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DebTech develops new diamond sorters to fill gap

29th August 2014

  

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De Beers Technologies South Africa (DebTech), part of global diamond miner De Beers, will again exhibit some of its latest technological developments together with the standard range of equipment at Electra Mining Africa. All these technologies have been researched, developed and commercialised at its facility in Crown Mines, Johannesburg.

A large portion of DebTech’s revenue is derived from exports as products are distributed to De Beers and other entities across the world.

The majority of DebTech’s products have a diamond specific application, but some will have application outside of diamonds. Examples of these include the X-ray transmission (XRT) diamond sorter, which is also used for coal and other ore types, and the densimetric profiler (Rhovol) unit that can measure individual particle density of a variety of materials.

During the last two years, DebTech has placed emphasis on filling a gap in the suite of diamond sorters on offer. The material top size of sorters was traditionally 32 mm, but owing to requests from industry, two new sorters were developed. The new BWX1112 and BWX118 increased the top size and throughput to much higher values than were previously on offer.

Rhovol Densimetric Profiler
Rhovol project manager Tinus Steyn says one of the key parameters in any mining processing environment is the density distribution of the material being processed. Upfront and timeous knowledge of the density distribution of the material and product being processed or sorted helps in optimising the process plant and control of the final product grade. Applications include dense-media separation (DMS) and jig optimisation and control. Currently, density estimation of material samples can take months to measure, depending on the accuracy and method used, leading to long control loops for optimisation and control purposes. Some of these methods also make use of harmful, heavy liquids.

DebTech succeeded in developing a single particle densimetric analysis system, ρVol, for ore particles using a fast weighing device coupled with a volume measurement by a simplified volume size frequency distribution (VSFD) system. The system is not material sensitive and can process a size range between –50 mm and +1 mm in defined splits. Material feed application is dry, sized and dust free. VSFD technology ensures accurate volume and shape measurement with an added benefit for metrological analyses. The system is small, easy to use and can be used on site by the operation, resulting in quick turnaround times without using consumables.

Diamond X-ray Sorting Machines
Larger diamonds are extremely rare and valuable. However, because of their rarity, many operations do not cater for specific upstream equipment to recover these larger stones. These diamonds are inadvertently crushed or break in diamond processing plants, are designed for smaller distinct size ranges.

DebTech says there has been renewed interest from diamond mining operations in recovering larger diamonds, as a single large diamond has significantly greater value than the same stone broken into smaller pieces.

DebTech took on the challenge to address the requirement in the market and developed the BWX1112 and BWX118 large diamond sorters.

The requirement was for these sorting machines to be placed further upstream, compared with traditional recovery machines and, therefore, needed to operate at a high-feed rate. A traditional sorting machine operates at a rate of 1 t/h to 2 t/h, whereas these large diamond sorting machines need to operate at 50 t/h to 100 t/h, but most importantly without missing that rare large diamond. This was the biggest challenge in designing a large diamond recovery machine.

DebTech project manager for this technology, Arshad Nabbie, comments that the company has succeeded in providing a solution with the launch of two large diamond sorting machines. The BWX1112 machine is designed inside a standard six-metre shipping container for ease of deployment in harsh environments and to minimise the infrastructure costs borne by the mining operation. It recovers diamonds between 30 mm and 80 mm in size at a throughput rate of up to 120 t/h. The recovery efficiency of these machine are >= 98%, no easy feat considering the high throughput rate of the machine. These machines use X-ray luminescence technology to detect diamonds as they speed through, together with the gravel, on an internal conveyor belt. The X-ray luminescence technology used in the machine is well established in the industry. Air ejectors are used to displace (and recover) the diamonds from the material path. Further, the BWX1112 can be supplied with a separate services container that provides clean compressed air, chilled water and UPS power – essential services needed by the BWX1112 sorting machine. Using the services container reduces the infrastructure the mining operation needs to provide.

The BWX118 is a smaller cabinet-based machine that can typically be housed inside a building. It recovers diamonds between 30 mm and 80 mm in size at a throughput rate of up to 20 t/h. This machine also uses the same X-ray luminescence technology to detect the diamonds and uses similar air ejectors to displace the diamonds from the material path. DebTech says the machine fills the gap between a traditional recovery machine running at 2 t/h and the large BWX1112 running at 120 t/h. It caters for both large and smaller mining operations.

Both these machines can process material that is wet, eliminating the need to dry the material, which is typically necessary in a recovery process plant. Dryers have a significant operational cost in terms of electricity used. These machines were first deployed in 2012/13 in Namibia.

XRT Diamond Sorter
DebTech is introducing a new range of diamond sorting machines employing XRT technology. These machines are specifically designed with the diamond industry in mind and cover a range of applications in the upstream diamond value chain. Three modes are available: The coarse concentrator aimed at coarse DMS replacement, treating dewatered material in a feed size range between –50 mm and +6 mm. The primary sorter for application in the recovery plant, treating material in a feed size range of –32 mm to +2 mm and the single particle sorter for final concentration, treating material in a feed size range of –32 mm to +1 mm. When compared with X-ray fluorescence, the XRT methodology features the added benefit of reduced yield. XRT is less influenced by dust and slime on the surface of diamonds and can be applied to other applications. This technology is insensitive to diamond temperature, type, colour or quality.

Depebbling of coal and electronic scrap sorting could be successful with these units.

XRT is known to us in the form of medical X-rays or baggage scanners. Using multiple X-ray energies allows the machine to discriminate between various materials based on a combination of the density, thickness and elemental composition of the material.

Hall 6 Stand F9

Edited by Creamer Media Reporter

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