Institute on Membrane Technology (CNR-ITM), Italy
Vacuum Membrane Dryers (VMDrs) are new membrane operations designed for the recovery of dry compounds from aqueous feeds. In this work, VMDrs development and application were reviewed and discussed. Flat and capillary membrane modules with feed recirculation and in static configuration (feed in contact with one side of the membrane without recirculation) were compared. VMDRs in static configuration were applied to the treatment of aqueous suspensions of 10 wt % polystyrene microparticles (size ranging from 0.3 micron to 7 micron) at 30°C and 4 mbar, and to the treatment of aqueous solutions of caffeine (concentration ranging from 0.1 wt % to 0.3 wt %) at 45°C and 4 mbar. In both cases, a 0.2 micron polypropylene flat membrane was used. Dry solids (polystyrene) and crystals (caffeine) were obtained, together with distillates free of solids and crystals. For the two case studies, the drying efficiency and main differences were underlined. Finally, benefits of VMDRs and further research needed were presented.