Mechanical properties of slow cooled copper slag
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School of Chemical Engineering |
Master's thesis
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en
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79
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Abstract
Production of copper creates slag, which still contains some amounts of copper. Considering the large amounts of slag, the recovery of copper from slag is important to ensure efficient copper production. Slag cleaning by flotation relies on slow cooling the slag which increases the size of copper containing particles and liberation of copper containing particles by comminution. Between these processes the slag needs to be disintegrated so it can be conveyed and stored properly. The slow cooled slag at Boliden Harjavalta’s smelter is normally quite brittle this disintegration happens when emptying the slag from ladles. However there has been occasionally observed though slag which does not disintegrate and can cause blockages and damage the equipment. While vastly studied material there are not many studies on mechanical properties of this type of slag. The purpose of this thesis was to find out a suitable method for testing slag strength and find out what chemical and mineralogical properties could affect the slag strength and hardness. X-ray fluorescence was used for chemical composition and x-ray diffraction and scanning electron microscopy with energy dispersive spectroscopy for mineralogical analysis. Vickers hardness and compressive strength were determined as mechanical properties. Seven sample batches was collected in five week sample campaign. Slag consisted mainly of fayalite (Fe2SiO4), magnetite (Fe3O4) and intergranular glass. Largest exception was high magnetite content in one batch which also had the highest compressive strength of 243MPa. Other batches were in the range of 80MPa and 160MPa. Thus, some correlation with strength and magnetite content observed but plotting magnetite content against compressive strength gives a correlation coefficient of 0.78. All batches had large deviation and therefore the results may not be completely reliable. The Vickers hardness values for all batches were in a range of 625 to 711.Description
Supervisor
Lindberg, DanielThesis advisor
Pankka, IidaTammela, Joonas