Britannica
Sources used in this answer
How does fire refining remove impurities from blister copper?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
copper processing
Molten copper being made into plates.
Fire refining removes impurities from blister copper through a process of selective oxidation, which relies on the fact that the impurities have a stronger affinity for oxygen than copper does.1
In this process, molten copper is held in a furnace—typically a reverberatory-type furnace—where compressed air is blown into the liquid metal through steel pipes submerged below the surface. This action causes the following reactions:1
- Gaseous removal: Impurities such as sulfur are oxidized and escape the molten bath as sulfur dioxide gas.1
- Slag formation: Other impurities, including zinc, tin, iron, lead, arsenic, and antimony, oxidize to form a slag that floats on the surface of the molten metal, where it can be skimmed off.1
This oxidation-reduction process is essential for reducing sulfur and oxygen levels, ensuring the copper reaches the purity required for subsequent electrolytic refining.2