Determination of maximum allowable water content for CO₂ pipelines

Abstract

The design consideration for carbon dioxide (CO₂) transportation via pipeline from different emitters necessitates the need to develop a CO₂ fluid specification at pipeline entry with defined impurity bands, particularly concerning the water (H₂O) content. The presence of CO₂ can lead to corrosion in carbon steel pipelines. Under-saturated water can also cause pitting corrosion when CO₂ interacts with acid-forming impurities. A logic chart that considers CO₂ rich mixture fluid components, operating scenarios and water conditions is developed to aid in determining the maximum allowable water content. Fluid components such as triethylene glycol (TEG), even in trace amounts, should not be overlooked as it can decrease the water solubility of CO₂ and increase corrosivity in the material. A fine balance should be made when setting the water content specification at pipeline entry as this can influence the choice of the dehydration technology and indirectly affect project economics.