Vinsamlegast notið þetta auðkenni þegar þið vitnið til verksins eða tengið í það: http://hdl.handle.net/1946/17345
In the process of aluminium electrolysis impurities play an important role in lowering the current effciency. Phosphorus is such an impurity which enters the electrolyte along with the alumina. It can have valence states from -3 to +5 and it can therefore take part in cyclic redox reactions. Phosphorus can be expelled with the anode gases, as elemental phosphorus or, attached to carbon dust .
However, due to the use of dry scrubbers it finds its way back to the electrolysis cell along with the secondary alumina.
Experiments were carried out in a laboratory cell at the Norwegian Institute of Science and Technology where different concentrations of AlPO4 were introduced in the melt. In order to notice the effects of phosphorus on the current effciency
a stable concentration of phosphorus was needed within the electrolyte for the duration of the experiments. The first step was to determine how much and if any phosphorus escapes the laboratory cell during the performance of the experiments.
It was found that that in the short time the experiments were running there was little to none phosphorus escaping the melt. Further experimental work with different current densities as well as phosphorus concentrations showed a correlation
between the initial amount of phosphorus and the current effciency.
The present thesis establishes the theoretical background along with the experi- mental details.