| As iron ore resource of high quality decreases gradually, steel enterprises begin topurchase varied iron ores with complex components which lower the ore grade.Somehigh-quality ores such as Australian ores are used to improve the ore grade for BF. ButAustralian ores are of high Al2O3, which will increase the content of Al2O3in ores forBF. Therefore, it is essentially important to study the physical chemistry properties ofBF slag of high Al2O3.This paper is based on the BF production condition of Nanjing Steel, in whichthermodynamic theoretical calculations and experimental study are made to analyze theinfluence of MgO/Al2O3and CaO/SiO2on metallurgical properties of BF slag such asfluidity, melting and desulfurization. Through analysis proper slagging regime isacquired with changing burden structure.The main conclusions:(1)Slags of Nanjing Steel have narrow melting regions of about7℃~18℃. And thetemperature range during which the slag can flow freely is about10℃~20℃. Sotemperature control is essentially important for good fluidity.(2)When CaO/SiO2is fixed at1.20, Al2O3at15%and18%, with increasingMgO/Al2O3, slag viscosity decreases by24.3%~32.5%and42.4%~44.8%respectively.Smelting temperature decreases, while melting temperature has its maximum atMgO/Al2O3=0.5. Melting region get narrower. When MgO/Al2O3is fixed at0.55, withincreasing CaO/SiO2, slag viscosity decreases by36.0%~42.8%, Smelting temperatureand melting temperature increases. Melting region has no change.(3) When CaO/SiO2is fixed at1.20, Al2O3at15%and18%, with increasingMgO/Al2O3, desulfurization ability improves and distribution ratio of sulfur betweenslag and iron increases by27.4%and43.1%respectively. When MgO/Al2O3is fixed at0.55, with increasing CaO/SiO2, distribution ratio increases by196.6%.By overall consideration proper MgO/Al2O3is0.55. Taking high smeltingtemperature and melting temperature into consideration, CaO/SiO2should not surpass1.25. Also it should not be less than1.15because of desulfurization ability. So properCaO/SiO2is1.20. When Al2O3surpass18%, slagging regime of high MgO/Al2O3（0.55~0.65）and proper CaO/SiO2between1.15and1.20is suggested. |
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