FeO-SiO₂系スラグ粉末の被還元性に及ぼすCaO添加の影響

抄録

Recently, it is strongly desired to lower slag content of iron are 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_xO-SiO₂ is considered. However, the reducibility of the sinter tends to become worse by increasing Fe_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 SiO₂. In the examination, it is important to know the reducibility of Fe_xO in CaO-SiO₂-Fe_xO slag. The hydrogen reduction rate of FexO in the formed slag and the precipitated phases by the addition of CaO to Fe_xO-SiO₂ melt at 1573K was measured at 1173K; the effect of CaO on the reducibility of FexO in CaO-SiO₂-Fe_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 SiO₂ after CaO addition. The reducibility of both 2FeO·SiO₂ and CaO ·FeO ·SiO₂ are very low. Accordingly, it is important to prevent the formation of 2FeO SiO₂ and CaO· FeO ·SiO₂ to attain the higher final fractional reduction. The reducibility of the slag containing 5 mass% Al₂O₃ is a little better than that of the Al₂O₃-free slag, and the dependence of the reducibility on slag composition shows the same tendency as that of the Al₂O₃-free slag.