The freeze-drying process of a square shaped freeze-drying machine (usually referring to freeze-drying equipment using square shaped compartments) is the process of sublimating and removing moisture from materials through low temperature and vacuum environment. The following are typical freeze-drying process steps suitable for square chamber freeze dryers:
1. Preprocessing stage
Sample preparation: Firstly, materials (such as food, drugs, cells, etc.) need to be pre treated. This may include cleaning, cutting, blending, etc. to ensure that the material is suitable for freeze-drying.
Freezing treatment: Quickly freeze the material to a temperature below its freezing point (usually between -40 ° C and -80 ° C) to form solid ice. The lower the freezing temperature, the better the freezing effect.
2. Sublimation stage (main drying stage)
Vacuum environment establishment: Place the frozen material into the square chamber of the freeze dryer, and use a vacuum pump to reduce the air pressure inside the chamber to a lower level (usually 0.1-0.2 mbar). In this vacuum environment, water no longer exists in liquid form, but directly transforms from ice to water vapor, known as the sublimation process.
Heating process: While maintaining low temperature, gradually heat the sample through a heat source (such as jacket heating or radiation heating). The heating temperature should be strictly controlled, generally not exceeding -20 ° C to -40 ° C, to avoid structural damage to the sample during sublimation due to excessive temperature.
Sublimation rate control: At this stage, it is necessary to control the sublimation rate to ensure that the structure and composition of the sample are not affected. Excessive sublimation rate may cause surface freezing or morphological changes in the sample.
3. Drying stage (sub drying stage)
Continuing to heat up: As sublimation progresses, the moisture content in the material gradually decreases. When entering the secondary drying stage, the temperature can be slightly increased, but it still needs to be maintained within a range where the material will not be damaged.
Maintain low vacuum: During the secondary drying stage, the vacuum environment continues to be maintained at a lower pressure to promote the removal of residual moisture. At this point, the moisture changes from the solid state of the sample to gas and is recovered through a condenser.
4. Condensation and dehumidification
Condensation system: The water vapor removed from the material is converted back into ice in the condenser, and after cooling, the frozen water no longer returns to the sample. This is an important step in the freeze-drying process to ensure that moisture does not re-enter the material.
Dehumidification process: After condensation, the moisture is discharged from the system and further removed by heating the pipes inside the dryer until the set drying target is achieved.
5. Thawing and packaging
Thawing stage: After freeze-drying is completed, the sample is taken out of the square warehouse. If it is medicine, food or other materials, they usually need to be thawed to restore their original form and function.
Packaging: After freeze-drying, materials are usually sealed to prevent moisture absorption, contamination, and other issues, maintaining long-term stability and effectiveness. During the packaging process, it is necessary to avoid high temperature and humid environments.
Notes:
Temperature and pressure control: In the freeze-drying process, temperature and pressure need to be strictly controlled. Excessive temperature may cause changes in sample structure or loss of thermosensitive components.
Differences in sample properties: Different types of samples require different time and conditions during the freeze-drying process, such as differences in freeze-drying processes for food, drugs, and cells.
The square chamber freeze dryer is commonly used in large-scale production environments due to its large processing capacity and uniform freeze drying effect. Adjusting appropriate freezing, sublimation, and drying parameters is key to ensuring the effectiveness of freeze-drying.