Sensitivity study of particle scale modelling in bioleaching

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School of Chemical Engineering | Master's thesis
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Kemian laitetekniikka
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v + 87
Bioleaching is an environmentally friendly extractive technology which allows the recovery of valuable metals from insoluble ores through chemical and biological oxidation. This process has become relevant because it allows processing of low grade ore resources of metals such as copper, nickel or zinc, which would be too expensive to treat by conventional methods. In this thesis, a sensitivity study was carried out on a particle scale bioleaching model developed at the Department of Biotechnology and Chemical Technology of Aalto University. The model describes the bioleaching process of a single ore particle consisting of pyrite, vaesite and silicate. The liquid phase consists of a leaching solution containing sulphuric acid, leaching reagent and dissolved oxygen. Bacteria are included implicitly in the model, represented by an increase in the ferrous oxidation reaction rate. The study examined the influence of certain parameters in order to perform a preliminary test of the model. The process occurring in the system involves chemical reaction, especially oxidation reactions and mass transfer of metal ions and oxygen. The parameters chosen to examine were therefore: Particle diameter, liquid film thickness, ratio of balance area thickness to the radius of the particle (DR) and temperature. Results were collected in terms of vaesite, pyrite, nickel, ferrous and ferric ions, and oxygen concentration, and pH on the particle surface. Temperature was found to be the most sensitive having the greatest effect on the bioleaching rate for both pyrite and vaesite. Particle diameter and liquid film layer thickness appear to be the least sensitive parameter for the concentrations at the particle surface. The model is a satisfactory approximation that describes the phenomenon of bioleaching a particle scale. It is still in the initial stages of construction and its development should be continued.
Alopaeus, Ville
Thesis advisor
Suntio, Ville
bioleaching, particle, modelling
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