Copper pyrometallurgical process

Copper conversion is accomplished by a pyrometallurgical process known as smelting. During smelting the concentrates are dried and fed into one of several different types of furnaces. There the sulfide minerals are partially oxidized and melted to yield a layer of matte, a mixed copper-iron sulfide, and slag, an upper layer of waste. 

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. 

Processes for extracting metals from their ores are generally classified as pyrometallurgical, if high temperatures are used, or hydrometallurgi-cal, if aqueous solutions are used. Copper is extracted by both methods. In the pyrometallurgical process for the extraction of copper, the enriched ore is roasted, or heated in air ... 

Outline a process, using chemical equations where possible, by which copper is extracted and purified from chalcopyrite by the pyrometallurgical process. 

Iron, copper, arsenic, and antimony can be readily removed by the above pyrometallurgical processes or variations of these (3). However, for the removal of large quantities of lead or bismuth, either separately or together, conventional electrolysis or anewly developed vacuum-refining process is used. The latter is now in use in Australia, Bolivia, Mexico, and the CIS (5). 

The conventional smelting and refining process for copper, nickel, lead and zinc sulfide ores result in the evolution of a large amount of sulfu dioxide gas which in most instances is released to the atmosphere. Ther have b( en attempts to recover part of the sulfur as sulfuric acid or in som form (HI, H4, H5) at various stages of the pyrometallurgical processing... 

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. 

Metals in Groups 11 and 12 are easily reduced from their compounds and have low reactivity as a result of poor shielding of the nuclear charge by the d-electrons. Copper is extracted from its ores by either pyrometallurgical or bydrometallurgical processes. 

Metals that have been produced by pyrometallurgical methods, such as copper, silver, nickel, and tin, are too impure for many purposes, and electrorefining is used to purify them further. Crude metallic copper is cast into slabs, which are used as anodes in electrolysis cells that contain a solution of CUSO4 in aqueous H2SO4. Thin sheets of pure copper serve as cathodes, and the copper that dissolves at the anodes is deposited in purer form on the cathodes (Fig. 17.18). Impurities that are more easily oxidized than copper, such as nickel, dissolve along with the copper but remain in solution elements that are less easily oxidized, such as silver and gold, do not dissolve but fall away from the anode as a metallic slime. Periodically, the anode slime and the solution are removed and further processed for recovery of the elements they contain. 

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