Copper (Extraction)
Extraction Of Copper
Copper is widely distributed in nature. It occurs in free as well as combined state. Blister copper is mainly extracted from sulphide ores (copper pyrite). The extraction of Blister Copper proceeds through following four steps.
Step I – Concentration
The sulphide ores are concentrated by any of the following methods.
a. Gravity Separation
The powdered ore is passed over a wheel so that it falls in two section due to difference in specific gravity.
b. Forth Floatation Process
The finely powdered copper pyrite ore is introduced into water containing Rine oil. The suspension is vigorously agitated with air. The stony matter settles to the bottom and the ore is carried to the top in the forth. The object of this process is to increase the concentration of copper in the ore.
Step II – Heating / Roasting
The concentrated ore is heated strongly (roasted) in a multiple heater roaster (Reverberatory Furnace) in excess of air in order to achieve the following.
1. To remove sulphur as sulphur dioxide.
2. To remove arsenic and antimony as their volatile oxides.
3. To convert the copper pyrite into a mixture of cuprous sulphide and ferrous sulphide.
4. To partially oxidize cuprous sulphide and ferrous sulphide to copper oxide and ferrous oxides respectively.
5. To remove fusible impurities and moisture.
6. To change the ore into porous form.
Step III – Smelting
The roasted ore is mixed with Silica (SiO2) and smelted in a water jacketed blast furnace about 5ft to 6ft high and 1.6 m in diameter. It is a tower like structure made of steel sheet and lined inside with firebricks. A blast of air is necessary for the combustion of ore. This ore is blown through the pipes provided at the base. Since, most of the heat is produced by the combustion of ore itself, therefore, small amount of fuel is required. The cuprous oxide formed during roasting react with unoxidized ferrous sulphide to form cuprous sulphide and ferrous oxide.
CuO + FeS —-> Cu2S + FeO
Silica act as flux, it reacts with ferrous oxide to form fusible slag (Ferrous Silicate) because iron has more affinity for oxygen than copper.
FeO + SiO2 —-> FeSiO3 (Slag)
Slag is removed from the slag hole while a molten mass containing mostly cuprous sulphide, with a very little ferrous sulphide is taken out from the bottom and is called Matte.
Step IV – Bessemerization
The molten is now transferred into Bessemer converter. It is a pear shaped furnace made of steel plates and provides with a basic lining like that of lime or Magnesium Oxide.
Diagram Coming Soon
The main features of this process is that air is blasted through the molten matte. As a result, ferrous sulphide still present gets oxidized to ferrous oxide and is removed as slag. Cuprous sulphide is partially oxidized to oxide, which reacts with remaining cuprous sulphide to form metallic copper.
Cu2S + 2Cu2O —-> 6Cu + SO2↑
The molten copper is run into sand moulds and allowed to solidify. When it gives out absorbed SO2, it leaves blister type appearance at the surface of the metal. The metal thus obtained is known as Blister Copper. It is about 98% pure.
Refining
The crude copper obtained by the above methods contain about 2% of impurities consisting of Fe, Ni, Zn and Ag. It is refined by electrolysis. The process is carried out in a large tank lined with lead. Thick plates of crude copper served as anode and thin plates of pure copper act as cathode. The cathode is coated with oil which helps in easy scraping of pure copper. These electrodes are dipped into electrolytic copper sulphate solution. The electrolysis is then carried out by a current of 1.3 volts. The pure copper is deposited at the cathode while impurities like Fe, Ni, Zn passes into solution and other like Ag and Au fall down as anode mud. During electrolysis following reactions occur.
Cu0 —-> Cu11 + 2e- (At Anode)
Cu11 + 2e- —-> Cu0 (At Cathode)
Copper thus obtained is 99.99% pure and is known as Electrolytic Copper.
Extraction Of Copper
Copper is widely distributed in nature. It occurs in free as well as combined state. Blister copper is mainly extracted from sulphide ores (copper pyrite). The extraction of Blister Copper proceeds through following four steps.
Step I – Concentration
The sulphide ores are concentrated by any of the following methods.
a. Gravity Separation
The powdered ore is passed over a wheel so that it falls in two section due to difference in specific gravity.
b. Forth Floatation Process
The finely powdered copper pyrite ore is introduced into water containing Rine oil. The suspension is vigorously agitated with air. The stony matter settles to the bottom and the ore is carried to the top in the forth. The object of this process is to increase the concentration of copper in the ore.
Step II – Heating / Roasting
The concentrated ore is heated strongly (roasted) in a multiple heater roaster (Reverberatory Furnace) in excess of air in order to achieve the following.
1. To remove sulphur as sulphur dioxide.
2. To remove arsenic and antimony as their volatile oxides.
3. To convert the copper pyrite into a mixture of cuprous sulphide and ferrous sulphide.
4. To partially oxidize cuprous sulphide and ferrous sulphide to copper oxide and ferrous oxides respectively.
5. To remove fusible impurities and moisture.
6. To change the ore into porous form.
Step III – Smelting
The roasted ore is mixed with Silica (SiO2) and smelted in a water jacketed blast furnace about 5ft to 6ft high and 1.6 m in diameter. It is a tower like structure made of steel sheet and lined inside with firebricks. A blast of air is necessary for the combustion of ore. This ore is blown through the pipes provided at the base. Since, most of the heat is produced by the combustion of ore itself, therefore, small amount of fuel is required. The cuprous oxide formed during roasting react with unoxidized ferrous sulphide to form cuprous sulphide and ferrous oxide.
CuO + FeS —-> Cu2S + FeO
Silica act as flux, it reacts with ferrous oxide to form fusible slag (Ferrous Silicate) because iron has more affinity for oxygen than copper.
FeO + SiO2 —-> FeSiO3 (Slag)
Slag is removed from the slag hole while a molten mass containing mostly cuprous sulphide, with a very little ferrous sulphide is taken out from the bottom and is called Matte.
Step IV – Bessemerization
The molten is now transferred into Bessemer converter. It is a pear shaped furnace made of steel plates and provides with a basic lining like that of lime or Magnesium Oxide.
Diagram Coming Soon
The main features of this process is that air is blasted through the molten matte. As a result, ferrous sulphide still present gets oxidized to ferrous oxide and is removed as slag. Cuprous sulphide is partially oxidized to oxide, which reacts with remaining cuprous sulphide to form metallic copper.
Cu2S + 2Cu2O —-> 6Cu + SO2↑
The molten copper is run into sand moulds and allowed to solidify. When it gives out absorbed SO2, it leaves blister type appearance at the surface of the metal. The metal thus obtained is known as Blister Copper. It is about 98% pure.
Refining
The crude copper obtained by the above methods contain about 2% of impurities consisting of Fe, Ni, Zn and Ag. It is refined by electrolysis. The process is carried out in a large tank lined with lead. Thick plates of crude copper served as anode and thin plates of pure copper act as cathode. The cathode is coated with oil which helps in easy scraping of pure copper. These electrodes are dipped into electrolytic copper sulphate solution. The electrolysis is then carried out by a current of 1.3 volts. The pure copper is deposited at the cathode while impurities like Fe, Ni, Zn passes into solution and other like Ag and Au fall down as anode mud. During electrolysis following reactions occur.
Cu0 —-> Cu11 + 2e- (At Anode)
Cu11 + 2e- —-> Cu0 (At Cathode)
Copper thus obtained is 99.99% pure and is known as Electrolytic Copper.
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