making metals

We think that stone age / bronze age man discovered iron by accident . Man must have used fire and probably had a firepit which was used every day. Over time charcoal ( which is mainly carbon) would have built up.

Ancient man probably used rocks to contain his firepit. It seems possible that some of these rocks were iron bearing rocks. Over time we imagine that the charcoal and iron mixed. With repeated heating together charcoal would reduce the ( iron oxide) to iron and so the smelting process was discovered.

Any old iron?

Drawbacks of iron as a material for making things:

it rusts!!
it is relatively dense

Advantages of iron

easy extraction makes it relatively cheap
iron is quite hard and therefore can be used for blades
iron is very strong

Rust can be prevented by sacrificial protection where a more reactive metal is put in contact with the iron. The more reactive metal corrodes and protects the iron.

A blast from the past

a modern blast furnace, can produce hundreds of tons of iron per day

We think the blast furnace is at least 20m tall. In the foreground we can see piles of limestone and coal. These materials together with the iron ore are the raw materials for the production of iron. Several different reactions happen within the blast furnace. These are shown below.

1. Carbon and oxygen

carbon and oxygen combine to form carbon dioxide

2. Carbon dioxide and carbon

carbon dioxide and carbon combine to make carbon monoxide

3. Limestone (calcium carbonate) is heated

calcium carbonate decomposes to produce calcium oxide and carbon dioxide

4. Carbon reduces iron oxide

Carbon reduces iron oxide

5. Carbon monoxide reduces iron oxide too

Iron oxide + carbon monoxide = carbon dioxide + iron