Phase equilibria in the ZnO-MgO-SiO₂ and PbO-ZnO-MgO-SiO₂ systems for characterizing MgO-based refractory - slag interactions

An integrated experimental and thermodynamic modelling investigation of the phase equilibria in the ZnO-MgOSiO2 and PbO-ZnO-MgO-SiO2 systems in air has been undertaken for characterizing the effect of Zn on MgObased refractory - slag interactions in the lead processing reactors. New experimental phase equilibria and liquidus data at 725-1740 degrees C were obtained using high-temperature equilibration of oxide powder mixtures followed by rapid quenching of the samples. Electron probe X-ray microanalysis was used to determine the compositions of the phases present at equilibrium conditions. Wide ranges of solid solutions were identified for periclase (Mg,Zn)O, zincite (Zn,Mg)O, olivine (Mg,Zn)2SiO4, willemite (Zn,Mg)2SiO4, pyroxene (Mg,Zn)SiO3, larsenite Pb(Zn,Mg)SiO4, barysilite Pb8(Zn,Mg)Si6O21 and melilite Pb2(Zn,Mg)Si2O7 phases, indicating possible stabilization of refractories in the presence of ZnO in slag. The experimental results were used for optimization of the parameters in a thermodynamic database that is subsequently used to describe the Pb/Cu-containing multicomponent multi-phase system for characterizing slag-refractory interactions.