Rheological properties of CO2 hydrate slurry produced in a stirred tank reactor and a secondary refrigeration loop

The aim of this paper is to present the rheological properties of CO2 hydrate slurry for a use as secondary fluids in refrigeration systems. A set-up composed of a stirred tank reactor and a circulation loop was used to study CO2 hydrate slurry formation and flowing. Rheological properties of CO2 hydrate slurries circulating in the loop were determined by the capillary viscometer method. The results show a shear thinning behaviour of the CO2 hydrate slurries for a solid fraction up to 22%. This behaviour is correlated by an Ostwald-de-Waele empirical equation, which takes into account the hydrate fraction of the slurry. The apparent viscosity of CO2 hydrate slurry was estimated from the model and a good agreement was found with the experimental data. A comparison with literature shows the importance of using a stirred reactor for slurry homogenisation, which allows the decrease of the apparent viscosity of the slurry.