Investigation on the Thermal Conductivity of the Molten Copper Slag Cooling and Solidification Process

Abstract

The slow cooling of ladle slag during copper smelting offers broad potential for recovering valuable metals. Thermal conductivity is a key parameter influencing the slag’s cooling rate. However, limited research on the thermal conductivity of copper slag constrains the development of effective cooling strategies. This study systematically investigates the effects of temperature, chemical composition, and microstructure on the thermal conductivity of the SiO₂–FeO–Al₂O₃–MgO–CaO-based copper slag using laser flash analysis. As the slag cooled from 1523 K to 1398 K, 723 K, and 323 K, the corresponding thermal conductivities were 0.3594, 0.8046, 0.7085, and 0.9388 W/(m·K), respectively. Increasing SiO₂ (from 31.44 wt.% to 45 wt.%) and Al₂O₃ (from 4.24 wt.% to 12 wt.%) promoted melt polymerization, enhancing thermal conductivity at 1523 K by 27–63% and 4–26 %, respectively. By contrast, increasing the Fe/SiO2 ratio (from 1.25 to 1.6) and CaO content (from 2.88 wt.% to 11 wt.%) induced depolymerization, decreasing thermal conductivity by 7–34% and 4–10%, respectively. Increasing MgO content (from 3.1 wt.% to 11 wt.%) elevated the melting point, improving thermal conductivity by 1–37 %. The impact of the crystallization of copper slag by increasing the content of SiO₂, Al₂O₃, MgO, and CaO resulted in a decrease in thermal conductivity of solid slag by 4–31 %, whereas FeO allowed an increase in thermal conductivity by 12–88 %. These findings provide a theoretical basis for optimizing the cooling process of copper slag in industrial applications.