As noted in Bulletin No. 4, the ball mill does the grinding. However, the pump and cyclones determine what material the mill grinds. Recall the term “CSE”, the circuit “Classification System Efficiency”, which is the percentage of coarse (plus P80 size) material inside the mill. So the “CSE” is also the percentage of the mill power doing useful grinding, the rest being wasted on over-grinding of what is already minus P80 size material. The role of the pump and cyclones is to maximize the “CSE”.
First and foremost, as also explained in Bulletin No. 4, we always want a high circulating load ratio (CLR). Given the same CLR of 350%, see below how increasing the cyclone water usage affects the ratio of the water going back to the mill. This ratio is called the ‘bypass fraction’, and carries fine solids with it back into the ball mill. By keeping the circulating load and underflow percent solids the same, while increasing water in the cyclone feed, we reduce the bypass fraction. In this example, the net result was close to a 10% increase in CSE, and so a net 10% increase in grinding circuit efficiency and capacity.
This process requires making pump and cyclone adjustments. The Streamline™ ball mill circuit modeling program can be used to determine the needed equipment adjustments and calculate the associated increase circuit efficiency.