thermal power plant

2. THERMAL POWER PLANT

3.  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.  Coal handling plant
 Pulverizing plant
 Draft fans
 Boiler
 Ash handling plant
 Turbine
 Condenser
 Cooling towers and ponds
 Feed water heater
 Economizer
 Superheated and Reheated
 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
FD fan)
Junction Tower
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.
BOILER
Secondary Crusher-The fine pieces of coal is crushed to
powder (to 25mm grit)

8.  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. Contact mill
2. Ball mill
3. Impact mill

9.  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

10. 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

11. 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

12. 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.

13.  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.

14. 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

15.  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

16.  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

17.  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

18.  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

19. 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

20. Reservoir
Water Clarification
DM Plant
(Demineralized Plant)
Chlorification
&
Filtration
Various Equipment
Cooling Water
Cooling Tower
CT
Auxiliary cooling
Water (ACW)
DMCWP
DMCW Demineralized
cooling Water
CWPCT CWP CWP
Condenser
Boiler
Steam
water
Cool water
Hot water
Hot WellDearator
25D  35D
25D  20D
PHE
Various Equipment
D-Degrees
CWP-cooling water Pump
PHE-Pre heat Exchange
Water Cycle

21.  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. 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.