Simulation of granular layer inversion in liquid fluidized beds

A hydrodynamic computer model for describing multiparticle fluidization has been developed. Each group of particles, identical in density and in diameter, is treated as a particulate phase in this model. The computer code solves the mass and momentum balance equations for the fluidizing fluid and for the required number of particulate phases. The model has been used to simulate granular layer inversion in a liquid fluidized bed. This phenomenon occurs during the fluidization of a binary mixture of particles in which the denser particles are smaller. In such a system at low fluid velocities, the larger particles segregate into a top layer; at higher fluid velocities, they sink to form a bottom layer. At intermediate fluid velocities, the extent to which the particles mix is determined by the fluid velocity. The simulation results using the multiparticle code are in good agreement with experimental data on granular layer inversion. It is also shown that under some conditions, a radial segregation pattern exists in addition to the experimentally observed axial segregation pattern.