Tag Archives: Adrian Dance

Pre-concentration: it’s worth asking the question

19th February 2024Comminution of minerals, Environmental, Mineral processing, Mining equipment, Mining services, Sustainable miningAdrian Dance, Bob McCarthy, mineral processing, ore sorting, pre-concentration, SRK ConsultingDaniel Gleeson

We’ve reviewed a novel, vendor-agnostic pre-concentration screening test in part one and explained a comprehensive five-step pre-concentration evaluation in part two…now for part three in the three-part series with SRK Consulting (Canada) Inc’s Adrian Dance (Principal Metallurgist) and Bob McCarthy (Principal Consultant)

SRK Consulting’s Adrian Dance and Bob McCarthy have devoted years to ensuring the mining industry can make informed decisions about preconcentration within their flowsheets and are now able to screen the opportunities quickly, cost-effectively and without vendor prejudice.

“We have been carrying out the different parts of the five-step evaluation process over the years, refining them independently and sometimes together,” McCarthy tells IM. “It is only now that we can present them all in a holistic way.”

This five-step process – which includes heterogeneity analyses; “size the prize” economics; laboratory test work that involves X-ray Transmission (XRT) based sensor technology; mine planning; and mine economics – has been deliberately designed to allow mining companies to pause at the end of each phase to re-evaluate if there is a strong enough case to continue with a preconcentration investigation.

BobMcCarthy-SRK — *Bob McCarthy, Principal Consultant), SRK Consulting (Canada) Inc*

The importance of such an approach has grown in recent years as more projects that are “grade-challenged” or metallurgically complex are being considered for exploitation by mining companies as the demand for metal increases worldwide.

Sensing this (pun intended), sorting and sensing manufacturers have been on the mining charm offensive, proclaiming the benefits of their technology – benefits that include cost reductions, improved metallurgical recoveries, rationalised use of energy and water, and more.

These market dynamics have created a void that SRK is looking to fill by providing the tools for both sides to assess the options and carry out informed decision making on which routes to pursue.

“We were concerned that the manufacturers didn’t have the background needed to understand the mining industry’s requirements,” Dance said. “At the same time, mining companies had difficult projects and deposits where they saw pre-concentration potential but didn’t know where to initially go to explore that potential.

“We saw a space for industry representatives like ourselves at SRK to bridge that divide.”

The independent testing that SRK has been able to offer for the last six or so months through its partnership with Base Metallurgical Labs (BML) in British Columbia was the final piece of the puzzle in establishing this nowestablished five-step process.

Able to not only indicate pre-concentration amenability but also provide key inputs into the pre-concentration strategy selection and evaluation, this has been employed for some 36 samples (close to 2,000 particles) being tested using the XRT unit situated in BML’s facility in Western Canada.

Demystifying the tech

While this XRT testing may have only recently become available to SRK and BML customers, the outcomes of SRK’s pre-concentration evaluation have been described to investors and stakeholders trawling through NI 43-101 reports up to the prefeasibility study (PFS) level for some time now. Various parts of the five-step evaluation have come into sections on metallurgical test work, mineral reserves, mining methods, costs and economics.

“Where the results feature is tied to what study stage the company is at and where people feel comfortable with pre-concentration,” McCarthy explains.

Providing comfort to mining companies and their investors is always difficult when examining any new flowsheet addition, hence the reason why many companies are initially pursuing pre-concentration or ore sorting in a ‘recovering ore out of waste’ scenario from material already deemed to be waste and having no economic value.

As a result, SRK has been very deliberate in the protocols it is pursuing.

Dance explains: “Because there is still a perceived ‘magical’ nature to preconcentration in that it can provide reserve upgrades and higher recoveries, we need to do more detailed evaluations at a preliminary economic assessment or PFS level than would be expected for other types of processing technology.”

For instance, the company is currently engaged on a gold operation where it has tested upwards of 22 samples (1,320 particles) for validation. “At this level of study, if you were working on comminution or leaching, the same process validation would be carried out with two or three tests,” Dance said.

McCarthy added: “We firmly believe that this five-step evaluation will allow people to sign off, at least at a PFS level, on whether pre-concentration is a viable route for them to take. Our process will prove this through testing and pulling different economic levers in the economic evaluation to quickly see where the value is, and where it isn’t.

“If pre-concentration is viable, you would then likely see clients moving on to performance testing with some of the sensing/sorting vendors at the feasibility study stage.”

Welcoming the independence

Those who understand the pre-concentration space have welcomed the involvement of SRK through its five-step process and, in particular, have highlighted the industry need for standardised and independent testing.

“They see where we are inserting ourselves into stages of the client and vendor relationship,” Dance said. “In no way are we competing with vendors – we are not suggesting we have the expertise they have. Rather, we are looking at the characteristics and amenability elements for the vendors to then truly apply their expertise, knowledge and sensor selection understanding.”

*Adrian Dance, Principal Metallurgist, SRK Consulting (Canada) Inc*

At the same time, Dance and McCarthy are looking to arm mining companies with relevant knowledge about pre-concentration principles, where the process could provide a grade uplift and what losses might be associated with the implementation. This is being done through gaining a better understand of their orebody through the testing.

It should result in mining companies providing a more representative sample to the pre-concentration vendors for the performance testing many of them offer. “Mining companies can then understand these pilot test results more broadly and ask more questions, if needed,” Dance said. At the same time, the vendors have a ‘pre-qualification’ check in hand: they would know from the SRK process if there is a strong basis for carrying out the performance test in the first place.

And, of course, SRK can get involved after the five steps are complete, carrying out small-scale work and integrating these results with the larger
scale performance testing that could eventually underpin a flowsheet developed by a third-party engineering company.

“We view pre-concentration as another aspect of geometallurgy that needs to be interrogated just like comminution and flotation,” Dance said.

The future focus

It is potential changes to both of those processes that could have positive implications for pre-concentration in the mining sector.

“We’re now seeing more flowsheets designed with a multi-stage comminution flowsheet that, at every stage, asks: ‘do I need to process the oversize material again?’” Dance said. “There is an opportunity for the right sensors to answer those questions. That is being highlighted in the design of some of this technology; some newer ore sorting units are reminiscent of cone crushers in size and shape, which means they can be inserted into this flowsheet with ease.

And, of course, some pre-concentration-focused companies have gone upstream of the plant to the pit to provide these readings: an area Dance sees as representing the future.

“Heterogeneity is better preserved the further upstream of the plant you go, so it is obvious to think that pre-concentration technology – which feeds off this heterogeneity – should be placed here,” he said. “The issue comes with getting a representative sample to test – whether that is a shovel load, or the equivalent of what a 200-t payload truck can carry. Ultimately the mining industry is at a ‘prove it’ stage when it comes to pre-concentration technology. The mining companies want to see results on paper or on a screen before they sign off on this technology and process. At the scale of a truck or shovel, this is very challenging.”

McCarthy added: “The Heterogeneity and Scale analysis we are doing in step one of the evaluation will identify some of these opportunities within the selective mining unit sizing, but it is still early days on factoring that into sorting at a truck or bucket scale.”

This work will require closer examination of the drill core than the typical 1-m assayed intervals, as well as a way to estimate the level of mixing that occurs between vertical blast holes, post-blasting, post-loading and post-conveying.

This comprehensive plan is broadening too, factoring in more than just economics.

For instance, SRK has made a case for carrying out the same sizing and XRT analysis included in the five-step evaluation for mill pebbles – which can represent up to 30% of the entire plant feed in some cases – to assess their true value.

This obviously has a cost benefit, as well as an energy benefit – avoiding recirculation of pebbles avoids excess energy use. This same testing is indicating there could be further energy benefits to be had by using preconcentration, too.

In addition, “We have recently expanded our testing protocol to now measure specific energy requirements of the concentrated material compared with the original feed,” Dance said. “This has shown (at times) a softening effect of pre-concentration that can produce measurable savings in power.”

And the impacts on water and energy use are another avenue that could come into the ‘size the prize’ economics McCarthy uses in step two of the five-step evaluation process. “There is no reason to think this could not be included in the analysis in the future; all we would need are the metrics for the existing proposed operation – the amount of water and energy used for the number of tonnes in the mill feed,” he said. “It will then just be a simple case of amending the two inputs based on the pre-concentration work.”

Against a backdrop of falling grades, increasing metallurgical complexity and perceived future demand for commodities, the pre-concentration question needs to be asked by all companies.

For more information on the XRT pre-concentration screening test SRK and Base Metallurgical Labs can provide, as well as the five-step evaluation process for pre-concentration amenability, click the link here

SRK’s stepwise approach to pre-concentration analysis

30th January 2024Bulk handling, Comminution of minerals, Environmental, Mineral processing, Mining services, Sustainable miningAdrian Dance, Base Metallurgical Laboratories Ltd, mineral processing, ore sorting, pre-concentration, SRK Consulting, x-ray transmission, XRTDaniel Gleeson

Having outlined a new vendor-agnostic, lab-based “pre concentration screening test” for mining in part one of this three-part series, SRK is back for part two, discussing the wider pre-concentration evaluation process that this testing fits into

“With any pre-concentration analysis, we need to, first, understand the heterogeneity of the deposit; simply put, if you don’t have heterogeneity, you don’t have the ability to separate the good stuff from the bad stuff and carry out pre-concentration,” Bob McCarthy, Principal Consultant, SRK Consulting (Canada) Inc, says.

With this baseline in mind, SRK Consulting has devised a pathway for companies with drill core at their disposal to analyse whether pre-concentration is a viable option for their flowsheet.

Made up of five steps, this staged approach is deliberately designed to allow companies to pause at the end of each phase to re-evaluate if there is a strong enough case to continue investing the time and finances required.

The heterogeneity analysis is first up, which, under SRK’s evaluation, includes two different approaches based off drill hole analysis: Heterogeneity and Scale and Composite-Sample Relationship Analysis.

“Heterogeneity and Scale involves a process of looking up and down the bore hole at different aggregation distances from every sample and interrogating the sample grade – or net smelter return – against the aggregations above and below that individual sample,” he explains. “We then increase the size of the aggregation to see how that relationship changes.”

Such analysis enables SRK experts to derive the heterogeneity measures typically dubbed ‘waste in ore’ (mineralisation below the cutoff grade within an above cutoff grade zone) or ‘ore in waste’ (mineralisation above the cutoff grade within a waste or marginally below cutoff grade zone). Using a cutoff grade derived from industry benchmarking, the consultants assess the aggregation distance, as resolved in the vertical direction, with the “selective mining unit” (SMU), which typically relates to equipment sizing for mining.

“The pitfall some companies go down is picking your SMU to match an equipment size and production rate typically aligned to a corporate or strategic objective,” McCarthy says. “This could mean generating a 12-14-year mine life for a gold operation, or some other investor-led metric that doesn’t necessarily respect the deposit’s heterogeneity.”

The second approach – Composite-Sample Relationship Analysis – allows consultants to further quantitatively assess those waste in ore/ore in waste heterogeneity measures.

“Those parameters have multiple uses after being determined,” McCarthy says. “For example, they help guide in the sample selection – you can even visualise them in 3D with something like Leapfrog. You can also see contiguous lengths of above or below cutoff grade material in ore zones or marginal waste zones, representing what an ore sorter may see. These would be targeted for testing.”

Responding to industry calls, SRK now offers a step between this fundamental heterogeneity analysis and the test work it can conduct at Base Metallurgical Labs’ Kamloops facility in British Columbia, with what McCarthy calls “size the prize” economics. It provides insight into possible pre-concentration strategy outcomes and, just as important, justification to continue to the next step of lab test work.

This process – carried out by SRK on several projects in the past – is designed to allow the mining company and consultant to test pre-concentration strategies from an economic perspective, assessing if an operation should be removing waste from ore or looking to recover above cut-off grade material from “marginal waste”.

McCarthy added: “It is about answering these questions: is it best to remove waste from mill feed, and to what maximum grade of feed, or to extract mineralised material from marginal, below cut-off grade material that increases the mineral reserve? And, of course, do the expected results of this process look promising?”

Gold is a good example here as the economic case study for pre-concentration often only stacks up when a “cap” is applied to the grade of ore subjected to pre-concentration. In other words, the highest-grade material should not be targeted. Even high-efficiency pre-concentration methods incur some metal loss, and any amount of “loss” that occurs in a gold project is difficult to make-up within a conventional flowsheet.

*Example of drill core intervals showing waste in ore percentages of up to 80%*

The third step in this five-step process is the lab test work McCarthy’s colleague, Adrian Dance (Principal Metallurgist at SRK Consulting), previously outlined in detail in the first article in this three-part series.

The “pre-concentration screening test” leveraging X-ray Transmission based sensor technology can not only indicate pre-concentration amenability, but also provide key inputs into the pre-concentration strategy selection and evaluation, Dance says. He says the testing offers an assessment of pre-concentration potential, as well as an estimate of material bypass and metal upgrade from samples as small as half cores.

Used in conjunction with crushing and screening, this testing rapidly – and cost effectively – assesses the potential for pre-concentration, which can then be applied to scoping or pre-feasibility studies, according to SRK and Base Metallurgical Labs.

Which is where steps four and five of the SRK evaluation – mine planning and mine economics – come in.

“With the heterogeneity measures assigning the distribution of waste in ore, ore in ore, and ore in marginal material in mining block models, the test results reflecting these conditions can be populated into those same models for mine planning,” McCarthy explains.

Typical mine planning steps of pit/stope optimisation, mine design and scheduling can proceed on the assumption of one or more pre concentration strategies, with different versions of mine schedules, reflecting different pre concentration strategies, evaluated.

This type of analysis typically works for a project in pre-feasibility study stage, where engineers can go into the existing block model, bringing the results from the heterogeneity and lab tests into the mine optimisation, design and scheduling process that takes place.

“The challenge is that the scheduling needs to assume a certain strategy – maybe you have determined what that strategy is close enough with the ‘size the prize’, but there are always a few elements you may want to tweak,” McCarthy says. “This could be the mass pull, or waste rejection targets, for instance.”

As a result, sensitivity analyses – mostly numerical tweaks – are embedded in the process.

When not dealing with a pre-feasibility-level project, the SRK team typically rely on an existing schedule that has been run during a scoping study or preliminary economic assessment. This model is modified and tested with different schedule scenarios and pre-concentration strategies based on the heterogeneity measures (step 1) integrated with the lab test results (step 3).

Out of the mine planning step comes a schedule that would go onto the next step: mine economics modelling.

“The model is configured to take in the heterogeneity measures, recovery curves, etc to change the amount of metal reporting to revenue and so forth,” McCarthy says. “Once I get schedules – based on the upgraded block models or it may be a pre-existing schedule – I would then put them into an economic model that has all the levers to pull for different pre-concentration strategies.”

Such a stepwise approach is indicative of where the mining industry is at the moment with vendor-agnostic pre-concentration analysis, enabling companies to get comfortable with the data and assessments as their understanding of their deposit’s heterogeneity grows.

There are potential refinements and fine-tuning opportunities too.

For example, if SRK was gifted with drill core or assay data that was more granular than the 1-2 m intervals typically taken at the exploration stage, it could indicate with greater certainty how particle sorting – typically analysing grades at intervals around a few centimetres – could benefit the deposit in question.

Also, if mine modelling software had matured to the point where block models could be tailored specifically to these waste-in-ore and ore-in-waste characteristics, SRK could segregate the areas in question, instead of applying the type of dilution factors they currently have in place to account for the grade-based realities. This would more clearly communicate the deposit’s heterogeneity to all stakeholders.

Yet, McCarthy and Dance know this will come in time, and are happy to work within the current confines to continue the industry’s education process and identify where the pre-concentration opportunities are

Further discussion on this and what SRK’s pre concentration analysis evaluation – with that embedded pre-concentration screening test – means within the broader mining industry context will follow in the final article in this three-part series later this year

SRK Consulting, Base Metallurgical Labs tackling pre-concentration amenability

31st October 2023Base metals, Mineral processing, Mining services, Mining software, Sustainable miningAdrian Dance, Base Metallurgical Labs, Bob McCarthy, mineral processing, ore sorting, pre-concentration, pre-concentration screening test, SRK Consulting, XRF, XRTDaniel Gleeson

In this first of a three-part series of articles on pre-concentration in the mining space, SRK’s Adrian Dance outlines a new vendor-agnostic, lab-based testing process that could have huge ramifications for a sector in need of guidance and strategy.

Stay tuned for part two in the series, which will see SRK’s Bob McCarthy explain how results of such testing can be used by the mining community.

The need to expand the values or lives of assets while reducing both energy and water use is leading to a flood of new enquiries landing on the doorsteps of the pre-concentration and ore sorting company fraternity.

Anybody that takes a passing interest in the junior mining sector has seen the TOMRAs and Steinerts referenced in numerous TSX-V, ASX and AIM releases, with early-stage test work often detailing results from particle sorting trials.

On the bulk sorting side of the business, more sensor-based solutions are emerging to cope with the need to build or expand copper assets in the most sustainable ways possible. Some progressive companies are including such innovations in initial flowsheet plans.

The bottleneck in the current environment is testing, according to Adrian Dance, Principal Metallurgist at SRK Consulting, with many of the vendors simply overrun with requests to test material or provide modular pilot plants that can be re-located after samples are processed.

At the same time as demand is outpacing supply, there is an argument that a standardised, vendor-agnostic test should be devised to screen for ore sorting or pre-concentration amenability before any vendors are even engaged.

SRK is one company arguing for this.

“At the moment, the manufacturers are driving the action, dictating what the sample has to look like for something that resembles a pilot plant trial,” Dance told IM. “Like any pilot plant run, these trials often give you an excellent result on that specific sample, but the question is: is that sample truly representative of the orebody? Or, is it representative of what a sorter would actually see in operation?”

An increase in available data and transfer of said data across the mine site is going some way to disproving the idea of mass homogeneity at many bulk mining operations – at copper porphyries, for example.

Dance believes this same thought process should be applied to pre-concentration.

This is where SRK Vancouver and Base Metallurgical Labs, both in British Columbia Canada, are looking to provide a “pre-concentration screening test” using X-ray Transmission (XRT) based sensor technology that can not only indicate pre-concentration amenability, but also provides key inputs into the pre-concentration strategy selection and evaluation.

The two companies are offering an assessment of pre-concentration potential, as well as an estimate of material bypass and metal upgrade from samples as small as half cores.

“The testing has two parts to it,” Dance explains. “It was originally designed to see what the grade distribution of fines is after crushing and to see how that grade distribution varies depending on the amount of crushing energy applied to the material.

“The second part is looking to see if the material is amenable to pre-concentration when it is coarse and dry – ie conveyable.”

According to the companies, the XRT-based test can provide this within 24 hours of a sample arriving at the lab.

All of this helps characterise deposits (or low-grade stockpiles) using small samples, cutting down sample mass requirements, and potentially running multiple scenarios to obtain what Dance refers to as the “optimal sort”.

The two companies are not looking to replicate what may be done at one of the sorting vendors’ testing facilities. Instead, they are looking at whether the material wants to respond to this type of particle sorting exercise in the first place and at what size fractions pre-concentration would make sense.

Should the indications prove positive, the information on what appears to be the optimal sort can be passed onto the vendors for more accurate follow-on testing of a bulk sample.

“In this way, we are qualifying the opportunity ahead of the vendors getting samples,” Dance said. “The vendors also have knowledge about how a sample has responded to amenability testing in the first place and what other tests were conducted concurrently.

“We will be providing complementary testing that will, ultimately, benefit the project in question.”

Dance says the aim is to create an industry standard test for pre-concentration that can be replicated by commercial laboratories all over the globe and is carried out routinely with hardness and crushing and grinding testing.

“One of the samples we have already tested was being assessed for rock hardness and we were able to offer them pre-concentration amenability results at the same time,” he said. “We’re not trying to provide the ultimate or ‘perfect’ test; it just needs to be a standard test that can be benchmarked and easily replicated across the industry.

“The value is in the data shared. People want to know how their sample compares with other operations, but this will only come with a large volume of testing.”

While XRT is first up, Dance says the company could soon add an X-ray Fluorescence option to the unit.

And, further out, he is confident this type of testing will open the door to more sensors coming into the mining sector outside of the ones already on offer.

“When we show the electronics industry that we have a viable market by dictating the terms of how we want to sort material through knowledge of such testing, the sensors will come,” he said.

“I’m not saying everyone should implement pre-concentration; far from it, as I expect a minority of the tests will show strong amenability. What I am saying is that everyone should test for it.

“By providing a no licence fee test that has no bias towards any vendor, we are allowing mining companies to scope that out.”

The venture is also part of Dance’s own ambitions to educate the mining sector on its waste-generating ways, he says.

“In the grinding space there is so much material that is recycled throughout the plant inefficiently,” he said. “We must question why we are putting things back in the mill to ultimately take it to tailings.

“There is simply no way we can carry on pursuing the economies of scale argument to reduce our energy consumption and water use. We need to embrace new technology in the right way – not running towards it but walking with purpose and data-backed decisions.”