Recycling Technology
Aurubis has options to flexibly utilize raw materials and is in a position to process highly complex raw materials at several sites as a multi-metal recycler.
The recycling processes at Aurubis depend on the consistency and chemical composition of the raw materials. Various procedures enable Aurubis to process an especially wide range of recycling materials in a competitive and environmentally sound manner. Apart from copper, these materials are used to produce by-products such as precious metals, nickel, tin, lead and zinc.
1. Multimetal recycling with the Kayser Recycling System (KRS) at the Aurubis recycling center in Lünen:
Copper scrap, electronic scrap and residues are used as input material in the Aurubis recycling center in Lünen. The Kayser Recycling System is well suited for utilizing recycling materials with low copper and precious metal contents and very complex materials such as electric and electronic scrap.
Material preparation
If necessary, processing begins with sampling, followed by a material preparation step. Depending on consistency and composition, the raw materials are then crushed, treated in a material preparation plant or directly conditioned into input mixtures. This ensures that very coarse, moist or dusty materials can be treated. Aluminum and plastics are separated from the materials in some cases and sold to other recycling companies.
Smelting and refining
Pyrometallurgical preparation – smelting and refining – begins in the Kayser Recycling System (KRS). The central operation is a submerged lance furnace which is almost 13 m high. A special feature is the use of a submerged combustion lance, which is immersed into the furnace from above and supplies the process with heating oil, oxygen and air.
The reduction process is very fast in the submerged lance furnace. Charging times are short. The iron silicate sand extracted in that step of the process has very low residual copper contents.
Copper, nickel, tin, lead and the precious metals contained in the raw materials are enriched in an alloy with a copper content of about 80 %. In a top blown rotary converter (TBRC) the copper content is further enriched to 95 % and tin and lead are separated into a slag. The tin-lead slag is subsequently processed into a tin-lead alloy in the directly connected tin-lead furnace. During the KRS process, zinc is enriched in the KRS oxide, a flue dust.
Secondary copper production
Unwrought copper is produced with an average copper content of 95 % and is further processed in the anode furnace in a molten form. It is refined with additional amounts of copper scrap. The melt is initially oxidized with air and oxygen and then deoxidized with natural gas after the slag that has formed has been removed. At the end of the pyrometallurgical process, the meanwhile 99 % pure copper is cast into copper anodes. This is the starting product for the final refining stage of secondary copper production, the copper tankhouse process, where high-grade copper cathodes are produced in a quality identical to copper cathodes from primary copper production. Important by-products, in particular gold and silver, are enriched in the anode slimes. Nickel is extracted as crude nickel sulfate from electrolyte treatment.
2. Precious metal and by-metal production at Aurubis
Copper scrap, electronic scrap and residues are used at Aurubis Hamburg (Germany). The basic material for Hamburg’s secondary copper production process consists of a variety of recycling materials rich in precious metals as well as intermediate smelter products originating both from Aurubis’ production plants and from external metal smelters and precious metal separating plants. The focus of secondary copper production in this case is on enriching and recovering precious metals and separating various by-metals that result from the copper production process.
In accordance with the requirements of the specific raw materials, these materials are processed in a modern electric furnace in various smelting campaigns. The most important target is the pyrometallurgical separation of lead and copper and the enrichment of precious metals.
By-elements still existing during copper production, such as lead, bismuth, antimony and tellurium, are separated in the connected lead refinery and sold as lead bullion, lead-bismuth alloy, antimony concentrates and tellurium concentrates. The precious metals are fortified in a so-called rich lead, which has a precious metal content of about 70 %.
Anode slime processing
The anode slimes from the Aurubis copper tankhouses are processed together with the rich lead from the lead refinery in the precious metal production plant. With Aurubis’ modern, environmentally friendly precious metal production facilities, the company covers a wide range of feed materials rich in precious metals. Thus, Aurubis also processes anode slimes from other copper smelters, bullion, precious metal and coin scrap as well as precious metal-bearing sweeps and slag. In addition to fine silver, fine gold and concentrates of the platinum group metals, sales products from this process include wet selenium, which is processed at the Aurubis subsidiary Retorte GmbH.