Tag Archives: Comminution

NioCorp working with Weir Minerals, NRRI on Elk Creek HPGR test work

NioCorp Developments Ltd is to initiate testing of Elk Creek project ore using high pressure grinding rolls (HPGR) technology from Weir Minerals.

HPGR technology is considered an energy efficient and low-emission alternative to conventional processing for reducing the size of the ore to enable the recovery of niobium, scandium, titanium, and potential rare earth products, NioCorp said.

The use of this technology in the project reinforces the company’s commitment to the environment and designing a sustainable operation, it added.

The testing is being conducted at the Natural Resources Research Institute (NRRI) of the University of Minnesota-Duluth, in partnership with Weir Minerals. During the testing, which is expected to take several weeks, around 3 t of Elk Creek drill core will be reduced to the 1-mm size needed for hydrometallurgical test work.

Working with Weir Minerals, NRRI acquired an industrial-scale Enduron® HPGR to carry out testing on a variety of ores with this process back in 2020. This is the only large scale HPGR dedicated to research in the US, NRRI claims.

“The network is expected to provide key data that will be used to properly size the HPGR unit for the potential ore throughput at the Elk Creek project, once project financing is secured and the project is operational,” NioCorp said.

The company is currently evaluating the next steps in its overall metallurgical test work program, which will focus on optimising and streamlining the existing processing flowsheet as well as establishing process routes for the potential recovery of rare earth products. The rare earth products that are of most interest to the company are, at present, neodymium-praseodymium (NdPr) oxide, terbium oxide and dysprosium oxide. As previously announced, the company has launched a review of the economic potential of expanding its currently planned product suite from the project to also include rare earth products.

An April 2019 feasibility study on Elk Creek, in Nebraska, USA, estimated average production of 7,220 t/y of ferroniobium, 95 t/y tpa of scandium trioxide and 11,642 t/y of titanium dioxide over the 36-year mine life.

Scott Honan, NioCorp COO, said: “After witnessing testing at NRRI, I was impressed with how the HPGR was able to handle the Elk Creek ore quickly and efficiently, with minimal noise and dust.

“We look forward to completing this phase of the test work and moving on to look at further improvements to the existing flowsheet, including our new emphasis around the rare earths.”

Metso Outotec ball mills, Vertimills heading to Mapa’s Liberia and Burkina Faso gold mines

The Turkish conglomerate, Mapa Group, has awarded Metso Outotec a contract for the delivery of key grinding technology to its gold mine expansion projects in Liberia and Burkina Faso.

The value of the order is approximately €19 million ($23 million), and it has been booked in the company’s Minerals June quarter orders received.

Mapa is a major conglomerate working in various industrial and construction sectors, including mining.

Mustafa Bülent Karaarslan, COO of the Mapa Group, said: “For us, good support, reliable project execution, and sustainable equipment and process performance are essential. Alongside the existing good relationship between the companies, they’re the reasons why we selected Metso Outotec for these projects.”

Metso Outotec will deliver identical grinding lines to both sites, consisting of state-of-the-art Premier™ ball mills (one pictured) and energy-efficient Vertimill® VTM-3000 stirred mills, each line featuring a capacity of 400 t/h. The deliveries are expected to take place in January 2022.

Mert Katkay, Head of Minerals Sales for Metso Outotec in the Middle East and Turkey, said: “We are excited that Mapa has chosen us to deliver the key equipment for the expansion of these two projects in Liberia and Burkina Faso. Previously, we have delivered the key crushing, screening and grinding equipment to these two mines.”

TruckMetrics and the true costs of lost crusher production

The importance of optimising blast parameters to reduce the cost of comminution and cut back on energy use is often stressed across the industry, but effective blasting can also reduce the likelihood of crusher obstructions, Motion Metrics says.

Most unplanned plant downtime is crusher-related and primarily due to blockages caused by oversized feed. These events can cause mines to incur significant financial losses due to unplanned downtime, a decrease in throughput, or an increase in energy use, according to the company.

When boulders are larger than the opening of the primary jaw crusher, they can build up in – and eventually block or obstruct – the crusher. In this case, production must be temporarily stopped to break down or remove the boulder. But even boulders small enough to be processed by the primary jaw crusher can cause problems as breaking down large rocks requires a great deal of energy and can result in power spikes, slower production rates, and wear and tear of the crusher liner, Motion Metrics says.

Even brief crusher delays can have massive effects over time.

“For example, one of our customers is a large copper mine in Kazakhstan that experienced average crusher delays of approximately seven minutes per incident,” the company said. “Although these delays were short, they add up to an estimated total cost of $650,000 in lost production each year.”

Another Motion Metrics customer, a Peruvian mine that is one of the largest copper producers in the world, experiences an average loss of $5.73 million/y, Motion Metrics says, while, at an iron ore mine in Brazil, production interruptions cost roughly $3.65 million/y.

“Mines have traditionally taken a reactive approach to mitigating the problems associated with oversized material,” Motion Metrics says. “A boulder obstruction is typically identified by monitoring trends in crusher throughput – a falling trend indicates that material is not able to pass through the crusher. At this point, the blockage or obstruction has already occurred. Mine personnel must halt production to dig out the boulders, or use rock breakers to clear the obstruction, creating a bottleneck and further decreasing production.”

Motion Metrics says a common misconception is that a grizzly can eliminate the problem of oversized material.

“It is true that, with a grizzly in place, boulders are less likely to enter the primary crusher, however, a grizzly is still susceptible to blockages – mine personnel need to remove oversized material or schedule rock breaking,” it explained.

The best way to manage oversized material is to avoid the situation entirely but, failing that, mines should aim to mitigate problems caused by boulders as early in the process as possible.

Motion Metrics developed TruckMetrics to prevent oversized material from reaching the processing plant in the first place.

Mounted on a gantry above the mine road, TruckMetrics monitors each passing haul truck to detect boulders and analyse particle size in real time – without interrupting production. Using artificial intelligence and stereo imaging, the system automatically analyses the truck bed, segments each visible rock, and identifies any oversized material. If a boulder is detected, the system automatically alerts dispatch so that trucks can be diverted.

“TruckMetrics, therefore, provides a two-pronged approach to mitigating problems caused by oversized material,” Motion Metrics said. “First, it helps keep boulders out of the crusher by identifying trucks that contain oversized material and diverting them before they reach the plant. Secondly, the particle size data TruckMetrics captures can be used to optimise blasting parameters so that fewer boulders are produced in the first place.”

TruckMetrics is just one of several services within the Motion Metrics ecosystem that boost productivity and energy efficiency without compromising on safety, the company says.

Weir-backed report highlights decarbonisation opportunities in mineral processing

An independent report, commissioned by the Weir Group, has highlighted the global mining industry’s energy usage, illuminating where energy is consumed and linking it with opportunities and pathways for sector-wide decarbonisation.

The report analyses mine energy use from over 40 published studies, centred on five commodities – copper, gold, iron ore, nickel and lithium. For these five metals, it finds comminution – the crushing and grinding of rocks – alone accounts for 25% of final energy consumption at an ‘average’ mine site. Extended across all hard-rock mining, this is equivalent to up to 1% of total final energy consumption globally.

The report reconfirms comminution as a key target for energy and emissions reduction efforts.

These findings align with the mission of the Coalition for Energy Efficient Comminution (CEEC), a global initiative to accelerate eco-efficient minerals, with a focus on energy-efficient comminution. It also extends on previous CEEC messaging, indicating up to 3% of global electrical energy is used in comminution when considering all mined commodities, quarrying and cement production.

In addition to optimising comminution, the report also highlights other energy and emissions reduction opportunities such as the redesign of grinding circuits at greenfield sites, improved drill and blast approaches, pre-concentration, and the use of artificial intelligence and machine learning to improve decision making.

The report emphasises the mining industry’s crucial role in supporting the transition to net zero emissions, needed to limit global temperatures in line with the Paris Agreement, CEEC says. This includes more efficient and sustainable technologies if the industry is to meet the challenge of decarbonisation.

“Despite the scale of the challenge, the report underlines that small improvements in existing mines can lead to large savings in both energy consumption and greenhouse gas (GHG) emissions,” CEEC said.

Report author, Marc Allen, states a 5% incremental improvement in energy efficiency across comminution could result in greenhouse gas emission reductions of more than 30 Mt of CO2e.

Allen said: “A relatively modest 5% improvement in comminution across the industry may result in emissions reductions close to the total emissions for New Zealand (35 Mt CO2e).

“A more robust energy audit process and implementation of low-cost opportunities across a mine and process plant may result in total energy savings of up to 10-15% and overall emissions reductions of over 200 Mt of CO2e per annum, depending on the source of electricity.

“Large-scale introduction of renewable energy provides the potential to reduce emissions significantly in the industry – hundreds of millions of tonnes of greenhouse gas savings when there is widespread adoption of renewable energy and energy storage.”

CEEC CEO, Alison Keogh, commended Weir for commissioning this timely work, and all industry leaders taking proactive steps to reduce mining’s footprint. She said outstanding CEEC Medal winning work and 700 published advances have already shared good options for miners to consider, thanks to CEEC sponsors, volunteers and authors.

She urged industry to collaborate to accelerate decarbonisation steps.

“More open knowledge sharing helps speed installations of renewables and energy-efficient approaches across all of industry,” Keogh said. “Benefits also include increased productivity, shareholder value, and financing as companies demonstrate performance towards net zero emissions sooner.”

She cited three key collaboration actions vital to success: (1) sharing best practices, to ensure existing mines and processing plants are better informed and take actions earlier to become more energy and water efficient; (2) sharing new technologies, designs and innovations; and (3) supporting test work and pilots of novel technology on sites and at increasing scales.

Keogh called for greater industry dialogue, noting: “This report highlights both a challenge and an opportunity to revitalise cross-industry discussion and actions on decarbonisation and ESG solutions. Weir is one of many visionary CEEC sponsors supporting public good initiatives like CEEC; we invite industry leaders to actively contribute and collaborate through mining-vendor-research partnerships and share knowledge, site case studies and net zero plans via independent organisations such as CEEC.

“Together, we can accelerate improved energy, emissions and water footprint across industry faster.”

Weir Group Chief Executive, Jon Stanton, commented: “Mining needs to become more sustainable and efficient if it is to provide essential resources the world needs for decarbonisation while reducing its own environmental impact. This report is an important contribution to that debate which we hope will spark thoughtful conversations around the world on the way forward.”

The Axora take on crushing and comminution

As we are continually told, comminution is one of the most energy intensive single steps in the resource extraction business.

One estimate is that it accounts for 36% of all the energy used in the extraction of copper and gold, which is only a shade over the 30% proposed as an average by another industry expert for all mining and mineral processing industries.

It also accounts for an estimated 3% of the global energy requirement for metal production.

These energy requirements are shocking from a sustainability and greenhouse gas emission perspective; they are also extremely costly regarding operating expenses on site.

It is with this in mind that IM touched base with Joe Carr, Industry Innovation Director of Mining at Axora.

A spinoff from the Boston Consulting Group, Axora has emerged as a business-to-business digital solutions marketplace and community for industrial innovators. It says it allows industrial companies to discover, buy and sell digital innovations and share knowledge in its community, powered by an advanced marketplace.

“We exist to transform industries to be digital, safer, more sustainable and efficient,” the company states on its website.

Having recently gone to press with the annual crushing and comminution feature (to be published in the IM April 2021 issue), IM spoke with Carr to find out what the Axora marketplace has to offer on the comminution and crushing front.

IM: What are the main issues/concerns you continuously hear from your mining clients when it comes to designing and maintaining comminution circuits? How many of these problems/issues can already be solved with existing technology/solutions?

JC: One of key issues in this area we hear from our customers at Axora is the blending quality of the input ores.

Joe Carr, Industry Innovation Director of Mining at Axora

This could be particularly relevant in the sulphide space, for instance.

I did some work years ago on Pueblo Viejo for Barrick. When I was there, one of the things we were working on was blending the sulphides as we were feeding the mill from numerous satellite pits with very different sulphide grades. Because we were processing the ore with an autoclave, high-grade sulphides would cause a temperature spike and the low-grade sulphides would lower the temperature. This constant yo-yoing of the feed into the autoclave was terrible for the recovery of metals against the plan.

Generally, the old school way of blending is setting up stockpiles of ore based on whatever variable you want to manage at your operation. You would put a defined amount of each into the primary crusher on the understanding this would create a ‘blended’ feed for the processing plant.

With the information we have at our fingertips today, this process seems outdated.

You could, for example, use HoloLens or another VR system in tandem with the shovel operator to be able to see exactly what material he or she is excavating. That can then be linked back to the geological block model, with this material then tracked in the trucks and onto the run of mine stockpile, before heading to the plant.

This is where something like Machine Max comes in. Machine Max is a bolt-on IoT sensor that tracks where your trucks are in real time – where they have been and where they are going. The processing piece requires block model integration into a mine plan system. If you have the building blocks in place – the networking, sensors, additional infrastructure, etc – Machine Max could, when integrated with this model, allow you to attempt real-time ore tracking.

“If you have the building blocks in place…Machine Max could, when integrated with this geological block model, allow you to attempt real-time ore tracking,” Joe Carr says

The issue is not that the technology doesn’t exist, but that the mining industry hasn’t yet cracked putting all of this together at an industry-wide scale, available to all miners.

You can carry out a project like this or go totally the other way and have a machine-learning or artificial intelligence algorithm in the plant that is constantly reading the incoming feed. These could be based around the block model inputs, or a digital XRF solution, which is able to constantly tweak or adjust the plant settings to the feed specifications. Process plants are generally setup to handle one type of feed. This is usually only tweaked in retrospect or for short periods of time when the mine plan moves into a different mining horizon.

We also have a comminution solution that understands the feed coming in and optimises the mill and power settings to get the optimal grind for flotation, maximising recovery at the back end. While the input is typically set up to be grind quality and hardness for optimal flotation, there is no reason why you couldn’t configure it for, say, sulphides going into an autoclave, tweaking the autoclave heat settings dependent on the feed.

Once that system is set up, it becomes a self-learning algorithm.

Saving operational costs is another pain point for mining companies we always hear about.

We have a solution on our marketplace from Opex Group, which is looking to optimise production while reducing power. Coming from the oil & gas space, this AI algorithm, X-PAS™, offers the operator an opportunity to adjust the settings while still achieving the same required outputs. This is tied to CO2 reduction, as well as power cost reductions.

Opex Group’s AI algorithm, X-PAS, offers the operator an opportunity to adjust the plant settings while still achieving the same required outputs

In mining, the plant is your largest drawer of power, hands down. Generally, if it is not powered on the grid, it is powered by diesel. Opex Group’s solution can save up to 10% of power, which is a significant amount of fuel and CO2.

The solution reads information from your pumps and motors, analyses the planned output of your plant using all the sensor feeds, and tweaks the variables while sustaining the required output. The algorithm slowly learns how you can change configurations to reduce power, while sustaining throughput. This results in lower power costs, without impacting the output.

Importantly, instead of automating the process, it offers the saving to the operator sat in the control room. Operators, in general, are incredibly reluctant to pass over control to an AI algorithm, but when faced with such power saving opportunities, they will often elect to accept such a change.

And, of course, plant maintenance is always on the agenda.

This is where Senseye, which has been used in the car industry by Nissan and the aluminium sector by Alcoa, is useful.

Essentially, this provides predictive maintenance analytics. It is also a no-risk solution with Senseye backed by an insurance guarantee. It is sold on the basis that if you do not earn your money back within the first 12 months, you get an insurance-backed refund.

There could also be openings in the plant for Razor Labs’ predictive maintenance solution, which is currently increasing the uptime of stackers, reclaimers and car dumpers for iron ore miners in the Pilbara.

IM: When it comes to future comminution equipment design, do you expect digitalisation, wear liner innovations, or equipment design to have more of a bearing on operational improvements at mine sites? Phrased another way; is more emphasis being given to refining and extending the life of existing products with digital technologies and wear solutions, than the design of brand-new equipment?

JC: We believe there is always going to be a focus on retrofit and extensions. Once a mill is built, changing the equipment, upgrading, etc is very hard and time consuming. The logistics of getting a new SAG mill to site, for example, are mind boggling. New technology will always come for new sites, but most of the world’s mining capacity is already in place. I would expect most digitalisation to focus on two areas:

  1. Getting more and longer life from all the assets. For example, extending liner life, reducing operating costs and shortening downtime between refits; and
  2. Drawing insights from the existing asset with a view to sweating it. No mill ever stays at nameplate; there is always an increase in production. One or two percent more throughput can put millions onto the bottom line of a company. No mill wants to be a bottleneck in the cycle. In a mine there are always two goals: the mine wants to produce as much ore as possible to put the pressure on the mill, and the mill wants to run as fast as possible to put pressure on the mine.

When it comes to extending liner life, we have a solution worth looking at.

One of the companies we work with out of Australia has an IIoT sensor all tied to wear and liner plates. It is a sensor that is embedded into a wear plate and wears at the same time as the wear plate itself wears. It provides this feedback in real time.

So, instead of the standard routine changeout, it gives you real-time knowledge of what it is happening to these wear parts.

We have a great case study from Glencore where they installed the sensors for around A$200,000 ($152,220) and it saved several million dollars. The payback period was just weeks.

Where I want to take it to the next level is pairing the wear plate monitoring technology on chutes and ore bins and looking into SAG mills and crushers. Relining your SAG mill or primary gyratory crusher is a massive job, which takes a lot of time and cuts your productivity and output by a huge amount. Wear plates are made as consumables, so if you can use 5% less over the space of a year, for instance, there are huge cost and sustainability benefits. You can also more accurately schedule in maintenance, as opposed to reacting to problems or sticking to a set routine.

IM: When compared with the rest of the mine site, how well ‘connected’ is the comminution line? For instance, are gyratory crushers regularly receiving particle size distribution info for the material about to be fed into it so they can ‘tailor’ their operations to the properties of the incoming feed?

JC: Generally, not really. The newer, better financed operations tend to have this. Taking the example above, when designing a plant flowsheet, the close side settings are used. But are they updated on the fly to optimise the plant? Not really. Most processes are designed with a set number of conditions to operate at their maximum.

Most plants dislike, and are not set up to handle, variation in their system, according to Carr

Most plants dislike, and are not set up to handle, variation in their system. They like consistent feed quality and grade to achieve maximum recoveries. Over the next few years, the companies that develop the best machine learning or AI models to run plants in a more real time, reactive way will see the biggest growth. A mill will always say it’s the mine that needs to be consistent, but the nature of geology means that you can never rely on this. As one geologist I knew said, “geology, she is a fickle mistress”.

IM: Where within the comminution section of the process flowsheet do you see most opportunity to achieve mining company sustainability and emission goals related to energy reductions, water use and emissions?

JC: In terms of emissions, at Axora we are actively looking at technology that can help across the entire plant. There was a great paper published in 2016 around this specific topic ‘Energy Consumption in Mining Comminution’ (J Jeswiet & A Szekeres). The authors found that the average mine used 21 kWh per tonne of ore processed. Given diesel produces 270 g per kWh, this means a plant produces 5.6 kg of CO2 per tonne of ore processed, on average. For a 90,000 t/day site, this might represent 510 t of CO2 per day (186,000 t/y), just for processing. To put that into context, you would need 9.3 million trees to offset that level of carbon.

If the industry is serious about lowering its carbon footprint, especially Scope 1 and 2 emissions, then the focus has to come into the process. There are easy wins available from proven solutions in other sectors for companies that want to take them.

Metso Outotec to supply Vertimills, cone crusher to IAMGOLD’s Côté project

Metso Outotec is to supply key comminution technology to IAMGOLD Corporation and Sumitomo Metal Mining’s joint venture Côté gold project, in north-eastern Ontario, Canada.

The delivery consists of two energy-efficient Vertimill® 4500 grinding mills (pictured) and one MP1250 cone crusher for the Côté gold project.

Andy Lingenfelter, Vice President, Minerals Sales, North & Central America, Metso Outotec, said: “Low energy and wear part consumption, as well as process flexibility, were decisive factors for the Côté gold project team when selecting the comminution equipment.

“Metso Outotec was consulted during the prefeasibility study and supported IAMGOLD on several projects. IAMGOLD’s technical team had solid confidence in the Vertimill technology, and they were also familiar with the high-performance capability of the MP crushers.”

The value of the order exceeds €10 million ($11.9 million) and has been booked in Minerals’ March quarter 2021 orders received.

Côté comes with estimated contained gold reserves of over 7 Moz. Construction of the gold mine commenced in late 2020, and is expected be completed in mid-2023.

eHPCC: the future of grinding in mining?

A lot has been made of the potential of high pressure grinding rolls (HPGRs) to facilitate the dry milling process many in the industry believe will help miners achieve their sustainability goals over the next few decades, but there is another novel technology ready to go that could, according to the inventor and an independent consultant, provide an even more effective alternative.

Eccentric High Pressure Centrifugal Comminution (eHPCC™) technology was conceived in 2013 and, according to inventor Linden Roper, has the potential to eliminate the inefficiencies and complexity of conventional crushing and/or tumbling mill circuits.

It complements any upstream feed source, Roper says, whether it be run of mine (ROM), primary crushed rock, or other conventional comminution streams such as tumbling mill oversize. It may also benefit downstream process requirements through selective mineral liberation, which is feasible as the ore is comminuted upon itself (autogenously) in the high pressure zone via synchronous rotating components. Significant product stream enrichment/depletion has been observed and reported, too.

As IM goes to press on its annual comminution and crushing feature for the April 2021 issue – and Dr Mike Daniel, an independent consultant engaged by Roper to review and critique the technology’s development, prepares a paper for MEI Conferences’ Comminution ’21 event – now was the right time to find out more.

IM: Considering the Comminution ’21 abstract draws parallels with HPGRs, can you clarify the similarities and differences between eHPCC and HPGR technology?

MD & LR: These are the similarities:

  • Both offer confined-bed high-pressure compression comminution, which results in micro fractures at grain boundaries;
  • Both have evidence of preferential liberation and separation of mineral grains from gangue grains at grain boundaries; and
  • Both have an autogenous protective layer formed on the compression roll surfaces between sintered tungsten carbide studs.

These are the differences:

  • eHPCC facilitates multiple cycles of comminution, fluidisation and classification within its grinding chamber, retaining oversize particles until the target product size is attained. The HPGR is a single pass technology dependent on separate materials handling and classification/screening equipment to recycle oversize particles for further comminution (in the event subsequent stages of comminution are not used);
  • Micro factures around grain boundaries and compacted flake product that are created within HPGRs need to be de-agglomerated with downstream processing either within materials handling or wet screening. In some instances, compacted flake may be processed in a downstream ball mill, whereas, in eHPCC, preferential mineral liberation is perfected by subsequent continuous cycles within the grinding chamber until mineral liberation is achieved within a bi-modal target size (minerals and gangue). The bi-modal effect differs from ore type to ore type and the natural size of the minerals of interest;
  • The preferential liberation of mineral grains from gangue grains generally occurs at significantly different grain sizes, respectively, due to the inherent difference in progeny hardness. eHPCC retains the larger, harder grains, hence ensuring thorough stripping/cleaning of other grain surfaces by shear and attrition forces;
  • eHPCC tolerates rounded tramp metal within its grinding chamber, however does not tolerate high quantities of sharp, fragmented tramp metal that create a non-compressible, non-free-flowing bridge between roll surfaces, which risks the damage of liner surfaces;
  • The coarse fraction ‘edge effect’ common in HPGR geometry is not an issue with eHPCC. In fact, the top zone of the eHPCC grinding chamber is presumed to be an additional portion of the primary classification zone within the grinding chamber. The oversize particles from the internal classification process are retained for subsequent comminution;
  • The maximum size of feed particle (f100) entering the eHPCC is not limited to roll geometry as is the case with HPGRs (typically 50-70 mm). eHPCC f100 is limited to feed spout diameter (for free flow) and dependent of machine size ie eHPCC-2, -5, -8 and -13 are anticipated to have f100 60 mm, 150 mm, 240 mm and 390 mm, respectively. The gap between rolling surfaces is greater than the respective f100; and
  • eHPCC technology shows scientifically significant product stream enrichment.

IM: What operating and capital cost benefits do you envisage when compared with typical HPGR installations?

MD & LR: Both operating and capital cost benefits of the eHPCC relative to HPGR technology are due to the eHPCC not requiring the pre-crushing and downstream classification equipment required by HPGRs.

The eHPCC operating cost benefits are associated with eliminating maintenance consumables, downtime, reliability issues and energy consumption associated with the equivalent HPGR downstream equipment listed above.

The eHPCC capital cost benefits are associated with eliminating the real estate (footprint) and all engineering procurement and construction management costs associated with the equivalent HPGR upstream/downstream equipment listed above. eHPCC flowsheets are likely to be installed as multiple ‘one-stop’ units that maintain high circuit availability due to ongoing cyclic preventative maintenance.

IM: Where has the design for the eHPCC technology come from?

LR: It was invented in early 2013 by me. I then pioneered proof-of-concept, prototyping, design and development, culminating in operational trials in a Kazakhstan gold mine in 2020. A commercial-grade detailed design-for-manufacture has since been undertaken by a senior team of heavy industry mechanical machine designers and engineers.

IM: In your conference abstract, I note that the eHPCC technology has been tested at both laboratory and semi-industrial scale with working prototypes. Can you clarify what throughputs and material characteristics you are talking about here?

LR: The first iteration of the technology, eHPCC-1, was tested at the laboratory scale from 2013-2015. This proof-of-concept machine successfully received and processed magnetite concentrate, copper-nickel sulphide ore, alkaline granite, marble and a wolfram clay ore dried in ambient conditions. The typical throughput was between 200-400 kg/h depending on the feed size, particle-size-reduction-ratios (dependent of grain size) and target product size. The feed size was limited to a maximum of 25 mm to ensure free flow of feed spout.

Alkaline granite: eHPCC-2 coarse product (left) and fine product (right)

MD & LR: From 2016-2020, we moved onto the semi-industrial scale testing with the eHPCC-2 (two times scaled up from eHPCC-1). This was designed for research and development (R&D) and tested on magnetite concentrate, alkaline granite, and hard underground quartz/gold ore. The throughput capabilities depended on the geo-metallurgical and geo-mechanical properties of feed material, such as particle size, strength, progeny (grain) size and particle size-reduction-ratios (subject to confined bed high pressure compression). Larger-scale machines are yet to be tested against traditional ‘Bond Theory’ norms.

The eHPCC, irrespective of the outcomes, should be evaluated on its ability to effectively liberate minerals of interest in a way that no other comminution device can do. The maximum feed size, f100, at the gold mine trials was limited to 50 mm to ensure free flow through the feed spout. R&D culminated in pilot-scale operational trials at the Akbakai gold mine (Kazakhstan), owned by JSC AK Altynalmas, in 2020, where SAG mill rejects of hard underground quartz/gold ore were processed. The mutual intent and purpose of the tests was to observe and define wear characteristics of the eHPCC grinding chamber liners (roll surfaces). These operational trials involved 80% of the feed size being less than 17 mm and a variety of targeted product sizes whereby 80% was less than 1 mm, 2 mm, 2.85 mm and 4.8 mm. The throughput ranged from 1-5 t/h based on the size.

IM: What throughputs and material characteristics will be set for the full-scale solution?

LR: There will be a select number of standard eHPCC sizes. Relative to the original eHPCC-1, the following scale-up factors are envisaged: -2, -3, -5, -8, and -13. These are geometrical linear scale-up factors; the actual volumetric capacity is a cube of this factor, with adjustments for centripetal acceleration. Currently -13 times seems to be the maximum feasible size of the present detailed design philosophy, but there are no foreseeable limitations in terms of feed materials with exception to moist clay. Clay was successfully processed after drying the feed in ambient temperatures during testing. Further testing of moist clays blended with other materials that can absorb the moisture as they comminute would be desirable.

IM: Other HPGRs can also be equipped with air classification technology to create dry comminution circuits. What is the difference between the type of attrition and air classification option you are offering with the eHPCC?

MD & LR: Two modes of comminution occur in the particle bed of eHPCC repetitively and simultaneously. First, confined bed pressure compression breakage occurs at a macro level that promotes shear/compression forces greater than the mineral grain boundaries. Second, Mohr-Coulomb Failure Criteria (shear/attrition) that completes the separation of micro fractures on subsequent cycles takes place.

The nip angle between the rotating components of eHPCC technology never exceed 5°. During the decompression and fluidisation portion of the cycle, the softer species – which are now much smaller – are swept out of the fluidised particle bed against centrifugal and gravitational forces by process air. The larger species, influenced by centripetal acceleration, concentrate at the outer diametric and lower limits of the conical rotating grinding chamber, continuing to work on each other during each subsequent compression phase.

HPGRs are limited to one single-pass comminution event, requiring downstream external classification and subsequent recycling/reprocessing of their oversize and/or flake product.

IM: How will it improve the mineral liberation and separation efficiency compared with other grinding solutions that combine both?

MD: eHPCC technology could compete with the Vertical Roller Mill and Horomill, however, eHPCC is likely to be more compact with high intensity breakage events contained within the all-inclusive system of breakage, classification and removal of products.

IM: When was it most recently tested and over what timeframe?

LR: The eHPCC-2 pilot plant was mobilised, setup and commissioned in March 2020, but its operation was suspended until June 2020 due to COVID-19 quarantine restrictions and a need to cater to abnormal amounts of ball fragments in the feed, the latter of which pushed the treatment of tramp metal to the extreme. The machine operated for the months of June and July using liners constructed of plasma transferred arc welded (PTAW) tungsten carbide (TC) overlay. During this period, a total of 795 t was processed at various targeted product sizes, with, overall, an average throughput of 3 t/h (nominally 265 operating hours) processed.

Side view of pilot system including feed hopper and weigh-scale feeder (right), feed conveyor (middle foreground), control and auxiliaries (middle background), eHPCC-2 (left foreground), dust bag-house (left background) and product conveyor and stockpile (not shown left background)
Front-end loader filling feed hopper with SAG mill rejects f80 18 mm

The PTAW-TC overlay was deemed unsustainable as it was consumed rapidly and demanded continuous rebuilding due to the high pressure intensive abrasive wear on the convex cone. The pilot plant operation was mostly suspended during the month of August while an alternative tungsten carbide studded liner, analogous to HPGR studded rolls, was manufactured for simulating a trial of this studded liner philosophy. The studded liner philosophy was operated in the eHPCC-2 in Kazakhstan for sufficiently long enough to ascertain the creation of the autogenous protective wear layer of rock between the studs, with the simulation trial deemed a success. The design philosophy shall be adapted on the commercial-grade eHPCC.

eHPCC-2 TungStud™ as-new (left) high-pressure-air-cleaned (middle) and brushed (right)

The pilot plant was demobilised from the Akbakai site laydown area on September 10, 2020, to release the area for construction of a non-related plant expansion. The operational experiences of the pilot plant at Akbakai provided valuable knowledge and experience pertaining to mechanical inertia dynamics and design for eliminating fatigue within eHPCC components.

IM: Aside from the test work on trommel oversize at the Kazakhstan gold mine, where else have you tested the technology?

LR: eHPCC has no other operational experiences so far. Investment and collaboration from the industry to progress the commercialisation of eHPCC is invited. The commercial-grade eHPCC-2.2 is designed and ready for manufacture.

IM: Is the technology more suited to projects where multiple streams can be produced (fines, coarse piles, etc)?

LR: eHPCC is configurable to meet the demands and liberality of a diverse spectrum of feed materials and the potential downstream extractive processes are complementary to eHPCC product streams. Therefore, it would be incorrect to categorise it as more suitable in any one niche; it is configurable, on a case-by-case basis, to meet the liberality of the specific progeny of the feed.

IM: What energy use benefits do you anticipate by creating a one-step comminution and classification process over the more conventional two-step process?

MD & LR: The energy saving benefits include:

  • Elimination of tumbling mill grinding media consumption;
  • Elimination of the liberal wastage of randomly directed attrition and/or impact events that indiscriminately reduce the size of any/all particles (gangue or precious mineral) with the conventional tumbling mill; and
  • Elimination of energy consumption of the materials handling systems between the various stages of comminution and classification, be it dry belt conveying, vibrating screens, classifiers, cyclone feed pumps, cyclones and their respective recirculating loads that can be upward of 300% of fresh feed.

IM: Do you anticipate more interest in this solution from certain regions? For instance, is it likely to appeal more to those locations that are suffering from water shortages (Australia, South America)?

MD & LR: We suspect the initial commercialisation growth market to be from base metals producers seeking to expand or retire existing aged/tired comminution classification capacity, followed by industry acknowledgement of the technology’s potential to shift the financial indicators of other potential undeveloped projects into more positive territory. This latter development could see the technology integrated into new projects.

In general, the technology will appeal to those companies looking for more efficient dry comminution processes. This is because it offers a pathway to rejection of gangue at larger particle sizes, early stream enrichment/depletion and minimal overgrinding that creates unnecessary silt, which, in turn, hinders or disrupts the integrity of downstream metallurgical extraction kinetics, and/or materials handling rheology, and/or tailings storage and management.

LR: There are a number of rhetorical questions the industry needs to be asking: why do we participate in the manufacture and consumption of grinding media considering the holistic end-to-end energy and mass balance of this (it’s crazy; really why?)? Why do we grind wet? What are the barriers preventing transition from philosophising over energy efficiency, sustainability etc and actually executing change? Who is up for a renaissance of bravely pioneering disruptive comminution and classification technology in the spirit of our pioneering forefathers?

The more these questions are asked, the more likely the industry will find the solutions it needs to achieve its future goals.

Dr Mike Daniel’s talk on eHPCC technology will be one of the presentations at the upcoming Comminution ’21 conference on April 19-22, 2021. For more information on the event, head to https://mei.eventsair.com/comminution-21/ International Mining is a media sponsor of the event

Second Cat 994K wheel loader arrives at Capstone’s Pinto Valley in latest innovation push

Capstone Mining has brought a second Caterpillar 994K wheel loader to its Pinto Valley operation in Arizona, USA, as it looks to reduce its emissions and improve its operating cost base at the copper mine.

Last year, the mine added to its fleet a Cat 994K loader, which, the company says, burns circa-30 less gallons of fuel per hour (1.9 litres/min) than its current shovels. “This reduced our CO2 emissions and operational cost savings on approximately 116,000 gallons of fuel in 2020,” Capstone said.

The second 994K, added last week, will, in partnership with the first wheel loader, displace around 10,000 shovel hours a year and save approximately 410,000 gallons of fuel and millions in maintenance costs, the company claimed.

Capstone concluded: “Pinto Valley is innovating and optimising for exciting times ahead.”

This is not the only area of innovation the company is currently pursuing at Pinto Valley, an operation it acquired from BHP back in in October 2013.

In its 2020 results, released last month, Capstone said the implementation of phase one of its PV3 Optimization project at Pinto Valley had delivered a 10% sustainable throughput improvement compared with 2019.

The PV3 Optimization project has been designed to achieve safer, more reliable and higher capacity operations without major investments in new comminution equipment. It is doing this by leveraging new inexpensive technologies.

Phase one work, which included improved blast fragmentation processes, installation of a new secondary crusher and screen decks as well as a new mill shell, was completed last year. This saw the mine achieve throughput of 57,168 t/d in the December quarter, 10% higher than the annual 2019 average of 51,137 t/d. December 2020 mill throughput achieved 60,717 t/d, which represents a new monthly record in the mine’s operating history.

Phase two of the PV3 Optimization project is expected to be completed in the second half of 2021, upon completion of upgrades to a conveyor, mill auto controls, cyclone packs and retrofits to the thickeners, it said.

During the month of December, the company conducted a pilot plant test of Eriez HydroFloat coarse particle technology at Pinto Valley, with Capstone saying the results had surpassed expectations of a 6% improvement target to overall copper recovery. In fact, the tests showed a 6-8% increase in overall copper recovery was achievable, which, when combined with expected higher throughput rates, could result in an additional 9-12 MIb/y (4,082-5,443 t/y) of copper production at the operation, it said.

“Additional benefits to the technology include allowing the operation increased throughput by operating at a coarser grind size, which is expected to lower power costs, improve water consumption and lead to improved stability in the tailings storage facility,” Capstone said in its 2020 results. “The estimated $70 million expansionary capital, which includes the installation of Eriez HydroFloat and related equipment, if approved by the board of directors, is expected to be spread over half two 2021 and early 2022, with start-up expected in Q2 (June quarter) 2022.”

Capstone said it expects to release an updated NI 43-101 technical report that encompasses the PV3 Optimization Phase 1 and Phase 2 projects and improvements in the second half of 2021.

At the same time, it is also looking into a PV4 study at Pinto Valley.

Capstone explained: “Feasibility work on scenarios to take advantage of approximately one billion tonnes of mineral resource not currently in the mineral reserve mine plan, which is at similar grade to the current mineral reserves, will be conducted for Pinto Valley.”

The PV4 study is expected to be released in late 2022 and will contemplate using existing mill infrastructure rather than building new facilities, with higher mining rates, higher cutoff grades to the mill and increased tonnage available for leaching.

Extensive column leach test work in collaboration with Jetti Resources LLC will take place over 2021. Jetti’s patented catalytic technology, designed to allow for the efficient and effective heap and stockpile leach extraction of copper, has been a success at Pinto Valley’s leaching operation, where it expects to recover up to 350 million pounds of cathode copper over the next two decades from historic and new mineralised waste piles.

“Capstone is a pioneer in the application of this leach technology and we intend to use it to enhance the economics of a future expansion at Pinto Valley,” it said.

Kwatani breathes new life into scalping screens with rubber, polyurethane wear panels

As mines move towards using one large scalping screen between primary and secondary crushers – rather than a modular approach using multiple smaller screens – Kwatani says it has found ways to triple the panel life in these single mission-critical units.

According to Kenny Mayhew-Ridgers, Chief Operating Officer of Kwatani, any downtime in this single-line stream would require the mine to store several hours of production. While some mines schedule regular weekly production halts during which an exciter or worn screen panels can be replaced, many operations are not so lenient, he said.

“The message from these mines is clear: the longer the scalper can run between maintenance interventions, the better,” Mayhew-Ridgers said. “Our research and development efforts, together with extensive testing in the field, have allowed us to extend the life of screen panels from eight weeks to over six months.”

While smaller screens use wire mesh screening media, Kwatani has evolved larger screens that use rubber or polyurethane screen panels. Although these panels present less open area, they deliver important advantages.

“Key to the success of our design is our integrated approach – which matches the panel design with that of the scalping screen itself,” Mayhew-Ridgers said. “This allows us to achieve a balance between screening area, aperture layout and screen panel life – a result based on a sound understanding of screen dynamics.”

Whereas wire mesh undergoes rapid wear from abrasive materials, the rubber or polyurethane panels are more wear resistant and deliver longer life, according to the company. The latter require gentler declines for effective stratification, but a key factor is the stiffness of the screen bed.

“The stiffness of the supporting structure must go hand-in-hand with the screen panel design to achieve our required results,” Mayhew-Ridgers said.

Polyurethane panels, while strong and lightweight, have screening apertures that tend to be too stiff for heavy-duty scalping applications. This leads to blinding. Rubber overcomes this problem, however, and also delivers improved wear life.

Kwatani has also developed a panel replacement system – with a fastening mechanism on the underframe – that improves safety and saves time, it says.

CMIC-backed novel comminution technology hits commissioning milestone

The Canada Mining Innovation Council’s (CMIC) Conjugate Anvil Hammer Mill (CAHM) and MonoRoll platform technology project has reached a new milestone with hot commissioning of the MonoRoll at COREM’s testing facility in Quebec, Canada.

CAHM is a platform technology advancing two technologies in parallel where both designs break particles in a highly efficient thin particle bed. CAHM, according to CMIC, provides a more efficient alternative to high pressure grinding rolls and SAG mills, while the MonoRoll variant is designed for finer grinds and to replace inefficient rod and ball mills.

In a recent post, CMIC said hot commissioning of the MonoRoll at COREM’s testing facility, using some of the 300 t of ore contributed by Agnico Eagle Mines, was now complete. Although the MonoRoll is being tested using hard rock, there is also significant interest from the iron ore, cement and aggregate industries, CMIC says.

It added: “Fabrication of the CAHM machine is underway and if the optimised discrete element method modelling results hold, we are confident that the MonoRoll and the CAHM are on track to achieve the following significant benefits in ore grinding:

  • “Reduce energy consumption by an estimated 50% compared to best available technology;
  • “Eliminate grinding media;
  • “Increase ore feed reduction ratio; and
  • “Simplify the comminution circuits.”

CMIC is leading a consortium including experts in comminution, product development, engineering and testing as well as six major hard-rock mining companies guiding the effort and participating as potential first adopters. Included among the consortium is CTTI, Hatch, Glencore Canada – XPS (Expert Process Solutions), COREM, Teck, Agnico Eagle, Newmont and Kinross.

The MonoRoll technology is one of only six finalists in Impact Canada’s Crush It! Challenge. Launched in October 2018, Crush It! challenged Canadian innovators to deliver game-changing solutions for cleaner, more efficient rock processing.

CMIC said: “The MonoRoll project is the only finalist developing a novel grinding mill, and if the project wins the C$5 million ($3.9 million) Grand Prize, the funds would be used to engineer a large-scale machine to test in active mining operations.”