Change of the Slag Composition in Tobata No1 BF

Abstract

Chemical and mineral composition of samples taken from the peripheral region of the blast furnace at the belly, bosh and tuyere level was examined. In the small lumps from the belly three kinds of primary slag were found, which were considered to correspond to FeO-Al₂O₃-SiO₂, K₂O-Al₂0₃-SiO₂ and CaO-K₂O-Al₂O₃-SiO₂, coexisting with the spinel, FeO·(Fe, Al) ₂O₃, in molten state. Bosh slag which remained in or separated from metallic iron granules consisted only of the CaO-K₂O-Al₂O₃-SiO₂ system. Most of the belly and bosh slags bad greater amount of K₂O, Al₂0₃ and SiO₂ than the final slag. The role of minor constituents in ascending gas, i. e. vapors of potassium cyanide and silicon mono-oxide and dusts of some aluminum compounds, is discussed in relation to the process of primary slag formation.