A joint venture between mining and mineral processing engineering specialist IMS Engineering and German separation technology company Steinert has borne fruit with the introduction of Steinert’s X-ray transmission (XRT) sorters in use in the diamond mining industry.
Two of the sorters have been used at a leading South African diamond mine famous for its large, top-quality diamonds, as part of the final recovery plant. These are among the first XRT sorters to be used in final recovery at diamond mines in the country.
According to IMS Engineering MD Paul Bracher, supply to and development of sensor sorting technology in the mining, industrial minerals and recycling industries, such as Steinert’s XRT technology, have developed rapidly over the past year or so.
“The development of unique sorting algorithms that allow for extremely high accuracy in the detection and ejection of diamonds has created significant opportunities for new and cost-effective ways to separate minerals from waste,” he says.
Bracher states that IMS has proved to the client through tests that the XRT system can detect diamonds.
“It was as a result of this testwork that we could provide our process guarantees. We tested both simulants and diamonds provided by the client. The goal was to achieve 100% recovery during testwork and we are proud to report that this was in fact achieved,” says Bracher.
Testing has also allowed the company to hone and further develop the algorithms detecting and ejecting diamonds, as well as simultaneously optimising hardware. Along with the optimisation, Bracher notes that the application of the equipment at the South African diamond mine’s plant required a redesign in accordance with the client’s footprint.
“The result was that we were able to customise the sorter to fit the required footprint, while retaining the maintainability through [the use of] standard components.”
“We have improved all areas of performance, including detection and ejection into a secure area, all while obtaining the lowest possible yield to increase the diamond by weight ejected,” says Bracher.
The installation of the diamond sorters has led to the recovery of a 52 ct GNT Type 2 diamond. It was recovered unbroken by the coarse sorter.
Bracher notes that the XRT sorter remains important in diamond recovery technology, as its main advantage remains that the ion detects different X-ray absorption levels of different material types. The resulting X-ray images relate to the atomic make-up of each particle going through the XRT detection zone of the machine.
The particles attenuate the transmitted X-rays that are detected and recorded. The signals are processed through an advanced algorithm that enables the program to differentiate between the less-dense carbon of diamonds and the denser minerals of kimberlite and other waste rock.
“Sensor-based sorting has brought about significant innovation in mineral processing technology and upfront beneficiation and that its time has come in South Africa has certainly become a reality.”