Thermodynamic behaviour of zinc in Fe-C and CaO-FeO-CaF₂ slag at high temperatures

The distribution ratio of zinc between Ag-Zn and Fe-Zn alloys was measured to clarify the thermodynamic behaviour of zinc in Fe-C melt at high temperatures. Also, the distribution ratio between Ag-Zn alloy and CaO-FeO-CaF₂ slag was measured to understand the dissolution mechanism of zinc in molten slags. The activity coefficient of zinc in Ag-Zn alloy was preliminarily measured as a fundamental thermodynamic data for the activity of zinc in Fe-C melt. From the dependence of the activity coefficient of zinc in Fe-C melts on temperature and carbon content, the following equation could be obtained at 1473 - 1623 K: In γ_Zn^Fe-C=35.1 42200/T+20.9(X_c-X_C^satd) (1573 K ≤ T ≤ 1623K). The distribution ratio of zinc between Ag-Zn alloy and CaO-FeO-CaF₂ slag increased by increasing both the oxygen potential and slag basicity. The stoichiometric coefficients of the dissolution reaction were obtained by considering the relationship between zinc distribution ratio and slag basicity or oxygen partial pressure, when one of these two independent variables was fixed. The dissolution reaction of zinc into the slags could be described as follows: Zn(I)+20^2-(slag)+1/2O₂(g)=ZnO₃^4- (slag).