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Fluidization of fine particles and its applications.

机译：细颗粒的流化及其应用。

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摘要

Based on the force balance of the particle bed under vibration, a new correlation for predicting of the minimum fluidization velocity ( umf) for fine particles has been derived by taking both the interparticle forces and the effects of vibration into consideration. A general correlation for the minimum fluidization voidage (&egr; mf) showing the relationship between &egr;mf and particle size as well as vibration intensity is also obtained from the experimental data. The newly derived correlation for the prediction of umf combined with the one for &egr;mf proves to be superior to the existing correlations for particles of Geldart groups A, B and D, although the application of the present correlations remains unsatisfactory for group C particles.;Fundamental studies of the influence of gas type and temperature on the fluidization behaviour of groups C and A particles have been carried out. For all the particles tested, the fluidization quality in different gases generally shows the following priority sequence: Ar > Air > N2> He > H2. It is also found that a higher bed temperature usually leads to a larger bed voidage, a higher bed pressure drop as well as a lower umf. Possible mechanisms governing the operations of gas type and temperature in influencing the fluidization behaviour of fine particles have been discussed with respect to the changes in both gas properties and interparticle forces. It is suggested that the influence of gas type and temperature on fine particle fluidization is mainly through varying the gas properties (especially the gas viscosity). The increased gas viscosity may account for the improved fluidization quality of fine particles, as shown by either using a gas of higher viscosity or elevating the bed temperature. (Abstract shortened by UMI.).;A novel "online sampling" technique that can prevent the disruption of agglomerates when sampling the agglomerates from a fluidized bed has been developed and has been applied to the investigation of the agglomeration behaviour of cohesive particles during fluidization with and without mechanical vibration. A new model for the prediction of agglomerate size has also been established on the basis of an energy balance. Effects of gas velocity and mechanical vibration on agglomeration for two group C powders in fluidization are examined experimentally and theoretically.
机译：基于颗粒床在振动下的力平衡，通过考虑颗粒间的作用力和振动的影响，得出了预测细颗粒的最小流化速度（umf）的新的相关性。还从实验数据中获得了最小流化空隙率（＆mf）的一般相关性，其显示了＆mf与粒度以及振动强度之间的关系。事实证明，新推导的umf预测的相关性与egmf的相关性优于Geldart A，B和D组的现有相关性，尽管当前相关性的应用对于C组粒子仍然不能令人满意。 ；基础研究了气体类型和温度对C和A族粒子流化行为的影响。对于所有测试的粒子，在不同气体中的流化质量通常显示以下优先级顺序：Ar>空气> N2> He> H2。还发现较高的床温通常导致较大的床空隙度，较高的床压降以及较低的umf。关于气体性质和颗粒间力的变化，已经讨论了控制气体类型和温度的操作以影响细颗粒的流化行为的可能机理。建议气体类型和温度对微粒流态化的影响主要是通过改变气体性质（尤其是气体粘度）来实现的。如通过使用较高粘度的气体或升高床温所显示的，增加的气体粘度可以解释细颗粒的改进的流化质量。 （摘要由UMI缩短。）；已开发出一种新颖的“在线采样”技术，该技术可防止在从流化床中取样附聚物时破坏附聚物，并将其用于研究流化过程中粘性颗粒的附聚行为有无机械振动。在能量平衡的基础上，还建立了一种预测团聚体尺寸的新模型。实验和理论上研究了气体速度和机械振动对两种C组粉末在流化过程中团聚的影响。

著录项

  • 作者

    Xu, Chunbao.;

  • 作者单位

    The University of Western Ontario (Canada).;

  • 授予单位 The University of Western Ontario (Canada).;
  • 学科 Chemical engineering.
  • 学位 Ph.D.
  • 年度 2005
  • 页码 307 p.
  • 总页数 307
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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