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   0.100xH2=0.020,0.075   and   0.100) have been determined at six temperatures from 288.15 to 333.15 K and pressures up to 23.0 MPa 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   0.100xH2=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.

► New density measurements of CO2 + H2 mixtures for CCS processes.
► Huge differences in density with low H2 (2%) content compared to pure CO2.
► Important new data for comparison and development of equations of state.