The Mechanism behind Vibro-Assisted Fluidization of Cohesive Micro-Silica

Rens Kamphorst,Kaiqiao Wu, P. Christian van der Sande, Evert C. Wagner, M. Kristen David, Gabrie M.H. Meesters, J. Ruud van Ommen

In sectors such as food, pharma and catalyst manufacturing we see an increasing interest of applying fluidization to particles in the Geldart C range. When it comes to these particles, fluidization becomes challenging due to strong attractive inter-particle forces. This results in channel formation and agglomeration, both of which lead to a reduction in gas-solid contact. To fluidize cohesive particles, assistance methods can be employed, which introduce additional manipulation. For most assistance methods, studies have concluded that the mechanism by which fluidization was improved, is by breaking up agglomerates. We hypothesized that it is not the agglomerates, but the channeling that is targeted by these assistance methods.

In this study, we used X-ray imaging to study channel formation and collapse within a fluidized bed of cohesive microparticles. Pressure drop, bed height and off-line agglomerate size measurements were performed as well, to decouple the effect of channel disruption and breaking of agglomerates.

It was observed that channeling is the main cause of poor fluidization of the micro-silica, resulting in poor gas-solid contact and little internal mixing. Improvement in fluidization upon starting the mechanical vibration was achieved by disrupting the channels. Agglomerate sizes were found to not significantly change during experiments.