Argon (Ar) is a colorless, odorless, tasteless, and harmless gas that exists in the atmosphere at a concentration of 0.934% by volume. Argon belongs to a class of gases known as “rare,” “noble,” or “inert” gases. Helium, neon, krypton, xenon, and radon are other gases in this class. They are monatomic gases with a completely filled outermost electron shell. The adjectives “noble” and “inert” have been used to describe materials’ inability to chemically interact with other materials. When electrically stimulated, all members of this category emit light. Argon emits a light that is pale blue-violet.
The usual boiling point of argon is -302.6°F (-185.9°C). The gas is about 1.4 times heavier than air and is just marginally soluble in water. Argon’s freezing point, -308.8°F (-199.3°C), is only a few degrees lower than its typical boiling point.
Argon is highly desired for its absolute inertness, especially at high temperatures. Argon is employed in important industrial processes such as the creation of high-quality stainless steels and the generation of impurity-free silicon crystals for the manufacture of semi-conductors. Argon is also utilized as an inert filler gas in light bulbs and as a dry, heavier-than-air or nitrogen filler between glass panels in high-efficiency multi-pane windows.
The most abundant of the truly inert or “rare” gases is argon. It is most typically generated in combination with the production of high purity oxygen via cryogenic distillation of air. Because the boiling point of argon is so near to that of oxygen (just 5.3°F or 2.9°C difference), separating pure argon from oxygen (while also obtaining good recovery of both products) necessitates multiple stages of distillation.
The most frequent argon recovery and purification procedure involved multiple processes for many decades:
1) removing a “side-draw” stream from the primary air separation distillation system at a point in the low-pressure column with the highest argon concentration,
2) processing the feed in a crude argon column, which returns the nitrogen to the low pressure column and creates crude argon
3) heating the crude argon and reacting the (usually approximately 2% oxygen impurity in the stream) with a regulated amount of hydrogen to generate water,
4) removing the water vapor by condensation and adsorption
5) Re-cooling the gas to cryogenic temperatures, and 6) distilling out the remaining non-argon components (small amounts of nitrogen and unconsumed hydrogen) in a pure argon distillation column.
Most new facilities currently use an all-cryogenic distillation process for argon recovery and purification due to the introduction of packed column technology, which allows cryogenic distillations to be performed with low-pressure-drop.
Argon is also known as “PLAR” (pure liquid argon) or “CLAR” (crude liquid argon), or by its chemical symbol, “Ar”. Crude argon is typically regarded as an intermediate product in a facility that produces pure argon, although it may also be a final product in some lesser capacity air separation plants that transport it to larger facilities for final purification. Some crude argon is also offered as a finished product for applications that do not require high purity oxygen, such as steelmaking and welding.
Commercial quantities of argon can also be produced in tandem with the production of ammonia. Although air is the ultimate source of argon, the path to argon recovery in the classic ammonia production process is considerably different. Natural gas is “reformed” with steam to create a “synthesis gas” that contains hydrogen, carbon monoxide, and carbon dioxide. “Secondary reforming” with air and steam transforms CO2 and extra hydrogen, as well as the nitrogen required to produce ammonia (NH3).
The nitrogen and hydrogen mixture (together with a trace of argon) is then compressed to high pressure and reacted with the help of a catalyst. Argon accumulates in the ammonia synthesis loop due to its non-reactivity, and it must be eliminated in a purge stream to maintain production capacity and process efficiency. UIG provides purge gas processing equipment. To increase overall process efficiency, ammonia is extracted and recovered, while hydrogen is withdrawn and recycled to the synthesis gas feed to the ammonia process. Methane produced during the ammonia process is recycled as fuel for the fired heater, which provides heat to power the synthesis gas generating process. Argon is recovered and cleaned before being sold commercially.
Some contemporary ammonia facilities do not use air directly as a feed to the ammonia production process, instead passing it through an air separation unit, with the argon eliminated upstream of the ammonia synthesis loop. The air separation unit’s high quality oxygen and nitrogen supply streams are fed separately to the ammonia plant’s hydrogen and ammonia producing sections. This innovative way to ammonia production prevents argon buildup in the ammonia synthesis loop and enables for direct recovery of argon as a valuable co-product.
here’s a table summarizing some important properties of Argon:
| Property | Value | Units |
|---|---|---|
| Symbol | Ar | |
| Atomic Number | 18 | |
| Atomic Mass | 39.948 | g/mol |
| Density | 1.784 | kg/m³ |
| Melting Point | 83.80 | K |
| Boiling Point | 87.30 | K |
| Phase at STP | Gas | |
| Group | 18 (Noble Gas) | |
| Period | 3 | |
| Block | p | |
| Electron Config | [Ne] 3s² 3p⁶ | |
| Electronegativity | – | |
| Heat of Fusion | 1.18 | kJ/mol |
| Heat of Vapor. | 6.53 | kJ/mol |
| Specific Heat | 0.52 | J/(g·K) |
| Abundance | 9.4 x 10^-3 | % in Earth’s crust |
Please keep in mind that the values displayed here are approximations and may change depending on the source. Because noble gases such as argon do not form chemical bonds, some values, such as electronegativity, are unavailable.
| Application/Use | Description |
|---|---|
| Welding | Argon is a shielding gas that is extensively used in welding operations, particularly Tungsten Inert Gas (TIG) and Gas Metal Arc Welding (GMAW). It protects the weld from impurities in the air and minimizes oxidation. |
| Lighting | Argon is utilized in a variety of lighting applications, such as fluorescent tubes, neon lights, and high-intensity discharge (HID) lamps. When combined with other gases or materials, it enables electrical discharges and creates light. |
| Laser Technology | Argon is a laser medium used in gas lasers such as argon-ion lasers. These lasers produce strong beams in the visible and ultraviolet ranges and are widely employed in scientific, medical, and industrial applications. |
| Cryogenics | Cryogenic applications use argon to provide a low-temperature environment for cooling and storing biological samples, superconducting magnets, and other materials. |
| Purging and Inerting | Argon is utilized in a variety of sectors to displace or purge air or other gases from equipment and containers, so generating an inert atmosphere and preventing combustion, oxidation, or contamination. |
| Metallurgy | Argon is used in the manufacture of reactive metals and alloys. It can also be used to prevent oxidation and maintain a clean surface during certain metallurgical operations such as annealing and heat treatment. |
| Scientific Research | Argon is used in laboratories for research that require an inert environment, as well as spectroscopic examinations and the calibration of analytical instruments. |
| Insulation | Because of its lower thermal conductivity, argon is occasionally employed as an insulating gas in double-pane windows, giving superior thermal insulation than air. |
| Fire Suppression | Argon has been utilized as a substitute to Halon and other more environmentally hazardous chemicals in some fire suppression systems. |
Multi-Industry Uses of Argon
Argon is the least priced and most abundant fully inert gas. It is utilized in situations where a completely non-reactive gas is required.Pure argon, as well as argon mixed with other gases, is used as a shield gas in TIG welding (“tungsten inert gas” or gas tungsten arc welding) with a non-consumable tungsten electrode, and in MIG welding (“metal inert gas”, also known as gas metal arc welding, or wire feed welding) with a consumable wire feed electrode. The shielding gas’s purpose is to protect the electrode and weld pool from the oxidizing influence of air. Pure argon is frequently used in conjunction with aluminum. For MIG welding of conventional structural steel, a combination of argon and carbon dioxide is frequently employed. When utilized with a specific torch, plasma-arc cutting and welding use plasma gas (argon and hydrogen) to provide an extremely high temperature.
Metals Manufacturing Uses of Argon
Steel is created in a converter by blowing oxygen and argon into the molten metal. The use of argon decreases chromium losses while achieving the appropriate carbon content at a lower temperature. To avoid the production of nitrides, argon is employed as a blowing gas during the fabrication of higher quality steels. Argon is also employed as a shield gas in ladle casting and stirring. Argon is used in the manufacturing of titanium as an inert gas to prevent oxidation and reactivity with nitrogen (titanium is the only metal that would burn in a 100% nitrogen atmosphere). The element argon is utilized in the production of zirconium.
Manufacturing and Construction Uses of Argon
Argon is utilized in fluorescent and incandescent light bulbs as a filler gas. This eliminates oxygen and other reactive gases, lowering the evaporation rate (sublimation rate) of the tungsten filament and allowing for higher filament temperatures. At a pressure of 70 kPa (10.15 psig), the most typical mixture is 93% argon and 7% nitrogen.
It is employed as a filler gas between the glass panels of high-efficiency thermo pane windows because it is not only dry and colorless, but also a relatively heavy gas that reduces heat transmission between panels through slower convective movement of the filler gas in the window.
Electronics Uses
Argon is utilized in the semiconductor industry as a filler gas with methane and as a high purity inert shield gas in the production of silicone and germanium crystals.
Food and Beverages Uses
Argon is used in winemaking to displace oxygen in barrels, preventing vinegar production. Similarly, it is used in restaurant, bar, and home wine dispensing machines to allow for the storage of opened bottles without causing the contents to deteriorate.
Health Care Uses
Argon is utilized in cryosurgery, which is the use of intense cold to selectively eliminate small regions of damaged or aberrant tissue, most notably on the skin. Controlled expansion of argon gas produces very cold argon at the site, which is guided to the treatment spot through a cryoneedle. This gives better process control than previous systems that used liquid nitrogen. Cryoablation, a related method, is used to treat heart arrhythmia by killing cells that interfere with the natural dispersion of electrical impulses.
Miscellaneous Uses
Argon is utilized to offer a protective environment for historic papers in storage and while they are on display.
Liquid Argon Temperature
| Pressure (kPa) | Boiling Point (K) | Boiling Point (°C) | Boiling Point (°F) |
|---|---|---|---|
| 101.325 | 87.30 | -185.85 | -302.53 |
| 200 | 85.41 | -187.74 | -305.93 |
| 400 | 80.86 | -192.29 | -314.13 |
| 600 | 76.31 | -196.84 | -322.33 |
| 800 | 71.76 | -201.39 | -330.53 |
| 1000 | 67.21 | -205.94 | -338.73 |
Please keep in mind that the boiling point of liquid Argon lowers with decreasing pressure. The values in this table are estimates and may differ significantly depending on the data source used.
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