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CFD Modelling of Laminar, Open-Channel Flows of Non-Newtonian Slurries
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- Author / Creator
- Montilla Pérez, César A
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Current oil sands mining and bitumen extraction methods produce a significant amount of tailings. Recent legislation in Alberta aims to guarantee operators treat their tailings and reclaim them 10 years after the end of mine life. Since 2012, oil sand companies have spent more than $1.3 billion in developing technologies to improve environmental performance and provide more sustainable operations. Generally, tailings are dewatered, and the solids concentration increases affecting the rheological properties of the mixtures. They can exhibit non-Newtonian, viscoplastic, and in some cases time-dependent behaviour which make them challenging to model. In this study, the behaviour of these clay-water-sand mixtures is studied using a commercially available CFD (Computational Fluids Dynamics) package. To achieve this, the physics of the laminar, open-channel flow of coarse particles suspended in a non-Newtonian fluid are broken down into smaller, less complex cases, to progressively validate the predictions of the CFD package. In all cases, the simulation results were compared with available experimental data. First, the laminar, open-channel flow non-Newtonian fluids is studied. The simulation results were able to predict the depth of flow, velocity field, and wall shear stress accurately. Next, fluid-particle systems are modelled in a way some mechanisms can be studied separately: shear-induced migration was studied and the simulated particle volume fraction and velocity profiles were in agreement with the experimental data. The model is unable to predict a depletion of the particle volume fraction at the wall as the experiments did. Single-particle settling in viscoplastic studied was also modelled using two available drag correlations and the particle settling velocity results were in good agreement when an equivalent Newtonian viscosity approach was used. The modelling of laminar pipeline transport of settling slurries captured the overall behaviour of the experiments; however, the CFD solver struggled with stability when the maximum particle packing concentration was approached anywhere in the flow domain. Finally, the knowledge gathered from previous modelling cases was used to study the laminar, open-channel flow of coarse particles in non-Newtonian suspension. The model developed in this study was able to predict the settling of coarse particles when compared with experimental data. It was found that particles settle predominantly in the sheared zone where they form a stationary bed, as also indicated by the velocity profiles. In addition, a parametric study was performed to determine which flow parameters and rheological properties have a significant impact on the transport of coarse particles suspended in a non-Newtonian carrier fluid. The simulation results showed that the flow rate, mixture density, and bulk particle volume fraction are the most impactful parameters in hindering coarse particle settling. The variation of the mixture yield stress had no significant effect on coarse particle settling. An increase in particle diameter had an increasing effect on particle settling. Replacing the semi-circular channel geometry by an equivalent rectangular channel increased the size the depth the settled bed. The model presented in this study can be used to evaluate multiple conditions and for scaling purposes, or to enable the selection of a limited experimental matrix.
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- Subjects / Keywords
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- Graduation date
- Fall 2017
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- Type of Item
- Thesis
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- Degree
- Master of Science
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- License
- This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.