3. Introduction
• A Thermal Power Plant converts the heat energy of
coal into electrical energy. Coal is burnt in a boiler
which converts water into steam. The expansion of
steam in turbine produces mechanical power which
drives the alternator coupled to the
turbine.Thermal Power Plants contribute maximum
to the generation of Power for any country
• Thermal Power Plants constitute 75.43% of the total
installed captive and non-captive power generation in India
• In thermal generating stations coal, oil, natural gas etc. are
employed as primary sources of energy.
5. Main and Auxiliary equipments
Coal handling plant
Pulverizing plant
Draft fans
Boiler
Ash handling plant
Turbine
Condenser
Cooling towers and ponds
Feed water heater
Economizer
Superheater and Reheater
Air preheated
6. Raw Coal Wagon- Coal is brought to the site through a
Wagon as per requirement.
Wagon tippler-The coal is unloaded from the Wagon
and is transported to crushers and for
storage place through conveyor.
Junction tower- JT’s are used where the conveyor has
any angular deviation.
Primary Crusher-The Raw coal is crushed into fine
pieces to 45mm grit). Primary crusher is also
called Rotary Breaker since the coal is
crushed by a rotating plate.
Rejected- The
stones and
unwanted coal is
rejected
Coal Handling Plant
7. Stacker & Reclaimer- It is
used to store the powdered
coal for emergency purpose
Two way conveyor
Atmospheric air (Through
PA fan)
Junction Tower
Mill Bunker-The 20mm grit coal is crushed into very fine
powder for feeding the boiler. We will have a spare
Bunker for each Boiler.
BOILER
Secondary Crusher-The fine pieces of coal is crushed to
powder (to 20mm grit)
8.
9. Pulverizing plant
• In modern thermal power plant , coal is pulverized i.e. ground to
dust like size and carried to the furnace in a stream of hot air.
Pulverizing is a means of exposing a large surface area to the
action of oxygen and consequently helping combustion.
• Pulverizing mills are further classified as:
1. Ball mill
2. Bowl mill
10. Draft system
• The circulation of air is caused by a difference in pressure, known as
Draft.
• Draft is a differential pressure b/w atmosphere and inside the boiler.
• It is necessary to cause the flow of gases through boiler setting
• It may be –
1. Natural draft
2. Mechanical draft
11. Boiler
Air
Air
Fuel
HFO,LDO & Coal
Boiler
Fuel
HFO,LDO & Coal
Dryer
Air compressor
FD Fan
Atmospheric Air
The boiler is fed with HFO and LDO initially to ignite the coal in the Boiler.
Types of boilers:
1. Water tube Boiler: A boiler in which water circulates in tubes heated externally by the fire.
2. Fire tube Boiler: Water is present in the drum inside the boiler and Hot air is circulated around maintain
the temperature.
•The fuel and air are feed from 2 directions to
increase the efficiency
12. Ash Handling Plant
The Ash from the boiler is collected in two forms:
1. Bottom Ash(Slurry):It’s a waste which is dumped into a Ash Pond
2. Fly ash: Fly ash is separated from Flue Gases in ESP(Electro static
Precipitator).
Fly Ash &
Flue
Gases
Economizer ESP
Bottom
ash(wet ash)
Ash Pond
Boiler
Cylo
Cement Factory
Economizer : Reduces the temperature
Chimney
Fly ash
Flue Gases
Flue Gases
13. Turbine
In a Thermal Power Plant generally 3 turbines are used to increase the efficiency.
• High Pressure Turbine(HPT): The superheated steam is directly fed to this turbine to
rotate it.
• Intermediate Pressure Turbine(IPT): The out put from the HPT is reheated in a
reheated(RH) and used to rotate IPT .
• Low Pressure Turbine(LPT): The Exhausted steam from the IPT is directly fed to
rotate the shaft of LPT.
Condenser
HPT IPT LPT
RH
Steam
Super
Heater
Generator
Steam
Shaft
*All the turbines are connected to a single shaft which is connected
to the Generator.
14. CONDENSER
• Steam after rotating
steam turbine comes
to condenser.
Condenser refers here
to the shell and tube
heat exchanger (or
surface condenser)
installed at the outlet
of every steam
turbine in Thermal
power stations of
utility companies
generally.
15. Cooling towers and ponds
o A condenser needs huge quantity of water to condense the
steam .
o Typically a 2000MW plant needs about 1500MGallon of
water.
o Most plants use a closed cooling system where warm water
coming from condenser is cooled and reused
o Small plants use spray ponds and medium and large plants
use cooling towers.
o Cooling tower is a steel or concrete hyperbolic structure
having a reservoir at the base for storage of cooled water
o Height of the cooling tower may be 150 m or so and
diameter at the
16. Feed water heater
• Advantages of heating water before feeding back to the
boiler:-
a) Feed water heating improves overall plant efficiency.
b) The dissolved oxygen and carbon dioxide which would
otherwise cause boiler corrosion are removed in feed water
heater
c) Thermal stresses due to cold water entering the boiler
drum are avoided.
d) Quantity of steam produced by the boiler is increased.
e) Some other impurities carried by the steam and
condensate, due to corrosion of boiler and condenser are
precipitated outside the boiler
17. Economizer
• Flue gases coming
out of the boiler
carry lot of heat.
An economizer
extracts a part of
this heat from flue
gases and uses it
for heating feed
water. This use of
economizer
results in saving
coal consumption
and higher boiler
efficiency
18. Super heater and Reheaters
• Super heater :
• Super heater is
a component of a steam-
generating unit in which
steam, after it has left the
boiler drum, is heated above
its saturation temperature
• Reheater : Some of the heat
of superheated steam is used
to rotate the turbine where it
loses some of its energy
19. Air preheaters
• After flue gases leave economizer, some further heat can
be extracted from them and used to heat incoming heat.
Cooling of flue gases by 20 degree centigrade increases the
plant efficiency by 1%.
• Air preheaters may be of three types
Plate type
Tubular type
Regenerative type
20. Water Handling Plant(WHP)
Water in a Power Plant is used for
1. Production of Steam- for rotating turbine.
2. Cooling Purpose- For cooling of various equipment .
Water is recycled and used for various purpose:
3% of water is wasted during this process. Appx 4
cubic mt water is lost /day/MW
Raw
Water
Purified
DM
water
For
cooling
purpose
Steam
Conden
ser
21. Operation Mechanism
• The coal is brought and crushed to powder. This is feed to Boiler for producing heat
• In Boiler the water is converted to steam.
• In Super heater the moisture content is removed from the steam and that steam is called
super heated steam
• The superheated steam rotates the shaft of the High pressure turbine
• The Exhausted steam is sent to preheater and the steam then rotates the Intermediate
pressure(IP) Turbine
• The steam from the IP turbine is then feed to low pressure turbine.
• The turbine shaft is connected to the Generator, which produces Electric Power.
• The power generated is then Transmitted.
22. Generator
The Synchronous Generator is used to Generate power by connecting the shaft of
the Turbine to the shaft of the generator which cuts the magnetic flux
producing Emf.
• The Generated Voltage will generally 11KV to 20 KV max.
• The Generated Voltage is stepped up by connecting Step up transformer and is
transmitted and is also used for Auxiliary purposes.
Bus Duct
Generator Transformer
20KV to 400KV
SYNCHRONOUS
GENERATOR
UAT
20Kv to 6.KV
Unit Auxiliary Transformer: This transformer is used to step down the produced
voltage and use for Auxiliary purpose.
