2. Helium purification

2.1 Impurities in helium

Prior to liquefaction, helium must be freed of impurities to prevent them from clogging the plant as they solidify during cooling. The main impurities contained in helium depend on its origin:

• when helium has been extracted from natural gas, the impurities it contains are essentially water, nitrogen, hydrocarbons, neon and hydrogen;

• when the helium to be liquefied comes from the recovery of vapors from liquid helium vaporized in laboratories, the impurities it contains are mainly water and air gases. If the helium has been recompressed at high pressure using lubricated compressors, it may also contain hydrocarbons, carbon dioxide and carbon monoxide, the latter two resulting from...