Dependence of Gas Hydrate Formation Kinetics on System Size from Lag Time Experiments in a Stirred Pipe

High-pressure, stirred, automated lag time apparatus (HPS-ALTA) with a vertical cylindrical geometry and a 10.8 mL volume has been used previously to characterize gas hydrate nucleation rates. However, the relevant scale parameter that determines how such nucleation rates change with system size remains uncertain. Herein, we present a new high-pressure stirred ALTA system with a horizontal, pipe-like geometry: Pipe-ALTA. Beyond enabling measurement of hydrate formation probability under stirred conditions in significantly larger fluid volumes (up to 300 mL), the pipe-like geometry also allows for system dimensions such as the gas–water interfacial area, α, to be modified by changing the water loading. In this study, we use Pipe-ALTA to measure induction times for gas hydrate formed from water and a synthetic natural gas mixture. Nucleation rates in the Pipe-ALTA are highest when the gas–water interface is large: up to an order of magnitude higher than those measured in the smaller HPS-ALTA (at comparable subcooling). We demonstrate that the nucleation rates from the three system geometries (Pipe-ALTA at two liquid loadings plus HPS-ALTA) can be reconciled if they are scaled by the gas–water interfacial area. In contrast, scaling by the three-phase contact line produces less consistent results, suggesting that the gas–water interfacial area is the most relevant scale parameter.