By Olivia Mejías, MSc and Javier Quevedo, Geology Researchers at SMI-ICE-Chile

Chile is recognized as the producer of 28.5% of the world’s copper, around 5.7 million metric tons[1], and 22% of lithium, around 18 thousand metric tons[2]. However, Chilean mineral deposits offer much more, and efforts have begun to focus on other metals and minerals in the primary and secondary resources. Chile’s long mining history includes copper, iron, gold, and molybdenum, mainly. This has meant that, according to the August 2020 update of the Tailings Deposits Registry of Sernageomin (Chilean National Geology and Mining Service), currently Chile hosts a total of 757 tailings deposits, of which 112 are active, 467 are inactive, 173 are abandoned, and 5 are under construction. Both industry and society are aware of the potential risks that tailings deposits can present, and that they require ongoing management. Nonetheless, they are also potential resources for helping supplement the demand for critical metals. Currently, the challenge in Chile is to acquire knowledge and apply it to critical metals recovery through a sustainable mining point of view.

What are critical metals?

It is generally agreed that critical metals are a formally defined term for metals that are economically important but have a high potential for supply disruption, often because one or two mines, or one country dominates the supply. Each geographical region considers different raw materials to be critical. For this reason, there are different lists of critical metals from the European Union, the United States and Australia. Some of the critical metals that have been declared by these countries include cobalt (Co), vanadium (V), gallium (Ga), germanium (Ge), and Rare Earth Elements (REE). Likewise, the list of critical metals changes with time as new manufacturing processes or new mines change the demand and supply situation.

Critical metals are essential components in the manufacturing of green technology, such as electromobility, wind turbines and solar panels, which are needed for the global transition to low-carbon emissions. The clean energy transition and growing availability of high-tech devices establishes a mineral intensive demand for critical metals, which provides enormous opportunities for mining operations (both small- and large-scale) from primary to secondary resources. Consequently, critical metals play a crucial role in ensuring compliance with the United Nations’ Sustainable Development Goals (SDGs), moving from “affordable and clean energy” to “responsible consumption and production”. According to “Risks and Opportunities of the Mining Industry” by EY in 2021[3], the radar -Decarbonization and green agenda- has been declared fourth as of 2020, which reflects the high challenge of industrial mining to turn to green energies and the introduction of greenhouse gas regulations in their operations. Undoubtedly, this new challenge must be tackled from a responsible perspective, continuing the strong commitment to environmental, social and governance sustainability. That being said, although critical metals have a huge demand worldwide, they remain greatly understudied from a geometallurgical point of view.

A vital step is understanding the controls on the distribution of critical metals, in terms of the tenor and deportment of them into ore and gangue minerals within different mineralization systems and, therefore, whether these critical metals can be processed and extracted at a profit. The use of advanced microanalytical techniques such as EPMA, LA-ICP-MS (Photo 1) among others and supported with advanced mineralogical techniques (a bulk mineralogy point of view) is imperative. If these are applied to secondary resources (e.g., tailings, waste rock, slag) characterization, it is a key step towards a revalorization of mine waste as a circular economy principle, an important approach to economic growth that is aligned with sustainable development.

Element distribution maps in pyrite, generated with LA-ICP-MS. Photo by Javier Quevedo, 2020.

In the mining industry, the circular economy is primarily related to the potential that exists in the reprocessing of tailings. However, recovery of other elements and minerals (beyond critical metals) may require consideration of a holistic innovative approach. This could provide secondary products for mining companies, which may choose to boost local markets by providing a regional entrepreneur with the opportunity to receive and manage material based on the exploitation of tailings, being a viable option for the development of economic, organizational, technological, environmental and social of the community.

In Chile

Joaquín González, a student of geology at Universidad de Chile, did his internship program at SMI-ICE-Chile, specifically with the Geology Research Area (Photo 2) focused on critical metals in several minerals hosted in Chilean ore deposits. Through a literature review, Joaquín created a database (n= 585 data values) where the critical metals evaluated were Co, Ni, Ga, Te, Ti, V -across different microanalytical techniques- in pyrite, chalcopyrite, bornite, chalcocite and magnetite hosted in IOA, IOCG[4], porphyry copper, epithermal and stratabound deposits.

Pyrite is the mineral that shows a highly enriched concentration of cobalt. For instance, (Co)-rich pyrites hosted in IOA deposit up to 40,000 ppm of Co, in IOCG deposit up to 25,000 ppm, in porphyry copper deposit up to 24,050 ppm, in epithermal deposit up to 3,000 ppm, and in stratabound deposit up to 400 ppm. Therefore, as a mining country, Chile has the opportunity to deeper evaluate the recovery of critical metals as by-products with promising returns.

Geology researchers at SMI-ICE-Chile and geology intern from Universidad de Chile

A Collaborative Team

The Geology and Mineral Processing’s Research Area at SMI-ICE-Chile has gained valuable experience about critical metals in recent years through studies applied to cobalt hosted in IOCG primary deposits through projects with major mining companies, research thesis and internships, as well as research carried out in-house. These projects have included exploratory analysis data (EDA) through sample results that have been subjected to geochemistry analysis, mineralogical assessments (XRD, SEM, MLA-SEM), mineral chemistry assessments (LA-ICPMS), and metallurgical testing (grinding and flotation tests). Due to the demand, critical metals are set to expand worldwide over the coming decades, it is important to encourage the understanding, knowledge, and applicability of critical metals recovery from primary and secondary Chilean deposits, bringing new opportunities for commodities beyond copper. SMI-ICE-Chile with the collaborative support of SMI-UQ are evaluating projects focused on the potential for critical metals extraction as a by-product from existing and new mines.

For more information, contact Javier Quevedo at j.quevedo@smiicechile.cl and Olivia Mejías at o.mejias@smiicechile.cl.

[1] https://www.statista.com/statistics/254845/copper-production-of-chile/

[2] https://www.statista.com/statistics/717594/chile-lithium-production/

[3] https://www.ey.com/en_gl/mining-metals/top-10-business-risks-and-opportunities-for-mining-and-metals-in-2021

[4] Iron oxide ± apatite (IOA), and iron oxide-copper-gold (IOCG) type mineral deposits.

References

Quevedo, Javier (2020) “Concentración y distribución de cobalto en piritas del depósito IOCG La Estrella, Región de Atacama, Chile”. Degree thesis, Universidad Mayor, Santiago, Chile http://repositorio.umayor.cl/xmlui/handle/sibum/6875

Mejías, Olivia (2020) “Geochemical assessment of critical metals: A geometallurgical guideline for the evaluation of by-products of an IOCG type deposit, Chile”. Procemin-Geomet conference proceedings, Santiago, Chile http://www.gecaminpublications.com/procemin-geomet2020/

An essential tool for the optimization of mining-metallurgical processes

By Solange Vera, Research Engineer at SMI-ICE-Chile

Mining has evolved exponentially during the last decades, with the implementation of new tools and technologies which have allowed for the adaptation of current operational requirements, as well as comply with existing environmental regulations and with the demands of all stakeholders.

Among the tools used by the industry, simulation software tools have gained great relevance in decision-making processes. These tools are used by process engineers, mine planners, metallurgists, among other due to the various applications that can predict the behaviour of a process or system through mathematical modelling. In other words, simulation software can anticipate real processes and obtain the best performance indicators, thus becoming a powerful tool for the evaluation and analysis of new and current systems.

Specifically in the mining industry, simulation software is used to evaluate the performance of mining-metallurgical processes in light of operational changes, like variation of feed tonnage, percent solids in streams or particle size, as well as changes in configuration such as design parameter modifications or the order and/or quantity of equipment. This helps the engineer or operator to consider the “what if” scenario, based on virtually reproducing processes and studying their behaviour under different scenarios, making the decision process easier.

Experts at the Sustainable Minerals Institute (SMI) work on simulation and modelling of metallurgical processes and they are involved in a great number of projects related to the continuous improvement of processes. Experts at the SMI work in projects aiming to increase energy and water efficiency and the reduction of operational variability, using one of the most used software for project development, the metallurgical simulator JKSimMet developed by JKTech. This software was designed based on 40 years of research on comminution and classification processes at the Julius Kruttschnitt Mineral Research Centre (JKMRC) from The University of Queensland, Australia.

Graphics from JKSimMet software

JKSimMet is a metallurgical simulation software that provides engineers with the capacity to design and simulate comminution circuits, one of the most critical processes of concentrator plants due to their heightened energy inefficiency. Among the distinctive features of the software is its ease of use, which allows for it to be used both by professionals who are experts in process modelling, as well as by any professional who understands the empirical aspects of comminution. Its primary application is to carry out process analysis and existing circuit optimizations to evaluate plant performance, as well as being extremely useful to carry out conceptual designs, with the purpose of evaluating the suitability of different flow diagrams to achieve performance objectives.

SMI’s International Centre of Excellence in Chile, SMI-ICE-Chile, was part of a project to increase energy efficiency for a comminution circuit of a national concentrator plant. This circuit is comprised of a closed ball mill circuit with hydrocyclones arranged in direct configuration, which was modelled using JKSimMet to evaluate the different alternatives that allow for the reduction of specific energy consumption of the circuit. As a result of the project, small operational changes in the classification process were detected, such as changes to the opening of apex/vortex of the cyclones, which had a positive impact on the circuit’s energy efficiency. Additionally, the project concluded that, by implementing an additional classification stage with screens prior to the ball mill, the energy efficiency of the circuit is favoured by avoiding over-grinding of fine particles. These particles being sent directly to the discharge sump of the mill. The results of this work were published at the Procemin-Geomet 2020 conference.

Aside from evaluating alternatives that mitigate intrinsic inefficiencies in the comminution process, simulation also allows to tend to other recurring issues in this area: mineral variability. This translates to changes in the mineralogical characteristics of the rock which directly affect the performance of the process. In this context, SMI-ICE-Chile has carried out various projects using the JKSimMet software to evaluate the impact of rock characteristics, like variations in the parameters of fracture resistance of the mineral feed (SPI, Axb and Wi), in operational performance. This type of work allows the team to generate a group of recommendations for mine sites to adopt different planning strategies based on geometallurgical studies using geological data for making decisions at a mine and plant level, thus further promoting the integration of all areas involved in the mining cycle.

Visit to pellet plant in Huasco, August 2019, Energy Efficiency Project for CAP Minería, Chile. From left to right: José Ojeda (SMI-ICE); Luis Diaz (CAP); Gustavo Ceballos (AMTC); Norelys Aguila (AMTC); Romke Kuyvenhoven (SMI-ICE); Solange Vera (SMI-ICE); Marcin Ziemski (SMI-JMRC); Rodrigo Martinez (CAP)

This and other projects demonstrate how process simulation is an essential tool for everything pertaining to circuit analysis, optimization, design and simulation; since it eases problem solving difficulties faced by mining today, such as mineral variability and its impact on product quality, added to the efficient use of natural resources such as water or energy.

This software requires training for optimal use. In Chile and other countries in Latin America, Hexagon is the only company certified by JKTech to train and issue software licenses.

Contact Solange Vera for further information on this topic s.vera@smiicechile.cl

Reference

Vera, S., Kuyvenhoven, R., Sepúlveda, J., Ziemski, M. 2020. Improved energy efficiency in the grinding and classification circuit of a magnetite concentration plant, 16^th International Mineral Processing Conference and 7^th International Conference on Geometallurgy, Procemin-Geomet 2020, Santiago, Chile, https://www.gecaminpublications.com/procemin-geomet2020/