The principle and characteristics of vacuum drying

    The process of vacuum drying is to place the material in a sealed container, apply a vacuum and heat the material at the same time, so that the water inside the material diffuses to the surface through the pressure difference or concentration difference between the inside and outside of the material, and the water molecules escape after obtaining sufficient kinetic energy on the surface of the material. The process of getting into the vacuum chamber and being pumped away by the vacuum pump.

    In the vacuum drying process, the pressure in the drying chamber is always lower than atmospheric pressure, the number of gas molecules is small, the density is low, and the oxygen content is low, so it can dry materials that are prone to oxidation and deterioration, and flammable and explosive dangerous goods. It can play a certain disinfection and sterilization effect on medicines, foods, and biological products, reduce the probability of bacterial infection of materials, or inhibit the growth of bacteria.

    Because the temperature of water in the vaporization process is proportional to the vapor pressure, the moisture in the material can be vaporized at low temperature during vacuum drying, and low-temperature drying can be achieved. This is beneficial to the drying of heat-sensitive materials in certain medicines, foods and agricultural and sideline products. In addition, drying at low temperature has a relatively low utilization rate of heat energy, which can realize energy saving and environmental protection.

    Vacuum drying can eliminate the surface hardening phenomenon that is easy to occur during normal pressure drying. The pressure difference between the inside and outside of the vacuum drying material is relatively large. Under the action of the pressure gradient, the water quickly moves to the surface without surface hardening. At the same time, it can improve the drying efficiency, shorten the drying time, and reduce the operating cost of the equipment.

    Vacuum drying can easily recover the useful or harmful substances lost in the material, and can achieve good airtightness.

    Although vacuum drying equipment has many advantages, it needs to be equipped with a vacuum system and also to prevent vacuum leakage. The equipment is expensive to manufacture and expensive to operate.

(huiputech)