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What should I pay attention to when purchasing a freeze dryer?

Technical Knowledge 2019-02-27 15:52:18
The main uses of modern freeze-drying technology are: freeze-drying storage of in vitro biological tissues; freeze-drying preservation of live bacteria; lyophilization of Chinese herbal medicines, western medicines, biological drugs and blood products; freezing of convenience foods, health foods, functional foods Dry storage and transportation; lyophilization preparation of nano ceramic materials and various metal micropowder materials. Therefore, freeze-drying technology has been widely used in the fields of chemicals, food, materials, medicine, and biological products. Vacuum freeze dryer (referred to as freeze dryer) is a device for realizing freeze-drying technology. It is a complex structure machine involving refrigeration, vacuum, thermal, mechanical, fluid, electrical control and pressure vessels.

Several parameters that should be paid attention to when purchasing a freeze dryer:

1. freeze-dried area

The number in the lyophilizer model represents the lyophilization area of the lyophilizer of this model. For example, the lyophilized area of the FD-1A-50 lyophilizer is 0.12 m2. The user should calculate the lyophilizer to be used according to his own needs. For example, for each batch of products that need to be lyophilized by 1.2 kg (liter) of liquid, and the materials are loaded with the material tray, each loaded with 10 mm thick, the load area of the lyophilized layer can be calculated:

A (area, m2) = V (volume, m3) / H (height, m) = 0.0012 m3 / 0.01 m = 0.12 m2

A lyophilizer with a laminar load area of 0.12 m2 is required.

2. cold trap temperature

The cold trap is a device for capturing moisture in the freeze-drying process. Theoretically, the lower the temperature of the cold trap, the stronger the water trapping ability of the cold trap, but the lower the temperature of the cold trap, the higher the cooling requirement, the higher the machine cost and the running cost. The cold trap temperature of the experimental series freeze dryer mainly has several grades of about -50 °C and -80 °C. Freeze-drying at -50 °C is suitable for some freeze-dried products. Freeze-drying at -80 °C is suitable for lyophilization of some special products. The effect of cold trap temperature on water-trapping capacity shows that the temperature of the cold trap drops from -35 °C to -55 °C, and the water-trapping capacity is improved significantly. The cold trap temperature is lower than -55 °C, and the water trap capacity of the cold trap is not significantly improved. Therefore, in the absence of special needs, the choice of cold trap temperature of about -50 °C is the ideal choice.

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 indicator within one hour. For example, a lyophilizer with a cold trap temperature ≤ -50 ° C, the machine starts timing when the refrigeration is turned on, and the cold trap temperature reaches -50 ° C for no more than 1 hour.

4. the ultimate vacuum

The ultimate vacuum reflects the leakage of the freeze dryer and the pumping efficiency of the vacuum pump. The degree of vacuum of the freeze-drying box, the past view that the higher the degree of vacuum, the better, the current view that the degree of vacuum should be within a reasonable range. The degree of vacuum is too high, which is not conducive to heat transfer, but the drying speed is reduced, but the vacuum limit of the freeze-drying box should reach 15Pa or more.

5. vacuum time

The emptying speed of the freeze-drying box should be pumped from atmospheric pressure to 15Pa within half an hour.

6. the layer temperature uniformity and flatness

The uniformity and flatness of the lamellar temperature have a great influence on the uniformity of product quality. The better the temperature uniformity and the flatness, the better the uniformity of the quality of the freeze-dried product. The lyophilizer shelf temperature control has a heater type and an intermediate fluid type, and the freeze-drying machine shelf with the intermediate fluid control plate layer has uniform temperature uniformity and flatness, and the lyophilizer layer is a hollow sandwich structure, the slab layer The cooling and heating are achieved by circulating the intermediate fluid in the fluid channel inside the ply, so the ply temperature is uniform. The  freeze dryer in the four-ring freeze dryer uses the technology of the intermediate fluid in the shelf. The shelf temperature control of the bell-type freeze dryer is basically a heater, and the temperature uniformity of the layer is slightly poor. However, in general, the temperature difference of the lyophilizer for medical use should be controlled at ±1.5 °C, the temperature difference within the plate is ±1 °C, and the food freeze dryer can be appropriately relaxed.

7. control system

The type and function of the control system of the freeze dryer are different. For the freeze dryer of the experimental series, it is mainly applied to the lyophilization process of the material and a small amount of trial production. Therefore, the control system should display the parameters of the freeze-drying process in real time and record automatically; set, modify and effectively execute the freeze-drying process program; have a communication interface to facilitate data collection and storage.

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