Drying is a very important industrial operation in society. In drying, solute may dissolve in an aqueous solvent, a nonaqueous solvent or a mixture of solvents. Many mathematical models have been published previously to model drying of solute in water. The reaction engineering approach (REA) is known to be an easy-to-use approach. It can describe well many drying cases of water removal. Currently, no simple lumped model has been attempted to describe drying of porous materials containing a mixture of solvents. In this study, for the first time, REA is constructively implemented to model drying in a mixture of one aqueous and one nonaqueous solvent. The REA is applied here to model the drying of polyvinyl alcohol/methanol/water under constant and time-varying environmental conditions. Similar to the relative activation energy of water, that of methanol is generated through one accurate drying run. For modeling the time-varying drying, the relative activation energies are the same as those for modeling convective drying under constant ambient conditions but combined with the equilibrium activation energies at the corresponding humidity, methanol concentration, and temperature for each drying period. The REA is accurate to model drying of a solute in nonaqueous solvent as well as in a mixture of noninteracting solvents. In the future, spatially distributed REA for nonaqueous or mixtures of both aqueous and nonaqueous solvent will be explored for fundamental understanding and for practical application.
- Reaction engineering approach