Role of Acoustic Fields in Promoting the Gas-Solid Contact in a Fluidized Bed of Fine Particles

Abstract

The present work is a review presenting the main results obtained by our research group in the field of soundassisted fluidization of fine particles. Our aim is to highlight the role of acoustic fields in enhancing the gas-solid contact efficiency, with specific attention to the phenomenological mechanism upon which this technique is based. In particular, the first section presents the characterization of the fluidization behaviour of four different nanopowders in terms of pressure drops, bed expansion, and minimum fluidization velocity as affected by acoustic fields of different intensity and frequency. The fluidization of binary mixtures comprising two powders is also investigated under the application of different acoustic fields and varying the amounts of the two powders. The second section focuses on the study of the mixing process between two different nanopowders both from a “global/macroscopic” and “local/microscopic” point of view and highlighting the effect of mixture composition, primary particles density and sound intensity. The last section presents a promising application of sound-assisted fluidization, i.e. CO 2 capture by adsorption on a fine activated carbon, pointing out the effect of CO 2 partial pressure, superficial gas velocity, sound intensity and frequency on the adsorption efficiency.