Reduction mechanism of composite consisted of coal and hematite ore by volatile matter at 700-1 100 K

In the drive to mitigate global warming, the iron and steel industry has made efforts to reduce carbon dioxide gas emissions. Utilization of a composite material consisting of carbonaceous material and iron ore is expected to be an effective way to solve the issue. Volatile matters in carbonaceous materials have a potential to reduce emissions by lowering the reduction temperature. In this study, the reduction by volatile matter in a coal/hematite ore composite was fundamentally examined. Different kinds of coal were chosen as carbonaceous material samples. The reduction experiment using the prepared composites was conducted by varying the heating rate as 0. 08, 0.17, and 0.33 K/s, up to a temperature of 1 473 K under Ar-5%N₂ gas flow. The outlet gas composition was analyzed and the results were used to calculate the reduction degree. Reduction degree of hematite ore initially increases with increasing content of volatile matter in coal. However, beyond a certain point, further increase in the volatile matter content of the coal did not give a significant change in the reduction degree. For the evaluated coals, the amounts and types of gases generated are not different each other. H₂ gas seems to form together with solid carbon via decomposition of hydrocarbon gases. Such gases and solid carbon may contribute to the reduction. Moreover, reduction by H₂ was promoted in the early stage of the reactions by decreasing heating rate. The data indicate that control of the heating rate is a possible way to promote reduction at low temperature.