The effect of bed material on emissions of N_2O and NO_x was evaluated using a bench-scale bubbling fluidized bed combustor. Two kinds of porous alumina were employed as alternative bed material instead of inert quartz sand. Both porous alumina particles suppressed N_2O emission. This result is explained by their catalytic activity to decompose N_2O. One of the porous alumina particles suppressed NO_x emission but the other increased NO_x emission. To clarify the mechanism of the increase or decrease in NO_x by the alternative bed materials, experiments on formation and reduction of NO_x were conducted by use of a fixed bed reactor; oxidation of volatile nitrogen compound (NH_3) and reduction of NO_x by the volatile matter catalyzed by the bed materials were investigated. The role of the present alternative bed materials to formation and reduction of NO_x is discussed.
