Modeling of thermodynamic derivative and transport properties of CO2 mixtures for pipeline transportation
Authors: Diamantonis Nikolaos 
Published: November 2013

Introduction Carbon Capture and Sequestration (CCS) is one of the most promising technologies for the reduction of CO2 accumulation in the atmosphere. Continuous research on the topic develops methods for utilising the captured CO2 for enhanced oil and gas recovery (EOR and EGR). Through the research in this field, challenges that regard the mitigation of environmental pollutants such as CO2, as well as the increase of efficiency of oil and gas production processes can be addressed. Quite an important role in the design of these processes, and especially for the transport of CO2 streams via pipelines, is held by the thermodynamic modeling of pure CO2 and CO2 mixtures. The stream in the pipeline contains mainly CO2, together with many other gases, depending on the source of the stream, and the capture technology that precedes the transport. Typical impurities include CH4, N2, O2, SO2, Ar, and H2S, all of which can have a substantial impact on the thermodynamic behavior of the stream, both in the pipeline and out of it, in the unwanted event of a fracture. Methodology In this work, cubic and SAFT-based equations of state are used in combination with specific models for the calculation of phase equilibria, derivative thermodynamic properties and transport properties of CO2 mixtures. Their performance is evaluated against available experimental data from the literature. Especially for transport properties, established viscosity models from the literature based on friction theory, are combined with the above mentioned equations, in order to assess their ability of predicting viscosity of CO2 mixtures of interest to the CCS and EOR processes. Diffusivity and thermal conductivity are also investigated with the use of models combined with a range of equations of state, towards a unified approach of the thermodynamic properties prediction for CO2 containing systems. Conclusion In most cases, the higher order EoS are more accurate than the cubic EoS in the case of predictive calculations (no binary parameters used) of phase equilibria. Nevertheless, the two classes of EoS provide similarly good results when using a temperature independent binary interaction parameter. Derivative properties are more accurately captured by the SAFT family EoS, due to the higher physical content that they have over the cubic EoS. The pure components viscosity calculations with the different types of EoS compared in this study do not exhibit great deviations, owing that to the fitting procedure that was necessary for each EoS. On a related note, the need for more experimental data of derivative and transport properties of CO2 mixtures at conditions that cover the design and operation of CO2 pipelines becomes obvious. Acknowledgment The authors acknowledge financial support from the 7th European Commission Framework Program for Research and Technological Development for the projects "Quantitative failure consequence hazard assessment for next generation CO2 pipelines" (CO2PipeHaz, Project No.: 241346) and "Techno-economic Assessment of CO2 Quality Effect on Capture, Transport and Storage" (CO2Quest, Project No.: 309102).