Answer. Smelting: It is further heating the roasted ore with sand flux and coke in the presence of excess of air in a blast furnace as shown in figure. It is highly exothermic process therefore; a small amount of coke is required in the process. In the process, first ferrous sulphide oxidizes to form ferrous oxide which reacts with sand to form iron silicate slag (FeSiO3). It being lighter rise to the top and is removed from the upper hole.
2 FeS(s) + 3O2(g) 2 FeO(s) + SO2(g) #
FeO(s) + SiO2(s) FeSiO3(s)
On the other hand, cuprous sulphide also oxidizes to form cuprous oxide which reacts with unreacted ferrous sulphide to form ferrous oxide and cuprous sulphide. In this way, cuprous sulphide and ferrous sulphide form a mixture (Cu2S.FeS). This molten mixture is called matte.
It is withdrawn from the lower hole. It contains about 45% of copper. 2 Cu2So(1) + 3O2(g) ———> 2Cu2O(1) + 2SO2(g) #
Cu2O(1) + FeS(1) ———> CU2S(1) + FeO(1)
Gases
Matte
Blast furnace for smelting of copper
Bessemerization: It is the further heating of the molten matte in a pear shaped bessemer converter as shown in figure below. It is fixed on a pivot, so that it can be tilted in any direction. Molten matte is mixed with sand and heated with a hot blast of air through tuyers. Ferrous sulphide is oxidized to form ferrous oxide. Which reacts with sand to form slag (FeSiO3) that float on the top?
2 FeS(s) + 3O2(g) 2 FeO(s) + 2SO2(g)
FeO(s) + SiO2(s) FeSiO3(slag)
On the other hand, cuprous sulphide is oxidized to form cuprous oxide, which again reacts with remaining cuprous sulphide to form metallic copper.
2 Cu2S(1) + 3O2(g) ———> 2Cu2O(1) + 2SO2(g) #
2Cu2O(1) + Cu2S(1) ———> 6Cu(s) + SO2 (1) #
Steel
-Air
Metallic copper
Pivot
Bessemer converter used for bessemerization of copper.