Energy conservation and emission reduction through utilization of latent heat of copper slag for iron and copper recovery

Abstract

Copper slag, a bulk solid waste in the copper smelting sector, has significant economic and environmental value and needs to be cleaned and utilized. Extended processing durations, limited effectiveness, and substantial energy requirements characterize conventional recycling techniques. A stirring-intensified short-duration depletion method is proposed using high-temperature hot copper slag as raw material. By efficiently using the latent heat of copper slag, 90.13% of copper in copper slag can be recovered in 45 min, and the copper content in the tailing slag is reduced to 0.23 wt%. Based on the systematic characterization, a three-stage model is developed to describe the depletion process of hot copper slag under stirring-intensified conditions: the hot-state modification stage of slag, the homogenization and modification stage of the copper matte composition, and the directed settling stage of tiny copper matte droplets assisted by mechanical stirring. The utilization of economic constraints and environmental impact indicators proves the green sustainability of the method. Compared with industrial flotation, this method can save no less than 1250 MJ of energy for every metric ton of copper slag and reduce 156 kg of carbon dioxide emissions. The method uses hot copper slag as a raw material to fully utilize the latent heat of the copper slag, realizes directional enrichment and recovery of copper and iron, and reduces the generation of copper slag from the source.