Numerical investigation on dynamic performance of vertical hydraulic transport in deepsea mining

Owing to great demands of natural resource and huge reserves of seabed minerals, deepsea mining technology has been proposed in the past decades. The most promising way to convey the deepsea ores to the sea surface is vertical hydraulic transport (VHT). Numerical investigations on dynamic performances of VHT were conducted by Computational Fluid Dynamics and Discrete Element Method (CFD-DEM). The convergence study on the pipe length, simulation duration, spacial and temporal resolutions were carried out, followed by the method validation through the experiments. The characteristics of particle and fluid were analyzed from different aspects. In most conditions, the local volume concentration of particles in the pipe is larger than the feeding concentration owing to the velocity lag of particles in the upward flow, indicating that instantaneous particle characteristics should be considered in engineering applications. Sensitivity analyses of transporting parameters and particle properties were conducted. Flow velocity and feeding concentration are two key factors dominating the dynamics of the mixture. A special range of particle diameter was recognized in which the particle accumulation was severe, whereas a proper particle size distribution would benefit VHT. Based on the numerical simulations, empirical formulas were proposed to have a rough estimation of particle velocity, slip velocity and local concentration for the initial design of VHT.