Solubility of Water in CO2 Mixtures at Pipeline Operation Conditions

Carbon capture, transport and underground storage have become a major solution to reduce CO₂ emissions from power plants and other large CO₂ sources. A big part of this captured CO₂ stream is transported at high pressure dense phase conditions and stored in offshore underground depleted oil and gas fields. CO₂ is also transported in offshore pipelines to be used for enhanced oil and gas recovery. The captured CO₂ stream with impurities may contain water that causes severe corrosion problems, flow assurance failure and might damage valves and instrumentations. Thus, free water formation should be strictly prevented. The purpose of this work is to study the solubility of water in pure CO₂ and in CO₂ mixtures under real pipeline pressure (90-150 bar) and temperature operation conditions (5-35°C). A set up was constructed to generate experimental data. The results show the solubility of water in CO₂ mixtures increasing with the increase of the temperature or/and with the increase in pressure. A drop in water solubility in CO₂ is observed in the presence of impurities. The data generated were then used to assess the capabilities of two mixture models: the GERG-2008 model and the EOS-CG model. By generating the solubility data, this study contributes to determine the maximum allowable water content in CO₂ pipelines.

• Mohammad Ahmad
• Sander Gersen
• Erwin Wilbers

• Carbon capture and storage
• water solubility
• equation of states.

[1] H. Van Dijk. Edgar CO2 purity: types and quantities of impurities related to CO2 point source and capture technology. ECN report: ECN-E-12-054, 2012.
[2] A. Chapoy, R.Burgass, B. Tohidi, J.M. Austell and C. Eickhoff C. Effect of Common Impurities on the Phase Behavior of Carbon-Dioxide-Rich Systems: Minimizing the Risk of Hydrate Formation and Two-Phase Flow. SPE Journal. Volume 16, Number 4, 2011.
[3] E. Goos, U. Riedel, L. Zhao and L. Blum. Phase diagrams of CO2 and CO2- N2 gas mixtures and their application in compression processes. Energy Procedia 4, 3778-3785, 10th International Conference on Greenhouse Gas Control Technologies, 2011.
[4] M. Seiersten, Material selection for separation, transportation and disposal of CO2, Proceedings Corrosion, National Association of Corrosion Engineers, paper 01042, 2001.
[5] E. De Visser, C. Hendriks, M. Barrio, M. Molnvik, G. de Koeijer, S. LiljemarkandY. Le Gallo. DynamisCO2 quality recommendations”, International Journal of Greenhouse Gas Control 2, 478 – 484, 2008.
[6] M. Mohitpour, H. Golshan and A. Murray. Pipeline Design & Construction, A practical approach, The American Society of Mechanical Engineers, Three Park Avenue, New York, United States, 2003.
[7] P. Odru, P. Broutin, A. Fradet, S. Saysset, J. RuerandL. Girod. Technical and economic assessment of CO2 transportation, Institute France Petrole, GHGT-8, Trondheim, 2006.
[8] A. Austegard and M. Barrio. Project Internal Memo DYNAMIS: Inert components, solubility of water in CO2 and mixtures of CO2 and CO2 hydrates, 2006.
[9] A. Austegard, E. Solbraa, G. de Koeijer G and M.J. Mølnvik. Thermodynamic Models for Calculating Mutual Solubilities in H2O-CO2-CH4 mixtures. Chemical Engineering Research and Design (ChERD), Part A, 2005. Special issue: Carbon Capture and Storage, V 84, A9, pp. 781-794, 2006.
[10] O. Kunz, and W. Wagner.The GERG-2008 Wide-Range Equation of State for Natural Gases and Other Mixtures: An Expansion of GERG-2004. Journal Chem. Eng. Data 57, 3032–3091, 2012.
[11] J. Gernert. A New Helmholtz Energy Model for Humid Gases and CCS mixtures, Dissertation, Ruhr-Universität Bochum, 2013.