Optimizing your copper making process

The demand for copper grows continuously. Thanks to sectors such as electronic products, industrial machinery, transportation equipment, etc. the refined usage of copper has more than tripled in the last 50 years.
To tackle the challenges of the customer, Heraeus Electro-Nite offers some unique solutions specific for the different copper process steps.

The refined copper production can be divided into two main production routes, primary and secondary copper production. Approximately 80% of that refined copper production is primary copper production, where copper is derived from ores.
The other important source of raw material is scrap. Copper scrap, derived from either metals discarded in manufacturing processes or end of life products, contributes to recycling of copper as raw material. This route is the secondary copper production.

Find out which solutions are applicable for your process and how they can help you to optimize your copper process.

Copper production

Copper production begins with the extraction of copper ores through surface (open-pit) or underground mining. Depending on the amount of copper scrap added to the process, the production can be classified as primary or secondary production.

Products:

Two main process routes are followed:

  • A hydro-metallurgical route or SX-EW process, where copper is directly extracted and refined from low grade ores
  • A pyro-metallurgical route where copper is extracted and refined from ores, copper scrap and/or spent anodes

In the pyro-metallurgical process route, raw mined ore is first upgraded to copper concentrate by means of crushing and flotation enrichment processes. This concentrate is subsequently melted and transformed into ‘matte’ containing around 60% pure copper. The liquid ‘matte’ is refined in a converter process where ‘blister’ copper is produced with > 98% copper content. Blister copper is then casted into intermediary anodes which are further refined into copper cathodes (99.99% pure copper) through an electro-refining process. Cathodes are re-melted and processed into final end user products. Blister copper feed can be partially or fully replaced by secondary scrap to recycle end of life copper.

Main challenges of the pyro-metallurgical process

Manage oxygen activity during refining

In the convertor blister copper and/or copper scrap are melted and oxidised at a temperature of around 1150-1250 °C. Ideal refining conditions are reached close to the oxygen saturation point. Substandard oxygen input results in insufficient refining and unacceptable high impurity levels. Excessive oxygen input increases significantly process yield losses.

After the refining treatment the oxygen content of the liquid copper has to be reduced enough to allow casting of 99% pure anodes. This is done by injecting natural gas in a poling furnace.

Using the Heraeus Electro-Nite’s oxygen activity control allows the customer to manage his process by:

  • Optimizing oxygen injection
  • Fine tuning natural gas injection

Manage oxygen activity during rod casting

Casted anodes are placed inside large electrolytic cells. By adding electric current, copper dissolves and is eventually deposited on stainless steel ’blanks’. As only copper particles are deposited on the blanks, after 7 days a copper cathode with 99.995% purity is produced. All other elements either sink to the bottom or dissolve in the sulphuric acid. Finally, the produced cathodes are re-melted and cast into eg. copper wire rod.
To produce copper with high performance properties for electrical, electronic and heat transfer applications, it’s imperative to cast copper with extremely low oxygen content of maximum 5 ppm.
Copper grades with higher oxygen content are more likely to react with hydrogen. At high temperature, hydrogen ions can diffuse into copper and create water pores with the oxygen atoms in the copper. This results in more brittle copper, causing problems when copper components are brazed or welded, subsequently affecting physical characteristics of copper, like the electrical and thermal conductivity.
Copper with low oxygen content is more immune to hydrogen and ensures a better joining with brazing or welding methods.

In order to monitor the oxygen content, Heraeus Electro-Nite’s oxygen activity control allows the customer to:

  • Limit hydrogen pick-up
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