The document discusses phase equilibrium studies of impure carbon dioxide systems relevant to carbon capture and storage technologies. It presents new vapor-liquid equilibrium and solubility data for binary and ternary mixtures of CO2, N2, H2, and H2O measured using high-pressure facilities. The data aims to expand understanding of thermodynamic properties to inform the design of CO2 compression, pipeline transport, and the presence of impurities like H2 which increase the pressure required for a homogeneous CO2 phase. Equations of state are evaluated against the experimental data.

1. Phase equilibrium studies of impure CO2 systems to underpin developments of CCS technologies
Jie Ke, Martyn Poliakoff and Michael W. George
School of Chemistry
The University of Nottingham
10 September, 2014, UKCCSRC Biannual Meeting, Cardiff

2. Vapour-liquid-equilibrium and other thermodynamic properties
•
CO2 compressor and pump design
•
Pipeline transport of CO2
•
Flow rate monitoring
Avoid phase separation
Impurity in CO2 streams: N2, H2, Ar, H2O etc,

3. Expansion of the database of the CO2 mixtures relevant to CCS
Number of data pointsCO2+ CH4CO2+ H2PVTVLE1050100200

4. Contents
•
High pressure facilities for measuring the phase equilibrium data of multicomponent CO2 mixtures
•
New VLE data of the binary/ternary mixtures of CO2, N2, and H2.
•
Validation of the equations of state with the new data
•
Solubility of water in impure CO2

5. Methods for measuring phase equilibria
Determination of phase composition
•
Synthetic methods
•
Analytical methods
Apparatus configuration
•
Static
•
Dynamic
Visual
Sensors
Online or offline sampling (GC)
in-situ (FTIR)

6. Sensors
t=0t=0Sound WaveΔt
IR
Holey fibre + GC
ATR
Shear-mode quartz
Optical fibre
Density meter
J. Phys. Chem. 1996, 100, 9522. J. Phys. Chem. 1997, 101, 5853. Fluid Phase Equilib. 1998, 150, 493. J. Supercrit. Fluids 2004, 30, 259. Phys . Chem. Chem. Phys. 2004, 6, 1258. J. Chem. Eng. Data 2009, 54, 1580.

7. Fibre-optic reflectometer
Optical fibre
2000       + − == ffRnnnnIIR(a) (b) (c) (d)
High-pressure vessel
Rev. of Sci. Instrum. 85, 085110 (2014)

8. Determination of phase transition using optical-fibre sensors
08001600-14.00-13.95-13.90 IR / a.u. t / s8.68.89.0(b) p / MPa (a) 0500100015002000-14-12-10 IR / a.u. t / s6.056.106.156.20(c) (b) p / MPa (a)
Bubble-point
Dew-point
pcTc T p Critical PointTwo-PhaseOne-Phase

9. 2602702802903002468101214 p / MPa T / K
p – T phase boundary of CO2 + N2 and CO2 + H2
260270280290300246810 p / MPa T / K
CO2 + N2
CO2 + H2
Pure CO2
14%
2%
5%
Pure CO2
9.1%
3%
4%

10. 26027028029030048120.95 CO2 + 0.05H20.95 CO2 + 0.05N2 p / MPa T / K0.95 CO2 + 0.02 N2 + 0.03 H2
p – T phase boundary of the ternary system of CO2 + N2 + H2
0.93 CO2 + 0.04 N2 + 0.03 H2
Pure CO2

11. 훼훼(훿훿,휏휏,푥푥̅)=훼훼표표(휌휌,푇푇,푥푥̅)+෍푥푥푖푖훼훼표표표푟푟 푁푁 푖푖=1(훿훿,휏휏)+Δ훼훼푟푟(훿훿,휏휏,푥푥̅)
The Peng-Robinson Equation of State
The GERG-2004/GERG-2008 Equation of State
Evaluation of equations of state
•
For each binary pair, 4 adjustable parameters are required to calculate δ and τ .
•
The departure functions need more adjustable parameters , e.g. The Δαr of the CO2-N2 pair uses 34 adjustable parameters.
)()(bvbbvvabvRTP−++ − − =
•
Requires binary interaction parameters (kij) to describe mixtures.
•
Temperature independent kij
•
Temperature dependent kij (linear fit and Boltzmann fit for the H2-CO2 pair)

12. Evaluation of equations of state
2.04.06.08.0(c) (b) pe / MPa (a) -0.8-0.40.00.4 (pc-pe)/MPa 250260270280290300-12-8-4 04 T / K(pc-pe) / pe × 100 2.04.06.08.010.012.0(c) (b) pe / MPa(a) -101 (pc-pe)/MPa 250260270280290300-8-4 04 T / K (pc-pe) / pe × 100
0.93 CO2 + 0.04 N2 + 0.03 H2
0.93 CO2 + 0.03 H2

13. Evaluation of equations of state
ABC 0369 ABC 0369 ABC 0369 ABC 0369 ABC 0369 ABC 0369 ABC 0369 ABC 0369 ABC 0369 ABC 0369 ABC 0369VLECO2 + N2VLECO2 + H2VLECO2 + N2 + H2DensityCO2 + H2Mole fraction of impurities2.0%7.5%10.0%2.0%4.0%14.0%3.0%5.0%9.1%7.0%
A – GERG-2004
B – PR with the linear fit
C – PR with the Boltzmann fit
AARD %

14. Solubility of H2O in CO2 + N2 (40 oC)
yH2O - mole fraction of H2O
Pure CO2
95% CO2 + 5% N2
90% CO2 + 10% N2

15. Solubility of H2O in CO2 + N2
cH2O – molar concentration of H2O
Pure CO2
 95% CO2 + 5% N2
 90% CO2 + 10% N2
cH2O (mol⋅dm-3)

16. Solubility of H2O in CO2 + N2
L
V
Equilibrium state
CH2O
yH2O
Dilute CO2 + N2 mixtures (yN2<0.1)
CO2, N2
CH2O = b0+b1ρ +b2 ρ 2
ρ = f(T,P,xi)
m
m
m
yH2O
510152048121620 95%CO2+10%N2 95%CO2+5%N2CO2 Density / (mol/dm3) p / MPa40 oC
N
25 oC
N
40 oC
CO2
4
1.4%
5
4.9%
95%CO2 + 5% N2
4
3.2%
7
3.9%
90% CO2 + 10% N2
3
4.2%
7
4.5%
All
11
2.8%
19
4.4%
Average of absolute relative deviations of yH2O

17. Conclusions
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New VLE data of binary/ternary mixtures of CO2, N2 and H2.
•
New water solubility data for impure CO2 systems.
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H2 and H2O are the key components in terms of understanding the thermodynamic properties of CO2 mixtures relevant to CO2 compression and transport.
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The presence of H2 significantly increases the pressures required to form a homogeneous phase of impure CO2.
•
Permeant gases (e.g. N2) decrease the solubility of H2O in CO2 under liquid or supercritical conditions.
•
Need rigours tests of the equations of state with the data collected at the conditions relevant to the CCS processes.

18. High-pressure facilities in Nottingham

19. Acknowledgements
EPSRC
TSB
ETI
National Grid
PSE
Our collaborators from the COZOC, MATTRAN and COOLTRANS projects
Dr. Stéphanie Foltran Dr. Yolanda Sanchez-Vicente Dr. Andrew J. Parrot Dr. James Calladine Dr. Maria-José Tenorio Dr. Alisdair Wriglesworth Matthew E. Vosper Norhidayah Suleiman Prof. Trevor Drage