Keeping up with the increasing mineral demand – especially those that are critical to the clean energy transition – is a challenge faced by mine operators around the world. Large-scale haul trucks, drill and blast technology and industrial automation are just some of the new technologies being deployed on mine sites to accelerate mining processes. Magnetic resonance (MR) technology, although not necessarily new, is making waves on mine sites for its ability to report grade measurements in real time.

In hard-rock mining, the process of extracting valuable metal components remains largely reliant on crushing, grinding and processing. Although innovations and advancements have improved these procedures, there is a growing need for other approaches that can significantly increase the productivity of mining in the face of intensive energy, water and chemical processes.

It was this challenge that CSIRO’s Mineral Resources scientists decided to tackle, setting out to create technology which could measure the ore concentrations of extracted material in bulk and at speed, enabling the rejection of low concentration matter before undergoing further processing.

Developing the technology

CSIRO’s Research Program Director, Sensing and Sorting, Mineral Resources, Dr David Miljak, said that CSIRO first embarked on developing the Magnetic Resonance (MR) technology in the early 2000s.

“Our first exploratory developments were small laboratory-scale, where sample volumes and sensors were just a few cubic centimetres. Gradually, we developed techniques for scaling the measurement to much larger volumes, now exceeding many cubic metres. Also, solutions for practical deployment were developed.

“As the MR technology is a radio-based method, solutions to avoid pickup of various radio sources in real-world environments must be applied to allow useful detection capability.”

Dr Miljak said that CSIRO has built considerable know-how and capability around various approaches for mitigating the effects of real-world, electrically “noisy” environments and, in parallel, have also had to re-examine the underlying ‘physics’ of the method, to reassess the best way to approach the measurements in very large volumes.

Since then, CSIRO has also completed more fundamental studies. This has led to the discovery of new mineral resonances that can be exploited for measurement in CSIRO-developed MR measurement systems.

“Despite the challenges in the huge engineering scale-up over the years, there were several major technical benefits to establishing the technology for mining applications that drove CSIRO to continue the work over a long period.

“Firstly, the method allows detection through thick layers of rock (sometimes many metres for some rock matrices). This is because the radio frequencies used in MR are relatively low. “Secondly, the method can be configured for a fully quantitative measurement of mineral targets, with relatively simple calibration requirements.

“Thirdly, depending on the mineral target, the method can rapidly detect very low mineral grades, well below typical mine cut-offs. Dr Miljak said that these attributes together provide a unique sensing offering that can be applied to new measurement applications.

Identifying a need in the market

The need for these kinds of technologies comes from longterm mining trends and they have begun to appear in earnest over recent years, with the decline of mined grades spurring an increasing need to find productivity improvements in mining and processing.

“Hand-in-hand with that trend, there is a parallel need to improve sustainability of mining, for example, in terms of water usage, footprint and emissions,” Dr Miljak said.

From quite early on, CSIRO’s target market involved applications that no other sensing technology could easily support.

“These included low level mineralogical phase measurement in processing plants for control purposes, the measurement of material on conveyors for bulk sorting and then later the adaption of the technology for measurement on haul vehicles or on mine benches at the pre-blast stage. Each of these applications benefit strongly from the unique MR measurement capability.

“The later applications are based squarely on the mining side, an area which historically has tended to be more difficult to apply sensing technology, but where the right sensing approach can deliver step change improvements through enabling bulk sorting or selective mining.”

Since the early development of the technology the target market has remained relatively unchanged, but the awareness around pre-concentration strategies like sorting or selective mining has been steadily growing since CSIRO first embarked on the developments.

“CSIRO was certainly aware from the early days around the potential for the technology to make a substantial difference to mining and processing productivity.”

How MR technology sorts ore at speed

“The MR technology developed by CSIRO is based on a ‘cousin’ of the more familiar spectroscopy used in clinical or chemistry applications, such as Magnetic Resonance Imaging (MRI) or Nuclear Magnetic Resonance (NMR),” Dr Miljak said.

In these methods, the subjects or materials are placed in a strong static magnetic field and radio waves are used to manipulate and detect hydrogen or other nuclei.

“The CSIRO technology uses other spectroscopies that are known to occur in solid crystalline materials, but which do not require the application of a static field; only the radio waves are required to detect the targeted material.

“This is an important advantage for real-time measurement, allowing reduction of the size and complexity of the measurement equipment.

“Unlike conventional NMR, the spectroscopies used are very sensitive to the particular mineral phase being targeted, allowing highly discriminating mineral measurement. On the other hand, the spectroscopies used in the CSIRO systems can only be practically applied for a more limited number of nuclei and mineral phases.”

Bringing the technology to market

Once this technology had been developed, it was necessary to commercialise it and take it to the market. This resulted in the creation of NextOre in 2017 – a company where commercial and technical expertise could be combined to guide companies through all the stages of sorting implementation.

According to NextOre CEO, Chris Beal, the technology was developed, and the company ultimately formed, to fill a gap in sensing solutions available to the mining industry.

“Existing sensor systems, the likes of XRF, XRT and PGNAA, have been in use now for decades across the mining industry. These have been very useful and successful, but they weren’t designed for the demands of bulk sorting. CSIRO realised there wasn’t a sensor which could give sufficiently precise, fast and reliable measurements that could be trusted by operators to separate waste and ore on a tonne-by-tonne basis.”

Mr Beal said that reliability is a major problem for traditional sensor technologies, as they often have to be recalibrated, which in turn has a profound effect on how the data can be used.

“If you take a measurement, but you don’t trust what it says until you go check it against a known quantity, then you simply can’t use that machine for real-time control. It’s certainly still a useful tool, but it doesn’t suit real-time applications. “Similarly, sampling bias is a real problem for point-type measurements. Some technologies only measure a small patch on the very top surface of ore, the very first few microns. With these, you often struggle to know whether that measurement is really properly representative; maybe it’s been raining and there was mud covering the rock. These types of variables can have huge consequences if they introduce bias.

“NextOre’s sensors resolve these reliability issues, MR does not need to be recalibrated and measures the entirety of what flows through it on a conveyor belt. It also retains these qualities and excels for very large throughput applications at the biggest mines, where most of the world’s metals are produced.”

From then to now: how the tech has changed

“The core MR technology we licensed from CSIRO is very solid, so our focus since NextOre began has been making these solutions practical and usable,” Mr Beal said.

“Mining projects are carefully balanced systems operated by hundreds or thousands of people who all rely on consistency. While the concept of keeping good material and rejecting bad in theory is fairly obvious, it can represent a significant change from operation as usual.

“Adding 10-20 per cent annually of metal production or, say, eliminating 30 per cent of waste dilution from the processing plant has significant effects across the operation.”

“There’s a rule of thumb in processing that each tonne of rock processed will require a cubic metre of water to be added during the processing stage. So a moderate-sized mining operation processing ten million tonnes per year is going to need ten million cubic metres of water, or ten billion litres.”

Mr Beal said that if 30 per cent of feed as waste is able to be cut out, and still deliver nominally the same copper product, water consumption has been reduced by three billion litres. This is the same for tailings production.

“Any removal of waste from the processing stream is a direct reduction in the amount of tailings produced, and at rates of 4.5 to 6.3 billion tonnes of tailings production per year (2013 figure) that’s a big impact as well. Likewise for reagent consumption, electricity, and fuel. There are potentially vast improvements across the board in terms of environmental benefits, and improvements that are sorely needed.”

Moreover, miners are aware that the cost of making even minor changes can be large, and the consequences of  incorrectly implementing new technology can be severe.

Mr Beal said that incorporating results into the complex feasibility and planning processes for setting up mining operations was a necessity to get it right. What this meant was demonstrations at full scale, fast installations, straightforward use and with minimal disruptions to the main production of the mine.

Two examples of outputs from this effort are the mobile bulk sorting plant and the truck analyser.

Mobile bulk sorting plant (MBSP)

“The mobile bulk sorting plant was developed to deliver mine-scale (400t per hour of feed) bulk sorting results quickly and cost-effectively. This can either be relied upon for feasibility work to justify larger scale implementation or used to solve an urgent problem for the mine.”

Mr Beal said that some common problems the MBSP has been used to solve are providing extra feed material to a processing plant from a mineralised waste stockpile or pulling high-grade rock out of geologically complex, low-grade ores.

The mobile bulk sorter offers a solution for one of bulk ore sorting’s biggest problems – lab testing. Using flotation as an example, to run a flotation test program the process involves sending ore samples weighing a few kilograms each to a lab. The lab will run tests and control for variables like chemistry and grind size before supplying the results. Despite the challenges in sampling and representativity, Mr Beal said you can depend on the results and be confident they will scale.

“With bulk sorting, we rely on the preservation of in-situ heterogeneity. The results of bulk sorting will change depending on how you handle the material, and they’ll change a lot based on the scale that you perform a test. For this reason, a test done outside of the full-scale production environment is unreliable.

“You essentially have to run bulk sorting at full scale to know what the results will be. It’s a chicken and egg problem.

“The solution is pretty obvious – you make a mobile version of the system that can be rented and easily deployed.”

Mr Beal said the reason it hasn’t been done before can be attributed to the strength of MR as a technology, and the real difference the mobile bulk analyser’s speed makes.

NextOre’s mobile bulk sorting analyser can measure the grade of material in less than ten second intervals, with some others on the market taking as long as two minutes.

“The length of the measurement interval dictates the length of the conveyor you need. All else equal, what MR can do with a 10m conveyor belt, other technologies may need a 300m convey belt to do. That’s not possible in a mobile solution,” Mr Beal said.

Truck analyser system

“We’ve also worked with CSIRO to develop the truck analyser system. This is something that miners have been making very clear that they want since before NextOre was formed.

“Having a reliable measurement solution for trucks gives miners the ability to improve mining recoveries and eliminate inefficiencies in real-time. It is also a very flexible solution that miners can use in ways that suit their operations.”

He said that there are a couple big benefits to measuring ore while it’s still in a truck – heterogeneity being one of them.

“In bulk sorting we rely on material being mixed as little as possible. The less ore is handled, the less it is mixed and the more benefit there is from bulk sorting, so we benefit from being “closer to the face” of the mining operation.

“The other benefit is that you’re catching misassignments earlier in the process. This can mean that you catch good ore which would otherwise have ended up on the waste dump, or vice versa, without first having to put it through a crusher and get it on a conveyor.

“The trade-off is that you’re making decisions at a ‘resolution’ of tens or hundreds of tonnes, whereas bulk sorting on a conveyor can be done at a resolution of individual tonnes or even less,” Mr Beal said.

The ripple effect in the industry

Mr Beal said a lot of mining companies are looking to use this high-quality data as a fundamental part of the mining strategy for developing new mines.

“Miners, by nature, are working on projects that will extend out decades into the future, and they want to make sure they are applying technologies from the start that will give them the best value.

“But we’re also seeing the technology used at existing and aging mining operations to make sure that no good material is being left behind. Our technology is often seen as a way of extending a mine life.”

The impact the technology is making to the industry was demonstrated in December 2022, when NextOre was awarded Mining Technology Company of the Year for excellence in innovation at the global Mines and Money Connect conference.

Mr Beal said the award further underscored the fact that industry participants see bulk sorting’s potential for improving the environmental impacts and fundamental economics of mines across the world.

“The judging panel for Mines and Money awards were a collection of roughly two dozen senior executives from mining organisations, investment funds, consultants and advisory panels to the mining industry.

“They’re professionals tasked with looking into the future and addressing the significant barriers that our industry faces, and their focus is on technologies that provide a step change in performance, not just tweaking the margins.

“The founders of NextOre started with just that vision and the way we seek to apply sensing and bulk sorting has very lofty ambitions. Knowing that the industry sees that vision as achievable as well will continue to push us further.”

Focusing on the future

Progressing the technology to encompass even more applications is on the agenda, with NextOre looking forward to showing off the 200t truck analyser system which is due to be commissioned in the middle of 2023.

“Our main focus for the past five years has been very much on-conveyor sorting for copper sulphides. Now that we’ve done that successfully and can show these units operating at full scale, you can expect to see this expanding further and becoming more widely adopted by those larger and more risk-averse companies,” Mr Beal said.

“You should also expect to see our truck analysers popping up at surface operations and underground. While we’ve really had our hands full to date with copper miners, you can also expect to see us expanding further into iron ore and gold commodities.”

With this MR technology, the long and tedious process of ore sorting is becoming a thing of the past and as this technology continues to innovate and expand its reach across the industry, mining corporations can expect to see new applications which will help to accelerate other mining processes on-site.

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