Carbon capture, utilization, and storage is expected to be an important method for reducing CO2 emissions to prevent global warming. Several species (impurities) could follow the CO2 through the capture plant as carry over. It is expected that nitrogen dioxide (NO2), sulfur dioxide (SO2), oxygen (O2), and water (H2O) can be present as impurities (concentrations at the ppmv level) in the captured CO2. The exact composition will depend on the flue gas type, the CO2 capturing process, and multiple other parameters. Some of these impurities are reactive and may cause corrosion in carbon steel pipelines and could therefore be a threat for safe CO2 transport. The present study used a novel experimental setup to realistically simulate a CO2 transport pipeline system with a controlled and variable concentration of impurities at a total pressure of 10 MPa and a temperature of 25°C. The water concentration was increased and decreased with constant concentration of SO2 and O2, to observe and identify possible reactions or threshold levels which could cause corrosion. A similar experiment was conducted with NO2. First, experiments were performed without steel coupons, to observe uncatalyzed reactions, and then with coupons to measure corrosion rates. The first sign of corrosion appeared at 350 ppmv of water with NO2 present. At 670 ppmv water with 75 ppmv NO2 the overall corrosion rate was about 0.57 mm/y and the main product was iron oxide. The corrosion process for SO2, O2, and water was much slower, and the first sign of corrosion appeared around 1,900 ppmv of water, with about 75 ppmv of SO2 and 230 ppmv of O2. The corrosion rate increased some when the water concentration was increased to 2,400 ppmv, but the overall corrosion rate was only 3.6 μm/y and the main product on the surface was iron sulfate.

Carbon capture and storage has gained increased attention during the last decade, and several full-scale projects are currently being planned. From economic and public acceptance point of view it is important to ensure that the transportation system is operated in a safe manner, avoiding threats such as corrosion or formation of solid matters. Thus, routine chemical analyses are required to ensure that the CO₂ stream complies with the required specifications. The CO₂ will usually be transported in the liquid or supercritical state (high pressure), which makes the practicalities around chemical analyses difficult. Phase transition from liquid or supercritical state to gaseous state may also introduce several physiochemical effects that may affect the analyses. This paper discusses technical and practical challenges with CO₂ stream analyses experienced in a joint industry project that studied corrosion and chemical reactions in a simulated CO₂ transport system.