Measured densities and derived thermodynamic properties of CO2-rich mixtures in gas, liquid and supercritical phases from 273 K to 423 K and pressures up to 126 MPa

The densities of three multi-component mixtures with high CO2 content and common impurities, i.e. hydrocarbons, nitrogen, hydrogen, oxygen, argon and carbon monoxide, were measured using an Anton Paar DMA-HPM densitometer. The mixtures include MIX 1 with 0.9564 mole fraction CO2 and 0.0436 mole fraction impurities of methane and non-condensable gases, MIX 2 with 0.8983 mole fraction CO2 and 0.1017 mole fraction impurity of non-condensable gases and MIX 3 with 0.6999 mole fraction of CO2 and 0.3001 mole fraction of light hydrocarbons. First, the densitometer was calibrated using pure CO2 and then the density measurements of mixtures were carried out in the gas, liquid and supercritical phases at pressures up to 126 MPa at various isotherms of T/K = 273, 283, 298, 323, 373 and 423. The obtained data then were employed to evaluate the classical cubic equations of state (SRK and PR). In addition, the CO2 volume correction term and the Peneloux shift parameter were introduced to improve density predictions. Comparisons show that applying CO2 volume correction term to SRK EoS with modified kij could improve the density predictions and the AAD was reduced from 4.7% to 1.9%. In addition to the classical cubic equations of state, the new measured data were used to evaluate the GERG EoS. The AAD of the GERG EoS from experimental data measured in this work are 2.8%, 1.0% and 1.2% in the gas, liquid and supercritical phases, respectively. The overall AAD of GERG EoS from the new density data in this work is 1.7%. Thermodynamic properties, i.e. compressibility factor, specific heat capacity, speed of sound and Joule-Thomson coefficient, were then calculated from the experimental density data using thermodynamic equations. Following this the derived properties were compared to the predictions made with the GERG equation of state.