Freeze drying is a method to remove moisture from water-containing substances by freezing them into solid state in advance and then sublimating the moisture from the solid state into gaseous freeze dryer equipment under vacuum. The original chemical and biological characteristics of the articles obtained by the drying method are basically unchanged, and the articles are easy to store for a long time; after being added with water, the articles can be restored to the form before freeze-drying, and the original biochemical characteristics can be maintained; therefore, the drying method is a high-quality drying method.
Freeze drying technology has been widely used in chemical industry, food, materials, medicine, biological products and other fields. Vacuum freeze dryer (abbreviated as freeze dryer) is a kind of equipment for realizing freeze drying technology. It is a kind of machine with complicated structure. It involves knowledge in refrigeration, vacuum, thermal engineering, machinery, fluid, electrical control and pressure vessel, etc.
- Classification of Quick Freezing Equipment
The performance indexes pursued by quick-freezing equipment are small volume, light weight, multiple functions, stable performance and high accuracy of testing system. It is a multi-purpose machine and can adapt to freeze-drying experiments of various materials. The main classification methods of quick freezing equipment include:
Bell-type freeze dryer: the freeze-drying chamber and the cold trap are of separate upper and lower structures, and the freeze-drying chamber has no pre-freezing function. This type of freeze dryer requires manual operation when the material is transferred to the drying process after pre-freezing. Most of the experimental freeze dryers are bell-type, with simple structure and low cost. Most of the freeze-drying chambers use transparent organic glass covers to facilitate observation of the freeze-drying of materials.
L in-situ freeze dryer: the freeze-drying chamber and the cold trap are two independent chambers. the shelf in the freeze-drying chamber has refrigeration function. after the material is placed in the freeze-drying chamber, manual operation is not required in the process of pre-freezing and drying the material. This type of freeze dryer has complex manufacturing process and high manufacturing cost. However, in-situ freeze dryer is the development direction of freeze dryer and is the ideal choice for freeze drying process exploration. It is especially suitable for freeze drying of medicine, biological products and other special products.
A, common type b, manifold type c, gland type
Ordinary shelf type: the material is in bulk in the material tray, suitable for freeze-drying of food, Chinese herbal medicine and powder materials.
Device with gland: suitable for drying vials of penicillin. during freeze-drying preparation, the materials shall be packed in vials as required, and freeze-drying shall be carried out after the cap is floating. after drying, the gland mechanism shall be operated to compress the cap, which can avoid secondary pollution and reabsorption of water and is easy for long-term storage.
With pre-freezing function: during the pre-freezing process of materials, the cold trap is used as the pre-freezing chamber to pre-freeze the materials. during the drying process, the cold trap is used as a water catcher to capture the water overflowing from the materials. The freeze dryer with pre-freezing function, the pre-freezing and drying of materials in the freeze drying process are all completed on the freeze dryer, the use efficiency of the freeze dryer is high, and the cost of a low-temperature refrigerator is saved.
Multi-manifold type: the flask is connected to the outside of the drying chamber to dry the materials that are frozen on the inner wall of the flask. at this time, the flask is connected to the manifold outside the drying oven as a container. the materials in the flask are heated at room temperature. through the multi-manifold switch device, the flask can be removed or installed at any time as required without shutdown.
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