Convective drying of porous material containing a partially miscible mixture

Non-hygroscopic capillary porous bodies were dried by convection to investigate the influence of a two-phase moisture on the drying characteristics. The samples were wetted with the ternary liquid mixture 2-propanol/water/1-butanol. This system forms two liquid phases at low propanol concentrations. The drying rate is not significantly influenced by a two-phase moisture. Selectivity is influenced by the drying conditions as well as the characteristics of the capillary porous body. In the two-phase region selectivity can be shifted most effectively by the temperature of the drying air and by the pore size of the porous body. Selectivity can even inverted if the initial moisture composition is close to the boundary line. In the porous body a moisture profile, as well as a concentration profile, was measured. (C) 1999 Elsevier Science S.A. All rights reserved.