Name of the Project
Cullinan processing plant project.

Location
Gauteng, South Africa.

Client
Petra Diamonds (74%), Kago Diamonds (14%) and the Itumeleng Petra Diamonds Employee Share Trust (12%).

Project Description
Petra Diamonds has built 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 protecting large stones from breakage. It will also improve the efficiency of the material flow, thereby significantly lowering operating costs and reducing the mine’s environmental footprint.

The new plant incorporates:
• 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.

The new plant replaces the old plant, which was originally commissioned in 1947, and thereby reduces the processing footprint at Cullinan from about 27 ha to an estimated 4 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, owing to increased energy efficiency and improved water consumption, as well as reduced circulation and maintenance requirements.

Potential Job Creation
Not stated.

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 is estimated at R1.65-billion to implement.

Duration
The new plant was commissioned during the fourth quarter of the 2017.

Latest Developments
The Cullinan processing plant was commissioned during the fourth quarter of the 2017 financial year except for the large diamond recovery section, which was scheduled for August.

Key Contracts and Suppliers
MDM Engineering (front-end engineering design), now part of Amec Foster Wheeler.

On Budget and on Time?
Unforeseen labour-related disruptions during the middle of financial year 2017, involving plant contractors at Cullinan, put some pressure on the commissioning schedule. The plant was therefore not fully operational by the end of June 2017 and is running about three months behind schedule.

Contact Details for Project Information
Petra Diamonds, email info@petradiamonds.com.