There are many drying methods, such as sun-drying, boil-drying, drying, spray drying and vacuum drying, etc., but common drying methods are usually carried out at a temperature above 0°C or higher. The dried products generally have the problems of reduced volume and hard texture. Most of the volatile components will be lost. Some heat-sensitive materials will be denatured and deactivated, and some materials may even be oxidized. Therefore, there is a big difference in the properties of the dried product compared to the one before drying.
First of all, understand the working principle of the freeze dryer, which is to freeze the water-containing substance at a low temperature to convert the water into ice, and then convert the ice into a vapor state under a higher vacuum, and sublimate it to remove the water and preserve the substance. the way. The so-called pre-freezing is the process of freezing products that contain a lot of water into solids.
At present, many companies are considering the use of freeze-drying technology for product production. Different companies have different characteristics and require different types of freeze-drying machines. At present, there are many manufacturers of freeze-drying machines in the world. How to choose the freeze-drying machine that suits the actual needs of the enterprise is a crucial issue. The following will list which parameters should be paid attention to when purchasing a freeze dryer:
No matter what kind of equipment, it needs maintenance after long-term use. The freeze dryer is no exception. When the freeze drying opportunities are frequently used by the enterprise, the freeze dryer can bring a lot of benefits to the enterprise, so for Extending the service life requires regular maintenance.
The freeze drying process of the freeze dryer is carried out at low temperature. Some volatile components in the material lose very little, and the growth of microorganisms and the action of enzymes cannot be carried out. Therefore, it is especially suitable for many heat-sensitive materials without denaturation or loss. Biological vitality is therefore widely used in the fields of biotechnology and medicine.
The entire process of freeze drying in a freeze dryer is actually a process of heat and mass transfer (water vapor) at the same time. The heat and mass transfer rate together affect the drying rate, thereby affecting the entire freeze drying cycle. All factors that affect heat and mass transfer Both will affect the drying rate, a simple analysis is as follows:
Compared with the traditional pilot freeze drying machine with the same freeze drying area, the laboratory vacuum freeze dryer has the advantages of small size and low price; compared with the traditional small scale freeze drying machine for the laboratory, it is easy to operate and freeze-dry on site , To avoid the pollution and tedious operation of material drying process and manual operation.
The refrigeration system of the freeze dryer is an important part. Theoretically, the refrigeration system is composed of a refrigeration compressor, a condenser, an evaporator and a thermal expansion valve. It is mainly used to provide cold energy for the pre-freezing of the products in the drying box; and for the later stage The cold trap coil captures the sublimation water vapor to supply cold energy.
The freeze dryer is composed of a refrigeration system, a vacuum system, a heating system, and an electrical instrument control system. The main components of the freeze dryer are drying box, condenser, refrigeration unit, vacuum pump, heating/cooling device, etc. The working principle of the freeze dryer is to freeze the dried items to below the triple point temperature, and then directly sublime the solid water (ice) in the item into water vapor under vacuum conditions, and remove it from the item to make the item dry. After pre-processing, the materials are sent to the quick-freezing warehouse for freezing, then sent to the drying warehouse for sublimation and dehydration, and then packaged in the post-processing workshop.