Components of the Thermal Power Plant

Components used in the thermal power plant is listed as below.

• Coal and ash handling plant
• Feed water and Steam generating plant
• Super heater
• Economizer
• Air Preheater
• Steam turbine
• Cooling towers
• Alternator

Coal and ash handling plant

The coal is transported to the power station by road or rail. Coal is stored in the coal storage plant. Storage of coal is primarily a matter of protection against coal strikes, failure of the transportation system, and general coal shortages.

From the coal storage plant, it is delivered to the coal handling plant. The coal handling plant is a place where it is pulverized (i.e., crushed into small pieces) to increase its surface exposure. Thus, it promoting rapid combustion without using a large quantity of excess air. After that, by belt conveyors, the pulverized coal is fed to the boiler.

The coal is burnt in the boiler and the ash is produced after the complete combustion of coal is removed to the ash handling plant and then delivered to the ash storage plant for disposal.

The removal of the ash from the boiler furnace is necessary for the proper burning of coal. It is worthwhile to give a passing reference to the amount of coal burnt and ash produced in a modern thermal power station. 

A 100 MW station operating at 50% load factor may burn about 20, 000 tons of coal per month, and ash produced may be to the tune of 10% to 15% of coal-fired i.e.,2,000 to 3,000 tons. In fact, in a thermal station, about 50% to 60% of the total operating cost consists of fuel purchasing and handling.

Feed Water

The condensate from the condenser is used as feed water to the boiler. Some water may be lost in the cycle which is suitably made up of external sources. The feed water passes to the boiler is heated by water heaters and economizer. This helps in raising the overall efficiency of the thermal power plant.

Steam Generating Plant

The heat of combustion of coal in the boiler is utilized to convert water into steam at high temperature and pressure. The flue gases from the boiler make their journey through the super-heater, economizer, air pre-heater. And finally exhausted to the atmosphere through the chimney.

Super Heater

The steam produced in the boiler is wet. And it is passed through a super heater where it is dried and super heated (i.e. the steam temperature increased above that of the boiling point of water) by the flue gases on their way to the chimney.

Super heating provides two principal benefits. Firstly, the overall efficiency is increased. Second thing is too much condensation in the last stages of the turbine (which would cause blade corrosion) is avoided. The super heated steam from the super heater is fed to the steam turbine through the main valve.

Economizer

An economizer is essentially a feed water heater and derives heat from the flue gases for this purpose. The feed water is fed to the economizer before supplying it to the boiler. The economizer extracts a part of the heat of flue gases to increase the feed water temperature.

Air Preheater

By deriving heat from flue gases, an air preheater increases the temperature of air supplied from burning coal. The air is drawn from the atmosphere by a forced draught fan and passed through air preheater before supplying to the boiler furnace. 

The air preheater extracts heat from flue gases and increases the temperature of the air used for coal combustion. The principal benefits of preheating the air are increased thermal efficiency and increased steam capacity per square meter of the boiler surface.

Steam Turbine

The dry and super heated steam from super heater fed to steam turbine through the main valve. The heat energy of steam is converted into mechanical energy when passing over the blades of the turbine.

After giving heat energy to the turbine, the steam is exhausted to the condenser which condenses the exhausted steam using cold-water circulation.

Cooling Arrangement

To improve the efficiency of the thermal power plant, the steam exhausted from the turbine is condensed through a condenser. Water is drawn from a natural source of supply such as a river, canal, or lake and is circulated through the condenser. 

The circulating water takes up heat of the exhausted steam and itself becomes hot. This hot water coming out from condenser discharged at a suitable location. In case the availability of water from the source of supply is not assured throughout the year.

Cooling Towers

It is used during the scarcity (not enough) of water in the river, hot water from the condenser is passed on to the cooling towers where it is cooled. The cold water from the cooling tower is reused in the condenser.

Alternator

The steam turbine is coupled to an alternator. The alternator converts the mechanical energy of the turbine into electrical energy.  The electrical output from the alternator delivered to bus bars through electrical equipment like transformer, circuit breakers, and isolators.