Drying characteristics of porous material immersed in a bed of glass beads fluidized by superheated steam under reduced pressure

In this study, relatively large material was immersed in the superheated steam fluidized bed of glass beads and the effect of operational conditions such as the pressures in the drying chamber (reduced pressure), temperature and mass velocity of the drying gas on the drying characteristics were examined experimentally and theoretically. In a part of study, the conventional superheated steam drying was also performed and the results were compared with those of superheated steam fluidized bed drying.The drying time is much shorter in the case of superheated steam fluidized bed drying than in the case of conventional superheated steam drying, and the drying time becomes shorter as the pressure in the drying chamber decreases. The sample temperature during drying is almost equal to the boiling point of water even in the case of superheated steam fluidized bed drying i.e., the sample temperature becomes lower as the pressure in the drying chamber decreases. The drying progresses when the temperature of the drying gas is higher than the boiling point of water, i.e., the temperature of the drying gas needed for the drying becomes lower as the pressure in the drying chamber decreases. The effect of mass velocity of the drying gas is small when the fluidization state is sufficiently vigorous.