H2S-driven sensitization and inhibition of CH4 oxidation: An experimental and wide-range kinetic-modeling study

The recent diversification of the energy sources has brought about a renewed interest in hydrogen sulfide (H2S) 2 S) chemistry and its mutual interaction with conventional fuels. In this work, the oxidation of methane (CH4) 4 ) with and without the addition of 500 ppm H2S 2 S was experimentally investigated in a jet-stirred reactor, at near-atmospheric conditions (107 kPa), low temperatures (450 to 1200 K) and lean-to-rich compositions (0.5 0 . 5 <= Phi <= 2 ), with a residence time = 2 s. At the same time, a kinetic model was set up to shed light on the fundamental couplings between carbon and sulfur chemistry. For all the conditions, the presence of H2S 2 S caused an earlier oxidation onset of CH4 4 consumption, compared to the pure fuel. On the other hand, H2S 2 S consumption occurred over a wider temperature range, starting at temperatures as low as 650 K. The kinetic model was able to unravel the interactions resulting in this behavior: the two fuels were found to interact at both radical pool level (OH/O/H), as well as at fuel radical level, through mutual H-abstraction (CH3+H2S 3 +H 2 S <-> CH4+SH) 4 +SH) and radical recombination providing methanethiol (CH3+SH 3 +SH <-> CH3SH). 3 SH). While fuel-fuel H-abstraction was found to significantly affect only the low-temperature behavior, the importance of CH3SH 3 SH chemistry was framed in a wider range of conditions. The extended model validation confirmed indeed an inhibiting effect of CH3SH 3 SH in the higher-temperature flame propagation of dual-fuel mixtures, whose flame speed had been previously observed to be lower than those of pure fuels.