UBC Theses and Dissertations
Probing mineral-bitumen liberation using rheological measurements Gutierrez, Leopoldo
The rheology of oil sand slurries was investigated under different physicochemical conditions in an attempt to establish a correlation between bitumen liberation and slurry rheology. Synthetic mixtures of bitumen with fine quartz of varying bitumen content, as well as actual oil sand ores, were used in all the tests. All rheological measurements were conducted using a rotational viscometer connected to a fixture specifically designed for testing settling suspensions. The results showed that for both synthetic mixtures and actual oil sand ores the viscosity of the slurries decreases with increasing bitumen liberation. It was found that at low bitumen contents (0 and 1 wt%) the pH of the slurries was the most important parameter that controlled the rheology of synthetic quartz-bitumen slurries. At higher bitumen contents (5 and 10 wt%), it was a combination of high temperature and high pH that gave the lowest viscosities and yield stresses of the model mixtures. The overall results were discussed in terms of aggregation-dispersion phenomena between bitumen and mineral particles. The effect of salts such as NaCl, CaCl₂ and KCl on the rheology of synthetic mixtures was found to be small compared to the effects of pH and temperature. Experiments performed on slurries where bitumen was added as an emulsion (no attachment to solids) showed that viscosity was significantly lower compared to a suspension in which bitumen coated the solid particles. Humic acids were tested also in slurries of synthetic bitumen-quartz mixtures at 10 wt% bitumen showing that they produce an important improvement in rheology when they are added at dosages of 100 g/t or higher. These observations on synthetic ores could qualitatively be used to predict the rheology data for slurries of four actual oil sand ores. In this case, it was also found that the content of very fine particles (% fraction finer than 3 microns) was the most significant variable that clearly correlated with the viscosity of the oil sand ore slurries.
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