Modern Mining January 2018

DIAMONDS

Petra’s new processing plant a ‘gentle giant’

will finish the project largely in line with the April 2015 cost estimate of R1,65 billion, ad- justed for escalation and currency fluctuations. The main contractor behind the engineering, procurement and construction of the plant was Amec Foster Wheeler’s South African arm, MDM Engineering. According to Petra, all components of the Cullinan plant are now fully operational, with ramp-up and optimisation activities ongoing; the plant is expected to achieve nameplate capacity of 6 Mt/a during the second half of the 2018 financial year. Key among the technology advances has been the focus on comminution through attri- tion, rather than the less forgiving high-impact crushing that characterised these functions in the old plant. This approach employs autog- enous (AG) milling for the +25 mm material,

Having provided two of the largest diamonds in the Crown Jewels, the legacy of large and high-quality stones being unearthed at Cullinan mine near Pretoria contin- ues; little wonder, then, that Petra Diamonds’ new pro- cessing plant at Cullinan promises to go gentler on the mine’s over-sized discoveries.

B y any standards, the installation of this exciting new and considerably more efficient plant is long over- due – replacing a sprawling 26 ha installation that was first commis- sioned in 1947 and evolved with multiple al- terations and upgrades since then. With the go- ahead for construction granted in April 2015, the project was completed and commissioned in September 2017. The company estimates it

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56  MODERN MINING  January 2018