First Al2O3 based catalytic filter candles operating in the fluidized bed gasifier freeboard

Al2O3 based grain-sintered filter element support was first impregnated with a fine, wet-milled suspension of a MgO–Al2O3 and successively with nickel nitrate hexahydrate. The catalytic filter candle was inserted in the freeboard of a 0.1 m I.D. fluidized bed biomass gasifier, in order to obtain a very compact gasification and hot gas cleaning unit. Continuous catalytic steam gasification runs of almond shells have been performed in a temperature range of 808–813 °C (maintained by means of an electric furnace), and the volume composition of the product gas has been analyzed by means of IR, UV and TCD facilities for online detection of CO, CO2, CH4, H2, NH3 and H2S. A 20 h test has been performed with intermediate char burning steps. The measured gas yield was 2.09 Nm3/kgdaf, meanwhile the gas composition in % by volume was H2 = 56, CO = 22, CO2 = 20, and CH4 = 2. NH3 and H2S in the dry gas were 60–80 ppmv and 10–15 ppmv, respectively.