An earlier developed hydrodynamic model describing dense gas-solid two
phase flow has been used to study the bubble formation process at a s
ingle orifice. A systematic experimental and theoretical study has bee
n conducted to investigate the effect of particle properties (i.e. par
ticle diameter and density) on the bubble growth process for Geldart t
ype B powders. Theoretical results, obtained for both two-dimensional
and three-dimensional geometries, have been compared with experimental
data and with predictions from approximate models reported in literat
ure. A comparison of the theoretical results and experimental data sho
ws that the advanced hydrodynamic model gives a satisfactory good desc
ription of the bubble growth process for several particle types which
makes this model a useful tool to study the bubble formation process i
n fluidised beds. It appears that the influence of particle size and p
article density on bubble formation can be related to the effect of th
e minimum fluidisation velocity on this process. At a constant gas inj
ection rate through the orifice higher minimum fluidisation velocities
result in larger bubbles and decreased leakage. Further, it has been
found that coarse particles give rise to the formation of relatively e
longated bubbles. The detachment times, on the other hand, seem to be
independent of the particle size used. Copyright (C) 1996 Elsevier Sci
ence Ltd