Study on NOx formation in oxygen-enriched ammonia/N2/O2 laminar flame

Abstract

Ammonia is regarded as one of the alternative fuels, since the physical properties of Ammonia is a suitable fuel for transportation and storage as a “hydrogen carrier”. Also, a large amount of ammonia can be produced easily through the Haber-Bosch process with low price. To use ammonia as the alternative fuel, it is necessary to pay attention to Fuel-NOx formation. In this study, the oxygen-enriched combustion was applied to an ammonia/N2/O2 premixed flame to make the flame stable. The effects of the oxygen-enriched combustion on characteristics of NOx formation and on the unburned ammonia remained in the burned gas were evaluated. Results showed that NO concentration reached to 1.2%, and unburned ammonia wasn't detected in all O2 concentration conditions of fuel lean mixture. Also, NO concentrations sharply decreased between φ = 1.0 to φ = 1.4. At the condition of φ = 1.4, NO concentration was 600 ppm. Unburned ammonia wasn't detected between the condition of φ = 0.9 to φ = 1.1, and over the condition of φ =1.2, ammonia concentration was increased steeply. The sum of (NO + NH3) became the minimum value around the condition of φ = 1.3 and φ = 1.4. These characteristics that the NOx formations depended on equivalence ratio were the same characteristics of NOx formation when propane is added to NH3 as a fuel.

Keywords

• renewable energy
• ammonia fuel
• alternative fuel
• carbon free fuel
• oxygen-enriched combustion