Methane/Ammonia Radical Formation during High Temperature Reactions in Swirl Burners

Air Quality Implications of Using Ammonia as a Renewable Fuel: How Low Can NOx Emissions Go?

In addition to their lifecycle carbon emissions, another important issue with decarbonized energy pathways is their air quality, water, or land use implications. This paper considers the air quality issue for ammonia combustion. When directly combusting ammonia, reactions of its N atom with atmospheric oxygen lead to NOx emissions that are O(103) ppm, 2 orders of magnitude higher than EPA limits or the amount emitted by current natural-gas-fired technologies. In order to provide guidance to policymakers and technologists on what is fundamentally possible, this Perspective analyzes the fundamental minimum NOx emissions that can be produced from ammonia combustion. The analysis shows that it is possible to achieve quite low NOx emission levels of O(10) ppm, but these designs differ markedly from those used in today's lean, premixed combustion systems.

Research on NO generation characteristics of ammonia-premixed flame

Ammonia is a promising fuel with high energy density, accessible storage, and no CO₂ production by combustion, but its combustion produces the pollutant NO. In this study, a Bunsen burner experimental bench was selected to investigate the concentration of NO generated by ammonia combustion at different initial oxygen concentrations. Further, the reaction pathways of NO were analyzed in depth, and sensitivity analysis was performed. The results show that the Konnov mechanism has an excellent predictive effect on NO generated by ammonia combustion. In the ammonia-premixed laminar flame at atmospheric pressure, the NO concentration peaked at an equivalence ratio of 0.9. The high initial oxygen concentration enhanced the combustion of ammonia-premixed flame and increased the conversion of NH₃ to NO. NO was not only a product but a contribution to the combustion of NH₃. As the equivalence ratio increases, NH₂ consumes a large amount of NO and reduces NO production. The high initial oxygen concentration enhanced NO production, and the effect was more pronounced at low equivalents. The study results provide theoretical guidance for the utilization of ammonia combustion and pollutant reduction and help to drive the process of ammonia combustion toward practicality.