TECHNOLOGY •
REVOLUTIONISING ORE PROCESSING
THROUGH SENSOR SORTING
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 .
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
Pexels | Curioso Photography 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 .
www . africanmining . co . za African Mining Publication African Mining African Mining • April 2024 • 21