Abstract:

A fluidized bed was partitioned internally into two compartments which are interconnected through a passage inside the bed.The particles, which represent a kind of solid feedstock, are fed into one of the compartments and flow out the bed from the other compartment, resulting in a U-shaped pathway of the particle flow.This kind of bed is thus called the U-shaped fluidized bed(UFB), and is suitable for conducting the decoupling gasification of biomass with high water contents.The fluid dynamics of the quartz sand fluidized by air in a laboratory cold UFB  were investigated via both experiment and the FLUENT modeling.The FLUENT modeling revealed that it was necessary to install a perforated plate into the compartment from which particles flow out for achieving the expected uniform distribution of gas entering this compartment from the other compartment.The cold model test results verified this point and demonstrated that the UFB required a range of fluidizing gas velocities for ensuring the normal operations of the UFB.The pressure balance between the two compartments of the bed was found to be the factor controlling the particle fluidization and gas distribution in the UFB.Analyzing the particle residence time in the UFB clarified further that the residence time distribution was very close to the predicted profile via the CSTR model.

摘要：

用内置隔板将流化床内反应空间分为左右两个反应室，并通过下部通道使两室连通，反应颗粒从一室连续供入、反应后颗粒从另一室连续排出，将在反应器结构和颗粒流动路径两方面均呈现“U”形特征的新型结构反应器称为U形流化床（UFB）。该反应器适合于高水分含量生物质的解耦气化。通过FLUENT模拟和二维冷态U形流化床实验相结合的方式，研究了U形流化床的流体动力学特性。结果表明：U形流化床左右两室的颗粒均能被充分流化，实现颗粒自一室向另一室的流动，且通过优化分隔板的结构及布置方式，使自一室流向另一室的气体可在流入反应室中较均匀分布。确立了实现上述流动特征的U形流化床的操作条件范围及其控制因素。颗粒停留时间的测试分析进一步阐明了颗粒经过U形流化床的停留时间分布特征及其与全混流模型的接近度。