High-temperature sulfidation behavior of reduced zinc ferrite in simulated coal gas revealed by in situ X-ray diffraction analysis and Mossbauer spectroscopy

The reactivity of zinc ferrite with hydrogen sulfide was examined at 550 C in a simulated coal gas condition at atmospheric pressure. The specimen of zinc ferrite had spinel structure and exhibited paramagnetism at room temperature. Complementary information on the reaction products of the double oxide were obtained by an in situ X-ray diffraction analysis and Fe-57 Mossbauer spectroscopy analysis. Reduction products of zinc ferrite were identified as zincite, zinc-dislocated franklinite. Sulfidation of the reduced zinc ferrite yields both zinc sulfides and iron sulfide when the concentration of hydrogen sulfide was sufficiently high. Zinc sulfides, however, were predominantly produced at sufficiently low sulfur concentration, typically less than 80 ppm. Consumption of the zinc portion at low sulfur sulfidation derived pure magnetite phase, which indicates the possibility of direct sulfidation of zinc-dislocated franklinite. Thus, both zincite and zinc-dislocated franklinite are considered to be the zinc source of the zinc sulfides production. These findings revealed that sulfur removal with zinc ferrite at lower concentration is attained by zincite and zinc-dislocated franklinite in the reduced zinc ferrite.