Modern Copper Smelting / being lectures delivered at Birmingham University, greatly extended and adapted and with and introduction on the history, uses and properties of copper.

by Donald M. Levy

B. i. Addition of Oxidised Charges in the Blast Furnace.—The tendency for oxidised cupriferous materials to interact with sulphides finds useful application in copper smelting, since it assists the concentration of the copper in the resulting mattes. The principal reactions involved in this method are—

2CuO + Cu₂S ➡ 4Cu + SO₂

2Cu₂O + Cu₂S ➡ 6Cu + SO₂

CuSO₄ + Cu₂S ➡ 3Cu + 2SO₂

whereby copper is produced and sulphur is eliminated as SO₂. The liberated copper interacts with the excess of iron sulphide usually present in the furnace charge, and enters the matte as sulphide, whilst the iron which is thus set free is oxidised and carried into the slag as silicate, the ultimate reactions being indicated approximately by the equation—

2Cu + FeS + xFeS ➡ Cu₂S . xFeS (matte) + Fe (oxidised and enters slag).

Copper silicates readily interact with iron sulphides in the charge, producing copper sulphides and iron silicates, thus—

Cu₂O . xSiO₂ + FeS ➡ Cu₂S (enters matte) + FeO . xSiO₂ (enters slag).

6(CuO . xSiO₂) + 4FeS ➡ 3Cu₂S (enters matte) + 4(FeO . xSiO₂) + 2xSiO₂ (enters slag). + SO₂.

All the above reactions lead to an enrichment of the matte in copper contents, and at the same time, to the transference of iron from the matte to the slag, and although the conditions in the more reducing atmosphere of the coke-fed blast furnace are not so favourable to the fullest operation of these reactions as are the more neutral conditions of the reverberatory, the addition of oxidised materials constitutes a valuable means of increasing the concentration in this method of smelting.