New technologies have to be developed to reach the future extraction areas of new materials like Seafloor Massive Sulphides (SMS). The challenges are not only related to technical difficulties but also to economical and environmental issues.
The floating concentrator presented in this paper for mineral processing application is identified as a more economical solution and expected to take less time to build than an onshore plant. Initial considerations, such as the sustainable development, industrial competitiveness and versatility for the investigation of the floating solution, are also discussed.
The basis of the concept is the marinization of the ore separation and concentration process. The Concentrator is a floating, production, storage and offloading (FPSO) ship-shaped vessel. Production facilities are mounted on raised supports above the vessel deck.
The FPSO will receive ore from Deepwater Mining support vessel, and the onboard flotation process will produce and offload the concentrates to barges for export to existing onshore smelters. The proposed concentrator vessel is a steel mono hull based on a converted tanker.
The future project presented in this paper is "fast track" and "construction & commissioning driven". Important aspects that should be considered in the design for a conversion of a tanker into a Floating Concentrator are described. Critical issues like selection of the vessel to be converted, structural design, installation of large processing facilities (grinders, flotation cells, mixer and settlers), vessel stability, mooring system configuration, ore and concentrate storage and offloading methods are addressed The key operating criteria such as angular motion and acceleration of a Floating Concentrator and their probability distributions are calculated to validate marinization and confirm feasibility of mineral processing.
This paper presents the concept selection process, the cases studied, FPSO layout, the results of computational simulations, and future challenges for floating solution for underwater mining.
Marine mining companies are currently exploring commercial scale mining of sea floor mineral deposit in several Pacific locations. These mineral deposits are a result of super heated water from volcanic hydrothermal vents reacting with rock. Approximately 350 of these vent fields have been found to date. The volcanic mineral ore deposits typically contain significantly higher concentrations of minerals (gold, copper, zinc & al) than typical onshore ore deposit.
The scheme currently proposed by mining companies is to extract and process these deposits using a purpose built deep sea mining vessel. The vessel will be capable of deploying mining equipment, pump, and riser system in water depths to 1700 meters.
The ore deposits would be dredged from seafloor and transported (air lift or other system) to the mining vessel, where it would be transferred to barges for transport to a concentration plant.
One option of this scheme requires the construction of a concentrator plant onshore at strategic locations within reasonable logistical range of the mining sites. This option also requires transportation of up to 2 millions metric tons per year of ore to the plants, as well disposal of the waste material from the concentrator plants. Environmental concerns associated with disposal of the waste products pose additional challenges to this option.
