The rise of bubbles in a fluidised bed

Abstract

The rate of rise of a bubble in an air-ftuidised bed of particles was measured by observing the time interval between the release of a shot of air injected at the base of the bed, and its arrival at the surface as a bubble. The main air supply was just greater than the minimum rate for ftuidisation. In these circumstances the injected bubble of air rises at the same rate as it would in an inviscid liquid of zero surface tension. The rate of rise U is therefore independent of the main air rate, and of the size or density of the particles. U is given in terms of the volume V of the bubble by the semi-empirical formula, derived for a gas bubble in an inviscid liquid by Davies and Taylor, U=0.792 V^1/6g^½.