Catalytic gasification of pinewood sawdust and peat in a pilot-scale air-blown fluidized bed gasifier

Effects of bed materials (olivine, limestone, dolomite, and a crushed iron ore) and equivalence ratios (ER, 0.20-0.35) on tar formation and gasification efficiencies were investigated on a pilot-scale air-blown fluidized bed gasifier using pine sawdust and crushed peat pellets. As expected, increasing the equivalence ratio generally led to decreased tar yield. Combustible gas (methane, hydrogen, and carbon monoxide) yields were generally highest at medium ER values (0.25-0.30). Tar and combustible gas yields were lower for crushed peat when compared with those for pine sawdust for all ER values under similar conditions. Calcined limestone exhibited the best catalytic activity for tar reduction at all ERs tested, leading to a very low tar yield of 3.5-8.3 g/kg biomass. Other bed materials were similar to each other in terms of activities for tar reduction, though dolomite and iron oxide appeared to be slightly more active than olivine. While dolomite and limestone produced the highest yields of H₂, olivine led to a higher CO formation. The gasification of pine sawdust with olivine attained the maximum cold gas efficiency (75%) at ER = 0.30.