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• Thermal Power Plant are those plants which produceelectricity by converting heat energy obtained by

combustion of non-renewable sources like Coal,

Petroleum etc.

• The basic principle behind the working of power 

 plant is that the heat energy obtained from coal is

used to get saturated pressurized steam which is then

to used to rotate the turbine of electric generator • The energy from shaft rotation is collected by a

generator which converts the motion to electrical

energy using a magnetic field.

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• Boiler 

• Turbine

• Generator 

•

Surface condenser • De-aerator 

• Boiler feed pump

• High pressure heating system

• Economizer 

• Boiler Drum

• Air Heater 

• Electrostatic Precipitator 

• Chimney

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These three cycles play a vital role in the running of 

a thermal power plant. They are:-

• Water Steam Cycle

• Fuel cycle

• Flue Gas Cycle

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o BOILER 

The boiler is a rectangular furnace. Its walls are made of aweb of high pressure steel tubes . Pulverized coal is air- blown into the furnace from fuel nozzles at the four corners

and it rapidly burns, forming a large fireball at the center.The thermal radiation of the fireball heats the water thatcirculates through the boiler tubes near the boiler  perimeter. As the water in the boiler circulates it absorbsheat and changes into steam. It is separated from the water inside a drum at the top of the furnace. The saturated steamis introduced into superheat pendant tubes that hang in thehottest part of the combustion gases as they exit thefurnace. Here the steam is superheated to 540 °C to prepareit for the turbine.

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o   TURBINE 

A turbine is a simple device with few parts that uses flowingfluids (liquids or gases) to produce electrical energy. Fluid isforced across blades mounted on a shaft, which causes theshaft to turn. The energy produced from the shaft rotation iscollected by a generator which converts the motion toelectrical energy using a magnetic field.

Most power plants use turbines to produce energy by burning coal or natural gas. The heat produced from combustion is used to heat water in boiler. Theliquid water is converted to steam upon heating and isexhausted through a pipe which feeds the steam to the

turbine. The pressurized steam flow imparts energy on the blades and shaft of the turbine causing it to rotate. Therotational mechanical energy is then converted to electricalenergy using a generator.

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GENERATOR 

The turbine is attached by a shaft to the turbo-generator. The

generator has a long, coiled wire on its shaft surrounded by agiant magnet. The shaft that comes out of the turbine isconnected to the generator. When the turbine turns, the shaftand rotor is turned. As the shaft inside the generator turns, anelectric current is produced in the wire. The electric generator 

is converting mechanical, moving energy into electricalenergy.

The generator is based on the principleof "electromagnetic induction" discovered in 1831 by MichaelFaraday, a British scientist. Faraday discovered that if anelectric conductor, like a copper wire, is moved through amagnetic field, electric current will flow (or "be induced") inthe conductor. So the mechanical energy of the moving wireis converted into the electric energy of the current that flowsin the wire.

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SURFACE CONDENSER 

A condenser is a device which condenses the steam at the

exhaust of turbine. It serves two important functions. Firstly,it creates a very low ( By liquidation steam at the exhaust of 

turbine, a region of emptiness is created. This results in a very

low pressure at the exhaust of turbine.) pressure at the exhaust

of turbine, thus permitting expansion of the steam in the prime mover to very low pressure. This helps converting heat

energy of steam into mechanical energy in the prime mover.

Secondly, the condensed steam can be used as feed water to

the boiler.

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DEAERATOR  

A de-aerator 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). Water alsocombines with any dissolved carbon dioxide to form carbonic

acid that causes further corrosion. Most de-aerators are

designed to remove oxygen down to levels of 7 ppb by weight

(0.005 cm³/L) or less.

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BOILER FEED PUMP

The principal governing these plants is intimate contact between the feed water and the steam which both heats the

water and strips dissolved gases from it. The three ways of 

achieving this are : (a) spraying fine water droplets into a

steam space; (b) bubbling steam through the body of water;

and (c) exposing falling water to steam over extendedsurfaces. Contact time for both spraying and bubbling is

short, so these processes are usually combined with, or 

replaced by, the extended liquid surface principle.

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ECONOMIZER  

Economisers are mechanical devices intended to reduce

energy consumption, or to perform another useful functionlike preheating a fluid. The term economizer is used for other 

 purposes as well. Boiler, power plant, and heating,

ventilating, and air-conditioning (HVAC) uses are discussed

in this article. In simple terms, an economizer is a heatexchanger.

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AIR HEATER 

The purpose of the air pre-heater is to recover the heat fromthe boiler flue gas which increases the thermal efficiency of 

the boiler by reducing the useful heat lost in the flue gas. As a

consequence, the flue gases are also sent to the flue gas stack 

(or chimney) at a lower temperature, allowing simplified

design of the ducting and the flue gas stack. It also allowscontrol over the temperature of gases leaving the stack (to

meet emissions regulations).

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In India , the major thermal power plants are

running under  NATIONAL THERMAL POWER 

CORPORATION ,one of the largest PSU’S of 

India.

About 65.34%of the electricity consumed in

India is generated by thermal power plants.

The state of Maharashtra is the largest producer of thermal power in the country.

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