Sub-Pilot Chemical Looping Biomass Gasification System Enabled By a Circulating Fluidized Bed Platform Characterized By a Moving Bed Reducer - Fluidized Bed Combustor Operating Scheme

Biomass is considered a renewable and less environmentally deleterious resource relative to traditional fossil fuels. Gasifying biomass to syngas, a precursor of many industrial products, via chemical looping process enabled by a circulating fluidized bed platform with connected reactors, is an economically attractive and practically feasible technology. The high quality syngas is generated in a co-current moving bed reducer with stoichiometrically limited amount of oxygen from iron-based oxygen carrier particles. The reduced oxygen carrier particles is then be regenerated in a fluidized bed combustor. A key for the viable, continuous operation of such a system is to strategically integrate a moving bed reducer to a fluidized bed combustor in a circulating fluidized bed configuration with controlled solids circulation between them. This work presents the design, construction and operation of a sub-pilot scale circulation fluidized bed system for biomass-to-syngas chemical looping process. An L-Valve is used to control the overall solids circulation of the system. A riser is used to transport the regenerated particles from the fluidized bed combustor to the moving bed reducer, thus establish an integrated loop. The system has been demonstrated continuously with smooth and stable temperature and pressure drop profiles of the system under different operational conditions. Three types of biomass, namely pelletized corn cob, woody pellets, and unpelletized loose corn cob, are used with a high quality of syngas generated at an H₂/CO ratio of ~2 and a high biomass conversion achieved. Adjustable H₂/CO ratios in the syngas by co-injecting steam with biomass are also achieved.