Project management company DRA Mineral Projects reports that it has completed Phase 2, or Khumani Expansion Project (KEP) of manganese ore and alloy company Assmang’s Khumani mine, in the Northern Cape, and comissioned a new wet, high-intensity magnetic separation (Whims) plant at the site.

Testwork programmes on the potential value that Whims adds to the Khumani operations were initiated and completed during 2010 and 2011.
“The results of these programmes established a high level of confidence that Khumani would be able to recover additional fine product if a super fine Whims processing section was added to the processing sections,” explains DRA senior project manager JC Heslinga.

“The project was particularly exciting for DRA, as it is the first iron-ore Whims beneficiation plant to be built in South Africa, and the first to be designed by the company. The success of this project has added considerably to our existing knowledge and allows us to further expand our offering to clients,” notes Heslinga.

Following on from the completion of the Khumani 16-million-ton-a-year expansion project in 2012, the Whims unit is essentially a magnetic separator which allows the deslimed –0.8 mm ore to pass through a primary and secondary stage of Whims.
The selected equipment, Jones DP 317, can process up to 120 t/h of solids and the overall plant consists of four primary and four secondary separation units.

DRA Mineral Projects was appointed the engineering, procurement and construction management (EPCM) contractor for the R6-billion project to increase Khumani mine’s capacity from 10-million tons a year to 16-million tons a year, with a scope of work that included the run-of-mine (RoM), crushing and processing facilities for the new King opencast mine, including workshops and associated mine infrastructure.

Further, additions were made to the materials handling facilities, including an overland conveyor, extra RoM stockpiles, and stacker and reclaimer machines. Washing, screening and jigging capacity was also increased; new primary and secondary thick- eners and extensions were made to the dewatering circuit; and extensions were made to the existing paste deposition facility and the product yard, including new stockpiles, stackers and reclaimers.

“We also added a second railway balloon and a second rapid load-out station, along with a new railway siding to access the local rail line, and doubled the export arrivals and departure rail line. A new robotics laboratory has also been built,” states Heslinga.

The new RoM crushing plant that DRA designed and engineered for the KEP project consists of a gyratory primary crusher, a scalping station and a cone crusher for secondary crushing.

“Additionally, the plant incorporates an 18 000 t buffer stockpile and a 3-km-long, 3 500 t/h overland conveyor. In order to accommodate the additional throughput, the wall of the existing paste disposal dam was lifted by 5 m,” states Heslinga.

By September 2012, the KEP project had clocked up 12-million fatality-free hours over the entire course of the project, with labour on site peaking at 2 700 during the middle of 2011, he adds.

“The project included three 14-day plant shutdowns, none of which were overrun, while all were completed successfully in terms of scope, quality and safety records,” Heslinga revealed.

“One of the main reasons for DRA’s success with KEP was the excellent cooperation and communications channels between the project team and mine operations, which ensured the process went smoothly and was trouble-free. In addition, the project team maintained close supervision of site contractors to ensure quality of construction work, as well as ensuring that suppliers and contractors were kept on track with the programme milestones,” says Heslinga.

“We are proud of our achievement in terms of safety and quality at KEP and, as a result of our team’s commitment to Assmang, a further EPCM contract for a super fines recovery plant at Khumani has been awarded. This project makes use of Whims to process tailings for the extraction of saleable product and is almost complete, with handover forecast to be two months ahead of scheduled by the end of May,” he says.

“The KEP project also required additional rail infrastructure to handle the increased product throughput and included a new rail load-out station. This allows the mine to load two trains simultaneously,” says Heslinga.

Additional Upgrades

DRA also engineered the extensions to the Parson processing plant used for the beneficiation of 16-million tons a year of iron-ore product, on the mine. The extensions include a new on/off grade stockpile, tertiary crusher unit, washing and screening systems, lumpy and fine jigs, as well as a high-pressure grinding rolls crushing and screening system.

“The plant’s water circuit required an extension of the existing dewatering plant and the addition of a 90 m primary thickener, an 18 m secondary thickener and 4 km of overland tailings pipe. In addition two 20 mℓ potable water tanks were built,” explains Heslinga.
The commissioning of the plant was undertaken by DRA with the assistance of contract operations provider Minopex, he concludes.