Study of quaternary hydrogen and biogas mixtures: An industrial safety approach

Hydrogen and biogas mixtures offer a promising solution to meet industrial heat demands that renewable electricity cannot fully supply. This study investigates the flammability characteristics of quaternary gas mixtures composed of methane (CH4), hydrogen (H2), carbon dioxide (CO2), and air, which are relevant for industrial safety in explosive atmospheres. A novel three-dimensional "flammability tetrahedron" is introduced to represent the flammable regions, limiting oxygen concentration (LOC), and ignition boundaries of these mixtures. Using the Spark Test Apparatus (STA), we experimentally determined the flammability limits for three biogas compositions (BG50, BG60, BG70) blended with varying hydrogen percentages (10-50%). The results demonstrate that hydrogen addition significantly alters the flammability limits and LOC, reducing the required inert gas for safety and extending the flammable range in hydrogen-enriched mixtures. The proposed flammability tetrahedron serves as an innovative tool for the real-time evaluation of gas mixtures, addressing gaps in current safety protocols. This research has substantial industrial applications, particularly in sectors handling methanehydrogen mixtures, enabling safer operations under the European Union's ATEX Directives. The findings provide critical insights into explosion prevention and leak detection in industrial processes, supporting the safe integration of hydrogen-enriched biogas into energy systems.