CHM 110 - CHEMISTRY AND ISSUES IN THE ENVIRONMENT

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Conversion of Iron Ore to Iron Metal

Blast Furnace

 

 

IRON AND STEEL PRODUCTION

 

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.

 

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 oxygenis 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).

 

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.

 

Much of the carbon dioxide is reduced with more carbon from the coke to make more carbon monoxide.

 

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 separtely.

 

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.

 

Photos of Steel Mills

near Gary, Indiana from the Indiana Toll Road