Experimental determination of minimum ignition current (MIC) ratio of hydrogen/methane (H2NG) blends up to 20 vol.% of hydrogen
Abstract
In the context of planning a decarburization of the European Union energy sector, in order toreach a reduction of carbon emissions up to 95% by 2050, several studies on the compatibilityof the existing gas networks with blends of natural gas/hydrogen up to 20% of hydrogen havebeen tested in industrial scale projects. In relationship to the European Union ATEX directive 2014/34/EU covering equipmentand protective systems intended for the use in potentially explosive atmospheres, gasesand dusts are classified according to their ignition properties. The explosion group forgases and vapors is determined by the maximum experimental safe gap (MESG) and/orminimum ignition current (MIC) ratio values, both defined in the IEC 60079-20-1 (Explo-sive Atmosphere—Part 20-1: Material characteristics for gas and vapour classification—Testmethods and data) standard. This paper reports the results of the experimental determination of MIC ofmethane/hydrogen mixtures up to 20 vol.% of hydrogen. We present the ratios of MIC forhydrogen/methane blends to the MIC of pure methane as well, in order to classify thesemixtures into gases groups. The interpretation of our results would lead us to conclude that methane/hydrogen mix-tures containing 16 vol.% of hydrogen or more should be Group IIB gases. However, otherresults available in scientific literature and standards lead to the conclusion that these con-centrations would still remain within the Group IIA classification. This issue was recentlydiscussed in the IEC subcommittee 31 M of the International Electrotechnical Commission,in order to resolve this contradiction