Tag Archives: high pressure grinding rolls

Swiss Tower Mills Minerals backs Coalition for Eco-Efficient Comminution

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)

NioCorp working with Weir Minerals, NRRI on Elk Creek HPGR test work

NioCorp Developments Ltd is to initiate testing of Elk Creek project ore using high pressure grinding rolls (HPGR) technology from Weir Minerals.

HPGR technology is considered an energy efficient and low-emission alternative to conventional processing for reducing the size of the ore to enable the recovery of niobium, scandium, titanium, and potential rare earth products, NioCorp said.

The use of this technology in the project reinforces the company’s commitment to the environment and designing a sustainable operation, it added.

The testing is being conducted at the Natural Resources Research Institute (NRRI) of the University of Minnesota-Duluth, in partnership with Weir Minerals. During the testing, which is expected to take several weeks, around 3 t of Elk Creek drill core will be reduced to the 1-mm size needed for hydrometallurgical test work.

Working with Weir Minerals, NRRI acquired an industrial-scale Enduron® HPGR to carry out testing on a variety of ores with this process back in 2020. This is the only large scale HPGR dedicated to research in the US, NRRI claims.

“The network is expected to provide key data that will be used to properly size the HPGR unit for the potential ore throughput at the Elk Creek project, once project financing is secured and the project is operational,” NioCorp said.

The company is currently evaluating the next steps in its overall metallurgical test work program, which will focus on optimising and streamlining the existing processing flowsheet as well as establishing process routes for the potential recovery of rare earth products. The rare earth products that are of most interest to the company are, at present, neodymium-praseodymium (NdPr) oxide, terbium oxide and dysprosium oxide. As previously announced, the company has launched a review of the economic potential of expanding its currently planned product suite from the project to also include rare earth products.

An April 2019 feasibility study on Elk Creek, in Nebraska, USA, estimated average production of 7,220 t/y of ferroniobium, 95 t/y tpa of scandium trioxide and 11,642 t/y of titanium dioxide over the 36-year mine life.

Scott Honan, NioCorp COO, said: “After witnessing testing at NRRI, I was impressed with how the HPGR was able to handle the Elk Creek ore quickly and efficiently, with minimal noise and dust.

“We look forward to completing this phase of the test work and moving on to look at further improvements to the existing flowsheet, including our new emphasis around the rare earths.”

Los Andes Copper commits to HPGR comminution route for Vizcachitas

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 delivers ‘next evolution’ in high pressure grinding rolls with HRCe

Metso Outotec has launched the “next evolution of the high pressure grinding roll”, with the delivery of its HRC™e HPGR.

The original HRC HPGR was launched back in 2014 by Metso (now Metso Outotec), pioneering the use of flanges and non-skewing design. The grinding performance that brings energy efficiency, lower circulating loads and increased throughput is now strengthened with an additional evolution in design, Metso Outotec says.

The new HRCe comes with a decreased installation capital expenditure compared with the original HRC. Changes in design allow for maximum productivity with proven technology that leads to superior grinding efficiency.

Christoph Hoetzel, Head of Grinding business line at Metso Outotec, said: “We are very excited about the new HRCe, which combines proven technology and customer-focused evolutions. Metso Outotec is the only OEM that has been able to design and develop reliable flanged HPGR technology that has demonstrated superior performance for many years in the mining industry. We will continue utilising our proven technology but have evolved the design to maximise value for our customers and superior grinding efficiency.”

The high throughput comes from the elimination of the edge effect with the flange design, which will ultimately maximise the amount of crushed material, the company says. With the anti-skew assembly, customers will find faster restarts and no downtime from skewing events, according to Metso Outotec.

The HRCe also comes with a large feed size acceptance of 60-120 mm and improved energy efficiency compared with similar HPGRs, the company says. It also boasts typical capacities of 1,810-6,930 t/h.

Key benefits of the new HPGR include:

  • Improved energy efficiency of up to 15%;
  • Lower circulating load of up to 24%;
  • Increased throughput of up to 19%;
  • Elimination of edge effect from combination of proven flange design and anti-skew assembly; and
  • Elimination of downtime caused by skewing events.

thyssenkrupp navigates South Africa lockdown to replace platinum mine HPGR roll

As the COVID-19 pandemic tightens its grip, thyssenkrupp Industrial Solutions says it is assisting customers in maintaining operational efficiencies through sustainable service delivery and innovative technologies.

“The global economic crisis, as a consequence of the COVID-19 pandemic, has put the drive for efficiency into top gear,” Philipp Nellessen, CEO of thyssenkrupp Industrial Solutions Sub Sahara Africa, said. “Fundamental to this drive is cutting-edge technology. Through our ongoing investment in people and R&D and our over 200 years of expertise, we are able to develop advanced technologies to assist mining and other industries in achieving maximum operational efficiencies.”

Although the South Africa mining industry was not operational during national lockdown Level 5, critical repairs were still permitted. As an essential service provider, thyssenkrupp has been delivering maintenance and repair as well as rebuild work to local mines.

The company assisted a platinum mine in Limpopo Province with a roll change on one of thyssenkrupp’s flagship products, a high pressure grinding roll (HPGR).

Nico Erasmus, thyssenkrupp Industrial Solutions Sub Sahara Africa Head of Service Operations, explained: “The scope of work required a rebuild on the HPGR set as well as the installation of the hardware on the mine site, making this our largest project in the national lockdown period.

“We are very pleased that even in a complete lockdown situation, we were able to complete the project in a healthy and safe manner, in excellent co-operation with our customer.”

The customer had “excellent controls” in place and thyssenkrupp complemented the risk mitigation with its own additional preventative protocols, he added.

Procedures included pre-selection of a team that falls inside the recommended age and health categories, pre-screening at both thyssenkrupp and customer sites, limiting the amount of people on shifts and in spaces, adhering to stringent hygiene measures (hand sanitising, wearing face masks, social distancing, cleaning of surfaces, tools and equipment), and implementing special transport and accommodation measures.

According to Erasmus, despite several challenges, the team adapted quickly to all the controls while still being responsive enough to get the work done safely and within the scheduled timelines.

“The transport of super loads (two trucks with 120 t loads each) was a real challenge, but our logistics team rose to the occasion and got the loads on site in no time and ready for installation,” Erasmus said.

To remain operational and continue seamless service delivery to customers, thyssenkrupp has implemented all necessary policies in line with South Africa Government COVID-19 regulations.

These include possession of all essential services permits and strict entry control protocols for employees, visitors and suppliers at all premises. Employees are required to attend mandatory training sessions conducted by the OSH department, wear all necessary personal protective equipment, sanitise regularly and maintain social distancing.

A dedicated COVID-19 committee has been set up to assess changing regulations and risks associated with office and site working environments, the company said.

“With the majority of employees working from home, we have faced our fair share of challenges but the process was very well organised with IT managing it all incredibly well ensuring that everybody was equipped in time,” Erasmus said. “We only had one day of downtime at our essential service workshop site.”

Wrapping up, an optimistic Nellessen says he is in no doubt that South Africa/Sub-Sahara Africa will recover.

“The people here are incredibly brave and innovative and companies will find their way out of the crisis,” he said.

“Despite tough times ahead for some industries, the mining sector continues to show growth and here I foresee a restart and a good recovery, depending on mining commodities probably taking anything between three to 12 months to reach previous and required pricing levels.”

Weir Minerals gives its skew view on HPGRs

With industry demand for high pressure grinding rolls (HPGR) on the up, Weir Minerals is arguing that skewing is a vital feature for modern HPGRs to reduce wear, save downstream energy and ensure optimal grinding across the whole feed.

The company was sharing its findings following the publication of a new white paper.

Weir said: “With their excellent throughput capacity, low maintenance requirements and energy efficiency, HPGRs are fast becoming a go-to for greenfield projects looking to maintain their margins despite commodity price pressures and declining ore grades.”

The mineral processing company said, in the June quarter, that it had registered strong demand for its Enduron® HPGR technology during the three-month period, later on in the year confirming a major order, which included this comminution equipment, from Fortescue Metals Group for its Iron Bridge magnetite project in Western Australia.

Henning Knapp, HPGR Process Team Leader for Weir Minerals, said the applications from this equipment have evolved from the cement production days of the 1980s and are increasingly being deployed as tertiary and quaternary crushers in mineral comminution circuits, dealing with tougher ores including iron, gold, copper and diamonds.

“As any engineer will tell you, it’s almost impossible to eliminate feed variance and segregation completely. In the past, this has posed a critical challenge for HPGR operators – but dynamic skewing such as that featured in the Enduron HPGR, maintains optimal pressure across the entire feed.”

Traditionally, HPGR manufacturers have shied away from skewing designs, for fear of roller misalignment creating unfavourable load distributions, and preventing the use of flanged guards to reduce the edge effect, the company said. “However, Weir Minerals’ unique roller bearings design allows for skewing alongside effective edge guards, reducing wear and promoting better grinding.”

The downside of static rollers

A HPGR reduces particles by compressing and crushing the feed between two equally sized, parallel rollers rotating in opposite directions, with a small gap between them. This compresses the feed to 80% of its solid density, where the force of the rollers pushes the rocks against each other and exceeds their compressive strength.

“Inter-particle comminution avoids the direct component wear caused by conventional comminution techniques, and applies immense pressure, up to 27,000 kN, across the entire particle size distribution, which creates the higher proportion of fines HPGRs are renowned for,” says Knapp.

However, segregated feeds can result in markedly uneven particle sizes across the width of the feed, creating high, abrasive pressure on one side of the roll and insufficient pressure on the other. It will also produce a coarser product, requiring more work downstream, according to Weir.

“To compensate for the edge effect, a lateral wall or ‘cheek plate’ is deployed on either side to prevent material exiting the gap between the rollers sideways. The closer this is to the rollers, the better – but that has prevented engineers from introducing the flexibility needed to cope with feed segregation,” explains Knapp.

How Enduron HPGRs skew to maintain optimum pressure

To accommodate this uneven pressure Enduron HPGRs use a spring-loaded lateral wall which not only reduces the edge effect (maintaining a gap of as little as 1 mm) but is specifically designed to facilitate roll skew.

As shown above, an uneven feed will lead to high pressure on one side and not enough on the other. Having one roller skew will facilitate larger material at one end while ensuring the smaller particles on the other side receive enough pressure to be ground down: it maintains an even pressure distribution across the entire feed, saving energy and reducing wear, Weir says.

“The degree to which the Enduron HPGRs skew is largely dependent on the width of the roll, with longer rolls skewing about 5 mm for every metre the roll is wide. However, the effect of even small changes can be significant on local pressure peaks,” says Knapp.

“The skewing should be managed by an advanced control system, which steers the rolls to satisfy the desired output pressure. This system also ensures the skew isn’t too great or maintained for too long, which both disrupt the compressive bed.”

In the case of prolonged or excessive skewing, Enduron HPGRs send a signal notifying the supervising control system and operating staff. Prolonged skewing generally is indicative of a disturbance or fault in up-stream facilities, such as low bunker filling, upstream crusher wear, screen deck wear, or conveyor failure, Weir says.

“Where static rolls suffer from differential pressure, creating undesired product, consuming more energy and suffering additional wear, Enduron HPGRs maintain optimum pressure across the entire feed thanks to their skewing, spring-loaded lateral walls,” Weir said.

Knapp concluded: “When dealing with competent mineral feeds in real-world conditions, there’s simply no substitute for the Enduron HPGR’s ability to maximise performance with skewing.”

Weir Minerals says Enduron HPGRs crush the competition

Weir Minerals says its range of Enduron® high pressure grinding rolls (HPGR) make for the perfect pebble crushers, offering highly efficient reduction and generating substantial amounts of fines that reduce the energy required for downstream milling.

These units also reduce water and energy consumption, two resources that miners are actively looking at within their operations.

In the company’s June quarter results, Weir noted that it had seen strong demand for its Enduron HPGR technology, adding that the company had been contracted to support a large greenfield development in the UK in the period.

Whether recirculated through primary milling or separated and sent to a dedicated downstream pebble mill, pebble crushing is an energy-intensive operation that ties up a site’s limited resources, Weir says.

“With their high throughput and capacity for dealing with competent ores, HPGRs make ideal pebble crushers,” the company said. The Enduron HPGR’s low operating costs (owing to its long component wear life and low specific energy requirements) makes it a competitive inclusion in pebble crushing circuits, offering short payback times, according to the company.

Ranging in size from 25-90 mm, pebbles are oversized material produced from autogenous and semi-autogenous grinding, which are too coarse to be crushed by larger lumps of ore and steel balls and too fine to act as grinding media themselves.

As such, pebbles (or critical particle size material) reduce the efficiency of any mill they’re returned to, increasing power consumption and decreasing throughput, Weir says.

When pebbles comprise a large proportion of a (S)AG mill’s feed as they’re returned multiple times, the proportion of large particles which have the power to crush with the force of their impact is reduced and new particles are instead subjected to additional attrition and abrasion. “This can over-grind fines, producing unsuitable ultra-fines,” Weir says.

Regardless of whether they’re receiving feed directly from an upstream SAG mill or further reducing pebbles that have passed through a dedicated cone crusher, HPGRs offer highly efficient reduction, generating substantial amounts of fines that reduce the energy required for downstream milling, Weir says.

“The fineness of products is one of the key compromises in conventional pebble circuits, with pebble crushers unable to maintain high throughput without sacrificing the proportion of well reduced particles.”

By virtue of their variable roll speeds, HPGRs can maintain high levels of throughput without generating a coarser product, allowing a significant amount of product to bypass downstream mills via pre-classification, the company explained.

To obtain the greatest efficiency, an appropriate control system should be selected to monitor and maintain the material level in the HPGR feed chute and control the roll speed and apply optimal operating pressure based on the presented pebble feed rate and quality, according to Weir.

One thing to note when deploying a HPGR in a pebble crushing circuit is that truncated feed (one with a narrow size distribution) may cause higher wear on the surface of the machine’s rollers than encountered in other applications. This is due to the more “mobile” particles generating a weaker autogenous wear layer where the coarse pebble fragments chip away at the coating on the roll-surface.

Oversized rocks that are larger than the machine’s operating gap will further wear away at the roller surface, making the use of a safety screen advisable if the preceding crusher’s output isn’t strictly controlled, Weir says.

Similarly, when placed after a (S)AG mill, a significant quantity of oversized or tramp materials can disrupt HPGR operations. “With their unique ability to dynamically skew their bearings to accommodate varying feed conditions, Enduron HPGRs cope better than other HPGRs under these conditions,” the company said.

However, to further reduce damage to wear materials, a well-designed detection and removal system should be applied, Weir advises. “This would consist of a tramp magnetic separator, a metal detector, and a subsequent tramp metal rejection facility. Such a system should preferably be installed as close as possible to the HPGR, preferentially directly ahead of the HPGR feed chute.”

In circuits with particularly heterogenous ore competencies, such as transition gold ores or coarsely-banded iron ores, HPGRs should be run at variable speeds to ensure throughput is maintained regardless of the feed conditions, according to Weir.

The company concluded: “With the ability to maintain this high level of throughput across a variety of ore types without compromising the fineness of their product, Enduron HPGRs represent an ideal, energy-efficient addition to most pebble crushing circuits.”

TAKRAF to focus on HPGR, technical studies and data collection at Bauma

Tenova TAKRAF says the company’s high pressure grinding roll (HPGR) technology, among other developments, will be highlighted at the upcoming Bauma fair in Munich, Germany, on April 8-14.

The company said, for the first time, show visitors will be able to have a complete overview of the company’s entire service portfolio, which ranges from project development services to technical studies on comminution and minerals processing, innovative fabrication solutions, various technical services and comprehensive after-sales support.

“With a view to further developing their capabilities within the market of the comminution industry, TAKRAF continues to develop their range of roller presses, with a scale model of a HPGR on display at the booth (pictured),” the company said.

Two of these machines are being manufactured at the company’s specialised fabrication facility in Lauchhammer, Germany. These machines can each handle more than 907 t/h of cement clinker, with each machine incorporating rolls with a diameter of 1,800 mm and a weight of more than 450 t per roller.

“In order to meet the challenging longevity requirements of such a machine, each roll surface is protected from wear by weld hardfacing for cement applications, and with tungsten carbide inserts for ore processing,” TAKRAF said.

The company continued: “With the integration of the well-known DELKOR and Tenova Advanced Technologies (formerly Bateman Advanced Technologies) brand of products into TAKRAF as specialised product lines, the company’s portfolio for the minerals processing and beneficiation sectors has been considerably enhanced.”

At Bauma, visitors will be able to focus upon the company’s capabilities in minerals processing, including solvent extraction and lithium recovery; as well as flotation, thickening, filtration and dry stack tailings, according to TAKRAF.

The company will also use the event to highlight its Mining Technology Centre, TAKRAF said.

“Technical studies, which compare the techno-economic aspects of different system or equipment layouts are an intrinsic part of every investment process. The quality of the study strongly depends on the experience of the study team and the level of customer involvement,” the company said.

“Based upon a common understanding of the weighting of all such decision criteria, the transfer of technical and operational experience and expertise, even beyond their own portfolio, is a key driver in enabling the customer to make a competent decision regarding the optimal solution for the specific conditions of their particular mine.

“More and more customers appreciate the added value provided by the studies as part of the engineering service portfolio, and for this reason, the company has decided to restructure and tailor their services even better in order to best meet customer requirements.

“TAKRAF’s Mining Technology Centre will be present and on hand to present the myriad of possibilities and benefits of innovative study approaches to demonstrate they are pursuing this strategy together with their customers.”

TAKRAF said, in order to provide additional benefits and services to the company’s customers based on new digital technologies, several R&D projects in the field of the industrial internet of things have also been advanced.

“In an attempt to find the most suitable technology, which results in the greatest possible benefit for the customer, first pilot machines were equipped with remote data collection and evaluation systems.

“Utilising a combination of edge computing and a proprietary azure-based platform established by Tenova, TAKRAF is able to develop applications that provide valuable insights of the company’s machines through modern and intuitive interfaces across any remote location.

“First results evince that this information can greatly assist in reducing downtime by identifying problems before they escalate into major issues and optimizing machine design, operation and performance.”

Implementation of more advanced analytics and machine learning strategies are currently on the company’s R&D agenda, TAKRAF said. “In addition, remote support solutions can also be offered.”

The company said: “This enables a remote experts-team to provide on-site assistance to the local commissioning or maintenance personnel using smart glasses and an appropriate software tool.

This is a great solution for reducing reaction times and as a side effect for reducing or even avoiding costs for expensive and time-consuming trips to the destination area.”

The company’s stand will be located in hall C2, stand 349 at Messe München in Munich, Germany, during the event.