Improving Copper Recovery from Production Slags by Advanced Stirring Methods

Slags resulting from pyrometallurgical copper processes are important by-products to be controlled in structure and composition. Due to the significant volumes of slag compared with those of the target metal it is mandatory – as already practiced today – to use the slag as a product e.g. for river embankments. After matte smelting and standard slag cleaning in submerged arc furnaces (SAF), the fayalitic slag still contains up to 1 % of copper and other valuable metals like nickel, cobalt or molybdenum. In addition future regulations may restrict the heavy metal contents both in the solid and eluate in slags used for construction purposes in the future. Furthermore, the metal contents in ores are decreasing in the available deposits, much below the upper value of discarded slags. Sustainable slag management is necessary from the economical and environmental point of view. In the frame of a current collaborative BMBF funded research project lab-scale experiments are realized at the IME in order to improve the metal recovery and to create mineral product from the original slag with expanded market potential. Results will show the influence of different stirring conditions on the settling behaviour of metallic / matte droplets. Furthermore, the charging of various additives is investigated in order to decrease the viscosity leading to an improved settling velocity of metallic / matte inclusions as the paper will present.