SELECTIVE DRYING OF HYGROSCOPIC MATERIALS WETTED WITH BINARY-MIXTURES

Drying experiments were carried out in a laboratory apparatus with differently hygroscopic materials wetted with binary mixtures. Composition curves were determined under variation of the drying conditions, the sample thickness, and the drying method. The results obtained are presented and compared with those of non-hygroscopic materials. In particular, the interactions between moisture and solid when using strongly hygroscopic products influence the composition curve from the very beginning of the drying process, contrary to weakly hygroscopic materials, where the selectivity is controlled by the sorption equilibrium only at the end of the drying process. A method to calculate the selectivity in knowledge of the binary adsorption equilibrium is given. For this purpose, it is necessary to split the total moisture into a free and a bounded share.