New results on moist CO oxidation: high pressure, high temperature experiments and comprehensive kinetic modeling

Tae J. Kim, Richard A. Yetter, Frederick L. Dryer

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Abstract

The kinetics of moist carbon monoxide oxidation have been studied experimentally for pressures from 1 to 9.6 atm, temperatures from 960 to 1200 K, and equivalence ratios from 0.33 to 2.1. New data were used in combination with prior flow reactor, shock tube, and static reactor data to develop a revised comprehensive reaction mechanism for the CO/H2O/O2 system. In particular, the new data span the explosion limit behavior of the system and place significantly increased emphasis on the kinetics involving the hydroperoxyl radical. Revisions of the rates recommended in an earlier comprehensive mechanism are needed in order to reproduce experimental observations. While six reaction recommendations were modified, the most important were the kinetic parameters for H2O+O=OH+OH and HO2+OH=H2O+O2. Experimentally, the second limit for this reaction system was determined at much higher pressure thanpreviously studied. Near the limit, an increase in pressure results in a two order of magnitude decrease in the oxidation rate. Away from the limit, the pressure dependence of the rate is similar in both the nonexplosive and explosive regimes. In the nonexplosive regime, the kinetics are straight chain in nature and governed by the reactions H+O2+M=HO2+M, CO+HO2=CO2+OH, and CO+OH=CO2+H. The overall temperature dependence of the oxidation is very large (77 kcal/mol). In the explosive regime, chain-branching phenomena dominate and are controlled by the reactions H+O2=OH+O, CO+OH=CO2+H, and O+H2O=OH+OH. The overall temperature dependence of the oxidation is significantly lower (40 kcal/mol). The sensitivity of the reaction rate to moisture saturates at much lower moisture concentration in the nonexplosive regime. At high pressures (>25 atm), the oxidation of CO through CO+OH=CO2+H and CO+HO2=CO2+OH is numerically predicted to approach a limiting ratio of one-half.

Original languageEnglish (US)
Pages (from-to)759-766
Number of pages8
JournalSymposium (International) on Combustion
Volume25
Issue number1
DOIs
StatePublished - 1994

All Science Journal Classification (ASJC) codes

  • Chemical Engineering(all)
  • Fuel Technology
  • Energy Engineering and Power Technology
  • Mechanical Engineering
  • Physical and Theoretical Chemistry
  • Fluid Flow and Transfer Processes

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