Effect of MgO/Al 2 O 3 Ratio on Viscosity of Blast Furnace Primary Slag

The effects of MgO, Al 2 O 3 , C/S (CaO/SiO 2 ) and FeO on the viscosity and the liquidus temperature ( T LQ ) of blast furnace (BF) primary slag were analyzed by using multiphase equilibrium. The results show that the T LQ of primary slag exhibits a minimum value at 12 wt% Al 2 O 3 and 14 wt% Al 2 O 3 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 Al 2 O 3 is different for smooth operation. The suitable value of MgO/Al 2 O 3 ratio increases with the increase of Al 2 O 3 content from 10 wt% to 18 wt% in the primary slag and the proper MgO/Al 2 O 3 ratio is 0.4–0.55. The T LQ of the slag increases with the increase of C/S when Al 2 O 3 content is lower than 14 wt%, while it decreases with the increase of the C/S when Al 2 O 3 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 Al 2 O 3 content, improving the reduction degree of iron ore in the upper area of the BF can achieve a lower T LQ and have a smooth operation.