Numerical simulations of contact drying in agitated filter-dryer

• We model three dimensional particle dynamic systems for an agitated filter-dryer.
• Effect of operating parameters on drying behavior was systematically studied.
• Favorable drying conditions depend on the operating parameters and also the material properties as well.

Continuum mechanics based computational methods were used to study the heat transfer and particulate flow in an agitated filter-dryer. Numerical simulations of granular flow are presented using thermal particle dynamics. A previously developed thermal particle dynamics model was modified to include the effects of interstitial fluid, and heat transfer through liquid bridges in an agitated vessel for a three dimensional granular system. Temperature, solvent concentration, and velocity profiles obtained from the simulations were used to study the effect of operational parameters (wall temperature, impeller speed, bed depth) and particle properties. Trends observed in contact drying experiments, namely the dependence of drying rate on the driving force and effect of material properties on drying behavior, have been reproduced by the model both qualitatively and quantitatively. Apart from the operational variables, frictional characteristics of model material were also found to affect the flow patterns and hence the drying kinetics. For low friction coefficients, three dimensional recirculation zones were not formed which was confirmed from the velocity profiles obtained from simulations.