Evaluation of dry grinding using HPGR in closed circuit with an air classifier

Testing determined that the specific energy consumption of the Option B circuit was 41.9% greater than Option A when evaluated using power logging, or 26.2% greater when calculated using Bond's law. Option A required 20.8-29.5% less energy per tonne of ore processed than Option B, a conservative estimate due to the finer grind size achieved. Further Bond tests showed that the work indices of standard crushed −3.35 mm and −2.36 mm feed were similar (15.0 and 15.3 kW h/t, respectively), while the HPGR crushed −2.36 mm feed produced a lower work index of 14.0 kW h/t. These results agree with observations by other workers that HPGR renders a sample more amenable to comminution, most likely due to the introduction of micro-cracks.