Phase Equilibria in Ferrous Calcium Silicate Slags: Part I. Intermediate Oxygen Partial Pressures in the Temperature Range 1200 °C to 1350 °C

Abstract

Ferrous calcium silicate slags are used in primary and secondary metallurgical processes (described by the FeO-Fe 2 O 3 -CaO-SiO 2 system). Despite the industrial and scientific importance of this system, the phase equilibria have not been fully investigated. Characterization of this slag system is necessary to improve the design and optimization of new and existing metallurgical processes, particularly in relation to fluxing practice and operating temperatures. Experimental methods have been developed to investigate the phase equilibria of these slags involving the equilibration of samples at fixed oxygen partial pressures, rapid quenching, and the analysis of the compositions of solid and liquid phases using electron probe X-ray microanalysis (EPMA) with wavelength dispersive detectors. Liquidus and solidus data are reported for the primary phase fields of spinel, pseudo-wollastonite, and tridymite in the temperature range of 1200°C to 1350°C at an oxygen partial pressure of 10 -6 atm, and at 1250°C at an oxygen partial pressure of 10 -5 atm. The resulting data have been used to construct liquidus and solidus isotherms in the ''FeO''-CaO-SiO 2 system directly relevant to industrial processes.

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

“…The use of platinum crucibles to contain slags, as used in the previous investigation [5] on the FeO-Fe 2 O 3 -CaO-SiO 2 system, is not feasible due to the dissolution of metallic copper in the platinum crucibles resulting in the melting of the crucible. Previous studies of copper-saturated slags were undertaken by Ilyushechkin et al [7] and Takeda [8] investigating calcium-ferrite slags.…”

“…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. [5] There has been some investigation into the ''Cu 2 O''-FeO-Fe 2 O 3 -CaOSiO 2 system in air by Hino et al, [6] who completed work at 1200°C and 1300°C with a total of 15 pct SiO 2 in the melt. Hino et al [6] did not report any results for the system at copper saturation involving SiO 2 in the melt.…”

Experimental Study and Thermodynamic Re-optimization of the FeO-Fe2O3-SiO2 System

“…Energy-dispersive x-ray spectroscopy spectrums of the phases are provided in the figure. The experimental results from the present and previous studies [41,42,44] are given in Table 1 respectively, while all iron oxides were recalculated to FeO. This was performed for presentation purposes only, and this is equivalent to projecting the slag compositions from the oxygen-corner of the Ca-Fe-O-Si compositional space onto the CaO-FeO-SiO 2 ternary plane.…”

“…and vacancies defects resulting wüstite non-stoichiometry toward oxygen. The Gibbs energy of the wüstite is therefore given as: [41,42,44] where g o M and X M are the molar Gibbs energy of pure component and the mole fraction of pure component, respectively. L M-N is the interaction energy parameter between two components which is expanded as polynomial in the mole fractions of the components.…”

High-temperature experimental and thermodynamic modelling research on the pyrometallurgical processing of copper

“…The experimental technique and equipment have been used to accurately characterize high-temperature phase equilibria in various slag systems including CaO-"FeO"-SiO2 system [8][9][10] , CaO-"FeO"-SiO2-S system 11 , CaO-"FeO"-SiO2-MeOx (Me=Al, Mg) systems 12 , "Cu2O"-SiO2-MeOx (Me=Al, Ca, Mg, Fe) systems 13,14 , "Cu2O"-CaO-"Fe2O3" system 15 , "Cu2O"-CaO-"FeO"-SiO2 system 16,17 , and more.…”