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.

Heat Transfer in Sound Assisted Fluidized Bed of Fine Powders : A Review

“…Raganati et al [13] reviewed characteristics of fluidizing bed like bed expansion, drop in bed pressure and the velocity of minimum fluidization for four various nano powders ; Al2O3, Fe2O3,CuO and ZrO2 with sizes less than 50nm and air as a fluidizing gas. They have found consistent condition of optimum fluidization for Al2O3, CuO and ZrO2 at particular fixed SPL value and the frequency range 100-125Hz and 90-120Hz.…”

“…Researchers studied for some external forces given to this system for effective fluidization quality of powders. Sound field shows capability to disturb all clusters [10,11,14] and decrease in the velocity of minimum fluidization [3,5,10,13,22], bubble free fluid-like behaviour is obtained [11]. The sound energy results for continues vibrations, replaces particle without channeling nature of the bed.…”

“…(a) Effect of SPL (f = 120Hz) and (b) effect of sound frequency (SPL =140 dB) on ∆Pmax/P0, Hmf/ H0 for all the powders[13].…”

Sound-Assisted Fluidization for Temperature Swing Adsorption and Calcium Looping: A Review

“…Indeed, these particles are characterized by strong interparticle forces (IPFs), causing the natural formation of large aggregates, due to the particles tendency to stick to one another giving rise to larger structures as large as hundreds of microns [ 1 , 2 , 53 ]. This agglomeration tendency causes, in turn, channeling/plugging phenomena, thus hindering the possibility to obtain a proper fluidization quality under ordinary conditions [ 2 , 53 , 54 , 55 , 56 ].…”

Sustainable Biomass Glucose-Derived Porous Carbon Spheres with High Nitrogen Doping: As a Promising Adsorbent for CO2/CH4/N2 Adsorptive Separation

“…However, the utilization rate of CBM is only about 40% in China, because low-concentration CBM (CH 4 less than 30%) is usually directly emitted into the atmosphere as drainage dynamic systems, such as fixed/fluidized bed reactors, facing the challenge of plug formation, channeling, and agglomeration because of cohesive forces (such as van der Waals, electrostatic, and moisture-induced surface tension forces) existing between particles [44,45]. Inspired by Raganati and his co-workers, temperature-controlled [46] and sound-assisted [47][48][49] fluidization can be used to achieve a fluidization regime of these cohesive particles, which makes such fine carbon powders not only easily testable for characterization in static analysis systems, but also capable of actual use in dynamic systems.…”