Introduction

INTRODUCTION

Rajasthan is well on its way for a 'brighter' future, a future that promises electricity to every

city, town and village of the state, a promise of making the state completely self-dependent in

power production. The state plans to add over 1500 megawatts of power supply to its present

capacity in the coming two years. Nine electricity generating units are being raised under

different power projects across the state that will increase the current capacity of 2,569 MW to

4084 MW. Kota Thermal Power Station is Rajasthan's First major coal power station. Presently

it is in operation with installed capacity of 1240 MW. And one more unit of 250MW is slated

for commissioning in March 2009.

The foundation of seventh unit of Kota Thermal Power Station (KTPS) was laid by Union

Minister of Power, Mr. Sushil Kumar Shinde on December 5, 2006. The unit is expected to be

ready by November, 2007. After this, the Kota power plant's present capacity of 1045 MW will

be expanded to 1240 MW.

STAGE UNIT NO. CAPACITY(MW) SYNCHRONIZING

DATE

COST

(Rs. crore)

I 1

2

110

110

17.01.1983 13.07.1983

143

II 3

4

210

210

25.09.1988 01.05.1989

480

III 5 210 26.03.1994 480

IV 6 195 31.07.2003 635

V 7 195 30.05.2009 880

1

Introduction

Location:

Kota Thermal Power Station is located on the left bank of river Chambal in Rajasthan's

principal Industrial city, Kota. Thermal power station to produce electrical power for

supply undertakings K.S.T.P.S. is designed for ultimate capacity of 1240 MW.

Excellent Performance:

Kota Thermal Power Station of RVUN is reckoned one of the best, efficient and

prestigious power stations of the country. KTPS has established a record of excellence

and has earned meritorious productivity awards from the Ministry of Power, Govt. of

India during 1984, 1987, 1989, 1991& every year since 1992-93 onwards. Kota Super

thermal power station have earned Golden Shield award from Union Ministry of power

for consistently outstanding performance during last four years (i.e. 2000-01,2001-

02,2002-03,2003-04). The Golden Shields were presented by H.E. President of India Dr.

A.P.J. Abdul Kalam on 24.08.2004.

2

Power Station Design

POWER STATION DESIGN

Power station design requires wide experience. A satisfactory design consists of the following

Steps:

Selection of site

Estimation of capacity of power station.

Selection of turbines and their auxiliaries.

Selection of boilers, and their auxiliaries.

Design of fuel handling system.

Selection of condensers.

Design of cooling system.

Design of piping system to carry steam and water.

Selection of electrical generator.

Characteristics of a Steam Power Plant : The desirable characteristic for a steam power plant are

as follows:

Higher efficiency.

Lower cost.

Ability to burn coal especially of high ash content and inferior coals.

Reduced environmental impact in terms of air pollution.

Reduced water requirement.

Higher reliability and availability.

3

Coal Handling Plant

COAL HANDLING PLANT

Coal delivery equipment is one of the major components of plant cost. The various steps involved

in coal handling are as follows:

3.1 Steps in coal handling

Fig. 1 Steps in Coal Handling.

Coal Delivery

Unloading

Preparation

Transfer

Outdoor Storage (Dead Storage)

Covered Storage (Live Storage)

In Plant Handling

Weighing and Measuring

Furnace

4

Coal Handling Plant

Coal Delivery

The coal from supply points is delivered by ships or boats to power stations situated near

to sea or river whereas coal is supplied by rail or trucks to the power stations which are situated

away from sea or river. The transportation of coal by trucks is used if the railway facilities are not

available.

Unloading

The type of equipment to be used for unloading the coal received at the power station

depends on how coal is received at the power station. If coal is delivered by trucks, there is no

need of unloading device as the trucks may dump the coal to the outdoor storage. Coal is easily

handled if the lift trucks with scoop are used. In case the coal is brought by railway wagons, ships

or boats, the unloading may be done by car shakes, rotary car dumpers, cranes, grab buckets and

coal accelerators. Rotary car dumpers although costly are quite efficient for unloading closed

wagons.

Fig. 2 Railway wagons

5

Coal Handling Plant

Preparation

When the coal delivered is in the form of big lumps and it is not of proper size, the

preparation (sizing) of coal can be achieved by crushers, breakers, sizers driers and magnetic

separators.

Transfer

After preparation coal is transferred to the dead storage by Belt conveyors, Screw

conveyors, Bucket elevators, Grab bucket elevators, Skip hoists, Flight conveyor.

Fig. 3 Receiving Conveyor System

6

Coal Handling Plant

Outdoor (Dead) Storage

It is desirable that sufficient quantity of coal should be stored. Storage of coal gives

protection against the interruption of coal supplies when there is delay in transportation of coal or

due to strikes in coal mines. Also when the prices are low, the coal can be purchased and stored for

future use. The amount of coal to be stored depends on the availability of space for storage,

transportation facilities, the amount of coal that will whether away and nearness to coal mines of

the power station. Usually coal required for one month operation of power plant is stored in case of

power stations situated at longer distance from the collieries whereas coal need for about 15 days is

stored in case of power station situated near to collieries. Storage of coal for longer periods is not

advantageous because it blocks the capital and results in deterioration of the quality of coal.

Indoor (Live) Storage

Such storage constitutes coal requirements of the plant for a day. The live storage can be

provided with bunkers and coal bins.

In Plant Handling

This refers to handling of coal between the final storage to the firing equipment. In case

of simple stoker firing only chutes may be required to feed the coal from storage bunker to firing

units.

Coal Weighing

The cost of the fuel is the major running cost of the plant. It is, therefore, very

necessary to weigh coal at unloading point and also that used as feed to individual boilers. A

correct measurement of coal enables one to have an idea of total quantity of coal delivered at the

site and also whether or not proper quantity has been burned as per load on the plant.

7

Coal Handling Plant

3.2 PULVERIZATION OF COAL

Fig. 4 coal pulverizer

Coal is pulverized (powdered) to increase its surface exposure thus

permitting rapid combustion. Efficient use of coal depends greatly on the combustion process

employed. For large scale generation of energy the efficient method of burning coal is confined

still to Pulverized coal combustion. The pulverized coal is obtained by grinding the raw coal in

pulverizing mills. The various pulverizing mills used are as follows:

Ball mill

Hammer mill

Ball and race mill

8

Coal Handling Plant

3.3 PULVERIZED COAL FIRING

Fig. 5 fuel burner

Hot air is passed through coal in the feeder to dry the coal. The coal is then transferred

to the pulverizing mill where it is pulverized. Primary air is supplied to the mill, by the fan. The

mixture of pulverized coal and primary air then flows to burner where secondary air is added. The

unit system is so called from the fact that each burner or a burner group and pulverising constitutes

a unit.

3.4 ASH DISPOSAL

A large quantity of ash is, produced in steam power plants using coal. Ash produced in

about 10 to 20% of the total coal burnt in the furnace. Handling of ash is a problem because ash

coming out of the furnace is too hot, it is dusty and irritating to handle and is accompanied by

some poisonous gases.(2)

9

Thermal Power Plant Equipment

EQUIPMENTS ON A THERMAL POWER STATION

4.1 Boiler

Boiler is a device meant for producing steam under pressure. Steam boilers are

broadly classified into fire tube and water tube. Generally water tube boilers are used for

electric power station. In water tube boilers, water circulates through the tubes and hot products

of combustion flow over these tubes. In fire tube boiler the hot products of combustion pass

through the tubes, which are surrounded, by water. But they are more likely to explosion, water

volume is large and due to poor circulation they cannot meet quickly the change in steam

demand. Water tube boilers require less weight of metal for a given size, are less liable to

explosion, produce higher pressure, are accessible and can response quickly to change in steam

demand. Tubes and drums of water-tube boilers are smaller than that of fire-tube boilers and

due to smaller size of drum higher pressure can be used easily. Water-tube boilers require lesser

floor space. The efficiency of water-tube boilers is more. (1)

Boiler is main equipment on a thermal power station. It made up of thousands of tubes

Generally called water walls. And these walls are insulated by the insulating material. And

water is flowing through these tubes. And the height of the boiler is approx. 55-60 meter. The

plant efficiency is mainly depending upon boiler efficiency.

Fig. 6 inside view of a boiler furnace

10

Thermal Power Plant Equipment

Fig. 7 Boiler house Component

TECHNICAL SPECIFICATION OF BOILER (2x110MW UNITS)

1. Type : Direct fired, natural circulation balance draft water tube

Boiler .

2. No. of Units. : Two.

3. Make : BHEL.

4. Capacity. : 375 tones per hour.

5. Steam Pressure. : 139 Kg./Cm2

6. Efficiency : 86.6 %.

11

Thermal Power Plant Equipment

7. No. of fans in service.

a) ID fans. : 2 Nos.

b) FD fans. : 2 Nos.

c) PA fans. : 2 Nos.

d) Seal Air fan. : 1 No.

e) Scanner Air fan. : 1 No.

f) Igniter fan. : 1 No.

8. Steam Temperature : 540oC.

9. No. of coal mills in service. : 3 Nos.

4.2 Boiler drum

Boiler drum is on the height of approx. 53 meters. The boiler drum contains both

steam and water, A number of accessories such as water level indicator, safety valve, automatic

alarms, pressure gauge etc. the use of these devices assists in adequate control and operation of

the boiler as also in safety against accidents. (1)

Fig. 8 Outer side view of boiler drum

12

Thermal Power Plant Equipment

4.3 Economizers:

The purpose of economizer is to heat feed water so as to recover a part of heat,

Which would otherwise be lost through flue gases.

Fig. 9 Economizer tubes

4.4 Air Preheater:

An Air preheater increases the temperature of the air supplied for coal burning by

deriving heat from flue gases. The air preheater extracts heat from flue gases and increases the

temperature of air used for coal combustion. The principal benefits of preheating the air are:

increased thermal efficiency.

The air pre heater is made up of Buckets, in which 3 layer of buckets are put on each other, in

the middle of layer, a motor is held, which is rotate on its own axis, Air pre heater heat up the

air given to the boiler. (2)

13

Thermal Power Plant Equipment

Fig. 10 Air preheater

4.5 Superheater:

A superheater is a device which superheats the steam; it raises the temperature of

steam above boiling point of water. This increases the overall efficiency of the steam. A

superheater consists of a group of tubes made of special alloy such as chromium-molybdenum.

These tubes are heated by the heat of the flue gases during their journey from the furnace to the

chimney.(2)

14

Thermal Power Plant Equipment

Fig. 11 Superheater

4.6 Steam turbine

The dry and superheated steam from the superheater is fed to the steam turbine

through main valve. It converts Kinetic energy to Mechanical Energy. ( i.e. The heat energy of

steam passing over the blades of turbine is converted into mechanical energy)

15

Thermal Power Plant Equipment

Fig. 12 Steam Turbine used in power plant

Classification of steam turbine:

(A) On the Basis of Principle of Operation :

i) Impulse turbine ii) Impulse-reaction turbine

4.6.1 Impulse Turbine: If the flow of steam through the nozzles and moving blades of a

turbine takes place in such a manner that the steam is expanded only in nozzles and pressure at

the outlet sides of the blades is equal to that at inlet side; such a turbine is termed as impulse

turbine because it works on the principle of impulse. In other words, in impulse turbine, the

drop in pressure of steam takes place only in nozzles and not in moving blades. This is obtained

by making the blade passage of constant cross- section area As a general statement it may be

stated that energy transformation takes place only in nozzles and moving blades (rotor) only

cause energy transfer. Since the rotor blade passages do not cause any acceleration of fluid,

hence chances of flow separation are greater which results in lower stage efficiency.

16

Thermal Power Plant Equipment

4.6.2 Impulse-Reaction Turbine: In this turbine, the drop in pressure of steam takes place in

fixed (nozzles) as well as moving blades. The pressure drop suffered by steam while passing

through the moving blades causes a further generation of kinetic energy within the moving

blades, giving rise to reaction and adds to the propelling force which is applied through the

rotor to the turbine shaft. Since this turbine works on the principle of impulse and reaction both,

so it is called impulse-reaction turbine. This is achieved by making the blade passage of

varying cross-sectional area (converging type) (1)

The various advantages of steam turbine are as follows:

It requires less space.

Absence of various links such as piston, piston rod, cross head etc. make the mechanism

simple. It is quiet and smooth in operation,

It can be designed for much greater capacities as compared to steam engine. Steam

turbines can be built in sizes ranging from a few horse powers to over 200,000 horse

power in single units.

In steam turbine power is generated at uniform rate, therefore, flywheel is not needed.

It can be designed for much higher speed and greater range of speed. 17

Thermal Power Plant Equipment

Technical data of steam turbine (210mw)

Rated Output : 210 MW.

Rated Speed. : 3000 rpm.

Main steam pressure. : 150 Kg./Cm2

Main steam temperature. : 535oC.

Reheat steam temperature. : 535oC.

Weight of turbine. : 475 T approx.

Overall length. : 16.975 Mtrs.approx.

Description of 210 MW Steam Turbine

1) Steam flow :

210 MW steam turbine is a tandem compound machine with HP, IP &

LP parts. The HP part is single flow cylinder and HP & LP parts are double flow

cylinders. The individual turbine rotors and generator rotor are rigidly coupled. The

HP cylinder has a throttle control. Main steam is admitted before blending by two

combined main stop and control valves. The HP turbine exhaust (CRH) leading to

reheat have tow swing check valves that prevent back flow of hot steam from reheated,

into HP turbine. The steam coming from reheated called HRH is passed to turbine via

two combined stop and control valves. The IP turbine exhausts directly goes to LP

turbine by cross ground pipes.(3)

2) HP Turbine

The HP casing is a barrel type casing without axial joint. Because of its

rotation symmetry the barrel type casing remain constant in shape and leak proof during

quick change in temperature. The inner casing too is cylinder in shape as horizontal

joint flange are relieved by higher pressure arising outside and this can kept small. Due

to this reason barrel type casing are especially suitable for quick start up and loading. 18

Thermal Power Plant Equipment

3) IP Turbine

The IP part of turbine is of double flow construction. The casing of IP turbine is split

horizontally and is of double shell construction. The double flow inner casing is

supported kinematically in the outer casing. The steam from HP turbine after reheating

enters the inner casing from above and below through two inlet nozzles. The center

flow compensates the axial thrust and prevents steam inlet temperature affecting

brackets, bearing etc. The arrangements of inner casing confines high steam inlet

condition to admission branch of casing, while the joints of outer casing is subjected

only to lower pressure and temperature at the exhaust of inner casing. The pressure in

outer casing relieves the joint of inner casing so that this joint is to be sealed only

against resulting differential pressure.

4) LP Turbine

The casing of double flow type LP turbine is of three shell design. The

shells are axially split and have rigidly welded construction. The outer casing consists

of the front and rear walls, the lateral longitudinal support bearing and upper part.

4.7 Turbo Generator

Generator is the main part of thermal power station or any power plant.

A generator is a machine which converts mechanical energy into electrical energy.

TURBO GENERATOR manufactured by B.H.E.L. and incorporated with most modern design

concepts and constructional features, which ensures reliability, with constructional &

operational economy.

Cooling medium hydrogen is contained within frame & circulated by fans mounted at either

ends of rotor. The generator is driven by directly coupled steam turbine at a speed of 3000

r.p.m. the Generator is designed for continuous operation at the rated output.

19

Thermal Power Plant Equipment

Temperature detectors and other devices installed or connected within then machine, permit the

windings, teeth core & hydrogen temperature, pressure & purity in machine under the

conditions. The source of excitation of rotor windings is Thyristor controlled D.C. supply. The

auxiliary equipment’s supplied with the machine suppresses and enables the control of

hydrogen pressure and purity, shaft sealing lubricating oils. There is a provision for cooling

water in order to maintain a constant temperature of coolant (hydrogen) which controls the

temperature of windings.(6)

Technical data of turbo-generator:

Make KWVC Craftworks, German

Manufacturer BHEL

Rated Capacity 247 MVA

Rated Output 210 MW

Rated Current 9050 Amp.

Rated Terminal Voltage 15.75 KV

Rated Speed 3000 Rpm

Power Factor 0.8 Lagging

Excitation Voltage 310 V

Fig. 14 Turbine and generator 20

Thermal Power Plant Equipment

4.8 Dearator

A Dearator is a device that is widely used for the removal of air and other

dissolved gases from the feed water to steam generating boilers. In particular, dissolved oxygen

in boiler feed waters will cause serious corrosion damage in steam systems by attaching to the

walls of metal piping and other metallic equipment and forming oxides (rust). It also combines

with any dissolved carbon dioxide to form carbonic acid that causes further corrosion. Most

Dearator is designed to remove oxygen down to levels of 7 ppm by weight (0.0005 cm³/L) or

less.(2)

Fig. 15 Dearator used in thermal power station

21

Thermal Power Plant Equipment

4.9 Condenser

The surface condenser is a shell and tube heat exchanger in which cooling water

is circulated through the tubes. The exhaust steam from the low pressure turbine enters the shell

where it is cooled and converted to condensate (water) by flowing over the tubes as shown in

the adjacent diagram. Such condensers use steam ejectors or rotary motor-driven exhausters for

continuous removal of air and gases from the steam side to maintain vacuum.

For best efficiency, the temperature in the condenser must be kept as low as practical in order

to achieve the lowest possible pressure in the condensing steam. Since the condenser

temperature can almost always be kept significantly below 100°C where the vapor pressure of

water is much less than atmospheric pressure, the condenser generally works under vacuum.(3)

Fig. 16 condenser

22

Thermal Power Plant Equipment

4.10 Electro Static precipitator

To remove fly ash from the flue gases electrostatic precipitators are used. They have

collection efficiency over 99.5%. The efficiency depends on various parameters such as

velocity of flow, quantity of gas, resistivity of ash, voltage of fields, temperature etc.

Principle of Operation:

The flue gas laden with fly ash is sent through ducts having negatively charged plates

which give the particles a negative charge. The particles are then routed past positively charged

plates, or grounded plates, which attract the now negatively-charged ash particles. The particles

stick to the positive plates until they are collected by periodically rapping. (4)

Fig. 17 ESP working

Fig. 18 Outer view of an electrostatic precipitator

23

Thermal Power Plant Equipment

4.11 Feed Water Heater:

In the case of a conventional steam-electric power plant utilizing a drum boiler, the

surface condenser removes the latent heat of vaporization from the steam as it changes states

from vapor to liquid. The heat content (btu) in the steam is referred to as Enthalpy. The

condensate pump then pumps the condensate water through a feed water heater. The feed water

heating equipment then raises the temperature of the water by utilizing extraction steam from

various stages of the turbine.

Preheating the feed water reduces the irreversibility involved in steam generation and therefore

improves the thermodynamic efficiency of the system. This reduces plant operating costs and

also helps to avoid thermal shock to the boiler metal when the feed water is introduced back

into the steam cycle.(5)

24

Fans used in a thermal power plant

Fans used in a Thermal Power Plant

5.1 Force draught fan

In order to burn the coal and convert it to heat, there should be a supply for

large amounts of air. Air combustion is supplied by force draught. Part of the air (primary air)

goes to the mills picking up the powdered coal. The rest of the air (secondary air) after passing

through the air preheater enters the furnace through the dampers (controlled openings).

Fig. 19 Force Draught fan

5.2 Induced Draught Fans

The function of induced draught fan is to draw the flue gas out of the furnace.it

is placed near the stack. In an Induced draught system, the blower is installed near the base of

the chimney and the burnt gases are sucked out of the boiler, reducing the pressure inside the

boiler to less than atmosphere one.

25

Fans used in a thermal power plant

Fig. 20 Induced draught fan

5.3 Natural Draught

The natural draught is provided by the action of chimney or stack and is used only in

small boilers. Its intensity depends upon the average temp. Difference between the flue gases

within the chimney and the outside air and also on the height of the chimney above the level

of the furnace grate. Its weather conditions and boiler operating conditions. Chimney, in

addition of providing natural draught, helps in reducing air pollution too, as it delivers the

products of combustion and fly ash to a high altitude. The height of chimney is 180 meters. (7)

26

Cooling tower

Cooling tower

A cooling tower is equipment used to reduce the temperature of a water

stream by extracting heat from water and emitting it to the atmosphere. Cooling towers make

use of evaporation whereby some of the water is evaporated into a moving air stream and

subsequently discharged into the atmosphere. As a result, the remainder of the water is cooled

down significantly. Cooling towers are able to lower the water temperatures more than devices

that use only air to reject heat and are therefore more cost-effective and energy efficient.(4)

Fig. 21 Natural draft wet cooling hyperbolic towers

27

stack

STACK

Fig. 22 Stack in KSTPS KOTA

A flue gas stack is a type of chimney, a vertical pipe, channel or similar structure through

which combustion product gases called flue gases are exhausted to the outside air. Flue gases

are produced when coal, oil, natural gas, wood or any other fuel is combusted in an industrial

furnace, a power plant's steam-generating boiler, or other large combustion device. Flue gas is

usually composed of carbon dioxide (CO2) and water vapor as well as nitrogen and excess

oxygen remaining from the intake combustion air. It also contains a small percentage of

pollutants such as particulate matter, carbon monoxide, nitrogen oxides and sulfur oxides.(9)

28

Conclusion

CONCLUSION

After the successive completion of my training I got the practical knowledge

of power plant and make my knowledge better than before.

I hope this training will help me for my career and to enrich my knowledge

to become a good engineer.

I am very thankful to everyone who helped me directly or indirectly during

my training.

It was a memorable experience for me to take training.

29