Laboratory test work completed on samples of Northparkes ore indicated that shifting from forged steel to more electrochemically inert high chrome grinding media produced a more oxidizing pulp potential and reduced the Ethylenediaminetetraacetic acid (EDTA) extractable iron due to the improved corrosion resistance.
These changes in pulp and surface chemistry were responsible for a significant increase in copper and gold recovery. Based on these results, a plant trial at Northparkes was completed.
Pulp chemistry surveys of the plant before and after purging the mill of forged steel again showed that the transition to high chrome grinding media resulted in the pulp potentials becoming more oxidizing and the EDTA extractable iron reducing.
A statistical analysis of the recoveries showed that this change in grinding chemistry resulted in improvements of 1.0 and 1.3 percent, for copper and gold respectively.
It was also noted that the final copper concentrate grade improved by at least 0.7 percent. Examination of monthly composite data on a recovery-by-size basis showed that the improvement in copper recovery when using high chrome grinding media occurred in the intermediate size fractions, between 10 and 90 microns (m).
The main losses for both grinding media types from the circuit occurred in the coarse (+ 90 m) and fine (- 10 m) size fractions.
The liberation data indicated that the higher recoveries for high chrome appeared to be related to increased recoveries of liberated copper sulfides. This paper describes both the laboratory and plant trial methodologies employed at Northparkes and relates the improvements to the changes on a recovery-by-size and liberation-by-size as well as on a mineral class basis.
CITATION:Greet, C, Morgan, D, Davis, J, Small, G and du Toit, X, 2019. Metallurgical Improvements at Northparkes Concentrator through the Application of High Chrome Grinding Media, in Proceedings MetPlant 2019, pp 150162 (The Australasian Institute of Mining and Metallurgy: Melbourne).