(270g) Integrated Exergy Recuperative Biomass Gasification and SOFC System for Hydrogen and Power Coproduction

Integrated Gasification Fuel Cell (IGFC) power generation system is being developed as high-efficiency power generation technology. However, the highest theoretical gross thermal efficiency of conventional IGFC is still below 52% because of large exergy destruction mainly due to partial oxidation gasification, air cooling of SOFC stacks, and the combustion in a gas turbine combustor. In order to obtain higher power generation efficiency, a novel hydrogen and power coproduction system based on the exergy recuperative biomass gasification integrated with solid oxide fuel cell was proposed. In the proposed system the exothermic heat from micro-tubular SOFC stacks immersed in the fluidized bed gasifier at a temperature range close to the SOFC operating temperature is recuperated and utilized for the endothermic heat of biomass gasification, preventing the exergy destruction due to the partial oxidation in gasifier and heat transfer for cooling SOFC. In addition, providing the recirculation system of unreacted hydrogen separated from SOFC anode exhaust, gas turbine can be eliminated. Since the exergy loss of SOFC is much smaller than that of gas turbine, the net power generation efficiency of the combination of gasification and SOFC power generation system can be considerably improved. Corresponding to this system, a novel triple-bed combined internal circulating fluidized bed gasifier, composed of a moving bed high-temperature pyrolyzer with the function of tar cracking, a bubbling bed char gasifier equipped with micro-tubular SOFC stacks, and a fluidized bed combustor of remained char, was proposed for 40kW class pilot plant. In the present study, the conceptual design of a integrated exergy recuperative biomass gasification and SOFC system for hydrogen and power coproduction by using a triple-bed combined internal circulated fluidized bed as a gsifier is described.