Study of mine exhaust heat recovery with fully-coupled direct capture and indirect delivery systems

•A fully-coupled model is developed for direct capture-indirect delivery mine exhaust heat recovery system.•Droplet sizes, air and water spray velocities, and height of the heat exchanger play vital roles on performance of the heat capturing unit.•The proposed heat recovery system will lead to considerable reductions in energy, costs, and carbon emissions.•Direct recovery system can over-perform its indirect counterpart in both energy and carbon savings. Mine exhaust heat recovery is deemed to be a promising solution to reduce the costs and carbon emissions associated with mine intake pre-heating systems. Although indirect shell and tube heat recovery units have been implemented, direct recovery (spray-based) systems with their high efficiency, easy-to-operate technology and lower capital costs can present a more techno-economic solution. This study aims to develop a numerical fully-coupled thermodynamic model to investigate the techno-economic-environmental viability of establishing a direct capture and indirect delivery mine exhaust heat recovery system for intake air heating. The key operating and design parameters affecting the performance of direct recovery system are identified through sensitivity analyses and optimized accordingly for a Canadian mining operation. The results of the direct recovery system are compared to its indirect counterpart indicating that the direct heat recovery system can over-perform its indirect counterpart in both energy cost savings and carbon emissions.