In the past ten years, the freeze-drying industry has made great progress, and its application fields have gradually expanded. In the field of life science research, lyophilization technology can be used for the research of antibodies, proteins, tissues and microorganisms, so it has been widely used in the field of biopharmaceuticals. In the pharmaceutical industry, it is widely used in the preparation of vaccines and antibiotics.
The freeze-drying method is basically carried out below 0 °C, that is, in the state of freezing the product. Only when the residual moisture content of the product is reduced in the later stage, the product is raised to a temperature above 0 °C, but generally not more than 40 °C.
Under vacuum conditions, when the water vapor sublimates directly, the drug remains in the frozen ice shelf, forming a sponge-like loose porous structure, so its volume is almost unchanged after drying. Before re-use, just add water for injection and it will dissolve immediately.
In order to make the cooling and heating temperature of the board layer uniform, most manufacturers currently use hollow sandwich boards with spacers inside, and the temperature transfer intermediate fluid circulates in the boards. The old-fashioned or backward manufacturing method is to punch a lot of holes in the upper and lower or one of the plates, and weld the metal plate and the spacer by plug welding, and then machine it.
Due to the special working conditions of low temperature, vacuum and even high temperature and pressure of the process, this welding method may leak temperature transfer fluid at the plug weld after a certain period of use. Cause the lyophilized product to be contaminated and scrapped.
The new or advanced manufacturing method is that the upper and lower metal plates are not punched, and are manufactured by special internal welding equipment, which fundamentally eliminates the occurrence of leakage.
The freeze dryer adopts the principle of sublimation to absorb water, so that the heat of the material is also reduced, so that the temperature of the material becomes lower, so that the saturated vapor pressure of the induced steam ice is reduced, and the sublimation speed is slowed down.
In order to maintain a certain sublimation rate, it is necessary to continuously add heat to the material. Too little heat supplementation will reduce the sublimation rate, and too fast heat supplementation will cause ice to melt, resulting in material collapse and freeze-drying failure.
The cold trap is used to capture water vapor and reduce the load of the vacuum pump. A properly designed cold trap will basically not cause the vacuum pump to fail, and the energy consumption is also low. However, the design requirements for the refrigeration system and cold trap are strict.
The freeze dryer not only needs to pay attention to its own function when using it, but also temperature uniformity, heating rate, vacuum stability, pumping rate and so on. Also to achieve energy saving effect:
1. Control the freezing point vacuum monotonic method
The vacuum monotonic method of controlling freezing point uses the respective advantages of freeze drying and vacuum monotonicity, and strictly controls the temperature of food close to the freezing point, but cannot freeze, which not only saves refrigeration energy consumption, but also avoids the problem of thermal denaturation of food. Damage to biological cells during the phase transition process.
2. Change the structure of the material tray
The material tray can be improved from the thermal conductivity of the tray material and the contact heat transfer surface between the material tray and the material. Selecting materials with good thermal conductivity can effectively strengthen the freezing monotonous process.
3. Control the pre-freezing speed and the loading capacity of the tray
The pre-freezing speed affects the composition of ice crystals. The faster the freezing rate is, the smaller the ice crystals are, which is not conducive to traveling.
The dehydration time is long, but it dissolves quickly after drying. The slower freezing rate has larger ice crystals, which is beneficial to monotonic dehydration, but dissolves slowly after drying. In addition, on the unit area of the material tray, the thinner the thickness of the material accumulation, the faster the heat transfer and mass transfer speed, and the shorter the monotonic time.
Application of freeze dryer Machine
Freeze dryers are widely used in medical, pharmaceutical, biological research, chemical, food and other fields.