Characterization of flow pattern of cohesive particles in gas-solid fluidized bed via axial distribution of particle motions

Abstract

Flow pattern of cohesive particles in gas-solid fluidized bed is complex, and particles in different regions exhibit various flow patterns. Characterization methods in literatures are deficient in detecting local motions of particles. In this work, particle motions distribution along the axial direction was investigated by acoustic emission detection and pressure fluctuation. The axial distribution of particle motions proved the “stratified fluidization” of cohesive particles and further investigation showed that the stratified fluidization was affected by both the superficial gas velocity and the initial height-to-diameter ratio (H0/D). Increasing the operating gas velocity, the fluidization of the fluidized bed with a relatively low H0/D changed from fixed bed with stable channeling to the two-layer stratified fluidization consisted of the fixed bed layer in the lower part and the bubbling fluidized bed layer in the upper part. While for the fluidized bed with a large H0/D, the fluidization transmitted from fixed bed with unstable channeling to two-layer stratified fluidization, then to multi-layer stratified fluidization with an inflatable fluidized bed layer appeared above the bubbling bed layer. Moreover, a flow pattern map of the fluidization of cohesive particles was established which could show guidance for the selection of optimized operation conditions for fluidization of cohesive particles.