Oxidation of hydrogen sulfide and corrosion of stainless steel in gas mixtures containing H2S, O2, H2O, and CO2

The composition of volatile and solid products of oxidation of hydrogen sulfide and stainless steel in gas mixtures containing H2S, O2, H2O, and CO2 has been determined using mass spectrometry, x-ray diffraction analysis, and scanning electron microscopy. It has been shown that holding an H2S–O2 mixture at 301 K results in prevailing formation of elemental sulfur and iron sulfides in the form of porous hygroscopic crust on the reactor wall surface. Formation of gas-phase sulfur causes self-acceleration of the oxidation of hydrogen sulfide; the resulting water triggers corrosion of the reactor wall. Heating of the resulting sulfur-sulfide crust in O2 medium is accompanied by formation of SO2 and heat release at T > 508 K. After heating of the H2S–CO2 mixture to 615 K, H2 and COS were found in the volatile reactants; no noticeable corrosion of the reactor wall has been detected. It has been established that addition of O2 to the H2S–CO2 mixture and its heating to 673 K leads to formation of ferrous sulfates. The mechanisms of the observed processes are discussed.