Page 24: of Marine Technology Magazine (November 2019)

2020 & Beyond: Subsea Mining

Regulations could be promulgated in circumstances must be properly planned design, it must be considered that once 2020. A link to the draft version of the and designed into the vessel or rig. the slurry reaches the mining support

Regulations can be found here https:// For many, the Solwara 1 Production vessel or rig at the surface, the water ran-s3.s3.amazonaws.com/isa.org.jm/ Support Vessel which was built and must be removed and returned to the s3fs-public/? les/documents/isba24_ltc- launched at Fujian Mawei Shipyard is approximately the same depth from wp1rev1-en_0.pdf an example that includes all of the key where it was extracted. Meanwhile the elements. remaining ores must be dried and stored

Challenges: Technical until they can be sent ashore. Much When transitioning from the prospect- Sea? oor Mining Tools thought has gone into how to design ing phase to the commercial exploitation Except for the nodular type of minerals environmentally sustainable dewatering phase, there are four main challenges to that can be directly collected and lifted and cargo handling systems, with most be faced: to the production vessel, many differ- designs contemplating some combina- 1. Designing and building a suitable ent varieties of sea? oor mining tools tion of settling, cyclone separation, and mining support vessel or installation. will be required to prepare the sea? oor heat drying. 2. Designing and building proper sub- mined material to the sizes that can be Produced water, because of micro- sea mining tools – that is, the machines effectively lifted to the production ves- bial content and temperature differ- actually perform the mineral extraction sels. For SMS mines, the mining tool ential cannot be discharged at the sur- on the sea? oor. prototypes have been built and to some face. Therefore, a system of pumps and 3. Designing and building the riser and degree successfully demonstrated. Oth- downcomers to the near seabed must lift system for transporting the mineral er sea? oor mining tool prototypes have also be designed. In order to be suc- slurry to the surface. been tested successfully. Most designs cessful, the amount of production from 4. Once on the surface, dewatering and involve a crawler of some type with ei- a single Mining Support ? oater would cargo handling. ther a cutter or a suction head depending entail producing at least 1000-6000 tons

However, the most daunting technical on the target materials. of dried ore per day; so the economics challenge of all is incorporating all these would seem to dictate the need for a ship new technologies into an integrated sys- Risers and lift systems. to ship transfer to a shuttle type of cargo tem that will work reliably, effectively, The dif? culty of moving many tons per handling vessel while the mining ves- and seamlessly for the entire mining day of dense slurry from depths of 1000 sel remains on station. In this area, the ? eld life. meters or more cannot be underestimat- dredging industry may offer a guide to

It must be remembered always with ed. For SMS projects where the depths similar technical solutions. the design of each of these systems that, may not exceed 2000 meters, steel ris- in addition to being capable of meeting ers of the vertical top tension design Stakeholders the technical design speci? cations, they are mainly contemplated. For mining It is important to identify what role also must meet the environmental rules nodules in depths greater than 3000 me- each stakeholder plays in full-scale sub- established with respect to biodiversity, ters, the weight of steel risers is a huge sea mining. plume density and extent, and sedimen- problem, so alternative materials are First and foremost is the Owner, or tation rates, rules either of the ISA in In- being considered. Pumping systems in- in the ISA terminology the Contractor. ternational Areas, or of the Coastal State volving centrifugal pumps are also quite This is the organization which is most within the EEZs. problematic for these lifting distances. directly responsible for implementation

A positive displacement design subsea of the design and operation of any un-

Mining Support Vessel pump was built by GE Subsea Sys- dertaking. In many cases, national orga-

The ? rst necessity in any subsea min- tems for the Solwara 1 project. An air nizations are contemplated for this role, ing plan is a suitable ? oating installa- lift system test loop and small-scale air as commercial entities are considered tion. In addition to the most basic mari- lift systems have been constructed and too risk averse, or underfunded. In the time design consideration of stability, tested so far but have not been scaled case of China, there are State Owned En- structural integrity, station keeping, and to deep-water for testing. Others have terprises (SOE) which are well funded, safety, special design considerations for proposed truly innovative designs which and deeply involved in several different support of subsea mining must be taken do not involve pumps or air lifts, such mining projects. Worldwide, there are into account. These include handing of as a continuous conveyor system or even many other state and commercial actors sea? oor mining tools, handling of riser magnetic induction systems. who are at various stages of readiness in and lift systems, cargo dewatering and their mining plans.

handling systems. As with oil and gas Dewatering and Cargo Handling. Regulators – The regulators are the In- installations, abandonment and recov- Although not as eye-catching as the ternational Seabed Authority in Interna- ery operations due to weather or other sea? oor mining tools or subsea pump tional Areas, the Coastal State authori-

November/December 2019 24 MTR

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