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MEI Online: Plant Operation News: Africa: August 9th 2006


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:: Upgrade of Namdeb's 3-Plant Diamond-Treatment Facility

Namdeb has awarded Bateman Engineering a R115 million contract to upgrade an existing diamond treatment facility in Oranjemund on the west coast of Namibia to re-treat tailings dump material. The dump contains about 24 million t of tailings accumulated during the past 30 years of diamond mining in the area.

The diamond-recovery processes used previously were not as efficient as they are today and these dumps are known to contain meaningful amounts of small diamonds and possibly also some larger stones.

Phase 1 of the project will comprise both modifications and additions to the plant. A new dump-reclaim section, utilising tipping hoppers and a conveyor, will feed the new front-end screening facility comprising receiving bins, brute-force feeders, vibrating scalping screens and associated conveyors to remove product and waste.

In the existing scrubbing facility three scrubbers will be removed and replaced with bypass chutes. Later, the remaining scrubbers will be removed and bypassed, leaving only the screening operation in place.

The existing secondary-crushing circuit will also be upgraded by replacing the three old-generation crushers and a small jaw crusher with four new-generation Sandvik cone crushers with fully automated on-line gap settings. Though smaller than the out-going crushers, they will liberate the diamonds more effectively. The crusher's discharge screens may also be replaced, depending on their performance during the commissioning and ramp up phase.

The feed to the existing dense-media separation (DMS) plant, which is currently split into two streams, will be converted to three-streams, with the third feeding a new 200 t/h Bateman Modular DMS Plant.

In the existing DMS building, the old mixing boxes will be replaced by more efficient standard units. The old cyclone feed system, comprising two Multotech 610 cyclones per stream, will be replaced with new distributors and feed hoses and four Multotech 420 cyclones per stream, to accommodate the change in the feed-size profile. It is also possible that a new silo system will be installed to control the collection of concentrate from all of the DMS plants.

When the current run-of-mine campaign at the mine is completed, the existing tailings conveyor will be stopped, swung through 180 and refurbished as necessary, and become the new tailings-dump start-up conveyor. A new environmentally friendly, low-profile tailings dump will be established on the existing mined out areas.

Phase 2 is scheduled to commence in 2007 and be completed in the third quarter of the year. A preferential jaw crushing plant will be installed to take crusher oversize material and further liberate any diamonds. This will convert the plant from a closed to an open circuit and effectively provide tertiary crushing at the plant. A study is still being conducted on the addition of a thickener to close-loop the water-reticulation system.

This is one of several projects to recover diamonds from tailings dumps at older mines in which De Beers has involved Bateman Engineering as part of the new partnership model between the companies introduced towards the end of 2003.




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