The steps of freeze drying processing

The working principle of a freeze dryer, also known as a lyophilizer, is based on the process of sublimation. Sublimation is the transition of a substance directly from the solid phase to the gas phase, without passing through the liquid phase.

The basic steps involved in the working principle of a freeze dryer are as follows:

Freezing:

The material to be dried is placed in the freeze dryer's drying chamber.
The material is cooled to a very low temperature, typically between -40°C to -80°C, using a refrigeration system.
This low temperature causes the water content in the material to freeze, forming ice crystals.

Vacuum creation:

The drying chamber is then sealed and a vacuum is created inside using a vacuum pump.
The vacuum lowers the pressure in the chamber, typically to a range of 0.1 to 0.001 mbar.

Sublimation:

The low pressure and low temperature in the drying chamber cause the ice crystals to sublimate directly into water vapor, bypassing the liquid phase.
The water vapor is then removed from the drying chamber and condensed on a refrigerated condenser or cold trap, which is kept at a temperature lower than the drying chamber.

Drying:
As the water is removed from the material through sublimation, the material becomes progressively drier.
The drying process continues until the desired level of dryness is achieved.

The main advantages of the freeze-drying process include:

Preservation of the original structure and properties of the material, as the material is not exposed to high temperatures.
Efficient removal of water without causing damage to heat-sensitive materials, such as pharmaceuticals, biological samples, or food products.
Improved shelf-life and stability of the dried products.
Ease of reconstitution, as the dried material can be easily rehydrated by adding water.

Freeze dryers are widely used in various industries, such as pharmaceuticals, biotechnology, food processing, and scientific research, where the preservation of delicate and sensitive materials is crucial.