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Abstract

This thesis evaluates the application of microwave systems for mineral drying through laboratory experiments and numerical modeling. Four types of minerals were procured from a mining partner, with moisture contents up to 25%. Their material properties – including thermal conductivity, heat capacity, density, initial moisture content, and dielectric loss factor – were characterized. Drying tests were conducted in a commercial microwave oven, with samples exposed to microwave irradiation to reduce moisture content to below 1%, while ensuring temperature control below a specified threshold. Materials were incrementally heated, with mass loss and surface temperature measured until target mass losses were achieved. Results revealed a two-stage drying regime: a constant-rate period up to a critical moisture content, followed by a falling-rate regime. A numerical replica of the commercial microwave oven was developed, including key components such as three rotating stirrers, a ceramic plate, and three separate magnetrons. Parameters such as air inflow, stirrer rotation speed, microwave generator ramp-up time, and forward power were measured and incorporated into the numerical model. The characterized material properties were integrated into a coupled electromagnetic and heat transfer finite element model implemented in COMSOL Multiphysics to investigate drying rates and temperature profiles. Predicted mass loss and temperature changes under experimental microwave heating conditions were compared with experimental results. Results indicated that microwave energy was predominantly consumed by water evaporation. For the studied material M2, which contained sulfur and required maintaining temperatures below 125 °C, the numerical model was particularly useful in determining internal temperatures that were experimentally inaccessible. The model predicted maximum material temperatures well below 100 °C during 60 s microwave exposures, sustaining an average drying rate of 2 g/s. These findings demonstrate that microwave heating offers a highly effective alternative for drying applications in mining, particularly where temperature sensitivity is a key operational requirement.