Aluminium fluoride


Symbol: AlF3

Appearance: Colourless Solid

Melting Point: 1291 C

Boiling Point: Not applicable

Aluminium fluoride

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This colourless solid can be prepared synthetically but also occurs in nature as the rare mineral rosenbergite.

Boliden's production of Aluminium fluoride and synthetic anhydrite

Aluminium fluoride and synthetic anhydrite (gypsum) is produced at the Noralf plant at Boliden Odda. The main product is aluminium fluoride (AlF3), which is produced through a process where the raw materials are sulphuric acid (H2SO4), fluorspar (CaF2) and aluminium hydrate (Al(OH)3). The annual production of aluminium fluoride is 40.000 tonnes and of synthetic anhydrite 95.000 tonnes.

Aluminium fluoride

Aluminium fluoride is primarily used in the production of aluminium. It is a critical additive to the molten electrolyte in aluminium metal production. Using today's technologies, it is impossible to manufacture aluminium without AIF3. Adding AIF3 allows the electrolytic process to take place at a temperature around 850°C, which is considerably lower than the melting point for aluminium oxide (Al2O3, mp ab. 1,500°C). As a result of its temperature-lowering properties, AlF3 has a definite energy saving effect.

Synthetic anhydrite (gypsum)

Synthetic anhydrite (CaSO4) is a by-product of the aluminium fluoride production. This gypsum differs from "regular" gypsum due to its lack of water and the slower hardening process. Anhydrite, which previously was a waste product, has seen wide use in recent years in Central Europe for fluid floor screed. It is also used as an additive in fertilisers and in cement.