Optional parameters of vacuum freeze dryer
Freeze-dried area
The number in the freeze dryer model represents the freeze-drying area of the freeze-dryer of this model. For example, the freeze-drying area of the LGJ-18C freeze-dryer is 0.18㎡. The user should determine the lyophilizer with a large freeze-drying area by calculation according to his own needs. For example, each batch needs to freeze-dried 1.8 kg (liter) of liquid volume, load the material in a material tray, and each tray is loaded with a thickness of 10mm, then the load area of the freeze-dried layer can be calculated:
A(area, ㎡)=V(volume, m)/H(height, m)=0.0018m/0.01m=0.18㎡
That is, a freeze dryer with a plate load area of 0.18 square meters needs to be selected.
cold trap temperature
The cold trap is a device for trapping water in the freeze-drying process. In theory, the lower the temperature of the cold trap, the stronger the water trapping ability of the cold trap. The cold trap temperature of the experimental series freeze dryer mainly has several grades such as about -45°C, about -60°C, and about -80°C. Freeze-drying with a cold trap temperature of -45°C is suitable for some products that are easy to freeze-dry. Freeze-drying machines with a cold trap temperature of about -60°C are suitable for freeze-drying of most products. Freeze-drying with a cold trap temperature of -80°C It is suitable for lyophilization of some special products. The effect of cold trap temperature on the water-capturing ability was experimentally demonstrated that when the temperature of the cold-trap dropped from -35°C to -55°C, the water-capturing capacity was significantly improved. Therefore, in the absence of special requirements, it is an ideal choice to use a cold trap temperature of about -60 °C.
3. Cooling rate
The cooling rate reflects the cooling capacity of the refrigeration system. Under no-load conditions, the temperature of the cold trap should reach the minimum temperature specified in the index within 1 hour. For example, for a freeze dryer with a cold trap temperature ≤ -60 °C, the machine starts timing from the time the machine is turned on for refrigeration, and the time for the cold trap temperature to reach -60 °C should not exceed 1 hour.
4. Ultimate vacuum degree
The ultimate vacuum degree reflects the leakage of the freeze dryer and the pumping efficiency of the vacuum pump. The vacuum degree of the freeze-drying box. In the past, the higher the vacuum degree, the better. The industry believes that the vacuum degree should be within a reasonable range. The vacuum degree is too high, which is not conducive to heat transfer, and the drying speed decreases, but in any case, the no-load limit vacuum degree of the freeze-drying box should reach more than 15Pa.
5. Vacuum time
The evacuation speed of the freeze-drying box with no load should be pumped from atmospheric pressure to 15Pa within half an hour.
6. Plate temperature uniformity and flatness:
The uniformity and flatness of the plate temperature have a great influence on the uniformity of product quality. The better the temperature uniformity and flatness, the better the uniformity of freeze-dried product quality. Freeze dryer shelf temperature control has heater type and intermediate fluid type. The freeze dryer shelf with intermediate fluid control layer has good temperature uniformity and flatness. This freeze dryer plate layer is a hollow sandwich structure. The cooling and heating of the plate are realized through the circulation of the intermediate fluid in the fluid channel inside the plate, so the temperature of the plate is uniform. The shelf temperature control of the bell-type freeze dryer basically uses a heater, and the temperature consistency of the plate layer is slightly worse. However, in general, the temperature difference between the layers of the medical freeze dryer should be controlled within ±1.5°C, and the temperature difference inside the plate should be ±1°C, and the food freeze dryer can be appropriately relaxed.
7. Control system
The types and functions of the control system of the freeze-drying machine are different. For the experimental series of freeze-drying machines, it is mainly used in the exploration of the freeze-drying process of materials and a small amount of trial production. Therefore, the control system should be able to display the freeze-drying process parameters in real time and record them automatically; set, modify and effectively execute the freeze-drying process procedures; and have a communication interface to facilitate data collection and storage.
