Tag Archives: tailings

SRK leveraging real-time data to improve tailings dam safety

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Renewed global concern about the risks of tailings dam failure is accelerating a revolution in the use of automated sensors to generate big, real-time data to better monitor and manage these facilities, according to SRK Consulting.

“The need for knowing more about tailings dam conditions – and in real time – has become a major focus within the mining sector, demanding a step change in the way we collect, process and interpret data,” Lyzandra Boshoff, Principal Engineering Geologist at SRK Consulting, said. “As part of these efforts, SRK has been rolling out initiatives using automated vibrating wire piezometers (VWPs) on tailings facilities.”

Boshoff highlighted the particular significance of seepage and the associated pore pressure regime within a tailings facility as a vital aspect of the integrity and stability of the structure. This has conventionally been tracked by manual standpipe piezometers whose performance, while accurate, depends on the quality of installation and aftercare, she said. And, of course, manual data collection is subject to human error.

“This means expending considerable effort for relatively little data, which may often not exactly reflect the current situation by the time the information reaches the engineer for analysis,” she said. “Even the automated sensors using vibrating wire technology tended to rely on manual data collection from the logging devices connected to the sensors.”

This is now changing as many telemetry hardware developers have improved their wireless capability and cloud technology to upload and store data, allowing data to be immediately accessed by engineers and management.

“This has changed the landscape of data flow and interpretation, as well as the potential size of the datasets that can be generated,” she said. “SRK has been at the forefront of rolling out automated VWP networks, using logging systems that can send data wirelessly to cloud-based databases and can then be visualised and analysed in real time.”

Among the technological innovations the company is developing is a customised database and visualisation platform specifically for VWP data. This includes built-in, automated validation and interpretive tools to automate some of the routine engineering interpretive work. It builds upon available software technologies to create a solution that is customised to the field of tailings dam management, while also presenting opportunities for applying the principles in a range of disciplines.

The datasets generated by VWP networks can be significantly large, depending on the frequency at which data is collected. Conditions on site would determine the detail required for tracking where potentially adverse circumstances may develop, the company said.

“These VWP networks are also useful when needing to confirm whether the mitigation measures in place are having the desired effect,” Boshoff said.

Applying these technologies, SRK says it has been able to review the impact of construction process and other site activities and incidents on pore pressure responses, and analyse the impact of depositional patterns on the seepage flow regime within a facility.

“For the first time, we can see and correlate in real time what we have always predicted using models and assumptions,” Boshoff said. “Harnessing the power of big data, we can now test our assumptions and substantially raise the confidence of our observations. With the exponential growth in the application of technology in this field, more data is being generated and is available to be harnessed and interpreted.”

The sheer quantity of data generated means that engineers must innovate, finding new and more efficient ways to validate, evaluate and interpret the large incoming datasets.

Boshoff notes, however, that harnessing the full power of big datasets demands the appropriate database structures and validation processes to be in place – which is where SRK is investing considerable effort.

“To support this need, we have recently put in place a data services department at SRK, pulling together some of our brightest minds and data analysts,” she said. “This is helping champion our initiatives to harness these growing datasets into sound engineering information – so they can contribute to making informed engineering decisions.”

Itronics’ Rock Kleen technology ready to clean up heap leach operations

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Itronics says test work on two separate precious metals closed heap leach materials pads has provided positive results in recovering metals and minerals using its proprietary “Zero Waste” technologies.

Rock Kleen Tailings Processing Technology neutralises the residual cyanide and removes nitrogen produced by blasting rocks in the mining process, making the materials available for use as industrial minerals, according to Itronics.

This means it offers potential value to miners through the recovery of precious and base metals, the removal of cyanide (from leaching) and nitrogen (from blasting), the potential to produce industrial minerals products from ‘waste’ rock, and the potential elimination or reduction of the capital costs associated with conventional tailings storage facilities.

Itronics said the test work at its metallurgical laboratory on two separate silver-rich closed heap leach materials pads had provided positive results in recovering precious metals, base metals and industrial minerals. The company said laboratory testing also indicated the technology would prove effective on copper heap leaches.

Whitney & Whitney, a wholly-owned subsidiary of Itronics, has designed flow sheets for two different heap leach waste materials processing operations, which recover gold, silver and various base metals based upon the processing test work completed by Itronics Metallurgical Inc.

“Mineralogical analysis has defined potential industrial mineral products for the two separate resources allowing for 100% of the available resources being converted to saleable products,” it said.

Rock Kleen tech neutralises the residual cyanide and removes nitrogen produced by blasting the rocks in the mining process, making the materials available for use as industrial minerals, according to Itronics. This is where the company’s GOLD’n GRO Multi-Nutrient fertilisers come into the equation, according to President, Dr John Whitney.

“Base metals recovered using Rock Kleen technology are perfect for use as raw materials in the Itronics GOLD’n GRO fertiliser manufacturing process,” he said. “Designing gold/silver heap leach mines using Rock Kleen, or Rock Kleen in conjunction with cyanide leaching, will ensure maximum heap leach recoveries while targeting 100% of the resource as profitable product.”

The company says Rock Kleen technology has the potential to turn lower grade gold/silver deposits into profitable operations.

“Conventional cyanide leaching may recover a high percentage of soluble gold and a portion of the silver, but all the remaining materials are left as a waste product,” the company says. “Rock Kleen recovers additional gold/silver and base metals, and then the remaining rock can be sized for commercial grades of industrial minerals for sale leaving zero waste from the mining enterprise.”

John Key, Vice President, Projects for Whitney & Whitney, said: “Pilot scale testing is very promising. Each deposit must be evaluated on a standalone basis but many existing operations and heap leach projects being designed now could potentially benefit greatly by including a design using Rock Kleen or including the Rock Kleen technology into their flowsheets in conjunction with cyanide leaching.”

Multotec builds integrity with hydrocyclone solution at Zambia tailings facility

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An innovative hydrocyclone solution from Multotec is allowing a large Zambian copper mine to develop a safe and cost effective tailings storage facility (TSF), the South Africa based company says.

The TSF faced a number of specific challenges, according to Frikkie Enslin, Senior Applications Engineer responsible for cyclones at Multotec, including its extensive planned capacity and the area’s flat topography. The mine’s process plant pumps some 10,000 m³/h of tailings to the TSF, requiring its final circumference to reach about 19 km.

“The flat area around the mine meant there was no suitable topography to provide a natural dam,” Enslin says. “It was therefore vital to create strong walls to retain the slurry from the plant, so that the integrity of the TSF could be assured.”

Simple gravity separation and sun-drying had proved unable to create material firm enough to constitute walls, according to Multotec. In the early days of the plant’s operation, it was shown material being deposited by means of plain spigoting could still not be walked on even after a month of drying in the sun. By contrast, Multotec’s 250 mm GV hydrocyclones were able to deliver an underflow discharge that could be walked on in just two days, the company said. After a week, the material could withstand the weight of an excavator.

The sheer volume of slurry being pumped into the TSF, however, created its own challenge. The hydrocyclones had initially been mounted on metal cradles, which were inundated within a couple of hours. Extracting the cyclone and cradle from the mud for the next placement was difficult and very time consuming.

“The customer needed a solution that would keep the cyclone above the slurry level for longer, and would be easier to move,” he says. “To do this, we designed a cyclone cradle that could be attached to a long wooden pole, giving much greater height, allowing the customer to leave the cyclones in the same position for a much longer time.”

With Multotec’s experience and facilities for custom design and manufacture, the hydrocyclones were then modified to be lighter. This made them easier to handle and manoeuvre, it said.

“Constructed with a lighter metal, these tailor-made units are industry leaders in terms of being lightweight and are rubber-lined to ensure long wear life,” he said. “We also made some innovative improvements to the vortex finders and the cone sections, which are now metal spun.”

Other changes were made to speed up the changing of a spigot, and the moving of the hydrocyclones from one point on the TSF wall to the next. The design now includes a threaded spigot coupling and quick-release connections on the cyclone.

The solution has been so successful to date that over 250 of Multotec’s modified GV hydrocyclones have been installed.

“Just as we collaborated closely with the customer in developing this solution, so we continue our partnership in monitoring the performance of our hydrocyclones as the project goes on,” Enslin says. “An expert applications engineer from our Johannesburg head office visits the site regularly, while our Zambia office in Chingola offers solid technical and field service support. We don’t just sell process equipment, but rather process solutions.”

Newmont turning to software for Peñasquito TSF planning

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Newmont is looking to leverage planning software already used in the oil sands industry to create a safe, stable and well-planned tailings storage facility at its Peñasquito gold mine, in Mexico, according to Ross Hunsaker.

Hunsaker, the gold miner’s Tailings and Fresh Water Manager, is due to present ‘Newmont Goldcorp Peñasquito Mine – How Technology has Enhanced Tailings Planning’ at the 2020 SME MineXchange Annual Conference & Expo, in Phoenix, Arizona, on Tuesday, with a presentation abstract revealing more about his talk.

As he said in this abstract, the oil sands industry operates large, complex tailings storage facility (TSF), with these operators taking advantage of tools generated for mining and using them for planning and scheduling TSFs.

“Several different software packages are needed to handle this planning due to beach slope changes, mature fine tailings and water management,” he said. “Mining lags behind the oil sands industry when it comes to tools for tailings planning.”

At the Peñasquito mine, which produced 272,000 oz of gold in 2018, the TSF dam spans 11 km and, at completion, will be 150 m high. It has a centreline raise for three sides and a downstream raise for the fourth side, according to Hunsaker. It is being constructed using a mine fleet of Komatsu 930Es for a buttress, and a fleet of Cat 777 haul trucks for a sliver fill, with 20-ton (18 t) dump trucks for rock fill and cycloned sand, he added.

According to Hunsaker, the Peñasquito team is implementing planning software to integrate all construction activities into one plan, with scenario planning enhanced by software to optimise resources, activity duration and constraint identification.

Back in 2018, Goldcorp (which later merged with Newmont) achieved commercial production at Pyrite Leach project (PLP) at Peñasquito, a project that has seen tailings reprocessed for metal recovery.

The PLP plant processes the existing plant tails, feeding a sequential flotation and leach circuit with precious metals recovered through a Merrill Crowe process, producing doré as the final product. Tails from the new plant report to the existing TSF.

Hunsaker concluded in the abstract: “The overall software implementation is a work in progress with the overall goal of a safe, stable and well planned TSF.”

ICMM’s Butler talks tailings on anniversary of Brumadinho collapse

Environmental, Sustainable mining, Water management, , , , , , , , , ,

One year on from the Brumadinho dam collapse, ICMM CEO, Tom Butler, says the mining industry may have made progress with how it operates, but it still has much more to do to on the environmental, social and governance front.

The collapse, which reportedly killed 270 people, was attributed to poor internal drainage and intense rain among other factors, Vale said back in December.

In a statement, he said: “The dam collapse at Vale’s Corrego do Feijão mine in Brumadinho, Brazil, on January 25, 2019, was a human and environmental tragedy. One year on, we remember the victims of this catastrophic event and our thoughts are with those who have lost loved ones.

“The anniversary is a stark reminder that, while the mining and metals industry has come a long way in improving how it operates, there is still much more to do to safeguard lives, improve its environmental performance and demonstrate transparency.

“Shortly after the disaster, in an effort to drive change and establish best practice, the International Council on Mining and Metals (ICMM), United Nations Environment Programme (UNEP) and Principles for Responsible Investment (PRI) co-convened the Global Tailings Review to establish an international standard for the safer management of tailings storage facilities. The Global Tailings Standard, once endorsed by all three co-conveners, will be published later this year. The standard will become a commitment of ICMM membership and we will encourage others to join us in advocating for it to be adopted more broadly across the industry.

“In addition, ICMM is taking action by working in partnership – with technology providers, experts and researchers – to promote innovation in the monitoring and surveillance of tailings storage facilities and the development of alternative methods of mineral recovery to significantly reduce or eliminate the generation of tailings.”

‘World-first’ public database of mine tailings dams launched

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Environmental organisation GRID-Arendal, with support from the UN Environment Program (UNEP), says it has launched the world’s first publicly accessible global database of mine tailings storage facilities.

The database, the Global Tailings Portal, was built by Norway-based GRID-Arendal as part of the Investor Mining and Tailings Safety Initiative, led by the Church of England Pensions Board and the Swedish National Pension Funds’ Council on Ethics, with support from the UNEP. The initiative is backed by funds with more than US$13 trillion under management, according to GRID-Arendal.

Professor Elaine Baker from the School of Geosciences is Director of the GRID-Arendal office at the University of Sydney. She said: “This portal could save lives. Tailing dams are getting bigger and bigger. Mining companies have found most of the highest-grade ores and are now mining lower-grade ones, which create more waste. With this information, the entire industry can work towards reducing dam failures in the future.”

The release of the Global Tailings Portal coincides with the one-year anniversary of the tailings dam collapse in Brumadinho, Brazil (pictured above – CREDIT:IDF/Flickr), which reportedly killed 270 people. After that event, a group of institutional investors led by the Church of England Pensions Board asked 726 of the world’s largest mining companies to disclose details about their tailings dams. Many of the companies complied, and the information they released has been incorporated into the database, GRID-Arendal said.

The database will allow users to view detailed information on more than 1,900 tailings dams, categorised by location, company, dam type, height, volume and risk, among other factors.

Kristina Thygesen, GRID-Arendal’s Program Leader for Geological Resources and a member of the team that worked on the portal, said: “Most of this information has never before been publicly available.”

When GRID-Arendal began in-depth research on mine tailings dams in 2016, very little data was accessible. In a 2017 report on tailings dams, co-published by GRID and the UN Environment Program, one of the key recommendations was to establish an accessible public-interest database of tailings storage facilities.

“This database brings a new level of transparency to the mining industry, which will benefit regulators, institutional investors, scientific researchers, local communities, the media and the industry itself,” Thygesen said.

MMG’s Las Bambas aims for tailings boost with SciDev MaxiFlox trial

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SciDev’s MaxiFlox® chemistries are to be used in the tailings thickener at the Las Bambas copper mine, in Peru, following a trial purchase order from mine owner MMG.

The commercial trial follows on from earlier successful technical evaluations that SciDev conducted during 2019, it said.

The aim of the trial is to improve water recovery and, ultimately, increase the available volume in the mines tailings storage facility, according to SciDev.

SciDev Managing Director and CEO, Lewis Utting, said: “The order from MMG Ltd at their Las Bambas operation represents SciDev’s first entry into the copper sector in South America. With both water and available land at a premium in the region, SciDev’s technology could add value to our customers.”

Back in September, SciDev was awarded a three-year contract with Iluka Resources for delivery of MaxiFlox chemistry to the Jacinth–Ambrosia zircon mine, in South Australia. This order followed the delivery of a chemical products trial for the miner in the December quarter of 2018.

MaxiFlox is specifically designed for use in solid liquid separation processes, SciDev says. Products in the MaxiFlox range are supplied in both liquid and powder form across an extensive range of molecular weights and charge densities to solve industrial challenges. Products include:

  • MaxiFlox organic liquid coagulants (based on synthetic organic monomers and naturally occurring polysaccharides);
  • MaxiFlox inorganic liquid coagulant blends;
  • MaxiFlox cationic and anionic flocculant emulsions;
  • MaxiFlox cationic and anionic flocculant powders;
  • MaxiFlox mud solidification polymers, and;
  • MaxiFlox antifoam products.

Outotec provides modular paste backfill solution

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Outotec says its new Modular Paste Backfill Plant (MPB 80) is a high-quality, cost-effective plant solution for underground non-ferrous mining applications with low-range backfill throughput requirements.

The MPB 80 acts as an “ideal alternative” to installing a concrete batching-style plant that has been reconfigured for producing paste backfill, according to the company. The wet tailings solution uses 80 m2 of vacuum disc filtration and is geared towards mines with an ore production capacity of between 700,000 t/y and 1 Mt/y.

As Outotec says, a high-quality backfill system is vital to ensure mine integrity and the safety of personnel, as well as to minimise the volume of tailings that need to be directed to tailings dams on the surface.

“With a dedicated paste backfill plant, mines can produce high-quality paste at a lower cost than is possible with modified concrete plants and larger, previous-generation paste backfill plants.”

Because the Outotec Modular Paste Backfill Plant features a combined paste mixer and hopper in place of separate units, it enables significant reductions in both plant size and maintenance requirements, the company says. “In addition to reducing the plant footprint, this unique process design significantly reduces the need for cleaning, meaning the plant can run for multiple shifts without having to shut down,” it said.

The plant components are pre-assembled off-site and delivered in larger, pre-engineered modules, enabling a significantly shorter interval between order placement and installation and start-up.

Other key benefits include a reduction in capital expenditure without compromising paste backfill quality; a reduction in the need to direct tailings to surface dams for deposition; lower operating expenditure over the mine life with highly accurate binder addition; and a full range of operations and maintenance services available to ensure smooth, efficient operation.

Vale and BHP cleared for Samarco iron ore restart

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Vale says its joint venture Samarco Mineração SA division has been given clearance to restart operating activities at its Germano Complex, in Minas Gerais, Brazil, some four years after a dam collapse shuttered the operation.

Vale said the division, owned 50:50 by it and BHP, had received the Corrective Operation License (LOC) for its operating activities in the complex, adding that the licence was approved by the Mining Activities Chamber (CMI) of the State Council for Environmental Policy (COPAM).

Following this authorisation, Samarco has now obtained all environmental licences required to restart its operations.

Samarco is due to restart its operations using dry stacking technologies that, Vale says, will reduce the risk of such an accident happening again.

“For this reason, the operational restart of iron ore extraction and beneficiation plants in Germano and the pelletisation plant in the Ubu Complex, located in Anchieta, state of Espírito Santo, will only occur after the implementation of a filtration system, which construction is expected to take around 12 months,” Vale said. During this period, Samarco will continue operational readiness activities including equipment maintenance.

Following the implementation of the filtration process, and subject to shareholder approval, Samarco currently expects to restart its operations around the end of 2020, Vale says.

With the filtration process, Samarco expects to be able to substantially dewater sand tailings, which represents 80% of total tailings by volume, and stack these filtered tailings safely. The remaining 20% of tailings will be deposited in Alegria Sul pit, a bedrock self-contained structure, to increase safety. Alegria Sul pit preparation works began in October 2018 and were concluded this month.

Following changes to the environmental and regulatory frameworks for mining in Brazil in 2019, Samarco adjusted its mining and tailings disposal assumptions, including a reduction in the capacity of the Alegria Sul pit, so tailings would be confined to the self-contained area. This also led to a reduction in the capacity to store filtered tailings due to the classification of the Germano pit as a dam, which will now be decommissioned in accordance with the regulation.

The above-mentioned changes to regulatory and tailings disposal assumptions materially impact the expected ramp up of Samarco operations given a range of factors, including but not limited to the completion of additional licensing processes and the development of additional tailings disposal sites, the company said.

Samarco expects to be able to restart operations through one concentrator and produce some 7-8 Mt/y following the installation of the filtration technology.

A second concentrator could be restarted in around six years to reach a range production of 14-16 Mt/y, while the restart of the third concentrator could happen in around 10 years after the issuance of the LOC, when Samarco expects to reach annual production volume in a range of approximately 22-24 Mt/y, it said.

Weba Chute Systems called in for Mexico gold tailings project

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As part of a significant investment to improve its processing facilities and enable the recovery of 40% of the gold that currently sits in its tailings as waste, a mining operation in Mexico called in a leading transfer point and chute systems equipment manufacturer to conduct a thorough assessment on the functionality of existing chutes in the plant.

Weba Chute Systems & Solutions, leveraging its knowledge of material behaviour in chute systems, was tasked with establishing the feasibility of introducing filtered tailings at a rate of 1,200 t/h onto the existing transfer system currently handling waste with a nominal size of 400 mm at a rate of 5,000 t/h.

While the intention is for the filtered tailings to be conveyed when the waste rock is available, it would still mean the same chutes would need to function transferring completely different material, according to Alwin Nienaber, Technical Director of Weba Chute Systems.

“Optimally, one should be able to assess a working transfer chute handling the actual material, however in the case of a feasibility assessment this is not possible, and we therefore started with a review of the test work and studies prepared by independent qualified professional materials handling experts.”

This was done by Weba Chute Systems & Solutions calibrating the material conditions and behaviour using discrete element method (DEM). Nienaber said: “Use of DEM allowed our technical team to model the interaction between individual particles and boundaries and, in so doing, to accurately predict the bulk solids behaviour.”

Access to DEM software allows engineers to predict bulk material flow patterns and flow rates as well as velocity patterns and dead zones within a transfer system, according to Weba. It also provides accurate information on particle distribution in segregation and blending and the impact forces on particles and boundary surfaces, showing wear patterns.

The feasibility assessment included the transfer of sedimentary dry tailings, sedimentary filter cake, breccia dry tailings and breccia filter cake. DEM modelling was carried out considering material on its own and conditions where blended material would be conveyed.

In total, there were four conveyor transfer points that had to be assessed. These included an inline transfer point, a 90° transfer point, a transfer from conveyor to radial spreader intermediate conveyor and then onto the spreader boom conveyor.