Microwaves take the grind out of mineral mining

Using microwaves in mineral mining could make rocks easier to grind, halving processing costs and significantly reducing energy consumption.

The technology was developed by researchers at the University of Nottingham, who claim that up to five per cent of the world’s electrical energy output is expended on grinding mined material.

Currently mills are used to crush chunks of ore, such as copper or zinc, into smaller pieces. But the process is inefficient, with only one per cent of the grinding energy resulting in nugget production.

Weakening the rocks before crushing using microwaves could significantly reduce the energy required to break them, said Dr. Sam Kingman of the university’s school of chemical, environmental and mining engineering, who led the project. ‘Grinding accounts for over half the operating costs in a typical metal ore mine,’ he said. ‘The new microwave technique could reduce costs by over 50 per cent.’

Ores are made up of many minerals, which are heated by microwaves at different rates. This difference in energy absorption causes stresses where the constituents of the rock meet, leading to weakening and cracking. The rock will then fall apart much more easily in the grinding mill.

The research team used computer simulation to calculate the power of the microwaves needed. During their investigations the team found that some rocks only need to be microwaved for less than one tenth of a second to produce the desired effect.

The seven-year project received £150,000 from the EPSRC and Kingham’s team has now been given additional funds by the organisation to take the work further through a collaboration with South Africa’s Stellenbosch University. An unnamed company has expressed interest in using the technology, if further tests prove successful.