Phase Equilibria in Ferrous Calcium Silicate Slags: Part II. Evaluation of Experimental Data and Computer Thermodynamic Models

Abstract

Ferrous calcium silicate slags (described by the FeO-Fe 2 O 3 -CaO-SiO 2 system) are the basis for a number of slag systems used in nonferrous smelting. Characterization of this slag system is necessary to improve the design and optimization parameters of new processes, including fluxing and operating temperatures. Particularly of interest are the phase relations at intermediate oxygen partial pressures relevant to processes such as copper converting. Experimental data on the phase equilibria of these slags at controlled oxygen partial pressures in the temperature range between 1200°C and 1350°C are discussed, differences between various data sources are analyzed, and discrepancies are resolved. An evaluation of two thermodynamic computer models is undertaken to verify the computer-aided predictions using the experimental data. New experimental data for this system are reported for the temperature condition of 1300°C, defined using the equilibration/rapid-quenching/electron probe microanalysis (EPMA) with wavelength dispersive detectors technique. This new information, combined with results from the previous study, has enabled the equilibrium liquidus compositions to be defined over a wide range of temperatures and oxygen partial pressures.

Thermodynamic Calculation of Liquidus Surface of FeOx–CaO–SiO2 System

“…The comparison of calculated liquidus in the SiO 2 and magnetite saturation region at the oxygen partial pressure of 4ϫ10 Ϫ4 atm and 1 573 K with the experimental data by Henao et al 5) and Nikolic et al 7) is plotted in Fig. 3.…”

“…However, the MPE fit to the liquidus of the FeO xCaO-SiO 2 system in the air is not accurate. In the present study, two Fe 2 O 3 -CaO-SiO 2 ternary parameters were introduced and the SiO 2 -Fe 2 O 3 binary parameters were re-optimized to fit the liquidus data of FeO x -CaO-SiO 2 system in the air at 1 573 K. 5,7,12,13) Figure 1 compares the liquidus surface of the FeO x -CaO-SiO 2 system in air at 1 573 K and 1 513 K measured by Henao et al, 5) by Nikolic et al, 7) by Phillips and Muan, 12) by Pownceby et al 13) and the model calculation. There is general agreement between these sets of data except for the region of SiO 2 content ranging from 10 to 20 mass%.…”

“…The literature data available up to Year 2000 on the effect of oxygen partial pressure and additions of Al 2 O 3 and MgO on the liquid region of the FeO x -CaO-SiO 2 and its sub-systems are critically reviewed by Yazawa. 2) More experimental [3][4][5][6][7][8] and modelling efforts 9,10) have since been made on the FeO x -CaO-SiO 2 system under the compositional conditions and oxygen partial pressures more relevant to the iron ore sintering process. However, the model prediction 9,10) does not agree with the experimental data by Shigaki et al, 11) particularly in magnetite saturation region.…”

“…ture [3][4][5][6][7][8][11][12][13] and between the experimental data [3][4][5][6][7][8]11) and modelling results. 9,10) In this paper, a modified version of the computational package: Multi-Phase Equilibrium (MPE) software developed by CSIRO, 14,15) was used to quantify the liquidus surface of the FeO x -CaO-SiO 2 system containing Al 2 O 3 and MgO at various intermediate oxygen partial pressures.…”

Copper Solubility and Redox Equilibria in Magnesia Saturated CaO-CuOx-FeOx Slags

“…[14,15] Most of the thermodynamic investigations into calcium ferrite slags have concentrated on liquidus boundaries at copper-making temperatures, [10,[16][17][18][19][20] iron redox equilibria, [16][17][18][21][22][23][24] and the solubility of copper in slag. [11,15,19,25,26] Nikolic et al [27] and Hidayat et al [28] investigated the thermodynamics of complex slag systems relevant to modern copper smelting and converting processes as part of a thermodynamic modeling study. Jak et al [5] also investigated calcium ferrite-based slag systems in a study on the control of slag freeze linings which are used in new copper converting processes.…”