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• Microwave dewatering of deep-sea nodules was demonstrated at bench (3.2 kW) and pilot (150 kW) scales. • Bench tests showed rapid drying and strong microwave absorption, classifying nodules as highly responsive (Class IV). • Pilot trials achieved 24 % mass loss at 397.3 kWh/t, demonstrating improved energy efficiency. • Scale-up showed faster drying and lower energy use, supporting continuous microwave processing design. Polymetallic nodules from the ocean floor are being considered as a significant potential resource for valuable metals such as manganese, nickel, copper, and cobalt. Various technologies are being investigated for the extraction of these metals, including hydrometallurgical, pyrometallurgical, and hybrid processes. In pyrometallurgical processing, a major challenge is the presence of water in various forms within the nodules, as its removal consumes a substantial amount of thermal energy. Consequently, more efficient and environmentally friendly dewatering techniques are being explored. One promising alternative is the use of electromagnetic radiation in the form of microwaves as a clean energy source. Microwave processing offers several potential advantages, including volumetric, selective, and rapid heating, and is in alignment with society’s future decarbonization directives. In the present study, bench-scale experiments were first conducted at a power level of 3.2 kW and a frequency of 2450 MHz to evaluate the microwave heating behaviour of nodules from the Clarion-Clipperton Zone. These experiments demonstrated that the nodules efficiently absorbed microwave energy, leading to rapid dewatering. Subsequently, pilot-scale studies were performed using a 150 kW microwave system operating at 915 MHz. The results confirmed that microwave dewatering is an effective pretreatment method for nodules prior to pyrometallurgical processing. Conclusions are drawn regarding the feasibility and applicability of microwave technology for the dewatering of polymetallic nodules and the potential advantages of further scale-up. The bench-scale tests achieved up to 31 % mass loss at an energy input of about 1067 kWh/t, while the pilot-scale trials removed up to 24 % moisture at about 397 kWh/t. These results demonstrate significant water removal with reduced energy demand compared to laboratory studies, highlighting the potential of microwave dewatering as a scalable pretreatment technology.
Marzoughi et al. (Tue,) studied this question.