The influence of impurities on the transportation safety of an anthropogenic CO2 pipeline

Transportation safety is a key aspect of carbon capture and storage (CCS), which is a major technology used to reduce greenhouse gas emissions. Supercritical CO2 pipelines have been certified as an optimised choice for CO2 transportation. The results of this study show that the Peng–Robinson (PR) equation of state is recommended for analysis of the properties of supercritical CO2. The influence of nonpolar and polar impurities on the two-phase region and the location of the sharp discontinuity in the density are found by analysing the ternary phase equilibrium and physical parameters using the PR equation of state. A transitional area between the supercritical phase and the dense phase, where the density changes abruptly, is defined as the quasi-critical region. This study describes the functional relation between the temperature and the pressure that defines the quasi-critical line by calculating the partial derivative equations and then determines the effect of impurities on the quasi-critical region of transported CO2. Operational recommendations for pipeline transportation of flue CO2 are developed using a pipeline operated by Sinopec as an example, demonstrating the influence of impurities in flue CO2 on saturation pressure for control and prevention of fractures in CO2 pipelines.