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

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.

KEYWORDS:

• Laminar burning velocity
• biogas
• hydrogen enrichment
• nitrous oxide
• flame instability

Acknowledgement

The authors would like to thank Universiti Teknologi Malaysia and Ministry of Higher Education Malaysia for supporting this research activity under the Research Grant Scheme No. Q.J130000.3551.07G58.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The work was supported by the Universiti Teknologi Malaysia [Q.J130000.3551.07G58].