Thermodynamic properties of a CO2 – rich mixture (CO2 + CH3OH) in conditions of interest for carbon dioxide capture and storage technology and other applications

• A thermodynamic study related to CCS technology and other applications is conducted for CO2 + (3%) CH3OH.
• Accurate experimental values for the speed of sound and density are presented.
• A calculation method for thermodynamic properties up to high pressures is applied.
• The calculation method is adapted for the first time to compressed gases.
• Both experimental and calculated values are compared with the PC-SAFT and GERG EoSs.

Methanol can be an impurity in transported and stored anthropogenic CO2 in carbon dioxide capture and storage technology; likewise, methanol is one of the most useful CO2 modifiers for supercritical processes. Therefore reliable values of thermodynamic properties of CO2 – rich mixtures CO2 + CH3OH are needed. We measured the following properties of a (CO2 + CH3OH) mixture with xCO2=0.9700xCO2=0.9700 in dense phase at six temperatures from 263.15 K to 313.15 K:
• The speed of sound, c, up to 194.49 MPa, using a double-path pulse-echo method at 5 MHz, for which a repeatability study gave an overall standard uncertainty of c, u(c) = 5.9 × 10−4c.
• The density, ρρ, at pressures ⩽20.00 MPa using a vibrating-tube densimeter with a standard uncertainty, u(ρ) = 0.4 kg/m−3.Combining our c   and ρρ experimental values and the isobaric specific heat capacity, cpcp, from the GERG equation of state (EoS), we calculated ρρ, cpcp, the volume-dependent solubility parameter, δVδV, and the Joule–Thomson coefficient, μJTμJT, at pressures ⩽195.0 MPa. We are the first to report the adaptation for compressed gases of a calculation method based on numerical integration previously used only for liquids. The experimental and calculated values were compared with those from the PC-SAFT and GERG EoSs, allowing us to validate both EoSs to represent the experimental properties of the system under most conditions studied and the calculation method up to 195.0 MPa.

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