Nucleation Curve of Carbon Dioxide Hydrate from a Linear Cooling Ramp Method

Area of Science:

• Thermodynamics
• Phase Transitions
• Chemical Engineering

Background:

• Gas hydrate formation is a critical phase transition impacting chemical processes and oil/gas flow assurance.
• Investigating gas hydrate nucleation is challenging due to difficulties in comparing rates across different systems and scales.
• Understanding nucleation is vital for both industrial applications and mitigating flow assurance issues.

Purpose of the Study:

• To determine the nucleation curve of structure I (sI) carbon dioxide hydrate using a novel apparatus.
• To establish a method for comparing gas hydrate nucleation rates across various systems.
• To provide a new physical interpretation of experimentally determined nucleation curves.

Main Methods:

• Utilized a high-pressure automated lag time apparatus (HP-ALTA MkI) for nucleation studies.
• Subjected quiescent water samples to isobaric linear cooling ramps to record hydrate formation temperatures.
• Constructed a survival curve and derived a nucleation curve using an empirical model-independent method.

Main Results:

• Determined the nucleation curve for carbon dioxide hydrate (sI).
• Observed significantly greater nucleation rates for carbon dioxide hydrate compared to pure methane hydrate and natural gas hydrate across all subcooling ranges.
• Provided a novel physical interpretation for experimentally derived nucleation curves.

Conclusions:

• The HP-ALTA MkI successfully determined the nucleation curve of carbon dioxide hydrate.
• Carbon dioxide hydrate exhibits a higher nucleation rate than methane hydrate under the studied conditions.
• This research offers a solution to a long-standing puzzle in HP-ALTA technology and enhances the understanding of gas hydrate nucleation kinetics.