Improving zinc recovery at Perilya Broken Hill concentrator by changing the grinding chemistry

An extensive body of work examining the electrochemical interactions between grinding media and sulphide minerals exists in academia however, the question on industries lips is: “Does this have relevance to an operating concentrator?”
This paper provides an account of the metallurgical test work completed at Perilya’s Broken Hill mine in far west New South Wales, Australia. The work completed extended over a number of years, and included laboratory studies using the Magotteaux Mill ®, which eventually lead to a full plant trial.
Broadly, the laboratory results indicated that a 21 percent chrome alloy would produce the optimum pulp chemical conditions for the best zinc metallurgy. The pulp chemical changes predicted by the laboratory work were achieved in the plant. Further, when the plant converted to 21 percent chrome grinding media in October 2007, the change in media type resulted in statistically significant improvements in the zinc concentrate grade (0.6 ± 0.3 percent), and zinc recovery (1.8±1.3 percent). The improvement in zinc concentrate grade can be attributed to better selectivity for sphalerite against iron sulphides (pyrrhotite).

C.J. Greet, M. Myllynen and D. MacKay