Experimental Data Assessment Test for Composition of Vapor Phase in Equilibrium with Gas Hydrate and Liquid Water for Carbon Dioxide + Methane or Nitrogen + Water System

Accurate knowledge of the compositions of the equilibrium
phases
in the systems containing gas hydrates is essential for many hydrate-based
separation processes. Unfortunately, there are limited sets of such
experimental data available in the literature partly due to the difficulties
in measurements of the compositions of the phases in equilibrium with
gas hydrate. Consequently, satisfactory accuracy of the measurements
may not be obvious. Therefore, reliability of the corresponding data
should be checked prior to their further applications. In this article,
we present a thermodynamic assessment test (consistency test) based
on the area test approach for the experimental compositional data
of vapor phase in equilibrium with gas hydrate + liquid water for
the carbon dioxide + methane or nitrogen + water system. The van der
Waals and Platteeuw (vdW-P) solid solution theory is used to model
the hydrate phase, and the Valderrama–Patel–Teja equation
of state (VPT-EoS) along with the nondensity dependent (NDD) mixing
rule is applied to deal with the fluid phases. The results show that
only one of the studied experimental data sets seems to be thermodynamically
consistent, and the rest of the data seem to be either not fully consistent
or inconsistent.