It is necessary to reveal the influences of coal and/or coal combustor types on combustion characteristics for effective utilization of coal. Experiments were performed using different types of fluidized bed combustor, i. e., (A) single-bed without secondary air injection, (B) single-bed with secondary air, and (C) dual-bed. The combustible components in carryover ash and emission levels of carbon monoxide and nitrogen oxides were measured for four different coal types. The results show that these values are different in coal type and the combustion efficiency is relatively high using the coal of which the fuel ratio is low. The dual-bed combustor has the possibility of an increase in combustion efficiency. From combustion experiments of coal without fine size it is clear that the larger coal size, the higher combustion efficiency.
