page_title: Copper extraction
section_title: Converting
hierarchical_section_title: Copper extraction / Sulfide smelting / Converting
caption_attribution_description: English: Tough-pitch copper, en:Oxygen-free copper, containing antimony and nickel. Deutsch: Rohkupfer (Glimmergarkupfer), antimon- und nickelhaltig.
context_page_description: Copper extraction refers to the methods used to obtain copper from its ores. The conversion of copper consists of a series of physical and electrochemical processes. Methods have evolved and vary with country depending on the ore source, local environmental regulations, and other factors.
  As in all mining operations, the ore must usually be beneficiated. The processing techniques depend on the nature of the ore. If the ore is primarily sulfide copper minerals, the ore is crushed and ground to liberate the valuable minerals from the waste minerals. It is then concentrated using mineral flotation. The concentrate is typically then sold to distant smelters, although some large mines have smelters located nearby. Such colocation of mines and smelters was more typical in the 19th and early 20th centuries, when smaller smelters could be economic. The sulfide concentrates are typically smelted in such furnaces as the Outokumpu or Inco flash furnace or the ISASMELT furnace to produce matte, which must be converted and refined to produce anode copper. Finally, the final refining process is electrolysis.
context_section_description: The matte, which is produced in the smelter, contains 30–70% copper (depending on the process used and the operating philosophy of the smelter), primarily as copper sulfide, as well as iron sulfide. The sulfur is removed at high temperature as sulfur dioxide by blowing air through molten matte:
  2 CuS + 3 O₂ → 2 CuO + 2 SO₂
  CuS + O₂ → Cu + SO₂
  In a parallel reaction the iron sulfide is converted to slag:
  2 FeS + 3 O₂ → 2 FeO + 2 SO₂
  2 FeO + SiO₂ → Fe₂SiO₄
  The purity of this product is 98%, it is known as blister because of the broken surface created by the escape of sulfur dioxide gas as blister copper pigs or ingots are cooled. By-products generated in the process are sulfur dioxide and slag. The sulfur dioxide is captured for use in earlier leaching processes.
caption: Oxygen-free copper aka "Tough-pitch" copper (ca. 98% pure), containing antimony and nickel
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