Standpipes, or downcomers, are commonly used in fluidized beds to transport particles. The outlet structure of the downcomer greatly affects the performance of flow from it and even overall reactor performance. In this study, the hydrodynamics in commercial-scale internally circulating fluidized beds (ICFBs) with central downcomers having different outlet structures was investigated using computational fluid dynamics simulations with an energy minimization multi-scale drag model. The predicted results closely agreed with experimental data. Results showed that in an ICFB with a downcomer outlet directly open to the bed (model A), nearly 12.7% to 5.4% of the gas in the draft tube bypasses into the downcomer. In the ICFB models B and C with a conic baffle below the downcomer, the gas bypass is significantly weakened or even eliminated when the diameter of the conic baffle is 1.1 times that of the downcomer (model C). In addition, the solids circulation mass flux in ICFBs increased by about 62.5%, from 126.8 kg/(m² s) in model A to 206 kg/(m² s) in model C.

竖管或降液管通常用于流化床中以输送颗粒。降液管的出口结构极大地影响了降液管的流动性能，甚至影响了反应器的整体性能。在这项研究中，使用带有能量最小化多尺度阻力模型的计算流体动力学模拟研究了具有不同出口结构的中央降液管的商业规模内部循环流化床（ICFB）的流体动力学。预测结果与实验数据非常吻合。结果表明，在具有直接向床敞开的降液管出口的ICFB中（A型），引流管中将近12.7％至5.4％的气体旁路进入降液管。在ICFB模型B和C中，降液管下方有一个锥形挡板，当圆锥形挡板的直径是降液管直径（C型）的1.1倍时，气体旁路会被显着削弱甚至消除。此外，ICFBs中的固体循环质量通量从126.8 kg /（m^2个 S）在模型中的至206千克/（米^2个 在模型C. S）