Abstract
The purification of recovery helium gas is a much annoyed problem for an operator of liquefier.
The purity of feed helium gas is one of the most important factors for a long-term stable running of liquefier. Accordingly much care is necessary for a purification process.
We previously made adsorption measurements and reported “The Problem of Separating Air from Recovery Helium Gas”. But the recovery helium gas generally contains Ar, CO2, H2, and Ne besides air as undesirable impurities. It seems we don't pay attention to the problem of separating such impurities, especially H2, in a commercially available purifier. We shouldn't forget the air contains 100ppm volume of H2, moreover the difficulty of separatingout H2 in a purification process owing to the very low boiling and freezing point.
Actually we were confronted with a trouble of blocking JT-heat exchanger by traces of H2. The traces of H2 in feed helium gas concentrated on JT-cycle in a long-term running. Therefore we have made H2-He gas adsorption measurements on charcoal, Molecular Sieves 13X, 5A, 4A and natural zeolite in the pressure range of 5-120atm and at liquid nitrogen temperature. The results show that the cocoanut shell charcoal adsorbs 100ml of H2 per gram, the possibility of separating out 0.5 volume % of H2 in recovery helium gas in a usual purifier with a help of small Deoxo unit.
