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

Abstract

The solubility of water (H2O) in carbon dioxide (CO2) and nitrogen (N2) mixtures (xN2=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.