Microwave Heating Behaviour of Ores and its Application to High-Power Microwave Assisted Comminution and Ore Sorting
J. Forster1, A. Olmsted2, X. Tian3, D. Boucher1, M. Goldbaum1, C. A. Pickles2, E. R. Bobicki4
1. University of Toronto, Toronto, ON, Canada
2. Queen’s University, Kingston, ON, Canada
3. Sepro Mineral Systems Corp., Langley, BC, Canada
4. University of Alberta, Edmonton, AB, Canada
Keywords: microwaves, heating rate, mineral processing, comminution, liberation, sorting
As the global demand for metal values expands, it becomes increasingly important to create more sustainable mining operations. Consequently, considerable research and technology development is required to produce processes which are both more energy efficient and have a minimal environmental impact. One potential technology is the utilization of microwave pretreatment to reduce the energy requirements in comminution. Microwaves can preferentially heat the valuable mineral phases in an ore and the resulting differential thermal expansion leads to the formation of microfractures along the grain boundaries. As a result of the preferential heating, ore competency is reduced, mineral liberation is enhanced, a coarser grind size can be employed, and plant throughput can be increased. Furthermore, microwave pretreatment can be combined with advanced ore sorting, to decrease the quantity of gangue material processed downstream and hence reduce tailings production. Previous studies on the microwave treatment of ores over the last thirty years have mainly been limited to low power bench-scale studies and there is a paucity of information on pilot and/or commercial scale studies. In the present research, the microwave heating behaviours of over forty ores have been studied at the bench-scale. These results were used to generate a database, from which a unique classification system was developed. This system was used to rank the amenability of any given ore for microwave pretreatment. This knowledge can be employed to predict the performance of the ores in the high-power pilot scale tests and thus can be used as a pre-screening tool. The effects of high-power microwave pretreatment on grindability and liberation were reported. Additionally, the ore sorting potential was evaluated using a combination of X-ray transmission (XRT) and microwave infrared (MW/IR).