Abstract
Traditional drying methods for minerals often rely on natural gas as their heat source, which results in substantial greenhouse gas emissions. Microwave heating presents a low-carbon, and efficient alternative for replacing or complementing conventional drying. The efficiency of microwave heating is rooted in the relative transparency of minerals to microwave radiation compared to water, which absorbs the microwaves more readily. To assess the feasibility of microwave-based drying systems, laboratory experiments were conducted on mineral samples using a commercial 2.45 GHz microwave oven. Mass loss and surface temperature were measured following the drying process. The experimental findings were then used to validate and evaluate numerical simulations of the microwave drying process. A finite element-based numerical model was also developed coupling electromagnetic and heat transfer physics, and its results were compared with the experimental measurements. The observed drying rates suggest that the microwave energy was predominantly used for water evaporation rather than heating the solid material, demonstrating the high efficiency of microwave-based drying for the tested mineral. The experimental surface temperature and mass loss were compared to results obtained from complementary numerical modeling and desirable agreement were found. Since the studied material could emit sulfur at temperatures above 125℃, raising health and safety concerns, the numerical modeling was particularly beneficial to determine the maximum temperatures inside material which were inaccessible experimentally. It was found that the material maximum temperature remained well below 100℃ for a 60 s long microwave exposure where a consistent average drying rate of 2 g/s was sustained. These results show that microwave heating is an excellent alternative for drying applications in mining with low net energy demands and greenhouse gas emissions.