NFL BATHINDA TRAINING FILE

NATIONAL FERTILIZERS LIMITED

SBSSTC, Ferozepur

INDUSTRIAL INDUSTR IAL TRAINING TRAINI NG REPORT REPORT

( Four Four Months ) PUNJAB TECHNICAL UNIVERSITY SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE AWARD ARD OF THE DEGREE O F

BACHELOR OF TECHNOLOGY SUBMITTED BY

Rahul Chadha Roll No. 1250718 1250718 (Batch 2012) 2012) AUGUST – AUGUST – DECEMBER DECEMBER 2015

Mechanical Engineering Shaheed Bhagat Singh State Technical Campus Moga Road, Ferozepur-1 Ferozepur-152004 52004

DECLARATION

Signature of the STUDENT (Roll No.: . . . . . . . . . . . . )

This is to certify that the above statement made by the candidate is correct to the best of my/our knowledge.

Signature of the TRAINING & PLACEMENT OFFICER, ME

The INDUSTRIAL TRAINING Viva-Voce Viva-Voce Examination of RAHUL RAHUL CHADHA CHADHA has been held on . . . . . . . . . . . . and accepted.

Signature of the EXTERNAL EXAMINER

Signature of the HEAD, DEPARTMENT OF ME

i

DECLARATION

Signature of the STUDENT (Roll No.: . . . . . . . . . . . . )

This is to certify that the above statement made by the candidate is correct to the best of my/our knowledge.

Signature of the TRAINING & PLACEMENT OFFICER, ME

The INDUSTRIAL TRAINING Viva-Voce Viva-Voce Examination of RAHUL RAHUL CHADHA CHADHA has been held on . . . . . . . . . . . . and accepted.

Signature of the EXTERNAL EXAMINER

Signature of the HEAD, DEPARTMENT OF ME

i

ABSTRACT The main idea behind the establishment of NFL, Bathinda is to manufacture and marketing of Urea and Neem Coated Urea. For the production it has five sections : 1. Ammonia Plant 2. Urea Plant 3. Captive Power Plant 4. Steam Generation Plant 5. Off-sites and Utilities

Place: Bathinda Bathinda

Rahul Chadha

Date: 3 August, 2015

iii

AKNOWLEDGEMENT The industrial training in an industry/project site is an essential part of curriculum for completion of degree. I am grateful to authorities at National Fertilizer Limited, Bathinda for permitting me to undergo six month industrial training in their esteemed organization. During this training I have learnt a lot for which I pay heartiest gratitude to Mr. Kulwant Singh (Sr. Manager of HRD) , Mr. Rajesh Maurya (Deputy Manager) and staff member of NFL Bathinda who helped in all

respects in fulfilling my cherished desired of getting a successful industrial training .

Place: Bathinda Bathinda

Rahul Chadha

Date: 3 AUGUST, 2015

iv

CONTENTS Declaration…………………………………………………....... Declaration………………………………………………… .......…………………………………… ……………………………………ii Certificate……………………………………………………… Certificate………………………………………………………...... ......………………………… ………………………….... ....…. ….ii ii Abstract…………………………………………………………...... Abstract………………………………………………………… ......……………… ………………..………...........iii ………...........iii Acknowledgements……………………………………………………...... Acknowledgements…………………………………………………… ......…… ……..………. ……….………....iv ………....iv List of Figures……………………… Figures………………………………………………… …………………………..... .....………… …………..…………….............vii …………….............vii List of Tables……………………… Tables…………………………………………………… ……………………………..... .....………………… …………………..……... ……...….. …..viii viii Abbreviations………………………………………………………...... Abbreviations……………………………………………………… ......………………… …………………..….….....ix Chapter 1: Introduction to organization…………………………………… organization……………………………………...... ......…………… ……………..……...1 ……...1 1.1 Brief introduction of Organization……………………………… Organization………………………………...... ......…………………1 …………………1 1.2Salient features of Bathinda Unit………………………………… Unit…………………………………...... ......…………… ……………... ...…2 …2 Chapter 2: Production sections……………………………………………….....……...……….......3 sections……………………………………………….....……...……….......3 2.1 Ammonia Plant………………………………………………….....……...……….…..3 Plant………………………………………………….....……...……….…..3 2.2 Urea Plant…………………………………………………………......……...…....…...8 Plant…………………………………………………………......……...…....…...8 2.3 Captive Power Plant……………………………………………………...….....….....11 Plant……………………………………………………...….....….....11 2.4 Steam Generation Plant………………………………………………...…….............17 Plant………………………………………………...…….............17 2.5 Off-sites and Utilities………………………………………………………….....…..20 Utilities ………………………………………………………….....…..20 2.6 Pumps…………………… Pumps………………………………………………… …………………………………………………….....…..22 ……………………….....…..22 2.7 Compressor ……………………………………………………………………......…25 ……………………………………………………………………......…25 2.8 Maintenance………………………………………………………………….......…..28 Maintenance………………………………………………………………….......…..28 Chapter 3: Project Review………………………………………………………………..….....….30 Review………………………………………………………………..….....….30 3.1 Objective…………………………… Objective……………………………………………………… ……………………………………..…....….…30 …………..…....….…30 3.2 Review…………………………… Review………………………………………………………… ……………………………………..…….....…...30 ………..…….....…...30 3.3 Observations deduced ………………………………………………..………......…..30 Chapter 4: Project Work …………………………………………………………..……....…….…31 …………………………………………………………..……....…….…31 4.1Study of Turbine, Nozzle ,Condenser and Turbo-Generator …….....….…………......31 4.2Study of Feed water heater and Feed water water Control station……..…………….....…35 station……..…………….....…35 4.3Study of Boilers…………………………………………………..……………....… Boilers…………………………………………………..……………....….37 .37 Chapter 5: Results and Discussions…………………………………………..……………....……39 Discussions…………………………………………..……………....……39 5.1 Observations…………………… Observations………………………………………………… ……………………………..………...……....……39 ..………...……....……39 5.2 Layout of Captive Power Plant and Steam Generation Plant..………..……….....…..40 Plant..………..……….....…..40 v

Chapter 6: Cautions during Problems...............................................................................................41 6.1 High Condenser Level..................................................................................................41 6.2 Polish water failed from DM plant...............................................................................41 6.3 TG Vibration High........................................................................................................41 6.4 Steam Temperature is low.............................................................................................42 6.5 Exhaust temperature High/Vacuum low.......................................................................42 Chapter 7: Conclusion.......................................................................................................................43 Bibliography.....................................................................................................................................44

vi

List of figures: Fig 1.1 Production Performance..................................................... ...................................................2 Fig 2.1 Block diagram of Ammonia Plant..........................................................................................7 Fig 2.2 Block diagram of Urea Synthesis...........................................................................................9 Fig 2.3 Urea Synthesis......................................................................................................................10 Fig 2.4 Water tube Boiler..................................................................................................................13 Fig 2.5. Shows General concept of power generation by Steam turbine..........................................14 Fig. 2.6 Cooling Tower.....................................................................................................................21 Fig 2.7 Rotary Pump.........................................................................................................................22 Fig 2.8 Centrifugal Pump..................................................................................................................23 Fig 2.9 Reciprocating Pump.............................................................................................................24 Fig 2.10 Reciprocating Compressor.................................................................................................26 Fig 2.11 Axial Flow compressor................................................... .................................................. 27 Fig 4.1 Steam passing through turbine.............................................................................................31 Fig 4.2 Shows steam processed through Turbine to boiler...............................................................32 Fig 4.3 shows 3D view of nozzle partitions and buckets placing.....................................................33 Fig 4.4 Sectional view of condenser.................................................................................................33 Fig 4.5Feed water heater...................................................................................................................35 Fig 4.6 feed water control station layout..........................................................................................36 Fig 4.7 sectional view of boiler..................................................... ...................................................37 Fig. 4.8 Economizer..........................................................................................................................38 Fig. 5.1 Layout of Captive Power Plant and Steam Generation Plant.............................................40

vii

List of tables: Table 2.1 Shows the sections of Ammonia Plant and its features..................................................... 3 Table 2.2 Shows Compressor in Ammonia Plant and its features......................................................4 Table2.3 Showing configurations of turbine.....................................................................................15 Table 4.1 TG operating parameters before and after Overhauling ..................................................34 Table 5.1 Boiler operation requirements...........................................................................................39 Table 5.2 Temperature of steam/water.............................................................................................39 Table 5.3Spray water quantity..........................................................................................................39

viii

List of abbreviations used: TG- Turbo-Generator H.P heater- High Pressure heater L.P heater- Low Pressure heater H.T.S.H- High Temperature Superheater I.TS.H- Intermediate Temperature Superheater L.T.S.H- Low Temperature Superheater Press.- Pressure Temp. – Temperature CV- Control Valve SV-Spring Valve FWT- Feed Water Tank BFW- Boiler Feed Water

ix

4 Months Industrial Training

Chapter 1 Introduction to organization 1.1 Brief introduction of Organization: NFL, a Schedule „A‟ & a Mini Ratna (Category-1) Company, having its registered office at New Delhi was incorporated on 23rd August 1974. Its Corporate Office is at NOIDA (U.P). It has an authorized capital of ₹1000 crore and a paid up capital of ₹490.58 crore out of which Government of India‟s share is 90% and 10% is held by financial institutions & others. NFL has five gas based Urea plants viz Nangal & Bathinda in Punjab, Panipat in Haryana and two plants at Vijaipur in District Guna, Madhya Pradesh. The above plants at Panipat, Bathinda & Nangal which were earlier based on fuel oil (LSHS) have recently been converted on Natural Gas, an eco-friendly fuel. Vijaipur plants of the company were also revamped for energy savings & capacity enhancement during 2012-13, thus increasing its total annual capacity from 20.66 LMT from 17.29 LMT, an increase of 20%. The company has a total annual installed capacity of 35.68 LMT and is the 2nd largest producer of Urea in the country with a share of about 16% of total Urea production in the country. The products being manufactured and sold by NFL under brand name „KISAN' include Urea, Neem Coated Urea, Bio-Fertilizers (solid & liquid). Besides manufacturing of fertilizers, the company is also producing allied Industrial products like Nitric Acid, Ammonium Nitrate & Ammonium Nitrite, Sodium Nitrite, Sodium Nitrate etc. The company is also endeavoring trading of imported fertilizers like DAP, MoP etc. The Company is also in the process of setting up a Bentonite Sulphur plant at its Panipat Unit to cater the requirement sulphur deficient soil. NFL has a wide marketing network ac ross major part of India comprising of a Central Marketing Office at NOIDA, three Zonal Offices at Bhopal, Luckno w & Chandigarh, 12 State Offices and 38 Area Offices. NFL has be en mandated to revive the closed plants of Fertilizer Corporation of India Limited (FCIL) at Ramagundam in co llaboration with M/s EIL and M/s FCIL by setting up a Urea plant of annual capacity of 12.71 LMT for which a Joint Venture (JV) Company has been formed as Ramagundam Fertilizers & Chemicals Limited (RFCL). Currently, various pre-project activities are in full swing.Presently, company has a total manpower of 3843 employees.

Shaheed Bhagat Singh State Technical Campus, Ferozepur 1


1.2Salient features of Bathinda Unit

Installed Capacity:

511500 MTPA

Capital Investment:

349.41 Crores

Initial Commencement of

October 1, 1979

Production: Commencement of Production on Gas

March 11, 2013

after Revamp:

1.2 Process Ammonia:

HTAS Steam Methane Reforming (SMR) Technology

Urea:

Mitsu Toastsu total Recycle C Improved

Raw material:

Coal , LNG/ RLNG, Power, Water

Captive Power Plant:

2 x 15 M

Fig.1.1 Production Performance



Chapter 2 Production sections 2.1 Ammonia Plant The ammonia plant NFL Bathinda is based on partial oxidation of fuel oil. The Ammonia Plant has the following processing units:Table 2.1 Shows the sections of Ammonia Plant and its features

Sr. No.

Unit/section

Supplier

Features

1.

Air separation unit

M/S HITACHI

Mol. Sieve and

JAPAN

activated alumina gel bed for CO2 & moisture removal, cold recovery from the products in plate and fin type heat exchangers and conventional double column for distillation

2.

Gasification

M/S TEC under

Refractory gasifiers of

process licence from

series 700.

m/S SHELL INTERNATIONAL 3.

4.

Recti sol(de-

M/S TEC under

Selective absorption of

sulphurisation)

process license from

H2S and CO2 by low

M/S LURGI

temperature methanol

Recti

M/S TEC under

Total rergeneration

sol(decarbonisation)


ofpartial steam only

M/S LURGI Shaheed Bhagat Singh State Technical Campus, Ferozepur 3


5.

CO shift

M/S TECH

Double bed high temperature CO shift converter.

6.

Absorption

M/S BORSIG

refrigeration

Part of heatis supplied by the converted gas from shift converter.

7.

Nitrogen wash unit

M/S HITACHI

Mol. Sieve adsorbers for removal of methanol and CO2

8.

Ammonia Synthesis

M/S TEC under

Topsoe S-100 radial


flow basket, waste

M/S HALDOR

heat recovery of the

TOPSOE

converter exit gases in BFW economizers

The compressor of ammonia plant has the following major equipment:Table 2.2 Shows Compressor in Ammonia Plant and its features

Sr. no.

Section

Supplier

Features

1.

Air compressor

M/S MITSUI JAPAN

1,40,000NM /hr capacity 15.45 KW turbine

2.

Nitrogen compressor

-do-

30,000 NM /hr capacity 6.9 MW turbine6.9

3.

4.

Oxygen compressor

Synthesis compressor

Compressor-DEMAG

24,970 N /hr capacity

Turbine-AEG

6.59 MW turbine

BHEL Hyderabad

1,10,000 NM /hr capacity 2.8MW turbine

Against the rated capacity of 900Te/day , plant has produced a record production of 1011Te and has been constantly running above 105% for past few years. The harmless gases like CO2 and are Shaheed Bhagat Singh State Technical Campus, Ferozepur 4


vented through a cold flare outlet of 80m height. The toxic gases are burnt so that there combustion products are not harmful to the environment.

2.1.1 Process description of Ammonia Plant: Various process involved for the production of A mmonia are as follows:

i) Air Separatioin Unit (A.S.U.): Air has following composition: Nitrogen

78.03%

Oxygen

20.93%

Argon

0.93%

Carbon

0.93%

It is provided for getting oxygen and nitrogen required for production of NH3 from air is the first section from atmosphere and is pre-cooled. Then further cooled in air chiller. Then moisture and dust etc. are removed by passing through alumunia molecular seves. Final products i.e. N2 and O2 are obtained when air is rectified in the rectifying column. Product O2 is the first compressed and then led to reactors in shell gasification process. For partial oxidation of food stock for producing raw gas is separated toH2, H2S and CO2, CO2 is send to the urea plant, H2S is sent to sulphur recovery plant. On the other hand N2 and H2 are given to N.W.U. in the ratio of 1:3 to get pure synthesis gas to manufacture NH3.

ii) Shell Gasification and Carbon Recovery: Lines of O2 feedback and stream led to the gasifier column where in the presence of high 0

temperature of the order 1350 C produce raw gas containing CO, H2S, HCN, heat is generated in this unit. This heat is not washed but utilized to produce steam in the waste boiler.Some unburnt carbon is also present along with other gases in raw gas, as it can check the line. It is removed by stages water wash and there is final scrubbing stage. HCN is also removed in this stage.



iii) De-Sulphurisation: Sulphur compound are removed in this section because otherwise these poison the catalyst present in the next section. Methanol has a property of absorbing different gases at different temp. Absorption process is carried out at low temp. and high pressure, H2O and COS are removed in the raw gas to only 0.1 PPM in this unit by absorbing with MeOH. MeOH is regenerated by N2 by stripping and H2S is sent to sulphur recovery plant. iv) Shift Converter:

In this unit get CO2 and H2 from CO and steam at high temp. by passing the gas catalyst as per the following reaction: CO(g) +H2O(steam) ......... H2 + CO2 In this industrial method of producing H2 as per le chatlier principle for high concentration of product excess is to be introduced and temp. should kept low and reaction rate is high. So o

compromise is made and temp. is around 350-500 C. Fe is used as catalyst in reaction.

v) CO2 Removal: In this unit we get a mixture of gas(H2, CO2) from shift conversion and CO2 is removed from H2 by absorbing CO2 with methanol of low temp. This mixture of MeOH and CO2 is stripped by N2 where CO2 is regenerated and send to UREA PLANT, in this unit we get 98% of H2 and send to N.W.U.

vi) Nitrogen Wash Unit (N.W.U.): Even a little of CO still remains in raw gas after the shift convertor process. This is removed in N.W.U. where liquid N2 is sprayed on raw gas of 98% H2 from the top of the tank. Before leaving this section, purified H2 gas is mixed with N 2 in the ratio 3:1 and forms an admixture without reaction, it is called synthesis gas.



Fig. 2.1 Block diagram of Ammonia Plant

vii) Ammonia Synthesis Section 2

2

The synthesis gas from N.W.U. is compressed from 37 kg/cm to 230 kg/cm in the centrifugal type synthesis compressor. Then the gas enters the synthesis hot exchanger with hot effluent gas from synthesis economizer. At the outlet of the comp ressor the gas contains 16% ammonia. N2 + 3H2

……………

2NH3



2.2 Urea Plant: 2.2.1 Conventional Process: Mole Ratio: NH3:CO2

4:1

H2O :CO2

0.54:1

%Conversion

70%

2.2.2 Reaction Condition: Pressure: CO2

250 kg/cm2

Carbonate

250 kg/cm2

Ammonia

250 kg/cm2

Temperature:

2000 C

2.2.3 Urea process classified into four sections: i) Synthesis section. ii) Decomposition section. iii) Crystallization & Prilling section. iv) Recovery section.

2.2.4 About Urea : Urea is an Organic compound. Its chemical formula is NH2-CO-NH2 Properties of Urea: 



Melting point at 1 atm: 132.47°C Nitrogen content: 46.6 %



Color: white



Raw material requirement for Urea production



Liquid Ammonia (NH3)



Carbon Di-Oxide (CO2)



2.2.5 Advantages of Urea 1. Nitrogen content is highest among various nitrogenous fertilizers (46%). 2. Cheapest fertilizer from transportation point of view 3. CO2 which is one of the raw materials for the manufacture of urea is a vailable at negligible cost from ammonia plant. 4. It is not subject to fire or explosion hazard 5. It has got better flowing characteristics 6. As such it is not toxic and used in preparation of various types of medicines and in other industries.

2.2.6 Urea Synthesis Reaction: 2NH3 liq. + CO2 = NH2-COO-NH4 + Heat (37.64 Kcal/mole) Fast & exothermic Ammonium Carbonate NH2-COO-NH4 = NH2-CO-NH2 +H20 - Heat (6.32 kcal/mole) slow & endothermic Urea

Fig.2.2 Block diagram of Urea Synthesis



Carbon dioxide from battery limit at 1.02 Kg/cm2 is compressed to 30 Kg/cm2 in a 3-stage centrifugal booster compressor which runs at 4730 kw and 7930 rpm. After first stage of compression the compressed air goes to the intercooler and then to heat exchanger and comes back for the second stage compression then again to the intercooler and then again to the heat exchanger. The lubrication is provided by mobile oil.The compressed air at 30 Kg/cm2 is sent to the 2-stage reciprocating kobe compressor in which air is firstly compressed to 90 Kg/cm2 to 250 Kg/cm2. Stage 1 consists of two cylinders and stage 2 consists of one cylinder. Now this compressed carbon dioxide is sent for reactor. Ammonia from battery limit is send for reciprocating pump which are 4 in number (4th being stand by) to be compressed. Large pumping action of pumps is achieved by 400 Kw,3300V Electric motor. The turbulent liquid is stabilized in spherical shaped resonator. now compressed NH3 is sent to the reactor at around 200 Kg/cm2.

2.2.7 Reactor Outlet : Carbamate pumps are required for pumping the recycle carbamate solution coming at the suction pressure of 24 Kg/cm2 and discharge pressure of 260 Kg/cm2. These are 8 stage centrifugal pumps with casing design pressure of 308 Kg/cm2. There are two such pumps out of which one is stand by. In order to handle corrosive carbamate solution, all components are made up of austenitic and ferritic duplex stainless steel. All the wearing parts are chromium plated.

Fig 2.3 Urea Synthesis



2.3 Captive Power Plant: 2.3.1 Introduction: National Fertilizers Limited has set a Captive Power Plant (CPP) at their complex at BATHINDA, to ensure availability of stable, uninterrupted power and stream to the Ammonia and Urea plant. This will minimize the tripping of the Fertilizer Plant due to transit vo ltage dips and power cuts.Since inception, Bathinda unit was drawing electric power from Punjab State Electricity Board (P.S.E.B). Electricity is the main driving force after steam in the plant, being used for moving auxiliary equipments. The unit requires 27MW of power/hr when running at full load. There are two 15 MW turbogenerators to generate power. Under normal running conditions of the plant and healthiness of the P.S.E.B. grid, we generally run in s ynchronism with the grid merely drawing the power corresponding to the minimum charges to be paid to state electricity board. In case of any disturbance in the grid, our system gets isolated from the grid automatically. With both generators running, we are able to feed power to the whole plant, thus production is not affected. In case only one turbo generator is in line and grid cuts off, urea plant is cut off automatically to balance the load with one generator. As soon as the grid becomes stable, the generators are again synchronized with it. The power generation of each generator can be varied with 2 MW to 15 MW maximum, provision exists to run the generator on 10 % extra load continuously for one hour only. Operation of C.P.P. is based upon microprocessor based computerized instrumentation which allows automatic operation, start up, shut down of the whole or part of the plant. Latest instrumentation has been used in this plant. It allows controlling process variables like flow, pressure, temperature, power factor, voltage, frequency, etc. There is operator interface unit (IOU) Like a TV screen on which various parameters can be displayed and controlled. It allows fully automatic start-up, shut-down of bo iler, turbine and other auxiliaries.



2.3.2 Need for CPP: It was thought to install a captive power plant in which electric power for our requirement shall be generated in a COAL FIRED BOILER. The benefits envisaged were: i) Any disturbance in the PSEB grid used to trip the whole plant. Lot of money was lost due to this as each re-startup costs around 40 to 50 lakhs rupees. Moreover, frequent tripping‟s had an ill effect on machines and equipments extending the re-startup period. ii) Three boilers of 150Te/hr steam capacity were initially installed in SGP to keep 25 boilers running and one stand by as designed steam requirement was less than 300Te/hr. but in actual operation steam requirement was more and all three boilers had to be run and there was no breathing time for their maintenance. iii) As new boiler was to be installed for CPP, its capacity was so designed that it could export around 60Te of steam for process requirement so t hat only boilers of SGP would be run keeping rd

the 3

as stand by.

With these points in mind CPP was installed. The functioning of CPP can be sub-divided into parts:

2.3.4 Boiler Requriement: For generation of high pressure superheated steam.

2.3.5 Boiler: The basic principle of this boiler is the same as d iscussed earlier for SGP boiler that is formation of steam by heating boiler feed water inside furnace fired by coal and heavy oil, utilization of heat of the gases and venting these gases at a safe height. Main differences between the two boilers are: SGP boiler is tangentially fired where as CPP boiler is front fired with 6 coal burners and 6 oil gun fixed inside the coal housing. SGP boiler can be loaded up to 30% load with oil firing only whereas CPP boiler can be fully loaded with oil alone. Height of combustible zone in CPP boiler is more and it has residence time of 1.5 sec where SGP boiler has 1.0 sec.Mills used for pulverizations of coal in SGP are negative pressure bowl mills whereas in CPP ball tube mill are used which are positive pressure mills. Due to more residence time and better pulverization the efficiency of CPP boiler is about 4%

higher. Boiler feed water required for steam generation can

be fully generated in CPP itself. A part of the steam generated is exported for process use in ammonia plant and rest is utilized for power gene ration in turbo generators as described below: Shaheed Bhagat Singh State Technical Campus, Ferozepur 12


Fig 2.4 Water tube Boiler

2.3.6 Descripton of the boiler: Mitsuy Relay Type Boiler Maximum evaporation

2, 30,000kg/hr

Design process for boiler

124 kg/cm G

Steam temp at outlet

495 C

Heating surface

1250M

2

0

2

2.3.7 Turbo-Generator Requirement: To generate power, using steam from the boiler.Operation of CP P is based upon microprocessor based computerized instrumentation which allows automatic operation, start up, shut down of the whole or the part of the plant.

2.3.8 Power Generation: In C.P.P., two generators of 15MW capacity generate a voltage of 11KV, which is fed to the two transformers in the yard. The rating of the transformers is 31.5/25 KVA, these two values depend upon the cooling which we provide, as here 25KVA capacity is when cooling is oil natural air natural and 31.5KVA capacity is when cooling is oil natural air forced. Both these transformers Shaheed Bhagat Singh State Technical Campus, Ferozepur 13


step up the voltage level to 132KV. From the transformers the three phases p ass through the lightning arrestors (LA). After this, they pass on to the isolator. After this the two lines pass on to the TRANSMISSION pole called DOUBLE CIRCUIT TRANSMISSION. Then these lines go to the M.R.S. i.e. main receiving station.

2.3.9 Turbine: M/S SGP of AUSTRIA supplies the turbine used. It is condensing cum extraction turbine designed as single casing reaction turbine with single control stage and high pressure (HP), mild pressure (MP) and low-pressure (LP) reaction parts. The turbine is fed with high-pressure steam at 100kg from boiler and flows through various control valves for normal and emergency operation. It gets high velocity through the nozzle group and then passes over the impellers fixed on to the rotor and fixed diffusers thus rotating the turbine. The enthalpy of steam is utilized in steps. Steam is also extracted from various stages. HP 1 at 2

2

2

2

10.4kg/cm , HP2 at 8.1kg/cm , feed water bleed at 4.3kg/cm and LP bleed at 0.9kg/cm .The exhaust steam from the turbine is condensed in a condenser maintained under vacuum to extract maximum steam enthalpy. The output of the turbine depends on flow of steam and heat difference that is on condition of steam at the main steam valve and the pressure at the turbine outlet or condenser pressure. The turbine is connected to the generator through speed reducing gears.The exhaust steam is condensed in a condenser using cooling water.

Fig 2.5. Shows General concept of power generation by Steam turbine



The resulting condensate can be fed back to LP heater but is normally sent to the polishing water plant. As shall be clear from the attached block diagram various bleeds from the turbine are utilized for heating purpose. HP1 and HP2 are used for heating boiler feed water in HP1 and HP2 heaters. Feed water bleeds is used for heating the feed water tank and LP bleed is used for heating the polish water make up to the feed water tank. A lubrication system is also there to lubricate the various bearings of the turbine, gears and generator. Normally the oil pump driven by the turbine shaft supplies oil but auxiliary motor driven pumps are used for start up and during shutdown. A turning gear has been provided for slow cooling of turbine rotor. Latest instrumentation has been used in this plant. Bailey‟s net work -90 microprocessor based instrumentation system is being used. The NETWORK 90 SYSTEM is a distributed process control system. Using a series of integrated control nodes. The network 90 system allows controlling process variables like flow, pressure and temperature according to a control configuration. There is operator interface unit (OIU) like a TV screen on which various parameters can be displayed and controlled. It allows fully automatic start-up/shut-down of boiler, turbine and other auxiliaries.

2.3.10 Description of Turbine:A simple tabular data shows the description and configurations of turbine currently operated in the plant: Table2.3 Showing configurationof turbine

Make

Simmering Graz Panker, Austria

Type

Multifunction (28 stages)

Capacity

65 T/H at 15 MW

RPM

6789 at 50 Hz

Critical speed

3200-3600 RPM



2.3.11 Genrator: CPP is having two number turbo generators of capacity 15MW each. The generators are type SAT three phase, 50Hz, 11kV, 984amps, at 0.8 power factor rating supplied by M/S JEUMONT SCHNEIDER OF FRANCE. These are totally enclosed self ventilated type with two lateral airs to water coolers for cooling. The alternators are able to bear 10% overload for one hr with an increase 0

in temp. of 10 C while maintaining the voltage as near as possible to the rated one. The excitation is compound and brush less with exciter rotor and Rectifier Bridge mounted on the extended main shaft on non driving end. The excitation is controlled automatically with automatic voltage regulator and a PLC controller. All protection relays installed for protection of generator are solid state having high accuracy, quick response and low power consumption. Under normal running conditions of the plant and healthiness of the PSEB grid, we generally run in synchronism with the grid merely drawing the power corresponding to minimum charges to be paid to state electricity board. In case of any disturbance in the grid measured by higher low frequency, high rate of change of frequency, low voltage etc. our system gets isolated from the grid automatically. With both generators running, we are able to feed power to the whole plant, thus production is not affected.

2.3.12 Uninterrupted Power Supply: The uninterruptible power supply system is connected between a critical load, such as digital drives & automation, distributed digital process control system, telecom equipment, programmable logic controller, mission critical applications, computer and its three phase mains power supply under all rated load and input supply conditions. The system offers the user with the following advantages: i) Increased power supply: ii) The UPS has its own internal voltage and frequency regulator circuits which ensure that its output is maintained within close tolerances independent of voltage and frequency variations on the mains power lines.



2.4 Steam Generation Plant Steam Generation plant is mainly installed for production of steam and then distributed to various parts of the plant. Here this section of plant installed in National Fertilizers Limited, Bathinda unit 2

produces and supplies steam at 100 Kg / cm pressure and nearly 480°C temperature to Ammonia Plant.In today‟s world steam has gained importance in Industries. It may be used for power processes and heating purposes as well.

2.4.1 Benefits of Steam: i) It is colorless, odourless and tasteless. ii) Very economical iii) Non-polluting iv) Can be used as heat exchanger. v) It can be easily distributed to various sections of plant.

2.4.2 Steam generation in Plant: Steam is generated in Boilers (Water tube boilers mounted on common base fitted with mountings and fittings) and then distributed to other parts of plants. For governing the quantity of fuel to be burned and for maintaining the required pressure their are many automatic fuel feeders, equipments and auxiliaries like pressure gauge etc. In the Boilers used at National Fertilizers Limited (Bathinda unit); coal, oil natural gas are used as a fuel for production of steam. NFL , Bathinda is using steam for two purposes ; first and the main reason is for running prime mover and other reason is to exchange heat in the processes taking place their. There are three boilers capable of producing steam at the rate of 150 Tonnes/hr installed in CPP which were supplied and erected by BHEL. Generally two boilers are enough to meet the requirements but third boiler is simultaneously running because if steam load consumption increases then the third boiler plays its part in order to avoid any faulty condition.



2.4.3 Fuel Used: There are presently two fuel are used for the steam generation:

i) Coal : To obtain steam of desired Temperature and pressure, coal is burned to give major source of heat.Initially coal is stored at Coal Handling plant brou ght from coal sites. It is this section of plant where coal is crushed by crushers in order to make small pieces of coal, then after crushing it the coal pieces rare passed through heavy electromagnet where iron is separated from coal if present. Coal is then sent to Bunkers from where it goes to Grinding mill. Grinding mill is grinding coal into powder form.Conveyor Belts are being used i n the whole plant for transportation of Coal. The powder form of coal is sent to the Boilers through pump as pump sucks the coal from grinding mills and throws it into the boiler for combustion.

ii) Oil : As the Boilers are designed to work on both Coal as well as Fuel Oil so fuel oil can also be pumped to Boiler for combustion. Generally coal alone is not burnt Initially but Fuel Oil (LSHS) is mixed coal and then sent to the furnace for combustion in order to get desired te mperature .

2.4.4 Steam Requirement at Plant: As National Fertilizers Ltd, Bathinda unit has its own Steam Generation Plant where steam is produced which is used for driving Turbo Compressors, Heating Purposes, for various reactions taking place in the plant itself. Steam is mainly consumed in the Ammonia Plant as nearly 6 to 7 tonne of steam is required to produce 1 tonne of Ammonia. High Pressure Turbines are being used where high pressure and temperature is to be maintained so SGP section plays a important role for maintaining the said condition. There are three boilers (VU-40 type supplied by M/S BHEL) of 150 tonne/hr capacity .These boilers are Water Tube Boilers i.e. water is inside the tubes and hot air surrounds it when coal is burnt, this makes the water in the tubes boil and steam formation takes place. In the beginning coal is burnt with fuel oil in order to get desired temperature. Shaheed Bhagat Singh State Technical Campus, Ferozepur 18


2.4.5 Water and Steam System: As the steam being used should be free from impurities like minerals, silica, oxygen, Iron etc. in order to insure Safe and Efficient working of Steam turbines and Boilers. For this purpose Raw Water is physically and chemically treated and finally supplied to Steam Generation Plant from Ammonia plant. This water is called Boiler Feed water which is further heated to 240º C by the flue Gases and taken to Steam Drum. Steam Drum Acts as storage tank and also separates water from the steam at 315º C and 106 kg/cm2 pressure water then enters the Ring Header formed at on the bottom of outside the furnace and rises by gravity through water wall tubes on the all the four .

sides, taken heat from furnace and enters steam d rum as a mixture of steam and water

2.4.6 Flue Gas System: The products of combustion in the furnace consist of carbon-di-oxide, nitrogen, ash, oxygen and sulphur-di-oxide. After leaving the furnace the heat Of these gases called FLUE GASES, is utilized at various levels. First the steam from steam drum is heated in two super heaters to get the required temperatures of 0

495 C and then feed water in BANK TUBES is also heated and the gases leave bank tubes at 0

around 497 C next the heat is utilized to heat feed water in the ECONOMIZER and gases are 0

0

cooled down to 320 C. These gases are further cooled down to 150 C in ROTARY AIR HEATER where the air is required for combustion and conveying the coal is heated up. Temperature is not reduced further because at lower temperature oxides of sulphur present in flue gases are converted to ACID which damages the down stream equipments. These gases then pass through ELECTRO STATIC PRECIPITATOR (ESP) where ash is removed.



2.5 Offsites and Utilies (O&U): The O & U group of plants consist of the following sections : i) Raw Water Plant. ii) D.M. Water Plant. iii) Instrument .Air Compressor House. iv) Cooling Tower.

i) Raw Water Filtering Plant: This water treatment plant has a design capacit y to treat 2400 NM3/hr of raw water into portable occasional over lead of 20%. The plant consists essentially of flash Mixers Clarifloculators, rapid gravity filters and a chemical House comprising of Alum tanks, lime tanks and a chlorine room etc.The raw water from the pumping main is received by the inlet of the RCC Ventury flume. In the ventury flume the calculated amount of alum solution is closed for mixing with the raw water. The chemically treated water then flows to clarifloculators. The pludge thus formed after chemical treatment settles down in the clarifloculator where from it is expelled ou t while the clear water overflows to the launder leading to filter beds. Th e filter water is disinfected with the addition of chlorine and then collected in filter eater sump.

ii) D.M. Water Plant D.M. water plant was supplied by M/s Ion Ex change (India) Ltd. It consists of cation units, Degasser Towers, An-ion units. Mixed bed units No.l&2. Filtered water coming from raw water filtration plant is received in filter water reservoir. From reservoir filter water passes through a strongly acidic cat-ion exchange resin where cat-ions like Ca, Ng & Na are removed, the water passes through degasser tower where dissolved, Ce2 is removed. Then water passes through Anion exchange resin and Anion like CI, S, Se4 and silica, are removed in this unit. Free from cations and anions water passes through mixed bed unit No.l, where further removal of cations and anions takes place. Then treated water coming out from MB, unit goes to DM water tank.Return condensate from Ammonia and Urea Plants is collected in D.M. water tank after treatment in cat-ion unit No.2. Then D.M. water is pumped from DM water tank to mixed bed No.2(MB) for further polishing and collected in polish water tank, which is supplied to boilers through Ammonia Plant. Shaheed Bhagat Singh State Technical Campus, Ferozepur 20


iii) Instrument Compressor House: The purpose of this section is to supply instrument air and service air to all the plants. The instrument air compressor house consists of three instrument air compressors and one service air compressor. One is kept in line generally. The compressed air from instrument air compressors at 9.3 kg/cm2 absolute pressure passes through two sets of d ryer, which is filled with silica-gel for removal of moisture. Air coming out from dryer is sent to instrument air feeder for supplying to different plants through instrument air receiver in order to drive various valves a nd instruments.

iv) Cooling Towers: The cooling water system provided in NFL, Bathinda is closed re-circulating system supplying cooling water to various consumers in the plant. T he system mainly consists of cooling towers, cooling water re-circulation pumps, supply & return headers and cooling water treatment facility. There are three cooling water systems : i) C.W. system supplies cooling water to Ammonia Plant. ii)Urea Plant and Boilers, Instrument -Air Compressor, Caustic dissolving facilities & Sulphur recovery Plant. Iii) C.W. system supplies cooling water to Crystallization section of Urea Plant.

Fig. 2.6 Cooling Tower



2.6 Pumps: Mechanical equipments used to propel liquid under pressure from one location to another through piping. It basically increases the liquid pressure as the liquid circulates through the pump.

2.6.1 Types of pumps : There are basically three types of pumps namely: i) Centrifugal Pump ii) Reciprocating Pump iii) Rotary Pump

i) Rotary Pumps: Rotary pumps are used for moving extremely heavy or viscous commodities such as grease, asphalt, heavy fuel oils and sometimes heav y crude oils. There are three main types of rotary pumps: gears, cams and screw

Fig.2.7 Rotary Pump



ii) Centrifugal Pumps: These create centrifugal force which creates rise in pressure to move the liquid by forcing it into a rotating impeller and literally throwing it out the discharge nozzle, p roducing a smooth, non pulsating flow in the piping system. Problem with centrifugal pumps is CAVITATION. When the liquid passes from the pump section to the eye of the impeller, the velocity increases and pressure decreases. There are also pressure losses due to shock and turbulence as the liquid strikes the impeller. The centrifugal force of the impeller vanes further increases the velocity and decreases the pressure of the liquid. The vaporization occurs when this pressure drops to atmospheric pressure. The vapor pressure occurs right at the impeller inlet where a sharp pressure drop occurs. The impeller rapidly builds up the pressure which collapses vapors bubbles c auses cavitation and damage the pump internals. This is avoided by maintaining NPSH (net positive suction head).

Fig. 2.8 Centrifugal Pump



ii) Reciprocating Pump Reciprocating pump has plungers that go back and forth like a cars pistons to displace liquid, forcing it violently out of the discharge nozzle. They operate at much lower rpm and each plungers thrust causes pulsation in suction and discharge piping. The pump is taking in liquids at the same rate at which it is discharging liquid, and by the same reciprocating action, thereby causing the suction line to pulsate too. This pulsating action causes the pipe to pulsate too and thereby if not held down, it will eventually fatigue.

Fig.2.9 Reciprocating Pump

2.5.3 Pump Maintenance: Effective problem identification and problem avoidance requires a rigorous investigation process. When a pump failure occurs, it is very tempting to remove the pump, replace the defective parts (or the entire pump), install the new or rebuilt unit, and get the unit back on line as quickly as possible. However if several checks are not made during the removal and disassembly process, important clues as to the cause of the problem will be overlooked. Below is a recommended checklist that should be done when any pump is removed from service to assist in identifying the source of the failure. In fact, it may not be a bad idea to perform many of these checks on an annual basis.



2.7 Compressor: Compressors, in simple words, can be described as a mechanical devices used to increase the pressure of air or gas. Compressors provide sufficient pressure for gases and vapors. In most piping installations, compressors are used primarily for the creation of highly pressurized air for different parts of the plant, such as utility air, pneumatic valves. Co mpressors can develop pressure as high as 20,000 psig. There is a wide range of compressors ranging from reciprocating to rotary. Filters, separators, receivers, silencers and coolers are pieces of equipmen t that make up a whole compressor unit. The compressor units are elevated above the grade level and are provided with an enclosed are to keep the unit dry. Two major problems associated with compressor units are : 

unwanted foreign material in the system and liquid retention. Both can cause serious damage to the unit.



Sufficient room around the compressor unit must be provided for maintenance and operation, including access to valving and piping.

2.7.1 Types of Compressors i) Centrifugal Compressor : Centrifugal compression is a force converted to pressure when a gas is ejected by an impeller at increasing velocity. These are specified for large q uantities of vapors. Pressure diffential may be small or large. There are two basic types of centrifugal compressors. VERTICALLY SPLIT case types are used for high pressures; HORIZONTALLY SPLIT case type for l ow to moderately high pressures. Centrifugal compressors may have upto ten stages of compression within one casing. If more than ten stages are needed two or more compressors can be coupled together and powered by a common driver. This is called tandem drive.



ii) Reciprocating Compressor: These are generally specified for lower volumes than centrifugal compressors. With several stages of compression, extremely high pressures may be develope d. Because of their reciprocating action, these machines cause piping to pulsate, to vibrate and generally to fatigue if it is not properly designed.

Fig.2.10 Reciprocating Compressor



iii) Aial Flow Compressor: Axial compressors consist of rotating and stationary components. A shaft drives a cen tral drum, retained by bearings, which has a number of annular airfoil rows attached usually in pa irs, one rotating and one stationary attached to a stationary tubular casing. A pair of rotating and stationar y airfoils is called a stage. The rotating airfoils, also known as blades or rotors, accelerate the fluid. The stationary airfoils, also known as stators or vanes, convert the in creased rotational kinetic energy into static pressure through diffusion and redirect the flow direction of the fluid, preparing it for the rotor blades of the next stage.The cross-sectional area between rotor drum and casing is reduced in the flow direction to maintain an optimum Mach number using variable geometry as the fluid is compressed.

Fig. 2.11 Axial Flow compressor



2.8 Maintenance: 2.8.1 Maintenance Objective: 1. To achieve minimum breakdown and to keep the plant in good working condition at lowest possible cost. 2. Machines and other facilities should be kept in such a condition which permits them to be used at their optimum capacity without any interruption or hindrance. 3. Availability of the machines, building and services required by other sections of the factory for the performance of their functions at optimum return on investment be in material, machinery or personnel.

2.8.2 Responsibilities of Maintenance Engineer: i) Inspection: Its concerned with the routine schedule checks of the plant facilities to examine their condition and to check for needed repairs. Frequency of inspections depends upon the intensity of the use of the equipment. Inspection section makes certain that every working equipment receives proper attention.

ii) Engineering: It involves alterations an improvements in existing equipments to minimize breakdowns. It also includes inventorying outside technical assistance.

iii) Repair: It includes carrying out corrective repairs to alleviate unsatisfactory conditions. Such a repair is usually of emergency nature.

iv) Overhaul: It includes planned , scheduled reconditioning of plant facilities such as machinery etc. It also involves replacement, reconditioning, reassembly, etc.



2.8.3 Actions Performed by Maintenance Department i) Condition monitoring ii) Spare procurement iii) Inventory control iv) Import substitution v) Development of manpower vi) Analysis of history such action should be taken of behavior of the machine and its vii) Replacement of worn out component . viii) Repair of cracks or restore the original operational o ther repairable capacity of the machine damages and prevent further damage. ix) Modification of design affect improvements to reduce the frequency of attention or location of the reduced cost of maintaining equipment. x) Capital replacement of the machine when the age of the existing machine requirements of quality and quantity of output and emergence of better machines make it economical to dislodge the present and install a new machine.

2.8.4 Maintenance Priorities: 

Emergency: Necessary to stop serious loss or violation, automatic approval, start within 24 hr., schedule or unscheduled.



Urgent: Necessary to ensure production reliability and/or prevent quality loss, approval required, schedule for specific date within 3 da ys.



Normal: Necessary to improve quantity or quality of p roduct and/or increase production reliability, approval required, scheduled, starts within 7 days.



Future : Work not covered by others priorities, approval required, schedul ed, starts within 30 days.



Shutdown : Work that can be postponed or can be completed when a unit is shut down, approval required, scheduled during shutdown. Unscheduled equipment breakdowns, requiring corrective maintenance, occur in all plants an usually warrant an “emergency” or “urgent” priority.



Chapter 3 Project Review 3.1 Objective: To study the process of steam generation in Steam Plant and Captive Power Plant.

3.2 Review: In Steam Generation Plant we study the various phases through which steam is generated to produce electricity for NFL Plant. We study these under the guidance of Mr. Rajesh Maurya (Deputy Manager) and Mr. Devinder Kumar (S.O. SG) who clear the path to understand the whole production system. The study of these plant includes: 

Study of Turbine, Nozzle, Generators



Study of H.P heater, L.P heater and Feed water Control station



Study of Boilers

3.3 Observations deduced: This project includes various observation deduced as a spectator in the industry.Some of the main observation deduced are: 

Minimum and maximum temperature requirement for plant working



Minimum and maximum pressure conditions that can bear ou t by the plant.



Boiler , L.P heater, H.P heaters and Feed water control Station brief working conditions with precaution to be taken during emergency conditions.

In the end we express our sincere thanks to most co-operative staff members because of this project study became successful.



Chapter 4 Project work 4.1 Study of Turbine, Nozzle, Condenser and Turbo-Generator: Here is the description of the Turbines , nozzle and generator which are currently operated in NFL, Bathinda unit.

4.1.1 Study of Turbine & Nozzle: Simply speaking, a turbine is like a windmill. A turbine, however, is much more complex with hundreds of rotating blades, called buckets, and stationary nozzles. The blades are arranged in groups, which are also known as stages. Steam enters the first stage, then passes from stage to stage, giving up energy and thus drops in pressure as the steam moves throu gh the stages. This movement causes the rotor to turn. Unlike the simple diagram you just saw, a turbine has multiple nozzles and blades that h ave curved entrances and exits. These blades are also known as buckets. The graphic on the left is a detailed drawing of the nozzle partition and buckets, and the graphic on the right is a cross-section of a turbine showing how they are arranged on the shaft. In an actual turbine, the steam flow begins when the high-pressure steam leaving the bo iler enters the turbine at speeds over 1000 miles per hour and temperatures of approximately 1000 degrees Fahrenheit. This high-temperature, high-pressure steam enters through the inlet co ntrol valves, which control the steam flow into the turbine. The steam then travels through the first-stage nozzles, and strikes the first row of buckets.

Fig 4.1 Steam passing through turbine Shaheed Bhagat Singh State Technical Campus, Ferozepur 31


At this point the pressure is decreasing as the steam is redirected through the nozzles. The expanding steam continues to flow through the rows of nozzles and buckets, each time striking the buckets which causes the main shaft to rotate and produce power. By the time the steam is ready to leave the turbine, almost all of its usable energ y has been removed. The pressure drops from inlet to exhaust can range from 300 PSI to over 3000 PSI and can vary considerably dependent upon the turbine and boiler design.

Fig 4.2 Shows steam processed through Turbine to boiler.

Fig 4.3 shows 3D view of nozzle part itions and buckets placing



4.1.2 Study of Condenser: The condenser is where the steam leaving the turbine (also known as the exhaust steam) is condensed by cooling water. The condenser is basically a box made of heavy steel that is attached to the exhaust opening of the turbine. It contains a bank of small tubes through which cold water flows. Therefore the steam leaving the turbine exhaust enters the condenser where it comes in contact with these cold tubes and is returned to its liquid state. The condensing of the steam creates a vacuum that reduces the atmospheric back pressure. In a turbine, vacuum is measured in inches of mercury (Hg), with 29.92 inches of mercury bein g a perfect vacuum. This is more efficient because without a vacuum the exhaust steam encounters resistance from the atmosphere and thus requires more work. B y removing this resistance the turbine has more power and the flow of the steam is no longer impeded. The condensed steam collects in the hot well, which is a reservoir at the bottom of the condenser, and is pumped back to the boiler where the cycle begins again.

Fig. 4.4 Sectional view of condenser



4.1.3 Study of Turbo-Generator: There are two generators of 15MW at NFL, Bathinda unit. A turbo generator is the combination of a turbine directly connected to an electric generator for the generation of electric power. Large steam-powered turbo generators provide the majority of the electricity. 

For base loads diesel generators are usually preferred, since the y offer better fuel efficiency, but on the other hand diesel generators have a lower power density and hence, require more space.



The efficiency of larger gas turbine plants can be enhanced by using a combined cycle, where the hot exhaust gases are used to generate steam which drives another turbo generator. Table 4.1 TG operating parameters before and after Overhauling

Sr.No.

Parameters

Date

(Before O/H)

(After O/H)

1

Turbine Load

MW

8.0

8.0

2

Steam Consm.

Te/Hr

42

37.0

3

Steam Cons.

Te/MWh

5.25

4.63

4

W.C.Press.

Kg/Cm2

24.8

28.36

Temp.

Deg.C

404

405

HP-2 press

Kg/Cm2

11.6

10.9

Temp.

Deg.C

345

339

HP-1 press.

Kg/Cm2

NA

NA

Temp

Deg.C

NA

NA

LP bleed Pr./

Kg/Cm2

0.11

-0.03

Temp.

Deg.C

212

FWT bleed Pr.

Kg/Cm2

*281 (not correct) 3.95

Temp

Deg.C

271

261.8

Exhaust Press.

Kg/Cm2

-0.91

-0.94

Temp.

Deg.C

47

41.36

Axial thrust

MM

0.15/0.13

0.17/0.18

5

6

7

8

9

10


3.1


4.2 Study of Feed water heaters and Feed water Control station: This section includes the whole feed water system comprising of feed water heater and feed water control station.

4.2.1 Feed water heaters: A feed water heater is a power plant component used to pre-heat water delivered to a steam generating boiler. Preheating the feed water reduces the irreversibilities involved in steam generation and therefore improves the thermodynamic efficiency of the system. This reduces plant operating costs and also helps to avoid thermal shock to the boiler metal when the feed water is introduced back into the steam c ycle. In a steam power plant feed water heaters allow the feed water to be brought up to the saturation temperature very gradually. This minimizes the inev itable irreversibilities associated with heat transfer to the working fluid (water). Closed feed water heaters are typically shell and tube heat exchangers where the feed water 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 feed water to the pressure of the extracted steam as with an open heater. However, the extracted steam must then be throttled to the condenser pressure, an isenthalpic process that results in some entropy gain with a slight penalty on overall cycle efficiency. Basically, two types of Feed water heater are used at NFL Bathinda are H.P heater and L.P heater.

Fig 4.5Feed water heater



4.2.2 Feed water control Station: All the feed water heater processing is monitored and controlled by the Feed water control station. Water-level controls continuously monitor the level of water in a steam boiler in order to control the flow of feed water into the boiler and to protect against a low water condition which may expose the heating surfaces with consequent damage.. The probes will be fitted in pads or standpipes on the crown of the shell or drum and enclosed in a protection tube which will extend to below the lowest water level. With water tube boilers the control of the water level needs to be precise and sensitive to fluctuating loads due to the high evaporative rates and relatively small steam drums and small water content. Three element control using the followings is applied during the normal operation : 

Drum level



Main steam flow



Feed water flow

In order to handle the situation, the steam flow rate should also be considered for drum level control. It can be done b y adding the steam flow rate as a feed forward signal to the output of the level controller. Hence, the supply of the feed water flow is compensated for changes in the steam flow rate demand. With this strategy as the steam flow rate changes the demand for the feed water flow rate also changes in the right direction and minimizes the effect of shrink and swell on the drum level.

Fig 4.6 feed water control station layout



4.3 Boiler: The NFL, Bathinda Plant uses water tube boiler for steam generation. Steam generation steps in boiler: i) The steam flow in the boiler begins when water enters thedrum from the economizer then travels to the furnace where it is heated. ii) A water-steam mixture is generated in the furnace water wall tub es and returns to the drum through a series of headers and connecting pipes. iii) Steam leaving the steam drum then passes through a bank of tubes known as the superheater where the steam is heated further. iv) The steam is then sent to the high-pressure turbine section.

Fig. 4.7 sectional view of boiler

4.3.1 Boiler Auxiliaries: There are five main boiler auxiliaries: i) Superheater ii) Air preheater iii) Reheater iv) Economizer



i) Superheater: A superheater is a device used to convert saturated steam or wet steam into dry steam used in steam engines or in processes, such as steam reforming. There are three types of superheaters namely: radiant, convection, and separately fired. A superheater can vary in size from a few tens of feet to several hundred feet (a few metres to some hundred metres).

ii) Air-Preheater: An air preheater (APH) is a general term used to describe any device designed to heat air before another process 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.

iii) Reheater: They are the same as the super-heaters but as their exit temperature is a little bite less than superheaters and their pressure is 20%-25% less than the super-heater, they can stand less quality material alloys.

iv) Economizer: An economizer 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 to occur 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.

Fig. 4.8 Economizer



Chapter 5 Results and Discussions 5.1 Observations: During the study of Captive Power Plant and Steam Generation Plant under which the various operating components are bounded to be kept in the maximum and minimum range so as the plant should work under optimum conditions. Here is the list of observation found during the working condition of plant are as follows: Table 5.1 Boiler operation requirements

Sr. no. 1 2 3 4 5 6

Operations

Observations 230 T/hr 124 Kg/cm 115.5 Kg/cm 10.5 Kg/cm 105 Kg/cm 3.2 Kg/cm

Evaporation capacity Design Pressure Drum Operating Pressure Drum Superheater system pressure drop Operating Pressure Superheater Economizer Pressure drop Table 5.2 Temperature of steam/water

Sr. no. 1 2 3 4 5 6 C 8 9

Operation Drum operation Entering low temperature superheater Leaving low temperature superheater Entering L.T.H.S after de-superheating Leaving L.T.H.S temperature Entering high temperature superheater Leaving high temperature superheater Entering economizer water Leaving economizer

Observations o 322 C o 322 C o 383 C o 347 C o 435 C o 414 C o 495 C o 200 C o 259 C

Table 5.3Spray water quantity

Sr. no. 1 2

Operation First spray water quantity between L.T.H.S & I.T.H.S Second spray water quantity between I.T.H.S & H.T.H.S


Observations 14.5 Ton/hr 6.60 Ton/hr


5.2 Layout of Captive Power Plant and Steam Generation Plant

Fig. 5.1 Layout of Captive Power Plant and Steam Generation Plant



Chapter 6 Cautions during Problems This chapter includes the measure and list of procedure to be followed to prevent accident and component losses. Here is the list of five main and common problems may occur during the general working of the plant.The set of procedure for :

6.1 High Condenser Level: i) Decrease the TG Load ii) Open the SV-118/218 (conform its opening from local.) iii) Open the local drain. iv) Open Bypass of CV-100/200. v) Check for malfunctioning of either CV-100/200 DM side outlet valve . vi) Or it may be maintained by openning recirculation valve at 4.5M.(in case CV 100/200 is open). ND

vii) 2

Condensate pump may be started.

6.2 Polish water failed from DM plant: i) Open condenste re-circulation valve (4.5M) to LP OF TG-1,TG-2. ii) Close main condensate valve (Common). iii) Maintain the FWT level either by regulating BFW pu mp. iv) Flow or throttling condensate outlet valve.

6.3 TG Vibration High: i) Check for Gland Steam low temperature. ii) Open Gland Steam Drain. iii) TG load may be reduced. iv) Check lubricating oil temperature.



6.4 Steam Temperature is low: i) Decrease TG load ii) Bypass low temperature and watchout for trip.(TG vibrations) iii) In case of abnormal vibrations trip TG.

6.5 Exhaust temperature High/Vacuum low: i) Open condenser re-circulation of CV-101/201 & make up for quenching. ii) Check cooling water flow temperature. iii) Decrease the TG load as the situation d emands.



Chapter 7 Conclusion The introduction of the system of a job training in industries added new dimension to the technical education in the state of Punjab . Such a practical training not only focuses visions of the students but also helps us to encounter heavy machinery and study its working . This goes a long way to understand the engineering theory more vividly a nd grasp it easily. Efforts have been made to study National Fertilizers Limited, Bathinda Unit. in systematic and proper wa y under the valuable guidance of Mr. Rajesh Maurya(DM) and expressed this in the report little bit I have understood. Working in an industry is quite different from college study. There is no prescribed book or syllabus and whatever is to be learnt has to be from hands on experience on the job. I feel that objectives of training are fully achieved and I have learnt a lot about functioning of an industry.


NFL BATHINDA TRAINING FILE

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