Fiscal metering and thermodynamics (Task 8)

Accurate thermophysical properties are needed for optimized design and operation of virtually all processes involved in CCS. This task aims to provide improved experimental data and models on properties of CO2-rich fluids relevant for CCS, and facilitate fiscal metering of the same fluids.

This task aims to provide improved experimental data and models on properties of CO2-rich fluids relevant for CCS, and facilitate fiscal metering of the same fluids.

Thermophysical properties

Vast amounts of CO2-rich fluids will have to be captured, transported, and stored if the goals of global warming mitigation are to be reached. Read more on this from IEA. Hence in order to avoid large excess costs, design and operations of all CCS systems have to be optimized, which again requires accurate data and models on the fluids involved exists.

For instance, it must be known whether the fluid is liquid, gas, or both. Properties like density, thermal conductivity, and viscosity, on which flow resistance depends, are important as well. In this task, we will measure and model these properties to great accuracy, filling important knowledge gaps.

Benefits of improved thermophysical property knowledge:
Accurate thermophysical properties are needed for optimized design and operation of virtually all processes involved in CCS e.g.:

  • Deployment Case 1: Optimization of liquefaction and ship transport requires accurate knowledge of VLE , freeze out (VLSE), and heat transfer (viscosity and thermal conductivity) (For more information on liquefaction see Task 4)
  • Deployment Case 2: Accurate properties are needed for fiscal metering.

See the page for Deployment Cases.

Fiscal metering

Fiscal metering is measurement of flow rate for legal or commercial purposes. For CCS in Europe, the ETS directive provides some legal requirements for mass flow measurements that have to be fulfilled in order to avoid purchasing Emission Unit Allowances for the stored CO2. Commercial transactions may have other requirements. Conventional flow metering techniques are not necessarily applicable to CO2-rich fluids for various reasons, and demonstration and verification lack at industrial relevant scale. In Task 8, the aim is to evaluate, develop and benchmark relevant fiscal flow metering concepts, and close knowledge gaps through experiments and modelling.

Results 2020

Fiscal metering

The properties of CO2 under transport are pressurized liquids, which set them apart from fluids like natural gas and water, in that small changes in composition, temperature, or pressure could lead to large changes in properties. In addition, CO2 also has large sound attenuation. There is hence a need for a facility to test flow meter technologies under realistic conditions, which also could enable calibration and hence traceability of fiscal flow meters. In 2020, Task 8 has this contributed to a design basis for a fiscal metering test loop for CO2, prepared for industrially relevant flow rates. This work will be the basis for developing a business plan for such a flow loop in 2021.

In addition, the industrially relevant technologies for density measurements associated with flow measurements have been evaluated. Density of the fluid transported is needed for fiscal metering for all flow meter technologies that do not measure the mass flow directly.

In 2020, Baker Hughes joined NCCS as a partner and as an active participant in Task 8. KROHNE has been an active partner in task 8 from the beginning of NCCS. The active participation of these leading flow meter suppliers, as well as experts from the end-user associated with e.g. Northern Lights, is indispensable.

Measurement of fluid properties

There are very little data available on viscosity and thermal conductivity for CCS relevant mixtures, especially in the liquid phase. Hence, estimates on laminar flow, e.g. in reservoirs, or heat transfer, in CCS processes are very crude. To alleviate this situation, both thermal conductivity of liquid CO2 mixed with nitrogen and methane, as well as viscosity of gaseous and supercritical CO2 mixed with hydrogen have been measured in the ImpreCCS project. In 2021, it is the aim to proceed with measurements of viscosity using a new ECCSEL facility of SINTEF Energy Research

Further, phase equilibria have been measured for the binary system of CO2+SO2 in Task 8. Although SO2 is an important impurity from many processes producing CO2, most of the data on this binary system are more than 100 years old with low accuracy.

The measurements of thermal conductivity at University of Western Australia, viscosity at Ruhr-Universität Bochum (RUB), and phase equilibria at SINTEF Energy Research have all been enabled through international collaboration and exchange of personnel within NCCS. 

Thermodynamic Modeling

Task 8 partner RUB has over the last decade developed a reference equation of state, EOS-CG. It is available through the thermodynamic tool TREND, but its routines are also expected to be used ahead in the thermodynamics of commercial process simulation tools, making it possible to improve the accuracy of their predictions. EOS-CG is continuously developed by adding new components and improving existing models. In 2020, ammonia was added to EOS-CG. Some of the components that so far have not been included in EOS-CG will react chemically with other components, greatly affecting the thermodynamic properties. Hence, a framework has been made for including reactive mixtures in EOS-CG, which will be demonstrated for mixtures of CO2 and the solvent MEA in 2021.

Measurements of phase equilibria using the ECCSEL CO2Mix facility of SINTEF Energy Research
Measurements of phase equilibria using the ECCSEL CO2Mix facility of SINTEF Energy Research

Impact and innovations

  • A new release of the thermodynamic tool TREND with the latest models has been made available for the partners of NCCS. The models are expected to find their way into leading commercial process simulators.
  • Two new facilities for accurate measurements of viscosity, density, and high pressure and complex phase equilibria with many innovative solutions have been developed.
  • A design basis for a test loop for fiscal metering has been completed. The test loop includes innovative processes, and realized, it will enable testing and calibration of fiscal flow meters needed to avoid the purchase of emission allowances as well as custody transfer between actors in a CCS network. Both applications are very important for large-scale deployment of CCS.

Main results 2019

The ImpreCCS KPN project, financed by CLIMIT R&D and the NCCS industry partners, is administered under Task 8. The objectives of ImpreCCS are to produce data on viscosity, density, and thermal conductivity and develop property models which will be applied in reservoir modelling. In addition to the NCCS consortium, NORCE is a research partner in ImpreCCS, and property models are developed in collaboration with NIST, USA.

Measurements of fluid properties and verification and development of thermodynamic models

Equations of state (EOS), used in e.g. all process engineering tools, are normally fitted to experimental data of only binary mixtures. As real-life fluids have multiple components, there is hence a need to verify EOS'es with more complex mixtures at relevant conditions. In CCS, low temperatures are encountered in CO2 liquefaction, separation, shipping and depressurization, whereas higher temperatures can be encountered in capture, pipeline transport and in reservoirs. Hence, the whole temperature range between the triple (-57°C) and critical point of CO(31°C) is relevant. In 2019, the reference EOS developed in NCCS was compared with new experimental phase equilibria data of the CO2-N2-CH4 system from -50 to 25°C. The deviations were similar to what are found for the binary data to which the EOS has been fitted. Hence, the EOS validity for the important impurities of nitrogen and methane, selected by the NCCS industry consortium, has been confirmed. These findings have been published in Fluid Phase Equilibria.

A revised long-term strategy for property measurements and fiscal metering has been made together with the task family.

A new version of the reference EOS for CCS developed in NCCS, EOS-CG 2019 was released, including description of new components. EOS-CG 2019 is documented through a PhD thesis and two journal papers and made available through the TREND thermodynamic library. Further model developments, including reactive systems and transport properties, are under way.

The new TREND thermodynamic library is directly available for the NCCS industry partners, but the routines of EOS-CG are also expected to eventually find their way to commercial process simulators. The impact is hence global.

EOS-CG 2019, expanded and verified with new ternary measurements in 2019, can now be used for more complex mixtures and with higher confidence thanks to the work of Task 8. Increased confidence of the thermo- dynamics means less risk in the design and operation of CCS processes, and hence saved costs! 

In addition, further measurements and modeling of thermal conductivity, phase equilibria, viscosity, and density were under way or under preparation in 2019 through ImpreCCS, including collaboration and exchange of personnel between SINTEF ER, NTNU, UWA, and NIST.

Fiscal metering

As discussed in the Impacts Study, qualified and traceable measurement of mass flow to satisfy public regulations, also called fiscal metering, is a prerequisite for large-scale deployment of CCS. Currently, no technologies have been verified at relevant conditions and flow rates.

Ultrasonic technologies have become a very popular for flow metering of e.g. natural gas, chiefly due to their high accuracy and low pressure drop. However, questions have been raised in the literature concerning their applicability to CCS due the high acousticattenuation of CO2. Hence, static testing of an ultrasonic fiscalmeter of industrial scale to investigate the impact of acoustic attenuationhasbeenpreparedasanactivityfor2020. These tests will confirm whether this technology is viable for CCS, which will be a very important result.

As an impact of the work in NCCS, the INFRASTRUKTUR program of the Research Council of Norway funds design of a fiscal metering test loop in 2020. Such a loop will enable verification of different fiscal metering technologies at a relevant industrial scale and at operational and varying conditions. This design will be developed in close collaboration with the NCCS industrial consortium. Without such a test loop, traceable mass flow measurements may not be possible, and CCS systems may be required to purchase emission allowances under the EU emission trading system (ETS). This would be a major blow to CCS profitability.

1 Ottøy S et al. "Thermodynamics of the carbon dioxide plus nitrogen plus methane (CO2 + N2 + CH4) system: Measurements of vapor-liquid equilibrium data at temperatures from 223 to 298 K and verification of EOS-CG-2019 equation of state," Fluid Phase Equilib. 2020;509:112444.

Deviations between ternary CO2 + N2+ CH4 VLE data and EOS-CG 2019 [1].

Results 2018

Main Results

  • First benchmarking of fiscal metering technologies for CO2 and strategy for verification test plan
  • Measurement of VLE on the ternary system CO2-N2-CH4
  • Improved models of the minor components in CCS mixtures, as well as CO2-CO, CO2-Ar, and initiation of work to include reactive mixtures
  • Initiation of NCCS / CLIMIT KPN "Impact of CO2 impurities and additives in CCS" (ImpreCCS)

Impact and innovations

  • New TREND library to be released, including the new mixture models
  • Published measurements are available also for other groups developing property models
  • New innovative experimental setup for viscosity and density measurements
  • Preparation for fiscal metering verification underway
Viscosity setup to be used in ImpreCCS

Results 2017

"Fiscal metering and thermodynamics properties" has produced new experimental data fully characterizing the phase equilibrium on mixtures between carbon monoxide (CO) and CO2 as a function of pressure at four different temperatures.

CO is an important impurity from many CO2 sources and capture processes, and a better description of its impact is now possible.

The new data cover important knowledge gaps and are under publishing. Further, Task 8 has significantly improved the thermodynamic model description for many other types of mixtures.

A first assessment of potential technologies for fiscal metering of CO2-rich flows has been performed, and specifications for fiscal meters for CCS have been proposed.

A new CLIMIT competence building project was granted for measurement and modelling of viscosity, density, and thermal conductivity. The project will be a part of NCCS ahead and apply new property correlations in reservoir simulations.


Journal Publications




Conference Publications


  • VLE Measurements and Verification of a state-of-the-art Helmholtz Energy Equation of State for the Ternary Mixture of CO2-N2-CH4 - Poster: S. Ottøy, J. Stang, T. Neumann, S. W. Løvseth, J. P. Jakobsen, TCCS-10 conference, Trondheim, Norway
  • New Helmholtz-Energy Equations of State for Ammonia as a Minor Component of CCS-Relevant Mixtures - Poster:  T. Neumann, M. Thol, R. Span, TCCS-10 conference, Trondheim, Norway
  • Helmholtz-energy equations of state for CCS-relevant binary mixtures containing ammonia - Oral presentation: T. Neumann, M. Thol, I. H. Bell, E. W. Lemmon, R. Span, ATCP 2019: The 12th Asian Thermophysical Properties Conference 2019, Xi'an, China


  • A new fundamental equation of state for the binary mixture of carbon dioxide and argon - T. Neumann, S. Herrig, R. Span. 20th Symposium on Thermophysical properties, Boulder, CO, USA
  • An extended fundamental equation of state for thermodynamic properties of mixtures relevant for CCS application - S. Herrig, I. Bell, T. Neumann, R. Span. 20th Symposium on Thermophysical properties, Boulder, CO, USA
  • Accurate phase equilibrium measurements for CCS using an analytical method - J. Stang, S.W. Løvseth, A. Austegard, S. Westman. 20th Symposium on Thermophysical properties, Boulder, CO, USA
  • Need and measurements of accurate thermodynamic data for CCS - S.W. Løvseth, S.F. Westmann, A. Austegard, H.G.J. Stang. GHGT-14, Melbourne
  • Eine neue Fundamentalgleichung für das binäre Gemisch Kohlendioxid und Argon - T. Neumann. Thermodynamik-Kolloquium 2018, Universität Kassel

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Task leader

Sigurd Weidemann Løvseth

Senior Research Scientist
411 29 840
Sigurd Weidemann Løvseth
Senior Research Scientist
411 29 840
Gas Technology