By Dr Nicolaas C Steenkamp
In the relentless pursuit of efficiency and sustainability, the mining industry has been continuously innovating to enhance ore processing techniques.
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Due to the depletion of high-grade and near surface deposits, a need arose to develop technologies to enable the processing of lower grade or near cut-off grade ore. Other motivating factors driving this trend are environmental considerations to reduce waste, both in the generation of tailings and rock dump waste and to reduce the amount of power utilised to process waste and gangue.
Among these advancements is sensor sorting which has emerged as a game-changer, revolutionising the way ores are separated and processed. Sensor sorting is showing promise to deliver a solution for the reduction of waste processing, higher ore throughputs and optimising power utilisation. The four key technologies: X-Ray Fluorescence (XRF), X-Ray Transmission (XRT), optical sorting and laser sorting are the systems being deployed to mining operations. Each method brings unique advantages to the table, allowing mining operations to optimise their mineral extraction processes and unlock unprecedented value.
X-ray Fluorescence (XRF)
XRF is a non-destructive analytical technique that provides invaluable insights into the elemental composition of ores. In sensor sorting, XRF technology is utilised to detect and measure the concentration of valuable minerals, such as copper, gold and iron, as well as deleterious elements, like arsenic and mercury.
The process involves exposing ore particles to high-energy X-rays, which cause the atoms in the sample to emit characteristic fluorescent X-rays. By measuring the energy and intensity of these emissions, XRF analysers can determine the abundance of target elements in real-time.
One of the major benefits of XRF sorting is its rapid analysis capability, allowing for high throughput and efficient sorting of bulk materials. This results in reduced energy and water consumption during downstream processing and lowers the overall environmental impact of mining operations.
X-Ray Transmission (XRT)
XRT is another X-ray-based sensor sorting technology, but it operates on a different principle than XRF. Instead of measuring the emitted X-rays, XRT sensors analyse the attenuation of X-rays passing through the ore particles. This technique is particularly effective in identifying and separating materials with different densities.
In XRT-based sorting systems, high-resolution X-ray cameras capture images of the ore particles as they pass through the conveyor belt. The resulting images are then processed using advanced algorithms to differentiate between high-density and low-density materials, enabling efficient separation.
The capability of XRT to identify and eliminate gangue materials early in the ore processing stream helps increase overall plant productivity and decreases the need for costly downstream processing steps.
Optical sorting
Optical sorting is a sensor-based method that relies on the analysis of colour, brightness and shape characteristics of ore particles. It is a versatile technology capable of sorting a wide range of materials, from industrial minerals to gemstones.
This method involves illuminating the ore particles with light of various wavelengths and capturing images of the particles using high-speed cameras. The acquired images are then processed by sophisticated software that classifies the particles based on predefined criteria.
Optical sorting excels in separating ores with complex mineralogy, where XRF or XRT methods might face limitations. It can accurately detect and sort particles with subtle differences in colour or luminescence, resulting in higher recovery rates and better quality of the final product.
Laser sorting
Laser sorting is an emerging technology that takes advantage of laser-induced breakdown spectroscopy (LIBS). This method involves focusing a high-energy laser beam onto the ore surface, causing it to vapourise and emit plasma. The emitted light is then analysed to identify the elemental composition of the material.
The key advantage of laser sorting lies in its ability to perform real-time, in-line elemental analysis without the need for sample preparation. It is particularly effective in sorting complex ores containing a wide range of elements and compounds.
Leveraging sensor sorting in mining operations
Each of these sensor sorting technologies offers unique benefits to mining operations and their successful integration can lead to substantial improvements in efficiency, productivity and sustainability.
Combining XRF and XRT sorting can yield superior results as the processes complement other’s strengths. XRF is excellent at identifying and quantifying major and trace elements, while XRT can efficiently separate materials based on density, effectively removing barren gangue early in the process.
The integration of optical and laser sorting technologies can be advantageous in dealing with complex ores. Optical sorting excels in recognising visual properties, while laser sorting provides detailed elemental information, creating a comprehensive and reliable sorting system.
Sensing the way forward
Sensor sorting of ores using XRF, XRT, optical and laser methods has ushered in a new era of efficiency and sustainability in the mining industry. These cutting-edge technologies enable real-time, automated ore separation, leading to reduced energy consumption, minimised waste generation and increased overall profitability.
As mining companies continue to invest in sensor sorting technologies, the mineral processing sector can expect even more advanced and integrated systems that further optimise the ore processing chain, ultimately benefiting both the industry and the environment. Through these innovations, mining operations are poised to extract maximum value from their resources while moving towards meeting their environmental goals.
 Dr Nicolaas Steenkamp |
Dr Nicolaas C Steenkamp is an independent consultant, specialising in geological, geotechnical and geometallurgical projects and mining project management. He has over two decades of industry experience with global exposure. (ncs.contract@gmail.com) |