Copper pyrometallurgical production

Sulfide ores are processed by a number of pyrometallurgical processes roasting, smelting, and converting. During these processes, sulfur and iron are removed to deld a sulfur-deficient copper-nickel matte. Especially after roasting and converting, the nickel in the matte may consist primarily of nickel subsulfide. After physical separation of the copper and nickel sulfides, the nickel is refined electrochemically or by the carbonyl process. The treatment of the matte depends on the end use of the nickel. Alternatively, the sulfide can be roasted to form a nickel oxide sinter that is used directly in steel production. 

Most pyrometallurgical processes are performed at temperatures high enough to ensure that all the possible reactions proceed very fast, but occasionally this is not so, and therefore the equilibrium condition of the system may not be optimal for the yield of a desired product of reaction. This is the case for the removal of copper from primary lead by reaction with elemental sulfur. It is highly desirable to know and understand this, in order to be able to specify the optimum conditions for the conduct of the process - in this case, known as decopperising, or fine decoppering or sulfur drossing. 

---