Modern Mining January 2016

DIAMONDS

New Cullinan plant will

commissioned nearly 70 years ago, has become increasingly expensive to maintain due to its age and operational complexity and has required the commitment of significant stay-in- business capex in recent years. Moreover, it is also based on old crushing technology, which Petra believes does not offer the best potential for optimal diamond recoveries. A feature of the new plant will be a much reduced footprint compared to the existing facility – it will cover just 5 ha compared to 26 ha. This will result in a commensurate reduction of the ‘infrastructure’ required. For example, only 22 conveyor belts totalling 3 km in length compared to the 151 conveyor belts used at present, which extend over a total dis- tance of 15 km, will be required. There will be only 22 screens compared to four times that number in the existing plant while the number of pumps will reduce from 121 to just seven and electric motors from 589 to 84. Moreover, only two substations will be needed as opposed to 17 currently. The plant – which will feature a high level of automation and a total ‘hands-off’ final recov- ery section – will have a throughput capacity of 6 Mt/a with the initial feed comprising 4 Mt/a of ROM and 2,3 to 2,5 Mt/a of tailings.

One of South Africa’s oldest andmost famous diamond mines is to get an entirely new, state-of-the-art processing plant which will replace the current sprawling treatment complex which dates back to 1947. Petra Diamonds, the owner of Cullinan, estimates that the energy-efficient facility – which will incorporate autogenous (AG) milling and X-ray fluorescence (XRF) technology – will improve revenue per tonne by 6-8 %and will pay for itself within about three years. The cost of the project is estimated at R1,65 billion.

P etra announced the approval for the project in April 2015. The con- tractor charged with delivering the plant is MDM Engineering and work on site has been on-going over the past several months, although the peak of construction is only due later this year (2016). The plant will be commissioned and enter operation in Petra’s H2 FY 2017 (i.e. by June 2017). Orders for all the long lead items – such as the AG mill and the High Pressure Grinding Rolls (HPGRs), which will both be supplied by Polysius – were in place by September 2015. The current plant, although it has under- gone various refurbishments since being

The base for the XRL (X-ray luminescence) plant at Cullinan.

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34  MODERN MINING  January 2016