Modeling of a Spray Coating Process In a Forberg Style Mixer/Coater: Particle Size Effect On the Coating Preference

The discrete element method (DEM) is applied to investigate the heterogeneous particle flow of a spray coating process with polydisperse particles in a Forberg style mixer/coater.  Simulation results of particle movement demonstrate radial convective flow with the rotating paddle and axial dispersion flow along the shaft.  A spray zone area is specified at the top bed surface, in which particles are being coated proportional to the surface area exposed under the spray.  Different segregation phenomena are observed when different ranges of particle sizes are used, resulting opposite coating preference over polydisperse particles.  Further DEM simulations are performed altering particle density, in order to understand that whether the segregation is induced by shape or by gravity.  Finally, a lumped growth rate expression is derived to be applied in the population balance (PB) modeling of particle coating distribution.