Combustion of Agricultural Wastes/Coal in Circulating Fluidized Bed

Abstract

This paper presents an experimental investigation on circulating fluidized bed (CFB) combustion of one of agricultural wastes (faba bean hulls) and co-combustion faba bean hulls and Egyptian (Sinai) coal. The test rig is a pilot scale CFB combustor of 145 mm inner diameter, 2 m tall and 100 kW thermal capacity. The influences of excess air, degree of air staging, bean hull particle size and coal share were studied. Temperature, heat flux, CO, NOx and SO2 concentrations along the reactor height and flue gas out from cyclone were measured. The combustion efficiency was calculated based on CO emission and unburned char in flue gas. The results showed that size reduction of bean hulls results in lower CO and NOx emissions. The induction of secondary air has a negative effect on combustion efficiency. The highest efficiency recorded for bean hulls combustion was 98.5% at excess air ratio (EA) =1.09 without secondary air. Co-combustion of Sinai coal and bean hulls reduced CO and NOx emissions but increased SO2 emissions. The results suggest that bean hulls are potential fuel that can be utilized for efficient and clean energy production by using CFB combustion system especially at co-combustion.