Investigations on biomass gasification of compact-fast dual fluidized bed calcium looping

Abstract

In this study, a 10 kWth hot rig of dual fluidized bed is developed to investigate the performance of the calcium looping process for biomass hydrogen-rich gasification and carbon dioxide capture. The system consists of a compact fluidized bed and a fast fluidized bed riser. The compact fluidized bed, which is comprised of a lower bubbling fluidized bed and an upper riser, is used as the gasifier, and the fast fluidized bed riser is used as the regenerator. The solid from the regenerator goes upward from the bottom of the upper riser gasifier, and then downward to the lower bubble fluidized bed gasifier, bringing heat from the generator to the gasifier, and is finally circulated to the regenerator form the bottom of the bubble fluidized bed, taking carbon dioxide from the gasifier to the regenerator. Dolomite and quartz sand are used as bed materials. The effects of variables such as temperature, bed material, and solid circulating flux on product gas compositions, yield, calorific value, tar content, and cold gas efficiency were investigated. The dolomite bed material has a more obvious improvement in hydrogen production as compared with quartz sand as bed material. The maximum H2 production is 0.46 Nm3/kgFuel, the purity reaches 70.88%, the cold gas efficiency is 45.93%, and the low calorific value is 13.26 MJ/Nm3. The high temperature of the upper riser favors tar conversion. When the riser temperature was 800 °C, the tar content decreased by 4.46 g/Nm3, and the total gas production increased by 0.03 Nm3/kgFuel. In addition, the increase of solid circulating flux can improve the concentration and the yield of hydrogen, and decrease the content of tar.