Hydrogen from the residue of biorefining via gasification and water gas shift reaction

The biorefineries exploit carbohydrates and leave solid residues containing most of the initial lignin and unconverted fiber. Most of this solid is used to fulfill the energy demand of the process; the excess can be sold as fuel, or converted on site to power and energy carriers, like hydrogen. In this work we used the residue for the production of H₂ rich syngas by using steam gasification and water gas shift (WGS) reaction. The used facility treated 20-30 kg/h and was composed of an updraft gasifier, a cleaning section based on a biodiesel scrubber and an upgrading section in which a Pt on Ce_xO_y   catalyst was used. The gasification media were: 1) air;  2) air and steam at 150°C; 3) O₂ ; 4) O₂ and steam at 150°C. The gasification at this scale was carried out without significant problems. The addition of steam increased the H₂ content in the cleaned syngas from 11% to 22% in the case of air gasification and from 25% to 41% in the case of O₂ gasification. The correspondent LHV of the syngas ranged from 5 to 11 MJ/Nm³. Concentration of H₂ as high as 50% were reached after the WGS. The efficiency of energy conversion from solid to cold gas was 74% and 80%, including the contribution of the condensable organic fraction using a steam/air mix and a O₂/steam mix as a gasification medium. Energy efficiencies, mass balances and gas quality obtained at different equivalence and steam to biomass ratios were assessed.