Cleaning and upgrading of the hot raw gas from a biomass gasifier, bubbling fluidized bed type, is studied at small pilot plant scale (10 kg biomass fed/h) using a calcined dolomite located downstream from the gasifier. Gasification is made with steam−oxygen mixtures at 800−850 °C and atmospheric pressure. Main variables studied are the gas residence time in the bed of dolomite and the gas atmosphere composition, which depends on the gasifying agent (H2O + O2)-to-biomass and H2O/O2 ratios. H2 and CO content in the flue gas increases by 16−23 vol % and decreases by 15−22 vol % (dry basis), respectively. Although CH4 conversion (elimination) higher than 30 vol % has never been reached, tar conversion (elimination) of 90−95 vol % are obtained with space times of 0.06−0.15 kg calcined dolomite h-1 m-3. A detailed study is here presented on how the calcined dolomite significantly cleans and upgrades the flue gas, increasing also the gas yield by 0.15−0.40 m3(STP)/kg daf biomass fed.

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