Mass transfer during hydrate-based HFC134a gas separation using a vertical pipe reactor with a static mixer

Hydrate-based gas separation has attracted attention for the recovery of greenhouse gases because of its low material and environmental costs. We have previously proposed the use of a static mixer for the continuous operation of hydrate-based gas separation. To optimize the process, it is essential to regulate the hydrate formation and decomposition rates, recover the gas generated from the hydrate slurry, and determine the optimal reactor design and operating conditions. Hydrate formation in practical processes is often complex because the gas, liquid, and solid phases have various influences on the overall mass transfer. In this study, mass transfer during hydrate formation was investigated using a vertical pipe reactor with a static mixer containing an inner diameter that was two times larger (23 mm) than that of the previous study (11 mm). Notably, many tiny bubbles (< 2 mm in diameter) were observed in the hydrate slurry in the reactor, which hindered the mass transfer of hydrates. The correlation equation for the mass transfer coefficients obtained during hydrate formation in the bubble-hydrate slurry was determined using dimensionless numbers, based on the correlation determined for other gas-liquid mass transfer coefficients in bubble columns. Bubble deformation, oscillation, and hydrate particles facilitated superficial mass transfer during hydrate formation. The results suggest that bubble deformation and oscillation were inhibited by the adsorption of hydrate particles on the bubble surfaces.