Steam is an important medium of producing mechanical energy. Steam has the advantages that it can be raised from water which is available in abundance it does not react much with the materials of the equipment of the power plant and is suitable at the temperature required in the plant.
Steam is used to drive steam engines, steam turbine etc. Thermal electrical power generation is one of the major methods. For a thermal power plant the range of pressure may vary from 10 kg/cm2 critical pressure and the range of temperature may be from 250 0C to650 0C.
Main parts of a steam power plant:
- Boiler (Babcock and Wilcox)
- Steam turbines (LPT, IPT and HPT)
- Super heater
- Heaters (LPH and HPH)
- Condenser
- Air Compressor
- Pumps
- Economizer
- Generator
Working principle:
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At first water is feed into the boiler and heated by the furnace heat. A boiler contains 9 furnace where each furnace having about 12000C.
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In boiler the separation line separates the steam from water. Water evaporates through natural circulation with down comer.
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Then steam is super heated and passed through the high pressure turbine (HPT).
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After discharging from HPT the temperature and pressure decreases and again reheated to get proper temperature.
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Then it passes through the intermediate and low pressure turbine. It rotates the turbine at a high speed.
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The shaft of the turbines is coupled with the shaft of generator. Since the turbine rotates, the generator shaft also rotates and produces electricity.
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Then the steam is condensed at condenser by river water. After condensing the steam turns into water. Then the water is pumped to the low pressure heater (LPH).
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Then the water is pumped into deareator and removed oxide particle and Oxygen gas.
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Then the water is pumped into Feed Water Tank (FWT) and passes through the High Pressure Heater (HPT).
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Finally the water is feed into boiler drum and the process circulated in cyclic order
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All the units are controlled by manually except the unit-5. It follows DCS (Digital Control System).