SAG Mill Precrushing

In this circuit, a portion of the semi autogenous grinding (SAG) mill feed is precrushed in a secondary crusher followed by an HPGR (with prescreening for top-size control, if necessary) before rejoining the main SAG mill feed stream. The total SAG mill feed is therefore correspondingly finer while some coarse particles are retained in the mill feed as media.

This is suitable for both new and existing operations and has the potential to increase mill throughput by 50% or more.

An alternative to this arrangement is to deliver the HPGR product to the SAG mill discharge screen, so that finished product and material of ball mill feed size bypasses the SAG mill.

These circuits are flexible in that milling can continue (albeit at reduced rates) with the precrushing circuit out of service. Also, if an HPGR bypass facility is provided, the secondary crushing component of the precrushing circuit can continue to operate when the HPGR is inactive.