argon

Argon

Argon (Ar) is a noble gas that comprises 0.93 percent of the earth's atmosphere. (Noble gases are a group of rare gases that include argon, helium, krypton, neon, xenon and sometimes radon. They exhibit great stability and extremely low reaction rates. Also called inert gases.

Colorless, odorless, tasteless and nontoxic, argon forms no known chemical compounds. A specific gravity of 1.38 makes argon 25 percent heavier than air. At atmospheric pressure, it becomes a liquid at -302° F (-186° C). Non corrosive and non-flammable, argon also exhibits low thermal conductivity and slight solubility in water.

Production of Argon

A co-product of oxygen and nitrogen production, argon is manufactured commercially by means of air separation technology. In a cryogenic process, atmospheric air is compressed and cooled. Following liquefaction, the air is fractionally distilled based on the different boiling points of each component. (The boiling point of argon is between those of nitrogen and oxygen.)

During distillation, liquid nitrogen is the first product extracted from the high-pressure column. Next, a stream containing oxygen and argon (plus other gases) is withdrawn. The crude stream, containing approximately 10 percent argon, is refined in a separate distillation column to produce argon with 98 percent purity.

Manufacturers can further refine the stream by mixing the argon with hydrogen, catalytically burning the trace oxygen to water, drying and, finally, distilling the stream to remove remaining hydrogen and nitrogen. Using this process, producers can achieve an argon product with 99.9995 percent purity.

Applications

Argon is used in diverse applications covering a number of industries, including:

  • aluminium to replace air or nitrogen, creating an inert atmosphere conducive to manufacturing aluminium; to assist in the removal of unwanted soluble gases during de gasification; and to remove dissolved hydrogen and particulates from molten aluminium.
  • Steel to displace gas or vapors and prevent oxidation during processing; to obtain temperature consistency and homogenous composition by stirring molten steel; to assist in the removal of unwanted soluble gases during de gasification; as a carrier gas, to determine the composition of a sample through gas chromatography; and to flush out carbon monoxide and reduce chromium losses in the Argon-Oxygen Destabilization (A.O.D.) used during stainless steel refining.

Argon Mixtures

Argon-CO2 mixtures are slow gasses with low diffusion, and are therefore used sometimes for high precision chambers. These mixtures are free of hydrocarbons, and are therefore fairly safe with respect to ageing in high rate environments. Other Mixtures are as follows:

(i) Ar + Co2
1. 86 : 14 Mix
2. 92 : 8 Mix
(ii) Ar + N2
1. 86 : 14 Mix
2. 90 : 10 Mix
(iii) Ar+He

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