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

Due to the carbon dioxide (CO2) content in biogas, using biogas is relatively limited in many industrial applications. Hydrogen (H-2) 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-N-2 O mixtures. However, the enhanced laminar burning velocities of biogas-N2O showed a more significant increase than biogashydrogen-air due to the significant energy released by the N-2 O decomposition reaction. The flame thickness of the biogas-N-2 O 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-N-2 O mixture showed lower values than all biogas-hydrogen mixtures, indicating higher diffusive-thermal instability influence on biogas' flame. The reactions of H + O-2 double left right arrow OH + O and H + CH3(+M) double left right arrow CH4(+M) represented the most significant reactions influencing the laminar burning velocities of biogas-hydrogen mixtures, while the N-2 O + H double left right arrow N-2 + OH, and N2O(+ M) double left right arrow N-2 + O(+M) reactions represented the most important reactions in biogas-N2O combustion.

Automated summary

This study investigates the effect of hydrogen (H2) and nitrous oxide (N2O) on the laminar burning velocity and flame instability of biogas. The results show that the laminar burning velocities are enhanced when biogas is mixed with hydrogen or nitrous oxide. However, the increase is more significant with nitrous oxide due to the energy released by its decomposition reaction. The flame thickness of the biogas-nitrous oxide mixture is lower than that of the biogas-hydrogen mixture, indicating higher flame instability. The Lewis number of the biogas-nitrous oxide mixture is also lower, suggesting a greater influence of diffusive-thermal instability on the flame. The reactions of H + O-2 and H + CH3(+M) have the most significant impact on the laminar burning velocities of biogas-hydrogen mixtures, while the reactions of N-2 O + H and N2O(+ M) are the most important for biogas-nitrous oxide combustion.