Effect of CaO addition on the reducibility of FeO-SiO{sub}2 based slag powder

摘要

Recently, it is strongly desired to lower slag content of iron ore sinter. In the sintering of the low slag ratio, one of the problems is the decrease of melt, which is needed to agglomerate the iron ores. As one of the methods to solve the problem, the use of silicate melt mainly composed of Fe{sub}xO-SiO{sub}2 is considered. However, the reducibility of the sinter tends to become worse by increasing Fe{sub}xO content. In the present study, the method is examined to improve the reducibility by adding CaO in the silicate melt and by precipitating the mineral phases composed of CaO and SiO{sub}2. In the examination, it is important to know the reducibility of Fe{sub}xO in CaO-SiO{sub}2-Fe{sub}xO slag. The hydrogen reduction rate of Fe{sub}xO in the formed slag and the precipitated phases by the addition of CaO to Fe{sub}xO-SiO{sub}2 melt at 1573K was measured at 1173K; the effect of CaO on the reducibility of Fe{sub}xO in CaO-SiO{sub}2-Fe{sub}xO slag has been investigated. From the results, it is found that the composition of the equilibrated slag at 1573K largely affects the reducibility of the slag at 1173K. The reducibility is improved by the precipitation of 2CaO SiO{sub}2 after CaO addition. The reducibility of both 2FeO 5i02 and CaO FeO SiO{sub}2 are very low. Accordingly, it is important to prevent the formation of 2FeO SiO{sub}2 and CaO FeO SiO{sub}2 to attain the higher final fractional reduction. The reducibility of the slag containing 5 mass% Al{sub}2O{sub}3 is a little better than that of the Al{sub}2O{sub}3-free slag, and the dependence of the reducibility on slag composition shows the same tendency as that of the Al{sub}2O{sub}3-free slag.