7TH EUROPEAN COKE AND IRONMAKING CONGRESS - ECIC 2016

According to the metallurgical conditions of CSC, the influences of MgO content, Al2O3 content and C/S (=CaO/SiO2) on slag fluidity are studied for blast furnace operation. The liquidus temperature and viscosity of a semi-synthetic slag are measured using an optical softening temperature device and a viscometer, respectively. Based on these measured data, equations of liquidus temperature and viscosity of semi-synthetic slags (SiO2-Al2O3-CaO-MgO-TiO2) are developed in the multiple-regression formula. In CSC, the index of slag liquidus temperature is often used to adjust the ratio of burden materials and to remedy the abnormal conditions in BF operation. To ensure a normal and stable BF operation with low production cost, the research results indicated that the tolerable Al2O3 content is ranged 15-17 mass% for the slag with 6-8 mass% MgO and C/S < 1.15 to obtain an acceptable viscosity (< 10 poise) at the hot metal temperature above 1495°C. Basically, the slag fluidity is mainly determined by both viscosity and liquidus temperature. A combined slag fluidity index, including viscosity and liquidus temperature, has been designed in this research to indicate appropriate slag fluidity. The combined slag fluidity index has been incorporated into the tapping system of CSC BFs. The system is able to predict the difficulty of slag flow based on real-time data of liquidus temperature and viscosity for the coming tapping. It can immediately provide BF staffs some information to control the variation of slag fluidity via the effective operating adjustment, such as enforcing management of thermal state or varying the chemical composition of final slag by adjusting BF burdens.