2017 Volume 57 Issue 4 Pages 681-688
Reducibilities of wüstite and calcio-wüstite have been examined using high temperature X-ray diffraction analysis including the effect of hydrogen on the reducibility. Fe2O3 reagent powders and hematite ore powders were used for reduction of wüstite (denoted as FeO) and sintered ore powders were used for reduction of FeO and calcio-wüstite (denoted as CW). High-temperature X-ray diffraction was applied to these samples in a flow of CO–CO2–He mixtures with and without 3.9 vol% of hydrogen during the heating cycle which simulates a blast furnace condition. The diffraction angle was scanned in the range from 33° to 55°. In experiment on sintered ore powders without hydrogen, the main peak around 48.5° shifted to lower angles with increasing temperature. This shift also continued while temperature was kept at 1000°C where wüstite was saturated with iron; on the contrary, the peak shift did not take place for hematite ore powders. This main peak is associated with wüstite (200), which is actually composed of peaks due to FeO and CW for sintered ore powders. The peak shift reflects that the peak intensity of CW increases relative to that of FeO, which suggests that the reduction of FeO proceeds faster than that of CW, and the reducibility of FeO is higher. In contrast, the peak shift did not take place in experiment on sintered ore powders with hydrogen additions. This suggests that the reducibility of CW is comparable to that of FeO in the presence of hydrogen.