Argon is a noble gas that is widely used in industry. It is highly inert and is neither flammable nor supportive of combustion. In the aircraft manufacturing, shipbuilding, nuclear energy, and machinery industries, argon is commonly used as a shielding gas when welding special metals such as aluminum, magnesium, copper and their alloys, as well as stainless steel. It helps prevent the welded materials from being oxidized or nitrided by the surrounding air.
In metallurgical applications, argon-oxygen blowing is an important process for producing high-quality steel. The typical argon consumption is approximately 1–3 m³ per ton of steel produced. Argon is also required as a protective gas in the smelting of special metals such as zirconium, titanium, and germanium, as well as in the electronics industry.
Argon accounts for approximately 0.932% of atmospheric air. Its boiling point lies between those of oxygen and nitrogen. In an air separation unit (ASU), argon reaches its highest concentration in the middle section of the upper distillation column, forming what is known as the crude argon fraction. During the separation of oxygen and nitrogen, this argon-rich fraction can be withdrawn and further separated and purified to produce argon as a by-product.
For a low-pressure air separation unit, approximately 30–35% of the argon contained in the processed air can generally be recovered as a product. With advanced process configurations, the argon recovery rate can be increased to more than 80%.
For a medium-pressure air separation unit, since the expansion air is introduced into the lower column and does not affect the rectification process in the upper column, the argon recovery rate can reach approximately 60%.
However, for small-scale air separation units, the total amount of processed air is relatively limited, and therefore the amount of argon that can be produced is also limited. Whether an argon extraction and purification system should be installed depends on the specific plant capacity, product requirements, and economic considerations.
