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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