Tag Archives: heap leaching

Rio Tinto’s Nuton ready to leverage its leaching R&D legacy

More than a few companies and technology providers claim to have solved the primary copper sulphide leaching conundrum, but only one has close to 30 years of R&D and the Rio Tinto name behind it.

Rio, through its Nuton venture, is the latest to table a solution to treat primary copper sulphides such as chalcopyrite, having introduced the company to the sector earlier this year in an attempt at growing the miner’s copper business.

At its centre is a portfolio of proprietary copper leach related technologies and capability that, Nuton says, offer the potential to economically unlock known low-grade copper sulphide resources, copper bearing waste and tailings, and achieve higher copper recoveries on oxide and transitional material. This allows for a significantly increased copper production outcome, according to the company.

One of the key differentiators of Nuton is the potential to deliver leading environmental performance, including more efficient water usage, lower carbon emissions and the ability to reclaim mine sites by reprocessing mine waste, it claims.

Column test work at Rio Tinto’s R&D centre in Bundoora, Melbourne

Adam Burley, Rio Tinto’s Nuton venture lead, said at the core of Nuton is an elevated temperature bioleaching process that can, in the right thermochemical conditions, deliver “peak” copper recovery from primary sulphides such as chalcopyrite.

“Taking advantage of naturally-occurring processes, we have nurtured a culture of microorganisms that establish and thrive in those optimised conditions,” he told IM. “The elevated temperatures are generated by the work of the bacteria; under the base case, we don’t need to heat the heap from external sources, which can often be financially and environmentally costly.”

This leaching core is enhanced by a range of “additives” and expertise that can, for example, deal with high precipitation and cold weather climates.

Having assembled and extensively tested this portfolio, Nuton and Burley are confident enough to state expectations of delivering greater than 80% copper recoveries from chalcopyrite ore with its process.

“This is, from our understanding, some way above the next best leaching technologies available,” Burley said.

The testing behind such numbers is extensive, dating back to 1994 when the company carried out its pilot heap leach operation and developed its initial predictive modelling capabilities at the Kennecott copper mine in Utah, USA.

“Since that time, we’ve conducted hundreds of column tests across tens of orebodies,” Burley said. “We have run columns at a range of scales – a metre high to 10 metres high – and a range of diameters – from tens of centimetres to 5-metre diameter cribs. Some of those range from tens of kilograms to 300 tonnes – large scale with a lot of instrumentation.”

Combining this body of work with a 70,000 t leaching trial the company carried out at Kennecott from 2012 to 2014, Nuton has been able to calibrate its computational fluid dynamic models to accurately predict a range of inputs and outputs for leaching suitability.

“We are left in a position today where we have a high degree of confidence in being able to evaluate the suitability of different ore types and Nuton’s leach response fairly quickly,” Burley said.

This has led to the company going out to market, partnering with companies that own deposits that pass the Nuton thresholds.

The company has signed deals with Lion Copper and Gold Corp, and Arizona Sonoran Copper Company to test out the technology on Lion’s copper assets in Mason Valley, Nevada, and Arizona Sonoran’s Cactus Mine and Parks/Salyer projects, in Arizona.

It has also more recently agreed a pact with McEwen Copper on the Los Azules project in Argentina.

These assets, agreements and potential leaching applications are all different – covering former operating mines and greenfield assets; earn-ins, exclusivity periods and equity stakes; and oxides and sulphides.

“We recognise that due to the high variability of copper deposits and mine waste that one size doesn’t fit all,” Burley said. “A single technology solution is unlikely to perform well at every site.

“Our approach is to work with our partners to understand site-specific characteristics, such as the mineralogy of the available ore and waste, designing a tailored approach by selecting the most applicable technology configuration from within the Nuton portfolio.”

And, according to Burley, these current and future agreements could see Nuton operate the equipment and plant associated with the Nuton process.

“In many cases, we envisage supporting our partners with an end-to-end process, including engineering, build out and operating the gear,” he said.

The test site at Kennecott being prepared and lined ready for the rock to be leached

While the sulphide copper recovery numbers are likely to take the headlines, Burley was able to point out several key differentiators from other leaching solutions targeting minerals such as chalcopyrite.

“Those recovery numbers are a step change, as opposed to an incremental improvement,” he said. “That gives us a lot more optionality in terms of the cutoff grade of the material we can process economically.”

And, with that higher resource utilisation, comes less waste and an overall higher process efficiency, meaning, under certain conditions, Nuton can compete with a pre-existing processing route such as a concentrator, Burley says.

“In some cases, in a greenfield setting, we could see a better economic and environmental outcome than a concentrator, particularly given no tailings or smelting is required, and you could have a finished product produced in country.”

He continued: “Our focus on ESG and our ability to process waste due to that low cutoff grade is one of the key differentiators that opens a whole set of use cases in the legacy mine domain too. Being able to restore and reclaim mine sites by reprocessing waste is very attractive.”

The eventual aim, according to Burley, is to deliver carbon-neutral copper from the Nuton process, yet Rio estimates it can already deliver 0.4 tonnes of CO2 equivalent for Scope 1 and 2 emissions per tonne of Nuton copper produced, compared with a global average of 5.2 tonnes of CO2 equivalent as per standard, conventional primary copper production.

Away from the technical elements, the “partnership” business model Nuton uses also stands out.

Nuton testing up and running at Kennecott (from previously mentioned trials)

“The approach is to work with our partners and assess the value case at specific sites, agreeing a commercial framework that works for everyone,” Burley said. “We are quite open minded as to what that might look like – it could be ownership and equity participation to royalty and licensing type arrangements.

“So, there is the financial strength Rio brings, as well as the deep technical expertise.”

These elements are clearly beneficial to any of Rio’s fellow mining companies that have projects with copper sulphides or those that will be transitioning to sulphide processing in the future, yet a lot of the progress made with these technologies was tied to the development of Rio’s own project, La Granja.

“In that case, part of the resource contains high arsenic and arsenic-related mineralogy,” Burley said of La Granja. “That was the trigger really for a concerted effort to look at an alternative to a concentrate and processing route. We made quite a number of Nuton breakthroughs in our study of that deposit.”

La Granja has been in Rio’s portfolio since winning the right to develop it in 2005, but is not currently in the development pipeline.

Asked if other assets within the company’s portfolio are potential Nuton candidates, Burley answered: “The potential exists to deploy Nuton within the Rio Tinto copper portfolio. We are currently evaluating a number of internal deployment options across our assets and joint ventures, but we also recognise the full value potential of Nuton – environmental and social, as well as financial – lies outside of the Rio Tinto portfolio.

“To capture the full size of prize that Nuton offers, we need to go out to market, which is what we have been doing pretty aggressively throughout the year and will continue to do going forward.”

Antofagasta readies primary sulphide leaching technology options

The ability to leach primary copper sulphides has, on many occasions, proved a hurdle too much, with conceptual work in the laboratory or pilot scale falling down on sub-economic or volatile recovery rates when working out in the field.

This problem tends to result in one of two things: new capital-intensive concentrators are brought into process these sulphides, or brownfield oxide operations are drafted up that prolong existing leaching operations for a few more years when – hopefully – copper prices are higher.

Antofagasta has come up with an alternative option that leverages chloride-based reagents and 20-years of knowledge leaching secondary sulphides.

Called Cuprochlor®-T, the proprietary process has undergone five years of intense development leading to the point that the company is now open to talking about its potential.

It leverages off the first iteration of leaching technology Antofagasta devised for secondary sulphides – Cuprochlor.

Cuprochlor, which is now working at the Michilla mine in Chile (which Antofagasta sold in 2016), effectively binds together the particles of mineral – particularly fine in the case of Michilla – into a porous but manageable material that can then be heap leached. The agglomeration is achieved by mixing the mineral and leach solution with chloride salts and sulphuric acid, which react to form a plaster-like paste.

Over the years, the process has been refined, going on to consistently deliver recovery rates of around 90%.

Sitting on an expansive base of primary sulphide resources – mainly chalcopyrite – and the success of Cuprochlor, Antofagasta, around five years ago, began a series of tests, adjusting variables such as temperature, reagent concentrations and particle size to see if the chloride leaching process could be adapted for the treatment of primary sulphides.

Temperature proved to be one of the keys, with tests showing that by elevating the temperature of the heap to around 30°C, Cuprochlor-T was able to stimulate the required chemical reaction for recovering copper from primary sulphides such as chalcopyrite.

Another key differentiator between the two chloride leaching technologies is the “reagent recipe” and particle size distribution (PSD), Alan Muchnik, VP Strategy & Innovation for Antofagasta, told IM.

“Providing a constant temperature throughout the process is very important, but the real innovation is the approach we have used,” he said. “It involves a combination of factors, including, among others, the recipe for reagent concentrations and the required PSD.”

While not wanting to reveal the ‘secret sauce’, Muchnik said the PSD consideration goes beyond the usual P80 industry reference point.

It is this balance that has landed the company with recoveries of over 70% after approximately 200 days of leaching on the heap in test work.

Muchnik expanded on this: “The Cuprochlor-T process, in simple terms, involves leaching in a chloride environment – where there are no passivation layer bonds. This allows for the copper, iron and chloride ions to react, which, at a controlled temperature, results in the economic production of copper.”

This is through three stages:

  • First up is an agglomeration stage where the necessary reagents are added and are left to rest at a constant aeration and temperature;
  • Second, the ore is irrigated intermittently with continued aeration, also maintained at a constant temperature; and
  • Finally, after 200 days, the ore completes the leaching cycle and allows the company to obtain recoveries of 70% copper or more.

What started with laboratory testing and progressed to pilot testing and a “semi-industrial” test on several different heaps at Centinela has recently concluded with an industrial test of over 40,000 t of primary sulphide material averaging 0.4% Cu – containing more than 90% chalcopyrite – that, using the same process outlined by Muchnik, showed consistent recoveries of over 70%, he said.

Alan Muchnik, VP Strategy & Innovation for Antofagasta

Asked if the company is eyeing even higher recoveries that can compete with the levels Cuprochlor is achieving on secondary sulphides, Muchnik said it was all about an economic tradeoff.

“It may be possible to hit such a percentage [as Cuprochlor], but that is not the aim or expectation with the kinetics we are currently seeing in Cuprochlor-T,” he said. “There is always a tradeoff between the length of irrigation time, the PSD and the recoveries, all of which are related to capital costs, operating costs and the payback associated with the process.”

The Antofagasta planning and operations teams have now got their hands on the Cuprochlor-T ‘licence’ and will be busy outlining potential deployments for consideration in the company’s annual planning cycles.

There are some obvious places to start.

The Zaldívar open-pit, heap-leach copper mine, 175 km southeast of Antofagasta, is currently in the process of transitioning to chloride leaching operations with Cuprochlor.

The project, which includes an upgrade of the SX plant and the construction of new reagent facilities and additional washing ponds for controlling chlorine levels, was completed in January 2022 and is now being commissioned. It is set to boost copper recoveries by approximately 10 percentage points, increasing production at Zaldívar by around 10,000–15,000 t/y over the remaining life of mine.

“In addition to transitioning to chloride leaching with Cuprochlor for secondary sulphides, we are currently progressing studies for the primary sulphide orebody that currently lies below the Zaldívar reserves to prove if Cuprochlor-T leaching can work,” Muchnik said. “Within our resource base, there are approximately 460 Mt of primary sulphide resources declared here.”

Both Centinela and Antucoya have primary sulphide resources and existing heap leach and SX-EW facilities that would fit the Cuprochlor-T blueprint too.

Muchnik said: “One of the technology attractions of Cuprochlor-T is the ability to use otherwise idle leach pad and SX-EW capacity. That it is the scale limitation at our current operations, but the technology can be gradually deployed within a plant that is already adapted for chloride leaching, phasing this in during the life of mine to fit requirements.

“It provides an ongoing adoption process option rather than an immediate infrastructure project that sees an operation shift from oxide leaching to a different kind of heap leaching in one go.”

The advent of Cuprochlor-T does not mean the company will completely drop potential concentration projects, Muchnik clarified, highlighting the second concentrator project currently subject to a feasibility study at Centinela.

In addition to the capital and operating cost benefits that would come with Cuprochlor-T over the concentration route, there is likely to be a sustainability benefit.

“It’s only an indicative reference as each case is different, but you would expect the energy consumption associated with Cuprochlor-T leaching and SX-EW treatment to be less than half of the normal route of copper concentration and SX-EW,” Muchnik said.

In this respect, it is a favourable consideration for Antofagasta’s long-term carbon-neutral goals.

While each potential Cuprochlor-T implementation will have to go through corresponding project studies, Muchnik was confident in predicting that new copper from Cuprochlor-T would be produced this decade.

With five years of substantial testing under its belt, not many metallurgists would bet against him.

McEwen Mining progresses gold-silver heap leach plan at Fenix

McEwen Mining looks to have found a way to prolong its operations at the El Gallo Complex in Sinaloa, Mexico, with the feasibility study for its 100%-owned Fenix project highlighting a 9.5-year operational blueprint.

Using gold and silver prices of $1,500/oz and $17/oz, McEwen has estimated an operation able to produce 26,000 oz of gold production in phase one (years one to six) and 4.2 Moz of silver-equivalent in phase two (years seven to nine-and-a-half).

Phase one comes with an initial capital bill of $42 million and an all-in sustaining cost (AISC) estimate of $1,042/oz of gold. Phase two would require a $24 million incremental capital injection in year six, with the AISC calculated at $14.28/oz of silver-equivalent.

The company’s El Gallo mine (pictured) produced 240,000 oz of gold and 125,000 oz of silver from 2012-2017, yet, due to the transition to deeper sulphide mineralisation not amenable to heap leaching, mining and crushing activities ceased in the June quarter of 2018.

While residual heap leaching is set to continue to produce gold for several years, the company has been working on a new project for the El Gallo Complex, which is where Fenix comes in.

The Fenix 2018 preliminary economic assessment evaluated the potential extension of production in the complex, based on a two-phased transformation of the processing from the El Gallo mine, innovative in-pit tailings disposal and sourcing from several deposits.

The latest feasibility study has run with that plan, with the critical path environmental permits in hand for the first phase of production, according to Rob McEwen, Chairman and Chief Owner of McEwen Mining.

“Our next steps will involve detailed engineering, assessment of procurement options and the evaluation of financing alternatives,” Rob McEwen said.

He added: “The project will incorporate an environmentally progressive method of tailings management, using in-pit storage that creates multiple benefits, most importantly a secure containment of tailings, enabling better reclamation results.”

Corvus Gold weighs heap leach, BIOX route at Mother Lode project

Corvus Gold has announced the results of a preliminary economic assessment (PEA) for its Mother Lode project (MLP) in southwest Nevada, USA.

The study outlines a project able to produce 170,980 oz/y of gold and 79,600 oz/y of silver through a combination of heap leaching and biological oxidation (BIOX).

Based off measured and indicated resources of 1.55 Moz of gold and 1.51 Moz of silver, and inferred resources of 170,000 oz of gold and 400,000 oz of silver, the study estimated an operation with an eight-year mine life and an initial price tag of $406 million. Using a $1,500/oz gold price, the payback period was estimated at 2.7 years.

Jeffrey Pontius, President and CEO of Corvus, said: “The results from our initial PEA study of the Mother Lode standalone project are encouraging. The potential projected annual gold production of over 200,000 oz/y during the first three years is significant, especially as a new project, which could provide an increase to the Corvus Gold future production profile. The PEA demonstrates the preliminary potential for the project, on its own, to produce significant free cash flow and after-tax NPV.

“Corvus now has a number of strategic alternatives available to it to drive shareholder value. Given the recent interest in the Bullfrog Gold District from multiple producing companies with adjacent land packages, Corvus’ compelling and accretive projects and its commanding land position with what we believe is demonstrated high exploration potential, has positioned the company to deliver increased shareholder value.”

The Mother Lode project is modelled as a large, open pit, with a biological oxidation mill to treat the higher-grade sulphide mineralisation and a heap leach pad for treatment of oxide mineralisation. The mining plan uses standard mining practices and has a production scale that is currently being used by many operating mines, the company said.

The new PEA study, which assumes a standalone project, also includes a number of other changes to the previously assumed concept for the combined Mother Lode-North Bullfrog project configuration, which enhance the project. This includes:

  • Employing BIOX to treat the MLP sulphide mineralisation would increase gold recovery by 11%. Metallurgical testing of a stirred BIOX process on the MLP whole sulphide mineralisation from Mother Lode demonstrated gold recoveries of 91-92% as compared with the previous testing on MLP flotation concentrate;
  • Eliminating the need for the concentrator, oxygen plant and autoclave components of the previous plant concept simplified the plant conceptual design and would reduce the process plant capital cost;
  • Ongoing work expanding Mother Lode resources in the CIZ area and the main Zone with ongoing work at improving the open-pit mining and development plans will enhance project economics; and
  • New experimental work on conducting the BIOX process in a heap is being tested as follow-up on past successful studies and could substantially cut operation and capital costs with the elimination of the mill circuit.

The PEA only includes drill results completed up until September 2020. In addition, Corvus will continue follow-up mineral resource expansion work and new discovery drilling on priority targets at both the North Bullfrog and Mother Lode properties through 2021, it said.

Rio2 to test Sixth Wave’s IXOS polymer tech at Fenix heap leach gold project

Sixth Wave Innovations Inc and Rio2 Ltd have executed a non-binding Letter of Intent for the trialling of Sixth Wave’s patented IXOS® purification polymer at the Fenix gold project in Chile.

Under the terms of the LOI, Rio2 will send representative ore samples from its Fenix project to Sixth Wave for testing and analysis in its Salt Lake City, Utah, facility. Sixth Wave will perform a combination of leaching and recovery tests using its IXOS technology on these samples consistent with protocols for the expected heap leach mining activity planned for Fenix.

Upon completion of the testing, to be performed in October, and pending positive results, the two companies will work to negotiate a definitive agreement to proceed to a complete on-site pilot adsorption/desorption/recovery (ADR) plant scaled to operate on a 400 t pilot leach pad.

A prefeasibility study on Fenix outlined a heap leach gold mine producing an average of 93,000 oz/y during the first 13 years and 50,000 oz/y during the final three years of production as stockpiled ore is being crushed and leached.

IXOS, meanwhile, has been demonstrated to capture up to 99% of gold from cyanide leach solutions in laboratory and mine site testing where the data was analysed by the mine operator, representing a material increase relative to activated carbon, which recovers between 85% and 95% of the gold, as reported by potential mining customers of IXOS. Additionally, the increased selectivity of IXOS results in the capture of fewer other competitive base metals, Sixth Wave says.

Testing at multiple mine sites has shown more than 90% gold purity captured on IXOS, as opposed to 40%-70% for those generated by activated carbon, resulting in efficiencies in the refining process used to generate higher purities of gold.

The objective of this work, from Rio2’s perspective, is to determine whether Sixth Wave’s IXOS technology can be successfully applied to enhance the extraction of gold from Fenix gold ore by using molecularly imprinted polymers rather than traditional carbon for the gold adsorption process.

If successful, the application of IXOS is expected to result in a reduction of capital expenditure and operating expenditure related to the gold extraction process.

Upon successful completion and positive results of the pilot program, the companies would then move to an implementation phase incorporating IXOS into the actual processing plant to be constructed at Fenix.

Dr Jon Gluckman, President and CEO of Sixth Wave Innovations Inc, said: “We are very excited about this project and working with Rio2. The IXOS process should excel in comparison to traditional activated carbon because of the high rejection of base metal and scaling and the smaller process plant required for IXOS. Substantially lower power consumption in the desorption and recovery stages, and no need for regeneration, will also play a large role in reduced opex.”

He added: “It is exciting to be involved with Rio2 at this phase of the Fenix gold project as it allows us the ability to optimise the design of the ADR circuit without having to worry about retrofit constraints.”

Alex Black, President and CEO of Rio2, said: “Rio2 is always looking to embrace and trial new technology with the objective of bringing enhanced value to our stakeholders through the reduced capex/opex opportunities that innovative technologies can bring.

“The Fenix gold project is currently the largest undeveloped gold heap leach project in the Americas and we look forward to working alongside Sixth Wave during the development phase of the project.”

Hycroft Mining ups the proprietary heap leach process ante

Hycroft Mining Holding Corp has continued to demonstrate the viability of its proprietary heap leach oxidation process at its Hycroft gold mine in Nevada, USA, over the June quarter, with the company hitting several milestones.

The Hycroft gold-silver mine was restarted in 2019 to demonstrate this process, which oxidises sulphides prior to leaching, on a commercial scale. Based on the success of initial operations and a 2019 feasibility study, Hycroft began implementing the long-term mine plan with the start of construction in April 2020 of the first phase of a large leach pad capable of processing the resource base with more than 30 years of mine life.

While gold and silver production fell below expectations over the period, the company was able to demonstrate the process on initial leach pads one and two at Hycroft, achieving higher than feasibility level gold recoveries for Brimstone ore (82% versus 65% in the feasibility study) and Central ore (91% versus 70% in the feasibility study).

It also improved the solution management system to increase solution distribution to the leach pads, while commencing the leach pad expansion on the north side of the mine in anticipation of starting heap leach stacking in the December quarter of 2020, Hycroft said.

The expansion project will provide the company with the leach pad space required for future operations, the company added.

“The initial stage of the leach pad project is being constructed in two phases by a contractor, with the first phase consisting of approximately 4 million sq.ft (3.7 million sq.m) of pad space and infrastructure for ponds, pipes and electricity, and the second phase consisting of approximately 4.6 million sq.ft, which we expect to construct in 2021,” the company said.

“With respect to the first phase, we expect the earthworks and leach pad construction to be completed in the fourth (December) quarter of 2020 and infrastructure completed and initially commissioned shortly thereafter.”

On the process side, the downstream process infrastructure is in place to ramp up operations. Hycroft is currently operating the Brimstone Merrill-Crowe facility and refinery, but it has begun planning to restart the 21,500 gallons/min (1,629 l/s) North Merrill-Crowe plant in 2021 to meet increasing solution flows from the new leach pad.

To facilitate these heap leach changes, the company expanded its mining fleet with the rental of seven 240 ton (218 t) trucks and one loader to increase mining capabilities over the quarter. It also improved its mobile equipment maintenance team to transition to self-performed maintenance and discontinue the contractor-led maintenance applied since start-up. Lastly, it began active in-pit drilling and blasting of fresh ore and reduced the mining of stockpiles.

On the crusher side, it refurbished and recommissioned the crushing system, which saw the average amount of material crushed go from 338,000 tons/mth (306,628 t/mth) in the March quarter to 459,000 tons/mth in the June quarter, an increase of 36%. It also established a comprehensive preventative maintenance program and initiated an ongoing operator training program to improve crusher efficiency and reduce downtime.

Steve Jones, Interim President and CEO of Hycroft Mining, said: “There have been a number of improvements at the mine recently that are building a strong foundation for the next phase of operations, including adding experienced technical people and increasing the reliability of process infrastructure.

“While the next few months are still considered to be transitional, we are looking forward to utilisation of the new leach pad and being able to ramp up to feasibility study operating levels.”

Centerra Gold’s Öksüt mine comes to life with first pour

Centerra Gold has achieved the first gold pour from its Öksüt mine, in Turkey, on schedule and ahead of budget.

Additionally, the project achieved a significant safety milestone last week, achieving two million work hours lost time injury free.

Scott Perry, President and Chief Executive Officer of Centerra, said: “This is an important milestone for the project and for the growth of the company as Öksüt is now our third operating mine and our third source of gold production going forward. Reaching the first gold pour is a testament to the dedication and hard work that our Öksüt team has put in to reach this goal safely.”

He added: “This milestone would not have been achieved without the initial conviction and perseverance from the Centerra exploration team given that the Öksüt mine, originally started as a greenfield exploration venture in 2009.”

Öksüt was planned as a conventional truck and shovel open-pit heap leach mining operation with a stacking rate of 11,000 t/d. The initial eight-year mine life was expected to process around 1.2 million contained ounces of gold from two open pits, the Keltepe pit and the smaller Güneytepe pit.

BHP’s Jurgens presents big picture automation plan

Diane Jurgens, BHP’s Chief Technology Officer, used her time on stage at the Bank of America Merrill Lynch SmartMine conference, in London, to highlight the company’s plan to introduce full or partial automation across its entire value chain.

The miner has already introduced automation across many of its operations – from haul trucks at Jimblebar (Western Australia) to drill rigs at Western Australia Iron Ore – but Jurgens said the company has bigger automated plans.

This includes considering opportunities to accelerate truck autonomy across the company’s Australia and Minerals Americas sites – the company previously detailed plans to automate around 500 haul trucks across its Western Australia Iron Ore and Queensland Coal sites – and introducing “Decision Automation” to link autonomous processes and data from different sources together to create “near instantaneous, optimised decision making”, Jurgens said.

While she talked up the use of automation in mining – referencing the experience she has in the automotive and aerospace industries – she admitted full automation across the BHP group was unlikely.

“This is because we automate equipment and processes where it provides the highest value,” she said, explaining that investment in technology competes against all of other projects in the BHP portfolio, “and alternative uses of cash, under BHP’s Capital Allocation Framework”.

To test this, the company has built proving grounds at two active mine sites (Eastern Ridge in Australia and Escondida in Chile) to trial new innovations in geology, extraction and processes, and “develop workforce capability so that our people are equipped for the rapid pace of change that lies ahead”, Jurgens said.

Just some of the new innovations Jurgens mentioned included the use of advanced geophysics modelling to reanalyse existing drilling data. This new approach led, in November last year, to the Oak Dam copper discovery, near its existing Olympic Dam operations in South Australia.

Recently, sensors were installed at the Escondida test grounds to prototype the use of real-time data to analyse the quality and grade of ores and inform, for example, whether to divert unprocessed ore for leaching, to concentrators or waste. Jurgens said: “The key to achieving this is using data collected through the sensors and combining it with proprietary algorithms. We then apply our knowledge of the ore body to optimise the processing methods. Once in production, we expect these to improve throughput performance.”

With access to more detailed data on extracted material, machine algorithms can automate decisions to identify and divert waste, which increases plant performance and reduces processing costs, she added.

New patented leaching technologies have, meanwhile, increased metal recoveries by 10-12% and shortened the processing time by 50%, according to Jurgens. “At Spence in Chile we increased copper recoveries by about 10% and helped offset grade decline through implementing the low-cost Spence Recovery Optimisation project,” she said. “The initiative improved heap leach kinetics which meant we could maximise utilisation of the leach pads and therefore use the full 200,000 t of tankhouse capacity.”

This breakthrough also informed the successful heap leach trial at Olympic Dam, which the company has just completed.

The company’s automation and innovation journey has already resulted in significant wins, according to Jurgens.
Equipment automation is creating more efficient, standardised and safer operations, she said:

  • Autonomous blast hole drills across BHP’s Western Australia Iron Ore assets have increased drill rates by 25%, and reduced monthly drill maintenance costs by over 40%;
  • Haulage automation at the Jimblebar operation, in the Pilbara, has reduced heavy vehicle safety incidents by 80%;
  • Machine learning is being applied to maintenance on trucks in iron ore and coal – to analyse component failure history;
  • At Yandi, haul truck maintenance analytics increased truck availability to above 90% and generated recurrent cost savings. Replicating these strategies to our trucks in energy coal in the Hunter Valley, BHP has also seen an increase in truck availability;
  • Automating key components of BHP’s rail network is supporting increased capacity, more reliable dispatch and improved maintenance outcomes;
  • In Western Australia, material density scanning and laser precision have delivered an additional 2.4 t of iron ore per car while reducing safety risks of overloading;
  • The automated rail network scheduling system, which controls over 10,000 ore cars and transports about 270 Mt/y of iron ore, is becoming more effective through self-learning algorithms, ensuring trains arrive at port, on-time, and;
  • LiDAR technologies are being used to automate the loading of ships that transport BHP’s product to customers around the world.

BHP and Bureau Veritas confirm heap leach viability for Olympic Dam

BHP says it has successfully completed its heap leach research and development trial in South Australia, confirming the viability of the technology to extract copper, uranium, gold and silver at Olympic Dam.

The program began in 2012 and was conducted at a purpose-built, small-scale heap leach facility at Wingfield run by Bureau Veritas, under direction from BHP and with support from the South Australia Government.

BHP’s General Manager of Olympic Dam’s Surface Processing, Chris Barnesby, made the announcement at the Copper to the World conference in Adelaide on June 18.

“The promising results from this trial supports our positive outlook for Olympic Dam, given forecast demand increases for copper and the optionality we are building for this world-scale resource,” he said.

“We safely and successfully produced 19 t of good quality copper, most of which went back into the smelter and off to customers, though we kept a little to ourselves to commemorate the achievement.”

Despite the success of the project, Barnesby said the deployment of such technology was a “matter for future consideration”, explaining that there were many factors involved in making this decision, including “passing through our Capital Allocation Framework”.

He concluded: “As it stands today, we have confirmed the viability of a technology with the potential to join our suite of growth options. However, our immediate focus is on operating safely and reliably, and setting a foundation to unlock more value for BHP and for South Australia over the long term.”

Heap leaching works by drip-feeding acid through a large stockpile (or heap) of ore to leach out metals. BHP uses heap leaching at its copper operations in Chile, however Olympic Dam’s polymetallic properties require a different approach, according to the miner.

BHP said: “The research and development program has the potential to benefit the mining industry more broadly in South Australia, as heap leaching has the potential to deliver lower capital and operating costs, increased scalability, reduced potable water use and the ability to process lower-grade ores.”

Separate to the trial, BHP continues to progress studies on the Brownfield Expansion project, or BFX, as part of Olympic Dam’s resource development strategy, which seeks to potentially increase production to between 240,000-3000,000 t/y of copper.

Eldorado Gold to continue heap leaching operations at Kisladag

Eldorado Gold has decided to resume mining, crushing, stacking and heap leaching at its Kisladag gold mine, in Turkey, and suspended plans to build a $500 million processing plant.

The decision comes following the receipt of metallurgical test work on material placed on the heap leach pad last year.

Not only will this move defer a significant amount of capital expenditure for the company, it is also expected to help production rise to 390,000-420,000 oz in 2019, compared with 349,147 oz in 2018, a year when Eldorado suspended mining operations at Kisladag due to lower than expected gold recoveries.

Eldorado’s President and CEO, George Burns, said: “The decision to restart mining and heap leaching at Kisladag is supported by improved heap leach recoveries and confirmed by a revised heap leaching plan developed in early 2019. The revised heap leaching plan results in favourable economics when compared to milling, without the risks associated with the construction and financing of a $500 million project.”

On October 23, 2017, the company provided an update on Kisladag operations based on laboratory testwork undertaken during the September quarter of that year, which indicated that lower recoveries were expected from the zone of mineralisation located around the base of the open pit where mining was underway.

Based on available information, in the March quarter 2018, Eldorado elected to suspend mining in order to evaluate processing options. Following a year of engineering and testwork, in October 2018 the company announced that the Board of Directors had approved the advancement of a mill project. Subsequent to that announcement, gold recovery from the leach pad increasingly exceeded expectations. The company then focused testwork and analysis on the viability of resuming mining and heap leaching at Kisladag.

In parallel to mill engineering and analysis, testwork to extract maximum value from material already placed on the heap leach pad and the remaining reserves was ongoing throughout 2018.

Approximately 900,000 t of ore was placed on an inter-lift lined test pad in the March quarter of 2018. Late in the year, results from this pad were showing recoveries of approximately 58% from an extended leach cycle approaching 250 days (compared with around 40% recoveries from the original 90-day column tests).

In early 2019, the company analysed the new data and developed revised heap leaching plans, showing improved economics for the heap leaching scenario, hence the recent decision.

Eldorado said mining was expected to recommence by the end of this quarter, with the three-year guidance of 145,000-165,000 oz (2019), 240,000-260,000 oz (2020) and 75,000-95,000 oz (2021) based on mining and stacking an initial 22 Mt of ore grading over 1.1 g/t over this period, as well as continuing to leach the material currently on the pad.

This would help overall group production go to 390,000-420,000 oz in 2019, 520,000-550,000 oz in 2020 and 350,000-380,000 oz in 2021.

Eldorado said on Kisladag: “While the mill project has been suspended, the project remains viable in the short-term. The viability of the mill project will continue to be assessed in light of the results from ongoing heap leach metallurgical testwork on deeper material and in view of other investment opportunities within the portfolio,” the company said.

The other piece of exciting news within the company’s results was developments at its Lamaque mine in Quebec, Canada.

The company poured first gold from the Sigma mill at Lamaque in December and, in the March quarter, the mine is expected to declare commercial production. This should set the operation up to produce 100,000-110,000 oz of gold in 2019 from the mining and processing of over 500,000 t of ore at an average grade of 7 g/t Au.

Burns said: “At Lamaque, we are very pleased with the performance of our project team who delivered the first gold pour from the Sigma mill in less than 18 months since acquisition.”

In addition, exploration success at Lamaque – which includes significant resource conversion in the C5 orebody, in particular – has led the company to review options to increase throughput at the Sigma mill.

Eldorado said: “The mill has a refurbished nameplate capacity of 2,200 t/d and the potential to expand to its former capacity of 5,000 t/d with a purchase and installation of a SAG mill. Based on planned drilling and the potential conversion of inferred resources in C4, C5 and C6, the company expects to explore options to increase mill feed.”

The Lamaque underground mine is currently expected to produce 125,000-135,000 oz of gold in both 2020 and 2021.