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.
Coal handling plant
Ash handling plant
Cooling towers and ponds
Feed water heater
Superheated and Reheated
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
Coal Handling Plant
Stacker & Reclaimer- It is used to
store the powdered coal for
Atmospheric air (Through
Mill Bunker-The 25mm grit coal is crushed into very fine
powder for feeding the boiler. We will have a spare
Bunker for each Boiler.
Secondary Crusher-The fine pieces of coal is crushed to
powder (to 25mm grit)
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
Pulverizing mills are further classified as:
1. Contact mill
2. Ball mill
3. Impact mill
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
HFO,LDO & Coal
HFO,LDO & Coal
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
•The fuel and air are feed from 2 directions to increase
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
Economizer : Reduces the temperature
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
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.
HPT IPT LPT
*All the turbines are connected to a single shaft which is connected
to the Generator.
Steam after rotating
steam turbine comes to
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
o A condenser needs huge quantity of water to
condense the steam .
o Typically a 2000MW plant needs about 1500MGallon
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
o Height of the cooling tower may be 150 m or so and
diameter at the
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
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
coming out of the
boiler carry lot of
extracts a part of
this heat from
flue gases and
uses it for
water. This use of
results in saving
and higher boiler
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
Reheater : Some of the heat
of superheated steam is used
to rotate the turbine where it
loses some of its energy
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
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
CWPCT CWP CWP
CWP-cooling water Pump
PHE-Pre heat Exchange
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
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)
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.
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.
20KV to 400KV
20Kv to 6.KV
Unit Auxiliary Transformer: This transformer is used to step down the produced voltage and
use for Auxiliary purpose.