Inhibition of hydrogen oxidation by HBr and Br2

Publication: Research - peer-reviewJournal article – Annual report year: 2012

  • Author: Dixon-Lewis, Graham

    University of Leeds, United Kingdom

  • Author: Marshall, Paul

    University of North Texas, United States

  • Author: Ruscic, Branko

    Argonne National Laboratory, United States

  • Author: Burcat, Alexander

    Faculty of Aerospace Engineering, Technion – Israel Institute of Technology, Israel

  • Author: Goos, Elke

    DLR Institute of Combustion Technology, Germany

  • Author: Cuoci, Alberto

    Dipartimento di Chimica, Materiali e Ingegneria Chimica “G. Natta”, Politecnico di Milano, Italy

  • Author: Frassoldati, Alessio

    Dipartimento di Chimica, Materiali e Ingegneria Chimica “G. Natta”, Politecnico di Milano, Italy

  • Author: Faravelli, Tiziano

    Dipartimento di Chimica, Materiali e Ingegneria Chimica “G. Natta”, Politecnico di Milano, Italy

  • Author: Glarborg, Peter

    CHEC Research Centre, Department of Chemical and Biochemical Engineering, Technical University of Denmark, Søltofts Plads, 2800, Kgs. Lyngby, Denmark

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The high-temperature bromine chemistry was updated and the inhibition mechanisms involving HBr and Br2 were re-examined. The thermochemistry of the bromine species was obtained using the Active Thermochemical Tables (ATcT) approach, resulting in improved data for, among others, Br, HBr, HOBr and BrO. Ab initio calculations were used to obtain rate coefficients for selected reactions of HBr and HOBr, and the hydrogen/bromine/oxygen reaction mechanism was updated. The resulting model was validated against selected experimental data from the literature and used to analyze the effect of HBr and Br2 on laminar, premixed hydrogen flames. Our work shows that hydrogen bromide and molecular bromine act differently as inhibitors in flames. For HBr, the reaction HBr+H⇌H2+Br (R2) is rapidly equilibrated, depleting HBr in favor of atomic Br, which is the major bromine species throughout the reaction zone. The chain-breaking steps are then H+Br+M→HBr+M (R1), Br+HO2→HBr+O2 (R7), and Br+Br+M→Br2+M (R8). In Br2-doped flames, the reaction Br2+H⇌HBr+Br (R9) is far from equilibration and serves to deplete H in the reaction zone by competing with H+O2→O+OH. The inhibition is augmented by recombination of Br (R8). If the inlet Br2 mole fraction exceeds about 20%, reactions (R8) and (R2) are both reversed, now acting to promote chain branching and increase the flame speed. According to the present model, cycles involving HOBr are not important for generation or removal of chain carriers in these flames.
Original languageEnglish
JournalCombustion and Flame
Publication date2012
Volume159
Issue2
Pages528-540
ISSN0010-2180
DOIs
StatePublished
CitationsWeb of Science® Times Cited: 5

Keywords

  • Bromine, Kinetics, Flame inhibition, Thermochemistry, Ab initio calculations
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