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Microwave-assisted crushing and grinding can improve efficiency and reduce energy consumption. This paper takes rock grains with galena and calcite as the research object to establish a two-dimensional computational model through the finite difference software FLAC2D. It analyzes the process and law of mineral boundary failure under microwave irradiation, and assesses the effects of four factors, namely, microwave irradiation time, power density, mineral crystal size, and mineral content, on mineral boundary failure. Results indicate an optimal microwave irradiation period for the rapid failure of mineral boundary. Moreover, irradiation time and energy consumption can be reduced by increasing the microwave power density. However, irradiation time and energy consumption are basically unchanged when the microwave power density is above a certain threshold. Mineral content slightly affects the microwave irradiation time, whereas mineral crystal size significantly affects the microwave irradiation time. In addition, a larger-sized mineral crystal requires less irradiation time and energy consumption to reach the same failure rate. However, irradiation time and energy consumption slightly change when the crystal size is larger than a certain value.

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ABSTRACT. Microwave heating-assisted ore grinding and crushing can effectively increase the dissociation energy of minerals and decrease energy consumption. Microcrack growth and distribution characteristics inside different shapes of ore particles, which are composed of galena and calcite under microwave irradiation, were analyzed using discrete element method to explore the effects of mineral shapes on microwave-assisted dissociation. Growth laws on the total number of microcracks, numbers of microcracks in galena and calcite, and boundary damage rate against irradiation time under high power and low power were studied. Research results demonstrated that mineral shape mainly affects the quantity of microcracks inside ores but does not their growth law.

Microwave heating could increase the efficiency of eliminating mortar in recycled concrete aggregate and improving recycled concrete aggregate quality. A 2D finite element model of microwave oven and concrete particles was established to study the distribution and evolution law of thermal stress field in concrete particles. In this model, influences of power, time, aggregate radius, and mortar thickness were considered. Results showed that the temperature and stress of concrete particles in a microwave field are in approximately symmetric distribution. The maximum stress of mortar is on the interface between mortar and the recycled concrete aggregate. The maximum tensile stress of mortar and recycled concrete aggregate was proportional to microwave power and irradiation time but inversely proportional to aggregate radius. The maximum tensile stress of mortar and recycled concrete aggregate initially increased and then decreased with increased mortar thickness. Given the same energy consumption, higher microwave power led to stronger tensile stress of concrete particles and higher energy use. With reasonable irradiation time, the mortar produced cracks, whereas the recycled concrete aggregate remained integral.