Chemical looping gasification and hydrogen (CLGH) process from solid biomass in a dual fluidized-bed system

摘要

Chemical looping gasification (CLG) process is one of CO2 capture technologies for producing syngas with high system conversion efficiency and inherent separation of CO2. Chemical looping hydrogen (CLH) process with renewable energy sources is the other promising technology for producing H2 and decreasing emission of greenhouse gas. Chemical looping gasification and hydrogen (CLGH) process from solid biomass is a promotion of the existing steam-iron process by combining CLG process and CLH process in one step. This process in a dual fluidized-bed system can not only avoid highly concentrated CO2 gas but also generate hydrogen with no direct efficiency loss. Meanwhile, the system offers two separate fluidized-bed reactors for biomass gasification and H2 production. Iron-based oxygen carrier is used as bed material in the two fluidized beds to provide with lattice oxygen for gasification in the fuel reactor (FR) and to create a reduced environment for H2 production in the steam reactor (SR). In this study, the experiment for CLGH process of pine sawdust was conducted in a dual fluidized-bed system, aiming to a suitable H2/CO-ratio syngas and the best H2 yield for the whole system. The effects of FR temperature, SR temperature, steam preheating temperature and steam-to-biomass ratio (S/B) on the process were investigated. The optimum operating conditions concluded in the experiment were: FR temperature at 820 °C, SR temperature at 910 °C, steam preheating temperature at 500 °C and S/B at 1.5 kg kg-1. At this condition, the cold gas efficiency of 77.21 % and H2 yield in the SR of 0.279 Nm3 kg-1 were obtained. And the results enhance understanding of CLGH process and facilitate commercial utilization of solid biomass.