The vacuum freeze dryer is designed based on the transformation and upgrading of the existing conventional vacuum drying and oven, which is mainly composed of two parts: a refrigeration system and a vacuum system. Its working principle is the principle of vacuum drying. By freezing the wet material to the eutectic point temperature, the moisture in the material becomes solid ice, and then in a higher vacuum environment, by heating the material, the ice is directly sublimated into water vapor, then the water vapor condenser in the vacuum system will condense the water vapor, so as to achieve the purpose of dehydration and drying of the material.
The operating procedures of the vacuum freeze dryer are as follows:
I. The surface area of the prepared sample should be expanded as much as possible, and it must not contain acid-base substances and volatile organic solvents. The sample must be completely frozen into ice because any residual liquid will cause vaporization jets. Note that the cold trap is about minus 65 degrees and can be used as a low-temperature refrigerator, and insulation gloves is required when operating it to prevent frostbite.
II. Before starting the vacuum pump, check whether the water outlet valve is tightened, whether the inflation valve is closed, and whether the contact surface between the organic glass cover and the rubber ring is free of dirt and well sealed.
III. Start the refrigerator to pre-cool for more than 30 minutes. Put the sample into the sample rack, cover the organic glass cover, and start the vacuum pump. After the air pressure is stable, record the temperature and air pressure.
IV. During the freezing process, the temperature of the sample gradually decreases. Therefore, the sample can be taken out to warm up for a period of time (still in a frozen state), and then continue drying to shorten the drying time.
V. Record the temperature and air pressure value before the vacuum freeze dryer stops.
VI. Turn off the vacuum pump and press the inflation valve on the control panel. When the air pressure is displayed as atmospheric pressure, open the organic glass cover and take out the sample.
VII. Turn off the refrigerator, press and hold the main switch for more than three seconds, and finally turn off the main power switch. After the ice in the cold trap is completely transformed into water, open the water outlet valve on the left side of the chassis to drain the water, and clean the inner wall of the cold trap with a dry cloth, and cover it with a large piece of filter paper to prevent dust.
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