MechChem Africa January 2019

⎪ Minerals processing, metallurgy and materials ⎪

Above: Multotec offers an extensive programme of customer training workshops that focus on principles of separation, operations and fault-finding. Left: This filter press is one of Multotec’s large production designs and can treat 35 t of coal an hour.

tonnages being fed to coal preparationplants. Not only can this circuit become a bottleneck if it is unable to process the full fines frac- tion stream but, as the separation process is mostlywater-based, this iswheremuchof the water is used. The objective herewould be to minimise excessive water use without sacri- ficing separation efficiencies. To achieve this objective a proper understanding is required of the limitations of each piece of equipment in the circuit as well as which process factors

will contribute the most towards separation efficiencywhilereducingwaterconsumption. Again, Multotec’s training courses focus on improving operation personnel’s un- derstanding of the equipment and how to improve its performance. If operators take the knowledge into their working environ- ments and look proactively for opportunities to reduce water usage, this kind of industry training can have a considerable impact on the sector’s water footprint, q

they reduce theneed toaddmore spraywater on the rinse section of the screen, saving wa- ter. The Multotec short course on screening principles transfers knowledge to customers and industry on how to achieve this. Thefines coal circuit is alsoanareadeserv- ing attention, especially with increasing feed

DebTech ore sorters for JWANENG Large Diamond Plant Two high-throughput x-ray transmis- sion (XRT) ore sorters from De Beers Technologies SA (DebTech) have been installed at Debswana’s Jwaneng diamond mine, as key elements of its new Large Diamond Recovery Pilot Plant. The CC+ machines are assembled, transported and operated in 12 m shipping containers, allowing them to be fully tested inworkshopconditions andquickly commis- sioned on site. Each unit is self-contained with its own power conditioning, com- pressed air generation, closed circuit water cooling and machine control room. and eject diamonds, but are also capable of generating online carat estimates and stone count values. XRT technology is also targeted at re- placing the coarse and middle dense media separation (DMS), says Taylor, as the typical XRT concentrate yield is significantly less than an equivalent DMS plant.

According to Gordon Taylor, head of DebTech,theXRTCoarseConcentratorPlus (CC+) units were specially developed for the Botswana mine to treat run-of-mine at combinedthroughputsofupto500t/hwhile allowing for the recovery of large diamonds with negligible extra material. Design and construction of the XRT CC+ units began in 2017 and they were delivered to Jwaneng in January 2018 for early integration into the construction of the Large Diamond Recovery Pilot Plant. Taylor highlights that recent develop- ments in XRT technology make the identi- fication of diamonds much more accurate, changing the economics of finding larger diamonds. The XRT CC+ units at Jwaneng are based on the original XRT Coarse Concentratormodel developedbyDebTech. They operate using imaging systems and sorting algorithms that have been proven at several De Beers Group operations.

Theyareoperated throughauser-friend- ly, menu-driven control interface, which allows real-time reporting and is fitted to provide remotediagnostics.Material enters the unit via an inlet chute and is conveyed between an x-ray source and an x-ray cam- era. Images capturedby the camera are ana- lysed via software algorithms and a pneumatic ejection sys- tem diverts a ny o b j e c t identified as a diamond. The ‘dual energy’ feature on the XRT sorting sys- tem enhances its ability to analyse materials of differing thickness. Its power- ful imaging capabilities not only identify

“This considerably reduces downstream infrastructure with further benefits of the technology including reductions in consum- ables, power and water require- ments,” he concludes. q

The XRT Coarse Concentrator Plus (CC+).

January 2019 • MechChem Africa ¦ 29