Evaluation of the Effects of Impurities on SAES ST198 Hydrogen Gettering

Various getter materials are used in the processing of hydrogen isotopes and associated impurities. SAES® ST198 is a zirconium-iron alloy that is typically used for the removal of low levels of hydrogen isotopes from a process gas stream. However, numerous impurities may be present in process gas streams and some of these impurities may have a deleterious effect on the hydrogen absorption capabilities of ST198.

A series of experiments were completed to determine the effects of various impurities on the hydrogen gettering ability of ST198 as a function of the bed operating temperature. Changes in hydrogen getter performance were tracked using the analysis of Residual Gas Analyzer data. Baseline conditions of 0.1% hydrogen within a nitrogen rich stream were evaluated at both 350°C and ambient temperature conditions (24°C). Various concentrations of impurities were also explored to determine the effects on the hydrogen gettering of ST198. It has been determined that one benefit of ST198 is that it shows no appreciable interaction with nitrogen at temperatures lower than 425°C. However, gas impurities of carbon monoxide, methane, and ammonia were shown in this work to have an effect on the hydrogen gettering abilities of ST198.

This paper presents findings relating to the evaluation of the effect of carbon monoxide, ammonia, and methane impurities on the hydrogen gettering ability of the ST198. Lower operating temperature conditions made the ST198 getter bed more susceptible to deactivation in the presence of impurities. In the event that the studied impurities exist in the process gas stream, the ST198 material could possibly become deactivated towards hydrogen isotope absorption at lower operating temperatures.