Principle, application and operation of freeze-drying machine

Laboratory freeze-drying machine, as one of the indispensable equipment in modern laboratories, plays an important role in many fields such as biomedicine, food science and environmental testing with its unique drying method. This paper aims to deeply discuss the basic principles, main application scenarios, operation guidelines, maintenance and maintenance of laboratory freeze-drying machines, and provide a comprehensive and practical reference manual for scientific researchers.

 

Laboratory freeze-drying machine, the full name of vacuum freeze-drying machine, its basic principle is based on the change of three states of water. Water exists in nature in three forms: solid, liquid and gas, and under certain temperature and pressure conditions, these three forms can be converted into each other and coexist. Freeze-drying machine is the use of this principle, in the state of high vacuum, through sublimation, so that the water in the pre-frozen material does not go through the liquid stage, directly sublimed from solid to gas, so as to achieve the purpose of drying. Specifically, the lyophilization process includes three stages: freezing, sublimation and analytical drying. In the freezing stage, the sample is exposed to low temperatures so that the water inside it gradually solidifies into ice crystals. This step is usually performed in the temperature range of -40 ° C to -60 ° C to ensure that all the moisture in the sample can be converted to solid ice. Subsequently, in the sublimation stage, the sample is transferred to a vacuum drying chamber, where the ice crystals directly change from solid to gas (i.e., sublimation) without going through the liquid phase. This process needs to be carried out at a low pressure (usually less than 100Pa) and at an appropriate temperature (close to the sublimation point of ice, about -25 ° C to 0 ° C) to promote the rapid sublimation of water molecules. Finally, in the analytical drying stage, the temperature is further increased and the pressure is reduced to promote the further sublimation and removal of residual moisture in the sample to obtain a completely dried sample.

Laboratory freeze-drying machines are widely used in many fields, especially in biomedicine, food science and environmental testing and other fields play an important role.

► Biomedical field

In the field of biomedicine, laboratory freeze-drying machines are widely used in the preparation of vaccines, sera, antibodies, enzymes, cell cultures and other biological products. Through freeze-drying technology, these biological products can be preserved for a long time and maintain their original activity and stability. This is particularly important for biochemical reagents and biological products that need to be stored at low temperatures, as lyophilization technology can effectively extend their shelf life while avoiding the effects of high temperatures on the substance and oxidation, thereby maintaining the long-term stability of the dried product.

► Food science field

In the field of food science, laboratory freeze-drying machines are used to make a variety of ready-to-eat foods, dried fruits, dried vegetables, dairy products, etc. Freeze-dried food not only maintains the original color, aroma, taste and nutritional composition, but also has a light texture and is easy to carry and store. This is extremely convenient for outdoor adventures, travel and daily eating. At the same time, freeze-drying technology can also extend the shelf life of food and meet consumers' high standards for food quality and taste.

► Environmental testing field

In the field of environmental testing, laboratory freeze-drying machines are used to preserve and analyze environmental samples such as soil, water and biological samples. Through freeze-drying technology, the water in the sample can be removed, reducing microbial activity, and thus extending the storage time of the sample. At the same time, lyophilization can also maintain the integrity and stability of samples, and provide reliable data support for environmental monitoring and pollution research.

 

► Preparations Before Startup

Before using a laboratory freeze-drying machine, a series of preparations are required. First, check that all parts are in good condition and clean. Secondly, make sure that the barometric display shows the normal atmospheric pressure. Then, start the chiller and pre-cool it for at least 30 minutes. During the pre-cooling process, check whether the outlet valve is tightened, whether the charging valve is closed, and whether the contact surface between the plexiglass cover and the rubber ring is clean and free of dirt to ensure a good seal.

► Sample placement and start-up

Place the pre-frozen sample into the sample rack and cover with plexiglass. Note that the sample must be completely frozen into ice, otherwise residual liquid may lead to vaporizing ejection. Then start the vacuum pump, and record the temperature and pressure before stopping. Before starting the vacuum pump, check the device status again to ensure that everything is normal.

► Monitoring the freeze-drying process

During the freeze-drying process, it is necessary to always pay attention to the temperature and vacuum state of the equipment. Ensure equipment is always in optimal working condition for optimal drying results. At the same time, frequent switching of the total power supply and refrigerator should be avoided, so as not to damage the equipment or affect the freeze-drying effect. If the refrigerator stops running due to operation error, wait at least 20 minutes before restarting.

► Sampling and Shutdown

After freeze-drying, slightly press and hold the charge valve of the control panel, wait for the pressure to rise, and then close the vacuum pump. When the barometric number returns to atmospheric pressure, open the plexiglass cover and remove the sample. Be careful to avoid contamination or damage to the sample during the sampling process. After sampling is complete, turn off the chiller and the main switch, and finally turn off the main power switch. Wait for the ice in the cold trap to melt completely, then open the water valve and drain the water, and clean the inner wall of the cold trap with a dry cloth.

 

 

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In order to maintain the good performance and extend the service life of the laboratory freeze-drying machine, regular maintenance and maintenance are required. Here are some key care and maintenance tips:

► Inspection and replacement of lubricating grease

The grease replacement cycle of the freeze-drying machine is affected by the temperature of the compression end. If the compression end temperature is high, the replacement cycle of the lubricating oil should be appropriately shortened. Under normal circumstances, the lubricating oil should be checked once every 10,000 hours of continuous operation. When the compressor is first run, it is recommended to change the lubricating oil and clean the oil filter in 2000 hours of operation. When checking and replacing lubricating oil, avoid exposing the air for a long time because the freeze-drying machine has water absorption.

► Vacuum pump oil replacement

When the accumulated working time of the vacuum pump reaches 200 hours or the color of the vacuum pump oil turns brown, the vacuum pump oil must be replaced. This can ensure the normal operation of the vacuum pump and extend its service life.

► Equipment cleaning and disinfection

After each use of the freeze-drying machine, the equipment should be cleaned and disinfected in time to avoid cross infection. Pay special attention to cleaning plexiglass cover and silicone sealing ring and other easily contaminated parts. At the same time, it should be regularly checked whether there is foreign matter or dirt accumulation inside the equipment and cleaned up in time.

► Ambient Temperature and Humidity Control

The ambient temperature and humidity of the freeze-drying machine should be kept within the appropriate range to ensure the normal operation of the equipment and extend the service life. It is recommended that the ambient temperature be kept between 10 ° C and 30 ° C and the relative humidity be less than 80%. At the same time, the distance between the freeze-drying machine and the wall should be greater than 30cm to ensure good ventilation and heat dissipation.

► Periodic Check and Maintenance

Regular and comprehensive inspection and maintenance of the equipment, including checking the power lines, control systems, vacuum systems and refrigeration systems are working properly. If any problem is found, handle it in time and record maintenance logs for follow-up tracking and resolution.