Project Overview

Current situation in Chile

Chile is, with 27 % of the global production, the largest producer of copper before Indonesia and the world´s largest exporter of copper. In addition, Chile has the world´s largest economically available deposits of copper ores. More than 50 % of Chilean export revenue is attributable to copper mining. However, mining has significant downsides. In the Chuquicamata mine alone, about 45 million tons of ores are mined annually. The concentration of copper in the ore is only 0.5-2 %.

Where the challenge begins

During the following process of increasing the concentration to a copper content of 30-35 %, large amounts of the introduced material ends up as waste that must be deposited accordingly. In Addition an enormous demand of water - a scarce resource especially in northern Chile – is needed and contaminated with chemicals and heavy metals in the course of copper production. Unclear is also the handling with the steadily increasing arsenic content in the remaining ores. In Chile copper is mostly found in sulfide ores. The continual mining of metallic reserves leads to the necessity of exploring lower positioned ores with increasing mineralogical complexity. Arsenic in particular is a highly toxic inorganic pollutant that not only poses a threat to the human health, but also to the entire ecosystem.

This led to the introduction of arsenic limits for imported copper concentrates (e.g. Japan and China). The simplest way to meet this Problem is to dilute arsenic-rich with arsenic-poor concentrates. However, this strategy will not be practicable in the long term due to rising arsenic levels. Real alternatives are already developed and in operation. For example, the roasting process is a technology that was recently installed at Codelco DMH and developed as well as built by Outotec GmbH & Co.KG (here partner). But since there are only a few plants (roasters) of this kind worldwide installed and because the process has so far only been used for a few concentrates, it is necessary to improve the understanding of the chemical reaction mechanism, the process engineering and the plant optimization.

In addition to the removal of arsenic from the various intermediates and residues of copper smelters (e.g. fly dust), the best possible fixation of arsenic is also a field of research interest. In Chile, arsenic is currently mostly bound as calcium arsenate. However landfilling in this form is only conceivable in very dry areas such as the Atacama Desert. Due to the climate change more and more precipitation is observed there (like on the excursion during the definition project), which of course raises the question of sustainability.
More stable arsenic compounds exist in the form of iron arsenates, in particular scorodite, or arsenic sulfide. Scorodite is an iron arsenate phase, which is considered to be one of the most stable forms to deposit arsenic under aerobic conditions, with a very high long-term stability. Although the Chilean company Ecometales has developed an industrial scaled process to bind arsenic as scorodite, unfortunately the conversion of the arsenic into this compound is more than twice as expensive as the binding as calcium arsenate. The primary rice drivers in this process, which are relevant for a cost reduction, are hydrogen peroxide (H2O2) and iron. For environmental reasons, Chile however wants to introduce this high standard and hence stabilize arsenic in the form of scorodite in the future. Therefore more efficient and above all more cost-effective processes for the production of scorodite have to be developed. Finally, it is important to find the best possible barrier system for the landfilling of the corresponding arsenic compounds so that any possible entry into the environment is kept as low as possible.

About the Project ReAK

In the first place, ReAK deals with the optimization and further developments of existing processes and the establishment of new processes for the treatment of arsenic-rich copper ores and their concentrates. Close attention is paid to the challenge of increasing arsenic levels in the ores and the concentrates produced out of them. Along the process chain, next to the separation of copper-rich and copper-poor ore fractions, the flotation should be as selective as possible against arsenic. Due to the separation existing copper smelters can continue with the processing of low-arsenic fractions.

Arsenic-rich copper concentrates and intermediates can then be treated with processes for the separation and stabilization of the arsenic. For this purpose, various approaches are investigated and/or developed, for example, oxidative extraction, roasting (sulfating and partial), innovative pyro-metallurgical approaches as well was conventional and biological extraction. New approaches for the conversion of intermediate occurring As(III) into As(V) (preferably scorodite) should also be developed. Process accompanying a sample management system in copper mining should be improved and adapted to the specific challenges.

In addition, investigations of the leaching behavior of the arsenic precipitates and their mobilization and immobilization processes as a function of different climatic conditions should answer the question which arsenic compound preferable for landfilling. For a better evaluation, both, the ecological (Life Cycle Assessment – LCA) and economic (Life Cycle Costing – LCC) aspects will be considered along the entire process chain to enable a better comparison of the different procedures. The summarized findings will serve as a decision-making support for industries and for the Chilean government, in terms of technology selection and disposal policies.

In the long term, not only the economic relations of both countries should be expanded and strengthened, also sustainable waste disposal and the implementation of corresponding barrier systems for environmentally hazardous residues should be promoted, as well as the acceptance of mining in the Chilean population should be strengthened.

Systematic characterization of the starting material (BGR)

Detailed knowledge of the starting material is necessary for the successful development and implementation of individually adapted processing methods. A changed composition of the starting material can strongly influence the yields of the treatment process.

In the first step the geochemical and mineralogical composition of the starting material and all intermediates will be studied in detail, in close collaboration of the German and Chilean partners, to elaborate strategies for a possible pre-separation of arsenic minerals dependent on particle size and degree of intergrowth. Planned is an investigation with different sensors (for example LIBS, XRF, Hyperspectral), which could also potentially be used for the real-time monitoring of conveyor belts. Additionally occurring analytics within the project will be coordinated by BGR across all work packages.

Selective flotation (Pionera, IWKS, PUC, SIM-ICE, Codelco)

In this work package the method of flotation will be optimized regarding to the separation of enargite from chalcopyrite. In the course of a close collaboration between Pionera and the Chilean university PUC, experimental setups and designs for the testing of biopolymers will be developed. PUC will perform the experiments and will submit the results to Pionera. Depending on the results, the polymers will be modified. Furthermore, it will be investigated whether a mechanical pretreatment by high-energy milling can improve the subsequent separation of the two phases during the flotation (IWKS). The plants of the Chilean partner Codelco can be used for the experiment phase on a pilot scale. The aim of this work package is to perform the improved flotation in a pilot scale and to provide the arsenic-rich fraction for further experiments in the following WPs.


Treatment of arsenic-rich copper concentrates und dusts

For the treatment of the arsenic-rich copper concentrates the work package is divided into three sub-packages. These in different ways all pursue the goal of removing the arsenic and binding it in a stable form. Both the optimization of existing technologies and the testing of new approaches are in focus.