A General Viscosity Model for Molten Blast Furnace Slag
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TRODUCTION
SLAGS play critical roles in the manufacturing and refining of metals. Careful and thorough understandings of their physical properties, specially, at high temperatures, would not only lead to higher efficiency and lower cost, but also provide insight into the dynamics and structures of slags.[1–3] Viscosity is the single most important physical property governing the production and transportation of slags. Therefore, accurate prediction of slag viscosity as a function of temperature and chemical compositions is of considerable importance for process optimization.[3–8] Blast furnace slag is the most abundant slag in the steel industry, and also it is one of the most studied slags. Establishing an accurate viscosity model for blast furnace slag would be significant for the ironmaking process. Meanwhile, blast furnace slag contains some of the highest quantity and quality of waste heat in the steel industry; the knowledge of viscosity would also important for its hot processing and heat recovery.[9–11] Measuring of viscosity of blast furnace slag has begun as early as the 1910s.[12] Up to now, a great number of composition–temperature–viscosity data are available from the literature, as listed in Table II, as shown later in this article. In Table II, the blast furnace slags were classified as synthetic and industrial. The synthetic slags are those prepared using high-purity chemicals. The industrial slags are those obtained from practical blast furnace operations. The slags that modified based on real slag by adding a small fraction of high-purity chemicals were also treated as industrial in this work. Nearly all the viscosity measurements on synthetic or LEI GAN, Lecturer, and CHAOBIN LAI, Professor, are with the School of Metallurgical and Chemical Engineering, Jiangxi University of Science and Technology, 341000 Ganzhou, Jiangxi Province, P.R. China. Contact e-mail: [email protected] Manuscript submitted July 12, 2013. Article published online November 14, 2013. METALLURGICAL AND MATERIALS TRANSACTIONS B
modified industrial slags involve premelting of the slag to ensure the homogeneity of the compositions; therefore, the only major difference between synthetic and industrial slags should be the compositions. It is obvious that the synthetic slags contain only the major components including CaO, SiO2, Al2O3 and MgO, whereas the industrial slags contain more minor components, like FeO, MnO, TiO2, P2O5, S, etc. The influence of minor components on the viscosity of industrial slags will be discussed in Part IV. Most of the viscosity data used in this study were obtained by rotating bob/crucible method, except some used the oscillating[13,14] or counterbalanced sphere[6,7,15] methods. In the current work, all these methods are considered to be reliable techniques for high-temperature viscosity measurement. Additionally, all the measurements listed in Table II were performed under neutral atmosphere, e.g., Ar or N2. However, the use of crucible material was different. More than half of the measurements on synthetic
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