Development of high power microwave applicator for rock preconditioning

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In hardrock mines, continuous mining method still faces many challenges and far from efficient. Started in 2008, our team had explored various possible method of continuous mining using explosive free rock breaking techniques. It was concluded that the most feasible technique for continuous excavation is to precondition the rock using microwave irradiation coupled with mechanical rock cutting tool. This conclusion drew the attention of mining companies and resulted in securing an NSERC CRD grant in 2011 - 2016 (Phase II). Basic parameters affecting the irradiation of rocks samples and its influence on the reduction of rock strength has been demonstrated. This study investigated and proved the feasibility of using microwave-assisted rock breaking technology in excavation. Also, this previous NSERC CRD grant enabled the applicants to build a state-of-the-art 15 kW microwave-assisted rock breakage test rig, unique to McGill University in Canada and one of the few in the world. In 2017 - 2022, our rock-microwave research entered Phase III. NSERC Discovery Grant (DG), CRD grant supported by three companies, along with NSERC RTI were successfully carried out. The objective of Phase III was large-scale proof of concept of microwave-assisted rock preconditioning. The equipment requested through NSERC RTI in Phase III was a 100 kW rock-microwave system to upgrade our old 15 kW rock-microwave system in order to be able to carry out large-scale tests for proof of concept under high-power microwave irradiation. The most significant outcome from our Phase III was an in-depth understanding and development of a secret recipe for a cost-effective and energy-efficient microwave irradiation for rock weakening in large-scale tests; that is, at high energy density and a very short period of time, such that the electromagnetic wave burst is effectively used to break intra-minerals bonds in grain boundaries, resulting to order-of-magnitude higher weakening over microwave energy (WOME) as compared to published data. Currently, our rock microwave project is entering Phase IV and is ready for prototyping and pilot testing in the mining face. NSERC Discovery Grant (DG), MITACS Accelerate and NSERC Alliance grants, supported by industry partners are underway. The objective of Phase IV is to develop a novel prototype of a microwave-assisted excavation machine for hardrock. Therefore, the equipment requested in this NSERC RTI grant is to develop a unique high-power microwave applicator for rock preconditioning to be integrated into our existing 100 kW microwave generator. This unique high-power applicator will enable us to develop the first prototype for microwave-assisted rock preconditioning testing in the mining face. The equipment is also vital for the HQP training of 1 RA, 1 PDF, 8 PhDs, 1 MSc and several undergraduate summer internship students. This will provide students with experience to develop and conduct in-field trial of the machine for the first time.