Generally, decreasing slag volume of blast furnace operation can lead to a lower fuel ratio and higher productivity. For high sinter ratio operation, one of effective ways to obtain a lower slag volume is to reduce the gangue content of sinter. Basically, lowering the amount of serpentine in the sinter mix is a feasible way to produce suitable sinter with a lower gangue content. However, this method may result in lower magnesium oxide content in the final slag that may affect its fluidity. Hence, the objective of this study was to understand the effect of MgO and Al(2)O(3) on the fluidity of blast furnace final slag. The liquidus temperature and viscosity of semi-synthetic slag were measured using optical softening temperature device and viscometer, respectively, and the data were calculated to develop the iso-liquidus temperature and iso-viscosity diagrams. The experimental results indicated that the lower liquidus temperature and the better viscosity stability lay in the area of MgO=5.4%, Al(2)O(3)=10-15%, and B2=1.2 for the range of composition studied. Several observations in the iso-fluidity diagrams of blast furnace final slag have shown that liquidus temperature decreased with decreasing MgO content and the viscosity of slag could be regarded as being independent of MgO content in the range of MgO=5-9%, Al(2)O(3)=15%, B2=1.0-1.2. And, slag fluidity became bad with increasing Al(2)O(3) content under the conditions of MgO=5.4%, B2=1.2. This study suggested the MgO contents could be lowered from current 6.5% to 5.4% in the conditions of Al(2)O(3)=15%, B2=1.2 under a stable blast furnace operation with a high thermal level, And, this suggestion had been implemented in the present blast furnace operation.
