DEM-CFD Coupling Simulation of Fluidized Behavior of Geldart’s Group A Particles: A Contact Force Model for Expressing Adhesion Force

A discrete particle model for flows of Group A particles in Geldart’s classification was studied. In general, Group A particles are fine and light, so that the adhesion force has a strong effect on their fluidization behavior. At first, interparticle adhesion force of Group A particle was measured. The DEM-CFD coupling simulation with the measured adhesion force was performed, and the simulated results were compared with experimental data about a small scale fluidized bed for verification of the simulation. It was found from the results that there were considerable differences between their flow patterns. In order to reveal the cause of the differences, we investigated the effect of the contact force model with adhesion force on the motion of a single particle colliding with a wall. Then, we focused on the critical relative velocity of particle before collision that the particle kept in contact by the adhesion force, and discussed about the correlation of key parameters in the contact force model. From the analysis on the particle-wall collision process, it is found that the spring constant used in the DEM model has a large effect on the particle’s sticking behavior on the wall. The dynamic adhesion force model is proposed based on the present analytical investigation, and it is shown that the present model well expresses the experimental Group A particle bed fluidization behavior.