for the generation of steam. Ash produced due to combustion of coal is removed to ash storage through ash-handling system.
Air and Gas Circuit:
Air is supplied to the combustion chamber of the boiler either through forced draught or induced draught fan or by using both. The dust from the air is removed before supplying to the combustion chamber. The exhaust gases carrying sufficient quantity of heat and ash are passed through the air-heater where the exhaust heat of the gases is given to the air and then it is passed through the dust collectors where most of the dust is removed before exhausting the gases to the atmosphere.
Feed Water and Steam Circuit: The steam generated in the boiler is fed to the steam prime mover to develop the power. The steam coming out of the prime mover is condensed in the condenser and then fed to the boiler with the help of pump. The condensate is heated in the feed-heaters using the steam tapped from different points of the turbine. The feed heaters may be of mixed type or indirect heating type. Some of the steam and water are lost passing through different components of the system, therefore, feed water is supplied from external source to compensate this loss. The feed water supplied from external source to compensate the loss. The feed water supplied from external source is passed through the purifying plant to reduce to reduce dissolve salts to an acceptable level. This purification is necessary to avoid the scaling of the boiler tubes.
Cooling Water Circuit: The quantity of cooling water required to condense the steam is considerably high and it is taken from a lake, river or sea. At the Columbia thermal power plant it is taken from an artificial lake created near the plant. The water is pumped in by means of pumps and the hot water after condensing the steam is cooled before sending back into the pond by means of cooling towers. This is done when there is not adequate natural water available close to the power plant. This is a closed system where the water goes to the pond and is re circulated back into the power plant. Generally open systems like rivers are more economical than closed systems. | 
