Abstract
There are significant technical challenges to be addressed in the design of transportation pipelines for Carbon Capture and Storage (CCS) projects, not least of which is the management of non-carbon dioxide (CO2) components (impurities).
Typical impurities such as glycols (diethylene glycol (DEG) and triethylene glycol (TEG)), amines (ethanolamine (MEA), diethanolamine (DEA), methyl diethanolamine (MDEA)) and alcohols (methanol) could be potentially carried over during transient or upset operations from gas processing units to the CO2 pipelines. Furthermore, impurities (for example monoethylene glycol (MEG)) could remain in the system following pre-commissioning depending on the approach to pipeline dewatering and conditioning.
These chemical impurities, though in very low amounts, can trigger water dropout and lead to the presence of a free aqueous phase. CO2 and reactive components such as hydrogen sulphide (H2S), sulphur dioxide SO2, nitrogen dioxide (NO2) and oxygen (O2) can dissolve in free water and form stronger acids such as carbonic or sulphuric acids that can influence the operation and material integrity of CO2 pipelines. Particularly, the heavier corrosive acidic liquids can be stagnant at low points and increase the risk of localised corrosion.
This paper reviews the research that has been conducted to date on chemical carry-over, risks of acid formation and component solubility limits in CO2 streams. The research is applied to a practical example of a post-combustion CO2 gas gathering pipeline to demonstrate the importance of controlling minor impurities to a tight specification in the CO2-rich fluid.
