Smelting: Getting Iron Out of Ore

0:00How do we get a metal like iron out of rock?

0:04An ore is a rock with enough metal to be worth extracting. Iron ore is mostly iron oxide.

0:11Heating an ore to extract its metal is called smelting. Iron is smelted in a blast furnace.

0:20Three raw materials go in at the top: iron ore, coke and limestone.

0:26Coke is mostly carbon, made from coal. Limestone is calcium carbonate.

0:33Hot air is blasted in near the bottom.

0:36The coke burns, making carbon dioxide and heating the furnace to over 1500 degrees Celsius.

0:44This carbon dioxide reacts with more hot coke to make carbon monoxide.

0:50Carbon monoxide rises through the furnace and takes oxygen from the iron oxide. Losing oxygen is called reduction.

1:00Iron oxide is reduced to iron, and carbon monoxide becomes carbon dioxide.

1:07The iron melts, trickles down and is tapped off at the bottom.

1:12Limestone breaks down to calcium oxide, which reacts with sand, silicon dioxide, to form slag.

1:19Slag is a molten waste. It is less dense than iron, so it floats on top and is tapped off.

1:27Zinc and copper ores are often sulfides. They are first roasted, or heated strongly in air, giving off sulfur dioxide.

1:37The zinc oxide is then reduced with carbon. Copper ores go through similar steps.

1:43So in a blast furnace, carbon monoxide from coke reduces iron oxide to molten iron.