Alumina, or aluminium oxide, is the largest single cost in connection with aluminium production. Top quality alumina is required to produce quality metal with low environmental impact. The worldwide production of close to 100 millions tonnes is mainly produced from Bauxite in the Bayer process.
- Hardness and strength
- Low heat retention and high melting point
- For production of Aluminium by the Hall–Héroult process
- Other industrial uses include abrasives, fillers in plastics and catalyst support for industrial catalysts
To turn bauxite into alumina, we grind the ore and mix it with lime and caustic soda, pump this mix into high-pressure containers, and heat it. The aluminium oxide we’re after is dissolved by the caustic soda, then precipitated out of this solution, washed, and heated to drive off water. What’s left is the sugar-like white powder called alumina, or aluminium oxide (Al2O3).
Alumina in the value chain
Our value chain
The mineral bauxite is the starting point for production of aluminium metal
Aluminium is the third-most abundant element in the earth's crust. It is found in different types of minerals. Bauxite is the primary raw material for refining aluminium oxide, or alumina, which is used to produce primary aluminium metal. Bauxite deposits are mainly found in a wide belt around the Equator.
Alumina is refined bauxite and is a raw material for making aluminium
The raw material required for the production of primary aluminium is aluminium oxide, or alumina, a white powder refined from bauxite. To produce one tonne of aluminium in an electrolytic reduction process requires approximately two tonnes of alumina.
A large amount of electricity is needed to produce aluminium metal
The aluminium electrolytic process requires electric energy, about 13 kWh per kilo aluminium produced in modern production lines. Energy accounts for roughly a third of the cost of production of aluminium. Therefore, an important factor is long-term supplies of energy at affordable prices.
The production of primary aluminium takes place in large production lines
Pure aluminium is made from the alumina by a process carried out in electrolytic cells, where a carbon cathode placed in the bottom of the cells acts as an electrode. The anodes, also made of carbon, are consumed during the electrolytic process when the anode reacts with the oxygen in the alumina. Molten aluminium is tapped from the cells.
Other metals are added to the molten aluminium to form various foundry alloys
Molten aluminium is tapped from the pots and cast into logs, rolling slabs or ingots, depending on whether further processing is extruding, rolling or remelting. Small quantities of other metals can be added to the liquid aluminium to produce foundry alloys of different durability and tensile strengths.
Aluminium can be processed
in a cold and hot condition
Aluminium is ductile. Foil can be rolled to only 0.007 mm thickness, but will still be completely impermeable and lets neither light, aroma nor taste substances in or out. The metal itself forms a protective oxide coating and is highly corrosion resistant. Different types of surface treatment can further improve these properties.
Aluminium can be extruded and shaped into a variety of tubes and profiles
Aluminium ingot is heated and pressed through shaping tools, to make profiles for various products. Aluminium is increasingly taking over from copper as preferred metal for tubing in heat exchangers and air conditioners. There is no end to what shapes aluminium end products can take.
Only your imagination can limit the use of aluminium
Windows, car parts, doors, tubes, façade panels, cans… Hydro is the industry leader in many product areas for aluminium, especially in transport, buildings, packaging and lithographic plates. And in the end, the used product can be recycled – again and again.