The document discusses the various types of thermal power plants, including coal, oil, gas, and diesel-fired plants, focusing on their components, operation, and site selection criteria. Key factors for site selection include land cost, population density, water and fuel availability, and transportation facilities, while also outlining the merits and demerits of thermal power generation. Additionally, it explains the working of thermal power plants and highlights components such as boilers, turbines, generators, and cooling systems.

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THERMAL POWER PLANT
Thermal Power Stations
• Coal Fired
– Turbo alternators driven by steam turbine
• Oil Fired
– Crude oil OR Residual oil
• Gas Fired
– Fastest growing primary fuel, worldwide
– Combined cycle
• First stage - Gas turbine & Second stage - Steam Turbine
• Diesel Fired
– IC Engine as prime mover
– Standby power plants

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Site Selection
• The site selection of steam power plant depends upon various factors.
• Cost of the land: The cost of the land which is selected for the installation should be
minimum or economical.
• Population density of the land: The distance of the steam power plant from the public area
should be at appropriate distance. So that in case of any failure or hazard happen in the
plant, the population of the area near to the power plant should not be affected.
• Availability of water sources: There should be a plenty of water sources in the selected area.
Since the power plant requires a large amount of water for the generation of steam.
• Availability of fuel: The availability of required fuel (coal) should be there because without
fuel the plant will not work.
• Type of land: The land which is selected for the power plant installation should be plain
enough and it is suitable for the strong foundation for the various machinery of the plant.
• Scope for the future demand: The size of the land should be such that it is capable for the
handling of future power demand.
• Availability of Ash handling facility: Proper ash handling facility should be available near the
power plant to minimise the adverse effect of the ash produced in the steam power plant
• Availability of transportation facility: The transportation facility is must in the installation for
the power plant, because any material cannot be transported to the power plant form its
required location in lack of transport. There should be easy availability of proper
transportation facility at the selected site.
• Nearness to load center
Merits & Demerits
Merits:
• Fuel used is cheaper
• Cheaper installation cost comparatively
• Cheaper production cost in comparison with diesel power
plant
• Can be installed at ay place irrespective of the existence of
fuels unlike HEPP
• Can be located near to load center unlike HEPP
• Able to respond rapidly changing loads without difficulty
• Steam engines and turbine can work under under 25% of
over load continuously
• Portion of steam raised can be used as process steam in
various industries (paper mills, textile mills etc)

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Merits & Demerits
Demerits:
• High maintenance and operating cost
• Pollution
• Requirement of water in huge quantity
• Handling of coal and ash is quite difficult
• The plant cost increases with the increases in the
operating temperature and pressure
• Require long time for construction and put into
action
• Efficiency fall rapidly below 75% of full load
Schematic diagram of Coal Fired Power Plant

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Schematic diagram of Coal Fired
Power Plant
• The simplest steam power cycle consists of
four changes of state:
• 1–2: Liquid pressurised water is evaporated
in a boiler by input of heat
• 2–4: The steamexpands associated with
mechanical power output. In power plants
the mechanical energy is transformed into
electrical energy by a generator.
• 4–5: The expanded steam is condensed to
water with associated heat output
• 5–1: The condensed water is pressurised by
a feed pump and delivered back into the
boiler Into the boiler

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Coal Storage: It is the place where coal is stored which can be utilised when required.
Coal Handling: Here the coal is converted into the pulverised form before feeding to the furnace. A
proper system is designed to transport the pulverised coal to the boiler furnace.
Boiler: It converts the water into high pressure steam. It contains the furnace inside or outside the
boiler shell. The combustion of coal takes place in the furnace.
Air-preheater: It is used to pre-heat the air before entering into the boiler furnace. The pre heating
of air helps in the burning of fuel to a greater extent. It takes the heat from the burnt gases from the
furnace to heat the air from the atmosphere.
Economiser: As its name indicates it economises the working of the boiler. It heats the feed water
to a specified temperature before it enters into the boiler drum. It takes the heat from the burnt gases
from the furnace to do so.
Turbine: It is the mechanical device which converts the kinetic energy of the steam to the
mechanical energy.
Generator: It is coupled with the turbine rotor and converts the mechanical energy of the turbine to
the electrical energy.
Ash Storage: It is used to store the ash after burning of the coal.
Dust Collector: It collects the dust particle from the burnt gases before it is released to the chimney.
Condenser: It condensate the steam that leaves out turbine. It converts the low pressure steam to
water. It is attached to the cooling tower.
Cooling Tower: It is a tower which contains cold water. Cold water is circulates to the condenser for
the cooling of the residual steam from the turbine.
Chimney: It is used to release the hot burnt gases or smoke from the furnace to the environment at
appropriate height. The height of the tower is very high such that it can easily throw the smoke and
exhaust gases at the appropriate height. And it cannot affect the population living near the steam
power plant.
Feed Water ump: It is used to transport the feed water to the boiler.
Working of thermal power plant
• For better understanding,the step by step working of steam power plant is as
follows
• The pulverised coal is fed into the boiler where the pulverised coal is burnt into
the furnace
• Due to heat from the furnace, the water present in the boiler drum changes to the
high pressure steam.
• From the boiler this high pressure steam is passed to the super heater where it is
again heated up to its dryness.
• After that this super heated steamstrikes the turbine blades with a high speed and
the turbine blades startsrotating to at high speed. Here the storedpotential
energy of the steamis gets converted into mechanical energy.
• A generator is coupled with the turbine rotor. As the turbine rotates,the generator
also rotate with same speed and mechanical energy of the turbine gets converted
into electricalenergy.

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Working of thermal power plant
• Steam after hitting the turbines blades lost its most of the energy and leaves the
turbine with low pressure steam.
• This low pressure steam enters into the condenser. Cold water circulates in the
condenserfrom the cooling tower. Here the low pressure wet steam is converted
into water.
• After that condensed water with the feed water passed to the economiser where
it gets heated up by the economiser.And finally the feed water enters into the
boiler by a feed water pump to repeat the cycle.
• The burnt flue gases from the furnace passes through the super heater,
economiserand air pre-heater.This heat of the flue gases is used to heat the
steamin the super heater to its dryness, to heat feed water in the economiser
before enteringinto the boiler and to heat air form the atmosphere in the air pre-
heater before it enters into the furnace.
• The ash from the furnace is transported to ash handling plant and finally to the ash
storage.
Components
1. Cooling tower 6. L.P turbine 11. H.P turbine 16. Coal pulverizer 21. Re-heater
2. Cooling water pump 7. Condensate pump 12. De-aerator 17. Boiler steam drum 22. Combustion
3. Transmission line 8. Surface condenser 13. Feed water heater 18. Bottom ash 23. Economizer
4. Transformer 9. I.P turbine 14. Coal conveyor 19. Super-heater 24. Air pre-heater
5. Generator 10. steam control valve 15. Coal hopper 20. Forced draught 25. Precipitator
26. Induced draught
27. Flue gas stack

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Fuel & Ash Handling
• Coal delivery: by trucks, wagons etc
• Coal storage:Dead & Live storage
• Crusher:coal is crushed to increase the area
• Magneticseparator: removes impurities
• Pulverizer:device to transform coal into fine powder
• Ash pit: when fuel gets burnt, ash is collected in ash pit
• Ash quenching: Ash is hot & dusty, hence needs to be quenched
• Ash delivery: Quenched ash is taken using conveyors to the site
Furnace
• A place where fuel is burnt
• Encloses burning equipments
Types
• Grate fired: uses stationary or movable grates, suited for solid fuels.
1. Hand fired – uses stationary grate, small size plants, discontinuous process
2. Stoker fired – uses movable grate, medium & large size plants, continuous process
A stoker is a power operated fuel feeding mechanism.
• Chamberfired: suited for pulverizedcoal, liquid or gaseous fuels.

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Boiler
• Watertube boiler: DM water circulates through tubes & hot flue gases flow
over them.
 Less liable to explosion, produce high pressure steam, high efficiency, heating surfaceis large
• Fire tube boiler: hot flue gases pass through the tubes which are surrounded
by water.
 Low cost, compact in size, heating surface is small, cannot produce high pressure steam, liable to explode, low efficiency
Water tube boiler Fire tube boiler
Methods to improve thermal efficiency
• Air pre-heater :
 hot flue gases are used to pre-heat the air
 pre-heats the air to be supplied to the furnace
 Accelerates combustion
• Economizer :
 hot flue gases are used to heat the feed water
 Improves efficiency
 Reduces heat losses of flue gas
 Reduces fuel consumption
• Super heater :
 Increases temperature of generated steam
 High thermal efficiency
 Avoids corrosion of turbine blades
• Re-heaters :
 Exhaust Steam from hp turbine is expanded
 High turbine efficiencyas the stages increase

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CONDENSER
Types
 Surface condenser
 No direct contact between steam & cooling
water
 Impure water can be used for cooling
 Low running cost , high vacuum is obtained
 Increased efficiency
 Requires large space
 High initial cost
 Jet Condenser
 Direct contact between steam & cooling
water
 Low initial cost
 Compact
 Low efficiency
Impulse -H.P turbine And
Reaction - L.P & I.P turbine

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TYPES OF TURBINE
Cooling towers
• To reduce thermal pollution which occurs in open system
• To cool water coming out of the condenser in a closed system
• Water cooled, Air cooled cooling towers
• Uses either natural draft or mechanical draft
• Natural draft – utilizes buoyancy large space, high cost, less efficient
• Mechanical draft uses fan, requires less space, improves efficiency
Forced draft tower: blower type fan is located at the base of the tower & forces air into the tower
Induced draft tower: fan is located at the top of the tower & pulls air through the tower.

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Contd..
• Differenttypes of cooling towers Induced draft
ELECTROSTATIC PRECIPITATOR

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Fuel and ash handling
Governing system
Functions:
• To maintain constant shaft speed at all loads
• To maintain constant steam flow through turbine
• To maintain constant pass out and inlet/outlet steam
pressures at all flows
Methods of governing:
• Throttle governing
• Nozzle control governing
• By-pass governing
• Fly ball speed governing etc