The axial distribution of gel beads suspended completely in a bubble column was measured by sampling the three-phase dispersion through a vertical pipe located at any height of the column axis under various operating conditions of superficial gas velocity U
G, average gel beads holdup
εS and unaerated slurry height
HD. The gel beads used were prepared by entrapping glucose oxidase as well as fine palladium particles within calcium alginate gel to catalyze the air oxidation of glucose for efficient production of calcium gluconate. The conventional sedimentation-diffusion model, which includes the gel beads dispersion coefficient
EP and their settling velocity
vP to describe the axial distribution, is found to give unreasonable
EP values being at least twice as high as than those predicted from the published correlations, and also twice as high as the estimated values of the liquid dispersion coefficient
EL in the three-phase bubble column. This was assumed to be ascribed to the reduced apparent values of
vP, since the intrinsic E
P value should be nearly equal to the
EL value. In view of the fact that the gel bead has almost the same density as the liquid phase and the size is comparable to the mean bubble size, the model was modified by introducing an additional parameter, the rise velocity of the gel beads swarm
um representing an effect of rising air bubbles on settling gel beads. The values of
um were determined from the observed axial distributions by assuming that the
EP values are given by the reported correlation of
EL in suspension of the inert calcium alginate gel beads, and empirically correlated with
UG and
εS. The axial distributions calculated from the modified model well agreed with the observed ones for the different
HD.
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