Aluminum Fact Sheet

 

For my LCA, I will be analyzing the CD. One of the most important parts of the CD is made out of aluminum.


Aluminum is luckily the easiest metallic element in the Earth's crust! Hydrogen and oxygen forms bauxite which is then mined for aluminum. Aluminum is silver and white with a specific gravity of 2.7. A great conductor of electricity, it is very resilient to atmospheric corrosion. Its greatest quality is that it combines lightness and strength and can be used in a variety of industries. Australia creates about 40% of the world's bauxite and more than 30% of the world's alumina.

The extraction of aluminum metal takes place in three main stages. First is the mining of bauxite. Done by surface methods in which the topsoil and overburden are removed by bulldozers and scrapers, the underlying bauxite is mined by front-end loaders, power shovels, and hydraulic excavators.  The bauxite is then crushed and washed to remove the clay and sand waste and dried in rotary kilns. This ore is then loaded into trucks, railway cars, and onto ships.

The next step is refining. This involves four separate stages. First, is the digestion. This is when the finely ground bauxite is fed into a steam heated unit called a digester. This forms a solution of sodium aluminate. Then comes the clarification. This is where the green liquor is seperated from the waste. Here, waste is removed, red mud is separated out, and the remaining green liquor is pumped through filters. Then in the precipitation stage, the alumina is precipitated from the liquor as crystals of alumina hydrate. The last stage is through calcination. Here, the alumina hydrate is washed to remove any remaining liquor and is dried. Then it is heated to remove the water of crystallization.

The last step is the smelting where aluminum and oxygen in the alumina are separated by electrolysis. This happens through passing an electric current through a molten solution of alumina and natural or synthetic crolite. Periodically, the molten metallic aluminum collects at the bottom of the pot and is siphoned off and transfered to large holding furnaces.

There are many uses of aluminum. These include electrical equipment, cars, ships, aircraft, chemical processes, packaging, kitchen utensils, and industrial construction to name a few.