Phase equilibria of carbon dioxide and methane gas-hydrates predicted with the modified analytical S-L-V equation of state

Václav Vinš¹, Andreas Jäger², Jan Hrubý¹ and Roland Span²

¹ Institute of Thermomechanics AS CR, v. v. i., Dolejškova 1402/5, 182 00 Prague 8, Czech Republic
vins.vaclav@seznam.cz, hruby@it.cas.cz
² Institute for Thermodynamics, Ruhr-Universität Bochum, Universitätsstr. 150, 44780 Bochum, Germany
a.jaeger@thermo.ruhr-uni-bochum.de, roland.span@thermo.rub.de

Published online: 16 April 2012

Abstract

Gas-hydrates (clathrates) are non-stoichiometric crystallized solutions of gas molecules in the metastable water lattice. Two or more components are associated without ordinary chemical union but through complete enclosure of gas molecules in a framework of water molecules linked together by hydrogen bonds. The clathrates are important in the following applications: the pipeline blockage in natural gas industry, potential energy source in the form of natural hydrates present in ocean bottom, and the CO₂ separation and storage. In this study, we have modified an analytical solid-liquid-vapor equation of state (EoS) [A. Yokozeki, Fluid Phase Equil. 222–223 (2004)] to improve its ability for modeling the phase equilibria of clathrates. The EoS can predict the formation conditions for CO₂- and CH₄-hydrates. It will be used as an initial estimate for a more complicated hydrate model based on the fundamental EoSs for fluid phases.