| Summary: | 碩士 === 國立成功大學 === 航空太空工程學系 === 107 === The dual fluidized bed gasifier used in this work is designed using the FICFB (Fast Internal Circulating Fluidized Bed) concept. It is separated into two parts: the gasification zone and the combustion zone. Two zones are linked together as a circulation loop by flowing solid particles, where the heat produced in the combustion zone can be transferred to the gasification zone, supplying the energy that biomass needs to gasify. In the loop seals, steam is injected for the purpose of fluidizing the solid particles and separating the gases produced from combustion and the gasification reaction. In this way, the syngas in the gasification zone is free of nitrogen. In the present study, an analytical technology used for the simulation of a dual fluidized bed gasifier was developed for the multi-phase reaction of biomass fuel using the commercial CFD software, FLUENT. In this study, a fluid dynamic analysis was conducted for the dual fluidized bed, where the stability, temperature, flow, etc. were analyzed. we focus on the temperature changing, the heat cycle of the combustion zone after the ignition, and the gasification of the gasifier after the biomass fuels are introduced into the gasifier zone. Thus, by adjusting the particle circulation rate and biomass load to observe their influence on gasification efficiency, it can be confirmed that the particle circulation rate and the load have a positive influence on gasification efficiency. A scale-up analysis is also carried out to determine the effect of size on the flow and gasification performance. Even after the bed is scaled-up, the dual-fluidized bed gasifier can still simulate and analyze successfully. Compare to the reference condition case, the reaction zone of the whole gasifier is reduced, the composition of the produced gas is similar, and the efficiency of the cold gas fluctuated.
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