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, 0.20-0.40) on tar formation and gasification efficiencies were investigated using pinewood sawdust and crushed peat pellets on a pilot-scale air-blown fluidized bed gasifier. As expected, increasing ER generally led to decreased tar yields. Combustible gas (methane, hydrogen, and carbon monoxide) yields were generally the highest at a medium ER value (0.25-0.30). The yields of tar and combustible gas were much lower in the gasification of crushed peat, compared with those for the pinewood sawdust under similar conditions. Calcined limestone exhibited the highest 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 tar reduction, though dolomite and iron oxide appeared to be more active than olivine, and dolomite and limestone produced larger yields of H2 in the gasification. Olivine showed the best attrition-resistance and thermal stability and it was more effective than the other bed materials for the formation of CO. The gasification of pinewood sawdust with olivine attained a very high cold gas efficiency of 74.8% at ER of 0.30.