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Unformatted text preview: Phase Equilibria in Ferrous Calcium Silicate Slags: Part III. Copper-Saturated Slag at 1250 C and 1300 C at an Oxygen Partial Pressure of 10- 6 atm STANKO NIKOLIC, PETER C. HAYES, and EVGUENI JAK Ferrous calcium silicate slags are potentially important for future practice in copper converting operations and process, and can be described by the Cu 2 O-FeO-Fe 2 O 3-CaO-SiO 2 system. Experimental methods, using the equilibration/quenching/electron probe X-ray microanalysis (EPMA) techniques, have been further developed to investigate the phase equilibria of these slags at copper saturation. Liquidus and solidus data are reported for the primary phase fields of spinel and pseudo-wollastonite at 1250 C and 1300 C, and at an oxygen partial pressure of 10- 6 atm. The resulting data have been used to construct liquidus and solidus isotherms in the FeO-CaO-SiO 2 system in equilibrium with metallic copper. DOI: 10.1007/s11663-008-9128-8 The Minerals, Metals & Materials Society and ASM International 2008 I. INTRODUCTION T RADITIONAL copper converting conducted in a PeirceSmith converter involves the use of iron-silicate slags. To overcome a number of practical issues asso- ciated with the use of PeirceSmith converters, including the ecient capture of sulfur dioxide gas, a number of continuous processes have been proposed. [ 1 ] Currently, the ISACONVERT* process [ 2 , 3 ] is under active devel- opment for the continuous converting of copper, and an appropriate slag system must be evaluated for use in this process. The Mitsubishi continuous process and the Outokumpu ash converting furnace use calcium-ferrite slags [ 1 ] for the production of copper due to their lower slag volume, lower copper losses, greater uidity, and more ecient impurity removal from the molten copper, when compared to iron-silicate slags. [ 1 ] However, cal- cium ferrite slags have limited silica solubility, low lead removablilty, and in some cases too high uidity. [ 4 ] To reach a balance between calcium-ferrite and iron-silicate slag systems, there has been interest in using ferrous calcium silicate (FeO-Fe 2 O 3-CaO-SiO 2 ) slags for the converting of copper. [ 4 ] Despite its industrial importance, the phase equilibria in the ferrous calcium silicate system at copper satura- tion have not been fully investigated. Characterization of this slag system at copper saturation is necessary to improve the design and optimization parameters of new and existing processes, and to evaluate its use in the industrial copper converting process. Previous work in this series of articles investigated this slag system at intermediate oxygen partial pressures relevant to copper converting in the absence of copper....
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