Natural gas and blends oxidation and ignition: Experiments and modeling

Abstract

The kinetics of the oxidation of natural gas and blends (CH 4 /C 2 H 6 , CH 4 /C 3 H 8 , CH 4 /C 2 H 6 /C 3 H 8 ) hasbeen studied in a jet-stirred reactor (800≤ T/K ≤1240, 1≤ P /atm≤10, 0.1≤equivalence ratio≤1.5). The concentration profiles of reactants, intermediates, and products measured in a jet-stirred reactor (JSR) have been used to validate a detailed kinetic reaction mechanism. Literature ignition delay times measured in shock tube have also been modeled. A generally good agreement between the data and the model is found. The same mechanism has also been used to successfully represent the oxidation of methane, ethyne, ethene, ethane, propene, propane, n -butane, and 1-butene in various conditions including JSR, shock tube, and flame. The present study clearly shows the importance of trace hydrocarbons in the oxidation of methane. The computations indicate that the oxidation of methane is initiated by its reaction with O 2 when no other hydrocarbon is present. In natural gas and blends, higher hydrocarbons react before methane, leading to the formation of OH, H, and O radicals, which in turn initiate methane oxidation. This work demonstrates that methane cannot be used safely to represent the kinetics of natural gas combustion. However, simple blends like methane-propane or methane-ethane-propane could be used.