Reprocessing of mining residues in Chile

Country / Region: Chile

Begin of project: August 1, 2013

End of project: December 31, 2018

Status of project: June 1, 2018

Tailings dump La Africana close to Santiago de Chile Source: BGR

In Chile there are mining activities since nearly 200 years. Copper is currently the main commodity of the country. According to conservative estimates every year a minimum of 350 million tons of residues are produced only from the processing of copper ore. Over the past 30 years, an estimated 6.8 billion tons of residues have been stockpiled, which still contains a residual content of copper and possibly other metals. The beneficiation techniques have improved over the last decades, additionally elements that are needed in the high-tech industry have come into the focus, which were not of interest in the past and were thus not recovered, but send to the tailings and waste dumps.

As part of the commodity partnership agreed with Chile, the BGR has initiated a project in 2013 to verify this potential and to determine the profitability of recycling mining residues. The goal is to achieve an economic recovery of metals for German companies of interest. This interest may exist both in the metals, as well as the sale of technologies that are needed for reprocessing. The project ceased in July 2015.

This project is performed together with the CAMCHAL (Cámera Chileno-Alemana de Comercio e Industria) in partnership with the Chilean mining association Sonami (Sociedad Nacional de Mineria) and the state-owned enterprises to promote small and medium-sized mining ENAMI (Empresa Nacional de Mineria). The Chilean Geological Survey (SERNAGEOMIN), with whom was signed a memorandum of understanding in 2013 regarding the mining residues among other topics, supported the project with field work, geochemical analysis, and data collection.

During the project twelve residues were chosen out the 500 known heaps in Chile (waste rock, tailings, slack), in order to carry out a survey sampling and to analyse the material geochemically. On the basis of these analyses, the four residues with the biggest potential were selected. From these residues a larger amount of material (20 – 25 kg) was taken, to carry out processing tests like gravity sorting, conventional sulfuric acid leaching and bioleaching. At the moment, the results are prepared to be published.

To improve the ability of verifying the potential of mining residues, starting in Mai 2016 a new project about the economic potential of mining residues will be conducted. The Chilean Geological Survey (SERNAGEOMIN) will be the exclusive partner. During this project it is planned to receive enough material for geochemical, mineralogical and processing tests, within a single sampling campaign, by sinking deeper boreholes with a bigger diameter, compared to the first project. Avoiding a second sampling campaign saves time and ensures the possibility to work always with the same sample material. Problems with sampling material that is probably not representative will not occur.

The subsequent assessment of the economic recoverability of raw materials from these tailings, provides the basis to stimulate the interest of companies for a further usage and a possible investment.
Sampling locations were Ovalle in the IV. Region and Talt in the II. Region.