COMMERCIAL STEAM REFORMING CATALYSTS TO IMPROVE BIOMASS GASIFICATION WITH STEAM-OXYGEN MIXTURES .1. HOT GAS UPGRADING BY THE CATALYTIC REACTOR

Commercial steam reforming (nickel-based) catalysts are used for hot g as cleaning and upgrading in biomass gasification with steam-oxygen mi xtures. The gasifier used was an atmospheric and bubbling fluidized be d with an internal diameter of 15 cm and a total height of 3.2 m and w as continuously fed with 5-20 kg of biomass/h. Eight different catalys ts from four different manufacturers (BASF AG, TOPSOE A/S, ICI, and UC I) have been tested. They were located in a downflow fixed-bed reactor of 4 cm i.d. placed in a slip flow after the gasifier. A guard bed wi th a calcined dolomite was also used before the catalytic bed to decre ase the tar content in the raw gas below the limit of 2 g of tar/mg(n) (3), thus avoiding the catalyst deactivation by coke formation. The ma in variables studied were the temperature of the catalytic bed and the gas composition in the bed. Effects concerning tar elimination will b e reported in part 2 of this work. This paper is mainly devoted to cha racterization of catalysts and to upgrading of the flue gas. H-2 and C O contents increased by 4-14 and 1-8 vol %, dry basis, respectively. C O2, CH4, and steam contents decreased by 0-14, 87-99, and 2-6 vol %, d ry basis, respectively. Other parameters varied in the following ways: the lower heating value decreased by 0.3-1.7 MJ/m(n)(3), gas yield in creased by 0.1-0.4 m(n)(3)/kg of biomass daf, and apparent thermal eff iciency increased by 1-20%. The results presented allow screening of t he best catalysts to get an upgraded and useful gas in biomass gasific ation with steam-oxygen mixtures.