Training Report On Water Treatment and Coal testing At Guru Nanak Dev Thermal Plant Bathinda

Submitted By: Mahinder Singh UE89034

Under the guidance of

Mrs. Er. Mechanical Dptt. Add. S.E. T.T. cell GNDTP,Bathinda

Department of Mechanical Engineering

U.I.E.T. PANJAB UNIVERSITY, CHANDIGARH

ACKNOWLEDGEMENT

DECLARATION

I hereby declare that the project work entitled ‘Water treatment and coal testing’

is an authentic record of my own work carried out at Bathinda as requirements of

six months Industrial Training for the award of the degree of B.E. at University

Institute of Engineering & Technology, Panjab University, Chandigarh under the

guidance of Er. T.N.Bansal and Mrs. Anjali Gupta, during 1jan-24May 2012.

student

Date: 28May2012

Certified that the above statement made by the student is correct to the best of

our knowledge and belief.

Mrs. Er.

Mechanical Dptt. Add. S.E. T.T.cell

UIET GNDTP, Bathinda

INTRODUCTION

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 20mm 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 phases electric supply is produced.

The basic requirements are:-

Fuel (coal)

Boiler

Steam turbine

Generator

Ash handling system

Unit auxiliaries

HISTORY

.

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, January 1979 respectively. The power available from this plant

gives spin to the wheels of industry and agricultural pumping sets.

LANDMARKS ACHIEVED

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.

WORKING AT GNDTP

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.

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.

PLANT’S SALIENT FEATURES

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)

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.

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 120/122 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

Forced draught fan 320 KW

Boiler feed pump 3500 KW

Induced draught fan 900/1000 KW

Condensate pump 175 KW

DIFFERENT CELLS OF PLANT

CHP (Coal Handling Plant)

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.

UNLOADING OF COAL:-

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

make are provided. Each is capable of unloading 12 open types 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 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.

IMPROVED DESIGN OF WAGON TIPPLER :-

We under the new scheme, propose to raise the level of hopper to the

ground level. Correspondingly, the level of the platform of wagon tippler will also

have to be adjusted. Also the building structure covering the hopper and tripper

will be done away with keeping the hopper open. In this way the screen of the

hopper becomes accessible to pay loader trucks. Now, when the screen gets

blocked, a pay loader truck can be employed which will lift all the over sized coal

and take it to a suitable place where it can be broken either manually or by a

crusher. Thus it will save time as the trolleys can be emptied faster, saving

damages.

USE OF LOAD CELL TYPE WEIGHBRIDGE FOR WEIGHMENT IN MOTION :-

Load ceil type weighbridges are sometimes called dynamic weighbridge because

the wagons can be handled over them at a maximum speed of up to 12 m.p.h.

They consists of two platforms one for gross and one for tare weights. Each

wagon weight is automatically printed out and so is the railway loop. First the

gross weights are established and memorized, then the train is moved over the

rail track hopper for discharge, after the empty train is moved out over the tare

weighbridge platform where the tare weights are printed out. Finally the total net

weight is computed and printed out. The load cells at each weighbridge are

connected to a digitizer suitable for converting the analogue output of the load

cell into digital form.

Wagon Tippler

When coal reaches the plant, normal size of coal is about 500mm primary

crusher 120mm secondary crusher 25mm coal mill pulvarised coal

,feeded in boiler.

Before this boiler is preheated with oil upto 3500c,then oil supply is cut down.

Conveyer Belt

Boilers

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, is 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.

Boilers burn the fuel transferred from the tank and use the resulting heat to

convert water into steam. Inside the boilers are tens of thousands of water-

carrying tubes. When combustion commences, the temperature inside the boilers

rises to between 1,100 and 1,500°C, the water inside the tubes is turned into

high-temperature and high-pressure steam, and the steam is transferred to the

steam turbines.

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.

Boiler

Boiler specifications

Feed water temperature 240C

Final super heater/reheater temperature 540C

Super heater outlet pressure 139kg/cm²

Efficiency 86%

Coal consumption per day per unit 1400 tones (Approximate)

Turbines

The steam rotates the turbine blades at a high speed of 3,000 rpm. This turns the

power generator, which is directly connected to the turbines, and electricity is

produced as a result. This electric power is then delivered along power

transmission lines and through substations to the homes of customers.

Turbine is a prime mover for the Generator in the power plant. In steam turbine,

the potential energy of steam is transformed into kinetic energy and later in its

turn is transformed into the mechanical energy of the rotation of the turbine

shaft. The common types of turbines are:-

IMPULSE TURBINE:- In this type of turbine, steam expands in the

nozzles and its pressure does not alter as it moves over the blades.

REACTION TURBINE:- In this type of turbine, the steam expands

continuously as it passes over the blades and thus there is a gradual fall in

pressure during expansion.

IMPULSE TURBINE

REACTION TURBINE

Different types of steam turbines are used in Thermal Power Plant but the

ones which are used at G.N.D.T.P. are categorized as follows:-

Sr. No. Type of Turbine Turbines at G.N.D.T.P.

1. Horizontal/Vertical Horizontal

2. Single/Multi-cylinder Multi-cylinder (3-cylinder)

3. Impulse/Reaction Impulse

4. Condensing/Non-condensing Condensing

5. Reheat/Non-reheat Reheat

6. Regenerative/Non- Regenerative With bypass (ST-1)

7. With bypass/Without bypass Without bypass (ST-2)

MAIN TECHNICAL DATA

a) The basic parameters:

Rated output measured at Terminal of the generator. 110.000KW

Economical output. 95.000KW

Rated speed. 3.000RPM

Rated temp. of stearn just before the stop valve. 535C

Max Temp. of steam before the stop valve. 545C

Rated pressure of steam before the MP casing. 31.63C

Max. pressure of steam before the MP casing 35C

Rated temp. of steam before the MP casing. 535C

Max. temp. of steam before the MP casing. 545C

b) System of turbine:

4 Governing valves +2 interceptor valves HP cylinder- 2 Row Curtis wheel +8

moving wheels.

Wt. Of HP rotor approx. 5,500 Kg.

MP cylinder - 12 Moving wheels.

Wt. Of MP rotor. Approx. 11,000 Kg.

LP cylinder - 4 Moving wheels of double flow design.

Wt. Of MP rotor approx. 24,000 Kg.

Direction of the turbine rotation - To the right, when looking at the turbine from

the front bearing pedestal.

General Specifications of 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

TURBO-GENERATOR:- The hydrogen-cooled generator is directly coupled to the turbine shaft

rotating at speed of 3000 rpm generating electricity at 11000 volts. The turbine is

horizontal, three casings, reheat, steam condensing, regenerative and of impulse

type equipped with a precise oil operated speed governor. The generated voltage

is stepped by unit power transformer to state grid system.

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.

NEED OF A CONDENSER:- A condenser where the exhaust steam from the turbine

is condensed, operates at a pressure lower than atmosphere. There are two

objects of using a condenser in a steam plant. There are two objects of using a

condenser in a steam plant:-

- To reduce the turbine exhaust pressure so as to increase the specific output

of turbine. If the CW cooling water temperature in a condenser is low

enough. It creates a back pressure (vacuum) for the turbine. This pressure is

equal to the saturation pressure corresponding to the condensing steam

temperature. Which is a function of cooling water temperature. It is known

that the enthalpy drop or turbine work per unit pressure drop is much

greater at the low pressure end than at the high pressure end of a turbine.

- A condenser by lowering the back pressure say 1.013 to 0.074 bar, thus

increases the plant efficiency and reduces the steam flow for a given

output. The lower the pressure, the greater the output and efficiency. It is

important to use lowest possible cooling water temperature.

This reduces the temperature rise of cooling water in the condenser tubes

to 5-8C so that the tube outer surface temperature remains low and

consequently, the condensing steam temperature is low and vacuum is

high.

- To recover high quality feed water in the form of condenser and feed it

back to the steam generator without any further treatment.

As a result only the make up water to replenish the water losses in the

cyclic plant needs be treated.

TYPES:- There are two broad classifications:-

a) Direct contact type condenser:- where the condensate and cooling

water directly mix and come out as a single stream.

b) Surface condenser:- which are shell and tube heat exchangers where the

two fluids do not come in direct contact and heat released by the

condensation of steam is transferred through walls of the tubes into the

cooling water continuously circulating inside them.

DIRECT CONTACT CONDENSERS:-

- Spray condenser

- Barometric condenser

- Jet condenser

In the spray condenser, the cooling water is sprayed into the steam. Steam by

mixing directly with cold water gets condensed. The exhaust steam from the

turbine at state 2 mixes with cooling water at state 5 to produce saturated

water at state 3, which is pumped to state 4.

In barometric condenser, the cooling water is made to fall in a series of

baffles to expose large surface area for the steam fed from below to come in

direct contact. The steam condenses and falls in a tail pipe to the hot well

below. By virtue of its static head, the tail pipe compresses the mixture to

atmospheric pressure.

In a jet condenser, the height of the tail pipe is reduced by replacing it with a

diffuser. The diffuser helps raising the pressure in a short distance than a tail

pipe.

SURFACE CONDENSERS:- Surface condenser is another type of condenser used

in power plants. In GURU NANAK DEV THERMAL PLANT surface condensers are

used. These are essentially shell and tube heat exchangers. For the

convenience of cleaning and maintenance cooling water flows through the

tubes and steam condenses outside the tubes. In our plant surface condenses

two passes of water boxes on each side. The hot well acts as a reservoir of the

condensate. The condenser plays a vital role. In our plant two surface

condensers are used in one plant’s unit. There are 6800 tubes in one

condenser.

CONDENSER

CONDENSATE CYCLE:- Steam after working in the three casings of the turbine

i.e. H.P., M.P. and L.P. casing is considered in two surface condensers in each

unit installed just below the L.P. turbine’s exhaust hood. The condenser so to

call hot well from where it is pumped up to deaerator by condensate

extraction pumps through different heating stages. The different heating

stages through which the condensate flows and gets heated up gradually

before finally reaching the deaerator (feed water tank) are as below:-

HEATING STAGE TEMP. RISE AT FULL LOAD

Main steam jet air ejector 43-48C

LPH-1 and LPH-2 48-73C

Chimney steam condenser 73-80C

Gland steam condenser 73-80C

LPH-3 80-97C

LPH-4 97-121C

LPH-5 121-152C

Deaerator 152-158C

The temperature rise of the condensate after passing through above heating

stages is from 45C at hot well to 145C at the deaerator (feed water tank). The

feed water tank acts as a feed water storage vessel and deaerator functions to

remove dissolved oxygen in the feed water.

CONDENSER:- The function of the surface condenser is to condense the steam

exhausted from the L.P. casing and to create vacuum in order to increase the

heat drop. Capacity of each hot well is 6200 liters and the temperature of

condensate in the hot well is about 40-45C.

PARTICULARS OF CONDENSATE:-

EXTRACTION PUMP:-

Number of pumps: 3 for each unit with 50% capacity each, one stand by.

Number of stages: 6

Discharge pressure: 20.5-24.5 kg/cm²

Suction pressure: -0.8 to –0.9 kg/cm²

STEAM JET AIR EJECTOR:-

The main function of steam jet air ejector is to maintain the vacuum in the

steam condenser by ejecting the air and non-condensate gases. The steam from

pressure reducing station is supplied to steam jet air ejector. This steam when

passed through the nozzles in a venturi develops pressure drop, which causes the

air and non considerable gases to rush from the condenser, thus maintaining the

required vacuum in the condenser. After that heat of this steam is utilized in

heating up the main condensate flowing through in the steam jet air ejector. The

steam jet air ejector is built up in the condenser.

LOW PRESSURE HEATERS:-

There are five numbers of L.P. heaters through which the main condensate

flows and gets heated up gradually in each stage of heaters before finally going to

the deaerator.

The L.P. heaters 1 and 2 are in two parts and placed in the exhaust hood of

condenser i.e. exhaust hood of L.P. turbine and are connected in series. L.P.H.-3,

L.P.H.-4 and L.P.H.-5 are placed in chimney steam condenser and gland steam

condenser in the condensate flow circuit. The charging steam to these heaters is

given from the steam extractions taken from the L.P. & M.P. cylinders of the

turbine. Steam extraction to L.P.H.-1 is taken from L.P. casing in two parallel

flows, same in L.P.H.-2. Steam to L.P.H.-3 is also taken from L.P. casing. Where as

steam to L.P.H.-4 and L.P.H.-5 is taken from M.P. casing.

The main condensate gets heated up by about 100C after passing through these

heating stages. The condensate of heating steam in these L.P. heaters is known as

drip.

CHIMNEY STEAM CONDENSER:-

It is a sort of heater in which waste chimney steam, taken from the outer leaks

of the gland seals of H.P., M.P. and L.P. cylinders of the turbine, is utilized in

heating up the main condensate. The drip of chimney steam condenser is

generally mixed with air and is collected in impure condensate tank from where it

is pumped to floor drains.

GLAND STEAM CONDENSER:-

It is also a sort of heaters, steam to gland steam condenser is taken from inner

leaks of the sealing glands of H.P. and front gland of M.P. cylinders of the turbine

and after heating the main condensate, the drip of gland steam condenser being

pure, is directly taken to the hot well.

Cooling towers:-

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.

Ash precipitators

WORKING PRINCIPLE OF ESP

The electrostatic precipitator installed at GNDTP,Bathinda units to extract

dust, utilizes electrostatic forces to separate dust particles from the gas be

cleaned. The gas is conducted to a chamber containing “Curtains” of vertical steel

plates. These curtains divide the chamber into a number of parallel gas passages.

A frame with secured wires is located within each passage. All the frames are

linked to each passage. The frames are linked to each other to form a rigid

framework.

The entire frame works is held in place by four support insulators, which is

electrically from all, which are grounded.

A high voltage direct current is applied between the framework the ground

thereby creating a strong electrical field between the wires in the framework and

the steel curtains. The electrical become strongest near the surface of the wires,

so strong that an electrical discharge. The corona “discharge” develops along the

wires. The gas is ionized in the corona discharge and large quantity of positive and

negative ions are formed. The positive ions are immediately attracted towards the

negative wires by the strength of the field indicate the negative ions however

have to traverse the entire space between the electrodes to reach positive

curtains.

Enroute towards the steel curtains, the ions collide and adhere to the

particles in the gas. The particles thereby become electrically charged and also

begin to travel in the same direction as the ions towards the steel curtains. The

electrical force on each particle becomes much greater than the gravitational

force on the particle. The speed of migration towards to steel curtains is therefore

much greater than the speed of sedimentation in free fall.

The fly ash carried by outgoing flue gases is arrested at two stages. In the

mechanical precipitators, the coarse ash particles are separated out by centrifugal

action. In the Electrostatic Precipitators, the finer ash particles in the flue gases

are made to pass through high voltage electric field, where these particles get

ionized and are attracted towards the collecting electrodes. The dry ash is

collected in the hoppers underneath and further deposited off in Ash Disposal

Area.

Project

Water treatment and Coal testing

Boiler is the heart of thermal plant, its main purpose is to convert water into steam.

N a t u r a l w a t e r i s a v a i l a b l e i n abundance, but it contains impurities in many forms which are as following types.

Types of impurities….

Water hardness is primarily because of calcium and magnesium minerals, and hardness is responsible for scale formation.

Carbonates or temporary hardness- ‘Ca’ and ‘Mg’ bicarbonates are responsible for alkaline hardness, but on applying heat release CO2

and form soft scale.

Non-Carbonates or permanent hardness- due to presence of salt of calcium and magnesium but in form of sulphates and chlorides. On applying heat these ppt. out and form hard scale, which is difficult to remove.

Water Alkalinity is because of bicarbonates, carbonates.

Alkalinity can convert to CO2 in steam. This causes corrosion.

When pH is below the recommended range chances of corrosion increases, and when it is above recommended value then chances of scaling increases.

Boiler scale lowers heat transfer due to low thermal conductivity. Heat transfer may be reduced as much as 5-10% by the presence of scale.

Due to scaling following are the negative effects on the working of plant

a. increased fuel bill by decreasing the operating efficiencyb. thermal damagec. increased cleaning time and cleaning costsd. reduced working life of a boiler.

Pre Treatment of Water

Clarifier (Alum dosing)

To make water free from suspended, colloidal and organic impurities, process involved in pre-treatment are:-

Canal water

Lake-1 Lake-2 Lake-3

Intake pump house

Clear well

A) Settling and Coagulation-

Coagulant (turbidity, micro-organisms) reacts with the alkalinity of the water to form a gelatinous precipitate

Clear well

Clear well Pump

Sand Filters

Sand filtersB) Filtration-

Passage of fluid through a porous medium using sand filter arrangement to remove matters holding suspension.

ii i iii

1. Suspended silt

2. Clay

3. Colloids

4. Micro organisms including algae, bacteria and virus

Demineralisation System

The process of demineralisation water by ion exchange comprises of:-

•Conversion of salts to their corresponding acids by hydrogen cat-ion exchanger.

•Removal of acids by anion exchangers.

•The two exchangers are normally in series. Normally cat-ion precedes the anionexchanger

Major ion exchange materials are synthetic resins made by the polymerization of various organic compounds, resins have strong affinity to attract the +ve charge towards itself.

Most frequently used compounds are:-

1. Styrene

2. Die vinyl – Benzene

DM Plant Layout

Cation exchanger mainly removes Calcium, Magnesium, sulfates, chloride, nitrates and sodium salts alkalinity from raw water.

In cation exchanger positive ion of the salt is exchanged by theH+ ion

On discharging, it is charged with 400Kg of 30%Hcl.

Cation Exchanger

Carbon dioxide generated by dissociation of carbonic acid at cation outlet

water, is removed by degasser system.

Water from outlet of cation exchanger is made to fall from a height,

and a pressurized air is blown upstream of the water flow to separate

gases.

Degasser Blower

Degasser Tank

Anion exchangers remove the highly dissociated acids (like H2So4, HNo3,

Hcl) from the effluent of cation exchanger.

In anion exchanger negative charged part of the salt is exchanged by

the OH- ion.

On discharging, it is charged with 200Kg of 47.5%NaOH.

Anion Exchanger

Mixed-bed DeionisationEffluent water after anion exchanger may still have some salts due to them its conductivity is around 14-15 micro.mhos. 7 < pH <10, so it is further passed through Mixed Bed Deioniser, as shown below. The mixed bed mixture of Cation and Anion resins form infinite numbers of demineralising stages through which DM water passing and thus removing the traces of minerals. By this method demineralised water of extremely pure quality is achieved.

Mix bed deioniser

On discharging, it is charged with 100kg injection of each Hcl and NaOH.

GNDTP has 2 units of DM Plant, each having capacity of 40 tonns/hr

DM water storage tank have capacity of 2456m3

Max running hrs 5(one unit)

Charging Hcl(400kg in cation exchanger)

NaOH (200kg in anion exchanger)

Hcl and NaOH (100kg each in mixed bed)

Treated water has pH 6.8-7.2 , conductivity < 1 micro.mhos

Cation Exchanger

Anion Exchanger

Mix bed deioniser

DM Water Storage Tank

Degasser

Water from sand filters

Hcl charging tank connected with cation exchanger

NaOH charging tank connected with anion exchanger

Coal Testing

Preparation of coal sample

360Kg of Raw coal

Feed size - up to 300mm

Capacity – 20mT/hr

Product size – 50mm

Rejected

X

Coning and quartering - in this method, we divide the total amount of coal in 4 equal parts as shown, then we ignore the 1st & 3rd part. After taking 2nd

Jaw Crusher - I

1 2

4 3

Conning & Quartering

& 4th part together (total mass 180Kg) we again use above method to take another half of earlier collected mass ‘X’ another half of it, but now we ignore 2nd and 3rd part and take 1st and 4th part and get a mass of 90kg.

With the output of jaw crusher – I, we do coning & quartering 2 times and hence we get sample of 90Kg.

Coal product produced by this jaw crusher is of size of 50mm.

This 90kg of coal is further crushed in Jaw Crusher – II, which having the capacity of 1 mT/hr

Jaw crusher - I

90Kg coal

(size-50mm)

Jaw Crusher –II

Feed size – 50mm

Capacity – 1mT/hr

Product Size- 12.5mm

Two times conning & quartering

22.5Kg Coal sample of size 12.5mm

22.5Kg Coal sample of size 12.5mm

Jaw Crusher - III

Feed size – 12.5mm

Product Size – 6mm

One time conning & quartering

11Kg sample of coal of size 6mm

11Kg sample of coal of size 6mm

Jaw Crusher - IV

Feed Size - 6mm

Product Size – 3mm

Conning & Quartering two times 2Kg sample of coal having size of 3mm

2Kg sample of coal having size of 3mm

Now coal sample of mass 2kg having size of 212microns is sent to chemical department for testing.

Coal used is Bituminous having following specifications

Grinder

Feed Size – 3mm

Product Size -212microns.

Coal powder having size of 212microns

Carbon = (60-70) %

Ash = (30-40) %

Moisture < (2) %

Calorific Value = (3500-4500) Kcal/Kg

Coal testing is done to check the grading of the coal.

We check the moisture, ash and volatile content of the coal.

Moisture Content Test

1gm sample of powdered coal is weighed and taken in the silicon dish. Then this sample is heated in oven at 1100C for 1hr.then sample is taken out and again weighed. Loss of weight is the water content.

Ash Content Test

In this test 1gm sample of powdered coal is weighed and taken in the silicon dish. Then this sample is heated in oven at 8100c

for 1hr.then Sample is taken out and again weighed. Remaining is the only ash content.

Volatile Matter Test

For this test 1-gram sample of powdered coal

is taken. This sample is taken in a silicon crucible dish and heated at 900C for 7

minutes. Then the remaining amount of sample is noted and the losses are noted.

Volatile metals are Hg and NH3

Conclusion

Spending my six months of training in Guru Nanak Dev Thermal Plant, Bathinda, I 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. I had an opportunity to work in various sections namely coal handling plant, Boiler section, Turbine section, De-mineralized water plant, Ash handling plant etc. while attending various equipments and machines. I 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 I got familiar with boiler, turbine, compressors, condenser etc. I 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 I had undergone in this industry will definitely help me to apply theoretical knowledge to the practical situation with confidence.