Effects of MgO/Al 2 O 3 Ratio and Basicity on the Viscosities of CaO-MgO-SiO 2 -Al 2 O 3 Slags: Experiments and Modeling
- PDF / 1,101,162 Bytes
- 12 Pages / 593.972 x 792 pts Page_size
- 91 Downloads / 224 Views
ON
IN the case of a blast furnace (BF) operation, it is of great importance to understand the viscous behavior of slags, which affects the gas permeability, heat transfer, reduction of FeO, the rate of desulphurization, etc. For these reasons, measuring the viscosities of BF-type slags or constructing viscosity prediction models has attracted tremendous attention in the past six decades.[1–24] In 1954, Bockris et al.[1,2] measured the viscosities of binary slags such as CaO-SiO2 slags, MgO-SiO2 slags, and Na2O-SiO2 slags, which led to a basic understanding of structural interpretation. Since then, the relationship between viscosity and structure changes has been further discussed and taken into account in many viscosity prediction models.[8,10,13,25–30] Machin and Hanna[3–6] measured the viscosities of CaO-MgO-SiO2-Al2O3 slags in the temperature range 1523 K to 1773 K (1250 °C to 1500 °C), and their experimental results with high accuracy were often chosen to be the criteria for evaluating the applicability of viscosity prediction models.[8,25,28,29] Tsunawaki et al.[31] first calculated the fractions of bridging oxygen, nonbridging oxygen, and free oxygen by using information from Raman spectra, and the experimental results were in good agreement with those obtained by the cell model. This phenomenon
LI PENGCHENG, Ph.D. Candidate and NING XIAOJUN, Associate Professor, are with the School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, P.R. China. Contact e-mail: [email protected] Manuscript submitted May 1, 2015. Article published online November 30, 2015. 446—VOLUME 47B, FEBRUARY 2016
suggested that the thermodynamical model can reliably reflect the existence of different oxygen linkages in silicate melts. In the work of Lin and Pelton,[32] a famous concept of ‘‘complete bridge breaking’’ was proposed, and this simple method can be reliably used to calculate the mole fractions of bridging oxygen, nonbridging oxygen, and free oxygen. Urbain[7] proposed an idea of obtaining the viscosity of complex slags by combining the results of simple binary or ternary slags in his model. Although the Urbain model was found not capable of predicting the viscosity of slags with enough accuracy,[8,25,28,29] it provided an important step in using simple binary or ternary systems to extrapolate complex systems. In the KTH model,[33–36] information from the Gibbs energy mixing or excess Gibbs energy mixing was taken into consideration, and the calculated results from the KTH model showed satisfactory agreement with the experimental measurements. Stebbins and Xu[37] have proposed that tricluster oxygens may behave as nonbridging oxygens (NBOs) and that these NBOs in the form of Al-O-Si linkages decreased the viscosity of slags. By using the concept of the cell model, Nakamoto et al.[8] have studied the viscosities of CaO-MgOSiO2-Al2O3 slags in the temperature range 1523 K to 1723 K (1250 °C to 1450 °C), and the chemical composition of 52.7 mass pct CaO-4.9 mass pct MgO-7.4 mass
Data Loading...
