Pipeline transport is commonly used in the oil sand industry to convey crushed oil sand ores and tailings. Bitumen residues in the oil sand tailings can be a threat to the environment that separating them from tailings before disposal is crucial. However, low bitumen concentration in the tailings slurry and the complex transport characteristics of the four-phase mixture make the process difficult. This study establishes an Eulerian-Eulerian CFD model for an industrial-scale oil sand tailings pipeline. A comprehensive sensitivity analysis was conducted on the selection of carrier-solid and solid-bitumen drag models. The combination of small and large particle sizes (i.e., 75 & 700 μm) and bitumen droplet size (i.e., 400 μm) provided good agreement with field data in velocity profiles and pressure drop. The validated model was subsequently extended to investigate the influence of the secondary phase (i.e., bitumen droplets and bubbles) on flow characteristics in a tailing pipeline. The investigation covered a range of bitumen droplet size (100-400 μm), bitumen fraction (0.0025-0.1), bubble size (5-1000 μm), and bubble fraction (0.0025-0.3) and their influences on the velocity, solids, and bitumen distribution are revealed. For an optimum bubble size of 500 μm, a maximum recovery of 59% from the top 50 % and 83 % from the top 75 % of the pipe cross-section was obtained. The present study demonstrates the preferential distribution of bitumen and provides valuable insight on bitumen recovery from an industrial-scale tailings pipeline.

No abstract

Understanding the flow behavior of complex concentrated slurries is of tremendous importance for industrial waste management. In this study, the transport of three-phase oil sands tailings in a horizontal pipeline is simulated 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. The simulation results showed exceptional agreement with the field data, with errors of < 3.5% for velocity distribution and < 15% for the pressure drop.A systematic parametric investigation was performed for a wide range of flow conditions, showing that the majority of bitumen droplets reside at the top region of the pipe.Our findings may help design an effective process for the separation of bitumen residues during pipeline transport.

No abstract