Iron

Iron is a chemical element in the periodic table that has the symbol Fe (L.: Ferrum) and atomic number 26. Iron is a group 8 and period 4 metal. Iron is notable for being the final element produced by stellar nucleosynthesis, and thus the heaviest element which does not require a supernova or similarly cataclysmic event for its formation. It is therefore the most abundant heavy metal in the universe.

Extraction from ore

Industrially, iron is extracted from its ores, principally hematite (nominally Fe2O3) and magnetite (Fe3O4) by a carbothermic reaction (reduction with carbon) in a blast furnace at temperatures of about 2000°C. In a blast furnace, iron ore, carbon in the form of coke, and a flux such as limestone are fed into the top of the furnace, while a blast of heated air is forced into the furnace at the bottom.

Related Topics:
Ores - Carbothermic - Carbon - Blast furnace - Coke - Limestone - Air

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

In the furnace, the coke reacts with oxygen in the air blast to produce carbon monoxide:

Related Topics:
Coke - Oxygen - Carbon monoxide

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

:6 C + 3 O2 → 6 CO

Related Topics:
C - O₂ - CO

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The carbon monoxide reduces the iron ore (in the chemical equation below, hematite) to molten iron, becoming carbon dioxide in the process:

Related Topics:
Chemical equation - Carbon dioxide

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

:6 CO + 2 Fe2O3 → 4 Fe + 6 CO2

Related Topics:
CO - Fe₂O₃ - CO₂

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The flux is present to melt impurities in the ore, principally silicon dioxide sand and other silicates. Common fluxes include limestone (principally calcium carbonate) and dolomite (magnesium carbonate). Other fluxes may be used depending on the impurities that need to be removed from the ore. In the heat of the furnace the limestone flux decomposes to calcium oxide (quicklime):

Related Topics:
Silicon dioxide - Sand - Silicate - Calcium carbonate - Magnesium carbonate - Calcium oxide

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

:CaCO3 → CaO + CO2

Related Topics:
CaCO₃ - CaO - CO₂

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Then calcium oxide combines then with silicon dioxide to form a slag.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

:CaO + SiO2 → CaSiO3

Related Topics:
CaO - SiO₂ - CaSiO₃

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The slag melts in the heat of the furnace, which silicon dioxide would not have. In the bottom of the furnace, the molten slag floats on top of the more dense liquid iron, and spouts in the side of the furnace may be opened to drain off either the iron or the slag. The iron, once cooled, is called pig iron, while the slag can be used as a material in road construction or to improve mineral-poor soils for agriculture.

Related Topics:
Pig iron - Road - Agriculture

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Approximately 1100Mt (million tons) of iron ore was produced in the world

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

in 2000, with a gross market value of approximately 25 billion US dollars. While ore production occurs in 48 countries, the five largest producers were China, Brazil, Australia, Russia and India, accounting for 70% of world iron ore production. The 1100Mt of iron ore was used to produce approximately 572Mt of pig iron.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~