Results from previous studies demonstrated that significant corrosion of carbon steel was observed when 1% SO2 impurity was contained in a supercritical CO2 phase in the presence of small amounts of water (650 ppm). Considering real situations for CO2 transportation pipelines, the effects of CO2 phase change, impurity concentration and flow were evaluated in the present study in order to establish a clearer understanding of the corrosion risk for such pipelines. Different CO2 phases (liquid and supercritical), concentrations of SO2 (<1%) and flow velocities were used in an autoclave based study. The corrosion rate of steel samples was determined by weight loss measurements. The surface morphology and the composition of the corrosion product layers were analyzed by using surface analytical techniques (SEM, EDS, and IFM). Results showed that the corrosion rate decreased with decreasing SO2 content in the supercritical CO2 phase containing 650 ppm of water. In addition, significant localized corrosion was observed when CO2 phase was liquid.

It has been acknowledged that green house gas (GHG) emissions due to human activities such as carbon dioxide (CO2), methane (CH4) and nitrous oxide N2O, are one of the principal reasons for climate change. Among them, CO2 has been given much attention because CO2 emissions from fossil fuel combustion have been increasing at an average annual rate of 0.4 percent from 1990 to 2009, representing 79 percent of the total emissions in 2009.1 Coal, natural gas and oil fired power plants are together the largest CO2 emitter. One way to reduce CO2 emissions to the atmosphere is through carbon capture and storage (CCS). Due to high pressures, the CO2 in these pipelines is typically in supercritical or liquid phase. Depending on the source and capture process, the CO2 can contain impurities.

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