Investigation of the influence of wetting on the particle dynamics in a fluidized bed rotor granulator by MPT measurements and CFD-DEM simulations

In many processes, particles are coated or agglomerated. Thus, it is of considerable interest how liquid affects the particle dynamics. The production of round, coated pellets is particularly important in the pharmaceutical industry, which is why fluidized bed rotor granulators (FBRG) are often used for this process. In this work, the influence of liquid content on the particle dynamics in a FBRG was investigated experimentally by magnetic particle tracking measurements (MPT) and numerically using Computational Fluid Dynamics coupled with Discrete Element Method (CFD-DEM coupling). A liquid bridge model was implemented in the DEM contact model to take the capillary and viscous forces during wet contact of particles into account. In addition, the model considers the influence of the relative contact velocity on the maximum liquid bridge length. In order to show that numerical simulations can correctly predict the particle dynamics in the process, the non-intrusive MPT technique was used for the continuous measurement of the particle position and orientation of a single tracer particle during experiments. Thus, the residence probability, the trajectories, as well as the translational and angular velocities of the particles were determined. The simulation results agree well with the experimental measurements.