| Biomass is an important part of clean and renewable energy sources. Dual fluidized bed biomass/lignite co-gasification is an important technology that transforms low-quality biomass and lignite into hydrogen. At present, there are still some problems such as low carbon conversion and tar catalytic conversion efficiency during dual fluidized bed biomass gasification.This paper proposes a design scheme of multi-combined circulating fluidized bed. Because of a baffle which has two holes and uneven air distribution, it enables the high speed and low speed area of gasification chamber to achieve inner circulation. The inner circulation is coupled with the external circulation between the combustion chamber and gasification chamber. The design scheme extends steam gasification reaction time of carbon. It reduces the inhibitory effect of H2 and volatile on steam gasification of carbon. It reinforces carbon and volatile interaction promoting effect on tar catalytic gasification process. In this way, it improves the carbon conversion and tar catalytic cracking.In order to reveal the material circulation and pressure distribution in the gasifier, a multi-combined circulating fluidized bed cold test system is designed and built. The cold experiment focus on the effects of bed material quantity, lower fluidized velocity in the gasification chamber, ratio of higher and lower fluidized velocity in the two areas of gasification chamber on pressure distribution and the external circulating material flow rate. A 100 kWth multi-combined circulating fluidized bed thermal test system is designed. The effects of reaction conditions, gasification temperature, steam to fuel quality ratio, on synthesis gas components,especially hydrogen content,are based on the thermal simulation analysis.In this paper, the cold experiment and thermal simulation study laid the foundation of building the multi-combined circulating fluidized bed cold test system and industrialized application in the future. |
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