Particle Velocity in a Dense Gas-Solid Fluidized Bed

Abstract

The upflowing and downflowing particle velocities are investigated by using a two-optical fiber probe system in the dense gas-solid fluidized bed with an inner diameter of 0.185 m and a height of 3.000 m. Two kinds of glass ballotinis, belonging to Geldart type B classification, are selected as solid material. Experiments are conducted under different operating gas velocities, static bed heights, and particle diameters. The results indicate that the upflowing particle velocity is a strong function of operating gas velocity and particle diameter, while the downflowing particle velocity depends mainly on the operating gas velocity. When the ratio of the operating gas velocity to the minimum fluidization velocity of the particles keeps the same constant, the effect of the particle diameter on the upflowing and downflowing particle velocities can be ignored. Both direction and size of the solid particle velocity are related to the bubble behaviors in the fluidized bed, and the upflowing particle velocity is lower than the bubble rise velocity. Furthermore, the across-sectional, non-uniform flow structure in the bed increases slightly with increasing static bed height at the high operating gas velocity.