This article explores industry drivers and challenges facing current projects. It provides insight into practical developments, including new and emerging approaches that are creating step-changes in projects, enabling producers to meet market expectations and improve a wide range of Environmental, Social and Governance (ESG) outcomes. Some examples of recent projects where innovation was key to achieving successful results are presented.

Industry context

There are a wide range of changing market forces that are reshaping projects and operations: Decreasing orebody grades, more complex metallurgy, shifting commodity focus, increasing demand for resources, high commodity prices, national sovereignty focus and a virus that has impacted travel and resulted in increasing freight, equipment and bulk materials costs are examples of changes that require response. In addition to these headwinds, the investment markets are demanding improved ESG performance and a drive toward net zero emissions.

We continue to see global copper projects decrease in grade and reserves, while larger projects with simple metallurgy tend to have increasingly complex social and environmental issues that impact permitting.

Supergene oxide gold projects are diminishing in frequency, scale and grade. Other gold projects in Australia and Africa are transitioning from non-refractory to refractory ore sources, requiring additional processing complexity through oxidation circuits to maintain acceptable recoveries.

Spiking demand for battery metals is driving development of new projects and markets. Circular economies are emerging to manage the battery revolution.

How to transform mining projects

As Ausenco's Greg Lane said, “Our aim is to maximise the value of a client’s project through smart thinking”.

Common pitfalls include a lack of focus on fundamental business economics, overcapitalisation, mismanaged constraints, conservatism, poor engineering, poor assumptions, or lack of good and timely decisions.

A good project manages the business and project constraints and improves the outcomes for all stakeholders. Improvements can be achieved through new and different approaches that fundamentally improve recoveries, increase product purities, shrink capital and operating costs and better manage project impacts.

With strong business economics as the basis, engineering solutions that may (or may not yet) exist in the market can be adapted to address specific technical challenges. For some projects, a ‘back to basics’ rethink is all that is required. Other times, an innovative approach is necessary which can involve researchers, technology start-ups, inhouse experts, commercialisation partners and forward-thinking clients in order to maintain a competitive edge. Successful methodologies and solutions from one project often translate to another.

Transformed projects

Some recent examples of Ausenco teams transforming projects to deliver great outcomes are presented below.

Mina Justa Oxide and Sulfide Copper Projects

At Mina Justa, we worked with Marcobre to understand the fundamental project economics and to drive value. We simultaneously designed and built a 6 Mt/y sulphide plant and a 12 Mt/y oxide plant. Andrew Hoyle, the Principal Process Engineer responsible for the study said about the approach “This enabled revenue to be generated from the 100 m deep layer of near surface lower-margin oxide ore whilst enabling access to deeper higher grade sulphide ore to generate returns earlier. This approach improved the economics of the project which had been studied for decades”.

Both the oxide and sulphide circuits include high pressure grinding roll comminution circuits to minimise energy and media consumption. The oxide circuit implemented an unusual vat leaching circuit, designed to maximise recovery of copper at optimum acid consumption. These vats comprised large concrete containers, each measuring 46 m x 36 m x 14 m, with 15 vats in the train, measuring 700 m in length, supported by travelling materials handling infrastructure. This approach at such a large scale was novel but was critical for the project to be successful.

Newcrest’s Cadia Coarse Particle Flotation Circuit

For Newcrest, at the Cadia mine site in Orange, NSW, Ausenco engineered a coarse particle flotation circuit that was commissioned in 2018. This was the first application of the Eriez Hydrofloat™ technology in a hard rock application. This circuit has enabled Newcrest to coarsen grind sizes, increase copper and gold recoveries, increase throughputs and reduce energy consumption, media consumption and operating costs per metal produced.

Coarse Particle Flotation can reduce energy and water consumption by 30% and reduce TSF volume and costs if sand (produced as byproduct) is used for TSF wall construction. The technology has widespread application within concentrators across a range of commodities and is well suited for projects with limited access to water. We are studying and implementing this technology for a range of clients for existing operations and new projects, and we expect this technology will continue to achieve step change reductions in energy, water and operating costs across the industry for both fine and coarse-grained ores.

Preconcentration at Ravenswood

Pre-concentration enables low-grade ore to be rejected earlier in the value chain, preserving energy and water. At a gold mine in North Queensland, we are completing an expansion that leverages a characteristic evidenced in some orebodies, where gold preferentially associates with finer (rather than coarser) particles in the crushing circuit. Matt Pyle, Ausenco’s Director of Technical Solutions said, “Rejecting coarser and lower grade ores at Ravenswood enables over 30% reduction in energy and water compared to milling those same particles. And this same approach can be applied to a range of other orebodies and commodities under the right conditions”.

Recent technology developments leverage bulk and particle sorting to similar effect and can create a step change improvement in business outcomes.

Delivery of a gold plant with dry tailings

The Las Chispas project in Mexico, which was entirely constructed during the COVID pandemic for a fixed price, is nearing completion ahead of schedule. The project also includes dry tailings (tailings filtration) to minimise tailings footprint and water consumption.

Novel Hydrometallurgy Projects

We are working on several bespoke hydrometallurgy flowsheets to unlock project value for our clients. According to Ben Strong, Director Minerals and Metals for APAC/Africa, “These projects require an ‘all in the one tent’ approach to be successful, requiring technology owners, test work laboratories, consultants and engineers to work together”. These projects are mostly focussed on battery metals and many are leveraging proprietary and patented chemistry and flowsheets.

Optimising Power, Tailings Sand and Price Certainty

For Mantos Copper on the Mantoverde project, we optimised the tailings transport system to install a second thickener and reduce the energy that would otherwise have been wasted pumping water for no gain. The project also includes a tailings sand cyclone station that produces sand for TSF wall construction (reducing the amount of fill required), while also increasing water recovery from the tailings facility. This tailings sand approach is common in South America but less so in Australia, in part due to finer mineralogies and finer grind sizes.

Tailings sands are likely to have greater applicability in Australia when coupled with coarse particle flotation (which can produce sand directly). The Mantoverde project is also delivered for a fixed price, giving Ausenco greater control of managing project risk factors while also improving cost certainty for the client.

Optimisation Projects Leveraging Data

We continue to provide consulting services to optimise operations, focusing on the use of data, particularly within the comminution circuit. Our success leverages small data, experience and expert knowledge of the cause and effects within systems to provide a quick return on investment to achieve specific objectives.

Once short-term gains are realised, the focus shifts to larger data sets with expanded focus on machine learning techniques, but still with defined objectives and outcomes. This methodology is continually driven by the fundamentals of the system by those with operations backgrounds who understand the practical context of the data. This approach mitigates against data 'analysis paralysis' and correlation versus causation errors which are common pitfalls for data-driven optimisation projects.

Sirpa Tennant, Study Manager for APAC/Africa said, “these examples of step-change outcomes demonstrate how we continue to redefine the paradigms for schedule and cost performance with people who know what good looks like and are able to adapt to fit the specific needs of the market and the project”.

If you’d like to know how we can tailor custom solutions and reshape your projects, please contact Matt Pyle.

Article first published in the Australian Mining Review, Mineral Processing Feature, Feb 2022. Reprinted with permission.

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