Name and Location
Cullinan processing plant project, Gauteng, South Africa.

Client
Petra Diamonds.

Project Description
Petra Diamonds plans on building a modern, fit-for-purpose processing plant at Cullinan, with a throughput capacity of six-million tonnes a year.

The new plant is expected to improve the recovery of the full spectrum of diamonds, thereby increasing the volume of stones recovered and the protection of large stones from breakage.

It will also improve the efficiency of the material flow, thereby significantly lowering operating costs.

The new plan will incorporate:
• autogenous milling – a gentler recovery process that breaks down ore using attrition rather than crushing, thereby better protecting the large, high-value stones for which the Cullinan mine is known;
• high-pressure grinding rolls technology – a gentler liberation technique incorporating interparticle crushing, thereby moving away from high-impact cone crushing; and
• XRF X-ray technology to replace conventional dense-media separation plants to treat coarser +12 mm material.

In addition to the benefits of large stone recoveries, the improved diamond liberation technologies outlined above are expected to lead to an increase of about 10% in the overall grade achieved at Cullinan.

Further, the new plant will reduce the processing footprint at Cullinan from about 26 ha to an estimated 5 ha, with the associated reduction of engineering infrastructure deployed, including an expected reduction in the number of conveyor belts used from 151 (spanning 15 km) to 22 (spanning 3 km).

The new plant is expected to yield a saving of between R20/t and R25/t in processing costs, due to increased energy efficiency, improved water consumption, reduced circulation and reduction in maintenance requirements.

No impact on current daily operations or throughput at Cullinan is expected while the new plant is being constructed.

Net Present Value/Internal Rate of Return
The project has an internal rate of return of 25%, with a payback of about three years.

Value
The project will cost about R1.65-billion to implement.

Duration
The new plant is expected to be commissioned and fully operational in the fourth quarter of the 2017 financial year.

Latest Developments
The project is being executed by MDM Engineering. Bulk earthworks have started on site and all long-lead time items have been ordered.
R106-million was spent on the new plant during the 2015 financial year, mainly on payments pertaining to long-lead time items.

Key Contracts and Suppliers
MDM Engineering (front-end engineering design).

On Budget and on Time?
The project is on time and within budget.

Contact Details for Project Information
Petra Diamonds, email info@petradiamonds.com.
MDM Engineering, tel +27 11 993 4300, fax +27 11 886 9306 or email info@mdm-engineering.com