Assessment of CO2 Specifications- when are they Safe?

Reasonably clean and dry CO2 has been safely transported in pipelines and used for enhanced oil recovery for decades. The primary impurities associated with corrosion and corrosive phases have been H2O, H2S, and in some cases also O2. When CO2 is captured from power plants and other anthropogenic sources (steel and cement production, waste incineration, etc.), new combinations of impurities like H2S, H2O, NOx, SOx, O2 and NH3, can be present. These impurities can react chemically at very low concentrations (less than 20 ppm-mol) leading to the formation of elemental sulfur, ammonium-based compounds, and acids (H2SO4 and HNO3. According to ISO standard 2913, one of the requirements for establishing a CO2 specification is that no corrosive phase should form. However, current standards and recommended practices lack specific specifications due to insufficient experimental data. The consequence is that the CO2 specifications used in ongoing projects and project development have very low limits of O2, H2S, NOx and SOx. The paper discusses the criteria and challenges related to the development of CO2 specifications, i.e. when are corrosive phases formed and when can the concentration of one impurity be increased if the concentration of another impurity is reduced.