Quantifying damage around grain boundaries in microwave treated ores

Thermally induced damage due to microwave heating of mineral ore particles was simulated numerically using a continuum approach. Particles were represented as dispersions of microwave-absorbing grains in a non-absorbing matrix. As the aim of microwave treatment of ores is liberation of the absorbing grains from the matrix rather than bulk damage to the particle, damage was quantified by comparing the tensile stress in the zones surrounding the absorbing grains with the tensile strength of the matrix. Through comparison of two different ores it was shown that the most energy-efficient method of maximising grain boundary damage is by increasing the microwave power density and decreasing the treatment time. The amount of damage incurred at a specific power density and energy input was dependent on the ore mineralogy and its texture. More grain boundary damage was induced in coarser textured ores for the same energy input and damage was maximised for ores with microwave-absorbing grains with a large thermal expansion coefficient.