The Viscous and Conductivity Behavior of Melts Containing Iron Oxide in the FeO t -SiO 2 -CaO-Cu 2 O System for Copper S
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INTRODUCTION
VISCOSITY and electrical conductivity are the most important physicochemical properties of slags that influence the performance of metallurgical processes such as extracting, refining, and slag cleaning. In the copper pyrometallurgical process, understanding the viscosity and electrical conductivity of the copper smelting slags is important to increase the process efficiency and obtain the discrete separation between the slags and the matte. The composition and temperature dependence of viscosity and electrical conductivity of various slag systems has been studied by some researchers through numerous experiments. The viscosity of the FeO-SiO2 has been studied by some researchers.[1,2] In this simple binary system, a local maximum has been observed at the fayalite composition in the various temperatures. Ducret and Rankin[3] studied the viscosity of Fe-saturated FeOFe2O3-SiO2 slags and found the viscosity to increase with the addition of SiO2. Lee et al.[4] found that FeO additions at low basicity (CaO/SiO2 < 1.86) resulted in the dissociation of FeO, which could depolymerize the silicate structure and decrease the viscosity. Mills and Keene[5] investigated the effect of (pct Fe2O3)/(pct FeO) ratio on the viscosity in the FeO-Fe2O3-SiO2. The results showed that the viscosity increased marginally with increasing the (pct Fe2O3)/(pct FeO) ratio. The same results were obtained by Bodnar et al.[6] However, Kaiura et al.[7] found that the viscosity decreased ZHANG HUAIWEI, Ph.D. Candidate, SUN FEI and SHI XIAOYAN, Masters, ZHANG BO, Post Doctoral, and HONG XIN, Professor, are with Shanghai University, Shanghai 200072, P.R. China. Contact e-mail: [email protected] Manuscript submitted March 2, 2012. Article published online July 11, 2012. 1046—VOLUME 43B, OCTOBER 2012
marginally with the (pct Fe2O3)/(pct FeO) ratio in FeO-Fe2O3-SiO2 system. In order to confirm the viscosities of the ferrous silicate slags, further experimental studies may be required. The effect of Al2O3 additions in the ternary FeOt-SiO2-Al2O3 slag system showed a characteristic V-shaped pattern, in which initial additions decreased the viscosity, reaching a minimum and subsequently increasing with the higher Al2O3 content.[8] Wright[9] measured the viscosity of CaO-CuXO-MgOSiO2 slags from 1653 K (1380 °C) to 1793 K (1520 °C), he observed that CuxO is slightly better in reducing the viscosity than FeO. Normally, alkaline oxides such as CaO and MgO could decrease the viscosity when the molten slag was the homogenous liquid.[10–13] Jiao and Themelis[14] considered that the electrical conductivity in molten slags is mainly due to the migration of cations, and the temperature coefficient is higher for ferrous smelting slags and for higher SiO2 or Al2O3 concentrations. The electrical conductivities of FexO-CaO-SiO2, FexO-CaO-MgO-SiO2, and FexOCaO-SiO2-Al2O3 slags[15–17] had been reported in published articles. In general, the electrical conductivities of those molten slags increased with the increases of temperature and contents of FexO, CaO, and MgO. As t
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