Could Microwaves Help Make Coarse Particle Flotation a Reality?

Coarse particle flotation continues to attract interest as mineral processors look for ways to reduce grinding energy while maintaining recovery. But as particle size increases, liberation, bubble attachment and particle suspension all become more challenging.

A recent development from Enginuity suggests that microwave ore preconditioning could offer an interesting way forward. As reported by International Mining, the company is applying industrial microwave technology to selectively heat minerals within an ore, creating stresses at mineral-gangue boundaries that can improve breakage and liberation. The potential benefit is not simply easier grinding, but the possibility of producing a particle population better suited to downstream processing.

This creates an intriguing link between comminution and flotation. If microwave treatment can improve liberation at a coarser size, could it reduce the amount of grinding required and, at the same time, create feed that can be recovered more effectively by coarse particle flotation?

Coarse particle flotation itself is developing rapidly. Conventional mechanical cells can be adapted to improve the suspension and recovery of larger particles, while other approaches include fluidised-bed flotation and pneumatic flotation. The challenge is to keep coarse particles suspended, promote effective bubble attachment and prevent them from detaching before they reach the froth.

The latest development is Metso's Sampo Cell, launched in September as a next-generation coarse particle flotation technology. The pneumatic design feeds slurry onto the top of a deep froth and, according to Metso, eliminates the need for a fluidised bed. An industrial demonstration in a Chilean copper concentrator operated at 22–28 t/h on final tailings scavenging duty.

The significance is potentially much broader than another flotation machine. If flotation technology can reliably recover coarser particles, while preconditioning technologies such as microwaves can deliver sufficient liberation at those sizes, the two developments could work together to shift the optimum grind size of the whole flowsheet. Microwaves could potentially help create the right particles; coarse particle flotation could provide the technology to recover them.

That makes the subject particularly relevant to both Comminution '27 and Flotation '27, but from opposite ends of the same flowsheet. At Comminution '27, the question is how preconditioning can change breakage and liberation, and potentially reduce grinding energy. At Flotation '27, the question is what happens when that coarser, differently liberated material reaches the flotation circuit.

In that sense, the real opportunity is not simply microwave-assisted comminution or microwave-assisted flotation. It is whether a change upstream can shift what is possible downstream, potentially allowing the whole flowsheet to operate at a coarser particle size.

That cross-disciplinary question could make this a particularly interesting topic for both conferences.

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