Until now most of the freeze dryers are of the tray dryer type. Despite the optimal structure of the individual product particles the product layer on the plates will usually form one piece of hard baked material. Often the product has to be crushed after freeze drying, which may lead to damage of the product structure. Another disadvantage is the relatively low heat transfer rate due to the dead state of the material on the plates. The Hosokawa stirred freeze dryer enables to produce at low temperature and low pressure a lump-free, free-flowing, freeze dried product. It also has a better heat transfer rate due to the continuous mixing of the product, resulting in shortening the drying process. Furthermore the freezing step is simplified because it can be done in the same vessel instead of having a separate freezing unit, which results in easy handling of the product compared to the tray dryer equipment. The stirred freeze dryer can also be used in continuous operation. Since the dried prod-uct is released from the frozen material during the drying process, these dry particles can be collected in a filter besides the actual dryer.
cpp 438
Share:
