Engineering, procurement, construction, maintenance (EPCM) and project man- agement services company Fluor South Africa reports that it has completed a prefeasibility study (PFS) for the Letlhakane diamond mine, in Botswana.

The mine is owned by Debswana Diamond Company, a joint venture between the government of Botswana and South African mining company De Beers, and is nearing the end of its life, as the openpit has been developed to the mining design limits.

As part of Debswana’s strategic planning, the company is continuously reviewing the viability of projects to improve or extend life-of-mine forecasts.

“The tailings resource at Letlhakane contains historical discard material that has proved to contain locked and free diamonds. Fluor was tasked to conduct the PFS,” says Fluor mining and metals project manager Karel Coetzee.

The project involved the development of various process plant options that could exploit the resource in a cost-effective and economically viable way.

The end product of the treatment plant will be a dense media separated concentrate that will be further processed through the existing recovery plant located at the nearby Orapa mine.

Coetzee notes that a structured approach was followed by Fluor, in conjunction with Debswana, to develop and rank the different options.

Nine process options were identified and evaluated at concept level.

These were reduced by process of elimination to two viable solutions. “The final two concepts, one brownfield, using existing plant elements, and one semi-brownfield, were further developed and financially evaluated,” he says.

Coetzee states that a new process plant utilising a high pressure rolls crusher, proved to offer a better financial and strategic fit to Debswana’s business strategy.

“Peer reviews were held with experts from all parties, including Fluor, Debswana and De Beers in order to select a go-forward option. Another major requirement was to have a modular design, so that the plant could be relocated, within a certain timeframe, to another site,” he says.

He adds that the scope of work was split between Fluor and Debswana, as some elements of the project were selected to be done by the owner, such as mining design and operational readiness, among others.

“The new treatment process developed by Fluor offers proven technologies, aligned with the other Debswana business units.

As part of Debswana’s long-term strategy, the ability to employ the basis of this design for future needs was an integral part of the design criteria,” explains Coetzee, adding that this requirement has led to a modular design approach, process flexibility and the ability to add modules to match various throughput requirements.

“Fluor was able to increase the benefit of best international practices by collaborating with modularisation experts from Fluor’s Construction Technical Services group, in Houston, in order to provide a fit-for-purpose modular concept for the project. Further, value was added through diamond simulation and Fluor’s value improvement practices,” he says.

Coetzee states that the engineering design effort has been continuous throughout various gate review interventions.

“Owing to the fact that the project will be a modular constructed plant, much of the work will be executed in a yard, and large modules will be transported to site. The modular design approach will lend
itself towards a small execution team. This offers more control and reduces construction and safety risks on site.

“The feasibility phase will define in more detail how the project will be executed, and the number of persons to be involved.