Question

Copper is extracted from the ore copper pyrite by smelting in a blast furnace. The flux used and the slag formed is :
(A) flux $CaO$, slag $CaSi{O_3}$
(B) flux $Si{O_2}$, slag $CaSi{O_3}$
(C) flux $FeO$, slag $FeSi{O_3}$
(D) flux $Si{O_2}$, slag $FeSi{O_3}$

Answer 1

In order to find the flux and slag formed during the extraction of copper by smelting process in the blast furnace, we must know the steps which are taking place and what are the different products formed in the reaction.

Complete Solution :
Let us now see the extraction of copper from its ore. The ore of copper which is used is the copper pyrite. Iron is one of the impurities present in the copper pyrite ore. We have to remove the iron by roasting the pyrite ore. Roasting is the process which involves heating with excess supply of oxygen. By doing this we would be able to remove the copper oxide and ferrous oxide. The reaction of this process is given below:
$2CuFe{S_2} + {O_2} \to C{u_2}S + 2FeS + S{O_2}$

- There will be some impurities present in the furnace such as cuprous sulphide, ferric oxide and some unreacted ferric sulphide. This roasted ore containing these impurities are passed into the blast furnace that is containing coke and flux i.e. silica. Ferric sulphide will react with the sulphur dioxide and we will obtain ferric oxide. This ferric oxide will react with the silicon dioxide which leads to the formation of $FeSi{O_3}$. $FeSi{O_3}$ is removed as a slag from the furnace. The reaction taking place is given below.
$FeO + Si{O_2} \to FeSi{O_3}$ (slag)
So, the correct answer is “Option D”.

Note: Smelting process can be done in different furnaces such as :
- Blast furnace
- Reverberatory furnace
- Flash furnace.
- Isasmelt furnace