Gewinnung von Rohstoffen aus der Tiefsee22.03.2000 - (idw) Universität Siegen
Die Entwicklung der Technologie zur Gewinnung von Rohstoffen (Manganknollen) vom Boden der Tiefsee macht Fortschritte. Vor wenigen Tagen wurde in einem Test im Indischen Ozean die hydraulische Förderung von Feststoffen durch einen flexiblen Schlauch vom Meeresboden auf das Mutterschiff erfolgreich demonstriert. Dabei wurde mit 410 m ein Tiefenrekord für ein mobiles Unterwasserbergbaugerät erzielt.
The National Institute of Ocean Technology (NIOT), Chennai, India, an autonomous institute under the Dept. of Ocean Development (DOD, Govt. of India) is implementing underwater mining technology programme through a joint project with the
University of Siegen (Institut für Konstruktion, IKS), Germany. This programme was started in January 1998. As a part of this programme, an underwater crawler mounted mining system has been developed initially for deployment in 500 metres depth and to be extended subsequently to 6000 m. This crawler mounted with sand mining system is remotely operated through a special cable wound on a heavy duty winch installed on board ORV Sagar Kanya. The complete weight of the crawler, about 12 tonnes, is lifted by the outer armour of the special cable. This cable supplies power of 110 kW for crawler locomotion and slurry pumping at 3000 V. The power for the computer control and instrumentation at 220 V and communication between crawler and ship computers through optical fibres is also through the same cable. The slurry is pumped through a flexible hose attached along with the umbilical cable.
This crawler mining system was tested off Goa (India) in a water depth of up to 60 m during October 1998. A second campaign was done off Tuticorin (India) around 120 metre. The improved crawler system was taken up for trials off Tuticorin from 1st March 2000 onwards. Detailed bathymetry survey up to 400 m was done and soil sampling using corers was also carried out. This crawler mounted mining system weighing about 12 tonnes, winches and control systems was tested on board ORV Sagar Kanya owned by DOD, Govt. of India. The soak test of the entire system was successfully completed within the Tuticorin port on 11th March 2000 and thereafter ORV Sagar Kanya sailed out to the testing site situated about 70 km off Tuticorin coast. The system was lowered and tried at various depths during the period 12-14 March 2000 and finally the crawler was lowered to 410 metres at 2.30 pm on 14th March 2000. The mining system consisting of crawler, cutter and slurry pump was successfully operated and slurry of different concentrations was pumped up to the ship deck. The flow was varied and the slurry by varying the pump speed and the density level went up 1170 kg per cubic metre.
Normally for Port and similar applications the dredging of seabed is only done up to 30 m and only in exceptional cases, up to 50 m. Dredging has been demonstrated in a depth of 410 m for the first time in India, now.
The mining system has a hydraulically operated locomotion for the crawler with rubber tracks. This has a hydraulically operated manipulator arm with a rotating cutter. The slurry is pumped by a twin cylinder single acting reciprocating pump over a height of 410 m through a flexible riser. The pump is driven by an underwater electric motor at 3000 V A/c. The crawler has a PC-based data acquisition and control system having sensors for motion, inclination, heading, slurry concentration, underwater camera for monitoring the performance of the total system. The equipment of such a sophistication and weight has been lowered to a depth of 410 m, operated successfully and recovered safely for the first time in India. Available literature has not reported any such mobile mining system anywhere in the world.
During the entire operation on the sea bed ORV Sagar Kanya was maintained on a particular location with the assistance of Tuticorin Port Trust tug Rajaji.
The entire operation was carried out by the joint team of NIOT & IKS scientists led by Prof. M. Ravindran and Prof. W. Schwarz with the active support and cooperation of scientists from National Ship Design and Research Centre, National Centre for Ocean and Antarctic Research (DOD, Govt. of India), NORINCO, Capt. K. Balachandran, Master Mariner and Capt. Varma and his team on board ORV Sagar Kanya.