Influence of a sound field on the flow pattern of hollow microbeads in a spout-fluidized bed with a draft tube

In this study, instead of ultrafine powder agglomerates, hollow microbeads with an average particle size of 150 pm were employed as raw materials in a half-cylindrical acoustic spout-fluidized bed with a draft tube, using a high-speed atmosphere jet as the spouting gas. Analyses of pressure drop-velocity curves and pressure fluctuations, as well as observations of the experimental phenomena, allowed determination of the flow patterns of the spout and annulus, as well as transition velocities. The influence of a sound field on the flow patterns was then investigated. The results showed that the sound field effectively inhibits gas channeling and bypass and promotes the breakup of bubbles and dispersion of particles. Under the influence of the sound field, the critical transition velocities of the flow pattern and the minimum fluidization velocity in the annulus decreased, whereas the operating flexibility of the spout-fluidized bed with a draft tube increased. (C) 2019 Elsevier B.V. All rights reserved.