Expansion three-phase fluidized beds

The cocurrent gas-liquid-solid fluidized beds considered are those in which the liquid supports and completely wets the solid. The gas flow thus constitutes a perturbation of a liquid fluidized bed. Unlike a gas-solid or a liquid-solid fluidized bed, a gas-liquid-solid fluidized bed may either contract or expand when gas bubbles are introduced into the bottom of the bed. Considerable work has been done on deriving the criteria for the bed contraction and expansion. The most up-to-date work on this subject is by Epstein.28 He derived the criterion for initial contraction and expansion of three-phase fluidized beds. He suggested that if the quantity... 

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... 

Prediction of Contraction/Expansion Behavior in Three-Phase Fluidized Beds... 

Joshi (1983) used a simpler form of this model for the prediction of contraction/expansion in three-phase fluidized beds. 

The phenomenon of expansion/contraction in three-phase fluidized beds was analyzed. A brief review of literature has been presented. Epstein and co-workers have made outstanding contributions in this area. An alternative method has been presented. A favorable comparison between the model predictions and the experimental observations was observed. 

Three-phase fluidized beds using small particles display unique bed expansion characteristics. Upon the initial... 

El Temtamy, S.A. Epstein, N. Contraction or expansion of three-phase fluidized beds containing fine/light solids. Can. J. Chem. Eng. 1979, 57 (4), 520-522. 

Jiang, P. Lin, T.J. Fan, L.-S. High temperature and high pressure three-phase fluidization—bed expansion phenomena. Powder Tech. 1997, 90, 103. 

Epstein, N. and D. Nicks, "Contraction or Expansion of Three-Phase Fluidized Beds". Fluidization Technology, ed. D. Keairns 389-397 (Washington, Hemisphere Publishing Corporation 1976). 

Epstein, N, "Criterion for Initial Contraction or Expansion of Three-Phase Fluidized Bed" Can. J. Chem. Engng. 54 (1976) 259-263. 

Various aspects of three-phase fluidization have been the subject of numerous investigations due to its high potential for industrial applications in areas such as catalytic processes, hydrocracking and desulphurization of petroleum products, coal liquefaction, hydrogenation of unsaturated fats, and production of calcium bisulfite liquor. Extensive studies have been published concerning the hydrodynamics of three-phase fluidized beds, such as expansion [l-S], pressure drop [ 9 J, gas and liquid hold up [10-14], minimum fluidization velocity [izj and axial mixing [8, 10, 14-17]. 

Findings with PDU. Work with the PDU largely paralleled the bench-scale reactor tests there was one important addition—extensive three-phase fluidization studies. As was mentioned, the PDU is equipped with a traversing gamma-ray density detector that is capable of measuring bed density to within dbO.Ol specific gravity units. Thus, we could measure and correlate fluidized bed expansion as a function of liquid and gas velocities and physical properties, and could also determine the... 

Bed expansion and contraction are important phenomena in three-phase fluidization, since these affect the bed volume and the residence time(s) of all the phase(s). The phenomenon of bed contraction/expansion is also very closely linked to the problem of transition. The relationship between the expansion/contraction behavior and the transition will be clearly brought out later. 

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