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Application of High Electric Fie


									Economic Microwave Processing of Ores
S.Kingman+ K. Jackson, .Nottingham Mining and Minerals Centre, University of Nottingham, Nottingham, NG7 2RD, UK, School of Chemical Engineering,

corresponding author: Abstract for oral presentation

Comminution forms a large proportion of any mineral processing plant’s capital and operating costs; 30-50% of the total plant power draw and up to 70% for hard ores is attributable to comminution, thus there is much to be gained from improving the process. The benefits of optimisation could include increased mill capacity, reduced mill wear, improved liberation and reduction in slimes production. Many approaches have been taken to improve the efficiency of comminution processes. One area that has seen considerable research is thermally assisted comminution, in which heating and quenching are used to induce fracture in the ore. Various studies have demonstrated that thermally assisted comminution can reduce significantly the energy required for grinding. However, in almost all cases it was shown that the energy balance was unfavourable. Most of the testwork carried out to date on microwave treatment of minerals has been at high specific energy consumption and low power density. This has largely been predictated by the use of multi-mode microwave cavities, similar to those found in a conventional kitchen microwave oven, in which it is difficult to achieve a high power density. Whilst the influence of microwave radiation from this type of cavity has been shown to have a significant influence in reducing the Bond Work index of ores, the benefits have not been sufficient to justify use of the technology. In contrast with the approach above, application of microwave energy at high power density and with short exposure time has been the focus of recent work at the University of Nottingham. This has aimed at achieving significant strength reduction of the ore, through intergranular cracking, at an economically viable specific microwave energy inputs. The benefits of treatment have been evaluated both by point load tests, to give a measure of change in compressive strength, grindability tests and by the JKMRC drop weight test. Liberation enhancement has been evaluated by QEM.SEM analysis. Data will be presented for various ores which shows that high power density short duration microwave treatment has a significant effect on both the strength and grindability of ores. Data will also be presented which indicates significantly enhanced liberation of the valuable mineral phases as a result of microwave treatment. An assessment of the impact of the results on the design of typical mineral processing flowsheets will be made The presentation will conclude with recommendations for the scale up of the technology and an assessment of the impact it may have on the European mining industry.

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