Tag Archives: dry stack tailings

Vale sells New Caledonia nickel-cobalt operations to consortium

Vale confirms that its Vale Canada Limited subsidiary has concluded the sale of its ownership interest in Vale Nouvelle-Calédonie SAS (VNC) to the Prony Resources New Caledonia consortium.

The consortium of investors, including Trafigura, comprises a majority and non-dilutable shareholding for New Caledonian interests, Vale said.

Eduardo Bartolomeo, CEO of Vale, said: “After several months of negotiations, I am pleased that we concluded our divestment of VNC, benefitting employees, New Caledonia and all its stakeholders. Vale is fully committed to this transaction. It meets the guarantees required at the financial, social and environmental levels and offers a sustainable future for the operations.”

Vale’s intent from the beginning of the divestment process was to withdraw from New Caledonia in an orderly and responsible manner, with the company saying the deal accomplishes that.

Vale previously tried to sell the operations to Australia-based New Century Resources, but the two parties failed to reach an agreement.

The deal provides the former VNC operations with a financial package totaling $1.1 billion, of which Vale Canada Limited is contributing $555 million to support the continuity of the operations. The financing of the “Pact for the Sustainable Development of the Deep South” will also be secured by Vale, it said.

The Pact for Sustainable Development of the Deep South was signed on September 27, 2008, between Vale New Caledonia and communities south of the “Grand” for a period of 30 years. It urges the industry to create and implement specific measures to support the development of the Deep South in a sustainable manner.

In addition to its financial commitment to continue operations, Vale will continue to have the right to a long-term nickel supply agreement for a proportion of the operation’s production, allowing it to, the company says, continue addressing the growing demand for nickel by the electric vehicle industry.

Mark Travers, Executive Vice President for Base Metals with Vale, said: “Along with the continuation of the Pact, the deal also allows the Lucy Project for dry storage of tailings to proceed. We want to acknowledge the time and effort of all stakeholders to achieving this deal, including the French State, and especially the employees of VNC for their trust and support through a lengthy and uncertain process.”

VNC is a producer of nickel and cobalt from the Goro mine. It also has a processing plant and a port.

Metso to help Gold Fields with dry tailings processing at Salares Norte

Metso says Salares Norte, a Chile greenfield project owned by Gold Fields, has ordered three of its Vertical Plate Pressure Filters with all the ancillary equipment for dry tailings processing.

The order has been booked in Metso’s June quarter orders received, with the filters expected to be commissioned in October 2022.

Francois Swanepoel, Technical Manager at Salares Norte, said Gold Fields’ vision is to be the global leader in sustainable gold mining.

“The Salares Norte greenfield project is located 4,500 m above sea level in the Andean Mountains, where water is scarce and needs to be used wisely,” he said.

“To minimise the use of water and improve the physical and chemical stability of our tailings, we have decided to adopt filtered tailings for the project. Salares Norte will be a benchmark plant for dry tailings processing.”

Earlier this month, Outotec announced it would provide one 4 MW SAG mill and one 4 MW ball mill as well as five thickeners and one clarifier to be used in different process phases at the project.

Metso said Salares Norte was an exciting project for the company to work on as it considers dry tailings as the “most socially responsible and economically viable solution for tailings management”.

Patricio Mujica Dominguez, Senior Manager, Mining Equipment at Metso, said: “Besides the front-running tailings management solution, Salares Norte has challenged its partners to come up with other innovative solutions. The location of the plant at a height of almost 5 km above the sea level comes with its own unique challenges.

“For example, the design and transportation of the equipment, as well as commissioning, needs to be done with special care. To save manpower at such a high altitude, Metso will semi-assemble the filters in its service centres and deliver them in six specially designed easy-to-assemble modules to the site.”

A 2019 feasibility study on Salares Norte envisages an open-pit mining operation with an initial mine life of 11.5 years, producing 450,000 oz/y of gold-equivalent for the first seven years.

Los Andes Copper engineers a Vizcachitas alternative

It is a combination of improved technology, reduced fine grind requirements and maintenance benefits that led to Los Andes Copper replacing the SAG and ball mill crushing circuit proposed in its Vizcachitas copper-molybdenum project preliminary economic assessment (PEA), with a three-stage crushing circuit that uses high pressure grinding roll (HPGR) technology in the tertiary crushing stage, according to Executive Chairman, Fernando Porcile.

In the middle of a prefeasibility study on the Vizcachitas project, Los Andes recently issued an update on the study progress.

A delay of PFS publication to the March quarter of 2021 due to the onset of COVID-19 impacting some of the metallurgical test work and field work at the project might have been the key takeaway for investors, but those in the mining technology game will be focusing on the revised process flowsheet being put forward at the Chile project.

One of the big changes was seen at the front end on the comminution side.

In the close to year since issuing the June 2019 PEA, and with the arrival of Porcile and his team, the company’s understanding of its orebody characteristics and the technology available to it as a new greenfield project owner has grown.

Porcile said the ore at Vizcachitas is very suitable to this energy efficient HPGR technology, with metallurgical test work showing an HPGR circuit can reduce the sensitivity to changes in hardness, providing a product that is more consistent in size. This will help reduce major process fluctuations downstream – where there have also been some changes.

The P80 target grind size of 240 microns hasn’t changed much – moving up to a P80 of 240-300 microns – but the SAG and ball mill circuit has been replaced with a three stage crushing circuit using secondary crushers in open circuit and HPGR as a tertiary crusher in closed circuit.

On the preliminary comminution process flowsheet, this includes the use of a Metso Superior™ MKIII primary gyratory crusher, feeding three Nordberg® MP2500™ cone crushers, which move into 40,000 t crushed ore bins. This material is then conveyed to two Metso HRC™ 2600 HPGRs.

Los Andes says the configuration of secondary cone crushers in an open circuit avoids the use of a coarse ore stockpile and recirculation conveyor belts – reducing dust emission sources – while the closed reverse grinding circuit allows less production of fines, which is helpful for the follow-on thickening and filtration stages.

On top of this, the secondary crushing and grinding plant in this setup is close to the primary crusher, which also reduces coarse ore conveying costs.

Porcile said HPGR technology has moved on a long way in the last decade and now represents a more reliable proposition than using the SAG and ball mill circuit previously proposed.

“There is much less risk associated with using HPGRs in a new operation,” he told IM. “Large SAG mills not only take up lots of space within the plant, they can also come with teething problems during start up.”

He added: “HPGRs used to come with lots of wear problems, meaning you had to replace the rollers often. The maintenance on them is that much better now; the rollers do not wear out as quickly and, when they do, you can easily replace them.”

On top of the obvious benefits in energy consumption that come with using HPGR technology, there are positives that can be felt further down the process flowsheet.

“We are very confident that HPGR is the best alternative for our project due to the nature and quality of our ore,” Porcile said. “We produce very little fines, which has an impact on the way we deal with tailings.”

The combination of a lack of fines and low presence of clays (mainly kaolinite) has helped filtration performance in test work, indicating that a dry-stacked tailings solution may be viable at Vizcachitas, Porcile said.

This could provide an up to 50% reduction in water consumption compared with the PEA at Vizcachitas. It could also see some 82% of water recovered throughout the process, in addition to a significant reduction in infrastructure requirements.

“We go from having infrastructure in two valleys in the PEA to one in the PFS,” Porcile said on the latter point.

One may think creating a dry-stacking operation at a 110,000 t/d throughput mine would prove costly and difficult, but the lack of fines and low presence of clays already mentioned means the process is a lot simpler to other dry-stacking projects currently on the table across the globe, according to Los Andes.

Test work to date has indicated that coarse material from the plant (plus-400 microns) could produce a cake with 14%-18% moisture through the use of belt conveyors. This material currently makes up 87% of the envisaged tonnage.

Only 13% of tonnage classed as fines (less than 400 microns) would have to go through pressure filters to produce a 16-19% moisture cake, according to the company.

Porcile says these belt filters work just as well as pressure filters on the coarse material from Vizcachitas but are that much more cost effective.

“Belt filters come with high filtration rates, are low cost (in terms of capex) and are reliable,” Porcile said. “In the study, we envisage saving pressure filters only for the very top level of material.”

While it is too early to talk about the impact these changes will have on the capital expenditure and net present value numbers to be included in the PFS, expect the $1.87 billion and $1.8 billion (after tax and with an 8% discount), respectively, to change.

Metso lines up LatAm tailings tests after setting up full-scale VPX filter in Brazil

Metso says it has started full-scale testing of its VPX™ filter for tailings dewatering in Brazil, with eight tailings tests lined up with companies that process iron ore, copper and gold.

In 2019, Metso launched Tailings Management Solutions (TMS), its response to the global challenge of managing mining tailings efficiently. The company sees the dewatering of waste as the future of mining, allowing the removal of water and its reuse in the plant, itself, or as part of restoration projects. Its VPX filter is part of this TMS platform.

With an operating pressure of up to 25 bar, the VPX can deal with difficult-to-dewater tailings and enable up to 90% water recovery, according to the company.

Metso says a full-scale VPX filter is now in place at its facilities in Sorocaba, Brazil, where the first tests from samples sent by several mining companies from Brazil and Latin America started in March.

“This is not a laboratory test, but filtration in industrial-scale conditions using VPX technology, which has the capacity to process high volumes of ores,” Rodrigo Gouveia, Metso’s Vice President, Tailings Management Systems, said. “Tailings dewatering is technically and economically a viable option for today and the future. Dry stacking is widely acknowledged to be the safest, most sustainable option for tailings storage. We see that there is a strong demand for short- and medium-term technical solutions.”

Fausto Rezende, Metso’s Mining Equipment Sales Director in charge of TMS in Brazil, said there is another potential application in the adoption of tailings management: legacy dams. “We can develop projects for the dredging and concentration of the tailings and, in many cases, it is possible that this operation is more economically viable than virgin ore,” he said.

Metso already has expertise in dewatering solutions and, depending on each mining application and customer needs, carries out engineering to determine the specifications for the most suitable dewatering technology. It can pick from lamella thickeners, hydrocyclones and filters to tailings stackers, through pumping solutions and conveyor belts.

Karara Mining to stack tailings high to keep costs, water use and footprint low

Bis, FLSmidth and Karara Mining have developed a “unique mobile stacking conveyor” solution that has cut water use, costs and the environmental footprint at the iron ore miner’s operation in Western Australia.

If Karara’s iron ore mine had chosen a wet tailings storage facility, the tailings pond would have been roughly 8 sq.km based on its 30-year mine life, according to FLSmidth.

The operation is also in the Mid-West region of Western Australia, an area with scarce water reserves, so losing so much water to wet tailings would have been costly to both the environment and Karara’s bottom line.

With these factors in mind, Karara looked at implementing a dry-stacked/filtered tailings system to allow for significant water recovery and reuse. As well as reducing costs, dry stack technology would reduce the tailings footprint to around 4 sq.km, according to FLSmidth.

Bis worked with Karara and FLSmidth to develop a solution to build, own, operate and maintain a “unique mobile stacking conveyor”, FLSmidth said. This fixed infrastructure solution was developed by the three companies to integrate a walking conveyor and stacking technology normally used in large-scale copper mining operations.

Aside from the significant reduction of the physical footprint compared with the wet tailings alternative, Karara was looking for cost efficiencies in other areas, FLSmidth said. “For instance, the planning of a wet tailings storage facility needs to factor in an ongoing maintenance strategy. This comes with a perpetual cost that can only be guessed at while the decades pass,” the company said. “With dry-stack tailings, the total cost of ownership over the mine’s lifetime is easier to estimate and Karara were confident the dry stack solution would be cost competitive.”

Water usage was another key consideration for Karara. With environmental and cost factors in mind, Karara wanted to look at ways to have greater control over water assets on site. The ability to reuse and recycle water in the mining process would lead to substantial cost efficiencies by minimising the amount of makeup water needed for the mining operation, FLSmidth said.

The technology implemented into Karara’s tailings storage facility was also an important factor as Karara wanted the flexibility to continually update the equipment with the view of running it more efficiently as new technology became available. It engaged Bis to operate the facility machinery based on its deep industry experience with materials handling and bulk logistics, FLSmidth said.

FLSmidth, meanwhile, was identified by Karara as being able to meet the project’s requirements and mine-specific needs.

The mining OEM said: “A primary demand was the ability to supply a cost-effective dry stacking technology ideal for dry climate mining operations that reduced water requirements. With FLSmidth’s advanced stacking capability (machinery working off stacked pile) and ability to stack tailings at 15% moisture content, this meant tangible water savings for Karara.

“At Karara, the dry tailings will be stacked in four lifts to the maximum height approved by the Western Australia Government. The solution proposed by FLSmidth also created a smaller tailings storage footprint, which also meant improved site rehabilitation potential.”

Karara worked closely with Bis and FLSmidth to get the project off the ground and make Karara the first mine in Australia to take full advantage of this dry-stack technology, FLSmidth said.

The tailings storage facility is fast approaching the completion of Lift 1 and, together with Karara, Bis and FLSmidth are already in the planning stage to lift the equipment to the second level.

South Star’s filtered tailings plan for Santa Cruz graphite project stacks up

South Star Mining Corp’s aim of using a filter press and eliminating the requirement for a tailings storage facility at its Santa Cruz graphite project in Bahia, Brazil, has been given a boost following positive bench scale test results.

The Toronto-listed company said it had received positive results for the laboratory bench scale filtered tailings tests performed on two simulated tailings samples from Santa Cruz. Two tailings samples (+325 mesh and -325 mesh) were generated and tested in laboratory facilities in Belo Horizonte, Brazil, it said.

Five scenarios were completed for the leaf filter tests with various solids densities, feed rates, vacuum pressures, and cake thickness:

  • -325 mesh sample at 10% solids;
  • -325 mesh sample at 10% solids at higher feed rate and vacuum pressures;
  • -325 mesh sample at 20% solids;
  • -325 mesh sample at 20% solids with minimized cake thickness, and;
  • +325 mesh sample at 10% solids.

The tests resulted in cake with humidity varying between 23% to 35% and cycle times ranging from 19:23 to 49:47 minutes, according to the company. Based on the bench scale leaf tests, additional pilot tests are being performed to better quantify the range of possible solutions and also test a mixture of the +325 and -325 mesh materials to create a third sample type, the company said, adding that results of the pilot tests were expected shortly.

South Star said the goal of the testing programme was to examine the potential for altering the proposed flow sheet from the process circuit presented in the preliminary economic assessment (PEA) to include a filter press and eliminate the requirement for a tailings storage facility.

“By incorporating filtered tailings technology, the majority of the water from the tailings would be removed and recirculated and allow the dried tails to be placed together with waste rock in a co-disposal waste facility,” the company said.

South Star CEO, Eric Allison, said: “We are very pleased with these initial results from our filtered tailings test programme and their positive implications for utilising dry stack tailings at Santa Cruz for both our trial mining plant and the final full-scale facility. Co-disposal of the waste should not only reduce the project’s environmental impact, risk profile and physical footprint, but should streamline our permitting and licensing processes as well.”

The company plans to incorporate the results of the programme into the prefeasibility report scheduled for completion in the September quarter, it said.

The mid-2017 PEA on Santa Cruz outlined an indicated resource of 14.99 Mt at 2.70% Cg with 404,741 t Cg, and inferred resources of 3.57 Mt at 2.90% Cg with 103,591 t Cg. Graphite deposition at Santa Cruz is found at surface within oxidised material providing a very favourable strip ratio, and requiring no crushing or blasting, according to the company.

The PEA stated Santa Cruz has a post-tax internal rate of return of 78% and a payback period of two years. Mine planning for the existing graphite deposit outlined a 12 Mt mineable resource with a diluted grade of 2.63% Cg providing support for a 19-year open-pit mine. Life of mine average yearly production came in at 15,800 t alongside operating costs of $413/t.

Hudbay’s Rosemont copper project moves forward with 404 Water Permit

The US Army Corps of Engineers has issued a Section 404 Water Permit for Hudbay Minerals’ Rosemont copper project in the US, the mining company says.

Rosemont has already received the Final Record of Decision from the US Forest Service (USFS), a process that involved 17 co-operating agencies at various levels of government, 16 hearings, over 1,000 studies, and 245 days of public comment resulting in more than 43,000 comments.

The company said: “Now that the 404 permit has been issued, Hudbay expects to receive Rosemont’s Mine Plan of Operations from the USFS shortly and looks forward to moving the project into development.”

Rosemont, around 48 km southeast of Tucson, Arizona, is envisaged as an open-pit mine producing copper, molybdenum and silver. It is expected to have an annual average life of mine copper production of 112,000 tons (101,605 t).

The Rosemont site will include a processing plant and associated facilities, transmission lines for power and water, the pit, and waste rock and dry-stack tailings storage facilities.

“Best available demonstrated control technologies will be the hallmark of Rosemont,” Hudbay said. “These technologies will contribute to maximising production while minimising environmental impact. At Rosemont, this will include the use of dry-stack tailings – a technology that significantly reduces water use and improves reclamation – along with leading-edge lighting designs to maintain dark skies, solar energy as a source of power, dust collectors with cartridge filters and trucks with Tier 4 engines to ensure compliance with air quality standards.”

Alan Hair, Hudbay’s President and CEO, said: “The receipt of Rosemont’s 404 Water Permit is a major milestone in our efforts to build a modern mine that will fulfil the requirements of its permits, create jobs and provide benefits for all of our stakeholders.

“We appreciate the diligence that the Army Corps has put into its consideration of Rosemont’s permit application, and look forward to advancing Rosemont into construction.”

Hudbay said it would continue to execute its plan regarding the Rosemont project and provide updates as developments warrant.