Technical Note

Effect of ball size change on the performance of grinding and flotation circuits

S. Banisi* and M. Farzaneh

Mining Engineering Department, Shahid Bahonar University of Kerman, P.O. Box 761-133, Iran

Received 23 August 2003; accepted 15 July 2004


At the Sarcheshmeh copper mine 41,000 t of ore per day with an average grade of 0.9% Cu is ground to 70% passing 75 microns. Grinding is effected in 8 parallel lines of 8x5m ball mills in a closed circuit with cyclones. The make-up balls are 80-mm forged alloy steel balls and the average ball consumption is 750g/t of ore ground. In order to optimize ball size distribution inside the mill, based on the previous investigation instead of using only 80 mm make-up balls a combination of 80 and 60mm (75% to 25% by weight) ball charge was used in one of the mills. To evaluate the performance of three ball types namely forged alloy steel balls (A), ductile cast iron (C), high chromium cast iron (D) and also a combined (80 and 60 mm) charge of forged alloy steel balls (B), four identical parallel mills were charged accordingly. These four mills were sampled during a period of one year. The amount of material finer than 75 microns of cyclone overflows was selected as a criterion for the performance evaluation. It was observed that in a mill with the combined make-up balls the amount of fine produced was 4% higher than the other mills. The consumption of ball types A, C and D were 730, 710 and 534g/t, respectively. The results of laboratory flotation tests showed that due to an improvement in the production of fines an increase of 1.4% in the overall copper recovery is obtainable. Due to the promising results, the new make-up ball regime was implemented in all mills in the plant.

Keywords: Ball size; Flotation; Grinding; Liberation degree

* Corresponding author
   E-mail : banisi@mail.uk.ac.ir