SIMULATION OF TRANSPORT DYNAMICS IN FLUIDIZED-BED DRYERS

A mathematical model for predicting three-dimensional, two-phase flow, heat and mass transfer inside fluidized-bed dryers has been developed . The model consists of the full set of partial-differential equations that describe the conservation of mass, momentum and energy for both phases inside the dryer, and is coupled with correlations concerning i nterphase momentum-, heat-, and mass-transfer. It is shown that the mo del can predict. the most important engineering aspects of a fluidized -bed dryer including pressure drop, particle holdup, temperature distr ibution in both phases as well as drying efficiency all over the fluid ized-bed. Plug-flow conditions are predicted for the gas phase, while back-mixing is predicted for the particles. The effect of particle mas s-flow-rate on fluidized-bed dryer performance is evaluated. It is sho wn that the lower the particle mass flow-fate, the more intense the ho rizontal moisture gradients, while the higher the particle rate the mo re uniform the moisture distribution throughout the bed.