Tag Archives: dry stacking

FLSmidth notes sustainability and digital mining developments in Q2 results

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FLSmidth’s June quarter saw an improvement in revenue and profitability as the company’s Mining and Cement divisions continued to perform strongly.

The company’s order intake for the June quarter amounted to DKK5 billion ($752 million), down 2% from the same period a year ago. Mining order intake, specifically, declined 7%, mainly due to a lower capital order intake, the company said. This included an order of around DKK375 million from Rio Tinto for its Koodaideri iron ore project.

During the quarter, the company also completed the acquisition of IMP Automation.

FLSmidth’s order backlog stood at DKK16.8 billion by the end of June, up 16% from the same time last year.

Revenue increased 16% year-on-year in the quarter to DKK5.5 billion on high activity level, while earnings before interest taxes and amortisation came in at DKK487 million, up 28% year-on-year.

FLSmidth Group CEO, Thomas Schulz, said: “The second (June) quarter showed a strong performance with improved revenue and profitability, driven by both Mining and Cement. Following a slow start to the year, we have been successful at converting backlog to revenue in the second quarter. In close cooperation with our customers, we have continued to deliver on our vision to provide sustainable productivity enhancement.”

Schulz continued: “Our success with both service and capital orders, demonstrates our customers’ confidence in our ability to enhance their productivity. This is supported by an increased push for sustainable solutions that ties in well with our position, capabilities and track record.”

In the company’s Mining division, Schulz said the company saw increased interest for new technologies such as dry stack tailings, but also a general need to reduce water consumption in the production process. The company said the mining market remained robust.

The company added on the mining market: “Equipment demand continues to evolve around replacement and brownfield projects, with select greenfield opportunities. Miners are attentive of rising global issues and remain cautious on large and high-risk investments. The long-term pipeline for larger projects is encouraging, but most projects are currently not reaching further than the engineering/prefeasibility stage.”

It continued: “Customers across regions and commodities are increasingly demanding digitalised solutions to improve performance, reduce operating costs and maximise safety in operations. Similarly, customers show increased interest in technology to obtain a more sustainable production, not least our effective solutions for tailings management given the latest issues with tailings dams failures and the related environmental impact.”

Coringa dry stacking plan finds favour with state environmental agency, Serabi says

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With Serabi Gold having supplied all required data for a preliminary economic assessment (PEA) on its Coringa gold project, in Brazil, to its independent consultants Global Resource Engineering Limited, CEO Mike Hodgson says the London- and Toronto-listed firm is now working hard on the permitting side.

Permitting a mine in Brazil – in particular the waste storage element – has become a lot trickier in the past few years following two major tailings dam collapses at iron ore mines in the country.

But, in the company’s June quarter results, Hodgson said Serabi was making good progress on permitting Coringa, a deposit that comes with 216,000 oz of indicated resources at an average in-situ grade of 7.95 g/t Au and inferred resources of 298,000 oz at 6.46 g/t.

He said: “The plan to replace a conventional tailings dam with installing a filtration plant allowing for the dry stacking of tails has been well received by the state environmental agency, SEMAS, who had already approved the original environmental impact assessment (EIA) on the basis of a conventional dam.”

The company is now completing an amendment to the EIA to reflect this design variation, he said, explaining that Serabi expects SEMAS to approve the amendment and, then, proceed with the necessary public hearings.

“We hope to be in a position to receive the Preliminary Licence during the second half of the year,” he said.

Coringa is located in north-central Brazil, in Pará State, 70 km southeast of the city of Novo Progresso.

Artisanal mining at Coringa produced an estimated 10 t of gold (322,600 oz) from alluvial and primary sources within the deep saprolite or oxidised parts of shear zones being mined using high-pressure water hoses or hand-cobbing to depths of 15 m, according to Serabi. Other than the artisanal workings, no other production has occurred at Coringa.

Serabi acquired Coringa from Anfield Mining on December 21, 2017, with management considering the asset to be very much a “carbon-copy” of Palito in terms of the geology, size and mining operations that will be used. The company’s Palito complex is made up of high grade, narrow vein underground mines that produce around 40,000 oz/y of gold.

The PEA on Coringa is still expected to be completed by the end of July, Serabi said.

Twin Metals looks to avoid tailings dam concerns with dry stacking plan

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The developer of the Twin Metals project, in the Iron Range region of northeast Minnesota, USA, has announced plans to use dry stacked tailings at the underground copper, nickel, platinum, palladium, gold and silver asset as the company looks to eliminate the perceived risk of a dam leakage or failure.

Twin Metals Minnesota (TMM), a company owned by Antofagasta, said the dry stack method eliminates the storage pond and dam associated with conventional tailings facilities and has been successfully used in four mines in the northern US and Canada with similar climates to Minnesota.

In 2018, an update of the prefeasibility study for Twin Metals outlined a 18,000 t/d ore project, producing an average of 42,000 t/y of copper, plus nickel and platinum group metals as by-products, the equivalent of some 65,000 t/y of copper.

TMM, like many other potential mine developers, said community concerns about copper-nickel mines have focused on fears of tailings dam failure or leaks that could threaten both nearby surface water and groundwater. This comes after several high profile dam failures in North and South America.

If all goes to plan, the company will use the dry stack method to store the leftover rock from its proposed underground mine on a lined ground facility near the plant site. This will allow reclamation of the tailing site to occur in stages, with the site capped or covered with natural vegetation.

Kelly Osborne, Chief Executive Officer of Twin Metals Minnesota, said: “Dry stack tailing storage is the most environmentally friendly tailings management approach for our site. The first key is that there’s no dam, no risk of dam failure. The moisture content of the filtered tailings is reduced to a material that we can compact and manage seasonally.

“Because there’s no risk of a dam failure, dry stack is considered the best available technology for tailings storage and, after a decade of study and consultation with concerned voices in our community, we determined that it will be an effective choice for our project.”

Equally important, TMM said, is the fact that the tailings from the Maturi deposit at Twin Metals will be non-acid-generating.

“The common concern about sulphides points to a basic misconception about our project,” Osborne said. “The geology of the Maturi deposit provides us with confidence that we can mine here safely and sustainably. The rock sandwiching the layer of copper, nickel and platinum group minerals in the deposit is almost completely free of sulphides. When the targeted minerals are removed during the concentration process and shipped to customers, only a minute amount of sulphides will remain in the tailings.”

Extensive testing over the past decade shows that Maturi deposit tailings will be non-acid-generating, the company clarified.

Dry stack tailings storage has been an option under consideration since Twin Metals began mine planning in 2010, the company said. “As technology has continued to advance, and the application of dry stack in cold, wet climates has proven successful at multiple locations, Twin Metals made the decision to move to it as the best available option,” TMM said, adding that The Minnesota Center for Environmental Advocacy hailed the advantages of dry stack tailings in a statement earlier this year.

Osborne concluded: “Dry stack is one of the ways we are making a 21st century mine that will be the most technologically advanced mine in Minnesota’s history and a model of how copper mining can be done safely and sustainably.”

The approach will be outlined in detail in TMM’s Mine Plan of Operation, to be submitted to state and federal regulators in the coming months. Regulatory review, including hearings for public comment, will cover compliance with regulations to protect water and air quality, drinking water, wetlands, endangered species, plant life and cultural resources. While the MPO is being reviewed the company will advance the feasibility study.

After reaffirming Twin Metal’s right to renew its two federal mineral leases, the Department of Interior reinstated the leases to TMM in May 2018. Antofagasta expects these to be renewed during 2019.

Metso commits to a filtered tailings future

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Metso might have just launched a new tailings management concept, but the management of tailings and dewatering solutions are nothing new for the mineral processing company.

Helsinki-headquartered Metso developed its first VPA filter for mining in the 1980s – the maiden unit being delivered to the Greens Creek mine in Alaska (now owned by Hecla Mining) – and has since dispatched hundreds of units to mines across the globe.

In addition, Metso has a long history of designing and manufacturing tube presses and other complementary dewatering solutions; its current membrane-type filter press offers pressures up to 100 bar for particularly difficult dewatering applications, such as china clay, while its inclined plate settler (IPS) and dewatering spirals offer separation and thickening options for miners.

The VPX™ filter is the launch product that comes with this new tailings management concept, but there is much more to this focus than a lone invention.

As Niclas Hällevall, VP, Process Equipment for Metso, told IM: “It is no longer a matter of just finding the most technically-suitable equipment or solutions to do the job. It is about how to transform mining into a sustainable and long-term development.”

Metso is intent on “challenging the conventional” in this regard. This includes looking at its own approach to designing mineral processing equipment – ensuring all products use, recycle and recover water in a responsible manner – as well as the industry’s way of thinking. Instead of pursuing short-term fixes, such as implementing tailings monitoring solutions using sensors, the company thinks miners should prepare for a future where wet tailings dams are eradicated from mine sites. Dry stacking – or filtering – tailings is the end goal Metso is pursuing.

This unconventional mindset is also apparent in the design of Metso’s VPX filter. Instead of equipping the machine for high throughputs alone, Metso has built the filter to manage varied input materials and to offer pressures up to 25 bars (and perhaps even higher pressures).

Metso has eliminated the use of hydraulics on this new filter, instead using electromechanical screws to achieve the high-pressure closing that turns wet material into dried cakes with as low as 7% moisture content in some applications. This electromechanical switch could cut operating costs due to a reduction in maintenance requirements, according to the company. The modular design, meanwhile, allows the filter to be scaled to any size, plus fit it into a container for easy logistics.

An advanced control system (ACS) using self-learning functions provide customers with a solution to monitor the operation of the filter, while there are plans to equip the machine with artificial intelligence functionality to monitor the conditions of the input material and select the optimal dewatering route.

Also, the filter press offers a variable and very fast opening and closing time thanks to the robust rack and pinion system, thus providing the high-capacity dewatering large mines require.

Metso is ready with its “future-ready” solution – a pilot VPX filter is currently in Sala, Sweden, about to be taken on a roadshow. This unit has already been tested on a mine tailings application in Sweden, IM understands, with the company expecting many more trials over the next year.

As Lars Gustavsson, Business Manager, Beneficiation Solutions, explained, the company’s filter press trial plan includes taking small size samples in its laboratory before graduating to the full-scale pilot unit, which is equipped with the same ACS and sensors commercial units will have. “This gives customers all they need to build the business case,” he said.

The Metso tailings management concept goes further: Hällevall says the use of the Metso IPS and Metso MHC™ hydrocyclone, in circuit with a VPX filter, results in less use of chemicals and energy in the dewatering process, on top of water recoveries of up to 90% in some applications. This is achieved by controlling the feed and optimising the filtration process. “We simply separate the stream into fine and coarse streams by using Metso MHC hydrocyclones,” Hällevall says, explaining that the overflow – the fines stream – is directed to the Metso IPS thickener, with the coarse stream going direct to the filter.

With two separate streams, the company can decide the optimum way to filter and dewater the material, with the IPC, in particular, offering the most “superior setting of fines using minimum amounts of flocculants and energy”, Hällevall says.

This new concept has allowed Metso to become one of only a few mining OEMs talking up the use of pressure filters – and accompanying separation and thickening infrastructure – to reprocess legacy tailings dams. The ability to “turn waste into value” could enable mining companies to not only clean up these dams, decrease their footprint and improve their sustainability credentials with local and other stakeholders, it could also allow them to generate additional revenue from the recovery of valuable minerals and metals.

This could potentially provide the positive investment case miners need to start making wet tailings dams a thing of the past.

Just 5% of all fresh tailings generated in 2018 were dewatered in some way, according to Metso’s data. With its own “future-ready” solution now in place, the company is doing its bit for industry to ensure this figure continues to rise.

Anglo American’s FutureSmart Mining on its way to tangible technology results

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“It’s clear that the pressures on us are unsustainable, whether it is around our carbon footprint, water footprint, or physical footprint, and we are always looking for different ways to push us in this future direction where our footprint will be very different.”

Tony O’Neill, Anglo American Technical Director, knows the company he works for is up against it when it comes to retaining its reputation as one of the world’s leading sustainable mining companies.

It’s clear from the company’s 2018 sustainability report – which saw it achieve a best-ever performance in terms of injuries, a cut in energy use and an increase in greenhouse gas emission savings – that Anglo is going down multiple paths to reach its goals. O’Neill, who joined the company almost six years ago, believes Anglo’s FutureSmart Mining™ programme will play a major role in confronting and overcoming many of the issues it (and the industry) is facing.

“If you look at FutureSmart Mining, at its absolute essence, it is about footprint; how do you change the footprint of mining? How do you have a mine that draws no fresh water? Mines without tailings dams? Mines that look very different?” he told IM.

“It’s getting people to believe there is a different way for mining in an industry that has, to this point, been quite traditional. It is not going to happen overnight, but I think we have a genuine vision that is, in my view, quite feasible.”

IM spoke with O’Neill and Donovan Waller, Group Head of Technology Development, this week to get to the bottom of how technology is making Anglo ever more sustainable.

IM: Could you explain how the Anglo operating model facilitates and fosters innovation within the context of FutureSmart Mining?

TO: The Anglo American operating model is the chassis that underpins everything, giving us certainty in the delivery of our work. When you have got that stability – and the lack of variability – in your business outputs, it is much easier to overlay new technologies and processes. When you then see a difference in operating or financial results, you can confirm it is down to what you have implemented, rather than the underlying processes.

I look at it a little bit like a three-legged stool: you have the operating model on one leg, the P101 benchmark-setting on another, and technology and data analytics on the third leg. They all co-exist in this system and work off each other. Without one, the stool falls over.

The operating model has given us a drumbeat of delivery, and we get the licence to innovate because of this drumbeat.

IM: Do you think FutureSmart Mining is starting to be understood and valued by investors?

TO: They’re awake to it now. I think it is still in the early stages of the story, but they can see what we are doing and the ambition behind it. Ultimately, it will result in a different investment profile, or more investors because of it, but I am not sure that it’s translated in full up to now. The recognition has been more around the general results of the company.

With all these technologies coming through – much of them driven by higher levels of data and the ability to interrogate that data – the vision we imagined way out into the future, I think, is a lot more tangible than when we started out four years ago.

IM: Out of all the tailings dam elimination work you are carrying out (around passive resistivity, fibre-optics, micro-seismic monitoring, coarse particle recovery, polymers, and dry stacking), which innovation will have an impact on Anglo’s operations in the next three-to-five years?

TO: All of them. We started out with our tailings programme in 2013; in fact, our group technical standards were re-issued at the beginning of 2014 and they are now one of the main guidelines the ICMM (International Council on Mining and Metals) uses.

Tailings dams have always been at the back end of the mining process and, in a way, the science behind them has never been part of the mainstream operation. Our view, internally for many years, is tailings dams are one of the industry’s greatest risks.

“Our view, internally for many years, is tailings dams are one of the industry’s greatest risks,” Tony O’Neill says

Ultimately our aim is to eliminate tailings dams. Period. Coarse particle flotation – getting that coarser particle size that drains much more freely – is core to that and you can see a development pathway there. For example, with some of these new flotation techniques, we now only need 1% exposure of the mineral for it to be effective. In the past, it was much higher.

When we upgraded the capability of our tailings organisation, it became clear we needed to get a lot more data off these tailings dams. About three years ago, we started putting fibre-optic sensors into the dams. We have since developed, through our exploration arm, passive resistivity seismic monitoring, which basically tells you where your water sits in the dams. And, we’re putting into Quellaveco micro-seismic measuring techniques, which will be more granular again. You can see the day coming really quickly where tailings dams are a real-time data source for mining companies.

We’re also, with our joint venture partner Debswana, building the first polymer plant in Botswana, which could have an impact on dry tailing disposal.

The thing we need to crack – both ourselves and the industry – is how to dry stack at scale. At the moment, that is still a work-in-progress, but it is doable in the long term.

IM: How is the bulk sorter you have operating at El Soldado, which is equipped with a neutron sensor, working? How has it made a difference to recoveries and grades at the operation?

TO: With the bulk sorter, we’re taking packages of tonnes rather than individual rocks to enable us to get both speed and volume. At El Soldado, we are sorting in four tonne packages. You can adapt the sorting profile by the characteristics of the orebody. We’re generally looking to sort tonnages that are less than you would put in a haul truck body or bucket.

If you step right back, in the past, most processing plants wanted to blend to get an average feed. We are going the other way. We want to use the heterogeneity of the orebody to its advantage; the less mixing we can get ahead of these sorting processes, the better it is for recoveries.

Being able to remove an orebody above the cut-off grade alongside waste tonnages and upgrade the latter has led to an effective lift in head grade. It has been enabled by new sensing technology with a particular type of neutron sensor.

What we have seen in early results has surprised us on the upside. We thought we would see a 5% uplift in head grade, but in fact we have seen about 20% – to qualify that, it’s in its early stages.

O’Neill says the bulk sorting trial at El Soldado has seen about a 20% uplift in head grade in its early stages

If you take this to its logical conclusion, you can see the day coming where you would cut the rock – no drilling and blasting – immediately sort the rock behind the machine cutting it and distribute said rock efficiently into its value in use; you don’t have stockpiles, you have plants sensing the material right through and adapting in real time to the change in mineralogy. I think there is another 3-4% increase in recovery in that whole process when we get it right.

Our sweet spot when we created FutureSmart Mining was always the orebody and processing plants, more so than automation (although that is part of the potential mix). That was different to a lot of the other players in the industry. This focus could lead to the development of different types of plants; ones that are flexible, more modular and you can plug and play.

IM: Do you see these type of neutron sensors being applied elsewhere across a mine site?

TO: Yes, through processing plants and conveyors. In fact, we’re preparing for this on conveyors right now.

What we have found with all this new technology is that, when we implement it, quite often another opportunity arrives. They end up playing off each other, and that is the context for the bulk sorting and coarse particle flotation.

IM: How have Anglo’s Open Forums played into these developments?

TO: We have held eight Open Forums on sustainability, processing, mining, exploration (two), future of work, energy and maintenance.

Out of those eight, I think we have got around 10,000 ideas from them. These forums have been specifically designed where only about a third of participants are from the mining industry, with the other two thirds coming from the best and brightest analogous industries we can tap into – automobile, oil & gas, food, construction, even Formula 1 racing and NASA.

The reality is that out of those 10,000 ideas, the success rate is about 1:1,000, but the one that makes it is quite often a game changer.

IM: Going back to the bulk sorters, am I right in thinking you plan to put these into Mogalakwena and Barro Alto too?

TO: The aim is to have them across our business. At El Soldado, the copper angle is very important. The technology – the sensing and using the data – is probably a touch more advanced in copper, but we are building one currently in our PGMs business at Mogalakwena and a bit behind that, but ready to be built, is one in nickel, yes.

In terms of our programme, you will see them spread across our business in the next, hopefully, 18 months.

IM: Where does your approach to advanced process control (APC) fit into the FutureSmart Mining platform?

TO: We want to have APC in some form across all our business by the end of this year. We have probably come from a little behind some of the other players in the industry, but we’re pushing it quite aggressively to give us the platform for data analytics. The upside we have seen just by putting the process control in so far has surprised me a bit – in a good way; power reductions, throughput, having this different level of control. All of it has been pleasing.

We spent about 12 months looking at the whole data analytics space to see how we were going to implement our solution. If you look around at the sector, everyone wants to be involved and profit share. If you add it all up, you could end up with not a lot of profitable pieces at the end. We have strategically chosen the pieces we think are important to us and our profit pool and have been happy to be a little looser on some of the non-core areas.

The other key plank to the APC is that we own the data. The reality is, in the new world, data is like a new orebody and we’re not willing to let go of that.

IM: Your Smart Energy project involving a haul truck powered on hydrogen has certainly caught the attention of the market: how did you come up with this innovation?

TO: Initially, we couldn’t make renewables work from an investment criteria perspective – it was always close, but never quite there. Donovan’s team then took an approach where they said, ‘forget the normal investment criteria. All we want to do is, make the business case wash its face.’ In doing so, it enabled them to oversize a renewable or photovoltaic energy source – the power plant – using that extra power to produce hydrogen and putting that hydrogen to use in the haulage fleet. Re-engineering the haulage fleet gave us the business outcomes we were looking for.

DW: These business cases bring you to temporary barriers. When you hit that temporary barrier, people normally stop, but what we said was, ‘OK, just assume it is not there and go forward.’ That brought the whole business case back again by looking at it differently again.

Anglo’s Smart Energy project is aiming to power a 300-t class truck with hydrogen fuel

IM: Where is this project likely to be situated within the group?

TO: We’re still not 100% fixed as the initial work will be done here (the UK). You are talking about quite specialist skills working with hydrogen.

When the system has gone past its initial testing, it will go to a site, probably in South Africa, but we are not 100% locked into that at this point.

IM: On the 12-month timeline you have given, when would you have to be on site?

TO: The infrastructure will be pre-built here in the UK. We’re effectively testing it here. In a way, the physical truck is the easy bit.

It’s going to be using a 300-t class truck. The guys have already done quite a bit of the detailed measuring and the design elements are well under way.

We’ve also taken the approach to use pre-approved technology, which Donovan can talk about.

DW: This minimises the risk on the first go and allows us to, later, tailor it. For example, if you don’t have a right sized fuel cell currently available off-the-shelf, you just use multiple standard-size fuel cells for now. Then, when you get into the final version you could tailor them into something more specific.

IM: On mechanised cutting, you recently mentioned the building of a “production-sized machine” for at least one of your mines in South Africa. Is this a variant of the Epiroc machine – the Rapid Mine Development System – you have been using at Twickenham?

TO: It’s the next generation of machines. It’s fair to say that, in the last 12 months, the technology has come to the point where we are confident it is viable.

What we’re looking for is a fundamental breakthrough where, for example, we can take the development rates up three or four times from what you would usually expect. That is what we’re chasing. It would involve some sort of pre-conditioning of the rock ahead of the cutting, but the cutting, itself, works.

For us, mechanised cutting is a real solution to some of the safety issues we have had on our plate. Regardless of whether it goes into South Africa or another underground mine, we see it as a key part of our future underground design and operation.

IM: What type of rock pre-conditioning is this likely to be?

TO: I think around the world, people are looking at electricity, microwave, laser, a whole suite of things. None of them have yet quite landed, but they all have potential.

IM: Where does haul truck automation fit into the pipeline for Anglo American?

TO: All the equipment we buy, going forward, will be autonomous-capable, which means we can run it in either format (manned or unmanned). You are then left with a number of decisions – have you got the design to retrofit automation? Is there a safety issue to be considered? Is there a weather issue to contend with? There are a whole series of gates that we’ll take it (automation projects) through.

It’s good to go back to P101 here. Where P100 is getting all of our key processes to world-class benchmarks, P101 is about establishing a new benchmark. By definition, if you get your operations to that point, the gap between that manned performance and autonomous performance is not that great.

Autonomy is part of our future armoury, but when and where and how, we’ll have to wait and see. For example, we are currently looking at the option of autonomous haulage trucks at one of our open-cut mines in Queensland.

When you look at our portfolio of operations, it’s often a more complex environment than when you are just working in the wide open Pilbara.

Vale exploring dry stacking/magnetic separation to eradicate tailings dams

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Vale has confirmed a Reuters news report from last week stating that it would spend an additional BRL11 billion ($2.5 billion) on dry iron ore processing over the next five years.

The company said it has invested nearly BRL66 billion installing and expanding the use of dry processing, using natural moisture, in iron ore production in its operations in Brazil over the last 10 years and it would carry on this trend.

“By not using water in the process, no tailings are generated and, therefore, there is no need for dams,” the company said, added that about 60% of Vale’s production today is dry, and the goal is to reach 70% in the next five years.

Dry processing is used in the mines of Carajás, Serra Leste and the S11D Eliezer Batista Complex (pictured), in Pará, Brazil, and in several plants in Minas Gerais. In Pará, in the Northern System, about 80%, of the almost 200 Mt produced in 2018 was through dry processing. The main Carajás plant, Plant 1, is in the process of conversion to natural moisture: of the 17 plant processing lines, 11 are already dry and the remaining six wet lines will be converted by 2022.

Serra Leste’s treatment plants, in Curionópolis, and S11D, in Canaã dos Carajás, also do not use water in ore treatment, according to Vale. In S11D, for example, the use dry processing, using natural humidity, reduces water consumption by 93% when compared to conventional iron ore production.

In Minas Gerais, dry processing increased from 20%, in 2016, to 32%, in 2018. Today, this type of processing is present in several units, such as Brucutu, Alegria, Fábrica Nova, Fazendão, Abóboras, Mutuca, Pica and Fábrica. “Over the following years, the objective is to roll it out at other locations in Minas Gerais, such as the Apolo and Capanema projects, which are currently under environmental licensing,” the company said.

Vale said: “Dry processing is linked to the quality of the iron ore extracted from mining. In Carajás, as the iron content is already high (above 64% Fe), the ore is only crushed and sieved, so it can be classified by size (granulometry).

“In Minas Gerais, the average content is 40% iron, contained in rocks known as itabirites. To increase the content, the ore is concentrated by means of wet processing (with water). The tailings, composed basically of silica, are deposited with water in the dams. The high-grade ore resulting from the process can then be transformed into pellets at the pelletising plants, increasing the added value of the product.”

The mills that operate dry processing in Minas Gerais depend on the availability of ore with higher levels – about 60% Fe – still found in some mines in the state. “In order to achieve the necessary quality, and be incorporated into Vale’s product portfolio, it is necessary to blend with Carajás ores, carried out at Vale’s distribution centres in China and Malaysia. The process allows Vale to offer excellent quality ore which can be tailored to meet the needs of our clients,” the company said.

The blending of the product with natural moisture does not eliminate the need for humid concentration of the low-grade itabirite used in the production of pellets. However, to reduce the use of dams, Vale plans to invest approximately BRL 1.5 billion on dry stacking technology in Minas Gerais between 2020 and 2023. This technique filters and reuses waste water and allows the latter to be stored in piles, thus reducing the use of dams. The goal is to achieve up to 70% of the waste disposed in the coming years, but success depends on the improvement of technology and external issues, such as environmental licences, Vale said.

“Today, Vale doesn’t have a dry stacking operation that can deal with the production quantity especially in a region with high rainfall indices, such as the Ferriferous four-side, in Minas Gerais. The available dry stacking technology is used on a small scale around the world – up to 10,000 t/d of tailings produced – in desert regions or with low rainfall. In Minas Gerais, Vale’s tailings production quantity is, on average, 50,000 t/d per unit,” Vale said. In 2011, the company developed a pilot project on the Cianita stack in Vargem Grande, after an investment of BRL100 million.

The studies were completed in 2018 and the technicians evaluated the geotechnical behaviour of piles under rainy conditions. The next tests will be applied on an industrial scale at the Pico mine in the municipality of Itabirito, Vale said.

“Another solution that has been studied is the dry magnetic concentration of iron ore based on the innovative technology developed by New Steel, a company acquired by Vale at the end of 2018 for BRL1.9 billion,” Vale said. “The dry magnetic concentration eliminates the use of water in the concentration process of the low-grade ore, which disposes the waste generated in sterile piles, similar to what happens in dry stacking. This technology, however, is in the industrial development stage and is not yet ready to be applied on a large scale.”