19-12-2012, 06:54 PM
Thermal ( Steam ) Power plants
1Thermal.ppt (Size: 2.43 MB / Downloads: 72)
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
Fuels used in thermal power plant
Combustion of fuel is accomplished by mixing with air at elevated temperatures
Oxygen in the air chemically unites with Carbon, Hydrogen of fuels and produce heat
In thermal power plants normally steam is produced from water by using combustion heat of fuels (Except in Gas turbines)
Various fuels were used in thermal power plants
Fossil fuels ( Coal, Oil & Gas)
Industrial waste gases
Synthetic fuels or SYNFUELS
Lignite (Brown coal)
Intermediate stage of coal development
High amount of moisture 30-40%
Brown in color
High heating value and carbon compared to peat
Should be stored to avoid spontaneous combustion
Used in pulverized form
Can be air dried easily
Suitable for local use instead of transporting