Properties and Uses of Ironmaking slag...

Properties and Uses of Ironmaking slag The majority of iron in the world is produced in the blast furnace (BF) and hence BF slag represents the largest quantity of ironmaking slag produced around the world. The BF is the primary means for reducing iron (Fe) oxides to molten, metallic iron. It is continuously charged with Fe oxide sources (ore, sinter, and pellet etc.), fluxes (limestone, and dolomite), and fuel (coke, and coal). Liquid iron collects in the bottom of the furnace and the liquid slag floats on it. Both are periodically tapped from the furnace. BF slag is defined by the American Society for Testing and Materials (ASTM). It defines BF slag as the non-metallic product consisting essentially of silicates and alumino-silicates of calcium and other bases which is developed in a molten condition simultaneously with iron in a BF. The slag consists primarily of the impurities from the iron ore, mainly silica (SiO2) and alumina (Al2O3), combined with calcium (Ca) and magnesium (Mg) oxides from the fluxes. Sulphur (S) and ash which normally come from coke and coal are also contained in the slag. Slag comes from the furnace as a liquid at temperatures of around 1500 deg C. It is a man-made molten rock, similar in many respects to volcanic lavas. Chemical and mineralogical composition of BF slag Chemical analysis of BF slag normally consists of four major oxides namely (i) SiO2, (ii) Al2O3, (iii) calcium oxide (CaO), and (iv) magnesia (MgO). These oxides make up around 95 % of the total quantity. Minor elements which are present in the slag are Fe, S, manganese (Mn), alkalis, and trace amounts of several other elements. Common composition range of various components of BF slag is given in Tab 1. Tab 1 Range of...