FUELS USED FOR POWER GENERATION

Classification of fuels:-

Fuels may be classified as Solid,Liquid and Gaseous and as natural or prepared.The various fuels commonly used for combustion in the Thermal Power Plants are coal,Oil and Gas.Gaseous fuel is rarely economical except when the Power Plant is located near natural gas field or Gas manufacturing industries.Oil is used only where it is plentiful and cheap.Coal is the most commonly used fuel in Thermal Power Plant.

               The coals can be classified in increasing order of heat value,namely peat,lignite,sub-bituminous,bituminous,semi-bituminous,semi-anthracite,anthracite and super anthracite coals.

Coal Mine

                        Peat is the first stage in the process of transformation of buried vegetarian into coal.Its enthalpy of combustion is about 700 kcal/kg.Owing to high moisture content,peat is not suitable for power plants.Lignite is the next stage in the development of coal.Its enthalpy of combustion is 3,300-4,200 kcal/kg.Lignite can be used for Power Generation but only locally owing to difficulties encountered in its transportation.Sub-bituminous coal is also called the black LIGNITE and has enthalpy of combustion of 4,500-5,500 kcal/kg.Bituminous coal may be classified as caking or coking and free burning.Its enthalpy of combustion is 6,500-8,500 kcal/kg.Semi-anthracite coals are harder than the bituminous coals,found in small quantities and harder than the bituminous coal,found in small quantities and are,therefore,costlier for Power Generation

                        Anthracite coals have the highest carbon content but do not have the highest heating value.Because of its high cost and scarcity,it is used mainly for domestic purpose.Super-anthracite coals are very hard with a shiny black surface.It is non-coking and is very difficult to ignite and so has little importance in the Power Generation.