Chemical Interactions and Corrosion in Impure CO2 Pipeline Transport

Abstract With the growing need for CCS (Carbon Capture and Storage) a range of new projects have been initiated to handle CO2 emissions from multiple industrial emitters (so called CCS Hub projects). The consequential mixed streams of CO2 will usually include a wide range of different impurities. A specific group of impurities (H2O, O2, SO2, H2S and NO2) have been identified as highly impactful on integrity due to potential formation of corrosive phases, requiring stringent control and limit setting. It is crucial to understand acid-formation, drop-out and corrosion to be able to control the integrity of the CO2 transport system. This paper summarizes the understanding of chemical interactions and corrosion. Chemical equilibrium calculations were deployed to review already published and some new test data. During testing a critical concentration of impurities could be identified by which acid formation and drop-out occurred. Deployment of chemical equilibration revealed worst-case compositions for acid drop-out below impurity upper limits, which are currently often used for limit setting in projects. The corrosion phenomena in impure CO2 streams are also reviewed and quantified to identify their potential impact. Based on chemical equilibration a worst-case for acid formation was tested, which confirmed new limits for acid formation and drop-out. Guidance for projects and suggestions for research are provided.