The 14-day test of Phase 5.5 of the expansion project at Mimosa Platinum Mine in Zimbabwe, a joint venture between Implats and Aquarius, has been completed. This stage included the second tertiary crusher and screen, new conveyors, modifications to existing conveyors and a second concrete mill feed silo.

This follows the expansion to the float section, which saw the addition of an extra 70m³ secondary rougher cell, another blower and the relevant circuit modifications, as well as improvements to the tailings disposal section where a new 200mm HDPE line from the plant to the intermediate pump station, a distance of 1.5 km, was installed. An additional 1.2km of lines was laid to improve the tailings distribution to the dam.

This brings the total capacity of the plant up to 185,000tpm with the crushing and tailings disposal sections now capable of handling in excess of 200,000tpm. Located 160km east of Bulawayo, the project has had its fair share of challenges – power outages, hyperinflation (which saw the loss of 25 zeroes off the local currency) and the recent cholera outbreak, which made getting through the border a whole lot more difficult.

However, as Clinton Swemmer from DRA says, the company managed to finish the upgrade in spite of these challenges. “We have managed to complete the work, even exceeding the design criteria. The benefits to the client include the potential to optimize: shift management; downtime; maintenance and resources. This project concentrated primarily on the dry end of the plant where it was necessary to completely replace two of the four existing conveyors in order to increase crushing capacity.”

“Whilst it was originally anticipated that a ten-day shutdown for work to be completed, DRA managed to reduce this to a planned seven days and achieved feeding ore through the plant after only six; beating our target by a wide margin thanks to months of planning and modifying the designs in line with risk management strategies.”

“This was accomplished by creating a diverter carriage at the original multi-slope screen and creating a parallel circuit rather than upgrading all four conveyors, screening building and crushing building.”

“It was critical to co-ordinate vendors, suppliers, head office, design and verification teams in order to ensure a smooth shutdown. Mimosa is a very cost-effective contributor to the Implats and Aquarius group of companies (50/50 JV partners) so success was paramount,” concludes Clinton Swemmer from DRA.