Functions of Chimney, Superheaters and Components in Steam generating unit in Thermal Power Point

Functions of Chimney, Superheaters and Components in Steam generating unit in Thermal Power Point

Chimney : A chimney is a structure for venting hot flue gases or smoke from a boiler, stove, furnace or fireplace to the outside atmosphere.

Superheater : A superheater is a device which removes the last traces of moisture from the steam which is saturated and on its way to furnace by leaving the boiler tubes and it also increases its temperature above the saturation temperature.

Percentage of heat losses
at different stages in a thermal power plant is as follows :

Stages	% Heat Losses
To dry flue gasses	5%
To moisture in gases	5% in boiler
To ash and unburnt carbon	1%
To radiation and leakage	2.5%
Unknown losses	2.5%
Heat rejected to the condenser	54%
Alternator losses	1%
	Total 71%

Steam generating unit (Boiler) is a closed vessel in which steam is produced from water by combustion of fuel.

Functions of boiler mountings :

1. Water level indicator : This is required to indicate the safety level of water inside the boiler shell.
2. Pressure gauge : This is required to indicate the steam pressure Inside the boiler shell.
3. Steam stop valve : The value used to regulate the supply of steam to the turbine.
4. Fusible plug : This is required to stop the boiler if the boiler gets dry to prevent damage to the boiler.
5. Safety valves : These are required to release the Internal boiler pressure if the pressure exceeds a predetermined safety level.

Functions of boiler accessories :

1. Air preheater : This is usually used to utilize the waste heat of the chimney to preheat the furnace air thus increasing the boiler efficiency.
2. Economizer : This is usually used to utilize the waste heat of the chimney to preheat the boiler feed water thus increasing the boiler efficiency.
3. Superheater : This is usually used to utilize the waste heat to dry and/ or superheat the steam leaving the boiler on the delivery side, thus increasing the steam quality and boiler efficiency.
4. Baffles : These are built Inside the boiler. These baffles significantly increase the efficiency by helping feed water in extracting heat from the flue gas.