Fundamental Study on the Hot-stage Copper Slag Engineering for High Added-value Applications

Promovendus/a: Yannan Wang

Promotor(en): Prof. dr. ir. Bart Blanpain, De heer Muxing Guo, De heer Shuigen Huang

To valorize the iron silicate slag after the Zn fuming process, the addition of CaO-rich Linz-Donawitz slag (LD slag) into the Zn fuming bath has been proposed. This endeavors to produce CaO-rich iron silicate slag, which has been reported as an excellent material for cement replacement in concrete production. This thesis aims to understand the influence of increasing CaO content in the Zn fuming bath on slag fuming behavior, high-temperature slag mineralogy, and slag rheological and solidification behavior. The industrial samples from the standard and LD slag modified Zn fuming processes were comprehensively characterized using cutting-edge analytical techniques to understand their features at high temperatures and their evolution during the Zn fuming process. The industrial fuming conditions, namely fuming temperature and pO2, were estimated by comparing the slag characterization results with FactSage simulation results. The effect of CaO content on the slag fuming process and the valorization of Zn-fumed slag was investigated in four aspects. First, CaO solubility in the liquid phase of copper slag (FeOt-SiO2-CaO-Al2O3-(ZnO, Cr2O3) system at 1200 and 1250°C was measured, and the influencing factors on the solubility were studied. Second, optimized fuming conditions, including slag chemistry, pO2, and temperature, were proposed for an efficient Zn recovery from copper slag without Fe generation. Next, the viscosity of CaO-modified copper slag under Zn fuming conditions was investigated with respect to the effects of slag chemistry (mainly the FeO/SiO2 ratio and CaO content) and operating temperature, cooling and shear rate. Finally, the slag solidification behavior was studied using the confocal laser scanning microscope (CLSM) along with equilibrium-quenching experiments. This thesis concluded that the Zn-fumed copper slag valorization can be achieved by adding CaO-rich materials to the copper slag during the Zn fuming process under optimized fuming conditions.