Share on: logo linkedin



ASU is the acronym of Air Separation Unit and refers to the Air separation plant to produce industrial gases

Air separation plants produce oxygen, nitrogen and argon from atmospheric air, normally by one of three processes:

 – Non-cryogenic plants produce oxygen or nitrogen gas product from compressed air at near ambient temperature by physical adsorption.

 – Cryogenic plants can produce either high production rates of gas and/or liquid products (oxygen, nitrogen and argon) at high purity levels.

 – Membrane technology is economical for the production of nitrogen and oxygen-enriched air (up to about 40% oxygen) at small scale


Nitrogen, oxygen, and argon are the primary constituents of air for separation.

Small quantities of neon, helium, krypton, and xenon are present at constant concentrations and can be separated as products.

Varying quantities of water, carbon dioxide, hydrocarbons, hydrogen, carbon monoxide, and trace environmental impurities (sulfur and nitrogen oxides, chlorine) are present depending upon location and climate.

Non-cryogenic plants can be a cost effective alternative where a single gas only product (either oxygen or nitrogen) is required, the production is relatively low and high purity is not required.

Cryogenic plants liquefy and distill ambient air to separate it into its components. 

Standard purity levels are 99.6% pure oxygen product, 2 PPM maximum oxygen in nitrogen product, 99.999% pure argon product.

Higher purity levels are available in certain process configurations. 

 The cryogenic process can generate oxygen or nitrogen at flows of 2500 tons/day from a single plant and make the full range of products.

Air separation is a major industry. Nitrogen and oxygen rank second and third in the scale of production of commodity chemicals; and air is the primary source of argon, neon, krypton, and xenon.

Oxygen is used for steel, chemicals manufacture, and waste processing.

Important uses are in integrated gasification combined cycle production of electricity, waste water treatment, and oxygen-enriched combustion.

Nitrogen provides inert atmospheres for fuel, steel, and chemical processing and for the production of semiconductors.

For more information and data about oil and gas and petrochemical projects go to Project Smart Explorer

Scroll to Top