airseparation

Air separation is the industrial process of separating atmospheric air into its constituent gases, typically nitrogen and oxygen, with argon and trace amounts of neon, helium, krypton, xenon, and carbon dioxide. The principal objective is to produce high-purity gas streams for various industrial uses, such as steelmaking, chemical processing, and healthcare.

Most large-scale air separation relies on cryogenic fractional distillation of liquid air. Alternative methods include adsorption-based processes such as pressure swing adsorption (PSA) and vacuum swing adsorption (VSA), and membrane-based separations for smaller scale or specific purity requirements. In a cryogenic air separation unit (ASU), inlet air is filtered, dried, and compressed, then cooled in a series of heat exchangers and expanded to cryogenic temperatures. The clean air is liquefied and fed to high- and low-pressure distillation columns where nitrogen and oxygen are separated by their boiling points, with argon and other trace gases recovered as side streams. Typical products are gaseous nitrogen and oxygen, liquids for industrial use, and a small amount of argon.

PSA and VSA units separate oxygen from nitrogen at or near ambient temperature by selective adsorption, producing a nitrogen-rich or oxygen-rich product depending on configuration. Membrane systems use selective permeability to separate gases while consuming less energy but may provide lower purities or flow rates.

Applications span steelmaking, chemical processing, electronics, healthcare oxygen supply, inerting and blanketing, food packaging, and welding. Air separation plants are energy-intensive and depend on electricity for compression and cooling; safety considerations include high-pressure equipment and the handling of cryogenic fluids and oxidizers.