A comparison between interparticle forces estimated with direct powder shear testing and with sound assisted fluidization

In recent years an increasing numbers of industries (e.g. interested in the manufacture of cosmetics, foods, plastics, catalysts, energetic materials, biomaterials, micro-electromechanical systems have been attracted to fine and ultrafine particles fluidization, particularly thanks to their special chemical and physical properties. It has become gradually more and more important to understand how to control and to process these particles. Although several studies have been carried out on the effect of IPFs on the fluidization, satisfactory understanding of the phenomena that governed the dynamics of the bed has not yet been achieved. Moreover, a direct measure of the particle-particle interactions and their dependency on the particle properties and on the process conditions in a fluid bed reactor is challenging. In the last years many researches started to look at the rheological measurements as a possible way to understand the fluidization behaviour. The aim of the work is to connect flow properties of the bulk solid evaluated with shear cell shear testing and with interparticle interactions in fluidization. In particular, IPFs of fine/ultrafine powders under actual fluidization conditions are obtained by using sound assisted fluidization. With this technique proper fluidization of these cohesive particles is achieved and the results obtained from the experimental tests are analysed in the view of the cluster/subcluster model to calculate IPFs. The obtained values of the IPF intensities were then compared to those evaluated by using direct powder shear testing characterization, analysed with the help of the Rumpf-Molerus approach. An excellent quantitative agreement between the forces found with these two completely independent techniques was found.