A freeze dryer is a scientific method that pre-freezes water-containing goods before sublimating their moisture in a vacuum state to produce dry items. The freeze-dried items can be preserved for an extended period of time and can be restored to their pre-freeze-drying state while retaining the original biochemical properties after adding water.

Vacuum freeze-drying technique has numerous applications in bioengineering, pharmaceutical industry, food industry, material science, and deep processing of agricultural and byproduct products, and the scale and field are continually developing. To that purpose, vacuum freeze-drying will be a significant application technology in the twenty-first century.

The structure of the Lab freeze dryer

A refrigeration system, a vacuum system, a heating system, and an electrical instrument control system comprise the freeze dryer. The drying box, condenser, refrigeration unit, vacuum pump, heating/cooling device, and so on are the essential components.

The refrigeration system, also known as the "heart of the freeze dryer," is the most critical component of the freeze dryer. Compressor, refrigerant, oil separator, water condenser, filter drier, intercooler, sight glass, solenoid valve, hand valve (top cover valve), expansion valve, evaporation (plate exchanger, rear box condensing coil), vapor-liquid separator, return air filter, pressure gauge, pressure control relay, CPCE (energy regulator), safety valve, refrigeration pipeline, and other components comprise its refrigeration system.

How does Freeze Dryer work？

Freeze drying is a drying process that works on the sublimation concept. It is a method that involves rapidly freezing dry material at a low temperature and then directly sublimating the frozen water molecules into water vapor in a suitable vacuum environment. Freezing The dried product is known as a lyophilizer, and the process is known as lyophilization.

After the liquid refrigerant absorbs the heat of the cooled material in the evaporator, it is vaporized into low-pressure and low-temperature steam, which is inhaled by the compressor, compressed into high-temperature and high-pressure steam, and then discharged into the condenser. It releases heat to the cooling medium (water or air), condenses into a high-pressure liquid, is throttled by a throttling device to a low-pressure and low-temperature liquid, and enters the evaporator again to absorb heat and vaporize.

How do I select a freeze dryer?

Many precise features must be considered while selecting a freeze drier. Customers must purchase a freeze dryer that meets their requirements. When selecting a freeze dryer, examine not only the price, but also the temperature of the cold trap, the cooling rate, the temperature homogeneity of the board, the flatness, and other indicators.

Cold Trap Temperature

A cold trap is a device that traps water during the freeze-drying process. In theory, the lower the temperature of the cold trap, the greater its ability to catch water. The experimental series freeze dryer's cold trap temperature has multiple classes, including -45°C, -60°C, and -80°C. Some items that are easily freeze-dried can benefit from freeze-drying with a cold trap temperature of -45°C. Most items can be freeze-dried using freeze-drying devices with a cold trap temperature of around -60°C. Freeze-drying with a -80°C cold trap temperature It is appropriate for the lyophilization of some specialty items. The influence of cold trap temperature on water-capturing ability was experimentally established, with the water-capturing capacity greatly increased when the temperature of the cold trap dropped from -35°C to -55°C. In the absence of unique requirements, a cold trap temperature of roughly -60 °C is an excellent choice.

Cooling Rate

The cooling rate reflects the refrigeration system's cooling capacity. The temperature of the cold trap shall reach the minimum temperature indicated in the index within 1 hour under no-load conditions. For a freeze dryer with a cold trap temperature of -60 °C, for example, the machine begins 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.

Ultimate Vacuum

The final vacuum degree shows the leaking of the freeze drier as well as the vacuum pump's pumping performance. The freeze-drying box's vacuum level. Previously, the higher the vacuum degree, the better. According to contemporary thinking, the vacuum degree should be within a tolerable range. The vacuum degree is too high, which inhibits heat transfer and slows drying, yet the no-load limit vacuum degree of the freeze-drying box should be greater than 15Pa.

Uniformity of plate temperature and flatness

The consistency and flatness of plate temperature have a significant impact on product quality uniformity. The higher the temperature uniformity and flatness, the higher the quality of the freeze-dried product. The temperature of the freeze dryer shelf can be controlled by a heater or an intermediate fluid. The temperature uniformity and flatness of the freeze dryer shelf with an intermediate fluid control layer are excellent. This layer of freeze dryer plate is a hollow sandwich structure. The cooling and heating of the plate are accomplished through the circulation of the intermediate fluid in the fluid channel within the plate, resulting in consistent plate temperature. The fluid in the centre of the shelf technology is used by the freeze dryer. The bell-type freeze dryer's shelf temperature control employs a heater, resulting in slightly poorer temperature uniformity of the plating layer. However, the temperature difference between the layers of the medical freeze dryer should be kept within 1.5 °C, and the temperature difference inside the plate should be kept within 1 °C, and the food freeze dryer can be suitably relaxed.

Summary

We can deduce from the preceding information that different types of laboratory freeze dryers should be used depending on the industry. For many years, DRAWELL has been the most successful freeze dryer producer in China, offering high-quality freeze dryers to laboratories all over the world. Please contact us if your laboratory requires a freeze dryer or other laboratory equipment; we will be your best choice.