Bed expansion and multi-bubble behavior of gas-liquid-solid micro-fluidized beds in sub-millimeter capillary
Bed expansion and multi-bubble behavior of gas-liquid-solid micro-fluidized beds in sub-millimeter capillary
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亚毫米毛细管气-液-固微流化床的床膨胀和多气泡行为
DOI：
10.1016/j.cej.2017.07.107
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发表时间：
2017
影响因子：
15.1
通讯作者：
Li Yanjun
中科院分区：
文献类型：
--
作者：
Li Xiangnan;Liu Mingyan;Li Yanjun
利用高速摄像系统对床层直径为0.8 mm、多气泡的气液固三相微流化床进行了流体力学研究。从多气泡流动中识别出分散气泡流动、聚合气泡流动和弹状流的流型。在较低固含率条件下，小床径比下的壁面效应导致气泡合并和流型转变。只有在较低的液体速度或较高的气速时，才会出现明显的床层收缩。微床内球形微气泡的直径范围为200~500nμm，分散气泡流中的气泡尺寸呈正态分布，并随着固含率的增加而略有增大。在聚结气泡流动中，气泡的大小由整体聚结概率决定，并呈特殊的阶跃分布。较大的聚结气泡集中了气泡末端速度的分布。气泡末端速度随固含率的增加而减小，与气泡大小成反比。在分散气泡流区，表观粘度与固含率呈线性正相关。三相微流化床是微反应器进一步发展的需要，对其流体力学特性的研究有助于其更广泛的应用。
Hydrodynamic study was performed on the gas-liquid-solid micro-fluidized beds with 0.8 mm bed diameter and multi-bubbles through high speed camera recording system. Flow regimes including dispersed bubble flow, coalesced bubble flow and slug flow were identified from the multi-bubble flow. Wall effect at the small bed-to-particle diameter ratio led to the occurrence of bubble coalescence and flow regime transition at lower solid holdups. Obvious bed contraction appeared only at lower liquid velocities or higher gas velocities. The diameter range of the spherical micro-bubbles in the micro-fluidized beds was 200–500 μm. The bubble size in dispersed bubble flow was normally distributed and slightly increased with the solid holdup. And in coalesced bubble flow, the bubble size was decided by the overall coalescence probability and presented a special step distribution. The larger coalesced bubbles concentrated the distribution of bubble terminal velocity. And the bubble terminal velocity decreased with the solid holdup and inversely with the bubble size. In dispersed bubble flow regime, there was positive linear relationship between the apparent viscosity and the solid holdup. Three-phase micro-fluidized beds meet the further development of micro-reactors, and this study on the hydrodynamic characteristics contributes to their wider application.