Experimental phase equilibria study in key low order systems for copper smelting slags

It has been an ongoing need in the industry to adequately describe the phase chemistry of complex slag systems using thermodynamic models in order to optimise process performance and improve productivity. The chemical thermodynamic modellings are therefore established for studying complex slag systems, which need to be derived from the experimental study of binary and ternary systems. Those thermodynamic modellings can only be as accurate as the experimental data used in their construction. Therefore, it is essential to obtain the best possible experimental data in the low order slag systems, which is the key to the modelling construction. In this study, the focus has been on some of the low order systems where (1) discrepancies need to be resolved and (2) new data are required, which have been indicated by evaluating existing experimental data via the initial thermodynamic modellings. The methodology of this study involves (1) a preliminary phase diagrams are constructed based on phase equilibrium and property data obtained by previous researchers. In the case of sparse data set, theoretical tools together with FactSage were used to help with the design, selection of experimental conditions. (2) the interpretations of experimental phase equilibrium data , which are obtained by using the isothermal equilibration / quenching / microanalysis approach. Repeated experiments have been conducted at extended equilibration time with compositions from two opposite directions to ensure the achievement of equilibrium. Crucibles are designed to achieve maximum cooling rate. Concentration profiles within the glass (liquid phase) were established to detect incomplete equilibration or any precipitation that may occur during quenching. For an accurate microprobe analysis, standards have been carefully selected and measured comparatively.