1. Freeze-dried area
The number in the lyophilizer model represents the lyophilized area of this model of lyophilizer. For example, the lyophilized area of the FD-18 laboratory lyophilizer is 0.18 square meters. Users should determine how much freeze drying area the freeze drying machine needs by calculation according to their own needs. For example, each batch of products that needs to be freeze-dried 1.8 kilograms (liters) of liquid, and the material tray is loaded with materials, and each tray is loaded with 10 mm thickness, 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㎡
It is necessary to select a freeze dryer with a load area of 0.18 square meters.
2. Cold trap temperature
The cold trap is a device that captures moisture during the freeze drying process. In theory, the lower the temperature of the cold trap, the stronger the water trapping capacity of the cold trap. However, the lower the temperature of the cold trap, the higher the requirement for refrigeration, the higher the machine cost and the operating cost. The cold trap temperature of a series of laboratory freeze dryers mainly has several grades such as -45℃, -60℃, and -80℃.
freeze drying with a cold trap temperature of -45°C is suitable for some products that are easy to freeze-dry, a freeze drying machine with a cold trap temperature of -60°C is suitable for most products, and a freeze drying machine with a cold trap temperature of -80°C Suitable for freeze drying of some special products.
The effect of cold trap temperature on water trapping capacity experiments showed that the cold trap temperature dropped from -35℃ to -55℃, and the water trapping capacity improved significantly. The cold trap temperature was lower than -55℃, and the water trapping capacity of the cold trap was not significantly improved. Therefore, in the absence of special requirements, it is an ideal choice to choose 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 by the index within 1 hour. For example, for a freeze dryer with a cold trap temperature ≤ -60°C, the machine starts counting from when the refrigeration is turned on, and the time for the cold trap temperature to reach -60°C should be no more than 1 hour.
4. Ultimate vacuum
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, the past view is that the higher the vacuum degree, the better, the current view is that the vacuum degree should be within a reasonable range. The vacuum is too high, which is not conducive to heat transfer, and the drying speed drops instead, but in any case, the no-load ultimate vacuum of the freeze drying box should reach more than 15Pa.
5. Vacuum time
The emptying speed of the lyophilized box should be pumped from atmospheric pressure to 15Pa within half an hour.
6. Temperature uniformity and flatness of the board
The uniformity and flatness of the slab 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. The freeze dryer shelf temperature control has a heater type and an intermediate fluid type. The freeze dryer shelf adopts the intermediate fluid control layer with good temperature uniformity and flatness. The layer of the freeze dryer has a hollow sandwich structure. Both cooling and heating are realized by circulating the intermediate fluid in the fluid channel inside the plate layer, so the plate layer temperature is uniform.
7. Control system
The control system of the freeze dryer has different types and functions. For freeze dryers applied to the freeze drying process of materials and a small amount of trial production, the control system should be able to display the freeze drying process parameters in real time and automatically record; set, modify and Effectively execute the freeze drying process; it has a communication interface to facilitate data collection and storage.