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1. Freeze dried area
The numbers in the model of Yetuo freeze dryer represent the freeze-drying area of that model of freeze dryer. Users should determine the required freeze-drying area based on their own needs through calculation. For example, if each batch of products requires a liquid volume of 1.8 kilograms (liters) to be freeze-dried, and materials are loaded onto material trays with a thickness of 10mm per tray, the load area of the freeze-drying board layer can be calculated as A (area, ㎡)=V (volume, m3)/H (height, m)=0.0018m3/0.01m/0.18 ㎡. Therefore, a freeze-drying machine with a board load area of 0.18 ㎡ needs to be selected.
2. Cold trap temperature
A cold trap is a device used in the freeze-drying process to capture water. In theory, the lower the temperature of the cold trap, the stronger its water capturing ability. However, a low temperature of the cold trap requires high refrigeration requirements, resulting in high machine and operating costs. The cold trap temperature of Shanghai Yetuo freeze-drying machine mainly has several levels such as -60 ℃ and -80 ℃. A freeze dryer with a cold trap temperature of around -60 ℃ is suitable for freeze-drying most products, while a freeze dryer with a cold trap temperature of -80 ℃ is suitable for freeze-drying some special products. The experiment on the effect of cold trap temperature on water capture capacity shows that when the cold trap temperature decreases from -35 ℃ to -55 ℃, the water capture capacity is significantly improved. When the cold trap temperature is below -55 ℃, the water capture capacity of the cold trap is not significantly improved. Therefore, in the absence of special requirements, choosing a cold trap temperature of around -60 ℃ is an ideal choice.
3. Cooling rate
The cooling rate reflects the refrigeration 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 Yetuo freeze dryer with a cold trap temperature of ≤ -60 ℃, the machine should start timing from the start of refrigeration, and the time for the cold trap temperature to reach -60 ℃ should not exceed 1 hour.
4. Ultimate vacuum degree
The ultimate vacuum degree reflects the leakage situation of the freeze dryer and the pumping efficiency of the vacuum pump. The vacuum degree of the freeze-drying box used to be believed to be better with a higher vacuum degree, but now the view is 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 actually decreases. However, the maximum vacuum degree of the freeze-drying box under no load should reach 2Pa or more.
5. Vacuum extraction time
The empty evacuation speed of the freeze-drying box should reach 2Pa from atmospheric pressure within half an hour.
6. Uniformity and flatness of plate temperature:
The uniformity and flatness of the layer temperature have a significant impact on the uniformity of product quality. The better the temperature uniformity and flatness, the better the uniformity of freeze-dried product quality. The temperature control of the freeze-drying machine shelf includes heater type and intermediate fluid type. The freeze-drying machine shelf with intermediate fluid control plate layer has good temperature uniformity and flatness. This freeze-drying machine plate layer is a hollow sandwich structure, and the cooling and heating of the plate layer are achieved through the circulation of the intermediate fluid in the fluid channel inside the plate layer, so the temperature of the plate layer is uniform and consistent. The shelf temperature control of the bell jar type freeze dryer basically uses heaters, and the consistency of the plate temperature is slightly poor. However, overall, the temperature difference between the layers of pharmaceutical lyophilizers should be controlled within ± 1.5 ℃, and the temperature difference inside the plates should be ± 1 ℃. Food lyophilizers can be appropriately relaxed.
7. Control system
The control system types and functions of Yetuo freeze-drying machines vary. For the experimental series of freeze-drying machines, they are mainly used for exploring the freeze-drying process of materials and small-scale trial production. Therefore, the control system should be able to display real-time freeze-drying process parameters and automatically record them; Set, modify, and effectively execute freeze-drying process procedures; Equipped with communication interfaces for easy data collection and storage.
