Fate of sulfur with H2S injection in methane/air flames

Investigation of sulfur chemistry of hydrogen sulfide in methane/air flame under different equivalence ratios is conducted. A range of equivalence ratios extending from fuel-lean (Φ = 0.5), stoichiometric (Φ = 1.0), to fuel-rich (Claus condition, Φ = 3.0) are examined here. Hydrogen sulfide, methane, and air were premixed prior to the injection of mixture into the combustor. Spatial gas sampling was carried out both axially and radially along the reactor at various locations downstream of the reactor. Oxidation competition between H2S and CH4 was found to be significant due to the premixed conditions. Subsequently, reaction of H2S formed SO2 rather than sulfur (S2). In addition, sulfur dioxide showed a consistent (almost-constant) trend under all equivalence ratios examined here. On the other hand, results showed the presence of carbon sulfide (CS2) under both lean and stoichiometric conditions. The formation of carbon disulfide was found to be due to the reaction of methane with sulfur compounds to form CS2. Moreover, intermediate species such as, CH react with H2S to form CS2. Higher hydrocarbons (ethane and ethylene) were observed under Claus conditions. This was due to the coupling catalytic effect of SO2 which enhances the dimerization of CH3 to form ethane. Dehydrogenation of ethane forms ethylene. Under stoichiometric and lean conditions higher hydrocarbons were not formed due to the lack of high SO2 concentration in the reaction pool.

► H2S was premixed with CH4/air mixture and burned at different equivalence ratios.
► Spatial gas sampling was conducted at various locations downstream of the reactor.
► Reactants premixing enhanced the oxidation competition between H2S and CH4.
► Carbon disulfide was formed due to the reaction of CH4 with S, S2, and CH.
► Higher hydrocarbons (C2H4 and C2H6) were formed due to the catalytic effect of SO2.