Rare technical gases are widely used in industrial production. Our air separation units can produce pure argon, neon-helium mixture for further process into pure neon and helium; and xenon-krypton mixture for further process into pure xenon and krypton using special equipment.
The most popular technology – is argon production by further distillation of the reflux remaining from the production of oxygen and nitrogen. This technology requires high financial investments, as it is an extension of the existing cold block with additional argon distillation columns. However, it is important to note that it is impossible to complete the set of existing cold block with argon production because for doing this it is required to change the configuration of the main heat-exchange unit, actually, it means to re-fabricate a cold box.
When producing argon and rare technical gases, it should be noticed that the part of argon in atmospheric air is 1/125, and the part of rare technical gases is much less, that is:
Ne content in the air — 18 ppm
He content in the air — 5,3 ppm
Kr content in the air — 1,14 ppm
Xe content in the air — 0,086 ppm
That is why production of rare technical gases from atmospheric air is worthwhile only in case of oxygen production in significant volumes (for example 30 000 Nm3/h and more), because in this case rare technical gases production will also have significant volumes.
Obtained in the previous section liquid nitrogen is used for neon-helium mixture production. Liquid nitrogen and nitrogen under pressure from the upper part of the lower column are fed to the column of crude Ne-He mixture for distillation, obtained crude Ne-He mixture is collected at the top of the column. Liquid nitrogen divides into two branches from the bottom part of the crude Ne-He mixture column. One branch reverses and is used as a source of cold for Ne-He mixture production, the other branch goes to the subcooler.
Obtained in the previous section liquid oxygen is used for xenon-krypton mixture production. Liquid oxygen from the bottom part of the upper column is fed to the column of the Kr-Xe pure mixture production for its distillation. Most of the liquid oxygen evaporates in the column and then returns to the upper column of the main ASU. Liquefied pure Kr-Xe mixture is produced in the bottom part of the lower column of pure Kr-Xe mixture production.