STEAM POWER PLANTS

SELECTION OF SITE FOR STEAM POWER PLANT Availability of land Availability of sufficient amount of good boiler feed water and cooling water Availability of fuel. Necessity for future expansion. Availability of other power other power services Away from urban areas Initial cost of plant Magnitude and nature of load to be handled

LAY OUT OF STEAM POWER PLANT

GENRAL LAYOUT Fuel handling unit Ash handling unit Boiler unit Feed water unit Cooling water unit Generator unit Turbine unit

MAIN FLOW CIRCUITS Fuel and ash circuit Air and gas circuit Feed water and steam circuit Cooling water circuit

FUEL AND ASH CIRCUIT Fuel stored is fed to boiler through conveyer belt. Coal – particular size for complete burning. Coal is passed through crushers , sizers and magnetic separators before feeding to boiler. As a result of combustion, ash is produced from coal fuel which is removed from boiler through ash handling equipments.

AIR AND GAS CIRCUIT Air is required for complete combustion of the fuel – supplied through Forced draught(FD) and Induced draught(ID) fans. Air which is fed to the boiler, is passed through preheater – to extract energy of flue gases from boiler. Flue gas consist of several gases and ash – passed through precipitator and finally go to atmosphere via chimney .

FEED WATER AND STEAM CIRCUIT Most power plants are condensing type – steam is converted to water by condenser. For safety of turbine water is demineralized – better economic operation Adding make up water in feed water system compensate leakages. The boiler feed pump (BFP) feeds water to boiler drum – heated to form steam. Wet steam heated in super heater passed to turbine and runs it

FEED WATER AND STEAM CIRCUIT Stages of prime mover depending on size of power plant High Pressure Turbine HP Intermediate Pressure Turbine IP Low Pressure turbine LP

FEED WATER AND STEAM CIRCUIT

COOLING WATER CIRCUIT To condensate the steam in condenser and maintaining low pressure in it, large quantity of cooling water is required. After passing it through condenser, it is fed back to river or pondage. Cooling tower or cooling ponds are used in case of shortage. Drawback- Excessive water loss

PARTS OF STEAM POWER PLANT Boiler- Water tube boiler Coal Mills Boiler feed pump- high capacity IM Air preheater- extract heat from flue gases Draught system- supply air to the furnace and to take the flue gases from the boiler Economizers- extract heat from flue gases

PARTS OF STEAM POWER PLANT Superheaters and Reheaters Turbines Condenser Cooling tower Alternators- high speed synchronous generators

COOLING OF ALTERNATOR Important due to damage of insulation at high temperature. Closed circuit cooling widely used in modern alternators (Hydrogen as cooling medium).

ADVANTAGES OF HYDROGEN COOLING More heat transfer and thermal conductivity is 7 times more than air. Low ventilation losses Life of insulation is more as no oxidation of insulating material . Fire hazards minimized Less noise Size of frame reduced

DISADVANTAGES OF HYDROGEN COOLING Chances of formation of explosive mixture. Expensive than air Special oil seals required Problem of ensuring complete tightness of hydrogen