Active Freeze Drying an ongoing innovation
Early experiments at Hosokawa Micron BV in Doetinchem, starting about 10 years ago, with a conventional vacuum dryer operated at low temperatures and ultra-low pressures showed that it was possible to operate a freeze dryer under active conditions. The result was a lump-free, free-flowing product.
Nowadays the Active Freeze Dryer consists of a dedicated designed drying chamber and collecting filter. In the chamber the material to be dried is frozen very fast with the aid of a freezing medium or jacket cooling. Typically a frozen granular structure is obtained after freezing in this way. Once the freezing step is completed the drying chamber is further evacuated. After evacuation of the eventual freezing agent the sublimation process will start. During sublimation the heat is supplied through the jacket and efficiently distributed throughout the product by the stirrer. The initially coarse granules will gradually reduce in size due to the sublimation of the connecting
