Sulfurization Roasting of Copper Bottom-Blown Slag for Zinc Removal Using Pyrite

Copper slag is a residue from the copper smelting process that not only takes up large amounts of space, but also contains harmful elements that can cause environmental pollution. In this paper, zinc in copper slag is sulfide-roasted using pyrite as a vulcanizing agent and anthracite and K₂CO₃ as additives, thus leaving zinc in the slag mainly in the form of ZnS. After sulfurization roasting, the slag can be stripped of Zn by flotation, and the remaining iron can be further applied in the blast furnace ironmaking process. The effects of temperature, holding time, pyrite addition, and K₂CO₃ addition on the Zn sulfation rate were investigated. The results showed that when pyrite, anthracite, and K₂CO₃ were added to the slag in amounts of 35, 2, and 10 pct of the slag’s original mass, respectively, the total Zn in the slag was 3.16 pct, and its sulfuration rate was 83.5 pct. When pyrite was used to sulfide and dezincify copper bottom-blown smelting slag, the ZnO content in the slag was effectively reduced in preparation for subsequent ironmaking after flotation. This approach not only solves the problem of large piles of copper slag that cannot be fully utilized, but also alleviates the current shortage of iron ore in China.