1 research outputs found
Surfactant Effect on Hydrate Crystallization at the Oil–Water Interface
Gas hydrates pose economic and environmental
risks to the oil and gas industry when plug formation occurs in pipelines.
A novel approach was applied to understand cyclopentane clathrate
hydrate formation in the presence of nonionic surfactant to achieve
hydrate inhibition at low percent weight compared to thermodynamic
inhibitors. The hydrate-inhibiting performance of low (CMC) concentrations of Span 20, Span
80, Pluronic L31, and Tween 65 at 2 °C on a manually nucleated
2 μL droplet showed a morphological shift in crystallization
from planar shell growth to conical growth. Monitoring the internal
pressure of the water droplet undergoing hydrate crystallization provides
information on the change in interfacial tension during the crystallization
process. The results of this study will provide information on the
surfactant effect on hydrate crystallization and inhibition. At low
surfactant concentrations (below CMC), a planar hydrate crystal was
formed. Decreasing interfacial tension was observed, which can be
related to the shrinking area of the water–cyclopentane interface.
At high surfactant concentration, the crystal morphology was shifted
to conical. Interfacial tension measurements reveal oscillations of
the interfacial tension during the crystallization process. The oscillations
of the interfacial tension result from the fact that once the crystal
has reached a critical size a portion of the cone breaks free from
the droplet surface, which results in a sudden increase in the available
surface for the surfactant molecules. Hence, a temporary increase
in the interfacial tension can be observed. The oscillatory behavior
of the interfacial tension is a result of the growth and release of
the hydrate cones from the surface of the droplet. We have found that
the most efficient surfactant in hydrate inhibition would be the one
with HLB closest to 10 (equal hydrophilic–hydrophobic parts).
In this way, the surfactant molecules will stay at the interface as
they observe equal affinities for both the oil and water phases. Surfactant
molecules that have the strongest affinity to the interface will be
able to inhibit the growth of the crystal as they will force the cones
to break and will not allow them to grow