Two grinding flowsheet: SAG mill - crushing critical size, Precrusing- SAG mill. What is better?

Question: Two grinding flowsheet: SAG mill - crushing critical size, Precrusing- SAG mill. What is better?

Reply: The case of a SAG mill followed by scats (oversize in mill discharge) crushing is usually used to reduce the oversize material by crushing because a) there is not enough competent coarse material in the SAG mill to do this at the required rate or b) there is a hard component in the mill feed which is resistant to breakage by the operating conditions in the mill. Precrushing part of the SAG feed on the other hand is a means of increasing mill throughput by reducing the coarse lump breakage energy required in the mill by reducing the quantity of coarse material which has to be broken by impact with balls or coarse ore lumps. You need to review the grinding characterisation data for the Novoi ore(s) and operating practices to detrmine which approach will achieve your objective. Simulations will be helpful if properly interpreted.