%, or (if) the heavy residue is further catalytically processed. The Benefits of this Process are; The dual polarity field delivers twice the voltage of an AC fields, using the same power supply/transformer requirement as an AC field. Because of the unchanging polarity of the DC field, water droplets respond by migrating between electrodes. Once water droplets approach one of the electro droplets they become charged with the same high voltage static charge that is on that plate. In a plate net charge is imparted to the water droplets causing the attraction of 147
water droplets causing coalescence. The DC field forces the water droplets into coalescence course for faster coalescence. These processes are operated at a lower temperature than the conventional de-salter. iii The lower operating temperatures mean lower fuel costs The dual polarity Electrostatic Treater is designed to operate at temperature lower than a conventional electrostatic treater and upto 600 F cooler than heater treaters. Consequently, it can process at higher viscosities, which means less heat is required to reduce the viscosity of the oil at processing conditions. It provides sizeable fuel cost for any gravity of crude oil. (For example, with 32.5° API gravity, 10,000 BOPD of crude and 1,000 BWPD of water, the dual polarity Treater achieves a savings of 1,156,250 Btu/Hr. At 60% heat results in a fuel savings of 46,250 scf/day). iv Enhancing the oil/water separation. Techniques applied: I.
Transfer the water effluent from desalting units to a settling drum where a further separation between oil and water can be achieved.
II. Choosing accurate optimum interface level controllers. As a function of specific gravity and range of crudes processed, sensors like displacers, capacitance probes or radio wave detectors are used to control interface level.
The following process water streams can be suitable for use as desalter wash water: I.
The accumulated water in the crude distillation unit overhead drum, usually 1-2% w/w on crude feed from steam injection. II. The (unstripped) steam condensates from the light and heavy gas oil dryers and the vacuum distillation overhead (about 3.5% w/w on feed) III. Stripped sour water and also other solid-free process water streams. IV. Blowdowns from cooling water and boilers. 4.5.2
Despite the high level of heat integration and heat recovery that is normally applied, crude distillation unit remains the most intensive energy-consuming process in a refinery. In a refinery, atmospheric and vacuum distillation units account for 3540% of the total process energy consumption followed by hydrotreating with approx. 18-20%. The various processes downstream of the CDU make use of the elevated temperatures of the product streams leaving the CDU. The number of sidestreams in a high vacuum unit is chosen to maximize heat integration of producing streams at different temperatures, rather than to match the number of products required. Heat is provided by process heaters and/or by steam. Energy efficiency opportunities exist in the heating side and by optimizing the operation of distillation column. The utility requirements for the atmospheric and vacuum distillation units are given in Table 4.8. Table - 4.8 The utility requirements for CDU
III. A good improvement in water-oil separation can be achieved by using "wetting" agents. IV. Use of non-toxic, biodegradable, crude specific demulsifying chemicals to promote fast coalescence of the water droplets. v
Enhance the solid/ water-oil separation
Unit Type
Fuel (MJ/t)
Atmospheric Vacuum
400 – 680 400 – 800
Electricity (kWh/t) 4–6 1.5 – 4.5
Steam consumed (kg/t) 25 – 30 20 – 60
Cooling water (m3/t, D T=10°C) 4.0 3 –5
Note: Replacement of the steam ejectors by vacuum pumps will reduce stea m consumption and waste water generation but increase the electricity consumption.
Energy Saving Opportunities in CDU/ VDU
Solids entering the crude distillation unit are likely to attract more oil and produce additional emulsions and sludge. The amount of solids removed from the desalting unit should, therefore, be maximized. The objective is to minimize solids leaving the desalter with the crude oil.
I
Optimization of Operational Parameters. The optimization of the reflux ratio of the distillation column can produce significant energy savings. The efficiency of a distillation column is determined by the characteristics of the feed. If the characteristics of the feed have changed over time or compared to the design conditions, calculations to derive new optimal operational parameters should be done to improve operational efficiency. Steam and/or fuel intensity can be compared to the reflux ratio, product purity, etc. and compared with calculated and design performance on a daily basis to improve the efficiency.
ii
Checking Product Purity. Many companies tend to excessively purify products and sometimes with good reason. However, purifying to 98% when 95% is acceptable is not necessary. In this case, the reflux rate should be decreased in small increments until the desired purity is obtained. This will decrease the reboiler duties. This change will require no or very low investments (Saxena, 1997).
Techniques Applied: I. Use low-pressure water in the desalter to avoid turbulence. II. Replace the water jets with mud rakes. They cause less turbulence when removing settled solids. III. The water phase (suspension) can be separated in a pressurized plate separator. Alternatively a combination of a hydrocyclone desalter and a hydrocyclone de-oiler can be used. IV. Evaluate the effectiveness of a sludge wash system. vi
Distillation CDU/ VDU
Re-use of water for the desalter
The desalting process plays an important role in the waste water management in a refinery. The water used in other processes can be re-used in the desalter. 148
149
iii
iv
v
Seasonal Operating Pressure Adjustments. For plants that are in locations that experience winter climates, the operating pressure can be reduced according to a decrease in cooling water temperatures (Saxena, 1997). However, this may not apply to the VDU or other separation processes operating under vacuum. These operational changes will generally not require any investment. Reducing Reboiler Duty. Reboilers consume a large part of total refinery energy use as part of the distillation process. By using chilled water, the reboiler duty can in principal be lowered by reducing the overhead condenser temperature. A study of using chilled water in a 100,000 bbl/day CDU has led to an estimated fuel saving of 12.2 MBtu/hr for a 5% increase in cooling duty (2.5 MBtu/hr) (Petrick and Pellegrino, 1999). Upgrading Column Internals. Damaged or worn internals can result in increased operation costs. As the internals become damaged, efficiency decreases and pressure drop rise. This causes the column to run at a higher reflux rate over time. With an increased reflux rate, energy costs will increase accordingly. Replacing the trays with new ones or adding a high performance packing can have the column operating like the day it was brought online. When replacing the trays, it will often be worthwhile to consider new efficient tray designs. New tray designs can result in enhanced separation efficiency and decrease pressure drop. This will result in reduced energy consumption. When considering new tray designs, the number of trays should be optimized.
vi
ReVamping of CDU column. By packing CDU HGO section by suitable packing material, contact time between the vapours and condensate increases which results in improved product quality and product volume in CDU. We can achieve better distillation and lower overflash resulting in lower VDU throughput by recovering more HGO at CDU.
A Refinery in Japan achieved the following ENCON effect by packing of CDU HGO section as seen in Table 4.9. Table - 4.9 Parameter
Before
After
HGO drawoff (kl/h)
10.2
22.9
HGO sec. Liq. Load (gpm/ft2)
0.45
0.12
VDU furnace duty (Gcal/h)
28.2
25.9
1.3
4.7
900 F recovery (%)
79.7
84.7
HGO properties Ni (ppm)
<0.1
<0.1
Different HGO yield (%) 0
vii Combination of GTG and CDU Furnace. Installation of GTG and utilization of GTG flue gas (550°C including 15% of oxygen) can be utilized as heat source for combustion of air for furnace resulting in low cost power production and minimizing the gas emissions. 150
A Refinery in Japan achieved the following energy conservation in their plant by the combination of GTG and CDU Furnace as seen in Table- 4.10: Table - 4.10 Parameter Fuel Consumption (Gcal/H) Flue Gas (O2)
Before 66
After 46
3.0
4.5
viii Reduction in CDU Operating Pressure. By reducing pressure at flash zone by 0.12 Kg/cm², temperature drop of 80°C is achieved at flash zone and temperature drop of around 120°C is achieved at furnace outlet resulting in fuel reduction of 0.3 litre/ kl. ix Stripper Optimization. Steam is injected into the process stream in strippers. Steam strippers are used in various processes and especially the CDU is a large user. The strip steam temperature may be too high and the strip steam use may be too high. Optimization of these parameters can reduce energy use considerably. This optimization can be part of a process integration (or pinch) analysis for the particular unit. x
Installation of Process Control Systems. A few companies supply control equipment for CDUs. Aspen technology has supplied over 70 control applications for CDUs and 10 optimization systems for CDUs. Typical cost savings are $0.05 - $0.12/bbl of feed, with paybacks less than 6 months. Key Control supplies an expert system advisor for CDUs. It has installed one system at a CDU, which resulted in reduced energy consumption and flaring and increased throughput with a payback of 1 year.
xi Process Integration/Pinch Analysis. Process integration is especially important in the CDU, as it is a large energy consumer processing all incoming crude oil. Older process integration studies show reductions in fuel use between 10 and 19% for the CDU (Clayton, 1986; Sunden, 1988; Lee, 1989) with payback periods less than 2 years. An interesting opportunity is the integration of the CDU and VDU, which can lead to fuel savings from 10-20% (Clayton, 1986; Petrick and Pellegrino, 1999) compared to non-integrated units, at relatively short paybacks. The actual payback period will depend heavily on the layout of the refinery, needed changes in the heat exchanger network and the fuel prices. xii Installation of Combustion air preheater. By installing a combustion air preheater, using the hot flue gas and an additional FD fan in one of the VDU which used natural draft and had no heat recovery, a refinery in UK by reducing flue gas temperature to 275°C achieved energy cost saving of Rs. 95 lakhs per year with a payback period of 2 years. xiii Modification in Reduced Crude Cut Point. Typically crude distillation units in India have been designed for reduced crude cut point of 370-380°C. The design also provides necessary features to limit the quantity of diesel range material which goes to the vacuum unit to about 6-8 per cent on reduced crude. This results in additional energy consumption. If the reduced crude oil (RCO) 151
cut point is reduced and the balance diesel (boiling between the reduced cut point and 370°C) is recovered as the top product in the vacuum column, there is a net saving in energy as can be seen in the following table 4.11.
cooling pumps and the consumption of agents used for conditioning of cooling water. Within the refinery there are many processes where surplus steam can be recovered and be used for the production of vacuum. However, an energy management analysis will help to decide, whether use of surplus steam for steam ejection instead of applying vacuum pumps is more efficient than using surplus steam for other purposes.
Table - 4.11 Net Saving of Energy S No. 1. 2. 3. 4. 5. 6. 7. 8.
Parameter
Case I
Case II
Case III
RCO cut point, °C
370
360
350
Crude feed, T/hr RCO, T/hr
206 93
206 96
206 100
PA heat recoveryAtm column (Million kcal/hr) PA heat re coveryVac. Column (Million kcal/hr) Furnace duty -Atm, Million kcal/hr Furnace duty -Vac., Million kcal/hr. Total Heat Duty of furnaces, Million kcal/hr
11.3
10.4
9.1
8.4
9.1
10.0
18.2
16.9
15.7
4.2
4.8
5.3
22.4
21.7
21.0
The total furnace duty is found to reduce as the RCO cut point is brought down, recovery in the atmospheric section. RCO cut point of 350-360°C has been found to be ideally suited resulting in low energy consumption and improved diesel quality. iv
Progressive Distillation Unit Progressive distillation is the extreme of heat integration between atmospheric and vacuum distillation. It also avoids superheating of light cuts to temperatures higher than strictly necessary for their separation and it avoids degrading the thermal levels associated with the drawing-off of heavy cuts. A progressive distillation unit with integrated CDU/ VDU, saves up to 30% on total energy consumption for these units. The heater process duty (MW/100 tonnes of crude) of a distillation capacity of 10 million tonnes per year is around 17.3 for light crude. Using progressive crude distillation it is reduced to 10.1. The specific energy consumption (overall energy consumption in tones of fuel equivalent per 100 tonnes of crude) for a distillation capacity of 10 million tones per year is 1.7 - 2.0 for light crude, whereas using the progressive distillation unit only consumes 1.15. The energy savings for a 10 million tonnes/year refinery is in the range of 50000 tonnes heavy fuel compared to conventional technology.
xv Use of vacuum pumps and surface condensers Vacuum pumps and surface condensers have largely replaced barometric condensers in many refineries to eliminate this oily wastewater stream. Replacing the steam ejectors by vacuum pumps will reduce the sour water flow from 10 to 2 m³/h. The vacuum may be generated by a combination of vacuum pumps and ejectors to optimize energy efficiency. Other benefits are cross linked with cross-media effects.
xvi Reduction of the vacuum pressure in the vacuum distillation unit Lowering the vacuum pressure, e.g. down to 20-25 mm Hg, will allow a reduction in the furnace outlet temperature, while maintaining the same target cut point of the vacuum residue. This technique would provide some benefits, both in terms of energy conservation and of pollution. The reduction benefits are:• • •
A lowered potential for cracking or coking at furnace tubes. A reduced cracking of feed to lighter products. A lowered furnace fired duty and hence lowered fuel consumption.
xvii Energy Efficient Design for CDU. Technip and Elf (France) developed an energy efficient design for a crude distillation unit, by redesigning the crude preheater and the distillation column. The crude preheat train was separated in several steps to recover fractions at different temperatures. The distillation tower was re-designed to work at low pressure and the outputs were changed to link to the other processes in the refinery and product mix of the refinery. The design resulted in reduced fuel consumption and better heat integration (reducing the net steam production of the CDU). Technip claims up to a 35% reduction in fuel use when compared to a conventional CDU. xviii
Other measures
•
Recycling of overhead steam injected into the atmospheric distillation column by using the injector into the VDU - Energy saving 8562 kl/ yr.
•
Installation of a side reboiler around the central levels of a distillation column to reduce consumption of heating steam - Energy saving in crude oil equivalent of 483 kl/ yr.
•
An increase in temperature of the feed charged from atmospheric distillation unit to the VDU, reduces the specific consumption of energy required for the VDU equivalent of 1314 kl/ yr.
•
Utilizing waste heat of heavy gas oil from the atmospheric column results in reduction in steam consumption for the reboiler of stripper - which is crude oil equivalent of 938 kl/ yr.
•
The utilization of waste heat of the overhead vapor as a heat source for preheating the water of the boiler reduces steam requirement for heating the deaerator which results in energy reduction in crude oil equivalent of 454 kl/ yr.
Replacement of the steam ejectors by vacuum pumps will increase the electricity consumption for vacuum generation, but will reduce the heat consumption, the cooling water consumption, the electricity consumed for 152
153
Case Study 1 : pump to
Trimming of impeller dia of crude boosters from 235 mm 220 mm.
Brief As the capacity utilization of CDU is 70% this modification called for trimming of pump impeller to reduce the motor power consumption by 15%. Energy Savings Before trimming of impeller 5 KWhr x 10 /year Consumption of Power for the booster pump
After trimming of impeller 5 KWhr x 10 /year
9.3
Energy Savings Saving of 1688 SRFT/year Investment amount Improvement Effect Pay back Period Case Study 4:
8
- Nil - Rs. 2.4 crores/year - Immediate
Energy Efficiency improvement through crude preheat train optimization in the refinery
Brief
Saving of 1.3 x 105/year KWhr. Investment amount - Rs. 0.5 Lakh Improvement effect - Rs. 1.02 Lakhs/year Pay back period - 6 months Case Study 2 :
This has resulted distillate yield improvement from 14% to 19% resulting less energy requirement for vaporization in the column and furnace resulting fuel saving of 1688 SRFT/annum. Hasys software was used to arrive at the energy saving effects operating pressure for various crudes.
The preheat temperature of crude before entering into the furnace of crude distillation unit (for the processing of LS crude) is on an average 225°C. Pinch technology was applied to optimize, reorient the preheat exchangers. This modification calls for installation of new exchangers (8 nos.) and new 13 nos. of pumps and rec-orientation of exchangers. The modification also calls for replacement of existing main fractionator for reflux drum and provision of boot in the stabilizer.
Installation of online oxygen analyzer
Brief Installation of online oxygen analyzer on the 2 nos. of AVU furnaces to measure and maintain the percentage of O2 level level in the range 2-3% so as to maintain furnace efficency beyond 85% maintaining the arch pressure level.
By carrying out the above modification crude preheat temperature increased from 225°C to 284°C min. thereby reducing the fuel consumption in the furnace by an amount 6874 kL/year. The investment for the total modification is 34.6 crores.
Energy savings Energy Savings Parameter
Before installation of new O2 analyser (the existing analyzer not working)
Fuel Gas Consumption in 2 nos. of furnaces
877 Nm³/hr
After installation of new O2 analyser 851 Nm³/hr
Annual Fuel Oil Saving Investment amount Improvement Effect Pay back Period
-
6874 kL of FO/year Rs. 34.6 crores Rs. 11.6 crores/year 3 years
Saving of 26Nm3/hr of fuel gas.
4.5.3
Production of Lube Oil Base Stock
Investment amount - Rs. 2 Lakhs (for 2 nos. of on line O2 analyser) Improvement effect - Rs. 7.64 Lakhs/year (Considering 8000 hrs of operation) Pay back Period - 16 months
i
Vaccum Distillation
Case Study 3 :
Reduction of top pressure of Pre flash Drum (PFD) of crude distillation unit
Brief Reduction of top pressure of PFD (Pre flash Drum) of crude distillation unit from the range 7.5 - 8.5 kg/cm²g to the range 5.5 - 6.5 kg/cm²g for LS crude and reduction of PFD top pressure from the range 10.0 - 12.0 kg/m²g (for various crudes) to the range 8.0-10.0 kg/m²g for HS crude. Fuel saving accrued by reduction the pressure is 1688 SRFT/yr and distillate yield improvement is from 14 to 19%.
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The atmospheric residuum or reduced crude leaving the bottom of the CDU column passes through the fired heater into the flash zone of the VDU where it is fractionated into lube distillates. Steam is introduced into the VDU flash zone to lower the vapor pressure of the distillates and permit removal of high boiling hydrocarbons. Refiners have in recent years refurbished existing VDUs and installed new VDUs with high efficiency internals to reduce the flash zone pressure and improve the purity and yield of lube oil distillates obtained from lube crudes. These changes result in improved processing response in down stream units and improve base oil viscosity.
155
Case Study 5 :
Reduction of injection steam in vacuum column by recycling overhead steam.
Brief Steam is injected into the vacuum distillation column to reduce the partial pressure of lighter fractions. The injected steam goes to the overhead condenser as overhead steam to be condensed to waste water. This modification recycled the injected steam back to the distillation column by means of an injector, thereby achieving energy saving.
iv Solvent Extraction of Lube Distillate EXON & Texaco Development Corporation Refining Processes based on the use of N-methyl-2-pyrrolidone (NMP) as the extraction solvent are being used in the refineries as NMP Process. This process is being used as a replacement for furfural and phenol in the extraction of lube base stocks. The by products from lube solvent refining processes are aromatic extracts which are used in manufacture of asphalt, carbon black, fuel, petrochemicals, rubber and as coker and FCCU feed.
The steam ejector generates vacuum inside the body by injecting high pressure (driving steam) at a high velocity from nozzles and induces the low pressure steam (supply steam) which is used as recycled steam in this case. This enables the hitherto unused and discharged low pressure steam to be pressurized and reused.
Solvent extraction is used for the purpose of removing aromatics and other undesirable constituents to improve the VI and quality of lube base stocks.
Energy Savings
v a
After improvement Steam consumption (for 5 MMT/year t’put)
Reduction of 120,000 t/year (15 tons/hr)
Operating hours : 8000 hr/year
Reduction of 15 Tonnes/hr. of Steam Investment amount Improvement effect Pay back Period ii
- 6 crores - 8 crores/year - 9 months
Deasphalting Process
Deasphalting is an extractive - precipitation process. The purpose of the process is the removal of asphaltenes, resins and metals from vacuum residua and very heavy vacuum gas oils. The deasphalted oils from atmospheric residua and very heavy vacuum distillates are used as feedstocks to lube processing units for the manufacture of lube base oils ranging from solvent neutral oils to cylinder oils and bright stocks. iii Solvent Recovery Techniques in propane Deasphalting unit Conventional Solvent Recovery Single effect evaporation Double effect evaporation Triple effect evaporation
Supercritical Solvent Recovery ROSE@ process
Multiple effect evaporation
The solvent based processes used for the manufacture of lube oils are energy intensive because large volumes of solvent must be recovered by flash distillation for recycle in the process. The number of stages used for evaporation of the solvent has a significant effect on the energy cost. b
Single effect
1. 2.
Solvent is vaporized at one pressure level Energy is wasted in condensation; it is not recovered
c
Double effect
1. 2. 3. 4.
Solvent is vaporized at two pressure levels. One half of he solvent is vaporized at each pressure level Condensing vapors are used to operate the first evaporator Energy requirements are reduced by 45 to 50 percent
d
Triple effect
1. 2. 3. 4.
Solvent is vaporized at three pressure levels One third of the solvent is removed at each pressure level Condensing vapors are used to operate the first two stages Energy requirements are reduced by an additional 30 - 33 percent compared to double effect evaporation Energy requirements are 30 to 33 percent of single effect.
5. DEMEX process
Energy Reduction Techniques for extraction of lube distillate
vi Solvent Dewaxing Process
Double and triple effect evaporation units use 40 to 50 percent of the energy of a single effect evaporation for solvent recovery. These reductions in energy are obtained because the heat required to vaporize the solvent in the higher pressure flash vaporization stages is used to vaporize solvent in the next lower pressure flash vaporization stages. The amount of energy saved is proportional to the solvent to feed ratio and the cost of steam, fuel and electrical power.
156
The raw paraffin distillates and residual oils leaving the crude stills contain wax and are normally solids at ambient temperature. The desphalting and refining processes concentrate the wax in the base oil feedstocks. Removal of wax from these fractions is necessary to permit manufacture of lubricating oils with the desired low temperature properties. Although the cold settling pressure filtration processes and centrifuge dewaxing processes have for the most part been replaced by solvent dewaxing using MEK (Methyl Ethyl Ketone)/Toluene and MIBK/ Toluene. The 157
wax produced in this process is separated by filtration and is a by product of this process called as Slack Wax. The solvent recovery units in this process consumes considerable amount of energy. a
Inert Gas Stripping
This involves using inert gas in place of steam for stripping the last traces of solvent from the dewaxed oil and wax. b
Benefits from use of Inert Gas Stripping
Energy requirements reduced Dewaxed oil yield increased Dewaxing differential decreased
Dilution ratios reduced Solvent losses reduced Maintenance costs reduced
vii Catalytic Dewaxing/isodewaxing Process Modern wax processing routes for producing VHVI LOBs is wax or paraffin waxy isomerisation straight away from the lube stocks by using catalyst to reduce pour point. Case Study 6 :
Use of controlled hot refrigerant gas by-passing SDU Plant Chiller
Brief Use of controlled hot refrigerant gas by-passing SDU Plant Chiller to maintain desired suction pressure and stop use of steam tracing on brine return line. For stable operation, the suction pressure should be maintained at a desired minimum level even in the absence of real heat load. This can be achieved by controlled discharge hot gas bypass arrangement with the control valve operating based on feed back of suction pressure. The control valve can be programmed to control the suction pressure in a tight bond. This can avoid the use of steam to create spurious heat load and save about 1.2 TPH steam. Energy Savings Steam saving potential is 1.2 TPH and 9600 T/year (considering 8000 hrs of operation) Investment amount - Rs. 10 Lakhs (for the modification i.e control valve, piping & instrumentation) Improvement effect - Rs. 30 Lakhs/year Pay back Period - 4 months
4.5.4
Hydrogen Management and Recovery
The major technology developments in hydrogen management within the refinery are hydrogen process integration or hydrogen cascading and hydrogen recovery technology (Zagoria and Huycke, 2003). Revamping and retrofitting of existing hydrogen networks can also increase hydrogen capacity between 3% and 30% (Ratan and Vales, 2002). i
Hydrogen network integration and optimization at refineries is an important application of pinch analysis. Most hydrogen systems in refineries feature limited integration and pure hydrogen flows are sent from the reformers to the different processes in the refinery. But as the use of hydrogen is increasing in refineries, the value of hydrogen is more and more appreciated. Using the approach of composition curves used in pinch analysis, the production and uses of hydrogen of a refinery can be made visible. ii
Hydrogen Recovery
a
Utilizing low purity hydrogen streams
Hydrogen recovery is an important technology development area to improve the efficiency of hydrogen recovery, reduce the costs of hydrogen recovered and increasing the purity of the resulting hydrogen flow. Hydrogen can be recovered indirectly by routing low-purity hydrogen streams to the hydrogen plant (Zagoria and Huycke, 2003). Hydrogen can also be recovered from offgases by routing it to the existing purifier of the hydrogen plant or by installing additional purifiers to treat the offgases and ventgases. Suitable gas streams for hydrogen recovery are the offgases from the hydrocracker, hydrotreater, coker, or FCC. The cost savings of recovered hydrogen is around 50% of the costs of hydrogen production (Zagoria and Huycke, 2003). b
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Using Absorption/ Membrane Technology
Hydrogen can also be recovered using various technologies, of which the most common are pressure swing and thermal swing absorption, cryogenic distillation, and membranes. The choice of separation technology is driven by desired purity, degree of recovery, pressure, and temperature. Various manufacturers supply different types of hydrogen recovery technologies, including Air Products, Air Liquide, and UOP.Membrane technology generally represents the lowest cost option for low product rates, but not necessarily for high flow rates (Zagoria and Hucyke, 2003). c
Hydrogen is used in the refinery in processes such as hydrocrackers and desulfurization using hydrotreaters. The production of hydrogen is an energy intensive process using naphtha reformers and natural gas-fueled reformers. These processes and other processes also generate gas streams that may contain a certain amount of hydrogen not used in the processes or generated as by-product of distillation of conversion processes. In addition, different processes have varying quality demands for the hydrogen feed. Reducing the need for hydrogen make-up will reduce energy use in the reformer and reduce the need for natural gas.
Hydrogen Integration
Using PSA Technology for High flow rates
For high-flow rates, PSA technology is often the conventional technology of choice. PSA is the common technology to separate hydrogen from the reformer product gas. Hundreds of PSA units are used around the world to recover hydrogen from various gas streams. Cryogenic units are favored if other gases, such as LPG, can be recovered from the gas stream as well. Cryogenic units produce a medium purity hydrogen gas stream (up to 96%). Membranes are an attractive technology for hydrogen recovery in the refinery. If the content of recoverable products is higher than 2-5% (or preferably 10%), recovery may make economic sense (Baker et al., 2000). 159
iii
Saving of 7.7 kW of power resulting 58,800 kWh/year of power saving.
Hydrogen Production
If there is excess steam available at a plant, a pre- reformer can be installed at the reformer. Adiabatic steam reforming uses a highly active nickel catalyst to reform a hydrocarbon feed, using waste heat (900°F) from the convection section of the reformer. This may result in a production increase of as much as 10% (Abrardo and Khurana, 1995). The technology can also be used to increase the production capacity at no additional energy cost, or to increase the feed flexibility of the reformer. This is especially attractive if a refinery faces increased hydrogen demand to achieve increased desulfurization needs or switches to heavier crudes. Various suppliers provide pre-reformers including Haldor-Topsoe, Süd-Chemie, and Technip-KTI. iv Other Options •
By reducing steam/ carbon ratio in the hydrogen production unit energy saving in crude oil equivalent of 3848 kl/ yr is achieved.
•
The minimization of surplus hydrogen production and reduction in energy consumption of flare required to combust the gas in a hydrogen production unit results in energy saving which is crude oil equivalent of 1431 kl/yr.
•
Installation of a membrane separator for hydrogen results in energy saving and reduction of cost by recovering hydrogen from refinery by-product gas Energy saving in crude oil equivalent of 6466 kl/yr.
Case Study 7 :
De-staging of 6 stages to 5 stages of HGU reformer boiler fuel pump
Investment amount Improvement effect Pay back Period
Case Study 8 : Reduction of steam / carbon ratio Brief The steam to carbon ratio of this hydrogen production unit was 5.5 and higher than other refineries values of 4.5 to 5.0 because of the specific energy consumption is high, the refinery embarked on a modification to reduce the steam to carbon ratio and successfully reduced it to 4.7 Problems that are anticipated when the steam to carbon ratio is reduced are as follows; • • • • •
By de-staging of the pump from 6 stages to 5 stages, the discharge pressure of the pump will come down from 44 kg/cm²g to 35 kg/cm²g eliminating/reducing the pressure drop in the boiler drum feed control valve. Power consumption of the pump motor will come down from 50.7 kW to 43 kW resulting saving of 58,000 kwh/year. Energy Savings Before de -staging of HGU boiler feed pump Power Consumption
50.7 kW
After de-staging of HGU boiler feed pump 43 kW
160
Increase carbon deposits on the catalysts Rise of surface temperature of the reaction tubes of the reforming furnace Insufficient steam supply to the conversion reactors Insufficient heat supply to the absorption agent regenerating column Foaming in the absorption tower
At steam to carbon ratio - 4.7 or higher none of the problems except foaming was encountered. Countermeasures to foaming: •
The cause of foaming was identified, blow velocity of the absorbent became too fast because the ceramic packing in the absorption tower had been broken into small pieces.
•
Replacement of the ceramic packing by more study stainless steel packing. Solved the foaming problem. As a result the steam to carbon ratio was reduced from 5.5 to 4.7
Brief De-staging of 6 stages to 5 stages of HGU reformer boiler fuel pump so as to elimate pressure difference between the pump discharge pressure, 44 kg/cm²g and boiler drum pressure 30kg/cm²g. This pressure drop is presently maintained by reduction of pressure through a control valve.
- Rs. 45,000/- (for de-staging) - Rs. 41,000/-/year - 1.1 year
Energy Savings Before modification
After modification
Fuel consumption – Fuel Oil Equivalent
3,630 kl/y reduction
Fuel Consumption – Crude Oil Equivalent
3,848 kl/y reduction
Investment amount Improvement effect
161
- Operational improvement without capital investment - 6 crores per annum
Case Study 9: Use of H2 rich gas catalytic reformer unit (via HGU) for recycling in CRU in place of use of pure H2 ex HGU and PSA.
Case Study 11 :
Brief
Brief
The H2 is generated from HGU and PSA using feed as Natural Gas. A part of pure H2 is being recycled to CRU. At the same time, H2 rich gas generated in the catalytic Reforming Unit (CRU) is routed to Fuel Gas. This Hydrogen rich gas ex CRU can be routed to HGU replacing NG feed and this H2 after HGU can be recycled back to CRU stopping recycling of pure H2 from HGU and PSA. This can save use of NG from outside source to HGU and PSA for the production of H2 and the net saving of natural gas is to the tune of 38 kg/hr.
The operation of the hydrogen production unit is required to ensure stable supply of hydrogen to the related units regardless of fluctuation of all operational variations. Because of this requirement, production quantity of purified hydrogen tends to be excessive, resulting in production loss. This method minimizes the surplus hydrogen production by computer control.
Higher chlorine content in the hydrogen rich gas is harmful to the reformer catalyst. The chlorine content of H2 rich gas is 3 ppm. When an amount of 38 kg/hr of H2 rich gas is mixed with 1229 kg/hr of natural gas feed going to HGU, the concentration of chlorine comes down to 0.09 ppm which is not at all harmful to CRU catalyst. (as it is less than 1 ppm. However, installation of chlorine guard at the downstream of HGU can also take care of chlorine shock to CRU catalyst.
Computer-controlled reduction of surplus hydrogen in Hydrogen production unit
Conventionally, the quantity of hydrogen production was manually controlled in response to the changes in demand for hydrogen as well as the changes in the amount of raw materials fed into the hydrogen production unit. However, the control was insufficient because of the manual operation, and the surplus hydrogen tends to be about 2.5% on an average. The surplus hydrogen had to be flared. After modification, production quantity of hydrogen was controlled by ACS computers in response to changes in hydrogen demand and in the amount of raw materials and production loss of the hydrogen production unit became 0 %. Energy Savings
Energy Savings NG Saving = 38 kg/hr Investment amount - Rs. 6 lakhs (For lying pipeline from CRU to PSA outlet line) Improvement effect - Rs. 18 lakhs/year Pay back Period - 4 months
Attribute Fuel consumption - heavy oil equivalent Fuel consumption - Crude oil equivalent
After improvement 1,350 kL/y reduction 1,431 kL/y reduction
Case Study 10 : Installation of a membrane separator for hydrogen Brief The hydrogen production cost of the existing hydrogen production plant is high. Installation of a membrane separator for hydrogen realized energy saving and reduction of cost by recovering hydrogen from refinery byproduct gas streams and consequently by reducing the operation rate of the existing hydrogen production plant Energy Savings
Attribute Fuel oil equivalent of fuel consumption Crude oil equivalent of fuel consumption Investment amount Improvement effect Investment payback
Effect by introduction Reduction of 6,100 kl/y Reduction of 6,466 kl/y
Investment amount Improvement effect Investment payback Case Study 12 :
Routing of excess low pressure separator off gas ex Hydrocracker to hydrogen generation plant
Brief Hydrocracker unit low pressure separator off gas which is in excess has been used as recycle H2 for HGU. This has resulted in the reduction of make up H2 production demand. Energy Saving Effects Fuel oil saving to the tune of 1740 MT per annum Investment amount Improvement effect Pay back Period
: Rs 120 million : Rs 52 million /year : 2.5 years
: Rs 4 million, : Rs 12 million/year : 0.4 year
: Nil : Rs. 1.74 crores : Immediate
4.5.5 Fluid Catalytic Cracker (FCC) Fluid catalytic crackers are net energy users, due to the energy needed to preheat the feed stream in a modern refinery, FCC energy use is estimated at 6% of total energy use.
162
163
The following table 4.12 shows the energy and process materials usage in the catcrackers:Table 4.12
Fuel (MJ/t) Electric ity (kWh/t) Steam consumed (kg/t Steam produced (kg/t) 3 Cooling water (m /t, D T -17ºC) Catalyst make -up (kg/t)
FCC 120 – 2000 8 – 50 30 – 90 40 – 60 5 – 20 0.4 – 2.5
RCC 120 – 1200 2 – 60 50 – 300 100 – 170 10 – 20 2 -4
Virtually all the heat required in a FCC unit is generated in the regenerator. The catalyst used depends greatly on the type of product required and can be silicaalumina substrate carrying rare earth and/ or precious metals or can be based on zeolites. The fuel oil from the CDU is converted into lighter products over a hot catalyst bed in the fluid catalytic cracker (FCC). FCC is the most widely used conversion process in refineries. The FCC produces high octane gasoline, diesel, and fuel oil. The FCC is mostly used to convert heavy fuel oils into gasoline and lighter products. The FCC has virtually replaced all thermal crackers.
maintenance stops (> 32,000 hours). There is wide and long-term experience with power recovery turbines for FCC applications. Various designs are marketed, and newer designs tend to be more efficient in power recovery. Recovery turbines are supplied by a small number of global suppliers, including GE Power Systems. A refinery in Houston, USA replaced an older power recovery turbine to enable increased blower capacity to allow an expansion of the FCC. The re-rating of the FCC power recovery train led to power savings of 22 MW. Petro Canada's Edmonton refinery replaced an older turbo expander by a new more efficient unit, saving around 18 TBtu annually. Power recovery turbines can also be applied at hydrocrackers. Power can be recovered from the pressure difference between the reactor and fractionation stages of the process. In 1993, the Total refinery in Vlissingen, the Netherlands, installed a 910 kW power recovery turbine to replace the throttle at its hydrocracker (get data on hydrocracker). The cracker operates at 160 bar. The power recovery turbine produces about 7.3 million kWh/year (assuming 8000 hours/year). The investment was equal to $1.2 million (1993$). This resulted in a payback period of approximately 2.5 years at the conditions in the Netherlands (Caddet, 2003). Iii
Optimisation of Process Design
Energy Conservation Options in FCC
The product quality demands and feeds of FCCs may change over time. The process design should remain optimized for this change. Increasing or changing the number of pumparounds can improve energy efficiency of the FCC, as it allows increased heat recovery (Golden and Fulton, 2000). A change in pumparounds may affect the potential combinations of heat sinks and sources.
i
iv
Installation of Process Control System
Several companies offer FCC control systems, including ABB Simcon, AspenTech, Honeywell, Invensys, and Yokogawa. Cost savings may vary between $0.02 to $0.40/bbl of feed with paybacks between 6 and 18 months. Timmons et al. (2000) report on the advantages of combining an online optimizer with an existing control system to optimize the operation of a FCC unit at the CITGO refinery in Corpus Christi, Texas. The Citgo refinery installed a modern control system and an online optimizer on a 65,000 bpd FCC unit. The combination of the two systems was effective in improving the economic operation of the FCC. The installation of the optimizer led to additional cost savings of approximately $0.05/barrel of feed to the FCC, which resulted in an attractive payback (Timmons et al., 2000). ii
Opportunities for Power Recovery
FCC runs at elevated pressures, enabling the opportunity for power recovery from the pressure in the flue gas. The major application for power recovery in the petroleum refinery is the fluid catalytic cracker (FCC). However, power recovery can also be applied to hydrocrackers or other equipment operated at elevated pressures. Modern FCC designs use a power recovery turbine or turbo expander to recover energy from the pressure. The recovered energy can be used to drive the FCC compressor or to generate power. Power recovery applications for FCC are characterized by high volumes of high temperature gases at relatively low pressures, while operating continuously over long periods of time between 164
Heat Recovery from the regenerator flue gas
Heat recovery from the regenerator flue gas is conducted in a waste heat boiler or in a CO-boiler. The steam produced in the CO boiler normally balances the steam consumed. Installing an expander in the flue gas stream from the regenerator can further increase the energy efficiency. The waste heat boiler recovers the heat from the flue gas and the expander can recover part of the pressure to be used in the compression of the air needed in the regenerator. An example of the application of an expander saved 15MWe for the flue gas generated by a FCC of a capacity of 5Mt/yr. v
Waste Water Management within FCCU
The latest design of catcrackers contained a cascading overhead wishing section which minimizes water usage. Re-use waste water generated in FCCU can be used for the desalters thereby reducing water usage and reuse of water refinery. New design and operational tools enable the optimization of FCC operating conditions to enhance product yields. Petrick and Pellegrino (1999) cite studies that have shown that optimization of the FCC-unit with appropriate modifications of equipment and operating conditions can increase the yield of high octane gasoline and alkylate from 3% to 7% per barrel of crude oil. This would result in energy savings.
165
vi Other Options •
Optimization of heat recovery from the overhead, middle and bottom refluxes improves the energy saving effects in FCCU - energy reduction in crude oil equivalent of 1884 kl/ yr.
•
In the FCC unit, the reduction of pressure inside the regeneration column reduces the consumption of steam for driving the air blower for the regeneration column resulting in energy saving of 1024 kl/ yr of oil equivalent.
Case Study 13 :
Energy saving by reducing the pressure inside the regeneration column.
Brief The pressure within the fluid catalytic cracking (FCC) unit can be reduced by increasing the capacity of the cooler at the top of the FCC distillation column. The modification achieves energy saving by reducing the pressure inside the regeneration column and thereby reducing, the consumption of steam for driving the air blower for the regeneration column.
reducing valve and pressure-reducing orifice. The present technology recovers a portion of the pressure energy of this gas in the form of power by installing an expander turbine for pressure reduction. The flue gas, after being de-pressured by the expander turbine, is sent to the CO boiler for combus- tion. The coke (CO gas) required for 10,000 BPD production is 3 to 6 tons. 11 to 14 kilograms of air is required for combustion of one kilogram of coke. The power required for feeding this combustion air accounts for more than 50 percent of the entire power requirement of the FCC unit. After modification 1) The gas expander turbine is connected with the air blower and a steam turbine on the same axis. 2) The coke combustion gas discharged from the regenerator has a pressure from 1.5 to 3.0 Kg/cm2 g and temperature from 620 to 730ºC. This flue gas is sent to a CO boiler where its CO content is burned to recover heat energy in the form of steam. Energy Savings
The possibility of the following items were examined before modification. (1) To reduce the pressure inside the system by increasing the capacity of the air cooler at the top of the distillation column. (2) To reduce the air volume of the air blower for the regeneration column. Air volume of the air blower and air pressure of the regeneration column before and after improvement.
2
Regeneration column air pressure (kg/cm ) 3 Air blower. Air volume (Nm /hr)
Before improvement 2.86 1755
After improvement 2.63 860
Effect 0.23 reduction 895 reduction
Energy Savings FCC oil throughout High Pressure Steam Consumption Crude oil equivalent
Investment amount Improvement effect Pay back Period
-
After improvement 8,42,000 Kl/y increase 12,557 t/y reduction 1,024 kl/y reduction
Rs. 14.5 lakhs (For modification of air cooler) Rs. 4.9 lakhs 3 years
Case Study 14 : Power recovery system in Fluid catalytic cracking (FCC) unit Brief The flue gas, or coke combustion gas (containing CO at a high content), generated from the regenerator of a fluid catalytic cracking (FCC) unit of petroleum refining process, is normally sent to a CO boiler after pressure reduction using a pressure-
Generation capacity (35,000 BPD)
Before installation -
After installation 7,000 kW
Annual generation capacity (8,000 hour/year)
-
56,000 MWh
Crude oil equivalent
-
Reduction of 13,600 kl/year
Investment amount Improvement effect Pay back Period
: Rs 800 million : Rs 336 million/year Investment : 2.5 years
4.5.6 Catalytic Reforming Reforming is undertaken by passing the hot feed stream through a catalytic reactor. In the reactor, various reactions such as isomerization, dehydrogenation and hydrocracking occur to reformulate the hydrocarbons in the stream. Some of these reactions are endothermic and others are exothermic. The types of reactions depend on the temperature, pressure and velocity in the reactor. Undesirable side reactions may also occur and need to be limited. Two techniques, namely Continuous regeneration and Semi-regeneration are employed in catalytic reforming. In the regeneration process of the catalyst in a continuous reforming unit, a slip stream of catalyst is withdrawn, 60-80 kg coke/ tonne feed is burned off with hot air/ steam. In the cyclic or semi-regenerative units, the regeneration of catalyst and the resulting emissions are discontinuous. While the continuous catalyst reformer process has higher energy efficiency due to the heat recovery from product, from pump around and due to integration with topping and vacuum units, the heat integration is lower in the semi-regenerative
166
167
reformer process. However, many semi-regenerative units have applied better feed affluent exchange to minimize energy consumption. Table 4.13 given below shows the summary of the utilities and catalyst requirement for the catalytic reforming. Table - 4.13 Parameter
Reforming
Electric power, kWh Specific consumption (kWh/t)
25-50
Fuel fired, GJ Specific fuel consumption (MJ/t)
1400 2900 1-3
Semi-regenerative process 246* 55
Continuous regeneration process 6142* -
185* 71.5 t/kt
232*
Increased Product Recovery
Product recovery from a reformer may be limited by the temperature of the distillation to separate the various products. An analysis of a reformer at the Colorado Refinery in Commerce City, showed increased LPG losses at increased summer temperatures. The LPG would either be flared or used as fuel gas. By installing a waste heat driven ammonia absorption refrigeration plant, the recovery temperature was lowered, debottlenecking the compressors and the unsaturated light-cycle oil streams (Petrick and Pellegrino, 1999). The heat pump uses a 150°F waste heat stream of the reformer to drive the compressor. The project resulted in annual savings of 65,000 barrels of LPG. The recovery rate varies with ambient temperature. The liquid product fraction contained a higher percentage of heavier carbon chain (C5, C6+) products. The payback period is estimated at 1.5 years. ii
Reduction of system pressure (Separator drum Pressure)
Modern CCR (Continuous Catalyst regeneration) process can maintain a very low pressure of about 3.5 kg/m2g. This low pressure obviously calls for high severity of operation and faster deposition of coke on catalyst. But the continuous regeneration can remove the coke from the catalyst. As a whole this can reduce the power consumption of recycle compressor and fetch energy saving as a whole. iii
Case Study 15 : Reduction of quantity of the recycle gas in the reforming unit Brief
Cooling water, 0.12 – 3 5.5 (m3/t, D T=10 0 C) High-pressure steam generated, 50-90 64 - 90 97 kg/t Boiler feed water, kg/t 170 22 * Values related to a capacity of 2351 t/d. Specific values related to capacity values. Note: First column gives ranges for all types of reformers.
i
Reduction in recycled gas quantity to the allowable limits in the catalytic reforming unit saves the power for recycling the gas and the heat power required for the furnace resulting in energy saving.
In the reforming unit a gas rich in hydrogen is circulated for maintaining the hydrogen concentration necessary for the reaction and for preventing deterioration of the catalyst due to carbon deposition on the catalyst. The volume of the recycling gas often becomes more than necessary. By reducing the volume of recycled gas, it is possible to reduce the power for driving the compressor as well as heat required for the furnace. However, as the decrease of the recycling gas may lead to the deterioration of the catalyst, the reduction of the recycle gas to be controlled within the allowable limit. Energy Savings Molar ratio of hydrogen/hydrocarbon Energy Fuel Consumption Electricity
Saving of Fuel Saving of Electricity Investment amount Improvement Effect Case Study 16 :
168
After 5.1
Effect
2.56 kl/d reduction 5,120 kWh/d reduction
2.5 Kl/day 5120 KWhr./day Operational improvement without capital investment Rs.1.33 crores/annum (Basis: 330 days of operation per annum)
Installation of 4 nos. of on line O2 analyzer in the four furnaces of CRU to maintain the O2 level
Brief By installing on line O2 analyser will allow the measurement and control of % O2 in the flue gas. By controlling % of O2 level at 2-3% will increase the furnace efficiency to 80% from the existing level of about 77%. This will ensure saving of 30 Nm3/hr of fuel gas saving. Energy Savings
Other Options
Recycle ratio (H2 recycle flow/feed) plays an important role in CRU for maintaining the catalyst health with respect to catalyst coking. The reduction of this ratio increases the coking tendency of the catalyst and decreases the cycle length (between two successive regeneration of catalyst in semi regeneration process). However optimization of the same can give reduction of power for driving the recycle compressor.
Before 6.4
Fuel Gas Consumption
169
Before installation on line O 2 After installation of online analyser in the 4 nos. of furnaces O2 analyser in the 4 nos. of in CRU furnaces in CRU 3 3 1000 Nm /hr 970 Nm /hr
Saving of 30 Nm3/hr of fuel gas. Investment amount Improvement effect Pay back Period 4.5.7
Table - 15
- Rs. 20 Lakhs (for 4 nos. of O2 analyser) - Rs. 12.6 Lakhs/year - 22 months
Electricity (kWh/t) 60 – 140
Cooling water (m3/t, D T=10 0C) 20 - 40
i
Heat Integration: The delayed coking process has a low level of heat integration. The heat to maintain the coke drums at coking temperature is supplied by heating feed and the recycle stream in a furnace. The atmospheric or vacuum residue can be fed straight into the delayed coking unit without intermediate cooling, which results in high heat integration level between the different units and saves considerable amount of cost on heat exchangers.
ii
Combustion of Coking Gas: - The Flexi Coking process has a high level of heat integration. The only source of heat in the Flexi Coking Process is the gasifier, where coke is partially oxidized. The remainder of the heat in the coker gas is recovered by generating steam. The energy efficiency can be further increased of the coking gas is combusted in a gas turbine of a combined cycle unit.
Coking processes : Two types of Coking processes are used in Petroleum refineries, the delayed and fluid coking processes that produce coke and the flexi coking process which gasifies the coke produced in a fluid coking process to produce coke gas. The Delayed and fluid coking
The basic process is the same as thermal cracking except that feed streams are allowed to react for longer without being cooled. The delayed coking feedstream of residual oil is first introduced to fractioning tower where residual lighter materials are drawn off and the heavy ends are condensed. The heavy ends are removed, heated in a furnace and then fed to a insulated vessel called the coke drum where the cracking takes place. In the case of fluid coking, the fluidized bed is used. Temperature (440 - 450 °C), pressure (1.5 - 7.0 bar g) and recycle ratio are the main process variables which contribute to the quality and yields of delayed coking products. Energy & process materials required in the Delayed coking Process are given in the Table 4.14 : Table - 4.14 Fuel Electricity Steam consumed Steam produced Cooling water (MJ/t) (kWh/t) (kg/t) (kg/t) (m3/t, D T = 17 °C) 800 – 1200 20 – 30 50 – 60 50 – 125 6 – 10 Note: Electricity including the electric motor drives for the hydraulic decoking pump.
ii
Steam produced (kg/t) 500 – 600 (HP)
Coking Process - Energy Conservation Measures
Coking
A new generation of coking processes has added additional flexibility to the refinery by converting the heavy bottom fed into lighter feedstocks and coke. Coking can be considered a severe thermal cracking process. Modern coking processes can also be used to prepare feed for the hydrocracker.
i
Steam consumed (kg/t) 300 – 500 (MP)
Flexi coking
iii Use of Oily Sludges as Coker feed stocker: - In the case of delayed coker, the sludge can be injected into the coking drum with the quench water or can be injected into the coker blowdown contactor used in separating the quenching products. In refineries with a coker, oily sludges from the waste water treatment plant can be used to produce coke which can be further used as fuel within the refinery. iv Water use in the cooling/ cutting processes: The water used in the cutting/ cooling operations is continuously re-circulated with a bleed-off to the refinery wastewater treatment. Settling and filtering over a vacuum filter enables the reuse of this water resulting in a "Closed Water Loop" for water make up to the quenching and cutting water loop. Case Study 17: Installation of VFD for ID & FD fans of DCU furnace. Brief This modification installs VFD for 1 No. each of ID and FD fan of 60 kW each.
In the Flexi coking process, a heavy feed is preheated to 315-370 °C and sprayed on a bed of hot fluidized coke (recycled internally). The coke bed has a reaction temperature between 510-540 °C. At this temperature, cracking reactions take place. Cracked vapor products are separated in cyclones and are quenched. Some of the products are condensed, while the vapors are led to a fractionator column, which separates various product streams. The coke is stripped from other products, and then processed in a second fluidized and reactor where it is heated to 590 °C. The hot coke is then gasified in a third reactor in the presence of steam and air to produce synthesis gas. Sulfur (in the form of H2S) is removed, and the synthesis gas (mainly consisting of CO, H2, CO2 and N2) can be used as fuel in (adapted) boilers or furnaces. The coking unit is a consumer of fuel (in preheating), steam and power. Utility requirement in the Flexi Coking Process is given in Table 15: -
170
Energy Savings
Consumption of Power in ID/FD
Before installation of VFD 60 kW
After installation of VFD 50 kW
Reduction of 1.60 lacs KWhr./year Investment amount Improvement effect
-
Pay back Period
-
171
15 lacs 5.6 lacs / yr (for 8000 hrs & electricity cost @ Rs. 3.5 per kWh 32 months
Case Study 18 : Proper insulation of DCU furnace.
Energy Savings
Brief
Fuel Saving Investment amount
Furnace surface temperature varied between 60 - 96°C proper insulation called for the safety and energy conservation point of view.
Improvement effect Pay back Period
- 1800 mt/year in DCU furnace - Rs. 1.06 crores (For installation of 2 nos. of exchangers and allied piping) - 1.70 crores/year - 8 months
Energy Savings 4.5.8 Hydrotreater Saving of 110 kl of FO Investment amount Improvement effect Pay back Period
- 32 lacs - 18 lacs - 1.8 years
Case Study 19 : Installation of the lowest sized impeller in the DCU Brief Installation of the lowest sized impeller as suggested by manufacture in the DCU (Delayed coking unit) fractionators bottom pump to reduce the operating point from 57 kg/cm2g to 40 kg/ cm2g to elimate the pressure drop in the feed control valve to Coker furnace. 1.
2.
In operation of DCU fractionator bottom pump which sends the material to furnace through a control valve where the pressure developed by the pump gets lost by 20 to 30 kg/cm2 (50% of the pressure developed by the fractionators bottom pump is lost). By replacing the existing impeller of the pump by the smallest impeller (as per manufacturer) the discharge pressure of the pump can be brought down to 40kg/cm2g thereby eliminating the pressure drop in the control valve.
Energy Savings Consumption of power by fractionators bottom pump motor
Before replacement of impeller of the fractionators bottom pump 215.5 kW
After replacement of impeller of the fractionators bottom pump 143.5 kW
Reduction of power 6.0 lakh kWh/year. Investment amount Improvement effect Pay back Period
- Rs. 1 Lakh (for 2 nos. of pump motor) - Rs. 4.2 Lakhs/year - 3 months
Case Study 20 : Heat recovery from RFO stream in DCU (Delayed Coking Unit). Brief The RFO was getting cooled by on open box cooler. Two new exchangers were installed. One exchangers is thermosyphon type where the RFO is routed first to bring down the temperature from 400oC to 200oC and to generate steam at low pressure. This stream of 2000C RFO then routed to normal shell and tube exchanger to heat BFW water. The additional steam generated was sent to furnace. This was resulted in FO saving of about 1860 MT/year. New lines were laid for interconnecting RFO stream to thermos phone exchanger. 172
Desulfurization is becoming more and more important as probable future regulations will demand a lower sulfur content of fuels. Desulfurization is currently mainly done by hydrotreaters. In a hydrotreater, the feedstream is mixed with hydrogen and heated to a temperature between 260-430ºC. In some designs, the feedstream is heated and then mixed with the hydrogen. The reaction temperature should not exceed 430ºC to minimize cracking. The gas mixture is led over a catalyst bed of metal oxides most often cobalt or molybdenum oxides on different metal carriers. The catalysts help the hydrogen to react with sulfur and nitrogen to form hydrogen sulfides H2S and ammonia. The reactor effluent is then cooled, and the oil feed and gas mixture is then separated in a stripper column. Part of the stripped gas may be recycled to the reactor. The operating conditions are dependent on feedstock composition (related to crude source as well as type and severity of prior processing), catalyst and product specifications. The feedstocks to hydrogen finishing processes include the following; Solvent extracted deasphalted oils Hydrocracked deasphalted oils Solvent refined distillates Unrefined distillates
Hydrocracked distillates Deasphalted oils Slack waxes Hard waxes
The effects of hydrogen finishing temperature and pressure are highly dependent on the quality of the feedstock, produce specifications and the type of catalyst used. An increase in temperature or pressure will normally improve neutralization, desulfurization, denitrification, product colour and product stability. However, increasing the temperature above some maximum which is related to the catalyst and feedstock quality will degrade the colour, colour stability, oxidation stability and other properties of the base oil and at the same time energy consumption will also increase. Hydrotreating Options • • • •
HDT heavy naptha pre-cat reforming is very common HDT of FCC napths becoming more common and more sophisticated 95 - 99% of sulfur may be removed Saturation of olefins and aromatics possible by typically avoided because of octane loss
Diesel Hydrotreating Technologies • •
Tightening sulfur specs have stimulated massive investment in new HDT technologies 95 - 99% sulphur typically removed 173
• • •
HDT improves cetane number and saturates some olefins and aromatics HAD techs have evolved to saturate aromatics and eliminate sulfur GTL technologies also evolving to produce zero - sulfur synthetic diesels.
Resid/VGO Hydrotreating Technologies • • •
RDS was rare outside of Japan (Belgium, Kuwait, S. Korea, UK, US also have) FCC feed (VGO) pretreatment more common, resulting in lower - sulfur light and middle distillate output May also be considered mild hydrocracking depending on level of conversion
Growth in World HDT Capacity • • • •
World HDT capacity grew from 24.9 mb/d in 1985 to 40.5 mb/d in 2003 -a 2.7% increase per year. CDU capacity grew at only 0.7% / year Further expansions expected with many markets working to improve fuel quality. Automakers ask for "as close to zero - sulfur as soon as possible"
A hydrotreater unit specifically employed to remove sulphur from, various feedstocks, is called a Hydro De-Sulphurisation Unit (HDS). The H2 consumption, and consequently the energy requirement, significantly increase in the order naphtha (0.05% H2), distillate (0.3% H2) and residue hydrotreating (1.8% H2). Table 16 shows the utility requirements for different hydrotreatments.
Naphtha processed Distillate processed Residue processed Hydroconversion
Electricity (kWh/t)
Steam consumed (kg/t)
200350 300500 300800 6001000
5-10
Energy Conservation Options
Installation of a multivariable predictive control. MPC system was demonstrated on a hydrotreater at a SASOL refinery in South Africa. The MPC aimed to improve the product yield while minimizing the utility costs. The implementation of the system led to improved yield of gasoline and diesel, reduction of flaring, and a 12% reduction in hydrogen consumption and an 18% reduction in fuel consumption of the heater (Taylor et al., 2000). Fuel consumption for the reboiler increased to improve throughput of the unit. With a payback period of 2 months, the project resulted in improved yield and in direct and indirect i.e., reduced hydrogen consumption and energy efficiency improvements. Case Study 21 : Improvement of heat recovery system in Vacuum gas oil hydrotreater unit Brief The existing vacuum gas oil desulfurization unit cools the reaction products to separate them into gas, including recycling gas, and oil, and then reheats the oil for fractionation. The amount of heat dissipated at this condensing cooler is great. To recover a portion of this heat loss on one hand, and to overcome the increasing fouling of the combined feed heat exchanger which increases restriction on throughput on the other, the heat recovery system of the entire plant was improved and a new hot separator was installed. Installation of a hot separator/heat exchanger
Table 4.16 - Utilities requirement of Hydrotreater Fuel (MJ/t)
i
Wash water (kg/t)
H2 (kg/t)
10-60
Cooling water (m3/t, D T=10°C) 2-3
40-50
1-15
10-20
60-150
2-3
30-40
1-15
10-30
60-150
2-3
30-40
10100 -
1) A hot separator was installed to reduce the heat loss at the effluent cooling condenser. 2) The combined heat exchanger system was expanded to increase heat recovery from the reactor effluent. 3) A preheater was added to the charge oil system to increase heat recovery from the fractionator bottom. Improvement effects and system flow
50-110
200-300 2-10 (steam produced) Note:Hydroconversion is an exothermic reaction and the heat generated in the reactor system is partially recovered in the feed product exchanger.
Hydrotreaters use a considerable amount of energy directly (fuel, steam, electricity) and indirectly (hydrogen). Various alternatives are demonstrated at refineries around the world, including the oxidative desulfurization process (Valero's Krotz Springs, Louisiana) and the S Zorb process at Philip's Borger (TX). The S Zorb process is a sorbent operated in a fluidized bed reactor. Philips Petroleum Co. claims a significant reduction in hydrogen consumption to produce low-sulfur gasoline and diesel (Gislason, 2001). A cursory comparison of the characteristics of the S Zorb process and that of selected hydrotreaters suggests a lower fuel and electricity consumption, but increased water consumption. 174
1) The temperature at the inlet to the reactor charge heater has risen from 3230C to 3440C. 2) The temperature at the fractionator charge heater has risen from 2300C to 2610C. 3) The throughput has increased because of the reduced loads on the heaters. Energy saving effects After improvement Fuel consumption - heavy fuel oil equivalent Fuel consumption - crude oil equivalent
Investment amount Improvement effect Investment payback
175
7,300 kl/y reduction 7,738 kl/y reduction
: Rs 200 million : Rs 87.2 million/year : 2.3 years
Case Study 22 :
Rotation control of the recycle gas compressor in Heavy oil direct hydrotreater unit
Brief The recycle gas of this unit is pressurized by the recycle gas compressor and loses pressure as it passes through the reactor, heat exchangers and control valves. If it is possible to operate the unit with the control valves, the major contributor to the pressure drop, nearly fully open, the power consumption of the compressor could be reduced. The improvement herein explained realized energy saving by controlling r.p.m. of the compressor in operation to reduce pressure drops across control valves The pressure loss at the control valves accounts for 17% of all losses in this system when the valves are 80% open. Control valves, if operated in full open, reduce most efficiently the power consumption required. However, in actual operations, RPM. of the compressor has been controlled so that control valves are 90 % open to accommodate the fluctuation of the process Energy savings
Steam consumption (t/h) Steam consumption (t/y) Crude oil equivalent
Investment amount (A) Improvement effect (B) Investment payback (A/B ) 4.5.9
Before improvement
After improvement
32.8 t/h
30.6 t/h
referred to as a sulfuric acid alkylation unit (SAAU) or a hydrofluoric alkylation Unit, (HFAU). However, oil refinery employees may simply refer to the unit as the Alkyl or Alky unit. The catalyst is able to protonate the alkenes (propylene, butylenes) to produce reactive carbocations, which alkylate isobutene. The reaction is carried out at mild temperatures (0 and 300C) in a two phase reaction. It is important to keep a high ratio of isobutene to olefin at the point of reaction to prevent side reactions that lead to a lower octane product, so the plants have a high recycle of isobutene back to feed. The phases separate spontaneously, so the acid phase is vigorously mixed with the hydrocarbon phase to create sufficient contact surface. The product is called alkylate and is composed of a mixture of high octane, branched chain paraffinic hydrocarbons (mostly isopentane and isooctane). Alkylate is a premium gasoline blending stock because it has exceptional antiknock properties. The octane number of the alkylate depends mainly upon the kind of olefins used and upon operating conditions. For example, isooctane results from combining butylenes with isobutene and has an octane rating of 100 by definition. As there are other products in the alkylate, so the octane rating will vary accordingly.
Effect
2.2 t/h reduction 18,400 t/y reduction 1,582 kl/y reduction
: a set of microcomputers: Rs 4.8 million, : Rs 24.4 million/year : 3 months
Alkylation
Alkylation is the transfer of an alkyl group from one molecule to another. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion or a carbine (or their equivalents).
Most crude oils conytain only 10 to 40 percent of their hydrocarbon constituents in the gasoline range, so refineries use a fluid catalytic cracking process to convert high molecular weight hydrocarbons into smaller and more volatile compounds. Polymerization converts small gaseous olefins into liquid gasoline size hydrocarbons. Alkylation processes transform small olefin and iso paraffin molecules into larger iso-paraffins with a high octane number. The summary of the utility consumptions in the two techniques currently used in the alkylation processes is given in the Table 4.17. Table 4.17 Estimated utilities and chemical consumption for the various alkylation techniques
Values per tonne of alkylate produced Utilities Electricity (kWh) Fuel (MJ) Steam (kg) Cooling water (m3) (D T = 11 °C) Industrial water (m3)
Alkylating agents are widely used in chemistry because the alkyl group is probably the most common group encountered in organic molecules. In oil refining contexts, alkylation refers to a particular alkylation of isobutene with olefins. It is a major aspect of the upgrading of petroleum. Options for Alkylation It depends upon the type of alkylating agents
Energy Conservation Opportunities
i ii iii iv
i
Nucleophilic alkylating agents Electrophilic alkylating agents Radical alkylating agents Carbene alkylating agents
In a standard oil refinery process, isobutene is alkylated with low molecular weight alkenes (primarily a mixture of propylene and butylenes) in the presence of a strong acid calatyst, either sulphuric acid or hydrofluoric acid. In an oil refinery it is 176
Sulphuric acid
Alkylation technique Hydrofluoric
4 n.a. 830 72
20 – 65 1000 – 3000 100 – 1000 62
0.08
Feedstock upgradation by selective hydrogenation
The naphtha hydrotreatment or isomerisation (e.g. hydrogenation of butadiene, isomerisation of 1-butene to 2-butene) helps the alkylation units to reduce the acid losses and consequently the waste generation. As consequence, the amount of caustic consumption is decreased. The reduction in acid and caustic consumption depends on the feed diene content, which varies widely at different refineries.
177
ii
Implementation of ACS
Soaker visbreaking versus coil visbreaking
Motiva's Convent (Louisiana) refinery implemented an advanced control system for their 100,000 bpd sulfuric acid alkylaiton plant. The software package integrates information from chemical reactor analysis, pinch analysis, information on flows, and information on energy use and emissions to optimize efficient operation of the plant. The system aims to increase product yield by approximately 1%, reduce electricity consumption by 4.4%, reduce steam use by 2.2%, reduce cooling water use by 4.9%, and reduce chemicals consumption by 5-6% (caustic soda by 5.15, sulfuric acid by 6.4%) (U.S.DOE-OIT, 2000). The companies offering alkylation controls are ABB Simcon, Aspen technology, Emerson, Honeywell, Invensys, and Yokogawa. The controls typically result in cost savings of $0.10 to $0.20/ bbl of feed with paybacks of 6 to 18 months. 4.5.10
Visbreaking
From the standpoint of yield, there is little or nothing to choose between the two approaches. However, each offers significant advantages in particular situations: "
Coil cracking uses higher furnace outlet temperatures (470-5000C) and reaction times from one to three minutes, while soaker cracking uses lower furnace outlet temperatures (430 - 440 0C) and longer reaction times. The product yields and properties are similar.
"
For visbreaking, fuel consumption accounts for about 80% of the operating costs with a net fuel consumption of 1-1.5% w/w on feed. Fuel requirements for soaker visbreaking are about 30 - 35% lower.
"
De-coking: The cracking reactions forms petroleum coke as a byproduct. In coil visbreaking, this lays down in the tubes of the furnace and will eventually lead to fouling or blocking of the tubes.
Visbreaking/ thermal cracking is one of the oldest conversion processes to upgrade heavy oil fractions. The fuel stock is heated above 500 0C and then fed to a reaction chamber which is kept at a presence of about 9.65 bar (g).
The same will occur in the drum of a soaker visbreasker, though the lower temperature used in the soaker drum lead to fouling at a much slower rate. Coil visbreakers therefore require frequent decoking. This is quite labour intensive. Soaker drums require far less frequent attention but while taken out of service normally requires a complete halt to the operation which is the more disruptive activity and will vary from refinery to refinery.
Options of Visbreaking i Coil Visbreaking: The term coil (or furnace) visbreaking is applied to units where the cracking process occurs in the furnace tubes (or "coils") . Material exiting the furnace is quenched to halt the cracking reactions: frequently this is achieved by heat exchange with the virgin material being fed to the furnace, which in turn is a good energy efficiency step, but sometimes a stream of cold oil (usually gas oil) is used to the same effect. The gas oil is recovered and re-used. The extent of the cracking reaction is controlled by regulation of the speed of flow of the oil through the furnace tubes. The quenched oil then passes to a fractionator where the products of the cracking (gas, LPG, gasoline, gas oil and tar) are separated and recoverd. ii Soaker Visbreaking:In soaker visbreaking, the bulk of the cracking reaction occurs not in the furnace but in a drum located after the furnace called the soaker. Here the oil is held at an elevated temperature for a pre-determined period of time to allow cracking to occur before being quenched. The oil then passes to a fractrionator. In soaker visbreaking, lower temperatures are used than in coil visbreaking. The comparatively long duration of the cracking reaction is used instead. Process Options Visbreaker tar can be further refined by feeding it to a vacuum fractionator. Here additional heavy gas oil may be recovered and routed either to catalytic cracking, hydrocracking or thermal cracking units on the refinery. The vacuum - flashed tar (sometimes referred to as pitch) is then routed to fuel oil blending. In a few refinery locations, visbreaker tar is routed to a delayed coker for the production of certain specialist cokes such as anode coke or needle coke.
178
"
Fuel Economy: The lower temperatures used in the soaker approach mean that these units use less fuel. In cases where a refinery buys fuel to support process operations, any savings in fuel consumption could be extremely valuable. In such cases, soaker visbreaking may be advantageous.
The typical utilities consumption for a visbreaker are: Table 4.18 Utility consumptions for a visbreaker Fuel (MJ/t) Electricity (kWh/t) S team consumed (kg/t)
400 – 800 10 – 15 5 – 30 3 2 - 10 Cooling water (m /t, D T = 10°C) Note: the power consumption given is for “furnace” cracking. The most important factor in controlling the cracking severity should always be stability and viscosity of the visbroken residue fed to the fuel oil pool. In general, an increase in the temperature or residence time results in an increase in severity. Increased severity produces higher gas-plus-gasoline yield and at the same time a cracked residue (fuel oil) of lower viscosity. Excessive cracking, however, leads to an unstable fuel oil, resulting in sludge and sediment formation during storage. Thermal cracking units to upgrade atmospheric residue have conversion levels of 35-45% and the viscosity of the atmospheric residue is reduced.
179
•
UTILITIES
4.5.11
Steam Generation and Distribution
An estimated 30% of all onsite energy use in Refineries is in the form of steam. The refining industry uses steam for a wide variety of purposes, the most important being process heating, drying or concentrating, steam cracking, and distillation. Steam can be generated through waste heat recovery from processes, cogeneration, and boilers. In most refineries, steam will be generated by all three sources, while some smaller refineries may not have cogeneration equipment installed. While the exact size and use of a modern steam systems varies greatly, there is an overall pattern that steam systems follow, as shown in Figure 3.
By combining an oxygen monitor with an intake airflow monitor, it is possible to detect small leaks. Using a combination of CO and oxygen readings, it is possible to optimize the fuel/air mixture for high flame temperature and thus the best energy efficiency and low emissions. The payback of improved process control is approximately 0.6 years (IAC, 1999). c Reduce Flue Gas Quantities. Often, excessive flue gas results from leaks in the boiler and the flue, reducing the heat transferred to the steam, and increasing pumping requirements. These leaks are often easily repaired. Savings amount to 25% (OIT, 1998). This measure consists of a periodic repair based on visual inspection. The savings from this measure and from flue gas monitoring are not cumulative, as they both address the same losses. d Reduce Excess Air. The more air is used to burn the fuel, the more heat is wasted in heating air. Air slightly in excess of the ideal stoichometric fuel/air ratio is required for safety, and to reduce NOx emissions, and is dependent on the type of fuel. For gas and oil-fired boilers, approximately 15% excess air is adequate (OIT, 1998; Ganapathy, 1994). Poorly maintained boilers can have up to 140% excess air. Reducing this back down to 15% even without continuous automatic monitoring would save 8%.
Figure 4.3 Schematic presentation of a steam production and distribution system
Whatever the use or the source of the steam, efficiency improvements in steam generation, distribution and end-use are possible. A recent study by the U.S. Department of Energy estimates the overall potential for energy savings in petroleum refineries at over 12% (U.S. DOE, 2002). i
Boilers
a Boiler Feed Water Preparation. Depending on the quality of incoming water, the boiler feed water (BFW) needs to be pre-treated to a varying degree. Various technologies may be used to clean the water. A new technology is based on the use of membranes. In reverse osmosis (RO), the pre-filtered water is pressed at increased pressure through a semi-permeable membrane. Reverse osmosis and other membrane technologies are used more and more in water treatment (Martin et al., 2000). The Flying J refinery in North Salt Lake Utah installed a RO-unit to remove hardness and reduce the alkalinity from boiler feed water, replacing a hot lime water softener, resulting in reduced boiler blowdown from 13.3% to 1.5% of steam produced and reduced chemical use, maintenance, and waste disposal costs. With an investment of $350,000 and annual benefits of approximately $200,000, the payback period amounted to less than 2 years. b Improved Process Control. Flue gas monitors are used to maintain optimum flame temperature, and to monitor CO, oxygen and smoke. The oxygen content of the exhaust gas is a combination of excess air deliberately introduced to improve safety or reduce emissions and air infiltration (air leaking into the boiler). 180
e Maintenance. A simple maintenance program to ensure that all components of the boiler are operating at peak performance can result in substantial savings. The absence of a good maintenance system can end up costing a steam system up to 2030% of initial efficiency over 2-3 years. On average, the possible energy savings are estimated at 10% (DOE, 2001a). Improved maintenance may also reduce the emission of criteria air pollutants. Fouling of the fireside of the boiler tubes or scaling on the waterside of the boiler should also be controlled. Tests show that a soot layer of 0.03 inches (0.8 mm) reduces heat transfer by 9.5%, while a 0.18-inch (4.5 mm) soot layer reduces heat transfer by 69% (CIPEC, 2001). For scaling, 0.04 inches (1 mm) of buildup can increase fuel consumption by 2% (CIPEC, 2001). Moreover, scaling may result in tube failures. f Recover Heat From Flue Gas. Heat from flue gases can be used to preheat boiler feed water in an economizer. While this measure is fairly common in large boilers, there is often still potential for more heat recovery. The limiting factor for flue gas heat recovery is the economizer wall temperature that should not drop below the dew point of acids in the flue gas. One percent of fuel use is saved for every 25°C reduction in exhaust gas temperature. (Ganapathy, 1994). Since exhaust gas temperatures are already quite low, limiting savings to 1% across all boilers, with a payback of 2 years (IAC, 1999). g Recover Steam From Blowdown. When the water is blown from the highpressure boiler tank, the pressure reduction often produces substantial amounts of steam. This steam is low grade, but can be used for space heating and feed water preheating. For larger high-pressure boilers, the losses may be less than 0.5%. It is estimated that this measure can save 1.3% of boiler fuel use for all boilers below 100 MMBtu/hr (approximately 5% of all boiler capacity in refineries). The payback period of blowdown steam recovery will vary between 1 and 2.7 years (IAC, 1999).
181
h Reduce Standby Losses. In refineries often one or more boilers are kept on standby in case of failure of the operating boiler. The steam production at standby can be reduced to virtually zero by modifying the burner, combustion air supply and boiler feed water supply. By installing an automatic control system the boiler can reach full capacity within 12 minutes. Installing the control system and modifying the boiler can result in energy savings up to 85% of the standby boiler, depending on the use pattern of the boiler. ii
Steam Distribution
When designing new steam distribution systems, it is very important to take into account the velocity and pressure drop (Van de Ruit, 2000). This reduces the risk of oversizing a steam pipe, which is not only a cost issue but would also lead to higher heat losses. However, it may be too expensive to optimize the system for changed steam demands. Still, checking for excess distribution lines and shutting off those lines is a cost-effective way to reduce steam distribution losses. Other maintenance measures for steam distribution systems are described below. a Improve Insulation: Crucial factors in choosing insulating material include low thermal conductivity, dimensional stability under temperature change, resistance to water absorption, and resistance to combustion. New materials insulate better, and have a lower heat capacity. Savings of 6-26% can be achieved if this improved insulation is combined with improved heater circuit controls. The shell losses of a well-maintained boiler should be less than 1%. b Maintain Insulation. It is often found that after repairs, the insulation is not replaced. In addition, some types of insulation can become brittle, or rot. As a result, energy can be saved by a regular inspection and maintenance system (CIBO, 1998). Exact energy savings and payback periods vary with the specific situation in the plant. Case Study 23: Replacing the Damaged Insulation to arrest Heat Losses. Brief In a gas based Petrochemical plant, the VHP steam is supplied from utility boilers (UB#2 & UB#3) to the process plants GCU and LPG. The length of the steam headers to these plants from the Utility Plant is approximately one kilometer. The discussions of the audit team with shift-in charge and respective Heads of the Plants revealed that the temperature drop across the pipeline has been significantly high as a result the steam temperature at the battery limit of LPG (4700C) and GCV (4600C) are lower. The high surface temperatures of insulated steam headers / pipes indicate the damaged or inadequate insulation. For the above-mentioned areas, it was recommended to replace the insulation to arrest the heat losses. Since the measured surface temperatures are significantly higher than the normal temperature, the anticipated energy savings will be substantial and the payback period will be attractive (less than a year). Table gives the cost-benefit analysis of replacing the insulation.
182
Energy Savings Area Identified
Surface o Temp C
Annual reduction in heat loss
Equivalent annual monetary saving
Approximate cost of insulation
Simple payback period
million Kcal
Rs. lacs
Rs. lacs
Months
HP steam pipeline
85
9.91
0.13
0.03
2.24
VHP steam header
70
21.96
0.30
0.09
3.79
Pipeline opposite compressor
200
214.89
2.92
0.10
0.41
VHP line near 90-JBA-207
75
7.13
0.10
0.03
3.10
Inlet vertical pipe
60
2.53
0.03
0.02
6.57
Drain pipe
75
7.16
0.10
0.03
3.10
HP line near condensate drum
91
11.64
0.16
0.03
1.90
Condensate header
75
7.16
0.10
0.03
3.10
HP header at B/l
90
11.34
0.15
0.03
1.95
HP line near PRDS
85
9.90
0.13
0.03
2.24
246.76
3.5
0.22
0.76
c Improve Steam Traps. Using modern thermostatic elements, steam traps can reduce energy use while improving reliability. The main advantages offered by these traps are that they open when the temperature is very close to that of the saturated steam (within 2°C), purge non-condensable gases after each opening, and are open on startup to allow a fast steam system warm-up. These traps are also very reliable, and useable for a wide variety of steam pressures (Alesson, 1995). Energy savings will vary depending on the steam traps installed and state of maintenance. d Maintain Steam Traps. A simple program of checking steam traps to ensure that they operate properly can save significant amounts of energy. If the steam traps are not regularly monitored, 15-20% of the traps can be malfunctioning. In some plants, as many as 40% of the steam traps were malfunctioning. Energy savings for a regular system of steam trap checks and follow-up maintenance is estimated at up to 10% (OIT, 1998; Jones 1997; Bloss, 1997) with a payback period of 0.5 years. e Monitor Steam Traps Automatically. Attaching automated monitors to steam traps in conjunction with a maintenance program can save even more energy, without significant added cost. This system is an improvement over steam trap maintenance alone, because it gives quicker notice of steam trap malfunctioning or failure. Using automatic monitoring is estimated to save an additional 5% over steam trap maintenance, with a payback of 1 year (Johnston, 1995; Jones, 1997).
183
Case Study 24 : Replacement of Damaged Steam Traps. Brief Study of Steam Traps In a gas based Petrochemical plant, there are over 1,000 steam traps in different sections of the plant for varying applications on the steam mains, condensate lines, and process requirement. The traps installed are of different types - Thermodynamic, Bucket, and Orifice, and of different sizes. Field testing of steam traps During an energy audit study, about 170 representative steam traps were tested using the portable steam trap tester "TRAPMAN", from different sections of the plant, viz., GCU, LPG, Butene - 1, Boiler & Power Plant, and GPU. The working condition of the traps in terms of Good / Blowing / Chocked / Low Temperature / Bypass was measured using the portable instrument. The findings of the steam traps performance evaluation are summarized below :
The traps which are chocked or indicated as low temperature needs to be repaired immediately to let the condensate flow smoothly out of the system and to ensure effective heat transfer. Though it is difficult to precisely estimate the achievable energy savings, it can be concluded that by ensuring effective operation of the remaining 45 traps, fuel savings worth more than Rs.10 lac per annum can be easily achieved. The investment required towards replacement of parts of the traps or replacement the traps itself can be paid back in less than an year. The improved steam trap performance also would ensure effective heat transfer hence enhanced throughput. Therefore, the overall savings that can accrued due to satisfactory functioning of traps would be many fold. f Repair Leaks. As with steam traps, the distribution pipes themselves often have leaks that go unnoticed without a program of regular inspection and maintenance. In addition to saving up to 3% of energy costs for steam production, having such a program can reduce the likelihood of having to repair major leaks (OIT, 1998).
Performance of Steam Traps Case study 25 : S. No. 1 2. 3. 4.
Item No. of traps in good condition No. of traps blowing / leaking No. of traps chocked No. of traps indicating low temperature Total No. of traps studied
No. of traps 81 44 16 29 170
% 48 26 9 17 100
As can be observed from the table, only 48% of the traps tested are in good working conditions. The remaining 52% of the traps are either blocked (chocked), leaking, or at low temperature. The following measures are recommended to improve the performance of the steam traps and reduce the steam losses and associated energy losses. It is recommended to replace all the 89 faulty steam traps immediately to arrest steam leakage and losses. The anticipated energy savings, investment required, and approximate payback period are as follows:
Unit
Value
No. of steam traps leaking
nos.
44
Estimated steam leakage per trap
kg/hr
7.5
kCal/kg
750
kCal/hr
247500
Enthalpy of leakage steam Heat loss due to leakage NCV of natural gas Boiler efficiency Loss of natural gas
Brief In one of the gas based Petrochemical plant the steam distribution network was studied in detail to identify steam leakage points and quantify the leakages. All the process sections, utilities, and headers were covered in the study. Leakages were identified from flanges, valves, joints, etc. The nature of leakage varies from medium to heavy in many places. The steam leakage points were identified during the survey and listed below: It is recommended to arrest the steam leakages from the above mentioned areas immediately by replacing the damaged valves, pipe fittings, flanges, traps, etc. The resultant monetary savings and payback period are as follows: Energy Savings Particulars
Energy Savings Description
Arresting the Steam Leakages
3
kCal/sm
8176
%
90
3
33.64
sm /hr
Operational hours per annum
hrs
Annual natural gas loss
sm
7200
3
242172
Cost of natural gas
Rs/sm
3
10
Annual monetary savings by stopping leakages
Rs. lacs
24
Anticipated Investment
Rs. lacs
4.5
Payback period
months
2
184
No of steam leakage points identified
20
Steam leakage per point
7.5 kg/hr
Working hours per annum
7200 hr
Steam savings due to arrest of leakages
1,080 Tonnes/annum
Equivalent natural gas savings
92,000 SM 3/annum
Annual monetary savings
Rs.9 lac
Investment required
Rs.5 lac
Simple payback period
7 months
185
As can be seen from the table above, by attending to steam leakages, monetary savings worth Rs.9 lac can be achieved with an investment of Rs.5 lac towards replacement of damaged pipe sections. The payback works out to be 7 months. g Recover Flash Steam. When a steam trap purges condensate from a pressurized steam distribution system to ambient pressure, flash steam is produced. This steam can be used for space heating or feed water preheating (Johnston, 1995). h Return Condensate. Reusing the hot condensate in the boiler saves energy and reduces the need for treated boiler feed water. The substantial savings in energy costs and purchased chemicals costs makes building a return piping system attractive. Care has to be taken to design the recovery system to reduce efficiency losses (van de Ruit, 2000). Maximum energy savings are estimated at 10% (OIT, 1998) with a payback of 1.1 years (IAC, 1999) for those sites without or with insufficient condensate return. An additional benefit of condensate recovery is the reduction of the blowdown flow rate because boiler feedwater quality has been increased. 4.5.12
Compressors and Compressed Air
Compressors consume about 12% of total electricity use in refineries. The major energy users are compressors for furnace combustion air and gas streams in the refinery. Compressed air is probably the most expensive form of energy available in an industrial plant because of its poor efficiency. Typically, efficiency from start to end-use is around 10% for compressed air systems (LBNL et al., 1998). In addition, the annual energy cost required to operate compressed air systems is greater than their initial cost. Many opportunities to reduce energy in compressed air systems are not prohibitively expensive; payback periods for some options are extremely short - less than one year. i Maintenance. Inadequate maintenance can lower compression efficiency, increase air leakage or pressure variability and lead to increased operating temperatures, poor moisture control and excessive contamination. Better maintenance will reduce these problems and save energy: •
Blocked pipeline filters increase pressure drop. A 2% reduction of annual energy consumption in compressed air systems is projected for more frequent filter changing (Radgen and Blaustein, 2001).
•
Poor motor cooling can increase motor temperature and winding resistance, shortening motor life, in addition to increasing energy consumption. In addition to energy savings, this can help avoid corrosion and degradation of the system.
•
Inspect fans and water pumps for peak performance.
•
Inspect drain traps periodically to ensure they are not stuck in either the open or closed position and are clean. According to vendors, inspecting and maintaining drains typically has a payback of less than 2 years (IngersollRand, 2001).
•
Maintain the coolers on the compressor to ensure that the dryer gets the lowest possible inlet temperature (Ingersoll-Rand, 2001). 186
•
Check belts for wear and adjust them. A good rule of thumb is to adjust them every 400 hours of operation.
•
Check water-cooling systems for water quality (pH and total dissolved solids), flow and temperature. Clean and replace filters and heat exchangers as per manufacturer's specifications.
•
Minimize leaks (see also Reduce leaks section, below).
•
Specify regulators that close when failed.
•
Applications requiring compressed air should be checked for excessive pressure, duration or volume. They should be regulated, either by production line sectioning or by pressure regulators on the equipment itself.
ii
Monitoring. Proper monitoring and maintenance can save a lot of energy and money in compressed air systems. Proper monitoring includes the following (CADDET, 1997):
•
Pressure gauges on each receiver or main branch line and differential gauges across dryers, filters, etc. Temperature gauges across the compressor and its cooling system to detect fouling and blockages Flow meters to measure the quantity of air used Dew point temperature gauges to monitor the effectiveness of air dryers kWh meters and hours run meters on the compressor drive Compressed air distribution systems when equipment has been reconfigured. Check for flow restrictions of any type in a system, pressure rise resulting from resistance to flow increases the drive energy on the compressor by 1% of connected power for every 2 psi of differential (LBNL et al., 1998; Ingersoll- Rand, 2001).
• • • • • •
iii
Reduce leaks in pipes and equipment. Leaks can be a significant source of wasted energy. A typical plant that has not been well maintained could have a leak rate between 20 to 50% of total compressed air production capacity (Ingersoll Rand, 2001). Overall, a 20% reduction of annual energy consumption in compressed air systems is projected for fixing leaks (Radgen and Blaustein, 2001).
iv Reducing the Inlet Air Temperature Reducing the inlet air temperature reduces energy used by the compressor. In many plants, it is possible to reduce inlet air temperature to the compressor by taking suction from outside the building. As a rule of thumb, each 3°C will save 1% compressor energy use (CADDET, 1997; Parekh, 2000). v Maximize Allowable Pressure Dew Point at Air Intake. Choose the dryer that has the maximum allowable pressure dew point and best efficiency. A rule of thumb is that desiccant dryers consume 7 to 14% of the total energy of the compressor, whereas refrigerated dryers consume 1 to 2% as much energy as the compressor (Ingersoll Rand, 2001). Consider using a dryer with a floating dew point. Note that where pneumatic lines are exposed to freezing conditions, refrigerated dryers are not an option. 187
vi Controls. The objective of any control strategy is to shut off unneeded compressors or delay bringing on additional compressors until needed. All compressors that are on should be running at full load. Positioning of the control loop is also important; reducing and controlling the system pressure downstream of the primary receiver results in reduced energy consumption of up to 10% or more (LBNL et al., 1998).
With the addition of more secondary units, air requirement had increased. To meet increased air requirement compressor with higher energy efficiencies have been installed. Thus, new Centrifugal Air Compressors of capacity 5000 NM3/Hr, 650 KW each were provided replacing four numbers of old reciprocating compressors. ith the provision of this centrifugal compressor savings of ~ 100 SRFT per compressor has been achieved.
•
Start/stop (on/off) is the simplest control available and can be applied to small reciprocating or rotary screw compressors.
4.5.13
•
Load/unload control, or constant speed control, allows the motor to run continuously but unloads the compressor when the discharge pressure is adequate. In most cases, unloaded rotary screw compressors still consume 15 to 35% of full-load power when fully unloaded, while delivering no useful work (LBNL et al., 1998).
Modulating or throttling controls allows the output of a compressor to be varied to meet flow requirements by closing down the inlet valve and restricting inlet air to the compressor. Changing the compressor control to a variable speed control saves up to 8% per year (CADDET, 1997). vii Properly Sized Regulators. Regulators sometimes contribute to the biggest savings in compressed air systems. By properly sizing regulators, compressed air will be saved that is otherwise wasted as excess air. viii Sizing Pipe Diameter Correctly. Inadequate pipe sizing can cause pressure losses, increase leaks, and increase generating costs. Pipes must be sized correctly for optimal performance or resized to fit the current compressor system. Increasing pipe diameter typically reduces annual energy consumption by 3% (Radgen and Blaustein, 2001). ix
x
xi
Over 60% of all fuel used in the refinery is used in furnaces and boilers. The average thermal efficiency of furnaces is estimated at 75-90%. Accounting for unavoidable heat losses and dewpoint considerations, the theoretical maximum efficiency is around 92% (HHV) (Petrick and Pellegrino, 1999). This suggests that on average a 10% improvement in energy efficiency can be achieved in furnace and burner design. The efficiency of heaters can be improved by improving heat transfer characteristics, enhancing flame luminosity, installing recuperators or airpreheaters, and improved controls. New burner designs aim at improved mixing of fuel and air and more efficient heat transfer. Many different concepts are developed to achieve these goals, including lean-premix burners (Seebold et al., 2001), swirl burners (Cheng, 1999), pulsating burners (Petrick and Pellegrino, 1999) and rotary burners (U.S. DOE-OIT, 2002e). Also, furnace and burner design has to address safety and environmental concerns. i
High Efficiency Motors. Installing high efficiency motors in compressor systems reduces annual energy consumption by 2%, and has a payback of less than 3 years (Radgen and Blaustein, 2001).
Case Study 26 : Replacement of reciprocating air compressor In a Petroleum refinery, there were 4 reciprocating air compressors, out of which 2 used to run to cater instrument air and service air requirement in the original refinery configuration. These compressors were lower energy efficient and obsolete in nature and had problems of frequent breakdowns and maintenance. 188
Maintenance Regular maintenance of burners, draft control and heat exchangers is essential to maintain safe and energy efficient operation of a process heater. Draft Control. Badly maintained process heaters may use excess air. This reduces the efficiency of the burners. Excess air should be limited to 2-3% oxygen to ensure complete combustion.
Heat Recovery For Water Preheating. As much as 80 to 93% of the electrical energy used by an industrial air compressor is converted into heat. In many cases, a heat recovery unit can recover 50 to 90% of the available thermal energy for space heating, industrial process heating, water heating, makeup air heating, boiler makeup water preheating, industrial drying, industrial cleaning processes, heat pumps, laundries or preheating aspirated air for oil burners (Parekh, 2000). Paybacks are typically less than one year. Adjustable Speed Drives (ASDs). Implementing adjustable speed drives in rotary compressor systems has saved 15% of the annual compressed air energy consumption (Radgen and Blaustein, 2001).
Process Heaters
Valero's Houston refinery has installed control systems to reduce excess combustion air at the three furnaces of the CDU. The control system allows running the furnace with 1% excess oxygen instead of the regular 3-4%. The system has not only reduced energy use by 3 to 6% but also reduced NOx emissions by 10-25%, and enhanced the safety of the heater. ii
Air Preheating Air preheating is an efficient way of improving the efficiency and increasing the capacity of a process heater. The flue gases of the furnace are used to preheat the combustion air. Every 35°F drop in the exit flue gas temperature increases the thermal efficiency of the furnace by 1% (Garg, 1998). Typical fuel savings range between 8 and 18% and is typically economically attractive if the flue gas temperature is higher than 650°F and the heater size is 50 MMBtu/hr or more (Garg, 1998). VDU. At a refinery in the United Kingdom, the temperature of the flue gas was reduced to 470°F. This led to energy cost savings of $109,000/year with a payback period of 2.2 years (Venkatesan and Iordanova, 2003). 189
Typically, high efficiency motors are economically justified when exchanging a motor that needs replacement. The best savings are achieved on motors running for long hours at high loads. Replacing a motor with a high efficiency motor is often a better choice than rewinding a motor. The practice of rewinding motors currently has no quality or efficiency standards.
iii New Burners In many areas, new air quality regulation will demand refineries to reduce NOx and VOC emissions from furnaces and boilers. Instead of installing expensive selective catalytic reduction (SCR) flue gas treatment plants, new burner technology developed by ChevronTexaco, in collaboration with John Zink Co., for refinery applications based on the lean premix concept, reduces NOx emissions from 180 ppm to below 20 ppm.
ii
Case Study 27 : Installation of High efficiency furnace in Hydro-finishing unit Brief In a refinery, the existing old furnace (with radiation section only) in HFU was replaced with new high efficiency furnace (with both radiation & convection section) and with Low NOx & low excess air burners. Energy Savings Investments Fuel Savings Savings 4.514
: Rs. 200.00 Lakhs : 215 MT of IFO /annum on full T'put Operation : Rs. 19.40 Lakhs
Electric Motors
Using a "systems approach" that looks at the entire motor system (pumps, compressors, motors, and fans) to optimize supply and demand of energy services often yields the most savings. For example, in pumping, a systems approach analyzes both the supply and demand sides and how they interact, shifting the focus of the analysis from individual components to total system performance. The measures identified below reflect aspects of this system approach including matching speed and load (adjustable speed drives), sizing the system correctly, as well as upgrading system components. i
Motor Optimization
a
Sizing of Motors. Motors and pumps that are sized inappropriately result in unnecessary energy losses. Where peak loads can be reduced, motor size can also be reduced. Correcting for motor over sizing saves 1.2% of their electricity consumption, and even larger percentages for smaller motors (Xenergy, 1998).
b
iii Voltage Unbalance. Voltage unbalance degrades the performance and shortens the life of three-phase motors. A voltage unbalance causes a current unbalance, which will result torque pulsations, increased vibration and mechanical stress, increased losses, motor overheating reducing the life of a motor. It is recommended that voltage unbalance at the motor terminals does not exceed 1%. For a 100 hp motor operating 8000 hours per year, a correction of the voltage unbalance from 2.5% to 1% will result in electricity savings of 9,500 kWh. iv
Electric motors are used throughout the refinery, and represent over 80% of all electricity use in the refinery. The major applications are pumps (60% of all motor use), air compressors (15% of all motor use), fans (9%), and other applications (16%).
Higher Efficiency Motors. High efficiency motors reduce energy losses through improved design, better materials, tighter tolerances, and improved manufacturing techniques. With proper installation, energy efficient motors run cooler and consequently have higher service factors, longer bearing and insulation life and less vibration.
190
Power Factor. Inductive loads like transformers, electric motors and HID lighting may cause a low power factor. A low power factor may result in increased power consumption, and hence increased electricity costs. The power factor can be corrected by minimizing idling of electric motors, avoiding operation of equipment over its rated voltage, replacing motors by energy efficient motors and installing capacitors in the AC circuit to reduce the magnitude of reactive power in the system.
Adjustable Speed Drives (ASDS)/Variable Speed Drives (VSDs). ASDs better match speed to load requirements for motor operations. Energy use on many centrifugal systems like pumps, fans and compressors is approximately proportional to the cube of the flow rate. Hence, small reductions in flow that are proportional to motor speed can sometimes yield large energy savings. Paybacks for installing new ASD motors in new systems or plants can be as low as 1.1 years (Martin et al., 2000). The installation of ASDs improves overall productivity, controls product quality and reduces wear on equipment, thereby reducing maintenance cost.
Case study 28 : Installation of Variable Speed Drives for pumps in DM plant and CPU plant Brief The major pumps in DM water plant and condensate polishing units have recirculation lines along with valves in order to maintain the desired line pressure in view of variable requirement. This recirculation results in bypassing of excess water from the discharge line to the supply source. The pump is operated with the constant load since variations are controlled by recirculation valve. The recirculation results in energy loss since the pump is operated on full load condition though there is variable requirement. The following table gives the measured water flows of discharge line and recirculation.
191
Energy Loss due to recirculation Pump ID code
71
59.7
37
34
27
45
Reduction in power consumption Operating hours Energy savings per annum Annual cost savings (Rs.4.50/kWh) Anticipated Investment Payback period
62
55
50.5
11.5
10
18
v
74.38
51.3
47.5
26.88
18
36
55
33
Pump discharge flow, lps
Degasser water -32
Power, Supply Recirculatio kW to n flow, lps users, lps
Energy loss % loss to due to the total recirculation, kW
: : : : : :
42 kW 8000 per year 3.36 lakh kWh Rs.15.12 lakh Rs. 21 lakh one year six months
PPP1A Condensate feed pump32 P 102 A Polished Condensate transfer pump- 32 P 101 A Total
166
Variable Voltage Controls (VVCs). In contrast to ASDs, which have variable flow requirements, VVCs are applicable to variable loads requiring constant speed. The principle of matching supply with demand, however, is the same as for ASDs.
4.5.15 It can be seen that on average about 33 % of energy is being lost due to recirculation. The energy loss due to recirculation can be avoided by installing the variable speed drives (VSD) to the pumps. Installation of variable speed drives will enable the pumps only to discharge as per the requirement by sensing the pressure in the discharge line. After installation of VSD, the recirculation valves should be fully closed to achieve the energy savings. Energy Savings Considering the minimum energy savings to the tune of 25 % (present average loss is of 33%) the total energy savings achievable in the above three pumping systems estimated and tabulated below:
In the petroleum refining industry, about 59% of all electricity use in motors is for pumps (Xenergy, 1998). This equals 48% of the total electrical energy in refineries, making pumps the single largest electricity user in a refinery. Pumps are used throughout the entire plant to generate a pressure and move liquids. Studies have shown that over 20% of the energy consumed by these systems could be saved through equipment or control system changes (Xenergy, 1998). It is important to note that initial costs are only a fraction of the life cycle costs of a pump system. In general, for a pump system with a lifetime of 20 years, the initial capital costs of the pump and motor make up merely 2.5% of the total costs (Best Practice Programme, 1998). Depending on the pump application, energy costs may make up about 95% of the lifetime costs of the pump.
Degasser water 32 PPP1A Condensate feed pump32 P 102 A Polished Condensate transfer pump32 P 101 A Total
In v e s tm e n t r e q u ir e d , R s . la k h s
Annual cost s a v in g s , R s . la k h
Annual e n e rg y s a v in g s , la k h k W h
E n e rg y s a v in g s
P o w e r, kW
No. of pum ps o p e r a te d
No. of pum ps in s ta lle d
i Pump ID code
3
1
59.7
15
1.20
5.40
5.00
3
1
55
14
1.12
5.04
5.00
3
1
51.3
13
1.04
4.68
5.00
166
42
3.36
15.12
15.00
192
Pumps
• • • • • • •
Operations and Maintenance. Inadequate maintenance at times lowers pump system efficiency, causes pumps to wear out more quickly and increases costs. Better maintenance will reduce these problems and save energy. Proper maintenance includes the following (Hydraulic Institute, 1994; LBNL et al., 1999): Replacement of worn impellers. Bearing inspection and repair. Bearing lubrication once annually or semiannually. Inspection and replacement of packing seals. Inspection and replacement of mechanical seals. Wear ring and impeller replacement. Pump/motor alignment check.
Typical energy savings for operations and maintenance are estimated to be between 2 and 7% of pumping electricity use. The payback is usually one year (Xenergy, 1998; U.S. DOE-OIT, 2002c). ii
Monitoring. Monitoring in conjunction with operations and maintenance can be used to detect problems and determine solutions to create a more efficient system. Monitoring can determine clearances that need be adjusted, indicate blockage, impeller damage, inadequate suction, operation outside preferences, clogged or gas-filled pumps or pipes, or worn out pumps. Monitoring should include:
193
• • • • • •
Wear monitoring Vibration analyses Pressure and flow monitoring Current or power monitoring Differential head and temperature rise across the pump/ thermodynamic monitoring Distribution system inspection for scaling or contaminant build-up
iii Reduce Need. Holding tanks can be used to equalize the flow over the production cycle, enhancing energy efficiency and potentially reducing the need to add pump capacity. In addition, bypass loops and other unnecessary flows should be eliminated. Energy savings may be as high as 5-10% for each of these steps (Easton Consultants, 1995).
vii Trimming Impeller or Shaving Sheaves. If a large differential pressure exists at the operating rate of flow, the impeller diameter can be trimmed so that the pump does not develop as much head Case study 30 : Trimming the Diameter of Pump Impeller Brief Salt Union Ltd. produces white salt by the multistage evaporation of brine. A byproduct of the process is condensate, which is exported to a nearby power station to feed the boiler. Operational analysis showed that the pressure generated by the condensate export pump was considerably higher than was necessary. The high degree of throttling that was consequently needed had led to instability in the system, resulting in mal-operation and high maintenance costs.
Case study 29 : Optimisation of Cooling Water Flow Energy savings Brief Three numbers of cooling water pumps were used to supply cooling water to refinery units. Excess flow /wastage of cooling water observed in AVU and DCU plant. The problem of cooling water system is not the flow but the low pressure of the cooling water, hence by stopping one of the cooling water pumps and optimizing cooling water in AVU and DCU and installation of one small booster pump of maintaining supply header pressure at 4.5 kg/cm2 can save 257 kW per hour, which is equivalent to 21.6 lakhs kwhr/year. Energy savings Investment costs : Rs. 10 lakhs (for the installation of booster pump) Savings achieved : Rs. 15 lakhs Pay back period : 8 months iv
More Efficient Pumps. According to Easton Consultants, 1995, pump efficiency may degrade 10 to 25% in its lifetime. Replacing a pump with a new efficient one saves between 2 to 10% of its energy consumption (Elliott, 1994).
v
Correct Sizing Of Pump(s) (Matching Pump To Intended Duty). Pumps that are sized inappropriately result in unnecessary losses. Where peak loads can be reduced, pump size can also be reduced. Correcting for pump over sizing can save 15 to 25% of electricity consumption for pumping (Easton Consultants, 1995).
vi
Use Multiple Pumps. Often using multiple pumps is the most cost-effective and most energy efficient solution for varying loads, particularly in a static head-dominated system. Installing parallel systems for highly variable loads saves 10 to 50% of the electricity consumption for pumping (Easton Consultants, 1995). Variable speed controls should also be considered for dynamic systems.
194
Trimming the diameter of pump impeller resulted in reducing power required by the pump and also allowed a smaller motor to be fitted which further resulted in energy savings. Potential users Investment costs Savings achieved (a) Energy Saving (b) Savings in repair & maintenance
: Any user of pumps : Rs. 20,000.00
Payback period
: 8 days
: Rs. 7,50,000.00 : Rs. 2,50,000.00
viii Controls. Remote controls enable pumping systems to be started and stopped more quickly and accurately when needed, and reduce the required labor. In addition to energy savings, the control system reduces maintenance costs and increases the pumping system's equipment life. ix
Adjustable Speed Drives (ASDs). ASDs better match speed to load requirements for pumps where, as for motors, energy use is approximately proportional to the cube of the flow rate. Hence, small reductions in flow that are proportional to pump speed may yield large energy savings. In addition, the installation of ASDs improves overall productivity, and product quality, and reduces wear on equipment, thereby reducing future maintenance costs.
x
Avoid Throttling Valves. Extensive use of throttling valves or bypass loops may be an indication of an oversized pump. Variable speed drives or on off regulated systems always save energy compared to throttling valves (Hovstadius, 2002).
195
xi
Correct Sizing Of Pipes. Similar to pumps, undersized pipes also result in unnecessary losses. Increasing the pipe diameter may save energy but must be balanced with costs for pump system components. Correct sizing of pipes should be done at the design or system retrofit stages where costs may not be restrictive.
xii Replace Belt Drives. Inventory data suggests 4% of pumps have V-belt drives, many of which can be replaced with direct couplings to save energy (Xenergy, 1998). Savings are estimated at 1%. xiii Precision Castings, Surface Coatings, Or Polishing. The use of castings, coatings, or polishing reduces surface roughness that in turn, increases energy efficiency. It may also help maintain efficiency over time. Energy savings for coating pump surfaces are estimated to be 2 to 3% over uncoated pumps (Best Practice Programme, 1998).
T-5 lights and ballasts in the market and the correct combination should be chosen for each system. iii Replace Mercury Lights by Metal Halide or High-Pressure Sodium Lights. In industries where color rendition is critical, metal halide lamps save 50% energy compared to mercury or fluorescent lamps. Where color rendition is not critical, high-pressure sodium lamps offer energy savings of 50 to 60% compared to mercury lamps. High-pressure sodium and metal halide lamps also produce less heat, reducing HVAC loads. In addition to energy reductions, the metal halide lights provide better lighting, provide better distribution of light across work surfaces, improve color rendition, and reduce operating costs (GM, 2001). iv
Replace Standard Metal Halide HID With High-Intensity Fluorescent Lights. Advantages of the high efficiency fluorescent lamps are many: lower energy consumption, lower lumen depreciation over the lifetime of the lamp, better dimming options, faster start-up and restrike capability, better color rendition, higher pupil lumens ratings, and less glare (Martin et al., 2000). High-intensity fluorescent systems yield 50% electricity savings over standard metal halide HID.
xiv Sealings. Seal failure accounts for up to 70% of pump failures in many applications (Hydraulic Institute and Europump, 2001). The sealing arrangements on pumps will contribute to the power absorbed. Often the use of gas barrier seals, balanced seals, and no- contacting labyrinth seals optimize pump efficiency. xv Curtailing Leakage Through Clearance Reduction. Internal leakage losses are a result of differential pressure across the clearance between the impeller and the pump casing. The larger the clearance, the greater is the internal leakage causing inefficiencies. The normal clearance in new pumps ranges from 0.35 to 1.0 mm (Hydraulic Institute and Europump, 2001). With wider clearances, the leakage increases almost linearly with the clearance. For example, a clearance of 5 mm decreases the efficiency by 7 to 15% in closed impellers and by 10 to 22% in semi-open impellers.
v
Replace Magnetic Ballasts With Electronic Ballasts. A ballast is a mechanism that regulates the amount of electricity required to start a lighting fixture and maintain a steady output of light. Electronic ballasts save 12 to 25% power over their magnetic predecessors (EPA, 2001). If automatic daylight sensing, occupancy sensing and manual dimming are included with the ballasts, savings can be greater than 65% (Turiel et al., 1995).
vi
xvi Dry Vacuum Pumps. Dry vacuum pumps were introduced in the semiconductor industry in Japan in the mid-1980s. The advantages of a dry vacuum pump are high energy efficiency, increased reliability, and reduced air and water pollution. It is expected that dry vacuum pumps will displace oilsealed pumps (Ryans and Bays, 2001) in the next 5 to 7 years. Dry pumps have major advantages in applications where contamination is a concern.
Reflectors. A reflector is a highly polished "mirror-like" component that directs light downward, reducing light loss within a fixture. Reflectors can minimize required wattage effectively.
vii Light Emitting Diodes (LEDs) or Radium Lights. One way to reduce energy costs is simply switching from incandescent lamps to LEDs or radium strips in exit sign lighting. LEDs use about 90% less energy than conventional exit signs (Anaheim Public Utilities, 2001).
4.5.16
Case study 31 : Using Energy Transformer for Plant Lighting
Lighting
Lighting and other utilities represent less than 3% of electricity use in refineries. Still, potential energy efficiency improvement measures exist, and may contribute to an overall energy management strategy. Because of the relative minor importance of lighting and other utilities, this Energy Guide focuses on the most important measures that can be undertaken. i
Lighting Controls. Lights can be shut off during non-working hours by automatic controls, such as occupancy sensors. Manual controls can also be used in addition to automatic controls to save additional energy in small areas.
ii
Replace T-12 Tubes by T-5 Tubes or Metal Halides. The initial output for T12 lights is high, but energy consumption is also high. T-12 tubes have poor efficacy, lamp life, lumen depreciation and color rendering index. Because of this, maintenance and energy costs are high. Replacing T-12 lamps with T-5 lamps approximately doubles the efficacy of the former. There are a number of 196
Brief The actual wattage of lamps used is always higher than the manufacturer's rated wattage and it depends mainly on the characteristic of the Ballast with which the particular lamp is operated on the mains supply voltage at any given time. Thus saving can be achieved. By using energy saving transformer for plant lighting in a refinery, 20% power consumption reduction has been possible in two major units, i.e. Crude Distillation unit and hydrocracker resulting in saving of 9 lakhs kwhr/year. Energy Savings Investment costs Savings achieved Pay back period 197
: Rs. 4.46 lakhs (for the transformer) : Rs. 27 Lakhs/annum : 2 months
Case study 32 : Replacement of conventional tube-lights with energy efficient tube-lights
iii
Brief During the course of the audit it was found that there are around 3500 nos. of conventional 40W fluorescent tube-lights installed in the plant and operating on the normal copper chokes. These type of fittings take more power as compared to the energy efficient tube-lights now available in the market. It is therefore recommended to replace all the existing conventional tube light fittings with the energy efficient tube-lights along-with electronic ballast. The cost benefit analysis of replacing the existing fluorescent tube-lights (FTLs) with T-5 is substantial. Energy Savings INSTALLATION OF T -5 FTLs WITH ELECTRONIC BALLAST IN PLACE OF EXISTING CONVENTIONAL FTLs Number of tube-lights
4.5.18
Power Generation
Most refineries have some form of onsite power generation. In fact, refineries offer an excellent opportunity for energy efficient power generation in the form of combined heat and power production (CHP). CHP provides the opportunity to use internally generated fuels for power production, and allowing greater independence of grid operation. This increases reliability of supply as well as the costeffectiveness.
3500
Present power consumption per tube-light
W
48
Total power consumption by these tube lights
kW
168
replacement with T-5 & electronic ballast
W
28
New power consumption
kW
98
Power saved
kW
70
Annual operating time
hrs
3300
Annual energy savings
kWh
231000
Cost benefit
Rs. Lacs
10.40
Expected Investment
Rs. Lacs
19.25
Payback period
months
22
Power consumption per tube light after
4.5.17
High Efficiency Belts (Cog Belts). Belts make up a variable, but significant portion of the fan system in many plants. It is estimated that about half of the fan systems use standard V- belts, and about two-thirds of these could be replaced by more efficient cog belts (Xenergy, 1998). Standard V-belts tend to stretch, slip, bend and compress, resulting in loss of efficiency. Replacing standard V-belts with cog belts can save energy, even as a retrofit. Cog belts run cooler, last longer, require less maintenance and have an efficiency that is about 2% higher than standard V-belts. Typical payback periods is less than one year.
Fans
Fans are used in boilers, furnaces, cooling towers, and many other applications. As in other motor applications, considerable opportunities exist to upgrade the performance and improve the energy efficiency of fan systems. Efficiencies of fan systems vary considerably across impeller types (Xenergy,1998). However, the cost-effectiveness of energy efficiency opportunities depends strongly on the characteristics of the individual system. i
Fan Oversizing. Most of the fans are oversized for the particular application, which can result in efficiency losses. However, it may often be more costeffective to control the speed, than to replace the fan system.
ii
Adjustable Speed Drive (ASD). Significant energy savings can be achieved by installing adjustable speed drives on fans. Savings may vary between 14 and 49% when retrofitting fans with ASDs (Xnergy, 1998)
198
i
Combined Heat and Power Generation (CHP)
The petroleum refining industry is one of the largest users of cogeneration or CHP in the country. Total installed capacity is next only to the chemical and pulp & paper industry. Still, only about 10% of all steam used in refineries is generated in cogeneration units. Hence, the petroleum refining industry is also identified as one of the industries with the largest potential for increased application of CHP. Wherever process heat, steam, or cooling and electricity are used, cogeneration plants are significantly more efficient than standard power plants because they take advantage of what are losses in conventional power plants by utilizing waste heat. In addition, transportation losses are minimized when CHP systems are located at or near the refinery. Innovative gas turbine technologies can make CHP more attractive for sites with large variations in heat demand. Steam injected gas turbines (STIG or Cheng cycle) can absorb excess steam, e.g., due to seasonal reduced heating needs, to boost power production by injecting the steam in the turbine. The size of typical STIGs starts around 5 MWe, and is currently scaled up to sizes of 125 MW. STIGs have been installed at various sites worldwide, especially in Japan, Europe and in the United States. Energy savings and payback period will depend on the local circumstances (e.g., energy patterns, power sales, conditions). Steam turbines are often used as part of the CHP system in a refinery or as standalone systems for power generation. The efficiency of the steam turbine is determined by the inlet steam pressure and temperature as well as the outlet pressure. Each turbine is designed for a certain steam inlet pressure and temperature. The operators should make sure that the steam inlet temperature and pressure are optimal. An 18°F decrease in steam inlet temperature will reduce the efficiency of the steam turbine by 1.1% (Patel and Nath, 2000). Similarly, maintaining exhaust vacuum of a condensing turbine or the outlet pressure of a backpressure turbine too high will result in efficiency losses.
199
Case study 33 : Installation of lower capacity Pump in HRSG Brief Installation of a smaller pump of rated capacity 37m3/hr for feeding water to Heat Recovery Steam Generator (HRSG-5) and input power requirement of new 45 kw pump motor is available from the steam turbine (which will be able to produce max 150 kw). This could replace the existing pump/motor which consumes 146 kw for supplying the water to HRSG-4. The saving of 146 kw is achieved by installing a lower capacity pump. By this, the requirement of PRV is to reduce 6.5 TPH of MP steam to LP steam for process required. Energy Savings Investment costs Savings achieved Pay back period ii
Entrained bed IGCC technology is basically developed for refinery applications, but is also used for the gasification of coal. Hence, the major gasification technology developers were oil companies like Shell and Texaco. IGCC provides a low-cost opportunity to reduce emissions (SOx, NOx) when compared to combustion of the residue, and to process the heavy bottoms and residues while producing power and/or feedstocks for the refinery.
: Rs. 22 lakhs : Rs. 8.6Lakhs : 2.6 years
Steam Expansion Turbines
Steam is generated at high pressures, but often the pressure is reduced to allow the steam to be used by different processes. For example, steam is generated at 120 to 150 psig. This steam then flows through the distribution system within the plant. The pressure is reduced to as low as 10-15 psig for use in different process. Once the heat has been extracted, the condensate is often returned to the steam generating plant. Typically, the pressure reduction is accomplished through a pressure reduction valve (PRV). These valves do not recover the energy embodied in the pressure drop. This energy could be recovered by using a micro scale backpressure steam turbine. Several manufactures produce these turbine sets. iii High-temperature CHP Turbines can be pre-coupled to a crude distillation unit (or other continuously operated processes with an applicable temperature range). The off gases of the gas turbine can be used to supply the heat for the distillation furnace, if the outlet temperature of the turbine is high enough. One option is the so-called 'repowering' option. In this option, the furnace is not modified, but the combustion air fans in the furnace are replaced by a gas turbine. The exhaust gases still contain a considerable amount of oxygen, and can thus be used as combustion air for the furnaces. The gas turbine can deliver up to 20% of the furnace heat. Another option, with a larger CHP potential and associated energy savings, is "high- temperature CHP". In this case, the flue gases of a CHP plant are used to heat the input of a furnace or to preheat the combustion air. iv
Due to the limited oxygen supply, the heavy fractions are gasified to a mixture of carbon monoxide and hydrogen. Sulfur can easily be removed in the form of H2S to produce elemental sulfur. The synthesis gas can be used as feedstock for chemical processes. However, the most attractive application seems to be generation of power in an Integrated Gasifier Combined Cycle (IGCC). In this installation the synthesis gas is combusted in a gas turbine (with an adapted combustion chamber to handle the low to medium-BTU gas) generating electricity. The hot flue gases are used to generate steam. The steam can be used onsite or used in a steam turbine to produce additional electricity (i.e., the combined cycle). Cogeneration efficiencies can be up to 75% (LHV) and for power production alone the efficiency is estimated at 38-39% (Marano, 2003).
Gasification
Gasification provides the opportunity for cogeneration using the heavy bottom fraction and refinery residues (Marano, 2003). Because of the increased demand for lighter products and increased use of conversion processes, refineries will have to manage an increasing stream of heavy bottoms and residues. Gasification of the heavy fractions and coke to produce synthesis gas can help to efficiently remove these by-products. The state-of-the-art gasification processes combine the heavy by-products with oxygen at high temperature in an entrained bed gasifier. 200
IGCC is being used by the Shell refinery in Netherlands to treat residues from the hydrocracker and other residues to generate 110 MWe of power and 285 tonnes of hydrogen for the refinery. The investment costs will vary by capacity and products of the installation. The capital costs of a gasification unit consuming 2,000 tons per day of heavy residue would cost about $229 million of the production of hydrogen and $347 million for an IGCC unit. The operating cost savings will depend on the costs of power, natural gas, and the costs of heavy residue disposal or processing. 4.6
Refinery Environmental Issues
Refineries are industrial sites that manage huge amounts of raw materials and products and are intensive consumers of energy and water. In their storage and refining processes, refineries generate emissions to the atmosphere, to the water and to the soil, to the extent that environmental management has become a major factor for refineries. The type and quantity of refinery emissions to the environment are oxides of carbon, nitrogen and sulphur, particulates mainly generated from combustion processes, and volatile organic carbons. Water is used intensively in a refinery as process water and for cooling purposes. The main water contaminates are hydrocarbons, sulphides, ammonia and some metals. In the context of the huge amount of raw material that are processed, refineries do not generate substantial quantities of waste. Currently, waste generated by refineries are dominated by sludges, and spent chemicals e.g. acids, amines, catalysts. Emissions to air are the main pollutants generated by the oil refineries. For every million ton of crude oil processed, refineries emit from 20000 - 820000 tonnes of carbon dioxide, 60-700 tonnes of nitrogen oxides, 10 - 3000 tonnes of particulate matter, 30 - 6000 tonnes of sulphur oxides and 50 - 6000 tonnes of volatile organic chemicals. To process per million tonnes of crude oil, refineries generated 0.1 to 5 Million of waste water and 10 - 2000 tonnes of solid waste. These big differences in emissions can be partially explained by the differences in integration and type of refineries e.g. simple vs. complex. A large number of techniques have been considered in the determination of best available techniques to combat emissions in various refining processes. 201
4.6.1 Crude Desalting Increased efficiency of desalters may reduce wash water usage. Other environmental benefits would be limited to energy savings, related to more efficient electric field. Available Techniques to Combat Emissions
The following table gives example of the air emissions generated by the atmospheric and vacuum distillation units by two European refineries. These tables include the emissions from combustion of fuels in the furnaces. Table 4.19 Examples of air emissions generated by crude oil and vacuum distillation units Installation
(i) Enhance the oil/water separation before discharge to the waste water treatment plant
Fuel Consumption (GWh/yr)
CDU 1138.8
The system results in oil/ water separation, reducing the charge of oil to the waste water treatment and recycling it to the process as well as reductions in the oily sludge generation. With the application of the technique some to the API separators. (ii)
Enhance the solid/ water-oil separation
By using water at low pressure and loss shear mixing device, the content of oil in the generated sludges can be decreased and the separation of the sludges from the water phase can be enhanced. In a few refineries, desalters have been equipped with a bottom flushing system. (iii)
Re-use of water for the desalter
By reusing the water, the refinery could reduce the hydraulic loading to the waste water treatment units and reduce consumption of water. (iv)
Stripping of the desalter brine
Strip desalter brine for hydrocarbons, sour components and ammonia removal before sending treatment This can be resulted in reduction of the hydrocarbon, sulphur and ammonia content of the waste water generated within the desalter. For example, phenol emissions can be reduced by 90% and benzene emissions by 95%. 4.6.2
Distillation CDU/ VDU
Potential releases into the air from primary distillation units are: • • • • •
• • •
Flue gases arising from the combustion of fuels in the furnaces to heat the crude oil. Pressure relief valves on column overheads; relief from overhead accumulator are piped to flare as well as the vent points. Poor containment in overhead systems, including barometric sumps and vents. Glands and seals on pumps, compressors and valves. De-coking vents from process heaters. During furnace decoking, some emission of soot can occur if operation is not properly controlled in terms of temperature or steam/ air injection. Venting during clean-out procedures. Some light gases leaving the top of the condensers on the vacuum distillation column. Fugitive emissions from atmospheric and vacuum distillation units alone account for 5-190 t/yr for a refinery with a crude capacity of around 8.5 MT/ yr.
202
Vacuum Distillation
639.5
Throughput (MT/yr)
8.5 Crude Oil 4.5 Atm. Res.
Units
SO2
3
35 35.2 35 19.8
mg/m t/yr 3 mg/m t/yr
NOx
CO
100 100.4 100 56.6
100 100.4 100 56.6
CO2
220927 182252
Particulates
5 5 5 2.8
Process Waste Water Process waste water generated in the atmospheric distillation units is 0.08 - 0.75 m3 per tonne of crude oil processed. It contains oil, H2S, suspended solids, chlorides, mercaptans, phenol, an elevated pH, and ammonia and caustic soda used in column overhead corrosion protection. It is generated in the overhead condensers, in the fractionators and can also become contaminated from spillages and leaks. The overheads reflux drum (gasoil dryer condensator) generates 0.5% water on crude + 1.5% steam on feed with a composition of H2S 10 - 200 mg/I and NH3 10 - 30 mg/I. Sour water is normally sent to water stripper/treatment. Wastewater (sour water) is generated in the vacuum distillation units from process steam injection in furnace and vacuum tower. It contains H2S, NH3 and dissolved hydrocarbons. If steam ejectors and barometric condensers are used in vacuum distillation, significant amounts of oily wastewater can be generated (+10 m3/h) containing also H2S, NH3. Residual Wastes Generated Sludges can be generated from the cleaning-out of the columns. The amount depends on the mode of desludging and the base solid and water content of the crude processed. The range of solid waste generation from a crude unit of 8.5 MT/ yr ranges from 6.3 - 20 t/day. Available techniques to combat emissions (i) Treatment of non-condensables from vacuum ejector set condensor uncondensable from overhead condensers can be passed to light ends treatment or recovery systems or refinery fuel gas systems; sour uncondensable gases vented from sealed barometric pumps of vacuum distillation units should be extracted and dealt with in a manner appropriate to the nature of the sour gas. Vacuum distillation column condensers may emit 0.14 kg/m3 of vacuum feed and can be reduced to negligible levels if they are vented to heater or incinerator. Pollution reduction is achieved if vacuum gaseous streams (vent gas) are routed to an appropriate amine scrubbing unit instead of being directly burned in the process heater.
203
(ii)
Waste Water treatment and re-use
(iii)
The overhead reflux drum generates some waste water. That water can be re-used as a desalter wash water. Sour water from atmospheric and vacuum unit condensates should pass to a sour water stripper in enclosed systems to optimize water re-use by application of side-stream softening to blowdown streams. This reduces water consumption and reabsorb pollutants. (iii)
Other techniques to consider in the atmospheric units are:-
4.6.3 Fluid Catalytic Cracking - FCC This section gives emission information from the FCC when it is run under favourable conditions and the regenerator in total combustion mode. The catcracker is the source of SO2 and Nox, CO2, CO, dust particulates, N2O, SO3, metals, hydrocarbons (ex. Aldehydes) and ammonia emissions. For example, the basic design of a FCC includes two-stage cyclones in the regenerator vessel, which prevent the bulk of the fine catalyst used from escaping from the system. However, smaller catalyst particles, some of which are introduced with fresh catalyst and some created by attrition in the circulating system, are not easily retained by the two-stage cyclone system. Consequently, in many cases, other abatement techniques can be included to complement the process abatement techniques. The table gives a summary of the lowest emissions of pollutants to the atmosphere due to an uncontrolled catcracker. Table 4.20 Emission factors in Kg. /1000 litres of fresh feedstock
PM 0.267 0.976
Sox CO (as SO2) – 0.286 – 39.2 1.505
HC 0.630
Nox (as No2) 0.107 – 0.416
Aldehydes NH3 0.054
These systems reduce the NOx emissions by 40-80%. The outlet concentrations can be down to <200 - 400 mg/Nm3@3% O2 depending on the nitrogen content of the feedstock. Instead of ammonia, urea can be also used. The use of urea has the advantage to be more soluble in water and consequently reduce the risk of handling/ storage of NH3. (iv)
a) De-coking vents to be provided with suitable knock-out and dust suppression facilities; suitable methods of preventing emissions during clean-out procedures need to be used. b) Many oily sludges can be sent to the crude distillation or in alternative to the coking unit where they become part of the refinery products. c) Use of spend caustic instead of fresh caustic for corrosion control on distillation unit.
Selective non-catalytic reduction (SNCR)
Wet scrubbing A suitably designed wet scrubbing process will normally provide an effective removal efficiency of both SO2/SO3 and particulates. With the inclusion of an extra treatment tower, to oxidize the NO to NO2, NOx can also be removed partially.
(v)
Venturi Scrubbing Venturi scrubbing can also remove most of the sulphur dioxide present in the flue gases. Tertiary cyclones with venturi scrubber in the FCCU regenerator have reached efficiencies of 93% in reducing SO2 and particulate emissions.
4.6.4 Catalytic Reforming Air emissions from catalytic reforming arise from the process heater gas, hydrocarbons from pressure relief valves and leakages and regeneration. Hydrocarbons and dust releases may arise from venting during catalyst replacement procedures and during clean-out operations. The table 4.21 shows an example of emissions to the air generated by reformers in two European refineries. The table also shows the emissions generated by the heaters. Table 4.21 Installation
Fuel Consumption
Platformer Mider (1)
753.4
Platformer OMV
494.1
Throughput (t/yr)
1000000 Naphtha
728000 Naphtha
0.155
3
mg/m t/yr kg/t feed 3 mg/m t/yr kg/t feed
SO2
NOx
CO
CO2
Particulars
35 24.1 0.024
100 68.7 0.069
100 68.7 0.069
146152 146
5 3.4 0.003
18 8.8 0.012
170 83 0.114
5 2.4 0.003
95848 132
1 0.5 0.001
Notes: Data are related to yearly average, 3% O 2, dry conditions. (1) Emissions from the Mider refinery, only limit values are given. Loads and specific emissions were calculated.
Available Techniques to combat Emissions (i) Partial combustion mode in the regenerator The use of partial combustion mode together with a CO boiler generates less CO and Nox emissions compared with full combustion. (ii) Hydrotreatment of feed to the catcracker FCC feed hydrotreatment can reduce the sulphur content to <0.1 - 0.5% w/w (depending on the feedstock).
The amount of waste water generated in the catalytic reforming is around 1-3 litres per tonne of feestock. The waste water contains high-level of oils, suspended solids, COD and relatively low levels of H2S (sulphides), chloride, ammonia and mercaptans. Spent catalyst fines (alumina silicate and metals) may be generated from the particulate abatement techniques. Spent catalyst generated is around 20 to 25 tonnes per year for a 5 Mtonnes per year refinery. Available Techniques to combat Emissions (I) Type of catalyst promoter Ozone depleting substances (e.g. carbon tetrachloride) are sometimes used during the regeneration of the catalyst of the reformer. Emissions of such
204
205
substances should be minimized by using less harmful substitutes or by using them in confined compartments.
a
Hydrotreating and hydroprocessing generate a flow of waste water of 30-55 l/tonne. It contains H2S, NH3, high pH, phenols, hydrocarbons, suspended solids, BOD and COD. This process sour water should be sent to the sour water stripper/ treatment. Potential releases into water include HC and sulphur compounds from spillages and leaks, particularly from sour water lines. In distillate hydro treatments, solid deposits such as (NH4)2SO4 and NH4CL are formed in the cooler parts of the unit and must be removed by water wash.
(ii) Cleaning of the regeneration flue gas Regenerator flue gas containing HCI, H2S, small quantities of catalyst fines, traces of Cl2, SO2 and dioxides can be sent to a scrubber prior to release to atmosphere. This results in reduction of particulates and volatile acids (HCI, H2S). It has been reported that Cl2 filter also traps dioxins. (iii) Electrostatic precipitator in the regeneration flue gas
b
Regenerator flue gas containing HCI, H2S, small quantities of catalyst fines, traces of Cl2, SO2 and dioxins can be sent to an electrostatic precipitator prior to release to atmosphere. This results in reduction of particulate content in the flue gas coming from the regenerator.
ii
Hydrotreating Air emissions from hydrotreating may arise from process heater flue gas vents, fugitive emissions and catalyst regeneration (CO2, CO, NOx, SOx). The offgas stream may be very rich in hydrogen sulphide and light fuel gas. The fuel gas and hydrogen sulphide are typically sent to the sour gas treatment unit and sulphur recovery unit. Hydrocarbons and sulphur compounds from pressure relief valves; leakages from flanges, glands and seals on pumps, compressors and valves, particularly on sour gas and sour water lines; venting during catalyst regeneration and replacement procedures or during cleaning operations. The following table 4.22 shows two examples of emissions from hydrotreating processes. These air emissions include the emissions generated by the combustion of fuel required in those processes.
Vacuum distillate
578.2
3000000 GO 2600000 VGO
Particulars
CO2
205.9
CO
Middle distillate
Naphtha
NOx
205.9
SO2
Hydrotreater
1500000
Units
Naphtha
Throughput (t/yr)
Installation Mider
Fuel consumptio n (GWh/yr)
Table 4.22
mg/m3 t/yr kg/t feed
35 7.1 0.005
100 20.3 0014
100 20.3 0.014
39937 27
5 1 0.001
35 7.1 0.002
100 20.3 0.007
100 20.3 0.007
39937 13
5 1 0
35 18.6
100 53.2
100 53.2
164776
0.007
0.02
0.02
63
5 2.7 0.001
3
mg/m t/yr kg/t feed 3
mg/m t/yr kg/t feed
Emissions are only limit values. Loads and specific emissions were calculated. Data are related to yearly average, 3% O2, dry conditions.
206
Hydrocracking Emissions from hydrocracking units included heater stack gas containing CO, SOx, NOx, hydrocarbons and particulates that generate smoke, grit and dust in the flue gas, fugitive emissions (hydrocarbons) and catalyst regeneration (CO2, CO, NOx, SOx, and catalyst dust). Fuel gas and bleed stream will contain H2S and should be further treated. VOCs are generated by the non-condensable from vacuum ejectors set condenser.
4.6.5 Hydrogen Consuming Processes (Hydrotreater/ Hydrocracker) i
Solid Wastes generated by hydrotreatments Those processes generate spent catalyst fines (aluminium silicate and metals Co/Mo and Ni/ Mo 50 - 200 t/yr for 5 Mt/ yr refinery). For process units using expensive catalysts, contracts with the supplier exist for taking the spent catalyst back for regeneration and/ or recycling. This practice is also being adopted for other types of catalysts. During the last 20 years the use of catalytic processes has increased considerably and hence also the regeneration and rework services, particularly used to capture the water content of some streams (e.g. distillate hydrodesulphurisation).
(iv) Dioxins formation in catalytic reforming units Dioxins are typically formed in the three types (continuous, cyclic and semi regenerative) of catalytic reforming during the regeneration of the catalyst. If the regenerator flue gas is treated in a water scrubber, dioxins are transferred in waste water. In some other cases, the use of fixed bed filters have resulted in combine reduction of chlorine and dioxins.
Waste Water generated by hydrotreatments
a
Waste Water Hydrocracking generates a flow of waste water of 50-110 I per tonne processed. It contains high COD, suspended solids, H2S, NH3 and relatively low levels of BOD. The sour water from the first stage HP separator, LP separator, and overhead accumulator should be sent to the sour water stripper/ treatment. Effluent from hydro conversion processes may contain occasionally metals (Ni/ V).
b
Solid wastes Hydrocracking also generates spent catalysts fines (metals from crude oil, and hydrocarbons). Catalyst should be replaced once per <1-3 years generating an average of 50-200 t/yr for a refinery of 5 Mt/ yr. Hydroconversion normally generates between 100 and 300 t/yr of spent catalysts which contain more heavy metals than hydrocracking catalysts.
4.6.6
Hydrogen Production
The feed for the hydrogen plant consists of hydrocarbons in the range from natural gas to heavy residue oils and coke. The conventional steam reformer process produces hydrogen of 97-98% v/v purity and is the most commonly used method for hydrogen production. The second commonly used route is to transform heavy oil residues to petroleum coke and its subsequent gasification 207
Emissions levels of <1mg HF/Nm3 can be achieved. The vent gas should pass to flare not to the refinery fuel gas system; a dedicated flare /stack is normally retained for this. Fugitive emissions are also generated by this process. KF or NaF is formed during the neutralization process. The spent solution is stored and then requires regeneration with lime (or alumina).
to produce syn gas. Hydrogen production through steam reformer and coke gasification results in various types of air emissions and generation of solid waste in case of coke gasification process. i
Steam Reforming Nox emissions are the most important to consider. Other emissions such as SOx or water emissions are minimal, because low-sulphur fuel is typically used and there are few emissions other than flue gas. The choice of heat recovery system can have a major effect on NOx production, since both the amount of fuel fired and the flame temperature will be affected. NOx emissions from a steam-reforming unit using gas or light gasoline as fuels and with low NOx burners are 25-40 mg/MJ (100-140 mg/ Nm3, 3% O2). Other emissions, such as CO2, originate from carbon in the feed.
ii
b
HF alkylation effluents are a potential cause of acid excursions in refinery effluents and a high standard of control should be exercised on the neutralization treatment system, e.g. online pH monitoring. The effluent containing HF acid can be treated with lime (CaO-Ca (OH)2), AlCl3 or CaCl2 or it can be neutralized indirectly in a KOH system to produce the desired CaF2 or AlF3 (insolubles) which is separated in a settlement basin.
Coke gasification c Sulphur sorbents, such as limestone (CaCO3) or dolomite (Mg, Ca carbonate), are normally used in the gasifier, reducing drastically the sulphur content. Sulphur composition in the exhaust gas ranges from 600 to 1200 mg/Nm3 of H2S and COS. If no sorbent is used, the sulphur content of the gas will be in proportion to the sulphur in the feed. In oxygen-blown gasification, the sulphur content will be about 10000 mg/ Nm3 per percent sulphur in the feed. Ammonia is formed in the gasifier from the fuel-bound nitrogen. Ammonia in the product gas typically contained less than 5% of the fuel-bound nitrogen when limestone was present in the gasifier.
iii
Water
Solid Waste The solid waste from the process consists mainly of spent limestone and metals from the petcoke. Volatile metals and alkalis tend to accumulate on the particulate as the gas is cooled. The particulates contain a high percentage of carbon and are usually sent with the ash to a combustor, where the remaining carbon is burned and the calcium sulphide is oxidized to sulphate.
4.6.7
Alkylation
As described earlier, the alkylation process is catalyzed by using hydrofluoric acid or sulphuric acid. The main advantages of the HF alkylation process are the regeneration of HF which minimizes waste formation and disposal and also lower acid/ catalyst consumption as well as less consumption of energy and cooling. In the sulphuric acid alkylation process, the major drawback is the disposal of spent acid. i
HF- Alkylation Process
a
Effluent gases
Wastes The HF process also yields tars (polymeric material) but these are essentially free from HF. HF-containing tars are neutralized (with lime or alumina) and disposed of by incineration or blended as a fuel-oil component in small amounts because its pronounced odours. However, technology and special operating techniques such as internal acid regeneration have virtually eliminated this liquid-waste stream.
ii
Sulphuric Acid - Alkylation Process Technologies using sulphuric acid as catalyst produce very large quantities of spent acid (sulphuric and sulphonic acids) that has to be regenerated. The transport of spent and fresh acid to and from the sulphuric acid regeneration has give rise to some concern and increased the pressur on refiners to establish sulphuric acid regeneration plants near the alkylation unit. In some cases this transport to/from the regeneration facility is by pipeline. However, no major new improvements have been introduced in sulphuric acid alkylation technology dealing with the spent acid issue. Fugitive emissions from this process is similar to the HF alkylation. Potential releases in terms of air pollutants, wastewater and solid waste generated by the alkylation processes are summarized in the tables 4.23, 4.24 & 4.25 given below: Table 4.23: Air emissions generated by the alkylation processes Air Pollutant CO2, SO2, NOx and other pollutants arise from the furnaces* Hydrocarbons
HF is a very dangerous compound because of its severe corrosive nature and burning effects of both liquid and fumes to skin, eyes and mucous membranes. Consequently, storage and handling it should comply with all safety rules. Scrubber using alkylation solution (NaOH or KOH) is necessary to remove HF from the incondensable gas stream. The acid relief neutralizer is operated so as to minimize the hydrogen fluoride content of the incondensable gas stream.
208
Sulphuric acid From column heating furnaces
May be released from pressure reliefs, storage, handling operations, spillages and fugitive emissions and water and waste discharges Halogens n.a. Fluoride compounds may be released from pressure reliefs, vent gas and spillages Odours n.a. Acid-sulphide oil may be released from process shutdown ponds during maintenance work, particularly the descaling of pipes conveying hydrogen fluoride. This may be odorous * Emissions from these combustion processes are addressed i n an integrated way.
209
May be released from pressure reliefs, storage, handling operations, spillages and fugitive emissions and water and waste discharges
Hydrofluoric From column heating furnaces
Table 4.24: Waste water generated by alkylation processes Water parameter Waste Water
Hydrocarbons
Acid
Sulphuric Waste water produced in the alkylation processes has low pH, suspended solids, dissolved solids, COD, H2S, and spend acid. n.a.
Sulphuric acid
HC from separator drains (surge drum, accumulator, dryer) and spillages, and of acidic effluent containing dissolved and suspended chlorides and fluorides from the settlement pit or the process shutdown ponds. Effluents from HF scrubber are 2-8 m3/h with compositions min/ max of 1000 – 10000 ppm F; after time treatment 10 – 40 ppm F.
Sulphuric
Sludge
n.a.
Hydrocarbons
Sludge generated in the neutralization process contains hydrocarbons. Dissolved polymerization products are removed from the acid as a thick dark oil.
Acid products in the sludge
Sludge generated in the neutralization process contains sulphuric acid.
Halides
n/a
Hydrofluoric The flow 7 – 70 kg sludge per kg used HF (dry solids contents 3 – 30%) HC from spent molecular sieves, carbon packings and acid-soluble oil. Sludge generated in the neutralization process contains hydrocarbons. Dissolved polymerization products are removed from the acid as a thick dark oil. Inorganic fluorides (Na/KF) and chlorides from treatment stages. Sludge generated in the neutralization process contains CaF2. Composition of sludge is 10 – 40 ppm F after lime treatment.
Waste Water Waste water is generated from the coke removal, water bleed from coke handling, sour water from fractionator overhead, cooling operations and from the steam injection and should be treated. The amount of waste water generated in the coking processes is around 25 litres per tonne of feedstock. It contains H2S, NH3 suspended solids (coke fines with high metal contents), COD, high pH, particulate matter, particulate matter, hydrocarbons, sulphur compounds, cyanides and phenols.
Hydrofluoric
Table 4.25: Solid waste generated by the alkylation techniques Solid waste
ii
iii
Solid Wastes Solid wastes generated in the coking processes are coke dust (carbon particles and hydrocarbons) and hot oil blowdown sludges containing hydrocarbons.
iv
Delayed Coking
1.
Uncondensable vapours generated in the coking processes should not pass to the flare system. Pressure reliefs from the coke drums should pass to the quench tower. Steam generated in this process can be used to heat up other refinery processes. The delayed coking process has a low level of heat integration. The heat to maintain the coke drums at coking temperature is supplied by heating the feed and the recycle stream in a furnace. The atmospheric residue and/ or vacuum residue can be fed straight into the delayed coking unit without intermediate cooling, which results in a high heat integration level between the different units and saves a considerable amount of capital on heat exchangers.
2. 3. 4.
v
Fluid Coking Another technique that can be used to prevent emissions or increase energy integration in the fluid coking is to use the coking gas in a gas turbine of a combined cycle unit. Extra information on the application of refinery fuel gas in combined cycle units appears in Table 4.26 . Table - 4.26
4.6.8 Coking Process The most important health and safety aspect of coking processes is the handling of the coke fines. i
Emissions to the air
Process
PM
Fluid coking units uncontrolled Fluid coking with ESP and CO boiler
1.5 0.019 6
SOx (as SO2) n.a.
CO
HC
Aldehyde
NH3
n.a.
NOx (as NO2) n.a.
n.a.
n.a.
n.a.
n.a.
Neg
Neg
n.a.
Neg
Neg
Neg: Negligible
Air emissions from coking operations include the process heater flue gas emissions and fugitive emissions. In addition, the removal of coke from the drum (delayed coking) can release particulate and any remaining hydrocarbons to the atmosphere. The main pollutants generated as well as the sources are described below: • •
•
Hydrogen sulphide and sulphur compounds in mercaptans may be released from the sour water stream from reflux condensers. Hydrocarbons may be released from pressure reliefs on reflux drums and vessels, quench tower emissions, storage and handling operations, spillages and waste and water discharges. Particulate matter may be released from the kiln gas cleaning system, the rotary cooker gas cleaning system, coke handling and storage, loading operations and from the calcinatory process. 210
Available techniques to combat emissions: I
Handling and storage of the coke
•
Cut the coke into a double roll cluster and convey it to an intermediate storage silo. Spray the coke with a very fine layer of oil, which sticks the dust fines to the coke. Covered and de-pressurized conveyor belts. Aspiration systems to extract or collect dust. Use of an enclosed hot blowdown system. Dust extraction systems can be incorporated with loading equipment.
• • • • •
211
ii
Particulate abatement in coking processes
References :
The particulate abatement technique used in the FCC (Cyclones or ESP) that may be also used here, bag filters can be used in this processes.
1. 2. 3. 4.
SO2 abatement techniques Sulphur oxides are emitted during the coking processes, especially during the calcinations processes. The principal option to reduce sulphur dioxide releases from the process is the use of the lowest possible sulphur-content feedstocks. In practice, low-sulphur feeds are typically used for product quality reasons, since a substantial part of the sulphur remains fixed in the product. iii
Separation of the oil/ coke fines from the coke-cutting water The proposed pollution prevention alternative was to retrofit the sump where the oil/ coke fines are collected with an inclined plate separator to increase the separation efficiency. Coke fines and water generated from the coke-cutting operation enter an inground sump where the solids and water are separated by gravity. A refinery study indicated that over twenty-five tones a year of coke fines entered the sewer system from that separator.
v
6.
Treatment of the waste water In the coking processes, sour water is generated (steam condensate). Consequently, all water from the coking process is send to the sour-water stripper before being sent to the waste water treatment plant.
iv
5.
7. 8. 9. 10. 11. 12. 13.
14. 15.
Control and re-use of the coke fines Coke fines are often present around the coker unit and coke storage areas. The coke fines can be collected and recycled before being washed to the sewers or migrating off-site via the wind. Collection techniques include dry sweeping the coke fines and sending the solids to be recycled or disposed of as nonhazardous waste. Another collection technique involves the use of vacuum ducts in dusty areas and vacuum hoses for manual collection which run to a small baghouse for collection. This results in reduced soil contamination by coke particulates including metals.
16. 17. 18.
19. 20.
21. 22. 23.
212
Teri Energy Data Directory & yearbook 2007, TERI Press, New Delhi World Energy Outlook, 2007, IEA Publication, Paris, France World Oil Outlook 2007, OPEC Publication, Vienna, Austria Energy Efficiency Improvement and Cost Saving opportunities for Petroleum Refineries, Ernest Worrell and Christina Galitsky, Energy Analysis Department, Ernest Orlando Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720 February, 2005 Integrated Pollution Prevention & Control Reference Document on Best Available Techniques for mineral oil & Refineries, European Union, February, 2003. Sectoral Trends in Global Energy use & GHG Emissions, Environmental Energy Technologies Divn. LBNL publication, July 2008, California Berkerley CA 94720 (USA) Annual Report 2007-08, Ministry of Petroleum and Natural Gas, GOI BP Statistical Review of World Energy, June, 2008, London UK Basic Statistics on Indian Petroleum & Natural Gas 2006-07, Ministry of Petroleum & Natural Gas, GOI India in Figures, 2007 Ministry of Statistics & Programme Implementation, GOI PPAC Ready Reckoner, Information as on 1.4.2008, PPAC, MOP&NG , New Delhi Report of the Working Group on Petroleum & Natural Gas Sector for the XI Plan (2007-2012), MOP&NG, GOI Worrel, E. and Galitsky, C. 2004, Profile of the Petroleum Refining Industry in California. Berkley, CA: Lawrence Berkley National Laboratory. LBNL55450 Zagoria, A. and R. Huycke, 2003. Refinery Hydrogen Management - The Big Picture. Hydrocarbon Processing 2 82 pp.41-46 (February, 2003) California Energy Commission (CEC) and the Office of Industrial Technologies (OIT), US Department of Energy, 2002. Case Study : Pump System Retrofit Results in Energy Savings for a Refinery, August, 2001. Van de Ruit, H. 2000. Improve Condensate Recovery Systems. Hydrocarbon Processing 12 79 pp.47-53 (December, 2000) Hydrogen Processing (HCP) 2001. Advanced Control and Information Systems 2001. Hydrogen Processing 9 80 pp.73-159 (September, 2001) Hodgson, J. and T. Walters. 2002 Optimizing Pumping systems to Minimize First or Life Cycle Costs. Proc. 19th International Pump Users Symposium, Houston, TX, February 25-28th, 2002. Copper Development Association (CDA). 2001. High-Efficiency Copper Wound Motors Mean Energy. http://energy.copper.org/motorad.html. Canadian Industry Program for Energy Conservation (CIPEC), 2001. Boilers and Heaters, Improving Energy Efficiency. Natural Resources Canada, Office of Energy Efficiency, Ottawa, Ontario, Canada. Fisher, PW and D. Brennan. 2002. Minimise Flaring with Flare Gas Recovery Hydrocarbon Processing 6 81 pp.83-85 (June, 2002) Hydraulic Institute and Europump. 2001. Pump Life Cycle Costs: A Guide to LCC Analysis for Pumping Systems. Parsippany, NJ Dunn, R.F. and G.E. Bush. 2001. Using Process Integration Technology for CLEANER production. Journal of Cleaner Production 1 9 pp.1-23.
213
24. Energy Information Administration (EIA), 2002. Petroleum Supply Annual 2001, Energy Information Administration, US Department of Energy, Washington, DC, June, 2002 25. Hydrocarbon Processing (HCP) 2001. Advanced Control and Information Systems 2001. Hydrocarbon Processing 9 80 pp.73-159 (September, 2001). 26. Integrated Pollution and Prevention Control. 2002. Reference Document on Best Available Techniques for Mineral Oil and Gas Refineries. Joint Research Centre, European Commission, Seville, Spain. 27. Ezersky, A., 2002. Technical Assessment Document: Further Study Measures 8 Flares (draft). Bay Area Air Quality Management District, San Francisco, CA 28. Golden, S.W. and S. Fulton. 2000. Low-cost Methods to Improve FCCU Energy Efficiency. Petroleum Technical Quarterly, Summer 2000, pp.95-103. 29. Hallale, N., 2001. Burning Bright : Trends in Process Integration. Chemical Engineering Progress 7 97 pp.30-41 (July, 2001) 30. Hydrocarbon Processing (HCP) 2000. Refining Processes 2000. Hydrocarbon Processing 11 79 pp.87-142 (November, 2000) 31. Parekh, P. (2000) Investment Grade Compressed Air System Audit, Analysis and Upgrade. In: Twenty-second National Industrial Energy Technology Conference Proceedings. Houston, Texas. April, 5-6: 270-279. 32. House, M.B., S.B. Lee, H. Weinstein and G. Flickinger.2002. consider Online Predictive Technology to reduce Electric Motor Maintenance Costs. Hydrocarbon Processing 7 81 pp.49-50 (July, 2002) 33. Panchal, CB and E-P. Huangfu, 2000. Effects of Mitigating Fouling on the Energy Efficiency of Crude Oil Distillation. Heat Transfer Engineering 21 pp. 3-9 34. Ingersoll Rand. 2001. Air Solutions Group-Compressed Air Systems Energy Reduction Basics. http://www.air.ingersoll-rand.com/NEW/pedward.htm. June, 2001. 35. Khorram, M. and T. Swaty.2002. US Refiners need more Hydrogen to Satisfy Future Gasoline and Diesel Specifications. Oil & Gas Journal, November 25th, 2002, pp.42-47. 36. Linnhoff March. 2000. The Methodology and Benefits of Total Site Pinch Analysis. Linnhoff March Energy Services. http://www.linnhoffmarch.com.com/resources/technical.html 37. Onsite Sycom Energy Corp. 2000. The Market and Technical Potential for Combined Heat and Power in the Industrial Sector. Energy Information Administration, US Department of Energy, Washington, DC. 38. Polley, G.T., S.J. Pugh and D.C. King. 2002. Emerging heat Exchanger Technologies for the Mitigation of Fouling in Crude Oil Preheat Trains. Proc. 24th Industrial Energy Technology Conference, Houston, TX, April 16-19, 2002. 39. Querzoli, A.L. AFA Hoadley and TES Dyron. 2002. Identification of Heat Integration Retrofit Opportunities for Crude Distillation and Residue Cracking Units. Proceedings of the 9th APCChE Congress and CHEMECA 2002, 29 September - 3 October 2002, Christchurch, NZ. 40. Radgen, P. and E. Blaustein (eds.), 2001. compressed Air Systems in the European Union, Energy, Emissions, Savings Potential and Policy Actions. Fraunhofer Institute, Karlsruhe, Germany.
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41. Integrated Pollution and Prevention Control. 2002. Reference Document on Best Available Techniques for Mineral Oil and Gas Refineries. Joint Research Centre, European Commission, Seville, Spain. 42. Venkatesan, VV and N. Iordanova. 2003. A Case Study of Steam Evaluation in a Petroleum Refinery Proc. 25th Industrial Energy Technology Conference, Houston, TX , May 13-16, 2003.
215
Notes
Chapter - 5 Exploration and Production 5.1
Introduction
India's GDP is growing at about 8-9% annually. Current projections are that this trend will continue. High growth rate demands enhanced energy inputs, particularly for a country like India where the per capita oil and gas consumption is almost onefifth of the global average. At the present rate of consumption, it is expected that India's crude oil reserves will exhaust in less than 20 years from now while its natural gas reserves will last for about 40 years. An additional strain is placed by the fluctuating price of crude. Currently, we import over 73% of our crude oil requirements. 5.1.1
Sedimentary Basins of India
India has 26 sedimentary basins of which only about 20% are moderately to well explored. The remaining sedimentary area remains to be intensively explored. Judging by the spate of recent discoveries, the areas that are yet to be explored hold enormous promise. Table - 5.1: Total Sedimentary Area: 3.14 Million Sq.Km. Level of Exploration Unexplored Exploration Initiated Poorly explored Moderate to well explored
1995-96 1.557 0.556 0.529 0.498
Area (Million Sq.Km.) 1998-99 2004-05 1.276 0.837 0.529 0.498
0.698 1.155 0.689 0.598
2006-07 0.468 1.376 0.655 0.641
Source : DGH
5.1.2
Production
Total oil production during 2007-08 was 34.11 MMT and that of gas 32.402 BCM. The contribution of Pvt/JV companies was about 18% of the total Oil & Gas production. 5.1.3
Drilling
Of the total of 415 wells drilled, 163 were exploratory and 252 were development wells. As in the previous year, the national oil companies contributed to the bulk of the drilling. A total of 1005050 meters were drilled which include 406960 meters of exploratory and 598090 meters of development drilling. 5.2
Energy Efficiency Improvement Scope In Upstream Sector
The upstream hydrocarbon sector can generally be divided into four distinct divisions: 1.
Seismic survey, Exploration & development of hydrocarbon reservoirs which primarily comprise of drilling rigs and allied equipment
217
2.
Each of these techniques has been hampered by its relatively high cost and in some cases, by the unpredictability of its effectiveness.
Production of Oil & Gas which may comprise of a. Oil collection stations b. Gas Compressor station c. Sucker Rod Pumps d. Water supply stations e. Power Station
3.
5.2.2
The EOR technique that is attracting the most new market interest is carbon dioxide (CO2)-EOR. First tried in 1972 in Scurry County, Texas, CO2 injection has been used successfully at number of locations today.
Transportation of Oil & Gas which may comprise of
The presence of an oil bearing transition zone beneath the traditionally defined base (oil-water contact) of an oil reservoir is well established. What is now clear is that, under certain geologic and hydrodynamic conditions, an additional residual oil zone (ROZ) exists below this transition zone and this resource could add further to oil resource in place and could be recoverable with state-of-the-art CO2-EOR technologies.
a. Crude Oil Pumping Stations b. Gas Compressor Stations 4.
Gas Based Petrochemical Complexes a. Petrochemical Plant b. LPG Recovery Plants c. LPG Bottling Plants
Effective and result oriented conservation methods adopted by the upstream undertakings include reduction of gas flaring by re-injection of gas to underground reservoir, installation of waste heat recovery systems, utilization of nonconventional energy sources, undertaking energy audits & efficiency up gradation of equipment & appliances, substitution of diesel with natural gas, deployment of solar-powered illumination panels, battery operated vehicles, bio-gas etc. 5.2.1
Enhanced Oil Recovery
Crude oil development and production in oil reservoirs can include up to three distinct phases: primary, secondary and tertiary (or enhanced) recovery. During primary recovery, the natural pressure of the reservoir or gravity, drive oil into the wellbore combined with artificial lift techniques (such as pumps), which bring the oil to the surface. But only about 10 percent of a reservoir's original oil in place is typically produced during primary recovery. Secondary recovery techniques to the field's productive life generally by injecting water or gas to displace oil and drive it to a production wellbore, resulting in the recovery of 20 to 40 percent of the original oil in place. However, with much of the easy-to-produce oil already recovered from oil fields, producers have attempted several tertiary, or Enhanced Oil Recovery (EOR), techniques that offer prospects for ultimately producing 30 to 60 percent or more of the reservoir's original oil in place. Three major categories of EOR have been found to be commercially successful to varying degrees: •
Thermal recovery, which involves the introduction of heat such as the injection of steam to lower the viscosity or thin the heavy viscous oil and improve its ability to flow through the reservoir.
•
Gas injection, which uses gases such as natural gas, nitrogen, or carbon dioxide that expand in a reservoir to push additional oil to a production wellbore or other gases that dissolve in the oil to lower its viscosity and improves its flow rate.
•
CO2 Injection
Chemical injection, which can involve the use of long-chained molecules called polymers to increase the effectiveness of waterfloods or the use of detergent-like surfactants to help lower the surface tension that often prevents oil droplets from moving through a reservoir. 218
Until recently, most of the CO2 used for EOR has come from naturally occurring reservoirs. But new technologies are being developed to produce CO2 from industrial applications such as natural gas processing, fertilizer, ethanol, and hydrogen plants in locations where naturally occurring reservoirs are not available. One demonstration at the Dakota Gasification Company's plant in Beulah, North Dakota is producing CO2 and delivering it by a new 204-mile pipeline to the Weyburn oil field in Saskatchewan, Canada. Encana, the field's operator, is injecting the CO2 to extend the field's productive life, hoping to add another 25 years and as much as 130 million barrels of oil that might otherwise have been abandoned. A turning point in CO2-EOR advances is a project funded by US DOE in the HallGurney field in Kansas that seeks to demonstrate this technology's time has come providing energy, economic and environmental benefits. A companion project underway in the Hall-Gurney field involves testing the feasibility of 4-D high resolution seismic monitoring of CO2 injection in thin, relatively shallow mature carbonate reservoirs. Incorporating such time-lapsed monitoring data into CO2EOR programs could dramatically improve the efficiency and economics of using the technology in many Mid-continent fields. Additional work has examined potential improvements in CO2-EOR technologies beyond the state-of-the-art that can further increase this potential. This work evaluating the potential of "game changing" improvements in oil recovery efficiency for CO2-EOR illustrates that the wide-scale implementation of next generation CO2-EOR technology advances have the potential to increase oil recovery efficiency from about one-third to over 60 percent. 5.2.3
Other Areas
Crude Oil exploration is the most energy intensive operation and is explained in detail in this chapter. The other major areas where energy is consumed and opportunities for conservation exists are listed below: 5.2.3.1 Pumping Stations The major energy consuming equipments generally are: 219
Electrical Motors: Improvement opportunity can be explored in appropriate Loading Pattern, Power Factor improvement, Mechanical Power Transmission Systems and other operational parameters. Pumping System: Improvement opportunity can be explored by optimising the pumping and allied system pressures, RPM of the engines, engine efficiencies and other operational parameters for crude oil driven engines for pumping of crude oil or product and fire fighting pumps (Engine or Motor Driven) and feasibility of reduction in the Power Consumption. Air Compressors: Improvement opportunity can be explored by analysis of various parameters like intake receiver capacity, operational Free Air Delivery (FAD) of the Air Compressors, leakages in the system, evaluation of the feasibility of Pressure Optimisation etc. Illumination System: Improvement opportunity can be explored by use of energy efficient lighting systems. DG Sets Performance: Improvement opportunity can be explored by operation of DG Sets to evaluate their average cost of Power Generation and subsequently identify areas wherein energy savings could be achieved after analysing the operational practices. Specific Energy Consumption: SEC per throughput of each station and comparison of SEC of each station should be found out and benchmarked. Diesel & Crude Oil Handling System: Improvement opportunity can be explored by monitoring energy consumption in heater in centrifuge unit, fuel forwarding modules, etc. and study the feasibility of energy conservation. 5.2.3.2
Gas Compressor Stations (GCS)
Study of Gas Compressors in GCS (Motor / Gas Engine Driven Unit): Improvement opportunity can be explored by Studying the Operational practices being adopted, Monitoring the Specific Energy Consumption, Scheduling of the Gas / Motor Driven Compressors, Formulation of specific recommendations for reduction in the overall Electrical energy/Gas Consumption. The major equipments are Motors, Air Compressors, Cooling Towers, Illumination systems. Cooling Towers: Improvement opportunity can be explored by studying the operational performance of the Cooling towers through measurements of temperature differential, air/ water flow rate and then evaluate specific performance parameters like approach, efficiency etc.
Consumption vs. Power Generated and by improving performance with reduced specific electrical energy consumption. The major equipments are electrical system network, motors, air compressors, Cooling Towers, Illumination systems, where energy conservation opportunities can be explored. Electrical System Network: Improvement opportunity can be explored by study of all the Transformer operations of various Ratings / Capacities, their Operational Pattern, Loading, No Load Losses, Power Factor Measurement on the Main Power Distribution Boards and possible improvements in energy metering systems for better control and monitoring. 5.2.3.5 Sucker Rod Pumps The major equipments are motors, DG Sets, Illumination systems, etc. 5.2.3.6 Gas Processing Plants The major equipments consists of motors, pumps, steam systems, HRSGs, Boilers, Captive Power houses, Gas Turbines, Steam turbines, Gas Compressors, Air Compressors, Steam Traps, Illumination, Heaters, distillation/ separation columns, cooling towers, transformers, electrical system networks, air conditioning etc. Case Study 1: Energy Audit of a major Gas based Petrochemical Complex Brief The Petrochemical Complex is designed to process 12 million metric standard cubic meter per day (MMSCMD) of natural gas to produce 440,000 TPA of Ethylene in the first phase and down stream products, such as the various grades of high density polyethylene (HDPE) and linear low density polyethylene (LLDPE). A LPG recovery unit is being installed and successfully producing 258250 TPA of LPG and 71,000 TPA of Propane from the natural gas. The main energy sources of the plant are electricity and Natural gas. The plant consumes about 42 Million kWh electrical units per annum (from the grid), around 240 Million from in-house and natural gas quantity of 363 Million sm3 per annum. Energy savings Summary of Energy Savings Description Electricity @ Rs. 4.5/kWh Lean Gas @ Rs. 10/SCM
Unit Million kWh/annum MMSCM*/annum
Quantity 25.8 13.0
* MMSCM = 106 Standard Cubic Metre
5.2.3.3 Water Supply Station The major equipments are motors, pumps and Illumination systems 5.2.3.4 Power Station Improvement opportunity can be explored by evaluating the operational efficiency of turbines & alternators, Evaluation of the Specific Energy Consumption pattern of the Gas/Steam Turbine as well as allied equipment, Load rationalization & overall reduction in the Specific Energy Consumption, Evaluation of Specific Gas/Steam
220
Annual savings Investment required Payback period
: Rs. 246.3 Million : Rs. 124.7 Million : 6 months
Thermal Energy Systems The Plant has three utility boilers UB#1, UB#2 & UB#3, each designed to generate VHP steam at 105 kg/cm2 and 515oC. The VHP steam generated in the utility boilers
221
is used in utility steam turbines for power generation and subsequently for driving the boiler auxiliaries and for process heat applications. The recommendations pertaining to the operation of the two boilers (UB#1 & UB#3), which were in operation during the field visit of the audit are as follows: •
Optimization of excess air in Utility Boiler UB#2
The boiler was operating at a high excess air level of 68%, whereas the recommended level is 10%, resulting in high flue gas losses. As a result, the boiler efficiency dropped by 4 percent points to 91% (NCV basis) as against the design value of 95%. By maintaining the O2% in flue gases always below 3% (in order to keep excess air level below 15%) by continuous monitoring of O2% in flue gases and thereby regulating the combustion airflow to the boiler, a saving of 1 MMSCM of gas per year can be achieved. Annual savings Investment required Payback period •
: Rs. 10.0 Million : Rs. 5.0 Million : 6 months
Optimization of excess air in Utility Boiler UB#3
The boiler was operating at a high excess air level of 46%, whereas the recommended level is 10%, resulting in high flue gas losses. As a result, the boiler efficiency dropped by 6 percent points to 80% (GCV basis) as against the design value of 86%. By maintaining the O2% in flue gases always below 3% (in order to keep excess air level below 15%) by continuous monitoring of O2% in flue gases and thereby regulating the combustion airflow to the boiler, a saving of 0.9 MMSCM of gas per year can be achieved. Annual savings Investment required Payback period •
It was found that the efficiency of the steam turbine driven UB#2 FD fan was much below (23%) the desirable efficiency level (60%). Hence, by replacing the existing FD Fan of UB#2 with an energy efficient fan, a saving of 0.3 Million kWh per year can be achieved.
•
•
The operational efficiency of UB#3 FD fan was poor (13%) compared to the desirable efficiency level (60%). Hence, by replacing the existing FD Fan with an energy efficient FD Fan, a saving of 0.82 Million kWh per year can be achieved.
222
Boiler feed water pump (Utility boiler#2)
Annual savings Investment required Payback period •
: Rs. 1.9 Million : Rs. 5.0 Million : 32 months
Utility Steam Turbines
The plant has installed two nos. of Steam Turbo Generators (STG#1 & STG#2); one is extraction type having a capacity of 15.5 MW and the other is condensing type of 25.5 MW, to meet the plant's electricity requirements. STG# 1 •
The observations and measurements showed that, the specific steam consumption per MW power generation is higher than the rated/design condition. This may be due to leakage in labyrinth-gland packing between two stages or any other maintenance reason like corrosion/erosion in turbine blade surface. Hence it was recommended to consult the manufacturer to ascertain the possible reasons. After rectifying the same the steam consumption may be reduced nearer to the designed requirement. The steam consumption (T/MW) in the HP and LP side is 21.23 and 12.21.
•
The measurements and analysis showed that Steam Turbine efficiency in both H.P. & L.P. stage was lower i.e. 61.8 % and 61.5 % than expected.
•
The loading of the turbine was 59%.
•
By enhancing the loading of the turbine, reducing the leakages, the operating efficiency of the turbine can be enhanced to 65% with an annual savings of 1.2 MMSCM per year.
: Rs. 1.4 Million : Rs. 3.5 Million : 29 months
Replacement of inefficient UB#3 FD Fan with that of energy efficient fan
: Rs. 3.7 Million : Rs. 3.5 Million : 11 months
The feed water pump operating efficiency was much below (38%) the desired pump efficiency level (60%) for efficient operation. By replacing the existing pump with an energy efficient pump, a saving of 0.42 Million kWh per year can be achieved.
: Rs. 9.1 Million : Rs. 5.0 Million : 6 months
Replacement of inefficient UB#2 FD Fan with that of energy efficient fan
Annual savings Investment required Payback period
Annual savings Investment required Payback period
Annual savings Investment required Payback period
: Rs. 11.9 Million : Rs. 5.0 Million : 5 months
STG#2 •
The turbine was running at low operating efficiency of 57.8 % because of operation of turbine at part load of 59 %.
•
By enhancing the loading of the turbine, reducing the leakages, the operating efficiency of the turbine can be enhanced to 65 % with an annual saving of 0.3 MMSCM per year
223
Annual savings Investment required Payback period •
: Rs. 3.3 Million : Rs. 2.5 Million : 9 months
Payback period •
Annual savings Investment required Payback period •
Steam Distribution System
-
Condensate recovery A total of 7 TPH of condensate can be recovered and reused as boiler feed water from HDPE and LPG Plants. The investment required would be in terms of additional condensate pipes, condensate pump, and insulation of the network. In addition to the fuel savings, the other benefits would be reduced costs of water treatment of 7 TPH water. The net savings would be the 0.6 MMSCM of natural gas per year. Annual savings Investment required Payback period
-
Replacement of damaged traps
Annual savings Investment required
: Rs. 2.1 Million : Rs. 0.45 Million
224
: Rs. 6.2 Million : Rs. 3.0 Million : 6 months
Arresting steam leakages The plant had steam leakages at a number of areas. By arresting the steam leakages from the identified areas (by replacing the damaged valves, pipefittings, flanges, traps, etc), a saving of 0.09 MMSCM of natural gas per year can be achieved.
: Rs. 1.7 Million : Not ascertained : NA
The plant had 44 faulty steam traps. By immediate replacement of these traps to arrest steam leakage and losses, a saving of 0.2 MMSCM of natural gas per year can be achieved.
Performance evaluation of all steam traps
•
Condensing Steam Turbine of Propylene (C3R )Refrigeration Compressor
Annual savings Investment required Payback period
: Rs. 1.0 Million : Rs. 1.0 Million approx : 12 months
The savings estimated above was based on the survey conducted on 170 traps, which form less than 20% of the total traps installed in the plant. The actual energy savings that can be achieved by steam traps maintenance would be several times higher than what has been estimated above. Therefore, it was recommended to get a survey done for all the steam traps in the plant and replace / repair the faulty traps immediately to arrest energy losses in the steam system.
: Rs. 10.2 Million : Rs. 3.0 Million : 4 months
The condensing steam turbine of C3R compressor was running at poor efficiency. This was due to leakage in labyrinth-gland packing between two stages or any other maintenance reason like corrosion/erosion in turbine blade surface. Hence it was recommended to consult the manufacturer to ascertain the possible reasons. After rectifying the same, a saving of 0.17 MMSCM of natural gas per year can be achieved.
•
•
Cracked Gas (CG) Compressor
Annual savings Investment required Payback period •
Annual savings Investment required Payback period
: Rs. 17.8 Million : Rs. 2.0 Million : 2 months
The specific steam consumption per KW shaft power in H.P. Stage was higher with respect to the rated designed condition because of low efficiency of steam turbine. By increasing the efficiency of HP as well as LP steam turbine a saving of 1 MMSCM fo natural gas can be achieved.
Maintenance of faulty steam traps By repairing the traps which are chocked and let the condensate flow smoothly out of the system to ensure effective heat transfer, a saving of 0.1 MMSCM of natural gas per year can be achieved.
Heat Recovery Steam Generators
By improving the efficiency of HRSG - I & II by de-scaling the water side surface, changing the layout of different components of the HRSG from the existing to the proposed i.e. in the sequence of Super Heater-II, Super Heater-I, Evaporator-II, Evaporator-I & Economizer, a saving of around 2% on a very conservative estimate can be achieved. The modifications will lead to increased steam generation. This increase will reduce the load on utility boilers, which will ultimately reduce the natural gas consumption by 1.8 MMSCM of natural gas per year.
: 3 months
Annual savings Investment required Payback period -
: Rs. 0.9 Million : Rs. 0.5 Million : 7 months
Improve insulation of pipes A number of areas in the steam lines had high surface temperatures. The high surface temperatures of insulated steam headers / pipes indicate the damaged or inadequate insulation. It was recommended to replace the insulation to arrest the heat losses thereby saving 0.04 MMSCM of natural gas per year.
225
Annual savings Investment required Payback period -
becomes imperative for the plant to keep a good power factor on the main incomer. For this, the plant has installed capacitors. The average PF being maintained was very close to unity, which is a good practice.
: Rs. 0.35 Million : Rs. 0.03 Million : 1 months
Installation of back pressure steam turbine in place of PRDS
•
To meet HP steam requirement, a PRDS was installed to convert VHP steam to HP steam. It was recommended to install a backpressure steam turbine in place of the PRDS. The turbine would facilitate power extraction to the extent of 2 MW and simultaneously expand the steam to the required level of 40 kg/cm2. A saving of 9.1 Million kWh per year can be achieved. Annual savings Investment required Payback period •
Furnaces
-
Improve the furnace insulation
A complete motor load survey was carried out during the energy audit so as to assess the motor loading pattern and assess the potential for motor down-sizing, application of VFD, soft starter etc. In all about 170 motors above 25kW were studied and the basis for categorising the motors as under-loaded was loading less than 50%. In all 44 motors were found to be under-loaded (26% of the motors studied). For the motors loaded less than 50%, an exercise was done to analyze the feasibility of replacement of these motors by suitably sized energy efficient motors (EEM). Few motors where the payback was less than 5 years are being recommended for such replacement. For motors that offer a payback of 5 years or less, the reduction in motor losses will be to the tune of 38.5 kW. An annual saving of 0.31 Million kWh per year can be achieved by replacing the under loaded motors.
: Rs. 40.9 Million : Rs. 37 Million : 11 months
The surface temperature at various portions of the operating furnaces were found to be high. By improving the insulation at hot spots, a saving of 0.22 MMSCM of natural gas per can be achieved. Annual savings Investment required Payback period -
: Rs. 22.3 Million : Rs. 1.75 Million : 1 month
Annual savings Investment required Payback period •
The blow down rate of Furnace#3 and Furnace#4 was high compared to that of Furnace#1 & 2. The excess blow down from these two furnaces is estimated to be 6 TPH. By reducing the blow down rate of these two furnaces to the optimum level, a saving of 0.3 MMSCM of natural gas per year can be achieved. : Rs. 3.3 Million : NIL : Immediate
Compressors:
•
It was recommended to operate 3 HT compressors in place of operating 2 LP air and 2 nitrogen compressors. The maximum air requirement for the plant is around 18400 CFM at a pressure of around 8 kg/cm2. Since three HT compressors alone can meet this requirement if scheduled properly, it is advised to operate only three HT compressors. This will save 5.7 Million kWh electrical units annually.
Transformers A complete loading analysis of the transformers was carried out. The loading pattern showed that in most of the cases, the loading was on the lower side. For most of the transformers the best efficiency point was in the loading range of 40-50%, but the transformers were found to be operating at a lesser load. This has basically been done so as to have high plant operating reliability. For the sake of reliability, the plant has compromised on higher transformer losses, which is justified owing to the critical & continuous operating schedule of the plant.
•
Capacitors:
Power Factor Study:
•
Electrical Systems •
Annual savings Investment required Payback period •
: Rs. 25.7 Million per annum : Rs. 4.0 Million : 2 months
Presently, the Khosla compressors are being used to supply air at 8 kg/cm2 to the boiler/instrumentation. During the audit it was found that the LP air compressors were also operating at 8 kg/cm2 and since there was surplus capacity of these compressors, seldom the excess air compressed by these air compressors is vented out at high pressure. It was recommended that instead of venting this high-pressure air, which represents energy loss, this air should be used to
The billing from the state electricity board was based on kVAh and hence it 226
: Rs. 1.4 Million : Rs. 0.5 Million : 5 months
During the audit of the electrical motors, the PF profiling was also done. For most of the motors it was found that the PF was quite healthy but for a few motors (20 in number out of a total of 170 studied), the PF was below 0.7, which may be due to the low loading at the point of measurements. It was advised that, for all motors, the PF should be kept as high as possible (ideally 0.95) so as to have reduced line losses, to ensure better voltage regulation at the motor end & healthy motor load performance, to take proper care regarding the loading pattern, over-hauling and re-winding practices.
Reduce blow down from Furnace # 3 and # 4
Annual savings Investment required Payback period
Motor Load Study:
227
supply boiler/instrumentation purposes & thus avoid the operation of the Khosla compressor. This will save 0.13 Million kWh electrical energy per year. Annual savings Investment required Payback period
kWh per year. Annual savings Investment required Payback period
: Rs. 0.6 Million : Rs. 0.1 Million : 2 months •
•
As service air application require air at low pressures, it was recommended to use transvector nozzles for cleaning & service air requirements. This exercise will help save 0.09 Million kWh electrical units per annum. Annual savings Investment required Payback period Lighting:
•
It was found that lighting transformers were all under-loaded. It was advised to explore the possibility of supplying adjacent areas by a single lighting transformer so as to improve the transformer loading.
•
Replacement of the conventional tube-lights, presently operating with copper chokes, around 3500 in number, by the energy efficient T-5 tube -lights and with electronic ballast was recommended. This measure will save 0.23 Million kWh units of electrical units annually. Annual savings Investment required Payback period
Installation of variable speed drives for pumps in DM plant and CPU plant Recirculation valves are installed to degasser water pump, condensate feed pump and polished condensate transfer pump. It was recommended to install VSD to these pumps to avoid recirculation thereby saving 0.33 Million kWh per year.
: Rs. 0.42 Million : Rs. 0.2 Million : 6 months
•
: Rs. 5.3 Million : Nominal : Immediate
Annual savings Investment required Payback period •
: Rs. 1.5 Million : Rs. 2.1 Million : 17 months
Replacement of DM water transfer pumps with one large pump coupled with VSD DM water transfer pumps were operating at poor efficiency and recirculation was observed across the valve. It was recommended to replace the present pumps with one large pump coupled with VSD, saving 0.34 Million kWh per year. Annual savings Investment required Payback period
: Rs. 1.04 Million : Rs. 1.93 Million : 22 months •
: Rs. 1.52 Million : Rs. 1.5 Million : 12 months
Replacement of raw water transfer pumps
Water Pumping System & Cooling Towers Raw water collected in Reservoir # 3 is transferred to Reservoir # 1 with the aid of two pumps. It was found that the actual head was too high compared to rated head and efficiency was low. It was recommended to replace the present pumps with required head pump (32 m) and thereby achieve energy savings of 0.2 Million kWh per year.
The Plant has several water pumping systems such as cooling water supply, raw water supply, DM water system in addition to three large cooling towers. •
Rationalisation of CT # 1 water pumps operation GCU (Gas Cracker Unit) section has a separate set of pumps while GPU (Gas Processing Unit) & IOP (Integrated Oxide Plant) has different set of pumps with dedicated headers. It was recommended to replace the impellers of pumps and operate as a common system thereby resulting in reduction of power consumption by 5.0 Million kWh per year. Annual savings Investment required Payback period
•
: Rs. 22.64 Million : Rs. 10.0 Million : 5 months
Reduce the discharge pressure of pumps (or) replace the pumps with suitable capacity (head and flow) for CT# 2
Annual savings Investment required Payback period •
Installation of variable speed drive to the cooling water make up pump During the audit study it was observed that there is wide variation in flow and pressure of cooling water make up pump. It was suggested to install variable speed drive to the motor and control the speed by monitoring the pressure, thereby saving 0.12 Million kWh per year of energy. Annual savings Investment required Payback period
It was recommended to verify the actual water pressure requirement and accordingly initiate the steps either to reduce the water pressure or replace the pumps with suitable head, resulting in an annual energy saving of 1.2 Million kWh per year. 228
: Rs. 0.9 Million : Rs. 0.6 Million : 8 months
229
: Rs. 0.54 Million : Rs. 0.7 Million : 16 months
•
Interconnection of RWTP # 1 and RWTP # 2 tanks and avoid the pump operation Filtered water is stored by the plant in two tanks. Both the tanks are at the same ground level. Water is transferred from one tank to the other using a pump. It was recommended to interconnect these two tanks at the bottom level to avoid the operation of pumps and result in annual energy saving of 0.3 Million kWh. Annual savings Investment required Payback period
: Rs. 1.3 Million : Rs. 0.5 Million : 5 months
5.3.1 Energy Consumption
Crude oil exploration is a very costly operation. The main equipment for oil exploration is a drilling Rig. Generally the Rig consists of the following machineries:
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
Spudding / Drilling phase: During this phase, almost all the machineries of the Rig are run and this phase consumes the maximum energy in terms of HSD. This phase continues for a period of about 100 to 120 days depending upon the depth of the well. Production Testing phase: During this phase, the samples of the well are tested and then Rig is dismantled. This stage takes about 60 days.
5.3 Energy Efficiency In Exploration Activity (Rigs)
1
takes around 20 days. For offshore operation rig moves from one location to another location either by towing or self propelled. Time taken depends on the distance to be moved.
Main Derrick consisting of a drilling platform, cat walk platform and two big pulleys. The upper pulley is called the Crown Block and the lower one called Traveling Block, through which, the winch is moved by Draw works. The Draw works may be electric driven or mechanical driven. The Draw works drills the well with the help of drilling bits and shrouded pipes. DG Sets, which are the heart of the Rig supplying power during drilling as well as Rig building phase. Mud pumps for the circulation of mud during drilling and well formation and as and when required. Supercharger pumps to supply mud to the suction of mud pumps Desilter pump for the purpose of desilting from dirty mud coming out from the well. Desander pump for the purpose of removing sand from the dirty mud coming out from the well Air compressors to cater air to winch, clutch and Twin stop cam counter of Draw works. Agitators for the purpose of mixing of mud Shale shakers Degasser Fuel Tanks & Fuel pumps Eddy current Brake for control of Draw works Bunker Lab for the testing of mud quality Bunker housing Cranes For floating rigs - anchors or dynamic positioning system. For self propelled drill ships - propulsion system. Water maker to produce drinking water on the rig Cementing unit - to cement casing against formation. Blow out preventor - to control well pressure.
Energy used in a Drilling rig is Electrical energy. This electrical energy is produced using captive mobile power generation units. In very rare cases, grid power is also used. The fuel for these power generation units is either HSD or Natural gas. The primary source of energy in a Drilling Rig is the Diesel Oil for DG sets. Most of the DGs in the exploration rigs in India are old and de-rated and are expected to consume higher fuel as compared to the design. 5.3.2
Basic Process Flow Diagram
SPUDDING
MUD CIRCULATION
DRILLING
if casing depth ok
YES
CASING
CEMENTING
HERMETICALLY SEALING
If target depth ok
Total operation of the Rig consists of following three phases:
YES
Rig building phase: During this phase, the skid mounted portable machineries are transported to the site by tailor trucks and are being installed. This stage
STOP
Figure - 5.1 230
NO
231
NO
5.3.3
Energy Management Plan
5.3.4.2 Efficient Operation of Mud Pumps
The measures identified may be short term, medium term or long term requiring nil to high investments. Medium & Long term efforts are structured and normally implemented without much efforts. One example of long-term efforts is the replacement of outdated, energy inefficient DG engines like D 399 by new energy efficient models like CAT 3516 requiring high investment of the tune of Rs 250 Crores.
This is the single largest load on a Rig consuming 50 to 60% of total energy consumed on a rig. These have an operating pressure of 5000 to 7000 psi and hydraulic efficiency is normally more than 90%. Reciprocating Pump operates at constant efficiency levels and hence has constant losses. Below are some general measures for energy conservation in a mud pump operation:
However short term programs are basically voluntary and needs to be push forwarded by:
•
• • •
Awareness generation Leadership demonstration Top management support
A good energy management plan for a Rig should generally comprise of: 5.3.4
Fuel consumption to be compared with specific energy generation. Proper log sheet for regular energy monitoring Instrumentation / software to facilitate energy logging and evaluation of specific energy generation. Energy monitoring based on norms developed. Energy monitoring to be based on drilling depth and soil condition. Segregation of AC and DC loads and have power packs dedicated to AC and DC operation. Best Operation Practices in Rigs
Best Operating Practices (BOP) is referred to operating procedures and good house keeping habits for reducing the wastage of energy, reducing & preventing environmental pollution. The overall philosophy of BOP is to conduct every day activity in more efficient, safe and environmentally sound manner.
•
•
•
•
5.3.4.3 Efficient Operation of Agitator The following information must be known to properly size an agitator system: • Tank and compartment dimensions • Compartment shape • Compartment duty (solids removal, testing, suction, storage, or pill/slug) • Maximum mud density expected • Coupling of multiple agitators to one motor • Agitator & mud gun combination gives better agitation 5.3.4.4 Efficient Operation of Air compressors
5.3.4.1 Efficient Operation of DG sets •
• • • • • •
The biggest culprit for energy wastage in mud pump is idling during lunch & shift changeover and higher discharge rate. Under loading of the prime mover is another fuel wasting situation. Suction starvation can cause performance loss and failure of pump. Entrained gas may reduce suction Efficiency Each pump should feed Separate Mud Processing Equipment. Mud temperatures of 660C can present critical suction problems A poorly designed discharge manifold can cause shock waves and excessive pressure peaks Excessive solids can: 1) cause wears on drilling equipment 2) reduce ROP (Rate of Penetration) 3) cause a thick and permeable filter cake and fluid loss 4) cause unwanted pump exertion
When the total running load during non-drilling days is small (in the range of 50 KVA), a smaller rating ( say 63 KVA) DG set should be used during non-drilling days Monitoring of specific energy generation ratio (SEGR). SEGR of a DG set is a performance indicator, which is proportional to the extent of loading of the set. At part load operation, the efficiency of the DG set drops with consequent decrease in the SEGR value. Proper monitoring of SEGR will help in conserving energy. Monitoring of Lube oil quality. The drain interval of lube oil specified by the manufacturer is based on worst operating conditions and a high factor of safety. By follow of good operating and maintenance practices, there is a distinct possibility that the condition of the lube oil remains good and usable even after the specified period. Testing of lube oil for certain physicochemical properties like viscosity, total base number, water content, insoluble build up etc, may extend the drain interval for lube oil. 232
• • • •
•
In a rig, compressed air is used for pneumatic control; start up operation of DG sets etc. Regular maintenance should be undertaken as per schedule All air leakages must be plugged In many installations, the compressors are manually switched on/off at the required pressure. Installation of automatic pressure switch with predetermined setting can save wastage of energy. Use of automatic drain valve in the air receiver. By using the auto drain valve, water would only be allowed to pass intermittently depending on the water level in the air receiver, thereby minimising the wastage of compressed air.
5.3.4.5 "Deep Trek" and Other Drilling R&D The U.S. Department of Energy's Office of Fossil Energy kicked off the 'Deep Trek' Program in 2002 to help develop high-tech drilling tools that industry needs to explore the deeper deposits of hydrocarbons. The goal was to develop a "smart" drilling system tough enough to withstand the extreme temperatures, 233
pressures and corrosive conditions of deep reservoirs, yet economical enough to make the hydrocarbons affordable to produce. The projects include advancing drilling performance, developing "smart" communication systems, instrumentation, novel drill bits and fluids, and novel pipe systems that are able to withstand the severe temperatures (over 400oF) and pressures in deep horizons.
horizontally. e)
The Microhole Technology drills small diameter boreholes (approximately two-inch diameter), using smaller sized equipments to complete microholes, and advanced diagnostic tools to measure important reservoir characteristics. The cost reduction using this technology is estimated to be nearly one-half the cost of traditional drilling rigs. The feasibility of microhole technology has been demonstrated by pioneering work conducted by Los Alamos National Laboratory (LANL) in collaboration with Maurer Technology. The team has successfully used coiled-tubing-deployed micro drilling to drill wells as small as 1-3/4-inch in diameter and as deep as 800 ft.
These "smart" drilling systems can report key measurements - temperature, pressure, fluid content, geology, etc. - as a well is drilled. Sophisticated electronic systems can identify potential trouble spots on a real-time basis, allowing operators to make adjustments without interruption or costly work stoppages. 5.3.4.6 Other Drilling Advancements a)
The Microhole Technology
5.3.5 Energy Conservation Measures In Drilling Rigs
Mud Pulse
The heart of the drilling rig is the Power Packs i.e., the DG sets which are generating power for the entire Rig by using HSD in diesel engines .The consumption of HSD in the DG sets varies between 500 lits per day to 2500 lits per day depending upon the following factors:
It is the first system to transmit drill bit location by sending pressure pulses through drilling mud, which was developed by the US Energy Department and Teleco, Inc. Today, this "mud pulse" measurement-while-drilling telemetry has become standard in the industry.
1. 2. 3. 4. 5.
b) IntelliPipe A new technology system in downhole telemetry, sponsored by US DOE called IntelliPipe turns an oil and gas drill pipe into a high-speed data transmission tool capable of sending data from the bottom of a well up to 200,000 times faster than mud pulse and other downhole telemetry technology in common use today. Potential benefits include decreased costs, improved safety, and reduced environmental impacts from drilling.
The most important factor out of the above points is the health of the DG engines. The health of engine plays the major role in the oil (HSD) consumption in the Rig. For example one of the Rigs operating in India in the north east part of India is being operated with maximum 3 nos. of DG sets for a drilling depth of about 2500 Meter and at the same time with almost same formation and same drilling depth the other Rig is being operated with 4 nos. of DG sets (both the places the ages of the engines are almost same). The reason for the same is better maintenance prevailing in the first site.
c) New drill bits The polycrystalline diamond (PDC) drill bit, now the industry standard for drilling into difficult formations, is a Revolutionary new drill bit developed by US Energy Department's research program. Scientists at the Energy Department's Sandia National Laboratories have successfully developed a "diffusion bonding" approach. More recently, Penn State University, working under an Office of Fossil Energy contract, developed a way to use microwaves to harden the tungsten carbide of deep drilling bits, resulting in a 30 percent increase in strength.
Location (formation type) Drilling hole diameter Drilling depth Health of the DG engines Pull out practice (operation of drillers foot, pull out time per pipe)
Good Maintenance Practices Checking schedule 1.
Name of the parts Liner Piston Valve insert Valve spring Valve cover gasket Water Valve Valve Sheet
d) Advanced composite drill pipe materials (Carbon fiber) The drilling system of the future may also employ new advances in drill pipe materials as a result of the Energy Department's research program. In mid 2004, the Department announced the development of a new "composite" drill pipe that is lighter, stronger and more flexible than steel, which could significantly alter the ability to drain substantially more oil and gas from rock than traditional vertical wells. The carbon fiber drill pipe is likely to weigh less than half the weight of steel drill pipe, and the lighter the pipe, the less torque and drag is created, and the greater distance a well can be drilled both vertically and 234
235
Checking after 200 Hrs 200 Hrs 24-36 Hrs 24-36 Hrs 24-36 Hrs 24-36 Hrs 24-36 Hrs
advantage of this is that at a time 3 strands can be put together for drilling operation. Hence the total time for drilling can be reduced considerably. But at the same time fuel consumption will increase during drilling phase because of additional load of electrical TOP DRIVE in place of conventional mechanical Rotary Drive. However overall energy saving is envisaged to be less in such rig operation due to less no of days required for drilling. As per GTO (Geo Technical Order) the total number of days envisaged was 368 days but as per actual status this rig operation has been estimated to be 300 days that too including 45 days of idling due to problem in the newly installed TOP DRIVE system.
Daily Checking Ø Lube oil Ø Radiator water & Radiator cap Ø Bearing condition (visually) Ø Belt Ø Leak of Fuel Ø Oil Ø Air cleaner box indicator
Quality of Radiator water plays a very important role. If possible DM water may be used and 20% coolant to be used along with the radiator water. This will ensure at least 0.5 % saving of fuel (HSD) in DG engine
Study Of Energy Consumption Pattern - Preceding Three Years Parameters
Fluid end part Name of the parts Valve insert Valve spring Valve cover gasket Water Valve Valve Sheet
HSD (LT) Consumption POL (LT) Consumption MTR DRILL kWh/MTR TOTAL kWh SFC
Checking after 24-36 Hrs 24-36 Hrs 24-36 Hrs 24-36 Hrs 24-36 Hrs
2002 - 2003 762098 14910 7869 352.53 2774058 0.2747
YEARS 2003 - 2004 1228036 28560 4752 940.67 4470064 0.2747
2004 - 2005 147420 1100 2335 134.76 314673 0.468
Rig was commissioned in March 2005 after total overhauling of DGs. Details Of DG Engines
Lube Oil
Sr No
Item
DG 1
DG 2
DG 3
DG 4
GENERAL
Lube oil selection and use plays an important role in the efficiency of DG engines Ø Lube oil consumption tells about the health of engine. Appropriate specific
lube oil consumption for D-399 Caterpillar engine is 0.5 lit/hr. If the oil consumption goes higher than this value, engine needs attention. Ø Lube oil to be changed after every 1000 Hrs (of course after checking the quality as mentioned below) Ø Use 15 W-40 after talking to OEM, in place of SAE30 as recommended by OEM. Ø Condition monitoring may be started after every 250 Hrs with the help of portable analyzer kit (cost around Rs 35000/-) Ø Lube oil to be changed when the following conditions appear • • •
TBN (Total Base Number) : Flash point : Viscosity (centistokes) :
Variation of 50% of original value. 50 Degree below the original value. 25 ± original value.
1
Engine serial no.
2XJ00014
36Z02060
36Z01988
36Z01525
2
Peak Load (kVA)
600
600
600
600
3
Total Working hrs. (Present Well)
276
276
276
276
4 5
Type of fuel Fuel Density
6
Method of checking fuel quantity
FUEL
17
Case Study 2: Energy Audit at an Onshore Drilling Rig
Manual By Tank Dip
Fuel Consumption of Present Well (as on 11.08.05 in Lts.)
HSD (Diesel) 0.865 at 150C
HSD (Diesel) 0.865 at 150C
Manual By Tank Dip
Manual By Tank Dip
HSD (Diesel) 0.865 at 150C Manual By Tank Dip
991037 Lts
SFC (Specific Fuel Consumption, lit/kWh) of DGs of the rig NO. OF DG SETS IN RIG: 04 (FOUR) ENGINE PARTICULARS
1
Present status (SFC) * Design parameter (SFC) Model Engine sl. Capacity No. 25% 50% 75% 100% 25% 50% 75% 100% DG 1 CATERPILLAR D 399 2XJ00014 1215 0.35 0.31 0.30 NA 0.324 0.2743 0.2617 0.2674
2
DG 2 CATERPILLAR D 399 36Z02060
1215
0.37 0.325 0.329 NA
0.324 0.2743 0.2617 0.2674
3
DG 3 CATERPILLAR D 399 36Z01988
1215
0.34 0.31
0.30 NA
0.324 0.2743 0.2617 0.2674
4
DG 4 CATERPILLAR D 399 36Z01523
1215
0.385 0.365 0.355 NA
0.324 0.2743 0.2617 0.2674
S.no. DG ID
Maintaining the condition of lube oil of DG set will ensure increased efficiency of the engine and a saving minimum 0.5 % HSD consumption as compared to deteriorated lube oil.
HSD (Diesel) 0.865 at 150C
Make
About The Rig All the DGs / Alternators are totally overhauled during July/ August 2004 and put back for use in THE RIG in March 2005. The Power Control Room (PCR) of the rig is absolutely new and its make is National Oil Well (Model 2001). The rig is unique as it is the only rig where Variable Frequency Driven TOP Drive system has been implemented in place of Rotary Drive System for the first time in Assam Region. The 236
* Trials were taken by isolating DGs from the existing fuel oil system and using half cut drum for supplying HSD fuel to DG set and recording the dip before and after the trial.
237
Present Fuel Consumption Of DG Sets
Estimation Of Saving Potential During Drilling Phase
SFC of DG 1 (at 35% loading) : 0.33 SFC of DG 2 (at 35% loading) : 0.33 SFC of DG 3 (at 35% loading) : 0.345 SFC of DG 4 (at 35% loading) : 0.37
Basis:
SFC Curve of DG 1 Actual vs Design SEC CURVE (% Loading of DG vs consumption of HSD) of DG engine will give the clear picture about the health of DG set at a particular point of time. More the gap between the actual and the design curve, more the aging of the engine and more care is required in terms of maintenance.
SFC,LIT/KWHr
0.45
0.4
Savings Due To Installation Of One 125 kVA DG Set For Running During Rig Building, Production Testing And Logging Operation And Simple Pay Back Period.
0.35
0.3
Basis:
0.25
0.2
0.15 0
20
40
60
80
100
% LOADING
120
SFC(DESIGN) SFC(ACTUAL)
Energy savings
SL. NO.
DESCRIPTION
SAVINGS POTENTIAL KLOE / MONTH
Running of each DG at minimum loading of 35%
21.2
Rs. (Million/ (Lakhs/m month) onth) 6.78 0.678
INVESTMENT (Rs. in lakhs)
PAYBACK MONTHS
-
Immediate
INVESTMENT (Rs. in lakhs)
PAYBACK MONTHS
8
22 months
Medium Cost Option
1
1. Load during day time 2. Load during night time 3. No. of days of duration for production testing and logging and Rig building phase 4. SFC with 125 kVA DG set with 75 % loading 5. SFC with existing big DG with 10% loading during production testing, logging operation
: 60 kW : 90 kW : 75 : 0.300 (at 75% load) : 0.40
Estimation For The Energy Saving
No Cost Option
SL. NO.
Estimation: Hence if the DGs are run at minimum loading of average 35% instead of average 25% loading monthly saving = 370800 (0.4249 - 0.3675) = 21284 lit = 21.2 KL of HSD = Rs. 0.678 Million
SFC CURVE OF DG 1 0.5
1
1. Average SFC estimated at an average loading of 25% (including drilling and idling period) during the drilling phase at 1400-23 Rig = 0.4249 lit/kWh (DG 1: 0.4219, DG2: 0.4295, DG3: 0.4269, DG4: 0.4212) 2. Average loading of DG set is increased to minimum 35% from the present average loading of 25% so as to decrease the average SFC from 0.4249 to 0 .3675 (DG 1: 0.36, DG2: 0.3675, DG3: 0.3825, DG4: 0.36) 3. Monthly average kWh measured during the trial = 370800 kWh.
DESCRIPTION
To install one no. of 125 KVA DG set to run during production testing, logging and rig building phase
SAVINGS POTENTIAL TOTAL KLOE 13.5
Rs. Millions (Lakhs) 4.32 0.432
DESCRIPTION
1
To run DG at 50% load min. in stead of 25% by installing 4 nos. of APFC at the PCR, 2 nos. of fixed capacitor bank at the DBs of 1000 HP DC motor and to install 6 nos. of soft starters
= 75 (days) x 60 (kW) x 12 hrs = 54,000 2. Total energy required during 75 days at night time = 76 (days) x 90 x 12 = 81,000 Hence total energy required during 75 days = 54000 + 81000 of production testing, logging period = 135,000 kWh 3. HSD consumption to generate 135,000 kWh of energy by big caterpillar engine with SFC of 0.4 lit/KWhr at an average loading of 10% = 135,000 x 0.40 = 54,000 lits of HSD 4. HSD consumption to generate 135,000 kWh of energy by 125 kVA DG set with SFC of 0.3 lit/KWhr at an average loading min 75% =1,35,000 X 0.3 = 40,500 lits of HSD 5. Hence total saving of HSD = 54,000 - 40,500 = 13,500 lits = Rs. 0.432 Million
Pay Back Period For The Installation Of 125 kVA Smaller DG Set
High Cost Option SL. NO.
1. Total Energy required during 75 days at day time
SAVINGS POTENTIAL TOTAL Rs. Millions KLOE (Lakhs) 45.6 14.59 1.459
INVESTMENT (Rs. in lakhs)
9
238
PAYBACK MONTHS
1. 2.
22 months
3.
The investment required = 0.8 Million Savings expected = 0.432 Million (during 75 days of production testing logging) Payback period = (0.8 / 0.432) x 12 = 22 months
239
Installation Of Capacitor Bank The main problem of a drilling RIG is the power factor of power generated by the DG engines. Due to sudden change of load in the RIG due various reasons the DC load of Draw works and mud pump (AC load of DG is getting changed to DC with the help of SCRs to supply DC power to Draw works and Mud pump). As the DC load increases or decreases the power fluctuates from as low as 0.2 to 0.65 resulting KVA demand (KW/PF) fluctuation. The poor factor actually force the electrical man in the RIG to run additional engines for safety factor so as to avoid black out situation. This results in poor loading of individual DGs resulting high consumption of HSD at poor loading. One solution for improving and sustaining the power can be installation of automated power factor controller. But globally there is no instance for adopting such APFC. However efforts can be made in this direction on experimental basis.
Total Saving = 45634 lit/kWh of HSD = 45.6 KL/HSD = Rs 1.459 Million 5. The payback period for the above investment = 0.9 Million (investment) x 12 = 7 months 1.459 Million 5.4 Activities of Conservation of Oil and Gas in ONGC ONGC has taken many steps for conservation of energy. One of the examples of its long-term efforts is the plan for replacement of all D-399 engines by new energy efficient engines model CAT 3516 at a cost of about Rs. 250 Crores. These CAT 3516 engines are 5% more efficient. 5.4.1
Year wise consumption in ONGC Year HSD in KL Natural Gas in MMSCM
Estimation Of kVAr Requirement For The Capacitor Banks Calculation of KVAR for APFC (for installation at the common outlet of all the DGs) kVAr requirement = Maximum load (kW) [tan (cos-1 Ø 1) - tan (cos-1 Ø 2)] Where Ø1 = 0.4 (av. PF of the system) Ø2 = 0.7 (max. PF that can be achieved) = 1250 [ tan (Cos-1 0.4) - tan (Cos-10.7)] = 1250 [tan (66.42) - tan (45.57)] = 1250 [2.29 - 1.02] = 1587 1600 Hence four nos. of APFCs of each 400 kVAr capacity in series can be put at the PCR (Power Control Room) to improve upon the PF. Estimation Of Savings Potential By Improving The Power Factor (From 0.4 To 0.7) And Reducing The kVA Demand Of The Rig Basis: 1. 2. 3.
Existing avg. PF of Rig = 0.4 Improved PF of Rig after installation of APFCs and fixed type Capacitor Bank = 0.65 Present average loading of DGs is 25%
Estimation For Saving 1.
2. 3.
4.
One DG can be stopped by reducing the peak demand from 1250 kW max (3125 kVA) to 1925 kVA with the help of capacitor (Automated and fixed). By this in extreme situation, instead of running 4 DGs (each DG can take care 970 kVA max (80% of 1215 kVA limited to alternator). 2 DGs can cater the same load. On the safer side if 3 DGs run in place of 4 DGs during the entire period of the rig operation, operation of 1 DG can be stopped. Considering stopping of one DG throughout the rig operation thereby increasing the loading by around 25% (from 25% loading to 50% loading) the SFC can be reduced from 0.3220 to 0.3025 (refer actual SFC curves of DGs) Considering the total power requirement of 2340200 kWh (estimated earlier) during the entire period of Rig Operation and a reduction of SFC by 0.0195 lit/kWh. 240
5.4.2
2006-07 196440.7
2007-08 215419.4
1602.5
1739.6
Steps initiated to conserve Petroleum products ONGC's program of oil conservation is briefly summarized as below:
(A) Action Taken In-house For Conservation a) b) c) d) e) • • f) g) • • •
Awareness Program is held every year under OGCF (Oil & Gas Conservation Fortnight) Seminar / Conference is organized for deliberation of issues on petroleum conservation. ONGC Energy policy is already framed Energy Conservation tips are continuously scrolled on ONGC's house portal. E.C. Committee has issued two policies on conservation as under Use of Solar Water Heating Systems in ONGC Use of Energy Efficient Lighting System in ONGC On line quiz being held every year for ONGC employees and their wards. Three booklets are issued on conservation of Oil & Gas. Urja Udai Energy Conservation Techniques Quest
h) A company wide training drive as "Energy Conservation Techniques Training" has been taken up with the help of PCRA for training about 20000 officials of ONGC. i)
All models of engines have been audited and corrected for their running efficiency. j) 285 CAT D-399 Engines being replaced in phased manner by CAT D-3816 Energy Efficient Engines. k) Solar Water Heating Systems of different capacity has already been installed on following locations in ONGC. 1. 1300 Litres Per Day (LPD) at ONGC Guest House Tel Bhawan, Dehradun. 2. 9000LPD at ONGC Hospital Dehradun. 3. 7200LPD at GT Hostel in ONGC Academy. 4. 7200LPD at ONGC Colony Dehradun. 241
l)
5. 800LPD at Officers Club ONGC Dehradun.
•
50MW Wind Power Project has been installed in Gujarat, near Bhuj. With a saving potential of Rs. 29.86 Crores/Year.
• •
m) More then 200 Energy Audits Carry outs on the different ONGC Installations.
•
(B) Expected reduction in consumption (from major initiatives) 1. 2. 3. 4. 5.
"Energy Conservation Techniques Training" Solar Water Heating Systems in ONGC Wind Power Projects By Energy Efficient Engines (Caterpiller) By Energy Efficient Engines (Cummins)
(C)
• •
3- 5% 5-10% 10-15% 14-17% 3-7%
5.5.2.2 Recovery of Condensate
Strategies for Conservation In Future
II. III. IV. V. VI. VII. VIII. IX. X. XI.
Additional awareness program in the organization to be taken up. More policies of Energy Conservation are to be put up for application. Additional Solar/Thermal systems to be installed on more areas. Additional new Wind Power Plants to be set up in future. First time Geothermal Energy project to be taken up. Replacement of inefficient equipments. Tapping up waste heat recovery from exhaust of engines. Waste heat recovery from Engines Jacket Water/Radiator Solar Electric System Ocean Energy
5.5
Energy conservation measures in Oil India Limited (OIL)
5.5.1
Use of Aluminium paint in all crude oil storage tanks to minimize evaporation loss. Use of Oil Soluble De-emulsifier (OSD). Use of dual fuel (Natural Gas and Crude Oil as fuel) engine in Crude Oil Dispatch Pumps in PS-1 & PS-2 since natural gas is available. Regular & proper maintenance of Crude Oil Transportation Trunk/ Branch Pipelines to minimize pumping power requirement. This is further reduced by treating the crude oil with flow improver chemical / heat treatment. Water Clarification Plant and use of De-Oiler. Retrieved from various pits and sumps.
Total volume of condensate recovered during the year was about 65604 kL, which in terms of money amounts to Rs. 13744 lakhs (approx.) • By the operation of condensate recovery plant (CRP) at Moran, a total quantity of 3957 kL condensate recovered. • Condensate recovered from Duliajan field -61236 kL • Condensate recovered from Rajasthan project- 356 kL 5.5.2.3 Conservation Of Natural Gas Reduction in natural gas consumption in COCP's at Duliajan and Moran During the year, the crude oil of both OIL & ONGC was treated with Flow Improver chemical instead of thermal conditioning and thereby the consumption of natural gas in COCPs at Duliajan has been reduced considerably and as a result the total saving of natural gas was around 6.84 MMSCM (amounts to Rs.218.8 lakhs approx.) during the year 2007-08.
Present Level Of Energy Consumption By OIL(During 2007-08) Reduction of Gas flare
Energy
Unit
Crude Oil Consumed for Transportation of OIL’s & ONGC’s crude Oil to refineries, etc. Natural Gas (industrial & domestic uses) Diesel oil (HSD) (Drilling & W.O. operations, prime mover operations, power generation, transport fleet, etc.) L.D.O. Petrol K.Oil Lube Oil Electricity TOTAL
5.5.2
kL
MMSCUM kL
Qty
8069.00
370.07 13397.64
Eqvt.kWh
78.269 × 10
Approx. Monetary value (Rs. in Lakh) 1690.50
6
4266.90 × 10
6
11842.24
107.964 × 10
6
4342.175
The following steps were taken for the reduction of natural gas flare during 2007-08. 1 2
3 kL kL kL kL kWh
7.20 68.77 0.942 771.061 -
6
0.07 × 10 6 0.65 ×10 6 0.09 ×10 *** 6 111.00 ×10 6 4564.947× 10
2.70 32.72 0.015 652.93 2053.50 20616.78
Various Measures Adopted By OIL For Conservation Of Energy During The Year 2007-08
4
5
6
5.5.2.1 Conservation Of Crude Oil 7 A total quantity of 4431 kL of Crude oil has been saved/retrieved from different operational activities during the year under review by adopting the following measures: 242
Gas flare in Moran field has been reduced to 0.05 %. A total of 1.1 MMSCM very low pressure gas (about 0.7 kg / cm2 stabilizer gas which is normally being flared in many OCSs) is being utilized from Moran OCS as domestic fuel in housing area. After commissioning of stabilizer compressor and water seal system at OCS-5, utilized 1.1 MMSCM low pressure stabilizer gas (0.7 kg / cm2) as housing fuel which otherwise would have been flared. After commissioning of two nos. gas distribution pipeline to utilize associated gas produced at Brekuri EPS and NKL/NKL QPS, resulted in reduced gas flaring and saving of 2102500 SCM of natural gas. During the year 160392 SCM low-pressure gas (30 psig) of Deroi EPS sold to Moran Gas Grid. When there is no demand of gas from Moran Gas Grid, 20892 SCM of 30 psig low pressure gas from Deroi EPS was diverted to Moran GCS-2, which otherwise would have been flared. Gas Holder: With the commissioning of the 30 psig Gas Holder the gas flaring caused by surging effect of the gas lift has been restrained. Setting of Flare Controller: Periodic (weekly) flare controller setting at 35 psig is being carried out to avoid flaring of 30 psig gas at various OCSs.
243
5.5.2.4 Supervisory Control And Data Acquisition (SCADA)
5.5.2.6
The SCADA project commissioned on 15 March 1998 is presently being used to control the gas flare, accurate gas measurement, monitor consumption of gas as fuel in both Oil Collecting Station (OCS) and Gas Compressor Station (GCS) and for maximum utilization of produced gas, etc.
1
5.5.2.5
Conservation Of Diesel (HSD) And Petrol
Total quantity of about 406 kL (amounts to about Rs. 132 lakhs) of diesel has been conserved during the year under review by adopting the following measures: 1
By installation of Gas Engine driven Crude Oil Dispatch (COD) pump in place ofDieselEngine Driven Bowser loading pump at Barekuri EPS about 25.55 kL of HSD are being saved.
2
Eight nos. of work over wells were provided with electrical power from nearest available source, resulted in saving of 9.6 kL of HSD.
3
Use of solar lighting at Tanot-GGS (Rajasthan) & Pilot Plant at Baghewala (Rajasthan), resulted in saving of 2.84 kL of HSD
4
In pipeline operation 45 Nos. of old Dorman engines of generating sets having fuel (HSD) consumption in the range 3.6 to 4.0 Ltr/Hr, at various repeater stations have been replaced by Koel engines having fuel consumption rate of 2.6 to 2.8 Ltr/Hr., which resulted in saving of about 150 kL of HSD.
5
By using PDC Bits that cuts down the round trip time and resulting in reduction of the rig hours consequently there is considerable reduction in HSD consumption.
6
By adopting and continuing cluster-drilling techniques, consumption of fuel (particularly HSD) is reduced considerably. Rig dragging were carried out at five different locations whereby a rig was moved onto next cluster location without any rigging down operation. This additionally eliminates rig movements, which resulted in considerable saving in HSD consumption.
7
By adopting Horizontal Drilling technique, three full plus three part horizontal well were completed. Production from a horizontal well is three times than of a conventional well thereby saving in construction cost of two well as well as considerable saving in HSD consumption.
8
By using motor driven hydraulic power unit instead of engine driven hydraulic power unit for torque up casings during drilling operation resulted in considerable saving in HSD consumption.
9
Minimized workover and swabbing operation wherever feasible by using Coil Tubing Units (CTU) - Nitrogen Pumping Units (NPU). During the year 2007-08 total 129 nos. of work-over equivalent job were carried out by deploying CTUs & NPUs, resulted in saving of 218.4 kL of HSD
Conservation Of Lube Oil
By using Lube oil analysis kit, carrying out Chemical analysis from time to time and revising and setting up of lube oil standard, the lube oil consumption has been optimized which in fact contributed to the conservation of lube oil. The lube oil change period for caterpillar engine has been re-scheduled from 500 Hrs. (manufacturer's recommendation) to around 1000 Hrs. (OIL's practice) without any adverse affect on the engine, which resulted considerable saving of lube oil. 2. Due to use of improved quality of gland packing of the plungers of the injection pumps in Water Injection operations the consumption of lube oil was reduced considerably. 5.5.2.7 Utilisation Of Non-Conventional Energy I.
A total of about 244 nos. of Multi Access Radio Telephone (MART) terminals were provided with Solar Photo Voltaic Panels to achieve energy saving and cost reduction. By adopting these measures about 0.61 kL of HSD was saved during 2007-08. II. Use of solar lighting at TANOT Gas Gathering Station and at Pilot plant, Baghewala resulted in saving of 2.84 kL of HSD. References 1.
Petroleum exploration and production activities, 2006-07, Directorate General of Hydrocarbons, Ministry of Petroleum & Natural Gas, GoI 2. Annual Report (2007-08) of Ministry of Petroleum & Natural Gas, GoI 3. World Energy Outlook 2007 4. TERI Energy Directory and Yearbook 2007 5. Statistical Abstract 2007-CSO 6. Report from Technical Services & Energy Conservation Cell of ONGC 7. Report from Technical Audit Department, OIL INDIA LIMITED 8. Energy Audit Reports of ONGC & OIL conducted by PCRA 9. BP Statistical Review, June 2008 10. PPAC Ready Recokner, April 2008 11. www.netl.doe.gov 12. www.fossil.energy.gov
10 By replacing diesel engine driven centrifugal pump by motor driven pump in drilling rig for pumping gauging water, considerable amount of HSD was saved. 244
245
Notes
Chapter - 6 LPG Bottling Plants 6.1
Introduction
Over 100 million LPG consumers in the domestic sector in India are serviced through a network of 9365 LPG distributors who are getting supply from 181 LPG bottling plants located across the country. In 2007-08, India consumed a total of about 1170 TMT of LPG which is around 10% of the consumption of total petroleum products in the country. Out of the total LPG consumption during the year 2007-08, almost 75% was used for cooking, 17% as auto LPG and the remaining 8% for industrial use. Of the total supply of 11.7 Million Tonnes of LPG during 2007-08, the indigenous production was 8868 TMT from crude oil and natural gas fractionation (3:1). Imports by PSUs and private entrepreneurs accounted for 2156 TMT and 673 TMT respectively. LPG is transported from production installations i.e. Refineries, Fractionation plants and Import terminals to the bottling plants through pipelines, Bulk LPG Wagons or Bulk LPG Tank Trucks. This LPG, subsequently, is bottled in 19 Kg, 14.2 Kg and 5 Kg cylinders and is then delivered to commercial consumers and individual households. Bottling operation of LPG is very critical, as LPG is a highly inflammable product and the systems are required to be intrinsically safe. The systems also require very comprehensive fire safety arrangements. A typical LPG bottling plant has the following major energy consuming equipment:1. 2. 3. 4. 5. 6. 7. 8. 9.
LPG pumps LPG compressors Conveyors Blowers Cold repair facilities including painting Air compressors and air drying units. Transformer, MCC & DG sets Fire fighting facilities Loading and unloading facilities
Some of the LPG bottling plants use a comprehensive monitoring technique for keeping track of energy / fuel Consumption on per tonne basis. PCRA's energy audit studies in various LPG plants have found 20-25% energy saving potential in the LPG Plant operations. The following are major energy conservation opportunities in a LPG Plant: 6.2
Energy Conservation Opportunities in Air Compressors
Compressed air system is one of the most inefficient operation for conversion and storage of energy. Typically, efficiency from start to end-use is around 10%. In any compressed air system with a saving potential of upto 30%. This saving potential is mainly, towards efficient compressed air generation system, efficient compressed air transportation system, maintenance of optimum pressure levels and reducing misuse and leakages.
247
6.2.1
Compressor Air Pressure Level
On overhauling the compressor, the Annual saving in energy
: 15120 kWh
In a bottling plant, compressed air is used as instrument air and service air. The pressure level of 5 Kg/cm 2 is sufficient for all the operations in a bottling plant.
Annual saving
: Rs.71000.00
Investment required
: Rs.25000.00
The requirement of air pressure for various devices is as under:
Payback Period
: 4 months
Remote Operated Valve(ROV) Deluge valve Stopper/pushing/pulling of cylinders Instrumentation Painting gun Hydrostatic testing of cylinders
-
5.0 Kg/cm2 3.5 Kg/cm2 5.0 Kg/cm2 2.0 kg/cm2 4.0 kg/cm2 5.0 Kg/cm2
6.2.3
Leakage of Compressed Air & Wastage:
Avoiding leakage is the largest opportunity of saving energy in a compressed air system. The leakage in compressed air system in a plant can be quantified by adopting the following process a)
Raising the receiver pressure to the designed pressure and stopping the air usage with all intermediate valves open. b) Keeping the complete line including pneumatic circuit pressurised c) Recording loading and unloading duration of the compressor
Case Study 1 : Air Pressure Level Optimization Brief Air pressure level in the plant is fixed by setting the loading and unloading pressure through pressure switch provided in Air Compressor.
% leakage can be calculated by
Energy Savings
% Leakage =
Generally, the air pressure maintained in a LPG bottling plant is of the order of 6 to 6.5 Kg/cm2 Reduction in pressure levels by 1.25 kg/cm2 would mean saving of 12.5% in energy consumption and saving of another 15% in compressed air consumption. For a plant having 1 carousel system requiring 150 CFM (27kW motor load) compressed air and working 16 hours per day and 350 days per year, savings of 12.5%: 19170 kWh worth Rs. 90000/- per year is possible. Additional saving of Rs. 0.11 Million per year can be achieved through reduction in compressed air consumption. This is a no cost proposition, requiring minimal technical skill in re-setting of pressure switches. 6.2.2
Performance test and measurement of output CFM of compressor:
Load Time Load Time + Unload Time
x 100
Case Study 3 : Arresting the leakage in a Compressed Air System Brief Leakage of anywhere between 40% to 90% has been observed in compressed air systems. Leakage can be arrested by conducting a leak test for identifying points of leakages and plugging the same. Leakage reduction is a continuous process and should be built into the system Energy Savings A reduction of 25% leakage in a typical 150 CFM system would mean saving of over 37 CFM. Equivalent power saving would be 6 kW having implication of 33600 kWh, worth Rs. 157000/- per year for a 16 hour per day operation for 350 days per year system.
Air compressors, specially reciprocating, suffer deterioration in performance over a period of time, resulting in lower volumetric efficiency. The drop in volumetric efficiency needs to be diagnosed and corrected at its earliest, so as to check the loss of energy.
It does not really cost much to arrest leakage, whereas the saving potential is very high.
Case Study 2 : Measurement of output CFM
6.3
Brief Assessment of volumetric efficiency can be done in-house with least instrumentation support. Finding the volumetric efficiency dropping by more than 10%, should trigger for initiating major overhaul. Typical overhaul of a 150 CFM Air Compressor would cost Rs. 25000/- approx. Energy Savings
Optimization of Power Supply System Billing and Demand Side Management
Various equipment forming the power supply system in a bottling plant are Transformers, Breakers, Switchgears, Changeover switches, PF controllers etc. Licensed area being a notified intrinsically safe area, all these circuit elements of the power supply system are installed outside the licensed area. Thus, the length of transmission cables is longer compared to any other application and hence demand side management becomes all the more important.
A 10% deterioration in volumetric efficiency in a 150 CFM system means, loss of 2.7 kW of power. For a 16 hour per day operation for 350 days in a year system, this works out to 15120 kWh. 248
249
6.3.1
Transformers
Transformers are very efficient electrical equipment. However, losses are still an issue in the transformers in a typical power transmission network. Normally, two number of transformers are installed in a bottling plant with one being stand-by and both are kept energised all the time so as to avoid any power failure due to break down in transformer. However, keeping two transformers energised (one being stand-by) is a wrong practice as the transformers are under charged condition for 24 hours everyday and losses are incurred even if no power is drawn from the transformer. Typically, a 1500 kVA modern transformer having amorphous core has a no load loss of 555 Watts. De-energisation may risk the transformer of moisture ingress. However, moisture ingress can be avoided by following a sequential on/off regime. De-energising the transformer is not always the solution. At times load redistribution among transformers helps reduce load losses resulting in reduction of overall loss. Typically no load losses of the transformer is of the order of 50% of load losses. Thus, opportunity for saving Energy in a transformer system needs to be assessed for the system as a whole. Implementation of the proposition involves no investment and very little technical skill. Keep the standby transformer De-energised and load the two transformers alternately every fortnight. This will save ½ KW worth power having yearly saving potential of 1/2X24X365 4381 kWh. This saving potential may be 7 times more if Silicon Core Transformer is used and over 3 times more, if Low Loss Silicon Core transformer is used. 6.3.2
Demand Side Management
Demand Side Management involves controlling various cost heads appearing in a typical electricity bill, with a view to optimise electricity bill. The factors appearing in electricity bill are Maximum Demand, Power Factor, Voltage Levels (HT/LT) etc. All these factors can be kept under strict control, resulting in substantial saving for units. Keeping Maximum Demand under control helps units save on demand charges, at the same time helps the utility by way of spare capacity. It is always advisable to keep maximum demand under check. This issue becomes of paramount importance, where snap loads are there. Like in a bottling plant, fire water pumps testing, service water pumping etc are not continuous loads and hence these jobs can be done in off peak hours to save on maximum demand. It will also help in cases where Time Of Day (TOD) tariff system exists. Equipment like Maximum Demand Controller is used for keeping maximum demand under control through user defined sequential switching off and on.
intelligent Maximum Demand Controllers, which keep check on maximum demand by switching off and deferring non essential loads. In two-part tariff system, Demand Charges are levied on the contract demand. The Demand Charges have been found to be higher up to 20% of net electricity bill in a Bottling Plant. The utility also levies penalty for exceeding contract demand. Thus keeping maximum demand under control, pays through saving in demand charges. 6.4
PF Control
Power Factor is a measure of the quantum of Inductive load present in an electrical system and also the extent of partial loading of these inductive loads. Utilities (Electricity Supply Companies) give incentive for maintaining higher Power Factor and the incentive may be upto 5% of the energy charges. Maintaining higher PF has the following advantages : i ii iii iv v
Keeps current under check and hence the I2R losses are reduced. Saves transmission losses, in systems having longer cable lengths. Power Utility companies pay incentive for maintaining higher PF. Helps to keep maximum demand under check and hence lowers outgo towards demand charges. Helps in keeping voltage drop lower and hence better voltage availability and very less voltage imbalance to help save electricity.
Automatic Power Factor Controller (APFC) helps improve Power Factor and reach near unity. Case Study 4 : Improving and maintaining the Power Factor Brief Improving and maintaining the power factor from 0.93 to near unity by providing additional capacitors having kVAh billing system. Energy Savings Annual energy consumption = 227340 kWh Existing Average pf = 0.93 Annual consumption in KVAh = 227340 kWh / 0.93 = 244452 kVAh On improving the power factor from 0.93 to 0.99 by installing required additional capacitors The same annual energy consumption in KVAh = 227340 kWh /0.99 =229636 kVAh Annual Saving of energy in KVAh = 229636 - 244452 = 14816 kVAh Average unit rate is Rs 3.57 / kVAh Annual Saving in Rs = Rs 52893.00 Cost of additional capacitors = Rs 10,000/Pay back period = 3 months Case Study 5 :
Average of the of time integrated load for every half an hour period is registered in the electronic meter for the entire month. The maximum value registered is considered to be the maximum demand. Maximum demand can be controlled by monitoring number of energy consuming equipments, operated at any point of time and also by improving Power Factor. Industries have started use of relay based 250
251
Improving and maintaining the power factor from 0.92 to near unity by providing additional capacitors for system having kWh billing system and having rebate of 0.5% for improvement in PF by 0.01, on its energy charges.
Energy Savings:
Case Study 5 : Voltage optimisation for lighting through AVR
Annual energy consumption = 442040 kWh Existing Average pf = 0.92 On improving the power factor from 0.92 to 0.99 by installing required additional capacitors the improvement is by 0.07. The plant is eligible for a rebate of 3.5 % on its energy charges.
(i) Existing Average voltage level in daytime (10 hrs)= 230 V
Annual energy charges @ Rs 4.09 / kWh The rebate on energy charges Annual Saving Cost of additional capacitors Pay back period
= 442040 x 4.09 = Rs 1807944.00 = 3.5 % of Rs 1807944 = Rs 63278.00 = Rs 50,000/= 10 months
The Demand control through scheduling of loads and also with the help of MDI controller is a proven solution working in industrial applications and is very reliable. Indian vendors are also available for the job. Reliable APFC and capacitors are very easily available and require little maintenance. The system may not work reliably and capacitors may fail, if harmonics are there in the system. APFC with harmonic filter gives comprehensive solution for systems having high harmonic distortions. 6.5
Voltage Optimization
Typically, in a transmission system, voltage at the load end, reduces with reduction in Power Factor or increase in current levels. Various loads, requiring electricity for its operation, are designed for a voltage of 415V. However, the voltage levels are generally higher and reach upto 460V during late night. This gives an opportunity to reduce voltage by upto 10%. A reduction in voltage by 10%, would give savings of upto 1.5% in motors because lowering voltage increases loading level of motors resulting in improvement in its efficiency. A 10% drop in voltage, also helps save upto 15% in energy consumption in lighting loads There are two ways in which voltage control may be implemented 6.5.1
Voltage control through Tap Changer
Use of Tap Changer - The provision for tap changing is an inbuilt feature of transformer / incomer system. Lowering the voltage through tap changing is the most convenient way of reducing voltage levels. It involves no cost and it is very convenient if the transformer has On Load Tap Changer (OLTC). Otherwise, every tap change involves switching off power and then effecting tap change. 6.5.2
Voltage Control through AVR
Use of AVR - Automatic Voltage Regulators have emerged as a worthy solution. AVR technology is very proven and very easily available. The advantage of having an AVR is that one can have the desired voltage out put , say 3 phase, 415 V, 24 hours a day, irrespective of the incoming voltage. This is not possible in tap changers. It immunes the system of voltage fluctuation and high voltages, especially during late night hours. AVR is a very good proposition for exclusively lighting load as the voltage levels are higher during night time when they are ON and the percentage saving is more i.e 15% for 10% reduction in voltage.
252
Proposed voltage Expected saving Total approx. lighting load Expected saving
= 210 V = 8.0% = 25 kW = 25 x 0.08 = 2 kW Annual power saving = 2 kW x 10 hrs.x 300 = 6000 kWh Annual monetary saving @ Rs 4.09 per kWh = Rs 24540 (ii) Existing avg. voltage level in off peak hrs Proposed voltage Expected saving Total lighting load in off peak hrs Expected saving Annual power saving Annual monetary savings @ Rs 4.09 per kWh
= 240 V (14 hrs) = 210 V = around 9% = 125 kW = 125 kW x 0.09 = 11.25 kW = 11.25 x 14 hrs. x 365 days = 57487 kWh = 57487 x 4.09 = Rs 2,35,122
Energy savings Net Annual saving potential Net investment in providing AVR Payback Period 6.6
= Rs. 235122+Rs. 24540= Rs. 259662.00 = Rs. 190000 = 9 months
Energy Saving Opportunities in LPG Pumps
LPG pumps consume around 14-15% power of the total plant consumption. These pumps run continuously for 16 hours per day. Other pumps are service water pump, bore well pump, fire-fighting pumps, which are run as per requirement in the plant. The filling rate at carousel varies depending upon the number of cylinders filled in the LPG bottling plant. This is controlled through return line (bypass) and is operated based on pressure in the header. The system operating with throttled valves or operated with bypass valves in partially open condition, leads to the wastage of significant energy. This wastage of energy can be eliminated / minimized by the following methods: • • •
By installing proper size pump By trimming the impeller of the pump By changing the speed of the pump through VSD
In the present system, the requirement of flow is not constant and it varies as per the filling rate and bullet pressure. Keeping this operational constraint in view, flow reduction through changing the speed of the pump by installing VSD with feedback from discharge pressure/ flow will be the best option to minimize the energy wastage.
253
Case Study 6 : Installation of Variable Speed Drive (VSD)
Case Study 8 : Replacing HPMV Lamp fittings with metal Halide fittings
Brief
Brief
For a typical bottling plant having one carousel, 1 pump having 50 kW motor and 96m head / 150 m3 per hour discharge is required to pump LPG from the storage tank to the carousel. Energy can be saved by closing the bypass valve on the return line and installing VSD on the motor of the pump to get the desired flow and Pressure at the carousel.
About 186 nos of 125 W HPMV lamp fittings in various sheds can be replaced by 70 W Metal halide fittings in a phased manner whenever any of the items of luminary goes out of order.
Total energy consumption by 186nos, 125W HPMV fittings, when operated for 12 hours for 300 days.
Energy Savings -
Present power consumption by pump Pump suction pr. Pump discharge pr. Expected power consumption by pump with VFD Saving in power consumption Annual operating Annual Savings in kWh Annual savings @ Rs 3.675 per kWh Investment required for VSD & automation (for pressure transmitter, cable) Payback period
6.7
Energy Savings
- 40 kW - 5-6 kg/cm2 - 10 - 12 kg/cm2 - 30 kW - 10 kW - 4200 hrs - 42000 kWh - Rs 1,54,350 - Rs 5,00,000 - 39 months
Energy Conservation in Lighting
Significant amount of energy is consumed in Lighting application in a bottling plant due to operation during the night and also security requirement in very large areas. The following saving opportunities exist in the lighting system in a LPG bottling plant Case Study 7 : Replacement of 96 T/Ls of 40 W (T12) (having electromagnetic chokes) operating in plant with 28W( T5) tubelights. Brief These are operated on an average for 12 hrs per day for 300 days in a year. the electromagnetic chokes in itself consume about 13W per tube light.
Total energy consumption by 186 nos. 70W Metal Halide fittings Total kWh saving per annum Monetary saving potential at Rs 4.09/ kWh Total investment@ Rs 1000 per light Pay back period 6.8
Total energy consumption by 96 nos. 40-Watt tube lights with Electromagnetic chokes for 12 hrs as mentioned above
= 96x (40 +13)x 300x 12
Total energy consumption by 96 nos.28 W(T5) tube lights
= 96x28x300x12 = 9677 kWh/year
So, total energy saving Monetary saving potential at Rs 4.09/ kWh Total investment@ Rs 500 per tube light Pay back period
= = = =
= 18316 kWh/year
8639 kWh/year Rs 35333/year Rs 48000 7 months
254
= 186x 70 x 12 x 300 = 46872 kWh/year = 36828 kWh = Rs 150636/year = Rs 186000.00 = 15 months
Energy Conservation Opportunity in LPG Compressor
Contribution of LPG Compressor in the energy consumption pattern of a LPG Bottling Plant is significant. LPG compressor is essentially a reciprocating compressor like air compressor and the saving potential in air compressor more or less holds good for LPG compressors as well, except leakage. Thus, volumetric efficiency assessment and corrective action thereof, happens to be a major energy saving opportunity in LPG compressors. Operating practices contribute a lot to energy consumption. The higher the specific pressure ratio, the higher is the energy consumption. Thus, the endeavour should be to keep the specific pressure ratio as low as possible. In actual practice, discharge pressure of LPG compressor is made higher for increasing bottling output or for hastening the process of LPG loading/ decantation. However, all these practices have implication on Energy consumption. 6.9
Energy Savings
= 186 x 125 x12x300 = 83700 kWh/year
Other Energy Conservation opportunities
1) Use energy efficient lamps and replace incandescent bulbs with Compact Fluorescent Lamp (CFL). 2) Use task lighting, as keeping the light source as close as possible to the work place; as the light intensity decreases exponentially as the distance from the light source to the task increases. 3) Provide reflectors on the tube lights to enhance lumens/m2 (LUX), always keep reflector clean. 4) Make effective use of daylight wherever possible. 5) Clean luminaries to increase illumination, normally 10 to 20 % light output reduces over a period of six months if not cleaned. 6) Improve colour & reflectivity of walls, ceilings to reduce lighting energy needs. 7) Whenever replacing a burnt out lamp, attempt should be made to replace it with a more efficient lamp and the ordinary T/L fitting with an electronic ballast fitting. 255
Electronic ballast consumes only 2 Watts in comparison to the electromagnetic ballast which consumes around 13 Watts of electrical energy. 8) Use time clocks or daylight sensor control for outdoor lighting. 9) Train personnel to switch off the light whenever not required, posters as reminders can be placed on the doors for this purpose. 10) Wherever LUX level is specified, it must be counter checked by LUX meter. 11) During breaks, the lights of a specific workplace should be switched off, for which individual switches hanging at the worktable shall be helpful. 12) Interlocking of chain conveyor with cylinder washing pump. 13) Avoiding idle running of pump conveyor system. References 1. PCRA Energy Audit Report, HPCL LPG Bottling Plant, Asauda Bahadurgarh (Haryana), December, 2006 2. PPAC Ready Reckoner, Information as on 1.4.2008, Petroleum Planning & Analysis Cell, MOP&NG, GOI New Delhi 3. Teri Energy Data Directory & yearbook 2007, TERI Press, New Delhi 4. World Energy Outlook, 2007, IEA Publication, Paris, France 5. Basic Statistics on Indian Petroleum & Natural Gas, 2006-07, Ministry of Petroleum & Natural Gas, (Economic Division), GOI
256
Chapter - 7 Marketing Terminals/ Depots 7.1 Introduction The biggest challenge in the complete supply chain of Petroleum Products is to reach out to almost-37000 retail outlets all over the country. Every element in this value chain has to have unfailing reliability in all circumstances. Building this reliability in the logistics is a marvel of supply chain management. The products from refinery are transported to the secondary points called Depots and Terminals through pipelines / wagons / tank trucks. The basic jobs undertaken at these depots / terminals is warehousing, wherein receipt, storage and dispatch of various products is accomplished. These secondary supply points are responsible for maintaining supply lines to Retail Outlets and numerous Institutional Customers. Terminals/Depots mainly undertake pumping operations. Any energy conservation initiative in Depots/Terminals should aim at improving energy efficiency in pumping operations. PCRA has found energy conservation potential of upto 30% in Depots/Terminals operation. A Depot/Terminal uses the following energy intensive machinery for accomplishing its operations:1. 2. 3. 4. 5.
Pumps DG Sets Lighting Air Conditioners Miscellaneous Machinery
7.2
Energy Conservation Opportunities
The major energy conservation opportunities, identified by PCRA, during its various energy audit studies are as per the following details: 7.2.1
Pumping System
From Energy Conservation point of view, the area of concern in a terminal / depot operation is over sizing. The typical protocols for handling the problem of over sizing in pumping operation needs to be customized to the terminal operation, as the flow requirement here may vary over a wide range. At the terminal, the number of bays operating at any particular instance is changing as a result of the change of flow requirement. Recirculation is the method of Capacity Control on Pumps being employed at present. In this method, a part of the product being pumped is recirculated back to the suction of the pump, to regulate the flow of the loading terminals/ bays. This type of control is the most energy inefficient, since only a part of the actual energy being consumed is useful and the rest is lost in re-circulation.
257
The average working hours of the pumps observed at one of the terminals is as follows: SKO Pump- 5 hrs per day with 1 to 3 bays operating at a time (1500 hrs/annum) MS Pump - 3 hrs per day with 1 to 2 bays operating at a time (900 hrs/annum) HSD Pump- 5 hrs per day with 1 to 3 bays operating at a time (1500 hrs/annum) From each bay, one tank lorry is filled Case Study 1 : Installation of Variable Frequency Drive (VFD) on HSD Pump
(ii)
Variable Frequency Drive (VFD) for SKO Pump
In case of SKO (40 HP motor), the savings shall be on the same lines • Total Energy Saving per annum
14000/0.93=15053 kVAh
• Annual Savings
Rs 0.504 Lakhs (@Rs 3.35 per kVAh)
• Estimated Investments
Rs 1.5 Lakhs
• Payback period
36 months
Energy Savings
Brief In order to eliminate / minimize the continuous Power losses in these systems, it is suggested to install a variable frequency drive (VFD) on the Pumps. This would enable the plant to control the flow through a feedback signal to the pump and vary the RPM to exactly match the requirement. With the installation of a Variable Frequency Drive, energy savings could be achieved by reducing the RPM of the pump and the subsequent reduction in the power consumption per litre of material actually delivered.
(iii) Operation by closing the bypass valve : By simply closing the return valve on the recirculation line, savings can be achieved. Average kW saving observed in HSD, MS & SKO Pumps Expected annual running hrs of HSD and SKO Pumps Average annual energy saving in HSD and SKO Pumps Expected annual running hrs of MS Pump Average annual energy saving in MS Pump Total annual energy saving in HSD, MS & SKO Pumps
= = = = = =
3 kW each 1500 x2 =3000hrs 9000 kWh 900hrs 2700 kWh 11700 kWh
Energy Savings
• Total Energy Savings per annum
11700/0.93=12581 kVAh
(i) Variable Frequency Drive (VFD) for HSD Pump of rated flow 2400 LPM
• Annual Savings
Rs 42146 (@Rs 3.35 per kVAh)
• Estimated Investments
Nil
• Payback period
Immediate
Material
HSD
HSD
Operation
If 1 bay in use If 2 bays are in use
Effective Flow after bypass – LPM
825 (34.3% of 2400)
Power Drawn in kW (measured values) At After present installing (with by VFD pass open) 11.6 3.6
1250 (52.08% of 2400)
Net reduction in the power drawn in kW
Estimated working hours of the Pumps per annum
Estimated energy savings kWh
8.0
1500
12000
10.0
1500
15000
7.2.2 Illumination 14
4.0
Avg
13500
Energy Savings Ø Energy Savings per annum
When, no receipt of the product is taking place at TLF area and the pump is run with bypass closed, only churning of the product takes place; the pump being centrifugal shall be able to bear the backpressure. In spite of this, the operator should take care to avoid prolonged idle running of the pump
= 13500/0.93 = 14516 kVAh
Illumination in Depot / Terminal is basically required for safety reasons. Receipt operation is conducted during the night in locations receiving supply through Railway Wagons / Pipelines. However, illumination in the tank lorry filling Area, tank farm area and the buffer area is provided through flame proof lighting fixtures. The lighting is predominantly through high mast towers. The following case study has been taken from the actual study taken up by PCRA.
Ø Monetary Savings per annum = Rs 0.486Lacs (@Rs 3.35 per kVAh) Ø Estimated Investments
= Rs 1.3 Lacs
Ø Payback period
= 33 months
258
259
Case study 2 : Replacement of 40W Tubelights having electromagnetic chokes by 36W T/L with Electronic chokes, assuming 0.8 as load factor
Case Study 4 : Replacement of 100W Incandescent lamps by 15W Compact Florescent lamps (CFL), assuming 0.8 as load factor:
Energy Savings
Energy Savings
Total energy consumption by 131 nos. 40 Watt Tubelights with electromagnetic chokes, taking working hours (12 hrs daily in 300 days). Total energy consumption by 131 nos. 36 Watt tubelights with electronic chokes, taking working hours (12 hrs daily in 300 days).
= = = = = =
(40+15)x 131 x 0.8 /1000 5.76 kW 3600 hrs 20736 kWh/year (36 + 2) x 131x 0.8 x 3600 14337 kWh/year
So, total energy saving taking pf as 0.82 monetary saving potential
= = =
Total investment @ Rs.400/- per choke
=
6399 kWh/year 7804 kVAh /year Rs 27, 860.00/year (@ Rs 3.57/kVAh) 400 x 131 = Rs.52400.00
Payback period
=
23 months
Total energy consumption by 77 nos. 100 Watt incandescent lamps, taking working hours (12 hrs daily in 300 days).
= (100)x 77 x 0.8 = 6.16 kW = 3600 hrs = 22176 kWh/year Total energy consumption by 77 nos. 15 Watt CFL = (15) x 77x 0.8 x 3600 lamps, taking working hours (12 hrs daily in 300 days). = 3326 kWh/year So, total energy saving = 18850 kWh/year taking pf as 1.0 = 18850 kVAh /year monetary saving potential = Rs 67294.00/year (@ Rs 3.57/kVAh Total investment = Rs 11,000 Payback period = 2 months Case study 5 : Installing daylight sensor for controlling street lights and out side lights, thereby saving 1hour of daily running, assuming 0.8 as load factor Energy Savings
Case Study 3 : Replacement of 40W tubelights with electromagnetic chokes by 28W T/L (T5), assuming 0.8 as load factor: Energy Savings Total energy consumption by 131 nos. 40 Watt = (40+15)x 131 x 0.8 tubelights with electromagnetic chokes, = 5.76 kW taking working hours (12 hrs daily in 300 days). = 3600 hrs = 20736 kWh/year Total energy consumption by 131 nos. 28 Watt tubelights (T5), taking working hours (12 hrs daily in 300 days).
= (28) x 131x 0.8 x 3600 = 10564 kWh/year
So, total energy saving taking pf as 0.82 monetary saving potential
= 10172 kWh/year = 12405 kVAh /year = Rs 44,286.00/year (@ Rs 3.57/kVAh)
Total investment @ Rs.700/- per retrofit
= Rs.91700.00
Payback period
= 25 months
260
Total energy consumption by 43 nos 250W sodium vapour lamps, 54 no 400W Sodium vapour lamp, 10 no 250W Mercury Vap lamp and 42 no 160W Mercury Vap Lamp , taking working hours (1 hrs daily in 365 days).
= (43x250 + 54x400 + = 10x250 + 42x160) x 0.8 = 33.26 kW = 365 hrs = 12138 kWh/year
So, total energy saving, taking pf as 0.82 Monetary saving potential
= 14802 kVAh/year = Rs 52843.00/year (@ Rs 3.57/kVAh
Total investment
= Rs 5,000
Payback period
= 2 months
7.2.3
Energy Saving Opportunity in DG Sets
The loading of the DG set as shown in the Figure- 7.1, significantly influences the fuel efficiency of a DG set. The associated losses due to operation of the DG set below the optimum limit is reflected by significant increase in the specific fuel consumption. As can be seen from the curve, the generator should be loaded between 65% to 85%. The loading beyond 85% does not give any extra efficiency, but it decreases engine life.
261
DG sets - Other recommendations: Fuel Consumption kwh/litre of oil
700
(i)
600 500
The DG set should be maintained properly and loading should be monitored so as to achieve specific power generation of 3.80 units per litre,
(ii) Energy meters may be installed in the DG panels, to enable the plant to monitor specific power generation of each of the DG set on regular basis.
400 300 I nefficient
range
Efficient
200
(iii) It should be ensured that the single phase loads on the DG set should be distributed appropriately so that the unbalance between the 3 phases is not more than 10% of the total DG set capacity.
range
100
(iv) The lube oil consumption should not exceed 1% of fuel consumption.
0
10
20
30
40
50
60
70
80
90
100
% Rated Load
Figure - 7.1 Load Characteristics of DG Set It is generally observed, that keeping the security lights on during nights is a security requirement. To keep the lights on, DG set is operated in case of power failure. It is further observed that if only lighting load is served by the DG set, the DG set becomes under loaded and hence the specific generation ratio of the DG set goes down drastically. It is suggested to have a smaller DG set to take care of lighting load only during nights. Case Study 6 : Improving the efficiency by overhauling of DG Sets
(v) DG room should be properly ventilated to achieve best results. The allowable temperature of inlet air is ambient ±5 0C. Arrangements should be made to maintain required inlet air temperature, because for every 3 0C rise in inlet air temperature, there is 1% loss of fuel. 7.2.4 Optimization of Power Supply System Billing and Demand Side Management The Energy conservation opportunities mentioned above in the Bottling Plant section under the following heads hold good for terminal / depots as well: a) b) c) d)
Transformers Demand Side Management Maximum Demand Control / PF Control Voltage Optimization
The specific power generation of two no. DG sets available in a terminal was assessed as per the following details :
References :
Equipment
1. PCRA Energy Audit Report, IOCL Jodhpur Terminal, Jodhpur (Rajasthan), August, 2006.
DG Set. - 1 (200 kVA) DG Set. - 2 (75 kVA)
Specific Power Generation (kWh/liter of fuel oil) 2.9 2.5
Remarks At 41% of rated load At 51% of rated load
The specific power generation of both the DG sets is very low, normally it should be > 3.8 units per litre of HSD. As can be seen from the table, the performance of 200 kVA DG set as compared with 75 kVA DG set is better. Corrective measure in the form of major overhauling was undertaken. This resulted in improvement of specific power generation. The yearly consumption could be reduced from 17 kl per year to 11.75 kl per year resulting in savings of 5.25 kl HSD worth Rs. 17,0000/- per year. Monitoring of specific power generation and early detection of deviation would help decide when to conduct major overhaul. Major overhaul may include : (I) (ii) (iii) (iv) (v)
2. PCRA Energy Audit Report, IOCL Najibabad Depot, Najibabad (UP), September, 2005. 3. PCRA Energy Audit Report, HPCL Mathura Terminal, Mathura (UP), April, 2007. 4. PPAC Ready Reckoner, Information as on 1.4.2008, Petroleum Planning & Analysis Cell, MOP&NG, GOI New Delhi 5. Teri Energy Data Directory & yearbook 2007, TERI Press, New Delhi 6. World Energy Outlook, 2007, IEA Publication, Paris, France 7. Basic Statistics on Indian Petroleum & Natural Gas, 2006-07, Ministry of Petroleum & Natural Gas, (Economic Division), GOI
Calibration of fuel injection system Setting of fuel discharge pattern Removal of hot spots Reduction of blow-by Replacement of cylinder liner/piston rings etc. 262
263
Section 4 Energy Conservation in other Industry sectors Ø Chapter - 8 Ø Chapter - 9 Ø Chapter - 10 Ø Chapter - 11 Ø Chapter - 12 Ø Chapter - 13 Ø Chapter - 14
Power Generation Iron and Steel Fertilizers Pulp and Paper Cement Sugar Aluminum
Chapter - 8 Power Generation 8.1
Overview
Availability of quality and affordable power is one of the driving force for industrial development. India is still lagging behind in terms of availability of quality, uninterrupted, clean and affordable power. Available power cannot meet the demand because of which the country experiences a perennial shortage of power. However, scenario of high power demand may change significantly as a result of implementation of energy efficiency measures across various sectors. 8.2
Installed capacity
The total installed capacity under the utilities in India increased to 143 GW (as on 30th April 2008) from 132 GW (as on 31st March 2007) representing an increase of 8.3%. Table - 8.1: Installed Capacity As On 30th April, 2008 (in MW)
Thermal Coal Gas
Diesel
76299 14656 1202
Total
Nuclear Hydro Wind & Other Grand Total Renewables
92157 4120
35908
11125
143311
Source: CEA
8.3
Generation
The overall electricity generation in the country, which was 532.69 BU (Billion Units i.e. Billion kWh) in 2002-03, has risen to 704.451 BU in 2007-08. The increase over last year is 6.83%. The all India PLF (plant load factor) of thermal utilities during 2007-08 was 78.61% as compared to 76.8% in 2006-07. 8.4
Power supply position
The country experienced an overall power shortage of 9.6% and peaking power shortage of 13.8% in 2006-07. The situation deteriorated further in 2007-08, with supply and peaking deficit rising to 9.8% and 16.6% respectively. 8.5
Potential For Energy Saving
Power cannot be generated; only converted from one form to another; what is implied is the generation of some useful power at the expense of some other lessconvenient power. Power generation efficiency can be defined as "useful output power divided by input power", but it is not rigorous enough since at least two choices exist for the evaluation of input power: a) heat-equivalent power, and b) work-equivalent power. Table 8.2 presents typical values of power generation efficiencies using the raw input power, the most commonly used, although the net input power criterion, i.e. the energy or available energy of the raw energy source, gives a more sound measure of the 'technological efficiency' of the power plant.
267
Table - 8.2: Power Generation Efficiencies Energy source
Photovoltaic Solar thermal Gas turbine Spark Ignition I.C. Engine Nuclear Steam turbine Wind turbine Compression Ignition I.C. Engine Fuel cell Combined GT -ST Hydro electrical
Typical efficiency [%] 10 15 30 30 33 33 40 40 45 50 85
Typical range [%] 5 -15 10 -25 15 -38 25 -35 32 -35 25-39 30 -50 35 -49 40 -70 45 -60 70 -90
The consumption of electricity by power plant auxiliaries and the efficiency of the plants depend on factors such as unit size, level of technology, plant load factor, fuel quality etc. The auxiliary consumption in general varies between 3 to 6% for larger plants and close to 10% for smaller captive power plants. Moreover, PCRA studies indicate that the Energy savings in small size power plants varies between 6 - 10% of auxiliary consumption. The overall efficiencies of power plants with sub critical parameters fall in the range of 35 - 39%, which can be improved to 45% using supercritical parameters with conventional steam turbines. Using combined cycle mode, the maximum efficiency can reach upto 50%. Power plants are adopting several latest technologies to improve the efficiency and operating practices. Some of the power plants are installed with multifuel capabilities by design for flexibility to use different fuels depending on availability and price and also to address environmental issues like NOx and SOx reduction. The National Energy Map for India "Technology Vision 2030" report has identified the following, as the preferred power generation technologies: (1)
Large Hydro
(2)
Refinery-residue-based IGCC (integrated gasification combined cycle)
(3)
Imported-coal based IGCC
(4)
High-efficiency CCGT (combined cycle gas turbine) (H-frame gas turbine)
(5)
Indigenous-coal-based IGCC
(6)
Normal CCGT
(7)
Ultra - Supercritical boiler
(8)
Supercritical boiler
(9)
Nuclear Fast Breeder Reactor based Power Plants. 268
Some of these latest technologies and measures available for efficiency improvement are briefly described as under: 8. 5.1
Super Critical Power Plants
New pulverized coal combustion systems utilizing supercritical and ultrasupercritical technology, operate at increasingly higher temperatures and pressures and consequently achieve higher efficiencies than conventional PCF (Pulverized Coal Fluidized) units and results in significant CO2 reduction. Supercritical steam cycle technology has been used for decades and is becoming the system of choice for new commercial coal-fired plants in many countries. Recent plants built in Europe and Asia use supercritical boiler-turbine technology and China has made this standard on all new plants of capacity 600 MWe and upward. Case Study 1: Comparison between conventional process and supercritical pressure steam generation process Conventional Process 1. Conventional steam pressure is around 170 kg/cm2. 2. From the Rankine cycle T-S diagram it has been known that the higher steam pressure & temperature produces the higher thermal efficiency, but it has not been put into practice due to the technological limitation in designing boilers and turbines. New Process 1. In the new process, the steam pressure is raised to a super critical region (higher than 246 kg/cm2), increasing thermal efficiency. 2. Consequently, the boiling of water to generate steam does not occur in the boiler drum. As the water in the liquid phase directly shifts to the vapor phase, therefore once - through boiler is required instead of the drum type boiler. 3. High temperature strength under high pressure was the problem confronting the designing of the super heater, reheater, main steam valve and turbine blades, etc. However, as high-temperature materials have become available economically of late, the supercritical pressure generation is now being widely adopted. 4. When the steam pressure is excessively high (300 kg/cm2 or higher), the gross thermal efficiency does not increase much due to the increase of power consumption by the feed water pump.
269
Process Comparison Process Steam Pressure Steam temperature Turbine Medium pressure rotor blade Pressure Strength
Minimum load Change of load Frequent starts and stops Starting-up loads Start and Stop Thermal efficiency Facility cost
New Process More than 246 kg/cm2 600/5600C High pressure in 11 steps Medium pressure in 6 steps. Ni-Cr-Mc-Ti heat resistant alloy steel. Each unit of the boiler, high pressure feed water heater pumps needs to be made high pressure resistant. 15% - 25% Fast response Suited
Conventional Process 169 kg/cm2 560/5400C High pressure in 9 steps Medium pressure in 6 steps. 12% Cr-Mc-V alloy steel
Ordinary Takes a long time 1-2% higher 1.5 times higher for the 246 kg/cm2 class.
Ordinary Ordinary Standard.
15% Ordinary response Suited
Up to an operating pressure of around 194 kg/cm2 in the evaporator part of the boiler, the cycle is sub-critical. This means, that there is a non-homogeneous mixture of water and steam in the evaporator part of the boiler. In this case, a drumtype boiler is used because the steam needs to be separated from water in the drum of the boiler before it is superheated and led into the turbine. Above an operating pressure of 225 kg/cm2 in the evaporator part of the boiler, the cycle is supercritical. The cycle medium is a single-phase fluid with homogeneous properties and there is no need to separate steam from water in a drum. Once-through boilers are therefore used in supercritical cycles. The traditional coal-fired power plants are marked with emissions of environmentally damaging gases such as CO2, NOx and SOx at alarmingly high levels. Adoption of Ultra Supercritical (USC) power plants with increased steam temperatures and pressures significantly improves efficiency, reducing fuel consumption and environmental emissions by a commensurate degree. Increase of steam parameters from around 180 bar and 540oC-560oC to ultra supercritical condition of 300 bar and 600oC have led to efficiency increases from around 40% in 1980 to 43-47% in 2006. A further enhancement of thermal efficiency may be obtained by combining an advanced steam cycle plant with a gas turbine; in this way efficiencies of over 60% are possible. 8.5.3
New Generation Gas Turbines
Source: Japan Energy Conservation Directory
8.5.2
Ultra Supercritical (USC) Power Plants
There's nothing “critical” about supercritical. “Supercritical” is a thermodynamic expression describing the state of a substance where there is no clear distinction between the liquid and the gaseous phase (i.e. they are a homogenous fluid). Water reaches this state at a pressure above 221 megapascals (MPa). The “efficiency” of the thermodynamic process of a coal-fired power plant describes how much of the energy that is fed into the cycle is converted into electrical energy. The greater the output of electrical energy for a given amount of energy input, the higher the efficiency. If the energy input to the cycle is kept constant, selecting elevated pressures and temperatures for the water-steam cycle can increase the output. Power plants operating at supercritical steam pressures are termed as “Supercritical” power plants. Supercritical power plants, due to their higher efficiencies, have significantly lower emissions of pollutants such as fly ash and Oxides of Sulphur and Nitrogen than sub-critical plants for a given power output. Table – 8.3: Average Efficiency Levels at Pulverised Coal-fired Power Plants Plant Average efficiency levels %
Low efficiency 29
High Super critical efficiency 39 Up to 46
UltraSupercritical 55
Source: World Coal Institute
270
For years, gas turbine manufacturers faced a barrier, that for all practical purposes, capped power generating efficiencies for turbine-based power generating systems. The barrier was heat. Above 1260 oC, the scorching heat of combustion gases caused metals in the turbine blades and in other internal components to begin degrading. Since higher temperatures are the key to higher efficiencies, this effectively limited the generating efficiency at which a turbine power plant could convert fuel into electricity. The US Department of Energy's Fossil Energy department took on the challenge of turbine temperatures in 1992 and nine years later, two of its private sector partners produced "breakthrough" turbine systems that pushed firing temperatures to 1426 oC and permitted combined cycle efficiencies that surpassed the 60 % mark the "four-minute mile" of turbine technology. Moreover, the advanced turbines achieved the higher firing temperatures while actually reducing the amount of nitrogen oxides formed to less than 10 parts per million (NOx is a product of high temperature combustion). Among the innovations that emerged from the Department's Advanced Turbine Systems program were single-crystal turbine blades and thermal barrier coatings that could withstand the high inlet temperatures, along with new firing techniques to stabilize combustion and minimize nitrogen oxide formation. H Series Turbines: 60% Efficient The H System of GE Power Systems was the first turbine to surpass the 60% efficiency threshold, nearly five percentage points better than the prior best available system, in an industry where improvements are typically measured in tenths of a percent. 271
G Series Gas Turbines: 58% Efficient The Siemens Westinghouse engine has demonstrated a net efficiency of approximately 58 percent in combined cycle application.
Annual savings Investment required Payback period 8.5.4
Case Study 2: Surface temperature measurement of steam distribution network at a Gas Turbine Power Station Brief Insulation break in the networking of the steam pipeline and other appliances leads to the loss of power production through Heat Recovery Steam turbine Generators (HRSG). At a Gas Turbine Power Station there are three steam turbines each of capacity 34 MW. Exhaust gases of gas turbine is used to produce steam, which is at temperature of 510OC. The superheated steam from HRSG is sent to steam turbine to produce power and condensate sent to the condenser. In condenser the temp is dropped from 125 to 560C, which is sent to Deaerator. This condensate is again sent to HRSG for Steam Generation. Heat loss takes place from steam distribution network components and is a direct loss of power. Energy savings Sr. 1 2
3 4 5 6 7 8 9 10 11 12 13 14 15 16
Description Total length of insulation break (m) Total area of insulation break/improvement 2 Required (m ) Heat Loss Coefficient 2 (kCal/M /hr) Total Heat Loss (kCal/hr) Steam Flow Rate in Pipeline (T/hr) Total Heat Flow in the 6 Pipeline(kCal/hr x 10 ) Heat Loss% Electrical Efficiency of STG kCal/kWh consumption by STG Heat loss, kCal /hr KWH Lossdue dueto to kWh Loss insulation break brake Working Hrs kWh Saving per Month kWh Saving per Annum Rs/kWh Annual saving in Rs
: Rs 14000 per year : Rs 25000 : 22 months
IGCC Technology (Integrated Gasification Combined Cycle)
An alternative to achieve efficiency improvements in conventional pulverized coal fired power stations is through the use of gasification technology. IGCC plants use a gasifier to convert coal (or other carbon-based materials) to Syngas, which drives a combined cycle turbine. IGCC technology, using coal gasification, allows the environmental benefits of a natural gas fueled plant and the thermal performance of a combined cycle. Coal is combined with oxygen and steam in the gasifier to produce the Syngas, which is mainly H2 and carbon monoxide (CO). The gas is then cleaned to remove impurities, such as sulphur and the Syngas is used in a gas turbine to produce electricity. Waste heat from the gas turbine is recovered to create steam, which drives a steam turbine, producing more electricity – hence, a combined cycle system. Case Study 3: Substitution of LDO By Coal Gasification in thermal power plant Brief
HRSG-3
HRSG-5
HRSG-6
0.25
0.55
0.50
0.471
1.036
0.942
1805.17 850.24
4149.52 4299.73
3663.50 3451.02
53.94
56.86
50.1
187.6 0.0010 STG-2
198.0 173.5 0.0021 0.0021 STG-3 STG-3
13.59
8.20 8.20 8.20
6328.18 850.24
10487.810487.8 7750.757750.75
0.134357 694 93.2 1118.9 2.23 2495.20
0.739025 0.739025 582 582 430.1 430.1 5161.3 5161.3 2.23 2.23 11509.81 11509.81
272
Before Improvement A thermal power station does not have buffer stock of coal for its boiler and therefore the temperature of the furnace goes down. This problem is presently solved by firing LDO, which is a costly proposition in view of increasing cost. Substitution of LDO by the Producer Gas can reduce cost incurred on LDO.
After Improvement Producer gas, with a calorific value of 1100 kcal/m3 is generated in indigenously designed plant. Producer gas at about 350 0 C is then led to use point, which can be 50-150 m away.
Energy savings Avg. expenses on the LDO are about = Rs 6, 01,942 per day Expenses on equivalent coal is = Rs 3,02,674 per day Thus, saving of about Rs 2,99,267 per day is achieved. Annual savings : Rs 109 Million Investment required : Rs 30 Million Payback period : 4 months 8.5.5 High efficiency steam turbine blade A steam turbine that provides a high thermal efficiency by adopting the latest blade design theories, such as the laminar flow blade (Shrinked blade) with the crosssection of the blade designed to cause the least turbulence to the steam flow, a nozzle with its tip twisted in consideration of the effect of the outer and inner walls on the tip and the root of the blade (controlled vortex nozzle) and the multiple fin sealing designed to prevent steam leak from the tip of the blade. 273
Case Study 4: High efficiency steam turbine blade Brief Internal heat efficiency of a 500,000 kW-class high-technology steam turbine is 2 - 2.5% (relative value) better than the conventional type. With the utilization rate of 38%, energy saving is 3,500 kL/y in crude oil equivalent. Energy savings Annual savings Investment required Payback period 8.5.6
: Rs 80 Million : Rs 160 Million : 2 years
Nuclear Power Generation
The use of nuclear power for electricity generation commenced about 50 years ago in India. Today, nuclear power produces 3% of the country's total energy generation. Expanding nuclear power is thus a matter of continuation of National strategies. More countries are embracing nuclear power as a part of their energy mix and as their Global environmental responsibility. 8.5.6.1 Three Stage Nuclear Power Programme The total energy content in the current known Indian nuclear resources is at least twenty times more than that of other non-renewable resources. With a view to utilize this huge resource for electricity generation, Department of Atomic Energy (DAE) has been working on a three-stage nuclear power programme based upon closed fuel cycle. The three stages need to be executed sequentially. The three stages are: • • •
Natural uranium fuelled Pressurized Heavy Water Reactors (PHWRs) Fast Breeder Reactors (FBRs) utilizing plutonium based fuel Advanced nuclear power systems for utilization of thorium
Work on the 1st stage is already on progress. The current Indian nuclear energy resource consists of 61,000 tonnes of Uranium (U235 & U238) and more than 225,000 tonnes of thorium (T 232). The Indian Nuclear power programme is based on closed nuclear fuel cycle, in which the spent fuel of the first stage Pressurised Heavy Water Reactors (PHWR) is reprocessed to obtain fissionable Plutonium. Table - 8.4: Three stages in Indian Nuclear Power Programme STAGE-I PHWRs -15 units operating. -3 units under construction -Scaling to 700 MWe -Power potential 10GWe
STAGE-II FBRs -Operational since 1985 -Technology realised. -40 MWth FBTR are in operation -500 MWe PFBR under construction -Power potential 530 GWe
STAGE-III TBRs
-30 kWth Operational-300 MWe under development -Power potential is very large
The first stage comprising setting up of PHWRs and associated fuel cycle facilities is already in the industrial domain. The technology for the manufacture of various components and equipment for PHWRs in India is now well established and has evolved through active collaboration between the DAE and the industry. Twelve PHWRs are operating and two more 220 MWe PHWRs and two PHWRs of 540 MWe rating are under construction. Construction of more such units is being planned. As DAE gains experience and masters various aspects of the nuclear technology, performance of nuclear power plants is continuously improving. Average capacity factor of nuclear power plants has steadily risen from 60% in 1995-96 to 82.5% in the year 2000-01. The second stage envisages setting up of Fast Breeder Reactors (FBRs) backed by reprocessing plants and plutonium-based fuel fabrication plants. In order to expand the nuclear power capacity in the country, fast breeder reactors are necessary. For the second stager reactors, plutonium, due to its highest value of eta (the ratio of neutrons produced to neutrons absorbed) of all fissile materials, is used in the fast breeder reactors (FBR). The current Indian programme in the 2nd stage starts with the well proven oxide fuel based FBRs and subsequently, at an appropriate stage, when all new necessary technologies have been developed & demonstrated, metallic fuel based FBRs will be introduced. A 40 MWt, Fast Breeder Test Reactor (FBTR) has been operating at Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam. FBTR has provided valuable experience with liquid metal Fast Breeder Reactor Technology and the confidence to embark upon construction of a 500 MWe Prototype Fast Breeder Reactor (PFBR). Detailed design, R&D and technology development of the PFBR is in advanced stage. Construction work on this is expected to start in a few months. This will also be located at Kalpakkam near Chennai. The third stage will be based on the Thorium-uranium-233 cycle. Uranium-233 is obtained by irradiation of Thorium in PHWRs and FBRs. An Advanced Heavy Water Reactor (AHWR) is being developed at Bhabha Atomic Research Centre (BARC) to expedite transition to thorium-based systems. The reactor physics design of AHWR is tuned to generate about 75% power in Thorium, and to maintain negative void co-efficient of reactivity under all operating conditions. 8.5.7
Advanced Cogeneration Systems
Combined heat and power systems (CHP, also called cogeneration) generate electricity (and/or mechanical energy) and thermal energy in a single, integrated system. Conventional electricity generation is inherently inefficient, converting only about one third of a fuels potential energy into usable energy. Because CHP captures the heat that would otherwise be rejected in traditional generation of electric or mechanical energy, the total efficiency of these integrated systems is much greater than from separate systems. The significant increase in efficiency with CHP results in lower fuel consumption and reduced emissions compared with separate generation of heat and power. CHP is not a specific technology, but rather an application of technologies to meet end-user needs for heating and/or cooling, and mechanical and/or electric power. Steam turbines, gas turbines, combined cycles, and reciprocating engines are the major current technologies used for power generation and CHP. Some basic overview of specific end-use applications of CHPs in varying capacity is as under:
Source : Department of Atomic Energy 274
275
Large scale (> 10 MW). Currently, most of the installed CHP plants have capacities over 20 MW. The future potential of large-scale conventional CHP systems is estimated at 48 GW. An increase in turbine-inlet temperature has led to increasing efficiencies in gas turbines. Industrial-sized turbines are available with efficiencies of 40 to 42%. The higher inlet temperature also allows a higher outlet temperature. The flue gas of the turbine can then be used to heat a chemical reactor, if the outlet and reactor temperatures can be matched. One option is the so-called “re-powering” option. In this option, the furnace is not modified, but the combustion air fans in the furnace are replaced by a gas turbine. The exhaust gases still contain a considerable amount of oxygen, and can thus be used as combustion air for the furnaces. The gas turbine can deliver up to 20% of the furnace heat. Another option, with a larger CHP potential and associated energy savings, is “high temperature CHP.” In this case, the flue gases of a CHP plant are used to heat the input of a furnace. High temperature CHP requires replacing the existing furnaces. This is due to the fact that the radiation heat transfer from gas turbine exhaust gases is much smaller than from combustion gases, due to their lower temperature. The main difference is that, in the first type the process exhaust gases directly heat feed, where the second type uses thermal oil as an intermediate, leading to larger flexibility. In the first type, the exhaust heat of a gas turbine is led to a waste recovery furnace in which the process feed is heated. In the second type the exhaust heat is led to a waste heat oil heater in which thermal oil is heated. The heat content of the oil is transferred to the process feed. The second type is more reliable, because a thermal oil buffer can be included.
connected power plants, but their use in CHP unit can provide substantial energy savings. Fuel cells generate direct current electricity and heat by combining fuel and oxygen in an electrochemical reaction. This technology is advancement in power generation that avoids the intermediate combustion step and boiling water associated with Rankine cycle technologies or efficiency losses associated with gas turbine technologies. Fuel to electricity conversion efficiencies can theoretically reach 80-83% for low temperature fuel cell stacks and 73-78% for high temperature stacks. In practice, efficiencies of 50-60% are achieved with hydrogen fuel cells while efficiencies of 42-65% are achievable with natural gas as a fuel. The main fuel cell types for industrial CHP applications are phosphoric acid (PAFC), molten carbonate (MCFC) and solid oxide (SOFC). Proton Exchange membrane (PEM) fuel cells are less suitable for cogeneration as they only produce hot water as byproduct. PAFC efficiencies are limited and the corrosive nature of the process reduces the economic attractiveness of the technology. Hence, MCFC and SOFC offer the most potential for industrial applications. Although PAFC fuel cell system is most commercially developed, MCFC and SOFC offer the most potential in terms of efficiency. Stand-alone SOFCs have achieved efficiencies of 47%, and in combination with a gas turbine in a pressurized system, efficiencies of 53% (LHV) have been achieved. Unfortunately, the production costs of SOFCs are still high. A comparison of different fuel cell technologies is given below in table no 8.5: Table - 8.5: Comparison of different Fuel Cell Technologies Electrolyte
Medium scale (< 20 MW). Research aims at developing medium-scale gas turbines with high efficiencies. Current turbines of this size have efficiencies of around 25%.
Operating temperature Efficiency Typical Electrical Power Possible Applications
Steam-injected gas turbines (STIG, or Cheng cycle) can absorb excess steam, e.g. generated due to seasonal reduced heating needs, to boost power production by injecting the steam in the turbine. Steam injection boosts the power output of the turbine. The size of typical STIGs starts around 5 MWe. Currently, over 100 STIGs are found around the world, especially in Japan as well as in Europe and the U.S. Many industrial sites have excess low-temperature waste heat that is currently not used due to a lack of suitable uses or due to poor economics.
AFC Potassium hydroxide
60-90 C
60-130 C
MCFC Immobilized Liquid Molten Carbonate o 650 C
45-60% Up to 20kW
40% <10 kW
45-60% >1 MW
o
DMFC Polymer membrane o
Submarines, Portable Power spacecraft applications stations
PAFC Immobilized Liquid Phosphoric acid o 200 C
PEMFC SOFC Ion Ceramic Exchange membrane 80 C
1000 C
35-40% > 50 kW
40-60% Up to 250 kW
50-65% > 200 kW
Power stations
Vehicles. Small stationary
Power stations
o
o
Source: www.fuelcellstoday.com
Pressure recovery turbines are an opportunity to recover power from the decompression of natural gas or pressurised fluid lines on industrial sites. Recovery turbines can recover part of this energy by producing power. Small scale (< 1 MW). For small scale industrial applications, the major developments are found in improved designs for reciprocating engines, fuel cells, micro turbines, and developments in integration of the unit in processes allowing more efficient operation (e.g. tri-generation of power, heat and cooling or drying and other direct process applications, see above). Micro-turbines and fuel cells are the most exciting developments in small-scale CHP technology. Micro turbines (25- 500 kW) are expected to have an efficiency of 26-30%. Although this is lower than the efficiency of power generation in large grid 276
Case Study 5: Air cooler for gas turbine combustion air in a CHP plant Brief • • • • •
An unvented type gas turbine has a characteristic that as intake-air temperature rises, the output drops. This is the main cause of the power drop in summer time of a combined steam and gas turbine cycle power plant of a high thermal efficiency. As a countermeasure for it, an air cooler using a spray nozzle utilizing latent heat of water has been developed. When the dry-bulb thermometer (DB) indicates 300C and the wet-bulb thermometer (WB) indicates 23.50C, relative humidity (RH) is 60%. In this case, cooling by water injection is performed with humidifying effect. 277
As the result, DB temperature becomes 28.20C and WB temperature, 23.50C respectively. The inlet temperature decreases by 1.5 0C because of which the output of gas turbine increases and thermal efficiency improves.
ii. iii. iv. v.
Improvement of the fuel preparation and firing system Implementation of techniques for further reduction of the NOx emissions Improvement of particles collecting systems Optimization of the existing fuel drying system or implementation of new effective drying techniques Replacement, rearrangement or resizing of heat exchange surfaces Supplementary heat exchange surfaces for further heat recovery from flue gas Improvement of air preheating system
Energy savings Increase of output from combined plant (at temperature 30°C, relative humidity 60%): 12,000 kW Reduction equivalent to crude oil consumption: 23,328 kL/year Case Study 6: Rotating regenerative air pre-heater automatic seal gap controller
vi. vii. viii.
Case Study 7: Operation method of increased temperature of main steam at boiler outlet
Brief A device to prevent air leakage in a rotating regenerative air preheater (hereafter referred to as A/H) adopted in a medium to large capacity boiler. 1)
Air leakage occurs through the gap between the rotating part and the stationary part of the A/H toward the gas side (ordinarily about 10%).
2)
The air leakage is caused by such factors as the radial seal at the high -temperature side, radial seal at the low temperature side, and post and axial seal entrainment (residual air in the heat conductive elements).
3)
Air leakage from the radial seal at the high temperature side is the most conspicuous, accounting for 40 - 50% of the total air leakage.
Energy savings
Brief A method to improve thermal efficiency and to reduce fuel consumption by raising the temperature of the main steam at the boiler outlet to 561°C (previously 541°C) Before improvement The following are the previous operational condition of the boiler and turbine. Temperature of main steam at the boiler outlet: 541°C Temperature of main steam at the turbine inlet: 538°C Vacuum of the condenser: 722mmHg Gross thermal consumption rate: 2,208kcal/kWh Thermal efficiency: 38.95% Secondary superheater heat transfer area: 390 m2 Secondary superheater tube material: SUS 321HTB
Forced draft power Heat recovery
After improvement
Before installation 8.32%
3,097.6kW
(Standard)
1)
After installation Reduction rate
3,038.6kW 59.3kW
+903,000kcal/h 96 liter/h (oil equivalent)
2)
Air leak rate
6.19% 2.13%
Annual savings Investment required Payback period
: Rs.19.4 Million : Rs.15 Million : Less than12 months
3) 4) t
Improvement of thermal efficiency by increasing the temperature of the main steam is evaluated by examining the T-S diagram of the Rankine cycle. For increasing the temperature of the main steam, it is necessary to increase the heat transfer area, for which space is needed. At the same time, high temperature corrosion resistance of the heat transfer tube needs to be increased. Based on the above examination, it was decided to raise the temperature of h e main steam to 561°C, and the following measures were implemented.
·
Temperature of main steam at the boiler outlet: 561°C (increased by 20°C)
Old power plants are modernized to keep up the operation of the equipment and its efficiencies. The advantages of Renovation & Modernization are:
·
Temperature of main steam at the turbine inlet: 556°C (increased by 18°C)
i. ii. iii. iv. v.
·
Secondary superheater heat transfer area: 750 m2 (approx. twofold increase)
·
Secondary superheater tube material SUS 347HTB
8.5.8
Renovation & Modernization
Enhancement of operational efficiency Improvement in Plant Load Factor (PLF) Meeting stringent environmental pollution control standards Extend plant life Capacity augmentation
Following renovation and retrofitting techniques are mostly adopted by power plants: i.
5)
The secondary superheating tube has been changed from the previous 1-loop
Steam turbine retrofitting (blades replacement and improvement of the labryrinths' operation and turbine control system etc) 278
279
· · ·
Energy savings The effect of this method applied to a 220,000 kW generation plant is shown below : Load Gross thermal consumption rate Thermal efficiency Improvement of thermal efficiency
220,000 kW (rated) 2,195 kcal/kWh 39.23% 0.28%(absolute value)
Annual fuel saving Approx. 1,100 kL (At a utilization rate of 30%)
· ·
Losses via the off-gas Losses through unburnt fuel Losses through unburnt material in the residues, such as carbon in bottom and fly ash Losses via the bottom and fly ash from a DBB (Dry Bottom Boiler) and the slag and fly ash from a WBB (Wet Bottom Boiler) Losses through conduction and radiation
8.5.9.1 Short-term Energy Efficiency Improvement projects for power plants Annual savings(at an utilization rate of 30%) : Rs 25.52 Million Investment required : Rs 47.2 Million Payback period : 22 months Case Study 8: Gas recirculating steam temperature control system Brief For the purpose of balancing the thermal absorption between the evaporation section of the boiler (mainly radiation heat in the furnace) and the superheating section for the steam (mainly convective heat transfer in the superheater, reheater, and the economizer), boiler exhaust gas at the economizer outlet is recirculated by the recirculation fan to the bottom of the furnace. Before replacement Previously, the thermal absorption balance would tilt toward the superheating section, and when the temperature of the superheated steam was in excess of the designated value, spray water was injected into the superheated steam to lower the temperature(water spray steam temperature control system). As the water spray method would lower the boiler efficiency, this method was not thermally efficient. Boiler efficiency is lowered by 1 - 1.5%. The thermal absorption balance depends on the kind of fuel used and changes by converting the fuel.
After replacement By the gas recirculation method, the amount of evaporated steam is decreased (or increased), and the temperature of the superheated steam goes up (or goes down), as the recirculation gas is increased (or decreased). As this adjustment is made easily by adjusting only the damper of the recirculation fan, it can be readily applied to various fuels such as heavy oil, crude oil, natural gas, etc.
Total
Brief Improvement by 0.48% in both SH and RH Saving of power for the recirculating fan equivalent to thermal efficiency of 0.02% Improvement equivalent to thermal efficiency of 0.5% (converted in fuel cost)
Annual savings (Boiler at 250MW class) Investment required Payback period 8.5.9
Installation of online oxygen analyzer to improve combustion efficiency of Boiler ii. Preventing air infiltration into boiler flue gas path particularly in waste heat recovery zone iii. Installation of waste heat recovery system for boiler blow down iv. Installation of LP steam air heater for FD fan air inlet to boiler v. Optimization of operating breakdown voltage of ESP's vi. Proper insulation of steam and condensate lines vii. Proper and regular monitoring & replacement of defective steam traps viii. Wetting of coal with higher fines percentage to avoid the segregation effect ix. Installation of delta to star converters for lightly loaded motors x. Use of translucent sheets to make use of daylight xi. Installation of timers for switching on/off yard & outside lighting xii. Switching off transformers based on loading xiii. Optimization of TG sets operating frequency based on user requirement xiv. Optimization of TG sets operating voltage xv. Replacement of aluminum blades with aerodynamic FRP blades in cooling towers xvi. Installation of Temperature Indicator Controller (TIC) for optimizing cooling tower fan operation based on ambient conditions xvii. Minimizing compressed air leakages and optimization of compressed air network operating pressures xviii. Segregation of service air and instrument air systems xix. Installation of VFD for cooling tower make up water pump with water basin level control feed back xx. Installation of VFD for DM water transfer pump xxi. Ensuring total closure of standby equipment dampers xxii. Reduction in RPM of Coal Handling Plant's Dust Extraction Blowers Case Study 9: Control of excess air by installing O2 monitoring system in boiler of CPP system
Energy savings Thermal efficiency Power cost
i.
: Rs 16 Million : Rs 20 Million : 16 months
Energy Efficiency Improvement through loss minimisation
The operation of the steam generator requires continuous surveillance. The heat losses from the steam generator can be categorised as: 280
By monitoring the O2 level of 5-6 % of the flue gas on continuous basis, the input of excess air level can be maintained, which shall help in regulating the heat loss to the environment. Before Improvement Presently, there is no indication of % O2 in flue gases of this boiler. Without this, optimization of efficiency of boilers is not possible on continuous basis, especially when BF gas and Mix gas availability is changing. 281
After Improvement By achieving 6% O2 by installation of monitoring systems (zirconium oxide online oxygen analyzer), following was achieved: Increase in boiler efficiency by 3.4%. Reduction in FD fan airflow by 60%. Reduction in ID fan flow by 60%.
Energy savings
Energy savings
The following table summarizes the overall effect of O2 monitoring control. Effect of O2 control on boiler performance
Energy savings by reducing the operating pressure to 7.5 kg/cm2 (cut-off pressure) is as follows:
Parameter
% O2 Excess air, % Boiler efficiency, % 3 FD fan airflow, Nm /h 3 ID fan airflow, Nm /h
Existing Condition
12.6 148 87 118976 232590
After installing O2 monitoring & control system 6 40 90.4 64392 149858
Annual hours of operation HP-4 boiler = 7690 hours Average steam generation = 77.48 TPH (average during trials) Annual saving in fuel = Steam flow x Enthalpy of steam x (1/Eff1 - 1/Eff2) x Annual running hours GCV of coal Where, Eff1 = Existing efficiency of boiler Eff2 = Likely efficiency of boiler after modifications in control GCV of coal is used to convert the fuel energy saved in terms of reduction in coal consumption for same total steam output of all boilers combined. Annual saving in fuel input = 77.48 x 639 x (1/0.87 - 1/0.904) x 7690 3825 = 4303 tonnes per year Price of Coal = Rs. 1000/ tonne Annual monetary saving = 4303 x 1000 = Rs. 43,03,000 Annual savings : Rs 4.3 Million Investment required : Rs. 5 Million Payback period : 13 months Case Study 10: Use of Variable frequency drives on FD fans in place of existing Inlet vane control Brief Before Improvement The existing FD fan motors are 45 & 85 kW rated at 415 V. Input power of each fan is about 50 and 68 kW. Annual savings Investment required Payback period
After Improvement For a flow reduction of about 50%, reduction in power input to FD fans is 50% as compared to the existing IGV control. The power saved is 60KW. : Rs. 1.16 Million : Rs 0.5 Million : 6 months
Case Study 11: Reduction of cutoff pressure of air compressor
% Savings by pressure reduction from9 kg/cm2 to 7.5 kg/cm2
=
Savings in Compressor kWh consumption/month
=
Annual savings
=
(Present kW/100 CFM – kW/100 CFM at suggested pressure)/ Present kW/100 CFM = (22.23 – 19.5) x 100/22.23 = 12.28% Monthly Compressor kWh consumption x % Savings = 110361 x 0.123 = 13574 kWh/month 13574 x 12 = 162888 kWh = Rs. 3, 48,580 per annum
Annual Savings Investment required Payback period
: Rs 0.35 Million : nil : Immediate
Case Study 12: Installation of Automatic Temperature Controller (ATC) for switching ON/OFF cooling tower fan Brief Before Improvement It was observed that the operations of the Cooling Tower Fan installed on the Cooling Tower is not controlled based on the ambient climatic conditions vis-à-vis temperature differential (delta T). As a result, CT fan was operating continuously without taking into account the inlet & outlet temperature variations.
After Improvement If outlet cooling water temperature is lower than the desired value, then natural cooling is sufficient. This means that the cooling tower fans can be switched off by installation of Automatic Temperature Controllers during this period.
Energy savings % Savings by temperature control = 15% Total Cooling Tower KWh = consumption/month Savings in Cooling Tower Fan = Electricity Consumption Annual savings in terms of Rupees =
Brief Before Improvement The compressed air in gas-based power plant is used for supplying to the instrumentation and plant air requirement and the pressure kept for cutoff is 9 kg/cm2.
After Improvement As the application is basically for instrumentation and plant air requirement, the pressure was reduced from 9 kg/cm2 to 7.5 kg/cm2. 282
Annual % savings in internal electricity consumption Annual savings Investment required Payback period 283
=
429.36 x 710 = 304845.6 KWh/month 304845.6 x 0.15 x 12 KWh/annum = 548722 KWh/Annum 548722 x 2.14 = Rs. 1174265.25 per annum 548722/(12 x 4.97 MU x 10^6) = 0.92%
: Rs 1.174 Million : Rs 0.2 Million : 2 months
8.5.9.2 Medium term Energy Efficiency Improvement projects for power plants
Case Study 14: Replacement of fin fan cooler by water-cooled Plate Heat Exchanger (PHE )
i. ii.
Brief
Installation of economizer / air pre-heater for Boiler Installation of VFD for Condensate Cooling Water (CCW) pump and closed loop control based on discharge header pressure iii. Reduction of heat rate of gas turbines by optimizing NOx water injection and arresting leakages through bypass dampers iv. Installation of Turbine inlet air cooling to increase power output of gas turbines v. Installation of low excess air burners vi. Installation of lower head fan for boiler ID fan vii. Installation of Variable fluid coupling or VFD for condensate extraction pump viii. Utilization of flash steam from boiler blow down for de-aerator heating ix. Installation of capacitor banks for PF improvement x. Replacement of rewound motor with high energy efficiency motors xi. Utilization of energy efficient lighting systems xii. Installation of LED panel lamps xiii. Replacement of old and inefficient compressors with screw or centrifugal compressors xiv. Replacement of V-belts with synthetic flat belts Case Study 13: Install VFD for boiler ID fans and PA fans Brief In a major captive power plant, three circulating fluidized bed combustor (CFBC) were in operation. Each boiler has two ID fans and three Primary Air (PA) fans. Energy savings Before Improvement
• • •
In tropical climates, for normal cooling application water-cooling is more energy efficient. Air-cooling is convenient when an average ambient temperature drop is below 20OC & ambience is relatively dust free. Therefore it was recommended to replace Fin-Fan coolers by water-cooled PHEs.
Energy savings Before Modification
After Modification
Energy being consumed by fin fan By replacing these with water cooled cooler with average running of 4 fans PHE, there was a saving of 30.55 kW. was 91.27 kW per hour. Thus there was a total saving of 60.72 kW per hour or 9.62 lakhs units/year. Annual savings Investment required Payback period
: Rs 2.0 Million : Rs 2.0 Million : 12 months
Case Study 15: Replacement of Conventional T-8 tube lights with T-5 tube lights with Electronic chokes in a power plant After Improvement
All the fans had higher capacity & head by design and controlled either by IGVs or Dampers to meet the operating requirements.
Variable frequency drives were installed for 6 nos of ID fans and 9 nos of PA fans to control the speed of the fan with respect to operation of the boiler. The The estimated operating efficiency inlet guide vanes (IGVs) were kept fully of the fans was in the range of 60% opened after the VFD was installed. - 65% as against design efficiency The advantage of installing a variable of 80%. It was confirmed that the frequency drive for the boiler ID fans fans were operating in an energy is as follows: inefficient zone on the fan § Energy saving performance curve. § Precise control of parameters
Annual savings Investment amount Payback period
Fin-Fan Cooler is used to cool GT Lube Oil, Turbine Legs, Atomized Air & Generator Air. Here the cooling is achieved by air-cooled heat exchanger. At a time on average basis 4 fans operate per GT with a combined power consumption in 4 fans = 91.27 kW.
: Rs. 6.0 Millions : Rs. 10.0 Million : 20 months
Brief The normal tube lights with conventional chokes consume about 54 W as compared to the T-5 tube lights, which consume about 30 W. By replacing them with T-5 tube lights, there is a saving of 24 W per light. The efficiency and the lux produced are better along with the longer life. Energy savings
Wattage Saving in Wattage Nos. in operation Hrs in operation kWh saving per year
Annual saving in term of Rs
284
285
T –8 54 Watt -
-
T -5 30 Watt 54 – 30 = 24 Watt 549 10 hrs/day 30 x 10 x 549 x 12 x 24 1000 = 47434 kWh/ year 47434 x 2.14 = Rs 1, 01,508
Annual savings Investment required Payback period
: Rs 0.1 Million : Rs 0.41 Million : 48 months approx
Case Study 17: Convert Spreader Stoker Boilers to Fluidized Bed Boilers Brief
Case Study 16: Removal method of scale from inside condenser tubes Brief The ball cleaning method for removing scales deposited inside the condenser tube becomes less effective as time goes by. The method introduced here is free from such deterioration, and is able to restore and maintain the heat exchanging effectiveness of the condenser as designed. The method involves use of 27 mm dia sponge balls followed by plastic coat ball (G-ball) & then Corborundum ball (C-ball). Besides cleaning is conducted once a week or when vacuum detoriates to 3mm Hg. 1)
For removing scales deposited inside the condenser tube, cleaning with sponge balls, 26mm diameter, was previously used. Sponge balls eventually lose their surface roughness, or become deformed, and become unable to contact the inside wall closely. Hard scales that cannot be removed by the sponge balls are gradually deposited. Soft scales consist of silica and organic substances, and hard scales consist of manganese substances. As a result, the vacuum of the condenser deteriorates from the original level by about 5mmHg.
2) 3) 4) 5)
o 78% with this modifica ulted in an annual coal s
Energy savings
Energy savings
Annual savings Investment amount Payback period
When applied to a 250 MW coal fired power plant (operating rate 82.2%):
Deterioration of vacuum Saving of fuel (under rated output)
Before improvement 6mmHg
After improvement 1mmHg
—
0.65 ton/h
Annual savings (operated for 300 days) Investment required Payback period
: Rs 14.96 million : Rs 0.12 million : Less than 1 month
8.5.9.3 Long-term Energy Efficiency Improvement projects for power plants i. ii. iii. iv. v. vi. vii.
Reduction of one stage of feed water pump or installation of VFD with feed back control to exactly match with system pressure Installation of VFD for Boiler ID/FD fans Installation of VFD for Boiler feed water pump Installation of CFBD boilers for efficient combustion Conversion to AFBC technology from chain grate/spreader stoker boilers Installation of high efficiency turbines Installation of Distributed control system (DCS) for plant operation and monitoring
286
: Rs. 10.50 Million : Rs. 27.0 Million : 31 months
Case Study 18: Reduction in stages in multistage pumps of LP and HP pumps of Boiler Feed Pumps Brief Reduction in number of stages of LP and HP pumps has led to reduction in head given by boiler feed pumps thus reducing the input power of the motors. •
Selection of operating/design pressure of pumps is made broadly as equal to working pressure plus margins considered safe at each level of decision-making.
•
Therefore, in the plant, control valves are provided and design values are met with by throttling.
`
Instead of throttling, if the number of stages is reduced, then the head developed is as per the actual requirement, which reduces the input power of the motor.
287
Energy savings
Case Study 20: Gravity feeding of make-up water at PPCL, Delhi Brief
Before Replacement
After Replacement
Boiler water handled for LP section is 75 m3/hr and HP section is 367 m 3 /hr. Desired flow rates are achieved by throttling the delivered head of pump.
LP Boiler feed pumps: The input power reduction by removal of stages = 48 kW Annual Saving in kWh = 48 x 24 x 330 = 3, 80,160 (Average working days per year = 330)
Before Modification The cooling tower make up at Pragati Power Station is fed with one pump of discharge capacity of 350m3/hr with 45 kW driving motor.
HP Boiler Feed Pumps: The input power reduction by removal of stages = 1316 kW Annual Saving in kWh = 1316 x 24 x 330 = 1, 04, 22,720
Onsite observation revealed the fact that the cooling tower basin is well below source of make up water.
For LP Boiler: From 214 to 41 m For HP Boiler: From 1440 to 756
Annual savings Investment required Payback period
After Modification Make up water is fed to CT basin under gravity instead of pumping it. Thus the make up pumps are kept as stand by and make up water is being fed due to gravity.
Energy savings Net electrical energy saving of 45 kW
: Rs 23.2 Million : Rs 3.6 Million : 2 months
Annual savings Investment required Payback period
Case Study 19: Use of split mechanical seal in Condensate Extraction Pumps
: Rs 1.5 Million : Rs 0.1 Million : One Month
Brief
8.10
Use of gland packing for sealing in pumps leads to the wastage of DM water at 1 ltr per hour. If mechanical seal replaces the gland packing, then reduction in leakage of DM water, reduction of downtime and reduction in maintenance cost takes place.
Case Study 21: Low-pressure operation of natural circulation boiler
Before Replacement
After Replacement
In case of gland packed CEP, almost 1 liter per hour of DM water is lost. Due to the more wear & tear of sleeve in case of gland packed CEP, the sleeve is replaced frequently and hence this adds to more maintenance cost of the pump.
By using mechanical seal on the CEP, the sleeve cost could be directly saved. Due to the mechanical seal installation on CEP, the pump runs for a longer time as compared to gland packed pumps where pump is required to be stop regularly for replacing the gland packing. This leads to save of down time and main power.
Energy savings • •
In one year about 8760 liter of DM water gets leaked from one pump. This is worth Rs. 123760 per year in terms of money Annual savings Investment required Payback period
: Rs 0.124 Million : Rs 0.13 Million : 12 months
288
Case Studies
Brief Fuel-saving operation through minimizing the reduction of thermal efficiency under low load operation of a natural circulation or forced circulation drum boiler. At a power plant relatively aged or the one operated to adjust the amount of power generated (i.e., an adjustment thermal power plant), the following problems are posed. 1) When operated for power adjustment, mainly during night, minimum load operation comes to around 40%. 2) When operated under minimum load at a constant pressure, there arise the following problems: • Increased pressure loss due to the narrowed regulation valve of the turbine. • Steam consumption of the steam turbine to drive the boiler feed water pump is not negligible from the point of the thermal efficiency of the plant. Energy savings 1)
Under low load operation, the gross thermal efficiency can be increased by 0.5 - 0.6% by reducing the pressure.
2)
When the low-pressure operation was applied to the minimum load (75,000kW) operation at a 350,000kW generation unit, consumption of C-grade heavy oil was saved by 291kl per year
289
Case Study 22: Reduction of starting-up time of cold plant
Case Study 24: Avoiding Unnecessary Pumping for CT make up water
Brief
Brief
When starting up a power plant after a long shutdown (a cold plant), energy loss in starting up is reduced by reducing the starting-up time by omitting/shortening certain steps like turbine warming time, hot water cleaning of turbine before start-up. Energy savings Before Improvement The conventional starting-up schedule of a cold plant requires 29 hours in total. In the starting-up time, a long time is required for warming up the turbine.
After Improvement The starting-up time is reduced by 4 hours and 45 minutes (from 29 hours to 24 hours and 15 minutes) by ommitting/shortening. Certain Step: viz turbine warming time, not water cleaning of turbine before start up making it possible to start supplying electric power earlier than before. Combustion of light oil in the boiler for starting up can be saved by 38kl per one starting-up. Saving per year, which depends on the number of starting up per year, cannot be stated definitely. With increasing operation of the adjustment thermal power plants, which have frequent stops and starts, there are significant savings by this operation method
Case Study 23: Separate type heat pipe exchanger Brief Before Improvement When wet-type desulfurization is applied to a power generation boiler, some problems are caused such as; insufficient diffusion from the stack and occurrence of white smoke (white steam), because treated gas is discharged from the stack as moisturesaturated gas at 52 - 56°C
After Improvement To solve these problems, a heat exchanger utilizing heat pipes is installed which reheats the treated exhaust gas through the heat exchange with the inlet gas to the desulfurization equipment.
Energy savings 1) 2) 3) 4)
Release of SOx and dust is less than an after-burner system. Low running cost and high reliability. In comparison with the after-burner system, burner fuel cost can be saved by 20 - 35 litre/kWh. With a 500MW class of boiler, saving of approximately 15000 kl/year is possible. Annual savings Investment required Payback period
: Rs 3.45 million : Rs 1.75 million : 6 months 290
Before Improvement Make up water comes to first filter on sand bed gravity filter. Output of filters is received in the storage tank through channels. From underground storage tank,water is pumped to cooling tower basin. Pump is consuming 31 kW
After Improvement Elevation of the filter and channel is above cooling tower basins. Thus, passing water directly from the channels to cooling tower basin has eliminated pumping. All the power 31 kW could be saved with direct piping. An auto control valve was however provided to stop flow if the level of the basin went up to basic requirement.
Energy savings Annual savings Investment required Payback period
: Rs 0.525 Million : Rs 0.9 Million : 21 months
Case Study 25: Attaining proper vacuum in condenser by providing spray pond for steam ejector Brief Before Improvement In a Power House, attaining required vacuum at condenser was a recurring problem. Reason for this appears to be dirt, soft scaling material or plastic in the incoming water.
After Improvement Spray pond can be created rather than cooling tower, which is a costly proposition. Saving results due to reduced steam consumption in ejectors.
Energy savings = 200 m3/hr = 950 + 50 + 100 = 1100 m WC = (200 x 9.8 x 1000 x 1100)/ (3600 x 1000 x 0.6) = 998 kW Existing Power consumption = 1182 kW Savings kW = (1182 – 998) = 184 kW At CEP side, potential (130 -54) = 76 kW Saving in monetary terms is (184 + 77) = 260 kW x 3.59 x24 x 330 = Rs 75 lakhs Required flow Head at inlet of economizer Estimated power at 60% efficiency
Annual savings Investment required Payback period
291
: Rs 7.5 Million : Rs 3.6 Million : 6 months
References 1. 2. 3. 4. 5. 6. 7. 8. 9.
10. 11. 12. 13. 14. 15. 16. 17. 18.
19. 20. 21. 22. 23.
Power Scenario at a Glance - CEA - May 2008 Kakodkar, Anil; "Evolving Indian Nuclear Programme: Rationale and Perspective"' Indian Academy of Science, Bangalore, July 2008 LBNL - 54828: Emerging Energy Efficient Technologies in Industry case studies of selected technologies - May 2004 Coal Meeting the Climate Challenge: Technology to reduce GHG emissions; World Coal Institute. Annual Report (2006-07) of Department of Atomic Energy (DAE), GoI Report of the working group on Power for 11th Plan (2007-12) Report of the working group on R&D for the Energy Sector for the formulation of the 11th Five Year Plan (2007-12) Report of the working group on new and renewable energy for 11th Five Year Plan (2007-12) "Clean Coal Technologies for Developing Countries", World Bank Technical paper no. 286, Energy Series, E. Stratos Tavonlareas & Jean- Pierre Charpentierre, 1995 National Energy Map of India: Technology Vision 2030 CII - IREDA Publication: "Investors Manual on Energy Efficiency". LBNL - 62806; World Best Practice Energy Intensity Value for Selected Industrial Sectors, February 2008. LBNL - 57293; Assessment of Energy use and energy savings potential in selected industrial sector in India, August 2005. TERI Energy Directory and Yearbook 2007 Statistical Abstract 2007-CSO Annual Report, NPCIL Japan Energy Conservation Directory Yadav, R.K., "Energy and water conservation in cooling water system of Thermal Power Station: A Case Study of Pragati Power Station", 9th Greentech Global Environment Conference 2008, Goa, Page 237-281 BP Statistical Review, June 2008 www.iea-coal.co.uk www.energymanagertraining.com www.fuelcells.com www.fuelcelltoday.com
292
Chapter - 9 Iron & Steel Industry 9.1
Introduction
Steel plays an important role for the development of infrastructure in the growing economy. With the economic growth rate of 8% - 9%, during the last few years, the demand for steel has touched new heights. In fact, with opening up of the economy in the early nineties, country experienced rapid growth in steel making capacity. Large integrated steel plants set up in private sector and capacity expansion of public sector plants has contributed to making India the 5th largest global crude steel producer in the year 2006. India is expected to become the second largest producer of steel in the world by the year 2015. 9.2
Present Capacity & Growth Potential
Data relating to production, consumption, import & export of finished steel (alloy & non-alloy) and crude steel from the year 2002-03 onwards is given in table 9.1 below:Table 9.1: Production, Consumption, Import, Export of Finished steel & crude steel production. (in million tonnes)
Finished Steel including Alloy Steel Crude Steel
Production Consumption Import Export Production
200203
2003- 04
2004 – 05
200506
200607
37.166 30.677 1.663 4.517 34.707
40.709 33.119 1.753 5.207 38.727
43.513 36.377 2.293 4.705 43.437
46.566 41.433 4.305 4.801 46.460
52.529 46.783 4.927 5.242 50.817
2007-08 (April – December)* 40.117 36.992 5.325 3.850 39.608
*Provisional (Source : Annual Report of Ministry of Steel, GoI, 2007-08)
The projected total demand of finished steel by the end of XIth plan (i.e. year 2011-12) is 70.34 million tonne and production of crude steel is 80.23 million tonne. These figures of demand and production are likely to increase to 90 million tonne and 110 million tonne respectively by the year 2019-20. 9.3
Iron & Steel Manufacturing Process
The two main routes for the production of steel are : • • 9.3.1
Production of primary steel using iron ore and scrap Production of secondary steel using only scrap. Steel Production from Iron Ore
Steel production at an integrated steel plant involves the following four basic steps i.e, i. Production of coke and sinter / pallets from iron fines - Material preparation ii. Reduction of iron ore in blast furnace-Iron making 293
iii. Processing of molten iron to produce steel -Steel making iv. Steel forming and finishing. In addition, the alternative route of iron making is Direct Reduction of Iron Process (DRI) 9.4
products produced & energy efficiency measures adopted by the plants. The details of specific energy consumption by the Indian steel plants (GJ/ tcs) is given in table 3 below:Table 9.3: SEC of Indian Steel Plants (GJ/ tcs)
Production of Crude steel in India through different processes
Plant
Traditionally, Indian steel industry were classified into Main Producers (also referred to as the integrated iron & steel plants for example SAIL (Steel Authority of India Ltd.) plants, Tata Steel and Vizag Steel / RINL (Rashtriya Ispat Nigam Ltd.) and the Secondary Producers. However, with the coming up of larger capacity Steel making units, of different process routes, the classification has been charcterised as Main Producers & Other Producers. Other Producers comprise of Major Producers namely Essar Steel, JSW Steel and Ispat Industries as well as large number of Mini Steel Plants based on Electric Furnaces and Energy Optimising Furnaces. Besides the steel producing units, there are a large number of Sponge Iron Plants, Mini Blast Furnace units, Hot & Cold Rolling Mills & Galvanising/Colour Coating units which are spread across the different states of the country. The following table 9.2 highlights the contribution of the private and public sector in crude steel production in the country:
(in million tonne) Public Sector Private sector TOTAL PRODUCTION % Share of public sector
2004-05 16.0 27.5 43.5 36.6
2005-06 17.0 29.5 46.5 36.5
Bhilai Steel Plant (BSP)
28.53
Durgapur Steel Plant (DSP)
29.58
Rourkela Steel Plant (RSP)
33.39
Bokaro Steel Plant (BSL)
29.66
IISCO Steel Plant (ISP)
34.26
SAIL (as a whole)
29.95
RINL
27.32
TATA Steel
28.07
JSW Steel
25.52
(Source : Annual Report of Ministry of Steel, GoI, 2007-08)
Table 9.2: Sectorial Production of Crude Steel 2003-04 15.8 22.9 38.7 40.0
2006-07
2006-07 17.0 33.8 50.8 33.5
The major energy consuming process in iron making are coking, sinter making & blast furnace. They consume about 61.3% of the total energy. The slabbing mill, and hot strip mill together with others account for 36.5% energy consumption. The table 9.4 gives the major portion of energy consumption in iron making. Table 9.4 : Major portion of energy consumed in iron making
(Source: Annual Report of Ministry of Steel, GOI, 2007-08)
9.5
Energy Consumption in Steel Plants
9.5.1
Energy Intensity
Process
Iron & Steel industry in India is highly energy intensive. Major energy inputs in the sector are coking coal, non-coking coal, coke & electricity. Energy demand in this sector is expected to be nearly 28% of the total industrial energy demand in 2030, which is roughly between 20-22% at present. The demand for coal in steel sector is expected to grow by 5.2% per year (upto2030) and natural gas demand to grow by 6% a year. The electricity demand in the same period is likely to grow 8% per year. 9.5.2
% of total energy
Energy consumed 6 10 kCal/tonne CS
Coking Sinter making Blast furnace
1.033 0.967 3.519
11.5 10.7 39.1
61.3% in iron making
BOF (LD)
0.202
Slabbing mill Hot strip mill Cold rolling mill Other (including losses)
0.483 1.080 1.025 0.91
2.2 5.4 12.0 11.4 7.7
2.2% in steel making
Total
9.000
100.0
36.5% in rolling and others
(Source : Handbook of Energy Conservation by H. M. Robert & J. H. Collins)
Energy Consumption
The specific energy consumption in Indian Steel plants is quite high. It ranges between 25.5 GJ/ tcs to 34.2 GJ/ tcs (tonne of crude steel). On an average, the SEC (Specific Energy Consumption) is 30 GJ/ tcs in India, which is almost double of the World's best plants. There is variation of specific energy consumption in different steel plants. This is mainly because of different processes, quality of coal, types of
294
295
The details of specific energy consumption by process in an Indian Steel Plant is given in table 9.5 below: Table 9.5 : Specific Energy Consumption
Description
Qty. of energy
1.489
-
10.423
-
1.0
-
7.000
Electricity (kWh)
27
-
0.067
-
208
416
0.853
1.706
100
-
0.087
-
Coke breeze (kg)
-
150
-
1.050
Crude tar (kg)
-
40
-
0.034
11.430
Net energy consumed per tonne of BF coke Net energy consumed per tonne of CS (at coke rate of 700 kg and HM ratio of 900 kg)
9.790
1.640 1.033
Sinter plant (per tonne of sinter) Coke breeze (kg)
100
-
0.700
-
Electricity (kWh)
100
-
0.250
-
COG (M³)
20
-
0.082
-
BFG (M³)
50
-
0.043
-
1.075
-
1.075
-
Total Net energy consumed per tonne of sinter) Net energy consumed per tonne CS (at sinter rate of 1000 kg and HM ratio of 900 kg)
0.967
Blast furnace (per tonne of hot metal) Coke (kg) Electricity (kWh)
700
-
4.900
-
30
-
0.075
-
BFG (M³)
1000
2500
0.870
2.075
Steam (kg)
160
-
0.140
-
5.985
2.075
Total Net energy consumed per tonne of HM
3.910
Net energy consumed per tonne of CS (at HM ratio of 900 kg)
3.519
-
BFG (M³)
450
-
0.371
-
Electricity (kWh)
40
-
0.100
-
Steam (kg)
25
140
0.022
0.122
COG (M³)
20
-
0.082
-
Oxygen (M³)
70
-
0.120
-
0.324 0.202
0.122
296
0.483
Net energy consumed per tonne of CS
0.483
Electricity (kWh)
150
-
0.375
-
COG
140
-
0.574
-
BFG (M³)
420
-
0.366
-
Steam (kg)
-
50
-
0.043
1.315
0.043
Total Net energy consumed per tonne of slab
1.272
Net energy consumed per tonne of CS
1.080
Cold rolling mill (per tonne of CR coils) Electricity (kWh)
250
-
0.625
-
Steam (kg)
250
-
0.219
-
COG
70
-
0.287
-
BFG (M³)
210
-
0.183
-
Total Net energy consumed per tonne of CRC
1.314 1.314
-
Net energy consumed per tonne of CS
1.025
(Source :Handbook on Energy Conservation by H.M. Robert & J.H. Collins)
9.6Energy Efficiency in Steel Industry in India In the journey of progress, the Indian Steel Industry has taken significant steps in improvement of productivity, conservation of natural resources, Research and Development, import substitution, quality upgradation and environment management. Some notable developments are: 1. Introduction of Stamp Charging and Partial Briqueting of Coal Charge (PBCC) for production of metallurgical coke - in this process, it has been made possible to replace part of the metallurgical coal requirements by non-coking/ semicoking coal, with higher strength of the coke and less emission. 2. Installation of energy recovery coke ovens - in order to meet the power requirements as well as to reduce emission.
Steel melting shop (per tonne of ingots)
Total Net energy consumed per tonne of CS
0.112
Hot strip mill (per tonne of slabs)
Produced
Total
-
consumed Produced
consumed
-
Steam (kg)
45
Total
BF coke (tonne) COG (M³)
Electricity (kWh)
Energy in heat values (106 kCal)
Coke oven (per tonne of coke) Coal (tonne)
Slabbing mill (per tonne of ingots)
3. Use of non-coking coal in iron making - processes such as Corex have now been introduced in some of the steel plants to produce hot metal by predominantly using non-coking coal. Coal Dust/ Pulverised Coal Injection System has been introduced in several blast furnaces to partially substitute Coke. In addition, there has been large scale growth of sponge iron units based on non-coking coal.
297
4. Use of Direct Reduced Iron (DRI) / Sponge iron in steel making-earlier, only scrap could be used as a feed material in electric arc furnaces. With growing scarcity of scrap, a replacement could be found in the form of DRI produced from iron ore with reformed natural gas/ non-coking coal as reluctant. 5. Use of hot metal in electric arc furnaces - setting up of Basic Oxygen Furnace is capital intensive and successful only at a large scale. 6. Adoption of continuous casting - The first solidified form of steel in the melting shops used to be ingots. With the advent of continuous casting in late seventies and now the adoption of thin slab casting has resulted in energy saving. Today the continuously cast steel output is 66%. 7. Reducing coke consumption in blast furnaces and improving productivity Indian blast furnaces used to consume as high as 850 kilograms of coke per tonne of hot metal and Blast Furnace productivity were hovering at less than one tonne per cubic meter per day. Introduction of modern technologies and practices viz. high top pressure, high blast temperature, pulverized coal injection, attention on burden preparation & distribution, and higher use of sinter in place of lumps have resulted in reduced coke consumption and improved productivity. Today, coke rate in some of the blast furnaces is less than 500 kg/ tonne hot metal & productivity exceeding 2 tonne per cubic meter per day. 8. Enhancing steel quality - Earlier the steel making furnaces used to complete the steel making within the furnaces itself. With the introduction of modern steel making technologies/practices and secondary refining technologies such as ladle metallurgy, vacuum degassing etc., it is now possible to produce steel of much lower inclusion and much lower content of oxygen, nitrogen and hydrogen. The ladle furnace technology has also made it possible to cut down the steel making time in converters or Electric Arc Furnaces and enable to produce steel of low sulphur and phosphorus content. 9. Efforts to reduce energy consumption and emissions - Iron and Steel making involves energy intensive processes. The international norm of energy consumption is 4.5 to 5 Giga calories per tonne of crude steel. With setting up of modern equipments and beneficiation of raw materials, Indian Steel plants have been able to achieve energy consumption at the level of 6.5 to 8.5 Giga calories only. Further, steps are being taken to achieve much lower energy consumption and corresponding lower Green House Gas (GHG) emissions by the end of 11th Five Year Plan. With the growth of steel industry, increasing attention is being paid to environment management. Steps such as afforestation, installation of pollution control equipments etc. are likely to abate the pollution emanating from steel industry. Further, the Indian iron and steel industry is now taking the advantages of Clean Development Mechanism under the Kyoto Protocol thereby reducing pollution and energy consumption.
9.6.1
In Indian steel industry, the specific energy consumption ranges from 25.5 GJ/ tcs to 34.2 GJ/ tcs, depending on the process & product produced. Average SEC of Steel Industry in India is 30 GJ/ tcs as compared to 26 GJ/ tcs of US & 18 GJ/ tcs of Japan. Over the years, a number of energy conservation measures have been taken by each plant. A Important energy conservation implementation are listed below : 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13.
14.
15. 16. 17. 18. 19. 20. 21. 22. 23.
298
Directory of ENCON measures by the Indian Steel Industry
schemes
implemented/under
Fabrication and erection of thyrister control for 800 tonnes shear in Blooming and Billet mill (BSP). Installation of energy efficient dry fog dust suppression system in Blast Furnace stock house (BSP). Installation of side burner in Furnace of Rail Mill (BSP). On-line sealing of steam blast and gas leakage (DSP). Insulation of steam lines and other hot surfaces (DSP). Commissioning of alternate Blast Furnace gas line for Blast Furnace stoves (RSP). Steam impingement on sinter bed introduced in both the strands of Sinter plant (RSP). Commissioning of vapour absorption chiller in Coal Chemicals Department (RSP). Change over from 9-2 pushing series to 5-2 pushing series(BSL). Resumption of coal dust injection in Blast Furnace after capital repair (BSL). Installation of 18 kW motors in place of 24 kW motors in 92 nos. of bases in Annealing Line of Cold Rolling Mill (BSL). Installation of electronic belt weigh feeder at coal handling bunker (IISCO). Conversion of four stroker type boilers at Power House from coal firing to By Product Gas firing thereby reducing the coal consumption in power generation (TISCO). Increased recovery of LD gas from a level of 37 Normal cubic metre per tonne of crude Steel to a level of 56 Normal cubic metre per tonne of crude Steel. The recovered LD gas is mixed with BF gas for utilisation at Power Houses (TISCO). Installation of variable frequency drive to reduce electrical energy consumption (TISCO). Increase in high top pressure at E Blast Furnace, thereby increasing the blast furnace productivity and reduction in blast furnace coke rate (TISCO). Installation of Top Recovery Turbine at H Blast Furnace (TISCO). Modification in LD gas network to recover additional LD gas from another LD Shop (TISCO). Split blowing at Blower Houses to reduce steam consumption for blast furnace blowing (TISCO). Introduction of COREX Technology for Iron Making (JSW). The first 1.2 MTPA non-recovery coke ovens with stamp charging and co -generation of 85 MW waste heat power (JSW). Main gates and street lights are replaced by solar lights (JSL). Installation of air-preheaters in waste heat recovery boilers (JSPL).
299
24. Installation of dual fired boiler (1×63 TPH) substituted coal by Blast Furnace Gas partially (JSPL). 25. Installation of non-recover type, environmental friendly coke oven plant(JSPL). 26. Replacement of petro-fuel by producer gas (JSPL). 27. Introduction of metallurgical coke fines in Electric Arc Furnace by coke injector as cheap substitute of CPC (JSPL). 28. Waste heat recovery boilers (WHRB) installed to utilise sensible heat of off-gas of DRI-Kilns to generate extra electrical power emission (JSPL). 29. Other conventional energy saving measures adopted are : a) LD Gas recovery, b) 100% Continuous Casting, c) Highest hot charging of slabs, d) Coal injection in Blast Furnaces, e) High Hot blast Temperature in stoves 9.7 Details of the World's Best Processes 9.7.1 Blast Furnace- Basic Oxygen Furnace (BOF) Route During the ironmaking process, sintered or pelletized iron ore is reduced using coke in combination with injected coal or oil to produce pig iron in a blast furnace. Limese is added as a fluxing agent. Reduction of the iron ore is the largest energyconsuming process in the production of primary steel. The best practice blast furnace is a modern large scale blast furnace. Fuel injection rates are similar to modern practices found at various plants around the world. The highlights of the process are given below :Blast Furnace and BOF • • • • • • •
Fuel injection rate approx. 125 kg/t hot metal Oxygen is used for enrichment Pressurized operation for blast furnace at four bar Power recovery using Top Gas Power Recovery Turbine (wet type) Heating efficiency of hot gas stoves is maintained at around 85% using staggered parallel operation of 3 to 4 stoves per furnace. Scrap input typically 10% - 25% in BOF Process BOF gas and sensible heat recovery
Coke Plant • • •
Electrical exhausters are installed VFDs for motors and fans Coke Dry Quenching (CDQ) saves additional 1.44 GJ/t (49 kgce/t) coke (kgce = kilograms coal equivalent)
Sinter Plant • • •
Coke and breeze is used as fuel and gas as ignition furnace fuel Moving Grate technology is used Waste heat recovery from sinter exhaust cooler
300
9.7.2 Smelt Reduction - Basic Oxygen Furnace Route Smelt reduction processes are the latest development in pig iron production and omit coke production by combining the gasification of coal with the melt reduction of iron ore. Energy consumption is reduced because production of coke is abolished and iron ore preparation is reduced. Currently, the COREX process (Voest-Alpine, Austria) is commercial and operating in South Africa, South Korea and India, and under construction in China. The COREX process uses agglomerated ore, which is pre- reduced by gases coming from a hot bath. The pre-reduced iron is then melted in the bath. The process produces excess gas, which is used for power generation, DRI - production, or as fuel gas. The best practice values for the COREX plant are based on the commercially operating plant at POSCO's Pohang site in Korea. The plant coal consumption is around 100 kgce/t (Kg Coal Equivalent), 75 kWh/t (9.2 kgce/t) hot metal electricity and 526 Nm3/t hot metal of oxygen. It exports offgases with an energy value of 13.4 GJ/t (457 kgce/t) hot metal. 9.7.3 Direct reduced Iron (DRI) - Electric Arc Furnace (EAF) Route DRI, Hot Briquetted Iron (HBI), and iron carbide are all alternative iron making processes. DRI, also called sponge iron, is produced by reduction of the ores below the melting point and has different properties than pig iron. DRI serves as a highquality alternative for scrap in secondary steelmaking. In the EAF steelmaking process, the coke production, pig iron production, and steel production steps are omitted, resulting in much lower energy consumption. To produce EAF steel, scrap is melted and refined, using a strong electric current. DRI is used to enhance steel quality or if high quality scrap is scarce or expensive. Several process variations exist using either AC or DC currents, and fuels can be injected to reduce electricity use. The best practice EAF plant is state-of-the-art facility with eccentric bottom tapping, ultra high power transformers, oxygen blowing, and carbon injection. The furnace uses a mix of 60% DRI and 40% high quality scrap. The high DRI charge rate limits the feasibility of fuel injection. The best practice excludes scrap preheating, although this is used in large scale furnaces. The best practice DRI-scrap-fed EAF consumes a mix of 60% DRI and 40% scrap. It consumes 530 kWh/t (65 kgce/t) liquid steel for the EAF and 65 kWh/t (8 kgce/t) liquid steel for gas cleaning and ladle refining, as well as 8 kg/t liquid steel of carbon. Installing a scrap preheater reduces power use in the EAF by 40 kWh/t (4.9 kgce/t) liquid steel, reducing total electricity use to 555 kWh/t (68.2 kgce/t) liquid steel. 9.7.4 Scrap - Electric Arc Furnace Route In the EAF steelmaking process, the coke production, pig iron production, and steel production steps are omitted, resulting in much lower energy consumption. To produce EAF steel, scrap is melted and refined, using a strong electric current. Several process variations exist, using either AC or DC currents and fuels can be injected to reduce electricity use. 301
The EAF is equipped with eccentric bottom tapping, ultra high power transformers, oxygen blowing, full foamy slag operation, oxy-fuel burners, and carbon injection. The "best practice" DRI-scrap-fed EAF consumes 100% scrap. It consumes 409 kWh/t (50.3 kgce/t) liquid steel for the EAF and 65 kWh/t (8 kgce/t) liquid steel for gas cleaning and ladle refining, as well as 0.15 GJ/t (5.1 kgce/t) liquid steel of natural gas and 8 kg/t liquid steel of carbon. Installing a scrap preheater would reduce power use in the EAF by 70 kWh/t (8.6 kgce/t), reducing total electricity use to 404 kWh/t (49.6 kgce/t) liquid steel. 9.7.5 Casting Casting can be either continuous casting or thin slab/near net shape casting. Best practice continuous casting uses 0.06 GJ/t (2.0 kgce/t) steel of final energy. Energy is only used to dry and preheat the ladles, heat the tundish, and for motors to drive the casting equipment. Thin slab/near net shape casting is a more advanced casting technique which reduces the need for hot rolling because products are initially cast closer to their final shape using a simplified rolling strand positioned behind the caster's reheating tunnel furnace, eliminating the need for a separate hot rolling mill. Final energy used for casting and rolling using thin slab casting is 0.20 GJ/t (6.9 kgce/t) steel. 9.7.6 Rolling & Finishing
Finishing Finishing is the final production step, and may include different processes such as annealing and surface treatment. The best practice final energy intensity for batch annealing is steam use of 0.173 GJ/t, fuel use of 0.9 GJ/t and 35 kWh/t of electricity, equivalent to 1.2 GJ/t (41.0 kgce/t). Best practice energy use for continuous annealing is assumed to be equal to fuel use of 0.73 GJ/t, steam use of 0.26 GJ/t, and electricity use of 35 kWh/t, equivalent to final energy use of 1.1 GJ/t (or 38.1 kgce/t). Continuous annealing is considered the state-of-the-art technology, and therefore assumed to be best practice technology. While the data describes best practices in energy efficiency for key processes, the integration of these individual technologies is key to obtain the full benefits of these technologies. For example, combined heat and power would increase the efficiency of steam supply for the described processes, while by-product energy flows may also be used more efficiently by implementing more efficient technologies (e.g. use of blast-furnace gas in a combined cycle instead of a boiler). Tables 9.6 and 9.7 below summarize the Energy Intensity Values of the Best Plants based on International Iron & Steel Institutes (IISI) Eco Tech Plant & All Tech plants in U.S. Table 9. 6 : Summary of World Best Practice "Final Energy Intensity Values" for Iron & Steel Sector Iron and Steel Technological Process
Unit
GJ/t
kgce/t
steel
14.8
504.5
steel
17.8
606.4
Direct Reduced Iron – Electric Arc Furnace – Thin Slab Casting
steel
16.9
576.2
Scrap - Electric Arc Furnace – Thin Slab Casting
steel
2.6
87.5
Hot Rolling Rolling of the cast steel begins in the hot rolling mill where the steel is heated and passed through heavy roller sections to reduce the thickness. Best practice values for hot rolling are 1.55 GJ/t (53.0 kgce/t), 1.75 GJ/t (59.6 kgce/t), and 1.98 GJ/t (67.5 kgce/t) of steel of final energy for rolling strip, bars, and wire, respectively. The best practice values assume 100% cold charging, a walking beam furnace with furnace controls and energy efficient burners, and efficient motors. Hot charging and premium efficiency motors may further reduce the rolling mill energy use. Cold Rolling The hot rolled sheets may be further reduced in thickness by cold rolling. The coils are first treated in a pickling line followed by treatment in a tandem mill. The best practice final energy intensity for cold rolling is 0.09 GJ/t (3.0 kgce/t) steam, fuel use of 0.053 GJ/t (1.8 kgce/t) and electricity use of 87 kWh/t (10.7 kgce/t) cold rolled sheet, equivalent to 0.47 GJ/t (13.7 kgce/t) cold sheet.
Blast Furnace – Basic Oxygen Furnace –Thin Slab Casting Slab Casting Smelt Reduction – Basic Oxygen Furnace – Thin Slab Casting
Source : LBNL; Environment Technologies Division; Feb'2008 by WorrellE., Price L., Neelis M., Galitsky C., Nan Z.)
Table 7 : Summary of World Best Practice “Primary Energy Intensity Values” for Iron & Steel Sector Unit
GJ/t
kgce/t
Thin Slab Casting
steel
16.3
555.1
Smelt Reduction – Basic Oxygen Furnace– Thin Slab Casting
steel
19.2
656.8
Direct Reduced Iron – Electric Arc Furnace – Thin Slab Casting
steel
18.6
635.8
Scrap - Electric Arc Furnace –
steel
6.0
205.1
Iron and Steel Technological Process Blast Furnace – Basic Oxygen Furnace–
Thin Slab Casting
(Source : LBNL; Environment Technologies Division; Feb'2008 by Worrell E., Price L., Neelis M., Galitsky C., Nan Z.)
9.8
World's Best Practices of Energy Efficiency
Some important measures of energy conversation in different processes taken by Steel Industry Internationally are highlighted in this section. 302
303
•
• • • • • •
• • •
• •
•
Coal is converted to coke by nitrogen injection process Coke dry quenching (CDQ) is done and the steam and CO gas is recovered. Moisture in coke is controlled by tube type dryer utilizing low temperature steam recovered in CDQ. Sensible heat of gas (CO) recovered from CDQ is used to generate steam, which is used in turbo - blower or moisture control equipment. Moisture is reduced from 8% - 10% to 5% - 7% to increase the density. About 5°C difference moisture control in coal increases the productivity directly by +5%. Exhaust gas heat is recovered from coke oven. Complete heat balance of coke oven is done.
•
• • • • •
•
Increase productivity by improvement of coiler and strip cooling Replacement of plunger pump (de-scaling pump). Waste water heat recovery
In cold rolling process, the following energy conservation measures are adopted: • •
Electric power conservation of dust collector and blower by use of VFD. High temperature and pressure of dust collector is used for generating power by top gas pressure recovery turbine (TRT). Waste heat is recovered from hot stove and it is used for heating combustion air. Granulated slag waste heat recovery is done. Reuse of dust as raw material in blast furnace (reduction in energy consumption in 0.4%). Prevention of molten iron temperature drop by using torpedo car. Complete heat balance of blast furnace and hot stove is done.
In re-heating furnace, the following are energy conservation measures: Extraction of slab at low temperature. Improvement of heat pattern Computer aided furnace temperature control. Proper upkeep of recuperator Improvement of heat transfer through proper design Optimisation of combustion air fan capacity Hot direct rolling through continuous casting Complete heat balance of reheating furnace
In hot rolling process, the following energy conservation measures are adopted: • • •
•
Gas recovery from converter is done. Continuous casting instead of ingots (transport without re-heating). Rolling Process
• • • • • • • • •
Blast furnace and Iron making process • •
•
Heat recovery from hot pallets is utilized to generate low temperature steam, which is used in turbo blower. Waste heat is recovered from cooler boiler VFD is used for speed control of dust collecting blower and boiler water feed pump Steam vapour is used for preheating the sinter. Complete heat balance is done in the sintering process.
Coking process • •
•
• •
Sintering process
Optimisation of motor cooling fan capacity Replacement of plunge pump (de-scaling pump).
In annealing process, the following energy conservation measures are taken: • •
Air and fuel preheating Continuous annealing and process line.
DRI Process • • • • • • • •
•
Optimization of fixed carbon / iron (C/Fe) in the range of 0.40 -0.42. Consistency in ash percentage of coal. Modification of equipments and reduction in motor rating. Optimization of operating parameters. Use Proper capacity shell air fan. Control in Carbon percentage in char (By-product) by efficient combustion. Control of Carbon % in fly ash through better combustion in After Burning Chamber. Effective, Efficient & Close monitoring of operating parameters. Steel Melting Process
• • •
Exhaust gas heat recovery from torpedo car and ladle. Heat recovery from converter slag. LD Converter Gas (Linz and Donawitz) sensible heat recovery. 304
305
The summary of the technological ENCON measures is diagrammatically shown in Fig. 9.1 below Iron making process
Steel making process
Rolling Process
9.9 Energy Efficient Technologies being used in Iron & Steel Industry in Japan Case Studies for different sections are given below for different areas of Iron & Steel Production to finishing and general utilities including Centralized Power Plant (CPP) in an integrated Iron & Steel Plant. 9.9.1 Case Studies in Iron Making Area Case Study 1 : Coal drying and humidity control equipment for coke oven Brief It is the equipment which reduces the humidity in the coal to be charged into a coke oven by heating in order to reduce fuel consumption in the coke oven. It reduces the heat consumption for carbonization and utilises a large amount of non-coking coal.
Technology Improvement in segregated charging of sintering materials. Coal drying and moisture control equipment for coke oven.
Technology
Technology DC arc furnace with water cooled furnace wall.
Pulverized coal injection for blast furnace.
Continuous casting machine.
BF top – pressure recovery turbine.
Channel induction furnace for cast iron melting.
High frequency melting furnace.
Coke dry quenching Exhaust heat recovery system for sintered ore cooling equipment. Sensible heat recovery from main exhaust gas of sintering machine.
The charging amount of coal in a coke chamber is increased, and coke quality is improved by the increased density of coal charging. Productivity is increased by about 5.9% when the water content is reduced by 2.9%. Fuel consumption in the coke oven is reduced by heating the coal and reducing the humidity. Mainly, steam is used for heating coal.
Ferroalloy furnace for effective energy utilization. Hot stove exhaust heat recovery equipment.
Automatic combustion control of coke oven.
BOF exhaust gas recovery device (including sealed BOF)
Blast furnace operation control system.
BOF gas sensible heat recovery apparatus.
Blast furnace hot blast valve control system.
Raw material preheater for electric arc furnace.
Blast furnace burden distribution control.
Heating furnace with regenerative burners. Ladle heating apparatus with regenerative burners. Energy saving operation of electric arc furnace.
Technol ogy Hot charging and direct rolling mill. Channel induction furnace for cast iron melting.
Water Content in coal
Before Improvement
After Improvement
7% - 11%
6%
Energy Saving Energy saving: 40,000-80,000 kcal/t-coal (18,000 kcal/t-coal per 1% of water-content reduction). Investment amount : Rs 800 Million for charge coal of 3,200 kt/year Annual Savings : Rs 400 Million Payback Period : 2 years
Technology Continuous annealing line.
Ferroalloy furnace for effective energy utilization.
Convection heating type heat treatment furnace for wire rod coil.
Heating furnace with regenerative burners.
Low temperature forge welded pipe production method.
High performance heating furnace.
High efficiency gas separation apparatus.
Recovery of sensible heat from skid cooling water in heating furnace.
Centralized energy management. (Energy centre)
Descaling pump (conversion to plunger pump) Operation Improvement of heat treatment furnace.
Case Study 2 : Coke Dry Quenching (CDQ) Brief This improvement is to use equipment which cools red hot coke produced in a coke oven by exchanging heat with inert gas in a sealed vessel, and recovers the heat as steam or electricity. Coke production consumes 7-8% of the whole energy consumed in an integrated steel plant. About 45% of it is the sensible heat of red heat cokes coming out of coke ovens. Conventionally the red heat cokes which have the temperature of 1,0001,200°C, are cooled by water spray, and the sensible heat is dissipated into the atmosphere. Coke dry quenching is to recover this waste heat by performing heat exchange with inert gas such as combustion exhaust gas in a sealed vessel, heating the gas to about 800°C, and generate steam by a boiler Before improvement After improvement
Figure 1 : Iron & Steel : Production Process and Energy Saving Technology Source : Directory of Energy Conservation Technology in Japan: ECCJ) 306
Reduction of energy consumption kcal/T pig 307
Base
291 x 103
(Specification: Coke treating capacity 150t/h, Coke temperature 1200°C, boiler efficiency 80%, BF coke ratio 480kg/t-pig)
Investment amount Annual Saving Payback period
: Rs 800 Million : Rs 200 Million : 4 years
Energy Saving Investment amount Annual Savings Payback period
: Rs 2.3 Billion : Rs 0.813 Billion : 3 years
Case Study 3 : Automatic combustion control of coke oven Brief Program heating adjusts and optimizes the heating condition in each coking chamber in accordance with the state of coal carbonization. It saves energy by reducing coking energy consumption. It also improves the coke quality. 1) Measurements are carried out on the flue temperature, generated gastemperature, red-heat coke temperature, exhaust gas composition, etc. 2) Electric valve controllers are installed on each of the existing adjusting cocks at the branches of the gas and air distribution piping, and the drafting pressure regulating waist dampers. 3) Combustion in each chamber is separately controlled in accordance with the conditions of the charged coal (charged volume, moisture content, etc.) and the operation (target time to finish heating, etc.). 4) The operation control system is integrated, which covers heating pattern control, air-fuel ratio control, program heating, charge scheduling, etc. Energy Saving Amount of carbonization energy reduced: 40,000 kcal/ t-coal at coke production of 1,500 kt/ year.
Case Study 5 : Sensible heat recovery from main exhaust gas of sintering machine Brief In a sintering machine, fine iron ore is mixed with fine coke, powdered limese, etc., heated, and agglomerated into sintered ore, which is used as a blast furnace raw material. In this improvement, the main exhaust gas heat recovery and circulation process was adopted in addition to the cooler exhaust heat recovery. The main exhaust gas, which was previously dissipated into the atmosphere once its heat was recovered, is now returned back to the sintering machine, further enhancing the heat recovery efficiency. In this process, using the waste heat boiler, the heat is recovered from the gas of the temperature of about 380°C exhausted from the sintering machine, and then the gas is returned back to the sintering machine. By this method, the heat recovery is increased by about 30% and at the same time, emission of NOx, SOx, etc., into the atmosphere is reduced. Energy Saving Reduction in crude oil equivalent: 8,430 kL/y Reduction of 30,000 kcal/t-sinter at sinter production of 2,600,000 t/year. Investment amount Annual Saving Payback period Steam generation from boiler is 10 t/h
: Rs 160 Million : Rs 60 Million : 3 years
Case Study 6 : Improvement in segregated charging of sintering materials Investment amount Annual Saving Payback period
: Rs 160 Million : Rs 60 Million : 3 years
Brief
Brief
This is an improvement of the charging device in the sintering process. By uniformly charging the materials along the width of the sinter bed and optimizing the size segregation along the height, the yield and quality are improved, resulting in energy saving.
In this, the red-heat sintered ore, just after sintering, is air- cooled in the cooler. Sensible heat of hot exhaust gas from the cooler is recovered.
The improvement of segregated charging is to optimize the size distribution along the height of the sinter bed.
Sintered ore discharged from the sintering machine has the temperature of 500750°C, and cannot be transported directly to the blast furnace. Therefore, the aircooling-type cooler is installed at the exit of the sintering machine. The sensible heat of the high-temperature part (250 - 450°C) of the cooler exhaust gas is recovered as steam. The power generation system using low-volatile flon-based medium (florinol) has been developed and put to practical use.
By this, the permeability increases, and the quality of the sintered ores in the upper layer is improved, resulting in the overall yield improvement. Further, the return ores are reduced. Accordingly, the coke consumption is reduced and the energy saving effect is achieved.
Case study 4 : Exhaust heat recovery system for sintered ore cooling equipment
Energy Saving
Energy Saving Reduction in crude oil equivalent Reduction in calorific value
: 3,500 (kL/y) : 60,000 kcal/t-sinter 308
Specific coke consumption (kg/Tsinter) Coal addition rate (%)
309
Before improvement Base
Base
After improvement (-) 2.8
(-) 0.54
Crude oil equivalent 6,600 kL/y
1,200 kL/y
Investment amount Annual Saving Payback period
energy by preheating combustion air and fuel gas for a blast-furnace hot stove by utilizing the sensible heat of combustion waste gas exhausted from the hot stove.
: Rs 75 Million : Rs 40 Million : 2 years
1) Case Study 7 : Pulverised Coal Injection (PCI) system for blast furnace: Brief This is a technology to inject pulverized coal directly into a blast furnace through tuyeres in place of using coke. Energy to produce cokes (coking energy) is reduced. • • •
Pulverized coal is injected into a blast furnace through tuyeres by a pulverized coal injection device. The type, size, etc. of pulverized coal injected differs by injection device and blast furnace. By improving the equipment and operation technology, injection of 50-200 kg/t-pig is now possible, resulting in a large energy saving.
Energy Saving At the pig iron production of 3,000 kt/year, Reduction in crude oil equivalent: 19,460 kL/year at pulverized coal injection of 100 kg/t-pig, plus longer coke-oven life. Reduction of energy consumption per tonne of pulverized coal: 600,000 kcal/tcoal, coal injection 300,000 t-coal/year Investment amount : Rs 1.25 Billion Annual Saving : Rs 0.4 Billion Payback period : 3.1 years
2)
There are two types: one has separate heat exchangers for heat receiving and heat radiating, and heat medium is forced to circulate between the two; the other uses a regenerative heat exchanger and directly preheats combustion air When preheating fuel gas, the type which has the heat exchangers completely separated is advantageous in view of safety, because fuel gas does not come in contact with high-temperature gas, and there is no danger of explosion.
Energy Saving Reduction in crude oil equivalent : 9,700 kL/y Reduction of 30,000 kcal/s-t at crude steel production of 3,000 kt/y (40 - 50% of the sensible heat of waste gas is recovered) Investment amount : Rs 200 Million Annual Saving : Rs 70 Million Payback period : 3 years Case Study 10 : Blast furnace hot blast valve control system Brief To improve the circumferential balance, hot blast control valves and their control system were adopted to individually control the hot blast flow rate at each of the tuyeres, hence saving energy.
Case Study 8: BF Top-Pressure Recovery Turbine (TRT) Brief A device which utilizes the furnace top gas pressure of a high pressure blast furnace for generating electric power by driving gas turbine. The pressure of the BF gas (B gas) generated in a blast furnace is 2-3kg/cm2 at the furnace top in high-pressure operation. In order to effectively utilize this gas in the downstream processes, conventionally its pressure was reduced by the septum valve after the dust was removed. A top-pressure recovery turbine (TRT) utilizes this pressure and temperature, and recovers them as electricity by a gas turbine.
The continuous control in accordance with the furnace condition was done with the help of hot blast control valves. Also, change in the fuel rate injection could be made possible. Energy Saving Energy saving Reduction in crude oil equivalent Reduction in SOx, NOx Investment amount Annual Saving Payback period
: : : : : :
]
134,000 kcal/t For Production 4,300 kL/y 3000 kt/y. 47% Rs 80 Million Rs 20 Million 4 years
9.9.2 Case Studies in Steel Making Area Energy Saving Case Study 11 : Continuous Casting Machine Reduction in crude oil equivalent:29,000 - 39,000 kL/y at power generation of 18 MW and hot metal production of 3,000 kt/y, wet type. Investment amount : Rs 600 Million Annual Saving : Rs 360 Million Payback period : 1.7 years Case Study 9 : Hot stove exhaust heat recovery equipment Brief
Brief The continuous casting machine achieves large energy saving by eliminating some of the process steps. Molten steel is continuously charged into the mold. It is control-cooled from outside, and withdrawn as it is solidified from the surface and formed into semis. This machine eliminates the ingot casting, soaking, and slab or billet rolling, and achieves large reduction in fuel and power consumption.
This is the equipment which improves the combustion heat efficiency and saves 310
311
Energy Saving Reduction in crude oil equivalent : 25,940 kL/y Reduction of 200,000 kL/t-steel at production of 1,200,000 t/year. Investment : Rs. 32.5 Million for casting capacity of 1,200,000 t/year Annual Saving : Rs 203 Million by energy saving and Rs 813 Million by yield improvement Payback period : 2 months
which are getting larger and it can collect the combustion gas as well. 2) The recovered gas has the CO content of more than 60% and the heating value of about 2,000 kcal/Nm3. It can be used as the fuel for boilers, rolling mills, and power generation plants. 3) Recently, the sealed-type OG method has been developed and is getting widely used, where the section between the furnace throat and the skirt is sealed during refining, in order to reduce the recovery loss of BOF gas. It has following advantages compared with the combustion-type exhaust gas treatment method:
Case Study 12: High frequency melting furnace Brief 1) Frequency and power are selected, and the high frequency induction current, with enhanced current density which is 2 ~ 5 times higher than that of the low frequency method, is generated. This current generates heat by internal resistance of the material, and performs melting. 2) Steel and alloy steel are melted by the resistant heat generated by the induction current that flows in the steel itself. 3) Nonferrous metals and nonmetals are heated and melted by the conduction heat from the induction heating element such as graphite and metallic crucibles.
Comparison of High-frequency and low-frequency melting furnaces Low-frequency High-frequency Melting furnace Melting Furnace
Energy-saving effect
Specific consumption (kWh/t)
719
630
Melting speed (kg/h)
910
1550
Total production of a plant: Increase by 19.5%
Electricity (kW)
750
1500
Annual Electricity savings : Rs 3.6 Million
Investment amount Annual Saving Payback period
It is compact. The construction cost is low. The operation cost is low. The efficiency of dust collection from the exhaust gas is high. Recovered gas can be used as a clean fuel of a negligible sulfur content.
Energy Saving Recovered energy from BOF exhaust gas is 2,00, 000 - 2,70,000 kCal per tonne of crude steel. The increased amount of BOF exhaust gas recovery by the sealed-type OG method is about 20,000 kcal per tonne of crude steel. Investment amount : Rs 800 Million ( BOF capacity 250 t/h) The investment per unit BOF capacity (t/charge) is Rs 4 Million.
Energy Saving
Furnace capacity: 3t
a) b) c) b) c)
12.3%
: Rs 40 Million : Rs 4 Million year by energy saving and Rs 8 Million by quality improvement : 3 – 4 years
Case Study 13 : BOF Exhaust gas recovery device (including sealed BOF)
Case Study 14 : Ladle heating apparatus with Regenerative burners Brief Large Energy is saved by incorporating Regenerative burners into the apparatus to heat the refractories of a ladle which receives molten steel. It also prolongs the life of the ladle refractories. A Regenerative burner system comprises of a pair of burners which burn alternately for a determined time period and function as a exhaust duct while not burning. The heat of the high-temperature exhaust gas is stored in the regenerator installed just after the burner, and the stored heat is used for preheating the combustion air. Before Improvement Fuel consumption during heating (Nm3 /h) Fuel consumption during soaking (Nm3 /h)
Brief Exhaust gas generated during a BOF (Basic Oxygen Furnace) refining process is high-temperature gas containing mainly CO. A large volume of gas is generated intermittently. Energy of BOF exhaust gas is recovered and utilized. 1) For cooling and dust removing of BOF gas, there are two types of systems: combustion type (full-boiler type, half-boiler type) and non-combustion type (OG type) In the past, the combustion-type gas recovery system was the mainstream. At present, the non-combustion type recovery system is mainly used due to the fact that small-sized facilities can cope with BOFs 312
Refractory life of ladles
200
After improvement 120
Remarks
Fuel saving of 56%
70-80 200 Base case
10% extension
Energy Saving Fuel saving of 56% corresponds to monthly consumption of 573 x 106 kcal. Increase of electric power consumption by auxiliaries : 23.9 x 106 kcal per month. Investment amount : Rs 10 Million Annual Saving : Rs 4 Million Payback period : 2.5 years (excluding the refractory life extension) 313
Case Study 15 : DC Arc Furnace with water cooled furnace wall Brief Large energy saving is achieved in an arc furnace which melts and refines ferrous materials such as steel scrap by changing its power source from the conventional 3-phase alternating current (AC) to the direct current (DC).
When fine chromium ore is agglomerated and calcined into pellets by the annular furnace and the pellets are charged to the electric furnace in place of fine chromium ore, permeability in the furnace increases, which increases the heat exchange rate among charged materials, and decreases specific power consumption. Exhaust gas from the furnace is used as a fuel of the burner for pellet calcination. Excess gas is converted into steam, and steam purchase from outside is reduced. Energy Saving
a. The largest advantage of the DC arc furnace over the 3-phase AC arc furnace is that it can melt the materials uniformly. b. In the DC arc furnace, the metal is melted and agitated by the electric current flowing through it and the magnetic field. c. By adopting the water-cooled furnace wall, high-efficiency operation is achievable d. Furnace maintenance materials are reduced. Energy Saving. 1) 2)
Reduction in crude oil equivalent : 12,570 tonnes/y. When applied to 7 electric furnaces of more than 10,000 KVA each, reduction in crude oil equivalent is 87,990 tonnes/y. Investment amount : Rs 400 Million Annual saving : Rs 100 Million Payback period : 4 years Case Study 18 : Raw material preheater for Electric Arc furnace
Reduction in Specific power consumption Specific electrode consumption reduction
Investment amount Annual Saving Payback period
: 5-10%. : 40-50%. : Rs 400 Million : Rs 100 Million : 4 years
Case Study 16 : Channel Induction Furnace for cast iron melting Brief Induction furnaces are two types: crucible type and channel type. The channel type is more widely used because of its higher overall heat efficiency. It can perform continuous operation and save energy. Energy saving can be achieved by conversion to channel type.
Brief In this system, the heat efficiency of the electric arc furnace is improved by utilizing the sensible heat of high-temperature exhaust gas from the electric furnace to preheat the scrap. Hence, its electric power consumption is reduced. 1)
With the 1-power-source 2-furnace method, the furnace itself is used for preheating the scrap instead of a scrap-charging bucket. While one furnace melts charged material, the other preheats the scrap. Scrap is heated to a higher temperature than by bucket preheating. 2) With the shaft-furnace method, scrap is preheated in the shaft furnace installed above the furnace
Energy Saving Before improvement
Energy Saving
1. Power efficiency 2. Overall efficiency 3. Specific power consumption 4. Need of heel 5. Intermittent operation
Investment amount Annual Saving Payback period
Before improvement (crucibletype) 60% - 80% 55% - 65% High Not needed Arbitrarily possible
After improvement (channeltype) 95% - 97% 75% - 85% Low Needed Principally 2 shifts or continuous operation
: Rs 40 Million : Rs 12 Million : 4 years
Exhaust Gas Temp.
500-1000°C
After improvement 150-400°C
Reduction of specific power consumption : 60,000-80,000 kcal/t (20% of the total heat of the electric- furnace exhaust gas is utilized. Electric power saving : 25-50 kwh/t-s Shortening of the steelmaking time : 5-8 min./charge Investment amount : Rs 400 Million Annual Saving : Rs 100 Million Payback period : 4 years (in the case of a 150t/charge furnace )
Case Study 17 : Ferroalloy furnace for effective energy utilization 9.9.3 Case Studies in Rolling / Finishing of Steel Brief
Case Study 19: Hot Charging and direct rolling mill
The electric furnace for smelting HC-FeCr (high-carbon ferrochromium) refines chromium ore using coke as a reducing agent. However, as the ratio of fine chromium ore increased in recent years, permeability in the electric furnace decreased, and specific consumption of electric power and coke increased. The system described here reduces energy consumption for producing HC-FeCr and recovers the combustible exhaust gas. 314
Brief High-temperature semi-finished materials (slab, bloom, or billet) just after continuous casting (CC) is charged into the heating furnace with the temperature maintained as high as possible, thus reducing the fuel consumption at the heating 315
furnace. Further, by improving the measures for preventing the temperature drop of the semis after CC, the semis are directly sent to the rolling mill without going through the heating furnace, eliminating the heating process and substantially reducing the fuel consumption. Energy Saving
Cooling time reduced by approx. 3 hours Fuel saving : Investment amount : Annual saving : Payback period :
Case Study 22 : Low temperature forge welded pipe production method
Reduction in crude oil equivalent : 16,200 kL/t Reduction of 50x103 kcal/t by coupling direct rolling with hot charging at rolling of 3,000 kt/y. Investment amount : Rs 200 Million Annual Saving : Rs 100 Million Payback period : 2 years Case Study 20 : Descaling pump (conversion to plunger pump)
Brief Electro-magnetic induction heating (an edge heater) was introduced in forgewelded pipe production, and the temperature of steel hoops at the exit of a continuous heating furnace was reduced from the previous high temperature (1300°C) to 1200°C, the edge being locally heated. Accordingly, specific fuel consumption of the heating furnace was reduced 1) The automatic control system is introduced to control the edge to the constant temperature (an electro- magnetic induction heating method). 2) A seam cooling device is installed to eliminate the temperature difference in the circumference direction of pipes. The prevention of beading and bending is made possible. 3) The forge welding roll in the mill has a motor driven screw down mechanism to control the forge welding stress.
Brief A descaling pump is used to apply high – pressure water jet to remove the scale during steel rolling operation. In order to reduce power consumption, various measures were taken, such as pressure and flow rate reduction. To achieve further power saving, the turbine pump was converted to the plunger pump. Since high-pressure jet is applied intermittently in short duration, a plunger pump, which can perform no-load operation at a low pressure, significantly saves power consumption during the time when high-pressure water jet is not applied. Energy Saving
Power Loaded consumption Unloaded Annual energy consumption Reduction in crude oil equivalent
25% Rs 80 Million Rs 20 Million 4 years
Before improvement 1930 kW 1210 kW 9456 MWh/y
After improvement Savings/ Improvement 1890 kW 40 kW 180 kW 1030 kW 3948 MWh/y 5508 MWh/y 1,338 kl/y
Energy Saving Reduction in crude oil equivalent Reduction of energy consumption Investment Amount Annual Saving Payback period
: 7,500 kL/y :115 x 103 kcal/t at the production of 50,000t/m. : Rs 500 Million : Rs 160 Million : 3.5 years
Case Study 23 : Energy saving operation of Electric Arc Furnace Brief
Investment amount Annual saving Investment payback
: Rs 80 Million : Rs 30 Million : 2.5 years at 2750 L/min x 175 kg/cm2 x 1 unit
An example of the operation improvement which targets at the reduction of electric power consumption of small and medium size electric arc furnaces is as follows :
Case Study 21 : Convection heating type heat treatment furnace for wire rod coil 1) Brief To shorten the time required for annealing of wire rod coils a forced circulation fan was installed. The outside of the wire rod coils is heated by the radiation from the radiant tube heat source as well as by the convection heat transfer by the forced circulation fan installed at the top cover. Hot air is forced into the inside of the coils by the fan. It passes through among the individual strands of the coils, and heats up the coils. Forced convection heat transfer by the fan improves the heat transfer efficiency, shortens the treatment time, and saves energy. At the time of cooling, an indirect gas cooler is employed for rapid cooling, instead of the radiant tubes. Energy Saving Heating time reduced by approx. 2.5 hours 316
2)
Use of a basic melting furnace - Electric arc furnaces are divided into two types by the lining refractories they use: acidic furnace (MgO-based refractories) and basic furnace (SiO2 refractories). The acidic furnace merits because of low power consumption and short melting time. On the other hand, it has a difficulty in removing harmful elements such as P and S, and therefore it has the limitation in the types of steel it can produce. - One of the furnaces was remodeled to an acidic type to deal with return scrap which contains relatively smaller amounts of P and S, and power saving was achieved. Shortened melting time by eliminating intermediate analysis - Earlier, for the purpose of checking the compositional specification in the arc furnace, composition analyses were performed four times: at melt down, at oxidation finishing, at the intermediate time, and in the ladle. It was 317
confirmed that the elimination of the intermediate analysis does not cause quality problems. The elimination shortened the melting time by about 5 minutes, and saved energy consumption by about 20 kWh/t.
Case Study 26 : Control of excess air by installing O2 monitoring system in highpressure boiler of CPP in a steel plant. Brief
Energy Saving Annual energy consumption Annual Reduction in crude oil equivalent Investment amount Annual Saving Payback period
: : : : :
3
2,460 x 10 kwh 600 kL Rs 4 Million Rs 4 Million 1 year
Presently, there is no monitoring of O2 in flue gases of this boiler, which is used, in captive power plant of steel plant. Without this, optimization of efficiency of boilers is not possible, especially when quality of coal and boiler load is also changing.
9.9.4 Case Studies in General Utilities and CPP
By continuous monitoring & controlling the excess air & maintaining the % O2 below 6%, the efficiency of boiler can be improved from 79.1% to 83.5%. Further improvement of boiler efficiency is possible by taking care of the unburnt carbon in ash.
Case Study 24 : Heating furnace with Regenerative burners
Energy Saving
Brief
The following table summarizes the overall effect of O2 monitoring & control effect on boiler performance :
A regenerative combustion system uses a pair of Regenerative burners, in each of which a burner for combustion and a regenerator for heat storing are incorporated. Each of the pair is used for combustion and heat storing alternately. It is a highly efficient combustion system which can recover more than 85% of the waste heat. A system is so constructed that one burner performs combustion and the exhaust gas from the combustion is led to the opposite side burner. Energy Saving Reduction of specific fuel consumption Investment amount Annual Saving Payback period Combustion volume
: : : : :
10-30%. Rs 12 Million per pair of burners Rs 4 Million 3 years 5,000 x 103 kCal/piece
Case Studies 25 : Recovery of sensible heat from skid cooling water in heating furnace Brief Skid beams in a heating furnace are cooled by passing water through their insides. Previously the cooling water was sent to a cooling tower and circulated. This improvement is to supply pure water as cooling water in place of previous industrial water, and recover the heat as steam of 12 kg/cm2. The inner temperature of the furnace is about 1300°C. Skid beams are used as heat transfer tubes of a boiler. A steam – water separation drum is installed outside the furnace, where steam is generated, recovering the heat.
Parameter
Existing condition
%O2 Excess air, % Boiler efficiency, % FD Fan airflow, Nm 3 /h ID fan airflow, Nm 3/h
13.7 189.6 79.1 264607 317528
After installing O2 monitoring & control system 6 40 83.5 127558 153069
Annual hours of operation HP-1 boiler = 4350 hours Average steam generation = 73.6 TPH (average during trials) Annual saving in fuel input = Steam flow x Enthalpy of steam x 1 - 1 x Annual operating hours GCV of coal Eff1 Eff2
(
)
Where Eff1 = Existing efficiency of boiler, Eff2 = Likely efficiency of boiler after modifications in control Annual saving in coal
= 73.6 x 639 x (1/0.79 – 1/0.84) x 4350 tonne 3825 = 3563 tonnes (Price of Coal : Rs. 1000 per tonne) Annual Saving Investment amount Payback period
: Rs 3563 x 1000 = 3.56 Million : Rs 0.5 Million : 2 month
Case Study 27 : Use of variable frequency drives on FD fans and ID fans in place of existing inlet
Energy Saving Recovery amount of steam : 9 t/h x 12 kg/cm2 Annual Recovered heat in crude oil equivalent: 23,000 kL at operation of 7900 tonne Investment amount : Rs 750 Million Annual Saving : Rs 280 Million Payback period : 3 years 318
Brief It was recommended to install VFDs in FD & ID fans for energy saving. After implementing the O2 monitoring system as explained above, the following operating parameters observed on FD and ID fans on boiler – 1 are given below : 319
Rating of FD fans kw) Rating of ID fans (kw) FD fan air flow (Nm3/h) ID fan air flow (Nm3/h)
Before improvement 275x2 310x2 264607 317528
After improvement 250x2 250x2 127558 153069
Energy Saving Assuming 25% time operating each at 60%, 70%, 80% and 90% of rated flow, energy savings are calculated as shown below: Annual Saving per fan= 2,20,000 kWh/ year : Rs 0.55 Million Total energy cost saving for 4 nos. fans : Rs 2.2 Million Investment : Rs 6 Million ( for 4 nos. motors): Payback period : 3 years Case Study 28: Reduction of number of stages of pump from existing 7 stages to 5 nos. stages Brief By reducing the number of stages of feed pumps (2 nos) from 7 stages to 5 stages, there will be a drop of head by 30 kg/cm2, which is still higher than the rated one by 15 %. This will reduce the power by about 400 kw. Energy Saving No. of stages of pumps Head (mwc) Power input (kw) Pump efficiency (%) Flow (m3/h)
Annual Saving Annual monetary saving Investment amount Payback period
Before improvement 7 750 1900 72 490
: : : :
After improvement 5 450 1500 72 490
32,00,000 KWh (at 8000 hrs. operation) Rs 8 Million Rs 1.2 Million 1 month
Energy Saving Annual energy saving Annual Saving Investment amount Payback period
1. IEA, World Energy Outlook 2007. 2. International Iron & Steel Institute Brussels Statistical Handbook. 3. Directory of Energy Conservation Technology in Japan, prepared by New Energy & Industrial Technology Development Organization, The Energy Conservation Centre, Japan. 4. Annual Report of Ministry of Steel, 2007-08, GoI. 5. The Energy Data Directory Yearbook, TEDDY, 2007. 6. World Best Practice Energy Intensity Values for Selected Industrial Sectors (Ernest Orlando Lawrence Berkeley National Laboratory), Environmental Energy Technologies Division; by Ernst Worrell, Lynn Price, Maarten Neelis, Christina Galitsky & Zhon Nan. 7. Energy Use & Carbon Dioxide Emissions in Steel Sector in Key Developing Countries by Lynn Price, Dian Phylispsen, Ernst Worrell; Energy Analysis Dept., Environmental Energy Technologies Division, Lawrence Berkeley National Laboratory. 8. International Iron & Steel Institute (IISI) Brussels-Energy use in Steel Industry. 9. Future Technologies for Energy-Efficient Iron & Steel Making-Annual Review of Energy & Environment. 10.Alternate Iron making update- Iron & Steelmaker; by Mc Aloon T.P. 11. National Commission on Energy Policy report www.energycommission.org/. 12.Potentials for Improved use of Industrial Energy & Materials ; Thesis Ph.D, Utrecht Univ. 13. Emerging Energy Efficient Technologies; Worrell E., Price L., Galitsky C. 14.The Steel Industry in India-Iron making & Steel making; by Chatterjee A. 15. Handbook of Energy Conservation (Vol-2) by H.M. Robert & J.H. Collins 16.websites : www. worldsteel.org/steeldatacentre/countries 1998.htm www.worldsteel.org/steeldatacentre/lgcountry.htm.
Brief At present, the throttling valves are used to throttle the flow upto 50 %. By installing the pumps of smaller capacity, a lot of power can be saved. Particulars
TG-4
TG-5
3
6800 m /hr
3
5340 m / hr
5188 m3/ hr
3500 m3/ hr
3500 m3/hr
6800 m /hr
3
Actual power drawn by two pumps at present 725 kW
700 kW
Estimated power drawn by each pump
327 kW (654 kW for two pumps) 71 kW
327 kW (654 kW for two pumps) 46 kW
70%
70%
Reduction in the power drawn Combined efficiency of the proposed pump/ motor
320
93,6000 kWh Rs 1.872 Million Rs 1.5 Million 10 months
References
Case Study 29 : Installation of appropriate/ smaller capacity CW pumps in CPP of steel plant
Design cooling water flow requirement for condensers Cooling water flow rate at present (combined for two pumps) Rated flow rate of the proposed individual pump
: : : :
321
Notes
Chapter - 10 Fertilizer 10.1
Introduction
The Indian fertilizer industry made a very humble beginning in 1906, when the first manufacturing unit of Single Super Phosphate (SSP) was set up in Ranipet near Chennai with an annual capacity of 6000 Tonnes of Rock Phosphate (P2O5). The Fertilizer & Chemicals Travancore of India Ltd. (FACT) at Cochin in Kerala and the Fertilizers Corporation of India (FCI) in Sindri in Bihar (now Jharkhand) were the first large sized fertilizer plants set up in the forties and fifties with a view to establish an industrial base to achieve self-sufficiency in food grains. Subsequently, the Green Revolution in the late sixties gave an impetus to the growth of fertilizer industry in India and the seventies and eighties witnessed a significant addition to the fertilizer production capacity. However, there has not been any substantive addition to fertilizer production capacity during the last 15 years. 10.1.1
Production of Fertilizers
Production of Urea, which was 186 lakh Tonnes in 2002-03, increased to 201 lakh Tonnes in 2005-06 and further to a record level of 203 lakh Tonnes in 2006-07. Production of Diammonium phosphate (DAP), however, declined in 2006-07 at 47 lakh Tonnes after reaching a peak at 52 lakh Tonnes in 2002-03, mainly because of feedstock problems and shift of phosphatic capacity towards production of complexes. Decline in production of phosphatic fertilizers has been due to constraints in availability of phosphoric acid and high prices of sulphur. Requirement of Muriate of Potash (MOP) is met fully by imports. The production of Urea, DAP and complexes during the last five years and during the current year up to December 2007 are given below: Table 10.1 (In lakh Tonnes) Product Urea DAP Complexes
2002- 03 186.21 52.36 48.61
2003–04 190.38 47.09 45.07
2004-05 202.39 51.72 52.59
2005-06 200.85 45.54 67.65
2006-07 202.71 47.13 73.13
2007-08 198.39 42.11 58.33
Source: FAI and Department of Chemicals & Fertilizers
10.1.2 Installed Capacity As on 31 March 08, the country has an installed capacity of 122.84 lakh Tonnes of nitrogen and 58.59 lakh Tonnes of Phosphate. Presently, there are 59 large size fertilizer plants operating in the country manufacturing a wide range of nitrogenous, phosphatic and complex fertilizers. Out of these, 31 (as on date 28 are functioning) units produce urea, 19 units produce DAP and complex fertilizers, 2 units produce Calcium Ammonium Nitrate (CAN) & Ammonium Chloride and the remaining 10 units manufacture ammonium suplhate as product. Besides, there are about 78 medium and small- scale units in operation producing SSP. The sector wise installed capacity is given in the table below: -
323
it serves as a major input to electricity generation and provides the preferred fuel input to many other industrial processes.
Table 10.2 Sector-wise & Nutrient - wise Installed Capacity Of Fertilizer Manufacturing Units as on 31.03.2008 (In lakh Tonnes) SNo.
Sector
1 2 3
Public Cooperative Private Total
Nitrogenous Capacity %Share 35.92 29.24 31.69 25.80 55.23 44.96 122.84 100.00
Phosphatic Capacity %Share 3.87 6.60 17.13 29.24 37.60 64.16 58.59 100.00
Source: FAI and Department of Chemicals & Fertilizers
10.1.3
Per Capita Consumption
The per capita consumption of fertilizer of agricultural population in India, which was a meager 1 kg in the early 50's, has increased substantially to about 32.7 kg in 2004-2005. The per capita fertilizer consumption of agricultural population in different countries is highlighted in the table below: Table 10.3 Country India China Japan Egypt Bangaladesh Pakistan France Russian Federation UK USA World
Fertilizer Consumption (kg Per capita)* 32.7 52.9 438.9 78.4 23.1 42.7 2492.0 131.8 1814.7 3463.0 59.7
Fertilizer Consumption (kg/ha)** 108.4 289.1 363.0 555.1 197.6 146.2 210.5 14.4 305.2 113.5 101.0
*of agricultural population ** of arable land and land under permanent crops Source: FAI and CII-IREDA
10.2
Raw Material Profile
The basic raw materials for the production of fertilizers are ammonia for nitrogenous fertilizers, phosphate for straight phosphatic fertilizers, and potash for potassic fertilizers. Out of the three fertilizer types, production of ammonia is most energy and resources intensive. 10.2.1 Nitrogenous fertilizers Domestic raw materials are available only for nitrogenous fertilizers. For the production of urea and other ammonia-based fertilizers, methane is the major input. Methane is obtained from natural gas/ associated gas, Naphtha, fuel oil, low sulfur heavy stock (LSHS) and coal. Of late, production has switched over to use of natural gas, associated gas and Naphtha as feedstock. Out of these, associated gas is most hydrogen rich and easiest to process, due to its lighter weight and fair abundance within the country. However, demand for gas is quite competitive since 324
10.2.2 Phosphatic fertilizers For production of phosphatic fertilizers, most of the raw materials have to be imported. India has no source of elemental sulfur, phosphoric acid and rock phosphate. Some low-grade rock phosphate is domestically mined and made available to rather small- scale single super phosphate fertilizer producers. Sulfur is produced as a by-product by some of the petroleum and steel industries. 10.2.3
Ammonia production
The most important step in producing ammonia (NH3) is the production of hydrogen, which is followed by the reaction between hydrogen and nitrogen. A number of processes are available to produce hydrogen, differing primarily in type of feedstock used. The hydrogen production route predominantly used worldwide is steam reforming of natural gas. In this process, natural gas (CH4) is mixed with water (steam) and air to produce hydrogen (H2), carbon monoxide (CO) and carbon dioxide (CO2). Waste heat is used for preheating and steam production, and part of the methane is burnt to generate the energy required to drive the reaction. CO is further converted to CO2 and H2 using the water gas shift reaction. After CO and CO2 is removed from the gas mixture ammonia (NH3) is obtained by synthesis reaction. Another route to produce ammonia is through partial oxidation. This process requires more energy (up to 40-50% more) and is more expensive than steam reforming. The advantage of partial oxidation is high feedstock flexibility; it can be used for any gaseous, liquid or solid hydrocarbon. In practice partial oxidation can be economically viable if used for conversion of relatively cheap raw materials like oil residues or coal. In the partial oxidation process, air is distilled to produce oxygen for the oxidation step. A mixture containing among others, H2, CO, CO2 and CH4 is formed. After desulfurization CO is converted to CO2 and H2O. CO2 is removed, and the gas mixture is washed with liquid nitrogen (obtained from the distillation of air). The nitrogen removes CO from the gas mixture and simultaneously provides the nitrogen required for the ammonia synthesis reaction. 10.3
Energy Profile
Production of nitrogenous fertilizers is highly energy intensive. Ammonia is used as the basic chemical in the production of nitrogenous fertilizer. Production of ammonia itself involves almost 80% of the energy consumption in the manufacturing processes of a variety of final fertiliser products. Therefore, ammonia is considered a key intermediate for determining the overall energy efficiency of fertiliser production. Besides air as the source of nitrogen, the ammonia-manufacturing process have choice of using raw materials such as water, natural gas, naphtha, fuel oil, coal, coke oven gas. Natural gas is the best feedstock for ammonia production. However, the use of natural gas in India for urea production is constrained due to its scarce availability. Better feedstock and process technologies, together with improved operation and maintenance practices, retrofitting, and so on have resulted in significant amount of energy savings during ammonia production. The average specific energy consumption for ammonia production in India has improved significantly from 57.35 Giga Joules (GJ)/tonne in 1985-86 to 37.53 GJ/tonne in 2007-08. The average energy consumption of 25% of the most efficient Indian ammonia plants is 32.7GJ/tonne in 2007-08. 325
10.3.1
Energy Intensity
The fertilizer industry is one of the major consumers of hydrocarbons. The fertilizer sector accounts for 8% of total fuels consumed in the manufacturing sector. Energy costs account for nearly 60 to 80% of the overall manufacturing cost. The absolute energy consumption by this sector has been estimated at 628 million GJ annually. The specific energy consumption per ton of urea varies between 21.59 GJ for the most efficiently operating plant to 52.38 GJ for the most inefficient plant during 2007-08. Energy intensity in India's fertilizer plants has decreased over time. This decrease is due to advances in process technology, better stream sizes of urea plants and increased capacity utilization.
Hence, efficient production of Ammonia has greatest impact on Specific Energy Consumption. The specific energy consumption comparison of Indian fertilizer industry with the World and China is as follows: Table 10.5(a) Specific Energy Consumption by Feedstock Type (GJ/tonne NH3) Feedstock based Plants Gas based plants
Energy is consumed in the form of natural gas, associated gas, Naphtha, fuel oil, low sulfur heavy stock and coal for process. LDO, LSHS, HFO and HSD are also used in diesel generators. Large fertilizer plants generate part of their own power through cogeneration mode in Turbo Generator (TG) sets, while smaller plants depend exclusively on purchased power or power from DG sets. With the everincreasing fuel prices and power tariffs, energy conservation is strongly pursued as one of the attractive options for improving the profitability in the Indian fertilizer industry. The feedstock mix used for ammonia production has changed over the last decade. The choice of the feedstock is dependent on the availability of feedstock and the plant location.
Naphtha based plants
FO based plants
Ammonia
TCL Babrala
25.8
World Best
20.9
28.0
China Average (2000) 36.7
Urea
26.5
22.5 (15%)
TCL Babrala
Ammonia
39.9
34 (15%)
CFCL Kota
38.7
Urea
29.1
24.3 (16%)
CFCL Kota
28.3
Ammonia
58.4
47.9 (18%)
GNFC Bharuch
Urea
40.5
31.3 (23%)
GNFC Bharuch
Feedstock
2007-2008 78% 11% 11%
Gas Naphtha Fuel Oil Total
26.3
Energy Consumption (GJ/Tonne) Ammonia Urea Urea Ammonia 35.54 24.99 41.23 30.01 49.06 33.45 37.55 26.33
Source: FAI
Source: FAI
The shift towards the increased use of natural/associated gas and Naphtha is beneficial as this feedstock is more efficient and less polluting than heavy fuels like fuel oil and coal. The production of phosphatic fertilizer requires much less energy than nitrogenous fertilizer. Depending on the fertilizer product, energy consumption varied from negative input for sulfuric acid to around 1.64 GJ/tonne of fertilizer for phosphoric acid. For sulfuric acid the energy input is negative since more steam (in energy equivalents) is generated in waste heat boilers than is needed as an input. 10.3.2
30.3 (17%)
World Average (1998) 36.6
Table 10.5(b) Feedstock-wise Capacity and Energy Consumption in Operating Ammonia Plants
Table 10.4 1997-1998 60.4 % 21.2% 15.0%
India Best (Improvement Potential)
Note: The urea figures include the embedded energy in the production of ammonia Source: LBNL
The shares of feedstock's in ammonia production are as follows:
Feedstock Natural Gas Naphtha Fuel oil
India Average (2001) 36.5
Specific Energy Consumption (SEC)
Ammonia is the intermediate product in Urea production. Out of total energy consumed for the production of Urea, 80% is consumed in Ammonia production. Hence, efficient production of Ammonia has greatest impact on Specific Energy Consumption.
326
10.4
Potential for Energy Efficiency Improvement
The biggest drawback of the Indian fertilizer industry is its reliance on non-natural gas-based plants. If we consider only the natural gas based plants, Indian plants compare favorably with international practices (Table 10.5a). The figures in brackets are the improvement potentials if plants were to reach best practices available in India. The highest energy saving potential is observed with fuel oil based plants. The best practice energy intensity worldwide is 28 GJ/Tonne of ammonia, and is a result of auto-thermal reforming technology process. Auto thermal reforming process is a mixture of partial oxidation and steam reforming technology. According to the European Fertilizer Manufacturing Association (EFMA), two plants of this kind are in operation and others are at the pilot stage. Tata Chemicals owns and operates one of the more energy-efficient plants for the production of ammonia and urea in India with an energy intensity of 30.3 GJ/Tonne of ammonia and 22.5 GJ/Tonne of urea. These energy intensity values are among 327
the lowest recorded internationally. Manufacturing facilities at Babrala comprise an ammonia plant of 1520 TPD and a urea plant of 2864 TPD capacity which were implemented and commissioned in December 1994. Even though the plant currently uses natural gas, it has been designed for full flexibility in the use of natural gas and naphtha as a feedstock and fuel.
energy efficiency does not necessarily require investment and can result from a better balancing of energy flow along the process. The optimization of operations and maintenance practices, by reducing waste heat and capturing excess heat to channel it back into the system, allows a better energy distribution and constitutes major energy efficiency improvements.
When only natural gas-based plants are considered, India appears to maintain very competitive plants compared to the world average (Table 10.5a). However with latest changeover of number of plants from naphtha to natural gas, India has now 80% ammonia capacity based on natural gas as of 2007.
Some plants in India have realized considerable energy savings by increasing awareness at all levels in the plant, monitoring energy consumption during production, and identifying potential energy-savings opportunities
India's national average figures of specific energy consumption for ammonia plants are close to the world average but there is wide variation in energy consumption of various plants. It varies from 32 GJ/Tonne to 63 GJ/Tonne with a weighted average of 37.55 GJ/Tonne. This wide variation is mainly because of the operation of Naphtha & fuel based plants, which have higher energy consumption than gasbased plants. In a competitive environment, with energy cost representing between 60% to 80% of total production cost depending on the type of plant, companies will be compelled to gradually switch over to natural gas in order to have an energy consumption per ton of output closer to world average and become more competitive in the international market. 10.4.1 Categories of Energy Efficiency Improvement Over the past 30 years, induced by major technological improvements and by a better energy management, the energy used to produce each ton of ammonia has declined by 30 to 50%. Technology-wise, three different process stages can be distinguished where energy improvements are possible: Steam reforming phase: This is the most energy intensive operation, with the highest energy losses. Different methods are available to reduce losses that occur in the primary reformer, viz., installing a pre-reformer, shifting part of the primary reformer load to the secondary with installation of a purge gas recovery unit, and upgrading the catalyst to reduce the steam/carbon ratio. It is possible to reduce energy losses by 3-5 GJ/Tonne of NH3. CO2 removal phase: The removal of CO2 from the synthesis gas stream is normally based on scrubbing with a solvent. A reduction of the energy requirement for recycling and regeneration of the solvent can be achieved by using advanced solvents, pressure swing absorption or membranes. Energy savings are in the order of 1 GJ/Tonne of NH3. Ammonia synthesis phase: A lower ammonia synthesis pressure reduces the requirement for compression power, and also reduces production yield. Less ammonia can be cooled out using cooling water so more refrigeration power is required. Also the recycling power increases, because larger gas volumes have to be handled. The overall energy demand reduction depends on the situation and varies from 0-0.5 GJ/Tonne of NH3. Another type of catalyst is required to achieve the lower synthesis pressure. Furthermore, adjustments have to be made to the power system and the recycle loop. Additionally, energy price escalation and growing concerns regarding pollution have intensified the attention on energy conservation at all levels. Improving 328
Some Technologies that can be adopted by fertilizer plants for energy efficiency improvement are briefly described below: 10.5
Technologies & Measures for Energy Efficiency Improvements
10.5.1
Haldor Topsoe Exchange Primary Reformer (HTER-p) (Ammonia Production)
Technology Description HTER-p is introduced reforming section in ammonia plant to reduce size of the primary reformer and at the same time reduce the HP steam production. HTER-p is a new feature, initially developed for use in synthesis gas plants. In ammonia plants this is operated in parallel with the primary reformer, and that is why the name is HTER-p. The exit gas from the secondary reformer heats the HTER-p, and thereby the waste heat normally used for HP steam production can be used for the reforming process down to typically 750-850oC, depending upon actual requirements. The technology was implemented in a synthesis gas plant in South Africa in the year 2003. Advantages Operating conditions in the HTER-p are adjusted independently of the reformer in order to get the optimum performance of the primary overall reforming unit. In this way, up to around 20% of the natural gas feed can by-pass the primary reformer. 10.5.2
Uhde Dual Pressure Ammonia Technology (Ammonia Production)
Technology Description At present, reducing the cost of plant by increasing the plant capacity is a major thrust in conventional ammonia process. To overcome the constraints in increasing the plant capacity beyond 2000 metric tons per day, Uhde has developed Dual Pressure technology. Dual Pressure process focuses on the de-bottlenecking of the conventional synthesis loop. A synthesis reactor has been introduced at an intermediate pressure level in the synthesis gas loop, which makes synthesis, and separation of ammonia possible in between compressor casing and the synthesis gas volume flow to the high-pressure loop is significantly reduced. Advantages The production can be raised by about 65%. Gives a superior hydrogen yield. Energy consumption is reduced by up to 4%. Cost of production is reduced by 10% to15%. 329
10.5.3
Megammonia (Ammonia Production)
10.5.5
Technology Description The Megammonia technology is designed in the year 2003 jointly by M/s Lurgi and M/s Ammonia Casale for large scale production capacity of 4000 TPD Ammonia. Using natural gas, steam and air as feedstock, following five principal steps as below produces ammonia: i.
Air separation: 95% oxygen and 99.99% pure nitrogen is produced from air.
ii. Catalytic Partial Oxidation: Desulphurised natural gas, after addition of steam is first preheated in a fired heater and then reformed over a nickel oxide catalyst to CO, H2 and CO2 following partial oxidation. iii. CO-Shift: Reformed gas is passed through two beds of conventional HT shift catalyst (Copper promoted Iron / chromia based) in series to convert remaining CO to H2 and CO2. iv. Gas Purification: CO2 is removed by absorption in cold methanol and other impurities like CO, CH4 and Ar are removed by washing the gas with liquid nitrogen. v.
Ammonia Synthesis: The extremely high purity of ammonia synthesis gas results in higher conversion of gas per pass, lower circulator duty and lower refrigeration duty.
Advantages
10.5.4
Technology Description The type of feedstock has a major influence on energy consumption in an Ammonia-Urea plant. Hydrogen to carbon ratio increases as we move from liquid hydrocarbons (Naphtha, FO, LSHS, etc.) to gaseous hydrocarbons (Natural Gas). Besides, associated impurities namely sulphur, etc. are present only in traces in the case of gas. With the steep rise in the cost of liquid hydrocarbons in the last five-tosix years, Ammonia- -Urea production from liquid hydrocarbons plants has become very costly. Most significant difference between Naphtha and Natural Gas based Ammonia plants are in the Desulphurization Section. Since gas does not contain much sulphur unlike in Naphtha, hence pre-desulphurization section need not be operated. Other important aspect is in the hydrogen to carbon ratio, which is high in case of gas. As a result, less steam is consumed in the reforming section and less CO2 is generated. After the reforming section, plants operating on Naphtha or gas are identical except in the quantum of generation of CO2. Advantages Natural gas is ideal feedstock for ammonia production. It has several advantages besides being cheaper and easy to handle. It allows easy and shorter start up of the plant, thereby lesser unproductive consumption. The burners choking phenomena is completely solved and CO2 emission from furnace has reduced. Plant also runs trouble free and the catalyst life is also increased 10.5.6
Reduction in the capital cost by 18-20%. Operating cost is expected to be lower around 12 -15% over the most advanced conventional technology. CO2 emission is expected to reduce by around 30% as compared to other conventional technologies. HydroMax Technology (Ammonia Production)
Technology Description Alchemix Corporation U.S.A developed the Hydromax technology. The technology is used for production of hydrogen using either relatively cheaper coal or using inexpensive fuels like municipal waste, biomass and petroleum coke etc. in presence of metal like iron. The technology involves a two-step process. In the first step, steam reacts with molten iron to form iron oxide and hydrogen and in the second step, iron oxide is reduced back to pure metal by adding carbon. Iron simply acts as a carrier for oxygen. In both steps, hydrogen production and reduction of iron oxide back into iron occur in the same reactor at the same temperature of 1250°C. Advantages Carbon dioxide and hydrogen are produced in separate compartments and do not require CO2 removal system. Cost of production is almost four times less than Steam Methane Reforming (SMR) production cost. Emission of greenhouse gases is 34% less than SMR process.
330
Feedstock conversion from Naphtha to Regassified Liquified Natural Gas (R-LNG) in Ammonia-Urea plants
Carbon Dioxide Recovery (CDR) Plant
Technology Description With the steep rise in the cost of liquid hydrocarbons, Ammonia -Urea production from liquid hydrocarbons plants has become very costly. As major disadvantage of RLNG conversion is lesser CO2 production due to lower C/H ratio in RLNG as compared to Naphtha. CO2 generated with lean RLNG is not adequate to convert total Ammonia produced to Urea. One of the possible options to overcome this problem is the recovery of CO2 from flue gas from various furnaces. CDR plant is basically a low pressure CO2 removal section in which CO2 present in flue gases is absorbed & then regenerated to produce CO2 having 99.93 % purity. CO2 recovery from flue gases is a new concept in fertilizer industries. Basic steps involved in CDR plant are: a) b) c) d)
Flue gas Pretreatment Low pressure CO2 absorption in special solution KS-1 CO2 regeneration CO2 compression to desired level
Advantages Though regeneration energy is very high in comparison to that of any normal CO2 removal section of ammonia plant, the cost effectiveness of the plant is very attractive because of the use of costlier Naphtha (as feed to balance the CO2 for Urea 331
production) shall be stopped completely. There is substantial reduction in CO2 Emission as well. 10.5.7
Parallel S-50 Converter
Technology Description The S-50 converter is a single bed radial flow converter, which is added downstream of the main converter to increase the ammonia conversion and at the same time improve the steam generation. Advantages The converter allows ammonia synthesis loop to operate at lower pressure with increased conversion per pass. 10.5.8
Conversion of Single Stage GV System to 2-Stage GV System for CO2
Technology Description Ammonia is manufactured by steam reforming of natural gas. During the process, CO2 is formed in the gaseous mixture and the same is removed from the gaseous mixture in the CO2 Removal Section designed by M/s. Giammarco Vetrocoke (GV) of Italy. The process gas containing CO2 enters the CO2 absorber where major amount of CO2 is absorbed in the lower portion of Absorber in semi-lean GV solution. Rest of the CO2 is absorbed in top portion of Absorber in lean GV solution. The process gas, with around 300 ppm of CO2, leaves the Absorber from top.
• Higher availability of CO2 for urea production. • Decrease in hydrogen consumption in Methanation Section. • Decrease in LP steam consumption in CO2 Removal System from 38 T/hr to 15 T/hr. • By this, an energy saving of around 1GJ/Tonne of ammonia can be achieved. 10.5.9
LTS Guard Reactor & BFW Preheater
Technology Description The reformed gas from Reforming Section flows to HT Shift Convertor after cooling in HP Waste Heat Boiler from 988oC to 380oC. The carbon monoxide content of the process gas is reduced from 12.96% to 3.46% in HT Shift Converter through shift reaction, which takes place in the reactor in presence of Iron-chromia catalyst. Process gas temperature of around 444oC at the outlet of HT Shift Convector is reduced to around 210oC by heat recovery in a Waste Heat Boiler and Boiler Feed Water Preheater. Installation of a new LT Shift Guard Reactor before LT Shift Converter reduces the CO slippage from the Shift Conversion Section. The CO slip gets considerably lowered with the LT Shift Guard in line. Lower CO slip in turn, results in additional Ammonia production due to reduction in the consumption of hydrogen in Methanator. Considerable energy saving can be achieved by installation of a BFW Preheater down stream of the new LT Shift Guard Reactor. Advantages Reduction of CO slip through Shift Conversion Section by around 300 ppm. This gives higher availability of CO2 for urea production. Hydrogen consumption in Methanation Section can also be considerably decreased. Installation of the BFW Preheater results in considerable energy savings.
The main feature of original single stage GV system are (1) Absorption by only lean GV solution and (2) Stripping only in one Regenerator. The heat of regeneration is provided by vapours generated in GV Reboilers heated by Process gas and live LP steam. Full quantity of GV solution is sent to flash tank after GV Reboilers to remove maximum amount of vapour and CO2. This lean GV solution goes to GV Absorber in two parts, the hot solution to the middle to absorb major amount of CO2 and cold GV solution to the top of GV Absorber to absorb the residual CO2.
Technology Description
The main features of the modified 2-stage GV process are (1) Absorption by lean & semi lean solutions in GV absorber (2) High pressure & low-pressure stripping in HP Regenerator and LP Regenerator. The heat of Regeneration is provided by vapours generated in GV Reboilers heated by Process gas, steam generated in LP Steam Boiler heated by process gas and live LP steam. Partially regenerated GV solution (Semilean Solution) from Regenerators goes to GV Absorber to the middle to absorb major amount of CO2 and strongly regenerated cold GV solution (Lean Solution) to the top of GV Absorber to absorb the residual CO2.
The Poolcondenser concept is introduced to de-bottleneck very large capacities indeed. In case a stripping plant is considered in urea plants, the Poolcondenser is installed with a parallel-operated stripper. Conventional urea plants are revamped by using this concept to change the plant into a stripping unit. In this way the plant capacity is increased and the utility consumption is decreased drastically. The Poolcondenser is a horizontal high-pressure vessel in which reaction volume and condensing including retention time, which is needed to produce urea, is already in this Poolcondenser. The technology is implemented at PIC in Kuwait.
Advantages
Advantages
The features result in better absorption of CO2 in Absorber and lower energy consumption for regeneration of the solution in Regenerators. Major benefits of the modification are:
Very large capacities are de-bottlenecked.
• Reduction of CO2 slip through Absorber by around 600 ppm, which has resulted in: 332
10.5.10 The Poolcondenser concept (Urea Production)
10.5.11 Modified trays in Urea reactor Technology Description Due to advancement in technology and current fertiliser scenario, it is necessary to 333
upgrade the plant equipments to reduce energy consumption. One new development is new modified tray design for Reactor in place of conventional design. Installation of these modified trays have further improved plug flow and reduced back mixing in the reactor and hence conversion of Ammonium Carbamate to Urea in the Reactor is enhanced. Advantages Conversion efficiency in Reactor is increased with considerable saving of medium pressure steam per tonne of production. Materials of construction of new trays are more corrosion resistant and have more life as compared to material used for conventional trays.
10.6
Case Studies
Case Study 1: Installation of a Pipe Reactor in Complex Plant Brief Before Improvement Before Improvement In a phosphatic fertiliser complex, producing Ammonium sulphate and Mono-ammonium phosphate, the phosphoric acid, sulphuric acid and ammonia are reacted in a tank reactor to produce a melt of 85 % solids.
10.5.12 Use of Advanced Process Control (APC) with Distributed Control System (DCS) In control theory, Advanced process control (APC) is a broad term composed of different kinds of process control tools, often used for solving multivariable control problems or discrete control problem. APC are often used for solving multivariable control problems or discrete control problem. APC makes it possible to control multivariable control problems. Since these controllers contain the dynamic relationships between variables, it can predict in the future how variables will behave. Based on these predictions, actions can be taken now to maintain variables within their limits. APC is used when the models can be estimated and do not vary too much. Normally an APC system is connected to a distributed control system (DCS). The APC application will calculate moves that are send to regulatory controllers. Historically, the interfaces between DCS and APC systems were dedicated software interfaces. Nowadays the communication protocol between these system is managed via the industry standard Object Linking and Embedding (OLE) for process control (OPC) protocol.
After Improvement After Improvement The plant replaced the existing tank reactor with a pipe reactor. The implementation of this project resulted in operation of the reactor at higher concentration. The outlet of the reactor was directly inserted into the granulator. Hence the concentration of the melt was maintained at about 95 %, as against < 85 % earlier. The increase in concentration of the melt reduced the drying requirement in the dryer. The furnace oil consumption came down from 20 liters/ton of product to 5 liters/ton of product.
Energy savings Annual savings Investment amount Payback period
: Rs. 21.0 Million : Rs. 80.00 Million : 45 months
Case Study 2: Replacing Reformer Tubes with Tubes of HPNb Material Stabilised with Micro-Alloys Brief Improvement Before Before Improvement In a 357 TPD Ammonia plant involved in production of Urea and other Phosphatic fertilisers, the reformer tubes were made of conventional material with 25 % Chromium & 20 % Nickel.
Advantages The key advantages of APC with DCS are: • Safer plant operations • Avoiding unnecessary plant trips • Better plant performance and maximized production
After Improvement After Improvement The Reformer tubes were replaced with ‘modified HPNb materials stabilised with micro-alloys’ with higher Chromium & Nickel and stabilised with Niobium (25 % Chromium, 35 % Nickel, 1.5 % Niobium and traces of Zirconium). The replacement of the reformer tubes with modified superior material resulted in the following benefits: • Reduction in thickness of tube from 20 mm to 10 mm • Increase in internal diameter of tubes from 100 mm to 120 mm –it aided in packing additional catalyst to the extent of 35 % • Increase in capacity of the plant by 15 % • Reduction in Reformer tube skin temperature The above benefits together resulted in reducing the energy consumption for production of Ammonia by 0.63 GJ / Tonne of Ammonia.
10.5.13 Simulation of Absorption and Desorption Columns for CO2 Removal Technology Description A computer programme has been developed which simulates the performance of an absorption column for CO2 removal by using chemical solvents such as DEA promoted carbonate solution. The computer predictions have been validated by using industrial column data from fertilizer industries. In addition, another computer program has also been developed to simulate the performance of steam desorption of bicarbonate solution for solvent regeneration in the CO2 removal systems of fertilizer plants. Advantages The modeling equations are rigorous as they take into account point to point variation of all important transport and physical parameters, heat effects, gas and liquid temperature profiles, enhancement in gas absorption due to mass transfer with chemical reaction, etc. 334
Energy savings Annual savings Investment amount Payback period
: Rs. 15.0 Million : Rs. 50.0 Million : 40 months
Case Study 3: Modernisation of the Ammonia Converter Basket Brief Before Improvement Before Improvement In a 357 TPD Ammonia plant, the Ammonia converter basket had a conventional axial type basket. This needed an operating synthesis loop pressure of 300 bar. The catalyst used was Topsoe supplied of 10 mm size with a pressure drop of 5 bars. The conversion per pass was around 16 %. In 1992, the bottom exchanger developed a leak, leading to further reduction of ammonia conversion and increased loop pressure. The total production loss was around 30 %.
335
After ImprovementAfter Improvement The converter basket was modified to an axial-radial type system. The replacement of the old axial type converter basket with the modern axial-radial system resulted in the following benefits: • Loop pressure reduced to 250 bar – reducing compression energy • Lower pressure drop in converter beds – 3 bar as against 5 bar before • Higher Ammonia production (a b o u t 10 TPD) The above benefits resulted in the reduction of energy consumption by 1.47 GJ / Tonne of Ammonia
Energy savings Annual savings Investment amount Payback period
: Rs. 20.0 Million : Rs. 50.00 Million : 30 months
Case Study 4: Installation of Waste Heat Boiler (WHB) at the Inlet of LTS Converter in Ammonia Plant Brief Before Improvement Before Improvement In an Ammonia plant, the Low Temperature Shift Converter (LTSC) was designed to operate at a inlet temperature of 238°C.
After Improvement After Improvement A Waste Heat Recovery Boiler (WHRB) was installed to reduce the temperature of the gases entering the LTSC to about 210°C. The installation of the WHRB resulted in the following benefits: • Reduction of LTSC inlet temperature to about 210°C and generation of 2 TPH of steam at 14 kg/cm2 • Prolonged life of LTSC catalyst • Increased process efficiency – Resulting in higher Ammonia production by 0.9 % (a b o u t 3 TPD) The above benefits resulted in the reduction of energy consumption by 0.34 GJ / Tonne of Ammonia.
Annual savings Investment amount Payback period
: Rs. 9.80 Million : Rs. 22.00 Million : 27 months
Case Study 6: Replacement of Air Inter-coolers in the Ammonia Plant Brief Before ImprovementBefore Improvement In a 1,00,000 ton per annum capacity Ammonia plant, the air requirements of the Ammonia converter were being met by two numbers of oil lubricated 4 stage reciprocating compressors. The compressors were provided with inter-coolers with finned tubes and were laid in a horizontal fashion. The oil in the air from cylinders used to plug the gap between the fins and reduce the heat transfer. The exit air from the inter-cooler used to be at 55 – 58°C as against the design of 42°C. The capacity of the subsequent stages was getting reduced leading to loss of Ammonia production.
After Improvement After Improvement The inter-coolers for the compressor was replaced with finless tubes and laid in a vertical fashion. The replacement of horizontal fin type cooler with vertical finless coolers resulted in reduction of exit air temperature to around 45°C. There was a reduction of power to the extent of 45 kW.
Energy savings
Energy savings Annual savings Investment amount Payback period
: Rs. 8.20 Million : Rs. 4.50 Million : 7 months
Case Study 5: Installation of Make-up Gas Chiller at Suction of Synthesis Gas Compressor at Ammonia Plant
: Rs. 0.85 Million : Rs. 2.00 Million : 28 months
Case Study 7: Routing of Ammonia Vapours from Urea Plant to Complex Plant Brief
Brief The compressor is the heart of nitrogenous fertiliser plant and is used for various purposes such as compressing the synthesis gas, air, re-cycle gas and ammonia. The compressor capacity is also one of the important parameters controlling the capacity of the plant. Hence, the design of the compressor and its effective utilisation is essential for achieving higher production and lower energy consumption. Before Improvement Before Improvement A ammonia fertiliser complex producing 900 tons per day of Urea was operating at about 920 TPD of ammonia production. The synthesis gas was entering the compressor at about 39°C.
After ImprovementAfterImprovement The plant installed a vapour absorption refrigeration system with LP steam for cooling the synthesis gas. The implementation of this project resulted in a saving of 117355 GJ per year, which amounted to 0.38 GJ / Tonne of ammonia
Energy savings
Parameter
Units
Ammonia Production
TPD
Syn. gas temperature
°C
39
13
RPM
13,142
13,071
Before After Implementation Implementation 920 944
336
Before Improvement Before Improvement In a Urea & Phophatic fertiliser complex, ammonia is compressed from vapour to liquid form by compression to 19 kg/cm2 in two reciprocating compressors and then condensed while in the other part of the plant, the liquid Ammonia (about 6 TPH) at 0°C was drawn from the storage spheres and vapourised at 6 kg/cm2 . Both these operation demand energy in the form of electricity for compression and steam for vapourisation.
After ImprovementAfter Improvement The system was modified as below: § Ammonia was compressed to only 6 kg/cm2 in the Urea plant. § The hot vapours were exported from the Urea to the complex plant. The implementation of this project resulted in the following benefits: • Reduction of electrical energy consumption for compression of Ammonia in the Urea plant. • LP steam saving in the Complex plant The above benefits resulted in the reduction of energy consumption by 6 lakh units per year and 2000 T of LSHS.
Energy savings Annual savings Investment amount Payback period
The implementation of this project resulted in the following benefits
Syn. gas compressor speed
Annual savings Investment amount Payback period
: Rs. 4.00 Million : Rs. 0.50 Million : 2 months
Case Study 8: Replacement of Pellet Type Catalyst with Ring Shaped Catalyst in Sulphuric Acid Plant
337
Brief Before Improvement Before Improvement In a sulphuric acid plant, wh ich was a part of the larger fertiliser complex plant, pellet shaped V2O5 catalyst was being used. The plant was frequently facing problems of dust accumulation and increase in pressure drop. Additionally the plant had to be shut down once every six months for screening and re-charging the catalyst.
Case Study 11: Optimisation of Vacuum Pump Operation After Improvement After Improvement The pellet shaped catalyst was replaced with ring shaped catalyst of the same material composition. The replacement of the pellet type catalyst with ring type catalyst resulted in the following benefits: • Reduction in the pressure drop build up of the converter • Reduction in the load of the main air blower • Shut down (for screening and recharging catalyst) frequency reduced from two per year to once per year The above benefits resulted in the reduction of energy consumption by 900 tonne of LSHS and additional production of 10,000 tonne of sulphuric acid per year
Energy savings Annual savings Investment amount Payback period
: Rs. 7.80 Million : Rs. 40.0 Million : 62 months
Case Study 9: Installation of High Efficiency Turbine for Air Blower in Sulphuric Acid Plant Brief Before Improvement Before Improvement In the sulphuric acid plant (1200 TPD capacity) of a huge fertilizer complex, the sulphur furnace blower was driven by a single stage turbine operating between 35 kg/cm2 and 3.5 kg/ cm2. The turbine had a specific steam consumption of 16.9 tons per MW. The turbine was consuming about 27 TPH of steam during normal operation. There was also a mis-match of LP steam generation and requirement, resulting in an average venting of LP steam (pressure of 3.5 kg/cm2) of about 4 TPH.
After Improvement After Improvement The single stage turbine was replaced with a new multi-stage steam turbine of higher efficiency. The improvement in efficiency was about 15 % resulting in reduction of steam consumption by about 3 TPH, even when operating at higher load.
: Rs.9.60 Million : Rs.15.0 Million : 19 months
Case Study 10: Installation of Variable Frequency Drive (VFD) for Sulphur Pump Brief Before Improvement In the sulphuric acid plant (1200 TPD capacity) of a huge fertiliser complex, the sulphur pump was being driven by a steam turbine with inlet steam at 35 kg/cm2. The pump was of 10.2 m3/h capacity and 265 m head and was being controlled by re- circulation. Also, the turbine driving the pump was a small one consuming a maximum of about 0.7 TPH of steam. Since the quantity of steam was less, the exhaust was let out into the atmosphere.
After Improvement The steam turbine was replaced with a motor of 22 kW with a variable frequency drive. There were two pumps and one was operated continuously. The replacement was done for one of the pumps and other turbine driven pump was kept as a stand-by. The implementation of this project resulted in the saving of about 0.4 TPH of steam. The motor installed along with VSD was consuming about 15 kW
Energy savings Annual savings Investment amount Payback period
Before Improvement Before Improvement In a phosphatic fertiliser unit, which is part of a bigger fertiliser complex involved in production of3 complex fertilisers, a long belt filter was being used for final filtration of the slurry of silica and AlF3. Two vacuum pumps of 500 m3/h capacity and 0.3 kg/cm2 vacuum were being used for creating vacuum. One of the vacuum pumps was being operated with valve throttling. The detailed study of the system revealed the following: · There were leaks in the vacuum line joints close to the belt filter. · The capacity of the vacuum pump was reduced due to uneven wearing of the pump
After Improvement After Improvement During a maintenance stoppage of the plant, the leakages were arrested and a trial was taken to operate the filter with one vacuum pump. The trial was satisfactory and the operation of one vacuum pump per filter was made into a standard operating procedure. The power saving was about 15 kW, which annually amounted to 1,20,000 units (8000 hrs/year operation)
Energy savings Annual savings Investment amount Payback period
: Rs. 0.37 Million : Minimal : Immediate
Case Study 12: Coating of Pump Impeller and Casing with Composite Resins Brief
The implementation of this project resulted in the saving of about 3 TPH of steam (35 kg/cm2).
Energy savings Annual savings Investment amount Payback period
Brief
: Rs. 0.75 Million : Rs. 0.50 Million : 8 months 338
Before Improvement Before Improvement In aa sulphuric sulphuric acid acid plant plant of of 600 600 TPD TPD capacity, capacity, In 3 there were were 44cooling cooling water water pumps pumps ofof2700 2700mm3/h there /h capacity and headdriven driven by by aa 500 500 kW capacity and 5050m mhead kW motor. The The pumps pumps were were operating operating at at an motor. an efficiency of 64.5 %, consuming about 430 kW. efficiency of 64.5%, consuming about 430 kW.
Energy savings Annual savings Investment amount Payback period
After Improvement After Improvement The casing of the pump was coated with epoxy resin coating. Consequent to the coating the efficiency of the pump had improved and there was a reduction of about 16 kW in the power consumed by each pump. The total saving was about 0.13 million units.
: Rs. 0.7 Million : Rs. 0.5 Million : 9 months
Case Study 13: Installation of Hydraulic Turbine in the CO2 Removal Section Brief Before Improvement Before Improvement In a particular nitrogenous fertiliser plant of about 1,00,000 tons per year capacity, the aqueous mono ethanol amine (MEA) process was being used for CO2 removal. This MEA absorbed in the CO2
After ImprovementAfter Improvement A Hydraulic Power Recovery Turbine (HPRT) was installed to recover the pressure energy being lost across the valve. The implementation of this project resulted in reduction of 2 the load on the steam turbine driving the lean MEA pump. absorber which is at a pressure of 24 kg/cm, , The steam saving on the steam turbine amounted to 2.5 enters the CO2 stripper operating at a lower TPH of high-pressure steam, which annually amounted pressure of around 0.4 kg/cm2. This pressure to about 600 tons of LSHS. The reduction in specific reduction is effected through a pressure- reducing energy consumption amounted to about 0.06 Gcal / valve. Tonne of ammonia.
339
Energy savings Annual savings Investment amount Payback period
Case Study 17: Re-use of Condensate Streams from Different Locations : Rs. 3.80 Million : Rs. 1.10 Million : 4 months
Case Study 14: Replacement of steam ejectors with vacuum pumps Brief Before Improvement Before Improvement In one of the complex fertilizer-manufacturing units, there were five evaporators for concentration of phosphoric acid. The evaporators were operated under vacuum using 2-stage steam ejectors. These ejectors consume about 1.5 TPH each of 27kg/cm2 pressure steam.
After Improvement After Improvement All the five steam ejectors in evaporator section were replaced with water ring vacuum pumps. The steam saved by replacement was equivalent to about 7.5 TPH of 27- k g / cm2 pressures. This can generate additional power equivalent to about 50 units/ ton of steam, thereby offsetting equivalent power drawn from the grid
Brief In the CO-shift reaction 50 T/hr of water is consumed from the saturated gas generated by gasification. Grey water circuit of carbon extraction unit supplies this water. Also about 20 Tonne/ hr of water is required to blow-down from the grey water drum to maintain chloride and TDS in the system. This 70 Tonne/ hr of water requirement is met by make-up of BFW or condensate to grey water drum as per design. This being very high consumption of BFW the use of waste streams available was thought of and the following streams were identified and connected with grey water circuit. 1. 2.
Energy savings 3. Annual savings Investment amount Payback period
: Rs. 10.00 Million : Rs. 7.50 Million : 9 months
Case Study 15: Re-processing of Purge Gas for Ammonia-fertiliser
Urea plant hydrolyser effluent : 30 Tonne/ hr is recycled to grey water drum through a control valve. The contaminants limits are fixed at 100-ppm ammonia and 50 ppm urea. Formic acid plant : 10 Tonne/ hr condensate of stream is taken to grey water drum by pump. Methanol plant : 20 Tonne/ hr condensate containing about 5 ppm methanol is diverted to grey water drum.
Energy savings Load on DM water and BFW system is reduced by about 60 Tonne/ hr giving considerable savings.
Brief Case Study 18: Installation of modified trays in Urea reactor Before Improvement Before Improvement The 10,000 TPA methanol plant based on natural gas reforming is designed with a purge of 5, 000 Nm3/ hr from methanol synthesis section, which is used as a part of fuel in reformer. The purge stream is having 70 percent of hydrogen, which is having low heating value.
After Improvement After Improvement Productive use of this stream containing about 3,500 Nm3/ hr available hydrogen was thought of to produce ammonia. The compatibility of the stream was established in ammonia plant upstream of rectisol wash unit after boosting the pressure from 54 to 75 bars by using a recycle compressor. After implementing the scheme, ammonia production could be increased to the tune of 40 T/ day on consistent basis. Also part of purge gas is reprocessed to pure hydrogen after installing pressure swing absorption unit. The hydrogen is supplied for producing aniline BAR (20,000 TPA) at 54 54 BAR
Brief
Case Study 16: Reprocessing of CO waste gas for ammonia/ methanol
A major plant had modified the old Reactor trays of 11 & 21 units of Urea Plant-I with new design trays .M/S Snamprogetti, Italy (technology supplier for Urea Plant) have developed a new modified tray design for Reactor. In place of 10 Nos. of identical sieve trays of conventional design (each having 363 nos. holes of 8 mm each on square pitch), 15 Nos. trays of modified Snamprogetti design have been installed. Each set of 5 new trays has 1922, 1281 & 941 holes of 8 mm dia. each on triangular pitch. Installation of these modified trays have further improved plug flow and reduced back mixing in the reactor and so conversion of Ammonium Carbamate to Urea in the Reactor is enhanced.
Brief
Energy savings
A stream of gas generated in gasification unit, containing mainly CO + H2 is used for 50,000 TPA acetic acid plant. This gas stream is purified to remove impurities of CO2 and H2S, followed by CO enrichment. This 99.5 percent pure CO is used for production of acetic acid. In the process of CO enrichment, a waste CO + H2 stream is generated. The hydrogen of this stream is reprocessed in nitrogen wash unit for enhancing ammonia production as in-built feature. However, CO content of the stream is lost in tail gas stream of nitrogen wash unit.
Saving of around 30 kg of medium pressure steam (24 ata) per tonne of fertliser produced has been achieved due to increased reactor efficiency. Material of construction of new trays is 2-RE-69, which is more corrosion resistant and shall have more life as compared to SS 316 LM material used for conventional trays.
Case Study 19: Conversion from Naphtha to R-LNG as feedstock
Energy savings
Brief
A scheme to use this stream in methanol plant is made which will spare hydrogen for increasing ammonia production by 7 TPD.
A major plant initiated the task of executing RLNG conversion along with Energy Saving Project. As the availability of indigenous natural gas was limited, the only possible alternative was to go for RLNG which was to be sourced from outside andmade available to the unit as per the requirement. The unit held discussions with
340
Energy Saving Achieved: 0.0063 GJ/Tonne of urea.
341
the concerned parties and finally an agreement was reached between the gas supplier and the unit for gas supply. A separate 140 KM pipeline was laid from Thulendi of District Rai Barelly to the Unit from the existing HBJ gas pipeline. Energy savings • • • • •
Easy and shorter start up of the plant, thereby lesser unproductive consumption No burners choking problem Reduced CO2 emission from furnace Trouble free running of plant Increased life of catalyst
Case Study 20: Installation of Carbon Dioxide Recovery (CDR) Plant
12. LBNL - 62806; World Best Practice Energy Intensity Value for Selected Industrial Sectors, February 2008 13. LBNL - 54828: Emerging Energy Efficient Technologies in Industry case studies of selected technologies - May 2004 14. National Energy Map of India: Technology Vision 2030 15. Report of the working group on Power for 11th Plan (2007-12) 16. Report of the working group on R&D for the Energy Sector for the formulation of the 11th Five Year Plan (2007-12) 17. BP Statistical Review, June 2008 18. http://fert.nic.in 19. www.energymanagertraining.com 20. www.faidelhi.org 21. www.eeii.org.in
Brief A major unit has installed a Carbon Dioxide Recovery (CDR) Plant, to recover CO2 from flue gases of Ammonia plant primary reformer furnace. The capacity of the plant is 450 TPD of CO2 and M/s MHI, Japan has provided the basic engineering for it. M/s TICB was engaged as turnkey contractor for detail engineering, procurement, erection and commissioning. CDR plant is basically a low pressure CO2 removal section in which CO2 present in flue gases is absorbed & then regenerated to produce CO2 having 99.93 % purity. Energy savings • Cost effectiveness of the plant is very attractive because the use of costlier Naphtha as feed to balance the CO2 for Urea production shall be stopped completely. This offsets higher conversion costs. • Reduced CO2 Emission References 1.
Annual Report 2007-08, Ministry of Chemicals & Fertilizer, Department of Fertilizers, GoI. 2. Technology Assessment Report - Fertiliser Sector: Fertiliser Association of India 3. "Energy Efficiency Gains in Indian Ammonia Plants Retrospect and Prospects", Sachchida Nand, Manish Goswami; 2006 IFA Technical Symposium, 25-28 April 2006, Vilnuus, Lithuania. 4. LBNL - 57293; Assessment of Energy use and energy savings potential in selected industrial sector in India, August 2005. 5. Indian Journal of Fertilizers, Vol - 4, No.9, September 2008 (ISSN 0973-1822) 6. Compendium of Workshop - "Adoption of Energy Efficient process technologies & practices and implementation of Energy Conservation Act 2001 in Fertilizer Sector" by BEE at New Delhi on 1st September, 2008. 7. TERI Energy Directory and Yearbook 2007 8. LBNL-41846: India's Fertilizer Industry: Productivity and Energy Efficiency; Katja Schumacher and Jayant Sathaye; Earnest Orlando Lawrence Berkley National Laboratory, Environmental Energy Technologies Division, July 1999 9. Statistical Abstract 2007 - CSO 10. CII - IREDA Publication: "Investors Manual on Energy Efficiency". 11. Japan Energy Conservation Directory 342
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Notes
Chapter - 11 Pulp & Paper 11.1
Introduction
The Indian pulp and paper industry is over a hundred years old. First mill in the country was commissioned in 1812 in Serampur (W. Bengal). Over the years, the installed capacity has grown from a paltry 0.15 million tonnes in the early fifties to the present level of 8.3 million tonnes. However, the growth of the industry has been uneven and as a result, the Indian paper industry is a mix of large integrated plants based on wood based raw material and medium and small size paper plants based on waste paper. The capacities of the mills range from 500 tonnes/annum to 2.0 lakh tonnes/ annum. There are about 700 units, which manufacture pulp, paper, paperboard and newsprint paper, out of which nearly 570 are in operation. The total installed capacity is nearly 83 lakh tonnes out of which 11 lakh tonnes are lying idle due to closure of many units. Based on the raw material utilized, the paper units can be classified into three broad categories as: • Wood based (Bamboo, hardwood etc.) • Agro-based (Bagasse, jute, rice & wheat straw) • Waste paper based The Indian scenario on production of paper and paperboard, import and export during the last 4 years is given below in Table 11.1 Table 11.1 : Installed Capacity, Production, Import & Export of Paper (In Lakh Tonnes)
Year 2004-05 2005-06 2006-07 2007-08
Installed Capacity 74.0 76.0 78.0 78.0
Production
Imports
Exports
58.90 59.00 61.40 41.58 (Upto November, 2007)
1.95 2.85 3.47 0.64 (upto May, 2007)
2.70 2.92 3.39 N.A.
(Source: CPPRI & CMIE)
11.2
Manufacturing Process
A variety of processes are in use in the paper industry depending on the type of raw material used and the end product desired. Among these, Kraft (Sulphate) process, Semi-Mechanical process and Sulphite process are the most popular ones. In the Indian pulp and paper industry, the Kraft process dominates the wood/bamboo pulping. Paper making essentially consists of following stages: • • •
Preparation of pulp Stock preparation Sheet formation & water removal
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11.2.1
Preparation of pulp
11.2.1.3 Bleaching Process
11.2.1.1 Wood preparation Hard wood logs are debarked by wet or dry process depending upon the size of the logs handled. Small diametric logs are debarked by dry process by friction. In wet process, debarking of larger logs of wood is done by drum or pocket barkers. Hydraulic barking uses high-pressure water jets to separate bark and log. Energy requirement for friction barking is lower than that for hydraulic barking. In India, most of the mills are not doing debarking as they receive either debarked wood or use them with bark due to difficulty in debarking of some hardwoods. The logs are chipped to size suitable for pulping using chippers. Dise and drum chippers are used for chipping. The oversized chips are rechipped, as under sized chips are rejected. 11.2.1.2 Pulp making Predominantly, pulp making is done either by mechanical or chemical means. In mechanical process, the wood is reduced to small particles by rubbing against huge grindstones revolving at high speeds. Groundwood mechanical process is the most commonly used and most of the Newsprint paper production is undertaken through groundwood pulp process. In India, chemi - mechanical pulping (CMP) is done by only one newsprint paper mill. In CMP, the wood chips are subjected to a mild chemical treatment prior to mechanical separation using a refiner. In the chemical process, the cellulose fibers of the wood are separated from the non-cellulose components by chemical action. Three primary chemical processes are in use, viz., Kraft or sulphate (alkaline), Sulphite (acidic) and Neutral Sulphite Semi Chemical (NSSC). As mentioned earlier, all large Pulp & Paper mills in India use the Kraft sulphate chemical process for pulping. In this process, the raw material (almost any kind of wood - soft or hard) is cut and chipped to produce chips of 0.5-1" size. These chips are fed into digesters, reacted with white liquor (80:20 NaOH and Na2S) and steamed for about two to three hours at high temperature and pressure (162 - 168 oC and 7-8 kg / cm2 ). Digesters may be batch or continuous type, the latter offering advantages such as increased throughput, reduced labour and better energy utilization. Continuous digesters are also very useful in agro fiber pulping. Many mills using agro residue use Pandia Continuous Digesters. The pulp is then washed to make the pulp free from soluble impurities and removal of black liquor through usual 3 or 4 stages of counter current washing using rotary drum filters. The washed pulp is sent for bleaching to increase the brightness of the pulp and the dilute black liquor is sent to evaporators. The treated pulp then goes for stock preparation. The black liquor after concentration is fired in recovery boilers. The residue "green liquor" is treated with lime to get white liquor for reuse. In Soda process, which is mostly used for pulping of agricultural residues, Sodium Hydroxide (NaOH) is the main cooking chemical. Other cooking parameters are almost same as Kraft process.
Pulp when it comes from digester, contains residual coloring matter. This unbleached pulp may be used for making heavy wrapping paper or bags. However, paper to be used for printing, writing or paper which is to be dyed, must first be bleached. The main object in bleaching is to remove residual lignin from the wood pulp fibers as well as to destroy or remove remaining colouring matter. Now a days, various bleaching agents are used to bleach the pulp like chlorine, chlorine dioxide, hydrogen peroxide, oxygen & calcium hypo chlorite 11.2.2
Stock preparation
Stock preparation is undertaken to give the pulp various desired qualities through refining. It is mostly accomplished in either double disk or conical refiners. A more vigorous and special type of refiner, known as Jordan, is used in mechanical pulp preparation method, in which a conical plug rotates in conical shell. The stock then undergoes addition of sizing, filling, and coloring agents. A final screening & centricleaning is carried out prior to paper making for removing the contaminants as they may lead to defects in paper. 11.2.3
Sheet formation & water removal
The feed to the paper machine consists of combination of refined pulp together with additives, such as fillers and wet end chemicals, having requisite stock consistency. Either Fourdrinier or cylindrical mould machines form the above feed into a sheet. Mills producing cultural and newsprint paper use high-speed fourdrinier and twin wire sheet formers. Mills producing packaging paper & board mainly use cylindrical mould machines. At wet end of paper machine, water is first removed by gravity, then by suction, then by pressing the sheet and lastly by drying by steam heated cylinders. 11.3
Per Capita Consumption
The per capita consumption of paper in the different parts of the world are depicted below: Figure - 11.1 Per Capita Consumption (kg/year) 350 300 250 200 150 100 50 0
India
Indonesia
China
Thailand
Brazil
Japan
USA
UK
Source : CII - IREDA & CPPRI
The Indian per capita consumption of paper is 7 kg, in comparison to the Asian average of 21 kg, World average of 55 kg and US average of 331.7 kg. So the Indian pulp and paper industry has got a tremendous growth potential estimated at about 8% per year. 346
347
11.4
Energy Profile
The specific energy consumption comparison of Indian paper industry vis-à-vis the international trends is as follows (Table -11.2):
The share of energy costs in the total manufacturing cost is close to 25%. Coal and electricity are the two major energy sources used in the paper production. Other fuels, such as low sulphur heavy stock (LSHS), furnace oil, etc. are also used to fire boilers. Light diesel oil (LDO) and high-speed diesel (HSD) are also used for captive power generation in diesel generator sets in plants. The Steam and Electricity generated by energy facilities as shown in figure 11.2 are used by various production facilities. Steam and electricity consumption per tonne of paper is 11-15 tonnes and 1500-1700 kWh respectively in Indian mills. The total specific energy consumption of Indian pulp and paper industry ranges from 31 to 52 GJ (Giga joules) per tonne of product, which is roughly double the norms compared to North American and Scandinavian units. The overall energy conservation and utilization efficiency in Indian Pulp & paper mills is very low compared to mills in developed countries. It shows that there is immense potential of energy savings in this sector.
Table 11.2: Comparison of Specific Energy Consumption Parameter Steam
Units MT/ MT of FNP
Power
KWh/ MT of FNP
Water
m3/ MT of FNP
Total energy
GCal/ MT of FNP
Norm Avg. Best Avg. Best Avg. Best Avg. Best
Indian Mills 11-14 7.5 1500-1700 1200-1300 150 75 52 31
International Mills 6.5-8.5 6.0 1150-1250 900-1000 50 25 28 18
Source: CII-IREDA & CPPRI
The typical break-up of steam and power of the various Indian mills vis-à-vis the international mills is shown in Table 11.3 (a) & (b): Table 11.3 (a) : Consumption of Section wise Steam consumption
Figure - 11.2: Conversion & Utilisation of Energy in Paper Industry
(MT/MT of FNP) Section Digester Bleach Plant Evaporator Paper Machine Soda Recovery Plant Total
Indian Mills 2.50-3.90 0.35-0.40 2.50-4.00 3.00-4.00 0.50-1.10 11.0 - 14.0
International Mills 1.9-2.3 0.20-0.25 1.50-2.30 0.70-2.00 0.30-0.50 6.5 - 8.5
Source: CII-IREDA & CPPRI Boiler Evaporator
Table 11.3 (b) Comparison of Section wise Power Consumption (kWh/MT of FNP)
Chemical Recovery Paper Machine Bleaching Digestor Stock Preparation Screening/centricleaning Washing Raw material Preparation
Source: CPPRI
The energy consumption pattern varies according to type of raw material and the technology used by a particular mill. 11.5
Energy Intensity
The paper industry is highly energy intensive and is the sixth largest consumer of commercial energy in the country. Large paper plants generate part of their own power through cogeneration, while smaller plants depend exclusively on purchased power. The energy cost, as a percentage of manufacturing cost, which was about 15% a few decades earlier is presently about 25%. This is mainly due to the increase in energy prices. The expenditure on energy ranks only next to the raw material in the manufacture of paper. With the ever-increasing fuel prices and power tariffs, energy conservation is strongly pursued as one of the attractive options for improving the profitability in the Indian pulp and paper industry.
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Section Digester Bleach Plant Paper Machine Soda Recovery Plant Stock Preparation Utilities & Others Chippers Washing & Screening Total
Indian Mills 58-62 88-92 465-475 170-190 275-286 246-252 112-128 145-155 1500-1700
International Mills 43-46 66-69 410-415 127-135 164-172 160-165 92-98 116-123 1150-1250
Source: CII-IREDA & CPPRI
11.6
Energy Saving Potential
The various energy conservation studies conducted by PCRA and feedback received from the various industries through questionnaire survey and plant visits indicate an energy savings potential of 20%. This is equivalent to an annual savings potential of about Rs.3000 million. The estimated investment required to realize this savings potential is Rs.5000 million. The pulp and paper industry has an attractive cogeneration potential of over 100 MW, in addition to the existing cogeneration plants.
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11.6.1
Major factors affecting energy consumption in paper mills
The major factors that affect energy consumption in the Indian pulp and paper industry are: • • • • • • • •
Low level of capacity utilisation Quality and type of paper produced Number and multiplicity of machinery Paper machine renewability and down time Finishing losses Boiler type & pressure levels Level of cogeneration Power generation
Type of raw material preparation section - Type of chippers/ cutters - Type of conveying system
•
Digesters system
Screening section
Stock Preparation
The break-up of the target specific steam, specific power and specific water consumption figures in the different sections of the plant are given in table 11.4 (a), 11.4 (b) and 11.4 (c) Table 11.4 (a): Specific Steam Consumption break-up (MT/MT of FNP)
Pulping & washing Bleaching Black Liquor Evaporation Chemical recovery boiler Recausticising & Lime kiln Paper machine Deaerator
Steam 1.2 0.4 2.4 0.8 0.5 2.0 1.4
Source: CII-IREDA & CPPRI
Paper machine -
•
= 9.00 MT/MT of finished paper = 1300 kWh/MT of finished paper = 100 m3/MT of finished paper
Section
- Type of refiners - Type of centri-cleaners (use of low pressure drop centri- cleaners reduce the pumping power consumption) •
Steam Power Water
Washing section
- Installation of advanced screening equipment •
The overall specific energy consumption norms for large integrated paper plants, producing writing and printing paper, using 100% chemical bleached pulp and operating on sulphate process, should be as highlighted below: • • •
- Utilisation of advanced washers, such as, flat belt wire washers, double wire press, DD washer and Twin drum washer •
- Type of river water pumping system and overall water consumption - Levels of instrumentation - Extent of utilisation of variable speed drives, such as, variable frequency drives (VFD), variable fluid couplings (VFC), DC drives, dyno drives etc.
11.6.2 Target specific energy consumption figures
- Type of pulping technology (RDH and extended dezincification preferred using oxygen dezincification) - Installation of blow heat recovery - Optimal bath liquor ratio •
Other Factors
Apart from the above factors, optimized operation and proper maintenance are also very important for energy efficiency.
Section-wise details of factors, which affect energy efficiency, are given below: •
•
Type of press Percentage moisture after press section On-line moisture control Type of hood system Type of siphon for condensate removal
Evaporation section - Type of evaporator and number of stages - Steam economy achieved (minimum should be 6) - Extent of condensate recovery
350
Table 11.4 (b): Specific Power Consumption break-up (kWh/ MT of FNP) Section Chippers Digester house Washing and Screening Bleaching plant Stock preparation, Paper m/c and Finishing Power boilers Intake well + Water treatment plant Recovery (Evaporator, recovery boiler, causticisers and lime kiln) Effluent treatment plant Lighting and workshop etc. Total Source: CII-IREDA & CPPRI
351
Power 30 55 105 105 500 170 60 175 60 50 1300
Table 11.4 (c): Specific water consumption break-up (100 m3/MT of FNP)
Section
Water
Pulp Mill Paper machine Boilers incl. WTP and Cooling tower Chemical recovery area Miscellaneous Total
30 20 30 10 10 100
Source: CII-IREDA & CPPRI
11.7
Technologies for Energy Conservation
11.7.1
Recovery of Chemicals from Spent Liquor Obtained from Counter Current Washing of Unbleached Pulp
Technology Description
Waste heat recovery from waste sludge in pulp and paper industry
Technology Description An efficient technology for processing of sludge including waste-to-energy aspect and energy recovery has been developed by University Department of Chemical Technology, Mumbai and Paper & Pulp Technology Department, Sant Gadgebaba Amaravati University, Amaravati. The retrofit has been realized in two stages. The waste sludge is burnt in a multiple hearth incinerator with a fluidized bed chamber. The different stages of retrofit, can be characterized as “waste-to-energy”, where heat from flue gas is utilized for generating the steam, drying the sludge, preheating air for combustion & fluidization and water preheating for steam generation. Off-gas cleaning system consists of a filter for particulate removal and a three-stage scrubber system is attached for cleaner stack. Advantages • The technology is favourable both economically and environmentally.
The chemical recovery systems (evaporators, recovery boilers etc.) are an integral part of any large integrated paper plant. The black liquor can be fired in the soda recovery boilers to generate steam. The sodium salts recovered in the process is reused in the digesters. The installation of such chemical recovery systems in the medium size paper plants is generally considered financially unattractive. Installation of Fluidized Bed Reactor to recover chemicals in medium size paper plant offers an attractive option. The reactor recovers chemicals from spent liquor and converts them into sodium carbonate pellets. These pellets are commercially sold, resulting in additional revenue generation. Advantages • Recovery of Chemicals (Sodium Carbonate) from spent liquor results in saving of power and savings of chemicals like Urea and DAP in the effluent treatment plant. Case Study 1: Recovery of Chemicals from Spent Liquor Obtained from Counter Current Washing of Unbleached Pulp in a Medium Size Paper Mill Brief Before Improvement
After Improvement
In an agro-based medium size paper plant, the spent liquor obtained from the counter current washing of unbleached agro-pulp, was getting mixed with wastewater and let out to effluent treatment plant. This increases the load on the effluent treatment plant, as it is not possible to bring down the Sodium ratio in the effluent.
A chemical recovery plant, to recover the chemicals from spent black liquor, obtained from the counter current washing of the unbleached agro-pulp, was installed. The following benefits were achieved on the installation of chemical recovery system: • Chemical recovery (Sodium Carbonate) • Savings in power at the effluent treatment plant • Savings in Urea and DAP at the effluent treatment plant
Energy savings Annual savings Investment Required Payback period
11.7.2
: Rs. 6.2 Million : Rs. 12.6 Million : 24 months 352
11.7.3
Seven Effect Free Flow Falling Film (FFFF) Evaporator
Technology Description Multiple effect evaporators are installed in the liquor line between the brown stock washers and the soda recovery boiler to efficiently remove large amounts of water from the liquor, so that, the recovery boiler produces steam from this liquor economically. The multiple effect evaporator is fed black liquor at 12-14% solids concentration and concentrated to 40-55% solids. Most of the paper plants use the short tube or long tube vertical evaporators, having five to seven effects, the first two effects being contained in one evaporator body. The latest trend among the large integrated paper plants is the installation of free flow falling film evaporators. They are characterised by higher steam economy and better operational performance. Advantages • The installation of 7-effect FFFF evaporator resulted in achieving steam economy of 6 tons of water evaporation per ton of steam. Case Study 2: Installation of Seven Effect Free Flow Falling Film (FFFF) Evaporator Brief Before Improvement A large integrated paper plant had a conventional quintuple effect short tube vertical evaporator system for the concentration of black liquor. The black liquor flow rate was about 2500 m3/h. The steam economy achieved was 2.8 tons of water evaporation per ton of steam. These evaporators had frequent operational problems, leading to increase mechanical down time. Also the chemical losses were more due to the frequent water boiling.
353
After Improvement The latest 7 - effect free flow falling film evaporator, was installed in place of the conventional short tube vertical evaporator. The installation of 7-effect FFFF evaporator resulted in achieving a steam economy of 6 tons of water evaporation per ton of steam. A net saving of about 9700 MT of lowpressure steam was achieved as a result of this modification.
Energy savings Annual savings @ Rs. 3.00 per kg of steam Investment required Investment required 11.7.4
: Rs. 29.1 Million : Rs. 36.9 Million : 15 months
Use of Variable Frequency Drives (VFD's) in Washer Drum Drives
Technology Description One step in paper manufacturing process is washing of pulp to remove free soluble impurities and black liquor, thereby recovering maximum amount of spent chemicals. The washing is done using rotary drum washers driven by variable speed systems to achieve desired speed variation, according to the throughput of the plant. The dyno-drives used for the purpose, though have lesser maintenance problems, are inefficient at lower speeds. The variable frequency drives (VFDs) are more efficient at lower/all speeds and require lesser maintenance, in comparison to the dyno-drive. Advantages • VFDs are more energy efficient at all speeds and enable precise control of speed. Case Study 3: Replacement of Dyno-drives with Variable Frequency Drives (VFD's) in Washer Drum Drives Brief The contents of the digester, after cooking, are blown down to a blow tank. The blown pulp is then washed, to remove the dissolved lignin and chemicals. Usually, washing is practiced in counter current fashion, involving 3 or 4 stages of washing, using rotary drum washers. The washed pulp is then sent for bleaching and further processing. The rotary drum washers are operated under vacuum, utilizing a barometric column. These drum washers are driven by a variable speed system, to achieve the desired speed variation, according to the throughput of the plant. Before Improvement
After Improvement
In one of the old integrated paper plant, the washer drum drives were fitted with dynodrives. The washers were operating at 50 - 60% of the rated speed for majority of the time. The dyno-drives are very inefficient at lower speeds.
The dyno-drives of the washers were replaced with variable frequency drives (VFD's). The replacement of dyno-drives with VFD's resulted in a net reduction in power consumption. The net power saving achieved was 36,024 units/year (equivalent of 5.23 kW). The other major advantage is, the precise speed variation, which can be achieved.
Advantages • • 11.7.6
Savings in steam consumption Less maintenance cost Conversion to Fluidised Bed Boilers
Technology Description The paper plant is a major consumer of thermal energy in the form of steam. This steam requirement is met by a battery of boilers fired by a solid fuel (coal) and also partly by the Soda Recovery Boiler (SRB) in the integrated plants. In the older paper plants, the conventional stoker boilers were in use. These boilers gave higher unburnts in ash and lower thermal efficiency. The latest trend is to install the fluidized bed boilers or conversion of the existing chain / spreader stoker boilers. The Fluidized Bed Combustion (FBC) boiler also enables the use of saw dust, which is generated in the chipper house. Advantages • • • •
Coal having high ash content / low calorific value can be used Biomass fuels can also be used Lesser unburnts in ash Higher thermal efficiency
Case Study 4: Conversion of Spreader Stoker Boilers to Fluidised Bed Boilers Brief Before Improvement
After Improvement
A large integrated paper plant had four numbers of spreader stoker boilers, operating to meet steam requirements of the plant. The steam generation was only 14 TPH, as against the design rating of 30 TPH. The boiler efficiency achieved was only 65 per cent.
Two of the four spreader stoker boilers were converted to fluidized bed combustion boilers. This conversion to fluidized bed combustion boilers enabled the use of sawdust, which is generated in the chipper house. Steam generation - 27 TPH Efficiency - 78% Coal Saving - 9239 T
Energy savings
Energy savings Annual savings @ Rs. 4.5/kWh Investment required Payback period
to ensure better heat transfer. Steam soot blowers do this normally. The steam consumption of the steam soot blowers is very high and results in drop in efficiency of the boilers. Replacing steam soot blowers with Sonic (Acoustic) blowers, offers a viable option for reducing steam consumption and maintenance cost.
: Rs. 0.16 Million per year. : Rs 0.25 Million : 19 months
11.7.4 Sonic Soot Blowers in Place of Steam Soot Blowers for Coal Fired Boilers Technology Description Coal fired boilers are installed to meet the steam requirements of the paper plant. The boiler water tubes get frequently coated with soot deposits, as a result of combustion of coal in coal-fired boilers. The cleaning of tubes has to be carried out 354
Annual savings @ Rs. 1.25/kg of coal Investment required Payback period 11.7.7
: Rs. 11.5 Million : Rs. 27.0 Million : 28 months.
Conversion of MP Steam Users to LP Steam Users to Maximize Cogeneration
Technology Description The paper industry is a major consumer of power and steam. In all the integrated plants and in a few medium sized plants, the co-generation system is installed to 355
meet the power and steam needs of the plant simultaneously. The paper plant should make every effort to increase the co-generation power to the extent possible. The generation of power from the turbine depends on the pressure level of the extraction. The lower the pressure, the higher will be the generation of power per unit of steam extracted. Hence, efforts should be made to replace the HP (HighPressure) / MP (Medium Pressure) steam with LP (Low Pressure) steam to the highest extent possible. Advantages • Increase in co-generation power. 11.7.8
Technology Description In paper manufacturing process after thorough washing, bleached pulp is collected in a storage tank and finally pulp is refined through DDR (Double Disc Refiners) and TDR (Tri Disc Refiners) to make pulp suitable for paper making and to impart better fiber bonding condition which improves the physical strength of the paper. Installation of TDR in place of DDR is observed to give fine quality refining and is energy efficient. The technology has been successfully installed in ITC, Bhadranchalam. Advantages
Deinking Process
• Energy saving of about 150 kW can be achieved.
Technology Description Stringent guidelines for environmental protection and the social obligations of providing a clean environment is forcing paper mills to explore alternate raw materials and cleaner technologies for long term survival. Deinking process has emerged very promising in these aspects. Old Newsprints (ONP) and Old Magazines (OMG) form the raw materials for deinking. The process involves detachment of ink from the surface of the fibre and its removal through washing and floatation. Unit operations in deinking include Pulping, Screening, Floatation, Fine Cleaning, Slot Screening, Thickening, Dispersing, Bleaching & Final Storage. The waste paper is slushed with warm water and chemicals like Hydrogen peroxide, caustic, soaps etc. in the pulper and cleaned through "Contaminex" followed by HD cleaners before feeding to Floatation cell. The main task of floatation cell is to improve the cleanliness and brightness of the pulp stock. Air in the form of very fine bubbles is sparged through the stock. The ink particles stick to the air bubbles and float. The stock from floatation is pumped to the centri-cleaners for fine screening and further thickened in a Disk Filter. The stock is dewatered in a screw press to a consistency of 28% for final storage. Hindustan Newsprint Ltd. (Kerala) has successfully implemented this technology. Advantages • Lesser energy and water consumption, less pollution. 11.7.9
11.7.10 Installation of Refiners (DDR/TDR)
Pressure screens
Technology Description The function of a pressure screen in a paper machine thin-stock recirculation system is to remove shives (fiber bundles) and other large, hard contaminants from the furnish. Conventional pressure screens use baskets with either slots or holes to admit the fibrous "accepts" flow and reject the contaminants. Slotted screens usually have a sculptured pattern that helps fibers to become aligned and pass through the screen. Pressure screens are equipped with various types of rotors to continuously redisperse any fibers that start to accumulate on the screen surface. Because fibers can pass through a slotted screen individually, but not as fiber flocs, papermakers sometimes choose to add retention aids ahead of pressure screens in order to achieve a favorable balance of formation uniformity and adequate retention of fine particles. Advantages • Reduced energy consumption, investment costs and improved cleaning efficiency. 356
11.7.11 Black Liquor Recycling in Agro Based Mills Technology Description In the agro based mills, although chemical recovery system has been installed in few mills, but due to unfavourable properties of black liquors, the chemical and thermal recovery efficiencies are much lower than in wood based mills. One of the major constraints while processing the agro-based liquors in the chemical recovery section is the low solids concentration of the weak black liquors in comparison to the wood/bamboo liquors. This results in substantial quantities of additional steam requirements during black liquor evaporation in the chemical recovery to remove that extra quantity of water present in the agro based black liquors. Recycling of black liquor during pulping results in improved black liquor solids concentrations. In the recycling process certain portion of the fresh water is replaced with the black liquor during cooking of the agro based raw materials. Advantages • Improves the pulp yield by 1.0-1.5%, without bringing about any significant change in kappa values (A measure of the amount of lignin remaining in pulp after cooking) of the pulp. • The net energy savings per tonne of pulp varies form 13-72 tonnes steam per day for a 100 tpd mill depending on the rise in solids concentrations. • Black liquor recycling can be practiced in mills using wet cleaning systems by using improved dewatering devices. 11.7.12 High Capacity Chippers in the Chipper House and Mechanical Conveying in Place of Pneumatic Conveying. Technology Description Mills installed before 1980's have many small capacity disc chippers and the wood chips are transported from the chipper house located at the ground floor to the top of the digester house (at a height of about 12-15 m) for pulping operations. Conventionally, the chips were being transported pneumatically. The pneumatic conveying, though simple and easy to install, consumes more energy. Mechanical conveying is more energy efficient and consumes only about 25-30% of energy consumed by pneumatic conveying. Installation of a high capacity drum chippers belt conveyor can be taken up in those plants where the horizontal distance between the digester and chipper is sufficiently large. In case, if the horizontal distance is less and the inclination of conveying required is more, then a belt conveyor will not be suitable. In such cases, modified systems such as the crated belt conveyors can be installed. 357
Advantages • • •
Lower specific power consumption Mechanical feeding, leading to higher throughput Uniform Chips size.
Case Study 5: Installation of High Capacity Chippers in the Chipper House Brief
as a bleaching agent is causing concern as this produces dioxin and other chlorinated organic compounds, which contributes to AOX (absorbable organic halides) in the recipient streams. In the technology developed in IIT, Delhi, an enzyme prepared from a thermophilic fungus has been shown to act as an effective pre-bleaching agent on soft and hard woods. The level of chlorine was reduced by 15%. AOX release was also less. Pilot scale runs have been planned in collaboration with two paper mills. Advantages
The recent technological advancements have led to the development of high capacity chippers. These chippers are provided with mechanical feeding mechanisms, enabling consistent feed to the chipper and high throughput from the chippers. This results in lower specific energy consumption of the chippers. Before Improvement
After Improvement
A 750 TPD plant had 5 numbers of older, low capacity disc chippers in operation, with specific energy consumption of 12 kWh/tonne.
Two numbers of high capacity drum chippers having lower specific energy consumption (about 7 kWh/ tonne) were installed in place of the earlier 5 numbers of the chippers.
Energy savings Annual savings @Rs.4.5/kWh Investment required Payback period
:Rs. 5.9 Million :Rs. 24.0 Million :49 months.
11.7.13 Dry Mechanical boosters in place of steam ejector
• The level of chlorine was reduced by 15% and lower AOX release was demonstrated. 11.7.15 High-Efficiency River Water Turbine Pumps for Raw Water Intake Technology Description Water is an essential commodity for pulp & paper industry, from both energy and environmental point of view. The overall water consumption of the Indian pulp and paper industry varies from 125 to 175 m3/ton of finished paper (depending on the product) in large integrated paper plants. Advantages • Efficiency of 87% possible. • Reduction in pumping power. Case Study 6: Installation of High-Efficiency Turbine Pumps for Raw Water Intake
Technology Description Steam ejectors find wide use in vacuum pumping applications such as in Vapour extraction, Chemical processing, Evaporative Cooling, Vacuum distillation, Vegetable oil de-odourization, Vacuum Refrigeration, Drying etc. In spite of the fact that steam ejectors have poor overall efficiency and relatively high-energy consumption, they are popular in vacuum applications because of their simplicity and ease of operation. Dry Mechanical Vacuum Booster offers an efficient replacement to steam ejector, for most of the applications as they overcome major drawbacks associated with steam ejectors. Advantages
Brief Water is an essential commodity for the pulp & paper industry from both energy and environmental point of view. The overall water consumption of the Indian pulp and paper industry varies from 125 - 175 m3/ton of finished paper (depending on the product) in large integrated paper plants. Before Improvement
• Mechanical Vacuum Boosters are more energy efficient. • Minimum of auxiliary equipment is needed; unlike for steam ejectors, which need large condensers, cooling towers, re-circulation pumps etc. • Mechanical Vacuum Boosters are dry pumping system and don't give rise to water and atmospheric pollution. • Startup time for mechanical booster is very low, making them ideal for Batch process operation where immediate startup and shut down is essential for energy conservation. • Operating costs for mechanical vacuum systems are low, resulting in extremely short payback period. 11.7.14 Xylanases as Pre - Bleaching Agents During Paper Making Technology Description Concern for environment-friendly technologies has lead to refocusing on the chemical route of paper bleaching in pulp and paper industry. The use of Chlorine 358
In one integrated paper plant, six pumps were installed at the raw water intake well to meet the raw water requirements of the entire plant. The pumps were of the following specification: Three Pumps
Three Pumps Capacity
Head Motor rating
= 772 m /h = 35 m WC = 25 HP
Head Motor rating
= 522 m3/h = 35 m WC = 75 HP
Design efficiency
= 86.5%
Design efficiency
= 80%
Capacity
3
On detailed analysis of the pumps, it was observed that the three 125 HP pumps were operating very close to the design efficiency. On the other hand, the two 75 HP pumps were operating much below their best efficiency points. The design efficiencies were not being achieved, on account of ageing and wear out of impellers. 359
The total power consumption (measured by a common energy meter) of the 5 pumps in operation, before modification, was on an average 8000 units per day.
Case Study 8: Utilisation of Bamboo Dust along with Coal Firing in the Coal Fired Boilers
After Improvement
Brief
Three new high-efficiency, 125 HP turbine pumps were installed, in place of the old 75 HP turbine pumps. Substantial energy savings can be achieved by the installation of high efficiency turbine pumps.
Coal is used conventionally as the basic fuel for combustion in the boilers for steam generation. The steam requirements of the entire plant are met by steam generated in these coal-fired boilers. This is supplemented by steam generation from the soda recovery boilers.
After the installation of new high efficiency turbine pumps for raw water intake, the total power consumption (measured by a common energy meter) of the four pumps in operation was on an average about 7000 units/day. Energy savings There was a net reduction in power consumption by an average of 1000 units/day (equivalent to 41.7 kW). Annual savings @ Rs. 4.5/ kWh Investment required Payback Period
= Rs. 1.6 Million = Rs. 1.5 MIllion = 1 month
Before Improvement In an integrated paper plant, two coal-fired boilers met the majority of the steam requirements of the entire plant.There was lot of bamboo dust generated in the chipper house, which was being sold-off to outside parties.
After Improvement Chipper dust was used to supplement the coal firing on a continuous basis except during the rainy season, due to the higher moisture content in the chipper dust. . With the use of bamboo dust as supplementary fuel to the coal firing in the coal-fired boilers, there was a net annual reduction in coal consumption by 3312 MT.
Energy savings Annual savings @ Rs. 1.25/kg of Coal Investment Required Payback period
11.8 Case Studies
: Rs. 4.14 Million : Minimal : Immediate
Case Study 7: Replacement of Suction Couch Roll by Solid Couch Roll in the Paper Machine
Case Study 9: Installation of Centralised Compressed Air System
Brief
Brief
The paper machine performs the important function of converting the low consistency pulp to dry paper. The water removal is initially done by high-speed drainage, suction through flat vacuum boxes, suction couch & mechanical presses and drying in steam cylinders.
A centralized compressed air system has a single large / multiple number of compressors at one location. On the other hand, a decentralised compressed air system has multiple numbers of compressors, distributed over various locations. Centralised compressor system is preferred in cases where a large capacity requirement is needed at identical pressure levels.
The latest paper machines have been installing the modern presses and reducing the load on the steam drying section. Another project, which has been taken up by some of the plants, is the replacement of the suction couch with the solid couch.The concept of this project is based on utilising the method, which removes the maximum quantity of water, with the least quantity of energy. This is particularly applicable to plants based on long fibre agro-pulp, which have a low drainage. Before Improvement
After Improvement
In a medium size agro-based paper plant, the major portion of water from the wet end is removed by suction couch roll. The moisture removal is effected by a vacuum pump of 200 kW rating. This is a highly energy intensive process. The quantity of water removed by the suction couch is very low and the energy consumption was disproportionately high.
The suction couch roll was replaced by a solid couch roll for the efficient removal of moisture in the wet end of the paper machine. The operation of the 200 kW vacuum pump was completely avoided with the implementation of this proposal.
After Improvement
A large integrated paper plant had two compressed air units catering to the compressed air requirements of the entire plant. These units were located at two different locations (decentralized). The decentralized system necessitates the operation of multiple compressor units. This leads to increase in both power consumption and mechanical maintenance problems.
The old compressed air pipelines were replaced with new pipelines, to reduce the leakage losses and line friction losses. Further, the compressors were located at one central location for ease of operation and maintenance. There was a substantial reduction in the leakage losses and significant savings of power. There was a net reduction in power consumption by 53 kW
Energy savings Annual savings @ Rs.4.5/kWh Investment required Payback period
: Rs. 2.0 Million : Rs. 1.0 Million : 6 months
Case Study 10: Installation of Heat of Compression (HOC) Air Dryers
Energy savings Annual savings @ Rs. 4.5 / kWh Investment required Payback period
Before Improvement
: Rs. 7.6 Million : Rs. 2.0 Million : 3 months 360
Brief Compressed air is an important utility in process and engineering industries. Instrumentation applications require dry air. Any moisture present in the 361
compressed air will condense at the point of utilisation causing damage to the instrumentation valves. Drying of compressed air is achieved through various methods. However, the latest trend is to install heat of compression (HOC) dryers. Heat of compression dryer is a major technological improvement, having the following distinct advantages: • • • •
Utilizes the heat in compressed air for regenerating the desiccant Electrical heaters are eliminated No purge air losses Low atmospheric dew point is achieved depending on the desiccant used. Before Improvement
After Improvement
A large integrated paper and board plant had compressed air requirements of about 112 m3/ min. About 50 m3/min of the compressed air was being dried using heater reactivated (lambda) type air dryer. The heater was rated for 32 kW heating capacity. The purge air loss in the dryer was about 10% of the total quantity of air being dried. This type of air dryer in addition to being highly energy intensive, also leads to substantial quantity of compressed air losses.
An HOC dryer was installed alongside the existing dryer and utilised for drying of compressed air. The desiccant used was activated alumina, which can give an atmospheric dew point of - 40°C. Power savings achieved on account of the elimination of heater operation was 0.075 Million kWh/yr. Also, compressed air losses were totally avoided, as there are no purge losses in HOC dryers with savings of 0.08 Million kWh/yr.
Energy savings Annual savings @ Rs. 3.00/kg of steam Investment required Payback period
Case Study 12: Installation of Extended De-lignification Pulping Process instead of Conventional Pulping Brief In a large integrated paper plant, the digester house had conventional vertical stationary digesters, having a combined capacity of 250 Tons of BD pulp/day. The plant replaced the conventional vertical digesters with 3 new digesters of 80tons/ day of BD pulp capacity, based on rapid displacement heating pulping process.
Steam consumption Batch time Kappa number Yield Washing loss
Energy savings Annual savings @ Rs. 4.5/kWh Investment required Payback period
: Rs. 0.7 Million : Rs. 1.48 Million : 25 months
: Rs. 0.9 Million : Rs. 2.4 Million : 32 months
Black liquor conc. Ash retention Paper breakage
Before Improvement 1.42 tons / ton of FNP 6 hours (avg. time) 21-22 45.3% 16 kg/ ton of pulp (as sodium sulphate) 14.2% 7% 3.3%
After Improvement 0.70 tons / ton of FNP 4 hours (avg. time) 12-13 46% 10 kg/ ton of pulp (as sodium sulphate) 16% 10% 1.5%
Case Study 11: Installation of Blind Drilled Rolls (Dri-Press Rolls) instead of Conventional Press Rolls in Press Section of Paper Machine
The reduction in chemical consumption was about 50%.
Brief
Energy savings
The press section has a very important role in the drying process and hence, steam consumption of paper machine depends upon the extent of mechanical dewatering. Many of the old paper plants, in general, have conventional press rolls for dewatering. This led to non-uniform moisture removal, which in turn affected the throughput through the system. This resulted in very high specific steam consumption in the paper machine. The recent technological advancements in water removal and increased runability of paper machines have led to the development of the blind-drilled rolls (or DriPress rolls). Before Improvement In a large integrated paper plant, the press section had the conventional press roll. The dryness achieved with the press roll was about 40-42%. This system had the following disadvantages: • Lower throughput • Increased de-watering requirement • Higher downtime due to higher breakages at wet end • Higher purging requirements • High specific steam consumption
After Improvement The plant replaced the conventional press rolls with blind-drilled rolls in the two paper machines in phases. The dryness with blind-drilled rolls (for writing & printing paper) improved to 4446%, as compared to 40-42% with conventional press rolls, thereby, achieving 2-6% improvement in dryness. This results in equivalent savings of 307 Tonne of steam consumption. Besides, there was tremendous improvement in machine run ability. 362
Annual savings Investment required Payback period
: Rs. 140 Million : Rs. 500 Million : 42 months
Case Study 13: Improved Paper Machine Design to Improve Production Brief The success of a paper mill is determined not only on the basis of quality and quantity of paper produced, but also on productivity. Efficiency of paper machine plays a vital role in achieving runability and hence, productivity. Before Improvement In an agro-residue based paper mill, renewable agro-waste, such as, wild grasses and straws were being used for making high quality writing & printing paper. A critical study was conducted to modify its paper machine to improve its efficiency in terms of quality and productivity.
363
After Improvement The plant team applied various modifications, right from head box to dryer part in paper machine. The details of the modifications are as follows: • Energy efficient rotary showers installed in head box, in place of stationary showers • Wire circuit provided with an additional roll to improve wrap on FDR (Felt Drilled Roll) • Motor used for wire return roll removed. Diameter of dandy rolls increased to 1200 mm to increase speed of paper machine, enhance production and provide for watermarks • Ceramic tops installed in place of HDPE tops in paper machine • Suction pick-up roll modified to suction cum BDR (Blind Drilled Roll) to avoid shadow marking and ensure better sheet dryness • Speed difference between wire and pickup roll reduced, resulting in improved life of pickup felt life • SLDF (Spiral Linked Drier Fabric) screen replaced with woven screen for better sheet flatness and prevent screen marking • Static current remover installed between calendar and pope reel
Brief Before Improvement
A paper manufacturing plant has a connected lighting load of nearly 370 kW. This consists of fluorescent fittings, HPSV, HPMV & CFL lamps for plant, office and area lighting. The lighting load is fed from 3.3 kV bus by 4 nos. of LT transformers. These transformers have lighting loads apart from other loads. Each transformer is connected to a Lighting circuit Distribution box. The total actual load varies between 300 to 350 kW during night. Meters are fitted at each DB to measure power consumption. The voltage levels at lighting DBs vary between 225 & 240 V.
After Improvement
The plant lighting voltages were at a level, which could be brought down further. The installation of lighting voltage controllers, of different kVA, on each DB brought down the lighting consumption by 20%. The output voltages were set at 210 V. 4 No. of DB lighting circuits had a total power consumption 338 kW. After installation, total power consumption came down to 275 kW with an annual total energy savings of 0.245 Million kWh.
Energy savings Annual savings @ Rs. 4.5/kWh Investment required Payback period
Energy savings Annual Savings Investment required Payback period
Case Study 15: Use of lighting voltage controller to reduce lighting energy consumption
: Rs. 18.3 Million : Rs. 5.0 Million : 3 months
: Rs. 1.1 Million : Rs. 1.2 Million : 13 months
Case Study 16: Replacement of desiccant (adsorption) type dryer with refrigerated dryer in compressed air systems Brief
Case Study 14: Replacement of metallic blades with Fibre Reinforced Plastic (FRP) blades in cooling towers Brief Before Improvement
After Improvement
A well-known paper manufacturing company had one centralized cooling tower consisting of 3 cells. The cells are fitted with fans having aluminium blades. The 3 cells of the cooling tower operate continuously. The fans are fitted with 55 kW motors. Metallic blades are heavy & consume more power.
Replacement of aluminium blades with lightweight FRP blades reduced the load on cooling tower fan motors & brought down energy consumption. With 3 nos of fan, total power consumption was 124.3 kW. After replacement, power consumption reduced to 98.7 kW with an annual total energy savings of 0.197 Million kWh.
Energy savings Annual savings @ Rs.4.5 / kWh Investment required Payback period
: Rs. 0.9 Million : Rs. 1.52 Million : 20 months
364
Before Improvement
A paper manufacturing plant has 5 reciprocating compressors. The compressed air is generated at 7.4-7.6 kg/cm2g. The compressed air in the plant is used primarily for instrumentation needs. The compressed air is needed to be dry for this usage and a desiccant type dryer was in use at the plant. The disadvantage with the desiccant type dryer is that energy is needed to drive off the moisture adsorbed by the desiccant. Though a much lower dew point (dryer air) can be obtained by this type of dryer, in this case, the dryer was over designed to provide much drier air than needed and was consuming energy unnecessarily. kW/1000m3/h: 20.7 Dew Pt. oC: -20 Purge: 10-15%
After Improvement
The dryer was replaced with a refrigerant type dryer, which consumes much less energy, as there is no desiccant to be dried. In the refrigerant type dryer, the air stream is cooled to nearly 0oC. In the process, it loses moisture to maintain the dew point. kW/1000m3/h: 2.9 Dew Pt. oC: 2 - 10 Purge: Nil Energy savings per hour by replacement of dryers: 37.75 kWh Operating annual hours: 8000 Annual energy savings: 3.02 lakh kWh
Energy savings Annual savings @ Rs. 4.5/kWh Investment required Payback period
365
: Rs. 1.4 Million : Rs. 1.0 Million : 9 months
Case Study 17: a) To conserve the electrical and thermal energy b) To reduce the cost of production to compete and survive in the paper manufacturing field.
Case Study 19:
Replacement of 4" pipeline by 6" pipeline for supplying Hot Water to Wood Brown Stock Washers
Brief
Brief
Before Improvement
Before Improvement After Improvement It is observed that the paper machine The "Kakati" vacuum pumps were efficiency can further be improved to get purchased and replaced. The driving motor more production with less power was also replaced from 75 HP to 50 HP. consumption per tonne of paper. Flowbox of the paper machine was a)The Vacuum pump used in the paper pressurized. The production of paper machine was found to be less increased from 33 MT/day to 40 MT/day e f f i c i e n c y a n d m o r e p o w e r and power consumption was reduced drastically from 720 kWh/MT to 640 consuming. kWh/MT. b)The water consumption was seen to be in the higher side in the pulp mill. A new Thickener in the pulp mill was c)The used steam in the paper machine installed. It was found that the 5 HP motor coming out after passing through a was stopped due to recycling of thickener series of dryer cylinders was found to be water. have more heat value for reuse. The vent out steam from dryer A “Forbes Marshall" make Thermo cylinder was measured as 600 compressor system was installed. It was found that the steam consumption came kg/hour. down drastically from 2.6 MT/Tonne of paper to 2.2 MT/Tonne of paper.
Energy savings Increase in productivity Power Consumption reduction Steam Consumption reduction
: 33 MT/day to 40 MT/day : 720 kWh/MT to 640 kWh/MT. : 2.6 MT/Tonne of paper to 2.2 MT/Tonne of paper.
Case Study 18: Revamping of Paper Mill with new machinery, retrofitting & capacity enhancement Brief Before Improvement
Low steam economy in Evaporator. Use of elemental chlorine for bleaching which is not environmental friendly and a power guzzler technology.
Energy savings Annual savings Investment required Payback period
In Pulp Mill Brown Stock Washers (BSW) were used for washing the cooked pulp. For this purpose hot water is used. Two pumps were provided each with the rating of 30 kW - one in service and the other as standby for supplying hot water to the washers. The wash water was supplied through 4” pipeline. As pulp production increased from 100 TPD to 140 TPD, more quantity of water was required for washing. To maintain the production level, both the pumps were put into operation consuming about 34 kW.
Since the volumetric flow rate increased, the pressure drop was also higher in the 4” line. A 6” line replaced the 4” line and the pressure drop was reduced. The same quantity of water could be handled by single pump since the pump had the required capacity. There was a power saving of about 11.5 kW
Energy savings Annual savings @ Rs. 4.5/kWh Investment required Payback period
: Rs. 0.43 Million : Rs. 0.19 Million : 5 months
Case Study 20: To down size Saveall Shower Water Pump impeller in MF Machine Brief Before Improvement MF 3 Paper Machine has a Polydisc Saveall for recovery of fillers and fines in the water and reuse of excess white water. The Polydisc Saveall has discs mounted with synthetic wire mesh that needs to be cleaned with high-pressure water. For this purpose a separate high-pressure pump is used. It was found that the high-pressure pump was oversized, as the system head was lower than the design head of the pump. This resulted in throttling of the valve at the delivery by about 35% to achieve the required flow rate and pressure.
After Improvement The performance curves of the pump were studied and it was found that the required duty conditions could be achieved by installing a lower diameter impeller. It was found that by replacing the impeller a saving of about 12 kW could be achieved.
After Improvement
Specific energy consumption of a Pulp Mill capacity enhanced to 300 TPD. Specific 200TPD plant was 16.44 % of energy consumption improved to 14.93% of total mill total mill power consumption. consumption, a saving of 34.96 lakh units. High effluent treatment load and high consumption of resources.
After Improvement
Energy savings Annual savings @ Rs. 4.5/kWh Investment required Payback period
Free Flow Falling Film (FFFF) black liquor evaporators of 125TPH water evaporation capacity was installed. Soda recovery boiler of 625 TPD solid firing capacity was installed.
References
New effluent free R8 process chlorine dioxide generation plant of 7 TPD capacity was installed.
1.
Recausticizing and limekiln of 130TPD lime production capacity was installed.
2.
: Rs. 516 Million : Rs. 2030 Million : 46 months 366
3. 4.
: Rs. 45 Million : Rs. 0.1 Million : 3 months
Annual Report - 2007-08, Ministry of Commerce & Industry, Department of Industrial Policy & Promotion, GoI. LBNL - 62806; World Best Practice Energy Intensity Value for Selected Industrial Sectors, February 2008. Statistical abstract - CSO CII - IREDA Publication: "Investors Manual on Energy Efficiency".
367
5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16.
Compendium of 'Energy Efficiency Workshop in Paper & Pulp Sector" by BEE on 3rd September 2008 at Shaharanpur, U.P. TERI Energy Directory and Yearbook 2007 Japan Energy Conservation Directory LBNL - 54828: Emerging Energy Efficient Technologies in Industry case studies of selected technologies - May 2004 LBNL - 57293; Assessment of Energy use and energy savings potential in selected industrial sector in India, August 2005. National Energy Map of India: Technology Vision 2030 Report of the working group on Power for 11th Plan (2007-12) Report of the working group on R&D for the Energy Sector for the formulation of the 11th Five Year Plan (2007-12) BP Statistical Review, June 2008 www.energymanagemetnraining.com www.cppri.org.in www.eeii.org.in
368
Chapter 12 Cement Industry 12.1 Introduction India is the world's second largest cement producer after China, accounting for about 6% of the world's production. Annual per-capita consumption of cement in India is around 150 Kg, which is much lower than the global average of 270 kg. Cement is one of the core industries, which plays a vital role in the growth of the nation. Limestone and coal being the basic materials for cement manufacturing, India has the requisite quantity of cement grade limestone deposits, backed by adequate reserves of coal. India also has the requisite technical expertise to produce the best quality of cement with the most energy efficient processes. Many Indian companies have attained high levels of energy efficiency in their plants, which are comparable to international benchmarks. For a variety of applications, various types and grades of cement are used. The most common types of cement are Ordinary Portland Cement (OPC), Portland Pozzolana Cement (PPC) and Portland Slag Cement (PSC). Indian cement industry produces various types of cements such as OPC, PPC, Portland Blast Furnace Slag Cement (PBFSC) or PSC, oil-well cement, rapid hardening - Portland cement, sulphate - resisting portland cement & white cement. In the year 2007-08, OPC production accounted for about 25% of the total production, while the blended cements, PPC & PSC accounted for 66% & 8% of the production respectively. 12.2 Present Capacity & Growth India has 142 large & 200 mini cement plants. The total installed capacity of large cement plants in India is around 198 million tonnes per year & that of mini cement plants is 11 million tonnes. The cement production from large plants in the year 2007-08 was 168 million tonnes. The capacity utilization of cement plants in India is about 85%. 12.3 Manufacturing Process of Cement Cement production involves the chemical combination of calcium carbonate (limestone), silica, alumina, iron ore and small amounts of other materials. Cement is produced by burning limestone to make clinker and the clinker is blended with additives and then finely ground to produce different cement types. Desired physical and chemical properties of cement can be obtained by changing the percentages of the basic chemical components i.e. CaO, Al2O3, Fe2O3, MgO, SiO2, etc.. Cement is manufactured from Limestone and involves the following unit operations: • • • • • • 368
Mining Crushing Raw meal grinding Pyro-processing Cement grinding Packing & dispatch 369
Raw Materials Preparation
Cement grinding
Raw material preparation involves crushing of the quarried material, further raw grinding and blending the materials. The specific electrical energy consumption in raw materials preparation accounts for a significant part of overall electrical energy consumption.
The clinker which is produced in the kiln is then grounded along with about 5% Gypsum to produce OPC. Ball mills have been generally used for grinding in cement plants in India either alone or in combination with roller press systems. In some of the recently installed plants, the VRM has been installed. The other types of cement such as PPC and PSC are also produced by grinding clinker with fly-ash and blast furnace slag respectively.
Fig 12.1: Block Diagram of Cement Industry - (Dry Process Precalciner Process)
12.3.1 Clinker Production Process Technology
Limestone
Clinker production is the most energy-intensive step, accounting for more than 80% of the energy used in cement production. Produced by burning a mixture of materials, mainly Limestone (CaCo3), Silicon Oxides (SiO2), Aluminum, and Iron Oxides, clinker is made through three processes :
Purchased Coal
• Dry process ~ 97 % of the production • Semi-Dry process ~ 1% of the production • Wet process ~ 2% of the production
(Source : Investors Manual for Energy Efficieny, EMC, CII & IREDA)
Mining The major raw material for cement manufacture is limestone, which is mined in open cast mines in the quarry and then transported to the crusher.
The Cement Industry today comprises mostly of Dry Suspension Preheater and Dry-Precalciner plants and a few old wet process and semi-dry process plants. Till late 70's, the Cement Industry had a major share of production through the inefficient wet process technology. The scenario changed to more efficient large size dry process technology since early eighties. In the year 1950, there were, only 33 kilns out of which 32 were based on wet process and only one based on semi-dry process. Today, there are 162 kilns in operation out of which 128 are based on dry process, 26 on wet process and 8 on semi-dry process. Basic principle of precalciner kiln is shown in figure 12.2:
Crushing
Fig 12.2: Pre-Calciner Kiln
The mined limestone is conveyed to the crusher through dumpers/ropeways/belt conveyors. The material is then crushed in the crusher to a size of about 25-75 mm. The crushing is done in two stages in the older plants while in the modern plants normally single stage crushing is done. The typical crushers used are jaw crusher and hammer crusher. Raw meal grinding The crushed limestone is grounded into fine powder in the dry condition. The Vertical Roller Mill (VRM) is comparatively more energy efficient than ball mill consuming only 65% of the energy consumption of the ball mill. The ball mill along with a pre-grinding system such as roll press is also used in some of the plants with very hard and abrasive limestone. Pyro-processing This takes place in the kiln system. The kiln is a major consumer of both the electrical and thermal energy in a cement plant. The calcination of limestone and the conversion into clinker takes place in the precalciner and kiln respectively.
370
(Source : Understanding Cement; Website : thecementkiln.mhtml)
371
The energy used in the above three processes is given in table 12.1 below Table 12.1: Energy Consumption Item Heat Consumption (kcal / kg clinker) Power Consumption (kWh/tonne of cement)
Wet Process
Dry Suspension Process
Dry Pre - Calciner Process
1250 –1450
800 – 950
680 – 770
100 – 115
100 - 105
70 – 95
Source: Handbook of Energy Conservation by H.M. Robert & J.H. Collins
12.3.2
Technology Status of the Industry
A comparison of the status of the modernization in equipment and also the technologies absorbed or implemented by the Indian cement industry alongwith status of Global Technology is as under: Table 12.2: Status of Technology Plant Size, TPD Mining & Material Handling Crushing Conveying of Limestone Grinding
Pyro Processing
Blending & Storage
Packing & Despatch
Low Technology Plants 300-1800 Conventional
Modern Plants 3000-6000 Computer aided
Global Technology 6000-12000 Computer aided
Two stage
Single stage
Dumpers/Ropeway/ Tippers Ball Mills with / without conventional classifier
Belt conveyors
Wet Semi Dry Dry - 4 stage preheater - Conventional cooler - Single channel burner
Dry 5/6 stage preheater High Efficiency Cooler Multi Channel Burner
In-pit crushing & conveying Pipe conveyors, Belt conveyors VRM’s, Roll Presses, Horo Mills with dynamic classifier Dry - 6 stage preheater - High Efficiency Cooler - Multi Channel Burner - Co-processing of WDF - Co-generation of power - Low NOx/SO2 emission technologies - Continuous Blending - Multi-Chamber Silos - Dome silos - Bulk - Palletizing & Shrink Wrapping - DDC - Neurofuzzy expert system 70-80 kWh/t cem. 680-725 kcal/kg cl
Batch-Blending Silos
VRM’s Roll Presses with dynamic classifier
Continuous Blending silos
Bag
-
Process Control
Relay Logic / Hard Wired / PLC
-
Energy consumption level
90-100 kWh/t cem. 900-1000 kcal/kg cl.
Bag Bulk
DDC Fuzzy Logic expert system 75-85 kWh/t cem. 700-800 kcal/kg cl.
(Source : NCB)
12.3.3
newer technologies and had thus remained at intermediate technology level. Also, the level of technology is not same at all the plants built during the same period. Majority of the cement plants in the country are in the capacity range of 0.4 to 1.0 MTPA. These were set up more than 15-20 years ago and were based on the latest technology available at that time. Since then, numerous developments have taken place in the cement manufacturing technology. Though some of the old plants have been modernized to a limited extent by retrofitting the new technologies, substantial scope still exists for adopting state-of-the-art technologies and bringing the old plants at par with world-class plants in terms of productivity, energy efficiency and environment friendliness, leading to cost competitiveness. Moreover, the emission norms are likely to become more stringent in future and at the same time, the cement plants will be required to utilize waste derived raw materials and fuels to a large extent. The modifications of old plants to comply with these future requirements will also become inevitable. Therefore, there is a need to carry out a comprehensive assessment of all the earlier generation plants in the country to identify the extent of modernization required to improve their all round efficiency and enable them to meet the future criteria of viability, competitiveness and compliance with regard to energy consumption enabling them to comply with the provision of the Energy Conservation Act 2001. 12.3.4
Although the industry has largely set up plants with energy efficient equipment, there are areas which require further improvements • • • • • • • • • • • 12.4
Upgradation of Technology of Low Technology Cement Plants
The technological spectrum in the industry is very wide. At one end of the spectrum are the old wet process plants, while at the other end, are the new state-of-the-art technology plants presently being built by the Industry. In between these two extremes, are the large number of dry process plants built during the period 196590. These plants could not fully modernise or upgrade side by side with advent of 372
Future Modernization Needs of the Indian Cement Industry
Appropriate pre-blending facilities for raw materials Fully automatic process control and monitoring facilities including auto samplers and controls. Appropriate co-processing technologies for use of hazardous and non hazardous wastes Interactive standard software expert packages for process and operation control with technical consultancy back-up Energy efficient equipment for auxiliary/minor operations Mechanized cement loading operations, palletization/shrink wrapping Bulk loading and transportation, pneumatic cement transport Low NOx/SO2 combustion systems and precalciners Co-generation of power through cost-effective waste heat recovery system Horizontal roller mills (Horo Mills) for raw material and cement grinding Advanced computerized kiln control system based on artificial intelligence Specific Energy Consumption in Cement Plants
Cement industry is highly energy intensive. The main source of energy is coal, followed by electricity. Energy accounts for almost 40% of the total manufacturing cost in some of the cement plants whereas Coal accounts for 15%-20% of the total cost. The industry's average consumption in 2006-07 for dry process plants was 730 kcal/kg clinker thermal energy and 77 kWh/tonne cement electrical energy. It is 373
expected that the industry's average thermal energy consumption by the end of 11th Five Plan (Year 2011-12) will come down to about 710 kcal/kg clinker and the average electrical energy consumption will come down to 75 kWh/tonne cement.
12.5
The best thermal and electrical energy consumption presently achieved in India is 685 kcal/kg clinker and 71 kWh/tonne cement which are comparable to the best figures of 650 kcal/kg clinker and 65 kWh/tonne cement in a developed country like Japan.
The Indian Cement Plants have achieved a high level of energy efficiency. The escalating costs of cement manufacturing over the years and increasing competitiveness have resulted in a focused approach by the cement industry in India to maximise the operational efficiency with respect to retrofitting of energy efficient equipment/systems, technology upgradation, process optimisation, effective maintenance management and above all, energy management including energy monitoring and energy audit. The comprehensive approach adopted by the Govt. of India, the National Council for Cement and Building Materials (NCB) and Cement Manufacturers Association (CMA) has resulted in significant reduction in specific energy consumption levels in cement plants.
The improvements in energy performance of cement plants in the recent past have been possible largely due to • • • • •
Retrofitting and adoption of energy efficient equipment Better operational control and Optimization Upgradation of process control and instrumentation facilities Better monitoring and Management Information System Active participation of employees and their continued exposure to energy conservation efforts etc.
Various energy audit studies have estimated that at least 5 to 10% energy saving is possible in both thermal & electrical consumption through adoption of various energy conservation measures. It is estimated that the saving of 5 kcal/kg of thermal energy and 1 kWh/t cement of electrical energy will result in total savings of about Rs 6 Million per annum in a 1 Million tonne plant. The average energy consumption values by process for Indian cement plants vs the best world practice is given in Table 12.3 below:
12.5.1 General Measures
NCB energy audit studies carried out in 36 Cement Plants during last five years indicated potential savings ranging from 4 to 210 kcal/kg clinker and 0.78 to 27 kWh/tonne cement. The estimated cost savings ranges between Rs 47 lakhs for 600 tpd plant to Rs 945 lakhs per annum for 4300 tpd for plant. Major factors identified for higher energy consumption are
Raw Materials Preparation Coal mill Crushing Raw mill Clinker Production Kiln & cooler Kiln & cooler Finish Grinding
Unit
India Average
High preheater exit gas temperature (25-50oC higher) High preheater exit gas volume (0.1-0.4 NM3/kg cl. higher) High pressure drop across preheater (upto 200 mmWG higher) High moisture in fine coal (upto 5.8%) Incomplete combustion of coal (CO - upto 1630 ppm) False air infiltration in kiln and mill circuits (upto 20%) Low heat recuperation efficiency of grate cooler (55-60%) High cooler air exhaust temperature (upto 100oC higher) High clinker temperature (upto 175oC against 90-100oC) Low efficiency of major process & cooler fans (<65%) Under-loading (<50% kW loading) of motors resulting in low operating efficiency
• • • • • • • • • • •
Table 12.3 : Average and Best Practice Energy Consumption Values for Indian Cement Plants by Process.
Process
Energy Efficiency measures adopted by Indian Cement Industry
World Best Practice
The potential savings identified in few plants are given in table-12.3 below :
kW h/t clinker kW h/t clinker kW h/t clinker
8 2 2
2 1 2
Table 12.3: Potential Savings Identified Plant
kcal/kg of clinker kW h/t clinker
77 2
6 2
Cement mill Miscellaneous Utilities: mining & transportation
kW h/t cement
3
2
kW h/t clinker
Utilities: packing house Utilities: misc.
kW h/t cement kW h/t cement
1 . 1 1
Total Electric
kW h/t cement
1 6 1 2 9
7
(Source: Cement Manufacturer's Association 2003; Worrell 2004)
1 2 3 4 5 6 7 8 9 10 11 13 14
•
Kiln(s) capacity and process (kwh/ton clinker)
1200 tpd, 6-ST, RSP Calciner 3800 tpd, 4-ST, PH & ILC 3225 tpd, 5-ST, Double String Precal (Pyroclone) 300 tpd, 4-ST Preheater 6000 tpd, 6-ST, Double String Precal 1800 tpd, 5-ST, PH & ILC 2500 tpd, 4-ST, SLC Calciner (F L SMIDTH) 1215 tpd, 4-ST Preheater 2400 tpd, 6-ST, Double String Preheater & Precalciner (Pyroclone) 3850 tpd, 5-ST PRECALCINER 4000 tpd, 4-ST ILC Precalciner 3700 tpd, 5-ST, PC 2400 tpd, 5-ST, ILC PC
kWh/t Clinker (Source : NCB)
374
(tpd)
375
Potential savings Thermal energy kcal/kg cl
Electrical Energy kWh/t CEM
Annual Savings Rs Lakhs
35 13 38 210 32 60 40 45 22
0.78 4.43 2.11 27 1.30 6.50 9.56* 14 5.68*
98 269 289 239 445 408 512 350 295
68 11
5.98 5.52
588 336
70 36
5.40 4.95
895 287
Some of the energy efficiency measures implemented in different cement plants in India are: (i) Operational Control and Optimisation Process optimisation, load management and operational improvement generally involve marginal financial investment and yet found to have produced encouraging results in energy saving. The different aspects explored in this direction are : • Plugging of leakages in kiln and preheater circuit, raw mill and coal mill circuits • Reducing idle running of equipments • Installation of Improved insulating bricks/blocks in kilns and preheaters • Effective utilisation of hot exit gases • Optimisation of cooler operation • Optimum loading of grinding media/grinding mill optimisation • Rationalisation of compressed air utilization • Redesigning of raw mix • Installation of capacitor banks for power factor improvement • Replacement of over-rated motors with optimally rated motors • Optimisation of kiln operation • Changing from V-belt to flat belt (ii) Energy Efficient Equipment Use of energy efficient equipment gives very encouraging results even at the cost of some capital investment. More and more plants are now going for these available energy saving equipment to improve the energy performance of the units. The energy efficient equipment being used by the cement industry are : • • • • • • • • • • • • • •
Slip Power Recovery System Variable Voltage & Frequency Drive Grid Rotor Resistance Soft Starter for Motors High Efficiency Fans High Efficiency Separators Vertical Roller Mill Pre-Grinder/Roller Press Low Pressure Preheater Cyclones Multi-channel Burner Bucket Elevator in place of pneumatic conveying Fuzzy Logic/Expert Kiln Control System Improved Ball Mill Internals High Efficiency Grate Cooler
covering the need for drying energy, there is still waste heat available which can be utilized for electrical power generation thereby making additional power available and reducing CO2 emission. The cement industry is yet to adopt the cogeneration technology due to various technical, financial and institutional barriers. Recently, a model demonstration project has been jointly implemented by New Energy and Industrial Technology Development Organisation of Japan (NEDO), and Govt. of India under Green Aid Plan (GAP). The system has been installed on a kiln of 4550 tpd clinker capacity with 4 stage suspension preheater and precalciner. The exhaust gas flow through preheater (PH) boiler is of the order of 3,60,750 Nm3/hr at 340oC whereas through Air Quench Cooler (AQC) boiler, it is 1,96,000 Nm3/hr at 360oC. The power generated is of the order of 7700 kW at 6.6 KV. The installation cost of the system is around Rs 84 crores. The economic efficiency analysis indicates reduction of : 56.07x106 kWh of power purchased - Rs 24 crores Fossil fuel consumption of 14517 tonnes/year CO2 emission of about 45098 tonnes/year
• • •
Case Study 1 : Installation of High Efficiency Dynamic Separator for Raw Mill Brief In a million tonne dry process pre-calciner plant, the existing static separator of the VRM was replaced with a new cage type dynamic high efficiency separator. There was an increase in the output of the Mill, finer product and reduction in the specific power consumption of the Mill. Additionally, the Mill vibration also got reduced resulting in trouble free operation. The Power Saving amounted to 2.5 units/tonne of Raw meal or 3.0 units/tonne of cement Energy Saving Annual Energy saving Annual Savings Investment Simple payback
: : : :
Rs 1.8 Million kWh Rs 270 Million Rs 300 Million 13 months
Case Study No. 2: Savings in Electrical Energy by increasing Kiln String Cyclone Diameter from 5.4 Mts to 6.6mts Brief Parameter
(iii) Waste heat recovery for cogeneration of power In case of dry process cement plants, nearly 40 percent of the total heat input is rejected as waste heat from exit gases of preheater and cooler. The quantity of heat lost from preheater exit gases ranges from 180 to 250 kcal/kg clinker at a temperature range of 300 to 400oC. In addition, 80 to 130 kcal/kg clinker heat is lost at a temperature range of 200 to 300oC from grate cooler exhaust. The waste heat has various applications such as drying of raw materials and coal, but even after 376
Cyclone dia. (m) Pressure drop (MMwg) Energy consumption kWh Kiln output (TPD)
377
Before Implementation 5.4 115
After Implementation 6.6 86
Saving/Improvement
750
722
( + ) 28
6281
6597
( + ) 316
( - ) 29
Energy Saving Energy Savings Annual Savings Investment Payback period
Case Study No.5: Installation of new correct head pump for raw mill slurry transfer to Silo
: 28 kWh : Rs 0.88 Million : Rs 2.2 Million : 2.5 years
Brief Suppose that there are 3 raw mills, out of which 2 to 3 are in normal operation. Limestone slurry from the raw-mill section is pumped to the low-grade silos. There are two slurry pumps of different capacities to meet the carrying capacity requirements.
Case Study No. 3: Optimisation of Crusher Output Brief The average output of Crusher is 205 TPH. The major constraints were the capacities of belt conveyor from Primary crusher to secondary Crusher. The feed was restricted due to spillage taking place at the belts. It was possible to increase the width of the belt and speed after changing the gear boxes. The capacity of belt was increased from 200 TPH by enlarging the belt size and gearbox. Energy Saving Parameter Output of crusher (TPH) Energy consumption kW h / tonne Annual saving (Rs.)
Before Implementation 205 2.1
-
After Implementation 235
Description
Head
Capacity
Smaller capacity pump
20 m
-
Larger pump capacity(54 KW)
40 m
175 m 3 / h
The large pump is operated, when 2 raw mills are in operation, while the smaller pump is in operation, when for 1 raw mill is in operation. On comparing the two pumps, it is evident that the larger pump is designed with a higher head. The maximum head required for the slurry pump is :
Saving/Improvement
Silo Height Pit Height Line loss Additional height
( + ) 30
1.8
-
The specifications of the two slurry pumps are as follows
( - ) 0.3
( + ) 66000
Actual head required for pump
The air-lift was replaced with a bucket elevator. The air-lift was retained to meet the stand-by requirements. The implementation of this project resulted in reduction of power from 140 units for the air-lift to 40 units for the Bucket elevator. The air to be ventilated from the silo also got reduced with the installation of the mechanical conveying system. The silo top fan was downsized to tap this saving potential.
Energy Saving Annual Energy Saving Annual Savings Investment Simple payback
: 0.68 Million kwh : Rs 2.24 Million : Rs 5.4 Million : 29 months
378
: 4 m (Pit height) + 16 m (Silo height) + 2 m (Additional height) + 3 m (Line loss) = 25 m (Say 30 m )
With one mill in operation & smaller pump started - head is only 20m. With 2 or 3 mills, bigger pump is operated & here the head is very high. Capacity required with 3 mill Operation Maximum power consumption
Annual Savings Low energy consumption (25 - 30% of Pneumatic conveying) Reduction in power consumption of silo top dedusting system
16 m 4m 3m 2m
It is recommended to install new correct head pump for slurry transfer from raw mill to LG silos, using the existing pump as standby.
Case Study No.4: Replacement of the Air-lift with Bucket Elevator for Raw-meal transport to the Silo Brief
: : : :
= 175 m3/h (Same as existing) = 175 m3/h x 30m x 1.69 kg/m3) 102 x 3.6 x 0.70 pump x 0.85 motor = 40.61 (Say 41 kW) = (54-41) kW x 8000 kWh x Rs. 2.26/kWh = Rs 0.235 Million
Energy Saving Annual savings Investment required (for new pump & motor) Pay back period
: 0.235 Million : 0.120 Million : 6 months
Case Study No.6 : Replacement of Existing Cyclones with Low Pressure Drop (LP) Cyclones
379
Brief
Compressor
Implementation methodology & time frame: The top cyclone was at a height of nearly 106 metres. The implementation of this project involved removal of the existing cyclone and fixing of the new LP cyclone. The replacement lead to an increase in the output of the Kiln, reduction in pressure drop of the pre-heater, reduction in Kiln section power consumption and reduction in Kiln specific thermal energy consumption. The comparison of the conditions and the energy consumption before and after installation of the LP cyclones are as below: Energy Saving Parameter
Before Implementation
After Implementation
Benefits
2650
2850
( + ) 200
100 – 125
70 – 90
( - ) 30-35
Kiln section Power (kWh/T)
30
28.5
( - ) 1.5
Heat Consumption (kcal/kg)
830
810
( - ) 20
Clinker Production (TPD) DP across Top Cyclone (mmWg)
Annual Savings Investment Payback period
: : :
Rs 2.4 Million Rs 2.2 Million 11 months
It was recommended to derate cement mill D-Pump compressor & filtration plant instrument compressor by 10%. The compressor drives were belt driven and derating was carried out by changing the pulley size suitably. Power consumption
Unload (S)
69
17
71 Average Unload = 22 %
23
Load (kW)
Unload (kW)
22
7
380
Unload (kW)
111
24
Average unload = 17 % Energy Saving Savings in power consumption Annual savings Investment Payback period
: : : :
3.1 kWh Rs 0.1 Million Negligible Immediate
There was a drastic reduction in the power consumed by the Cooler ID fan. The comparison of the conditions and the power consumption before and after installation of the VFC are as below:
The cement mill D-pump compressor was found to unload for 17% of time. The load and unload power consumption was measured to be 111 kW and 24kW.
Load (S)
Load (kW)
A Variable Fluid Coupling (VFC) was installed for the Cooler ID fan. The hood draught was maintained by varying the speed through the VFC. The existing 315 kW, 750 rpm & 6.6 kV motor was replaced with a 230 kW, 750 rpm & 6.6 kV motor.
The Filteration plant instrument compressor is observed to unload for 22% of time. Power consumption measurements indicate that the load power consumption is 22 kW and the unload power consumption is 7 kW.
Filtration plant Instrumentation Compressor
Unload (S) 16 18
Brief
Brief
Timings
Load (S) 90 72
Power consumption
Case Study 8 : Variable Speed Fluid Coupling for Cooler ID Fan and replacement with lower capacity motor
Case Study 7: Derating Compressors to optimize the unload power consumption
Compressor
Cement Mill D-Pump
Timings
Energy Saving Power consumption with damper control Power consumption with VFC Energy saving Annual Energy saving Annual Savings Investment Payback period
: : : : : : :
123 kW 76 kW 47 kW 0.384 Million kWh Rs 1.15 Million Rs 0.5 Million 5 months
Case Study 9: Delta Start Star Run Operation of Dust Collector Brief i) The Dust Collectors are installed in the cement plant for collection of dust emission. The dust collector is provided with the filter bags and blower motor. The dust is collected in the bags and prevented from going in the air to control air pollution. ii) It was observed during analysis of drive loading that the Dust Collector motor was operating below 50% loading. The loading on the motor has been reduced due to optimization of dust collector and pipelines bends. The starting torque requirement of the equipment is high hence Delta start and star run arrangement was suggested to reduce the power consumption. 381
iii) The Delta start and star run operation of the motor was technically viable, as the motor will operate in equipment safe operation and energy saving mode. The star operation of the drive will reduce the loading of the motor with reduction in copper losses and improvement in the efficiency of the motor. The PLC logic was prepared to start the motor in delta mode and shifting to star mode when full speed was pick up by the motor. The financial implications are nil, as no capital investment needed. Energy Saving Sno.
Perticulars
Before
Annual energy saving Annual Savings Investment Payback period
: : : :
0.46 Million kWh Rs 1.5 Million Rs 2.5 Million 20 months
Case Study 11: Installation of Variable Frequency Drive for MFC Fluidizing Air Blower
kW SAVING
Brief
13.46
The Blower used for fludisation air is of the following specifications - 165 m3/hr flow, 1000 mm WC pressure rise and 40kW motor rating - for supplying fluidizing air. The actual power consumption of the fan is 37 kW.
After
Modification Modification (A)
1 Operation
Energy Saving
Saving
Delta mode Star mode
20 10.46
2 Power Intake /Hr. a) Load Current b) Power Factor c) Voltage
20.9 AMPs 0.93 400 Volts
15.4 AMPs 0.98 400 Volts
d) Power (1.73 xVxIxP.F)
13.46 kWH
10.46 kWH
13.46
10.46
3 Saving in KW
The suction area of the fan is about 70% closed and the inlet guide vane is controlled to the extent of 70% open. This indicates that the rated flow is much higher that actual requirement. After installing the VFD, open the suction area fully and gradually reduce the rpm till the discharge pressure is the same as before. Subsequently, open the IGVcompletely to 100% open position and further reduce the speed of the blower till the pressure difference across the blower is maintained at present values. Blower specification (WC) : 165 m3/h, 1000 mm Motor Rating (kW) : 40
3 kw 0 DELTA
STAR
Case Study 10 : Variable Frequency Drives for Cooler Fans Brief Four cooler fans were installed with Variable Frequency Drives (VFDs). There was a drastic reduction in the power consumed by the Cooler fans. The power saving in the fans is on account of • Saving in the energy lost across the dampers • Increase in the operating efficiency of the motor. The efficiency of the motor depends on the V/f ratio. In the case of the VFD, the voltage is varied to maintain the V/f ratio at the designed value. Hence, the efficiency of the motor is maintained at a higher level even at lower loading of the motor. The comparison of the conditions and the power consumption before and after installation of the VFDs are as below: Equipment
Rating (kW)
Power consumption beforeVFD
Saving through VFD
Power consumption after VFD
Fan – IA (kW)
75
45
32
13
Fan – IB (kW)
75
44
30
14
Fan – IC (kW)
110
68
54
14
Fan – IC (kW)
110
59
44
15
Total Saving (kW)
57
-
382
Energy Saving Energy savings Annual savings Investment Payback period
: : : :
0.3 x 37 kW = 11.1 kW Rs 0.37 Million Rs 0.35 Million 11 months
Case Study 12 : Replacement of Existing Cooler I Grate with High Efficiency Cooler System Brief The plant replaced the I grate with high efficiency cooler system. This was done to increase the capacity of the Cooler and also improve the thermal efficiency of the system. Additionally the following capacity upgradation measures were also implemented simultaneously : • Increasing the height of the Calciner • Installation of high efficiency classifier for both Raw mill and Coal Mill • Conversion of the existing two fan system to three fan system • Installation of high efficiency nozzles for GCT On account of the capacity upgradation projects the capacity of the Kiln increased from 2800 TPD to 3000 TPD. The installation of the high efficiency Cooler resulted in reduction in the Cooler air quantity and cooler exhaust air
383
quantity. There was also an improvement in the steady operation of the Kiln, better quality and lower temperature Clinker. The over-all benefits achieved are as below:
m3/min of flow 500 mm pressure rise with a motor rating of 470 kW. The measured power consumption of this fan is 270 kW. The Recirculation fan flow was controlled by damper . This indicated the excess capacity/head availed in the fan. The damper opening was observed to vary from 45% to 80% depending on the separator output.
Energy Saving Parameter
Before Implementation
Clinker Production TPD 3
Cooler air Nm /kg 3
PH outlet air Nm /kg
After Implementation
Savings/Improvement
2800
3000
( + ) 200
2.6
2.1
( - ) 0.5
1.475
1.444
( - ) 0.031
Clinker Temperature C
180
120
( - ) 60
PH outlet Temperature 0 C
370
336
( - ) 34
PH loss kCal/kg
217
1 19
( - ) 26
Cooler & Clinker loss kCal/kg
131
120
( - ) 11
Radiation loss kCal/kg
69
65
(-)4
Heat Consumption kCal/kg
780
745
( - ) 35
0
Annual Savings Investment Payback period
: Rs 12 Million : Rs 29 Million : 30 months
At 80% of the damper opening (the normal maximum damper opening), the damper is observed to offer a pressure drop of 18.9%. This indicates that 18.9% of the power consumed by the fan is lost across the damper. The capacity of the fan cannot be permanently derated because the capacity of the fan needs to be varied with time. It was concluded that good energy saving potential exists by installing a speed control device and varying the speed of the fan. Hence, it was required to install a Grid Rotor Resistance (GRR) control to the recirculating fan and vary the capacity as required. The damper must be fully opened once the GRR is installed to the recirculating fan. Damper position of recirculation fan varies from 45% to 80% opening based on the separator output. At 80% damper opening, damper loss is calculated
Case Study 13: Usage of High Efficiency Crusher as a Pre-grinder before the Cement Mill
Damper loss
= -320 - (-390) -20 - (-390) = 18.9% = 270 kW
Brief Actual power consumption The plant installed a Horizontal Impact Crusher (HIC) of 300 TPH capacity (including recirculation). The HIC was to act as a pre-grinder and perform the initial size reduction before the Mill. The HIC had a three deck-vibrating screen to separate and return the coarse material back to the HIC. The coarse was sent to the HIC back by gravity while the fines were conveyed to the hopper through a belt conveyor. The fines from the hopper can be later fed to the Mill through a belt conveyor. Thus the HIC and the Mill were made independent so that the operation of one does not affect the other. Energy Saving Increase in capacity from 125 TPH to 175 TPH Reduction in power consumption from 29.0 units to 25.7 units per tonne of O P C 4 3 Annual Savings : Rs 15 Million Investment : Rs 40 Million Simple payback : 32 months Case Study 14: Installation of Grid Rotor Resistance (GRR) Control and varying the Speed of the Recirculation Fan
Install a GRR and vary the speed of the fan instead of the damper position. Measured Savings, after considering GRR's power consumption (kW) : 51. Energy Saving Savings in power consumption (kW) Annual savings Investment Payback period
: : : :
30 Rs 0.64 Million Rs 0.5 Million 10 months
Case Study 15: Reducing the Speed of Cement Mill's Dust Collection Fan Brief A Cement Mill's dust collection fan was observed to operate with damper control. The damper was open to the extent of about 40%. Pressure measurements before and after the damper and at the fan delivery indicated that the pressure drop across the damper is about 73%. The motor rating of this fan is 22 kW and the measured power consumption of the fan is 17 kW.
Brief
The pressure loss of 73% across the damper indicates that nearly three-fourth of the power consumption of the fan is lost across the damper.
The Cement mill is a close circuit mill. The recirculation fan in the cement mill draws air from Separator through Cyclone. The recirculation fan is rated for 3800
Good potential for energy saving exists by reducing the speed of the fan.
384
385
Reduce the speed of the fan by 30%. The speed reduction should be done in stages of 10% each. This fan being a belt driven equipment, the speed reduction could be carried out by pulley size reduction. Loss across damper Energy loss
Table 12.5: 'Primary Energy Intensity Values' for Cement Plants following World Best Practice.
Cement Portland Cement Fly Ash Cement Blast Furnace Slag Cement
= -48-(-175) (All measurements in mmWC) = 73 % -1-(-175) = 0.73 x 17 kW = 12.4kW
12.7
Savings in energy consumption Annual savings Investment Payback period
: : : :
i)
Other Best Practices of Energy Efficiency in Cement Industry
Raw Material Preparation • • •
The specific energy consumption of cement plants in developed countries like Japan is 650 kcal/kg of clinker as thermal energy and 65 kwh / tonne of cement as electrical energy. This is mainly because of advanced technologies, process designs and best energy efficiency practices adopted. The 'World's Best Practices represent the most energy efficient processes that are in commercial use in at least in one location, worldwide. The Energy Intensity values are defined as:
• •
(i) "Final Energy Intensity Values", i.e. the energy used at the production facility
•
(ii) "Primary Energy Intensity Values" i.e. the sum of energy used at the production facility, plus the energy used to produce electricity consumed at the facility.
•
The process in cement plant based on the energy consumption can be divided into following parts: Raw materials preparation (limestone & fuels). Clinker making (fuel use & electricity use) Additive drying Cement drying Other energy uses (quarrying, auxiliaries, conveyers and packing)
The World Best Practice Values based on the above processes for 'Final Energy' and 'Primary Energy' are given in tables 12.4 & 12.5 for Portland Cement, Fly Ash Cement and Blast Furnace Slag Cement respectively. Table 12.4: 'Final Energy Intensity Values' for Cement Plants following World Best Practice. Cement Portland Cement Fly Ash Cement Blast Furnace Slag Cement
Unit t Cement t Cement t Cement
GJ/t
*kgce / t
2.9 2.0 1.7
100 70 57
*kgce = kg of coal equivalent (Source : World Best Practice Energy Intensity Values; LBNL; Worrell E., Price L., Neelisy Galitsky C.) 386
Kgce/t 115 84 73
Some of the best ENCON practices being used in cement industry Internationally are:
8.5 kW Rs. 66,000 Rs. 10,000/2 months
12.6 Energy Consumption in Cement Plants - World's Best Practice
a) b) c) d) e)
GJ/t 3.4 2.5 2.1
(Source : World Best Practice Energy Intensity Values; LBNL; Worrell E., Price L., Neelisy Galitsky C.)
By reducing the speed of the fan by 30%, 50% savings in energy Consumption is possible. Energy Saving
Unit t Cement t Cement t Cement
•
Mechanical conveyors, in place of pneumatic conveyers, which consume 2 kwh/t less energy for dry process. On line analysers used for raw mix control. Gravity type homogenizing silos (or continuous blending & storage silos) reduce power consumption by 0.9 - 2.3 kWh/t raw material. Reduction in compressed air losses by plugging of leakages in slurry blending & homogenizing (wet process). Replacement of tube mill by a wash mill in wet process leads to reduction in electricity consumption by 5-7 kWh/t. High efficiency vertical roller mills in place of balls mills, saves energy of 6-7 kWh/t raw material. A multi variable controller in vertical roller mills to maximize the total feed while maintaining a target residue and enforcing a safe range of trip-level vibration. The throughput increases by 6% and SEC reduces by 6% or 0.8 1.0 kwh/t of raw material. Using high efficiency classifiers or separators, the material stays longer in the separator, leading to shaper separation, thus reducing over - grinding & saving 8% of electricity.
ii)
Fuel Preparation
-
Installation of roller presses for coal grinding in place of conventional grinding mills.
iii) Clinker Production a) Wet Process : • Wet process conversion to semi-dry process through slurry gas driers. Evaporation energy is reduced to half in this process, reducing fuel consumption by 1 MBtu/t clinker. • Wet process conversion to semi-wet process by installing filter press to reduce moisture content to about 20% of the slurry and obtain a paste, ready for extrusion into pellets.
387
• Wet process conversion to dry process production by installing multi pre heater / pre - calciner. Fuel saving of upto 2.9 MBtu/ ton can be achieved. b)
Dry Process pre-heater Kilns : • Low pressure drop cyclones for suspension pre - heaters can save 0.6 - 0.7 kWh/t clinker for each 50mm WC (Water column). • Heat recovery from the kiln exit gases for co-generation, either by installing direct gas turbines that utilize the waste heat (top cycle) or by installing waste heat recovery boiler system that runs a steam turbine system (bottom cycle). Power generation may vary from 10 to 23 kWh/t clinker, saving electrical energy of 20 kWh/t clinker. • Dry process conversion to multi - stage pre - heater by installing multi stage suspension pre heating (4 or 5 stage) reduces heat loss and thus increases efficiency. Kiln length is also shortened by 20% to 30%, thereby reducing radiation losses. • Conversion of Long Dry Kilns to multi - stage pre heater / pre calciner kiln can save 1.2 MBtu / tonne clinker.
c)
Other measures : •
• • • •
• • •
•
Advanced process control through online analyzers to recover heat from kilns (e.g. 'fuzzy logic' or 'ABB LINKman' control system) to save 2.5% 5% energy and reduce NOx emissions by 20%. Gyro - thermal technology for kiln construction system improves gas flame quality while reducing NOx emissions. Oxygen enrichment in the kiln to increase production capacity. Upgradation of pneumatic seals at the kiln inlet and outlet reduces false air penetration as well as heat losses. Use of better insulating refractories with high temperature insulating lining reduces kiln shell heat losses thereby saving 0.1 - 0.34 Btu/ton fuel use. Use of high efficiency AC variable frequency drives in place of DC drives for rotating the kiln. Use of VFD in kiln fan reduces 40% of energy. Replacement of rotary or shaft coolers by Reciprocating Grate coolers in the cooling of clinker and efficient heat recovery (almost by 65%) saves about 8% of the fuel consumption in the kiln. Optimization of heat recovery by using reciprocating grate coolers for large kilns (upto 10,000 tpd) for recovery of sensible heat upto 1.4 MBtu/t.
v) Plant-wide measures • • • • •
Preventive maintenance of the plant. Use of High - Efficiency Motors & Drives. VFDs for clinker fans, fans in kiln, cooler, pre heater, separator and mills. Reduction is losses in compressed air system. Energy Efficient lighting.
12.7.1 The energy efficiency measures in 'Dry Process Cement Plants' in US Energy Efficiency Measures in Dry Process Cement Plants are summarized in table 12.6. The estimated savings and payback periods are averages for indication, based on the average performance of the U.S. cement industry (e.g. clinker to cement ratio). The actual savings and payback period may vary by project, based on the specific conditions in the individual plant. Table 12.6 : Energy Efficiency Measures in Dry Process Cement Plants Energy Efficiency Measure
Fuel Preparation: Clinker Making Roller Mills Energy Management & Control Systems Seal Replacement Combustion System Improvement Indirect Firing Optimize Grate Cooler Conversion to Grate Cooler Heat Recovery for Power Generation Low-pressure Drop Suspension Preheaters
Specific Fuel Savings (MBtu/tonne 0.10 – 0.20 0.02 0.10 – 0.39 0.09 – 0.31 0.06- 0.12 0.23 -
Specific Electricity Savings (kWh/tonne 0.7 – 1.1 1.2 – 2.6 -
Estimated Payback Period (1) (years) N/A (1) 1–3 <1 2–3
0 – (-1.8) -2.4 18
1 1–2 1–2 3
0.8 – 3.21.6 -
<11 1
Finish Grinding Energy Management & Process Control Improved Grinding Media in Ball Mills
> 0.5
Plant Wide Measures Preventative Maintenance High Efficiency Motors Adjustable Speed Drives Optimization of Compressed Air Systems
0.04 -
1.7 – 6.0 0–5 0–5 5.5 – 7.0 0–2
1.21 0.30 0.16
-15 3.0 N/A 0 – 14
> 10 (1) <1 <1 2- 3 <3
iv) Finish Grinding • • • •
Process control and management of Grinding mills. Advanced grinding concepts by installing high pressure roller presses. Use of high efficiency classifiers increases production by 20% to 25% and reduces 8% electricity. Improved wear grinding materials such as chromium steel can be installed for grinding media. Potential savings 5% to 10%.
Product Change Blended Cement Limestone Portland Cement Use of Steel Slag in Clinker (CemStar) Low Alkali Cement Reduced Fineness of Cement for Selected Uses
0.16 – 0.4 -
<1 <1 <2 Immediate Immediate
Notes: Payback periods are calculated on the basis of energy savings alone. (Source : Energy Efficiency Improvement Opportunities for Cement Making; An Energy Star Guide; LBNL; by Worrell E., Galitsky C.) 388
389
12.8
Energy Efficient Technologies being used in Cement Plants in Japan
Case Study 16: Cement clinker burning process (a) Adoption of suspension preheater (SP) Brief This modification represents installation of a facility to effectively dry and preheat the feed previously blended in the raw material blending section using the flue gas stream from the kiln. This improvement has achieved marked energy saving compared with the conventional wet process. The exhaust gas from the kiln in the dry burning process is about 10500C. Formerly, the sensible heat of this flue gas was partly recovered by exhaust gas boiler for power generation.
1)
2) The roller mill mechanism is primarily to crush coal between the disc table and rolls which are pressed hydraulically onto the table. 3) Ground coal is fed upward to the classifier placed above by the hot air blown into the mill from below. Coal is dried while it is being brought upward by the hot air. Use of the vertical roller mill can reduce specific consumption of electric power by 20 to 25 percent compared with the conventional combination of tube mill and separator. Energy Saving Investment amount Improvement Effect
: Rs. 250 Million for 20 tonne/hour size : Reduction of SEC by 20% - 25%
(c) Adoption of high-efficiency quenching cooler
2)
The new facility represents a modification which instead directly recovers the sensible heat for drying and preheating the kiln feed.
Brief
3)
The Suspension preheater is a multistage cyclone and the temperature of these gas at he outlet of cyclone was 3500 -3800c.
This modification represents adoption of a high-efficiency quenching cooler. The high-efficiency quenching cooler rapidly cools burned clinkers from the kiln by air to improve the cement quality. At the same time the air heated by the burned clinkers is used as combustion air for kiln burner to achieve energy saving.
Energy Saving (1) Energy saving effect of the suspension preheater (Production: 4,000 t/D) Savings / Improvement
Note
400 to 500 x 103
Av. 450 x 103
594 x 109
Operation: 330 D/y
Modification: Modification into high-efficiency cooler with the capacity of 5,000 tonne / day Energy Saving Energy saving effect of clinker cooler
Specific heat recovery kcal/(t-clinker) Annual total heat recovery kcal/y Crude oil equivalent (kL/y)
Savings /Improvement
Specific heat consump tion for cement (kcal/kg) Crude oil equivalent (kL/y)
264,000
(2) Productivity of burning process will be improved. Capacity of the kiln: one series of 4,000 tons/day facilities (raw materials preparation through burning to finishing) Investment
Heat recovery rate
: Rs 1.2 Billion
Equipment modification cost Reduction of SEC
56.9% to 62.3% (Increased) 20.5 (Reduced)
2,240 (reduction)
: Rs. 20 - 80 Million : 2.8%
Case Study 18 : Cement production finishing section : Brief
(b) Adoption of vertical roller mill for coal crushing Brief Formerly, combination of a tube mill and a separator was used mainly for crushing coal. Nowadays, highly efficient vertical roller mills capable of crushing and drying coal, and classifying crushed coal have been com- mercialized. As a result, significant reduction of specific electric power consumption has been achieved.
The present case installs a vertical roll crusher of high grinding efficiency as a pregrinding crusher in the step previous to the ball mill, the finishing grinder of cement. Crushing clinkers before they are fed into the ball mill of high power consumption, the efficiency of the ball mill was increased because its load was greatly reduced and the specific electric power consumption was significantly saved.
1) Moist coal is fed either from the top or side to the rotating table of the vertical roller mill. 390
391
A mixture of clinkers and gypsum was crushed by the compression and shear force between the table and three rollers, the latter being hydraulically pressed onto the former. Energy Saving Before improvement After improvement Savings / Improvement Production capacity(t/hr)
107
160
1.5 times (increase)
Specific electric power consumption (kWh/t) Electric power consumption* (MWh/y)
36
29
7 (19% reduction)
32,400
26,100
Crude oil equivalent (kl/y)
6,300 (reduction) 1,531 (reduction)
Note: * Production : 3,000 tonnes/day at 300 days/year operation
Investment amount Reduction in SEC
: Rs. 250 Million for a 100 tonne / hour grinder : 19%
References 1. IEA, World Energy Outlook 2007. 2. Directory of Energy Conservation Technology in Japan, prepared by New Energy & Industrial Technology Development Organization, The Energy Conservation Centre, Japan. 3. Investors Manual for Energy Efficiency, EMC, CII & IREDA.. 4. Bureau of Energy Efficiency. 5. NCCBM (National Council for Cement & Building Materials). 6. Portland Cement Association : Innovations in Portland Cement; Shokil IL, PCA. 7. Energy Management Policy-Guidelines for Energy Intensive Industry in India, Bureau of Energy Efficiency. www.bee-india.com/aboutbee/Action %20 Plan/ 05. tal, html. 8. Energy Efficiency Improvement opportunities for Cement making : An Energy Star Guide for Energy & Plant Managers. Lawrence Berkeley National Laboratory; Ernst Worrell & Christina Galitsky. 9. Assessment of Energy use & Energy Saving Potential in Selected Industrial Sectors in India (Ernest Orland Deptt. Of Environmental Energy Technologies Division; by Jayant Sathaye, Lynn Price, Stephane delaPue can & David Fridley. 10. Energy Efficiency Programmes & Policies in the Industrial Sector in Industrialised Countries, Berkelay, LBNL. 11. Indo-German Energy Efficiency & Environment Project (IGEEP); India.com/aboutsee/implementation/designated/ 12. Statistical Pocket Book, India, 45th Edition, 2006-07, Central Statistical Organisation; www.mospi.gov.in. 13. Website : www.ibef.org/artdisprirew.aspx art 14. Handbook of Energy Conservation by H.M.Robert & J.H. Collins.
392
Chapter 13 Sugar 13.1
Introduction
India has been known as the original home of sugar and sugarcane. Indian mythology supports the above fact as it contains legends showing the origin of sugarcane. India is the second largest producer of sugarcane next to Brazil. Apart from sugar, the sugar industry produces certain by-products, which can be used for production of other industrial products. The most important by-product is molasses, which is utilized for production of chemicals and alcohol. In addition, the other important by product is bagasse. It is mainly utilised as a captive fuel in the boilers but it is also used as a raw material in the paper industry. 13.1.2
Number of Sugar Factories
There were 608 installed sugar factories in the country as on 31.12.2007. The sector-wise breakup is as follows: Table 13.1 Sector Cooperative Private Public TOTAL
Number of factories 317 229 62 608 *
* This Includes closed sugar factories also Source: Department of Food & Public Distribution
13.1.3
Production of Sugar
During the sugar season 2007-2008, production of sugar is estimated at about 270 lakh tonnes as against the production of 280 lakh tonnes during the previous season 2006-2007. Table 13.2: Production of Sugar (Lakh Tonnes)
1997- 1998- 1999- 2000- 2001- 2002- 2003- 2004- 2005- 2006-2007 98 99 00 01 02 03 04 05 06 (Provisional) 128.44 154.52 181.93 185.10 184.98 201.32 139.58 130.00 193.21 280.00 Source: Department of Food & Public Distribution
13.2
Energy Profile
The energy requirements in a sugar mill are in the form of steam for process heating/turbo drives and electricity for running various drives. The sugar industry has the unique advantage of utilizing a captive fuel-bagasse, to meet its energy requirements. However, depending upon various factors like fibre content in the cane, quantity of juice, type of clarification process and evaporation effects, type of prime movers (steam driven or electric driven) etc., some sugar mills produce a 392
393
small quantity of surplus bagasse while others are deficient by a small quantity. These mills, therefore, have to depend in a very limited way on external fuels like fuel oil, LSH, coal etc to supplement their energy requirements. Likewise, some sugar mills during the season can produce a little surplus power while others would be deficient in power by a small margin and hence the dependence on grid power is minimal. Energy consumption in sugar plants depends on various factors such as its capacity, steam generation parameters, vintage, equipment used etc. Analysis of the energy consumption pattern in the sugar mills reveals that there exists significant scope for improving the energy efficiency in the Indian Sugar Industry. The major reason for the high energy consumption in the industry is the presence of large number of old, small capacity sugar mills which have not invested much over the years in modernizing or upgrading various process equipment. Apart from improving the end use efficiency in the plants, the other most promising energy conservation measure for the industry is to set up high-pressure cogeneration systems. This not only has the potential of opening up additional revenue streams for the sugar plants by way of sale of electricity, it can effectively contribute in reducing the ever widening gap between demand and supply of electricity in various power deficit regions in the country. 13.2.1
Energy consumption in Sugar Industry Table 13.3
Specific Electrical Energy consumption
30 units/tonne of cane with electric motors & DC Drives 24 units / tonne of cane with diffusers
Specific Thermal Energy steam consumption 38% on cane Source: CII-IREDA
Energy efficiency in sugar industry
Energy efficiency in sugar industry offers the following benefits: •
The Indian sugar industry offers good potential for energy saving. The estimated energy saving potential in the Indian sugar industry is about 20%. This offers potential of about 650 MW of electrical energy. 13.3
Sugar Manufacturing process
The sugar manufacturing process normally comprises of juice extraction, juice clarification, evaporation, crystallization, centrifuging, drying, and packing. Steam generation using bagasse as the fuel and electricity generation, mostly through backpressure turbines forms an important part of any sugar factory. 13.3.1
Juice Extraction
The juice extraction plant consists of cane handling, cane preparation and milling sections. a) Cane handling Cane is brought mainly by trucks, trollies and bullock carts to the mill. The load is first weighed on a weighing bridge. The sugarcane is mechanically unloaded by a grab type attachment. A truck tippler is also sometimes provided to unload cane, facilitating loading of the sugar cane on to the cane carrier. b) Cane Preparation The sugarcane after delivery to the cane carrier is levelled in the leveler before it is fed to the cutter. The cutter shreds the cane to smaller sizes and prepares it for the fibrisor where the cane is converted to a pulp-like mass. c) Milling
The energy consumption in Indian sugar mills range from 0.7 to 0.87 GJ/ tonne of cane against a world average of 0.5 to 0.6 GJ/Tonne of cane crushed. 13.2.2
profitability to the plant as well as significant reduction in GHG emission. These plants, however, are very few in number.
In plants having cogeneration facility and where the state utility is able to purchase additional power generated from sugar plants, any improvement in energy efficiency levels of the plant results in increased export to the grid. This reduces the equivalent reduction in power generation from fossil fuel based power plants. This has a significant reduction in carbon emissions.
•
In plants having cogeneration facility, but the state utility is not ready to purchase power, improvement in energy efficiency in the plant results in saving in bagasse. This either could be exported to other sugar plants, having cogeneration facility with state utility ready to purchase power, or can be sold to paper plants.
•
In plants, which do not have cogeneration facility, energy efficiency directly results in reduced power demand from the state utility. This results in higher 394
The prepared cane is passed through a milling tandem composed of four to six three-roller mills. The juice is extracted from the cane by squeezing under high pressure in these rollers. Extraction is maximised by leaching the disintegrated exposed cane with weak juice and make-up water in a counter current system. In the sugar industry, this leaching system is called "imbibition". Mixed juice, which is a mixture of juice extracted normally from the first and second stage milling is fed to the next production stage. The fibrous matter or bagasse', which is left after milling, is used as a fuel for steam generation. 13.3.2
Juice clarification
The purification of juice involves (a) juice heating (b) sulphitation (c) clarification and (d) filtration. The mixed juice from the mills is heated in raw juice heater(s). The common process employed in most of the mills in India is Double Sulphitation process. The heated juice is treated with chemicals like milk of lime and sulphur dioxide gas in a juice sulphiter. Various dissolved impurities in the mixed juice are precipitated out. The impurities precipitated are separated to obtain clear sparkle juice in clarifiers. Muddy juice, which settles at the bottom, is filtered in vacuum filters and the filtrate is recycled back to the system. The retention time in the clarifiers is 395
about 2-3 hours and this invariably results in an appreciable temperature drop. Hence the juice is again heated to obtain a temperature of about 1050C. 13.3.3
Evaporation
The juice is concentrated from 15 Brix to around 60 Brix in a multiple-effect evaporator. The vapours are bled from evaporators for juice heating in various heat exchangers and for boiling of massecuite in vacuum pans. This is the major steam consuming section of plant. 13.3.4
Crystallisation
Crystallisation is an important unit operation, which in sugar industry is known as Pan boiling. Major part of the crystallization process is done in most of the sugar plants in batch type vacuum pans. A mixture of the molten liquid and crystals, known as "massecuite" is then transferred to crystallizers where the process is completed by cooling the mass under stirred condition. 13.3.5 Centrifuging The massecuite from the vacuum pans is sent to the centrifuges, where the sugar crystals are separated from molasses. These centrifugal machines can be batch type or continuous type. There are separate centrifugal machines for `A' type, `B' type and `C' type massecuites. The molasses separated out from this section is a useful byproduct, which is an excellent raw material for distilleries. 13.3.6
Drying, grading and packing
13.4.1
By-products
The main by-products from any sugar industry are: (i) bagasse (ii) molasses and (iii) filter cake. Bagasse: Bagasse is an important by-product of sugar. It is rich in cellulose fibre and can be used as a major substitute raw material in the paper and pulp industry, replacing wood and bamboo thus reducing deforestation. Costly imports of pulp and waste paper can be avoided thus conserving the outflow of foreign exchange. Bagasse has also been suggested as a base material for cattle feed after mixing with molasses in varying proportions. The other important product, which can be manufactured from bagasse, is furfural, which is a very versatile chemical with good potential for commercial usage. Presently, almost all the sugar mills utilize this bagasse as an in-house fuel in boilers for steam generation. Number of mills are now planning to utilise the bagasse efficiently in high-pressure boilers for co generating electricity for export to the grid/neighboring units. Molasses: Molasses, the other important by-product, is a storehouse of organic chemicals. Industrial alcohol is produced from molasses, which in turn can be used to manufacture chemicals like ethyl benzene, lactic acid, tartaric acid, citric acid, diethyl phthalate, etc. Industrial alcohol can be used as a fuel extender as a substitute to the scarce petroleum products. 396
Co- Gen in Sugar Mills
The sugar industry by its inherent nature can generate surplus energy in contrast to the other industries, which are only consumers of energy. With liberalization and increased competition, the generation and selling of excess power to the electricity boards, offers an excellent source of revenue generation to the sugar plants. This is referred to as commercial cogeneration and has been only marginally tapped in our country. The sugar plants have been adopting co-generation right from the beginning. However, the co-generation has been restricted to generating power and steam only to meet the operational requirements of the plant. Only in the recent years, with the increasing power demand and shortage, commercial cogeneration has been found to be attractive, both from the state utility point of view as well as the sugar plant point of view. The sugar plant derives additional revenue by selling power to the grid, while the state is able to marginally reduce the 'demand-supply' gap, with reduced investments. 13.5
The moist crystals obtained from centrifugal machines normally contain about 15-20% surface moisture. They are dried in traditional dryers, graded according to crystal sizes and then packed in bags. 13.4
Filter cake: When cane juice is clarified and filtered, the resulting cake is known as filter mud or filter cake. It contains most of the colloidal matter precipitated during clarification and has around 63% organic matter. This cake is of great manurial value and is mostly taken by the growers in their own transport after delivering cane to the factory, for use in the fields.
Technologies & Measures for Energy Efficiency Improvements
Various technologies for energy efficiency improvement are discussed briefly. Some of these technologies are already in use in India while many are in the development phase or not yet commercialized in India. Besides these technologies, one very important step, Indian sugar mills can adopt is to produce smaller sized sugar instead of bolder sugar grains. Simply because of the bolder grain size, 2 to 3% more energy is consumed by the industry. 13.5.1
Improved reliability, economics of steam and power generating systems with film forming polyamines
Technology Description Corrosion and scaling in boilers and turbines continue to pose problems in maximizing steam and power generation at a minimum cost. The corrosion products (iron and copper oxides) coming with the condensate cause heat insulating deposits in boilers resulting in failures, loss of efficiency, frequent cleaning and increased cost of operations. Traditionally, multiple chemicals like phosphates hydrazine or sulfite have been used to reduce the corrosion and scaling but due to its major drawbacks a " film barrier approach" has been gaining increasing acceptance. It utilizes the film forming properties of aliphatic amines on divalent wet metal surfaces. Organic formulations containing film-forming amines, combination of neutralizing amines, dispersants and complexing agents provide much superior protection to the metal surfaces in boilers and turbines against corrosion scaling and carryover. The selection of the types of amines to be used, is determined by the properties such as vapor/liquid distribution ratio, dissociation constant, basicity, 397
etc. The product has been applied in sugar mills in India for more than five years.
quality sugar and final molasses. Molasses is a by-product in the process and can be used as raw material for alcohol industries.
Advantages Advantages • • • • • •
Complete protection against corrosion and scaling. Clean and scale free surface. No cleaning of boilers/turbines required for years. Simplified dosing and monitoring. Flexibility in operation, as film stable over a pH range of 4 to 11. Cost saving due to improved heat transfer and reduced blow downs.
•
In non-sulphitation plants, suphitation processing equipment is eliminated from the process.
13.5.4 Sugar-cane waste conversion into char Technology Description
13.5.2
Direct production of white sugar in a cane sugar mill
Technology Description An economical process is disclosed for the direct production of white sugar from clarified juice. Juice from a cane sugar mill, or sugar beet juice, is first contacted with hydrogen peroxide, before passing through granular activated carbon. The juice is then passed through cationic and anionic resins to remove inorganic compounds, colorants, and other impurities. Then the juice may be concentrated and sugar crystallized. White sugar is produced directly, without the need for an intermediate raw sugar crystallization. Advantages •
•
The process does not require membrane separation and involves adsorption of colour and other impurities using granular activated carbon and ion exchange resins. Chemical regeneration of the carbon is utilized, which enhances the attractiveness of the process.
The Appropriate Rural Technology Institute (ARTI), India, at pune has developed a charring process for converting sugar-cane trash into high-value char. Dried leaves of sugar cane, or sugar-cane trash, resist biodegradation and cannot be used either as cattle fodder or as a raw material for making compost. The innovative process is especially suitable for handling large amounts of loose biomass at high speeds and on a continuous basis. Char obtained by this process can be converted into briquettes easily by a variety of well-established briquetting methods. The ecofriendly oven-and-retort type kiln from ARTI is constructed using bricks and mud. The oven is loaded with a retort (1 kg capacity) filled with sugar-cane trash and a fire is lit below the oven using some of the trash itself as fuel. As the retort heats, the trash inside is converted to char and the pyrolysis gas escapes from a hole in the lid of the retort. A cast-iron grate separates the firebox of the chulha and the retort inside the oven. The retort is loaded upside down in the oven so that the pyrolysis gas passes into the firebox and burns, thereby generating additional heat for charring. Moreover, as the pyrolysis gas is used in the kiln itself, venting or flaring is prevented. Advantages •
13.5.3 Mini Sugar Plant (Khandsari plants)
The kiln has a conversion efficiency of 30 per cent and operates as a continuous-batch process.
Technology Description 13.5.5 Quintuple 3rd effect vapour for sugar melting The sugarcane is fed to the cane carrier provided with Cutters. Sugarcane is chopped into pieces and conveyed to the sugarcane mill. Juice is extracted by crushing unit, screened and collected in raw juice tank and pumped into sulphitation towers. Lime and compressed sulphur-di-oxide gas is mixed with juice. After sulphitation, juice is discharged into cracking bels for single boiling where non-sugars become precipitated from the cracking bel. Juice is pumped into settling tank. The heavy precipitated mud and other impurities settle down at the bottom and clear juice is discharged from the valves of the settling tanks and flows by gravity to boiling bels. The muddy juice from the bottom of the settling tanks is discharged in mud tank and is forced into filter press by means of a mud pump. Filtered juice also goes to the juice boiling bels and mud cake is retained in the press and removed when the press is opened. Clear juice from settling tank and filter press is boiled in open pan juice boiling bels and concentrated. The syrup thus formed is sent manually to crystallizers. Proper crystallization takes place in 48 to 72 hours. After washing, sugar is taken out of centrifugal machine and dried. First quality sugar is dried, graded and bagged. Molasses, which come out of centrifugal machine, is reboiled in Molasses Boiling Bels and sent to crystallizers. The process of crystallization, centrifuging, drying and bagging is repeated to obtain second 398
Technology Description In a multiple effect evaporator, vapour bleeding in the later bodies will bring steam economy. But extensive use of this vapour is presently limited to first two bodies due to low temperature of vapours and high scaling patterns in later bodies. With the installation of condensate flashing system, vapour generation in individual bodies is being augmented by flash vapor in condensate and hence requiring less evaporation. This is leading to more vapours to condenser, as waste. To avoid this, extensive use of vapour of the third body in a quintuple effect evaporator is planned. With increase in pressure of exhaust steam used at first body of evaporator, the pressure conditions of individual bodies changed to higher side matching with the pressures of quadruple effect. Navbharat Ventures has initiated a project replacing vapour of the second body being used at pan floor and SJ1 heating with vapour of the third body. There is no financial requirement as the same vapour line is used to draw vapour from the third body of quintuple effect evaporator to utility points. Steam saving achieved through extensive use of vapour from third body by converting evaporator system in to 399
quintuple from quadruple is upto 3.5%. Advantages •
Reduction in steam consumption
13.5.6 Condensate flashing system Technology Description Cane contains about 70% of water. This water is extracted along with juice in milling by adding some more water to the cane bagasse, which is called imbibition. Mixed juice is required to be heated up to 102oC to stall microbiological action on it and to increase the rate of reaction with chemicals (lime and SO2 gas) added. When concentrated by separating water content in multiple effect evaporation, the vapor condensate takes away heat utilized for heating, often into drain. As was the case of reducing pressure in bodies of multiple effect evaporators in sequence enabling use of vapor for boiling in the subsequent bodies, it is proper to use flash heat in hotter vapor condensates, in subsequent bodies by circulating the condensate sequentially. SEDL (Spray Engineering Devices Ltd.) has improvised the design of the flash vessel for heat recovery from condensate of evaporator, pans and surface contact heaters. Haidergarh Chini Mills, Barabanki (UP), with help of SEDL has installed a Condensate Cigar along with Plate Heat Exchanger (PHE) at the evaporator station to utilize the waste heat of excess condensate by using flash vapour. Further, PHE facilitated to recover extra heat going along with exhaust condensate to boiler feed water tank. This has stopped the usages steam, which was required for super heating the wash water (up to 115º C) during centrifugal operation. Advantages • It reduces the steam consumption in the boiling house by 2.0- 3.0% on Cane depending on the operating conditions of the Boiling House. • It improves the water management of the Plant. • Space requirement is less due to its compact size and alignment. • The sparge tube entry for condensate helps in proper diffusing of condensate and hence improves the efficiency for flashing. • Easy to maintain, trouble free, reliable and long life due to stainless steel construction. 13.5.7 Film Type Sulphur Burner Technology Description Sugar juice clarification (purification) process requires sulphur dioxide as a clarification and bleaching agent. It is produced from expensive (imported) sulphur in the conventional tray type batch burners, in Indian sugar factories, which are inefficient, resulting in high processing cost, poor clarification and poor sugar quality. The new "film type sulphur burner" which was tried at Upper Doab Sugar Mills, Shamli in collaboration with M/s. Digital Utilities (India) Pvt. Ltd., New Delhi, produces SO2 with consistent quality, high efficiency, low consumption and well regulated operation made possible by the new 'film burning' concept and requisite automation. The film type sulphur burner technology has been adopted in 400
more than 64 sugar factories all over India. The system consists of Sulphur Melter, Variable Flow Sulphur Pump, Sulphur Furnace with Checkered Refractory Bricks and refractory lining. SO2 cooler and instrumentation and control system for control of Sulphur feed, combustion air feed etc. The Molten Sulphur flows from top of the furnace downward forming a thin film on the refractory bricks. The film burns efficiently in contact with air to produce SO2. SO3 formation is negligible. Depending on the temperature of the furnace, 6-9% SO2 can be obtained in the exit gases. Operation of the burner is controlled in accordance with process demands i.e SO2 quantity and quality, sulphur feed rate etc. through use of instrumentation and control system etc . Advantages • • • • • •
Extremely steady burning, with capacity variation 70- 300 kg/hr, Zero sublimation and minimal SO3 generation, Optimum sulphur consumption, Burning rate variation without any change in concentration, Compatible to automation for juice sulphitation & pH control, Maintenance free, long life and zero pollution
13.5.8 Bagasse Drier Technology Description This is a novel concept of drying bagasse as well as controlling the air pollution. Bagasse Drier is a unique device wherein the hot flue gases are mixed with the wet bagasse from mills. This wet bagasse gets dried up and accumulates all the ash and unburnt carbon with it. This dried bagasse with all the unburnt and ash is fed into the boiler. Thus it acts in two ways. One it dries the wet bagasse there by increasing the system efficiency and saving bagasse. Second, it acts as pollution control device and reduces the SPM of the flue gas. DSCL sugar, Rupapur implemented this technology in the year 2005-2006. Advantages •
Improved efficiency with better pollution control.
13.5.9 Planetary Gearbox for crystalliser Technology Description The mill drive and transmission of its power to mills is an important area of the sugar factory in respect of investment and maintenance cost and energy saving. The conventional mill drive of the present day consists of either DC motor or steam turbines. These drives are operated at about 1000/5000 rpm whereas the power developed by the prime movers is required to be transmitted to the mills at less than 5 rpm. Therefore, a set of high speed and slow motor gear trains is used to achieve the eventual operating speed and the power requirement at the mill. These drives are not only cumbersome occupying huge space but also needs high maintenance and operating cost. The sugar industry has been in search of an efficient and compact alternative to the above inefficient system. Planetary gearbox is an energy efficient, cost effective compact alternative to the conventional drive comprising of gear trains and also hydraulic drive. EID Parry has successfully replaced the existing worm wheel reduction system with the planetary gearbox arrangement for all 401
crystallizers under its energy saving schemes for the year 2005-2006.
13.5.11 Wet Cell Gasification
Advantages
Technology Description
•
Bagasse has traditionally been burned in boilers to help fuel the operations for sugar mills. The problem with burn boilers, particularly older burn boilers is their outputs, not only of useful process heat, but pollution. The burn boilers also require dry feedstock, as very wet feedstock will choke the boiler. Slag and residue forming on boiler tubes and the system can also pose a challenge for consistent operations. The wet cell gasification technology is generally far cleaner than burning or burn boilers. The EWC (Ecology Wet Cell) gasification unit is a two-stage updraft gasifier. In the first stage, the biomass is gasified in a starved oxygen environment. In the second stage, the producer gas is consumed in a powerful double vortex combustor producing 100,000,000 (one hundred million) Btu per hour of heat at approximately 1010oC. The temperature has been successfully varied for particular applications to as high as consistent 1204oC. Where there is a large amount of waste or biomass by products and agricultural residue this robust gasification to heat system can provide a very useful solution. This gasification unit can also handle human and animal waste mixed in with biomass, a very fibrous materials that cause real problems with other feed systems.
Improved efficiency resulting in energy savings
13.5.10 Advanced bagasse based cogeneration Technology Description Cogeneration is broadly defined as the coincident generation of useful thermal energy and electrical power from the same input fuel. Any process plant requiring steam for process, the pressure of steam required for most of the process applications being low, holds very good potential for cogeneration of power. Sugar plants are particularly interesting applications for cogeneration, since bagasse, one of the by-product from the mill, is available almost at no cost as feed stock to fuel the steam generators of the cogeneration plant. The sugar manufacturing process requires a large quantum of thermal energy in the form of steam and also the bulk of the steam required for the processing is needed at low pressure i.e. in the range of 2.0 to 2.5 bar (atm). However, to date, sugar plants had limited power and heat generation to meet only their own in-house demands, which is called as an incidental cogeneration, and hence their existing energy potentials had not been fully exploited. The advanced cogeneration system, aims at significantly improving the overall energy efficiency of the sugar factory, enabling the plant to generate surplus power. The surplus power could be exported to the electricity grid, which can generate additional financial resources for the plant. Energy efficiency and the export of power to the grid is made feasible by the employment of high pressure and high temperature steam cycles and by the utilization of the surplus bagasse to produce more steam and hence more electricity. Thermodynamically, energy recovery from the Rankine cycle is more dependent on the steam inlet temperature than the pressure and the higher the inlet steam temperature; higher will be the cycle efficiency. However, the practically attainable limits of temperatures are influenced by the metallurgy of the boiler tubing, piping and the turbine components and the complexity of the creep fatigue interaction for the materials at higher temperatures. Temperatures up to 400oC require use of ordinary carbon steel and beyond 400oC, low-grade alloy steels are employed. Above 500oC, the requirements with regard to the material selection are stringent and expensive. Above 550oC, the requirements are very stringent and prohibitively expensive. It is extremely important that the selection of temperature is done keeping in mind the nature of industry, and the experience gained in that industry. The sugar factories employ cogeneration system of 480oC and 65 bar (atm). With the technological advancement, some sugar plants in India implemented the advanced cogeneration system of 515oC and 105 bar (atm) pressure for increasing energy efficiency and the financial profitability.
Thermal separation processes such, as evaporation and distillation are energy intensive. The need for reducing energy costs has led to multi-effect plants, then to thermal vapour compression and finally to the use of mechanical vapour compression systems. In mechanical vapour compression, positive displacement compressions or multi-stage centrifugal compressors are generally used to raise the pressure and temperature of the generated vapours. Since mechanical compressors do not require any motive steam, all vapours can be compressed to elevated pressure and temperature, eliminating the need for a subsequent recovery system. The energy supplied to the compressor constitutes the additional energy input to vapours. After the compression of the vapour and its subsequent condensation through transfer of heat to process fluid, the hot condensate leaves the system, which can be used as feed water/liquid for boilers. The technology was developed in the year 2005.
Advantages
Advantages
• • • •
High efficiency of the plant as well as reduced cost of energy (heat and electricity) Increased power reliability and quality Increased financial profitability of the plant Reduced emissions.
Advantages • •
Produces large volume of heat effectively and reliably for various applications Running on a combination of biomass sources.
13.5.12 Mechanical Vapour Compression (MVR) technology to recover lowpressure waste steam Technology Description
• • • • •
Low specific energy consumption. High performance co-efficient. Gentle evaporation of the product due to low temperature differences. Reduced load on cooling towers. Simple process for operation and maintenance.
Taking the ratio of cost of steam-generation of the equivalent cost of electrical 402
403
energy as 1:3, the MVR gives economic effect of 17/3 =5.66. The capital cost, installation and operation costs are much lower. 13.5.13 Mill Drives (AC/DC) Technology Description DC mill drives are used in most sugar plants in India to drive the milling tandem with four to five 500-1000 HP drives. This is in vogue in most of the plants now with conversion of turbo-steam drive to electrical drive with cogeneration of power for export being the order of the day. However, the new development of using AC drive instead of DC drive has the following advantages. Advantages • • • •
Efficiency of AC motor is higher than DC motor Low maintenance cost than DC motor Less harmonics than DC motor Overall power saving of 3-5% is possible with AC drive for milling tandem in place of DC drives.
13.5.14 Adoption of Falling Film Evaporator Technology Description The steam consumption of sugar factory, mainly depends upon the system available for the concentration of juice. Adoption of falling film evaporator at the evaporator station, offers better steam economy. Falling film evaporator is usually a conventional 1-1 exchanger designed to operate vertically. The liquid solution enters from the top at such a rate that the tubes do not flow full of liquid, but instead, liquid descends downwards along the inner walls of the tubes as a thin film. Vapour evolved from the liquid is carried downwards with the liquid, and leaves from the bottom of the unit. Since a large number of mills are planning to increase their installed capacities, one of the cost effective ways to achieve the dual objective of better steam economy and increase of throughput in the evaporator section would probably be to add a first evaporator as a falling film evaporator. The concentrated juice from this evaporator body, which can be falling film evaporator, can thus be fed to the existing evaporator setups to continue further evaporation. Advantages • • • •
Reduced steam consumption High heat transfer rates. Increased throughput of the evaporator Minimal internal pressure drop.
other stations and imbalances steam balance of the plant. The use of fully autocontrolled continuous pan has many advantages over the conventional batch pans. It helps in maintaining a steady consumption of vapours thus eliminating the problems associated with fluctuating vapour flows. Accordingly, there will not be any variations in the syrup brix. This ensures the uniform functioning of the evaporator station, and also boiler steam generation. This system automatically manages the steady conditions for development and uniform growth of crystals eliminating the uncertainties of human operational errors. Advantages • Reduction in steam consumption eliminates the fluctuations in the vapour demand thus steadiness of operation is achieved. • Reduction in boiling point elevation avoids heat injury and colour formation. • Maximum exhaustion of mother liquor. • No fines and conglomerates. 13.5.16 Low Pressure Extraction (LPE) System Technology Description The conventional methods of juice extraction suffer from drawbacks of high power consumption, high maintenance costs and require skilled operators. The new LPE system is an efficient alternative, which utilizes combination of solid-liquid extraction and conventional milling technology at low hydraulic pressures. Further, it is not dependent on operator's skill. The system uses perforated rollers in modules of 2. A total of 8 modules (16 rollers) were used during the trial runs. Hydraulic pressure of 110 bar is used. Due to perforations in the rollers extracted juice is quickly drained out. Re-absorption of juice is negligible. The system is driven by electric motors and operation is automatically controlled. The system was successfully commissioned in 1999 for commercial use. Commercial plant at a capacity of 5000 TCD commissioned at Shree Renuka Sugars in 2006. Advantages • • • • • • •
Low capital cost (about 60%) Low power consumption to the extent of 35% Extraction comparable to 4-mill system (about 95%) Low maintenance cost No special skills required Very low retention time No chemical control.
13.5.17 Membrane filtration for Sugar Manufacturing
13.5.15 Vertical Continuous Vacuum Pan for Massecuite Boiling Technology Description After concentration of juice in multiple effect evaporators, the subsequent process to turn the thick juice into crystal form is accomplished in the vacuum pans. The use of batch type vacuum pans in most of the mills results in considerable fluctuations of steam consumption and irregular sugar quality. It results in variation in syrup brix of about 4-4.5 Bx. The batch pan boiling destabilises the continuous process in 404
Technology Description The conventional method of manufacturing produces sugar with high sulphur content. That is also brown in colour due to which it does not attract many takers in the export market. Membrane filtration is the process for production of sulphur free, refined quality sugar without going through conventional refining. In this process, high temperature tolerant polymeric membrane modules are employed for sugarcane juice clarification for production of high quality sugar. These membrane modules are capable of withstanding continuous exposure to hot juice without any 405
visible signs of deterioration. The pilot plant was successfully commissioned and operated at Simbholi Sugar mills in 2000-2001. Advantages Greater Sugar recovery since less sugar loss in molasses Sparkling clear sugar cane juice with purity higher (by 0.9 units), reduced juice colour (by about 50%) Shorter juice boiling times and faster crystal growth rates increase productivity Easy to integrate, install and scale up with limited space requirement Easy to operate with minimum maintenance requirement. 13.6
Case Study 2: Energy conservation projects at a major unit at Villupuram 1. Replacement of Low-pressure cogeneration system with High-pressure cogeneration system: Brief The cogeneration set up had three low-pressure boilers providing steam to the process and turbine generators. Historically the factory has not exported any power to the grid. It was decided to install high-pressure cogeneration system. The configuration of the system is as follows
Case Studies
Boilers 1 x 120 TPH, 87 kg/cm2
Case Study 1: Energy Conservation Achievements at a Major Sugar Industry
Turbines 1 x 22 MW
The plant was commissioned during June 2005. After captive consumption the surplus power has been fed to the State grid.
Brief During the period 2006-2007, the unit implemented 15 energy conservation projects with an investment of Rs.17.2 Million achieving a saving of Rs. 7.742 Million.
Energy Savings
Energy Savings Surplus power exported to grid
The major energy conservation projects are presented below: Project Quintuple 3rd effect vapour for sugar melting Plate heat exchanger for turbine condensate heating Avoiding FFE transfer pump
Quintuple 1st effect vapour for FBD sugar dryer air heating Quintuple 1st effect vapour condensate as superheated wash water Clear juice in place of hot condensate
Description
A new sugar melter for B & C sugar was designed in -house to utilize quintuple 3 rd effect vapour instead of exhaust steam Installing the plate heat exchanger enabled heating turbine condensate along with DM water make -up from 40 0C to 980C with qui ntuple 3 rd effect vapour avoiding use of LP steam Juice transfer scheme was modified and resulting head difference was utilized to completely avoid 15 kW juice transfer pump at falling film evaporator It is general practice to use MP steam for heating air in fluidized bed sugar dryer. The project utilized the same heat exchanger with quintuple 1st vapour as heating medium to heat FD air Replaced usage of MP steam heated condensate with Quintuple 1st effect vapour condensate for washing sugar crystals in batch centrifugals
Clear juice is utilized to the possible extent at pans, continuous centrifugals and melter replacing the use of hot process condensate. Thus reduced evaporation load Pipe line to The vapour from soda boiling are being utilize sodaeffectively utilized for process heating by boiling vapour mixing them with the vapour of the main stream, instead of venting to atmosphere as a normal practice
Annual Investment Savings (Rs. (Rs. Million) Million) 1.171 1.082
Payback Period (months) 11
15 MWh
Power exported to State grid for the year 2005-06
40.1 Million kWh
Revenue from power export /for the year 2005-06 in Million Rs
125.3
Actual investment in Million Rs
80
Payback Period
8 months
2. Replacement of Eddy current drive with Variable frequency drive for Cane carrier & Rake carrier: 0.643
0.270
5
Brief
0.1113
Nil
Immediate
0.1098
Nil
Immediate
The speed control of the cane carrier and the rake carrier were accomplished by eddy current drives. The eddy current drives were replaced with energy efficient variable frequency drives. Energy Savings Energy consumption /day with Eddy current drive
0.072
0.084
0.042
0.065
7
9
3.
2160 kWh
Energy consumption/day with VFD's
1680 kWh
Energy savings/day
480 kWh
Annual Energy savings
86400 kWh
Excess revenue generated Rs in Million
0.26
Replacement of slat type bagasse conveyor with belt conveyor:
Brief 0.263
Nil
406
Immediate
A 45 kW slat conveyor was being used to convey bagasse from the mills to the cogeneration power plant material handling system. A 15 kW belt conveyor replaced this slot type conveyor
407
Energy Savings Slat conveyor Energy consumption /day
756 kWh
Belt conveyor Energy consumption/day
360 kWh
Energy savings/day
396 kWh
Annual Energy savings
71280 kWh
Excess revenue generated Rs in Million
0.214 kWh
available for different spraying applications. Most of them aim to give a water spray the form of a hollow cone. A good spray nozzle should be of simple design, high capacity and high efficiency. Of the various types of spray nozzles, the conical jet nozzles have been found far superior on all the above parameters. Hence, the recent trend among the new sugar mills is to install the conical jet nozzles, to achieve maximum dispersion of water particles and cooling.
Before Improvement
Case Study 3: Install diffusers in lieu of milling tandem Brief Installation of milling tandem is practiced conventionally in sugar plants in India. Milling is highly power and labour oriented equipment. The present trend is to adopt diffusion as an alternative to Milling, considering several advantages diffusion offers over milling. Before Improvement
After Improvement
A new sugar mill initially decided to
The mill was later on opted for the
adopt milling in tandem
diffuser and it was installed by design
In a 4000 TCD sugar mill, the cooling system consisted of a spray pond. There were 5 pumps of 75 HP rating operating continuously, to achieve the desired cooling parameters. The materials of construction of the spray nozzles were Cast Iron (C.I). The maximum cooling that could be achieved with the spray pond was about 34 - 35 °C.
Energy savings Reduction in power consumption (Considering an average crushing of 500 TCD for an operating season of 180 days) Energy cost saving (Considering power export cost of Rs. 2.75 / kWh)
: 2.88 Million units
: Rs. 8.0 Million / season
Case Study 4: Utilisation of Exhaust Steam for Sugar Drier and Sugar Melter Brief Before Improvement
After Improvement
In this 2500 TCD sugar mill, medium pressure steam at 7.0 kg/cm2, generated by passing live steam at 42 kg/cm2, through a pressure reducing valve (PRV), was being used for sugar drying and melting
Exhaust steam generated by passing live steam through the turbine was available at around 1.2 kg/cm2. The exhaust steam was utilised in place of live steam for sugar melting (blow-up) and sugar drying. Replacement of live steam with exhaust steam in these two users increased the cogeneration by about 35 units, which could be sold to the grid.
Energy savings Annual savings Investment required Payback Period
: Rs. 0.2 Million : Rs. 0.02 Million : 2 months
Case Study 5: Installation of Conical Jet Nozzles for Mist Cooling System Brief The spray pond is one of the most common types of cooling system in a sugar mill. In a spray pond, warm water is broken into a spray by means of nozzles. The evaporation and the contact of the ambient air with the fine drops of water produce the required degree of cooling. There are many types of nozzle configurations 408
After Improvement The spray pond system was modified and conical jet nozzles were installed to achieve mist cooling. The material of construction of the conical jet nozzles is PVC, which enables better nozzle configuration achievement. The cooling achieved with the mist cooling system was about 31 - 32 °C (i.e., a sub-cooling of 2 - 4 °C was achieved). This resulted in avoiding the operation of one 75 HP pump completely. The better cooling water temperatures, maintained steady vacuum conditions in the condensers thus minimising the frequent vacuum breaks, which occurred in the condensers.
Energy savings Annual savings Investment required Payback period
: Rs. 0.32 Million : Rs. 0.50 Million : 19 months
Case Study 6: Installation of Regenerative Type Continuous Flat Bottom High Speed Centrifugal for A - Massecuite Curing Brief
Before Improvement One of the 4000 TCD sugar mills, had DC drives for their flat bottom high speed centrifugal of 1200 kg/h capacity used for A - massecuite separation. These centrifugal had the conventional type of braking system, with no provisions for recovery of energy expended during changeover to low speed or discharging speed
409
After Improvement The regenerative type of braking system was installed for the entire flat bottom high speed centrifugal used for A - massecuite curing. One of the most important characteristics of a regenerative braking system in an electric centrifugal is that, it permits the partial recovery of the energy expended, during the discharge cycle.
Energy savings
Case Study 8: Installation of 30 MW Commercial Co-generation Plant
The regenerative braking system recovers about 1.34 kW/100 kg of sugar produced, during the discharge cycle and feeds it back into the system. Hence, the net power consumption of the centrifugal with the regenerative braking system is only 0.66 kW/100 kg of sugar produced.
Brief
Case Study 7: Installation of Jet Condenser with External Extraction of Air Brief The evaporators and pans are maintained at low pressures, through injection water pumps. These are one of the highest electrical energy consumers in a sugar mill. The multi-jet condenser, which are presently used in the sugar plants, do both the jobs of providing the barometric leg, as well as removing the non-condensables. Before Improvement One of the sugar mills with an installed capacity of 2500 TCD had the multi-jet condensers for the creation of vacuum and condensation of vapours, from the vacuum pans and evaporator. There were 11 injection water pumps of 100 HP rating, catering to the cooling water requirements of these condensers. These pumps were designed to handle an average maximum crushing capacity of 3200 TCD.
After Improvement The jet condensers with external extraction of air system were installed. There was a significant drop in water consumption in these condensers, in spite of an increase in crushing capacity (average maximum crushing of 4800 TCD). This resulted in reduction in the number of injection water pumps in operation. The new injection water pumping system includes - 5 nos. of 100 HP pump and 1 no. of 250 HP pump. Thus, there is a net reduction in the installed injection water pumping capacity of about 350 HP (30% reduction). The actual average power consumption also has registered a significant drop of nearly 180 kW, which amounts to an annual energy saving of 5,18,400 units (for 120 days of sugar season).
Before Improvement A 5000 TCD sugar mill in Tamilnadu operating for about 200 days in a year had the following equipment: Boilers 2 numbers of 18 TPH, 12 ATA 2 numbers of 29 TPH, 15 ATA 1 number of 50 TPH, 15 ATA Turbines 1 number 2.5 MW 1 number 2.0 MW 1 number 1.5 MW Mill drives 6 numbers 750 BHP steam turbines 1 number 900 BHP shredder turbine
After Improvement The old boilers and turbine were replaced with high- pressure boilers and a single high capacity turbine. The new turbine installed was an extraction-cumcondensing turbine. A provision was also made, for exporting (transmitting) the excess power generated, to the state grid. The mill steam turbines, were replaced with DC drives. The details of the new boilers, turbines and the steam distribution are as indicated below: Boilers 2 numbers of 70 TPH, 67 ATA Multi-fuel fired boilers
Turbines 1 number of 30 MW turbo-alternator set The plant had an average steam (Extraction-cum-condensing type) consumption of 52%. The power requirement of the plant during the Mill drives sugar-season was met by the internal 4 numbers of 900 HP DC motors for mills generation and during the non- season 2 numbers of 750 HP DC motors for mills from the grid. The plant went in for a 2 numbers of 1100 kW AC motors for commercial co-generation plant. fibrizer.
Energy savings Enhancement in power generation Surplus power generation for exporting to the grid
: 9 MW to 23 MW. : 14 MW
Annual savings Investment required Payback period
: Rs. 204.13 Million : Rs. 820.6 Million : 48 months
Case Study 9: Replacement of Steam Driven Mill Drives with Electric DC Motor Brief
Energy savings Annual savings Investment required Payback period
: Rs. 1.30 Million : Rs. 2.53 Million : 24 months
410
Before Improvement A 5000 TCD sugar mill had six numbers of 750 HP mill turbines and one number of 900 HP shredder turbine. The average steam consumption per mill (average load of 300 kW) was about 7.5 TPH steam @ 15 Ata. The steam driven mill drives had an efficiency of about 35%, in the case of single stage turbine and about 50%, in the case of two-stage turbines.
411
After Improvement The plant team decided to replace the steam driven mills with electric DC motors, along with the commissioning of the cogeneration plant. These drives have very high efficiencies of 90%. Benefits of electric DC drives for mill prime movers • Increased drive efficiency • Additional power export to grid The power saved (850 kW/mill) by the implementation of this project, could be exported to the grid
Energy savings Annual savings Investment required Payback period
: Rs. 62.37 Million : Rs. 42.00 Million : 9 months
Case Study 10: Installation of an Extensive Vapour Bleeding System at the Evaporators Brief Before Improvement
After Improvement
In a typical 2500 TCD sugar mill, the quintuple effect evaporators were in operation. The specific steam consumption with such a system for a 2500 TCD sugar mill is about 45 to 53 % on cane, depending on the crushing rate. The typical vapour utilisation system in the evaporators comprises of: • Vapour bleeding from II- or III- effect for heating (from 35 °C to 70 °C) in the raw (or dynamic) juice heaters • Vapour bleeding from I- effect for heating (from 65 °C to 90 °C) in the first stage of the sulphited juice heater • Exhaust steam for heating (from 90 °C to 105 °C) in the second stage of the sulphited juice heater • Exhaust steam for heating (from 94 °C to 105 °C) in the clear juice heaters • Exhaust steam for heating in the vacuum pans (C pans) However, maximum steam economy is achieved, if the vapour from the last two effects can be effectively utilised in the process, as the vapour would be otherwise lost. Also, the load on the evaporator condenser will reduce drastically.
The plant upgraded by installation of the extensive vapour utilisation system at the evaporators. The extensive use of vapour bleeding at evaporators was adopted at the design stage itself in this case. This has resulted in improved steam economy. However, to ensure the efficient and stable operation of such a system, the exhaust steam pressure has to be maintained uniformly at an average of 1.2 - 1.4 kg/cm2. In this particular plant, this was being achieved, through an electronic governor control system for the turbo-alternator sets, in closed loop with the exhaust steam pressure. Whenever, the exhaust steam pressure decreases, the control system will send a signal to the alternator, to reduce the speed. This will reduce the power export to the grid and help achieve steady exhaust pressure and vice-versa.
Brief Before Improvement
After Improvement
In a 2600 TCD sugar mill, there was a weighed juice pump operating continuously to meet the process requirements. The pump had the following specifications: • Capacity: 27.77 lps • Head: 45 m • Power consumed: 23 kW
Variable Frequency Drive was installed for the weighed juice pump and resulted in the following benefits: • Consistent and steady flow to the juice heaters • Improved quality of sulphitation, as the juice flow was steady • Reduced power consumption by an average of 11 kW (a reduction of about 30 - 40%).
The flow from the weighed juice tank was not uniform. Moreover, the pump was designed for handling the maximum cane-crushing rate.
Energy savings Annual savings Investment required Payback period
: Rs. 0.24 Million : Rs. 0.25 Million : 12 months
Case Study 12: Installation of Thermo-compressor for use of Low Pressure Steam Brief
The specific steam consumption achieved (as % cane crushed) is: 41% on cane
Before Improvement
After Improvement
Thus, the specific steam consumption (% on cane) is lower by atleast 7%. This means a saving of 3.5% of bagasse percent cane (or 35 kg of bagasse per ton of cane crushed).
In a typical 4000 TCD sugar mill in Maharashtra, the turbine exhaust steam at 0.40 kg/cm2 was continuously vented out. The quantity of the steam vented, amounted to about 6300 kg/h. There were no process users in the sugar mill or the distillery, which could utilise this exhaust steam of 0.40 kg/cm2. The distillery required 10 TPH of steam at 1.5 kg/cm2. A separate boiler was meeting the steam requirements of the distillery. The sugar mill boiler met any additional requirement of steam. In both the cases, steam was generated at 8 kg/cm2 and reduced to 1.5 kg/cm2 through a pressure-reducing valve.
A thermo-compressor system was installed, for reusing the turbine exhaust steam, in the distillery. The resultant MP steam saved in the distillery, was passed through the power generating turbines, for generation of additional power. The resultant 1.5 kg/cm2 steam obtained by thermocompression of exhaust steam, was directly used in the distillery. This reduced the passing of high/ medium-pressure steam through the pressurereducing valve.
Energy savings Annual savings Investment required Payback period
Case Study 11: Installation of Variable Speed Drive (VSD) for the Weighed Juice Pump
: Rs. 11.00 Million : Rs. 6.50 Million : 8 months
Energy savings Annual savings Investment required Payback period
412
413
: Rs. 6.0 Million : Rs. 2.0 Million : 4 months
Case Study 13: Installation of Hydraulic Drives for Mill Prime Movers
Energy Savings •
Brief Before Improvement One of the sugar mills had the following mill drive configuration: For 6 mill system- 600 BHP rating steam turbine x 3 nos. (2 mills driven by a single steam turbine) For 4 mill system - 600 BHP rating steam turbine x 2 Nos. (2 mills driven by a single steam turbine) This configuration was designed to cater to the initial installed capacity of 2500 TCD.
After Improvement The plant teams had plans to increase the cane crushing capacity to 4000 TCD. The inherent disadvantages of the steam turbines can be overcome, especially after the proposed increase in cane crushing rate, by the installation of hydraulic drives. The modified 4-mill system was provided with a hydraulic drive of 600 kW rating.
Reduction (10 - 20%) in steam consumption as mentioned below: Steam consumption (kg/ ton of massecuite) Identity
With batch Vacuum pan
A - massecuite
Not available
With continuous Vacuum pan Not available
B - massecuite
242
229
C - massecuite
354
313
Annual savings Investment required Payback period
: Rs. 19.26 Million : Rs. 100 Million : 63 months
Energy savings The net installed power consumption reduced from 0.895 kW/TCD (for average crushing of 2500 TCD) to 0.509 kW/TCD (for average crushing of 4800 TCD). In addition, very stable operating conditions (constant crushing) are being achieved, at almost negligible maintenance costs. Case Study 14: Install nozzle governing system for multi jet condensers Brief Before Improvement
After Improvement
A 6750 TCD Plant was consuming 1150 A nozzle governing system was introduced for kWh of Power at Cooling & Condensing controlling the water flow to the condenser. There System was a substantial reduction in power consumption of the injection water pumps. The power consumption of injection with pumps reduced from 1150 units/ton to 450 units/ton.
Energy savings Annual savings Investment required Payback period
: Rs. 19 Million per year : Rs. 5 Million : 3 months
Case Study 15: Installation of Fully Automated Continuous Vacuum Pans for Curing Brief
References 1. Annual Report 2007-08 Ministry of Consumer Affairs, Food & Public Distribution, GoI. 2. The Indian Sugar Industry Sector Road map 2017; KPMG in India 3. CII - IREDA Publication: "Investors Manual on Energy Efficiency". 4. Stasticial Abstract 2007- CSO 5. LBNL - 62806; World Best Practice Energy Intensity Value for Selected Industrial Sectors, February 2008. 6. TERI Energy Directory and Yearbook 2007 7. LBNL - 57293; Assessment of Energy use and energy savings potential in selected industrial sector in India, August 2005. 8. Japan Energy Conservation Directory 9. LBNL - 54828: Emerging Energy Efficient Technologies in Industry case studies of selected technologies - May 2004 10. National Energy Map of India: Technology Vision 2030 11. Report of the working group on Power for 11th Plan (2007-12) 12. Report of the working group on R&D for the Energy Sector for the formulation of the 11th Five Year Plan (2007-12) 13. Report of the working group on new and renewable energy for 10th Five Year Plan (2007-12) 14. BP Statistical Review, June 2008 15. www.indiansugar.com 16. www.eeii.org.in 17. www.energymanagertraining.com 18. www.avantgarde-india.org
Energy savings Before Improvement In a 6000 TCD plant,batch vacuum pans were installed for Amassecuite and B- massecuite and continuous vacuum pans for Cmassecuite curing.
After Improvement Consequent to the capacity upgradation to 8000 TCD, continuous vacuum pans were installed for Amassecuite, B- massecuite and Cmassecuite curing. 414
415
Notes
Chapter 14 Aluminium Industry 14.1 Introduction India has the fifth largest reserves of Bauxite in the world, the main raw material for making Aluminium. The per capita Aluminium consumption in India is only 1.6 kg as against 8 kgs in China and 30 kgs in developed countries. The World's average per capita consumption of Aluminium is about 10 times of that of India. The demand of Aluminium is expected to grow by about 9 percent per annum from the present consumption levels. India is a net exporter of Alumina and Aluminium metal. Four Aluminium plants in the country i.e., NALCO (National Aluminium Company Ltd.), HINDALCO (Hindustan Aluminium Company Ltd.), MALCO (Madras Aluminium Company Ltd. & BALCO (Bharat Aluminium Company Ltd.) account for the entire production of Aluminium in the country. 14.2
Present Capacity & Growth Potential
The total installed capacity of Aluminium is about 3% of the global capacity. The installed capacity in 2006-07 of Alumina & primary Aluminium was about 3.02 MT & 1.18 MT (Million tonnes) respectively. The production of Aluminium from 200405 to 2006-07 is shown in figure 14.1 below :
Fig - 14.1 : Production of Aluminium (Source : The Energy Data Directory & Yearbook, Teddy, 2007 & individual company websites)
14.3 Aluminium manufacturing process Primary Aluminium process consists of four stages : I. Mining of Bauxite II. Refining of Bauxite ore to produce Alumina (Bayer's process) III. Smelting of Alumina to produce Aluminium (Electrolysis process) 417
• • IV.
Soderberg system Pre-baked system
Bauxite 49 % Al203 2247 kg
Casting & Rolling CaO 39 kg Na2Co3 74 kg Water 921 litre
14.3.1 Alumina Refining (Bayer's Process) Alumina is the basic raw material for production of Aluminium and is obtained from Bauxite, a mineral containing upto 60% in the form of mono/trihydratec. The Bayer process is the most economical route for production of Alumina, used throughout the world. The production of Alumina from Bauxite is carried out through the Bayer route, an extractive hydro- metallurgical process which belongs to the alkaline group of processes. Alumina production process consists of crushing and grinding of Bauxite with caustic liquor in ball/rod mills. The slurry after desilication is pumped into large tanks/autoclaves/tubes for digestion at 110°C to 300°C depending upon the mineralogy of Bauxite. The digested slurry is diluted and classified in thickeners. The overflow (Aluminate liquor) is pumped for controlled filtration and underflow containing red mud is washed / filtered and disposed to red mud pond. The filtered Aluminate liquor is cooled to 50-85°C in plate heat exchanger/flash tanks and pumped to precipitation tanks with addition of seed hydrate and retained for 30-75 hours with finishing temperature of 40-55°C depending on the type of Alumina to be produced. The precipitated hydrate slurry is classified and the coarser part (under flow) is filtered and washed to obtain the product hydrate and the fine part is recycled as seed hydrate. The hydrate containing 10-20% moisture, is calcined in rotary kilns/stationary calciners at 1000°C -1200°C to obtain calcined Alumina. Generally two tonnes of Bauxite is required to produce one tonne of Alumina. Figure 14.2 shows the flow diagram of the Bayer Process & Figure 14.3 shows the material balance for the production of one tonne of Alumina.
ALUMINA REFININGS 90.9 % EFFICIENT RED MUD 1963 kg Alumina 1000 kg
Fig 14.3 : Material balance for production of one tonne of Alumina (Source : Investors Manual for Energy Efficiency; EMC; CII & IREDA)
14.3.2
Smelting of Alumina to Aluminium (Electrolysis process)
Alumina is the main input for the production of Aluminium through electrolysis process. The Aluminium metal is produced through electrolytic reduction of calcined Alumina, based on the process invented by C.M. Hall of USA and P.L.T. Heroult of France. However, there are two technologies used in smelting process i.e., Pre-baked system & Soderberg system. The Pre-baked technology uses multiple anodes in each cell, which are pre-baked in a separate facility and attached to rods to suspend the anodes in the cell. New anodes are exchanged for spent anodes, i.e. anodes butts, recycled into new anodes. This technology is more prevalent in industries. The Soderberg technology uses a continuous anode which is delivered to the cell (pot) in the form of paste, which bakes in the cell itself. In the Electrolysis process, Alumina is dissolved in fused electrolyte bath of cryolite at operating temperature ranging from 920oC to 970oC. Under the influence of high intensity direct current, Alumina gets dissociated to Aluminium and Oxygen ions in the electrolytic cells. Gases evolved are cleaned to recover the valuable fluorides and reduce the concentration of noxious contaminants before discharge to the atmosphere. Molten Aluminium is tapped from the bottom of electrolytic cells and cast into ingots, billets, etc. for conversion to semis. On an average, it takes 15.7 kWh of electricity to produce one kg of Aluminium from Alumina.
Fig 14.2 : Bayer's Process for production of Alumina
418
Thereafter, Aluminium semis covering flat and non-flat products are produced utilizing the processes of DC casting, continuous casting, extrusion, hot and cold rolling. Generally about two tonnes of Alumina is required to produce one tonne of Aluminium. Material balance for producing one tonne of Aluminium from Alumina is shown in Figure 14.4 :
419
Both Make-up 43 kg
99 % Alumina Carbon Anode
Electrohytic Reduction
Molten Aluminium
Gas 1340 kg
The technologies adopted both in India & abroad are same but they differ in energy efficiencies as some of the units in India are still using self-baking anodes, (Soderberg technology) instead of multiple pre-baked anodes. 40% of the installed capacity in India is based on Soderberg technology, whereas 60% of it has switched over to the new more efficient pre-baked technology. The Aluminium plants have set a target of 1-2% reduction in SEC in the next 5 yrs. High electrical energy saving potential exists in the smelter section for the production of Aluminium. The major energy consumption in the Aluminium refining process (Bayers's process) are the digestion and calcination stages. About 30% of the total energy consumption is utilized in digestion process, whereas calcination consumes about 32% of the total energy. Typical energy consumption in different stages is given in the Table 14.1 : Table 14.1: Typical Energy Consumption in Bayer's Process
Blending Slag (Al=Al203)
Process
Flux C 12 etc
Energy (GJ/t)
Preparation Digestion Settling / Washing Precipitation Evaporation Calcination
Al INGOTS 1000 kg
0.37 4.79 0.65 1.06 4.3 5.07
% of total Energy Consumption 2.3 29.5 4.0 6.5 26.5 31.2
(Source : Energy Requirements for Aluminium Production )
Fig 14.4 : Material balance for production of one tonne of Aluminium
14.5
Energy Efficiency measures undertaken in Aluminium Plants in India
(Source: Investors Manual for Energy Efficiency, EMC, CII & IREDA)
14.4
Energy Consumption in Aluminium Plants
14.4.1
Energy Intensity
Most of the plants have implemented a number of energy conservation measures in the past and have specific plans to implement a few in the near future. Major energy conservation measures implemented during the last three years in this sector are given below:
Coal, furnace oil and electricity are primary energy inputs for Aluminium production. Coal is primarily used to generate steam, which is used in the process while fuel oil is mainly used in calcination of Alumina and various furnaces in fabrication plants. Electricity is the major energy input in Aluminium production and is considered to be a prime factor in determining economics of Aluminium production. Energy accounts for nearly 40% of Aluminium production costs for metal. Hence, all primary metal producers have installed their own captive power plants to have uninterrupted power supply for their use. Aluminium has a long working life and can be easily recycled. Recycling would require less energy i.e., about 5% of the total energy required to manufacture primary Aluminium from Bauxite. As compared to the production of other metals, Aluminium industry is most energy intensive consuming energy to the tune of 80 GJ/tonne (including smelting) of metal, whereas Copper and Zinc production consumes 20 GJ/tonne and 15 GJ/tonne of energy respectively. 14.4.2
Specific Energy Consumption
The specific energy consumption in Indian Aluminium plants is quite high. It ranges between 75.6 GJ/t - 83.2 GJ/t (including smelting) for primary Aluminium. The specific energy consumption in smelting of Aluminium is 15000 - 16500 kWh per tonne. The operating efficiency in terms of energy consumption is only 40%, which theoretically should be about 5990 kWh per tonne of Aluminium metal. 420
14.5.1 Aluminium Refining Medium term projects • Installation of Programmable Logic Controller (PLC) controlled burners in furnaces. • Installation of Variable Frequency Drives (VFD) for spent liquor pump feeding to evaporator • Installation of VFD for red mud pond feed pump • Installation of VFD for filtered aluminate liquor pump • Installation of seal pots for condensate recovery in digesters, evaporators, HP and LP heaters • Installation of VFD for spent liquor pump feeding to Plate Heat Exchanger (PHE) • Optimizing the operation of filter feed pumping system • Optimizing the operation of the slurry pumps in precipitation area • Optimizing excess O2 % in kiln by continuous monitoring • Avoiding air infiltration in kiln by continuous monitoring • Avoiding air infiltration in kiln flue gas exhaust line
421
Replacing red mud filter vacuum pumps with new high efficiency vacuum pumps • Utilizing the standby body in evaporator and increasing the steam economy
•
Long-term projects • Installation of de-super heaters for better heat transfer and steam saving in Aluminium refining. • Installation of energy efficient screw compressors. • Installation of liquid vapour hydro cyclone in evaporation feed flash tank to avoid caustic entrainment to the hotwell water and facilities. • Installation of thermo-compressor to recover flash steam from pure condensate tank in evaporator section. • Segregation of pick-up and drying zone vacuum in red mud filters • Sweetening the digestion process by adding Gibbsitic Bauxite having higher solubility in downstream of higher temperature digestion circuit. • Installation of technology upgraded recuperator in place of shell type in melting furnace. 14.5.2 Aluminium Smelter Medium term projects: • • • • • • • •
Installation of data acquisition system Installation of thyristor control in coke conveying vibrators in carbon plant Installation of correct size cooling water supply pump for rectifier cooling Installation of screw conveyor and avoiding the operation of a centrifugal fan in Carbon plant. Installation of variable frequency drive for fire hydrant pump Installation of variable fluid coupling for scrubber fans Reducing external bus-bar voltage drop across bypass joints and across rod to stud joints Improvement of insulation of sidewalls of the pots to minimize the heat loss due to convection and radiation
Long term projects • Conversion of the Soderberg technology to the Pre Baked Cathode Technology in the pots • Installation of point feeding in the Aluminium pots • Coating of cathode surface of electrolytic cells with Titanium Boride (TINOR) • Replacement of hot tamping mix with cold tamping mix • Installation of variable fluid coupling for scrubber ID fans and avoiding damper control 14.6 Case Studies of Energy Conversation in Indian Aluminium Plants Case Study 1 : Energy Conservation in Mining area
diesel operated only. NALCO has introduced Trench concept of mining with staggered movement of faces following the mineralized thickness enabling economical extraction of ore. Selective extraction of contaminated ore at the bottom layer is another important feature of this method of mining. Each trench is mined in two distinct phases: Mass mining of bauxite up to a depth of 10 m by front end loader and dumper combination and selective mining of the remaining bauxite in contact with the wall in the 2nd phase by hydraulic back hoe shovel and dumper combination. HSD accounts for over 90% of the power cost of the mine and 7 % of the total mining cost, and the management had initiated lot of action in this area. PCRA had conducted the Energy Audit for the HEMMs deployed at this mine. Energy Savings: 1. Recycling of hydraulic and transmission oil, contribute an annual saving of Rs 4.2 Million. It was proposed to adopt 'Electrostatic Liquid Cleaner in series with Vaccum Dehydration Machine' with a meager investment of Rs 0.4 Million. Annual consumption at the present production level is 35 kL of Hydraulic Oil and 50 kL of Transmission Oil. 2. Recycling of engine oil : The total annual consumption level is to the tune of 3000 kL. By recycling, Rs 1.4 Million can be saved, in addition to improving upon the engine efficiency. 3. Use of Mineral Water in radiators: An amount of Rs 0.57 Million can be saved annually by replacing the present system of using industrial water in radiators alongwith high value coolants. 4. Installing Load Cell in each Dumper : By installing load cells the percentage productivity of the dumpers when loaded by loaders can be improved and quantified. It has been observed that there has been wide variation at times in the percentage loading into the dumpers. By installing load cells in 14 nos. of 50Tonne dumpers, a total saving of Rs 0.34 Million can be achieved. Investment in installing load cells will be about Rs 1.2 Million and payback period is 3 years. 5. Construction of RCC road in permanent haul roads : This can generate a saving of Rs 1.7 Million due to improvement in engine life, fuel saving, better tyre life etc. Investment is Rs 14 Million. 6. Additive dosing in HSD: A total saving of Rs 0.57 Million can be achieved through improvement in efficiency of diesel operated HEMMs like dumpers, dozers, drills, loaders. 7. Performance improvement in blasting : Less generation of oversize boulders result in better productivity of loading and dumping machineries. This also improves productivity of the crusher due to less jamming, uniform feeding, resulting in better electrical motor life. Some of the other Energy Conservation Initiatives undertaken by the mine are : • •
Brief Selection of mining equipment is the thrust area for energy conservation in a mine. The NALCO mine is a highly mechanized mine operated with different types of suitable equipment. All the major HEMM (Heavy Earth Moving Machinery) are 422
Variable Frequency Drive in Crusher and conveying system Semi-Mobile Crusher Conveyor system
As part of their 6.0 Million Tonnes expansion plan NALCO management had approved commissioning of 'Semi-Mobile Crusher Conveyor' system. M/s ThyssenKrupp of Pune will execute the work at a cost of over Rs 1 Billion. This 423
will further reduce HSD consumption of the mine and the total energy bill, since this system will reduce the hauling length of the Dumpers.
Thermo Compressor Motive Steam 14-15 kg/cm2
Case Study 2 : Improved Energy through slotted anode Brief
3 TPH
A mixture of computational and physical modelling techniques helps conserve energy by improving slotted anode designs, making aluminium reduction cells more efficient. The project was taken up by engineers in their plant. The reducing of 0.10 volt / pot has the potential of saving 325 kWh / t (at 94% current efficiency) & also enhance production of aluminium. In this system, the voltage saving was done by modifying the anode to 'slotted anode' to reduce bubble resistance. The slots were cut width-wise. Energy Savings 1. Saving of 0.105 volts / pot led to the energy saving of 341 kWh/t aluminium. 2. Total Power saving is 116.62 million kWh per year. 3. Increase in potline amperage led to increase in smelter production of 8155 MT/yr. 4. GHG reduction by 357 kg CO2 / MT or 122104 t CO2 /year @ smelter capacity of 342000 MT & emission factor as 1047 gm/kwh based on IAI guidelines. Annual Saving Investment Payback Period
: Rs. 434 Million (energy saving plus production increase) : In-house design & modification. : Immediate
Case Study 3 : Installing variable frequency drive for spent liquor pump feeding to evaporator
Flash Steam
PCT Steam Plant
Fig 14.5 : Installation of thermo-compressor for recovery of flash steam Energy Savings Quantity of steam recovered Annual Savings Investment Payback period Case Study 5 :
: 3 TPH : Rs 5.48 Million : Rs 3 Million : 7 months
Installing seal pot system for condensate recovery
Brief The latest trend is to replace steam traps with seal pots wherever steam consumption is more than 1 tonne per hour. Seal pots were installed for condensate recovery in the following equipment: a) Digesters b) Evaporators c) HP heaters & LP heaters Energy Savings
Brief Variable frequency drive (VFD) with feed back control for the spent liquor feed pump to new evaporator was installed. Reduction in power consumption of about 400 units/day was achieved. Energy Savings Annual Savings Investment Payback period
Evaporator or LP header
Steam saved Annual Savings Investment Payback period
: 250 Kg/hr. : Rs 0.45 Million : Rs 0.75 Million : 20 months
Case Study 6 : Optimizing excess O2 in kiln by continuous monitoring : Rs 0.18 Million : Rs 0.45 Million : 30 months
Brief
Case Study 4: Installing thermo-compressor and recovering flash steam from pure condensate tank in evaporator section
Online oxygen analyser was installed and the % of oxygen level in the flue gas is continuously monitored. The combustion air supply to the kiln is controlled and percentage oxygen of 3% is maintained in the flue gas.
Brief
Energy Savings
Thermo compressor was installed to recover the flash steam from the pure condensate tank and the recovered steam is sent to low pressure steam header.
Increase in combustion efficiency (%) Annual Savings Investment Payback period
The motive steam used is about 18-20 TPH at a pressure of 12 kg/cm2. The schematic diagram of the modified system is shown in figure 14.5 below 424
425
:2 : Rs 2.95 Million : Rs 0.7 Million : 3 months
Case Study 7 : Replacing old Horizontal Stud Soderberg (HSS) cells with modern point feeder prebake cells
Table 14.2 : World Best Practice "Final Energy Intensity" Values for Aluminum Production (values are per metric tonnes aluminium).
Brief It was proposed to revamp the entire system by installing modern point feeder prebake (PFPB) cells. The proposed system require energy consumption of about 990 million kWh/year to produce 29500 tonnes/year of aluminium.
Alumina Production (Bayer) Anode Manufacture (Carbon)
The specific energy consumption for producing one tonnes of Aluminum during electrolysis would be 14 kWh/kg (Electrical Energy).
AluminumSmelting (Electrolysis)
Energy Savings
Ingot Casting
Increase in energy efficiency of retrofit prebake cells :10% GHG emission reduction : 50% Water consumption reduction : 30% Reduction in specific consumption of raw materials - Coal tar pitch, aluminium fluride and petroleum coke. Annual Savings : Rs 84 Million
Digesting (fuel) Calcining Kiln (fuel) Electricity Fuel Electricity Electricity Electricity
Total
Primary Aluminium kgce*/t GJ/t 414 12.1 223 6.5 48 1.4 35 1.0 7 0.21 1671 49.0 12
0.35
2411
70.6
Secondary Aluminium kgce/t GJ/t
85
2.5
* kgce= kilograms of coal equivalent (Source: World Best Practice Energy Intensity Values for selected Industrial Sectors; LBNL; by Worrel E., Price L., Neelis M., Galitsky C. & Nan Z.)
Table 14.3 : World Best Practice "Primary Energy Intensity" Values for Aluminum Production (values are per metric tonnes aluminium).
14.7 Energy Consumption (World's Best Practice) The specific energy consumption of Aluminium plants in key developed countries ranges between 70.5 GJ/t - 73 GJ/t for primary Aluminium. However, considering the best processes in one of the best plants in the World, the SEC is 70.6 GJ/t of primary Aluminium. The specific energy consumption in smelting of Aluminium is 14000 - 14500 kwh per tonne. This is because of the best energy efficiency measures adopted. The 'World's Best Practice Values' for Aluminum production are given in table 14. 2 & 14.3 below. These values consist of : (i) Final Energy Intensity Values, i.e. Energy used at the production facility. (ii) Primary Energy Intensity Values, i.e. sum of the energy used at the production facility plus energy used to produce electricity consumed at the facility. In this assessment, the energy used for Bauxite extraction is not included because it depends on the ore deposit characteristics. Also, the secondary Aluminium production is based on melting and reshaping scrap Aluminium. Table 14.2 provides best practice final energy intensity values for the process steps for primary Aluminium production along with the best practice energy intensity value for secondary Aluminium production. Table 14.3 provides primary energy values for these two Aluminium production processes.
Digesting (fuel) Calcining Kiln (fuel)
Primary Aluminium kgce/t GJ/t 414 12.1 223 6.5
(Carbon) AluminumSmelting (Electrolysis)
Electricity Fuel Electricity Electricity
145 35 22 5064
4.3 1.0 0.64 148.4
Ingot Casting
Electricity
36
1.06
5940
174.0
Alumina Production (Bayer)
Anode Manufacture
Total
259
7.6
Note: Primary energy includes electricity generation, transmission, and distribution losses of 67%. (Source: World Best Practice Energy Intensity Values for selected Industrial Sectors; LBNL; by Worrel E., Price L., Neelis M., Galitsky C. & Nan Z.)
14.8
World Best Practices for Energy Efficiency in Aluminum Industry
Considerable developments have taken place in the process for production of Alumina, Aluminium and semis in the developed countries. Some of these are given below : 14.8.1 • • • •
426
Secondary Aluminium kgce/t GJ/t
Alumina Plants Use of rod mills with classifiers for wet grinding of Bauxite. Adoption of tube digestion system in order to achieve improved digestion yield. Adoption of Alcoa combination process for digestion and extraction of Trihydrate as well as Monohydrate Alumina. Adoption of direct filtration technology to separate the red mud directly downstream the digestion under the same conditions of pressure and temperature. 427
• • • • • • •
Liquor purification system for removal of carbonates and organic matters. Improved mechanical agitation system for precipitators. Adoption of special disc filters for filtration of seed and product hydrate. Adoption of multistage falling film evaporation systems in place of conventional single stage system. Installation of stationary calciners in place of conventional rotary kilns. Adoption of dry disposal system of red mud. Automation and computerized process control systems for better operation of the plants.
14.8.2 Aluminum Smelters • • • • • •
Improvement in electrolyte bath chemistry to minimize re-oxidation of metal. Improvement in Alumina feeding system by adopting point feeding for proper distribution of Alumina in the electrolyte. Improvement on magnetic field characteristics through bus-bar network redesign for stable metal pad. Increase in the current efficiency by accurate control of process parameters. Possibility of lowering anode current density by increasing the anode size. Replacement of monolithic cathode lining with prebaked cathode blocks for better cell life.
Investment Payback period
: Rs 1.8 Million(@65Kg. /hr. production rate & 1600 hrs./yr. Operation & holding time of 2 hrs./day) : Rs 2 Million : 13months
Case Study 9 : Installation of a small capacity variable pump for keeping hydraulic pressure Brief Even when pressure oil was not needed for the pressure-oil system, the main pump of the hydraulic unit was operated in order to compensate leaks. Instead, a smallcapacity pump is installed to compensate leaks. The main pump operation requires 11 kW of electric power whereas, the small-capacity pump operation requires only 3.7 kW. Energy Savings Energy Savings (kW) Annual saving Investment amount Payback: period
: 7.3 : Rs 0.2 Million : Rs 0.2 Million : 1 year
Case Study 10 : Variable Voltage Variable Frequency (VVVF) control of pumps and fume blowers, and flow rate reduction of by-pass circuit
14.8.3 Semis Production •
New processes like CONFORM extrusion and hydro-static extrusion for improved extruded products.
14.9
Energy Efficient Technologies being used in Aluminum Plants in Japan
Case Study 8 : Immersion melting plating furnace Brief A conventional furnace indirectly heats the metal in a vessel made of steel from outside through the vessel bottom or side wall. An immersion melting furnace is an energy-saving type furnace which heats the metal directly with a combustionheating immersion tube. The furnace has a combustion-heating immersion tube integrated with a special gas burner made of ceramic, a temperature sensor, and specially-designed furnace- temperature control device. Energy Savings Before Improvement Specific energy consumption (kCal/kg) Holding energy consumption (kCal/kg)
Annual saving
2500
62,000
After Improvement
Saving / Improvement
700
1800
23,000
39,000
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Brief In a rolling schedule, the time ratio between the rolling operation and the set-up operation is 3:2. The conventional method was as follows: 1) Coolant pumps and fume blowers were operated continuously. 2) During the set-up, output of the coolant pumps was returned to the coolant tank through the bypass by switching the 3-way valve. However, power consumption in the set-up time was greater than that in the rolling operation. The following measures were taken: 1) The numbers of revolutions of the coolant pumps and fume blowers are controlled in accordance with the rolling schedule by introducing the VVVF apparatus. 2) Power consumption by the coolant pumps during the set-up time is reduced by throttling the valve of the bypass circuit to the coolant pumps. Energy savings Reduction of power consumption by VVVF control Reduction of power consumption by throttling the bypass valve Annual Saving Investment Payback period
429
: 2 Million kWh/year : 1.2 Million kWh/yr : Rs 2 Million : Rs 4 Million : 2 years
Case Study 11 : Improvement of thermal efficiency for rapid aluminium melting furnace Brief Approximately 30% reduction of unit requirement of energy has been achieved through measures as : • • • • •
mixing of molten metal burner combustion control controlling the molten metal temperature controlling furnace pressure installation of recuperator.
: Rs 10 Million : Rs 28 Million : 3 years
Case Study 13 : Improving Operation by reduced number of revolutions of circulating fan Brief A circulating fan of a soaking pit was constantly operated at 100% of the number of revolutions from the start to the end of the operation. Energy saving is realized by the improvement of operation, where the number of revolutions of the circulating fan is reduced.
Energy savings Conventional iron melting furnace
Annual saving Investment Payback period
After improvement (immersion type holding furnace)
Saving/ Improvement
Energy unit requirement (kcal/kg)
50 (100%)
22 ( 44%)
28
Yield (metal loss) ( kg/T)
7 (100%)
2 (29%)
5
Following two points are found by controlling the number of revolutions of the circulating fan: 1) Reducing the number of revolutions of the circulating fan for a few hours after the start of heating does not change the heating time. 2) Reducing the number of revolutions of the circulating fan after the end of soaking gives no effects on material temperature. Energy saving From start to 3 hours After end of soaking Annual saving Investment Payback period
Energy savings Energy savings (kL/yr.) Annual saving Investment Payback period
: 184 : Rs 16 Million : Rs 24 Million : 1.5 years
: 70 kW to 35 kW : 56 kW to 28 kW : Rs 2 Million : Rs 2.8 Million : 1.5 years
Case Study 12 : Regenerative burner type aluminium melting furnace
Case Study 14 : Heat loss improvement of energy saving type electric holding furnace
Brief
Brief
This improvement is to use a highly efficient furnace for melting aluminium. The furnace employs oil or gas fired regenerative type burners and reduces the specific fuel consumption by more than 30 % compared with a conventional melting furnace. Operating condition of furnace is 40 T/charge, 4 charges/day & 300 days/yr.
This is an example of improvement of heat loss at electric holding furnaces used near the casting machine following the melting work of aluminium alloy ingot. Although individual energy consumption is not large, it has a huge effect considering that a number of electric holding furnaces have been already installed.
Energy savings
Energy savings Conventional melting furnace
Waste heat recovery method Combustion air temperature Air ratio Waste heat recovery ratio Specific fuel consumption Heat efficiency Reduction in crude oil equivalent
Recuperator 0
200 C on average 1.2 on average 15.1 % 3
682 x 10 kCal/t 40.2 %
Regenerative melting furnace Regenerative substance (alumina ball) 0
800 C on average
Before Improvement
Effect Increase by 6000C
1.1 on average
Reduced
68.2 %
Increased by 53.1% 3
478 x 10 kCal/t 57.5 %
Electricity consumption amount (kWh/y) Crude oil saving amount rate (kL/y)
156,000
-
After Improvement
Saving/ Improvement
42,000
114,000
-
28
3
204 x 10 kCal/t (30% reduced) Increased by 17.3% 1,058.6 kL/year
430
Annual saving Investment Payback period 431
: Rs 0.8 Million : Rs 2 Million : 2.5 years
Case Study 15 : Improvement of operation of hot air circulation fan for the Aluminium annealing furnace Brief
e) Provision of dry scrubbing system for gas cleaning and recovery of fluorides. f)
Computerisation of baking furnace firing system.
14.10.3 Semis
This is an example of remodeling the operation pattern of the hot air circulation fan of an annealing furnace for aluminium coil heat treatment to contribute to energy saving. The coil annealing furnace is a batch type electric furnace. Without replacing the existing motor, a frequency converter has been installed in the control board of the fan motor.
a) Electromagnetic casting of slabs and billets. b) Hot top casting of billets with air-slip process. (ii) Rolling a) Thin strip casting with cold rolling. b) Introduction of automatic gauge, flatness and crown control systems.
Energy Savings
e) Improved design features for heat treatment furnaces.
Production volume (t/y) Electric power consumption (kWh/y) Electric power unit requirement (kWh/t)
Before improvement
After improvement
Saving / Improvement
29,568
29,616
48 (increased)
1,502,904
1,284,400
218,504 (reduced)
50.8
43.4
7.4 (reduced) 53
: Rs 1.6 Million : Rs 2.5 Million : 1.5 years
14.10 Directory of ENCON Measures with expected benefits 14.10.1
b) Introduction of efficient heat treatment (Air & Water quenching on run-out table). d) Installation of combined direct/indirect extrusion press. e) Installation of Confirm extrusion process. References:
Reduction converted into crude oil (kL/y)
Annual saving Investment Payback period
(iii) Extrusion
Alumina
a) Replacement of existing rotary kilns with stationary calciners. b) Adoption of tube digestion system for dissolution of predominantly monohydrate Bauxites. c) Removal of impurities from plant liquor. d) Adoption of dry disposal of red mud. e) Use of Variable Speed Drives for major process pumps and large motors in the plant. f) Provision of mechanical agitation or improved air agitation system in precipitation unit. g) Modernization of process control system in plants. 14.10.2 Aluminium a) Improvement in cell design b) Redesigning of bus bar arrangement. c) Provision of improved Alumina transportation system. d) Provision of mechanized and automated cell operations.
432
1. 'Technology Evaluation in Aluminum Industry' by Department of Scientific & Industrial Research-2006. 2. Directory of Energy Conservation Technology in Japan, prepared by New Energy & Industrial Technology Development Organization, The Energy Conversation Centre, Japan. 3. Investors Manual for Energy Efficiency, Energy Management Centre, CII & IREDA. 4. Energy Management Policy -Guidelines for Energy Intensive Industry of India, Bureau of Energy Efficiency. 5. Websites : http://www.qal.com.au/ : http://www.mam.gov.tr/ 6. The Energy Data Directory & Yearbook, TEDDY, 2007 7. World Best Practice Energy Intensity Values for Selected Industrial Sectors (Ernest Orlando Lawrence Berkeley National Laboratory), Environmental Energy Technologies Division; by Ernst Worrell, Lynn Price, Maarten Neelis, Christina Galitsky & Zhon Nan, 2008. 8. A book on Life cycle Assessment of Aluminum - Inventory Data for the Worldwide Primary Aluminum Industry, International Aluminum Institute. 9. Energy Requirements in Relation to Prevention & Re-use of waste streams. Report : Aluminum, Worrell, E. & de Beer J, 2006. 10. A book on Process Heating in the Metals Industry by Flannagam J.M. 11. A book on Energy Requirements for Aluminum Production : Historical Perspectives, Theoretical Limits & New opportunities by Choate W.T., Green J.A.S. 12. Electrolytic Production of Aluminium, Electrochemistry Encyclopedia, Electrochemical Technology Corpn., Beck T.R., (http:// electrochem.cwru.edu/ed/encycl/art-a01-al-prod.htm) 13. IEA, World Energy Outlook, 2007.
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Section 5 Climate Change Ø Chapter - 15 Impact of climate change in India
Chapter 15 Impact of Climate Change in India 15.1 Introduction: A sustainable energy future would mean society's energy needs are met using resources that are available to us over the short, medium & long-term basis. At the same time, it would mean producing and utilizing all these energy resources in a way that minimizes adverse impact on the environment and maximizes economic & social benefits. Creating a sustainable energy future is a significant challenge, because of : • Surging energy demand driven by population growth and economic development • Environmental impact of energy production and consumption, particularly those associated with Green House Gas (GHG) emissions • Concern about security of supplies It is the rapid pace of industrialization during the last 70 years, that has contributed immensely to the surge in energy demand, increased emissions and Global warming leading to climate change. 15.2
Global Warming:
Global warming is the increase in the average measured temperature of the Earth's near-surface air and oceans since the mid-twentieth century. The average global air temperature near the Earth's surface increased by 0.74 ± 0.18°C (1.33 ± 0.32°F) during the last hundred years ending 2005. Climate model projections summarized by the Intergovernmental Panel on Climate Change (IPCC) indicate that average Global surface temperature is likely to rise further by 1.1 to 6.4°C (2.0 to 11.5°F) during the twenty-first century. The climate model further projects that, "most of the observed increase in Globally averaged temperature since the mid-twentieth century is very likely due to the observed increase in anthropogenic (man-made) Green House Gas concentrations" via an enhanced greenhouse effect. 15.3
Green House Gases (GHG) in the atmosphere:
The greenhouse effect is the process by which absorption and emission of infrared radiations by atmospheric gases warm a planet's lower atmosphere and surface. As can be seen from figure -15.1, the monthly CO2 measurements display small seasonal oscillations in an overall yearly uptrend; each year's maximum is reached during the Northern Hemisphere's late spring and declines during the Northern Hemisphere growing season as plants remove some CO2 from the atmosphere. Existence of the greenhouse effect as such is not disputed. Naturally occurring greenhouse gases have a mean warming effect of about 33°C (59°F), without which Earth would be uninhabitable. On Earth, the major greenhouse gases are water vapor, which causes about 36-70% of the greenhouse effect (not including clouds), carbon dioxide (CO2), which causes 9-26% methane (CH4), which causes 4-9% and ozone, which causes 3-7% green house effect. The concern is how the strength of the greenhouse effect changes when human activity increases the atmospheric concentrations of some greenhouse gases. 437
15.3.1 Attributed & expected effects of Green House Gases : Fig 1 : 15.1 Increases in atmospheric carbon dioxide (CO2). since 1960 Although it is difficult to connect specific weather events to Global warming, an increase in Global temperatures may in turn cause broader changes, including glaciers retreat, arctic shrinkage and worldwide sea level rise. Changes in the amount and pattern of precipitation may result in flooding and drought. There may also be changes in the frequency and intensity of extreme weather events. Other effects may include changes in agricultural yields, addition of new trade routes, reduced summer stream flows, species extinctions and increases in the range of disease vectors. One study predicts 18 to 35% of a sample of 1,103 animal and plant species would be extinct by 2050, based on future climate projections. 15.3.2 Carbon Footprint The carbon footprint is a measure of the impact our activities have on the environment and in particular climate change. It relates to the amount of greenhouse gases produced in our day-to-day lives through burning of fossil fuels for electricity generation, heating and transportation etc. The carbon footprint is a measure of all greenhouse gases we individually produce and has units of tonne (or kg) of carbon dioxide equivalent.
(Source :http://en.wikipedia.org/wiki/globalwarming)
Human like: -
induced anthropogenic green-house gases emissions are from activities Energy production from fossil fuels Industrial activities Transport Construction Agriculture Land use change & deforestration
Fig. 15.2 : Carbon Footprints
The Global Warming Potential (GWP) of the 6 GHG gases accounted in terms of their CO2 equivalent are given in Table - 15.1 Table - 15.1 Gas Carbon Dioxide (CO2) Methane (CH4) Nitrous Oxide (N2O) Hydro-fluoracarbons (HFC) Perfluorocarbon (PFC) Sulphur Hexaflouride (SF6 )
The pie chart below shows the main elements which make up the total of a typical person's carbon footprint in the developed world. A carbon footprint is made up of the sum of two parts, the primary footprint (shown on the right side of the pie chart) and the secondary footprint (shown on the left side of the pie chart).
GWP 1 1 21 21 310 310 11700 11700 9500 9500 23900 23900
Source : www.unfccc.com
Financial service 3%
Home-gas, oil and coal 15%
Share of public services 12%
Home-electricity 12%
Recreation & leisure 14% House-buildings and fumishings 9%
Private transport 10%
Car manufacture & Food & drink delivery 5% 7% Clothes and personal effects 4%
Secondary Footprint
Public transport 3% Holiday flights 6%
Primary Footprint
Source : www.carbonprint.com
The present atmospheric concentration of CO2 is about 385 parts per million (ppm) by volume. Future CO2 levels are expected to rise due to ongoing burning of fossil fuels and land-use change. The rate of rise will depend on uncertain economic, sociological, technological and natural developments, but may be ultimately limited by the availability of fossil fuels. The IPCC special report on 'Emissions Scenarios' gives a wide range of future CO2 scenarios, ranging from 541 to 970 ppm by the year 2100. Fossil fuel reserves are expected to be sufficient to reach this level and continue emissions past 2100 as well.
438
i. The primary footprint is a measure of our direct emissions of CO2 from the burning of fossil fuels including domestic energy consumption and transportation. We have direct control of these. ii. The secondary footprint is a measure of the indirect CO2 emissions from the whole lifecycle of products we use - those associated with their manufacture and eventual breakdown. To put it very simply, the more we buy the more emissions will be caused on our behalf.
439
15.4
United Nations Framework Convention on Climate Change (UNFCCC)
15.4.2
Kyoto Protocol:
The United Nations Framework Convention on Climate Change (UNFCCC) is an international environmental treaty produced at the United Nations Conference on Environment and Development (UNCED), informally known as the 'Earth Summit', held in Rio de Janeiro from 3 to 14 June 1992. The treaty is aimed at stabilizing greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system.
The Kyoto Protocol adopted by the 3rd Conference Of Parties (COP) on 11th December 1997 in Kyoto (Japan) and entered into force on 16th February 2005, is an international agreement linked to the UNFCCC. The major feature of the Kyoto Protocol is that it sets binding targets for 37 industrialized countries including the European Union for reducing Green House Gas (GHG) emissions. These amount to an average of five percent against 1990 levels over the five-year period 2008-2012.
On June 12, 1992, 154 nations signed the UNFCCC, that upon ratification committed signatories' Governments to a voluntary "non-binding aim" to reduce atmospheric concentrations of greenhouse gases with the goal of "preventing dangerous anthropogenic interference with Earth's Climate System." These actions were aimed primarily at industrialized countries, with the intention of stabilizing their emissions of greenhouse gases at 1990 levels by the year 2000.
The major distinction between the Protocol and the Convention is that, while the Convention encouraged industrialized countries to stabilize GHG emissions, the Protocol commits them to do so. Recognizing that developed countries are principally responsible for the current high levels of GHG emissions in the atmosphere as a result of more than 150 years of industrial activity, the Protocol places a heavier burden on developed nations under the principle of "common but differentiated responsibilities". 183 Parties of the Convention have ratified the Protocol till date.
Since the UNFCCC entered into force, the parties have been meeting annually in Conferences of the Parties (COP) to assess progress in dealing with climate change. The last COP i.e. COP 14, was held from Dec. 01-12, 2008 at Poznan, Poland. 15.4.1 Annexure I, Annexure II Countries & Developing Countries: Signatories to the UNFCCC are split into three groups: • • •
Annex I countries (industrialized countries) Annex II countries (developed countries which pay for costs of developing countries) Developing countries (also known as non- Annex I countries)
Annex I countries agree to reduce their emissions (particularly carbon dioxide) to target levels below their 1990 emissions. If they cannot do so, they must buy emission credits or invest in conservation projects. Annex II countries, that have to provide financial resources for the developing countries, are a sub-group of the annex I countries consisting of the OECD members, without those that were with transition economy in 1992. Developing countries have no immediate restrictions under the UNFCCC. This serves three purposes: • • •
Avoids restrictions on growth because pollution is strongly linked to industrial growth, and developing economies can potentially grow very fast. They cannot sell emissions credits to industrialized nations to permit them to over-pollute. Money and technologies are readily available from the developed countries in Annex II.
Developing countries are not expected to implement their commitments under the convention unless developed countries supply enough funding and technology and this has lower priority than economic and social development in dealing with poverty. Developing countries may volunteer to become Annex I countries, when they are sufficiently developed.
15.4.3
The Kyoto Mechanisms
Under the Treaty, countries must meet their targets primarily through national measures. However, the Kyoto Protocol offers them an additional means of meeting their targets by way of three market-based mechanisms. The Kyoto mechanisms are: • • •
Emissions trading - known as "the carbon market" Clean Development Mechanism (CDM) Joint implementation
The mechanisms help stimulate green investment and help Parties meet their emission targets in a cost-effective way. The Kyoto Protocol is generally seen as an important first step towards a truly Global emission reduction regime that will stablise GHG emissions and provide the essential architecture for any future international agreement on climate change. By the end of the first commitment period of the Kyoto Protocol in 2012, a new international framework needs to be negotiated and ratified that can deliver the stringent emission reductions, the intergovernmental Panel on Climate Change (IPCC) has clearly indicated are needed. 15.4.4. Clean Development Mechanism (CDM): To help countries meet their emission targets and to encourage the private sector and developing countries to contribute to emission reduction efforts, negotiators of the Protocol included three market-based mechanisms - Emission Trading, the Clean Development Mechanism (CDM) and Joint Implementation The CDM defined in Article 12 of the Kyoto Protocol allows emission-reduction or emission removal projects in developing countries to earn Certified Emission Reduction (CER) credits, each equivalent to one tonne of CO2. These CERs can be traded and sold and used by industrialized countries to meet a part of their emission reduction targets under the Kyoto Protocol.
The list of Annex I, Annex II & Non - Annex I countries is available on website of UNFCCC. (http://unfccc.int/) 440
441
The mechanism stimulates sustainable development and emission reductions, while giving industrialized countries some flexibility in how they meet their emission reduction limitation targets. The projects must qualify through a rigorous public registration and issuance process designed to ensure real, measurable and verifiable emission reductions that are additional to what would have occurred without the project. The mechanism is overseen by the CDM Executive Board, answerable ultimately to the countries that have ratified the Kyoto Protocol.
15.4.6
The various stakeholders in CDM project are: •
•
In order to be considered for registration, a project must first be approved by the Designated National Association (DNA). Public funding of CDM project activities must not result in the diversion of official development assistance. Operational since the beginning of 2006, the mechanism has already registered more than 1133 projects and is anticipated to produce CERs amounting to more than 2.7 billion tonnes of CO2 equivalent in the first commitment period of the Kyoto Protocol, 2008-2012. 15.4.5
• •
•
•
The project developer: for project design, implementation and emissions monitoring. This includes the industry, CDM consultant and implementing agency. The Host Country's Designated National Authority (DNA): who would approve the project based on national sustainable development objectives. In India, the DNA is Ministry of Environment & Forest (MoEF). The Designated Operating Entities (DOE): for Validation against CDM rules and Verification &Certification of actual emissions in terms of tonnes of CO2 reduction. The Executive Board of UNFCCC: for issuance of Certified Emission Reductions (CERs) certificate.
The total time required from the date of conception of the project to issuance of CERs is normally 90-100 weeks.
CDM eligibility:
For a project to be considered for CDM, it should fulfill the following eligibility criteria: • •
Stakeholders in CDM project:
The project must be in non - annexure 1 countries. The projects to reduce / eliminate emission than the usual measures taken to achieve the same objective (e.g. use of biomass / windmill in place of coal to generate electricity). Participation in CDM is voluntary The project contributes to the Sustainable Development of the host country, i.e. the country where the project is being implemented. The sustainable development indicators are:
15.4.7
Scale of CDM projects :
All the CDM projects in developing countries (non-annexure I countries) can be categorized into: i. ii.
Small Scale Projects Large Scale Projects
Small Scale project are those which are eligible for fast-track procedures (including simplified baselines) provided by the CDM Executive Board and monitoring requirements. The various categories of Small Scale projects are:
•
The project results in real, measurable and long term benefits in terms of climate change mitigation, i.e. to assist in environment friendly technology transfer, generate investment in developing countries and promote sustainable development.
: Renewable Energy Projects with a maximum output capacity upto 15 MW •Type II : Energy Efficiency improvement projects, which reduce energy consumption on the supply and / or demand side, upto 60 Gwh per year annually •Type III : Other project activities that both reduce emissions by sources and that directly emit less than 60, 000 tonnes CO2 equivalent annually. The projects which do not fall under Small Scale projects are categorized into largescale projects.
•
The emission reduction must be 'Additional' to any reduction that would have occurred without the project .
The number of approved 'Methodologies' for CDM projects by the EB of UNFCCC upto March 2008 are:
• • • •
•Type I
Social well-being. Economic well-being. Environmental well-being and Technological well-being.
• • •
To satisfy the "Additional" criteria, the project: • • • •
Should have started after the year 2000. Should not be the only alternative consistent with current laws and legislations. Should not be the most lucrative investment option Is not a 'common practice', i.e. 'Business As Usual' (BAU)
The above additional criteria have an impact on CDM registration.
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15.5
For large-scale projects = 80 For consolidated projects = 19 For small-scale projects = 38 Indian Scenario on Climate Change :
India's per capita CO2 emissions are very low, at just over one tonne in 2005, compared to 11 tonnes in the OECD countries. They are about half those of the developing countries on an average. However, the emissions are expected to rise by almost 60% by the year 2015. In 2005, India had released about 1.1 Gt of CO2, which is 4% of the world total. It is estimated that by 2030, per capita emissions in
443
India are projected to double, but still these will be well below those of the OECD countries. India signed and ratified the Kyoto Protocol in August, 2002. Since India is exempted from the framework of the treaty, it is expected to gain from the protocol in terms of transfer of technology and related foreign investments. Following the principle of common but differentiated responsibility, India maintains that the major responsibility of curbing emissions rests with the developed countries, which have accumulated emissions over a long period of time. However, the U.S. and other Western nations assert that India and China will account for most of the emissions in the coming decades, owing to their rapid industrialization and economic growth. 15.5.1 The Indian climate-friendly initiatives The GHG intensity of the Indian economy in the year 2000, in terms of the purchasing power parity, is estimated to be little above 0.4 tonne CO2 equivalent per 1000 US dollars, which is lower than that of the USA and the global average. The Indian Government has targeted around 8-9% GDP growth rate per annum for 2007-12 to achieve its development priorities. In order to achieve these developmental aspirations, substantial additional energy consumption will be necessary and coal, being the largest domestic energy source, would continue to play a dominant role. Since GHG emissions are directly linked to economic growth, India's economic activities will necessarily involve increase in GHG emissions from the current level. The CO2 equivalent emissions from India are set to increase up to 3000 million tonnes by 2020. Any constraint will hamper the economic development.
Table 15.2 : The energy sector CO2 emissions in the baseline scenario * (Tg CO2) * Tg - Terra gms.
1990 2010 2020 Baseline 532 1555 2308 Coal 327 895 1336 Oil 178 553 777 Gas 27 107 198 (Source : CDM Implementation in India; The National Strategy Studies, MOEF & TERI)
15.5.3 Clean Development Mechanism in India India has given host-country approval for 969 CDM projects as of July 2008. Renewable energy, including the renewable biomass, accounted for the largest number of projects (533), followed by energy efficiency (303). Very few projects in the forestry (6) and municipal solid waste (18) were included, despite their large potential. The expected investments in these 753 projects (if all go on stream) is about Rs. 1,06,900 crores. Of the 969 projects, 347 projects have been registered by the Multilateral Executive Board (CDMEB). India accounts for about 32% of the world total of 1133 projects registered with the CDM EB till July 2008, followed by China, 22%, Brazil, 13%, and Mexico, 10% (Source: UNFCCC). About 493 million Certified Emission Reductions (CERs) are expected to be generated until 2012 if all these host-country approved projects in India go on stream. As of July 2008, 173 million CERs had been issued to projects worldwide, of which India accounted for 26.17%, CERs (39.33 million), China, 35.22%, Korea, 15.73% and Brazil, 12.99%. The type of CDM projects registered in India are given below: Fig 15.3 : Type of registered CDM projects in India
The GHG emissions in the years 1990, 1994 and 2000 increased from 988 to 1228 to 1484 million tonnes respectively and the compounded annual growth rate of these emissions between 1990 and 2000 has been 4.2 per cent. A comparison of the Indian emissions with some of the largest global emitters, indicates that the absolute value of Indian emissions is 24% of the US, 31% of China in 2000. The Indian per capita emissions are only 7% of the US, 13% of Germany, 14% of UK, 15% of Japan, 45% of China and 38% of global average in 2000. The Indian GHG emissions are projected to increase by almost two times with respect to the 1990 emissions in 2020. 15.5.2
GHG mitigation potential in India:
The National strategy study for CDM implementation in India conducted by TERI has made projections of CO2 emissions in India in different sectors of economy and the mitigation potential thereof. The ALGAS (Asia Least-Cost Greenhouse Gas Abatement Strategy) study, made projections for sectoral GHG emissions from India for the period 1990-2020 in order to identify the key areas for developing an abatement strategy for the country. The energy sector projections for India are summarized in Table 15.2. The baseline scenario represents the most likely situation. Rather than projecting past trend, it includes some carbon abatement technologies and energy efficiency improvements that are likely to occur in the future, irrespective of the concerns for CO2 emission reduction.
444
(Source : Institute of Global Warming Environmental Strategy) Some cross-cutting challenges in CDM implementation in India are listed below: •
The projects from India are generally small. Of the 347 projects registered with the CDM EB till July 2008, more than 60% are small-scale projects (in terms of the protocol definition).
•
The portfolio is dominated by unilateral projects, i.e. the investors are Indian parties, employ locally available technologies and use domestic financial resources. While this has provided a significant impetus to local innovation, 445
CDM has not led to the technology transfer from industrialized to developing countries as envisaged by the Protocol. • • • • •
Industrialized countries have not participated significantly in project financing and the project risks are mostly taken up by the host countries. Insurance companies in general have shown little interest in CDM projects, which is unfortunate since they can catalyze carbon trading by providing risk and financial analysis skills. There is much subjectivity in the multilateral CDM process and divergent interpretations are given by different designated operating entities (DOEs) accredited by the CDM EB. High transaction costs prevent the small-scale sector (in the Indian definition) from participating in CDM. In the absence of an International Transactions Log (ITL), there is lack of reliable information in the carbon market on CDM transactions.
Despite the above, there is encouraging response from Indian entrepreneurs to the CDM across different sectors. 15.6 GHG mitigation in different Sectors in India: Based on the targets and plans of the Government of India regarding capacity additions in power and renewable energy sectors and the energy efficiency and technological upgradation being adopted by different industries, the GHG mitigation potential in key sectors, till the first commitment period i.e., till 2012 has been estimated and presented in Figure 15.4.
Table 15.3: India's perspective plan for electric power during the 11th Plan period Power generation
Installed capacity as on Jan. 2008 Addition of capacity till March 2012 Total capacity as on March 2012
Thermal (coal and lignite) (MW) 75002
NG/LNG/di esel (MW)
Nuclear (MW)
Hydro (MW)
Total (MW)
4120
35209
141080
39488
NG:14692 Diesel : 1202 15531
7980
22580
74724
114490
31425
12100
57789
215804
(Source : Ministry of Power, GoI)
The future capacity additions in the power sector are expected to be largely in the thermal sector with coal being the predominant and cost effective fossil fuel in the country. This being the case, the emission of GHGs from the power sector are likely to increase significantly in the future. Any strategy for mitigation of emissions of GHGs from the power sector would center around improvement in efficiency of the fossil fuel-based power plants by technology upgradation both for the existing plants as well as for the plants to be established in future. The potential technologies that can be adopted are: i. ii. iii. iv. v. vi.
Fig 15.4 : GHG mitigation potential in key sectors till 2012
Pulversied Fluidized Bed Combustion ( PFBC) Supercritical & Ultra-supercritical (SC&USC) power plants Integrated Gasification Combined Cycle (IGCC) power plants Underground coal gasification (UGC) technology Coal cleaning technologies Renovation & Modernisation (R&M) of existing power plants.
15.6.1.1 GHG Mitigation options in Thermal Power Plants The present energy mix in India for electricity generation is shown in table-15.4: Table 15.4 : % Energy use for Power Generation
Source Coal Hydropower Oil and gas Wind and solar power Nuclear Power
(Source : CDM Implementation in India; The National Strategy Study by MOEF & TERI)
15.6.1
GHG mitigation in Power Sector
Percentage % 55 26 10 6 3
(Source : National Action Plan on Climate Change, GoI)
The power generation efficiency in India is very low by international standards. India's power sector is one of the most CO2 intensive in the world. Coal based thermal power stations emitted on an average, 943 grams of CO2 per kwh of electricity produced in 2005-more than 50% higher than the world's average. The total emissions of CO2 from power plants in 2005 were 659Mt, nearly 60% of the total CO2 emissions in India. The installed generation capacity of India is 1,41,080 MW as of Jan. 2008, yet there are peaking shortages of 12.2% and energy deficit of 8.8%. The Government of India has set a target of 215804 MW power generation capacities by March 2012 (Table 15.3), requiring a capacity addition of 74724 MW in the next four years.
446
At present, fossil fuels which account for 65% of the total power generation are responsible for most of the GHG emissions. During the 11th Five-Year Plan, utilitybased generation capacity is expected to increase by 78,000 MW. A significant proportion of this increase will be thermal - coal based. While the new investments in the thermal power sector, which are substantial, have high efficiencies, the aggregate efficiency of the older plants is low. In addition, high ATCL (Aggregate Technical and Commercial Loss) in power transmission and distribution is an area of key concern. There are three ways of lowering the emissions from coal based Thermal Power Plants: (i) (ii)
Increasing efficiency of existing power plants; using clean coal technologies (relative emissions are 78% of conventional coal-thermal) 447
(iii)
switching to fuels other than coal. These measures are complementary and not mutually exclusive.
Another option that has been suggested is carbon capture and sequestration (CCS). However, feasible technologies for this have not yet been developed and there are serious questions about the cost as well as permanence of the CO2 storage repositories. Approximately 5000 MW out of total installed capacity of coal based thermal plants have low capacity utilization of less than 5%, as well as low conversion efficiency. As per the Govt. plan, during the 11th Plan, these units would be retired, and during the 12th Plan period, an additional 10,000 MW of the least efficient operating plants would be retired or reconditioned to improve their operating efficiency.
can be put under two broad categories (i) Energy Conservation and (ii) Load Levelling. Energy Conversation include: (a) Mass awareness / education to conserve energy. (b) Development and spread of highly energy efficient products / appliances and (c) Enhanced utilization of untapped energy sources. Load leveling amounts to promotion of load level management through the use of regenerative systems. (ii) Clean Coal Technologies (a) Pressurized Fluidized-Bed Combustion (PFBC)
(i) Efficiency Improvements Significant efficiency improvements and CO2 reductions can be achieved as the existing fleet of power plants are replaced over the next 10-20 years with new, higher efficiency supercritical (SC) and ultra-supercritical (USC) plants. A onepercentage point improvement in the efficiency of a conventional pulverised coal combustion plant results in a 2-3% reduction in CO2 emissions, depending on the level of efficiency prior to the change. Some of the efficiency improvements efforts are:
PFBC is a clean and efficient technology for coal-based power generation which can increase the efficiency of plants up to 43% in a combined cycle arrangement. PFBC technology has the ability to burn low quality fuels. The CO2 reduction from per unit of power supplied at busbar using PFBC, over the conventional technology is estimated to be 0.18 kg. Replacing a conventional plant of 500 MW capacity with a PFBC plant will result in estimated CO2 reduction of 0.58 MT (million tonnes) a year.
(a) Renovation and modernization (R&M)
(b) Supercritical (SC) & Ultra-supercritical (USC) Technology
Renovation and Modernization (R&M) of power plants can improve the efficiency and reduce GHG emissions at a lower cost without additional infrastructure requirement. However, constraints of the nature of resources, lack of public and government determination and the absence of stringent environmental laws have always acted as a barrier towards the move. The Accelerated Power Development Programme (APDP) of the Ministry of Power, launched in 2000/01, provides financial assistance to the States for undertaking R&M programmes and also for strengthening of T&D (Transmission and Distribution) network.
New pulverised coal combustion systems, utilising supercritical and ultrasupercritical technology, operate at increasingly higher temperatures and pressures and consequently achieve higher efficiencies than conventional PCF units resulting in significant CO2 reductions.
In a recent study undertaken by TERI, for the Ministry of Power, two technological options were considered and examined in the context of CDM, viz., adoption of super critical power plants and the R&M of existing plants. (b) Transmission & Distribution loss reduction: In India, average T&D losses have been officially indicated as 25% of the electricity generated. The major reasons for high technical losses in India include overloading of the distribution system, haphazard transformations, improper load management, inadequate reactive compensation and poor quality of equipment used in the rural as well as suburban areas. Thefts and pilferages also account for a substantial part of the high T&D losses. It is estimated that the upgradation of the agricultural distribution system can reduce the distribution losses in the sector by 5% to 6%, equivalent to an annual energy saving of 6.75 billion units. (c) Demand-Side Management Demand-Side Management (DSM) represents a revolutionary approach for planning the electric utilities. Essentially, it broadens the scope of planning to integrate the customer's needs and desires with the utility's goal. DSM activities 448
In India, three 660 MW SC units are under construction. India has announced plans for a series of 4000 MW 'ultra-mega' power projects in future. Research and Development is under way to improve energy efficiency of ultra-supercritical units from the existing 45% to around 50%. (c) Integrated gasification combined cycle power plant (IGCC) In IGCC Power Plants, coal is combined with oxygen and steam in the gasifier to produce the syngas, which is mainly H2 and carbon monoxide (CO). The gas is then cleaned to remove impurities, such as sulphur and the syngas is used in a gas turbine to produce electricity. Waste heat from the gas turbine is recovered to create steam which drives a steam turbine, producing more electricity. Hence, it is a combined cycle system. The efficiency of the IGCC power plant is the product of the gasification system efficiency and combined cycle efficiency. These plants are expected to have a net efficiency of 46%, compared to an average of 36% for existing plants. Although, IGCC technology is more efficient and environmentally less polluting than ordinary pulverized coal plants, its application requires high investments compared to conventional pulverized coal technology. It is estimated that IGCC technology will result in CO2 emission reductions of 0.25 kg/KWh. Replacing a 500 MW conventional plant with an IGCC plant will result in CO2 emission reduction of 0.69 MT. The proposed IGCC power plant will reduce the emissions of CO2, SO2, NOx and SPM (Suspended particulate matter). It will also reduce solid waste disposal by nearly 70% compared to direct coal-fired plants. 449
Depending upon the application, the various renewable energy technologies can be broadly classified into three groups.
(iii) Switching to fuels other than coal (a) Natural Gas based Power Plants Natural gas based power generation is cleaner than coal-based generation as CO2 emissions are only 50% compared to coal. Besides, natural gas can be used for electricity generation by adopting advanced gas turbines in a combined cycle mode. Introduction of advanced class turbines with inlet temperature in the range 12500C-13500C has led to combined cycle power plant efficiency of about 55% under Indian conditions. Many such plants are in operation in India. With the discovery of significant reserves of natural gas in the KG basin, setting up of more combined cycle natural gas plants is an attractive GHG mitigation option in India. (b) Underground Coal Gasification (UCG) UCG is a method of injecting air or oxygen into a coal seam to support an in-situ gasification process. This process converts the unmined coal into a combustible gas, which can be brought to the surface to be used for industrial heating or power generation. Current UCG projects are relatively small-scale, but if the process can be developed as a reliable, large-scale source of coal syngas, it could also potentially be used to feed capital intensive plants producing hydrogen, synthetic natural gas or diesel fuel. UCG in combination with CCS is also recognised as a potential route to carbon abatement from coal. (c) Coal Cleaning Coal cleaning reduces the ash content of coal by over 50%, resulting in less waste, lower sulphur dioxide (SO2) emissions and improved thermal efficiencies, leading to lower CO2 emissions. While coal preparation is standard practice in many countries, in India, if a greater proportion of this coal were cleaned, there is the potential for thermal efficiency improvements of at least 2-3% extending up to 4-5%. A number of technologies have been developed to control particulate emissions and are widely deployed in both developed and developing countries. These are : • • • •
Electrostatic precipitators Fabric filters or baghouses Wet particulate scrubbers Hot gas filtration systems.
15.6.1.2.GHG mitigation through Renewable Energy Power Plants: The renewable energy technologies offer a centralized as well decentralized supply side options. With policy initiatives, financial and infrastructural support from the Ministry of New Renewable Energy (MNRE), many of the renewable energy technologies have reached near commercialization stage. The status of different renewable energy technologies and their respective potential is given in Table 15.5. Table 15.5 : Potential and achievements for renewable energy technologies Source / system
Wind energy Small hydro power Biomass power/ cogeneration Waste-to-energy Biomass gasifiers Solar photovoltaic systems Solar water heating (collector area) sq.m Biogas plants (nos.) Improved cook stoves (nos.)
Approximate potential 45000 MW 15000 MW 19500 MW 1700 MW
140 million sq.m 12 million 120 million
Cumulative physical achievements (as on 30.9.06) 6070 1850 1039 35 76 2.74 2.74 1.5 million s.q.m.
Proposed during XIth Plan Period 10,500 1400 1700 400 N/A 50 10 million
3.9 million 33.9 million as on 31.3.04
2 million N/A
• • •
Grid-connected power generation. Off-grid power generation and Renewable energy projects for thermal energy and mechanical use.
Considering an additional capacity addition of 10,000 MW by 2012, as projected by the MNRE and power generation from various other applications, the cumulative GHG abatement potential from grid-connected RE (renewable energy) power projects, up to 2012 has been estimated. The PLF considered for biomass, wind, small hydro and Waste To Energy (WTE) are 80%, 25%, 35% and 70% respectively. Out of the annual capacity addition in the Waste To Energy (WTE) sector, around 80% is assumed to come from MSW (municipal solid waste) and methane from the sewage liquid waste. The cumulative GHG abatement potential up to 2012 from RE power projects is 154 MT and from the MSW to energy about 65 MT. The investment required to implement RE projects to the tune of an additional capacity of 10,000 MW by 2012 is estimated to be about 9628 million USD. 15.7 GHG mitigation in Industrial Sector : During the year 2005, Industry sector in India accounted for about 13% of the total CO2 emissions. As per the National Strategy Study on CDM implementation in India conducted by TERI, the CO2 emissions from the industrial sector can be broadly categorized into two heads: (a) emissions due to fuel combustion in the industries and (b) process related emissions. Of the total CO2 emissions from the industry in 2005, nearly 60% were accounted for due to energy use only. The process related emissions are the result of non-energy related activities that result in the emission of CO2. Cement and Steel industry, accounted for nearly 75% of the total process related CO2 emissions. The other major processes that result in CO2 emissions are soda ash use, ammonia production, lime production and processes in the ferroalloys industry. Detailed analysis of the industrial energy-use pattern reveals that around 65% of the total energy consumption in the industrial sector is accounted for by seven sectors namely (1) cement (2) pulp and paper (3) fertilizer (4) iron and steel (5) textiles (6) aluminum and (7) chemicals and petrochemicals. In addition to these sectors, there are a few energy intensive sub-sectors operating under the small scale, where energy cost accounts for a major share of the operating cost. Some of the examples of energy intensive small-scale industries are ceramics & glass, foundry, forging, brick manufacture, and lime kilns etc. Energy efficiency programs across all industry sectors hold the promise for costeffective CO2 abatement, as a large number of plants in India operate well below the world energy efficiency standards. The CO2 mitigation projects in the industrial sector could be broadly grouped under four major heads. (a) (b) (c) (d)
Sector-specific technological options, Cross-cutting technologies, Fuel- switch options, and Recycling and use of secondary materials.
(Source : Report on working group on New & Renewable Energy for XI Plan, GoI) 450
451
Figure 15.5 below gives a general classification for the types of projects that could be considered under the above four heads. Fig 15.5: CO2 mitigation options: Energy-Efficient technologies in industry sector Adoption of energy-efficient technologies
Cross-cutting technologies
Fuel-switch options Recycling and use of secondary materials
15.7.1
Large industries · Cement · Fertilizer · Iron and Steel · Textiles · Pulp and paper Small-scale industries · Foundry · Brick kilns · Glass · Others
The energy efficient technologies which can reduce CO2 emissions in cement production are: (a) Large Scale rotary kilns in place of vertical kilns for clinker production. (b) Dry process in place of wet process. (c) Pre-calcination technology. (d) Pre-heating (e) Use of Clean energies from biomass wastes. (f) Use of fly-ash as substitute of clinker. Iron and steel
Most of the emissions from the steel industry are related to processes such as quenching, gas recovery, casting and rolling. In addition, the use of different types of furnaces and fuels also determines the extent of emissions. During the year 2005, Carbon dioxide emissions from steel production were responsible for 7% of total emissions in India. While CO2 intensity tc/tonne from the steel sector in India is comparable to China, it is much higher compared to Brazil, Mexico and South Africa. Energy Saving and GHG Emissions Reduction Technologies in steel sector : • • • • • • •
Coal drying and humidity control equipment for coke oven. Sensible heat recovery from main exhaust gas of sintering machine. Exhaust heat recovery system for sintered ore cooling equipment. Pulverised Coal Injection for blast furnace. BOF exhaust gas recovery device (including sealed BOF). Ladle heating apparatus with regenerative burners. Recovery of sensible heat from skid cooling water in heating furnace. 452
Control of excess air by installing O2 monitoring system in high-pressure boiler of CPP in a steel plant.
Environment Management measures by Steel Industry in India • • • • • • •
15.7.3
Cement
GHG mitigation potential in the cement sector lies in bringing down specific power consumption and specific thermal energy consumption. There lies a large scope for improving energy efficiency in the relatively older installation. The possibility for energy saving in different plants varies from 10% to as high as 30%. In addition, there also exists about 160 MW of cogeneration potential in the Indian cement industry.
15.7.2
•
Commissioning of wastewater recycling projects at plants and townships to utilize treated water for green belt development. Commissioning of incinerator to incinerate waste organic materials. Utilisation of 100% slurry in pellet and sinter plant. Technology upgradation and revamping in acid recovery plant, to ensure continual improvement in emissions levels. Provision of High Efficiency Venturi Scrubbers in Hot Briquetted Iron (HBI) plant to control emission of particulate matter. (This also helps in recovery of iron ore fines and its reuse after pelletization). Installation of Central Vaccum De-dusting System for control of emission of Particulate Matter (PM). Use of low NOx generating burners in natural gas/ liquefied natural gas / Naphtha based Power Plants for control of emission of Oxides of Nitrogen. Aluminum
The Aluminum manufacturing process is electrical energy intensive. The major energy saving opportunities in this sector lie in the switchover to gas suspension calciners as against rotary kilns and waste heat utilization in converting the smelters from Soderberg systems to pre-baked systems. The other operational improvements include current efficiency improvements and reduction in operating voltage. Energy Saving and GHG Emissions Reduction Technologies in Aluminum sector : • • • • • • • • 15.7.4
Improvement of operation of hot air circulation fan for the Aluminum annealing furnace Replacement of existing rotary kilns with stationary calciners. Adoption of tube digestion system for dissolution of predominantly monohydrate Bauxites. Redesigning of bus bar arrangement. Provision of mechanized and automated cell operations. Provision of dry scrubbing system for gas cleaning and recovery of fluorides. Improved design features for heat treatment furnaces. Installation of combined direct/indirect extrusion press. Fertilizer
Of the four types of fertilizers-nitrogenous, phosphate, potash, and complex fertilizers, the nitrogenous fertilizer production is highly energy intensive and is one of the largest consumers of petroleum-based fuels. Many of the older ammonia/urea manufacturing plants use liquid fuels (naphtha, furnace oil) as the feedstock but in newer plants, natural gas is the preferred feedstock. The Indian fertilizer industry has witnessed many changes in the feedstock and technology during the last few decades, resulting in substantial reduction in the overall energy-use efficiency. However, by switching over from fuel oil/naphtha to natural gas and by adopting other energy conservation schemes, potential for CO2 mitigation exists in older plants. Energy Saving and GHG Emissions Reduction Technologies in Fertilizer sector: 453
15.7.4.1 Megammonia (Ammonia Production) Operating cost is expected to be lower by around 12 -15% over the most advanced conventional technology. CO2 emission is expected to reduce by around 30% as compared to other conventional technologies. 15.7.4.2 HydroMax Technology (Ammonia Production) Carbon dioxide and hydrogen are produced in separate compartments and do not require CO2 removal system. Cost of production is almost four times less than Steam Methane Reforming (SMR) production cost. Emission of greenhouse gases is 34% less than SMR process. 15.7.4.3 Feedstock conversion from Naphtha to NG in Ammonia-Urea plants Natural gas is ideal feedstock for ammonia production. It has several advantages besides being cheaper and easy to handle. It also allows easy and shorter start up of the plant, thereby lesser unproductive consumption. The burners choking phenomena is completely solved and CO2 emission from furnace has reduced. Plant also runs trouble free and the catalyst life has also increased 15.7.4.4 Installation of Carbon Dioxide Recovery (CDR) Plant Though regeneration energy is very high in comparison to that of any normal CO2 removal section of ammonia plant, the cost effectiveness of the plant is very attractive because the use of costlier Naphtha (as feed to balance the CO2 for Urea production) shall be stopped completely. 15.7.4.5 Conversion of Single Stage GV System to 2-Stage GV System for CO2 The system designed by M/s. Giammarco Vetro Cokes, Italy, results in better absorption of CO2 in absorber and lower energy consumption for regeneration of the solution in regenerators. Major benefits of the modification are reduction of CO2 slip through absorber by around 600 ppm, which has resulted in higher availability of CO2 for urea production, decrease in hydrogen consumption in methanation section and decrease in LP steam consumption in CO2 removal system from 38 MT/hr to 15 MT/hr. Energy saving of around 1GJ/MT of ammonia can be achieved.
in the production of Hydro Chloro Fluoro Carbon (HCFC22). HFC 23 is used in a specific fire fighting application, ultra low temperature application and in the processing of semi-conductors, but the volume of use is limited. The Gujarat Fluorochemcials Ltd, in its HCFC production plant is introducing thermal oxidation of HFC 23, the by-product of HCFC 22, as a CDM project. N2O emission reduction is possible through thermal and catalytic destruction processes in adipic acid production. A N2O emission reduction project from India is under the consideration of Prototype Carbon Fund (PCF). 15.8 GHG mitigation in Transport Sector The transport sector in India accounts for 8% of India's CO2 emissions. This share is likely to grow to 13% in 2030 with rapidly rising transport demand, particularly after 2015 as vehicle ownership increases. The share of transport in total CO2 emissions in 2015 was 31% in US and 24% in European Union, which is much higher than India. Though theoretically, a very attractive sector in terms of mitigation, individual projects might be too large-scale for CDM and include such activities as engine modifications, road-to-rail modality shift, replacement of 2-stroke by 4-storke two-wheelers and greener fuels eg. Compressed natural gas (CNG) etc. Mitigation of GHG emissions in the transport sector can be achieved through the combination of various measures. There needs to be attractive transportation options that include energy-efficient automobiles, motorized two-wheelers, efficient and affordable public transport, minicars, 4-stroke engines in twowheelers and setting fuel efficiency norms and labeling of Motorised Vehicles etc. In addition to this, policies should address externalities caused by vehicles like, drivers to face the full social cost of their use through permits and fees to enter cities, parking fees, road tolls and in general, raising public awareness. Finally, the government should attempt to make available to users, an alternative to fossil fuel consuming vehicles by subsidizing bicycles, linking rail and bus services and rewarding the car sharing programmes. The studies list a number of mitigation areas including BOV (battery-operated vehicle), MRTS (mass rapid transport system), CNG bus, CNG car, and the efficient two-wheelers. In two Asian Institute of Technology (AIT) case studies on Delhi and Mumbai, mitigation options analysed are CNG for buses and cars, shift from 2-stroke to 4-stroke two-wheelers and BOVs.
15.7.4.6 Other options • • • • • • • 15.7.5
Installation of a Parallel S-50 Converter Installation of modified trays in Urea reactor Use of Advanced Process Control (APC) with Distributed Control System (DCS) Installation of Waste Heat Boiler (WHB) at the Inlet of LTS Converter in Ammonia Plant Installation of Make-up Gas Chiller at suction of Synthesis Gas Compressor at Ammonia Plant Installation of High Efficiency Turbine for air blower in Sulphuric Acid Plant Re-processing of purge gas for Ammonia fertilizer GHG mitigation of Industrial gases
In the industrial gases category, the options considered are HFC (Hydro Fluoro Carbon) waste stream incineration, and N2O (nitrous oxide) emission reduction. HFC 23, a GHG under the Kyoto Protocol, is inevitably generated as a by-product 454
15.9 GHG mitigation in Residential, Commercial and Institutional Buildings Sector According to the study conducted by IPCC, Global carbon dioxide (CO2) emissions from residential, commercial, and institutional buildings are projected to grow from 1.9 Gt C/yr in 1990 to 2.9 Gt C/yr in 2010, 3.3 Gt C/yr in 2020, and 5.3 Gt C/yr in 2050. While 75% of the 1990 emissions are attributed to energy use in Annex I countries, only slightly over 50% of global buildings-related emissions are expected to be from Annex I countries by 2050. Energy-efficiency technologies for building equipment like : Improvements in the building envelop (through reducing heat transfer and use of proper building orientation, energy-efficient windows and climate-appropriate building albedo) with paybacks to the consumer of five years or less have the economic potential to reduce CO2 emissions from both residential and commercial buildings of the order of 20% by 2010, 25% by 2020 and up to 40% by 2050. 455
A significant means of reducing GHG emissions in the buildings sector involves more rapid deployment of technologies aimed at reducing energy use in building equipment (appliances, heating and cooling systems, lighting and all plug loads, including office equipment) and reducing heating and cooling energy losses through improvement in building thermal integrity. Other effective methods to reduce emissions include urban design and land-use planning that facilitate lower energy-use patterns. Improving the combustion of solid biofuels or replacing them with a liquid or gaseous fuel are important means for reducing non-CO2 GHG emissions. 15.10
15.11
National Action Plan on Climate Change (NAPCC) :
15.11.1 Principles Maintaining a high growth rate is essential for increasing living standards of the vast majority of people and reducing their vulnerability to the impacts of climate change. In order to achieve a sustainable development path that simultaneously advances economic and environmental objectives, the National Action Plan for Climate Change (NAPCC) will be guided by the following principles: •
Other GHG Mitigation Options :
Protecting the poor and vulnerable sections of society through an inclusive and sustainable development strategy, sensitive to climate change. Achieving national growth objectives through a qualitative change in direction that enhances ecological sustainability, leading to further mitigation of greenhouse gas emissions. Devising efficient and cost-effective strategies for end use Demand Side Management. Deploying appropriate technologies for both adaptation and mitigation of greenhouse gases emissions extensively as well as at an accelerated pace. Engineering new and innovative forms of market, regulatory and voluntary mechanisms to promote sustainable development. Effecting implementation of programmes through unique linkages, including with civil society and local government institutions and through public-private-partnership. Welcoming international cooperation for research, development, sharing and transfer of technologies enabled by additional funding and a global IPR regime that enables technology transfer to developing countries under the UNFCC.
15.10.1 Energy Labeling Programme for Appliances • An energy labeling programme for appliances was launched in 2006 and comparative star-based labeling has been introduced for fluorescent tube-lights, air conditioners, refrigerators, and distribution transformers. The labels provide information about the energy consumption of an appliance and thus enable consumers to make informed decisions. The Bureau of Energy Efficiency (BEE) has made it mandatory for refrigerators and air conditioners to display energy efficiency labels. The standards and labeling programme for manufacturers of electrical appliances is expected to lead to significant savings in electricity.
• • • •
15.10.2 Energy Conservation Building Code An Energy Conservation Building Code (ECBC) was launched by BEE in May 2007, which addresses the design of new large commercial buildings to optimize the energy demand based on their location in different climate zones. Commercial buildings are one of the fastest growing sectors of the Indian economy, reflecting the increasing share of the services sector in the economy. Nearly one hundred buildings are already following the code. Compliance with the code has been incorporated into the mandatory environmental impact assessment requirements for large buildings. It has been estimated that if all the commercial space in India conform to ECBC norms, energy consumption in this sector can be reduced by 3040%. Compliance with ECBC norms is voluntary at present but it is expected to soon become mandatory. 15.10.3 GHG mitigation in Municipal Waste : Though MSW (Municipal Solid Waste) projects are often seen as low-hanging fruits, ideally suitable for early CDM projects, none of the reports investigate this area in great detail. Arguably, the validity of projects generated in this areas is dependent on the absence of legislation mandating the flaring of landfill gas. There is also the possibility, that even in metropolitan areas, waste is not compacted enough to generate the anaerobic conditions needed for optimal methane generation. Methane emissions in India, have their origins mainly from livestock (42%), paddy cultivation (23%) and biomass burning (16%). The attributable 10% emissions, to waste is more easily measureable and thus provides the easiest baseline estimation for CDM projects. The hotspots for methane generation from MSW disposal are above all the metro-districts of Ahmedabad, Bangalore, Chennai, Calcutta, Delhi, and Greater Mumbai (Garg and Shukla 2002).
456
•
15.11.2
Summary of eight National Missions of NAPCC:
There are Eight National Missions, which form the core of the National Action Plan, representing multi-pronged, long-term and integrated strategies for achieving key goals in the context of climate change. While several of these programmes are already part of our current actions, they may need a change in direction, enhancement of scope and effectiveness and accelerated implementation of timebound plans. (i) National Solar Mission India is a tropical country, where sunshine is available for longer hours per day and in great intensity. Solar energy, therefore, has great potential as future energy source. Photovoltaic cells are becoming cheaper with new technology. There are newer, reflector-based technologies that could enable setting up megawatt scale solar power plant across the country. Another aspect of the Solar Mission would be to launch a major R&D programme, to enable the storage of solar power for sustained, long-term use. (ii) National Mission for Enhanced Energy Efficiency The Energy Conservation Act of 2001 provides a legal mandate for the implementation of the energy efficiency measures through the institutional mechanism of the Bureau of Energy Efficiency (BEE) in the Central Government and designated agencies in each state. A number of schemes and programmes have been initiated and it sis anticipated that these would result in a saving of 10000 MW by the end of 11th Five Year Plan in 2012. 457
(iii) National Mission on Sustainable Habitat A National Mission on Sustainable Habitat will be launched to make habitat sustainable through improvements in energy efficiency in buildings, management of solid waste and modal shift ot public transport. The Mission will promote energy efficiency as an integral component of urban planning and urban renewal. In addition, the Mission will address the need to adapt to future climate change by improving the resilience of infrastructure, community based disaster management, and measures for improving the warning system for extreme weather events. Capacity building would be an important component of this Mission. (iv) National Water Mission A National Water Mission will be mounted to ensure integrated water resource management helping to conserve water, minimize wastage and ensure more equitable distribution both across and within states. The Mission will take into account the provisions of the National Water Policy and develop a framework to optimize water use by increasing water use efficiency by 20% through regulatory mechanisms with differential entitlements and pricing. (v) National Mission for sustaining the Himalayan Ecosystem A Mission for sustaining the Himalayan Eco-system will be launched to evolve management measures for sustaining and safeguarding the Himalayan glacier and mountain eco-system. This will require the joint effort of climatoglogists, glaciologists and other experts. We will need to exchange information with the South Asian countries and countries sharing the Himalayan ecology. (vi) National Mission for a Green India A National Mission will be launched to enhance eco-system services including carbon sinks to be called Green India. The Prime Minister has already announced a Green India campaign for the afforestation of 6 million hectares. The national target of area under forest and tree cover is 33% while the current area under forests is 23%. (vii) National Mission for Sustainable Agriculture The Mission would develop strategies to make Indian agriculture more resilient to climate change. It would identify and develop new varieties of crops and especially thermal resistant crops and alternative cropping patterns, capable of withstanding extremes of weather, long dry spells, flooding, and variable moisture availability. (viii) National Mission on Strategic Knowledge for Climate Change To enlist the global community in research and technology development and collaboration through mechanisms including open source platforms, a Strategic Knowledge Mission will be set up to identify the challenges of, and the responses to, climate change. It would ensure funding of high quality and focused research into various aspect of climate change. 15.11.3
Implementation of Missions
Each Mission will be tasked to evolve specific objectives spanning the remaining years of the 11th Plan and the 12th Plan period 2012-13 to 2016-17.
458
Building public awareness will be vital in supporting implementation of the NAPCC. This will be achieved through national portals, media engagement, civil society involvement, curricula reform and recognition / awards. 15.11.4 Institutional Arrangements for Managing Climate Change Agenda In order to respond effectively to the challenge of climate change, the Government has created an Advisory Council on Climate Change, chaired by the Prime Minister. The Council has broad based representation from key stake-holders, including Government, Industry and Civil Society and sets out broad directions for National Actions in respect of Climate Change. The Council will also provide guidance on the domestic agenda and review of the implementation of the National Action Plan on Climate Change including its R&D agenda. The Council would also provide guidance on matters relating to international negotiations including bilateral, multilateral programmes for collaboration, research and development. References 1. 2. 3.
Annual Report of Ministry of Environment & Forest (MoEF), 2007-08, GoI IPCC Technical Paper VI; Climate Change & Water ; June 2008. 'Coal Meeting the Climate Change', Technology to reduce GHG emissions, World Coal Institute. 4. 'National Action Plan on Climate Change'; Prime Ministers' Council on Climate Change; GoI. 5. CDM Implementation in India; The National Strategy Study; MoEF & TERI. 6. 'Energy Use and Carbon Dioxide Emissions in the Steel Sector in Key Developing Countries' by Lynn Price, Dian Phylipsen, Ernst Worrell. 7. GHG Inventory Information ; India's Initial National Communication, GoI. 8. Greenhouse Gas Emissions from India: A perspective; Subodh Sharma, Bhattacharya, Amit Garg, PMC:, MoEF. 9. Report on Working Group on National Action Plan for Operationalising Clean Development Mechanism (CDM); Planning Commission, GoI. 10. Integrated Energy Policy; Planning Commission, GoI. 11. IEA, World Energy Outlook 2007. 12. Report on Working Group on R&D for the Energy Sector, XI Plan; Office of the Principal Scientific Adviser to GoI. 13. Maarland et al., 1999 14. Lynn, Ernst, and Dian 1999 15. NATCOM 2004 16. Report on working group on New & Renewable Energy for XI Plan. 17. IEACCC 2003a 18. Institute of Global Environment Strategies (IGES) 19. Asia Least-Cost Greenhouse Gas Abatement Strategy 20. Websites : http://www.unfccc.com www.iges.or.jp www.carbonyatra.com www.globalwarming.org http://en.wikipedia.org/wiki/UNFCCC http://en.wikipedia.org/wiki/global_warming http://cdm.unfccc.int.statistics/index.html http://cdm.unfccc.int/statistics/registeredprojbyscalepiechart.html http://cdm.unfccc.int.statistics/methodologies/approvemethpiechart.html http://www.physicalgeography.net/fundamentals/7h.html
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Pamphlet
Language
Corporate
Pamphlet Domestic Single page leaflet for Domestic Sector
Quarterly technical journal titled as ‘Active Conservation Techniques’ (ACT)
English
Cooking gas - How to make it last longer.
Corporate profile
English
Good cooking habits (Poster)
Energy booklet for school children (Urban)
English
Industrial
Energy booklet for school children (Rural)
English
Tips for conservation of energy in the industrial sector
Poster on Energy Conservation (Hello Friend)
English/Hindi
Stickers All about oii - Tel ke sambandh main (Poster) English/Hindi Use of Car Pool (Transport) Bio-diesel Stop leakages (Industry) Leaflet on bio-diesel (8 pages)
Hindi
Leaflet on bio-diesel (1 page)
Hindi
Leaflet on bio-diesel (4 pages)
English
Transport
and evaluation/certification of additives)
Booklet for four wheeler vehicles
English
vapour recovery plant for textile industry
Single page leaflet for Transport Sector
English
English English
English
R&D leaflet- Design and development of English/Hindi
English/Hindi
Agriculture English/Hindi
Save diesel - Saving diesel used in lift irrigation pump set - 7 points (Poster)
English
R&D leaflet- Design and development of
English/Hindi used in textile industry
Save diesel - Tips on better maintenance of
Single page leaflet for Agriculture Sector
English
lubricating oil and grease dispensing equipments
Save petrol - Get more kilometres
buses/trucks - 15 points (Poster)
Engish/Hindi
innovative technologies, equipments, appliances
R&D leaflet - Design and development of kerosene
per litre - 14 points (Poster)
Engish/Hindi
R&D booklet (Design/development of
English
Save diesel - Simple tips on better driving of
English
R&D
Booklet on Driver Training Programme
buses/trucks - 6 points (Poster)
Language
English/Hindi
PCRA's low excess air industrial film burner suitable for dual fuel operations and preheated air for combustion
English
Energy efficiency in pulp and paper industry
English
Leaflet on Sona ESV
Hindi
Save fuel in whiteware industry
English
Improving the rural life through...(Energy
Operation and maintenance of tractors - 10 points English/Hindi efficient durable cook stoves for rural areas)
If you wish to order any of the above literature, please write to us at the following address: Additional Director (EC), PCRA, Sanrakshan Bhawan, 10, Bhikaiji Cama Place, New Delhi - 110066
English
