Pressure swing adsorption

It operates at near-ambient temperature and significantly differs from the cryogenic distillation commonly used to separate gases.

For example, if a gas mixture such as air is passed under pressure through a vessel containing an adsorbent bed of zeolite that attracts nitrogen more strongly than oxygen, a fraction of nitrogen will stay in the bed, and the gas exiting the vessel will be richer in oxygen than the mixture entering.

Aside from their ability to discriminate between different gases, adsorbents for PSA systems are usually very porous materials chosen because of their large specific surface areas.

Typical adsorbents are zeolite, activated carbon, silica gel, alumina, or synthetic resins.

One of the primary applications of PSA is in the removal of carbon dioxide (CO2) as the final step in the large-scale commercial synthesis of hydrogen (H2) for use in oil refineries and in the production of ammonia (NH3).

[6] This is the process used in medical oxygen concentrators used by emphysema and COVID-19 patients and others requiring oxygen-enriched air for breathing.

It allows a large reduction in the size of the adsorbent bed when high purity is not essential and when the feed gas (air) can be discarded.

[7] It works by quickly cycling the pressure while alternately venting opposite ends of the column at the same rate.

Generally, higher recovery leads to a smaller compressor, blower, or other compressed gas or vacuum source and lower power consumption.