Solid-Liquid-Vapor Phases of Water and Water-Carbon Dioxide

0,29

MB

Mixtures Using a Simple Analytical Equation of State

33

stron

2395

ID

DuPont Fluoroproducts Laboratory

2003

rok

ABSTRACT

Recently we have proposed a unified analytical equation of state (EOS) for solid-liquid-vapor

phases, and successfully applied the EOS for the solid-liquid-vapor states of pure substances, as

well as binary mixtures. The present study is an extension of the earlier EOS work to water and its

binary mixtures with carbon dioxide. It is found that the our proposed EOS can describe reasonably

well the thermodynamic properties of water (having unordinary melting/freezing behaviors) around

the triple point, although to set up the EOS parameters requires a special procedure different from

the ordinary compounds like CO2. A simplified version of EOS for water has also been developed

by sacrificing accuracy in some of the water properties, in order to model water-containing

mixtures.

Using such a simplified EOS of water, we examine the feasibility of phase behavior prediction

including the solid (clathrate hydrate) state for binary mixtures of water and CO2. All important

three-phase (triple-point) equilibrium lines (vapor-liquid-liquid, solid-liquid-liquid, solid-liquid-vapor

equilibria) are fairly well predicted, using only the information of vapor-liquid equilibrium data and the

quadruple points. Results are still tentative but are encouraging for further improvement. This is a

completely new way to model the clathrate-forming system.