Chemical Engineering and Processing, Vol.46, No.4, 291-299, 2007
The influence of microwave energy delivery method on strength reduction in ore samples
Recent work has shown for the first time that high electric field strength microwave energy can facilitate comminution of ores, at energy inputs considered economically viable. However, due to difficulties in measuring stress formation inside a solid being exposed to microwave energy, the accuracy of a suggested thermal stress weakening mechanism has not been quantified. It is thought that microwave induced differential thermal expansion of certain mineral phases is sufficient to cause stresses that exceed the strength of the material. This study simulated this proposed weakening mechanism using a quasi-static thermo-mechanical 2D model of a simplified pyrite/calcite system formulated in commercial finite difference numerical modelling software. The effects of microwave power density and exposure time on simulated uniaxial compressive strength are quantified. Power densities expected in both continuous wave and pulsed microwave applications are examined, and the work concludes that pulsed treatment is more effective for weakening rocks. The paper makes recommendations as to the future operating requirements of microwave equipment for the most effective weakening at economic energy inputs. (c) 2006 Elsevier B.V. All rights reserved.