Sichuan variable pressure adsorption oxygen plant adsorbent type how to choose

      The adsorption performance of the adsorbent on each gas component is evaluated by experimentally determining the isothermal adsorption curve under static condition and the outflow curve under dynamic condition. Good adsorption performance of the adsorbent is the basic condition for the adsorption separation process.

      In the variable pressure adsorption process adsorbent selection should also be considered to solve the contradiction between adsorption and desorption. For example, for benzene, toluene and other strong adsorbents should be used for its adsorption capacity is weaker adsorbent, such as silica gel, in order to make the adsorption capacity is appropriate, but also conducive to the desorption operation. For weak adsorbents such as methane, nitrogen, carbon monoxide, etc., it is necessary to choose the adsorbent with stronger adsorption capacity such as molecular sieve, etc., in order to adsorption capacity. Another important point of selecting adsorbent is that the separation factor between components should be as large as possible.

      A component adsorption equilibrium, the total amount in the adsorption bed has two parts: one is in the dead space; the other part of the adsorbent adsorption. The sum is called the retention of a component in the adsorption bed. Weakly adsorbed components and strong adsorption components contained in the dead space of the respective amount of retention in the adsorption bed of the ratio of the ratio is called the separation coefficient. The larger the separation factor, the easier the separation. The separation coefficient of the two components to be separated in variable pressure adsorption should not be less than 2.

      The main components in the air are nitrogen and oxygen, so we can choose the adsorbent with different adsorption selectivity for nitrogen and oxygen, and design the appropriate process to separate nitrogen and oxygen to make oxygen. Both nitrogen and oxygen have quadrupole moments, but the quadrupole moment of nitrogen (0.31 Å) is much larger than that of oxygen (0.10 Å), so the adsorption capacity of nitrogen on zeolite molecular sieve is stronger than that of oxygen. When air passes through the adsorption bed equipped with zeolite molecular sieve adsorbent under pressure, nitrogen is adsorbed by the molecular sieve, and oxygen, due to less adsorption, is enriched in the gas phase and flows out of the adsorption bed, which separates oxygen and nitrogen to obtain oxygen.

     At present, the common VPSA oxygen adsorbents are LiLSX lithium-based adsorbent and 5A oxygen adsorbent. LiLSX lithium-based adsorbent has good performance, long service life, and good sulphur resistance; the common 5A adsorbent has poor performance, large dosage, short service life, and needs to be desulphurised (desulphurisation agent needs to be replaced regularly).