Activity and Activity Coefficient of Iron Oxides in the Liquid FeO-Fe2O3-CaO-SiO2 Slag Systems at Intermediate Oxygen Partial Pressures

Abstract

At present, there is a scarcity of data on the activities of iron oxides in the FeO-Fe 2 O 3 -CaO-SiO 2 slag system at intermediate oxygen partial pressures and temperatures relevant to sulfide smelting and nonferrous metallurgy. The present study provides relevant data at temperatures between 1573 and 1673 K and partial pressures of oxygen between 10 -9 and 10 -4 atm. The experiments were carried out by equilibrating the slag in a CO-CO 2 gas mixture in a platinum crucible, after which the phases of all the experimental samples, including the platinum foil, were analyzed by electron probe microanalysis (EPMA). Where only liquid phase or liquid phase and tridymite (SiO 2 ) were observed, wet chemical analysis was used to determine the ratio of (mass pct Fe 2+ )/(mass pct Fe 3+ ). Activity and activity coefficients for FeO (liquid) and FeO 1.33 (solid) were calculated. Tendencies of the effect of the (CaO/SiO 2 ) ratio, temperature, and oxygen partial pressure on these thermochemical quantities are discussed in this article.

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

“…This relationship [12] is solely used for comparison to the results of this study and the relationship defined by Henao and Itagaki. [10] The results of the current study showed excellent agreement with the curves defined by the equations of both Henao and Itagaki [10] and Fredriksson and Seetharaman. [12] Since the difference in the position of the liquidus in Figures 2 and 4 was greater than can be accounted for by the uncertainty in the experimental technique of Henao et al [2] and this study [1] and that Figures 3 and 5 showed good correlation between the experimental results, a targeted program was undertaken at the Pyrometallurgy Research Centre at the University of Queensland involving the authors of this article and Henao et al A number of steps were undertaken, summarized in Table VI, to eliminate each potential source of inaccuracy on the resulting differences between the studies.…”

“…The results of this study are shown together with the result of the equation that relates the mole fraction of iron in the platinum crucible to the logarithm of the activity coefficient of iron of Henao and Itagaki [10] ( Figure 5). Included in this figure is the polynomial curve defined by Fredriksson and Seetharaman, [12] which relates the mole fraction of iron in an iron platinum alloy to the logarithm of the activity coefficient of iron with the equation log ðc Fe Þ ¼ À3:11 þ 3:383N FeðinPtÞ þ 10:749 N FeðinPtÞ À Á 2 À 19:467 N FeðinPtÞ À Á 3 þ 8:620 N FeðinPtÞ À Á 4…”

“…The details of this work are contained in the article by Henao and Itagaki, [10] which states that at a fixed oxygen partial pressure the concentration of iron within the platinum crucible is fixed by the equation…”

Effect of Al2O3 or MgO on Liquidus Line in the FeOX Corner of FeOX-SiO2-CaO System at 1523 K under Various Oxygen Partial Pressures

“…Details of the experimental method and procedure were reported in the previous papers [5,6]. Firstly, the liquidus lines were determined for the plain slag without Al 2 O 3 and MgO; (1) the desired temperature and oxygen pressure.…”

“…In the present study, followed by the investigations on the plain FeO X -SiO 2 -CaO ternary system at 1573 K [5,6], the liquidus lines were experimentally determined for the system containing given amounts of Al 2 O 3 or MgO at 1523 K under a very wide range of oxygen partial pressure between about 10 12 corresponding to the iron saturation and about 10 4 corresponding to the CO 2 atmosphere, and for the (mass% CaO=mass% SiO 2 / ratio of the system between 0 and about 1.…”