Most SAG grinding operations currently use ball size between 5.5 and 6 inch maximum size, However, in most cases the use of these ball sizes hasn't been justified by a phenomenological analysis of the real effect on the grinding process, but rather by trial and error. The analysis of the influence of ball sizes in SAG grinding hasn't been developed in detail by considering the effect on process parameters inside the mill, grinding efficiency or internal classification. Historically a conventional grinding reference has been made on the empirical procedure developed by Azzaroni (1980). Further to Azzaroni's methodology, Sepulveda ( Sepulveda, 2007) developed the SPEC methodology, incorporating the ball size effect on the grinding efficiency parameters using a population balance model included on Moly-Cop tool spreadsheets.
This paper demonstrates a detailed analysis at pilot scale of the ball size employed in SAG grinding and scaling that exists between the different levels. This analysis includes assessing the effect of balls sizes on parameters associated with grinding efficiency and its effect on the total fill level, product size distribution and specific energy consumption, among others. In a complementary way it develops a technical -economical evaluation from industrial data comparing two different ball sizes and its effect on the grinding process analyzed integrally.