ASSESSMENT OF POWER REQUIREMENTS FOR ALTERNATIVE VERTICAL TRANSPORTATION SYSTEM FOR DEEPSEA MINING

The continuous expansion of the technology sector is dependent on metals currently found at very low concentrations on land-based mining operations. Therefore, mineral deposits located on the seafloor are considered future valuable resources, given the high concentration of sought-after metals. Considerable research has been made in concepts and technologies to ensure the safety and viability of seafloor mining. Because the mining operation could take place under water depths of up to 6000 m, transporting the ore to the surface is a critical part of the operation, for which different concepts have been proposed. An often-observed concept in publications is to use a free hanging riser with pumps installed along it as the conduit to the slurry. However, other concepts may be feasible. In fact, seafloor mining may benefit from copying the practices of the offshore oil and gas industry. Drilling offshore wells employs a drill string and a riser. Drilling fluid is pumped into the well through the drill string, and it returns to the surface through the annular space between drill string and riser. Among other purposes, this fluid removes the rock cuttings from the bottom of the well and transports them to the drilling rig. This paper proposes that a system which employs much of the equipment already available in conventional offshore drilling rigs is used for transporting the production of seafloor mining. This system is compared to other transport concepts typically proposed for seafloor mining. The analyses presented in this paper focus on power requirements for delivering the design ore production. The calculations conducted take into consideration the extensive published research on vertical transport of slurries. The annular vertical transport of slurries, as proposed in this paper, presents several advantages with consideration to required power, flow circulation, mineral production rates, handling of plugs, and maintenance of equipment. These results justify future further analyses of the proposed transport system.