A thermodynamic database for copper smelting and converting

Abstract

The thermodynamic properties of the slag, matte, and liquid copper phases in the Cu-Ca-Fe-Si-O-S system have been critically assessed and optimized over the ranges of compositions of importance to copper smelting/converting based on thermodynamic and phase equilibria information available in the literature and using the modified quasichemical model. A thermodynamic database has been developed, which can be used for the calculation of matte-slag-copper-gas phase equilibria of interest for the production of copper. The model reproduces within experimental error limits all available experimental data on phase diagrams, matte-alloy miscibility gap and tie-lines, enthalpies of mixing, and activities of Cu and S in the matte and liquid alloy. The calculated solubilities of Cu in both Sfree slag and slag equilibrated with matte are also in good agreement with experiment under all studied conditions, such as at SiO 2 saturation, in equilibrium with Fe, Cu, or Cu-Au alloys, at fixed oxygen or SO 2 partial pressures and at different contents of CaO in the slag. Sulfide contents (sulfide capacities) of the slags are predicted within experimental error limits from the modified Reddy-Blander model, with no adjustable parameters. As an example of the application of the database, the stability field of matte/slag equilibrium is calculated, and the matte and slag compositions are plotted vs iron to silica ratio in the slag at various SO 2 pressures over this field. The matte-slag two-phase field is limited by the calculated lines corresponding to precipitation of copper, silica, and magnetite.

The modified quasichemical model I—Binary solutions

“…The Gibbs energy of the solution is given by In the modified quasichemical model in the pair approximation, as proposed by Pelton and Blander [1,2,3] for a liquid G ϭ (n A gЊ A ϩ n B gЊ B ) Ϫ T⌬S config ϩ (n AB /2) ⌬g AB [9] where gЊ A and gЊ B are the molar Gibbs energies of the pure [10] Because no exact expression is known for the entropy of this distribution in three dimensions, Eq. [10] is an approximate equation.…”

“…[2], [3], and [4] gives n AA , n BB , n AB , which can then be substituted into Eqs. [9] and [10]. Equation [13] is the "equilibrium constant" for the "quasichemical reaction" at 1000 ЊC with Z A ϭ Z B ϭ 2 from the quasichemical model for shortrange ordering with ⌬g AB ϭ constant ϭ 0, Ϫ21, Ϫ42, and Ϫ84 kJ.…”

“…Hence, we set Z Ni ϭ Z S . molten sulfide solutions [6,7] molten alloys, [7,8,9] and oxide In Cu-S solutions, on the other hand, maximum short-range slags/glasses [9][10][11][12][13][14][15][16][17][18][19][20][21] such as molten silicates. ordering occurs at the composition corresponding to Cu 2 S where X s ϭ 1/3.…”

“…Substitution into Eq. [9] then gives, in the Braggtional empirical parameters by expanding ⌬g AB as a polynoWilliams limit for small ⌬g AB mial in the component fractions:…”

Thermodynamic Modeling of Peirce‐Smith Converter Slag at the Chagres Smelter, Chile

“…The minor elements such as Pb, As, Sb, Bi, Cr and Ni were neglected as their level was too low (less than 0.5%) to significantly affect the slag chemistry. The thermodynamic property of each component was taken from the FactSage™ database; the molten phases (copper, matte and slag) and the solubility of copper in slag were described using the modified quasichemical model [2,3], with the sulfide solubility according to the Kang and Pelton quadruplet approximation [4]. A detailed methodology for the slag calculations has been described in Cardona et al [5].…”