Chapter 11 - Copper Loss in Slag

Abstract

This chapter discusses the nature of copper in smelting and converting slags. It also describes the strategies for minimizing the amount of copper loss from their disposal. The main strategies include minimizing the mass of slag generated, minimizing the percentage of copper in the slags, and processing the slags to recover copper. Pyrometallurgical production of molten copper generates two slags: smelting furnace slag with one to two percent copper and converter slag with four to eight percent copper. Discarding these slags would waste considerable copper, so they are always treated for copper recovery. The copper in smelting and converting slags is present in two forms: dissolved copper, which is present mostly as copper ions, and entrained droplets of matte. The entrained droplets are recovered by settling in a slag-cleaning furnace, whereas dissolved copper is recovered by hydrocarbon reduction and settling of matte. Other methods of recovering copper from slag is slow-cooling or solidification, crushing or grinding, and froth flotation. Electric furnace and slag flotation both have advantages for efficient copper recovery.