Wake model, three-phase fluidized beds

Zhang, J. P., Jin. Y and Yu, Z. Q. Estimation of General Wake Model Parameters for a Three-Phase Fluidized Bed by Bed Collapse Technique (Chinese), in The Proceeding of 5th National Conference on Fluidization, pp. 327-331 (1990). 

Epstein and co-workers (Bhatia and Epstein, 1974 Epstein, 1976 Epstein and Nicks, 1976 El-Temtamy and Epstein, 1978, 1979) have made very valuable contributions to the understanding of expansion/contraction characteristics of three-phase fluidized beds. Bhatia and Epstein (1974) proposed a wake model in which the solid contents of the liquid wakes behind the gas bubbles is negligible compared to the solid contents of the remaining... 

On the basis of the generalized wake model of Bhatia and Epstein, " a criterion for the bed contraction was developed. In the generalized wake model, the three-phase fluidized bed is assumed fo consist of three regions, the gas bubble region, the wake region, and the liquid-solid fluidized region. Bed contraction will occur when the following criterion is satisfied, ij/ < 0 where... 

An alternative model for slugging fluidized bed reactors was proposed by Raghuraman and Potter (48). This Is an extension of their three-phase (bubbles, cloud-wake phase, emulsion phase) countercurrent backmlxlng model (21) which accounts for gas downflow In the dense-phase, said to occur for slugging beds when U > 2.5 U f Agreement with experimental results Is said (48,49) to be somewhat better for this model than for the Hovmand-... 

The most advanced and realistic description of fluidized beds is the Kunii-Levenspiel model [18]. According to this model, the bubble phase is assumed to move in the reactor following the characteristics of a plug flow, while the gas flow in the emulsion phase is assumed to be negligible. The cloud and wake phases are presumed to possess similar chemical contents. The transport of the reacting gas from the bubble phase to the cloud and wake phases and vice versa prevails. The volume element, AV, therefore consists of three parts, as in Figure 5.34 ... 

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