Argon is a colorless, odorless, and tasteless noble gas that is chemically inert, resisting reaction with other substances. This non-reactive nature allows for its widespread use across various industries. As the third most abundant gas in the Earth’s atmosphere, argon is not synthesized in a lab but is extracted directly from the air. Industrial production focuses on separating this gas from the atmosphere’s other components to meet high-purity demands.
The Atmospheric Source of Argon
The raw material for industrial argon production is the air that surrounds us. Dry atmospheric air is composed primarily of nitrogen (about 78.1%) and oxygen (approximately 20.9%). Argon is the third most common gas, consistently present at a concentration of about 0.93% by volume.
This concentration is significantly higher than all other noble gases combined, making argon the most abundant rare gas commercially harvested. Argon exists as free atoms and is not chemically bonded to other elements in the atmosphere. Therefore, manufacturers must employ physical separation techniques to isolate it from nitrogen and oxygen. Argon production is intrinsically linked to the production of its more abundant co-components, nitrogen and oxygen.
The Cryogenic Air Separation Process
The industrial extraction of argon is achieved almost exclusively through cryogenic air separation, which takes place inside an Air Separation Unit (ASU). The process begins by drawing in atmospheric air, which must first undergo rigorous cleaning. Pre-treatment stages remove impurities like dust, moisture, and carbon dioxide, which would otherwise freeze and clog the machinery at the extremely low temperatures required.
Once clean, the air is compressed to a high pressure, often between 6 and 8 bars, and then cooled significantly. It is channeled through heat exchangers where it is rapidly cooled to cryogenic temperatures, typically approaching -170°C to -180°C. This rapid cooling causes the air mixture to condense into a liquid state. This liquid air mixture is the feed material for the next stage, though the individual components are not yet separated.
Isolating Pure Argon Through Distillation
The core of the separation process is fractional distillation, which exploits the slight differences in the boiling points of the liquefied gases. The liquid air is introduced into a double distillation column system, where the components separate based on their volatility. Nitrogen has the lowest boiling point (-196°C), followed by argon (-186°C), and then oxygen (-183°C).
During distillation, nitrogen vaporizes first and rises to the top of the column due to its lowest boiling point. Oxygen, with the highest boiling point, remains as a liquid at the bottom. Argon’s boiling point lies between the two, causing it to concentrate in a specific middle section of the low-pressure column, often called the “argon belly.” From this location, a concentrated stream of “crude argon” is withdrawn, which typically contains a high percentage of argon and 3% to 5% oxygen.
This crude argon stream requires further purification to meet commercial purity standards. A common technique involves a secondary distillation column to reduce the remaining oxygen. This is followed by a catalytic process where hydrogen is introduced to react with the oxygen, forming water vapor. The resulting water is then removed, yielding high-purity argon, often exceeding 99.999% purity for specialized applications.
Commercial Applications and Delivery Methods
The extraction and purification of argon is justified by its unique properties and extensive industrial demand. As an inert shielding gas, argon is heavily used in welding and metal fabrication, such as Gas Tungsten Arc Welding (GTAW) or TIG welding. It creates a protective, oxygen-free atmosphere to prevent molten metals from oxidizing. Its non-reactive nature also makes it invaluable in the electronics industry for manufacturing semiconductors and integrated circuits, providing an inert environment for processes like plasma etching and sputtering.
Beyond metallurgy and electronics, argon is utilized in lighting, filling incandescent bulbs to prevent the tungsten filament from deteriorating. It is also employed in specialized double-pane windows to enhance thermal insulation, and in food packaging to displace oxygen, extending the shelf life of perishable goods. Once produced, high-purity argon is stored and delivered to users in two primary forms.
For large-volume consumers, argon is typically stored as a cryogenic liquid in heavily insulated bulk tanks at the customer’s site. The liquid form allows for more gas to be stored in a smaller footprint. For smaller-scale users, the gas is compressed and stored in high-pressure gas cylinders or cylinder bundles. These delivery methods ensure a constant supply of the inert gas, supporting a wide range of manufacturing and specialized processes.