The purpose of this study was to investigate the effect of bed height on the quality of rice husk ash in a 210–mm diameter pilot scale fluidised bed combustor. The degree of rice husk burning in the fluidised bed could be deduced from the temperature of the combustor and the particle size of the resulting ash. The turbulence in the bed would break down the char skeleton of the rice husk into finer size. From this study, the bed height of 0.5 Dc was found to give the lowest residual carbon content in the ash (1.9%) and the highest bed temperature (670°C). Moreover, the problem of contamination of amorphous rice husk ash with sand increased as the bed height was increased. Nevertheless, the results from the current study need to be validated in larger–scale fluidised beds to determine whether the bed height of 0.5 Dc is still applicable.
Keywords: fluidised bed combustors, combustion, bed height, temperature, ash quality, residual carbon, XRD, rice husk ash, turbulence, ash contamination