Energy Sustainability: The Case of Blending Hydrogen with Methane for Carbon Emission Reduction

This study investigates the safety measures associated with blending hydrogen (H₂) with methane (CH₄) to reduce carbon emissions in the hard-to-abate industries, trans-portation sectors and domestic uses. The results highlighted significant safety risks due to hydrogen's lower ignition energy (IE) and broader flammability range, especially under high-pressure conditions. Using Aspen HYSYS chemical process simulation and the HSC Chemistry platform, the study quantified carbon emissions and combustion heat release of H₂-CH₄ mixtures at various H₂ contents, temperatures, and pressures. The results suggest that blending H₂ with CH₄ can be beneficial, provided H₂ content does not exceed safe thresholds and stays within a recommended Wobbe Index (WI) range of 45 - 55 MJ/m³. The WI increases with H₂ concentration exceeding 50 mole% due to density effects outweighing HHV reductions. Hydrogen's high buoyancy and diffusivity reduce localized accumulation in open areas but pose risks in confined spaces due to its wide flammability range. H₂-CH₄ blends with ≤ 20 mole% H₂ are safer than higher concentrations or pure H₂. For blends with > 20 mole% H₂, engineered safety features (ESF) like leak detection, alarms, ventilation, and spark-free environ-ments are essential. Managing concentrations to avoid the detonation range (pure H₂: 18 - 59 mole% & pure CH₄: 6.3 - 13.5 mole%) is critical. Adhering to H2 safety codes limiting H₂ to ≤ 20 mole% in pipelines is recommended. Conservatively, < 18 mole% H2 reduces detonation risk, and ≤ 10 mole% provides added safety margins. These find-ings can guide policymakers and industry stakeholders in developing safe, efficient hydrogen-enhanced energy systems, hence supporting carbon reduction goals.