Study on the transportation characteristics of wastewater-driven deep-sea diaphragm pumps for slurry transportation

• The flow pressure characteristics of the dual-hydraulic-driven pump are revealed. • The Slurry Transportation characteristics of the diaphragm pump are analyzed. • The feasibility of the diaphragm pump in deep-sea mining is verified. In deep-sea mining, there are two critical requirements: discharging mining wastewater to the seabed and providing energy for seabed slurry transportation. Previous studies have proposed a novel deep-sea mining system that employs a wastewater-driven diaphragm pump for slurry transportation. In this scheme, wastewater delivered from the surface drives the deep-sea diaphragm pump to convey slurry upward, while the pump on the seabed mining vehicle conveys slurry into the diaphragm pump, thereby driving the diaphragm to discharge wastewater into the deep sea. This paper analyzes the working mechanism and structural characteristics of this “dual-fluid driven” diaphragm pump, and compares it with conventional “suction-discharge” diaphragm pumps. Simulated experiments and Computational Fluid Dynamics (CFD) methods are employed to investigate the pump's flow and pressure characteristics during fluid transport, as well as to explore the particle motion patterns and slurry transportation behavior in solid-liquid two-phase flow. Furthermore, with deep-sea polymetallic nodule commercial mining serving as the context, the structural design and process parameters for a wastewater-driven deep-sea diaphragm pump within a mining system are proposed. Additionally, the Computational Fluid Dynamics–Discrete Element Method (CFD-DEM) is applied to resolve the particle movement and concentration variations of the mineral slurry within the pump. This paper examines the adaptability of utilizing mining wastewater to drive the diaphragm pump for deep-sea solid mineral transport, thereby providing feasibility analysis and theoretical guidance for its application in deep-sea mining.