Effect of MgO/Al2O3 Ratio on Viscosity of Blast Furnace Primary Slag

The effects of MgO, Al2O3, C/S (CaO/SiO2) and FeO on the viscosity and the liquidus temperature (TLQ) of blast furnace (BF) primary slag were analyzed by using multiphase equilibrium. The results show that the TLQ of primary slag exhibits a minimum value at 12 wt% Al2O3 and 14 wt% Al2O3 when MgO contents are 8 wt% and 10 wt%, respectively. It can be suggested that the content of MgO in primary slag is prone to be retained at different value when Al2O3 is different for smooth operation. The suitable value of MgO/Al2O3 ratio increases with the increase of Al2O3 content from 10 wt% to 18 wt% in the primary slag and the proper MgO/Al2O3 ratio is 0.4–0.55. The TLQ of the slag increases with the increase of C/S when Al2O3 content is lower than 14 wt%, while it decreases with the increase of the C/S when Al2O3 is higher than 14 wt%. The slag viscosity decreases with the increase of FeO content. The isoviscosity curves become closer and closer when FeO is in a low level. In the condition of the high Al2O3 content, improving the reduction degree of iron ore in the upper area of the BF can achieve a lower TLQ and have a smooth operation