Experimental Phase Equilibria Study and Thermodynamic Modelling of the PbO-'FeO'-SiO2, PbO-'FeO'-CaO and PbO-'FeO'-CaO-SiO2 Systems in Equilibrium with Metallic Pb and Fe

Phase equilibria of the PbO-“FeO”-SiO2 and PbO-“FeO”-CaO-SiO2 slags with liquid Pb metal, solid or liquid Fe metal and solid oxides [cristobalite and tridymite SiO2, wustite (Fe,Ca)O1+x, olivine (Fe,Ca)2SiO4, dicalcium silicate (Ca,Fe)2SiO4, wollastonite (Ca,Fe)SiO3 and lime (Ca,Fe)O] were investigated at 1100-1689 °C. These conditions correspond to the minimum solubility of PbO in slag in presence of Pb and Fe metals at reducing conditions and represent the limit of lead smelting and slag cleaning process. High-temperature equilibration on silica or iron foil substrates, followed by quenching and direct measurement of Pb, Fe, Ca, and Si concentrations in the phases with the electron probe x-ray microanalysis (EPMA) was used to accurately characterize the system. Present results provide important basis for improvement of the thermodynamic models for all phases in this system.