The method for recovering the manganese nodules works with the help of a gentle suction method.
Compressed air is released under water through a suction line, whereby suction is obtained. The operation intends in the first instance to use air-lift technology.
One or more suction lines will run from the production platform at the surface down to the seabed. At the end of the suction line is a suction nozzle. The nozzle is around ten metres wide, and the production platform will thus be equipped with up to four nozzles, distributed across the same number of suction lines, and can thereby achieve a suction width of at most 40 metres.
The nozzle is constructed so that its height above the seabed is regulated with the help of winches mounted on the production platform. On the outer edges of the nozzle are skids that keep the nozzle from coming too close to the bottom and thereby reduce damage to the seabed.
How the nozzle works.
The optimal height above the seabed for the nozzle’s intake channels is about 10 to 20 cm. Soft brushes can surround the intake channels on the nozzle to shoo away any fish. Water jetting can be applied in front of the nozzle to reduce the amount of unwanted sediment drawn up together with the nodules. The sediment then swirls up and the nozzle can pass beneath the sediment cloud. The suction force in the nozzle falls off very sharply once the optimal distance from the intake channels is exceeded. As the nozzle passes over the seabed the nodules lift because of their volume and are thereby drawn into the intake channel.
