Impact of CO2 Impurities on Pipeline Corrosion. Experimental Evaluation of Reaction Kinetics

Abstract Despite the vast research being carried out, no consensus exists regarding impurity limits to prevent the formation of a corrosive phase (e.g., water, acid, solids) in pipelines transporting CO2, mainly if commingled from different sources. Due to the complex and still not well understood interactions among different impurities that may be present in the transported stream, each CO2 pipeline is currently developing its own specification and conducting experimental validation in the laboratory. An experimental set up was designed and commissioned to assess the impact of CO2 impurities on reaction kinetics, second phase (acid or solid) drop out and carbon steel corrosion. The system is capable of continuously replenishing the concentration of commonly evaluated CO2 impurities (e.g., H2O, NO2, SO2, H2S, O2) as well as other water-soluble components (e.g., glycol, amine, ammonia). This paper presents test results conducted at 25°C under a total pressure of 100 bar. The occurrence of a second phase (i.e., acid, water dropout, solid precipitation) or initiation of carbon steel corrosion was determined through visual observation and subsequent coupon analyses. Reaction kinetics were evaluated by analyzing concentration transients following controlled adjustments in the concentrations of individual components.