Gettering of hydrogen and methane from a helium gas mixture

Abstract

In this study, the authors developed an approach for accurately quantifying the helium content in a gas mixture also containing hydrogen and methane using commercially available getters. The authors performed a systematic study to examine how both H2 and CH4 can be removed simultaneously from the mixture using two SAES St 172® getters operating at different temperatures. The remaining He within the gas mixture can then be measured directly using a capacitance manometer. The optimum combination involved operating one getter at 650 °C to decompose the methane, and the second at 110 °C to remove the hydrogen. This approach eliminated the need to reactivate the getters between measurements, thereby enabling multiple measurements to be made within a short time interval, with accuracy better than 1%. The authors anticipate that such an approach will be particularly useful for quantifying the He-3 in mixtures that include tritium, tritiated methane, and helium-3. The presence of tritiated methane, generated by tritium activity, often complicates such measurements.

Evaluation of Alternate Impurity Removal Getters - Year 2

“…Methane has been shown to decompose at temperatures greater than 650°C into hydrogen and zirconium carbides [15]. Some researchers have indicated that methane removal generally requires temperatures greater than 400°C [16]. Carbon monoxide was not present within these tests but the temperature would likely need to be elevated to prevent deactivation.…”

“…A zirconium, vanadium, iron alloy, ST172, can be operated at various temperatures to achieve varying results [16]. If two beds of the material are operated at 650°C and 110°C, respectively, the first bed will crack methane and the second could be used to getter hydrogen.…”