A
Practical Training Taken At
“Kota Super Thermal Power Station”
1
Submitted to the
Rajasthan Technical University, Kota
Training held from (1 June – 30th June, 2012) st
Submitted To: -
Submitted By:-
Mr. Mahesh Sharma
Gaurav Panjwani B.Tech. (3rd year)
Head of Department
Roll no. 09/EPK/ME/015
MAHARISHI ARVIND COLLEGE OF ENGGINERING AND TECHNOLOGY KOTA, (RAJ) INDIA
2
Submitted to the
Rajasthan Technical University, Kota
Training held from (1 June – 30th June, 2012) st
Submitted To: -
Submitted By:-
Mr. Mahesh Sharma
Gaurav Panjwani B.Tech. (3rd year)
Head of Department
Roll no. 09/EPK/ME/015
MAHARISHI ARVIND COLLEGE OF ENGGINERING AND TECHNOLOGY KOTA, (RAJ) INDIA
2
PREFACE The rise in civilization is closely related to improvements in transportation and requi require reme ment nt of energy energy that that is not readi readily ly avail availabl ablee in larg largee quant quantit itie iess but but is also also readi readily ly transportable. A very peculiar fact about electrical energy is that neither it is directly available in nature nor it is directly used finally in this form, yet it is so widely produced and is the most popular high high grade grade energy. The purpose behind training is to understand the difficult concepts in a better way with gain of knowledge. knowledge. Report starts with a brief introduction introduction of KSTPS followed followed by Generator, Generator, Turbine, switch gear, switch yard etc. While writing the report and while I was on my training I was wondering that science is as ever expanding field and the engineers working hard day and night and make the life a gift for us.
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Acknowledgement I express my sincere thanks to my project guide Mr. Sunil Madan Designation, Course Coordinator, for guiding me right form the inception till the successful completion of the summer training. I sincerely acknowledge him for extending their valuable guidance, support for literature, critical reviews of project and the report and above all the moral support he had provided to me with all stages of this report.
I would also like to thank the other supporting staff, for their help and cooperation throughout my summer training. Mahesh Sharma Sharma Sir , HOD, I use this opportunity to express gratitude and debtness to Er. Mahesh
MECHANICAL DEPARTEMENT, MACET, Kota.
Gaurav Panjwani (Name of the Student)
4
Abstract Kota is a rambling city that rests on the banks of the Chambal River and proudly testifies the triumphs of the gallant Rajputs. The city's architectural wonders, manifested by the majestic palaces and crenelated forts are a stunning sight to behold.
The large industrial powerhouses like the Kota Super Thermal Power Plant stand tall in the city and beautifully complement the grandiose heritage edifices. In order to bring about changes that would escalate the prospects of growth and development in the power sector and to enforce the Power Sector Reforms, the Government of Rajasthan set up the Rajasthan Rajya Vidyut Utpadan Nigam Ltd. (RVUN) in accordance with the promulgations promulgations of the Companies Companies Act-1956 Act-1956.. Established Established on 19th 19th July, July, 2000 the commit committee tee is a torchbearer of Rajashthan's power sector. Under its aegis, the Kota Super Thermal Power Station has total installed capacity of 1045 Megawatts. The Kota Super Thermal Power Station has added another feather to its already brimming cap after receiving the Union Ministry's Golden Shield award for four consecutive years spanning from 20002004.
Kota Super Thermal Power Station has reached such dizzying heights of success that its sixth unit was set up on 30th July, 2003. In this unit, maximum capacity on coal firing was attained in less than 10 hours and the phenomenal completion of the project in less than two years is a groundbreaking achievement for the nation. Besides the philanthropic organization also has a social conscience. The organization plants nearly 3.5 lakhs saplings every year, digs up dykes and water bodies and monitors the effusion of effluent materials and ambient air quality in order to check the pollution level.
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Index of Contents Serial No.
Particulars
1.
Indian Power Industry
2.
Profile of thermal industry in
Page No.
Rajasthan. 3.
Introduction to Kota Super Thermal Power Station.
5.
History of thermal power plants.
6.
General definition of thermal power plant.
7.
Operations in a thermal power station.
8.
Main parts of thermal power station.
9.
Other systems
10
Fly ash utilization
11.
SWOT Analysis
12.
Conclusion
13.
References
6
List of Figures
7
FIG. NO. Fig.1 Fig.2 Fig.3 Fig.4 Fig.5 Fig.6 Fig.7 Fig.8 Fig.9 Fig.10 Fig.11 Fig.12 Fig.13 Fig.14 Fig.15 Fig.16 Fig.17 Fig.18 Fig.19 Fig.20 Fig.21 Fig.22 Fig.23
DESCRIPTION Different views of KTPS View of KTPS from Chambal river Block Diagram of Thermal Power Station Operations In Thermal Power Station Main Parts Of Thermal Power station Cooling towers Crossflow and Counterflow cooling towers
PAGE NO.
design Transmission lines Diagram of an electrical system. Modern Steam Turbine Generator. A rotor of a modern steam turbine, used in a power plant Diagram of a typical water-cooled surface condenser A simple control valve Different types of deaerator A Rankine cycle with a two-stage steam turbine and a single feedwater heater. marine-type water tube boiler-see the steam drum at the top and feed drum General view of superheater Components of a centrifugal fan Different Types Of Reheaters The flames resulting from combustion Economiser at KTPS Schematic diagram of air preheater (APH) location. Flue gas stack at KTPS ,kota
List of Tables
8
Table No. Table 1
Description
Page No.
Present Installed capacity of Rajasthan Rajya Vidyut Utpadan Nigam
Table 2
Kota Thermal Power Station installed capacity
Table 3
Awards received by KTPS
List of Abbreviations
1). KSTPS
- Kota Super Thermal Power Station.
2). NTPC
- National Thermal Power Corporation.
3). RVUN
- Rajasthan Vidhut Utpadan Nigam.
4). Ltd.
- Limited
9
5). (BUs)
- Billion Units
6). (SEBs)
- State Electricity Boards
7).TPS
- Thermal power station
8).EMF
- Electro-motive force
9). HRSG
- High recovery steam generator
10). FBA
- Furnace Bottom Ash
11). IBA
- Incinerator bottom ash
12). ESP
- Electrostatic precipitator
13). APH
- Air preheater
14). TBCCW
- Turbine Building Closed Cooling Water
15). RPD
- Rotating-plate design
16). DFT
- Deareating feed tank
17). AC
- Alternating current
18). RAPH
- Regenerative air preheaters
19). HRSGs
- Heat Recovery Steam Generators
20). SWOT
- strength, weakness, opportunity, threat
Indian Power Industry Growth of Power Sector infrastructure in India since its Independence has been noteworthy making India the third largest producer of electricity in Asia. Generating capacity has grown manifold from 1,362 MW in 1947 to 141GW (as on 30.09.2004)... India’s Total 10
installed capacity of power sector has been 141 GW. This India’s 141GW of total power is generated by its three different sectors, i.e., state sector, central sector and private sector.
India has fifth largest generation capacity in the world. India’s transmission and distribution network is of 6.6 million circuit km. This is considered to be third largest in the world. As per above chart, thermal fuels like Coal, gas, oil constitute 64.6% of India’s total installed capacity, followed by 24.7% from hydro power, 2.9% nuclear energy and 7.7% from other energy sources.
Industry Structure
Power sector structure in India has been very simple yet well defined. Majority of Generation, Transmission and Distribution capacities are with either public sector companies or with State Electricity Boards (SEBs). National thermal power corporation, Nuclear Power Corporation, National Hydro Electric Power Corporation are the public sector companies in India which are into power generation. TATA power, Reliance Energy
is domestic private players; Marubeni Corporation is international private players in power sector. public sector is only power generation. Private sector participation is increasing especially in Generation, transmission and Distribution. Distribution licences for several cities are already with the private sector. Three large ultra-mega power projects of 4000MW each have been recently awarded to the private sector on the basis of global tenders.
Profile of Thermal Industry in Rajasthan
Present Installed capacity of Rajasthan Rajya Vidyut Utpadan Nigam is 3847.35 MW
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Power Station
Capacity as on 31.03.09
Present Capacity
Suratgarh TPS
1500 MW
1500 MW
Kota STPS
1045 MW
1045 + 195 MW
Chhabra Super Thermal Power Station
-
250 MW
Ramgarh Gas Power Plant
113.50MW
113.50MW
Mahi Hydel
140 MW
140 MW
MMH Schemes
23.85 MW
23.85 MW
Giral Lignite TPS
250 MW
250 MW
Dholpur CCPP
330 MW
330 MW
Total
3402.35 MW
3847 .35 MW
Rana Pratap Sagar Hydel PS (4X43 MW)
172 MW
Jawahar Sagar Hydel PS (3X33 MW)
99 MW
Total
271 MW
(Table 1)
Introduction to Kota Super Thermal Power Station ` Kota Thermal Power Station is Rajasthan's First major coal power station. Presently it is in operation with installed capacity of 1045MW.And one more unit of 250MW is slated for commissioning in March 2009. Stage Unit No. Capacity(MW)
Synchronising
Cost(Rs. Crore)
12
Date
I
1
110
17.1.1983
143
2
110
13.7.1983
II
3 4
210 210
25.9.1988 1.5.1989
480
III IV V
5 6 7
210 195MW 195MW
26.3.1994 31.7.2003 30.5 2009
480 635 880
(Table 2)
Excellent Performance Kota Thermal Power Station of RVUN is reckoned one of the best, efficient and prestigious power stations of the country. KSTPS has established a record of excellence and has earned meritorious productivity awards from the Ministry of Power, Govt.of India during 1984, 1987, 1989, 1991& every year since 1992-93 onwards. Planned maintenance period reduced to 7% Approx. Expected Power generation during 2007-08 around 90%· Man Power is only 1.4 per MW· Ash Utilisation 80% (Dry fly ash 100%) Environmental Profile Adequate measures have been taken to control pollution and ensure atmospheric emission within
the prescribed limits of Environment (Protection) Act1986.
180 meter high stack have been provided to release flue gases into the atmosphere at an approx. velocity 25m/sec. so as to disperse the emitted particulate matter over a wide spread area. Adequate water spraying arrangements have been provided at coal unloading, transfer and conveying system to arrest and restrict Fugitive Emission. Regular monitoring of Stack Emission,Ambient Air Quality and Trade Effluent is carried out
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Year
Million Units Generated
Plant Load factor (%)
1999-00
6314
84.44
2000-01 2001-02 2002-03 2003-04
6437 6351 6553 6424
86.60 85.30 88.01 86.04
Award Cash award of Rs.8.31.Lacs for productivity and Rs.6.19.Lacs each for saving in specific oil consumption for the years 1999 and 2000, Shields and Bronze medal.
Golden Shield award from Union Ministry of power
(Table 3)
(fig1).
Different views of KSTPS
History of Thermal Power Plants.
Reciprocating steam engines have been used for mechanical power sources since the 18th Century, with notable improvements being made by James Watt. The very first commercial central electrical generating stations in New York and London, in 1882, also used reciprocating steam engines. As generator sizes increased, eventually turbines took over due to higher efficiency and lower cost of construction. By the 1920s any central station larger than a few thousand kilowatts would use a turbine prime mover.
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(Fig.2) View of KTPS from Chambal River
Definition of Thermal Power Station
A thermal power station is a power plant in which the prime mover is steam driven. Water is heated, turns into steam and spins a steam turbine which either drives an electrical generator or does some other work, like ship propulsion. After it passes through the turbine, the steam is condensed in a condenser and recycled to where it was heated; this is known as a Rankine cycle. The greatest variation in the design of thermal power stations is due to the different fuel sources. Some prefer to use the term energy center because such facilities convert forms of heat energy into electrical energy.
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(Fig.3)
Block Diagram of Thermal Power Station
Operations in Thermal Power Station
Step wise operations in a thermal power plant are as follows:1).Coal is used as a fuel to boil the water. 2).Water is boiled to form pressurized steam. 3).Pressurised steam is the force that causes the turbine to rotate at a very high speed. 4).Low pressure steam after pushing through the turbine, it’s going into the condenser. 5).Condenser – the place where the steam is condensed back ti its liquid form .Then the process is repeated.
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(Fig 4.) Operations in Thermal Power Station
Main Parts of Thermal Power station
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(Fig. 5) Main Parts of Thermal Power station
1).
Cooling Tower
1. Cooling tower
9. Steam Control valve
2. Cooling water pump
10. Deaerator
3. Transmission line (3-phase)
11. Feedwater heater
4. Step-up transformer (3-phase) 5. Electrical generator (3-phase) 6. Low,intermediate,high pressure steam
12. Coal hopper 13. Coal pulverizer 14. Boiler & steam
turbine 7. Condensate pump 8. Surface condenser
17. Forced,induced draught (draft) fan 18. Reheater 19. Combustion air intake 20. Economiser 21. Air preheater
22. Precipitator drum 15. Bottom ash hopper 23. Flue gas stack 16. superheater
Cooling towers are heat removal devices used to transfer process waste heat to
the atmosphere. Cooling towers may either use the evaporation of water to remove process heat and cool the working fluid to near the wet-bulb air temperature or rely solely on air to cool the working fluid to near the dry-bulb air temperature. Common applications include
18
cooling the circulating water used in oil refineries, chemical plants, power stations and building cooling. The towers vary in size from small roof-top units to very large hyperboloid structures (as in Image 1) that can be up to 200 metres tall and 100 metres in diameter, or rectangular structures (as in Image 2) that can be over 40 metres tall and 80 metres long. Smaller towers are normally factory-built, while larger ones are constructed on site.
(Fig. 6)
cooling towers
Classification of cooling towers
- Crossflow Crossflow is a design in which the air flow is directed perpendicular to the water flow (see diagram below). Air flow enters one or more vertical faces of the cooling tower to meet the fill material. Water flows (perpendicular to the air) through the fill by gravity. The air continues through the fill and thus past the water flow into an open plenum area. A distribution or hot water basin consisting of a deep pan with holes or nozzles in the bottom is utilized in a crossflow tower. Gravity distributes the water through the nozzles uniformly across the fill material.
- Counterflow In a counterflow design the air flow is directly opposite of the water flow (see diagram below). Air flow first enters an open area beneath the fill media and is then drawn up vertically. The water is sprayed through pressurized nozzles and flows downward through the fill, opposite to the air flow.
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(Fig 7.) Crossflow and Counterflow cooling towers design
iii). Cooling tower as a flue gas stack At some modern power stations, equipped with flue gas purification like Kota Super Thermal Power Station the cooling tower is used as a flue gas stack (industrial chimney). At plants without flue gas purification, this causes problems with corrosion.
Cooling Water Pump
2).
•
In power plants, water cooling systems are typically used for removing heat (cooling). These water cooling systems are, in turn, then cooled by the ultimate cooling system river, lake, sea, or ocean water
•
These cooling water systems have separate subsystems, each with: one or more pumps for circulating fluid through the watercooling systems one heat exchanger to
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transfer heat to the Ultimate water Cooling System an automatic valve to regulate the heat removed from the Component Cooling system to the Ultimate cooling system. There is usually a shared tank, called a surge tank, for the redundant subsystems is used as a makeup supply if there is not enough water in the system, or to handle the surge (increase in level) if there is too much water in the system. Turbine Building Closed Cooling Water Systems The Turbine Building Closed Cooling Water (TBCCW) Systems cool heat exchangers for:
1. Feedwater Pump Seal Water 2. Condensate Pump Seal Water 3. Heater Drain Pump Seal Wate
3).
Electric Power Transmission
Electric power transmission is the bulk transfer of electrical energy, a process in the
delivery of electricity to consumers. A power transmission network typically Connects power plants to multiple substations near a populated area. The wiring from substations to customers is referred to as electricity distribution, following the historic
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business
model
separating
the
wholesale electricity
transmission
business
from distributors who deliver the electricity to the homes. [1] Electric power transmission allows distant energy sources (such as hydroelectric power plants) to be connected to consumers in population centers, and may allow exploitation of low-grade fuel resources such as coal that would otherwise be too costly to transport to generating facilities.
(Fig 8) Transmission lines
Transmission lines;-
Usually transmission lines use three phase alternating current (AC). Single phase AC current is sometimes used in a railway electrification system.High-voltage direct current systems are used for long distance transmission, or some undersea cables, or for connecting two different ac networks. Electricity is transmitted at high voltages (110 kV or above) to reduce the energy lost in transmission. Power is usually transmitted as alternating current through overhead power lines. Underground power transmission is used only in densely populated areas because of its higher cost of installation and maintenance when compared with overhead wires, and the difficulty of voltage control on long cables.
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(Fig.9) Diagram of an electrical system.
i). Overhead transmission:Overhead conductors are not covered by insulation. The conductor material is nearly always an aluminium alloy, made into several strands and possibly reinforced with steel strands. Copper was sometimes used for overhead transmission but aluminium is lower in weight for equivalent performance, and much lower in cost. Overhead conductors are a commodity supplied by several companies worldwide. Improved conductor material and shapes are regularly used to allow increased capacity and modernize transmission circuits. Thicker wires would lead to a relatively small increase in capacity due to the skin effect that causes most of the current to flow close to the surface of the wire.
ii). Underground transmission:Electric power can also be transmitted by underground power cables instead of overhead power lines. They can assist the transmission of power across.Densely populated urban Areas where land is unavailable or planning consent is difficult Rivers and other natural obstacles Land with outstanding natural or environmental heritage Areas of significant or prestigious infrastructural development Land whose value must be maintained for future urban expansion and rural development
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4).
Transformer
A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core, and thus a varying magnetic field through the secondar y winding. This varying magnetic field induces a varying electromotive force (EMF) or "voltage" in the secondary winding. This effect is called mutual induction. Transformers can be classified in different ways: •
By power capacity: from a fraction of a volt-ampere (VA) to over a thousand MVA;
•
By frequency range: power-, audio-, or radio frequency;
•
By voltage class: from a few volts to hundreds of kilovolts;
•
By cooling type: air cooled, oil filled, fan cooled, or water cooled;
•
By application: such as power supply, impedance matching, output voltage and current stabilizer, or circuit isolation;
•
By end purpose: distribution, rectifier , arc furnace, amplifier output;
•
By winding turns ratio: step-up, step-down, isolating (equal or near-equal ratio), variable.
5).
Electrical Generator 24
In electricity generation, an electrical generator is a device that converts mechanical energy to electrical energy, generally using electromagnetic induction. The reverse conversion of electrical energy into mechanical energy is done by a motor ; motors and generators have many similarities. A generator forces electric charges to move through an external electrical circuit, but it does not create electricity or charge, which is already present in the wire of its windings. It is somewhat analogous to a water pump, which creates a flow of water but does not create the water inside. Thesource of mechanical energy may be a reciprocating or turbine steam engine, water falling through a turbine or waterwheel, an internal combustion engine, a wind turbine, a hand crank , compressed air or any other source of mechanical energy.
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(Fig.10)
Steam Turbine Generator.
6).
A steam
Steam Turbine
turbine is
a
mechanical
device
that
extracts thermal
energy from
pressurized steam, and converts it into rotary motion. It has
almost completely
replaced
the reciprocating piston steam
engine(invented
by Thomas Newcomen and greatly improved by James Watt) primarily because of its greater thermal efficiency and higher power-to-weight ratio. Because the turbine
26
generates rotary motion, it is particularly suited to be used to drive an electrical generator about 80% of all electricity generation in the world is by use of steam turbines. The steam turbine is a form of heat engine that derives much of its improvement inthermodynamic efficiency through the use of multiple stages in the expansion of the steam, which results in a closer approach to the idealreversible process.
(Fig.11) A rotor of a modern steam turbine, used in a power plant
Types of turbines
a). Impulse turbines An impulse turbine has fixed nozzles that orient the steam flow into high speed jets. These jets contain significant kinetic energy, which the rotor blades, shaped like buckets, convert into shaft rotation as the steam jet changes direction. A pressure drop occurs across only the stationary blades, with a net increase in steam velocity across the stage. As the steam flows through the nozzle its pressure falls from inlet pressure to the exit pressure (atmospheric pressure, or more usually, the condenser vacuum). Due to this higher ratio of expansion of steam in the nozzle the steam leaves the nozzle with a very high velocity. The steam leaving the moving blades is a large portion of the maximum velocity of the steam when leaving the nozzle. The loss of energy due to this higher exit velocity is commonly called the "carry over velocity”.
b). Reaction turbines
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In the reaction turbine, the rotor blades themselves are arranged to form convergent nozzles. This type of turbine makes use of the reaction force produced as the steam accelerates through the nozzles formed by the rotor. Steam is directed onto the rotor by the fixed vanes of the stator. It leaves the stator as a jet that fills the entire circumference of the rotor. The steam then changes direction and increases its speed relative to the speed of the blades. A pressure drop occurs across both the stator and the rotor, with steam accelerating through the stator and decelerating through the rotor, with no net change in steam velocity across the stage but with a decrease in both pressure and temperature, reflecting the work performed in the driving of the rotor.
Types
Steam turbines are made in a variety of sizes ranging from small 1 hp (0.75 kW) units (rare) used as mechanical drives for pumps, compressors and other shaft driven equipment, to 2,000,000 hp (1,500,000 kW) turbines used to generate electricity. There are several classifications for modern steam turbines.
7).
Condensate Pump
A condensate pump is a specific type of pump used to pump the condensate (water ) produced in an HVAC (heating or cooling),refrigeration, condensing boiler furnace or steam system. They may be used to pump the condensate produced from latent water vapor in any of the following gas mixtures: -
conditioned (cooled or heated) building air
-
refrigerated air in cooling and freezing systems
-
Steam in heat exchangers and radiators
-
the exhaust stream of very-high-efficiency furnaces
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Construction and operation
Condensate pumps as used in hydro systems are usually electrically powered centrifugal pumps. As used in homes and individual heat exchangers, they are often small and rated at a fraction of a horsepower , but in commercial applications they range in size up to many horsepower and the electric motor are usually separated from the pump body by some form of mechanical coupling. Large industrial pumps may also serve as the feedwater pump for returning the condensate under pressure to a boiler. Condensate pumps usually run intermittently and have a tank in which condensate can accumulate. Eventually, the accumulating liquid raises afloat switch energizing the pump. The pump then runs until the level of liquid in the tank is substantially lowered. Some pumps contain a two-stage switch. As liquid rises to the trigger point of the first stage, the pump is activated. If the liquid continues to rise (perhaps because the pump has failed or its discharge is blocked), the second stage will be triggered. This stage may switch off the HVAC equipment (preventing the production of further condensate); trigger an alarm, or both.
8).
Surface Condenser
i). Purpose In thermal power plants, the primary purpose of a surface condenser is to condense the exhaust steam from a steam turbine to obtain maximum efficiency and also to convert the turbine exhaust steam into pure water (referred to as steam condensate) so that it may be reused in the steam generator or boiler as boiler feed water.
ii). Diagram of water-cooled surface condenser
29
(Fig 12) Diagram of a typical water-cooled surface condenser
The surface condenser is a shell and tube heat exchanger in which cooling water is circulated through the tubes. The exhaust steam from the low pressure turbine enters the shell where it is cooled and converted to condensate (water) by flowing over the tubes.
Such condensers use steam ejectors or rotary motor-driven exhausters for continuous removal of air and gases from the steam side to maintain vacuum. For best efficiency, the temperature in the condenser must be kept as low as practical in order to achieve the lowest possible pressure in the condensing steam. Since the condenser temperature can almost always be kept significantly below 100 oC where the vapor pressure of water is much less than atmospheric pressure, the condenser generally works under vacuum.
9).
Steam Control Valves
Control valves are valves used to control conditions such as flow, pressure, temperature,
and liquid level by fully or partially opening or closing in response to signals received from controllers that compare a "set point" to a "process variable" whose value is provided by sensors that monitor changes in such conditions. [1] The opening or closing of control valves is done by means of electrical, hydraulic or pneumatic systems. Petitioners are used to control the opening or closing of the actuator based on Electric, or Pneumatic Signals. These control signals, traditionally
30
based on 3-15psi (0.2-1.0bar), more common now are 4-20mA signals for industry, 0-10V for HVAC systems, & the introduction of "Smart" systems, HART, Field bus Foundation, & Prefabs being the more common protocols.
(Fig 13) A simple control valve
10).
Deaerator
A Deaerator is a device that is widely used for the removal of air and other dissolved gases from
the
feedwater
to
steam-generating boilers.
In
particular,
dissolved oxygen in boiler feed waters will cause serious corrosion damage in steam systems by attaching to the walls of metal piping and other metallic equipment and forming oxides (rust). It also combines with any dissolved carbon dioxide to form carbonic acid that causes further corrosion. Most Deaerator is designed to remove oxygen down to levels of 7 ppb by weight (0.0005 cm³/L) or less.
31
There are two basic types of deaerators, the tray-type and the spray-type: The tray-type (also called the cascade-type) includes a vertical domed deaeration section mounted on top of a horizontal cylindrical vessel which serves as the deaerated boiler feedwater storage tank. The spray-type consists only of a horizontal (or vertical) cylindrical vessel which serves as both the deaeration section and the boiler feedwater storage tank.
a). Tray-type deaerator
b). Spray-type deaerator
(Fig 14)
11).
Different types of deaerator
Feedwater Heater
32
(Fig. 15) A Rankine cycle with a two-stage steam turbine and a single feedwater heater.
A feedwater heater is a power plant component used to pre-heat water delivered to a steam generating boiler . Preheating the feedwater reduces the irreversibility’s involved in steam generation and therefore improves the thermodynamic efficiency of the system. [4] This reduces plant operating costs and also helps to avoid thermal shock to the boiler metal when the feedwater is introduced back into the steam cycle. In a steam power plant (usually modeled as a modified Rankine cycle), feedwater heaters allow the feedwater to be brought up to the saturation temperature very gradually. This minimizes the inevitable irreversibility’s associated with heat transfer to the working fluid (water). See the article on the Second Law of Thermodynamics for a further discussion of such irreversibility’s.
33
i). Cycle discussion and explanation
It should be noted that the energy used to heat the feedwater is usually derived from steam extracted between the stages of the steam turbine. Therefore, the steam that would be used to perform expansion work in the turbine (and therefore generate power) is not utilized for that purpose. The percentage of the total cycle steam mass flow used for the feedwater heater is termed the extraction fraction [4] and must be carefully optimized for maximum power plant thermal efficiency since increasing this fraction causes a decrease in turbine power output. Feedwater heaters can also be open and closed heat exchangers. An open feedwater heater is merely a direct-contact heat exchanger in which extracted steam is allowed to mix with the feedwater. This kind of heater will normally require a feed pump at both the feed inlet and outlet since the pressure in the heater is between the boiler pressure and the condenser pressure. A deaerator is a special case of the open feedwater heater which is specifically designed to remove non-condensable gases from the feedwater. Closed feedwater heaters are typically exchangers where the feedwater passes throughout the tubes and is heated by turbine extraction steam. These do not require separate pumps before and after the heater to boost the feedwater to the pressure of the extracted steam as with an open heater.
Feedwater heaters are used in both fossil- and nuclear-fueled power plants. Smaller versions have also been installed on locomotives, portable andstationary engines. An economiser serves a similar purpose to a feedwater heater, but is technically different. Instead of using actual cycle steam for heating, it uses the lowest-temperature flue gas from the furnace (and therefore does not apply to nuclear plants) to heat the water before it enters the boiler proper. This allows for the heat transfer between the furnace and the feedwater occurring across a smaller average temperature gradient (for the steam generator as a whole). System efficiency is therefore further increased when viewed with respect to actual energy content of the fuel.
12).
Coal Hopper
34
Coal is
a
readily combustible black
or
brownish-black sedimentary
rock normally
occurring in rock strata in layers or veins called coal beds. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure. It is composed primarily of carbon along with variable quantities of other elements, chiefly sulfur, hydrogen, oxygen and nitrogen.
•
Peat, considered to be a precursor of coal, has industrial importance as a fuel in some regions, for example, Ireland and Finland.
•
Lignite, also referred to as brown coal, is the lowest rank of coal and used almost exclusively as fuel for electric power generation. Jet is a compact form of lignite that is sometimes polished and has been used as an ornamental stone since the Iron Age.
•
Sub-bituminous coal, whose properties range from those of lignite to those of bituminous coal are used primarily as fuel for steam-electric power generation. Additionally, it is an important source of light aromatic hydrocarbons for the chemical synthesis industry.
•
Bituminous coal, dense mineral, black but sometimes dark brown, often with welldefined bands of bright and dull material, used primarily as fuel in steam-electric power generation, with substantial quantities also used for heat and power applications in manufacturing and to make coke.
•
Anthracite, the highest rank; a harder, glossy, black coal used primarily for residential and commercial space heating. It may be divided further into metamorphically altered bituminous coal and petrified oil , as from the deposits in Pennsylvania.
•
Graphite, technically the highest rank, but difficult to ignite and is not so commonly used as fuel: it is mostly used in pencils and, when powdered, as a lubricant
Coal is primarily used as a solid fuel to produce electricity and heat through combustion. World coal consumption was about 6,743,786,000 short tons in 2006 and is expected to increase 48% to 9.98 billion short tons by 2030. China produced 2.38 billion tons in
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2006. India produced about 447.3 million tons in 2006. 68.7% of China's electricity comes from coal. The USA consumes about 14% of the world total, using 90% of it for generation of electricity. Fuel processing
Coal is prepared for use by crushing the rough coal to pieces less than 2 inches (5 cm) in size. The coal is then transported from the storage yard to in-plant storage silos by rubberized conveyor belts at rates up to 4,000 tons/hour. In plants that burn pulverized coal, silos feed coal pulverizers (coal mills) that take the larger 2-inch pieces, grind them to the consistency of face powder , sort them, and mix them with primary combustion air which transports the coal to the furnace and preheats the coal to drive off excess moisture content. A 500 MWe plant will have six such pulverizers, five of which can supply coal to the furnace at 250 tons per hour under full load. In plants that do not burn pulverized coal, the larger 2-inch pieces may be directly fed into the silos which then feed the cyclone burners, a specific kind of combustor that can efficiently burn larger pieces of fuel.
13).
Coal Pulverizer
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A pulverizer is a mechanical device for the grinding of many different types of materials. For
example,
they
are
used
to
pulverize coal for
combustion in
the
steam-
generating furnaces of fossil fuel power plants.
Types of pulverizers
- Ball and tube mills A ball mill is a pulverizer that consists of a horizontal rotating cylinder, up to three diameters in length, containing a charge of tumbling or cascading steel balls, pebbles, or rods. A tube mill is a revolving cylinder of up to five diameters in length used for fine pulverization of ore, rock, and other such materials; the material, mixed with water, is fed into the chamber from one end, and passes out the other end as slime. - Ring and ball mill This type of mill consists of two rings separated by a series of large balls. The lower ring rotates, while the upper ring presses down on the balls via a set of spring and adjuster assemblies. The material to be pulverized is introduced into the center or side of the pulverizer (depending on the design) and is ground as the lower ring rotates causing the balls to orbit between the upper and lower rings. - Demolition pulverizer An attachment fitted to an excavator. Commonly used in demolition work to break up large pieces of concrete.
14).
Boiler and Boiler Steam Drum
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A boiler is an enclosed vessel that provides a means for combustion heat to be transferred into water until it becomes heated water or steam. The hot water or steam under pressure is then usable for transferring the heat to a process. Water is a useful and cheap medium for transferring heat to a process. When water is boiled into steam its volume increases about 1,600 times, producing a force that is almost as explosive as gunpowder. This causes the boiler to be extremely dangerous equipment that must be treated with utmost care.
Boiler operation
The boiler is a rectangular furnace about 50 feet (15 m) on a side and 130 feet (40 m) tall. Its walls are made of a web of high pressure steel tubes about 2.3 inches (60 mm) in diameter. Pulverized coal is air-blown into the furnace from fuel nozzles at the four corners and it rapidly burns, forming a large fireball at the center. The thermal radiation of the fireball heats the water that circulates through the boiler tubes near the boiler perimeter. The water circulation rate in the boiler is three to four times the throughput and is typically driven by pumps. As the water in the boiler circulates it absorbs heat and changes into steam at 700 °F (370 °C) and 3,200 psi (22 MPa). It is separated from the water inside a drum at the top of the furnace. The saturated steam is introduced into superheat pendant tubes that hang in the hottest part of the combustion gases as they exit the furnace. Here the steam is superheated to 1,000 °F (540 °C) to prepare it for the turbine. Plants that use gas turbines to heat the water for conversion into steam use boilers known as HRSGs, Heat Recovery Steam Generators. The exhaust heat from the gas turbines is used to make superheated steam that is then used in a conventional water-steam generation cycle, as described in Gas turbine combined-cycle plants section below
The water supplied to the boiler that is converted into steam is called feed water. There are virtually infinite numbers of boiler designs but generally they fit into one of two categories:
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1. Fire tube or "fire in tube" boilers; contain long steel tubes through which the hot gasses from a furnace pass and around which the water to be converted to steam circulates. Fire tube boilers, typically have a lower initial cost, are more fuel efficient and easier to operate, but they are limited generally to capacities of 25 tons/hr and pressures of 17.5 Kg/cm 2. Water tube or "water in tube" boilers in which the conditions are reversed with the water passing through the tubes and the hot gasses passing outside the tubes. These boilers can be of single- or multipledrum type. These boilers can be built to any steam capacities and pressures, and have higher efficiencies than fire tube boilers.
Steam drums are a regular feature of water tube boilers. It is a reservoir of water/steam at
the top end of the water tubes in the water-tube boiler . They store the steam generated in the water tubes and act as a phase separator. The difference in densities between hot and cold water helps in the accumulation of the "hotter"-water/and saturated-steam into the steam-drum.
(Fig 16) marine-type water tube boiler-see the steam drum at the top and feed drum
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15).
Bottom Ash Hopper
Bottom ash refers to the non-combustible constituents of coal with traces of combustibles
embedded in forming clinkers and sticking to hot side walls of a coal-burning furnace during its operation. The portion of the ash that escapes up the chimney or stack is, however, referred to as fly ash. The clinkers fall by themselves into the water or sometimes by poking manually, and get cooled. The clinker lumps get crushed to small sizes by clinker grinders mounted under water and fall down into a trough from where a water ejector takes them out to a sump. From there it is pumped out by suitable rotary pumps to dumping yard far away. In another arrangement a continuous link chain scrapes out the clinkers from under water and feeds them to clinker grinders outside the bottom ash hopper.
Bottom ash may be used as an aggregate in road construction and concrete, where it is known as furnace bottom ash (FBA), to distinguish it from incinerator bottom ash (IBA), the non-combustible elements remaining after incineration. It was also used in the making of the concrete blocks used to construct many high-rise flats in London in the 1960s
16).
Superheater
A super heater is a device in a steam engine that heats the steam generated by the boiler again, increasing its thermal energy and decreasing the likelihood that it will condense inside the engine. Super heaters increase the efficiency of the steam engine, and were widely adopted. Steam which has been superheated is logically known as superheated steam; non-superheated steam
40
is called saturated steam or wet steam.
Super heaters were applied to steam locomotives in quantity from the early 20th century, to most steam vehicles, and to stationary steam engines including power stations.
(Fig. 17) General view of superheater
17).
Centrifugal Fan
A centrifugal fan (also squirrel-cage fan, as it looks like a hamster wheel) i s a mechanical device for moving air or gases. It has a fan wheel composed of a number of fan blades, or ribs, mounted around a hub. As shown in Figure 1, the hub turns on a driveshaft that passes through the fan housing. The gas enters from the side of the
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fan wheel, turns 90 degrees and accelerates due to centrifugal force as it flows over the fan blades and exits the fan housing. [1]
(Fig 18): Components of a centrifugal fan
Centrifugal fans can generate pressure rises in the gas stream. Accordingly, they are wellsuited for industrial processes and air pollution control systems. They are also common in central heating/cooling systems. a) Fan components
The major components of a typical centrifugal fan include the fan wheel, fan housing, drive mechanism, and inlet and/or outlet dampers. b). Fan dampers
Fan dampers are used to control gas flow into and out of the centrifugal fan. They may be installed on the inlet side or on the outlet side of the fan, or both. Dampers on the outlet side impose a flow resistance that is used to control gas flow. Dampers on the inlet side are designed to control gas flow and to change how the gas enters the fan wheel.Inlet dampers reduce fan energy usage due to their ability to affect the airflow pattern into the fan.
18).
Reheater
Power plant furnaces may have a reheater section containing tubes heated by hot flue gases outside the tubes. Exhaust steam from the high pressure turbine is rerouted to go inside the reheater tubes to pickup more energy to go drive intermediate or lower pressure turbines.
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(Fig 19). Different Types of Reheaters
19).
Combustion
Combustion or burning is a complex sequence of exothermic chemical reactions between
a fuel (usually hydrocarbon) and an oxidant accompanied by the production of heat or both heat and light in the form of either a glow or flames, appearance of light flickering.
43
(Fig. 20)The flames resulting from combustion
Direct combustion by atmospheric oxygen is a reaction mediated by radical intermediates. The conditions for radical production are naturally produced by thermal runaway, where the heat generated by combustion is necessary to maintain the high temperature necessary for radical production. In a complete combustion reaction, a compound reacts with an oxidizing element, such as oxygen or fluorine, and the products are compounds of each element in the fuel with the oxidizing element. For example: CH4 + 2O2 → CO2 + 2H2O CH2S + 6F2 → CF4 + 2HF + SF6 A simpler example can be seen in the combustion of hydrogen and oxygen, which is a commonly used reaction in rocket engines: 2H2 + O2 → 2H2O (g) + heat The result is water vapor. In the large majority of real-world uses of combustion, air is the source of oxygen (O2). In air, each kg (lab) of oxygen is mixed with approximately 3.76 kg (lbm) of nitrogen. The resultant flue gas from the combustion will contain nitrogen: CH4 + 2O2 + 7.52N2 → CO2 + 2H2O + 7.52N2 + heat When air is the source of the oxygen, nitrogen is by far the largest part of the resultant flue gas.
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In reality, combustion processes are never perfect or complete. In flue gases from combustion of carbon (as in coal combustion) or carbon compounds (as in combustion of hydrocarbons, wood etc.) both unburned carbon (as soot) and carbon compounds (CO and others) will be present. Also, when air is the oxidant, some nitrogen can be oxidized to various nitrogen oxides (NOx).
20).
Economizer
Economizers, or in British English economisers, are mechanical devices intended to
reduce energy consumption, or to perform another useful function like preheating a fluid. The term economizer is used for other purposes as well. Boiler, powerplant, and heating,
45
ventilating, and air-conditioning (HVAC) uses are discussed in this article. In simple terms, an economizer is a heat exchanger.
i). Powerplant
Economizers are commonly used as part of a heat recovery steam generator in a combined cycle power plant. In an HRSG, water passes through an economizer, then a boiler and then a superheater . The economizer also prevents flooding of the boiler with liquid water that is too cold to be boiled given the flow rates and design of the boiler. A common application of economizers in steam powerplant is to capture the waste heat from boiler stack gases (flue gas) and transfer it to the boiler feedwater. This raises the temperature of the boiler feedwater thus lowering the needed energy input, in turn reducing the firing rates to accomplish the rated boiler output. Economizers lower stack temperatures which may cause condensation of acidic combustion gases and serious equipment corrosion damage if care is not taken in their design and material selection.
(Fig 21): Economizer at KSTPS
21).
Air Preheater
An air preheater (APH) is a general term to describe any device designed to heat air before another process (for example, combustion in a boiler ) with the primary objective of increasing the thermal efficiency of the process. They may be used alone or to replace a recuperative heat system or to replace a steam coil. 46
In particular, this article describes the combustion air preheaters used in large boilers found in thermal power stations producing power from e.g. fossil fuels, biomasses or waste.
(Fig. 22) Schematic diagram of air preheater (APH) location.
The purpose of the air preheater is to recover the heat from the boiler flue gas which increases the thermal efficiency of the boiler by reducing the useful heat lost in the flue gas. As a consequence, the flue gases are also sent to the flue gas stack (or chimney) at a lower temperature, allowing simplified design of the ducting and the flue gas stack. It also allows control over the temperature of gases leaving the stack (to meet emissions regulations, for example).
22).
Electrostatic Precipitator
An electrostatic precipitator (ESP), or electrostatic air cleaner is particulate collection device that removes particles from a flowing gas (such as air) using the force of an induced electrostatic charge. Electrostatic precipitators are highly efficient filtration devices that minimally impede the flow of gases through the device, and
47
can easily remove fine particulate matter such as dust and smoke from the air stream. [1] . In contrast to wet scrubbers which apply energy directly to the flowing fluid medium, an ESP applies energy only to the particulate matter being collected and therefore is very efficient in its consumption of energy (in the form of electricity).
i). Modern industrial electrostatic precipitators
ESOPs continue to be excellent devices for control of many industrial particulate emissions, including smoke from electricity-generating utilities (coal and oil fired), salt cake collection from black liquor boilers in pulp mills, and catalyst collection from fluidized bed catalytic cracker units in oil refineries to name a few. These devices treat gas volumes from several hundred thousand ACFM to 2.5 million ACFM (1,180 m³/s) in the largest coal-fired boiler applications. For a coal-fired boiler the collection is usually performed downstream of the air preheater at about 320 dig’s which provides optimal resistively of the coal-ash particles.. The original parallel plate-weighted wire design (described above) has evolved as more efficient (and robust) discharge electrode designs were developed, today focusing on rigid (pipe-frame) discharge electrodes to which many sharpened spikes are attached (barbed wire), maximizing corona production. Modern controls, such as an automatic voltage control, minimize sparking and prevent arcing (sparks are quenched within 1/2 cycle of the TR set), avoiding damage to the components.
48
49
23).
Flue gas stack
A flue gas stack is a type of chimney, a vertical pipe, channel or similar structure through which combustion product gases called flue gases are exhausted to the outside air. Flue gases are produced when coal, oil,natural gas, wood or any other fuel is combusted in an industrial furnace, a power plant's steam-generating boiler , or other large combustion device. Flue gas is usually composed of carbon dioxide (CO2) and water vapor as well as nitrogen and excess oxygen remaining from the intake combustion air. It also contains a small percentage of pollutants such as particulate matter , carbon monoxide, nitrogen oxides and sulfur oxides. The flue gas stacks are often quite tall, up to 400 meters (1300 feet) or more, so as to disperse the exhaust pollutants over a greater area and thereby reduce theconcentration of the pollutants to the levels required by governmental environmental policy and environmental regulation.
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(Fig. 23)
When the flue gases are exhausted from stoves, ovens, fireplaces, or other small sources within residential abodes, restaurants, hotels, or other public buildings and small commercial enterprises, their flue gas stacks are referred to as chimneys.
i).Stack design
Designing chimneys and stacks to provide the correct amount of natural draft involves a great many factors such as: 1. The height and diameter of the stack.
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2. The desired amount of excess combustion air needed to assure complete combustion. 3. The temperature of the flue gases leaving the combustion zone. 4. The composition of the combustion flue gas, which determines the flue gasdensity. 5. The frictional resistance to the flow of the flue gases through the chimney or stack, which will vary with the materials used to construct the chimney or stack. 6. The heat loss from the flue gases as they flow through the chimney or stack. 7. The local atmospheric pressure of the ambient air, which is determined by the local elevation above sea level.
Other Systems (1). Monitoring and alarm system
Most of the power plant operational controls are automatic. However, at times, manual intervention may be required. Thus, the plant is provided with monitors and alarm systems that alert the plant operators when certain operating parameters are seriously deviating from their normal range. (2). Battery supplied emergency lighting and communication
A central battery system consisting of lead acid cell units is provided to supply emergency electric power, when needed, to essential items such as the power plant's control systems,
52
communication systems, turbine lube oil pumps, and emergency lighting. This is essential for a safe, damage-free shutdown of the units in an emergency situation. (3). Transport of coal fuel to site and to storage
Most thermal stations use coal as the main fuel. Raw coal is transported from coal mines to a power station site by trucks, barges, bulk cargo ships or railway cars. Generally, when shipped by railways, the coal cars are sent as a full train of cars. The coal received at site may be of different sizes. The railway cars are unloaded at site by rotary dumpers or side tilt dumpers to tip over onto conveyor belts below. The coal is generally conveyed to crushers which crush the coal to about ¾ inch (6 mm) size. The crushed coal is then sent by belt conveyors to a storage pile. Normally, the crushed coal is compacted by bulldozers, as compacting of highly volatile coal avoids spontaneous ignition. The crushed coal is conveyed from the storage pile to silos or hoppers at the boilers by another belt conveyor system.
Fly Ash Utilization FLY ASH UTILIZATION AT KSTPS :-
• Concerted efforts have been made towards encouraging entrepreneurs for utilizing the ash generated at Kota Thermal Power Station. 100% fly ash utilization is expected upto March, 2009. The ash is being provided free of cost to various Cement Industries and brick kiln owners and other Industrialists. Pond Ash which was stored during earlier years has also been utilized in road works. The ash utilization at Kota TPS is highest in the Country. • For achieving 100% Dry Fly Ash utilization KTPS has signed agreements with Cement manufacturing companies with dedicated unit allocations. The complete Dry Fly Ash evacuation system from each unit in 2 phases i.e. from ESP to intermediate silo to main supplying silo near KTPS boundary has
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been erected, tested, commissioned and operated by the respective Cement companies at their own cost. • KOTA THERMAL POWER STATION ACHIEVED 98.48% DRY FLY ASH UTILIZATION DURING 2007-08
DRY FLY ASH UTILIZATION- ADVANTAGES
1. Minimum land requirement for ash storage. 2. Minimum water requirement for conveying of ash. 3. High ash storage density. 4. ECO friendly – less airborne / water pollution. 5. Reduction in Auxiliary Power Consumption 6.100% fly ash utilization prospects.
SWOT Analysis "SWOT" is an acronym which represents "Strengths", "Weaknesses", "Opportunities",
and "Threats". Note that a company's "Strengths" and its "Weaknesses" (its "flaws") are obviously internal considerations. . In "Weaknesses", list any weaknesses along the value chain of venture that must be strengthened to ensure success. Note that a company's "Opportunities" and "Threats" in a company's operating environment are clearly external considerations. Equally obvious is the fact that "Strengths" and "Opportunities" are both positive considerations. "Weaknesses" and "Threats" are both negative considerations. To express these relationships, it can be helpful to think of these factors in a 2 × 2 matrix In order to do effective strategic planning, there are specific ways that this information can be used by the company. In general, it is clear that the company should attempt
to build its Strengths
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to reverse (or disguise) its Weaknesses
to maximize the response to its Opportunities, and
to overcome its Threats.
Strengths • •
• •
It has the largest electricity generation capacity in Rajasthan Transmission & Distribution network of 1.1 million circuit km - the largest in Rajasthan Potential for growth in this sector (demand exceeding supply) Increasing focus on renewable sources of energy Government presence in this enterprise
Weaknesses Public sector players are only into generation of power • Large demand-supply gap • Unavailability of fuel and unwillingness of fuel suppliers to enter into bankable • contarcts Lack of necessary infrastructure to transport and store fuel, high cost risk involved • in transporting fuel •
Opportunities Huge population base • Opportunities in Generation • Ultra Mega Power Plants should be made into existence. • Coal based plants at pithead which are untapped. • Hydel power potential of 150,000 MW is untapped as assessed by the Government • of India. Renovation, modernisation, up-rating and life extension of old thermal and hydro • power plants. •
Threats Competition from domestic players like NTPC • Not a lucrative option for investors(ROE ) • Rise in price of raw materials • Tariffs are distorted and do not cover cost
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Conclusion
-- KSTPS should emphasize on the conservation of environment, hazardous waste should be properly eliminated but this is not the scene, some percentage of this killer waste goes into the water of Chambal which is the drinking water source of Kota city, moreover fly ash mixes with the surrounding air and can lead to chronic problems this need to be checked
-- The machinery including boilers cooling pumps and other production equipments should be regularly checked by best engineers so that they properly work and wastage of fuel and water can be eliminated
-- The old machinery can be replaced with new and modern machinery.
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-- The KSTPS can make contracts with other big players of the cement industry on the India level like Ambuja Cement beside at Rajasthan level like Shree Cement Ltd. To purchase their fly ash and use it as an ingredient of cement, this will help in some revenue generation.
-- Collaboration with PSU’s like NTPC should be undertaken to have the advantage of latest technology and knowledge workforce to improve the effectiveness and efficiency.
References
1. http://en.wikipedia.org/wiki/Thermal_power_station 2. http://en.wikipedia.org/wiki/Deaerator 3. http://en.wikipedia.org/wiki/Economiser 4. http://en.wikipedia.org/wiki/Regenerative_heat_exchanger 5. http://www.tva.gov/power/coalart.htm 6. http://www.google.co.in/images 7. http://wapedia.mobi 8. http://images.google.co.in/images 9. http://www.rerc.gov.in 10. http://www.rvunl.com
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