Macro-scale numerical investigation of the contribution of Van der Waals force to the pressure-drop overshoot in fine-particle fluidized beds

Interparticle Van der Waals force contributes to the overshoot in the bed pressure drop at the minimum fluidization velocity during the transition from static to fluidized bed conditions, which is a well-known phenomenon in the fluidization of fine particles. In this study, two adhesive particle pressure closures considering the effect of interparticle Van der Waals force are used in two-fluid model simulations with the intention to generate the pressure overshoot. The first adhesive pressure model developed within the context of the kinetic theory of rapid granular flows failed to produce the overshoot due to the dominance of multiple and long duration contacts in the fixed-bed flow. Another closure based on the coordination number was then proposed to represent long-lasting interparticle contacts, which gave an adhesive contribution much larger than the one of the kinetic theory model and was able to create the pressure drop overshoot.

Mots clés

gas-solid fluidized beds; interparticle forces; Van der Waals adhesion; grannular media; two-fluid model; kinetic theory