The freeze drying process consists of three steps
Pre-freezing, preparing samples for the next ascent process.
Primary drying, during which the ice rises without melting.
Secondary drying, during which the residual moisture of the bond and the solid matter is removed, leaving a dry sample, which is very important for preserving the stability of the sample.
In shell pre-freezing, the sample in the lyophilized bottle is immersed in a low temperature heat transfer liquid, and the liquid sample is frozen along the inner wall of the lyophilized bottle to achieve a larger surface area. This thin layer of frozen layer allows water molecules to pass through more easily. Once the sample is frozen, it can be connected to the Lyophilization Equipment system.
Primary and secondary drying occurs when the vial is attached to the Lyophilization Equipment system and the sample is immediately exposed to a vacuum condition to overcome airflow resistance. At the same time, heat is used for energy. The heat source for providing heat to other glass containers for lyophilization bottles in a dry box or manifolds is a room temperature air bath. In the case of automatic glanding, the heating layer is supplied. Conditions such as vacuum and heat help the water vapor ascending from the ice to more easily flow away from the sample and the surface of the lyophilized material.
Several factors in the freeze drying process
The efficiency of the rise of frozen samples depends on several factors. The difference between the most important frozen product and the collector. The most effective freeze-drying occurs when the sample is at the highest temperature it can withstand while still maintaining a frozen state, while the collector temperature and system vacuum are maintained at the lowest values that can be achieved. The change in drying time depends on the eutectic temperature of the lyophilized material. For most biomaterials, this temperature is below 0 °C, and some even below -40 °C. High air pressure differences and temperature differences will result in effective drying.
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