Non-Isothermal Convective Drying of Solids Wetted with Multicomponent Liquid Mixtures

The non-isothermal convective drying of an impermeable solid substrate covered with multicomponent solvent mixture was studied. The aim was to simulate the nonsteady-state evaporation process under the control of both the gas side heat and mass transfer, and in the presence of diffusional resistances in the liquid layer. Diffusional interactions in both phases were accounted for by applying the generalized Fick's formulation of diffusion with a temperature and composition dependent matrix of multicomponent diffusivities. In the experimental part, a teflon substrate covered with the ternary mixture ethanol-methylethylketone-toluene was dried using air flowing parallel to the evaporation surface as drying agent. Good agreement was obtained between experiments and simulations. Calculations show that liquid composition, liquid temperature, gas composition and diffusional interactions have a significant influence on the instantaneous selectivity while the effect of gas temperature and gas velocity is less important. Selectivity can be controlled by using a gas preloaded with an appropriate composition.