Effect of sulfur on hydrogen-reduction behavior of iron oxide during microwave heating

Hydrogen-reduction behavior of a high-sulfur magnetite sample was investigated in the presence of CaO under microwave irradiation at 1050 W and 2.45 GHz to clarify the effect of sulfur on the microwave-assisted reduction reaction of iron oxides. Results of the microscope observations showed a gap between the reduced metallic iron and its surrounding, which is a high-sulfur iron oxide. Formation of such a gap is likely attributed to a lower microwave absorbability of the reduced Fe than the sulfur-contained iron oxide which results in a different thermal expansion in the phases during microwave heating. Such a gap in the high-sulfur magnetite sample enhances the hydrogen-reduction reaction as compared with a pure magnetite sample owing to higher gas accessibility to un-reacted parts in the former sample.