Application of laboratory and on field techniques to determine the risk of hydrogen embrittlement in gaseous hydrogen and relative mixtures transport and storage

Abstract

The European Green Deal aims to achieve the climate neutrality in Europe by 2050; furthermore, an intermediate target fixes a first reduction of greenhouse gas emissions by minimum 55% within 2030, with reference to 1990 levels. In these contexts, and in particular in hard-to-abate processes as steelmaking, hydrogen could be a key instrument to achieve the above-mentioned sustainability targets. It can be produced from renewables and does not produce direct CO2 emission when used. On the other side, one of the main issues related to hydrogen use is the fact that it involves a certain risk linked to potential susceptibility of steels to hydrogen embrittlement phenomenon that could also lead to catastrophic failures. Suitable materials should be used in these applications by performing a prior evaluation of material susceptibility. The characterization consists in determining the behaviour of materials when exposed to hydrogen atmosphere, in order to determine a hydrogen threshold value for failure. To approach this theme, a first experimental was carried out on steels typically applied in oil and gas industry. Experimental included hydrogen diffusivity, solubility and mechanical tests. Moreover, electrochemical charging was compared to gaseous charging, confirming the first methodology is much more severe and thus not very significant for high-pressure gas applications. Furthermore, a continuous monitoring technique for hydrogen embrittlement risk assessment is under development. The methodology is based on high-resolution gas sensors used to measure the hydrogen flux permeating through the metal wall of transport and storage components. Relative signal can be correlated with the material susceptibility to hydrogen embrittlement in order to assess related failure risk. The device was tried on a pressure vessel containing pure hydrogen to assess the system’s sensitivity.