Slug flow in fluidised beds

The paper begins by summarising theory and experimental data concerning the rate of rise of a large gas bubble or slug through an inviscid liquid in a vertical tube, or between two flat plates. Experimental data show that the theory can be used to predict the rise of slugs in fluidised beds. Theory is also given to predict the penetration of fluidising fluid from a slug into the particles; this agrees well with experiment, and is important in the design of catalytic reactors operating in the slug flow regime. A tentative theory (due to P.S.B.S.) predicts the transition from the bubble regime to the slug flow regime in a fluidised bed. The result is that slug flow will occur in a tube of diameter D if (U-Uo)/0.35 (gD)12 is greater than about 0.2, where U is the superficial velocity, Uo is the superficial velocity at incipient fluidisation, and g is the acceleration of gravity. This theory does not conflict with published observations by various authors as to the flow regime in given circumstances.

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