TOPIC 1: Gas Hydrates
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NIVERSITY B41OA December 2018 v3
Passing the water phase freezing point is the Water-Hydrate-Vapour (LW-H-V)
line – the intersection of this line with the vapour pressure line results in the
upper quadruple point (Q2) where Water-Hydrate-Vapour-Liquid
Hydrocarbon
(LW-H-V-LHC) are in equilibrium.
Finally, we have the three phase line of Water-Hydrate-Liquid Hydrocarbon
(LW-H-LHC). Some compounds present exception to the above general rule
(for example methane, where there is no intersection between the LW-H-V line
and the vapour pressure line).
Typical hydrate stability zones for a binary or
multi-component system are
presented in Figure 20. Also shown in the figure is a typical phase envelope
for binary or multicomponent system.
The hydrate phase boundary is essentially similar to that of pure compounds,
with the exception of the upper quadruple point. As shown in the figure 20, the
upper
quadruple point, where Water-Hydrate-Vapour-Liquid Hydrocarbon are
in equilibrium, is converted into a line (corresponding to the two phase region
inside the phase envelope).
Figure 20: Hydrate Stability Zone – Binary & Multicomponent Systems.
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