Progress of Cryogenics and Isotopes Separation , ISSN: 1582-2575
2018, Volume 21, Issue 2
Pages 5-10

The technological chain of enrichment of 3He

Abstract

Currently, the most suitable raw material for the production of ³He is natural helium, which is a natural mixture of ⁴He and ³He isotopes. Natural helium is produced at large air separation plants. The concentration of ³He in natural helium is only 1.4 ppm, but this is about ten times higher than the concentration of ³He in helium from natural gas fields.
The use of traditional technologies for the enrichment of ³He to high concentrations is practically impossible because of the meager concentration of ³He at the initial stage. Therefore, in order to enrich ³He in the first stage, it is better to use filtration at a temperature level below the lambda transition temperature T_λ of ⁴He, at which the concentration of the ³He isotope can be increased up to 103 ... 104 ppm. After the filtration process, a rectification or adsorption can be used to further enrichment of ³He.
A technological chain for an enrichment of the isotope of ³He from the initial low concentration with several ppm to high concentrations up to 95 ... 97 vol.% of ³He, as well as the main economic indicators of the system is reported in this paper. The proposed technological chain consists of two stages. In the first stage ³He is preliminarily enriched (filtered) at a temperature below T_λ. The second stage uses a distillation column operating at a temperature level of 1.3 ... 3.0 K.

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