Steam-oxygen gasification of forest residues and bark followed by hot gas filtration and catalytic reforming of tars

Steam-oxygen gasification in a Circulating Fluidized-Bed (CFB) reactor has been developed for producing transportation fuels from different wood residues. This paper present the results from a two week test campaign, where crushed forest residues and industrial bark mixture was used as the feedstocks. The aim of the work was to carry out extended time testing of the developed gasification and hot gas cleaning process and to determine the fate of different gas contaminants and trace components of wood. In the test runs, wood fuels were gasified in CFB reactor at 2-2.5 bar(a) pressure using a mixture of steam and oxygen as the gasification agent. Mixture of sand and dolomite was used as the bed material in order to maintain stable fluidization and to catalyze in-situ tar decomposition before hot filtration. Raw gas was filtered at ca. 550 °C and led into a two stage catalytic tar reformer. The gasifier performance and the concentrations of different gas contaminants were determined for eight different operating variable set points during a total of 215 hours of operation. The results on carbon conversion efficiency, raw gas composition and the fate of fuel nitrogen, chlorine and trace metals will be presented. The concentrations of gas contaminants were determined after the ceramic filter unit and after the catalytic reformer.