Research Overview

Research on Seabed Mineral Resource Development

Japan's Exclusive Economic Zone contains many mineral resources, such as seafloor hydrothermal deposits (*1), cobalt-rich crusts, and manganese nodules. Therefore, research and development of mining systems for these resources are being carried out as a national project. However, many technical challenges need to be resolved in the development and operation of these mining systems.
The Deep Sea Technology Research Group is conducting research on the following four themes to contribute to the development of seabed mineral resources:

• Research on Elemental Technologies for Excavating Seabed Mineral Resources
• Research on Elemental Technologies for Lifting Seabed Mineral Resources(*2)
• Research on Processing Seabed Mineral Resources on the Seafloor
• Research on the Operability, Safety, and Economic Aspects of Seabed Mineral Resource Development

Here, we introduce our research on the evaluation of lifting pipes (*3), which is part of our study on the elemental technologies for lifting seabed mineral resources.

• Pressure drop in the dynamic lifting pipe

As a method for lifting ores excavated from submarine hydrothermal deposits, it is assumed that the ores and seawater will be conveyed as a slurry (*4) using a pump. Evaluating the pressure drop in the lifting pipes when conveying ore from the seabed to the surface is crucial for designing the pumps. This group has been developing a model to estimate pressure loss using fixed pipes through experiments. However, in actual sea conditions, the lifting pipes are suspended from a surface vessel and are expected to oscillate due to the vessel's movement influenced by waves and other factors. Therefore, this group conducted a reduced-scale model experiment (Figure 1) (Figure 2) to investigate the effect of the lifting pipe oscillation on pressure loss. By comparing the calculated results assuming a model for fixed pipes with the experimental results, it was found that vertical oscillation of the pipes does not significantly affect pressure loss (Figure 3). On the other hand, for horizontal oscillation, although most ranges of velocities are not affected by the oscillation, the test results tend to show higher pressure loss than the calculated results in the range of low internal flow velocity (Figure 4). In the future, we intend to evaluate the effects of pipe oscillation in more detail through more detailed experiments.