A shock-tube and modeling study of syngas ignition delay times in rich CO2 environment at elevated pressures

Abstract

Oxy-fuel combustion techniques are crucial for fossil fuel power plants with substantially reduced greenhouse gas emission. The chemical effect of CO2 as a reactant/product or a third-body is important in modeling oxy-fuel combustion. Many previous kinetic studies focused on evaluating the rate parameters in relevant reactions, but less attention was paid to CO2 collision efficiencies. In this study, ignition delay time data were measured in a shock-tube facility for stoichiometric syngas mixtures with 50%, 70% and 90% CO in fuel at 1 and 5 atm, diluted in 85% CO2 bath gas. Among the chemical effect of CO2, the CO2 collision efficiency in reaction H+O2(+M) = HO2(+M) shows a dominantly high sensitivity value to model prediction over the present experimental conditions. Therefore, the CO2 collision efficiency was evaluated using the current data and a recommended value was reported with uncertainty analysis. Moreover, the CO2 collision efficiencies in reaction H2O2(+M) = OH+OH(+M), HCO(+M) = H+CO(+M), H2+M = H+H+M and O+O+M = O2+M were evaluated using ignition delay time data at higher pressures (40 atm to 200 atm) and recommended CO2 collision efficiency values were reported with uncertainty analysis. The model with recommended CO2 collision efficiency values significantly improved prediction performance at 5 atm and was validated over a comprehensive set of syngas ignition delay time and laminar flame speed data.