Flotation Equipment works very well for particles that are typically in the range 20 to 150 μm in diameter, for base metal ores. In this range, it is possible to obtain quite high recoveries in conventional flotation machines. Outside this range, the recoveries decline progressively, whether it is with the very fine or thecoarse end of the size spectrum. For coarse particles, the reasons for the drop-off in recovery can be related to the highly turbulent nature of the pulp in a conventional flotation cell.
To improve recovery, it is necessary to find a way of bringing particles and bubbles into contact in a quiescent environment. A new process for coarse particle flotation is described in which a fluidized bed is created in the flotation cell. The flow conditions are very gentle and the high solids concentration leads to rapid rates of capture of the particles. Experimental results are presented. It is apparent that the maximum floatable size for coal and minerals can be increased by a factor of ten over the limits found in current practice.
The theoretical background for flotation kinetics of ultrafine and coarse particles are explored. Recent advances in flotation technology for these difficult areas are reviewed, with a focus on improving the flotation rate of ultrafines, and extending the upper limit for coarse particle flotation.
The performance of a Flotation Machine is described in terms of a number of transport processes that one would expect a flotation machine designer to exploit to achieve efficient mineral separation. The magnitude of these transport processes, and the mechanisms giving rise to them are claimed to be poorly understood. As a result, proponents of various types of machine have been able to present exceedingly favorable reports of their machine's performance without justifying these rigorously in terms of a set of firmly established design principles.