How to choose the type of adsorbent for Sichuan pressure swing adsorption oxygen production equipment

The adsorption performance of adsorbents for various gas components is evaluated by experimentally measuring the isothermal adsorption curve under static conditions and the outflow curve under dynamic conditions. The good adsorption performance of adsorbents is a fundamental condition for the adsorption separation process.

In the process of pressure swing adsorption, the choice of adsorbent should also consider resolving the contradiction between adsorption and desorption. For example, for strong adsorbates such as benzene and toluene, weaker adsorbents such as silica gel should be used to achieve appropriate adsorption capacity and facilitate desorption operations. For weakly adsorbates such as methane, nitrogen, carbon monoxide, etc., it is necessary to use adsorbents with strong adsorption capacity, such as molecular sieves, in order to achieve a larger adsorption capacity. Another key point in selecting adsorbents is to maximize the separation coefficient between components.

When a certain component reaches adsorption equilibrium, the total amount in the adsorption bed consists of two parts: one part is in the dead space; The other part is adsorbed by the adsorbent. The total amount is called the retention of a component in the adsorption bed. The ratio of the amount of weakly adsorbed component and strongly adsorbed component contained in the dead space to the remaining amount in the adsorption bed is called the separation coefficient. The larger the separation coefficient, the easier the separation. The separation coefficient of the two components separated in pressure swing adsorption should not be less than 2.

The main components in the air are nitrogen and oxygen, so adsorbents with different adsorption selectivity for nitrogen and oxygen can be selected, and appropriate processes can be designed to separate nitrogen and oxygen to produce oxygen. Both nitrogen and oxygen have a quadrupole moment, but the quadrupole moment of nitrogen (0.31 Å) is much larger than that of oxygen (0.10 Å), so nitrogen has a stronger adsorption capacity on zeolite molecular sieves than oxygen. When air passes through an adsorption bed containing zeolite molecular sieve adsorbent under pressure, nitrogen is adsorbed by the molecular sieve, and oxygen is enriched in the gas phase and flows out of the adsorption bed due to less adsorption, separating oxygen and nitrogen to obtain oxygen.

At present, the common VPSA oxygen adsorbent includes LiLSX lithium based adsorbent and 5A oxygen adsorbent. LiLSX lithium based adsorbent has good performance, long service life, and good sulfur resistance; Ordinary 5A adsorbents have poor performance, large dosage, and short lifespan, and require desulfurization (desulfurizers need to be replaced regularly).

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