Experimental Study of Ferrous Calcium Silicate Slags: Phase Equilibria at $$ {\text{P}}_{{{\text{O}}_{2} }} $$ Between 1
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MOST primary copper sulfide smelting, copper converting, and direct-to-copper smelting processes operate with silicate-based slags.[1,2] Despite the widespread use of silicate-based slags in copper-making processes, as well as in other nonferrous smelting, certain aspects of the chemistries and phase equilibria of the systems remain uncertain. Information on the chemistries and phase equilibria of the systems is needed for improvements of the current operations and the development of new processes. The principal components present in these silicatebased slags are ‘‘FeOx’’-CaO-SiO2. A review of the literature shows that several studies are available on phase equilibria of ‘‘FeO’’-CaO-SiO2 system that have been carried out at conditions relevant to copper production. Shigaki et al.[3] investigated the phase diagram of the ‘‘FeO’’-CaO-SiO2 system at 1573 K (1300 C) and an oxygen partial pressure of 107 atm. The equilibration of 1 g of sample in Pt foil crucible was carried out at the target temperature for 3 hours. After the equilibration, the sample was quenched into water and the electron probe X-ray microanalysis (EPMA) technique was used to analyze the composition of phases in the sample. Kimura et al.[4] studied the effect of oxygen partial pressure (between 102.68 and 107.75 atm) on the liquidus of the ‘‘FeO’’-CaO-SiO2 system at 1573 K (1300 C). A platinum crucible was used to contain 8 g of sample. The equilibrated samples were cooled under an argon gas flow. The fully liquid slag in the sample was separated from the solid phases and was analyzed by using a bulk wet chemical analysis technique. TAUFIQ HIDAYAT, Postgraduate Student, PETER C. HAYES, Xstrata Professor, and EVGUENI JAK, Professor, are with the Pyrometallurgy Research Centre (PYROSEARCH), School of Chemical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia. Contact e-mail: [email protected] Manuscript submitted May 3, 2011. Article published online September 16, 2011. 14—VOLUME 43B, FEBRUARY 2012
Henao et al.[5] investigated phase equilibria of the ‘‘FeO’’-CaO-SiO2 system at oxygen partial pressures between 103.4 atm and 109 atm at a fixed temperature of 1573 K (1300 C). Henao et al.[5] also investigated the system at a constant oxygen partial pressure of 106 atm at temperatures between 1623 K and 1673 K (1350 C and 1400 C). Equilibrations of samples were carried out in Pt foil crucibles for 24 hours. An argon gas stream was used to cool the equilibrated samples. The compositions of liquid and solid phases formed in the sample were determined using EPMA. Nikolic et al.[6] carried out phase equilibria studies on the ‘‘FeO’’-CaO-SiO2 system at 1473 K and 1573 K (1200 C and 1300 C) at an oxygen partial pressure of 106 atm, and at 1523 K (1250 C) at an oxygen partial pressure of 105 atm. Equilibration of the samples in this study was carried out in Pt foil envelope for 24 hours followed by quenching of the samples into water. The compositions of the liquid and solid phases were determined by using EPMA. A cr
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