Dependence of Gas Hydrate Formation Kinetics on System Size from Lag Time Experiments in a Stirred Pipe
Year: 2024
Type: article
Abstract: Gas hydrate nucleation rates have previously been rigorously characterized using a high-pressure, stirred automated lag time apparatus (HPS-ALTA) that has a vertical cylindrical geometry (24 mm diameter; 10 mL volume). However, the relevant scale parameter that determines how such nucleation rates change with system size remains uncertain. In this work, we present a newly developed 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 enables system dimensions such as the gas-water interfacial area, A, to be changed by adjusting the water loading. Induction times measured for hydrates formed from a synthetic natural gas mixture are exponentially distributed at fixed subcoolings ((4.0, 4.5, and 5.0) K) with nucleation rates in the physically larger Pipe-ALTA being an order of magnitude higher than those obtained in the HPS-ALTA at the same subcooling (e.g. (0.631 vs 0.074)×10-3 s-1 at 5 K subcooling). In the Pipe-ALTA, nucleation rates were found to decrease upon reducing A (achieved by increasing the liquid loading to 300 mL). Nucleation rates across the two apparatus and two liquid loadings could be reconciled well by scaling by either A or the three-phase-contact-line length. At 5 K subcooling, nucleation rates scaled by the system gas-water interfacial area from the Pipe-ALTA and HPS-ALTA agreed within a factor of two (34 × 10-3 m-2s-1 and 67 × 10-3 m-2s-1). For data from a single apparatus, the highest level of agreement was obtained when scaling by A (agreement within a factor of 1.3) rather than the three-phase-contact line.
Source: Energy & Fuels
Institution: The University of Western Australia
Language: English
Subfield: Environmental Chemistry
Field: Environmental Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W4405925283