Flow characteristics and rheological properties of natural gas hydrate slurry in the presence of anti-agglomerant in a flow loop apparatus

highlights
• Hydrate slurry presents obvious shear-thinning behaviour with increase of hydrate ratio.
• Hydrate slurry is transported as a solid dispersion system with addition of AAs.
• A Herschel-Bulkley-type equation was built by considering the hydrate volume fraction.
• Shutting-down/restarting tests show that the hydrate slurry is easily and safely restarted.
• Hydrate slurry exhibits obvious thixotropic behaviour with increasing shutting-down time.

The flow characteristics and rheological properties of natural gas hydrate slurry, with initial water cuts ranging from 5 to 30 vol%, were investigated in a flow loop. The experimental results indicate that the hydrate slurry can be considered a pseudoplastic fluid and presents more obvious shear-thinning behaviour with the increase in the hydrate volume fraction. The study on the fluid morphology demonstrated that the original structure of the water-in-oil emulsion is destroyed by the formation of gas hydrate, and the hydrate slurry is ultimately transported as a solid dispersion system. An empirical Herschel–Bulkley-type equation that considers the hydrate volume fraction was developed to improve the description of the rheological properties of the hydrate slurry. The apparent viscosities of the hydrate slurry calculated by the new equation were in accordance with the experimental data. Shutting-down/restarting tests using three shutting-down times (2 h, 4 h, and 8 h) were performed. The experimental results indicate that the hydrate slurry can be easily and safely restarted from the static state after a long shutting-down period and exhibits obvious thixotropic behaviour with increasing shutting-down time.