Simulation of a Vibrated Fluidised Bed Dryer for Solids Containing a Multicomponent Moisture

The drying of solids in a continuously worked vibrated fluidised bed dryer is studied by simulations. A model considering the drying of a thin layer of particles wetted with a multicomponent mixture is developed. Particles are assumed well mixed in the direction of the airflow and only the longitudinal changes of liquid content, liquid composition and particle temperature are considered. Interactive diffusion and heat conduction are considered the main mechanisms for mass and heat transfer within the particles. Assuming a constant matrix of effective multicomponent diffusion coefficients and thermal conductivity of the wet particles analytical solutions of the diffusion and conduction equations are obtained. The variation of both the diffusion coefficients and the effective thermal conductivity of the particles along the dryer is taken into account by a stepwise application of the analytical solution in space intervals with averaged coefficients from previous locations in the dryer. The analytical solution gives a good insight into the selectivity of the drying process and can be used to estimate aroma retention during drying. The solution is * To whom all correspondence should be addressed XXII IACChE (CIIQ) 2006 / V CAIQ AAIQ Asociación Argentina de Ingenieros Químicos IACCHE Interamerican Confederation of Chemical Engineering computationally fast; therefore, the experimental verification of this approximate model would introduce an important computational economy since the rigorous treatment of multicomponent drying involves tedious and time-consuming calculations.