2019年5月21日星期二

Vacuum pump in vacuum drying

Vacuum pumps are widely used in vacuum drying process. The so-called vacuum drying is a kind of drying method in which the material is placed under negative pressure and the boiling point under negative pressure is appropriately reached by heating or the material is dried through the melting point after solidification by cooling. The boiling point of water in the material under negative pressure decreases with the increase of vacuum. At the same time, vacuum pump clearance dehumidification is used to reduce water vapor content, which makes the solution such as water in the material get enough kinetic energy to separate from the material surface.

Vacuum drying, because of the isolation of air under negative pressure, makes some materials which are easy to oxidize and other chemical changes in the drying process better maintain their original characteristics. It can also better protect materials by injecting inert gas and vacuum. Common vacuum drying equipment are: vacuum drying box, continuous vacuum drying equipment, etc.

The process of vacuum drying is to place the drying material in a sealed drying chamber and heat the drying material continuously while vacuuming with a vacuum system, so that the moisture in the material can diffuse to the surface through pressure difference or concentration difference. The water molecule can obtain enough kinetic energy on the surface of the material and escape to the low-pressure space of the vacuum chamber after overcoming the mutual attraction of the molecules. The process of empty pumping. In the vacuum drying process, the pressure in the drying chamber is always lower than the atmospheric pressure, the number of gas molecules is small, the density is low, the oxygen content is low, so it can dry materials which are easy to oxidize and deteriorate, inflammable and explosive dangerous goods, etc. It can play a certain role in disinfection and sterilization of drugs, food and biological products, and can reduce the chance of material contamination or inhibit the growth of some bacteria.

Because the temperature of water is proportional to the vapor pressure in the process of vaporization, the moisture in the material can vaporize at low temperature during vacuum drying, which can realize low temperature drying. This is beneficial to the drying of thermosensitive materials in some medicines, food and agricultural by-products.

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