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This | [[File:Freeze_Dryers.jpg|thumb|200px|right|Freeze Dryers]] | ||
The '''Freeze Dryers''' are mainly used for freeze dying process. The freeze dying process is widely used in recent times. Freeze-drying or commonly known as Lyophilization (executed by [[Lyophilizers]]) is a gentle, but technically complex drying process during which moisture is extracted from the frozen goods under vacuum conditions. So, many liquid active pharmaceutical ingredients for the pharmaceutical industry are quickly deep-frozen at temperatures of -70 to -100°C. Then, the frozen material is dried in a vacuum chamber. The ice evaporates at under pressure without becoming liquid - it sublimates. The water vapor is then extracted at increased vacuum and higher temperatures. For some types, the encapsulation of the glass bottles containing the ingredient is carried out under clean room conditions. Of all types of drying, freeze-drying leads to the least product changes and losses of ingredients. The Freeze Dryers operate in 3 steps: freezing, main drying, final drying. As from the second step, a vacuum pump is connected to the drying chamber to initiate the sublimation. Here, extreme parameters are reached. The vacuum sensor must withstand 5 x 10-3 mbar. This means no external particles must enter into the drying chamber, as they would contaminate the product. | |||
==='''Why Freeze Dryers are required?'''=== | |||
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. Also the handling of the product is quite labor intensive because the trays have to be filled and discharged manually. In this context active freezing came into existent. For this active freezing process a special kind of dryers were emerged named Freeze Dryers. | |||
==='''Advantages'''=== | |||
* Freeze Dryer enables to produce at low temperature and low pressure a lump-free, free-flowing, freeze dried product. | |||
* The Freeze Dryer also has a better heat transfer rate due to the continuous mixing of the product, resulting in shortening the drying process. | |||
* The freezing dryer follows such a freezing step that 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 it's predecessor tray dryer equipment. | |||
* The Freeze Dryer can also be used in continuous operation. | |||
* Since the dried product is released from the frozen material during the drying process, these dry particles can be collected separate from the actual dryer. | |||
==='''Typical Applications'''=== | |||
* Temperature sensitive materials | |||
* Delicate structured materials | |||
* Pro-biotics (bacteria as food additives) | |||
* Pharmaceuticals | |||
* Blood serum | |||
* Ultra-fine (nano) materials | |||