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Simulation study on the effect of gas permeation on the hydrodynamic characteristics of membrane-assisted micro fluidized beds

机译：气体渗透对膜辅助微流化床水动力特性影响的模拟研究

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摘要

Recent research has shown the potential of membrane-assisted fluidized bed reactors for various applications, and for ultra-pure hydrogen production in particular. Due to the excellent mass transfer characteristics of fluidized beds, concentration polarization (i.e. mass transfer limitation) can be overcome and the production capacity of membrane-assisted fluidized bed reactors could be further improved by maximizing the installed membrane area per unit volume, leading to the concept of a micro-structured membrane-assisted fluidized bed reactor. In this study, numerical simulations have been systematically carried out with a discrete particle model to investigate in detail the effects of gas addition and extraction through the confining porous membrane walls on the hydro-dynamic characteristics of a single membrane-assisted micro fluidized bed compartment. In particular, the effect of the permeation ratio (amount of gas permeated through the membrane relative to the amount fed) and the installed membrane area on the hydrodynamics was investigated. Gas addition or extraction via the porous membrane walls confining the emulsion phase was simulated via inward or outward directed fluxes of the gas phase, which was found to have a very pronounced influence on the bed hydrodynamics. The effects of gas permeation on the solids circulation pattern, solids holdup distribution and porosity probability density function in membrane-assisted micro fluidized beds have been discussed in great detail. It has been found that gas permeation can have an adverse effect on the bed expansion caused by gas by-passing either through the bed center for the case of gas extraction or close to the membrane walls for the case of gas addition. In addition, the formation of densified zones (increased solids holdup) close to the membrane wall that was observed in case of gas extraction may increase the bed-to-membrane mass transfer resistance. These effects may strongly decrease the gas-solid contacting and the gas residence time, which may deteriorate the reactor performance. On the other hand, it is shown that these problems caused by gas permeation may be avoided by properly tuning the gas velocity through the membrane via membrane area and other design parameters and operating conditions.
机译：最近的研究表明膜辅助流化床反应器在各种应用中，特别是在超纯氢生产中的潜力。由于流化床优良的传质特性，可以克服浓度极化（即传质限制）的问题，并且通过使每单位体积的安装膜面积最大，可以进一步提高膜辅助流化床反应器的生产能力。结构的膜辅助流化床反应器的概念。在这项研究中，已经使用离散颗粒模型系统地进行了数值模拟，以详细研究气体通过限制多孔膜壁的添加和抽出对单个膜辅助微流化床隔室的水动力特性的影响。尤其是，研究了渗透率（透过膜的气体量相对于进料量）和膜的安装面积对流体力学的影响。通过限制气体相向内或向外的通量模拟了通过限制乳液相的多孔膜壁进行的气体添加或萃取，发现这对床层流体动力学有非常明显的影响。讨论了气体渗透对膜辅助微流化床中固体循环模式，固体固着率分布和孔隙率密度函数的影响。业已发现，气体的渗透可能对由气体绕过床中心引起的床膨胀产生不利影响，对于气体的提取，气体绕过床中心，而对于气体的添加，气体则绕过膜壁。此外，在抽气情况下观察到的靠近膜壁的致密区（增加的固体滞留量）的形成可能会增加床到膜的传质阻力。这些效果可能会大大降低气固接触和气体停留时间，这可能会使反应器性能下降。另一方面，显示出通过适当地调节经由膜面积和其他设计参数以及操作条件通过膜的气体速度可以避免由气体渗透引起的这些问题。

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  • 来源
    《Applied Mathematical Modelling》 |2014年第18期|4291-4307|共17页
  • 作者

    Lianghui Tan; Ivo Roghair; Martin van Sint Annaland;

  • 作者单位

    Chemical Process Intensification, Multiphase Reactors Group, Department of Chemical Engineering & Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands;

    Chemical Process Intensification, Multiphase Reactors Group, Department of Chemical Engineering & Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands;

    Chemical Process Intensification, Multiphase Reactors Group, Department of Chemical Engineering & Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    Membrane; Discrete particle model; Micro fluidized beds; Gas permeation; Gas by-passing;

    机译：膜;离散粒子模型;微流化床;气体渗透气体旁路;

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