Development status and development trend of vacuum freeze dryer
Because the vacuum freeze-drying is carried out at low temperature and vacuum, the moisture in the material is directly sublimated from solid to gaseous, so the cell activity of the dried material and the color, fragrance, taste, shape and nutrient composition of the dried material can be maintained to the maximum extent, and the rehydration performance is good. Vacuum freeze-drying technology is widely used in drying and storage of various thermosensitive substances, such as the production of biological products and drugs, food freeze-drying and dehydration, storage of human tissues and organs, and preparation of superconducting materials powder. With the increasing demand for freeze-dried products, the freeze-drying equipment has also made great progress.
The working principle of vacuum freeze dryer equipment is: firstly, freeze the material below the eutectic point temperature to make the water become solid ice, then put the pre-frozen material after pretreatment into the drying bin, in the low-temperature vacuum state, heat energy is supplied by heat conduction or radiation of heating plate, so that the moisture in the material is directly raised by ice. Hua Cheng water vapor. The sublimated water vapor is pumped from the vacuum pump group into the water catcher, condensated and arrested on the outer wall of the exhaust pipe from - 40 to - 45 C, until the heating and vacuum are stopped according to the freeze-drying curve to meet the required requirements, and the whole process of material freeze-drying is completed. Vacuum freeze dryer is mainly composed of vacuum freeze drying.
Vacuum system includes vacuum drying chamber, isolation valve, water vapor trapping condenser, real rotary vane vacuum pump, connecting pipeline and vent valve. The removal of air and water vapor in the system is accomplished by a vacuum pump. When the vacuum pump is working, the isolation valve is opened, and the air and steam in the vacuum drying chamber catch water through the steam trapping condenser and enter the vacuum pump, which is discharged from the exhaust port of the vacuum pump. In order to prevent a very small amount of water vapor from entering the pump, the system valves. When refrigerating and drying, turn on the gas valve. An oil mist trap is installed at the exhaust port of the vacuum pump to prevent smoke from polluting the indoor environment.
In order to make the water vapor in frozen products sublimate continuously from ice crystals, heating system must provide enough heat for water vapor sublimation, so there must be heating system. In addition to heating plate, heating system also includes heating tank, heat exchanger, pneumatic regulating valve, circulating pump and pipeline, valve, level gauge, temperature sensor and so on. 2.4 the steam condenser of refrigeration system, also known as cold trap, is the main component of refrigeration system. Under 13. 3Pa vacuum, the ice sublimation of mass 1g can generate 100m 3 water vapor. If this large amount of water vapor is pumped out by a vacuum pump without treatment, a large capacity of pumps is needed to maintain the required vacuum. The function of the cold trap is to change the water vapor condensation and adsorption into ice in the drying chamber so as to avoid entering the vacuum pump. On the one hand, it can reduce the working load of the vacuum pump, on the other hand, it can ensure that the drying chamber has a low vacuum.
At present, there are more than 130 large-scale vacuum freeze-drying food enterprises in the world, and many factories have been invested in all parts of China, so freeze-drying equipment has great market potential. In addition, the increasing demand for freeze-dried food in the international market, China's successful accession to the WTO and China's western development strategy will have an impact on the freeze-dried food industry (for example, deeper processing of agricultural and sideline products in remote areas). It can be predicted that freeze-dried food will have a better domestic quality. Prospects for development.