Vacuum contact drying of mechanically agitated beds: The influence of hygroscopic behaviour on the drying rate curve

Abstract This paper reports on a theoretical and experimental investigation on the vacuum contact drying of agitated particulate material containing free as well as hygroscopic moisture. The penetration model is extended in order to account for the influence of bounded moisture on the drying rate. To this purpose an effective heat capacity of the bed, taking into account the sorption equilibrium, is introduced. Calculations are compared to measured drying rate curves. The measurements have been made in a disc dryer, using a molecular sieve as the model material.