And now for something completely different: a robotic bulk cutter designed for underwater mining of seafloor massive sulphide (SMS) deposits of copper, gold, zinc and silver at depths of up to 2,500m and operated by Nautilus Minerals.
The machine, which excavates material by a continuous cutting process similar to land-based coal or other bulk continuous mining machines, is one of three seafloor production tools (SPTs) made for Nautilus at the Soil Machine Dynamics (SMD) facility in the British city of Newcastle upon Tyne, and destined for wet-testing in the first half of 2016.
The first piece of equipment in the deep sea mining chain is an auxiliary cutter (AC) – a preparatory machine that deals with rough terrain and creates benches for the other machines to work.
With a length of 15.8m, width of 6m and a height of 7.6 m, the 250-tonne machine operates on tracks and has a boom-mounted cutting head for flexibility.
The bulk cutter has higher cutting capacity but is limited to working on flatter areas and benches created by the AC. It measures 14.2m in length, 4.2m wide and 6.8m high, and weighs in at 310 tonnes. Its cutter width is 4.2m.
These types of machines are to be used because mineralised material generally sits proud on the seafloor with minimal overburden.
Both machines leave cut material in temporary positions on the seafloor for collection by the third robotic machine, the collecting machine (CM).
The 16.5m x 6m x 7.6m CM will collect the cut material by drawing it in as seawater slurry with internal pumps and pushing it through a flexible pipe to the riser and lifting system (RALS).
The RALS consists of a large pump and rigid riser pipe which delivers the slurry to the production support vessel (PSV). The pump is supported on a solid vertical (riser) pipe suspended beneath the support vessel.
On deck of the PSV the slurry is dewatered, with the resulting solid material stored temporarily in the PSV’s hull, and then discharged to a transportation vessel moored alongside.
Nautilus says filtered seawater is pumped back to the seafloor through the riser pipes and provides hydraulic power to operate the RALS pump.
“Discharge of the return water at the seafloor from where it came eliminates mixing of the water column, and minimises the environmental impact of the operation,” the company says.
Components for the launch and recovery system (LARS) which will be used to lift the tools in and out of the water have been made by factories in Poland, Korea and Norway.
Nautilus has been granted an Environment Permit and Mining Lease for resource development at its copper-gold project, Solwara 1, in Papua New Guinean territorial waters. The company says it also “has tenement holdings in the exclusive economic zones and territorial waters of Papua New Guinea, Fiji, Tonga, the Solomon Islands, Vanuatu and New Zealand as well as other areas outside the Western Pacific.”
Production from Solwara 1 is planned to come on stream in the first quarter of 2018.
So why mine the seabed?
Nautilus Minerals president and CEO Mike Johnston says the International Seabed Authority (ISA) has published that there is more copper on the seafloor than all the reserves known on land.
“Copper on the seafloor is on average at a much higher grade than on land,” he says. “For example, at Solwara 1, the copper grade averages 7 percent, which is some 10 times higher than what is typically found on land.
“It only stands to reason that as the demand for minerals continues to rise, land resources will struggle more and more to meet this rising demand.
I believe the mining industry is at the same juncture the oil and gas industry was at 50 years ago when it first started to go offshore,” Johnston adds. “Now around 30 percent of the world’s oil and gas comes from offshore sources.”
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The Nautilus Minerals seafloor production system.
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