Vibro-fluidization of cohesive particles

Abstract

The paper assesses the behavior of cohesive Geldart C-type particles, when fluidized by air with the aid of vibration. Together with their poor flowability and irregular hopper discharge, bubbling fluidization is very difficult to achieve due to the possible particle agglomeration and gas channeling. When trying to fluidize cohesive particles, the gas drag force cannot break the inter-particle bonds. Despite all these handling and operation problems, ultrafine particles of micron- or nanosize are increasingly applied in industrial processes. To disrupt the stable gas channels and cracks, a mechanical vibration is one of the easier and preferred methods to improve the fluidity of the cohesive particles. In the present study, several 2 to 40 μm particles were used. A comparison with Geldart A-type particles was also made. Experimental results were used to validate a more fundamental approach based upon the balance of forces acting on the particles. This resulted in a new delineation of the Geldart C/A boundary where the critical transition particle size for particles of given absolute density, ρp, Hamaker constant, H, and inter-particle distance, z0, decreases with an increasing vibration intensity, I, according to dcrit2ρp=8.03Hz021+Ig.