In the furnace, chemical energy of fuel is converted into the of combustion products as pulverised fuel is burned in suspension in the furnace space. Combustion products give up part of their heat by radiation to water walls. Thus they leave the furnace at a safe temperature, which will not cause clinkering of the subsequent convective heating surface. Factors important for combustion = 3 T : 1) TIME = Residence time of fuel 2) TEMPERATURE = Furnace gas temp. (Must be > fuel ignition temp.) 3) TURBULENCE 1) => Furnace volume is large enough to give the mix. time to complete combustion. (Height of boiler is governed by the residence time of fuel) . 2) => Fuel + air mixture maintained at > ignition temp. 3) => Adequate quantity of air supply to fuel, so that O2 + fuel are thoroughly mixed. Amount of excess air required is dependent on load. Furnace cross-section area & design must support full load gas flow rate at acceptable velocities. However,
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