Minerals Report - International Seabed Authority
Minerals Report - International Seabed Authority Minerals Report - International Seabed Authority
Detailed exploration has not been conducted to precisely delineate mine-able fields. Table 4: Metal recovery from polymetallic nodules processing Smelting Sulphuric leach Manganese 87% 85% Nickel 95% 96% Copper 86% 95% Cobalt 83% 94% One can assume from the information disclosed however, that at least three, and likely six, similar mining sites exist in the north Pacific ocean and probably two in the Indian ocean. Polymetallic nodules cannot be enriched by ore processing techniques. They must be treated by metallurgical processes. Several methods have been examined. Afernod considered two of them. These were smelting and sulphuric-acid leaching [12-14-48]. During the prefeasibility study, no difference was found between the two processes in relation to their profitability. The results from testing the two processes are the recoveries for the four metals indicated in Table 4. The French prefeasibility study concluded that the Afernod site could be mined subject to higher metal prices and deep-sea technology reliability improvements. Therefore, the nodules in the site are being considered as sub economic resource. 2.3.2. Cobalt-rich crusts Several engineering studies have been carried out to define possible methods of mining and processing cobalt-rich crusts [24-49-50]. The studies highlight the current lack of knowledge and the need for better information to be able to design efficient systems. A revised continuous line bucket (CLB) system was proposed by its inventor for crust recovery [51-52]. Besides the apparent simplicity of the INTERNATIONAL SEABED AUTHORITY 436
system, strong reservations must be made about its efficiency. It is doubtful that the buckets will be able to extract large slabs of crust that are firmly attached to their substrate. Buckets could be also severely damaged when they impact the bottom of the deposits. The blocks containing crusts will be low grade, retaining a significant amount of waste material. In slope deposits, blocks of lava and volcanic breccias will also be retrieved, as the buckets cannot be manipulated to discriminate between ore and waste. In 1985, Halkyard [50] proposed a hydraulic lifting system with a selfpropelled bottom crawler equipped with cutting devices as suitable technology for mining crusts. The cutting devices would create incisions on the surface layers of the crust, permitting their extraction by suction to the pipe system. In a study conducted during the same year by Gemonod for the Niau deposit, a similar system was envisaged. The proposed cutting device would be a set of hammer drills or a row of rotary cutting drums. A crusher would also be installed on the self-propelled crawling dredge, in order to produce slurry (60% solid) to be pumped to the surface. Chung [24] considered the possibility of using water-jet cutting or fracturing to slice or break the crust top-layers. He also considered adopting a hydraulic lifting system, with a towed or self-propelled bottom collector. Zaiger proposed an innovative system in 1994, known as "solution mining" [53-54]. A large "containment and regulation cover" (CRC: up to 40 000 m 2 ), consisting of an impermeable membrane, is sealed on the bottom by tubes filled with a heavy medium such as barite mud. A leaching solution is introduced between the CRC and the seafloor. After sufficient time, the enriched solution is pumped to the surface platform for metal extraction. The CRC is then moved to another area. Preliminary tests have raised more problems than providing solutions. Research on processing has been limited owing to the lack of information on the composition and physical properties of the possible raw ore [55-56]. However, some studies have shown possibilities of using ore processing to concentrate the minerals. Magnetic separation, followed by froth INTERNATIONAL SEABED AUTHORITY 437
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Detailed exploration has not been conducted to precisely delineate mine-able<br />
fields.<br />
Table 4: Metal recovery from polymetallic nodules processing<br />
Smelting Sulphuric leach<br />
Manganese 87% 85%<br />
Nickel 95% 96%<br />
Copper 86% 95%<br />
Cobalt 83% 94%<br />
One can assume from the information disclosed however, that at least<br />
three, and likely six, similar mining sites exist in the north Pacific ocean and<br />
probably two in the Indian ocean.<br />
Polymetallic nodules cannot be enriched by ore processing techniques.<br />
They must be treated by metallurgical processes. Several methods have been<br />
examined. Afernod considered two of them. These were smelting and<br />
sulphuric-acid leaching [12-14-48]. During the prefeasibility study, no<br />
difference was found between the two processes in relation to their<br />
profitability. The results from testing the two processes are the recoveries for<br />
the four metals indicated in Table 4.<br />
The French prefeasibility study concluded that the Afernod site could<br />
be mined subject to higher metal prices and deep-sea technology reliability<br />
improvements. Therefore, the nodules in the site are being considered as sub<br />
economic resource.<br />
2.3.2. Cobalt-rich crusts<br />
Several engineering studies have been carried out to define possible<br />
methods of mining and processing cobalt-rich crusts [24-49-50]. The studies<br />
highlight the current lack of knowledge and the need for better information to<br />
be able to design efficient systems.<br />
A revised continuous line bucket (CLB) system was proposed by its<br />
inventor for crust recovery [51-52]. Besides the apparent simplicity of the<br />
INTERNATIONAL SEABED AUTHORITY 436
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