Helium Production
Helium Production
Helium is extracted by from natural combustible gas. Dried gas, purified from CO2, is supplied to heat exchanger and separator system. Since helium has a lower boiling point than any other element, low temperature and high pressure are used to liquefy nearly all the other gases (mostly nitrogen and methane) resulting in crude helium gas purified by successive exposures to lowering temperatures. Throttling to a pressure of 2 MPa and distillation under temperature -28°C, -41°C and -110°C makes all hydrocarbons separated away; under pressure of 1.2 MPa, nitrogen and other gases are precipitated out, which results the gaseous mixture enriched by 3% helium. The last throttling to the pressure of 1.0 MPa makes the helium concentration increased to 30-50%, and then, cooling by boiling nitrogen at -203°C and 0.04 MPa raises it to 90%. Crude Helium (70 - 90 vol. %) is rectified of hydrogen (4 - 5%) at 650-800°K and dried by silica gel. The fine rectification is completed by cooling crude helium boiling under vacuum. Adsorption on activated charcoal in adsorbers is used as a final purification step, usually resulting in 99.995% purity of Grade A helium. The purity of Grade B helium purification is about 99.80%