Effect of methanol and CO on NH3 Oxidation and SNCR process

NH 3 oxidation and the Thermal DeNO x process in the presence of CH 3 OH and CO have been investigated through a combination of flow reactor experiments and detailed chemical kinetic modeling. The experiments were performed at atmospheric pressure using NH 3 /O 2 /H 2 O mixtures, investigating the effect of adding NO, CH 3 OH and CO. The experiments were highly diluted in N 2 and the temperature was varied from 973 to 1473 K ( τ = 101/T[K] s). The reaction mechanism was based on the nitrogen chemistry review by Glarborg et al. (2018), with updates to the amine, HNCO, N 2 O and CH 3 OH subsets based on more recent studies. Both methanol and CO enhanced the NH 3 oxidation rate and promoted NO and N 2 O formation by increasing the radical pool. In the presence of methanol, HO 2 radicals played an important role in NH 3 oxidation, promoting NH 2 + NO 2 reactions. Methanol negatively affected the Thermal DeNO x process, lowering the NO x reduction efficiency and, at high CH 3 OH/NH 3 ratios, even leading to net NO x formation. It also enhanced N 2 O formation and did not mitigate the impact of CO on Thermal DeNO x . The presence of CO in Thermal DeNO x shifted the NO removal temperature window by up to 150 K toward lower temperatures, while higher CO levels narrowed this window and reduced its efficiency. The results emphasize the importance of measuring NO 2 in the presence of methanol. Relying on NO measurements alone may lead to an apparent NO reduction window that actually reflects oxidation of NO to NO 2 rather than conversion to N 2 , potentially giving the misleading impression that methanol is an effective additive for the SNCR process. Overall, the modeling predictions were in good agreement with both the experimental data from this study and literature data.