Spotlight on ore sorting and dense media separation
By Lucy Hunt, Saskatchewan Research Council
As ore grades decline and mineralization becomes more complex, many operations must process larger volumes of material to recover the same amount of value. At the same time, increasing material volumes place greater demands on energy use, water management, and tailings handling. These pressures are driving interest in technologies that reduce the amount of material entering downstream processing.
One approach receiving renewed attention is preconcentration. A well-established method in minerals processing, preconcentration removes waste earlier in the processing sequence, reducing the volume of material entering more energy- and cost-intensive stages such as milling and tailings treatment.
In many cases, the primary goal of preconcentration is to reduce the material volume reporting to downstream processing, while additional benefits may include upgrading ore prior to final recovery, reducing the amount of material requiring finer crushing or milling, lowering water use, and creating additional value streams from rejected material.
At the Saskatchewan Research Council (SRC), a staged testing approach to preconcentration is used, ranging from bench-scale studies through to industrial-scale testing. This allows a range of preconcentration technologies to be evaluated as part of a broader flowsheet.
Understanding how the ore behaves through characterization is therefore critical to determining whether preconcentration is suitable, and if so, which technologies can be applied effectively.
Understanding distribution and liberation
Preconcentration technologies separate particles containing valuable minerals from lower-value or waste material, rather than extracting individual elements directly. Understanding how minerals are distributed within the ore is therefore a critical first step.
In some cases, minerals are concentrated within distinct particles, making separation at coarse sizes relatively straightforward. In others, they are finely and uniformly disseminated throughout the rock, making early-stage separation more challenging and limiting its effectiveness.
Preconcentration is most effective when the valuable mineral is unevenly distributed, a measurable contrast exists between ore and waste, and contrast can be detected at a coarse particle size.
From ore characteristics to technology selection
Understanding how minerals are distributed and whether meaningful differences in their properties exist provides the basis for selecting an appropriate preconcentration method.
Two commonly applied approaches are sensor-based sorting and dense media separation (DMS), which address similar challenges in different ways. Sorting offers higher selectivity at the particle level, typically at coarser particle sizes, while DMS can be applied at finer particle sizes as a high-throughput bulk-separation method.
Sensor-based sorting uses technologies such as X-ray transmission (XRT), laser and optical sensors to measure individual particles and separate them in real time based on their properties. DMS relies on differences in particle density to separate ore from waste as a bulk process.
Factors such as mineral distribution, particle size, water availability, process complexity, and operational constraints influence which technology is most suitable. In some cases, one technology may be clearly suited to the application. In others, a combination of approaches may provide the most effective solution.
From theory to application
Evaluating preconcentration requires moving from theoretical potential to practical performance. Testing begins by identifying whether measurable physical or mineralogical differences exist that can be targeted by a given technology, followed by controlled separation under ideal conditions. The final stage assesses performance at higher, more representative throughputs, where mechanical and operational factors begin to influence separation efficiency.
SRC provides production-scale XRT and laser sorting test work, along with a five-tonne-per-hour rated DMS plant and heavy liquid separation facilities, enabling evaluation at all scales. Combined with mineralogical characterization, this staged approach allows preconcentration strategies to be refined and adapted to specific ore types before full-scale implementation.
As an independent testing facility, SRC can assess both emerging and established technologies without bias, ensuring that the most appropriate solution is identified for each application. In an environment where uncertainty carries real cost, understanding whether and how preconcentration can be applied early can make a meaningful difference in both technical performance and project outcomes.
Read the full article at src.sk.ca/blog.
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