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Minerals Report - International Seabed Authority

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MAJOR DIMENSIONS<br />

Length : 13 m<br />

Width : 8 m<br />

Height : 6 m<br />

Weight : 100 t<br />

Installed Power : 900 KW<br />

Power Tracks<br />

Diffusers<br />

Separator<br />

Cutter Heads<br />

Lift Pipe<br />

Hydraulic<br />

Dredge Head<br />

Figure 9. Schematic representation of a deep-sea mining vehicle for Fe-Mn<br />

crusts (from DOI-MMS (127); designed by J. E. Halkyard, OTC Corporation)<br />

Hydraulic suction dredges are similar to trailing suction dredge heads<br />

commonly used with hopper dredges for sand and gravel mining. About 95%<br />

of the fragmented material would be picked up and processed through a<br />

gravity separator prior to lifting. Material throughput for the base-case<br />

mining scenario (128) is 1,000,000 t/y. That scenario allows 80% fragmentation<br />

efficiency and 25% dilution of crust with substrate during fragmentation as<br />

reasonable miner capabilities. The net recovery of crusts depends on<br />

fragmentation efficiency, pickup efficiency, and separation losses.<br />

Fragmentation efficiencies depend on small-scale topography and depth of<br />

the cut. Pickup efficiencies also depend on seafloor roughness, but to a lesser<br />

extent than fragmentation efficiency, and on the size of fragmented particles<br />

and type of pickup device (129).<br />

The Japan Resource Association (130) studied the applicability of a<br />

continuous line bucket (CLB) system as a method of crust mining. The CLB<br />

could be competitive in an area where crusts are easily separated from<br />

substrate rock, or where the substrate is soft enough to be removed by<br />

INTERNATIONAL SEABED AUTHORITY 230

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