CFD simulation of turbulent non-Newtonian slurry flows in horizontal pipelines
Creators: Sadeghi, Mohsen
Publisher: name: University of Alberta Library
Year: 2022

<p>Complex concentrated slurry flows in horizontal pipelines are widely seen in many<br>
industries for transportation of solid particles or process wastes. i.e., tailings. Slurry<br>
flows can occur in a turbulent regime, and the carrier fluid usually shows a non–Newtonian behavior. Understanding the flow behavior of slurries and the ability to predict the changes in the behavior with respect to variations in the flow conditions are of great importance and help the operators in pipeline design and optimization, and possibly development of separation processes. CFD simulation is a powerful tool to study the multiphase slurry systems, and can be applied to a wide variaty of configurations, flow conditions, and number of phases. In this work, CFD models were developed using ANSYS® FLUENT 2020 R2 commercial package to investigate the flow behavior of slurries in laboratory and industrial scale pipelines.</p>

<p>The first part of this thesis investigates a model system in a lab–scale pipeline by studying the transport of monodisperse and bimodal particles in a turbulent non-<br>
Newtonian carrier using an Eulerian-Eulerian CFD model coupled with granular kinetic theory. The CFD predictions agreed satisfactorily with experimental data<br>
of solids concentration and pressure drop reported in the literature. The effects of the diameter of monodispersed particles (0.5-2 mm), solids concentration (0.1-<br>
0.4), mixture velocity (3-6 m/s), and carrier fluid density (1000-1400 kg/m3) on flow behavior and specific energy consumption were investigated. The mixture velocity<br>
has the most significant effect on pressure drop and radial solids distribution. An increase in mixture velocity or solids concentration led to a larger pressure drop, primarily due to the intensified particle-wall and particle-particle interactions. At the maximum velocity of 6 m/s, the solids concentration distribution reversed near the pipe invert with a local maximum in turbulent kinetic energy from a low solids concentration, while turbulence was dampened at the pipe core where the solids concentration is higher. A higher solids concentration and lower mixture velocity led<br>
to lower specific energy consumption. </p>

<p>In the second part, the work was extended to an industrial–scale pipeline with the study of transport of three–phase oil sands tailings in a horizontal pipeline using the CFD technique via the mixture multiphase model coupled with the kinetic theory of granular flow. The solid particles and bitumen droplets are conveyed via a non–Newtonian carrier fluid in a turbulent regime inside an industrial–scale pipeline with 74 cm diameter and 220m length. Ten sets of field data of velocity distribution and pressure drop were collected and used for the validation of the model. Overall, the CFD results showed exceptional agreement with the field data, with errors of &lt;3.5% for velocity distribution and &lt;15% for the pressure drop. A systematic parametric investigation was performed on the effect of mixture velocity, particles<br>
size distribution, non–Newtonian viscosity, and pipe angle on the carrier velocity distribution, pressure gradient, radial distributions of turbulent kinetic energy, and<br>
solids and bitumen concentration. Overall, our results showed the nontrivial effects of the mentioned parameters on the flow behavior, but less pronounced effects on the bitumen concentration distribution. Moreover, the majority of bitumen droplets reside at the top region of the pipe thus selective treatment of the top flow may lead to an acceptable recovery of bitumen.</p>

<p>Overall, this thesis presents a reliable and affordable simulation approach for modeling turbulent non-Newtonian slurries. The results and findings would be helpful to better understand the behavior two and three–phase slurry flows, and to optimize the slurry transport processes. Moreover, this thesis may help the design of a new process for separation of bitumen residues from the tailings stream.</p>