General Layout of Steam Power Plant

The general layout of a steam power plant, is shown in Figure. It consists of mainly the following four circuits

1. Coal and ash circuit
2. Air and gas circuit
3. Feed water and steam circuit
4. Cooling water circuit

Coal and ash circuit :

1. Coal received at the coal storage is supplied to the boiler furnace after necessary coal handling process through fuel feeding devices.
2. After combustion of coal, the ash is collected from the boiler furnace and it is removed to ash storage yard through ash handling equipment 

1. Air is drawn from atmosphere by the forced or induced draught fan.
2. This air is passed on to the boiler furnace after it is heated in the air preheater by the flue gases before these are discharged through the chimney.
3. High temperature flue gases formed in the combustion chamber are used for transferring heat to feed water and steam in boiler tubes and to steam in the superheater tubes.
4. These gases are then passed over the reheater section where its heat energy is utilised for reheating the steam drawn from high pressure (H.P.) turbine.
5. Then these flue gases carrying ash are passed through dust collector device in order to remove ash, and finally these are passed over the economiser and the air preheater.

Feed water and steam circuit :

1. Steam generated in the boiler tubes and superheated in the superheater tubes is fed to H.P.I.P and L.P turbine to develop mechanical power.
2. After expansion of steam in H.P turbine, a part of the steam is bled for feed water heating in H.P feed water heater and the remainder is passed through reheater for reheating the steam.
3. This steam now passes for further expansion in L.P. turbine.
4. After expansion, again a part of the steam is bled for feed water heating in L.P. feed water heater and the remainder of the steam expands in L.P. turbine.
5. The mechanical power developed by the turbines is supplied to the alternator where the mechanical energy is converted into electrical energy.

Cooling water circuit :

1. The quantity of cooling water required to be circulated in the condenser for condensing the steam of turbine exhaust is very large.
2. This water is usually taken from various sources such as river, lake or sea.
3. If sufficient quantity of water is not available, the heated water coming out of the condenser is cooled in cooling towers by evaporative cooling and it is re-circulated through the condenser.
4. The evaporated water is made up from external source of water supply.