Heavy oil slurry transportation through horizontal pipelines: Experiments and CFD simulations

The pressure-driven slurry flow of heavy oil in a horizontal pipe is investigated experimentally and numerically for Reynolds numbers in the range 44-805, solid concentrations by weight between 1 and 12%, and mean slurry velocities of ∼0.2-2.3 m s−1. A three-dimensional, algebraic slip mixture (ASM) model is used as part of the CFD software FLUENT 6.3 to obtain the numerical solutions. The results for the pressure drop are compared with experimental data of slurry prepared with de-asphalted oil as the liquid phase and asphaltic residues as the solid phase with mean particle sizes of 500 µm. Based on the experimental measurements, the critical deposition velocity for these slurries was estimated to vary from 0.171 m s−1 (for 1% solid concentration and mean slurry velocity of 0.22 m s−1) to 0.66 m s−1 (for 12% concentration and mean slurry velocity of 2.3 m s−1). However, for the full range of mean velocities tested, the flow of these highly viscous mixtures was found to be in a homogeneous regime. The numerically predicted pressure drops are in good agreement with the experimental data with relative deviations of ∼0.8-13%. In contrast, errors of ∼3-24% are obtained when comparing the experimental results with the Fanning friction factor correlation. While the temperature of the circulating slurry rises with the flow rate due to viscous heating and friction of the solid particles with the pipe walls, we find that at the moderate flow velocities and efflux concentrations considered the slurry morphology is not affected by the gradual dissolution of the solid particles (asphaltenes) into the liquid phase. Other important slurry flow characteristics, such as the mean slurry friction coefficient and slurry velocity distribution, are also analyzed, which predict the homogeneous, symmetric character of the flow.