FöRFATTARE
Bäckström, Jonas

INSTITUTION
Tillämpad kemi och geovetenskap / Processmetallurgi

SAMMANFATTNING
This project has been performed as a thesis work in the final year of an MSc Programme in Chemical Engineering with specialisation in Minerals and Metallurgical Engineering. The work has been done at New Boliden's smelter, Rönnskärsverken, near Skelleftehamn in Sweden.

The aim of the project was to get a better understanding of the copper, nickel and tellurium leaching process at the precious metals plant in general. But also to find out if there are improvement potential in the yield of tellurium in particular. Some process parameters have been studied in both laboratory and full-scale production units. Some of the adjacent processes have also been involved in the investigations.

Complementary to the practical work a thorough study of available literature in the field of interest has been done. The results of the laboratory leaching tests gave some clues, but to be able to draw certain conclusions more work has to be done. Combined with the literature survey, full-scale trials and analysis of statistics it is however possible to say that: Silver and tellurium are leached simultaneously after most of the copper and nickel have been leached. The raw slime composition and mineralogy have an impact on the tellurium yield. The tellurium yield is often low, possibly due to re-precipitation or formation of tellurium bearing, refractory slime components.

It would be possible to leach a substantial amount of copper by supplying air and sulphuric acid in e.g. a storage tank before the slime is fed to the autoclave. A washing experiment with leached slime shows that the observed occasional high copper content of the leached slime more likely is due to an insufficient washing rather than lack of dissolution during the leaching.

ISSN 1402-1617 / ISRN LTU-EX--10/119--SE / NR 2010:119