Catalytic gasification of biomass and coal blend with Fe2O3/olivine in a decoupled triple bed

Abstract

Steam co-gasification of pine sawdust and bituminous coal blend was performed in a pyrolysis-reforming-combustion decoupled triple bed gasification (DTBG) system with Fe2O3/olivine as both solid heat carrier and in-situ tar cracking/reforming catalyst. The effects of reformer temperature (RT) and circulation rate (CR) of catalyst on gasification performance were investigated. Besides, X-ray diffraction (XRD) and temperature programmed reduction (TPR) are employed to reveal the properties of Fe2O3/olivine catalyst during the continuous redox cycle between those decoupled reactors. The results indicated that, the configuration of the DTBG system favor tar cracking/reforming reaction to enhance H2 yield. Higher RT promotes the gas yield, H2 content in product gas, carbon conversion and cold gas efficiency of the process. Specifically, a gas yield of 0.66 Nm3/kg, tar content as low as 4.87 g/Nm3 with the H2 content of 42.2 vol% has been obtained at the RT of 850 °C. Lower CR of catalyst leads further reduction of Fe2O3 that allows increment on the gas yield and H2 content. The H2 content reduced from 44.5 vol% to 40.8 vol% and CO2 increased from 37.3 vol% to 41.4 vol% with increasing catalyst CR from 1.9 kg/h to 4.5 kg/h. Reduction level of Fe2O3/olivine increased with decreasing catalyst CR. Fe2O3/olivine not only has catalytic effect on tar cracking/reforming but also acts as an oxygen carrier transports oxygen from the combustor to the reformer.