SPOTLIGHT: Ecometales' concentrate recovery plant

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Friday, May 5, 2017

Chilean firm Ecometales, a subsidiary of state-owned copper giant Codelco, submitted last October to environmental authorities a US$370mn project to treat copper concentrates rich in arsenic.

The project aims to address one of the key aspects of Chile's mining future. As deposits get deeper, the ores are "dirtier," meaning they have higher levels of arsenic. And this could represent a problem for Chile, as some countries have banned the entrance of arsenic-rich ore over pollution concerns.

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Codelco is also in the process of transforming its Chuquicamata mine into an underground operation, and as such, it is likely to encounter more complex copper ore that contains 0.5% or more arsenic, on top of the arsenic-rich ore it mines from its newest mine, Ministro Hales (pictured).

It is estimated that as of 2016, production of impurities-rich concentrates from Codelco's northern district (Chuquicamata, Radomiro Tomic and Ministro Hales) was between 1.8Mt to 2Mt per year, according to Ecometales.

Additionally, the country is due in 2018 to enforce stricter rules for its smelters, which will now be required to capture 95% of arsenic. As such, the elimination, or reduction, of arsenic at an early stage of the process will help Codelco to achieve its target at the Chuquicamata smelter.

The complexity of concentrates is rising (Source: Ecometales)

PROJECT SPECS

The process is a fairly straightforward one. It takes the impurities-rich concentrates from Chuquicamata and Ministro Hales and then them feeds it to an autoclave, where through high pressure and high temperature, and after a thickening process, it obtains a copper-rich solution and arsenic-rich waste.

The waste is then transported to its final disposal, while the copper solution, known as copper-rich pregnant leach solution (PLS), is then processed via a solvent extraction and electrowinning (SX/EW) plant, which are available at both Chuquicamata and Radomiro Tomic.

The autoclave will have the capacity to process 220,000t of concentrates per year, and as a result, it will produce 242m3 per hour of PLS and approximately 133,000t/y of arsenic residue, according to the project's environmental permit documents.

Diagram of the plant (Source: Ecometales)

Another characteristic of the project is that it does not generate either arsenic or sulfur air emissions, and that it consumes less water than other alternatives, which is key for Codelco's northern mines that are located in the parched Atacama desert.

The plant could also recover some trace elements, like silver, bismuth, antimony and germanium, which are currently lost as the focus is put on copper recovery.

FUTURE

The project is currently under consideration by environmental authorities, and the company said it expects to obtain the permit later this year. One key aspect that is still pending is the financing of the US$370mn project, which the company is still working to secure.

If approved, and financing is secured, Ecometales expects the new plant to be operational in 2020.