Effect of Axial Density Distribution in Liquid–Solid Flow in Pipes on the Jumper for Deep Sea Mining

Subsea minerals have been found in the deep water within Japan’s exclusive economic zone. However, the development of subsea minerals has not reached the commercialization stage because many technical issues still need to be addressed. When slurry pumps are used for lifting seafloor massive sulfides, internal flow in pipes becomes liquid-solid flow. The slurry pump is connected to seafloor production tools by a jumper so that the seafloor production tools can move to collect subsea minerals. To operate the production system safely, simulating the behavior of the jumper is necessary. There is axial density distribution in internal flows in the jumper because of the slip velocity between liquid velocity and solid velocity, and simulating the behavior of the jumper with consideration of density distribution is essential. Thus, we simulated the behavior of the jumper with consideration of density distribution by lumped mass model. We calculated the density distribution at each delivered concentration by equations of hindered settling velocity of solid particles and mixture velocity. The calculated results were compared with experimental results to validate the lumped mass model. The experimental apparatus had a flexible hose of 38 mm in internal diameter, and we used alumina beads of 4 mm in diameter. The comparison showed the behavior by considering density distribution and that with the homogeneous flow which has the uniform density of internal flows. Their comparison showed that the calculated results considering density distribution were more consistent with experimental results than those with the homogeneous flow. In calculating the behavior of the jumper with liquid-solid internal flow, it was important to consider the density distribution.