Tag Archives: HPGR

FLSmidth wins multi-year contract to service HPGRs at Chile mines

Comminution of minerals, Equipment maintenance, Mineral processing, Mining equipment, Mining services, , , , ,

A leading Chile-based iron ore miner has awarded FLSmidth with a multiple year contract to service its five high pressure grinding rolls (HPGRs) across three of its mines in Chile, with the key focus for the customer to enhance productivity and extend the lifetime of its HPGRs.

HPGRs are subject to significant wear and tear. Consequently, keeping them in operation is key to securing a mine’s productivity and throughput as well as reducing customers’ operational costs. To facilitate to this, having a strong service setup around HPGRs is paramount.

The new service order on these five HPGRs, which originally have been installed by another equipment provider, proves that FLSmidth’s HPGR service offerings are among the most attractive in the market, the company says. All assembly works as well as repairs on shafts are included in the contract.

The service contract will be managed and executed by FLSmidth’s Chilean service centre, which is in close proximity to the three mines, thereby reducing logistic costs to customer and providing best in class services, it added. FLSmidth’s service centre is fully equipped to manufacture large HPGR parts and allows all work to be performed in a clean environment and using best in class tools.

Prior to winning this new service contract, FLSmidth has previously delivered HPGR roll tyres to the customer, which have proven to last more than three times as long as the originally installed roll tyres as well as increased operational availability and significantly reduced recirculation, the company says.

Joshua Meyer, Service Business Line President at FLSmidth, says: “For long our HPGR solution has been regarded among the best in the industry. The fact that we can win a large service contract on a non-FLSmidth HPGR platform proves that we have the service concept to back up the technology, securing enhanced productivity and extended lifetime.”

FLSmidth to deliver ball mills, HPGRs to South America copper miner

Base metals, Comminution of minerals, Mineral project development, Mining equipment, Mining services, , , , , ,

Following a long-standing relationship with the customer, FLSmidth says it has received an order to supply comminution technologies to a leading copper miner in South America for its new greenfield concentrator.

The order is valued at approximately DKK380 million ($56 million) and was booked in the March quarter of 2024. The equipment is due to be delivered during 2025.

The order includes the delivery of two ball mills and three high pressure grinding rolls (HPGRs). The latter is among the most energy-efficient comminution technologies, as it lowers power consumption, while providing a more stable grinding operation and eliminating the need for grinding media, according to the OEM.

This new order builds on a long-standing relationship with the customer, where FLSmidth has supplied most of the equipment for its original concentrator as well as provided maintenance, spare parts and process support services over the years.

Mikko Keto, CEO at FLSmidth, said: “Receiving new orders from existing customers is always confirmation of a healthy and strong customer relationship. And it is particularly satisfying in this case as the customer is purchasing their first HPGRs and have selected our market leading technology. We look forward to supplying this best-in-class comminution package to positively contribute to both the output and operation of this new copper concentrator.

“This order not only supports our MissionZero ambition, it also clearly underpins FLSmidth’s market leading position within large grinding mills and HPGR.”

Metso books €12 million worth of high pressure grinding roll spare part orders

Comminution of minerals, Equipment maintenance, Mining consumables, Mining equipment, Mining services, , , ,

Metso says it has received several orders for the supply of HRC™ Series high pressure grinding roll (HPGR) replacement tyres in the US, with the scope of supply including five replacement tyres with studs and another order for a spare reducer for a Metso HRC 3000.

The value of the orders amounts to more than €12 million ($13 million), the OEM says.

Rodrigo Rizzoli, Vice President, Stirred Mills & HPGR Services, Metso, said: “This milestone not only marks our growing success but also highlights the fact that customers trust Metso’s spare parts to ensure equipment performance and reliability. Our customers will benefit from the proven technology optimising their operations and simultaneously eliminating potential grinding challenges for long-term sustainability.”

Last month, Metso announced it is strengthening its service capability by expanding its service centre in Arizona and by establishing a training centre to improve competence development in the region to support the growing needs of mining customers. This investment not only improves the capacity, but also the ability to perform heavy equipment maintenance and service a wide range of equipment, HPGRs included.

The HRC HPGR is a part of Metso’s grinding portfolio. Metso’s HPGR has been proven to improve energy efficiency by up to 15% and decrease recirculating loads by up to 24%, the company says.

Weir Group highlights energy, emission reduction opportunities in comminution study

Comminution of minerals, Environmental, Mining equipment, Mining events, Mining services, Power supply for mines, Sustainable mining, Water management, , , , , , , , ,

The Weir Group has completed a comprehensive study that highlights a significant opportunity to reduce energy use and emissions in comminution by leveraging three alternative technology combinations.

The study, presented by Paula Cousins, Chief Strategy and Sustainability Officer at Weir, during a COP28 panel discussion hosted by the Ministry of Economy, Trade and Industry of Japan and moderated by the World Business Council for Sustainable Development (WBCSD), showed that replacing conventional technology with innovative new solutions can cut energy use by 40% while also avoiding 50% of CO2e emissions.

Weir’s study focuses on comminution – the crushing process that turns big rocks into tiny particles to expose the entrapped mineral so that it can be extracted later in the mining process. Comminution is the most energy intensive stage of a typical mine site process. It is already electrified and is responsible for at least one-third of an average mine’s energy use and CO2e emissions1 and globally consumes around 3% of the world’s electrical power, according to studies.

The study is the first to use WBCSD’s Avoided Emissions Guidance to study mining processes and the avoided emissions results have been independently assured by SLR Consulting Limited, Weir says. Three of Weir’s technology combinations were evaluated against a conventional comminution circuit design for an archetypal mine processing 15 Mt/y of copper ore in Chile. All three of the technology combinations are shown to yield sizeable benefits versus the traditional circuit.

In the optimal combination, the comminution process consumes around 40% less energy and can avoid up to 50% of CO2e emissions. Importantly, there is no trade off elsewhere, as the redefined process uses less water too, according to the study.

Each circuit is based on a ‘rock to recovery’ system boundary – reducing rock direct from the mine to a size that enables the mineral to be recovered. The four configurations are:

  • Conventional comminution circuit based on a Semi-Autogenous Grinding (SAG) mill and ball mill (SABC circuit);
  • Weir High Pressure Grinding Roller (HPGR) replacing the SAG mill at the initial grinding stage (2C HPGR BM);
  • HPGR, plus vertical stirred mill (VSM) replacing the ball mill (2C HPGR VSM); and
  • Addition of a coarse particle flotation (CPF) unit (2C HPGR VSM and CPF).

These assessments focus on the use-phase of the life-cycle only; other life-cycle phases have been excluded because previously studies have shown these to be immaterially small across all comparisons (<1% of energy and emissions impact). Assessments have been made using a “year-on-year” timeframe approach. Comparative impacts have been assessed only in terms of energy use, grinding media consumption, and associated emissions, since other environmental trade-offs were deemed immaterial for comparison.

Given its energy intensity, the decarbonisation opportunities in comminution are huge, with the basic comminution process not having changed significantly for many decades, Weir says.

The company is collaborating with customers and other partners to redefine the process, developing innovative combinations of proven technologies to make significant improvements to efficiency and environmental performance.

Cousins said: “The need for technology solutions in mining is compelling – the world needs more transition metals to achieve net zero, but the mining industry needs to extract these using significantly less energy and water.

“By adopting a systems-based approach to technology collaborations, we can help the mining industry scale up and clean up at the same time.”

 

Brownfield expansions and sustainable mining projects boost Weir Group Q1 orders

Base metals, Comminution of minerals, Environmental, Mining equipment, Mining finance, Mining services, Sustainable mining, Water management, , , , , , , , ,

Weir Group continued to benefit from relatively high commodity prices, tightness in physical inventories of metals and minerals, and strong end market demand for commodities in the March quarter, registering a 22% boost in original equipment order growth in the three-month period.

The company said brownfield activity and sustainability projects were behind this leap in orders.

“Customers are ordering Weir solutions to debottleneck, expand and improve the sustainability of existing mines, while also increasingly engaging on new sustainability driven technologies, such as our redefined mill circuit and the Motion Metrics digital offering,” the company said in its results.

Weir Group’s “redefined mill circuit” encompasses Weir Minerals’ Enduron® high pressure grinding rolls, along with the additions of technologies from Eriez and Swiss Tower Mills (STM) Minerals, which are part of specific partnerships. These solutions are enabling it to redefine the mining mill circuit so customers can use less energy, use water wisely and create less waste during minerals processing, it says.

Weir Minerals recently announced the completion of the STM Minerals AG vertical stirred mill commissioning at the Weir Technology Hub in the Netherland. Regarding Eriez, the combination of pumps, cyclones, classification equipment, and other mill circuit products supplied by Weir Minerals, along with Eriez’s HydroFloat, StackCell®, columns and sparging systems, allows owners to take advantage of well-matched equipment designed and tested as a system, Weir says. This makes Weir a natural fit for contributing to Coarse Particle Flotation flowsheets, it added.

In terms of the Weir’s outlook, it said in its March quarter results: “The business is executing well and conditions in our mining markets are positive. High levels of activity and demand for our aftermarket spares and brownfield original equipment solutions are driving order book growth. Our guidance for 2023 is reiterated and we expect to deliver growth in constant currency revenue, profit and operating margin. We are on track to deliver our target of 17% operating margin in 2023, supported by operational efficiencies and early benefits from Performance Excellence.

“Further out, the long-term fundamentals for mining and our business are highly attractive, underpinned by decarbonisation, GDP growth and the transition to sustainable mining. We have a clear strategy to grow ahead of our markets, with specific growth initiatives underpinning our ambition to deliver through-cycle mid-to-high single digit percentage revenue growth.”

MetsoOutotec-testing

Metso Outotec on the need for holistic testing

Automation, Base metals, Comminution of minerals, Energy minerals, Environmental, Metallurgy, Mineral exploration, Mineral processing, Mining equipment, Mining services, Precious metals, Sustainable mining, Water management, , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , ,

The Metso Outotec global network of testing, research and product development facilities covers the whole process flowsheet from comminution through separation, to filtration, refining and pyrometallurgical/hydrometallurgical processing.

It has centres all over the globe – in Australia, Brazil, Chile, Germany, Finland, Peru, USA and more – able to, the company says, offer extensive expertise and circuit simulation to a wide range of industries.

Metso Outotec’s research and testing services include evaluation of ore types, mineralogical characterisation, feed material testing, sampling, materials selection, analytical chemistry and flowsheet development.

To get a flavour of this extensive research and testing portfolio, IM spoke to Alan Boylston, Director, Process Engineering at Metso Outotec, and Rodrigo Grau, Technology Director – Minerals Processing at Metso Outotec, about the capabilities of two of the company’s facilities – York (USA) and Pori (Finland), respectively, while also touching on Metso Outotec’s global testing and research capabilities.

In 2022, the company announced a consolidation of its minerals testing services in USA into a single 5,500 sq.m facility in York able to eventually cover the full minerals value chain and support the mining industry worldwide. Pori, meanwhile, focuses on mineral technology, hydrometallurgical processes development, pyrometallurgy and ferroalloys technology and material technology. In other words, the company conducts laboratory and pilot test work, flowsheet development as well as validation and development of new technologies for the industry.

IM: Will the York facility now be seen as your ‘testing centre of excellence’?

AB: The York facility is a centre of excellence for testing, but we have many of these within the company. Our global presence, the knowledge and our expertise at each of these locations is one of the factors that sets us apart.

Each of our locations is a centre for excellence in its own field. Pori, for example, has extensive research capabilities, Sorocaba in Brazil focuses on comminution and beneficiation testing, while Lappeenranta Dewatering Technology Center concentrates on thickening and filtration. Each location is an integral part of our global testing offering. In addition to these, we have various facilities around the globe covering also aggregates and pyrometallurgical testing, research and development.

That being said, the effort we have made to expand the York Test Center gives us a much better advantage for research and testing in North America, compared to a few years ago. We can now do more pilot-scale testing, especially with equipment like our HRC™800e high pressure grinding roll (HPGR). We can also carry out pyrometallurgical testing, plus conduct magnetic separation tests. At some point in 2023, we also expect to add thickening and filtration testing to this remit. But this is a very high-level view of what we have to offer in the York location.

Metso Outotec has a global network of testing, research and product development locations

IM: Even with this consolidation in USA, are you expecting to collaborate with other global facilities when it comes to testing processes throughout the flowsheet?

AB: Yes, absolutely. For example, we have a project coming in right now where the sample was first in Tampere (Finland) for some crushing test work, before they split off a sample for us for grinding test work in York and then Pori is also receiving a sample for some broader mineralogy testing.

This speaks to why we are able to claim to have global capabilities. No matter the testing or research need, we are able to assist our customers to get the job done. This all goes towards one goal – the customer’s benefit.

IM: How do you see these testing capabilities interacting and benefitting from other modelling work you carry out in-house? For example, do you anticipate using these facilities and the likes of the Geminex digital twin in unison to offer clients physical and digital representations of flowsheet options?

RG: Modelling is very important for us. In each project we work on, modelling and simulation are at the heart. Here in Pori, we carry out flowsheet development and technology validation. One of the outputs of our work is to end with a simulation of an industrial plant. Going from that simulation into Geminex is just one more step we will be taking in the future.

AB: At the York lab, we are now moving to a SCADA-based system to run everything: when a sample comes in, it gets tagged and identified and we then automatically know what test to run. We have tablets to, for instance, setup all the parameters of a test for an HRC 800e. We can start and stop the test on that tablet and see the real-time information coming in as the test is being carried out. That data is also being stored for future use.

We’re undergoing a program right now to build out a database function where all the post processing of this data goes on in the background and can then be seamlessly integrated into things like our HRC simulation software. We are building the backbone to carry out that real-time digital twinning.

IM: Do you anticipate your global testing capabilities to lead to a higher uptake of Planet Positive solutions?

AB: With our customers having a huge focus on sustainability, I do. As an example, since we have had the pilot-scale HRC 800e available for testing, it has been fully booked. In 2023, we are preparing for a test plan where we could take the HRC product and go directly into a pilot Vertimill. Those are two Planet Positive approaches we are putting together in a single test plant to show how far we can push energy efficiency and media consumption reduction.

RG: I would definitely agree with Alan. And to add to that – for example at Pori, we do a lot of hydrometallurgical testing and piloting, and that is only increasing with the rising demand for lithium and other battery minerals. And our customers are really looking at how our equipment is reducing their carbon footprint and other sustainability benefits.

You will hear us say it time and time again, but this is definitely a trend that we are seeing at all of our facilities.

Metso Outotec testing and research capabilities cover the entire flowsheet – from comminution through the entire operation to pyrometallurgical/hydrometallurgical processing

IM: Will these expanded testing facilities also benefit your equipment and process R&D work?

AB: I think so. We built this lab to not just be a materials testing facility, but also a research hub, especially for grinding, but also for any other Metso Outotec business area needs. There is definitely a huge opportunity out there for us!

RG: And this rings true around the globe at all our facilities. For example, in separation, we have been testing the Concorde Cell™ flotation technology in Pori for a long time. And that is how we’ve approached development of a lot of our other innovations that go to market.

IM: How would you say industry testing requirements have changed over, say, the last five years?

AB: From our perspective, I am seeing more comprehensive test programs come through.

Instead of, say, one certain test, it is an entire test program with specific timings around evaluations and the ability to develop the flowsheet through the testing required. There is more collaborative designing of the flowsheet taking place through testing than there was five or 10 years ago.

RG: It is certainly more comprehensive now than it previously was.

For example, we carry out early engagement with our customers in Pori and start developing a flowsheet and evaluating the ore types.

The amount of material that is tested nowadays is much bigger than it was before. Obviously, it is not just limited to this example, because, as Alan mentioned before, we’ve got this connection between all our facilities to ensure our customers get exactly what they need from their testing program.

Also, our customers think about different drivers in the process very carefully and want that reflected in the test work. That could be more evaluation on the water they consume. They also look at the energy expended, on top of the expected recoveries and metal grades.

There is more emphasis on sustainability, even at these early stages, in addition to looking at how the ore types may change over time and what impact this will have on the processing requirements.

This is where our extensive simulation and modelling capabilities are leveraged for the biggest impact.

IM: Anything else to add?

RG: Pori and York are but a fraction of the expertise of the wider Metso Outotec research and testing portfolio; one that continues to expand in line with customer requirements. We don’t just cover mining, either – like our equipment offering, we provide research and testing services for the whole flowsheet.

And we are continually improving our capabilities in this space for our customers. So, stay tuned for the future and where we can take research and testing!

Multotec pulping chute advances at Ekapa open opportunities for fines scrubbing tech

Comminution of minerals, Diamond mining, Mineral processing, Mining equipment, Mining services, , , , , , , , ,

The performance of Multotec’s pulping chutes at Ekapa’s diamond treatment operation in Kimberley, South Africa, over the past couple of years has, the company says, opened the door to quicker and more cost effective fines scrubbing.

According to John Britton, Technical Consultant at Multotec, the two pulping chutes have achieved outstanding results, helping the customer’s facility to cost effectively increase the throughput of its Combined Treatment Plant (CTP).

“At our recent two-year inspection of the plant, we found that the wear rate on the ceramic lining of the wave generator was only 20 mm over that 24-month period,” Britton says. “Each chute was processing 380 t/h of recrushed kimberlite product with 380 cu.m of water, rushing down a 28° incline.”

Multotec’s patented wave generators use gravity to create a constant turbulent mixing action in the slurry flow that releases the mud, clay and slime sticking to the kimberlite particles. The chutes are positioned to receive material from the high pressure grinding rolls’ interparticle tertiary crushing circuit. Multotec’s engineered alumina ceramic tiles give the chutes and wave generators high wear resistance, it says.

“The chutes exceeded our expectations in how well they separated the clay from the kimberlite ore and broke up clay balls in the material stream,” Britton says. “This has really demonstrated the long-term capacity of our design to deliver results with hardly any maintenance or operator intervention.”

He highlights that the chutes are stationery structures that rely on the kinetic energy being created by the in-rush of slurry flow over the wave generators. This makes the solution much simpler and less energy-intensive than traditional rotary scrubbers with motors, drives and gearboxes. The chute can also achieve its results much quicker, as the material flow passes through in just three to four seconds.

Ekapa CEO, Jahn Hohne, says he has been impressed by how well the chutes have performed as an alternative to a considerably more costly scrubber circuit, and having delivered a 20% increase in throughput through the plant and making a positive economic contribution to overall efficiency. Hohne says he admired Multotec’s innovation capability and looked forward to even further improvements in the design.

Britton notes that, after conducting the wear inspection of the chutes, there were modifications Multotec was planning. One of these related to the retarder bars, which slow down and divert the slurry flow.

“We believe we can achieve even better results if we remove some of the retarder bars and install another set of wave generators,” he says. “Our results suggest that this will get the ore material even cleaner, before it reports to the screen, the conveyor belt and finally the dense medium circuit.”

The success of the pulping chutes at Ekapa has led to considerable interest from other diamond producers in southern Africa, he added.

Kwatani wins major screening order from Central Asia copper mine

Base metals, Comminution of minerals, Mineral processing, Mining equipment, Mining services, , , , , , , ,

Competing with leading OEMs from around the world, vibrating screen specialist OEM Kwatani says it has snatched a mammoth export order for over 70 screens from a mining operation in Central Asia.

The order was signed in April with a large copper mine in the region, which boasts a production rate of 35 Mt/y. According to Kwatani General Manager Sales and Service, Jan Schoepflin, the machines will be rolled out and delivered over a tight schedule of just eight months.

Kwatani, now part of the Sandvik group within the Sandvik Rock Processing Solutions division, is already hard at work manufacturing the large and medium-sized screens at its South Africa-based manufacturing facility.

“This is Kwatani’s largest order to date and is probably the largest single order for screens ever placed with a company in Africa,” Schoepflin says. “We are proud to have won such a prestigious bid in the face of intense competition, showing how our global reputation has been growing.”

The order is for large double-deck multi-slope screens, which feed high pressure grinding rolls, as well as for single-deck linear screens feeding concentrators. The screens in this order will be installed on isolation frames to minimise the extent to which dynamic loads affect the plant’s building structures, the company says.

Kwatani says it is well known for its design, manufacture and servicing of large, robust screens which are engineered for tonnage.

“As the largest OEM for vibrating screens and feeders in Africa, we have had great success on the continent and abroad with our large ‘banana’ screens,” Schoepflin says. “These and our other custom-engineered screens have been supplied to over 50 countries to date.”

The stringent and lengthy technical adjudication for this project was conducted for the mine by two leading international project engineering houses. The size and value of the order ensured all the mining industry’s foremost screen suppliers participated in the bid. Other indicators of the order’s scale are that the screens will consume around 700 t of steel, and will altogether be fitted with 21,000 screening panels.

Schoepflin notes that an important consideration for customers is not only the proven quality and performance of its screens, but Kwatani’s ability to deliver on time.

“Any large capital expenditure decision on a mine is taken with time-sensitive factors in mind,” he says. “For instance, the delayed delivery of critical equipment can prevent a mine from meeting its planned production targets. This undermines the financial basis for that decision – an eventuality that no mine can afford.”

The end-customer and the project houses, therefore, had to have full confidence in Kwatani’s capacity.

With growing demand from a buoyant mining sector, the company recently added another 3,000 sq.m to its existing 17,000 sq.m facility in Spartan, Johannesburg. Its design and manufacturing capabilities are ISO 9001:2015 certified, ensuring that the latest order to Asia will comply with the highest global standards, he says.

“We also pride ourselves on the quality and resilience of our supply chain, which underpins our ability to manufacture to demanding deadlines,” Schoepflin says. “We carefully select our supply partners – most of whom are local enterprises – and collaborate closely with them to build their sustainability and responsiveness.”

To keep the project’s schedule on track, dedicated in-house project managers and procurement specialists meet regularly with supply partners to ensure a smooth and streamlined process. This has required alignment of all local and global procurement, including motors, drives and steel. The company’s agility allowed contracts and prices to be tied down for timeous delivery, despite the global supply chain disruption that lingers from the COVID-19 lockdowns, Kwatani says.

Kwatani will conduct training of the mine staff in maintenance and troubleshooting, so that they can fulfil these essential duties independently. The mine will be able to source all the necessary spares from Kwatani, who will also send an engineer or technician to site to supervise and sign off on certain major tasks.

Meeting delivery deadlines and avoiding penalties will require detailed logistical planning for the completed units, Schoepflin notes. The screens will be delivered in batches to a South African port, and shipped as break bulk due to their size. Production of the screens is expected to be complete by early 2023.

Wood tradeoff study puts HPGR, POx processing ahead at De Grey’s Mallina gold project

Comminution of minerals, Environmental, Mineral processing, Mineral project development, Mining equipment, Mining services, Precious metals, Sustainable mining, , , , , , ,

Prefeasibility process engineer Wood Australia has completed a comprehensive nine-month trade-off study into the preferred process flowsheet design for De Grey Mining’s Mallina gold project, selecting a process flowsheet that incorporates high pressure grinding roll (HPGR) and pressure oxidation (POx) technology.

The project, which includes the Hemi Deposit, is in the Pilbara region of Western Australia.

In late 2019, De Grey made a large scale, high value, near surface gold discovery at Hemi – an intrusion-hosted form of gold mineralisation new to the Pilbara region that, the company says, shows a scale of mineralisation not previously encountered in the Mallina Basin. The company currently has 6.9 Moz of measured and indicated resources declared at the project, with plans to turn this into an open-pit mining operation down the line.

The findings have come out ahead of the full PFS, which is due for announcement in the September quarter of this year.

The trade-off study has confirmed that Hemi mineralisation has excellent recovery and is amenable to HPGR and POx processing technologies, the company said. The process route chosen has demonstrated advantages relative to other processing technologies including:

  • Proven and accepted technology for the scale of operation and style of mineralisation;
  • Lower capital and operating costs;
  • Higher gold recovery between 93% and 95% depending on average feed grades;
  • Circa-20% lower energy consumption;
  • Circa-25% lower reagent (lime) consumption;
  • Circa-25% lower CO2 emissions;
  • No heat addition required to sustain – or cooling to control – the POx process; and
  • Robust and proven equipment.

The flowsheet selections have the benefit of lower carbon emissions through lower energy requirements and lower greenhouse gas emissions as a result of improved neutralisation and consequent lower lime consumption, De Grey added.
“Further studies are in progress as part of the PFS on the carbon intensity and greenhouse gas emissions for the Mallina Gold Project development,” it said.

The currently envisaged flowsheet at Hemi sees ore crushed and ground in the comminution circuit before being fed to the flotation circuit. Any gravity recoverable gold will be recovered prior to flotation with the use of, for example, a Knelson or Falcon concentrator. Test work has shown gravity recoverable gold is present in the Hemi and regional mineralisation, and the extent of gravity-recoverable gold will continue to be assessed through test work.

The flotation circuit will process gold bearing sulphides in Hemi ore producing a “low mass pull” gold-rich sulphide concentrate. The POx circuit is designed to receive the gold-rich sulphide concentrate from the flotation circuit. The POx circuit will have a throughput of 8% (800,000 t/y) of the throughput of the comminution circuit.

The POx circuit will convert the sulphide concentrate to a gold bearing residue amenable to standard carbon in leach (CIL) processing. The underflow from flotation is also amenable to standard CIL processing. Both streams will enter the CIL circuit followed by electrowinning to produce gold bars on site. This has numerous benefits for the POx circuit including lower capital and operating costs compared with projects that require whole of ore treatment through POx.

Tailings from the CIL circuit will be pumped to a tailing storage facility.

Hemi mineralisation has two significant and attractive mineralogical characteristics that lead to the overall expected metallurgical recovery of between 93% and 95% at expected mined grades, namely:

  • The majority of gold at Hemi can be floated into a low mass pull concentrate that recovers very high levels of sulphides and gold ahead of oxidation; and
  • The flotation tail contains gold that can be successfully recovered using standard CIL processing.

The crushing circuit will include a primary gyratory crusher, a secondary cone crusher and. The secondary cone crusher will operate in closed circuit with a sizing screen while the HPGR will operate in closed circuit with wet sizing screens to produce a nominal less than 7 mm mill feed. The grinding circuit will consist of two ball mills with conventional pinion drives each with their own classification circuit.

The oxidation circuit throughput for Hemi is proposed to be 800,000 t/y, or 8% of the proposed comminution circuit throughput of 10 Mt/y. The oxidation circuit will treat the gold-bearing sulphide concentrate generated by the flotation circuit. The POx circuit will consist of flotation concentrate thickening and storage, POx utilising autoclave technology and neutralisation in association with the flotation tail prior to co-leaching in a CIL circuit.

The oxidation circuit will be designed to have sufficient storage capacity prior to the autoclave to allow for maintenance shutdowns without the need for a mill shutdown. This decouples the comminution and oxidation circuits ensuring that each circuit does not impact on the availability of the other.

Kwatani’s mill discharge screen expertise to pay off at Namibia gold mine

Comminution of minerals, Mineral processing, Mining equipment, Precious metals, , , , , ,

Namibia’s mining scene is seeing an exciting expansion and technological innovation at a leading gold mining operation, with Kwatani supplying five mill discharge screens – all custom designed and manufactured at its Gauteng facilities.

Kim Schoepflin, CEO of Kwatani, says her company has a long history in Namibia and a strong footprint across various commodities there – including an established presence at this gold mine. It has worked with the engineering, procurement and construction contractor and the end-customer for two to three years on conceptualising the optimal solution.

“The mine is gearing up to increase its production by 50%, to take advantage of the strong gold price,” Schoepflin says. “Our role was to ensure that our discharge screens meet their exact process requirements – with our efficiencies of up to 95% – while delivering mechanical integrity for minimal maintenance downtime.”

The expansion includes the installation of two latest-technology mills – a high-pressure grinding roll (HPGR) and a vertical mill – which will boost production while reducing energy demand. Kwatani’s mill discharge screens, each measuring 3-m wide by 8-m long, will handle the coarse and fine material from the HPGR and the vertical mill. The company will also supply three silo feeders of 1.2 m by 2.5 m in size, to feed material from the silo to conveyors.

“Our screen design optimises the retention time on the deck, allowing for better screening and stratification,” Schoepflin says. “Due to the volume of slurry and water sprayed onto the screens, the added retention time assists with better drainage at lower cut points.”

The coarse screens were designed at a decline, and feature a larger screening media aperture with higher amplitude and stroke. Together with lower speed, this achieves better screening efficiency for the coarser particles. The fine horizontal screens, with smaller aperture screening media for the finer feed, were designed with a higher speed and lower amplitude and stroke; this will optimise the screening efficiency of the finer feed to these screens.

She also highlights the attention paid to the isolation of the vibrating screens. In this case, Kwatani engineers selected rubber buffers, which have higher dynamic loads but are more suited to wet applications and screens with a heavier mass.

“The number and type of buffers were defined according to the mass of the screens,” Schoepflin says. “The selection of rubber buffers for larger screens also assists with start-up and shutdown time, allowing the screens to come to rest more effectively.”

For these five screens, Kwatani, now part of Sandvik Rock Processing Solutions,  designed and supplied custom counter-balance frames to minimise the dynamic load to the plant infrastructure. The company’s screen technology includes designing its exciters in-house. This ensures that screens receive the necessary G-forces for optimal material stratification and screening, matching customers’ process requirements with the best possible efficiencies.

“To make sure our screens cope with the high capacity demands of modern processing plants, we rigorously test all units in our in-house testing facility before dispatch,” Schoepflin said. “These units began their journey to Namibia at the end of November 2021, and our team will support the commissioning when the customer requires.”