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:: Diamond-treatment Plant for De Beers’ Marine Vessel
In a R150 million (US$21 million) contract, Bateman Engineering designed the 250 t/h diamond-processing plant installed on board De Beers Marine (Pty) Ltd’s vessel mv Peace in Africa. The objective of the project was to establish a viable, sustainable marine mine producing 240,000 carats of diamonds in the South African Sea Areas (SASA) off the west coast of South Africa, based on De Beers’ new sub-sea mining technology and exploration data on the area.
Bateman Engineering’s role in the project was to design the treatment plant as well as to supply components of the concentration circuit for the plant. The processing plant comprised feed-preparation, comminution, concentration and diamond-recovery circuits.
In designing the circuits of the ship’s processing plant, Bateman Engineering drew upon its considerable experience in the design and engineering of diamond-process plants. The plant was, however, designed strictly in accordance with the De Beers specifications for marine-processing plants. Particular attention had to be given to the design of the structure of the processing plant to enable it to handle the motion of the vessel up to a 15° roll.
Bateman Engineering supplied all the components of the concentration plant. A purpose-designed DMS plant was designed and installed, as a standard Bateman Modular Plant could not be used because its footprint was too large to fit onto the vessel. The equipment for the feed-preparation, comminution and diamond-recovery circuits was obtained from outside suppliers.
The submersible mining vehicle sucks about 1,250 t/h of diamond-bearing gravel from the seabed and pumps it to the ship on the sea surface, using about 10,000 m3/h of seawater. The gravel entering the feed-preparation circuit is first dewatered and then screened to remove the finer material, which is returned to the sea.
The oversize fraction proceeds to the comminution circuit where the material is again screened. Oversize material is returned to the sea and the remainder is milled at a rate of about 110 t/h and sent to the concentration circuit.
The concentration circuit consists of screens and a dense-medium separation (DMS) cyclone. Here the more dense material (i.e. the concentrate containing the diamonds) is separated from the waste gravel, which is discarded in the sea. The concentrate, at a rate of 1 t/h, passes into the diamond-recovery circuit equipped with X-ray recovery modules that separate and recover the diamonds from the waste material.
The installation of a diamond-processing plant on the mv Peace in Africa involved the conversion of a dock vessel to an ocean-going vessel capable of carrying both the undersea-mining vehicle and the processing plant. The Bateman Engineering team designing the process plant therefore had to liaise very closely with the naval architects in Norway, the shipyard contractor in the UK, and the client who undertook the erection of the plant in Cape Town.
The project commenced in 2006 and was completed in 2007. It was preceded by a feasibility study conducted by Bateman Engineering in 2005.
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