Imilingo Mineral Processing has made massive inroads into Africa’s alluvial diamond mining sector thanks to its unique dredging and sorting technology.
Its latest technological innovation, the iDredgeXRT – which combines dredging with sensor-based sorting – will be instrumental in changing the alluvial mining game in Africa and will help unlock its diamond wealth, MD Jaco Prinsloo tells Chantelle Kotze.
This article first appeared in Mining Review Africa Issue 11 2018.
No stranger to diamonds or minerals processing, Prinsloo, a mechanical engineer by profession, has gained extensive knowledge in diamond processing while working as lead engineer for DRA Global on several large diamond mining projects.
These projects included the incorporation of an X-Ray transmission (XRT) circuit into the processing plant at Lucara Diamond Corp.’s Karowe diamond mine in Botswana and the design of an XRT diamond sorting machine and recovery area for Stornoway’s Renard diamond mine in Quebec, Canada.
Understanding the breakthrough that XRT sorting brings to the diamond mining industry, and as a result of the surge in the application of sensor based sorting, Prinsloo joined Imilingo in 2015 as general manager.
In 2017 he acquired a 50% shareholding in the company and was appointed MD. He joined Imilingo with a clear goal in mind – to develop new technologies, not only to improve the efficiency of mining operations, but also to help solve complex problems in the mining sector.
With a concept in hand, the Imilingo team spent time in the Democratic Republic of Congo (DRC) and Angola understanding how the company’s dredging and sorting technology could be implemented to improve the conventional mining method using barges equipped with centrifugal pumps and suction hoses guided by underwater divers to transfer the recovered material to surface, which is then sorted by hand.
While in the DRC, Imilingo was enlisted by privately-owned Swedish company Africa Resources AB to provide a solution for the profitable recovery of greater volumes of alluvial diamonds from its 674 concession along the Tshikapa River in the south eastern part of the country.
Following a site visit in late 2016 to assess the needs and requirements of Africa Resources AB, Imilingo set out to design a fit-for-purpose vessel at its head offices and manufacturing facility in Centurion, South Africa.
It was for this project that the company conceptualised, designed and fabricated the iDredge – a 6 x 6 m modular dredging unit.
The iDredge consists of a 60 kW Dragflow submersible pump and high depth pressure compensators housed within a pontoon structure. The electrically-driven pump, supplied by Tsurumi Pumps Africa, is designed to accommodate 200 m3/h of gravel, and can operate at depths of up to 50 m pumping particle sizes of between 0 and 60 mm through a 150 NB pipe.
The pump is suspended from a rotatable crane structure, which also functions as the lifting equipment for maintenance tasks, while an on-board control panel enables the operator to determine the position and movement of the iDredge.
A 150 kVA diesel generator supplies power to the iDredge and the mined material is fed onto a double-deck vibrating screen – both of which remain on the riverbank.
While the diamond-bearing gravel is currently being hand sorted at the Africa Resources AB site, Prinsloo explains that the iDredge can be complemented with Imilingo’s modular sorting plant – the iPlant – for a complete onsite mining and sorting solution.
The iDredge has been in operation in the DRC since May 2018.
Combining dredging and sensorbased sorting into a single solution
Imilingo’s innovation did not end with the development of its iDredge.
By consulting with Angolanowned MONTHE REAL LDA – a business incorporated by three Angolan entrepreneurs with oil & gas and logistics experience – and having the first mining venture to be funded by Banco de Comercio e Industria through the “Angola Investe” programme, Imilingo has taken its iDredge technology to new heights by incorporating XRT sorting on board a larger, more refined version of the iDredge – to form a single step mining and sorting solution.
The company’s iDredgeXRT, a world first in alluvial diamond mining, consists of a larger 20 x 20 m dredging unit, a 200 m3/h submersible pump with excavators, a clamshell, a sizing screen fitted with two TOMRA XRT sorting machines and two diesel-electric generators to power the system.
The dredge also includes 3D sonar scanner technology for viewing the pumping operations and a GPS to track the locations where mining has been done. The iDredgeXRT works by pumping diamond-bearing gravel from depths of up to 80 m onto a sizing screen which then sizes the material into three different size fractions (3-9 mm, 9-20 mm and 20-50 mm).
The 3-9 mm material reports to the first XRT sorting unit while the other two size fractions report to the second XRT sorting unit.
The tailings material from the sorters report to two sumps located beneath the dredge where the material is collected for deposition. The level of water and gravel in these pumps also act as a level control for the dredging unit, explains Prinsloo.
Meanwhile, a clamshell is used to scoop up any large rocks that may be encountered. These are discharged onto a controlled tailings barge positioned next to the iDredgeXRT.
The tailings barge is also used to deposit the tailings about 500 m away back onto the river bed by means of a discharge pipe.
"Imilingo is still underway with the detailed design of the iDredgeXRT while MONTHE REAL finalises its funding.
Once complete, the fabrication of the unit will begin,” says Prinsloo, adding that once manufactured, the unit will be tested in South Africa and then transported to site (Angola) in modular units.
An alternative minerals processing method
“The fact that only one processing step is required when using the iDredgeXRT makes this solution a huge win in terms of process efficiency,” says Prinsloo, explaining that there is no need to further process a sorter’s concentrate before final hand sorting.
Moreover, diamond recovery by means of XRT sorting replaces the conventional concentration and recovery stages such as dense media separation (DMS) for the size fractions above 3 mm in a diamond recovery process.
The use of XRT technology also ensures a compact footprint, lower operating costs, high diamond recovery rates and extremely low concentrate yields.
The iDredgeXRT is proof that Imilingo is driven to fundamentally change alluvial diamond mining for the better.
“We believe we are able to capture the opportunities within the mining industry to innovate and execute cutting-edge technology.
"We are excited about the prospects of this latest innovation in drastically changing the way alluvial mining is executed. Any opportunity to actively contribute to the sustainable transformation of the mining industry is a massive driving force for us,” concludes Prinsloo.