Enhancement of Biogas Laminar Burning Velocity Using Nitrous Oxide and Hydrogen Enrichment

Abstract

ABSTRACT Due to the carbon dioxide (CO2) content in biogas, using biogas is relatively limited in many industrial applications. Hydrogen (H2) is a highly reactive gas that is used extensively to enhance the burning rate of biogas, on the other hand, nitrous oxide (N2O) is a powerful oxidizer that can improve the burning rate of biogas. The laminar burning velocities of biogas-hydrogen-air and biogas-N2O mixtures at various equivalence ratios were investigated experimentally using the spherical flame methodology. It was found that the laminar burning velocities were enhanced in biogas-hydrogen-air and biogas-N2O mixtures. However, the enhanced laminar burning velocities of biogas-N2O showed a more significant increase than biogas-hydrogen-air due to the significant energy released by the N2O decomposition reaction. The flame thickness of the biogas-N2O mixture indicated lower values than biogas-hydrogen-air mixtures, suggesting a higher flame instability of the biogas-N2O mixture than biogas-hydrogen-air mixtures. The Lewis number of biogas-N2O mixture showed lower values than all biogas-hydrogen mixtures, indicating higher diffusive-thermal instability influence on biogas’ flame. The reactions of H + O2⇔ OH + O and H + CH3(+M) ⇔ CH4(+M) represented the most significant reactions influencing the laminar burning velocities of biogas-hydrogen mixtures, while the N2O + H⇔N2 + OH, and N2O(+M) ⇔ N2 + O(+M) reactions represented the most important reactions in biogas-N2O combustion.