Towards large scale microwave treatment of ores: Part 1 – Basis of design, construction and commissioning

Abstract

Highlights A pilot scale system for microwave treatment of ores is presented  Materials handling concepts and justification for packed bed mass flow are discussed  Microwave applicator and choke modelling is validated against real ores  Control of material flow and presentation is discussed  The operating microwave treatment system performance is described AbstractDespite over thirty years of work, microwave pre-treatment processes for beneficiation of ores have not progressed much further than laboratory testing. In this paper we present a scaleable pilot-scale system for the microwave treatment of ores capable of operating at throughputs of up to 150tph. This has been achieved by confining the electric field produced from two 100kW generators operating at 896MHz in a gravity fed vertical flow system using circular choking structures yielding power densities of at least 6x10 8 W/m 3 in the heated mineral phases. Measured S11 scattering parameters for a quartzite ore (-3.69±0.4dB) in the as-built applicator correlated well with the simulation (-3.25dB), thereby validating our design approach. We then show that by fully integrating the applicator with a materials handling system based on the concept of mass flow, we achieve a reliable, continuous process. The system was used to treat a range of porphyry copper ores. Minerals Engineering 109 (2017) 169-832 http://doi.org/10.1016/j.mineng.2017.03.006 IntroductionMicrowave treatment of metalliferous ores has long been investigated as a means to enhance the recovery of valuable minerals and reduce the comminution resistance of ores (Chen et al., 1984;Walkiewicz et al., 1988;Walkiewicz et al., 1989). The underpinning mechanism and textural characteristics of amenable ores has been described by Batchelor et al. (2015). Selective heating of microwave-absorbent sulphides and metal oxides deported in a microwave-transparent gangue matrix results in differential thermal expansion of the heated phase, yielding micro-fracture around grain margins Jones et al., 2005Jones et al., , 2007Kingman et al., 2004a;Kingman et al., 2004b;Kingman et al., 2000a). Subsequent downstream processing may then yield higher recovery of valuable mineral sulphides and/or lower specific comminution energy, compared to non-microwave treated ore.While the mechanistic principles are well established, the scientific and engineering challenges of developing a commercial scale system are immense. Typical throughputs of a large copper mine can be in excess of 5,000 tph of milled ore (Brininstool, 2015) and a microwave based treatment system would need to handle equivalent throughputs. This is at least an order of magnitude higher than any other microwave process ever built.The following paper details the design, commissioning and operation of a system which was the culmination of over fifteen years of research and development activity. This resulted in a high power microwave treatment process, capable of operating continuously at throughputs of up to 150tph, but crucially, scaleable up to several th...

Localized microwave-heating (LMH) of basalt – Lava, dusty-plasma, and ball-lightning ejection by a “miniature volcano”

“…In a more technology-oriented approach, this study of LMH in basalts could be relevant to various potential applications, including for instance (a) microwave-assisted drilling in basalts 20 , (b) cracking and crushing of basalts for mining and construction operations 43 , (c) basalt vitrification, glass production and coating, (d) joining of basalt bricks, (e) direct extraction of minerals in a powder forms by means of dusty-plasma production from basalts, and (f) analyses and identification of rock contents in the field by portable microwave-induced breakdown spectroscopy (MIBS) systems 44 (as a variation of the laser-based LIBS technique 45 ).…”

Pretreatment of Copper Sulphide Ores Prior to Heap Leaching: A Review

“…Once the microwave pretreatment is complete, it can generate a lower consumption of grinding energy, in addition to achieving a better extraction of valuable metals [64]. however, energy greater than 10 kW h/t is generally required for a low power density, which means that no energy savings are generated during the crushing operations.…”

Microwave Treatment of Ultramafic Nickel Ores: Heating Behavior, Mineralogy, and Comminution Effects

“…The fracturing often occurs along mineral grain boundaries, which can result in improved mineral liberation and grinding efficiency [12,13]. A number of researchers have reported an improvement in the grindability of ores and the liberation of valuable minerals after microwave treatment [12][13][14][15][16][17].…”