Thermal power plants are backbone of electricity generation. They play a important role in meeting the world energy demands by converting heat energy from fuel combustion into electricity.
How electricity is generated in thermal power plant?
The process of generating electricity in a thermal power plant involves the following steps:
Combustion of Fuel: Heat energy is produced by burning of fuel such as coal or natural gas.
Steam Generation: This heat is used to convert water into high-temperature, high-pressure steam.
Turbine Operation: The steam drives the turbine blades, causing the turbine shaft to rotate.
Electricity Production: The rotating turbine shaft is connected to a generator, which converts the kinetic energy into electrical energy.
Thermal Power Plant Layout
Important Terms Used In Thermal Power Plant Or Steam Power Plant
Saturation Temperature – It is the temperature for a corresponding saturation pressure at which a liquid boil into its vapor phase.
Wet Steam or Unsaturated Steam – It is a mixture which contain both water vapor and liquid water droplets. Most of the best boiler discharge steam containing 3% to 5% wetness. If the mass of steam contains 5 % water it’s said to be 5% wet & 95 % dry.
Dry Steam or Saturated Steam – Dry steam is steam that is at the temperature of saturation, but does not contain water particles in suspension.
Superheated Steam – It is an extremely high temperature vapour generated by heating the saturated steam or wet steam beyond the saturation point.
Condensate – A liquid phase produced by the condensation of steam.
How does a coal power plant work?
The coal based thermal power plant comprises of four main working circuits:
Coal and ash circuit
Air & gas circuit
Feed water and steam flow circuit
Cooling water circuit
Coal and Ash Circuit
Coal Handling: Coal is transported to the coal handling plant, processed, and fed into the furnace through pulverizers and fuel feeding devices.
Air is taken from atmosphere through the action of forced draught (FD) fan and preheated using air preheater. Flue gases are produced when coal is combusted in the boiler. The flue gases after passing around boiler tubes and superheater tubes in the furnace pass through an economiser and finally through the air preheater before being exhausted to the atmosphere via electrostatic precipitator (ESP) & chimney.
In the water and steam circuit condensate leaving the condenser is passes through the deaerator and water heaters before going the boiler through economiser.
In the boiler drum and tubes, water circulates due to the difference between the density of water in the lower temperature and the higher temperature section of the boiler. Wet steam from the drum is further heated up in the superheater before being supplied to the turbine. After expanding in turbine steam is condensed in the condenser. The condensate leaving the condenser is circulated to boiler. A part of steam and water is lost while passing through different components and this compensated by supplying additional feed water. This feed water is purified & softened before going the boiler, to avoid the scaling of the tubes of the boiler. The purification and softening of water are done in water treatment plant.
The cooling water supply to the condenser helps in maintaining a low pressure in it. The cooled water extract heats from turbine exhaust steam in the condenser and become hot. Hot water gets cooled after passing through cooling tower and again circulated to condenser through circulating water pump.
A part of water is lost in the cooling tower and this compensated by supplying the water from a natural source such as river, lake or sea.
