Prediction of the mean velocity following a flow-pattern transition and apparent viscosity for various fluorinated gas hydrate slurries in a pipeline

Abstract

Fluorinated gases (F-gases, such as R32, R134a, and SF₆) are potent greenhouse gases. These gases can be effectively recovered using hydrate-based gas separation, during which water flow results in the formation of a hydrate slurry. It is critical to develop prediction equations for changes in flow patterns and rheological properties that are not specific to gas species for practical handling of these slurries. The objective of this study was to determine the mean velocity following a change in the flow pattern and apparent viscosity of R32, R134a, and SF₆ hydrate slurries. We developed generalized empirical equations to estimate the mean velocity of the hydrate slurry after the flow pattern changed from homogeneous to heterogeneous as well as from heterogeneous to a moving-bed flow. The mean velocities were estimated within an error of ± 20 %. In a pseudo-homogeneous flow, the apparent viscosity of F-gas hydrate slurries with a solid fraction of 3–5 vol% was estimated to be 0.003–0.005 Pa·s, demonstrating the slurries behaved as Newtonian fluids. Adding sodium dodecyl sulfate to the slurry decreased the mean velocity after the flow-pattern change, apparent viscosity, and the pseudoplasticity of the slurry by inhibiting the agglomeration of hydrate particles.