Experimental study on combustion of oil palm shells in a conical fluidized-bed combustor using an alternative bed material

This paper reports an experimental study on burning of oil palm shells in a 200 kW_th fluidized-bed combustor with a cone-shaped bed (conical FBC). To prevent bed agglomeration, alumina sand was used as the bed material in this combustor. A fluidized bed was induced and sustained in a conical module of the reactor by a nineteen-bubble-cap air distributor. Prior to combustion tests, a thermogravimetric analysis was performed to examine thermal and combustion characteristics of the shells for four size groups of biomass particles. The TG/DTG curves exhibited substantial effects of biomass particle size on the fuel burnout temperature. In the combustion experiments, oil palm shells of each size group were burned at the fuel feed rate of 45 kg/h, while ranging excess air from 20% to 80%. The effects of biomass particle size and excess air on combustion and emission performance of the conical FBC were found to be sensible. An effective control of gaseous (CO, C_xH_y and NO) emissions as well as high combustion efficiency (~99%) can be achieved when firing oil palm of 3-6 mm particle sizes and maintaining excess air at about 40%. No evidence of bed agglomeration in the reactor was observed during the 30-h combustion tests.