Simple analysis of the working principle and basic characteristics of lyophilizer

　　The lyophilizer originated from the vacuum freeze-drying technology in the 1920s and entered the 21st century. The vacuum freeze-drying technology has been widely used in fields other than medicine, biological products, food, blood products, and active substances. The basic principle of freeze-drying is based on the three-state change of water. Water has a solid state, a liquid state, and a gas state, and the three states can both switch between each other and coexist.
　　When water is at the triple point (temperature is 0.01 ℃, water vapor pressure is 610.5Pa), water, ice and water vapor can coexist and balance each other. Under the high vacuum state, the principle of sublimation is used to make the water in the pre-frozen material be directly sublimated into water vapor without being melted by ice, so as to achieve the purpose of freeze drying. The freeze-dried products are sponge-shaped, without shrinkage, excellent rehydration, and very little water content, after corresponding packaging, they can be stored and transported at normal temperature for a long time. Since vacuum freeze drying has unparalleled advantages of other drying methods, the technology has been more and more popular since the advent of the technology.
　　Freeze-drying is a technique that uses the principle of sublimation to dry. It is a process of quickly freezing the dried substance at low temperature, and then in a suitable vacuum environment, the frozen water molecules are directly sublimated into a process of water vapor escape. The product obtained by freeze-drying is called lyophilisate, and this process is called lyophilization. The material is always at a low temperature (frozen state) before drying, and the ice crystals are evenly distributed in the material. The sublimation process will not be concentrated due to dehydration, which avoids the side effects of foaming and oxidation caused by steam.
　　The dry substance is porous and dry, the volume is basically unchanged, and it is easily dissolved in water and restored to its original state. To prevent the physical and chemical and biological denaturation of dry matter to the greatest extent. The lyophilizer is composed of refrigeration system, vacuum system, heating system, electrical instrument control system. The main components are drying oven, condenser, freezing unit, vacuum pump, heating / cooling device, etc. Its working principle is to freeze the dried items to below the triple point temperature, and then to directly sublimate the solid water (ice) in the items into water vapor under vacuum conditions, and remove them from the items to dry the items.