Phosphate Mining Offshore New Zealand

摘要

Phosphate nodules are present at 400 m water depth on the Chatham Rise, 240 nautical miles east of the South Island NewrnZealand, within the New Zealand EEZ. They occur as nodules of 1 mm to 150 mm size within a silt/sand layer generally lessrnthan 70 cm thick. Their P2O5 content averages about 22%. They can be ground and applied as direct application fertilizer orrnused for super phosphate fertilizer manufacture.rnMining design studies have examined a range of options including seabed separation of the nodules from the silty sand, selfrnpropelled crawlers, towed sleds and on site mining vessel to transport barge transfer. The preferred option is trailer suctionrnhopper dredging, with all the material being brought to the surface. The drag head plus underwater pumps will be suspendedrnfrom winches, some of which will be motion compensated. The riser system will be a flexible hose. Separation will take placernonboard with the silt/sand tailings returned to the seabed. The mining vessel will mine for several days recovering 30,000 tonsrnof phosphate, then deliver it to New Zealand ports. Annual production of 1.5 million tons is planned. Current plans are forrnproduction mining in 2014.rnExisting data of 1200 samples has identified 25 million tons over 380 sqkm. An extensive program of geotechnical sampling,rnadditional resource detail and environmental studies is planned for early 2012. Detailed engineering design studies are underway.rnDetails of this work will be presented.rnWhen the Chatham Rise phosphate mining commences it is likely to be the deepest application of trailer suction hopper dredgingrnand the deepest marine production mining to date.