Abstract
Carrier material circulating method was proposed to transport heavy and coarse ores from deep seafloor to sea surface. Then, experimental apparatus was developed. In the model tests, vertical movements of ores must be monitored from the outside of the riser pipe to study the feasibility of carrier materials. However, visual observation cannot be used since carrier materials are not transparent. In this paper, a new observation system was developed using RFID (Radio Frequency Identification).
Appropriate configuration to install antenna to the experimental apparatus and suitable method to install RF tag on the ore models were found by measuring the read ranges of RFID under expected experimental environments. In addition, measuring accuracy of RF tag movement by RFID was confirmed by RF tag falling experiment.
Finally, the vertical movements of ore models were observed in the lifting experiment by the RFID system. As a result, the carrier material comprised of viscous fluid with fine particles was found to lift heavier ore models faster. These results demonstrated that thickener and fine particles in carrier materials contribute to enhance effectiveness of ores transportation.
Large amount of mineral resources such as manganese nodules or submarine hydrothermal deposits exist on the deep seafloor around Japan. Lifting heavier and coarser ores from deep seafloor to sea surface effectively is necessary for commercial development.
For this purpose, circulating carrier material method was proposed (Tani et al., 2018; 2019). Fig. 1 (a) shows the concept of the proposed method. Carrier materials are comprised of viscous fluid and fine particle. They can prevent sinking of ores by their high viscosity and shear strength, which are expected to contribute to effective ore lifting. In addition, reusing carrier materials by circulation within the riser and return pipe will reduce environmental impacts by preventing toxic metal rich drainage from being released to the ocean.
Fig. 1 (b) shows the relevant experimental apparatus (Suzuki et al., 2018). This was developed to study the feasibility of the proposed system by monitoring lifting speed of ore models in the riser pipe about 1.2 m long. However, optical measurement method cannot be used since carrier materials are not transparent. Therefore, new instrumentation technique was developed to monitor the movements of ore models using RFID. In this paper, concept of this RFID technique, its feasibility and result of monitoring the movement of ore models will be indicated.
