Shock-tube water time-histories and ignition delay time measurements for H2S near atmospheric pressure

Hydrogen sulfide combustion has been of interest in recent years due to its presence in coal-derived syngas and in sour gas. However, there are limited data available for the calibration of chemical kinetics models of high-temperature H2S oxidation. Ignition delay times and laser-absorption water time histories were therefore measured in two different shock tubes around atmospheric pressure over a range of temperatures from 1445 to 2210 K for H2S-O2 mixtures diluted in 98% Ar. While modern H2S models from the literature predicted the ignition delay times with fair accuracy, the water profiles were initially very poorly predicted with the same kinetic mechanisms. A model analysis showed that the reaction R62, SH + HO2 ⇆ H2S + O2 (in reverse), was chiefly responsible for these poor predictions. It was possible to obtain better water predictions when the rate for R62 was divided by 10. A tentative model is proposed herein, based on this assumption for R62, and good predictions were obtained for both the ignition delay times and water profiles, as well as for former high-pressure shock-tube data with H2-H2S mixtures. The present study shows that more accurate rates for the reactions R62 (SH + HO2 ⇆ H2S + O2), R75 (SH + O2 ⇆ HSO + O), and R46 (SH + SH (+M) ⇆ HSSH (+M)) would be needed to better predict H2S combustion chemistry.