Properties of Low-MgO Ironmaking Blast Furnace Slags

Low slag volume ironmaking blast furnace (BF) operation can reduce the cost of ironmaking by lower flux rate and fuel ratio, meanwhile the operation should be maintained safely in terms of operational temperature, fluidity and desulphurization. One of the approaches for low slag volume BF operation is to decrease MgO content in the slag. In this study, the properties of BF slag have been experimentally investigated in the CaO-SiO2-Al2O3-MgO system from the aspects of phase equilibria, viscosity and sulphide capacity. The liquidus temperature of slag is not sensitive to the MgO concentration. The viscosity of slag increases slightly with decreasing MgO concentration. The sulphide capacity of slag decreases slightly with decreasing MgO concentration. It is suggested that the MgO concentration in the BF slag can be reduced to 5 wt% at the CaO/SiO2 weight ratio of 1.10 to 1.30 and Al2O3 of around 15 wt% under stable BF operation.