Conversion of H2S/O2/NO mixtures at different pressures. Experiments and kinetic modeling

• Published in: Fuel (Guildford) 2021-04, Vol.290, p.120060, Article 120060
• Main Authors: Colom-Díaz, J.M., Millera, Á., Bilbao, R., Alzueta, M.U.
• Format: Article
• Language: English
• Subjects: Atmospheric models; Atmospheric pressure; Conversion; Experiments; H2S; High pressure; High temperature; Hydrogen sulfide; Kinetic modeling; Low temperature; Nitrogen dioxide; NOx; Oxidation; Sulfur
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2020.120060

•Conversion of H2S/O2/NO mixtures up to 20 bar is studied.•H2S conversion is slightly promoted by NO at atmospheric pressure under oxidizing and stoichiometric conditions.•Increasing pressure and oxidizing conditions shift H2S conversion to low temperatures.•A reaction between NO2 and H2S may be the responsible for the early conversion of H2S.•Kinetic modelling of the conversion process gives reasonably good results. The present study deals with the oxidation of H2S/NO mixtures, in the temperature range of 475–1400 K, at atmospheric pressure and 20 bar of manometric pressure. The experiments have been performed in two different set-ups, using tubular flow reactors, for different air excess ratios (λH2S = 0.3–6). A kinetic model has been updated with recent reactions from the literature. When NO is present, the oxidation of H2S at atmospheric pressure proceeds at slightly higher temperatures (25 K) with respect to neat H2S oxidation. At high pressure (20 bar), the experiments of the oxidation of H2S in the absence and presence of NO have been performed only at oxidizing conditions (λH2S = 2 and λH2S = 6), in order to avoid sulfur formation under reducing conditions. The outcomes of these experiments show that, in presence of NO, at the lowest temperature considered (475 K), at least 50% of H2S conversion for λH2S = 2 and 90% for λH2S = 6 is obtained. In order to further evaluate the influence of the presence of NO in H2S oxidation, additional experiments of neat NO oxidation have been performed. As NO2 formation is favored at high pressures and high O2 concentrations, the NO2-H2S interaction is thought to be responsible for the consumption of H2S, even at low temperatures (475 K). While the kinetic mechanism is able to reproduce the experimental results at atmospheric pressure, discrepancies are more relevant at high pressure (20 bar).