Combustion Science and Technology · 1992 · 51 citations · 11 references
Natural SciencesChemical EngineeringChemistryAtmospheric ChemistryChemical KineticsReaction EngineeringAtmospheric Oxidation ProcessesCatalytic Reaction KineticsChemical Kinetics ModelingChemical Reaction KineticsKinetic ModelingOxidizer EffectsAtmospheric Chemical KineticsAtmospheric Oxidation ChemistryAtmospheric Reaction KineticsCo OxidationOxidation KineticsOxidizer Ratio EffectsOxidizer-fuel RatioTemperature Profiles
Abstract A detailed kinetic model for moist CO oxidation chemistry inhibited by HCl is developed and analyzed by sensitivity and reaction flux analyses. The model is validated against experimental data obtained from an atmospheric pressure flow reactor. The kinetics were studied experimentally and numerically with dilute mixtures of CO (∼ 1%), H2O (∼ 0.5%), O2 and HCl reacting in N2 at a temperature near 1000 K. The effect of increasing the Cl/H ratio was investigated by increasing HCl concentrations from 0 to 200 ppm while the effect of excess O2 was studied by varying the fuel oxidizer equivalence ratio from 1.0 to 0.33. The results showed that small quantities of HCl inhibit CO oxidation and that increasing O2 concentrations to stoichiometric mixtures further decreases the oxidation rate, a counter intuitive result. The model predictions for CO, O2, CO2 and temperature profiles agree well with the experimental results (within 10%). Thus the inhibiting characteristics of HCl are well described. However, the model predictions of the HCl profiles were found to be only within 30% or the experimental data. Both experimental and model deficiencies may be responsible for this larger discrepancy. Sensitivity and reaction flux analyses were used to determine the rate-controlling inhibitory steps and major inhibitory pathways created by HCl respectively. At high temperatures the chain termination reactions in the inhibitory cycles generated by HCl have been reported to be primarily H + Cl + M → HCl + M and Cl + CI + M → Cl2 + M. The principal chain terminating step at 1000 K was found to be the reaction Cl + HO2 → HCl + O2, Reactions involving COCl were also found to generate chain terminating cycles not previously reported in the literature. Extension of the modeling calculations lo higher temperatures and Cl/H ratios showed the relative importance of these two additional inhibitory mechanisms to decrease and increase, respectively.
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