"Chemistry in charge"

Group manager Ole Wærnes of SINTEF Industrial Chemistry regards the project as successful.

The iron chloride and aluminium chloride plants have been designed to carry out a series of sub-processes. In physical terms, they look like a multi-storey jungle of pipework, containers and tanks. What you do not see in the plant are people. "The chemistry is in charge," says process development engineer Ane Kristiansen, who has been involved in the scrubbing technology projects and has worked with the SINTEF/NTH scientists since 1989.

The smelter hall.

Bremanger produces silicon by means of the patented Silgrain process. An alloy of silicon, iron, aluminium and calcium is dissolved in an acid solution that consists for the most part of iron chloride and hydrochloric acid (Silgrain acid). The last three metals dissolve in the acid while the silicon is separated out in the form of tiny grains. The metal has a reputation for being of high quality.

Iron, aluminium and calcium stay dissolved in the Silgrain acid in the form of chlorides. This solution used to be pumped into the sea. Now the iron is removed. A combination of oxidation and liquid-liquid extraction breaks the acid down into two components, one of which contains iron chloride while the other contains the remainders of the metals.

Aluminium chloride is separated out of the solution via a complex crystallization process. The crystals are subsequently dissolved in water to the appropriate concentration.

The remaining liquid, which contains the remaining metals, is evaporated and its solids are transported to a dump. "I think it should be possible to utilize even more of these wastes," says SINTEF's Ole Wærnes. "However, the financial aspects are still uncertain."