Development of a subsea continuous feed rotary system for local transport of Polymetallic nodules to the intermediate pump system

Deep-sea mining consists of a mining support vessel at the surface, a seafloor pickup and collector on the seabed, and a vertical hanging pump with associated sensors and a slurry transport system connecting them using a flexible riser concept. The transport of slurry from the mining machine to the high-pressure positive displacement pump (PD) is discussed in this paper. The PD pumps transport the slurry from the pump system to the mother ship. Three conceptual designs for local transportation of nodules were studied to adopt in the mining system. A subsea rotary valve system was adopted to the mining system among the three. The critical challenge in the designed system is to have lesser power, size, and weight. The vanes that arrest the leakage have to withstand the pressure at a particular water depth with proper sealing to maintain the desired head. This research intends to design and develop a system to achieve a controlled uniform feed of polymetallic nodules at 6000m water depth. The system has to operate for a continuous mining operation in subsea with ultra high-pressure applications (600 bar) by incorporating suitable seals and bearings. The most interesting feature of the system was that it only requires several vanes, which provides sealing without leakage. The study observed that the sealing of vanes contributes to better Polymetallic nodule transport by holding the pressure and achieving the required transport velocity for calculated system design requirements. The laboratory-based experimental and computational fluid dynamics (CFD) results are validated and presented below in this research.