Computational fluid dynamics investigation of bitumen residues in oil sands tailings transport in an industrial horizontal pipe

TL;DR

This study develops and validates a CFD model to analyze the flow and separation of bitumen residues in oil sands tailings pipelines, revealing optimal conditions for bitumen recovery.

Contribution

It introduces a comprehensive Eulerian-Eulerian CFD model for industrial-scale tailings pipelines, including sensitivity analysis and investigation of secondary phase effects.

Findings

Good agreement with field data for velocity and pressure profiles.

Optimal bubble size of 500 um yields up to 83% bitumen recovery.

Distribution patterns of bitumen and solids are characterized.

Abstract

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 um) and bitumen droplet size (i.e., 400 um) 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 um), bitumen fraction (0.0025-0.1), bubble size (5-1000 um), 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 um, 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.