Flotation of coarse composite particles in mechanical cell vs. the fluidised-bed separator (The HydroFloat™)

• Composite particles of different locking textures have been fabricated.
• Fluidised-bed recover complex locking composite better than mechanical cell.
• Quiescent flow of fluidised-bed improves recovery of composite particles.
• Coarse grind favours simple locking composite than complex locking in mechanical cell.

In principle, carrying out flotation of coarse and composite particles in a quiescent flow field is decisive to prevent particles detaching from bubbles. To overcome or limit detachment of coarse composite particles from bubbles in flotation, a fluidised bed separator, the HydroFloat™, which provides a quiescent environment has been used, and the results compared to the performance of a mechanical (Denver) cell. Model synthetic composites of quartz (value mineral) in lead borate (gangue) matrix with simple and complex locking texture were used for the study. The flotation behaviour of particles with different locking textures was studied at a coarse size distribution of 250–600 μm in both the HydroFloat separator and the Denver cell. The recovery of composite particles with the different locking textures was analysed on an un-sized and size-by-size basis. Recovery was improved in the HydroFloat separator, with both simple and complex locking composite particles having almost the same recovery. Again, comparison of recovery with the HydroFloat to the Denver cell indicates that the separator greatly out-performs mechanically agitated cells for the upper particle size of about 500 μm, with a significant effect on complex locking texture composites. This is attributed to the minimum or absence of turbulence and minimal froth zone which causes detachment of coarse particles in most conventional cells.