Improvement of CO2 hydrate slurry transportation in flow loop: Effect of anti-agglomerant additive on rheological properties

Previous studies showed that CO2 hydrate slurries are potentially one of the top PCM slurries used as a secondary refrigerant, due to high dissociation enthalpy. However, crystal agglomeration phenomenon observed with solid-rich slurry that can lead to pipe plugging is a real limitation for an industrial application, and use of additives could be a way to prevent it. Experimental rheological behaviour of CO2 hydrate suspensions with a rheology modifier additive in various concentrations was studied in a dynamic flow loop using gaseous CO2 injection in a precooled water to crystallize CO2 hydrates and to measure pressure drops as a function of volume flow rate for various solid particle fractions. The Herschel-Bulkley model was used to characterize the laminar flow regime and a shear-thinning behaviour was obtained. A FBRM probe was used to characterise chord length distributions of CO2 hydrates and exhibited a threshold effect for this additive for the slurry. The results showed that the use of the additive avoids slurry agglomeration phenomenon, bring a threshold to the slurry and improves their flow properties due to the affinity of additive to CO2 hydrates.