Partnership in Copper-Arsenic Processing
Teck, Canada’s largest diversified resource company, has partnered with Aurubis, Europe’s largest refined copper producer, to advance the application of CESL Copper-Arsenic Technology for high arsenic bearing copper resources. Together, we provide strong technical capabilities and extensive industry experience in the copper business.
Overall, the policies and guidelines of both Teck and Aurubis fully support the strengthening of sustainable development by setting new environmental standards in complex ore refinement. The key element for this basis is the introduction of a novel, integrated, low-emission mine-to-metal process based on the commercial-ready CESL Cu-Au Technology.
Need for the Technology
There will be an estimated 59,000,000 tonnes of copper concentrate produced worldwide in 2015. Global production of copper concentrates is expected to increase by 3% year-on-year from 2015 - 2024. Arsenic is the main impurity present in copper concentrates, and is predicted to be above penalty limits in 10% of all copper concentrates produced in 2015. The arsenic content in copper concentrates is expected to grow from ~80,000 tonnes/year in 2013, to ~165,000 tonnes/year in 2020. [Wood Mackenzie 2013].
With standard smelting techniques used to recover copper, arsenic presents itself in potentially hazardous forms that are challenging from an occupational exposure and disposal perspective. These challenges are becoming increasingly significant with growing awareness in the areas of environmental responsibility and materials stewardship. During smelting or roasting processes, arsenic deports to dust in a hazardous oxidized state creating material handling and disposal challenges. This results in higher marketing or processing costs for miners that has the effect of discouraging the development of copper resources containing appreciable amounts of arsenic. Revenue certainty from a project with >0.5% arsenic in the concentrate is dependent in part on treatment and refining charges which are likely to increase significantly as smelter capacity is insufficient to process certain impurities and as regulations reduce the marketability of high arsenic bearing copper concentrates. While marketing of arsenic challenged copper concentrates to traditional smelting and refining requires blending of these penalized concentrates to maximize revenue, the use of the CESL Cu-As technology creates revenue certainty for the duration of the mining operation which mitigates the supply-chain risk.
A Proven Technology
The CESL Process uses existing technologies such as pressure oxidation, solvent extraction and electrowinning but combines them in a novel way. Solvent extraction and electrowinning are used world-wide and these metal refining methods have proven to be robust, well-understood processes which produce a premium cathode product.
Over 50,000 hours of operation have been invested in treating 20 concentrates of varying mineralogies at CESL’s integrated pilot plant. Nearly 300 tonnes of LME Grade A copper have been produced in 5000 hours of demonstration plant operations.
The CESL Cu-As Process has achieved greater than 99% deportment of arsenic to leach residues (the by-product of the metallurgical process). Arsenic components in the residue have been identified, with the use of advanced mineralogical methods, as basic ferric arsenate (BFAS) and scorodite – both of which are considered the most stable forms for arsenic fixation. Furthermore, air quality monitoring during pilot operations confirmed concentrations well-below the government occupational exposure levels.
Short and long term testing was conducted to assess the stability of arsenic in residues that were generated in continuous pilot plant trials. Short term testing was conducted on 59 pilot samples containing arsenic up to 9.7% using the Environmental Protection Agency’s (EPA) standard hazardous material characterization procedure (Toxicity Characteristic Leaching Procedure, TCLP). The testing consistently demonstrated that the residue was non-hazardous, with leached arsenic more than an order of magnitude below the EPA classification limit.
To confirm long term stability, a more rigorous testing program was developed. This ongoing test program has demonstrated excellent residue stability, with arsenic concentrations well below the 5 milligrams per litre EPA limit after over 700 days plus of testing.
CESL Copper-Arsenic Process Results
Over 20 different arsenic-bearing concentrate samples have been tested since 2010. This has included over 10-months of pilot plant operations to verify the flowsheet using fully-integrated continuous operations. Pilot plant operation result highlights include:
Achieved high copper (>97%) and gold and silver (>90%) extractions
- Produced LME Grade A Copper Cathode
- [Produced saleable Au-Ag dore]
Demonstrated the ability to process arsenic-bearing copper concentrates in an environmentally superior manner
- Processed concentrates ranging from 1.4% – 10.0% arsenic
Collected design criteria data for commercial design and economic evaluations