Modeling of liquid-film three-phase fluidised bed
Three-phase fluidised bed bioreactors with a discrete liquid phase offer numerous advantages over conventional packed bed reactors. Since the particulate phase can be used as a support medium for a gel-like biofilm surface, several physical constraints arise. As a result of these constraints, the cohesiveness of the particles greatly increases, making smooth fluidisation more difficult and causing the particles to aggregate and eventually, the bed to defluidise. In the present paper, a model is developed to predict the critical fluidisation at a variety of binder thicknesses in a cohesive three-phase fluidised bed. Collisions of particles with a cohesive film and interparticle forces due to liquid bridges and capillary forces are modeled. The model predictions are compared with results of experiments in a three-phase fluidised bed containing cohesive particles.