CO₂ Hydrate Slurry Flow Characteristics Using Tetrahydrofuran as a Promoter for Carbon Capture, Transportation, and Sequestration

Carbon capture and sequestration (CCS) through hydrates offers environmental benefits, as mostly water is used during hydrate formation. Hydrate formation from gaseous CO2 is well explored in the literature; however, studies from liquid-phase CO2 need more attention, as liquid CO2 offers higher hydrate formation rates and thermodynamic conditions of oceanic sequestration mostly in the liquid state. CO2 hydrate in water is often a stochastic and slow kinetic process, especially from liquid CO2, affecting the overall process efficiency. Tetrahydrofuran (THF) is one of the potential hydrate promoters that can aid the process favorably, forming CO2 hydrate slurries. The formation kinetics of hydrate slurries are often characterized by their rheological behavior. In this study, we investigate the high-pressure rheology of a CO2 hydrate slurry formed from gaseous and liquid CO2 using various concentrations of the THF promoter at a constant temperature of 274.15 ± 0.5 K and at 3.5 MPa (gaseous CO2) and 5 MPa (liquid CO2). CO2 hydrate slurries formed from pure water are observed to agglomerate at a lower shear rate. However, the antiagglomeration effect is shown by CO2 hydrate slurries formed in the presence of THF. THF+CO2 hydrate has shown pseudoplastic behavior, and THF inclusion reduces typical hydrate nucleation time and delays hydrate dissociation. A small amount of THF, about 1 to 2 wt %, can be effective in improving the rheology of the CO2 hydrate slurry for efficient capture, storage, and transportation of CO2.