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How to choose a suitable freeze dryer?

Technical Knowledge 2019-03-31 15:48:32
The principle of a freeze dryer is a technical method of preliminarily freezing an aqueous article and then sublimating its water under vacuum to obtain a dried article. The freeze-dried articles are easy to store for a long time, and can be restored to the state before lyophilization and retain the original biochemical characteristics after adding water.

A lyophilizer is a device that provides a frozen environment for materials that is primarily used to make biological products and store biological products. With the continuous development of biotechnology, more and more companies are investing in the manufacturing of freeze dryers. When selecting freeze dryers, it is necessary to conduct a comprehensive inspection of their overall performance to ensure that the equipment meets the needs of production. Here are some things to keep in mind when choosing a freeze dryer:

1. Freeze-dried area

The user should calculate the freeze dryer according to his own needs to determine the lyophilized area. Taking water as an example, each batch needs to be lyophilized by 1.2 kg (liter), and the material is loaded with the material tray. When each tray is loaded with 10 mm thick, the load area of the freeze-dried 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 freeze dryer is divided into -50 ° C, -80 ° C (also customized according to user needs). 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, in a freeze dryer with a cold trap temperature of ≤ -50 ° C, the machine should be timed from the time of opening the refrigeration, and the time of the cold trap temperature reaching -50 ° C should be no more than 1 hour.

4. 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. Generally, the vacuum limit of the freeze-drying box should reach 15Pa or more.

5. Vacuuming time

The evacuation speed of the freeze-drying tank at no load should be completed within half an hour from atmospheric pressure to 15Pa.

6. Laminate 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. The freeze dryer layer is a hollow sandwich structure, and 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 TF-SFD series production lyophilizer is based on this structure. The shelf temperature control of Tuo TF-FD series experimental freeze dryers is basically based on heaters, and the temperature uniformity of the lamellar layer is slightly poor. Generally, 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 experimental freeze dryer, it is mainly used for the lyophilization process of materials and a small amount of trial production. 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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