CHPATER NO 9

   EXTRACTION OF IRON                                       

	INTRODUCTION
	Iron is extracted from its oxide	ore called HAEMATITE (Fe2O3).
	PRINCIPLE OF EXTRACTION
	Extraction of iron is based on the reduction of HAEMATITE (Fe2O3) with carbon..
	DETAILS OF EXTRACTION
	The process of the extraction of iron is carried out by the following steps:
	Concentration of ore  Calcination or Roasting of ore  Reduction of ore
	Concentration of ore: In this metallurgical operation, the ore is concentrated by removing impurities like soil etc. The process involves the crushing and washing of ore.
	Calcination or Roasting of ore: The concentrated ore is now heated in the presence of air. The process of roasting is performed to remove moisture, CO2, impurities of sulphur, arsenic. Ferrous oxide is also oxidized to ferric oxide.
	Reduction of ore
	The process of reduction is carried out in a blast furnace.
	Blast Furnace
	The blast furnace is a cylindrical tower like structure about 25m to 35m high. It has an outer shell of steel. Inside of furnace is lined with fire bricks. The top of the furnace is closed by a cup-cone feeder.
	The charge
	The charge consists of : roasted ore Coke Limestone
	Details of reduction
	The charge is fed into the furnace from its top. A preheated blast of air at 1500OC, is blown into the furnace under pressure near to the bottom. The blast oxidizes carbon to CO2.
	C + O2  CO2 + heat
	Formation of CO2 is an exothermic reaction in which a huge amount of heat is liberated which rises the temperature to 1900OC in this region. As the CO2 passes upwards, it reacts more coke to form carbon monoxide.
	CO2 + C  2CO + heat
	Formation of CO is an endothermic reaction and the temperature in this region falls to 1100OC. CO is the main reducing agent in the upper portion of blast furnace.
	Reactions in blast furnace
	Fe2O3 + 3C  2Fe + 3CO Fe3O4 + 4CO  3Fe + 4CO2  CO2 + C  2CO
	Overall reaction
	Fe2O3 + 3CO  2Fe + 3CO2
	The liquid iron runs downward to the bottom of the furnace and is withdrawn through tap hole.
	Slag formation
	Lime stone on heating decomposes to CaO and CO2.
	CaCO3  CaO + CO2
	CaO now reacts the impurities of ore called GANGUE to form slag. Slag is the mixture of CaSiO3 and Ca(AlO2)2. The slag floats over the top of molten iron. Slag is a useful byproduct. It is used in road making, cement manufacturing a light weight building materials.
	Flux + Gangue  Slag            CaO + SiO2  CaSiO3     CaO + Al2O3  Ca(AlO2)2

When iron is exposed to air and moisture, its surface gradually corroded and converted in to a brown    mass. This brown mass is called rust and this phenomenon is known as rusting.
CAUSE OF RUSTING
The rusting of iron is due to the formation of hydrated iron (III) oxide (Fe2O3.H2O).
NATURE OF RUSTING
Rusting is an electro-chemical process. Different parts of the surface of iron act as a cathode and anode.    Moisture on the surface of iron plays a role of electrolyte between cathode and anode.
HOW RUSTING TAKES PLACE
At anode iron is oxidized to Fe+2 ions and forms precipitates of Fe(OH)2. These precipitates are then    oxidized in to Fe2O3.H2O which is known as rust.
ELECTROCHEMICAL CHANGES
Fe ® Fe+2 + 2e- Fe+2 + 2OH- ® Fe(OH)2 4Fe(OH)2 + O2 + 2H2O ® 4Fe(OH)3
DESCRIBE DIFFERENT METHODS TO PROTECT IRON FROM RUSTING?
CATHODE PROTECTION
In this method any reactive metal such as Mg+2, Zn+2 or Al+3 which is more reactive than Fe+2 small    blocks of any of the above metals is connected to the iron objects such as pipes, when corrosion starts,    only more reactive element is corroded and iron is prevented from rusting.
USE OF OIL PAINT
Large objects such as bridge or ship can be protected from rusting by using oil paints.
USE OF GREASE
Moving parts of machinery are protected from rusting by using grease or oils.
GALVANIZING METHOD
Iron objects can be protected by thin layers of zinc from rusting. This process is called galvanizing.
TINNING
In this process a thin layer of tin is coated over the iron object.
ELECTROPLATING
We can protect rusting of iron by electroplating of nickel or chromium.
ALLOY FORMATION
Iron can also be protected from rusting by converting it in to alloys such as stainless steel.

STEEL
DEFINITION
Steel is an alloy of iron that contains little amount of Carbon, Nickel, Chromium, Manganese and     Molybdenum. There are a number of types of steel such as carbon steel, stainless steel, alloy steel etc.     Steel is made from pig iron by reducing carbon and adding small amounts of other metals. These metals     impart particular properties to steel.
MANUFACTURING OF STEEL
Steel is manufactured by a number of processes such as:  Bessemer process (Basic Oxygen Process)  Open hearth process  Electric furnace process
BESSEMER PROCESS
This method is also known as Basic Oxygen Process. PRINCIPLE OF BESSEMER PROCESS     In this process impurities in molten pig iron are oxidized and removed by blowing oxygen gas in Bessemer     converter.                                                         OXIDATION OF PIG IRON    In this step pure oxygen is blown through the molten pig iron in Bessemer converter. During the oxidation     of pig iron, following changes take place.
OXIDATION OF CARBON
Carbon is converted in to CO2.
C + O2 ®CO2
OXIDATION OF SILICON
Silicon is converted in to SiO2.
Si + O2 ®SiO2
OXIDATION OF PHOSPHOROUS
Phosphorus is converted in to P4O10.
4P + 5O2 ® P4O10
SLAG FORMATION
Most of the oxides escape in the form of gases.     To remove oxides of phosphorus and silicon, CaO (quick lime) is added in the furnace. They are combined     with CaO to produce slag.
P4O10 + 6CaO ®2Ca3(PO4)2 SiO2 + CaO ®CaSiO3
ADDITION OF METALS
Calculated amount of suitable metals such as nickel, chromium or manganese are added to purified     molten iron to form desired type of steel.
TYPES OF STEEL CARBON STEEL     Steels containing 0.2% C to 1.5% C are known as carbon steel. They are of three types.  Low Carbon Steel     It contains 0.2% carbon.      Uses:     Sheets, wires, pipes.  Mild Carbon Steel     It contains 0.3% to 0.7% carbon.     Uses:     Rails, boilers, plates, axles, structures.  High Carbon Steel     It contains 0.7% to 1.5% carbon.     Uses:      Surgical instruments, razor blades, cutlery, spring.    STAINLESS STEEL     It contains 14% to 18% chromium and 7% to 9% nickel.      Uses      Car accessories, watch case, utensils, cutlery. ALLOY STEEL     There are three types of alloy steel.   Mn-Steel     It contains 10%-18% Mn.     Uses:     Rail tracks, armor plate, safe.  Si-Steel      It contains 1% to 5% Si.     Uses:      Permanent magnet.  Ni-Steel     It contains 2% to 4% Ni.     Uses:
EXTRACTION OF COPPER On industrial scale copper is extracted from its sulphide ore known as copper pyrite (CuFeS2) by smelting method. STEPS OF EXTRACTION For more details CLICK HERE  Concentration  Roasting  Smelting  Bessemerization CONCENTRATION Finely divided CuFeS2 is concentrated by "Froth-floatation method". Crushed ore is suspended in water containing pine oil. A blast of air is passed through the suspension. The particles of ore get wetted by oil and floats as a froth which is skimmed. The gangue sink to the bottom. ROASTING The concentrated ore is then roasted in the furnace in the presence of oxygen. During roasting sulphur, arsenic, antimony are converted into oxides and are removed. 4CuFeS2 + SO2 ® 2CuS2 + 2FeO + 2FeS + 2SO2       SMELTING Roasted ore is then mixed with coke and sand and is fed into a blast furnace. Hot air converts FeO to iron silicate (FeSiO3). FeO + SiO2 ® FeSiO3 + molten mass BESSEMERIZATION Matte is converted into copper in a special furnace which is known as "Bessemer converter". When air is blown through the matte following reactions take place. 2Cu2S + 3O2 ® 2Cu2O + 2SO22Cu2O + Cu2S ® 6Cu + SO22FeS + 3O2 ® 2FeO + 2SO2 Copper obtained by this process is called blister copper. It is 97.98% pure. REFINING OF BLISTER COPPER Blister copper is refined by an electrolytic process. Blister copper in the form of a large plate is made as anode. A thin plate of pure copper is cathode. A solution of CuSO4is used as an electrolyte. The impure blister copper dissolves at the anode. During electrolysis pure copper is deposited in the form of pure copper at the cathode. REACTION AT ANODE At anode oxidation of copper takes place. Cu ® Cu+2 + 2e- REACTION AT CATHODE At cathode reduction of copper-ions takes place. Cu+2 + 2e- ® Cu     ORE Those minerals which are considered worth mining commercially form the extraction of one or more metals are known as ores. GANGUE Ores mostly consists of a mixture of minerals with useless or worth less rocky materials which are called gangue. USES OF LEAD  It is used in the preparation of Tel (C2H5)4Pb tetra ethyl lead which is used to increase the efficiency     of petrol.  Lead is also used in car batteries.  Lead is used in the manufacture of paints and pigments.  Lead is used in alloy formation such as "solder".  Lead is used in the glazing of pottery. WRITE THE NAME AND FORMULA OF THE IMPORTANT ORES OF IRON?  Heamatite (Fe2O3)  Limonite (2Fe2O3.3H2O)  Magnetite (Fe3O4)  Iron pyrite (FeS2) (fool’s gold) WHAT ARE THE IMPORTANT ORES OF COPPER?  Chalopyrite (CuFe2S3)  Copper glance (CuS)  Malachite (CuCO3.Cu(OH)2)  Chalcocite (Cu2S)  Cuprite (Cu2O) WRITE THE NAMES OF IMPORTANT ORES OF Zn? Zinc blende (ZnS) Zincite (ZnO) Smithsonite (ZnCO3) SLAG Slag is the by-product of the extraction of iron. Slag is a mixture of calcium silicate and calcium aluminate. It is used in the manufacture of cement and building materials WRITE THE FORMULA OF THE FOLLOWING? Galena Cerussite Anglesite Whitelead pigment Alumina