Tag Archives: Los Andes Copper

TAKRAF dry-stacked tailings test work boost for Los Andes Copper’s Vizcachitas project

Los Andes Copper says it has received additional positive results from the ongoing prefeasibility study (PFS) metallurgical test work at its Vizcachitas project in Chile.

These results show improved filtration rates for both the fine and coarse fraction tailings compared with previous testing, it said, reinforcing the decision to adopt dry-stacked tailings at the project.

An October press release regarding PFS metallurgical test work carried out by SGS demonstrated that the Vizcachitas tailings were amenable to being filtered and dry-stacked.

These same coarse and fine representative tailings samples were sent to the TAKRAF laboratories for further settling and filtration assessments. Los Andes said the TAKRAF work tested various settling and filtration parameters, including those previously tested.

The studies demonstrated that for the coarse fraction vacuum filtration, the rates improved from 1.9 t/h/sq.m to 3.4 t/h/sq.m when compared with the previous results. For the finer fraction, the settling velocities improved from 8.4 m/h to 16 m/h and the pressure filtration rates improved from 0.6 t/h/sq.m to 0.7 t/h/sq.m. The expected cake moistures for both filtration technologies were 15%.

These positive results mean that the Vizcachitas project, processing 110,000 t/d of ore, would only need to use eleven standard 162 sq.m belt filters and four 2.5 m x 2.5 m pressure filters for the tailings dewatering operation, Los Andes said, noting that other operations in the world were successfully operating with similar filter arrangements.

“Tailings filtration reduces water consumption by 50% when compared to thickened tailings disposal alternatives,” Los Andes said. “Furthermore, filtered tailings can be handled by trucks, conveyors and shovels, eliminating the need for the construction and operation of a tailings dam.

“The adoption of this technology puts the Vizcachitas project at the forefront of the environmentally responsible practices being adopted for the future of sustainable mining globally.”

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.”

Los Andes Copper confirms dry stacked tailings plan at Vizcachitas

Los Andes Copper has received results from the ongoing prefeasibility metallurgical study on its Vizcachitas copper project which, consistent with all prior test work conducted, confirms the adoption of dry stacked tailings at the Chile asset.

During 2020, Los Andes has continued metallurgical testing at the SGS laboratory in Santiago, Chile. The test work was carried out on representative samples from locked cycle flotation tailings that reproduce the expected particle size distribution for the coarse and fine tailings fractions at Vizcachitas, it explained.

The planned prefeasibility study (PFS) system for the water recovery is to use vacuum belts for the coarse tailings and pressure filters for the fine tailings. The filtration rates for coarse fraction vacuum filtration are between 1.8-2.0 t/h/sq.m and the fine fraction pressure filtration rates between 0.5-0.6 t/h/sq.m. The expected average filtered cake moisture is between 15-18%, confirming that the Vizcachitas ore is amenable to being filtered and dry stacked.

As the PFS advances, the decision to implement filtered tailings for dry stacking reflects the commitment of Vizcachitas to become one of the early adopters of the environmental friendly technology that will guide global mining in the future, Los Andes said.

Filtration reduces water consumption by 50% when compared with thickened tailings disposal alternatives (60-70% reduction when compared to traditional disposal alternatives), according to the company. Furthermore, filtered tailings can be handled by trucks, conveyors and shovels, as other solid bulk materials, eliminating the need for the construction and operation of a tailings dam.

“The latter is a milestone in operational flexibility and safety standards of particular relevance in a seismic country such as Chile,” the company said.

Fernando Porcile, Executive Chairman, said: “The verification that dry stacked filtered tailings is a viable option for Vizcachitas puts us on the forefront of environmentally responsible practices being adopted for the future of sustainable mining globally.

“Water conservation is high on the agenda for many mining companies, especially in Chile, and therefore the fact that we can reduce our water consumption by approximately 60-70% by using this method is a really positive development.

“This is a proven technology which is now being carried over into Tier One copper projects and I am excited that we will be one of the first, large scale, copper mines to utilise it.”

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.

Los Andes Copper addressing Vizcachitas project energy and water needs in PFS

Los Andes Copper has ideas on adding to the number of large open-pit mines in Chile’s copper industry with the development of its Vizcachitas project, but it is eyeing up a different route to many of them that includes the use of energy-efficient HPGR technology and dry-stacked tailings.

In an update on its pending prefeasibility study (PFS), the company said it was re-evaluating the conceptual plan it laid out in its June 2019 preliminary economic assessment, which envisaged a base case 110,000 t/d operation using a SAG mill grinding circuit and thickened tailings dam.

The PFS is currently underway and areas of work being advanced include processing, the tailings facility, infrastructure, geology, the mine plan, environmental and social and community engagement, it said.

While delaying some of the metallurgical test work and field work, the current COVID-19 situation had not impacted the progress of the main engineering study, according to Los Andes. “All employees and subcontractors are working from home where possible and only a small group of individuals are working to prepare samples in the company’s Santiago core storage area,” it said.

The full PFS is not expected until the March quarter of 2021, but the company did outline some engineering leaps it has made since the PEA publication.

It said test work had shown that a HPGR circuit is feasible for the project and could provide “enhanced project economics with lower energy consumption and increased operating flexibility”.

The PEA outlined a SAG and ball mill crushing circuit with a target grind size of P80 (240 microns), but the more recent test work had shown room for an alternative with a three-stage crushing circuit using secondary crushers in open circuit and HPGR as a tertiary crusher in closed circuit. This circuit would target a grind size of P80 between 240-300 microns, the company said.

Such a change would avoid the use of a coarse ore stockpile, reduce energy consumption, reduce maintenance, and reduce the project footprint, it said.

HPGRs have previously been used at Chile mining operations, including the Compañía Minera del Pacífico-owned Mina Los Colorados iron ore mine and KGHM’s majority-owned Sierra Gorda operation.

Los Andes clarified: “HPGR technology has been identified as the most attractive grinding alternative given the data obtained from the preliminary test work conducted to date.”

The next big advance was made on the tailings side, with the company saying test work had shown that the project is amenable to filtering and dry-stacked tailings.

“This change would significantly reduce the project’s water consumption, footprint and environmental impact,” it said. It would also, one would expect, provide a much smoother environmental permitting route for Vizcachitas considering the negative sentiment surrounding thickened tailings dams in the industry.

There are knock-on benefits to this move too, with the reduced footprint required for dry-stacked tailings meaning all project infrastructure could fit into one operating complex in the Rocin Valley of Chile, around 150 km northeast of Santiago. The PEA previously outlined the use of infrastructure in both the Rocin Valley and the Chalaco Valley.

The preliminary filtration circuit Los Andes is working with shows the coarse fraction (87% of total tailings) could be filtered in belt filters, with the fine fraction (13%) filtered in pressure filters.

Recent studies on other dry-stack tailings project have tended to use either belt filters or pressure filters, but Los Andes said the combination of the two added flexibility to the tailings filtration operation at Vizcachitas and reduced operational risks due to variability of the finer fraction in tailings.

This would see the company require 12 belt filters and three filter presses for the 110,000 t/d copper-molybdenum operation.

According to the company, dry-stacked tailings would:

  • Reduce water consumption by around 50%;
  • Reduce the project’s footprint;
  • Be better suited for areas of high seismic activity;
  • Be transported by trucks or conveyors;
  • Eliminate the need for a traditional dam wall; and
  • Reduce the environmental risk by avoiding contact with ground water.