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The freeze-drying process of four-ring lyophilization experimental freeze dryer mainly includes two parts: low temperature pre-freezing and vacuum freeze drying, the drying process is actually the process of water state change and movement, this change and movement occurs at low temperature and low pressure, so it is called freeze drying (also called freeze drying, English abbreviated FD) So how long does it take for vacuum freeze drying in the freeze dryer, and how long is the general freeze drying? Because the whole process of vacuum freeze drying of the lyophilizer is carried out in a vacuum low temperature and low pressure environment, it can effectively retain the heat-sensitive components of the lyophilized product, so freeze drying once generally takes about 24 hours, the specific lyophilized products are also different, freeze-dried vegetables and fruits are generally crispy for more than ten hours, if it is a biological product with low crystallization point, it generally takes thirty hours
.
Four major components of the four-ring freeze-drying experimental freeze dryer: 1.
Heating system The function of the heating system is to heat the materials in the drying silo, so that the materials are continuously heated and sublimated, so as to meet the specified moisture content requirements
.
In contact heating, the circulating medium heating method is used, when the heating system is working, the circulating liquid is heated first, the liquid temperature is automatically controlled by the temperature selected by the liquid tank control regulator, after the pipeline pump is opened, the circulating liquid can be sent into the shelf in the drying box, the shelf is heated, and then returned to the liquid tank for heating cycle
.
In radiant heating, we usually use steam heating, when the circulating medium is silicone oil, the temperature of the separator can reach (+60~+70) °C
.
2.
Vacuum system The vacuum system is composed of vacuum pump and roots vacuum pump, roots pump for booster pump can not be used alone, to first use the vacuum pump, so that it works for a period of time, when the vacuum degree in the system reaches below 1Kpa, and then automatically start the roots pump
.
The structure of the vacuum pump, the structure of the roots pump, etc.
are shown in the manual
.
The vacuum gauge for the vacuum system uses an electrical contact vacuum gauge to automatically control the start-up of the roots pump according to a pre-selected
vacuum degree value.
3.
Refrigeration system The refrigeration system is composed of
a refrigeration compressor unit, R22 or R404a refrigerant.
Usually the quick-freezing refrigeration system of the lyophilization equipment and the refrigeration system of the water trap share a common refrigeration system
.
When the system is operating, the shelf temperature can be reduced to -35°C
in the contact heating method.
When the refrigeration system is working, the surface temperature of the condensing coil can reach -35~-65 °C, and the low-temperature screw or double-stage piston refrigeration compressor unit can be adopted according to customer needs, usually the two-stage piston compressor has a better refrigeration effect and a lower refrigeration temperature 4.
Electrical control system The electrical control system of vacuum freeze dryer is composed of PLC, touch screen, control cabinet, control instrument, adjustment instrument and other automatic devices and circuits
.
Its function is to manually or automatically control the lyophilizer and control the normal operation
of the equipment.