Thermodynamic characterization of the (CO2 + O2) binary system for the development of models for CCS processes: Accurate experimental (p, ρ, T) data and virial coefficients
Introduction
High-accuracy density data are of great relevance for the development of reliable equations of state. In part one of this study [1], we reported accurate density measurements for three binary mixtures of carbon dioxide with oxygen (amount-of-substance fraction x(O2) = 0.05, 0.10, 0.20) in the temperature range T = (250–375) K and maximum pressures up to p = 13 MPa, together with the corresponding calculations using the two equation-of-state models GERG-2008 [2] and EOS-CG [3]. It could be observed that the GERG-2008 EoS fitted the experimental data within its claimed uncertainty in density (1 %) only for the mixture with the lowest oxygen content (amount-of-substance fraction x(O2) = 0.05). When the oxygen content increased (x(O2) = 0.10, 0.20), the deviations increased above the claimed uncertainty of the EoS and became more visible at lower temperatures and higher pressures. These deviations could be as high as 4.4 % for the mixture with x(O2) = 0.10, and 6.6 % for the mixture with x(O2) = 0.20. The deviations always had a positive value, i.e., the GERG-2008 underestimates the density of (CO2 + O2) mixtures, particularly for mixtures with a high oxygen content at high pressures and low temperatures. Another result of that study was that the EOS-CG performed much better in processing these density data. The relative deviations of the experimental density data from the EOS-CG remained within the claimed uncertainty of the equation of state (1 %) for all the 162 experimental points, with three exceptions only, namely at (x(O2) = 0.10, T = 293.15 K, p = 6.0 MPa), (x(O2) = 0.20, T =300 K, p = 11.0 MPa), and (x(O2) = 0.20, T =300 K, p = 12.2 MPa), where the relative deviation increased up to 1.2 %, −2.0 %, and −3.2 %, respectively.
In order to complete the characterization of the (CO2 + O2) binary mixture over the entire composition range, accurate density measurements for two new binary mixtures with higher oxygen content (x(O2) = 0.50, 0.75) are presented in this work. Measurements were performed at temperatures between (250 and 375) K and pressures up to 20 MPa using a single-sinker densimeter with magnetic suspension coupling, which is the same experimental technique used in the previous work. In order to achieve the highest accuracy in composition, the binary mixtures for this investigation were also prepared gravimetrically according to the ISO 6142-1 [4], a method that qualifies for the production of reference materials. The experimental results were compared with the GERG-2008 equation of state as well as with the more specific EOS-CG.
The complete set of density data for the binary system (CO2 + O2) presented in this work, and in the previous work [1], covers a wide range of temperature (from T = 250 K to T = 375 K), pressure (up to p = 20 MPa), and composition (from x(O2) = 0.05 to x(O2) = 0.75). This complete set of new experimental data from both studies is used in this work to calculate the virial coefficients B(T, x) and C(T, x), as well as the second interaction virial coefficient B12(T) for the (CO2 + O2) binary mixture.
The characterization of the binary system (CO2 + O2) is relevant not only for the development of accurate models for Carbon Capture and Storage (CCS) processes and for the modeling of combustion processes, but also for the improvement of the models used when dealing with natural gas and natural-gas-related mixtures. The deviations of the theoretical models from the actual values of the thermodynamic properties of the mixtures have relevant implications in the design and operation of processes and in the commercial transfer and pricing of products.
Section snippets
Mixture preparation
Two (CO2 + O2) binary mixtures were prepared at the Federal Institute for Materials Research and Testing (Bundesanstalt für Materialforschung und -prüfung, BAM) in Berlin, Germany, according to the ISO 6142-1 [4].
Purity, supplier, molar mass, and critical parameters of the pure compounds (obtained from the reference equations of state for carbon dioxide [5] and oxygen [6]) are given in Table 1. The cylinder identifiers (BAM reference gas mixture G 033), the gravimetric composition, and the
Experimental results
Table 5, Table 6 show the 274 experimental (p, ρ, T) data measured for the two (CO2 + O2) binary mixtures. The temperature, pressure, and density of each measured point were calculated as the arithmetic mean of the last ten consecutive measurements of a series of thirty. Table 5, Table 6 also show the expanded uncertainty in density U(ρexp) (k = 2), calculated by Eq. (4) and expressed in absolute density units and as a percentage of the measured density.
The experimental data were compared to
Relative deviation of the experimental data from the reference equations of state
The plot in Fig. 2 shows the relative deviations of the experimentally determined density data of the (0.50 CO2 + 0.50 O2) mixture from the corresponding density data calculated by the GERG-2008 (a) and the EOS-CG (b) models, respectively. In the same way, Fig. 3 shows the deviations for the (0.25 CO2 + 0.75 O2) mixture.
Both equations of state claim an uncertainty in density of 1.0 % for mixtures of CO2 and O2 over the temperature range from (250 to 450) K and at pressures up to 35 MPa. The
Conclusions
New (p, ρ, T) high-precision experimental data for two binary mixtures of carbon dioxide and oxygen, with nominal compositions of (0.50 CO2 + 0.50 O2) and (0.25 CO2 + 0.75 O2), at temperatures between (250 and 375) K and pressures up to 20 MPa, are reported. The gravimetrically prepared mixtures were of reference quality and the experimental device used was a single-sinker densimeter with magnetic suspension coupling.
The new experimental data were compared to the corresponding densities
Declaration of Competing Interest
The authors report no declarations of competing interest.
Acknowledgments
The authors wish to thank for their support the Ministerio de Economía, Industria y Competitividad project ENE2017-88474-R and the Junta de Castilla y León project VA280P18.
References (54)
- et al.
Accurate experimental (p, ρ, T) data of the (CO2 + O2) binary system for the development of models for CCS processes
J. Chem. Thermodyn.
(2020) - et al.
EOS-CG: A Helmholtz energy mixture model for humid gases and CCS mixtures
J. Chem. Thermodyn.
(2016) - et al.
A new form of the equation of state for pure substances and its application to oxygen
Fluid Phase Equilib
(1985) - et al.
Measurement of the (pressure, density, temperature) relation of two (methane+nitrogen) gas mixtures at temperatures between 240 and 400 K and pressures up to 20 MPa using an accurate single-sinker densimeter
J. Chem. Thermodyn.
(2006) - et al.
Improvement of the measurement uncertainty of a high accuracy single sinker densimeter via setup modifications based on a state point uncertainty analysis
Measurement
(2011) - et al.
An accurate single-sinker densimeter and measurements of the (p, ρ, T) relation of argon and nitrogen in the temperature range from (235 to 520) K at pressures up to 30 MPa
J. Chem. Thermodyn.
(1998) - et al.
Influence of adsorption and desorption on accurate density measurements of gas mixtures
J. Chem. Thermodyn.
(2014) - et al.
Characterization of a biomethane-like synthetic gas mixture through accurate density measurements from (240 to 350) K and pressures up to 14 MPa
Fuel
(2017) - et al.
New (p, ρ, T) data for carbon dioxide – nitrogen mixtures from (250 to 400) K at pressures up to 20 MPa
J. Chem. Thermodyn.
(2011) - et al.
Accurate (p, ρ, T) data for two new (carbon dioxide + nitrogen) mixtures from (250 to 400) K at pressures up to 20 MPa
J. Chem. Thermodyn.
(2012)
Integration of biogas in the natural gas grid: thermodynamic characterization of a biogas-like mixture
J. Chem. Thermodyn.
Accurate thermodynamic characterization of a synthetic coal mine methane mixture
J. Chem. Thermodyn.
Accurate experimental (p, ρ, T) data and virial coefficients for the (methane and helium) binary system
J. Chem. Thermodyn.
Accurate experimental (p, ρ, T) data of natural gas mixtures for the assessment of reference equations of state when dealing with hydrogen-enriched natural gas
Int. J. Hydrogen Energy
Vapor-liquid equilibrium data for the carbon dioxide and oxygen (CO2 + O2) system at the temperatures 218, 233, 253, 273, 288 and 298 K and pressures up to 14 MPa
Fluid Phase Equilib.
Effect of impurities in captured CO2 on liquid–vapor equilibrium
Fluid Phase Equilib.
Classification of global fluid-phase equilibrium behaviors in binary systems
Chem. Eng. Res. Des.
Volumetric properties and phase behavior of sulfur dioxide, carbon disulfide and oxygen in high-pressure carbon dioxide fluid
Fluid Phase Equilib.
The GERG-2008 wide-range equation of state for natural gases and other mixtures: an expansion of GERG-2004
J. Chem. Eng. Data
Gas Analysis – Preparation of Calibration Gas Mixtures – Part 1: Gravimetric Method for Class I Mixtures
A new equation of state for carbon dioxide covering the fluid region from the triple-point temperature to 1100 K at pressures up to 800 MPa
J. Phys. Chem. Ref. Data
Determination of the force transmission error in a single-sinker magnetic suspension densimeter due to the fluid-specific effect and its correction for use with gas mixtures containing oxygen
Measurement
Entwicklung eines neuen Dichtemeßverfahrens und Aufbau einer Hochtemperatur-Hochdruck-Dichtemeßanlage
Entwicklung eines neuen Dichtemeßverfahrens und Aufbau einer Hochtemperatur-Hochdruck-Dichtemeßanlage
Accurate experimental (p, ρ, T) data for the introduction of hydrogen into the natural gas grid: thermodynamic characterization of the nitrogen–hydrogen binary system from 240 to 350 K and pressures up to 20 MPa
J. Chem. Eng. Data
Experimental techniques 1: direct methods
Force transmission errors in magnetic suspension densimeters
Int. J. Thermophys.
The magnetic susceptibilities of several organic gases
Phys. Rev.
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