Page 307 - Handbook Of Multiphase Flow Assurance

306 10. Research methods in flow assurance

FIG. 10.65 Side view of the planar crystal of THF hydrate grown (a) with 0.5 wt% of high molecular weight PVP
in solution at 1 °C (supercooling of 3.4 K), and (b) with 0.1 wt% of high molecular weight PVP in solution at 3 °C
(supercooling of 1.4 K).

the hydrate melt the plate perimeters may no longer be {111}, but of a different crystallo-
graphic orientation. Why do the plate faces grow much more slowly than the perimeters,
when they all are {111}?
One hypothesis would appeal to stacking faults providing reentrant edges that encour-
age nucleation of new layers (Hamilton and Seidensticker, 1960; Wagner, 1960; van de Waal,
1996). Stacking faults on {111} are very likely in structure II hydrates, since in certain positions