STEAM GASIFICATION OF CELLULOSIC WASTES IN A FLUIDIZED-BED WITH DOWNSTREAM VESSELS

In order to further use catalysts in a two- and three-stage process, advanced steam gasification of cellulosic wastes in a fluidized bed has been studied with and without a downstream high-temperature metallic filter and with and without a secondary vessel operating both empty and as a fluidized bed of calcined silica sand. Product distribution (gas, tar, char yields) and gas composition (H2, CO, CO2, CH4, C2) are given for all the operational variables studied: gasification temperatures, superficial velocity of the gas at the gasifier inlet, residence time (space-time) of the gas in the gasifier, gasifier bed height, temperature of the filter chamber, state and temperature of the secondary vessel (empty and with a bed of sand), space-time and height of the second bed, size of the sand, and time on stream. The hot filter chamber, the silica sand in the second bed, and the carbonaceous solids formed are not inerts but they crack the produced tars, modifying the product distribution from the gasifier exit.