Types and functions of adsorbents for drying machines

Types and functions of adsorbents for drying machines

The working principle of the suction dryer (also known as the adsorption dryer) is to reduce the moisture content in the compressed air by using the characteristics of the adsorbent to absorb moisture. Generally speaking, the pressure dew point of the outlet air of the suction dryer reaches -20℃~-70℃ . Common adsorbents for drier are activated alumina, silica gel, molecular sieve, etc., and when the drier is to obtain extremely dry compressed air (the dew point is below -60℃), molecular sieve is the choice of world.

　　Activated alumina

Activated alumina, also known as activated alumina, is called Activated Alumina or Reactive alumina in English. It is a porous, highly dispersed solid material with a large surface area and its microporous surface has the characteristics required for catalysis , Such as adsorption performance, surface activity, excellent thermal stability, etc., so it is widely used as a catalyst and catalyst carrier for chemical reactions.

　　 Activated alumina has selective adsorption capacity for gas, water vapor and some liquid moisture. After the adsorption is saturated, it can be revived by heating at about 175-315°C to remove water. Adsorption and resurrection can be performed multiple times. In addition to being used as a desiccant, it can also adsorb the vapor of lubricating oil from polluted oxygen, hydrogen, carbon dioxide, natural gas, etc. It can also be used as catalyst and catalyst carrier and chromatography carrier.

　　Activated alumina has a pressure swing adsorption dew point of -55 degrees in the air separation industry.

Silica gel

　　 Silica gel (Silica gel; Silica) alias: Silicone rubber is a highly active adsorbent, which is an amorphous substance, and its chemical formula is mSiO2·nH2O. The chemical composition and physical structure of silica gel determine that it has many other similar materials that are difficult to replace: high adsorption performance, good thermal stability, stable chemical properties, and high mechanical strength.

　　 molecular sieve

　　 Molecular sieve refers to a class of materials with uniform micropores and the pore size is equivalent to the general molecular size. Molecular sieves are widely used and can be used as high-efficiency desiccants, selective adsorbents, catalysts, ion exchangers, etc. Compared with other adsorbent materials, the most important feature of molecular sieve is that it has a uniform diameter of microporous structure, so it can selectively adsorb gaseous molecules with a diameter smaller than its pore size.

　　Molecular sieves are generally synthesized artificially. In the air drying (separation) process, more molecular sieves are polyhydrate crystals of zeolite aluminosilicate. Its thermal stability and chemical stability are very high, and it also has the characteristics of screening performance, ion exchange performance, unity of selection and good adsorption performance. It is usually used in the adsorption chamber of adsorption dryer.