Theses

Thesis Works

Urrutia, N. (2016). "RHEOLOGICAL STUDY OF TAILINGS BASED ON ADVANCED MINERAL CHARACTERISATION TECHNIQUES". M.Sc Extractive Metallurgy degree thesis, University of Chile.

Committee: Leandro Voisin, Víctor Montenegro, Christian Ihle & Carsten Laukamp.

Tailings disposal is crucial in mining industry due to environmental impact and long-term risks. Transport of these materials involves pumping systems which can face detentions and massive failure due to dramatic changes in its rheological properties. Therefore, tailings control is necessary in order to avoid extreme changes in its rheology and mitigate the negative consequences of this situations.

The objective of this work is to quantify the effect of solids content by volume, clays (phyllosilicates) content in solid phase and particle size, in the viscosity and yield stress of phyllosilicate-rich tailings. Also, the use of advanced mineral characterization techniques is assessed as supporting tool for predictive control of tailings rheology.

A total of 108 rheometry tests were performed on tailings with different particle size, solids and clays content. This results were adjusted using Bingham plastics rheological model. Subsequently, linear regression models were adjusted on yield stress and viscosity, using solids content by volume, clays (phyllosilicates) content in solid phase, particle size (as d80) and clay type as explanatory variables. Then, models were assessed with information obtained by using advanced mineral characterization techniques (QXRD, hyperspectral analysis on HyLogger3 and laser diffraction particle size measurements) measuring the quality of adjustment.

Obtained regression models show good adjustment quality over viscosity and yield stress (R2>0.9). Subsequent models implementation with advanced mineral characterization techniques information overestimate viscosity and yield stress due to detection of higher levels of phyllosilicates than real contents in samples. Used regression models are shown below.

Captura

The influence of pH in phyllosilicates-rich tailings seems to be fundamental, since it regulates structure formations in these minerals, having great influence in yield stress and viscosity of this type of suspensions. This property should be considered as explanatory variable in further works involving rheological models.

It must therefore be concluded that the proposed tailings rheology determining variables (solids content by volume, clays (phyllosilicates) content in solid phase, particle size and clay type) are useful to estimate with great precision the viscosity and yield stress of this suspensions, making possible the implementation of predictive control systems of tailings rheology, based on advanced mineral characterization techniques.

 

Merrill, J. (2016). "STUDY OF THE EFFECT OF THE MINERALOGICAL COMPOSITION UPON PULP RHEOLOGY BASED ON ADVANCED CHARACTERIZATION TECHNIQUES". M.Sc Extractive Metallurgy degree thesis, University of Chile.

Committee: Leandro Voisin, Christian Ihle, Víctor Montenegro & Angus McFarlane.

Pulps are widely used in minerals processing, since they enable the transportation of fine granulometry rock, as well as allowing for the extraction of the ore, this is why it becomes interesting to study their rheological properties such as viscosity and yield stress, which on many occasions act as limiting characteristics for some processes, delimiting the treatment capacity of the equipment, as well as increasing the energy consumption in pumping and water consumption, among others.

The experimental work of this study implies the execution of rheological testing at a laboratory scale and the hyper-spectral characterization of pulps, taking into account controlled variables such as: composition, solids concentration and pH; always measuring variables that affect such as granulometry, temperature, etc. Minerals used in said pulps are known by their incidence upon the properties of interest (viscosity and yield stress) as well as forming part of highly abundant gangue minerals in the Chilean mining industry, with the purpose of identifying possible non intuitive interactions or any other rheological phenomenon whose understanding may mean a benefit towards the labor of concentration.

On the other hand, hyper-spectral analysis appears as a technology with the necessary qualities towards mineralogical characterization for control and forecasting purposes concerning pulp rheology. The development of this thesis is framed within the development of the INNOVA CSIRO – CHILE 10CEII-9007 project, which provided HyLogger-3 as hyper-spectral characterization tool.

After the work carried out, several synergistic effects were found between minerals in pulp rheology, with a potential benefit for industrial processes. Also, the detection and quantification of the minerals used in this study through the HyLogger-3 hyper-spectral technology, evidencing high accuracy, thus enabling the development of a forecasting model for the viscosity and shear effort of the synthetic pulps analyzed.

The study of the physical-chemical mechanism of the synergistic effects found is proposed, as well as the expansion of the models for other pH levels, and the comparison of rheology for pulps with the same minerals from different origins.