PROJECT DESCRIPTION
BACKGROUND
Copper is a raw material of high economic importance in the EU. While the world’s largest copper reserves are found in the Americas (Chile, USA, Peru and Mexico), Europe has significant deposits in Poland. EU-27 production of copper was 814 277 tonnes in 2010, but this is not sufficient to meet EU demands. Copper mining and refining is highly energy demanding and as the more easily mineable ‘virgin’ copper ore becomes depleted, greater effort is needed to extract the same amount of copper. Copper mining also has a significant negative impact
on the environment through particulate matter, sulphur dioxide (SO2),
sulphuric acid aerosols and other emissions.
To meet demand, the EU is therefore highly dependent on the refining and smelting of imported copper concentrates, as well as on the recycling of production scrap, end-of-life products and bottom-ash produced by Waste-to-Energy plants. Nearly all copper products can be recycled repeatedly without loss of product properties. The average global end-of-life recycling rate of copper from 2000 to 2010 is given at 45%.
Zinc is another important non-ferrous metal, whose uses range from metal products to rubber and medicines. About three-fourths of zinc used is consumed as metal, mainly as a coating to protect iron and steel from corrosion (galvanized metal), as alloying metal to make bronze and brass, as zinc-based die casting alloy, and as rolled zinc. Zinc is present as well in bottom-ash produced by Waste-to-Energy plants.
In Europe more than 100 million tonnes of residual waste is being incinerated annually resulting in more than 25 million tonnes of bottom ash. Thus, the potentially recoverable amounts of copper and zinc from such ashes is very significant.
OBJECTIVES
The overall project objective was to demonstrate the technical and economic feasibility of the Elemetal Copper Recovery (ECR) process at full-scale. At an early stage of the project implementation, the initial goal of copper recovery was enlarged to copper and zinc recovery.
The ECR process is an innovative technology for the recovery of copper from the bottom-ash produced by Waste-to-Energy plants (WtE bottom-ash). The process as described initially consisted of five steps: WtE bottom-ash pretreatment, heap leaching of the concentrated bottom-ashes, copper solvent extraction, zinc solvent extraction and copper electro-winning.
The specific project objectives were to:
- demonstrate the beneficiation of the WtE bottom ash process during 1 year;
- run a prototype to demonstrate recovery of copper and zinc;
- construct the ECR installation at full-scale and test the process during 5 months;
- elaborate a Life Cycle Analysis (LCA) and compare the process to primary or secondary copper and zinc production, and to the state of the art copper/zinc recovery from WtE bottom-ash.
RESULTS
The PCR project demonstrated different production steps to obtain copper and zinc out of WtE bottom-ashes.
A WtE bottom-ash washing plant was constructed, commissioned and taken into production in Nauerna. This plant can produce ‘clean free applicable’ bottom ash aggregates with an annual production capacity of up to 600,000 MT. Although this plant was implemented without LIFE subsidy, its product - the heavy non-ferrous (HNF) fraction - is used as a raw material in the ECR process.
The zinc- and copper-rich HNF fraction obtained after pre-treatment of the WtE bottom ashes is upgraded in a sensor sorting line which was successfully implemented, commissioned and demonstrated in Maastricht. The sensor sorter is designed to produce a copper-rich (CuR) and a zinc-rich fraction (ZnR) which then undergoes a treatment in the ECR process.
Based on a first LCA and an economic assessment, it became apparent that the ECR process cannot compete with traditional copper smelters. Therefore, copper recovery via the ECR process was abandoned and the CuR fraction is sent to traditional copper smelters. The outcome from the aforementioned LCA was that the environmental benefits could be optimized by fully focusing the project on zinc recovery.
In a last step, the full-scale demonstration of the ECR process was executed in two phases.
- Demo phase 1, implemented in 2019/2020, successfully demonstrated the leaching of zinc. During this demonstration, 120 tonnes of zinc were leached and the product (ZnSO4 solution) was sold.
- Demo phase 2, initiated in 2021 and designed to produce ZnSO4 crystals, has seen successful operation of the leaching and purification sections. The crystallisation process also runs smoothly, but the initial drying section did not perform as expected. An improved section was ready for commissioning only in June 2023.
Until the project’s end in March 2023, approximately 1,000 tonnes of copper and 130 tonnes of zinc were produced. First promising results have been obtained to produce ZnSO4 crystals: about 1 ton of crystals were produced, complying with the specification for a technical grade product. The installation was set to continue until the end of 2024.
In conclusion, the ECR process has been successfully demonstrated at a full-scale. The preliminary business outlook is positive, and replication of the technique is anticipated.
