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Equations of state (EoS) are essential in the modeling of a wide range of industrial and natural processes. Desired qualities of EoS are accuracy, consistency, computational speed, robustness, and predictive ability outside of the domain where they have been fitted. In this work, we review present challenges associated with established models, and give suggestions on how to overcome them in the future. The most accurate EoS available, multiparameter EoS, have a second artificial Maxwell loop in the two-phase region that gives problems in phase-equilibrium calculations and excludes them from important applications such as treatment of interfacial phenomena with mass-based density functional theory. Suggestions are provided on how this can be improved. Cubic EoS are among the most computationally efficient EoS, but they often lack sufficient accuracy. We show that extended corresponding state EoS are capable of providing significantly more accurate single-phase predictions than cubic EoS with only a doubling of the computational time. In comparison, the computational time of multiparameter EoS can be orders of magnitude larger. For mixtures in the two-phase region, however, the accuracy of extended corresponding state EoS has a large potential for improvement. The molecular-based SAFT family of EoS is preferred when predictive ability is important, for example, for systems with strongly associating fluids or polymers where few experimental data are available. We discuss some of their benefits and present challenges. A discussion is presented on why predictive thermodynamic models for reactive mixtures such as CO2–NH3 and CO2–H2O–H2S must be developed in close combination with phase- and reaction equilibrium theory, regardless of the choice of EoS. After overcoming present challenges, a next-generation thermodynamic modeling framework holds the potential to improve the accuracy and predictive ability in a wide range of applications such as process optimization, computational fluid dynamics, treatment of interfacial phenomena, and processes with reactive mixtures.

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This study analyses the effect of transporting 13.1 MTPA CO 2 with impurities over a distance of 500 km on the operating and investment costs. In the cases study, two different impurity levels coming as a result of gas sweetening (GAS) and from capture from oxy-fuel combustion (OXY). The analysis includes the cost for the conditioning and the compression of the CO 2 stream after capture, from atmospheric conditions to transport conditions in the dense phase. In the calculation of the operating cost in terms of compression power and cooling requirements, the effect of the impurities are taken into account by using real thermo-physical properties depending of local fluid temperature and pressure and including heat transfer with the surroundings. The analysis investigates the total cost of choosing different pipeline diameters for transporting CO 2. The technical analysis shows that the number of required booster stations increases from 2 to 17 going from a 28" to an 18" pipeline and from 3 to 25 in the worst case with (GAS). In the second technical comparison, the feed flow rate for the CO 2 mixtures has been reduced so that the installed compression power for transport will be equal for all three cases. In this analysis a 24" pipeline with 4 booster stations was used. The techno-economic assessments show a significant impact of the impurity cases considered on the CO 2 conditioning and transport design and cost. Indeed, in the Oxy-feed and Gas-feed cases, the specific conditioning and transport costs are respectively 13 and 22% higher than in the Base-feed case for the cost-optimal diameter. In absolute value, this represents a direct increase of the specific conditioning and transport cost of 2.3 and 3.8 €/t CO2,avoided . Even if the cost evaluation leads to the same cost optimal diameter for the three impurity cases considered, it is important to note that this result is specific to the transport system considered in this paper and that in principle different impurity cases can lead to different cost-optimal diameters especially for low pipeline diameters. The impact of impurities on an existing pipeline infrastructure design not taking into account these potential impurities show an even stronger cost impact. Indeed, the cost evaluations shows that the specific cost of the Oxy-feed and Gas-feed cases can be expected to be respectively at least around 20 and 40% more expensive than in the Base-feed case due to the lower amounts of CO 2 transported and the important cost-penalty associated with the CO 2 emissions not transported. Finally, while the cost presented here considered only the impact of impurities on the conditioning and transport cost, impurities can also be expected to have a significant impact on the technical and economic performances of the whole CCS chain. This therefore highlights the importance of evaluating, on a case-to-case basis, the tradeoffs between impact of impurities on the CCS cost and cost of impurities removal in order to provide recommendations on cost-optimal level of imp...