High Pressure Grinding Rolls Applications in Mining

Figures 1 through 11 show some typical applications for HPGRs to increase throughput and lower specific energy consumption of a grinding circuit. Figure 1 shows the HPGR after a semiautogenous grinding (SAG) mill for pebble grinding. The HPGR product is returned either to the SAG mill or to the screen. In Figure 2, the HPGR is located after the secondary crusher. The HPGR product is screened, and the oversize is returned to the HPGR. Figure 10 has the HPGR as single-pass pregrinder in front of the milling plant.

The HPGR can apply about 2.3 kWh/t to the feed material. At a bonus of, for example, 1.8, it would add 2.3 1.8 = 4.14 kWh/t ball-mill equivalent to the grinding circuit. The HPGR can also be located after heavy-media separation (HMS) with or without a crusher grinding the wet oversize.

The best HPGR location for a given mine needs to be decided for each case; bottleneck identification, space availability, conveying distances, power grid, and other conditions must be considered.

HPGR after SAG mill for pebbles grinding

HPGR after secondary crusher with screen

Versatility and efficient energy utilization have made high-pressure grinding an established comminution technology in the minerals processing industries. Relatively simple formulae can be used to describe and understand the underlying mechanics of HPGRs. Careful consideration must be given to the overall grinding process in order to take full advantage of the special features offered by high-pressure comminution.