16-10-2012, 01:57 PM
Thermal ( Steam ) Power plants mainly consists of 4 circuits
coalhandling.ppt (Size: 2.45 MB / Downloads: 44)
Coal and ash Circuit
Coal produced in the mining site is transported to power plant site
Coal handling equipment for generation of steam
The combustion of coal produces ash which is collected and removed to ash storage yard through ash handling equipments
Air and gas circuit
FD or ID fans are used for supply the air to combustion chamber of the boiler through air-preheater
The air preheater is placed in the path of flue gases to preheat the air
The flue gases produced by combustion of fuels in the boiler furnaces after passing around boiler tubes and super heater tubes
Pass through a dust collector or precipitator where most of dust is removed before venting it of to atmosphere through chimney
Feed water and steam circuit:
Prime mover develops power by utilizing steam generated in the boiler
Then condenser is used to condense the steam coming out of prime mover
A pump is used to feed the condensate to the boiler
The condensate leaving the condenser is heated in feed heaters through extracted steam from lowest pressure extraction point of the turbine
The feed water may also be supplied from external source to compensate any loss of steam and water.
In the boiler shell and tubes water circulation is setup due to density difference of water between low and high temperature sections
A super heater is used to super heat the wet steam from boiler drum and is then supplied to prime movers
Cooling water circuit
In the condenser, quantity of cooling water required to condense the steam is large and is taken either from lake, river or sea
The cooling water is taken from upper side of the river and then passed through the condenser
The hot water is then discharged to lower side of the river
The system is known as open system
Where water is not available in abundant water from condenser is cooled either in cooling pond or in cooling tower the system is known as closed system
Coal
Coal is the principal energy source for India because of its large deposits and availability
Coal originated from vegetable matter, which grew millions of years ago
Trees and plants falling into water decayed and later produced peat bogs
Huge geological upheavals buried these bogs under layers of silt
Subterranean heat, soil pressure and movement of earth's crust distilled off some of the bog's moisture and hardened it to form coal
Basically classification of coal is based on Physical and chemical composition
Peat
Lignite and brown coal
Bituminous coal
Anthracite