Bubble Phenomena in Relation to Bed Performance

The bubble holdup Cb for a bubble column or for a fluidized bed is easily obtained as a function of superficial gas velocity Uq. Useful information 

In this chapter, the equation is further examined in relation to bed performance, since the turbulence properties of the bed result from interaction between bubbles and the continuous phase. As shown in Fig. 34, the mean slip velocity of bubbles in a fluidized catalyst bed of good fluidity is essentially the same as that for a bubble column when Uq 20 cm/sec. A criterion under which bubble size approaches a dynamic equilibrium is obviously needed for predicting or evaluating the performance of scaled-up beds. 

Mean Bubble Velocity without Bulk Recirculation 

A brief survey is needed here of bubble flow, with or without a bubble wake. Bubbles of a uniform size are generated by a gas distributor and rise uniformly through the continuous liquid phase in a bubble column, or 

Case a of Fig. 42 shows the steady bubbling of gas through stagnant liquid in a bubble column, according to Nicklin (N4), where J/l = 0-Superficial gas velocity Uq is related to the ascending velocity b of bubbles relative to the wall  

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