Catalytic gasification of woody biomass in an air-blown fluidized-bed reactor using Canadian limonite iron ore as the bed material

A Canadian limonite iron ore was tested for the first time as a catalytic bed material for air-blown gasification of pine sawdust at various equivalence ratios (ER, 0.20-0.35) on a pilot-scale fluidized bed gasifier, in comparison to a conventional olivine bed material. Effects of bed materials (iron ore and olivine) on tar formation and gasification efficiencies were comparatively investigated. The use of Canadian limonite iron ore as the bed material was found to be more active than olivine for tar reduction in the fluidized bed gasification of biomass at a small ER (≤0.3), leading to a very low tar yield of 15-25 g/kg biomass at ER = 0.30. The yields of combustible gas (carbon monoxide hydrogen, methane and C₂ hydrocarbon gases) and cold gas efficiency were generally the highest at medium values of ER (0.25-0.30) for both bed materials. The iron ore was less active than olivine for producing combustible gases, leading to a lower cold gas efficiency (50% at ER = 0.30) compared to 75% for olivine. However, the use of the iron ore produced a higher yield of hydrogen than that of olivine in the gasification: 5.0 mol hydrogen per kg of biomass with the iron ore at ER = 0.30 which was about 25% higher than that with olivine.