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Abstract
The sensitization of ethane oxidation by NO above 800 K and the oxidation of HCN-natural gas blend (CH4-C2H6, 10:1) mixtures at 1050 to 1450 K, with and without NO, have been studied in a fused silica jet-stirred reactor (JSR) at 1 atm. A detailed chemical kinetic model developed for NO-reburning by natural gas (754 reactions and 102 species), including a low-temperature reaction sub-mechanism, was used to simulate the present experiments. A good agreement between the experimental results and the modeling was generally obtained. According to the proposed kinetic mechanism, in the present conditions, the mutual sensitization of the oxidation of ethane and NO proceeds through the following sequence: C2H6 + OH → C2H5 + H2O; C2H5 + O2 → C2H4 + HO2 followed by the oxidation of NO and production of OH sustaining ethane oxidation, NO + H02 -> N02 + OH. Other reactions yield mutual sensitization of the oxidation of ethane and NO: C2H5O2 + NO → C2H50 + N02 and CH302 + NO -> CH3O + N02 followed by thermal decomposition of alkoxy radicals (C2H50 -> CH3HCO + H, CH3O -* CH20 + H) and production of H02, H + 02 -> H02. The present modeling also shows that the oxidation of HCN-natural gas blend proceeds through the following routes: HCN + O -" NCO + H followed by NCO + CH4 -> HNCO + CH3. NCO + C2H6 -> HNCO + C2H5 and HNCO + H -" NH2+ CO. NO addition yields a strong sensitization of the oxidation process. The proposed kinetic model indicates that the reaction path is: HCN + O -> NCO + H followed by NCO + NO -> N20, CO, C02, and N2. N20 is mostly converted to N2 through reaction with H and CO. In the NO-seeded experiments, the NCO + NO reactions dominate resulting in an increased production of N20 and a reduction of HNCO yield.
