X-ray transmission (XRT) sorting has become the preferred recovery technology option in several parts of diamond-mining across Africa. This, according to research, is due to its high selectivity using atomic number as the main discriminating material property. This is also supported by major advances in the underlying enabling technologies. The latter is inclusive of increased computational speeds, improved algorithm design as well as advances in camera and X-ray source technology.
Over the past decade, there have been major advancements in the alluvial diamond mining industry, with particular growth and development in X-Ray Transmission (XRT) technology. Unlike near-infrared (NIR) and X-ray luminescence (XRL), XRT is not dependent on a visible colour difference or clean, reflective particle surfaces. XRT has a significantly higher detection rate for Type II diamonds compared to traditional XRL sorters that have an order-of-magnitude lower concentrate yield percentage. XRT technology provides a single-stage alternative to traditional recovery techniques used in the diamond mining industry.
Imilingo Mineral Processing, who specialize in the integration of sensor-based sorting technology and dredging, has made massive inroads into Africa’s alluvial diamond mining sector. Imilingo showcased their modular iPlant products as well as their iDredge and launched their latest innovation the iDredgeXRT, a world first in alluvial diamond mining at the show. According to media reports, the iDredge has been in operation since May 2018 and is currently producing great success and prospects for Africa Resources in the DRC. Meanwhile, the iDredgeXRT commissioned by Mon the Real LDA in Angola is currently in the final design stages before fabrication which is expected to start early this year.
In a press statement from Imilingo, the iDredgeXRT will consist of a dredge housing two TOMRAXRT sorting machines, a submersible pump with excavators, a clamshell, a sizing screen and two diesel-electric generators to power the system.
The iDredgeXRT combines dredging with sensor-based sorting. This, according to MD Jack Prinsloo, will be instrumental in changing the alluvial mining game in Africa and will help unlock its diamond wealth.
Imilingo designs and builds bespoke systems supporting XRT technology integration into mining operations such as the fully equipped iPlant, iSamplePlant and iDredgeXRT. The XRT sorting machine forms the heart of their systems. Furthermore, Imilingo develops and builds all technologies supporting the sorting machine to ensure proper and efficient operation of the machines and maximal productivity and profitability of the mining operation. “Ultimately, results continually confirm the major advantages that XRT technology bring to a mining operation,” comments Prinsloo.
Some of the projects undertaken thus far include 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.
Mr. Prinsloo explains that the opportunity to combine various processing steps into one single step with the use of an XRT sorting machine in order to achieve a hand sortable product has revolutionized diamond processing efficiency.
Advantages of XRT technology
The benefits of using XRT technology are numerous, for one XRT technology has a smaller overall footprint and the technology delivers a significantly lower percentage yield than traditional dense media separation (DMS) plants, which allows for vastly reduced running costs relating to consumables and utilities.
“The fact that many process-steps in a typical diamond recovery flow sheet are replaced by one sorting machine results in much greater productivity by reducing the losses encountered with each additional step,” states Prinsloo. He adds that “process flows are simplified dramatically and XRT sorting has in many cases been responsible for transforming borderline viable projects into profitable ones.
In a process like tungsten mining, for example, XRT technology sorts the waste material out earlier in the process, which results in the material being upgraded very efficiently. Thus, the grade of material fed to the wet circuit is much higher- which maximises cost efficiency during this expensive process.” Another advantage Prinsloo notes, is that “the process is digitised, resulting in a greater requirement for Electrical Controls and Instrumentation (EC&I) skills, which would previously have been done by mechanical resources operating a DMS etc.” During processing operations, XRT technology is also particularly effective in preventing the breakage of large diamonds by recovering the diamonds before they are crushed in a next process step.
According to Prinsloo, there are various very successful XRT sorting machines running across the globe, which suggests that the technology has been well adopted within the industry. “Having said this, there is constant Research and Development taking place to improve efficiencies and cement the place of XRT sorting in the market,” he notes.
The use of bulk XRT sorting machines is easily the greatest advancement within XRT technology. Prinsloo adds that “previous technologies, such as XRL have lower throughput and would normally need DMS as a first process step to pre-concentrate the material before final sorting, whilst XRT eliminates the need for pre-processing resulting in greater overall process efficiency.”
Overall, with further development and advancement of XRT bulk sorting machines, the sustainability of alluvial diamond mining will be positively affected across the globe.