Study of the effect of glycine on the growth and mobility of CO2 hydrate slurries in the loop

The stability of CO2 hydrate slurry mobility is essential for the progression of diverse potential Carbon Capture, Utilization, and Storage (CCUS) applications, while also playing a critical role in maintaining the safety of gas-liquid two-phase flow transportation pipelines. In this study, the effect of glycine on the growth and flowing characteristics of CO2 hydrate slurry was investigated for the first time using a high-pressure recirculating flow loop. A comprehensive analysis of the hydrate growth, morphology, and rheological behavior was performed. The results show that the induction time of CO2 hydrate formation could be effectively prolonged by the presence of glycine in the loop, but it cannot inhibit its rapid formation in the rapid growth period. Meanwhile, agglomeration of the slurry and adsorption on the pipe wall during the flow process were observed with the presence of glycine. The flow pattern of pure CO2 hydrate slurry was gradually transitioned from expansion flow to pseudoplastic flow with the increase of hydrate amount, and shear thinning was observed when the slurry content was not less than 7.6%. The addition of glycine significantly increases the viscosity of the slurry, which makes the slurry behave as an expanding fluid in a wider range. The tendency of shear thickening and the range of shear thickening of the slurry were enlarged. This study raises mobility security concerns for the potential application value of glycine as an LDHI. It also serves as a valuable reference for furthering the advancement of CO2 slurry as a potential application for CCUS.