Reduction in minimum fluidization velocity and minimum bubbling velocity in gas-solid fluidized beds due to vibration

Abstract

Vibration of gas-solid fluidized beds is often used to enable fluidization of cohesive particles; however, it has also been shown to reduce the minimum fluidization velocity (Umf). Here, we show via experiments that vibration can reduce both Umf and the minimum bubbling velocity (Umb) in Geldart Group B and D particles. We observe that Umf is reduced more than Umb, thereby creating a densely packed, bubble-free fluidization state when the superficial gas velocity is in between Umf and Umb. Umf and Umb decrease with increasing vibration frequency and amplitude and the results for Umf and Umb across a variety of vibration conditions could be plotted along a single curve when plotted versus vibration strength, i.e. the ratio of peak vibration acceleration to gravitational acceleration. Changes in Umf and Umb due to vibration are not affected significantly by changing particle density, but in a non-monotonic way by changing particle diameter.