In a vertical gas-liquid-solid fluidized bed of 4.2 cm in diameter and 130 cm in height

the axial solid concentration distribution is investigated for both particles with different properties. Two distinguishing systems can be formed upon the wettable property of particle materials. One is called as a no-attached system in which the solid holdup decreases with increasing bed height. Another is named as an attached system in which solid holdup increases with the bed height. The sedimentation-dispersion model can be employed better to describe both above systems by modifying only a model parameter

i.e.the particle terminal settling velocity

which considers the effect of an additional drag force resulting from attached up-flowing bobbles and subtracts a certain value obtained by a function formula relating to the gas velocity. It is found that the axial concentration profiles of solid particles predicted by the modified sedimentation-dispersion model are in good agreement with experimental results for both no-attached and attached systems.