Air Fractionation by Adsorption

Pressure swing adsorption (PSA) processes for air separation differ by the modes and conditions of operation of the adsorption, the desorption, and the complementary steps, as well as by the types of adsorbents used. Three commercial PSA processes for air separation are reviewed and compared. The first process uses a zeolitic adsorbent and produces only an oxygen-enriched product gas. The second process uses a carbon molecular sieve and produces only a nitrogen-enriched product gas. The third process uses a zeolite and simultaneously produces both oxygen-and nitrogen-enriched product gases. The performance and separation efficiency of the last process, called the ‘vacuum swing adsorption (VSA) process’, are reported to be superior to the others.