Effect of impurities in captured CO2 on liquid–vapor equilibrium

• The impact of impurities on the phase diagram of CO2 was studied and the capabilities of three mixture models were assessed.
• An expansion in the phase transition envelope was observed in all mixtures compared to pure CO2.
• The phase transition zone for CO2-impurities mixtures is located at higher pressures in comparison with pure CO2.
• Looking to the models predictions, simulation deviations were observed close to the critical point.
• Transporting liquid CO2 in pipelines with the presence of impurities requires higher pipeline pressure.

The capture of large amounts of CO2 from power plants and other large CO2 point sources has become relevant within the concept to mitigate CO2 emissions via carbon capture and storage. The objective of this study was to investigate the impact of some major impurities found in the CO2 stream captured from power plants and other large point sources on the liquid–vapor phase change compared to pure CO2. The study contributes to a better understanding of how and within which boundary conditions transmission of impure CO2 from an emission and capture point to a storage location can be realized.A set up was constructed to provide the experimental data needed to trace the phase diagrams of the CO2-impurities mixtures. The data show an expansion of the liquid–vapor phase envelope and a start of boiling (in liquid) or condensation (in vapor) at relatively higher pressures. The experimental data were later used to assess the capabilities of three mixture models: the Soave–Redlich–Kwong cubic equation of state, the GERG-2008 model, and the EOS-CG model.