Reaction Thermodynamics and Slag-Metal Separation Behavior during Copper Slag Cleaning

Abstract

The reduction reaction and slag-metal separation behavior are important factors influencing metal recovery rates during copper slag cleaning. In this study, theoretical calculations combined with experiments were carried out to investigate the effects of temperature, reductant dosage and CaO on the recovery of Cu and Fe, while revealing the separation behavior of metal particles from slag. Theoretically, the Fe₃O₄ reduction is cascaded and prioritized over Fe₂SiO₄ reduction. Increase of temperature and reductant dosage effectively promotes the recycling of Cu and Fe, and the appropriate amount of CaO promotes the depolymerization of complex silicate structure of slag and the aggregation of metal particles. The temperature was increased from 1623 K to 1698 K, the recoveries of Cu and Fe were increased from 88.46% and 73.68% to 96.78% and 95.88%, respectively. During initial stage of copper slag cleaning, Fe₃O₄ is reduced, and metal particles aggregate and settle in the middle and lower layers. Subsequently, Fe₂SiO₄ is reduced to metallic Fe, which combines with matte to form alloy and settle to bottom slag. The optimal recovery rates for Cu and Fe are 96.78% and 95.88%, respectively. The results of this study provide a reliable reference for strengthening the slag-metal separation, recovering Cu-Fe binary liquid alloy and improving the utilization rate of copper slag in the copper slag cleaning.