Enhanced hydrate formation at the liquid CO2-brine interface with shear flow for solid CO2 sequestration

Abstract

The hydrate-based CO2 sequestration provides an alternative solution for reducing CO2 emissions. However, the hydrate film that forms preferentially at the CO2-water interface can severely restrict hydrate conversion rate. How to enhance CO2 hydrate formation remains a crucial question. Here, we constructed static and shear flow contact models of liquid CO2 and brine in a cubic cavity and investigated their hydrate growth behavior at different subcoolings from perspectives of morphology and kinetics. For static contact, nucleation usually occurs at the CO2-brine interface, and high subcooling increases the degree of hydrate film wrinkling and the CO2 hydrate formation amount. The shear flow can delay the explosive growth of hydrates and tends to nucleate in bottom water; meanwhile, the continuous flow causes the overall extrusion deformation of hydrate film until the injection hole is blocked. Compared to static contact, this forced CO2-H2O contact caused by film deformation enhanced the CO2 hydration amount by 2.68–3.62 times at the subcoolings of 6.94–3.25 K. Increasing the flow rate can further delay hydrate appearance and enhance hydrate growth. We also speculate on the hydration patterns of CO2 in sediment pores under static and flowing conditions, and think that maintaining long-term flow can be an effective means to improve CO2 hydrate storage and prevent blockage occurring in the pore throat. Our work provides new insights into the growth behavior of CO2 hydrate for future CO2 storage in submarine sediments.