Steam Power Plant

• Generally, a Thermal power plant is one which is used to produce electrical power on a large scale. Usually, the steam power plant are used in which the chemical energy of a fuel is utilized to generate high pressure, high temperature steam in a boiler.
• This steam is used in a turbine to produce mechanical power which is finally converted into electrical energy by a alternator.                                                                                                                                                                                                                                                                
   
• In a steam power plant, various heat recovery systems like air preheat-er, economizer are used to improve the thermal efficiency of the steam power plant.                                                                                                                                                                                                                     Various components of a steam power plant with their function                                                                                                                                                                                                      (1) Blower : The function of the blower is to draw the surrounding air needed for combustion of fuel. The air drawn by  blower is supplied to air preheat-er.                                                        (2) Air preheat-er: It is a heat transfer device in which the air drawn from surrounding is heated with the help of hot flue gases before discharging to atmosphere through the chimney. The heated air is supplied to the furnace. It improves the combustion efficiency of the fuel.        (3) Furnace: Heated air from air preheat-er is supplied to the furnace where fuel is burnt. The products of combustion of fuel and air are called flue gases.                                                          (4) Economizer : The feed water before supplied tot he boiler tubes is heated with the help of flue gases. It reduce the energy needed for formation of steam.                                                      (5) Boiler : It consists of boiler shell, water, tubes and super heater. Feed water supplied from the economizer is first converted into wet steam in water tubes and then into super heated steam in the super heater due to the heat supplied by the hot flue gases. Steam is generated at high pressure in the boiler.                                                                                                                 (6) Steam Turbine and Generator : High pressure, super heated steam of the boiler expands in the produces the mechanical work. This work is utilized to drive a generator which convert the mechanical energy into electrical energy.                                                                                  (7) Condenser and condensate extraction pump: Steam from steam turbine is exhausted to the condenser where the steam is condensed by rejecting heat to circulated cooling water.The condensed steam is called the condensate which is drawn with the help of condensate extraction pump and supplied to hot-well.                                                                                       (8) Feed pump: The condensate collected in the hot well with make up water is fed back with the help of feed pump at boiler pressure to the economizer.                                                           (9) Cooling tower: Cooling water from cooling is circulated into the condenser and absorbs heat from the exhaust steam of the stem turbine. The resultant heated water from condenser is supplied at the top of cooling tower.                                                                                                (10) Condenser water circulating pump: This pump circulates the cooling water from the cooling tower to the condenser and the heated water from the condenser back to the cooling tower.