Copper Shortages and Sustainability Goals: is Ore Sorting the Solution?

Written by Ellen Thomson, PGNAA & Minerals Senior Applications Specialist, Thermo Fisher Scientific 

COP26, net zero targets and an accelerating shift towards greater sustainability all have profound implications for the mining industry across the globe. The ongoing transition to green energy is anticipated to significantly increase the demand for copper because of its many uses in expanding electricity networks and cleaner technologies, such as electric vehicles. This article will take a closer look at approaches to ore sorting, a pre-concentration process that has long-term potential for efficiently processing lower grade copper ore bodies, and how it helps the mining industry to keep pace with the shift towards more eco-friendly transportation and energy sources.

It has been predicted that there will be a worldwide copper shortfall of 15 million tonnes per annum by 2034, and so major and sustained increases in mine output will be required to meet the growing demand in the coming years. (1) Canada was once the world’s third-largest miner of copper but, over the last few years, it has slid down the rankings to number 11. While copper is still widespread in Canada, the areas where it is concentrated enough to be mined profitably are very limited, with British Columbia alone producing over half of the country’s total output. In 2020, Canadian mines produced 475,898 tonnes of copper in concentrate, a 12 per cent decrease from 2019, which is largely attributable to declining mine productivity and the complications of the COVID-19 pandemic. (2) On top of this, social licenses and the government’s strict environmental policies make it very difficult for new mines to be brought online. 

Optimizing the efficiency of Canadian mining operations has therefore never been more important. 

Ore sorting can greatly benefit copper mines, by reducing variability and delivering more value to the concentrator on an hourly basis. Some deposits are extremely heterogeneous in grade distribution and composition, so many concentrators face a highly variable feedstock. This means that material above the cut-off grade may routinely be sent to waste, or on the other end of the spectrum, the feed stockpile can drift below the specified cut-off grade. Ore sorting separates out gangue and low-grade ore at the earliest opportunity, helping to preconcentrate the process plant feed and optimize downstream processing. This produces higher, more stable head feed grades and improves the efficiency of the concentrator. Given that Canada exports over CA$7.3 billion of copper every year, the case for ore sorting is compelling, and is becoming ever more urgent. (2)

However, ore sorting technology is far from a one-size-fits-all approach, and numerous factors need to be considered when tailoring sorting solutions to each mine’s particular needs and orebody. For example, mineralogy and the presence of different elements can influence the effectiveness of different technologies. Ore sorting depends heavily on sensors which differentiate ore through either particle or bulk analysis. In either case, a strong sensor technology will offer good sensitivity around the cut-off grade and will reliably and accurately differentiate the material that you want to process at an acceptable speed. 

Particle sorting technologies separate rock particles based on properties such as colour, density, magnetism, transparency, and conductivity.  It then separates the particles by high pressure air jets, maximizing ore recovery. However, it is important to consider that sensor-based particle sorting is affected by ore heterogeneity, differential sensor response and preparation of the feed.

Bulk analysis methods look at the composition of larger samples of the incoming ore, continuously scanning across a moving conveyor belt using Prompt Gamma Neutron Activation Analysis (PGNAA) or Pulsed Fast Thermal Neutral Activation (PFTNA). PGNAA and PFTNA analyzers penetrate the entire incoming ore stream, ensuring that all the material is analyzed equally and accurately. Unlike methods like X-ray fluorescence, which only scan surface composition and are sensitive to the presence of dust, this approach provides a more representative analysis of the whole stream. Bulk ore sorting is reliant on high spec analytical technology that can rapidly differentiate material that is at or below cut-off grade, minimizing the loss of valuable material sent to waste while directing only economically viable ore downstream. Driven by this need, PGNAA and PFTNA techniques are now able to provide measurements at time increments of just 30 seconds, offering real-time feedback to miners in the field.

Bulk and particle sorting approaches are not mutually exclusive and combining multiple analytical methods can also be a good option, for example using bulk analysis for primary sorting, and following up with particle sorting for a final quality check. This helps to circumvent throughput limitations caused by particle sorting, while at the same time minimizing the amount of valuable mineral mistakenly sent to waste. 

In the long run, ore sorting has the potential to extend mine life, prolonging economic operation despite declining ore grade. For a new mine, it can reduce the size of the processing plant required, which improves the investment case and project acceptability. The process also has some major advantages for sustainability initiatives, as it drives down energy consumption per tonne of concentrate produced, by reducing the grinding of waste material. It also lowers the consumption of water and reagents in the flotation circuit and decreases the quantities of fines that end up in the tailings by extracting waste early, another important environmental gain. In Canada, and elsewhere in the world, ore sorting during copper mining could ultimately contribute significantly to net zero carbon targets, and holds great promise for increasing copper output, speeding the nation’s move towards electric vehicles and a greener future. 

Additional information on implementing optimal sampling and analysis solutions for mining can be found at thermofisher.com/copper.

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References

1. O Da Silva. Rio Tinto Copper CEO: Copper Market to See Deficit by 2020s. Accessed 18th May 2022: https://investingnews.com/daily/resource-investing/base-metals-investing/copper-investing/rio-tinto-ceo-copper-market-deficit/
2. Copper facts. Government of Canada. Accessed 18th May 2022: https://www.nrcan.gc.ca/our-natural-resources/minerals-mining/minerals-metals-facts/copper-facts/20506