Influence of SO2 on CO2 storage for CCS technology: Evaluation of CO2/SO2 co-capture

In this work, we determined the influence of SO2 as an impurity in anthropogenic CO2 on carbon capture and storage (CCS) technology. We evaluated the impact on selected injection and storage parameters and the Joule Thomson coefficient to assess the safety of long-term geological storage of CO2. For this purpose, we obtained new pressure-density-temperature-composition, vapor-liquid-equilibrium, and pressure-speed of sound-temperature-composition experimental data for CO2-rich mixtures containing SO2. To increase the general understanding of the impact of SO2, the compositions cover possible co-capture mixtures, SO2-enriched mixtures, and mixtures similar to industrial emissions. Temperatures and pressures were based on relevant geological storage site values. Our experimental results were used to validate the EOS-CG and PC-SAFT equations of state (EoSs) for CO2 + SO2 under the studied CCS conditions. On the understanding that the chemical reactivity effects due to SO2 have not been considered, we concluded that the presence of SO2 is profitable in most of the studied aspects, especially in the case of shallow reservoirs, and that CO2/SO2 co-capture may be considered as an alternative approach to reduce the costs of CO2 purification. Based on the assessment of the impact of 5 mol% SO2 in the injected fluid in seven saline aquifers, we determined that the reservoirs that would receive the most benefit were Sleipner, Nagaoka and Frio.