Luftfrånskiljning

Luftfrånskiljning, or air separation, is the set of industrial processes used to separate atmospheric air into its constituent gases, primarily nitrogen, oxygen, and argon. It underpins many manufacturing sectors by providing gases with defined properties for processes and protective atmospheres.

The most common methods are cryogenic distillation of liquefied air, membrane separation, and adsorption-based technologies such as pressure swing adsorption (PSA) and vacuum swing adsorption (VSA). Cryogenic distillation involves cooling and compressing air to cryogenic temperatures so it becomes a liquid. The liquid is separated in a distillation column by differences in boiling points, producing high-purity nitrogen or oxygen streams; argon is often obtained as a byproduct or via additional steps. This method is energy-intensive but enables very high purities, suitable for steelmaking, petrochemicals, and electronics.

Membrane systems rely on selectively permeable polymers to separate gases; they are compact and energy-efficient for moderate purities and flow rates, often used for nitrogen generation and oxygen enrichment at smaller scales. PSA and VSA use adsorbent materials to preferentially hold certain gases at specific pressures, producing nitrogen- or oxygen-enriched streams in compact packages; these are widely used for on-site gas generation in hospitals, industries, and food packaging.

Applications include inert atmospheres for metal fabrication and chemical processing, purging and blanketing, oxygen for combustion and medical use, nitrogen for inerting and packaging, and argon for welding and electronics.

Safety considerations cover the handling of cryogenic liquids, asphyxiation risk in enclosed spaces with inert nitrogen, and oxygen enrichment hazards in confined areas. History highlights the development of large-scale cryogenic air liquefaction and subsequent advances in membrane and adsorption technologies.