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Flow structure in a liquid-solids circulating fluidized bed.

机译：液固循环流化床中的流动结构。

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摘要

Flow behavior was systematically studied in a liquid-solids circulating fluidized bed of 76 mm I.D. and 3 m in height with three different types of particles. The axial and radial distribution of local solids holdup was obtained using a fiber optic probe and the radial distribution of liquid velocity at the axial position of 0.8 m from the main liquid distributor were measured by a dual conductivity probe. The results show that the solids holdup distributes fairly uniformly along the riser for relatively light particles but a dense-bottom-dilute-top axial flow structure exists in the heavy steel particle system under relatively low liquid flowrates. Radial nonuniformity in both solids holdup and liquid velocity was identified in the circulating fluidization regime, with low solids concentration/high liquid velocity in the center region and high solids concentration/low liquid velocity in the wall region. The radial profile becomes steeper with increasing solids circulation rate. The radial nonuniform distribution was also studied through the analysis microflow structure, which further confirmed the results obtained in the macroflow study. The transition criteria from the conventional fluidization regime to the circulating fluidization regime has also been properly defined. In addition, a pressure balance analysis has been carried out to predict the stable operating conditions and explain the origin of the unstable operation phenomena of the liquid-solids circulating fluidized bed. The stable operating window is proved to be significantly affected by the particle properties, the solids inventory and the unit geometry.
机译：在76mm I.D.的液-固循环流化床中系统地研究了流动行为。和3 m高的3种不同类型的粒子。使用光纤探头获得了局部固体滞留量的轴向和径向分布，并通过双电导率探头测量了距主液体分配器0.8 m的轴向位置处液体速度的径向分布。结果表明，固含量比相对较轻的颗粒沿着立管相当均匀地分布，但是在液体流量相对较低的情况下，重钢颗粒体系中存在着浓密的底部-顶部-底部的轴向流动结构。在循环流化过程中，固体滞留率和液体速度在径向上均不均匀，中心区域的固体浓度低/液体速度高，而壁区域的固体浓度高/液体速度低。随着固体循环速率的增加，径向轮廓变得更加陡峭。还通过分析微流结构研究了径向不均匀分布，这进一步证实了在大流研究中获得的结果。从常规流态化方案到循环流态化方案的过渡标准也已经适当定义。另外，已经进行了压力平衡分析以预测稳定的操作条件并解释液固循环流化床的不稳定操作现象的根源。事实证明，稳定的工作窗口受颗粒性质，固体存量和单位几何形状的影响很大。

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  • 作者

    Zheng, Ying.;

  • 作者单位

    The University of Western Ontario (Canada).;

  • 授予单位 The University of Western Ontario (Canada).;
  • 学科 Engineering Chemical.
  • 学位 Ph.D.
  • 年度 1999
  • 页码 242 p.
  • 总页数 242
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 化工过程（物理过程及物理化学过程）;
  • 关键词

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