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

Sindre Ottøy,Tobias Neumann,Hans Georg Jacob Stang,Jana Poplsteinova Jakobsen,Anders Austegard,Sigurd Weidemann Løvseth

doi:10.1016/j.fluid.2019.112444

Sindre Ottøy, Tobias Neumann + Show 4 more

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https://doi.org/10.1016/j.fluid.2019.112444

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Abstract

Vapor-liquid equilibria (VLE) data of the ternary mixture of CO2 + N2 + CH4 were measured at the isotherms 223 K, 253 K, 273 K, 283 K, and 298 K and for pressures in the range of 0.8 MPa–9.3 MPa. The 62 experimental dew or bubble point data points have been measured using an analytical technique. For each temperature, the ratio between N2 and CH4 mole fraction in the total composition has been close to constant, enabling the data to be visualized as quasi phase envelopes. Estimated standard measurement uncertainties (k = 1) better than 14 mK in temperature, 1.5 kPa in pressure, and 0.06 mol% in composition are reported, yielding a total uncertainty in terms of composition better than 0.07 mol%. The experimental data were compared to the EOS-CG-2019 model, which is a state-of-the-art Helmholtz energy-based equation of state for the mixture of CO2 + N2 + CH4. All deviations between model and experimental data points are below 0.5 mol% for liquid compositions and 1.0 mol% for vapor compositions. The deviations between model and experimental points in the ternary mixture of CO2 + N2 + CH4 follow the same trends seen in earlier reports between model and experimental data for the binary mixtures of CO2 + N2 and CO2 + CH4. In addition, the model was analysed with respect to other thermophysical properties available in the literature. To a large extent, the results presented in this work validate the assumption that the thermodynamic properties of the multicomponent system CO2 + N2 + CH4 can be described purely based on the pure component and binary mixture contributions.

Highlights

The fluid properties of CO2 mixed with other components are receiving intensified interest due to the need of reducing anthropic global warming
Carbon capture and storage (CCS) will be a vital technology in order to avoid the catastrophic consequences of global climate change caused by continued largely unchecked emissions of CO2 and other greenhouse gases (GHG) to the atmosphere
The experimental points L1eL5, L10eL31, V1eV5 and V10eV31 were measured with approximately equal amounts of nitrogen and methane in the total composition of the cell

Summary

Introduction

The fluid properties of CO2 mixed with other components are receiving intensified interest due to the need of reducing anthropic global warming. Carbon capture and storage (CCS) will be a vital technology in order to avoid the catastrophic consequences of global climate change caused by continued largely unchecked emissions of CO2 and other greenhouse gases (GHG) to the atmosphere. This view is strongly supported by recent international studies [1e3]. As a step-stone to global large-scale CCS, further industrially driven projects are currently under planning One of these is the Norwegian Full-Scale project [4], where CO2 emissions from industrial point sources will be captured, liquefied, transported by ship to a coastal terminal close to a reservoir suitable for storage to which the CO2 will be transported by pipeline. The thermodynamic equilibrium properties of pure CO2 are known to relatively high degree of accuracy [6,7]

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