Page 250 - Handbook Of Multiphase Flow Assurance

Hydrate stability and crystal growth 249

FIG. 10.19 Calculated and experimental data for pure xenon and for xenon + neohexane mixture above 273 K.
□—CSM data for pure xenon (1992), △—data by Aaldijk for xenon (1971), ⊙—CSM data for xenon+neohexane
(1992), - -, HYDR_88 program predicted data.

Evaluation of experimental results

Study of the phase transition possibility for methane hydrate at subzero temperatures was
investigated. Results of this study are summarized earlier in this chapter. It was shown that
in the temperature interval of 154–273 K no sI to sII structural transition of the hydrate hap-
pened. It is possible, however, that the structural transition may occur at temperatures below
154 K where no experimental data exist.
Experiments on xenon sI and xenon + neohexane sH hydrate equilibria resulted in a gen-
eration of two phase diagrams in the temperature region of 228–288 K. It was found from the
generated equilibrium curves that a quintuple point sH-sI-Lw-Lh-V point should be present
in the temperature interval of 278–283 K. This phase diagram does not violate the Gibbs's
phase rule.