Experimental and Kinetic Study on the Oxidation of Syngas-Ammonia under Both N2 and CO2 Atmospheres in a Jet-Stirred Reactor

Although syngas combustion has been extensively investigated, previous studies did not systematically examine the fuel-NO x formation from ammonia-containing syngas in both N 2 and CO 2 atmospheres. Investigations on syngas-ammonia oxidation are significant for suppressing the fuel-NO x emission from the combustion of actual syngas containing NH 3 . This study presents new experimental results on syngas-ammonia oxidation under both N 2 and CO 2 atmospheres in a jet-stirred reactor. The effects of CO 2 concentration ( X CO2: 0–60%), temperature ( T: 900–1400 K), equivalence ratio (Φ: 0.4–1.65), initial CH 4 concentration ( X CH4: 0–2000 ppm), CO/H 2 ratio, and residence time (τ: 0.001–10 s) are investigated. For the oxidation of syngas-ammonia, the reactant consumption is delayed and more CO is produced in high CO 2 concentration. A critical temperature to obtain the peak N 2 O production is found, and it is slightly reduced from 1000 to 950 K with Φ increasing from 0.63 to 1.25. Moreover, the N 2 O concentration is basically insensitive to the concentration of CH 4 and the CO/H 2 ratio in syngas. The NO production is enhanced with the increase of T, X CH4, and the CO/H 2 ratio, while it is reduced with increasing Φ. Interestingly, the high concentration of CO 2 suppresses the fuel-NO formation in fuel-lean conditions, while it significantly enhances the fuel-NO production in fuel-rich conditions. To minimize emissions of NO, N 2 O, and CO, it is recommended to operate the reaction at T > 1000 K and simultaneously avoid significantly high temperatures at the equivalence ratio of approximately 0.9, low values of initial CH 4 concentration and the CO/H 2 ratio (e.g., <1), long residence times (τ > 2 s), and high concentrations of CO 2 ( X CO2 > 30%). Furthermore, the numerical simulations agree well with the vast majority of measurements, and the dependence of NO on Φ at X CO2 = 30% is also well predicted. The present study provides new fundamental understandings of the fuel-NO x formation from ammonia-containing syngas.