Dvc Andal Vt Report

Training Report 2014

VOCATIONAL TRAININGDSTPS, DVC ANDAL

Project Report

Submitted by:

Satyaki DuttaDepartment of Mechanical Engineering

Jadavpur University

Under the guidance of

Mr. P. K. SIKDARDy. Chief Engineer (M), DVC, DSTPS

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The dissertation has been prepared based on the vocational training undergone in a highly esteemed organisation of Eastern region, a pioneer in Generation Transmission & Distribution of power, one of the most technically advanced thermal power stations in India, the Durgapur Steel Thermal Power Station (D.S.T.P.S), under DVC. We would like to express our heartfelt gratitude to the authorities of Durgapur Steel Thermal Power Station for providing us such an opportunity to undergo training in the thermal power plant of DVC, DSTPS.

I would also like to thank the highly experienced Engineers, without whom such type of concept building in respect of thermal power plant would not have been possible. Some of them are:

1) Mr. P.K.Sikdar, Dy. CHIEF ENGINEER (M), DVC, DSTPS

2) Mr. M.K.Singh, SE (M), CHP, DVC, DSTPS

3) Mr. A. Kumar, SE (M), BOILER & AUXILIARIES, DVC, DSTPS

4) Mr. S.N.Dutta, SE (M), TURBINE & AUXILIARIES, DVC, DSTPS

5) Mr. V.N.Sharma, SE (M), OPERATION SUPERINTENDENT, DVC, DSTPS

INTRODUCTION

DVC (Damodar Valley Corporation) a legacy to the people of India, emerged as a culmination of attempts made over a whole century to control the wild and erratic Damodar

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river. The river spans over an area of 25,000 sq. kms covering the states of Bihar (now Jharkhand) & West Bengal. The Corporation came into existence on 7th July, 1948 as the first multipurpose river valley project of independent India.

DSTPS or Durgapur Steel Thermal Power Station is one of the eight thermal coal based power plants of DVC, situated at Andal , Durgapur in the district of Burdwan , West Bengal , India having co ordinates 23°34'48"N , 87°12'19"E.

TECHNICAL SPECIFICATION OF DSTPS

INSTALLED CAPACITY: -

1) Total number of Units: - 2 X 500 MW (unit 1 to 2)

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2) Total Energy Generation: - 1000MW

3) Source of Water: - Damodar River

4) Sources of Coal: - BCCL, CCL with FSA (Fuel Supply Agreement)

5) Sources of Oil :- Indian Oil Corporation

OVERVIEW OF A THERMAL POWER PLANT

In a Thermal Power generating unit, combustion of fossil fuel (coal, oil natural gas) in Boiler generates heat energy. This heat energy transforms water steam at high pressure and temperature. This steam is utilised to generate mechanical energy in a Turbine. This mechanical energy, in turn is converted into electrical energy with the help of an Alternator coupled with the Turbine. The production of electric energy utilising heat energy is known as thermal power generation.

The heat energy changes into mechanical energy following the principle of Rankine reheat-regenerative cycle and this mechanical energy transforms into electrical energy based on Faraday’s laws of electromagnetic induction.

General Layout of Thermal Power Station

OVERVIEW OF A THERMAL POWER PLANT

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1. Cooling tower 12. De-aerator 23. Economiser

2. Cooling water pump 13. Feed heater 24. Air pre heater

3. Transmission line (3-phase) 14. Coal conveyor 25. Precipitator

4. Unit transformer (3-phase) 15. Coal hopper 26. Induced draught fan

5. Electric generator (3-phase) 16. Pulverised fuel mill 27. Chimney Stack

6. Low pressure turbine 17. Boiler drums

7. Condensate extraction pump 18. Ash hopper

8. Condenser 19. Super heater

9. Intermediate pressure turbine 20. Forced draught fan

10. Steam governor valve 21. Re-heater

11. High pressure turbine 22. Air intake

COAL HANDLING PLANT

INTRODUCTION

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What is CHP??

CHP is (C- Coal, H- Handling, P- Plant) a plant which handles the coal from its receipt to transporting it to Boiler and store in Bunkers. It also processes the raw coal to make it suitable for Boiler Operation.

BASICS OF OPERATION The sizes of coal lumps is about to the 600mm. This coal is fed to single rotary crusher and after that the size become 300mm. This coal is again fed to the double rotary crusher and the size become 80mm. This coal is again fed to the crusher and the size become less than 20 mm or 20mm. Then this coal is fed to the coal mill for pulverization. Even when the bunker is full this coal is used for stacking or storage of coal in coal storage area.OBJECTIVE OF CHP: Objective of CHP is to supply the quanta of processed coal to bunkers of Coal mills for Boiler operation and to stack the coal to coal storage area. • Coal is a hard black or dark brown sedimentary rock formed by the decomposition of plant material, widely used as a fuel. • A piece of coal called Coal Lumps. Mostly E and F grade coal used in India. In brief we can say that receipt of coal from coal mines, weighing of coal, crushing it to required size and transferring the quantity of coal to various coal mill bunkers. This is the responsibility and duty of the CHP and its staff.

Fig: COAL HANDLING PLANT

L I ST OF MA JOR EQU I P M ENT/ S Y ST EM OF CO AL HAND LING P LANT OF DS TP S UNIT

N O: 1, 2, UN D ER T HE CONTR A C TO R ’S S C O PE OF WOR K.

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1. Tr a c k unlo a ding hopp e r a nd a c c e s s o r i e s :

(A) RCC Track Hopper – 1 (Length – 250 M width - 6M), Capacity – 5500MT

(B) Steel grating over hopper – 300MM X 300 MM Mesh

(C) Track Hopper Beams all sides (except bottom) and inclined portion of inner surface all through lined with replaceable SAILHARD/ SAILMA Plates.

(D) Concrete table top all through lined with 16MM thick SAILHARD/SAILMA Plates (removable).

(E) Paddle Feeders – 4 Nos. (Each of Capacity 900 TPH)

2. B e l t c onv e y ors a n d acc e s s or ie s :-

Capacity 1600 TPH (rated) Design 1760 TPH, Troughing Angle – 35.

A) 2 nos.1400 mm belt conveyors(Horizontal) 1A and 1B each of approximate length – 302mtrs. complete with belting, idlers, pulleys, speed reducer, drives and motors, tension devices, cleaning devices, pulleys and coupling, hold backs, transfer chutes and accessories for carrying coal of 350 mm and down lump size.

B) 2 nos. 1400 mm belt conveyors (inclined) nos. 2A and 2B each of approx length 109mtrs. complete with usual accessories

C) 2 nos. 1400 mm belt conveyor(Horizontal) no. 3A and 3B each of approx length – 308 mtrs. respectively with all usual accessories mentioned in 2 (A) including in-line Magnetic separators ,Metal Detector ,suspended magnet at head end along with non-magnetic pulleys and belt weighers. To carry crushed coal of 350 mm and down up to Crusher house discharging to Roller screen.

D) 2 no. 1400 mm belt conveyor(Horizontal) no. 4A/4B of approximate length 250 mtrs. with usual accessories inter connecting conveyor no5 to 6.

E) 2 nos. 1400 mm belt conveyors(inclined) no. 5and 6 each of approx 450 mtrs. with usual accessories for carrying coal (20mm and down) from transfer points to conveyor no. 7A and 7B.

F) 2 nos. 1400 mm belt conveyors(inclined) no. 7A and 7B each of approx. length – 250 mtrs. with usual accessories to discharge coal to conveyor belt 8A and 8B.

G) 2 Nos. 1400 mm belt conveyors(Horizontal) no 8A & 8B each of approx. length-360 mtrs with usual accessories for feeding coal to belt conveyors no. 10A and 10B each of approx. length 680 mtrs. with usual accessories mentioned in 2 (A) including in-line Magnetic separators ,Metal Detector ,suspended magnet at head end along with non-magnetic pulleys. for transfer of coal to conveyor no 11A/11B.

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H) 02 Nos. 1400 mm belt conveyors(Horizontal) no 11A & 11B each of approx. length-200 mtrs with usual accessories for feeding coal to belt conveyors no. 12A and 12B each of approx. length 140mtrs. with usual accessories mentioned in 2 (A) Accessories fitted with Conveyors. Conveyors 11A/11B also transfer the coal to bunker conveyor B1 and B2 each of approximate length 80 mtrs. Belt conveyors no. 12A and 12B also transfer the coal to bunker conveyor B3 and B4 each of approximate length 80 mtrs. There are 4 nos of travelling tripper for transferring the coal from bunker conveyors B1,B2,B3 and B4 to coal bunkers.Belt wiper units, pull cord type emergency switches, belt sway limit switches, foundation plate, anchor bolts, fasteners etc. counter weight, one zero speed switches for each conveyor, brakes and hold-backs, steel structures/CGI sheet enclosure for all outdoor conveyors.

4. Cr u s h e r H o u s e E qu i p m e n t :

a) Ring type Granulator Crusher (900 TPH rated each) – 4nos. with motors and fluid couplings.

b) Roller screen (900 TPH rated each) . with motors and fluid couplings to receive coal from Conv. # 3A/3B& discharge to Cr- 1, 2, 3 and4.Coal sampling unit

c) Linear actuator operated flap gates, belt feeders ,rack and pinion gate ,rod gates etc. One number rack and pinion elevator, Vibration monitoring and vibration isolation system

5. T r a v e l i ng S tac k e r - c u m - R e c la im e r : Stacker-cum-Reclaimer for Stacking and reclaiming mounted on Conv. no. 5 & 6 with all accessories like tripper Unit, boom conveyor, bucket wheel control panel etc. 2 nos.

6. Track hopper Maint. Bay, Wagon tippler, tunnel area and sump pump pits.

7. Coal bunkers for Unit 1,2, with ten hoppers in each Unit, each capacity of 600 MT.

8. Structure, Structural steel construction etc. for conveyor frames, head frames, stringers, hand rails, walk ways, safety guards, stairs etc.

9. a) Travelling tripper – 4 nos.b) Magnetic separators – 4nos.c) Metal detectors – 4

nos.d) Coal samplers – 2 nos.e) Belt weighers – 4 nos(2 nos. in crushing side and 2 nos. in feeding side)

10. A i r p o ll u ti o n c on t r o l s y s t e m : a)Ventilation system – Ventilation system in Track Hopper, wagon tippler,MCC(3 nos),TP1b)Dust extraction system DE – In all Bunkers and crusher housec) Dust suppression system-Dry fog system in all TPs and wet system in track hopper and

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crushed coal stock pile area.

COMPRESSOR - 2nos for BOBR opening.

Pump house A

DS pump-6 nos SWS pump-2nos CWS pump-2 nos DEWS pump-2nos WSS pump-2 nos DFS pump-2 nos Compressor for DFS -2

nos

Pump house B

DFS pump-2 nos SWS pump-2nos CWS pump-2 nos

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WATER TREATMENT PLANT

Raw water supply: Raw water received at the thermal power plant is passed through Water Treatment Plant to separate suspended impurities and dissolved gases including organic substance and then through De-mineralised Plant to separate soluble impurities.

Deaeration: In this process, the raw water is sprayed over cascade aerator in which water flows downwards over many steps in the form of thin waterfalls. Cascading increases surface area water to facilitate easy separation of dissolved undesirable gases (like hydrogen sulphide, ammonia, volatile organic compound etc.) or to help in oxygenation of mainly ferrous ions in presence of atmospheric oxygen to ferric ions.

Coagulation: Coagulation takes place in clariflocculator. Coagulant destabilises suspended solids and agglomerates them into heavier floc, which is separated out through sedimentation. Prime chemicals used for coagulation are alum, poly-aluminium chloride (PAC).

Filtration: Filters remove coarse suspended matter and remaining floc or sludge after coagulation and also reduce the chlorine demand of the water.

Chlorination: Neutral organic matter is very heterogeneous i.e. it contains many classes of high molecular weight organic compounds. Humic substances constitute a major portion of the dissolved organic carbon from surface waters. They are complex mixtures of organic compounds with relatively unknown structures and chemical composition.

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DM (Demineralised Water) Plant: In De-mineralised Plant, the filter water of Water Treatment Plant is passed through the pressure sand filter (PSF) to reduce turbidity and then through activated charcoal filter (ACF) to adsorb the residual chlorine and iron in filter water.

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BOILER & AUXILIARIES

Boiler

Working principle of Boiler (Steam Generator): In Boiler, steam is generated from demineralised water by the addition of heat. The heat added has two parts: sensible heat and latent heat. The sensible heat raises the temperature and pressure of water as well as steam. The latent heat converts water into steam (phase change). This conversion is also known as boiling of water, which is dependent on pressure and corresponding temperature. Thermodynamically, boiling is a process of heat addition to water at constant pressure & temperature. The quantity of latent heat decreases with increase in pressure of water and it becomes zero at 221.06 bars. This pressure is termed as Critical Pressure. The steam generators are designated as sub-critical or super critical based on its working pressure as below critical or above critical pressure. The steam, thus formed is dry & saturated. Further, addition of heat raises the temperature and pressure of steam, which is known as superheated steam. The differential specific weight between steam and water provides the driving force for natural circulation during the steam generation process. This driving force considerably reduces at pressure around 175 Kg/cm2 and is not able to overcome the frictional resistance of its flow path. For this, forced or assisted circulation is employed at higher sub-critical pressure range due to the reason of economy. But, at supercritical pressures and above, circulation is forced one (such boiler is called once through boiler).

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Fig: BOILER

Important parts of Boiler & their functions:

Economizer:

Feed water enters into the boiler through economizer. Its function is to recover residual heat of flue gas before leaving boiler to preheat feed water prior to its entry into boiler drum. The drum water is passed through down-comers for Circulation through the water wall for absorbing heat from furnace. The economizer recirculation line connects down-comer with the economizer inlet header through an isolating valve and a non-return valve to protect economizer tubes from overheating caused by steam entrapment and starvation. This is done to ensure circulation of water through the tubes during initial lighting up of boiler, when there is no feed water flow through economizer.

Drum:

Boiler drum is located outside the furnace region or flue gas path. This stores certain amount of water and separates steam from steam-water mixture. The minimum drum water level is always maintained so as to prevent formation of vortex and to protect water wall tubes (especially its corner tubes) from steam entrapment / starvation due to higher circulation ratio of boiler.

Superheater:

Superheaters (SH) are meant for elevating the steam temperature above the saturation temperature in phases; so that maximum work can be extracted from high energy (enthalpy) steam and after expansion in Turbine, the dryness fraction does not reach below 80%, for avoiding Turbine blade erosion/damage and attaining maximum Turbine internal efficiency. Steam from Boiler Drum passes through primary superheater placed in the convective zone of the furnace, then through platen superheater placed in the radiant zone of furnace and thereafter, through final superheater placed in the convective zone. The superheated steam at requisite pressure and temperature is taken out of boiler to rotate turbo-generator.

Reheater:

In order to improve the cycle efficiency, HP turbine exhaust steam is taken back to boiler to increase temperature by reheating process. The steam is passed through Reheater, placed in between final superheater bank of tubes & platen SH and finally taken out of boiler to extract work out of it in the IP and LP turbine.

De-superheater (Attemperator):

Though superheaters are designed to maintain requisite steam temperature, it is necessary to use de-superheater to control steam temperature. Feed water, generally taken before feed

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water control station, is used for de-superheating steam to control its temperature at desired level.

Technical data of the Boiler:

Manufacturer - M/s BHEL (C.E. Design)

Type Balanced Draft, Dry bottom, Single Drum Controlled Circulation plus.

Type of FIRING Tilting TANGENTIAL

Minimum load at which steam generator can be operated continuously with complete flame, stability without oil support (& MCR)

2 adjacent, Mills at 50% capacity.

Minimum load at which the steam generator can be operated continuously with complete flame stability with oil support (% MCR)

20%

Maximum load for which individual mill beyond which no oil support is required

50%

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TURBINE & AUXILIARIES

Steam turbine converts the heat energy to mechanical energy and drives the alternator. The velocity during expansion of steam depends on the initial and final heat content of the steam . The turbines consist number of stages where the pressure drop takes place .

MAIN COMPONENTS OF TURBINES AND AUXILIARIES:

1. Turbine2. Generator and Exciter3. Condenser4. LP and HP heater5. Deareator6. Boiler Feed Pump7. Condensate extraction pump8. Auxiliary oil pump

1. Turbine: A turbine is a series of fixed and rotating blades that extract the mechanical and thermal energy from the steam. According to pressure of steam flow turbines can be classified as

1. High Pressure Turbine2. Intermediate pressure Turbine and 3. Low pressure turbine.

The specifications are given below:

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2. Generator and Exciter: The Generator generates electrical power by the interaction of the rotating magnetic fields of the stator and rotor. The Exciter supplies direct current power to the electromagnet to produce the magnetic field within the generator.

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Fig: Turbine & Generator3. Condenser: After expansion at the turbine the wet vapour comes to condenser and condensed to liquid water. The condenser used in DVC is a surface condenser which of consist a large no of small diameter tubes. the cooling water passes through individual tubes and steam flows over and around the tube bundles. The condensate is collected at the bottom of the condenser known as the Hotwell.

4. LP and HP Heater : Both LP and HP heater are used to increase the temperature of water or wet steam which enters the boiler, for increasing the mean temperature of heat addition in the boiler to increase the overall efficiency.

5. Deareator: Deareator is used for the removal of oxygen and other dissolved gases from the feed water to boilers.

6. Boiler feed pump: Boiler feed pump extracts water from de-aerator and feed it to the boiler drum via H.P heaters and economizer. This is usually accomplished through the use of a centrifugal pump. BFP is two types

Turbine driven boiler feed pump : It works with the steam extraction from Intermediate Pressure (I.P.) turbine exhaust.

Motor driven boiler feed pump: It works with a motor as the name specifies

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7. Condensate extraction pump: It extracts the condensate from the condenser and sends it to the feed water tank after passing it through LP heater and deareator .

8. Auxiliary oil pump: Auxiliary oil system pump is used to supply oil at the start-up of the steam turbine generator. It supplies the hydraulic oil system required for steam turbine's main inlet steam stop valve, the governing control valves, the bearing and seal oil systems, the relevant hydraulic relays and other mechanisms.

AIR AND FLUE GAS SYSTEM

AIR SYSTEM

Correct amount of air is the most essential ingredient for Combustion. More air or less air both makes the combustion process inefficient.

Forced Draft Fan supplies most of the Combustion air. This fan takes air from the atmosphere and blows it into the furnace through air ducts. The Air Heater heats the air before it enters the Furnace.

Air Heater utilises the heat of the hot flue gases that leave the boiler to heat the combustion air. Hot air improves the efficiency of combustion. The Air Heater works on the regenerative principle. Steel plates alternatively placed in the hot flue gas path and then in the air path heats the cold air entering the Air Heater.

Primary Air Fan supplies the air to the pulverisers for drying and transporting coal. This air called the Primary air also is heated in the Air Heater.

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FLUE GAS SYSTEM.

Coal burns in the furnace giving out heat and forming flue gases.

Induced Draft Fan . The hot flue gases from the furnace is drawn out by the Induced draft fan. The gases passes through the various heating surfaces of the boiler, the Electrostatic Precipitator and discharges to the atmosphere at the top of the stack. Induced Draft Fan provides the energy for this flow of flue gases. The Induced Draft Fan is normally located adjacent to the Stack.

Electrostatic Precipitators capture the fly ash in the flue gases without letting them out into the atmosphere. High voltage electrodes placed in the gas path ionise the ash particles which collects on collecting electrodes and falls into ash hoppers.

Stack or the Chimney disperses the hot gases and any other particles at a great height. The height enables a very large dispersion area and regulates emission concentrations at ground levels to the level acceptable to humans and vegetation. Stack heights for large power plants are around 250 to 280 meters.

Balanced Draft. The Forced Draft fan and the Induced Draft fan operate in such a way that the air pressure in the furnace is at zero pressure ie: at atmospheric pressure. This is called the ‘Balanced Draft system’.

ASH HANDLING PLANT

INTRODUCTION

Ash is the residue remaining after the coal is incinerated. The composition of ash are SiO2,

Al2O3, Fe2O3, CaO, MgO etc . In Thermal Power Plant’s coal is used as fuel and hence the ash is produced as the byproduct of Combustion. Ash generated in power plant is about 30-40% of total coal consumption and hence the system is required to handle Ash for its proper utilization or disposal. The ash produced is two types , Fly ash and Bottom ash.

Ash generated in the ESP which got carried out with the flue gas is generally called Fly ash. It also consists of Air pre heater ash & Economiser ash (it is about 2 % of the total ash content). Ash generated below furnace of the steam generator is called the bottom ash.

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ASH HANDLING SYSTEM

The ash handling system handles the ash by bottom ash handling system, coarse ash handling system, fly ash handling system, ash disposal system up to the ash disposal area and water recovery system from ash pond and Bottom ash overflow. Description is as follows:

Bottom Ash Handling System

Bottom ash resulting from the combustion of coal in the boiler shall fall into the over ground, refractory lined, water impounded, maintained level, double V-Section type/ W type steel- fabricated bottom ash hopper having a hold up volume to store bottom ash and economizer ash of maximum allowable condition with the rate specified. The slurry formed shall be transported to slurry sump through pipe.

Coarse Ash (Economizer Ash) handling System

Ash generated in Economizer hoppers shall be evacuated continuously through flushing boxes. Continuous generated Economizer slurry shall be fed by gravity into respective bottom ash hopper pipes with necessary slope.

Air Pre Heater ash handling system

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Ash generated from APH hoppers shall be evacuated once in a shift by vacuum conveying system connected with the ESP hopper vacuum conveying system.

Fly Ash Handling System

Fly ash is considered to be collected in ESP Hoppers. Fly ash from ESP hoppers extracted by Vacuum Pumps up to Intermediate Surge Hopper cum Bag Filter for further Dry Conveying to fly ash silo. Under each surge hopper ash vessels shall be connected with Oil free screw compressor for conveying the fly ash from Intermediate Surge Hopper to silo. Total fly ash generated from each unit will be conveyed through streams operating simultaneously and in parallel.

Ash Slurry Disposal System

Bottom Ash slurry, Fly ash slurry and the Coarse Ash slurry shall be pumped from the common ash slurry sump up to the dyke area which is located at a distance from Slurry pump house.

The practical experience that I have gathered during the overview training of large thermal power plant having a large capacity of 1000 MW for Unit# I to II in two weeks will be very useful as a stepping stone in building bright professional career in future life. It gave me large spectrum to utilize the theoretical knowledge and to put it into practice. The trouble shooting activities in operation and decision making in case of crisis made me more confident to work in the industrial atmosphere. Moreover, this overview training has also given a self realization & hands-on experience in developing the personality, interpersonal relationship with the professional executives, staffs and to develop the leadership ability in industry dealing with workers of all categories. I would like to thank everybody who has been a part of this project, without whom this project would never be completed with such ease.

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Dvc Andal Vt Report