Diffusion coefficients of CO2–SO2–water and CO2–N2–water systems and their impact on the CO2 sequestration process: Molecular dynamics and dissolution process simulations

The high cost of the CO2 sequestration in saline aquifers is a barrier to the implementation of them. However, a large portion of the cost is invested to purify and transport the CO2 from the flue gas stream of the emission sources. Therefore, the possibility of injecting impure CO2 will reduce the costs strongly. The diffusion coefficient is an important factor that plays a significant role in different aspects of the process. In spite of its importance, it is got less attention due to complex experimental procedures and low range of temperature and pressure applicability in the experimental conditions. To shed light on the effects of the impurity on the diffusion coefficient of CO2‐water systems, two types of impurities (SO2 and N2) in two levels are considered in this study through the molecular dynamics simulation approach. Simulations are done on a wide range of pressure and temperature conditions to cover a wide range of operational conditions for CO2 sequestration projects. The outcomes of these simulations were used in the direct numerical simulations to analyze the effect of the diffusion coefficient matrix changes on the CO2 dissolution process such as dissolution flux, the motion and shape of convective fingers, and their patterns. Results indicate that impurity has a great impact on the diffusion coefficient, and consequently on the CO2 dissolution behavior. We hope that reported results will pave the way for future studies regarding impure CO2 sequestration in saline aquifers. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd.