In literature little attempt has been made to verify experimentally Eu
lerian-Eulerian gas-solid model simulations of bubbling fluidised beds
with existing correlations for bubble size or bubble velocity. In the
present study, a CFD model for a free bubbling fluidised bed was impl
emented in the commercial code CFX of AEA Technology. This CFD model i
s based on a two fluid model including the kinetic theory of granular
flow. Simulations of the bubble behaviour in fluidised beds at differe
nt superficial gas velocities and at different column diameters are co
mpared to the Darton et al. (1977) equation for the bubble diameter ve
rsus the height in the column and to the Hilligardt and Werther (1986)
equation, corrected for the two dimensional geometry using the bubble
rise velocity correlation of Pyle and Harrison (1967). It is shown th
at the predicted bubble sizes are in agreement with the Darton et al.
(1977) bubble size equation. Comparison of the predicted bubble veloci
ty with the Hilligardt and Werther (1986) equation shows a deviation f
or the velocity of smaller bubbles. To explain this, the predicted bub
bles are divided into two bubble classes : bubbles that have either co
alesced, broken-up or have touched the wall, and bubbles without these
occurrences. The bubbles of this second class are in agreement with t
he Hilligardt and Werther (1986) equation. Fit parameters of Hilligard
t and Werther (1986) are compared to the fit parameters obtained in th
is work. It is shown that coalescence, break-up, and direct wall inter
actions are very important effects, often dominating the dynamic bubbl
e behaviour, but these effects are not accounted for by the Hilligardt
and Werther (1986) equation. (C) 1998 Elsevier Science Ltd. All right
s reserved.