Influence of additives on sulfide capacity of CaO-CaF2-SiO2 slags

Abstract

In most Japanese integrated steelmaking plants, hot metal pretreatment is a common practice, because the combination of the pretreatment with the combined blowing converter minimized the production cost of high-quality steel. The CaO-CaF{sub 2}-SiO{sub 2} system containing low SiO{sub 2} is an excellent slag for desulfurization, as reported elsewhere. In the actual hot metal pretreatment, the oxides, such as alumina, magnesia, and manganese oxide, are inevitable because of the erosion of refractory or residues in previous processes. Sometimes even additions of such oxides are made in the pretreatment. Therefore, it is of practical importance to know how these additives or contaminants affect the desulfurization capacity of slags. In the paper, the influences of Na{sub 2}O, Al{sub 2}O{sub 3}, MgO, and MnO on the sulfide capacity of CaO-CaF{sub 2}-SiO{sub 2} slags were studied. The addition of Na{sub 2}O was also investigated to understand how it enhanced the sulfide capacity. Emphasis was given to slags of CaO-saturated composition, not only because they have the highest sulfide capacity but also because of the presence of excess CaO in the commercial slags.