Tag Archives: leaching

Draslovka about to move into glycine leaching mining demonstration phase

Czech Republic-based Draslovka Holding is heading into a busy 12-month period where its glycine leaching technology will be showcased at numerous mining projects across the globe, the company told IM on the side lines of the Resourcing Tomorrow conference, in London, this week.

According to Ivor Bryan, Director of Mining Innovation at Draslovka Mining Solutions and the former MD of Mining & Process Solutions (MPS), the entity responsible for the development of the GlyCat™ and GlyLeach™ technologies, the company is embarking on around 10 projects in the mining space, which will prove up the 3,500 hours of testing that has been conducted at MPS’ facilities in Perth, Western Australia.

MPS was acquired by Draslovka, a major sodium cyanide producer in 2022, with the aim of the transaction being to grow and develop the glycine leaching business.

Gold leach testing via GlyCat has been the major area of focus over the last decade. The process was invented to reduce cyanide consumption while maintaining gold recovery for gold ores from deposits containing nuisance copper. It has been designed to enhance the dissolution of gold and copper in gold/copper ores where glycine is used as a catalyst with cyanide in a cyanide-starved leaching environment. It doesn’t replace cyanide, but, in fact, enhances its leaching capabilities by dealing with the high-cyanide consuming copper within these gold-copper orebodies.

Yet, the company is also now starting to make inroads into the base metal space through GlyLeach, with nickel and cobalt two specific areas of interest. The technology is able to leach the targeted metals with enhanced selectivity compared with conventional methods. It will solubilise copper, nickel, cobalt and zinc, while gangue minerals such as iron, manganese, silicates and carbonates remain in the leach residue, Draslovka says.

This is allowing the company to promote that it can reduce the capital expenditure associated with processing these metals by removing the need for smelting, or in the case of tailings deposits, helping recover metal from assets previously written off as ‘waste’.

While the technology could have applications at run of mine operations, Bryan and his colleague Jackson Briggs, Corporate Development Manager of Draslovka, believe the most immediate opportunity is in tailings where the application of glycine leaching on ‘waste’ material could recover valuable metals while reducing the potential liabilities associated with such storage facilities.

Of the 10 or so projects the company has ahead of it, one is situated in Western Australia where the company is looking to recover nickel and cobalt metals from a tailings deposit of a major mining company.

Another project – much closer to fruition – is in Chile and involves leaching a carbonate-hosted copper oxide deposit containing some 600 t of material.

In both cases, the company is looking to demonstrate that it can recover valuable metals at high recovery rates, with low impact – namely rationalising reagent and water use and, in the case of nickel-cobalt, removing smelting from the equation.

This, according to Draslovka CEO, Pavel Bruzek, is a “win-win” for mining companies and their stakeholders, benefitting both the balance sheet and the operational environmental footprint.

“While we are a major sodium cyanide producer, when we saw the potential of MPS’ glycine leaching technology and the increase in metallurgical complexity of orebodies looking to be exploited, it made perfect sense to work with and promote this technology,” he told IM. “It is the responsible thing to do for the industry.”

Rio Tinto’s Nuton to test leaching tech at McEwen Copper’s Los Azules project

McEwen Copper’s Los Azules project in Argentina looks like becoming the latest potential leaching asset put under the Nuton® Technologies microscope after the signing of a collaboration agreement between McEwen Copper and Nuton.

The agreement, tied to an oversubscribed $81.85 million offering of McEwen Copper shares, will see Nuton, a Rio Tinto Venture, test its technology for compatibility with Los Azules copper mineralisation.

Nuton, for its part, also contributed $25 million into the funds raised by McEwen Copper.

Rio Tinto’s copper leaching technology venture has been in the headlines of late, signing deals with, among other companies, Arizona Sonoran Copper Company Inc and Lion Copper and Gold, to test out its solutions.

Nuton is aimed at growing Rio Tinto’s copper business. At its core is a portfolio of proprietary copper leach related technologies and capability – a product of almost 30 years of research and development.

Rio says the Nuton technologies 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, allowing for a significantly increased copper production outcome, according to Rio. 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, Rio claims.

McEwen Copper and Nuton will jointly undertake copper leach testing using Nuton Technologies with samples from Los Azules. McEwen Copper has agreed to grant exclusivity to Nuton for one year in the area of novel, patented or trade secret leaching technology, while it will continue its independent test work and studies using conventional leach technologies.

McEwen Copper Chief Executive, Rob McEwen, said: “We recognise the potential opportunity of using Nuton Technologies to produce copper in greater amounts, more rapidly, and with less impact on the environment and water resources. I trust that our relationship with Nuton and Rio Tinto will accelerate the process of realising the enormous potential of Los Azules.”

Rio Tinto Chief Executive Copper, Bold Baatar said: “This agreement will allow us to evaluate the potential to commercially deploy Rio Tinto’s innovative Nuton Technologies for copper leaching in McEwen Copper’s planned development of Los Azules. Our Nuton Technologies have the capacity to unlock increased copper production for Rio Tinto and our partners, with a low carbon footprint and leading environmental performance.”

The next milestones at Los Azules are the upcoming drilling season from October 2022 to June 2023, the completion of an updated preliminary economic assessment early in the March quarter, and the planned initial public offering of McEwen Copper in the first half of 2023.

Los Azules’ current copper resources are estimated at 10.2 billion pounds (4.6 Mt) at a grade of 0.48% Cu (indicated category) and an additional 19.3 billion pounds (8.8 Mt) at a grade of 0.33% Cu (inferred category).

Orica’s Chemicals business eyes new complementary opportunities

Orica’s Investor Day, taking place last week, highlighted potential growth areas in one of the company’s less-publicised ‘verticals’, its Chemicals business.

Mining, Quarry & Construction and Digital solutions often steal the headlines in quarterly updates, but Adam Hall, Group Executive & President of Asia & Chemicals, showed there is plenty going on within the company’s fourth vertical.

This business, which covers the fields of ore processing, chemical stabilisation and recovery & treatment, strengthens Orica’s presence across the mining value chain, having a strong alignment with its global footprint and understanding of customer needs, the company says. It also acts as a complementary component of Orica’s “new solutions offerings”.

Orica’s current exposure is to leaching agents and emulsifiers, with cyanide making up its biggest product today.

As one of the largest producers of sodium cyanide for mining, Orica delivers the leaching agent in briquette form in circa-1 tonne boxes that are easily containerised, or within an Orica-designed Sparge isotainer system, or in liquid form via purpose-built iso tanks suitable for safe road or rail transport around the world.

It relies on the Yarwun, Gladstone Cyanide Manufacturing Facility in Queensland for this supply, which has an annual capacity of 95,000 t/y and is compliant with ISO9002 and the International Cyanide Management Code. This facility is complemented by the company’s sodium cyanide transfer stations in Peru, Ghana and Malaysia.

Hall was positive about potential growth opportunities in the cyanide space, explaining demand for cyanide was expected to outpace the predicted growth in gold ore treated to 2026 as the complexities involved with treating orebodies continued to increase.

He said the Yarwun facility had great brownfield growth opportunities around the site, with the company evaluating potential expansions in the region of “high single digit” or “low double digit” percentages.

Hall was equally positive about cyanide retaining its presence in the gold leaching process, saying that, while substitution questions continued to come up, the realities associated with such a transition meant it was infrequently feasible.

“There is one major mine that has switched away from using cyanide into a different reagent,” he said. “That cost them north of $100 million, and our understanding is they would not necessarily do it again. Also, that specific mine has a certain lithography that lent itself to using that reagent.”

Hall said Orica’s emulsifiers – which allow it to differentiate its explosives products through maintaining the stability of the mixture – represented “a small but mighty part” of the company’s product suite. He saw potential growth opportunities for emulsifiers, which he said contained the “secret sauce for emulsification”.

Outside of these two Orica mainstays, Hall highlighted the potential for Orica to play in both flotation and solvent extraction markets as part of growth opportunities that added up to A$23 billion ($16 billion).

In flotation, collectors, frothers and flocculants are integral to optimising the process. The same can be said for solvent extractants in the SX space.

“We see all of these as potentially interesting for Orica,” Hall said. “These are all big fields…but each of them has something we could potentially partner or bring to our clients, and something we will be looking to do over the next five years or so.”

Partnerships could potentially see Orica team up with big chemical players that have a by-product or comparatively small value stream coming out of an integrated facility where Orica could bring its “deep understanding of what the miners need and how we can deliver against that using the products that are produced”, he explained.

This could see Orica act as an agent, an offtaker, or purchaser of the by-product production unit.

As with all other Orica verticals, the Chemicals business will be looking at any potential bolt-on to the emulsifier and cyanide offering as a way to influence more of the value chain, ensuring changes made up- or down-stream provide value throughout the full flowsheet.

Draslovka eyes base metal leaching prize with MPS glycine technology

Draslovka Holding made its presence felt in the mining chemicals space about a year ago when it announced plans to acquire Chemours Company’s Mining Solutions business, a deal that has since seen it become one of the largest North American producers of solid sodium cyanide.

This acquisition, completed in December for $521 million, also laid the groundwork for a separate transaction that could see the Czech Republic-based company diversify into the in-demand battery metals arena.

Australia-based Mining & Process Solutions (MPS) had been on the Mining Solutions business radar for at least two years prior to the Draslovka transaction, according to James Stockbridge, Director of Draslovka Mining Solutions. Stockbridge, formerly of Chemours and DuPont, said that his team at Draslovka realised MPS had something on its books that could solve many of the challenges the industry was experiencing and transform mining solutions by using an amino acid called glycine.

“For more than a decade now, the industry has recognised that orebodies are becoming lower grade, processing them is becoming more complex and the environmental regulations associated with leaching are becoming stricter,” Stockbridge told IM.

“It is the challenge of our time, and we think MPS has something quite unique to offer here.”

With roots in the gold technology group at the renowned Curtin University in Western Australia, MPS’ glycine leaching technology has the potential to change both the gold and base metal leaching space.

In gold, MPS’ GlyCat™ process was invented to reduce cyanide consumption while maintaining gold recovery for gold ores from deposits containing nuisance copper. GlyCat has been designed to enhance the dissolution of gold and copper in gold/copper ores where glycine is used as a catalyst with cyanide in a cyanide-starved leaching environment. It doesn’t replace cyanide, but, in fact, enhances its leaching capabilities by dealing with the high-cyanide consuming copper within these gold-copper orebodies.

In copper, nickel, cobalt and zinc leaching, GlyLeach™ is able to leach the targeted metals with enhanced selectivity compared with conventional methods. It will solubilise copper, nickel, cobalt and zinc, while gangue minerals such as iron, manganese, silicates and carbonates remain in the leach residue, MPS says.

Both technologies are environmentally safe, work effectively at alkaline pHs and ambient temperatures (with no heating cost or pressure vessels) and come with low operating costs due to their low consumption and recovery/recycling traits, according to the company.

While it is the gold side of glycine leaching testing that has, so far, taken the headlines thanks to several trials with mining companies in Australia (including Evolution Mining) and the technology’s potential ability to partially replace cyanide in the leaching process, Stockbridge and his colleague Jackson Briggs (Corporate Development Manager for Draslovka) said Draslovka was most excited about what the technology could offer the base metal space.

Briggs said: “It gives us the opportunity to expand our leadership position in gold leaching agents into base metals. At the same time, it also allows us to incorporate our expertise in that chemistry and chemical manufacturing side of things.”

Stockbridge – not wanting to give away too much – hinted at how this latter opportunity could play out.

“The leaching technology will also influence the way you, for instance, operate, monitor and control the plant,” he said. “This process will be different, and we will be bringing in new technologies to cater to this.”

Considering Draslovka can produce glycine from its existing hydrogen cyanide production footprint, there is potential for a very smooth integration on the supply chain side of things.

Asked to quantify some of the benefits of the technology, Stockbridge was happy to point out GlyLeach’s potential to “simplify the flowsheet” for, say, nickel production, removing the smelting aspect and resultant ore transportation – providing capital and carbon footprint benefits.

Briggs added: “It can change a lot from ore-to-ore with GlyLeach, but, in a really strong business case, you are looking at a 25% reduction in processing costs.”

This is on top of a 10-35% improvement on the recovery side, compared with conventional leaching, Stockbridge said, citing “proof of concept” studies.

As for GlyCat, the sweet spot – as already hinted at – is in gold-copper orebodies where copper is a large cyanide consumer, with the technology allowing cyanide to work more efficiently and effectively.

Both technologies recently featured in OZ Minerals Ingenious Extraction Innovator challenge outcomes publication, while GlyCat has also been the subject of a one-off study looking at combining it with Sixth Wave Innovations’ IXOS® molecular imprinted polymer for gold extraction.

Australia’s Future Battery Industry Cooperative Research Centre, which is sponsored by the likes of Sandfire Resources, Barrick Gold, Coda Minerals (previously Gindalbie Metals) and Poseidon Nickel, is also coordinating some of the work towards commercialising GlyLeach.

There is a strong business case for both technologies first being deployed at scale on tailings deposits that have been deemed to have no associated value – a point both Stockbridge and Briggs acknowledged.

Briggs said: “In terms of accelerating the development of the technologies, there are tailings deposits and waste piles situated all over the globe with high amounts of precious and base metals that have not been extracted due to the limitations and economies associated with current processing technology. We could provide an economic way of extracting those.

“It would also provide us a project with much reduced start-up times compared with, say, a greenfield project.”

Stockbridge added: “We have carried out some work on this type of application before and believe there is the potential to extract 50% of the nickel that they couldn’t access with existing technology by using GlyLeach.”

From the mining company perspective, deploying a new technology on material already written off comes with a lot less risk too.

That is before appreciating that the material won’t have to be smelted on site, that the process produces no free cyanide and that gangue materials do not come out in solution.

It is no wonder the Draslovka duo are excited about the technology’s potential; GlyLeach in particular.

“The ability to help nickel and copper miners produce more metal to rescue some of these deposits that have been forgotten or under-developed because of technology limitations and be able to do so in a way that is more environmentally friendly is exciting.

“Potentially, this technology could help localise more electric vehicle supply chains by removing the need for smelting and providing a cost-effective and environmentally friendly means of extracting metals.

“We cannot wait to get started.”

Gekko Systems partners with Quadra Chemicals to expand GoldiLOX leach reach

Gekko Systems says it has entered into an agreement with Quadra Chemicals Ltd to represent its GoldiLOX leach accelerant exclusively in Canada and the USA, and non-exclusively in Mexico.

GoldiLOX is an advanced leach accelerant able to, the company says, increase gold recovery while shortening intensive cyanidation times, making gold production a faster and more effective process. Compatible with all intensive reactors in the marketplace, GoldiLOX is either added as a single manual addition or by an automated chemical dosing system to the intense leach reactor.

“Gekko is pleased to enter an agreement with Quadra Chemicals to provide a cost effective and efficient leach accelerant, GoldiLOX, to our clients in Canada, the USA and Mexico to add further value to their projects,” Andrew Edmondston, CEO of Gekko Systems, said.

Ian Holden, Product Manager, Mining Group of Quadra Chemicals Ltd, added: “Partnering with innovative solution providers to the mining industry, such as Gekko, allows us to continue to provide technologies which will help to ensure our client’s competitiveness in the market. We are excited about this new partnership and look forward to working in collaboration with Gekko.”

Hycroft Mining continues evaluation of novel sulphide heap oxidation/leach process

After testing out a “novel” oxidation and leaching process at the Hycroft Mine in Nevada, USA, Hycroft Mining Holding Corp is making plans to go back to a conventional oxide leaching setup in 2021.

The company produced 27,392 oz of gold and 178,836 oz of silver in 2020, an almost three-fold increase over 2019. It hit these numbers while operating at a pre-commercial scale using the novel process, which oxidises sulphides ahead of leaching.

It is now planning for run-of-mine production of 45,000-55,000 oz of gold and 400,000-450,000 oz of silver in 2021 using conventional cyanide heap leach.

It is anticipated that mining in the first four months of 2021 will be performed using the existing Hycroft fleet and a rental fleet, moving approximately 1.5 Mt/mth of ore and waste. For the remainder of the year, Hycroft intends to mine some 500,000 t of oxide and transitional ore and waste per month with a more cost-effective mining fleet.

Diane R Garrett, President & Chief Executive Officer, reflected on the results: “2020 was an important year for Hycroft as the company continued to focus on the restart of the Hycroft Mine. Throughout the year, we advanced work on the proprietary two-stage sulphide heap oxidation and leach process and made several important findings that will need to be addressed prior to our implementing the novel technology on a commercial scale.

“In 2021, we expect to mine predominantly oxide and transition material, which are more economic when treated using a conventional run-of-mine heap leaching method, which gives us the opportunity to continue to refine the operating parameters and flowsheet for the new heap leach pad and novel process. While the company continued to make significant progress in better understanding this proprietary process and its application on a commercial scale, the past year also presented some operational challenges, including learning to navigate in a newly emerged COVID-19 world.”

In the last few months, Hycroft says it has worked alongside consultants to identify and investigate opportunities for improvements in operating parameters for the two-stage sulphide heap oxidisation and leach process. The result of the work to date has identified several items that were not considered or included in the original plan and design but are critical to the success of this process. These findings include:

  • Adding a forced air injection system for the leach pad which is a key component of the oxidation process;
  • Developing a system for segregating solution flows to and from the heap leach pad to avoid co-mingling of solutions among heap lifts and ore processing stages that negatively impact recoveries and conditions on the leach pads;
  • Identifying that the finer crushed material requires agglomeration in order to achieve optimal permeability and gold/silver recoveries;
  • Understanding that higher soda ash, caustic soda, and cyanide consumption will be required which Hycroft experienced throughout the 2020 pre-commercial test pad programs and recently confirmed through the review of the test work;
  • Determining that some transitional ores are more economically attractive when processed as direct leach, run-of-mine material; and
  • Concluding that additional variability metallurgical and mineralogy studies will be required to better understand each of the geometallurgical domains in the orebody. While there was some variability work completed in the past, the recent test work has revealed that additional variability test work and compositing is necessary to fully understand the geometallurgy of each domain, and that additional sampling, including sampling below the water table where the predominance of the sulphide resources exist, is required given the complexity and variability of the large orebody.

The additional variability test work will also include detailed mineralogy studies as it is important to understand the role other minerals may play in the overall oxidation process and to enhance Hycroft’s ability to measure oxidation rates accurately and consistently, it said.

The team at Hycroft has developed an approximate $10 million program for drilling and additional metallurgical and mineralogical studies in 2021. This program of work has been approved by the Board of Directors of Hycroft and can be funded from existing cash and Hycroft’s current operating plans.

Hycroft expects to mine and stockpile at least 300,000 tons (272,155 t) of sulphide ore in 2021 that, once sufficient additional work on the novel process has been completed, will be available for testing to further refine operating parameters and measure its performance for large scale application of the oxidation heap leach.

Garrett added: “2021 is a foundational year designed to advance the work necessary in preparation for larger-scale sulphide operations. The team is working diligently to optimise current and future heap leach mine plans and to evaluate all opportunities for more profitable mine plans in the near and medium term. This work involves taking a ‘ground up’ approach working from the orebody out. The company’s prior plan was developed using a $1,200/oz gold price pit shell which leaves profitable ore behind in the current gold and silver price environment. By running pit shells at recent gold and silver prices, we have identified additional areas of oxide mineralisation that can generate cash flows over the next several years and we have already begun to identify areas of higher-grade mineralisation that will become important for mine sequencing and further improving cash flows prior to accessing sulphide material.”

As the company considers life-of-mine development and planning for the Hycroft deposit, particularly in the current gold and silver price environment, Hycroft says it is prudent to evaluate proven processing technologies for treating some ore types that may be more profitable than only using the two-stage sulphide heap oxidation and leaching process.

Potential opportunities being examined by the company in 2021 include: developing an understanding of the grade range distribution of the sulphide material; completing on-going work on the higher-grade areas of Hycroft; and following up on historical high-grade intercepts.

In order to capitalise on these potential opportunities, which take advantage of the current commodity price environment, Hycroft believes that it should also evaluate the benefits of a multi-process operation. Long-term operating scenarios may include conventional run-of-mine cyanide heap leaching for the oxide and transitional material, sulphide heap oxidation and leaching using the novel process, and an appropriately sized milling and flotation plant for processing the higher-grade ranges of sulphide material.

“The company believes that the plan it has put in place for 2021 will provide the new team the time to fully consider and evaluate these opportunities and make any necessary changes to improve the leach pads, process plants and process flowsheet, maintain and develop its workforce, and advance the project, in order to further enhance the value of the project,” it said. “As the test work advances and alternative processes are considered, the company expects to perform technical studies and trade-off evaluations which may result in an updated feasibility study.”

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.

Nitrogen tyres and oxygen generators bring safety and sustainability to mines

David Cheeseman*, Chief Engineer of Oxair Gas Systems, believes the mining industry should take on board the latest on-site gas generation technology to help improve safety and reduce its carbon footprint.

The mining industry is becoming a lot more technology-focused, with advancements in autonomous mining technology and automated surface vehicles, as the industry presses ahead to reduce carbon emissions and boost safety in mining.

The International Council on Mining & Metals’ (ICMM) Innovation for Cleaner, Safer Vehicles (ICSV) initiative – a supply chain collaboration with original equipment manufacturers (OEM) – is to be applauded. However, in the meantime, rugged terrain will still be taking its toll on the tyres of mining vehicles, which are the workhorses of the extraction process.

These trucks operate in harsh environments and extremes of temperatures, which is why nitrogen-filled tyres are ideal, because they remain inflated for longer and are more resistant to hot climates and freezing at high altitudes, making them safer for operators and site staff alike. Unlike compressed air, nitrogen is an inert gas that does not react with other materials, so it is resistant to corrosion and, therefore, provides an extra tier of safety where critical applications are involved.

It is imperative that tyres are fully inflated to reduce the risk of critical air leaks and rapid deflation when the vehicles are under pressure. But being at the mercy of the supply chain for bottled nitrogen, especially in extreme locations where conditions are challenging, is costly. Nitrogen can be difficult to transport, not to mention the additional carbon footprint of delivery vehicles and safety risks for staff manually moving cylinders from one place to another, especially with the new threat of contamination posed by the coronavirus pandemic.

However, companies can avoid the hassle of having to outsource their gas from conventional cylinders by switching to an on-tap supply through a nitrogen generator. A nitrogen generator on site is the ideal alternative choice to manhandling canisters for heavy-duty equipment where precise or constant pressure is vital.

Oxair’s nitrogen generators are efficient and compact, making them an ideal solution for mining sites. They offer a continuous flow of gas extracted from the atmosphere and are an environmentally friendlier method of delivery, as they reduce the carbon footprint associated with having

Oxair’s nitrogen generators are efficient and compact, making them an ideal solution for mining sites, David Cheeseman says

cylinders transported from an off-site facility and then the return journey when they are empty.

Nitrogen generators are cheap to run and, once installed, require minimal maintenance. Nitrogen plants are built to last and are operator friendly, making them crucial where tyres need to perform well in a remote location or challenging environment.

As with all high-quality engineering solutions, nitrogen generators can be tailored exactly to suit an individual mine’s requirements. They can be designed for outdoor or covered facilities and, as well as offering low energy consumption, a supplier should be able to provide on-site training to enable local employees to properly calibrate and easily maintain the system once it is operational, as well as full ongoing maintenance support.

Some of the world’s leading gold mining companies are already seeing the benefits of gas on tap at sites rather than taking deliveries of traditional cylinders. Pressure Swing Adsorption (PSA) oxygen equipment supplied by Oxair is helping AngloGold Ashanti extract more of the precious metal from one of its flagship gold mines, potentially extending the life of the open-pit operation in Tanzania.

Two booster processors for increasing oxygen pressure and two oxygen generator tonnage plants to further improve the efficiency of the leaching process are in operation at AngloGold’s Geita Gold Mine, enhancing gold recoveries and protecting the environment by reducing cyanide consumption.

This equipment is helping to increase production and extend the mine’s lifespan beyond 2025, when it was originally set for closure. The state-of-the-art equipment supplied, which includes upgraded control systems, will double the reliable source of pure oxygen for the future activities planned at Geita. It will mean significant efficiencies in carbon in the leach technology method of gold recovery and should help the mine be both economically and environmentally sound for its extended lifespan.

Using oxygen generators significantly improves the gold dissolution process through adding highly purified oxygen at the slurry stage of leaching. Mined rock is usually ground up and turned into a slurry by adding lime, cyanide, oxygen and water before being fed through a carbon bed to extract the gold. Incorporating highly purified oxygen allows cyanide to work more efficiently and, thus, reduces the quantity of cyanide needed in the process.

A PSA tonnage plant takes oxygen directly from the air using on average of only 3 kW of electricity per 100 cu.ft of oxygen produced and transforms it into highly purified oxygen by removing nitrogen entrainments (which are useless to the leaching process).

Using oxygen generators significantly improves the gold dissolution process through adding highly purified oxygen at the slurry stage of leaching

Oxygen tonnage plants are designed for on-site applications requiring large amounts of oxygen, such as mining, with outdoor or covered standard installations – PSA equipment is bringing numerous advantages to the mining industry, as well as eliminating the need for expensive and unreliable deliveries of liquid or cylinder oxygen.

On-site generators provide mines with a turnkey solution for getting a constant, reliable source of high-quality oxygen and nitrogen where it is needed. It is clear that with responsible mining practices geared up for long-term sustainability, investments in quality equipment will be key to achieving both safety and sustainability goals.

*This piece was written by David Cheeseman, Chief Engineer of Oxair Gas Systems. Oxair is an ISO 9001 certified company focused on the design and manufacture of packaged oxygen PSA Systems, as well as Nitrogen PSA systems up to 1,000 Nm3/h.

SGS to bring Glencore Technology’s Albion Process testing to Africa mining market

SGS Minerals is to offer Glencore Technology’s Albion Process™ test work to mining companies in Africa after the two extended an agreement and certification related to the hydrometallurgical process.

While SGS already has a relationship with Glencore Technology through SGS Lakefield – through an agreement signed last year – the extension opens up the potential for more large packages of work of “high relevance and value”, Glencore Technology says.

“For Glencore Technology, it extends further the global reach of Albion Process test work as it has grown 300% in the last 12-24 months and is seen as uniquely viable in terms of capital costs, operational costs and project feasibility,” the company said.

The new test work locations will now include Randberg in South Africa, with other locations being discussed elsewhere around the world, according to Glencore Technology.

The Albion Process uses a combination of ultrafine grinding and oxidative leaching at atmospheric pressure to work. It also tolerates a more variable feed and lower grade than other processes, according to Glencore Technology, meaning it can make some projects feasible and profitable where alternative technologies could not. The sulphides in the feed are oxidised and valuable metals liberated, with the economic metals recovered by conventional downstream processing. Test work requires only small sample masses with no pilot plant, Glencore Technology says.

The process has produced high recoveries in refractory gold and in base metal concentrates at the six Albion Process plants in operation across the globe, according to the company.

Glencore Technology’s Paul Voigt said: “The extension to Africa has been under discussion for quite some time. We know the importance of local contact and context. It’s also part of a wider focus we have for the African continent.”

SGS’ Niels Verbaan, said: “This is a natural and highly relevant extension of our work with Glencore Technology on Albion Process test work. We look forward to a larger global footprint to help operations in Africa and the Americas, especially those with complex mineralogies, to get an objective opinion on process options.”

SGS is the third certified provider of test work, joining Core Resources in Australia and TOMS Institute in Russia.

ValeOre Metals considering Platsol, Falcon separator, Steinert ore sorting for Pedra Branca

ValeOre Metals Corp’s Pedra Branca platinum group element (PGE) project, in north-eastern Brazil, looks increasingly like leveraging the Platsol™ high temperature pressure leaching process judging by the latest test work.

Metallurgical results from sample material collected from outcrops at the Trapia and Curiu deposits areas at Pedra Branca for two preliminary Platsol tests conducted at SGS Lakefield, Ontario, have shown recoveries of 93.4-93.6% for palladium and 95.3-95.7% for platinum were achieved.

The company now plans two additional Platsol tests, to be performed by SGS, to determine the effects of adding elemental sulphur to the autoclave to optimise conditions required for PGE and gold recoveries, it said.

Platsol is a high temperature (>200°C) pressure leaching process designed to recover PGEs, gold and base metals. It has been shown to be particularly effective with PGE ore feeds characterised by high concentrations of chromium and low concentrations of sulphide, much like Pedra Branca, according to ValeOre Metals. The PGEs and gold are solubilised as chloro-complexes by the addition of chloride salt to the autoclave, while base metal sulphides are oxidised to form soluble metal sulphate complexes. The precious metals can be recovered directly from the autoclave discharge slurry by carbon absorption, or by precipitation with sulphide ions.

Platsol consists of standard, proven traditional technologies that are in use in mines around the world, according to the company.

The Platsol tests are part of a comprehensive mineralogical evaluation ongoing at SGS to characterise the speciation of palladium and platinum in Pedra Branca mineralisation to guide future process optimisation initiatives.

As part of this, the company is continuing with Falcon Ultrafine gravity separation test work as a potential pre-concentration circuit to upgrade feed material and improve mass pull.

The company has also initiated hot cyanide leach test work to assess the recovery rates of palladium, platinum and gold in a cyanide leaching process, and will shortly commence shipment of 100 representative chip samples from historic drilling at the Esbarro deposit to Steinert’s facility in Minas Gerais, to evaluate the potential of sensor-based ore sorting test work.

ValOre’s Chairman and CEO, Jim Paterson, said: “The pace of success at Pedra Branca has increased dramatically in the last three months, including today’s release of PGE metallurgical recovery rates of in excess of 93% for palladium and 95% for platinum using the Platsol process.

“Together with an aggressive property-wide exploration program, we are now focused on rapidly optimising the conditions, procedures and processes to further maximise the upside potential of the Pedra Branca project.”