Research on a coupled system design for mineral lifting and wastewater drainage in deep-sea mining applications

Deep-sea mining requires lifting minerals from the seabed, at depths of thousands of meters, to the surface. Presently, the most prevalent method involves the use of hydraulic pipeline lifting systems. Meanwhile, for environmental protection requirements, returning the dewatered mining wastewater from the mining vessel back to the seabed for drainage is also becoming a standard practice. However, there are a series of technical, cost and safety concerns associated with the use of deep-water cables in hydraulic lifting systems for deep-sea mining, as well as issues related to the seabed disposal of mining wastewater. A coupled system is herein proposed that utilizes wastewater drainage to operate seabed pumps for slurry transportation. The main technical structure of the coupled system is designed in the context of commercial exploitation of polymetallic nodules at depths of 6000 m. The basic process and structural parameters of the system are determined by means of a computational analysis of mineral lifting and resistance in water pipes. Comparing this coupled system with traditional deep-sea mining designs, the results indicate that this solution can reduce the reliance on deep-water cables, lower the overall volume of the lifting system, and improve the efficiency of mineral lifting.