STEAM DRYING OF PRODUCTS CONTAINING SOLVENT MIXTURES

Drying experiments with single, porous spheres wetted with mixtures of 2-propanol and water were performed using superheated steam, air, or steam-air mixtures as drying agent. Both the drying rate and the moist ure composition were determined experimentally for different temperatu res and compositions of the drying agent and for different initial com positions of the moisture. It is shown that evaporation of 2-propanol is enhanced by using superheated steam as drying agent instead of air due to steam condensing on the sample. While the overall drying rate i ncreases with rising steam temperature, the evaporation rate of 2-prop anol is hardly affected. When drying samples containing mixtures of 2- propanol and water, internal boiling can occur depending on the vapor- liquid equilibrium. Vapor generated inside the sample may cause mechan ical dewatering of the sample which greatly increases the drying rate.