No abstract

Sulfidic polymetallic ore deposits, known as seafloor massive sulfides (SMS) occur on the seabed as precipitation products from hot hydrothermal solutions as a result of mixing with cold seawater and are usually found at depths between 1,500 and 4,100 m. These deposits are formed basically in tectonically active spreading zones of oceans (mid-ocean ridges and "back-arc" spreading systems) and are the result of the global heat transfer from the mantle above the oceanic crust into the water column. In these SMS deposits, metals such as copper (Cu), zinc (Zn) and lead (Pb) as well as trace elements of silver (Ag), gold (Au) and rare antimony (Sb), cadmium (Cd), gallium (Ga), germanium (Ge), and indium (In) are present. This paper describes a novel technology for mining SMS deposits based on the vertical cutting approach developed by a joint research between BAUER Maschinen GmbH and Technip. A hyperbaric mathematical cutting model has been used to calculate the forces needed to excavate SMS deposits in water depth up to 2,000m. The model shows that in hyperbaric conditions, what influences the cutting energy is the water column rather than the geomechanical properties of the rock. Based on the mathematical model a preliminary cutting tool design is shown.

During subsea mining operations, minerals are extracted from the seabed, typically at about 2000m depth, and pumped with water through a riser pipe to a surface processing vessel. TechnipFMC, through its subsidiary Technip France, is the lead of a consortium comprising COMEX and DCNS which has been awarded a contract by BPIFrance to develop a pilot subsea mining system. The scope includes the development of a flexible riser. This flexible riser comprises an inner wear protection layer to resist the wear from the slurry, covered by a structure to withstand mechanical loads applied to the flexible during its lifetime. In order to select the most appropriate anti-abrasion material, a large scale bench test has been built to reproduce realistic flow in a piping system and compare wear on different materials; rubber, polyethylene and stainless steels. Complete analysis of the wear patterns has been conducted with the expertise of a laboratory. A statistical comparison between materials is presented. The response to wear, depending on material, geometry and position, is better known. One of the materials shows much better wear resistance than the others and is selected for further development. The next step is the development and qualification of the manufacturing process for the wear protection layer. This process has to be as much as possible compatible with current flexible pipe manufacturing plant. Parameters such as thickness, diameter or length of the layer should be adaptable according to needs. The compatibility with the pipe mechanical structure has to be tested as well. To meet these requirements, existing manufacturing processes are limited. At the time of writing this paper, different manufacturing methods to incorporate this wear protection layer within a continuous industrial flexible production are currently under investigation. Several prototypes will be realized for each manufacturing step. Prototyping is under test and will be presented in a forthcoming presentation.