Experimental Study On Coal Gasification Process In Dual Circulating Fluidized Beds

Low rank coal pyrolysis and gasification is a hotspot in the research field of clean coal technology. The advanced coal gasification technology can not only reduce the air pollution caused by combustion emissions, but also improve the utilization ratio.The lignite has high reactivity and high content of volatile matter. According to this characteristic, this paper proposed a novel dual-fluidized bed coal gasification process; which combines the gasification technology in circulating fluidized bed with pyrolysis technology in moving bed. The pressure balance between the gasifier, pyrolysis furnace and loop seal is investigated in the cold experimental device. The characteristics of material circulation are also introduced. The model and calculation method of pressure balance between gasifier and pyrolysis furnace are established.The experiments of high temperature pyrolysis and gasification of Shenmu bituminous coal were conducted in0.25t/d dual fluidized bed device. The results show that the gasification process in dual fluidized bed is a potential technology. The heat balance and mass balance are analyzed as well.Shigouyi lignite was pyrolyzed and then gasified in the hot-state test rig of2.5t/d dual fluidized bed in order to investigate the operation characteristics, and coal gasification characteristics and product distribution. The results reveal that the production rate of mixed gas is1.71m3/kg with the low heat value of about4.09MJ/m3, and that of pyrolysis gas is0.17m3/kg with the low heat value of about12~14MJ/m3. The cold gas efficient is40.28%and carbon conversion rate is72.8%. Compared with the gasification process in single bed, at the condition of the same temperature, the process in dual fluidized bed can effectively improve gasification intensity and productivity, and the low heat value of mixed gas is higher than that of gasification process in single bed. The calculation results indicate that for the gasification process in duel circulating fluidized beds, the predictive cold gas efficient is54.19%and carbon conversion rate is91.98%.According to the results above, a5t/d dual fluidized bed gasification pilot plant has been designed. The design principle and method are introduced, and the heat balance and mass balance are also analyzed.