Development status and development trend of vacuum freeze dryer
Because vacuum freeze dryer is carried out at low temperature and vacuum, the moisture in the material is directly sublimated from solid to gaseous, so it can maximize the cell activity of the dried material, as well as the color, fragrance, taste, shape and nutrient components of the dried material, and has good rehydration performance.
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-drying 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, under the low temperature and vacuum state, heat energy is supplied by the heat conduction or radiation mode of heating plate, so that the moisture in the material is sublimated directly from ice. 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 (referred to as freeze-dryer) mainly consists of vacuum freeze-drying vacuum system, including vacuum drying chamber, isolation valve, water vapor trapping condenser, real rotary vane vacuum pump, connecting pipeline and exhaust 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.
Steam condensers, also known as cold traps, are the main components of refrigeration systems. 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. 2.5 the automatic control system of the automatic control system is the command organization of the freeze dryer.
The control of freeze dryer includes the start and stop of refrigerator and vacuum pump, the control of heating temperature, the test and control of material temperature, cold trap temperature, vacuum degree, automatic protection and alarm device, etc. The function of the automatic control system is to measure and display the important parameters of the freeze-dryer. According to the pre-set, the freeze-dryer can be accurately controlled so that it can run in the prescribed state and alarm the failure state and deal with the emergency automatically. By measuring and recording the technological parameters of freeze-drying process, the whole freeze-drying process can be fully understood. By effectively controlling these parameters, the optimization of the whole freeze-drying process can be realized, that is, improving production efficiency and reducing energy consumption on the premise of ensuring product quality.