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Copper Processing

Copper, chemical element, reddish, extremely ductile metal, unusually good conductor of electricity and heat has a melting point 1084.5 ⁰C, density (t-18⁰C) 8.96 g/cm³. The symbol for copper is Cu and comes from the Latin cuprum meaning from the island of Cypus.

Copper compound are diamagnetic and, with few exception, colourless. Among the important industrial compound of copper are curprous oxide (Cu₂O), cuprous chloride (Cu₂ Cl₂) and cuprous sulfide (Cu₂S). Cuprous oxide is red or reddish brown crystal or powder that occurs in nature as mineral cuprite. It is produced on a large scale by reduction of mixed copper oxide ores with copper metal or by electrolysis of an aqueous solution of sodium choride using copper electrodes. The pure compound is insoluble in water but soluble in hydrochloric acid or ammonia. Cuprous oxide is used principally as red pigment for antifouling paints, glasses, porcelain glazes and ceramics. Cuprous chloride is whitish or grayish solid that occurs as the mineral nantokite. It is usually prepared by reduction of copper chloride with metallic copper. The pure compound is stable in dry air, moist air converts it o a greenish oxygenated compound. Cuprous chroride is used as a catalyst in a number of organic reactions and as a condensing agent for soaps, fats and oils.

Cuprous sulfide occurs in the form of black powder or lumps and is found as the mineral chalcocite. Large quantities of the compound are obtained by heating cupric sulfide in a stream of hydrogen. It is insoluble in water but soluble in ammonium hydroxide and nitric acid. Its application includes use in solar cells, electrodes, etc.

Native copper is found at many location as a primary mineral in basaltic lavals and also as reduced from copper compounds. Copper occurs combined in many mineral, such as chalcocite, chalcopyrite, cuprity, malachite.

Copper is commercially produced mainly by smelting or leaching, usually followed by electrolytic refining or recovery.

The major portion of copper produced in the world is used by the electrical industries; most of the remainder is combined with other metals to form alloys. Important series of alloys in which copper is the chief constituents are brasses (copper and zinc), bronzes (copper and tin) and nickel silvers (copper, zink and nickel, no silver). There are many useful alloys of copper and nickel; the two metals are comparatively miscible. Copper also forms an important series of alloys with aluminium called aluminium bronzes. Beryllium copper is a usual copper alloy in that it can’t be hardened by heat treatment. Copper is a part of nearly all coinage metals.

In non-ferrous metallurgy some semi-products for example matte are used. Copper ore is smelt to produce matte, cuprous sulfide and iron sulfide alloys which may be converted by electrolytic refining to obtain blister copper.

The primary purposes of mattes melting is to melt and recombine the charge into a homogeneous matte of metallic copper, nickel, cobalt and iron sulfides and to give an iron and silicon oxides slag.

Shaft furnaces reverberatory furnaces and electric furnaces are used to smelt copper matte and to obtain copper.

The shaft furnace has some advantages over the reverberatory furnace:

1. It has a higher specific productivity 100-150 t/m² per day instead of 7-10 t/m² per day in the reverberatory furnace.

2. Thanks to intensive cooling of furnaces expensive refractory materials are reduced.

3. Even furnaces with low capacity are profitable.

Electric furnaces are used when electric power is cheap. But the most out looking method is autogenous smelting.

Copper is one of the most ductile metals not especially strong or hard. Strength and hardness are appreciably increased by cold-working because of the formation of elongated crystals of the same face-centred cubic structure that is presented in the softer annealing copper. Common gases such as oxygen nitrogen, carbon dioxide and sulfur dioxide are soluble in molten copper and greatly affect the mechanical and electrical properties of the solidified metal.