People often hear the term helium in industry, so what is helium? What are the uses of helium gas? Below is a detailed introduction.

Helium (He) gas is a rare inert gas with strong diffusivity, good thermal conductivity, low density, low solubility, low latent heat of evaporation, and other properties. It is inert to general chemical reactions and radioactivity. The liquefaction temperature of helium under normal pressure is -269 ℃. Liquid helium is an extremely fluid liquid, colorless, with extremely low surface tension, only 1.3 × 10N/cm, and a refractive index of 1.02. Helium does not have a triple point, and cooling helium alone cannot solidify. Solid helium can only be obtained by increasing the pressure to 2.5 MPa or above while cooling. At 2.19K, the physical properties such as density, specific heat, and thermal conductivity of liquid helium undergo a sudden change, resulting in "superfluidity" that allows liquid helium to quickly pass through capillaries with a diameter less than 10cm.

The properties of helium determine its applications in industry, technology, and national defense. Due to the inertness of helium, it is commonly used as a protective agent in high-temperature processing technologies in industry, such as special metal smelting and plasma welding. Helium and oxygen are mixed in a certain proportion to create artificial air, which can be used as breathing gas in deepwater operations and spacecraft. Helium is a refrigerant used in various fields such as low-temperature physics, low-temperature electronics, space technology, superconducting technology, etc. Helium is also used in optical instruments and the production of helium neon lasers. Filling balloons and airships with helium instead of hydrogen is safer and more reliable, and helium was also used as a fuel delivery agent in rocket and missile technology. In addition, the excellent thermal conductivity of helium makes it a thermal conductor for air-cooled nuclear reactors.

Although helium has many uses, its concentration in nature is not high. For industrial helium extraction, there are only two sources of helium: by-products from air separation and extraction from helium containing natural gas. Due to the low content of helium in the air, air separation generally produces very little helium. The helium content in natural gas containing helium is about 0.2%, much higher than that in air, and has high extraction value.

There are three methods for extracting helium from natural gas containing helium: low-temperature condensation, low-temperature washing, and membrane separation. The most commonly used methods in industry are low-temperature condensation and membrane separation.