Some aspects of fluidized bed combustion of paddy husk

Some agricultural wastes--for example, bagasse, paddy husk, etc.--are frequently used as fuels, paddy husk appearing, in particular, to be quite suitable for fluidized bed combustion. The conventional method of combustion of paddy husk in grate-type furnaces is slow and inefficient. This paper reports certain aspects of the fluidized bed combustion of paddy husk. Fluidized bed combustion was carried out by feeding husk in a bed of sand particles. The unexpanded bed height was 10 cm and the size of the sand particles, 351-420 [mu]m. The superficial velocity of the ambient fluidization air through the bed ranged from 11·1 to 22·2 m/min. A combustion intensity of about 530 kg/h/m2 of distributor area could be achieved. This is about 7·5 times higher than the maximum combustion intensity possible in a grate-type furnace per unit grate area. The efficiency of combustion, which ranged from 81 to 98 per cent was found to increase with the air flow rate. There was significant carry-over of inert sand particles from the bed under conditions of high air flow rate. Combustion intensity increased as the bed height rose from 10 cm to 15 cm, but increased sand entrainment also occurred.