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Numerical simulation of counter-current flow field in the downcomer of a liquid-solid circulating fluidized bed

Particuology 2015年第4期13卷 48-54页

作者： Abbas Dadashi Chao Zhang Jingxu(Jesse)Zhu Department of Mechanical and Materials Engineering Western University Department of Chemical and Biochemical Engineering Western University

A comprehensive study on the hydrodynamics in the downcomer of a liquid-solid circulating fluidized bed （LSCFB） is crucial in the control and optimization of the extraction process using an ion exchange LSCFB. A computational fluid dynamics model is proposed in this study to simulate the counter-current two-phase flow in the downcomer of the LSCFB. The model is based on the Eulerian-Eulerian approach incorporating the kinetic theory of granular flow. The predicted results agree well with our earlier experimental data. Furthermore, it is shown that the bed expansion of the particles in the downcomer is directly affected by the superfcial liquid velocity in downcomer and solids circulation rate. The model also predicts the residence time of solid particles in the downcomer using a pulse technique. It is demonstrated that the increase in the superficial liquid velocity decreases the solids dispersion in the downcomer of the LSCFB,

关键词： Liquid-solid circulating fluidized bed Computational fluid dynamics downcomer Two-phase flow Ion-exchange system

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LIQUID BACKMIXING AND CIRCULATION IN RECTANGULAR downcomer

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Chinese Journal of Chemical Engineering 1997年第4期5卷 89-93页

作者：俞晓梅田军 Department of Chemical Engineering Zhejiang University of Technology

1 INTRODUCTIONdowncomers,employed in tray columns,are widely used nowadays in industrialseparation *** function as channels for the liquid phase to fall fluentlyfrom one tray onto its neighbouring places for the held-up bubble to separate fromthe liquid *** is well known that liquid flow patterns and mixing characteristicsin downcomers are closely related to the initial liquid distribution on the tray,andhence to tray *** a long period of time,little attention has been paid

关键词： rectangular downcomer backmixing circulation square deviation

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Rigorous design and economic optimization of reactive distillation column considering real liquid hold-up and hydraulic conditions of industrial device

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CHINESE JOURNAL OF CHEMICAL ENGINEERING 2024年第12期76卷 211-226页

作者： Du, Yuchang Luo, Yiqing Yang, Peilin Jia, Shengkun Yuan, Xigang Tianjin Univ Chem Engn Res Ctr Tianjin 300354 Peoples R China Tianjin Univ Sch Chem Engn & Technol Tianjin 300354 Peoples R China Tianjin Univ State Key Lab Chem Engn Tianjin 300354 Peoples R China

The liquid hold-up in a reactive distillation (RD) column not only has a significant impact on the extent of reactions, but also affects the pressure drop and hydraulic conditions in the column. Therefore, the liquid hold-up would be a critical design factor for RD columns. However, the existing design methods for RD columns typically neglect the influence of considerable amount of liquid hold-up in downcomers owing to the difficulties of solving a large-scale nonlinear model system by considering downcomer hydraulics, resulting in significant deviations from actual situation and even operation infeasibility of the designed column. In this paper, a pseudo-transient (PT) RD model based on equilibrium model considering tray hydraulics was established for rigorous simulation and optimization of RD plate columns considering the liquid hold-up both in downcomers and column trays, and a steady-state optimization algorithm assisted by the PT model was adopted to robustly solve the optimization problem. The optimization results of either ethylene glycol RD or methyl acetate RD demonstrated that assuming all the liquid hold-up of a stage belonged to the tray will cause significant deviations in the column diameter, weir height, and the number of stages, which leads to not meeting the separation requirements and even operation hydraulic infeasibility. The rigorous model proposed in this study which considers the liquid hold-up both on trays and in downcomers as well as hydraulic constraints can be applied to systematically design industrial RD plate columns to simultaneously obtain optimal operating variables and equipment structure variables. (c) 2024 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

关键词： Reactive distillation Liquid hold-up downcomer Tray hydraulics Pseudo-transient modeling method

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