研究業績

REE-rich mud and polymetallic nodules located under the seabed at water depth of 5500–5700 m around Minamitorishima island are highly attractive for exploration and development, given the recent paradigm shift towards renewable energies based on green technologies. A numerical analysis was conducted to investigate the flow characteristics and lifting performance of hybrid mining, which involves transporting both REE-rich mud and polymetallic nodules using an air-lift pump for a commercial production system and a pilot test-scale system in the deep sea around Minamitorishima island. The one-dimensional drift-flux model was adopted for analyzing the gas–liquid–solid three-phase flow and gas–liquid two-phase flow in the system. A new scheme, called “the multi solid-phase scheme”, was also developed and devised in the program to account for the particle size distribution of transported ores, such as degraded polymetallic nodules. The results revealed that the program and the scheme could simulate the flow characteristics and the lifting performance of hybrid mining using the air-lift pump well. From the parametric studies regarding the dimensions and operational conditions of the systems, they could also derive useful information and know-how. Further information, such as degradation of polymetallic nodules during the practical operation, is required.