Four-ring freeze-drying experimental freeze-drying process mainly includes two parts: low-temperature prefreezing and vacuum freeze-drying. The drying process is actually the process of changes in the body state of water and movement. This change and movement occur under low temperature and low pressure, so it is called freeze-drying (also called freeze-drying , English for short, FD). So how long does freeze-drying take for vacuum freeze-drying, and how long does it take to lyophilize? Because the entire process of vacuum freeze-drying of the freeze-dryer is carried out under a vacuum low-temperature and low-pressure environment, it can effectively retain the thermally sensitive ingredients of the freeze-dried product. Therefore, freeze-drying usually takes about 24 hours to dry once, and the specific freeze-dried products are also different. Freeze-dried fruits and vegetables are usually crispy for more than ten hours. If it is a biological product with a low crystallization point, it usually takes more than thirty hours.
Four-ring freeze-drying experimental freeze-dryer four-ring freeze-drying machine:
1. Heating system
The function of the heating system is to heat the materials in the drying chamber, so that the materials are continuously heated and sublimated, thereby meeting 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 first heated, and the liquid temperature is automatically controlled by the temperature selected by the liquid tank control regulator. After the pipeline pump is turned on, the circulating liquid can be sent into the inner shelf of the drying box , heat the shelf, and then return to the liquid tank for heating cycle. In radiation heating, we usually use steam heating. When the circulation medium is silicone oil , the temperature of the partition can reach (+60~+70)℃.
2. Vacuum system
The vacuum system consists of vacuum pump and Roots vacuum pump . The Roots pump is an booster pump that cannot be used alone. The vacuum pump must be enabled first to make it work for a period of time. When the vacuum degree in the system reaches below 1Kpa, the Roots pump will be automatically started. See the instructions for vacuum pump structure, Roots pump structure, etc. The vacuum meter of the vacuum system can use an electrical contact vacuum meter, which can automatically control the start of the Roots pump based on the pre-selected vacuum degree value.
3. Refrigeration system
The refrigeration system consists of refrigeration compressor unit , R22 or R404a refrigerant. Usually, the quick-freezing refrigeration system and the water trap refrigeration system of the freeze-drying equipment share a refrigeration system. When the system is working, the shelf temperature can drop to -35°C during contact heating. When the refrigeration system is working, the surface temperature of the condensation coil can reach -35~-65℃. Low-temperature screw or double-stage piston refrigeration compressor units can be used according to customer needs. Usually, the dual-stage piston compressor has better cooling effect and lower refrigeration temperature
4. Electrical control system
vacuum freeze dryer electrical control system consists of automatic devices and circuits such as PLCh, touch screen, control cabinet , control instruments, and adjustment instruments. Its function is to manually or automatically control the freeze-dryer to control the normal operation of the equipment.
