Viscosity Studies of High-Temperature Metallurgical Slags Relevant to Ironmaking Process
2017
Slags are molten oxides presenting in a number of high-temperature processes. In ironmaking process, the metallurgical properties of blast furnace slags are determined largely by its viscosity. Understanding and controlling the behavior of the slag phase is crucial in improving the operational and economical efficiencies. However, high-temperature viscosity measurement is practically difficult, time- and cost-consuming. There is a necessity to develop a reliable mathematical model for the viscosity prediction through the review of experimental data and fundamental theory.As foundation work, abundant viscosity measurements and models have been examined and evaluated, including over 3000 viscosity data in the CaO-MgO-Al2O3-SiO2 system and 16 viscosity models. Over the past 10 years, there has been increasing attentions on wide composition range of slag viscosity due to the continuous consumption of complex iron ores. In addition, the impacts of eight minor elements (including F, Ti, B, Fe, Mn, Na, K, and S) on slag viscosity have been studied for practical purpose.Slag viscosity is determined by its structure, which is the theoretical base of the mathematical model. The structures of the quenched silicate slags were quantitatively investigated utilizing Raman spectroscopy. It is accepted that the application of Raman spectroscopy can disclosure the vibration units of molten slag, which can be interpreted the structural of silicate melts (amorphous glass phase).In the blast furnace operations, some solid phases such as oxide precipitates, coke or Ti(CN) can be present in the slag. In addition, the precipitation of solid particles was commonly observed in iron, steel, copper and other pyrometallurgy process. These solids can significantly increase the viscosity of the slag causing operating difficulty. There is a research gap that the solid impact on suspension was limited investigated under high-temperature condition due to uncertainty.Referring to the research gap of viscosity study of blast furnace slag, the following goals have been achieved by the Ph.D. candidate:1. Review and evaluated the experimental methodologies, viscosity data, and models relevant to the blast furnace slag in CaO-MgO-Al2O3-SiO2 system (Chapter 2)2. Based on the collected data and models, an accurate viscosity model has been developed to predict the viscosity of blast furnace slag in CaO-MgO-Al2O3-SiO2 system (Chapter 4-5)3. Research on the viscosity impact of minor elements on the blast furnace final slag in CaOMgO-Al2O3-SiO2 based system. (Chapter 4-5)4. Quantitative investigation of the microstructural units of silicate slag utilizing Raman spectroscopy. (Chapter 6)5. Investigation of the solid phase impact on the viscosity of liquid slag. (Chapter 7)
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