Freeze drying, also known as freeze drying, is a dehydration process, usually used to preserve perishable materials or make materials easier to transport.
The principle of freeze-drying is to freeze the material first, then reduce the surrounding pressure, so that the frozen water in the material can sublimate directly from the solid phase to the gas phase.
Freeze drying main advantages:
1. Freeze dried products can be stored at ambient temperature
2. Compared with other dehydration methods with higher temperature, the damage to substances is less: especially the color and shape
3. Generally, it will not cause the shrinkage of the material to be dried (it will not reduce the volume)
4. Freeze drying, because the processing of frozen products can be carried out throughout the year (no seasonal impact)
Vacuum freeze-drying is a better method for dehydration of substances. It can freeze the freeze-dried substances in advance, and then sublimate the moisture of substances under low temperature and pressure to achieve the purpose of dehydration. The sublimated water vapor is collected by condensation. After the vacuum freeze-drying operation, the material becomes dehydrated.
After vacuum freeze-drying, the enzyme action of the material is weak, the original chemical and physiological properties are basically unchanged, the dried material is porous structure, the volume is basically unchanged, easy to recover. Especially, the material after vacuum freeze-drying can be preserved for several years without deterioration.
The condenser is used to condense the sublimated water vapor. Its working overflow can reach – 45 ℃ ~ – 60 ℃. The cooling source is provided by two 2f6.3 freon refrigeration units.
The vacuum unit of the dryer is composed of two 2XZ type rotary vane mechanical vacuum pumps and one roots type mechanical booster pump. The vacuum unit is connected with drying box and condenser through vacuum pipeline and vacuum valve to form a sealed vacuum system. The vacuum unit is equipped with electric contact vacuum gauge, which can automatically control the start of roots pump according to the pre selected vacuum level.
A vacuum butterfly valve is installed in the vacuum pipeline between the drying box and the condenser, which can be opened and closed at any time according to the use requirements. The bottom of the condenser is equipped with a branch vacuum pipeline to the hot air blower, and the middle valve is separated by a 50 butterfly valve. The valve and the branch pipeline are used for defrosting and drying of the condenser. The vacuum branch pipe on the roots pump is the path when the mechanical vacuum pump is used alone, and the upper part is equipped with a solenoid valve. When the roots pump is started, the width will automatically close. The vacuum pipeline is equipped with the electromagnetic belt air release stop valve. When the vacuum pump stops, the vacuum pipeline can be automatically closed. At the same time, the air will be put into the pump to prevent the vacuum pump oil from rushing into the vacuum pipeline due to the negative pressure. A corrugated hose is arranged between the connecting pipes of the vacuum pump to prevent the vibration from being transmitted to its components during operation.