Understanding the solubility of water in carbon capture and storage mixtures: An FTIR spectroscopic study of H₂O+CO₂+N₂ ternary mixtures

The solubility of water (H₂O) in carbon dioxide (CO₂) and nitrogen (N₂) mixtures (x_N2=0.050 and 0.100, mole fraction) has been investigated at 25 and 40°C in the pressure range between 8 and 18MPa. The motivation for this work is to aid the understanding of water solubility in complex CO₂-based mixtures, which is required for the safety of anthropogenic CO₂ transport via pipeline for carbon capture and storage (CCS) technology. The measurements have been performed using an FTIR spectroscopic approach and demonstrate that this method is a suitable technique to determine the concentration of water in both pure CO₂ and CO₂+N₂ mixtures. The presence of N₂ lowers the mole concentration of water in CO₂ by up to 42% for a given pressure in the studied conditions and this represents important data for the development of pipelines for CCS. This work also provides preliminary indications that the key parameters for the solubility of H₂O in such CO₂+N₂ mixtures are the temperature and the overall density of the fluid mixture and not solely the given pressure of the CCS mixture. This could have implications for understanding the parameters required to be monitored during the safer transportation of CO₂ mixtures in CCS pipelines.