Effect of comminution mechanism on flotation of coarse composites

• GRolls® demonstrated superior coarse particle flotation performance. • Rod mills were more effective at liberating intermediate-size particles. • Elongated particles improved coarse flotation grade; rounded particles increased fine gangue entrainment. • Fluidized bed behaviour was similar for both comminution products at comparable particle sizes. This study investigates the impact of comminution mechanisms of GRolls® and rod mills on particle characteristics and flotation performance. Particular focus is given to coarse particles flotation, aiming at energy reduction in the grinding circuit. Experiments were carried out using both HydroFloat™ and mechanically agitated cells using porphyry copper–gold ore. GRolls® demonstrated superior coarse particle flotation due to preferential breakage along mineral boundaries, producing better-liberated particles with higher Cu exposure. In the HydroFloat™, GRolls® products achieved a Cu grade of 3.6 % in the + 150 µm fraction, compared to 2.8 % for rod mill products. In mechanically agitated cells, GRolls® products also delivered superior performance in the + 150 µm fraction, with a Cu recovery of 60 % and grade of 5.8 %, while rod mill products achieved 52 % recovery and 3.9 % grade. Particle morphology also influenced the flotation performance, with elongated particles correlating with higher grades in coarser fractions and rounded particles linked to increased gangue entrainment in finer fractions. Fluidized bed properties in the HydroFloat™ were similar for both comminution methods, indicating that when particle size distributions are closely matched and relatively coarse particles are used at low superficial water velocities, particle morphology has minimal impact on bed dynamics. These findings highlight the importance of comminution strategies and particle shape in optimizing flotation performance for energy-efficient ore processing.