VISUALIZATION OF GAS VOIDS BEHAVIOR ABOVE THE DISTRIBUTOR IN A THREE-DIMENSIONAL GAS FLUIDIZED BED

Abstract

A new system, consisting of a two-dimensional optical fiber array probe, video system and microcomputer, was used to visualize the behavior of jets and bubbles in a three-dimensional fluidized bed. By this system a series of successive pictures with time difference 1/30 s was obtained. The bed was 28 cm in diameter, provided with a nozzle of 0.325 cm i.d. fixed at the center of the gas distributor.
The behavior of jets and initial bubbles in the grid region was visualized. The effect of bed material, distributor configuration, superficial gas velocity and nozzle gas velocity on this behavior was examined. The results showed that the jet height was affected by the properties of the bed material, but that the initial bubble diameter was scarcely affected thereby. Gas distributor configuration had an important effect on jet height and initial bubble properties other than frequency. Initial bubble shape and frequency were strongly dependent on superficial gas velocity rather than on nozzle gas velocity. A correlation to evaluate the jet height is proposed.