Densities of the carbon dioxide+hydrogen, a system of relevance to carbon capture and storage

The densities of the carbon dioxide (CO₂) and hydrogen (H₂) mixtures (xH2=0.020,0.075 and 0.100) have been determined at six temperatures from 288.15 to 333.15K and pressures up to 23.0MPa using a high-pressure vibrating-tube densitometer. The experimental temperatures and pressures cover a range of sub- and supercritical conditions, providing essential information for the optimum design and operation of compressors and pipeline networks in carbon capture and storage (CCS). It was found that a concentration of H₂ as low as 2% could lower the density by as much as 25% compared to pure CO₂. The data were used to calculate the excess molar volumes, showing highly non-ideal mixing behaviour of the binary system of CO₂+H₂. The new density data were also compared to those predicted using the GERG-2004 equation of state (Kunz, O. et al., 2007. The GERG-2004. Wide-range equation of state for natural gases and other mixtures, Düsseldorf). The deviations between the calculated and experimental data are 0.6%, 1.7% and 1.8%, respectively, for the mixtures with xH2=0.020,0.075 and 0.100. These results suggest that the GERG-2004 equation of state has the potential for accurate prediction of the volumetric property of CO₂ mixtures containing H₂ in the CCS processes, and further parameterisation of GERG-2004 or development of new equations of state specifically tailored for CCS mixtures is required.