Freeze drying is a method of drying items at low temperatures, and the process includes the following steps:
1.Pre-freezing. Prefreezing is an important step in the lyophilization process to convert the moisture in an item from a liquid state to a solid state. This process entails placing the item in a freeze dryer for freezing. In order to ensure the freezing effect of the item, it is necessary to add the appropriate refrigerant such as liquid nitrogen or dry ice to the freeze dryer. During the pre-freezing process, the temperature of the item drops rapidly, allowing the moisture to change from a liquid state to a solid state.
2.Vacuuming.
Once the pre-freezing is complete, the temperature and pressure in the freezer are rapidly reduced, allowing the moisture in the item to change from a solid state to a gaseous state. In this process, the gas from the lyophilizer is pumped out to reduce the pressure. This step is done using a vacuum pump.
3.Dry. During the vacuuming process, the water in the item is gradually evaporated, and this process is drying. During this process, the temperature and pressure in the freeze dryer need to be kept within a certain range so that the moisture in the item can be evaporated. At the same time, it is also necessary to ensure that the item will not crack or deform due to drying.
4.Resolve drying.
When the moisture in the item is evaporated, the dryness of the item reaches a relatively high level. However, if you want to dry the item completely, you also need to do analytical drying. This process involves adding an appropriate desiccant to the lyophilizer, such as high-purity nitrogen or inert gas. These desiccants can help items further remove residual moisture and other impurities.
5.Finish drying.
After analytic drying, the item is completely dry. At this point, you can turn off the freeze dryer and remove the items. It should be noted that the item needs to be placed at room temperature for a slow temperature rise after being taken out to avoid cracking or deformation due to excessive temperature changes.
In conclusion, freeze drying is a very complex process that requires multiple steps and operations to complete. At the same time, in order to ensure the drying effect and quality of the items, strict control and monitoring are required throughout the process.