Guru Nanak Dev Thermal Power Plant is a coal-based plant. The requirement of

coal for four units based on specific fuel consumption of 0.60 kg / kWh. The conveying

and crushing system will have the same capacity as that of the unloading system. The

coal comes in as large pieces. This coal is fed to primary crushers, which reduce the size

of coal pieces from 400mm to 150mm. Then the coal is sent to secondary crusher through

forward conveyors where it is crushed from 150mm to 200mm as required at the mills.

Then the coal is sent to boilers with the help of primary fans. The coal is burnt in the

boiler. Boiler includes the pipes carrying water through them; heat produced from the

combustion of coal is used to convert water in pipes into steam. This steam generated is

used to run the turbine. When turbine rotates, the shaft of generator, which is

mechanically coupled to the shaft of turbine, gets rotated so, three phase electric supply is

produced.

The basic requirements are:-

♣ Fuel (coal)

♣ Boiler

♣ Steam turbine

♣ Generator

♣ Ash handling system

♣ Unit auxiliaries

1

INTRODUCTION

Due to high rate of increasing population day by day, widening gap between power

demand and its availability was one the basic reason for envisaging the G.N.D.T.P. for

the state of Punjab. The other factors favoring the installation of the thermal power

station were low initial cost and comparatively less gestation period as compared to

hydro electric generating stations. The foundation stone of G.N.D.T.P. at bathinda was

laid on 19th November 1969, the auspicious occasion of 500th birth anniversary of great

Guru Nanak Dev Ji.

The historic town of bathinda was selected for this first and prestigious thermal

project of the state due to its good railway connections for fast transportations of coal,

availability of canal water and proximity to load center.

The total installed capacity of the power station 440MW with four units of

110MW each. The first unit of the plant was commissioned in September, 1974.

Subsequently second, third and fourth units started generation in September 1975, March

1978, and January 1979 respectively. The power available from this plant gives spin to

the wheels of industry and agricultural pumping sets.

2

BRIEF HISTORY OF PLANT

R&M of GNDTP unit 1&2 has already been completed pending PG Test. R&M works of

unit 3&4 is underway to improve performance, enhance capacity and extend operating

life of the units. The present status of R&M works of GNDTP units is as under:

Unit I&II: - Against approved project Report of Rs. 229 Crores, Order was placed on

M/S NASL, New Delhi for major R&M works on Turnkey basis at a total of Rs.183

Crores.

Unit II: R&M works completed in October, 2005 (Pending attending to some deficiencies

by the firm). Average PLF achieved post R&M works is 87%.

Unit I: - R&M works completed and taken for normal operation in May, 2007(Pending

attending to some deficiencies by the firm). Average PLF achieved post R&M during

May’07 and June ’07 is 95.65%.

Unit III & IV: - Order for executing R&M works on Turnkey basis already placed on

M/S BHEL at a total cost of Rs. 465.36 Crores. 10% advance payment has been made to

M/S BHEL on 22/12/2006 and design and drawing work is in progress. As per Schedule,

work is to be completed in a phased manner upto July 2009. Apart from enhancing the

operating life and performance level of the units, it is also planned to upgrade the

capacity from 110 MW to 120 MW each resulting in total capacity addition of 20 MW.

3

R&M WORKS AT GNDTP, BATHINDA

The selection of site for Thermal Power Plant is more difficult compared to Hydro

Power Plant, as it involves number of factors to be considered for its economic

justification. The following consideration should be examined in detail before selection

of the site for the Plant. The location for plant should be made with full consideration not

only of the trends in the development and location but also the availability and location of

the cheapest source of primary energy:-

Availability of fuel

Ash disposal facilities

Space requirement

Nature of land

Availability of labour

Transport facilities

Public society problems

Development of Backward Area

4

SITE SELECTION

G.N.D.T.P. won an award of Rs. 3.16 crores from Govt. of India for better

performance in 1983-84.

It achieved a rare distinction of scoring hart Rick by winning meritorious

productivity awards of Govt. of India, Ministry of Energy for year 1987, 1988 and

1989 due to its better performance.

It again won meritorious productivity awards during the year 1992-1993 and

1993-94 and has become entitled for the year 1996-1997 for better performance.

It also won awards for reduction in fuel oil consumption under Govt. of India

incentive scheme years from 1992-1993 (awards money for 1992, 1993 and 1994

already released for 1995, 1996 and 1997 under the consideration of Govt. of

India).

G.N.D.T.P. had achieved a generation of 2724240 LU’s (at a PLf of 70%) and

registering an oil consumption as low as 1.76ml/kwh during the year 1993-94 has

broken all previous records of performance since the inception of plant.

5

LANDMARK ACHIEVED

Guru Nanak Dev Thermal Plant, Bathinda, in addition to indirect contribution in various

facts of state economy, is also responsible for:-

Narrowing the gap between power demand and power availability of the state.

Providing employment potentials to thousands of workers.

Covering the backward surrounding area into fully developed Industrial

Township.

Providing additional relief to agricultural pumping sets to meet the irrigation

needs for enhancing the agriculture production.

Reliability and improvement in continuity of supply and system voltage.

Achieving cent percent rural electrification of the state.

6

CONTRIBUTION OF THE PLANT

PROJECT AREA:-

Power plant 238 acres

Ash disposal 845

Lake 180

Residential colony 285

Marshalling yard 256

Total area 1804

TOTAL COST: - Rs. 115 crores

STATION CAPACITY: - four units of 110MW.each

BOILER:-

Manufacturers B.H.E.L.

Maximum continuous rating (M.C.R.) 375 T/hr.

Superheater outlet pressure 139 kg/cm²

Reheater outlet pressure 33.8 kg/cm²

Final superheater/reheater temperature 540C

Feed water temperature 240C

Efficiency 86%

Coal consumption per day per unit 1400 tones (Approximate)

7

PLANT SALIENT FEATURESTHE PLANT

STEAM TURBINE:-

Manufacturers B.H.E.L.

Rated output 110 MW.

Rated speed 3000 r.p.m.

Number of cylinders three

Rated pressure 130 kg/cm²

Rated temperature 535C

Condenser vacuum 0.9 kg/cm²

GENERATOR:-

Manufacturers B.H.E.L.

Rated output

(Unit- 1 & 2) 125000KVA

(Unit -3 & 4) 137000KVA

Generator voltage 11000 volts

Rated phase current

(unit –1 & 2) 6560 Amps.

(unit –3 & 4) 7220 Amps.

Generator cooling hydrogen

BOILER FEED PUMPS:-

Number per unit two of 100% duty each

Type centrifugal

Rated discharge 445 T/hr.

Discharge head 1960 MWC.

Speed 4500 r.p.m.

8

CIRCULATING WATER PUMPS:-

Numbers for two units five of 50% duty each

Type mixed flow

Rated discharge 8600 T/hr.

Discharge head 24 MWC.

COOLING TOWERS:-

Numbers four

Water cooled 18000 T/hr.

Cooling range 10C

Height 120/12 metres

COAL PULVERISING MILLS:-

Numbers three per unit

Type drum-ball

Rated output 27 T/hr.

Coal bunkers 16 per unit

RATING OF 6.6 KV AUXILLIARY MOTORS:-

Coal mill 630 KW

Vapour fan 320 KW

C.W. Fan 800/746 KW

Coal crusher 520 KW

Primary air fan 320 KW

9

Forced draught fan 320 KW

Boiler feed pump 3500 KW

Induced draught fan 900/1000 KW

Condensate pump 175 KW

10

Coal received from collieries in the rail wagon is mechanically unloaded by

Wagon Tippler and carried by belt Conveyor System Boiler Raw Coal Bunkers after

crushing in the coal crusher. The crushed coal when not required for Raw Coal Bunker is

carried to the coal storage area through belt conveyor. The raw coal feeder regulates the

quantity of coal from coal bunker to the coal mill, where the coal is pulverized to a fine

powder. The pulverized coal is then sucked by the vapour fan and finally stored in

pulverized coal bunkers. The pulverized coal is then pushed to boiler furnace with the

help of hot air steam supplied by primary air fan. The coal being in pulverized state gets

burnt immediately in the boiler furnace, which is comprised of water tube wall all around

through which water circulates. The water gets converted into steam by heat released by

the combustion of fuel in the furnace. The air required for the combustion if coal is

supplied by forced draught fan. This air is however heated by the outgoing flue gases in

the air heaters before entering the furnace.

The products of combustion in the furnace are the flue gases and the ash. About

20% of the ash falls in the bottom ash hopper of the boiler and is periodically removed

mechanically. The remaining ash carried by the flue gases, is separated in the

electrostatic precipitators and further disposed off in the ash damping area. The cleaner

flue gases are let off to atmosphere through the chimney by induced draught fan.

The chemically treated water running through the water walls of boiler furnace

gets evaporated at high temperature into steam by absorption of furnace heat. The steam

is further heated in the super heater. The dry steam at high temperature is then led to the

turbine comprising of three cylinders. The thermal energy of this steam is utilized in

turbine for rotating its shaft at high speed. The steam discharged from high pressure

(H.P.) turbine is returned to boiler reheater for heating it once again before passing it into

the medium pressure (M.P.) turbine. The steam is then let to the coupled to turbine shaft

is the rotor of the generator, which produces electricity. The power from the generator is

pumped into power grid system through the generator transformer by stepping up the

voltage.

11

WORKING OF THERMAL PLANT

Fig No.1.1

12

The steam after doing the useful work in turbine is condensed to water in the

condenser for recycling in the boiler. The water is pumped to deaerator from the

condenser by the condensate extraction pumps after being heated in the low pressure

heater (L.P.H) from the deaerator, a hot water storage tank. The boiler feed pump

discharge feed water to boiler at the economizer by the hot flue gases leaving the boiler,

before entering the boiler drum to which the water walls and super heater of boiler are

connected.

The condenser is having a large number of brass tubes through which the cold

water is circulated continuously for condensing the steam passing out sides the surface of

the brass tubes, which has discharged down by circulating it through the cooling tower

shell. The natural draught of cold air is created in the cooling tower, cools the water fall

in the sump and is then recirculated by circulating water pumps to the condenser.

13

BOILER FEED PUMP:-

As the heart is to human body, so is the boiler feed pump to the steam power plant. It is

used for recycling feed water into the boiler at a high pressure for reconversion into

steam. Two nos. 100% duty, barrel design, horizontal, centrifugal multistage feed pumps

with hydraulic coupling are provided for each unit. This is the largest auxiliary of the

power plant driven by 3500 KW electric motor.

The capacity of each boiler at GURU NANAK DEV THERMAL PLANT is

375 tones/hr. The pump which supplies feed water to the boiler is named as boiler feed

pump. This is the largest auxiliary in the unit with 100% capacity which takes suction of

feed water from feed water tank and supplies to the boiler drum after preheating the same

in HP-1, HP-2 and economizer. The delivery capacity of each boiler feed pump is 445

tones/hr. to meet better requirements corresponding to the various loads, to control steam

temperature, boiler make up water etc. The detailed particulars checking of protections

and inter locks, starting permission etc. are as below:-

Particulars of BFP and its main motor:- BOILER FEED PUMP : - The 110 MW turboset is provided with two boiler feed

pumps, each of 100% of total quantity. It is of barrel design and is of horizontal

arrangement, driven by an electric motor through a hydraulic coupling.

Type 200 KHI

No. of stages 6

Delivery capacity 445 t/hr.

Feed water temperature 158C

Speed 4500 rpm

Pressure at suction 8.30 kg/cm²

Stuffing box mechanical seal

Lubrication of pump by oil under pressure

And motor bearing supplied by hydraulic coupling

Consumption of cooling water 230 L/min.

14

GENERAL DESCRIPTION

WATER TREATMENT PLANT:-

The water before it can be used in the boiler has to be chemically treated, since untreated

water results in scale formation in the boiler tubes especially at high pressure and

temperatures. The water is demineralised by Ion Exchange Process. The water treatment

plant has production capacity of 1800 Tonnes per day for meeting the make-up water

requirement of the power station.

COAL MILL:-

Coal Mill pulverizes the raw coal into a fine powder before it is burnt in the boiler

furnace. The pulverizing of coal is achieved with the impact of falling steel balls,

weighing 52.5 tonnes, contained in the mill drum rotating at a slow speed of 17.5 r.p.m.

The raw coal is dried, before pulverizing, with inert hot flue gases tapped from the boiler.

Three coal mills each with a pulverizing capacity of 27 T/hr. are provided for one unit.

INDUCED DRAUGHT FAN:-

Two nos. axial flow Induced Draught Fans are provided for each unit to exhaust ash

laden flue gases from boiler furnace through dust extraction equipment and to chimney.

The fan is driven by an electric motor through a flexible coupling and is equipped with

remote controlled regulating vanes to balance draught conditions in the furnace. The fan

is designed to handle hot flue gases with a small percentage of abrasive particles in

suspension.

CONTROL ROOM:-

The control room is the operational nerve center of the power plant. The performance of

all the equipments of the plant is constantly monitored here with the help of sophisticated

instrumentation and controllers. Any adverse deviation in the parameters of various

systems is immediately indicated by visual and audio warning and suitable corrective

action is taken, accordingly. The control room is air conditioned to maintain the desired

temperature for proper functioning of the instruments.

15

SWITCH YARD:-

Electricity generated at 11 KV by the turbo-set is stepped-up by unit transformers to

132/220 KV for further transmission through high tension lines to Maur, Muktsar,

Malout, N.F.L., Sangrur and Ludhiana. Transmission of power to grid is controlled

through 7 nos. 220 KV and 15 nos. 132 KV. Air Blast Circuit Breakers along with their

associated protective systems.

WAGON TIPPLER:-

The coal received from the collieries, in more than 100 rail wagons a day, is unloaded

mechanically by two nos. wagon tipplers out of which one serves as a standby. Each

loaded wagon is emptied by tippling it in the underground coal hopper from where the

coal is carried by conveyor to the crusher house. Arrangements have been provided for

weighing each rail wagon before and after tippling. Each tippler is capable of unloading

6-8 rail wagons of 55 tonnes capacity in an hour.

CRUSHER HOUSE:-

Coal unloaded by the wagon tippler is carried to crusher house through conveyors for

crushing. Two nos. hammer type coal crushers are provided, which can crush coal to a

size of 10 mm. The crushed coal is then supplied to Boiler Raw Coal Bunkers. The

surplus coal is carried to coal storage area by series of conveyors. Crushing of coal is an

essential requirement for its optimum pulverizing and safe storage.

COOLING TOWERS:-

Cooling Towers of the power plant are the land mark of the Bathinda City even for a far

distance of 8-10 kilometers. One cooling tower is provided for each unit for cooling

18000 tones of water per hour by 10C. cooling towers are massive Ferro-concrete

structure having hyperbolic profile creating natural draught of air responsible for

achieving the cooling effect. Cooling tower is as high as 40 storey building.

16

BOILER:-

It is a single drum, balanced draught, natural circulation, reheat type, vertical combustion

chamber consists of seamless steel tubes on all its sides through which water circulates

and is converted into steam with the combustion of fuel. The temperature inside the

furnace where the fuel is burnt is of the order of 1500C. The entire boiler structure is of

42meter height.

BOILER CHIMNEY:-

The flue from the boiler, after removal of ash in the precipitators, are let off to

atmosphere through boiler chimney, a tall ferro-concrete structure standing as high as the

historic Qutab Minar. Four chimneys, one for each unit, are installed. The chimney is

lined with fire bricks for protection of ferro-concrete against hot flue gases. A protective

coating of acid resistant paint is applied outside on its top 10 meters.

CIRCULATING WATER PUMP:-

Two nos. of circulating water pumps provided for each unit, circulate water at the rate of

17200 T/hr. in a closed cycle comprising of Turbine Condenser and Cooling Tower. An

additional Circulating Water Pump provided serves by for two units. The water

requirement for bearing cooling of all the plant auxiliaries is also catered by these pumps.

17

COAL MILLING PLANT

Since G.N.D.T.P. units are primarily coal fired units so each boiler is

provided with closed milling circuits to pulverize the raw coal which is

received from coal conveying system after coal crushes before it is fired in

the furnace. The necessity of pulverizing the coal is to be ensuring its

maximum possible combustion in the furnace. The coal data for units are: -

COAL DATA UNITS 1 & 2 UNITS 3 & 4

Type of Coal

Net Calorific Value

Moisture

Ash Content

Volatile Matter Incombustible

Inlet of Coal

Bituminous

4300 Kcal/kg

10 %

30 %

24 %

10 mm

Bituminous

4727 Kcal/Kg

7.5 %

32 %

27 %

20 mm

Raw coal of maximum size 10 mm – 20 mm is pulverized in the milling

circuit and the output from the mill is fine coal. Milling circuits of the

following main constituents: -

18

1. Raw Coal Bunkers (R.C. Bunkers).

2. Raw Coal Chain Feeders.

3. Drum Mill or Coal Mill.

4. Classifiers.

5. Cyclone Separator.

6. Vapour Fan.

7. Pulverized Coal Bunkers (P.C. Bunkers).

COAL MILL

Fig No.2.1

19

RAW COAL BUNKER:-

Each of three raw coal bunkers is fabricated from the sheet metal and is well stiffened all

around. The storage capacity of each raw coal bunker is about 500 tones. There are four

outlet gates with each bunker. The gates are electrically operated from site. In case of

failure of the electric motors the gate can be hand operated from site. At a time only one

gate opening is suffices but should be changed so that there is no pilling within the

bunker.

RAW COAL CHAIN FEEDER:-The raw coal chain feeder transports coal from raw coal bunker to the inlet chute leading

to the pulverized/coal mills. There is a double link chain of high tensile strength steel,

which moves on wheels and sweeps the raw coal falling over the top of the raw coal

chute of the mill. The height of the coal bed in the chain feeder can be adjusted manually

by means of lever operated damper. The maximum and minimum heights of the coal bed

are 200mm and 120mm respectively. The signaling equipment indicates the absence of

coal flow in the feeder, which is annunciated in the unit control board (U.C.B.). The main

shaft on the driving end is connected to the driving unit, consisting of variator, a gear box

and a motor all mounted as a single unit. The chain wheel on the driving end shaft is

provided with a shear pin, which will shear off and disconnect the driving mechanism if

there is any overload on the feeder. The speed of the chain feeder is regulated

automatically/remotely by actuating the control spindle of the variator through a

servomotor. A pump for circulating the oil in the gear box of variator is an integral part of

variator driven by a separator motor. Some of the technical data about the raw coal chain

feeder is given here:-

1. Output of the chain feeder 10-45 tonnes/hr.

2. Speed variations 0.0503-0.151m/sec.

3. Main motor 7.5kW, 415V, 50Hz.

4. Oil pump motor 0.05kW, 220V

5. Operating motor of each gate 3HP, 415V and 50Hz.

20

DRUM MILL:-

Each mill consists of single compartment drum, bearings driving motor, coal inlet

and discharge piping, ball change and lubricating equipment for mill bearings. Mill drum

is fabricated from thick steel plates and is supported on to the anti-friction bearings. The

mill is driven by an electric motor of capacity 630kW, 990 rpm, 6.6kV through a

reduction gear, which reduces the speed to 17.5 rpm. The ball charge for the mill consists

of the three different sizes of forged steel balls detailed as below. The capacity of each

mill is 27 T/hr. in case of unit 1 & 2 and 28 T/hr.

1. 40mm diameter 22500 kg

2. 50mm diameter 20000kg

3. 60mm diameter 10000kg

4. Total Ball Charge 52500kg

During operation only 60mm diameter balls are added is approx. 500 kg per week

and the guiding factor is the amperage of the coal mill, normally it should be 66-ampere

approx. at full load and when it falls below the above value ball charging of the mill is

carried out. Lubricating system consists of the oil tank, gear pump, oil cooler and base

frame to mount all these equipments. Gear pump is driven by an electric motor of rating 1

H.P., 415 V, 1440 rpm. Suction side of the gear pump is connected to the tube oil tank

and the delivery side is connected to inlet of the oil cooler and after cooling oil goes to

the bearings. The oil from the bearings is cooled to the required temperature in the cooler

by the means of plant bearing cooler water.

CLASSIFIER:-

The classifier is fabricated from the steel plates. It is an equipment that separates fine

pulverized coal from the coarser pieces. The pulverized coal along with the carrying as

well as drying medium (flue gas) strikes the impact plate in the classifier and the coarser

pieces get separated due to the change in the direction of flow and go back to mill. The

stream then passes to the outlet branch of the classifier through an adjustable telescopic

tube. At the outlet adjustable vanes are provided to change the size of coal when required.

21

CYCLONE SEPARATOR:-

The centrifugal type cyclone separator consists of two cyclones made up of welded

sheets. It is equipment in the milling plant, which serves for separating the pulverized

coal from the vapours i.e. carrying medium. The pulverized coal gets stored in the

pulverized coal bunkers and vapours go to suction of vapour fan. At the bottom of the

cyclone separator a rotary valve (Turnikete) is provided to transport coal from cyclone

separator to P.C. bunker on the worm conveyor as the case may be.

VAPOUR FAN:-

Pulverized coal bunker is welded from thick steel sheets and has a capacity of 4 hours

coal consumption at maximum continuous rating of the boiler. The whole bunker is

insulated externally. The carbon-dioxide blanketing system has been provided in the P.C.

bunker to prevent fire hazards inside the bunker. The while storage bunker is divide into

four parts namely A, B C & D. Further four coal feeders are taken out from each bunker

leading to each corner of the furnace.

CRUSHING OF COAL:-When coal reaches the plant, normal size of coal is about 500mm. After unloading the

coal from the rake is fed to primary crusher, which reduces the size to 120mm. Then coal

is fed to secondary crusher which reduces the size to 25mm and this coal goes to bunker

with the help of conveyor belt from where coal finally goes to coal mill where coal is

transferred in form of pulverized coal. The coal is heated with the help of hot primary air.

We maintain the temperature of about 70C in coal mill. This temperature is maintained

with the help of cold air and a hot air damper.

USE OF OIL:-Before the coal reaches the furnace, we preheat the furnace in order to remove the

moisture and raise the temperature of furnace, so that coal can catch fire easily without

any delay. This preheating of furnace is done with the help of oil. With burning of oil, we

maintain the temperature of furnace at 350C. we cut the oil supply after 350C because

22

oil is very costly. Source of oil for G.N.D.T.P., Bathinda is Mathura Oil Refinery. Other

use of oil is in bearing system for cooling. There are large number of bearings for plant.

For example bearing system of turbine. These bearings get heated upto high temperature,

which is dangerous. So we cool the bearing by circulating water in bearing.

COAL FEEDING AND COAL MILL:-From the coal handling plant, coal comes in two belts namely 5A and 5B and then by

belts 6A and 6B coal comes in bunkers. Bunker capacity is 300 tonnes. Number of outlets

of bunker is three. First gate is opened for one hour and second and then third. If open the

one gate for long time, then coal will stop going to mill. That is why we open the gate

turn by turn.

RAW COAL CHAIN FEEDER:-Raw coal chain feeder is just below raw coal bunker. It is a sliding chain which feed the

coal to mill. We can change the quantity of coal which is fed to mill in two ways.

By changing the speed of chain

By changing the depth of coal in chain

Speed of chain can be changed by adding a gear system to motor. We connect the

gear system with motor with a pin called shear pin. The prevent the overloading of motor

because when the coal quantity of coal on chain is greater than its capacity then the pin

will break and prevent the pin from overloading. Speed of Raw Coal chain is 2” to 6”/sec.

COAL MILL:-These are mainly of two types:-

i) Ball Mills

ii) Bowl Mills

23

Ball Mills: - In Ball Mills there are steel balls which are revolving in horizontal

cylindrical drum. These balls are free from any shaft and balls are touching with each

other and with internal body of drum. These types of mills are at Bathinda Thermal Plant.

On the other hand, bowl mills part of the mill contain drive system i.e. it contains 6.6 kV

electric motor and gear system which translates the revolution about horizontal axis to

revolve about vertical axis. The revolving vertical axis contains a bowl about the driving

system. This bowl is fixed with driving and revolving with shaft. There are also three

rollers which are suspended at some inclination, so that there is a gap of few mm between

roller surface. These rollers are free to rotate about the axis.

Bowl Mills: - The coal is grinded and then fed into the mill at the center or near of

revolving bowl. It passes between the grinding ring in revolving bowl and rolls as

centrifugal force causes the material to travel towards the out perimeter of bowl. The

springs, which load the rolls, impart the necessary force for grinding. The partially

pulverized coal continue going up and down and over the edge of bowl.

24

The G.N.D.T.P. units are primarily coal-fired units and the coal consumption at

maximum continuous rating (M.C.R.) per unit is about 58 T/Hr. the coal used at

G.N.D.T.P. is of bituminous and sub-bituminous type and this is received from some

collieries of M.P. and Bihar. The designed composition of coal is as below:-

Type Bituminous Coal

Net calorific value 4300 kcal/kg

Moisture content in coal 10%

Ash content 30%

Volatile matter in combustibles 24%

Grind ability index 50 Hard Groove

The coal handling plant at G.N.D.T.P. has been supplied and erected by M/s

Elecon Engineering Company Limited, Vallabh Vidya Nagar, Gugarat. Coal is

transported from the coal mines to the plant site by Railways. Generally, the raw coal

comes by railway wagons of either eight wheels weighing about 75 to 80 tones each or

four wheels weighing about 35 to 40 tones each. The loaded wagon rake is brought by

railways main line loco and left on one of the loaded wagon tracks in the power station

marshalling yard. The main line loco escapes through the engine track. The station

marshalling yard is provided with 8 tracks. The arrangement of the tracks in the

marshalling yard is as follows:-

DESTINATION NO. OF TRACKSLoaded wagons receiving tracks Four

Empty wagon standing tracks Three

Engine escape tracks One

25

COAL HANDLING PLANT (CHP)

UNLOADING OF COAL:-

In order to unload coal from the wagons, two Roadside Tipplers of Elecon make

are provided. Each is capable of unloading 12 open type of wagons per hour. Normally

one tippler will be in operation while the other will be standby. The loaded wagons are

brought to the tippler side by the loco shunters. Then with the help of inhaul beetle one

wagon is brought on the tippler table. The wagon is then tilted upside down and emptied

in the hopper down below. The emptied wagon comes back to the tippler table and the

outhaul beetle handles the empty wagons on the discharge side of the tippler. The tippler

is equipped with the integral weighbridge machine. This machine consists of a set of

weighing levers centrally disposed relative to tippler. The rail platform rests on the

weighing girders and free from rest of the tippler when the wagon is being weighed. After

weighing the loaded wagons is tipped and returned empty to the weighing girders and

again weighed. Thus the difference of the gross weight and the tare weight gives the

weight of the wagon contents. The tipplers are run by motors of 80 H.P. each through

gears only.

WAGON TIPPLER

Fig No.3.1

26

The tippler is designed to work on the following cycle of operation:-

Tipping 90 seconds

Pause 5-12 seconds

Return 90 secondS

Weighing 30 seconds

Total 215-222 seconds

Allowing 85 seconds for wagon changing it will be seen that 12 eight-wheel wagons or

24 four-wheel wagons per hours can be tipped. However since the coal carrying capacity

is 500 tones per hour load of 12 wagons comes to 8 to 9 per hour.

DUST TRAPPING SYSTEM:-

The tippler is also provided with the dust trapping systems by which the dust nuisance

will be minimized. As the tippler rotates, a normally closed hopper valve opens

automatically and the discharged material passes through it into the hopper with its dust-

setting chamber, there is an air valve of large area, which opens, simultaneously with the

hopper valve. The object of this air valve is to blow back through the hopper valve into

the tipping chamber, which must occur if, the settling chamber were closed, it being

remembered that a large wagon contains some 240 cubic feet of material and that this

volume of dust air would be forced back at each tip if the hopper chamber were a “closed

bottle”. The air valve and the hopper valve are shut immediately on reversal of the tippler

and are kept shut at all times except during the actual discharge. The hopper valve is

operated by a motor of 10 H.P., 415 Volts and the air valve is operated by electro-

hydraulic thruster. Inlet valve consists of large number of plates sliding under the wagon

tippler grating. Coal in the wagon tippler hopper forms the heap and as such obstructs the

movement of sliding valve and damaging the plates. The inlet and outlet valves have

therefore been bypassed.

The unloaded material falls into the wagon tippler hopper (common to both

tipplers) having a capacity of 210 tones. The hopper has been provided with a grating of

300mm X 300mm size at the top so as to large size boulders getting into the coal stream.

27

There is also a provision of unloading the wagons manually into the MANUALLY

UNLOADED HOPPER of 110 tones capacity. Manually unloading will be restored to

while unloading coal from sick wagons or closed wagons.

MAGNETIC PULLEYS:-

On belt conveyor no. 4A and 4B, there have been provided high intensity

electromagnetic pulleys for separating out tramp iron particles/pieces from the main

stream of coal conveying. D.C. supply for the magnet is taken on 415 volt, 3 phase, 50

cycles A.C. supply system.

In addition to above high intensity suspension type electromagnets have also been

provided on belt conveyors 4A and 4B for separating out tramp iron pieces/particles.

RECLAIMING:-

If the receipt of coal on any day more than the requirement of the boilers, the

balanced material will be stocked via conveyor 7Aand 7B and through telescopic chute

fitted at the end of the conveyor. At the end of the chute one tele level switch is provided,

which automatically lifts the telescopic chute to a predetermined height every time. The

tele level switch is actuated by the coal pile. When the telescopic chute reaches maximum

height during operation, which will be cut off by limit, switch and stop the conveying

system. When the pile under the telescopic chute is cleared, the telescopic chute can be

independently lower manually by push buttons.

There are five bulldozers to spread and compact the coal pile. Bulldozers of Bharat Earth

Movers Limited Make are fitted with 250 H.P. diesel engines. Each bulldozer is able to

spread the crushed coal at the rate of 250 tones/hr. over a load distance of 60m the coal

can be stacked to a height of 6m the stockpile stores coal for about 45 days for four units

with an annual load factor of 0.66.

Whenever coal is to be reclaimed the bulldozers are employed to push the coal in

the reclaim hopper having a capacity of 110 tones. The coal from the reclaim hopper is

fed either 9A or 9B belt conveyor through vibratory feeders 8A and 8B.

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CRUSHER HOUSE:-

The crusher house accommodates the discharge ends of the conveyor 4A, 4B receiving

ends of conveyor 5A, 5B and conveyor 7A and 7B, two crushers, vibrating feeders and

necessary chute work. There are two crushers each driven by 700H.P. electric motor, 3

phase, 50 cycles and 6.6 kV supply. The maximum size of the crushed coal is 10mm. The

capacity of each crusher is 500 tones/hr. one crusher works at a time and the other is

standby. From the crusher the coal can be fed either to the conveyors 5A, 5B or 7A, 7B

by adjusting the flap provided for this purpose. There is built in arrangement of bypassing

the crusher by which the coal can be fed directly to the conveyors bypassing crusher.

CONVEYOR BELT AND CRUSHER HOUSE

Fig No.3.2

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30

Boiler section

The steam generating unit is designed to meet the nominal requirements of 110MW turbo

generator set. The unit is designed for a maximum continuous rating of 375 tones/hr. at a

pressure of 139kg/cm2 and a steam temperature of 5400C. the reheated steam flows at

MCR 32H tones/hr. at the feed water temp at MCR is 2400C. The unit is a balance

draught dry bottom; single drum natural circulation, vertical water tube type, construction

with skin casing and a single reheat system. The furnace is arranged for dry ash discharge

and is fitted with burners located at the four corners. Each corner burner comprises coal,

vapour oil and secondary air compartments. The unit is provided with three ball mills and

arranged to operate with intermediate cool powder bunker. The steam super heater

consists of 4 stages Viz. Ceiling, convection, platen and final superheated. The ceiling

super heated forms the roof of the furnace and horizontal pass and finishes as the rear

wall of the second pass. The convection super heated is made up of horizontal banks

located in the second pass. While the platens are located at the furnace exit, the portion

above the furnace nose encloses the final superheated reheater are in two stages, first

stage is the triflux heat exchangers located in the second pass, which absorbs heat from

superheated steam as well as from the flue gases. The second stage is exit reheater

located in the horizontal pass as pendant tubular loops.

(a) The flue gas for drying the cool in the mills is tapped off after the triflux heat

exchangers. The damper located in the hot flue gases pipe leading to mill controls the

quantity. Control the circulating vapour of the mill entry effect temperature control.

Immediately after the triflux heat exchanger, the air heaters and economizers are located.

The air heater is in 2 stages.

(b) The hot air for combustion from air heater stage 2 is led into the common wind box

located on the sided of the furnace. 4 cool air mixed pipes from pulverized coal bounders

are connected to 4 cool burners’ nozzle at the corners. There will be totally 16 coal

nozzles. 4 located in each corner. Oil guns will be located in the secondary air nozzle for

coal burning. The turn down ratio of the guns will be so selected that it will be possible to

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use them also for pulverized fuels flame stabilization while operating under load below

the control point.

(c) Take into consideration the high % age of ash and the relatively poor quality of coal

due regards has been paid to wide pitching the tubes and to the gas velocity across the

heating surface areas. In order to insure reliable and continuous operation sample sot

blowing equipment is provided. There are short retractable steam root blowers provide at

the top of furnace fully retractable rotary type blowers are located for cleaning of the

secondary super heater and final heater partly retractable steam blowers are arranged for

the horizontal reheater and super heaters in the second pass. The steam root blowers are

electrically operated.

(d) Root blowing nozzles using blow down from boilers drum are provide for the

cleaning of areas around the burners nozzles zone for dislodging of slag boulder if any in

the bottom ash hopper in the furnace.

(e) Two FD fans are provided per boiler. The FD fans are of the axial type driven by

constant speed motor. The regulation of quantity and pressure is done by inlet vane

control. The flue gases are sucked through the mechanical and electrostatic precipitators

by I.D. fans and delivered into the chimney. Two I.D. fans are provided for each boiler

and they are of the axial type driven by constant speed motors. Inlet vane control effects

the capacity change with reference to load. Both the I.D. and FD fans have been

dimensioned taking into account the minimum margins of 15% on volume and 32% on

pressure.

Specification

Manufacturer B.H.E.L

Maximum continuous rating 375tones/hr.

Super heater outlet pressure 139kg /cm2

Reheater outlet pressure 33.8 kg/cm2

Final super heater temperature 540 deg.c

Feed water temperature 240deg.c

Efficiency 86% (stage-1)

87% (stage-2)

Coal consumption per day 1500 tones

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33

TURBINE SECTION

The turbine is the prime mover for the generator in the power plant Different

types of steam turbines used in thermal power plants, but the ones. Which

are used at G.N.D.T. P. are categorized as follows

S.No. Type of Turbine Turbine at G.N.D.T.P.

1. Horizontal/vertical Horizontal

2. Single/multi cylinder Multi cylinder

3. Condensing/non condensing condensing

4. Reheat/ non-reheat Reheat

5. Regenerative/non regenerative Regenerative

6. With by pas/without by pass with by pass (stage-1)

Without by pass (stage-2)

BASIC WORKING OF TURBINE

First of all the turbine is run on gear motor with the help of exciter. At that

time steam is kept on recirculating with the help of by pass valve. When the

pressure of steam is increased to on optimum level and turbine acquires a

particular rpm then steam is introduced in the H.P. (high-pressure) cylinder

first. The temperature of steam at entrance is 540C and pressure is about

139 Kg/cm2. After doing its work on the H.P. Turbine, the steam is taken out

for reheating rated temperature of steam at reheater inlet is 360C. The

temperature of steam is increased upto 535C in the boiler shell and steam is

34

again introduced in M.P (Medium pressure) turbine. After M.P.turbine, the

steam is passed on to L.P. (Low-pressure) turbine. This process helps the

turbine to reach the speed of 3000 rpm. After L.P. turbine, the steam is

condensed in condenser, build below the turbine unit. The condenser

contains a number of brass tubes through which cooling out from L.P.

turbine it comes in contact with colder brass tubes then steam get

transformed into water. This water get collected in HOT WELL just below

the condenser. From here the hot water is again pumped with the help of

condensate pumps. The cooling water is used to condense steam gets heated

up and is cooled by falling from cooling tower. This completes the

processing of steam through turbine and condenser.

ROTOR OF TURBINE

All the rotors are manually by means of rigid coupling, including the rotors

of the generator. The speed of whole system of rotor lies in the following

ranges of the speed at the operating conditions: -

1900 to 2000 rpm Best noticed on the M.P. and L.P. rotors and generators.

2350 rpm Best noticed on H.P. rotor.

1. BEARING OF ROTORS

The axial load of the entire system of rotors is taken up by a double-sided

axial bearing located in the bearing stand between the H.P. and M.P casing.

These are two protections mounted near the axial bearing one hydro

35

chemical and one electromagnetic, which fouls the turboset during the non-

permissible movement of the rotor.

The rotors are placed on radial bearing which are machined to elliptical

shape. Further scrapping operations or change top and side clearances and

change in temperature of oil, influence the oil wedge and the position of the

journal bearing to maintain the same condition as existed during the initial

assembly.

In the lower half of bearing a hollow groove is provided in the babbit metal

through which oil the supplied through a drilled hole through H.P. jacking

oil pumps.

The high-pressure oil rotors are lifted in the bearing so that any scrapping of

the bearing is prevented.

2. TURBINE CASING

The high-pressure part of turbine is consisted of two-concentric horizontal

casing. Inner casing is connected in such a way to the other casing that it

enables to expand in all direction. The nozzles are attached to the inner

casing. The steam pipe is connected to the condensers and the condensers

are supported by springs. The casings are inter connected by the system of

guide keys through bearing pedestals in such a way that thermal expansion

of casing does not destroy the various parts of turbine.

36

The displacement-bearing pedestal between M.P. and H.P parts is measured

by the electromagnetic pick up. This valve is about of 15 mm to prevent

deformation at the casing. It is very important that sliding part clean

lubricated and free from hazard for connecting parts bolts elements. The

heating of bolts before tightening up and before the locking presents. The

flanges of M.P. and H.P. casings are designed to heat up by steam during the

starting up of turbo boost by which the difference in temperature between

the cylindrical position of the casing flanges and connected bolts is reduced

to limited deformation. The thermo couples are used for measuring

temperatures. The thermo couple is partially connected to the indicated

apparatus. Cooling fluid is generally used for reducing the temperature of

various parts.

37

Fig No.4.1

3. REGULATION AND SAFETY EQUIPMENT FOR TURBINE

GOVERNING

The quality of steam entering in the turbine is regulated by the four

governing valves on the inlet to the M.P. part. The amount of opening at any

instant of these valves is controlled by the pressure of secondary oil, which

38

is indirectly depending on the primary oil pressure and directly depending

upon the spring force in the transformer during the stand still and during

starting of the turbo set. The pressure of primary oil is directly depending on

the speed of the set through the speed-sensing element. Operating the speed

changer or the normal speed changer can very the tension in the spring in the

transformer.

Thus make it possible to vary the speed before synchronizing. In case break

down of any equipment of the block the quick closing devices are provided

in the regulation system of the turbo set. H.P. quick closing valves

(H.P.Q.C) M.P. quick closing valves (M.P.Q.C) at return flap valves are

operated by either directly by the tripling lever or through the relay magnet

on the main relay which creates instantaneously loss of pressure of the quick

closing oil by the change of flow of oil inside the relay.

Distribution is used for checking the function of H.P.Q.C and M.P.Q.C

valves. The H.P. and M.P quick closing valves, the non return flaps and non

return extraction valves during normal operating condition have only two

positions one is fully opened another fully closed.

4. STEAM CYCLE

The design of the power cycle based on the modern concept, where a unit

consists of a steam generator with its independent firing system tied to the

steam generation. The steam generator is designed for maximum continuous

rating of 375-tonnes/hr. and steam Pressure of 139-kg/cm2 at temperature of

540C respectively. The steam generator is designed to supply to a single

reheat type condensing steam turbine with a 8 non regulated extraction

points of steam for heading the condensate and feed water. The steam cycle

can be classified into the following three divisions: -

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(a) Main steam (b) Reheat steam (c) extraction steam

(a) MAIN STEAM

Saturated steam from the steam generator drum is led to the super heater

bank to heat if up to 540C saturated steam from the drum is led to the

ceiling super hearter (between SHH1 and SHH2) from ceiling super steam

goes to convection

40

Spending Our six months of training in Guru Nanak Dev Thermal Plant, Bathinda, We

concluded that this is a very excellent industry of its own type. They have achieved

milestones in the field of power generation. They guide well to every person in the

industry i.e. trainees or any worker. We had an opportunity to work in various sections

namely switch gear, Boiler section, Turbine section, EM-2 CELL etc. while attending

various equipments and machines. We had got an endeverous knowledge about the

handling of coal, various processes involved like unloading, belting, crushing and firing

of coal. The other machines related to my field that We got familiar with boiler, turbine,

compressors, condenser etc. We found that there existed a big gap between the working

in an institute workshop and that in the industry. Above all the knowledge about the

production of electricity from steam helped me a lot to discover and sort out my problems

in my mind related to the steam turbine, their manufacture, their capacity, their angle of

blades and their manufacturing. The training that We had undergone in this industry will

definitely help me to apply theoretical knowledge to the practical situation with

confidence.

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CONCLUSION