Kjeller Dense Phase CO₂ Corrosion III (KDC-III)

Background
The KDC-III project is a continuation of the previous KDC projects (I and II).
The main projective purpose is to create experimental data, knowledge and tools that can be used to set limits for impurities in CO₂ transportation systems. This will contribute to enhanced safety and reduced cost for CO₂ transportation.

Objective
The main objective was to establish knowledge base and tools that can be used to set safe operation windows for CO₂ transportation, such that corrosion and undesirable chemical reactions are avoided. Both pipeline transport and ship transport was studied.

Activities
A significant number of experiments with impurities in CO₂ has been carried out, both with and without corrosion coupons. Several new impurities, that had not been tested before, were included in the testing. The experiments were mostly carried out under simulated ship-transport condition (low pressure, low temperature) or pipeline conditions (high pressure).

The results from KDC (all phases) have been used to improve the thermodynamic software from OLI. The present version (OLI studio v11.5) can now be used to study chemical reactions in liquid and supercritical CO₂. Results from KDC-III were compared with calculations from OLI. Some areas where kinetical factors prevent full thermodynamic equilibrium were identified. This is useful knowledge for end-users that will apply such thermodynamic tools when working with real projects, for example when making a design basis or during operation of full scale transportation systems.

Achievement
KDC-III has provided extensive knowledge of corrosion and chemical reactions in CO₂ with low temperature (particularly relevant for ship transport). The project has demonstrated experimentally that the temperature has a significant effect on chemical reactions among impurities in the CO₂ phase. Therefore, a CO₂ specification that is valid for a given temperature (e.g +25) may not be valid for a lower temperature (e.g. -25°C that is typical for ship transport) Unfortunately, due to time constraints, it was not possible to establish a safe operation window for ship transport with five impurities (H2O, H2S, SO2, NO2 and O2). However, the present results indicate that the NO2 limit in the Northern Lights specification might have to be reduced for low temperatures.

KDC-III carried out experiments with “new” impurities that had not been tested before, e.g. NH3, CO, COS and acetaldehyde. It was demonstrated that there is high risk of forming solid ammonium carbamate if NH3 is present in the CO₂ stream. The concentration of NH3 that is needed to form carbamate varies with pressure and temperature, and the limit will be very low if a single limit is to be used.

Several publications have been made with KDC data:
• B. H. Morland, G. Svenningsen, “Pitfalls and artefacts in corrosion experiments with dense phase CO₂”, CORROSION/2021, paper no. 16667 (Houston, TX: NACE International, 2021).
• B. H. Morland, A. Dugstad, G. Svenningsen, Experimental based CO₂ transport specification ensuring material integrity, International Journal of Greenhouse Gas Control, 119, (2022) p. 103697.
• B. H. Morland, G. Svenningsen, A. Dugstad, The Challenge of Monitoring Impurity Content of CO₂ Streams, Processes, 9, 4 (2021) p. 570.
• B. H. Morland, G. Svenningsen, “Corrosion of carbon steel in simulated CCS streams”, 15th International Conference on Greenhouse Gas Control Technologies (GHGT-15) (2021).
• B. H. Morland, M. Tjelta, T. Norby, G. Svenningsen, Acid reactions in hub systems consisting of separate non-reactive CO₂ transport lines, International Journal of Greenhouse Gas Control, 87, (2019) pp. 246-255.

Most of these publications were based on KDC-II results, where the confidentiality period is over. More KDC-III data will be published in near future.

Future plans
IFE is currently working with establishing a fourth phase of KDC (KDC-IV). IFE have gotten good feedback from the present participants and most of them are interested in participating in the new phase. The KDC-III participants have mentioned several topics that should be studied in the next phase:
• Reactions and corrosion in gas phase CO₂
• Asymmetric impurity concentrations (one impurity significantly reduced while the other impurities are unchanged or even increased)
• Partitioning of impurities between gas and liquid phase CO₂
• Further improve the thermodynamic modelling (OLI)

IFE will continue to be an active participant on conferences and workshops. Data from KDC projects will be published in relevant channels (AMPP, GHGT).