Cao Enhong, Radhakrishnan Anand N P, Hasanudin Redza Bin, Gavriilidis Asterios
Department of Chemical Engineering, University College London, London WC1E 7JE United Kingdom.
Ind Eng Chem Res. 2021 Jul 28;60(29):10489-10501. doi: 10.1021/acs.iecr.1c00089. Epub 2021 May 24.
The volumetric liquid-solid (L-S) mass transfer coefficient under gas-liquid (G-L) two-phase flow in a silicon-chip-based micropacked bed reactor (MPBR) was studied using the copper dissolution method and was related to the reactor hydrodynamic behavior. Using a high-speed camera and a robust computational image analysis method that selectively analyzed the bed voidage around the copper particles, the observed hydrodynamics were directly related to the L-S mass transfer rates in the MPBR. This hydrodynamic study revealed different pulsing structures inside the packed copper bed depending on the flow patterns established preceding the packed bed upon increasing gas velocity. A "liquid-dominated slug" flow regime was associated with an upstream slug flow feed. A "sparse slug" flow regime developed with an upstream slug-annular flow feed. At higher gas velocity, a "gas continuous with pulsing" regime developed with an annular flow feed, which had similar features to the pulsing flow in macroscale packed beds, but it was sensitive and easily destabilized by disturbances from upstream or downstream pressure fluctuations. The volumetric L-S mass transfer coefficient decreased with increasing gas velocity under the liquid-dominated slug flow regime and became rather less affected under the sparse slug flow regime. By resolving the transition from the liquid-dominated slug flow to the sparse slug flow and capturing the onset of the gas-continuous with pulsing regime, we gained new insights into the hydrodynamic effects of G-L flows on the L-S mass transfer rates in a MPBR.
采用铜溶解法研究了基于硅芯片的微填充床反应器（MPBR）中气液（G-L）两相流条件下的体积液固（L-S）传质系数，并将其与反应器的流体动力学行为相关联。使用高速摄像机和一种强大的计算图像分析方法，该方法选择性地分析铜颗粒周围的床层空隙率，观察到的流体动力学与MPBR中的L-S传质速率直接相关。这项流体动力学研究揭示了在填充铜床内部存在不同的脉冲结构，这取决于在增加气体流速时填充床之前建立的流动模式。“液体主导的弹状流”流型与上游弹状流进料相关。“稀疏弹状流”流型是由上游弹状-环状流进料发展而来的。在较高气体流速下，“脉冲气连续流”流型由环状流进料发展而来，它具有与宏观填充床中的脉冲流相似的特征，但对上游或下游压力波动引起的干扰敏感且容易失稳。在液体主导的弹状流流型下，体积L-S传质系数随气体流速的增加而降低，而在稀疏弹状流流型下受影响较小。通过解析从液体主导的弹状流到稀疏弹状流的转变，并捕捉脉冲气连续流流型的起始点，我们对G-L流对MPBR中L-S传质速率的流体动力学效应有了新的认识。
