Tag Archives: HPGR

Kışladağ and Weir Minerals on the HPGR-backed gold recovery trail

Comminution of minerals, Environmental, Metallurgy, Mine operation news, Mineral processing, Mining consumables, Mining equipment, Mining services, Power supply for mines, Precious metals, Sustainable mining, , , , , , , , , , , , , ,

The story that led to the installation of a Weir Minerals Enduron® high pressure grinding roll (HPGR) at Eldorado Gold’s Kışladağ heap leach operation in Turkey is a fascinating read, as well as a great example of the benefits of using such technology.

Back in March 2018, Eldorado announced it would suspend mining to evaluate processing options for the operation. This decision followed extensive laboratory tests that indicated gold recoveries would continue to trend downwards around the base of the open pit where mining was underway.

This suspension, plus further engineering and test work, led to the company advancing the potential development of a mill project. The transition away from its heap leaching roots to a possible mill and carbon-in-leach (CIL) process would have added significant capital costs and shortened the mine life significantly.

Before making this significant capital decision, Eldorado paused to take time to undertake the necessary technical work and sought the technical collaboration of Weir Minerals on a solution.

“It was a very challenging period,” George Burns, President & CEO of Eldorado Gold Corporation, told IM. “Kışladağ is a cornerstone asset in our portfolio. It required collaboration with our geologists, metallurgists, site teams and technology providers, including Weir, working together on a solution.”

(Credit: Eldorado Gold)

In late 2018, results showed increased recoveries from an extended leach cycle. Following a deeper understanding of the geometallurgical drivers of the sulphide component of the deposit, improved heap leach recoveries were realised by optimising the metallurgical conditions. With these improved recoveries confirmed, the heap leach plan was revised in early 2019. Eldorado announced plans to resume mining, crushing, stacking and heap leaching at Kışladağ, and suspended plans to build the processing plant.

The decision came following metallurgical test work on the material placed on the heap leach pad in 2018. Gold recovery had increasingly exceeded expectations throughout the year, providing a new, positive heap leaching outlook beyond the near term. At the same time, Eldorado worked with Weir Minerals on the potential use of an HPGR at the operation.

HPGR creates a finer particle size, which helps to liberate the gold particles, resulting in increased recoveries.

An improved understanding of the leaching process on its low-grade ore and the potential of this cost-effective grinding addition provided it with the confidence to continue heap leaching beyond the short-term time horizon previously envisaged.

“Our collaboration with Weir on this effort is an excellent example of how Eldorado collaborates with technology leaders and seeks out solutions,” Burns said. “We believe this is a strength of the company’s core business values. We are agile and flexible ‒ a good example in both business and operations to find innovative, technical solutions and demonstrate prudent capital discipline. Ultimately, the solution was the best technical and economic decision for Eldorado.”

Testing, testing, testing

“The relationship between Weir Minerals’ and Kışladağ goes back to 2013,” Bjorn Dierx, Global Product Manager Enduron HPGR, told IM.

The OEM had been provided with samples on several occasions to investigate different flowsheet possibilities.

“The benefits of HPGR in heap leaching recovery were known by the site’s crew,” he said.

Enduron technology was tested at the quaternary crushing stage before heap leaching, in the quaternary crushing stage before ball milling and at the tertiary crushing directly before heap leaching.

All the time, the mine operator, Tuprag, Eldorado Gold’s subsidiary in Turkey, was evaluating the impact on gold recovery.

Although HPGR in closed circuit with screening was also tested, most of the test campaigns were focused on a configuration with so-called ‘Partial Product Recycling’ (PPR), according to Serhat Onol, Weir Minerals Senior Process Engineer.

“This system includes splitter plates underneath the rolls which ‘cut’ a proportion of the product discharge and reverts this back to the HPGR head feed,” he explained. “This recycle stream can be adjusted online to adapt the product grind towards the downstream requirements.”

PPR is not an option for every application but for Tuprag – due to the feed and desired product size – all specifications showed it was the best route.

“The hybrid solution with screening serves to increase the flexibility and to control the circulating load to the HPGR,” Onol said.

With capacity rates of around 4,200 t/h at Kışladağ, the screening area requirement was reasonably high, he explained.

“The hybrid solution uses screening only for the recirculating stream: the centre product of the HPGR reports to downstream leaching, whereas the rest is recirculated,” he said. This not only removes the fines re-entering the HPGR and, thus, reduces the circulating load, but also avoids the over-grinding of fines before leaching.

The PPR option, itself, is a very flexible operation, with the adjustable discharge splitter plates providing the best circuit flexibility in terms of throughput and product size, according to Onol.

(Credit: Eldorado Gold)

Great expectations

With the main driver of the HPGR installation being an improved gold recovery scenario, leading to an increased heap leach life, the pressure has been on Weir Minerals to come up with the goods.

The final flowsheet, which includes a 2.4 m diameter by 2.2 m long Enduron HPGR with the capacity to process 4,200 t/h, is much simpler than the existing circuit, according to Dierx, with less equipment to maintain, control and monitor.

“A single Enduron HPGR will replace all of the five existing tertiary crushers of which liners would have an average lifetime of circa-one month with a crusher availability of 85%,” he said. “The HPGR tyres have a wear life close to 18 months, with the HPGR achieving a high asset availability of more than 95%.

“Additionally, as a result of the HPGR combined with the hybrid PPR system, the existing four tertiary screens are also being decommissioned.”

Not only has the HPGR alleviated the use of this equipment, it is also set to boost that bottom line gold recovery.

“During testing, it was determined that the circuit configuration and HPGR operating conditions, such as pressure, have a direct influence on the gold recovery,” Dierx said. “The current expectation is that the average recovery increase after the commissioning of the Enduron solution will be approximately 4%.”

This could bring gold recovery to approximately 56%, as was declared in a 2020 press release from Eldorado that highlighted a 15-year mine life at Kışladağ with an average annual production of 160,000 oz.

In action

One of the largest brownfield HPGRs Weir Minerals has ever installed has just processed its first material at Kışladağ, which is testament to the hurdles both the Weir Minerals and Tuprag teams overcame during the height of the COVID-19 pandemic.

“Despite the challenges we faced during the pandemic, we were able to fully install the machine, including pre-commissioning, in only 22 weeks,” Dierx said.

(Credit: Eldorado Gold)

This was achieved by minimising the amount of work carried out on site via pre-site testing and modular HPGR assembly.

“As the available footprint in existing sites is limited, the unique Enduron design (length:diameter ratio) not only improves the grinding efficiency but also allows for easier implementation with less civil requirements,” Dierx said.

The machine has the potential to be digitally connected to the Weir Synertrex® IoT platform where operators can benefit from direct access to maintenance specialists, who will be monitoring performance and provide necessary operating guidance.

And the Weir Minerals team is confident more Enduron HPGR installations will follow the one at Kışladağ.

“We are very proud of the product’s recognition by our customers as the Enduron HPGR has been selected for all major greenfield HPGR projects in the hard-rock space,” Dierx said. “Despite all the key Enduron differentiators, it is not only merely about the product but particularly the wider experience across Weir Minerals in both the upstream and downstream processes via our wide product portfolio.

“Particularly in these brownfield applications, the system is not operating in a vacuum and every process change influences how the overall circuit works. This requires tacit knowledge, which Weir Minerals holds across their global teams.”

Eldorado’s Burns concluded: “We are pleased to implement a solution that increases gold recovery and supports a 15-year mine life at Kışladağ, allowing Eldorado to continue to provide employment and economic opportunity in the region, as well as provide a solid foundation for future growth.

“Kışladağ has been the cornerstone asset of Eldorado for over a decade, producing over 3 Moz of gold and generating significant value for all stakeholders during that period. This project is a testament to our exceptional team and technology partners working together to execute in challenging circumstances during the pandemic.”

Enter Engineering, thyssenkrupp to tackle Tebinbulak iron ore deposit in Uzbekistan

Comminution of minerals, Mineral processing, Mineral project development, Mining equipment, Mining services, Steel and iron ore, Sustainable mining, , , , , , , , , , , ,

Enter Engineering and thyssenkrupp AG have signed an Agreement of Intent that could see the engineering procurement and construction (EPC) contractor take the exclusive role as construction partner in building an integrated mining metallurgical complex at the Tebinbulak iron ore deposit in Uzbekistan.

The pact, worth €50 million ($58 million), comes on top of a signed agreement for the start of preparatory work on the project, including a contract for the supply of equipment, its design, supervision during installation and commissioning at the facility.

The high pressure grinding roll (HPGR) technology will be used to help process up to 60 Mt/y of iron ore, according to the EPC firm.

The implementation period for Enter Engineering’s construction role is two years with the plant launch anticipated for September 2023.

Bakhtiyor Fazylov, Chairman of the Board of Directors of Enter Engineering, said: “We are delighted to partner with a leading global company such as thyssenkrupp. Applying German standards, we will create a high-quality raw material base for the domestic metallurgical industry. This project also embodies all the goals Enter Engineering strives for: protecting Uzbekistan’s national interests in the international market, supporting the interests of domestic consumers and creating jobs.”

Reza Poorvash, CEO thyssenkrupp Mining Technologies Europe and Asia, said: “To date, more than 140 units of HPGR equipment have been sold in the mining industry. In the CIS countries, thyssenkrupp takes a leading position among mining companies that use this technology, in practice confirming the high quality and reliability of the German brand.”

Roman Karl, Managing Director thyssenkrupp Mining Technologies CIS, added: “We are delighted to partner with such a well-known company in Uzbekistan as Enter Engineering, who have a long track record of successful execution in major engineering construction projects.

“The project will use one of the most energy efficient and innovative technologies to significantly reduce energy consumption. HPGR has been used since 1985 in the cement industry, and since 1986 in the mining industry for use in the grinding process to ensure a high level of product fineness. Full integration of this technology within Industry 4.0 is also important.”

The Tebinbulak complex is significant for Uzbekistan because of its multiplier effect. As well as creating new jobs in remote areas, it will help develop domestic iron ore to provide the country’s existing metallurgical complexes with raw materials. It will also support development of infrastructure, creation of service enterprises and an increase in trade between countries.

Tebinbulak is located in the Karauzyak district of Karakalpakstan, in the north-west part of Uzbekistan. The field covers 5.2 sq.km and comes with a predicted mine life of 27 years.

Cooperation between Enter Engineering and thyssenkrupp is supported at a high inter-governmental level, with the agreement signing ceremony attended by Alisher Sultanov, Uzbekistan’s Minister of Energy.

Swiss Tower Mills Minerals backs Coalition for Eco-Efficient Comminution

Comminution of minerals, Mineral processing, Mining equipment, Mining industry recognition, Mining services, Sustainable mining, , , , , , , , , , , , ,

Swiss Tower Mills Minerals AG (STM) has become the latest sponsor to support the work of the not-for-profit Coalition for Eco-Efficient Comminution (CEEC).

An innovative company that has successfully translated the vertical stirred milling technology of industrial minerals to hard-rock minerals processing, STM’s support of CEEC’s work was a natural fit for the company, according to Managing Director, Ralf Hesemann.

“The uptake of new technology in the mining industry is traditionally a slow process,” Hesemann said. “Tapping into a trusted independent body that communicates the latest technical findings on efficient comminution practices is a win-win for both of us.

“I look forward to our collaboration.”

Swiss-based STM developed the Vertical Regrind Mill (VRM) and released it to the minerals market in 2012. More than 60 of the stirred media grinding mills have been sold to mines across the Americas, Europe, Africa, Asia and Australia. For fine and ultra-fine grinding applications, it is marketed under the name HIGmill, through the exclusive partner Metso:Outotec. For coarse regrind applications, STM offers the VRM mill directly to customers in the minerals market.

Since the grinding principle of multi-compartment grinding offers substantial energy savings, a new stirred mill has been developed for coarse grinding applications up to 6 mm feed size, the Vertical Power Mill™ (VPM). Mill sizes range from 700 kW to 12,500 kW with high flow rates, and potential energy savings of up to 40%. Due to its small footprint, STM is marketing the VPM as a viable ball mill replacement in HPGR circuits or for capacity increase in existing plants.

The energy savings are achieved through uniquely designed rotors and stator rings in a vertical arrangement that enable high power intensities, even with relatively low tip speeds, STM says. This results in higher energy efficiency, a smaller footprint and the potential for increased recoveries. Power intensities of 200-300 kW/cu.m are typical, and operational tip speeds range between 6-12 m/s, depending on application and mill size.

CEEC Director, Chris Rule, said it was encouraging to see energy efficient, stirred media mills being installed by industry as a step towards more sustainable mining practices, in line with ESG considerations and net zero emissions commitments.

One of the first HIGmills be commissioned, in 2015, was a 700 kW mill for a copper concentrate regrind application at the Kevitsa mine in Finland. Several papers have been published on the energy efficiency and metallurgical performance of this mill, including an Outotec paper presented at Comminution Capetown 2016, and ‘A Review of Published Full-Scale Stirred Mill Results’ by Michael Larson, Molycop, USA, presented at the SAG 2019 Conference.

The technology will also be installed at the Iron Bridge Magnetite Project in Western Australia. The joint venture between Fortescue Metals Group and Formosa Steel IB Pty Ltd is the world’s first large-scale plant without horizontal milling. The flowsheet consists of a two-stage HPGR circuit feeding in total 10 advanced HIGmill grinding mills.

Rule said stirred mill grinding technology had been well proven for decades in industrial mineral applications such as in the opacifiers, fillers, ceramics, paint and pharmaceutical industries.

“We commend STM for translating this technology to mineral processing, offering miners an energy-efficient, low footprint alternative to high-intensity ball milling,” Rule said.

“Having STM on board as a CEEC sponsor means greater opportunities for us to learn about and share alternative comminution approaches. This support from our valued sponsors over the past 10 years is what enables CEEC to help keep industry aware of demonstrated advances that help mining leaders tackle the challenges of reducing the energy consumption, emissions and overall footprint of their operations.”

Hesemann said declining ore quality meant energy efficient comminution was becoming a more critical stage for realising profit.

“We’re proud of the part our technology plays in lowering the footprint of mineral processing, while at the same time decreasing capital expenditure and operating expenditure and improving the bottom line.

“Being a CEEC sponsor will enable us to more widely share any advances in this field, as well as learning from the global network of industry experts that CEEC brings together through its events and online resources.”

Pictured is the factory acceptance test success for a new 50,000 litre Vertical Regrind Mill (VRM50000)

eHPCC: the future of grinding in mining?

Base metals, Bulk handling, Comminution of minerals, Environmental, Equipment maintenance, Mineral processing, Mining equipment, Mining events, Mining maintenance, Mining services, Precious metals, Sustainable mining, Water management, , , , , , , , , , , , , , , , , , , , , , , , ,

A lot has been made of the potential of high pressure grinding rolls (HPGRs) to facilitate the dry milling process many in the industry believe will help miners achieve their sustainability goals over the next few decades, but there is another novel technology ready to go that could, according to the inventor and an independent consultant, provide an even more effective alternative.

Eccentric High Pressure Centrifugal Comminution (eHPCC™) technology was conceived in 2013 and, according to inventor Linden Roper, has the potential to eliminate the inefficiencies and complexity of conventional crushing and/or tumbling mill circuits.

It complements any upstream feed source, Roper says, whether it be run of mine (ROM), primary crushed rock, or other conventional comminution streams such as tumbling mill oversize. It may also benefit downstream process requirements through selective mineral liberation, which is feasible as the ore is comminuted upon itself (autogenously) in the high pressure zone via synchronous rotating components. Significant product stream enrichment/depletion has been observed and reported, too.

As IM goes to press on its annual comminution and crushing feature for the April 2021 issue – and Dr Mike Daniel, an independent consultant engaged by Roper to review and critique the technology’s development, prepares a paper for MEI Conferences’ Comminution ’21 event – now was the right time to find out more.

IM: Considering the Comminution ’21 abstract draws parallels with HPGRs, can you clarify the similarities and differences between eHPCC and HPGR technology?

MD & LR: These are the similarities:

  • Both offer confined-bed high-pressure compression comminution, which results in micro fractures at grain boundaries;
  • Both have evidence of preferential liberation and separation of mineral grains from gangue grains at grain boundaries; and
  • Both have an autogenous protective layer formed on the compression roll surfaces between sintered tungsten carbide studs.

These are the differences:

  • eHPCC facilitates multiple cycles of comminution, fluidisation and classification within its grinding chamber, retaining oversize particles until the target product size is attained. The HPGR is a single pass technology dependent on separate materials handling and classification/screening equipment to recycle oversize particles for further comminution (in the event subsequent stages of comminution are not used);
  • Micro factures around grain boundaries and compacted flake product that are created within HPGRs need to be de-agglomerated with downstream processing either within materials handling or wet screening. In some instances, compacted flake may be processed in a downstream ball mill, whereas, in eHPCC, preferential mineral liberation is perfected by subsequent continuous cycles within the grinding chamber until mineral liberation is achieved within a bi-modal target size (minerals and gangue). The bi-modal effect differs from ore type to ore type and the natural size of the minerals of interest;
  • The preferential liberation of mineral grains from gangue grains generally occurs at significantly different grain sizes, respectively, due to the inherent difference in progeny hardness. eHPCC retains the larger, harder grains, hence ensuring thorough stripping/cleaning of other grain surfaces by shear and attrition forces;
  • eHPCC tolerates rounded tramp metal within its grinding chamber, however does not tolerate high quantities of sharp, fragmented tramp metal that create a non-compressible, non-free-flowing bridge between roll surfaces, which risks the damage of liner surfaces;
  • The coarse fraction ‘edge effect’ common in HPGR geometry is not an issue with eHPCC. In fact, the top zone of the eHPCC grinding chamber is presumed to be an additional portion of the primary classification zone within the grinding chamber. The oversize particles from the internal classification process are retained for subsequent comminution;
  • The maximum size of feed particle (f100) entering the eHPCC is not limited to roll geometry as is the case with HPGRs (typically 50-70 mm). eHPCC f100 is limited to feed spout diameter (for free flow) and dependent of machine size ie eHPCC-2, -5, -8 and -13 are anticipated to have f100 60 mm, 150 mm, 240 mm and 390 mm, respectively. The gap between rolling surfaces is greater than the respective f100; and
  • eHPCC technology shows scientifically significant product stream enrichment.

IM: What operating and capital cost benefits do you envisage when compared with typical HPGR installations?

MD & LR: Both operating and capital cost benefits of the eHPCC relative to HPGR technology are due to the eHPCC not requiring the pre-crushing and downstream classification equipment required by HPGRs.

The eHPCC operating cost benefits are associated with eliminating maintenance consumables, downtime, reliability issues and energy consumption associated with the equivalent HPGR downstream equipment listed above.

The eHPCC capital cost benefits are associated with eliminating the real estate (footprint) and all engineering procurement and construction management costs associated with the equivalent HPGR upstream/downstream equipment listed above. eHPCC flowsheets are likely to be installed as multiple ‘one-stop’ units that maintain high circuit availability due to ongoing cyclic preventative maintenance.

IM: Where has the design for the eHPCC technology come from?

LR: It was invented in early 2013 by me. I then pioneered proof-of-concept, prototyping, design and development, culminating in operational trials in a Kazakhstan gold mine in 2020. A commercial-grade detailed design-for-manufacture has since been undertaken by a senior team of heavy industry mechanical machine designers and engineers.

IM: In your conference abstract, I note that the eHPCC technology has been tested at both laboratory and semi-industrial scale with working prototypes. Can you clarify what throughputs and material characteristics you are talking about here?

LR: The first iteration of the technology, eHPCC-1, was tested at the laboratory scale from 2013-2015. This proof-of-concept machine successfully received and processed magnetite concentrate, copper-nickel sulphide ore, alkaline granite, marble and a wolfram clay ore dried in ambient conditions. The typical throughput was between 200-400 kg/h depending on the feed size, particle-size-reduction-ratios (dependent of grain size) and target product size. The feed size was limited to a maximum of 25 mm to ensure free flow of feed spout.

Alkaline granite: eHPCC-2 coarse product (left) and fine product (right)

MD & LR: From 2016-2020, we moved onto the semi-industrial scale testing with the eHPCC-2 (two times scaled up from eHPCC-1). This was designed for research and development (R&D) and tested on magnetite concentrate, alkaline granite, and hard underground quartz/gold ore. The throughput capabilities depended on the geo-metallurgical and geo-mechanical properties of feed material, such as particle size, strength, progeny (grain) size and particle size-reduction-ratios (subject to confined bed high pressure compression). Larger-scale machines are yet to be tested against traditional ‘Bond Theory’ norms.

The eHPCC, irrespective of the outcomes, should be evaluated on its ability to effectively liberate minerals of interest in a way that no other comminution device can do. The maximum feed size, f100, at the gold mine trials was limited to 50 mm to ensure free flow through the feed spout. R&D culminated in pilot-scale operational trials at the Akbakai gold mine (Kazakhstan), owned by JSC AK Altynalmas, in 2020, where SAG mill rejects of hard underground quartz/gold ore were processed. The mutual intent and purpose of the tests was to observe and define wear characteristics of the eHPCC grinding chamber liners (roll surfaces). These operational trials involved 80% of the feed size being less than 17 mm and a variety of targeted product sizes whereby 80% was less than 1 mm, 2 mm, 2.85 mm and 4.8 mm. The throughput ranged from 1-5 t/h based on the size.

IM: What throughputs and material characteristics will be set for the full-scale solution?

LR: There will be a select number of standard eHPCC sizes. Relative to the original eHPCC-1, the following scale-up factors are envisaged: -2, -3, -5, -8, and -13. These are geometrical linear scale-up factors; the actual volumetric capacity is a cube of this factor, with adjustments for centripetal acceleration. Currently -13 times seems to be the maximum feasible size of the present detailed design philosophy, but there are no foreseeable limitations in terms of feed materials with exception to moist clay. Clay was successfully processed after drying the feed in ambient temperatures during testing. Further testing of moist clays blended with other materials that can absorb the moisture as they comminute would be desirable.

IM: Other HPGRs can also be equipped with air classification technology to create dry comminution circuits. What is the difference between the type of attrition and air classification option you are offering with the eHPCC?

MD & LR: Two modes of comminution occur in the particle bed of eHPCC repetitively and simultaneously. First, confined bed pressure compression breakage occurs at a macro level that promotes shear/compression forces greater than the mineral grain boundaries. Second, Mohr-Coulomb Failure Criteria (shear/attrition) that completes the separation of micro fractures on subsequent cycles takes place.

The nip angle between the rotating components of eHPCC technology never exceed 5°. During the decompression and fluidisation portion of the cycle, the softer species – which are now much smaller – are swept out of the fluidised particle bed against centrifugal and gravitational forces by process air. The larger species, influenced by centripetal acceleration, concentrate at the outer diametric and lower limits of the conical rotating grinding chamber, continuing to work on each other during each subsequent compression phase.

HPGRs are limited to one single-pass comminution event, requiring downstream external classification and subsequent recycling/reprocessing of their oversize and/or flake product.

IM: How will it improve the mineral liberation and separation efficiency compared with other grinding solutions that combine both?

MD: eHPCC technology could compete with the Vertical Roller Mill and Horomill, however, eHPCC is likely to be more compact with high intensity breakage events contained within the all-inclusive system of breakage, classification and removal of products.

IM: When was it most recently tested and over what timeframe?

LR: The eHPCC-2 pilot plant was mobilised, setup and commissioned in March 2020, but its operation was suspended until June 2020 due to COVID-19 quarantine restrictions and a need to cater to abnormal amounts of ball fragments in the feed, the latter of which pushed the treatment of tramp metal to the extreme. The machine operated for the months of June and July using liners constructed of plasma transferred arc welded (PTAW) tungsten carbide (TC) overlay. During this period, a total of 795 t was processed at various targeted product sizes, with, overall, an average throughput of 3 t/h (nominally 265 operating hours) processed.

Side view of pilot system including feed hopper and weigh-scale feeder (right), feed conveyor (middle foreground), control and auxiliaries (middle background), eHPCC-2 (left foreground), dust bag-house (left background) and product conveyor and stockpile (not shown left background)
Front-end loader filling feed hopper with SAG mill rejects f80 18 mm

The PTAW-TC overlay was deemed unsustainable as it was consumed rapidly and demanded continuous rebuilding due to the high pressure intensive abrasive wear on the convex cone. The pilot plant operation was mostly suspended during the month of August while an alternative tungsten carbide studded liner, analogous to HPGR studded rolls, was manufactured for simulating a trial of this studded liner philosophy. The studded liner philosophy was operated in the eHPCC-2 in Kazakhstan for sufficiently long enough to ascertain the creation of the autogenous protective wear layer of rock between the studs, with the simulation trial deemed a success. The design philosophy shall be adapted on the commercial-grade eHPCC.

eHPCC-2 TungStud™ as-new (left) high-pressure-air-cleaned (middle) and brushed (right)

The pilot plant was demobilised from the Akbakai site laydown area on September 10, 2020, to release the area for construction of a non-related plant expansion. The operational experiences of the pilot plant at Akbakai provided valuable knowledge and experience pertaining to mechanical inertia dynamics and design for eliminating fatigue within eHPCC components.

IM: Aside from the test work on trommel oversize at the Kazakhstan gold mine, where else have you tested the technology?

LR: eHPCC has no other operational experiences so far. Investment and collaboration from the industry to progress the commercialisation of eHPCC is invited. The commercial-grade eHPCC-2.2 is designed and ready for manufacture.

IM: Is the technology more suited to projects where multiple streams can be produced (fines, coarse piles, etc)?

LR: eHPCC is configurable to meet the demands and liberality of a diverse spectrum of feed materials and the potential downstream extractive processes are complementary to eHPCC product streams. Therefore, it would be incorrect to categorise it as more suitable in any one niche; it is configurable, on a case-by-case basis, to meet the liberality of the specific progeny of the feed.

IM: What energy use benefits do you anticipate by creating a one-step comminution and classification process over the more conventional two-step process?

MD & LR: The energy saving benefits include:

  • Elimination of tumbling mill grinding media consumption;
  • Elimination of the liberal wastage of randomly directed attrition and/or impact events that indiscriminately reduce the size of any/all particles (gangue or precious mineral) with the conventional tumbling mill; and
  • Elimination of energy consumption of the materials handling systems between the various stages of comminution and classification, be it dry belt conveying, vibrating screens, classifiers, cyclone feed pumps, cyclones and their respective recirculating loads that can be upward of 300% of fresh feed.

IM: Do you anticipate more interest in this solution from certain regions? For instance, is it likely to appeal more to those locations that are suffering from water shortages (Australia, South America)?

MD & LR: We suspect the initial commercialisation growth market to be from base metals producers seeking to expand or retire existing aged/tired comminution classification capacity, followed by industry acknowledgement of the technology’s potential to shift the financial indicators of other potential undeveloped projects into more positive territory. This latter development could see the technology integrated into new projects.

In general, the technology will appeal to those companies looking for more efficient dry comminution processes. This is because it offers a pathway to rejection of gangue at larger particle sizes, early stream enrichment/depletion and minimal overgrinding that creates unnecessary silt, which, in turn, hinders or disrupts the integrity of downstream metallurgical extraction kinetics, and/or materials handling rheology, and/or tailings storage and management.

LR: There are a number of rhetorical questions the industry needs to be asking: why do we participate in the manufacture and consumption of grinding media considering the holistic end-to-end energy and mass balance of this (it’s crazy; really why?)? Why do we grind wet? What are the barriers preventing transition from philosophising over energy efficiency, sustainability etc and actually executing change? Who is up for a renaissance of bravely pioneering disruptive comminution and classification technology in the spirit of our pioneering forefathers?

The more these questions are asked, the more likely the industry will find the solutions it needs to achieve its future goals.

Dr Mike Daniel’s talk on eHPCC technology will be one of the presentations at the upcoming Comminution ’21 conference on April 19-22, 2021. For more information on the event, head to https://mei.eventsair.com/comminution-21/ International Mining is a media sponsor of the event

SNC-Lavalin to manage construction of Coeur’s Rochester silver-gold mine expansion

Comminution of minerals, Mine operation news, Mineral processing, Mineral project development, Mining services, Precious metals, , , , , , , , ,

SNC-Lavalin has been awarded a $30 million contract by Coeur Rochester Inc, a wholly-owned subsidiary of Coeur Mining, to provide construction management services for the Plan of Operations, Amendment Number 11 (POA 11) expansion project, at Coeur’s Rochester mine near Lovelock, Nevada, USA.

The contract commenced in the December quarter and is estimated to be completed by the end of 2022. This win is aligned with SNC-Lavalin’s new strategy moving forward in the Services segment, it said.

The POA 11 expansion project includes the construction of a new crushing plant, including a primary, secondary and tertiary crushing circuit (high pressure grinding rolls), a new heap leach pad (272 Mt), a new Merrill-Crowe process plant (62,509 litres/min), and upgrades to existing electrical utility system infrastructure, including a new substation and power distribution lines.

Coeur says this will more than double planned annual crusher throughput capacity from around 12.7 Mt to over 25.4 Mt, post-expansion. This will see average annual silver and gold production total over 8 Moz and some 80,000 oz, respectively, for the initial 10 years, post-expansion

SNC-Lavalin said: “This mandate is well aligned with our expertise in silver, gold and base metal project delivery as well as our commitment to delivering real value to our clients.”

SNC-Lavalin’s offices in Reno, Nevada, and Toronto, Ontario, will continue to support the construction management phase of the project. In addition, a team based locally at the site will manage construction-related activities.

César Inostroza, Senior Vice-President, Mining & Metallurgy, SNC-Lavalin, said: “SNC-Lavalin’s Mining & Metallurgy strategic plan is gaining traction with this mandate. It is an example of the mining services work that our team is winning across our core geographies, including the USA. SNC-Lavalin and Coeur continue to foster a strong relationship that finds and executes services solutions to create world-class operations

“This award is a testament to the continued partnership between SNC-Lavalin and Coeur. It leverages our knowledge of the Rochester mine and engineering expertise from the previous phase of this project and expands our work in the US.”

Terrence FD Smith, Coeur’s Senior Vice President and Chief Development Officer, added: “The strong business partnership between Coeur and SNC-Lavalin will help ensure a robust project delivery for Rochester, paving the way for improved performance in the future.”

Since approval of the initial Plan of Operation in 1986, the Rochester mine has undergone periodic mine plan amendments to support development projects and continued operations. The POA 11 proposes another mine life extension, which is expected to maintain the current workforce and support full production activities at Rochester until 2033.

AngloGold Ashanti confirms caving plans in Colombia

Automation, Base metals, Bulk handling, Comminution of minerals, Environmental, Explosives and blasting, Mine shafts and equipment, Mineral project development, Mining equipment, Mining events, Mining services, Power supply for mines, Precious metals, Sustainable mining, Water management, , , , , , , , , , , , , , , , ,

The Massmin 2020 crowd got a glimpse of just what will be required to build Colombia’s first underground caving mine during a presentation from AngloGold Ashanti’s Lammie Nienaber this week.

Nienaber, Manager of Geotechnical Engineering for the miner and the presenter of the ‘Building Colombia’s first caving mine’ paper authored by himself, AngloGold Ashanti Australia’s A McCaule and Caveman Consulting’s G Dunstan, went into some detail about how the company would extract the circa-8.7 Moz of gold equivalent from the deposit.

The Nuevo Chaquiro deposit is part of the Minera de Cobre Quebradona (MCQ) project, which is in the southwest of Antioquia, Colombia, around 104 km southwest of Medellin.

A feasibility study on MCQ is expected soon, but the 2019 prefeasibility study outlined a circa-$1 billion sublevel caving (SLC) project able to generate an internal rate of return of 15%. Using the SLC mining method, a production rate of 6.2 Mt/y was estimated, with a forecast life of mine of 23 years.

The MCQ deposit is a large, blind copper-gold-silver porphyry-style deposit with a ground surface elevation of 2,200 metres above sea level (masl, on mountain) and around 400 m of caprock above the economic mineralisation.

Due to the caving constraints of the deposit, the first production level to initiate caving (undercut) is expected to be located around 100 m below the top of the mineralisation at 1,675 masl (circa-525 m below the top of the mountain), with the mining block extended around 550 m in depth (20 production levels at 27.5 m interlevel spacings).

The main ore transfer horizon is located 75 m higher in elevation than the mine access portals at 1,080 masl and the proposed valley infrastructure. The initial mining block will be accessed by twin tunnels developed in parallel for 2 km at which point a single access ramp will branch up towards the undercut; the twin tunnels will continue another 3.7 km to the base of the SLC where the crushing and conveying facilities will be located.

The company is currently weighing up whether to use tunnel boring machines or drill and blast to establish these tunnels.

Nienaber confirmed the 20 level SLC panel cave layout would involve 161 km of lateral development and 14 km of vertical development. There would be six ore pass connections on each level, four of these being ‘primary’ and two acting as backups. The crusher would be located on the 1155 bottom production level.

Due to the ventilation requirements in Colombia the mining fleet selected for Quebradona is predominantly electric, Nienaber said, adding that the units will initially be electric cable loaders powered by 1,000 v infrastructure.

Fourteen tonne LHDs were selected for the production levels based on their speed, bucket size (enables side-to-side loading in the crosscut and identification of oversize material) and cable length, the authors said. On the transfer level, 25 t loaders were specified to accommodate the shorter tramming lengths and limited operating areas (there are a maximum of two loaders per side of the crusher due to the layout).

As battery technology improves in the coming years, the selection of loader sizes may change as additional options become available, according to the authors.

The selection of the present Sandvik fleet was predominantly based on the electric loaders and the OEM’s ability to provide other front-line development and production machines required to undertake SLC mining, the authors said.

This decision also accounted for the use of automation for the majority of production activities, with the use of a common platform seen as the most pragmatic option at this stage.

It has also been proposed that the maintenance of the machines be carried out by Sandvik under a maintenance and repair style contract since there is a heavy reliance on the OEM’s equipment and systems.

An integrated materials handling system for the SLC was designed from the ore pass grizzlies, located on the production levels, to the process plant.

Due to the length of the ore passes (up to 500 m), and the predicted comminution expected by the time the rock appears on the transfer level, larger than industry standard grizzly apertures of 1,500 mm have been selected.

The design criteria for the underground crusher was that it needed to reduce the ore to a size suitable for placement on the conveyor belt and delivery to the surface coarse ore stockpile, after which secondary crushing prior to delivery at the process plant will be undertaken.

Assuming the maximum size reduction ratio for the crusher of circa-6:1 at a throughput rate of 6.2 Mt/y, a 51 in (1,295 mm) gyratory crusher was selected. This crusher is also suitable to support block cave mining should the conversion of mining method occur, according to the authors.

The process plant will include high pressure grinding rolls as the main crushing unit on the surface, supported by a secondary crusher to deal with oversize material. The ore then feeds to a ball mill before being discharged to the flotation circuit.

The gold-enriched copper concentrate will be piped to the filter plant for drying and the removal of water down to a moisture content of 10%, according to the company, while the tailings will be segregated to pyrite and non-pyrite streams before being distributed to one of two filter presses.

Dry stacking of the tailings will be used, with the pyrite-bearing tailings being encapsulated within the larger inert tailings footprint.

With the feasibility study due before the end of the year – and, pending a successful outcome – the proposed site execution works could start in the September quarter of 2021, Nienaber said.

Weir adds aftermarket and service contract to Iron Bridge remit

Comminution of minerals, Equipment maintenance, Mineral processing, Mineral project development, Mining equipment, Mining maintenance, Mining services, Steel and iron ore, , , , , , , , , , , , , , , , ,

The Weir Group says it has won a £95 million ($127 million) order to provide aftermarket components and service to the Iron Bridge magnetite project in Western Australia.

The aftermarket contract follows Weir’s success in winning a record £100 million order for original equipment for the Iron Bridge project in 2019, including its Enduron® High Pressure Grinding Rolls (HPGRs, pictured) that, it says, will enable dry processing of ore and use at least 30% less energy than traditional alternatives.

The Iron Bridge magnetite project is a $2.6 billion joint venture between Fortescue Metals Group’s subsidiary FMG Magnetite Pty Ltd and Formosa Steel IB Pty Ltd located in the Pilbara region, around 145 km south of Port Hedland.

Both the aftermarket order and revenues will be recognised over the seven-year period of the agreement, which starts in 2022, in line with the 22 Mt/y project’s initial production.

Ricardo Garib, President of Weir Minerals, said: “This is another landmark order for Weir. Having helped design an energy and water efficient magnetite processing plant, we are delighted to provide operational support for Iron Bridge from 2022. It is an excellent example of the value that Weir’s innovative engineering and close customer support can create for all our stakeholders and reflects the key role we have to play in making mining operations more sustainable and efficient.”

Weir’s Enduron HPGRs are increasingly replacing conventional mills in comminution circuits, Weir says. In addition to their energy and water savings, they also reduce grinding media consumption, while their wearable components last longer, reducing maintenance costs. Additionally, HPGRs contribute significantly to carbon dioxide emission savings.

Stuart Hayton, Managing Director of Weir Minerals Netherlands, where the Enduron HPGRs are designed and manufactured, said: “This is an important project for Weir and for the broader mining industry. We know comminution is one of the most energy intensive parts of the mineral process and, with our Enduron HPGRs, we have a unique ability to offer significant cost, energy and water savings to customers around the world. As the mining industry evolves, we are commited to continuing to innovate, reducing miners’ costs and environmental impact.”

This latest contract award means Weir now has more than £200 million of orders from the Iron Bridge project including its Enduron HPGRs, GEHO® and Warman® pumps, Cavex® hydrocyclones and Isogate® valves.

To support the project and future growth, Weir says it will build a new service centre in Port Hedland, Western Australia, thereby providing employment and training opportunities in the area, with a particular emphasis on supporting greater Aboriginal representation in the broader mining workforce.

ABB to deliver drives and motors to Fortescue’s Iron Bridge Magnetite project

Comminution of minerals, Mineral processing, Mineral project development, Mining equipment, Mining services, Power supply for mines, Steel and iron ore, , , , , , , , , , ,

ABB has won a $26 million order from Fortescue Metals Group to deliver water-cooled variable speed drives and high voltage induction motors to FMG’s majority-owned Iron Bridge Magnetite project in Western Australia.

The project, operated under an unincorporated joint venture between Fortescue subsidiary, FMG Magnetite Pty Ltd, and Formosa Steel IB, covers the development of a new magnetite mine, including processing and transport facilities. The $2.6 billion development is expected to produce 22 Mt/y (wet) of high grade, magnetite concentrate, with first ore in 2022.

As part of the project, the Iron Bridge Joint Venture required a cost-effective energy efficient variable speed drive solution, according to ABB. These drives, to be installed in eight switch rooms, operate with a separate transformer that is located outside the room. This reduces the heat generated inside, resulting in less energy required to maintain the 25°C room temperature.

ABB’s water-cooled drives also directly support a higher voltage 33 kV network, it said. “This eliminates the need for a lower voltage intermediate switchboard and additional components, which ultimately reduces the total cost of the project,” the company explained.

Iron Bridge also selected ABB high voltage induction motors to power high pressure grinding rolls, grinding mills and baghouse fans used to separate the ore from the dust at Iron Bridge. Engineered to withstand harsh conditions, the motors offer high power efficiency, but in a frame size smaller than competitive alternatives, it said.

Mike Briggs, Business Manager for ABB Motion, Australia, said: “We have worked closely with the Iron Bridge team to ensure that we delivered an energy efficient, reliable and innovative solution. We are especially pleased to have won both the drive and the motor business, and look forward to continuing our strong relationship with Fortescue beyond the delivery of this project and supporting them throughout the mine’s lifecycle.”

Los Andes Copper commits to HPGR comminution route for Vizcachitas

Base metals, Comminution of minerals, Environmental, Mineral processing, Mineral project development, Mining services, Sustainable mining, Water management, , , , , , , , , ,

Los Andes Copper says additional comminution test work has confirmed the selection of high pressure grinding rolls (HPGR) circuit technology for use in the processing circuit at its Vizcachitas copper project in Chile.

The use of HPGR, and the adoption of the previously announced dry-stack tailings, reinforces the company’s commitment to the environment and designing a sustainable operation with low energy and water consumption, it said.

At early stages of the Vizcachitas prefeasibility study (PFS), HPGR technology had been identified as the most attractive grinding alternative, given the data obtained from preliminary test work conducted in 2009, and in 2017-2018. As part of the PFS metallurgical test work, four representative samples from the mine plan were sent to a laboratory for pressure bed testing. The results of this test work confirmed the equipment sizing and its performance for a PFS-level study.

The results provided specific energy consumption readings of 2.17 kWh/t in the case of a HPGR circuit, which results in a global specific energy consumption of the comminution circuit of approximately 14 kWh/t. As compared with the semi-autogenous grinding alternative, the HPGR showed a reduction of up to 20% in energy and up to 50% in grinding media consumption, Los Andes Copper said. These results confirm the advantages of adopting this technology at the project.

The comminution circuit at Vizcachitas, where the HPGR circuit will be incorporated, is a three-stage crushing circuit using a gyratory primary crusher, three cone crushers in open circuit and two HPGR as a tertiary stage arranged in a closed circuit followed by ball mills. Through this process, and in addition to the lower energy consumption, the use of HPGR will reduce dust emissions related to dry crushing due to the removal of coarse recirculation in the secondary crushing stage, the company said.

Fernando Porcile, Executive Chairman of Los Andes, said: “I am pleased that the results from the test work carried out to date have confirmed the advantages of using HPGR in terms of enhancing project economics, lowering energy consumption and increasing operational flexibility.

“The use of HPGR technology favours the stability of the dry stacked tailings operation, as well as reducing the environmental impact by minimising energy usage, water consumption and dust emissions.”

Metso Outotec to bring HRC benefits to other OEM’s HPGRs

Comminution of minerals, Mineral processing, , , , , ,

Metso Outotec says it is launching the mechanical skew control HPGR (High Pressure Grinding Roll) retrofit kit for improved throughput and energy efficiency on the heels of its new HRC™e HPGR release.

The HRC HPGR was launched back in 2014 pioneering the use of flanges and non-skewing design and, now, those same benefits can be had on existing, non-Metso Outotec machines, the company says.

The new HPGR retrofit kit takes the key components responsible for minimising skew from the HRC and makes the technology more accessible without the major investment or need to acquire a new machine, according to the company.

“We are very excited to introduce the new flanged roll with mechanical skew control HPGR retrofit kit, which allows customers to maximise the performance of their existing equipment without the capital expenditure investment of purchasing expansion machines,” Jack Meegan, Product Director, SVS, Stirred Mills and HPGR at Metso Outotec, says. “This is truly a value option for an extended customer reach.”

Key benefits of Metso Outotec HPGR retrofit kit include the ability to increase throughput by up to plus-20%; improved energy efficiency with the flanges ensuring even breakage rates across the whole width of the roll; reduced circulating loads as less material bypasses the rolls and more ore continues to the next stage of the process; and reduced wear costs with the flanges allowing harder studs for longer tire life.