Iron Extraction Manufacturing Process - Blast Furnace Method

Iron is extracted from different ores exist in the world. Hematite (Fe2O3) is reduced to iron metal in the blast furnace under several steps. Limestone and coke are used as other raw materials to generate heat and reducing agents. Iron extraction is one of the largest chemical industry in the world because iron is a very useful metal to manufacture lot of things in our daily life.

Reducing iron oxides | Ferric oxide (Fe2O3) and Ferrous oxide (FeO)

Iron is located in the middle part of the electrochemistry series. Therefore Ferric oxide and Ferrous oxide can be reduced to iron by reducing agents such as carbon monoxide or coke.

  • Fe2O3 - Iron(III) oxide
  • FeO - Iron(II) oxide

What is ore?

When a mineral is available for using a metal in useful way, it is defined as ore.

Types of ores containing Iron

Following ores contain iron. But according to the amount of existing iron amount, ability of extraction is depend. If iron percentage is high, it is a good for extraction because it will give good yield. When other metals exist with those ores they make problems in iron extraction.

  • Hematite - Fe2O3
  • Siderite - FeCO3
  • Copper pyrites - CuFeS2
  • Magnetite - Fe2O3FeO
  • Limonite - Fe2O3.xH2O
  • Iron Pyrites - FeS2
  • Ilmenite - Feo.TiO2

How iron is extracted?

Iron is fairly reactive element. Because of that it does not exist as a free substance in the world (iron reacts with oxygen to form oxides).

Iron locates at middle part in the activity series. Hence oxides of Iron can be reduced by carbon monoxide and coke.

Extraction of Iron using Blast Furnace

Raw Materials for Iron extraction

  • A mineral which contains iron (Hematite - Fe2O3)
  • Limestone (CaCO3)
  • Coke - C

Hematite - Fe2O3

SiO2, Al2O3 is mixed with hematite.

Why we use limestone in iron extraction?

  • to make slag
  • Amount of CaCO3 depends on amount of silicate materials.

Why we use coke in iron extraction?

To produce heat and increase the temperature in burst furnace.

Complete iron extraction process

  • Mixture is smashed into tiny parts and heated into high temperature.
  • Hot air is entered from bottom of the furnace. Heat is generated by burning coke. Also carbon monoxide gas is produced by burning coke.
  • In the furnace, bottom and top temperatures are about 15000C and 2000C respectively.
  • Fe2O3 is reduced to iron mainly by carbon monoxide and to some extent by coke.

Reactions of iron extraction

Fe2O3 reduction to iron is done step by step. Temperature variation along the blast furnace will help to occur these reactions. Now, we can study what are the reactions occurring inside the blast furnace at different temperatures.

at 4000C

Reduction of Ferric oxide by carbon monoxide | Fe2O3 + CO

Ferric oxide (Fe2O3) is reduced Fe3O4 by carbon monoxide. Fe3O4 contains FeO and Fe2O3.

Fe3O4 = FeO.Fe2O3

ferric oxide reduced by carbon monoxide

at 5000C - 6000C

CO is reduced to carbon and oxidized CO2.

CO oxidized to CO2 and reduced to C

at 8000C

FeO is reduced liquid Fe by CO. CO is oxidized to CO2.

FeO + CO = Fe + CO2

at 9000C

Limestone decomposes to CaO and CO2.

CaCO3 = CaO + CO2

at 10000C

FeO is again reduced to liquid Fe at this temperature. Also, CO2 combines with C to give CO.

CO2 + C = 2CO

at 18000C

Slag is produced at this temperature. It exists as a liquid. Mixture of liquid CaSiO3 and liquid Ca(AlO2)2 is the slag.

slag producing in iron extraction

Melting pointof pure Iron is 10150C. But including impurities will reduce the melting point to 1015 0C.

CaO reacts with SiO2 and Al2O3. It produce slag which is CaSiO3 and Ca(AlO2)2. Slag exist in liquid state. Liquid slag floats on liquid iron bottom of the blast furnace. Therefore oxidization of iron is prevented by entering air.

Environmental Pollution in Iron Production

Iron manufacturing process makes a lot of environmental pollution problems.

  • CO is emitted to the atmosphere. CO causes to breathing problems, deadly diseases, increasing green house effect (increase global temperature).
  • CO2 also increases the global temperature.
  • SO2 can be released to atmosphere due to use of ores which contains sulfur. It also contribute to increasing green house effect and acid rains.
  • Releasing slag pollutes soil and water.
  • High heat, dust also pollute environment.

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