Kinetic study of CO2 hydrates crystallization: Characterization using FTIR/ATR spectroscopy and contribution modeling of equilibrium/non-equilibrium phase-behavior

By comparing the measured concentration to calculations based on the assumptions of (a) a liquid-vapor equilibrium (LVE) and (b) a hydrate-liquid equilibrium (HLE), it was deduced that the crystallization kinetic is limited by CO2 transfers from the vapor phase to the liquid phase, whatever the experimental conditions tested. As soon as hydrates start forming, the CO2 concentration in the liquid phase almost instantaneously reaches the hydrate-vapor equilibrium (HVE) value at the experimental temperature, while the reactor pressure slowly decreases towards the LVE value defined by Henry's law. Different stirring speeds were experimented in order to check the effect of enhancing CO2 dissolution during hydrate formation. This resulted in faster dissolution of CO2, though still transfer-limited formation kinetics.