Some chemical kinetics issues in reburning: The branching fraction of the HCCO + NO Reaction
- Sandia National Labs., Livermore, CA (United States). Combustion Research Facility
- Technical Univ. of Denmark, Lyngby (Denmark). Dept. of Chemical Engineering
The authors have determined theoretically some critical kinetic parameters in the mechanism of NOx reburning under flow-reactor conditions. Specifically, using a variety of electronic structure methods to investigate the potential energy surfaces and the maximum free energy method of Quack and Troe to determine the resulting rate coefficients, they have deduced the values of k{sub 2} and k{sub 3} for the reactions, HCNO+O {leftrightarrow} HCO+NO (R2) and HCNO + OH {leftrightarrow} HCOH + NO, (R3) to be k{sub 2} {approx} 7 x 10{sup 13} cm{sup 3}/mole-sec. and k{sub 3} {approx} 2 x 10{sup 13} cm{sup 3}/mole-sec. independent of temperature for 300 K < T < 2,700 K. With such fast reactions converting HCNO to NO, a critical parameter in the reburn mechanism is {alpha}(T) = k{sub 1b}(T)/k{sub 1}(T), the branching fraction of the HCCO + NO reaction, HCCO + NO {leftrightarrow} HCNO+CO (R1a); HCCO + NO {leftrightarrow} HCN + CO{sub 2} (R1b); HCCO + NO {leftrightarrow} HONC + CO (R1c). Again using PES information from a variety of electronic-structure methods, the authors have used the statistical-theoretical methodology of Miller, Parrish, and Brown to determine {alpha} (T) = 0.985 exp({minus}T/1,748), valid for 300 K < T < 2,000 K. Using a value of k{sub 1} = k{sub 1a} + k{sub 1b} + k{sub 1c} = 2.4 x 10{sup 13} cm{sup 3}/mole-sec. independent of temperature (consistent with experiment) they have determined modified Arrhenius expressions for k{sub 1a} and k{sub 1b}, k{sub 1a} = 1.17 x 10{sup 13} T{sup 0.65} cm{sup 3}/mole-sec. and k{sub 1b} = 1.45 x 10{sup 16} T{sup {minus}0.968} exp({minus}648/RT) cm{sup 3}/mole-sec for 300 K < T < 2,000 K. Reaction (R1c) never contributes as much as 1% to the total rate coefficient. The theoretical analyses and the reburn mechanism are discussed in detail.
- Research Organization:
- Sandia National Labs., Livermore, CA (United States)
- Sponsoring Organization:
- USDOE Assistant Secretary for Energy Efficiency and Renewable Energy, Washington, DC (United States)
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 658154
- Report Number(s):
- SAND--98-8450C; CONF-980804--; ON: DE98052520
- Country of Publication:
- United States
- Language:
- English
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