Effect of particle parameters on the hydraulic transport characteristics in a vertical pipeline for deep-sea mining

Pipeline hydraulic transport represents a pivotal aspect of deep-sea mining operations, involving a highly intricate particle-fluid mixing flow. This work presents a numeric investigation of particle-fluid mixing transporting within a vertically-oriented mining pipe, utilizing a combined computational fluid dynamics and discrete element method (CFD-DEM). The effects exerted by feeding concentrations, particle gradations, and particle densities alike upon particle flow characteristics within the pipeline are investigated. The results demonstrate that in comparison with the initial feed concentration (4–10%), the localized particle concentrations increase exhibited a range of 15–20%. Whereas, the elevation in feed concentration exerts a slight impact with regard to the trend of particle distribution aligned with the radial direction. A rise with regard to the standard deviation in particle size distribution results in a more unstable particle-fluid mixing flow. Compared to a single particle size, the localized particle concentration exhibits a slight increase with varying standard deviations, with an estimated increase of 0–2%. As the standard deviation increases or the median particle size decreases, the local particle velocity also increases. When particle densities reached 1500 kg/m³, 2000 kg/m³, and 2500 kg/m³, the localized particle concentrations increased by 9.8%, 16.5%, and 20%, respectively. Hence, the transportation of high-density particles may necessitate elevated lift flow rates. Furthermore, the rise in feeding concentration and particle density engenders an enhanced differential pressure along the pipeline. In contrast, the pressure drop tends to be insignificantly impacted by particle size distribution. The results can provide guidance for vertical pipe mineral transport.