Specific Energy Consumption (SEC) for pipeline transport of liquid CO2 slurries

Abstract

In this study, Specific Energy Consumption (SEC) was used as a basis to optimize the operating conditions (pipe diameter, particle size and solids concentration) for a hypothetical liquid CO2 slurry pipeline, carrying petroleum coke (“pet coke”) or sulfur particles. The optimum particle size and solids concentration were found to be 100-150μm and approximately 30% by volume respectively. Calculations of SEC involve prediction of the flowing slurry’s frictional pressure gradient, obtained here using the Saskatchewan Research Council’s two-layer model. However, the model and some of the correlations it contains have not yet been tested for low carrier fluid viscosities, which is the case for liquid CO2, whose viscosity is one order of magnitude lower than water. To test the applicability of the model’s kinematic friction correlation for slurries with low carrier fluid viscosities, a 50 mm (diameter) pipe loop was designed and built to test slurries of pet coke in hot water at 700C. The performance of the correlation gave a direct indication of the error in the SEC calculations made for liquid CO2 slurries in industrial pipe sizes. In addition to evaluating the performance of the model’s kinematic friction correlation for slurries with low carrier fluid viscosities, effort was put to improve the model’s Coulombic friction estimation. As Coulombic friction estimation in the model requires knowledge of the coefficient of friction, a simple technique to measure this parameter for various particle-pipe material combinations was proposed.