Rei Arai

Preliminary Economic Feasibility Analysis of Cobalt-Rich Manganese Crust Mining for Rare Metal Recovery

The importance of cobalt-rich manganese crusts on the Pacific seamounts for possible future rare metal sources has currently been recognized. The thin layer-type deposit characteristics affect not only the excavation efficiency but also the economy of mining venture. Considering the thin layer-type distribution and the utilization of some rare metals in cobalt-rich manganese crusts, a preliminary economic feasibility of the mining venture is evaluated. Under some preliminary technical assumptions, the possibility of cobalt-rich manganese crusts for future rare metal sources for Japan is examined. The important role of utilization of rare metals in the crusts is highlighted.Copyright

Simplified automatic measurement method for nutrient at coastal field

Some of the environmental factors such as dissolved oxygen, chlorophyll, and so on can be measured by electric sensor recently. It enables to measure these continually and automatically. This kind measurement is very important for monitoring of the environments of coastal area. However, it is difficult to measure the chemical parameters continuously, because it always should be obtained by chemical analysis. In This work, simplified measurement system using the method of absorption rate measurement of processed water by the visible ray is developed. The effectiveness of the present method is shown in the field measurement in Osaka Bay.

Waste Rejection on Seafloor by Hydrocyclone for Economic Seafloor Massive Sulfide Mining

Many seafloor massive sulfide (SMS) deposits have been discovered in Japan’s exclusive economic zones (EEZ). They have some useful metals and are expected to become future metal resources. In Japan, because of an expensive waste disposal cost, it seems to be difficult to realize the SMS mining. Adding a function of primary waste separation from metal-rich parts of SMS ore on seafloor by a hyrocyclone is proposed to overcome the problem. The water flow structure in a model hydrocyclone is observed in the study at first. Secondly, the performance of separation using differences in specific gravities of particles by the hydrocyclone is experimentally examined. Finally, the application of hydrocyclone in the actual sea area is examined. The result shows that 67% of larger specific gravity are collected and 67% of smaller one are rejected. From the separation efficiency, the hydrocyclone method is recognized to have a high possibility of application in the actual sea area.Copyright

Economic Seafloor Massive Sulfide Mining by Japan’s Model

Because of the higher Au, Ag, and Cu contents, seafloor massive sulfides (SMS) have received much attention as future commercial mining targets by private companies and nations. One of them, Solwara 1 Project in Papua New Guinea (PNG), is scheduled to start the commercial mining operation from 2018. Because the mining site is inter-island area and almost no cost is necessary for the waste disposal in PNG, the economy of the mining is expected very well. In contrast with this, because all the SMS distribution sites in Japan locate outer ocean areas and the waste disposal cost on land in Japan is very expensive, the economy of SMS mining in Japan is quite negative. In order to overcome the problems, a self-standing riser with flexible link to the sea surface platform and a primary ore separation on the seafloor prior to the ore lift-up are proposed. The improved SMS mining concept named Japan’s model is examined.Copyright

Effect of Micro-Bubbling on Settling Behavior of Fine Particles for Deep-Sea Mining

A preliminary tank experiment for clarifying the effect of micro-bubbles on settling behavior of fine particles was conducted. The behavior of the particles was continuously photographed by a still camera and the images were analyzed by the gray scale intensity. From the results the authors found a suspension effect of micro-bubbles for the settling of fine particles. The effect should be studied in detail for preventing some serious environmental impacts during deep-sea mining.Copyright

Preliminary Economic Examination of Seafloor Massive Mining Venture Under Japan’s Conditions

In Papua New Guinea (PNG), a seafloor massive sulfide (SMS) mining venture has been proposed to start in 2013 and the expected high profitability was presented. However, the geophysical and social conditions are quite different from Japan’s ones. The technologies and model used for the PNG mining are difficult to apply under Japan’s conditions. The economy of SMS mining has no reality in Japan, because the tailing waste disposal is very expensive. Based on a preliminary economic evaluation of seafloor massive sulfide mining venture under Japan’s conditions, some modifications in the mining system and material flow are proposed for the improvement of the economy.Copyright

Laboratory Experimentations for New Hydrothermal Monitoring Systems Using ADCPs

Deep ocean mining in a hydrothermal area needs careful environmental impact assessments in terms of preservation and mitigation of biodiversity. The General Environmental Technos Co. Ltd., or KANSO TECHNOS, for short, has participated in environmental impact assessments in hydrothermal areas in the Izu-Ogasawara and the East China Sea areas (Ishida et al., 2011). Through the experience, we suggest a method of using acoustic systems such as acoustic Doppler current profilers (ADCPs) for monitoring of suspended matters and benthos in hydrothermal areas. Thus, we try to do in-situ observations, called Tow-yo (or Towing) observations with ADCPs (Komaki and Ura, 2009; Komaki et al., 2010). This system has a great advantage in enabling the measurement of great environmental factors, echo intensity and current velocity in a large range. To confirm exactly what the substances are and how large they are from the measured echo intensity data, we tried laboratory experiments in water tanks with echo sounders and turbidity sensors. These results will finally be integrated in a simulation model to predict substances from in-situ data in deep water for future monitoring systems.Copyright

Measurement Method for the Concentration of Hydrogen Sulfide in Pore Water Applying Sensor Part of Undersea Systems

In enclosed sea area, a large amount of organic matter deposit in seabed sediment because rich nutrient through the river causes the massive generation of phytoplankton and seaweeds. As the result, hydrogen sulfide is eluted from the organic-rich sediment and stimulates the additional hypertrophic effect. However, there is an incomplete understanding of a mineralization process from sediment to bottom layer water upper seafloor. The purpose of this study is to develop measurement method for hydrogen sulfide concentration in pore water for undersea systems. The authors propose the new method for absorptiometric analysis of ultraviolet spectrometry spectrum from pore water in sediment using screw cap cell.

Seafloor Primary Ore Dressing System for Economic Sulfide Mining

Because of the higher Au, Ag, and Cu contents, seafloor massive sulfides (SMS) have received much attention as immediate commercial mining targets by private companies and nations. One of them is scheduled to start the commercial mining program in the end of 2013 and the expected profitability is presented. However, the geophysical and social conditions are quite different from Japans ones. The material flow selected for the mining program, for example, has no economy under Japans social condition. One of the key technologies necessary for improving the economy in Japan, a primary ore dressing of excavated SMS ores on the seafloor, is introduced in this issue.

Conceptual Design of TMR-Less Manganese Nodule Mining System and the Economy Examination

Manganese nodules on deep ocean floors have been interested in as future metal resources these forty years. The Total Materials Requirement (TMR) of the conventional proposed mining method, however, is very high because of the much lifted water with the nodules from the seafloor to the sea surface and the longer transportation from the mining site to the smelting plant. An innovative conceptual design of the TMR-less mining system is presented. The economy is examined and compared with the one of the conventional method.Copyright