Iron Ore

Question 1

Outline the steps of removing iron from iron ore in the smelting process

Answer 1

• involves a large blast furnace
• a mixture called CHARGE, contains pulverized iron ore (usually hematite), limestone, and coke; coke is prepared by heating coal in the absence of oxygen, which drives off most of the impurities and makes iron smelting less expensive and more efficient)
• as the charge is poured onto the top of the blast furnace, blasts of hot air travel up through the particles as they fall
• in the lowest level of the furnace, where oxygen from injected air is available, carbon in the form of coke burns, heating the air to about 2000°C
• if you control the amount of air and coke, the burning of the coke can be made incomplete, producing carbon monoxide which will act as the reducing agent for the ore
• the CO travels up the furnace and reacts with the compounds from the iron ore that are following
• complete reduction of the hematite occurs in three steps and finally, the metallic iron melts and pools into the bottom of the furnace
• The lime then reacts with impurities and produces a liquid called slag
• the slag is less dense than the molten iron and floats on top of the iron —> slag and molten iron are drawn off at different levels

Question 2

Outline the process for how pig iron is converted to steel

Answer 2

• the process of smelting reduced the iron ions in the ore to metallic iron, however, several contaminants were also reduced to their elemental form
• most of the impurities must be removed through a process called refining
• by refining, the pig iron is converted into steel
• molten pig iron is poured into an upright vessel; oxygen gas is pumped into the vessel over the iron
• lime, called flux, is poured into the mixture; the impurities oxidize more readily than the iron
• these oxidized compounds than react with the lime and the reactions produce a SLAG that is similar to the slag in the smelting process
• the slag is less dense than the molten iron and floats on it
• when the reactions are complete, the vessel is tilted on its hinges, the slag is poured off the top and the refined steel is recovered