Entrainment and elutriation modelling in bubbling fluidized beds
Entrainment and elutriation modelling in bubbling fluidized beds
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DOI：
10.1016/0032-5910(94)02970-y
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发表时间：
1995-06
影响因子：
5.2
通讯作者：
F. E. Milioli;P. J. Foster
中科院分区：
文献类型：
--
作者：
F. E. Milioli;P. J. Foster
在鼓泡流化床燃烧和催化裂化中，淘析是效率低下的主要原因，而在例如污泥焚烧中，淘析是非常可取的。无论目的是抑制还是促进淘析，如果要有效地控制该过程，必须正确地了解所涉及的现象。在这项工作中，夹带和淘洗进行审查和建模建议的开发。主要关注的是在剧烈流化条件下具有宽粒度分布的鼓泡床。颗粒被细分为三类：临界细颗粒、小颗粒和大颗粒。临界细颗粒是指其终端速度远低于气体表观速度的颗粒，并被假定为瞬间夹带在床面。小颗粒和大颗粒的终端速度分别低于和高于气体的表观速度，并被认为是通过气泡尾流喷射机制夹带。床面夹带模型提供的参数必须根据经验数据进行评估。与实验结果的比较表明，当Umf≥10时，fw_k应随Umf的增大而增大，并提出了一个关联式来解释这种变化。淘析模型是基于实验的现象学观察，得出了必须针对特定情况设置的参数。
In bubbling fluidized bed combustion and catalytic cracking, elutriation is a major cause of inefficiency, while it is highly desirable, for instance, in sludge incineration. Whether the intention is to quench or promote elutriation, the involved phenomena must be properly known if the process is to be efficiently controlled. In this work, entrainment and elutriation are reviewed and a modelling proposal is developed. The main concern relates to bubbling beds of wide spread particle size distributions under vigorous fluidization. The particles are subdivided into three classes: critical fines, smalls and larges. Critical fines are particles whose terminal velocities are much lower than the gas superficial velocity, and are assumed to be instantaneously entrained at the bed surface. Smalls and larges are particles whose terminal velocities are respectively lower and higher than the gas superficial velocity, and are assumed to be entrained through the bubble wake ejection mechanism. The bed surface entrainment model presents parameters which must be evaluated from empirical data. Comparison to experiment shows that, for U Umf≥10 , fwξkshould increase with U Umf, and a correlation is proposed to account for this variation. The elutriation model is based on phenomenological observations from experiment, coming out with parameters which must be set for specific situations.