- IRON AND STEEL PRODUCTION
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- Historically, most iron ore is converted to iron using a
blast furnace, although a number of newer technologies are replacing
this process. The production of iron requires three important
raw materials: iron ore, coal converted to "coke",
and limestone.
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- The coal is converted to a product called coke in coking
ovens. The three raw materials are added to the top of the blast
furnace. A blast of air containing oxygen is forced in from the
bottom of the furnace. This causes the coke to burn with an intense
heat of almost 2000 C. The reaction is carbon plus oxygen to
produce carbon monoxide (incomplete combustion due to lack of
air).
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- The main reaction is then between the iron oxide, Fe2O3,
with the carbon monoxide to produce molten iron metal and carbon
dioxide. An alternate reaction is with the coke, C, to produce
iron and more carbon monoxide. The molten iron collects on the
bottom of the furnace and when cooled is called pig iron with
many impurities.
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- Much of the carbon dioxide is reduced with more carbon from
the coke to make more carbon monoxide.
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- Impurities in the iron ore such as silicon dioxide react
with the limestone to produce slag, CaSiO3, and carbon
dioxide. The slag floats on top of the molten iron and can be
drawn off separately.
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- The pig iron is treated in a second step called the basic
oxygen furnace. Pure oxygen is blown into the molten pig iron
to oxidize the impurities of sulfur, phosphorus, and carbon to
their respective oxides: SO2, P2O5,
CO2. The result of this operation is the production
of carbon steel. Other transition elements may be added to impart
a variety of other properties. For example stainless steel contains
14-18% chromium and 7-9% nickel.
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