Understanding microwave assisted breakage

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

“…The power density then created in each phase of the particle is then also variable. Previous work has shown that micro-fracture around grain margins and resulting macrofracture though the matrix is dependent on the evolved power density in the heated phases of each specific particle (Jones et al, 2005). For a particular ore fragment, beneficial effect is then dependant on which position in the applicator it moves through and its specific mineralogy.…”

“…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.…”

Microwave Heating Applications in Mineral Processing

“…Jones et al, 2005 41 , also investigated the effect of microwave treatment through numerical simulations of a system of microwave absorbing pyrite grains in a microwave transparent calcite host. An important result of this work was the verification and explanation of the observations of Wills et al, 1987 10 , who determined that regularly shaped mineral inclusions with smooth boundaries were much more likely to result in thermally induced intergranular fracture than irregular grains which tend to be damaged by transgranular fracturing as a direct result of thermal treatment.…”

High-resolution dielectric characterization of minerals: A step towards understanding the basic interactions between microwaves and rocks

“…For example, the effectiveness of the microwave-induced thermally assisted liberation was extensively demonstrated (Kingman et al, 2004;Walkiewicz et al, 1989). Microwave fields induce volumetric and selective heating; in a heterogeneous material only the 'lossy' phases absorb electromagnetic energy, avoiding the waste through the 'bulk-heating' of the surrounding rock (Jones et al, 2005). Due to the different expansion rates of the minerals in the rock, micro-fractures are induced, theoretically making the grinding process less energy-consuming (Kingman and Rowson, 1998).…”

“…The reasons are multiple but certainly can be ascribed to a lack of fundamental understanding of the interacting mechanisms between minerals and the microwave field itself. In particular, few pioneering studies were proposed for correlating physical effects (mechanical, thermal) to the electromagnetic energy absorbed (Jones et al, 2005;Whittles et al, 2006;Ali and Bradshaw, 2009, 2011, and a sparse literature base was developed so far for correlating these effects to the electromagnetic properties that are the most important for understanding the microwave-matter interactions.…”