Vol 2 Chapter 15: CO2 Conditioning and Transportation
Geir Heggum, Torleif Weydahl, Roald Mo, Mona Mølnvik and Anders Austegaard
Abstract: The aim of the CO2 Conditioning and Pipeline Transportation project is to advance the development of cost effective and safe methods for CO2 compression and pipeline transportation. Optimized design for the compression process and pipeline system requires accurate and reliable predictions of fluid properties, particularly density and water solubility. Existing CO2 pipeline transportation systems (onshore USA and Canada; offshore Norway) are reviewed in terms of operational parameters, particularly drying specifications. Based on calculations of water solubility for a selected case, it is found that the most stringent drying requirements (e.g. 50 ppm proposed for Hammerfest LNG) may be relaxed to ,600 ppm (present USA Kinder Morgan specification). Today there is little experience with subsea pipelines for CO2 transportation, particularly in deep waters and over long distances. The intension of this study is to build up confidence in the technology and save costs for future projects. Thermodynamic models and tools for calculating properties for CO2 and CO2-rich mixtures have been verified against experimental data. For CO2 density the Lee–Kesler model is in satisfactory agreement with National Institute of Standards and Technology (NIST) data both in gas and liquid phase. For solubility of water in pure CO2, the Soave–Redlich–Kwong equation of state with adjusted binary coefficient to 0.193 in van der Waals mixing rule can be applied, and gives a good approximation to the data collected from literature. Adding impurities as CH4, N2, H2S and amines to the CO2 mixture will affect the solubility of water, e.g. adding 5% methane lowers the water solubility in the liquid phase considerably. However, very little experimental data on water solubility in these mixtures is available in the literature. In order to inhibit hydrate formation and prevent excessive corrosion rates for carbon steel, no free water should be allowed in the pipeline. Thus, water removal is usually required upstream of the pipeline inlet. For a typical case, theoretical calculations show that the limit for free water precipitation at supercritical conditions in the pipeline averages ,1300 ppm. This suggests that water content requirements might be relaxed and opportunities for alternative, more cost-effective water removal solutions are provided.
Carbon Dioxide Capture for Storage in Deep Geologic Formations – Results from the CO2 Capture
Project Geologic Storage of Carbon Dioxide with Monitoring and Verification - Volume 2
Edited by: Sally M. Benson, Lawrence Berkeley Laboratory, Berkeley, CA, USA
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