Testing of CO2 Specifications With Respect to Corrosion and Bulk Phase Reactions

Captured anthropogenic CO2 contains impurities that might react and form solids and separate corrosive phases when the impurity concentrations exceed the limit where the impurity combination becomes thermodynamically unstable. A number of tentative CO2 specifications and recommendations for the maximum acceptable impurity concentrations have been published. The recommendations include impurity combinations and impurity levels that are not found in the published CO2 specifications for pipelines that are or have been in operation. The lack of field experience and the lack of published lab data that support these specifications are a concern. The most referred recommendations have been challenged in the present work. Experiments were performed with dense phase CO2 containing 300 ppmv water, 350 ppmv O2, 100 ppmv SO2, 100 ppmv NO2 and 100 ppmv H2S. The CO2 and the impurities were continuously injected in the test autoclaves and the consumption rate of the impurities was measured. The experiments showed that the carbon steel corroded and that elemental sulfur formed together with a liquid phase containing sulfuric and nitric acid. The paper discusses the experimental technique and the results obtained in four autoclave experiments. The paper also discusses how the lack of fundamental data and understanding makes it difficult to predict corrosion rates and define a safe operation window for transport of dense phase CO2 originating from different sources with different contaminants.