Phase equilibrium studies of impure CO 2 systems to underpin developments of CCS technologies

Transcription

1 Phase equilibrium studies of impure CO 2 systems to underpin developments of CCS technologies Jie Ke, Martyn Poliakoff and Michael W. George School of Chemistry The University of Nottingham 1 September, 214, UKCCSRC Biannual Meeting, Cardiff

2 Vapour-liquid-equilibrium and other thermodynamic properties CO 2 compressor and pump design Pipeline transport of CO 2 Flow rate monitoring Avoid phase separation Impurity in CO 2 streams: N 2, H 2, Ar, H 2 O etc,

3 Expansion of the database of the CO 2 mixtures relevant to CCS CO 2 + CH 4 PVT VLE Number of data points CO 2 + H

4 Contents High pressure facilities for measuring the phase equilibrium data of multicomponent CO 2 mixtures New VLE data of the binary/ternary mixtures of CO 2, N 2, and H 2. Validation of the equations of state with the new data Solubility of water in impure CO 2

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

6 Sensors t t= t= Sound Wave Density meter Holey fibre + GC Optical fibre IR ATR Shear-mode quartz J. Phys. Chem. 1, 1, 522. J. Phys. Chem. 17, 11, 585. Fluid Phase Equilib. 18, 15, 4. J. Supercrit. Fluids 24,, 25. Phys. Chem. Chem. Phys. 24,, J. Chem. Eng. Data 2, 54, 158.

7 Fibre-optic reflectometer Optical fibre 2 R = I I R n = n n + n (a) (b) (c) (d) f f High-pressure vessel Rev. of Sci. Instrum. 85, 8511 (214)

8 Determination of phase transition using optical-fibre sensors Bubble-point Dew-point. (a).2 (a) p / MPa p / MPa.15.1 I R / a.u (b) t / s I R / a.u. T c Critical Point Two-Phase (b) (c) p c t / s p One-Phase

9 p T phase boundary of CO 2 + N 2 and CO 2 + H 2 CO 2 + N 2 CO 2 + H % 14.1% 8 2% % p / MPa 4% p / MPa 8 % 4 Pure CO Pure CO T / K T / K

10 p T phase boundary of the ternary system of CO 2 + N 2 + H CO N 2 +. H 2.5 CO 2 +.5H 2 p / MPa 8.5 CO N 2 +. H 2.5 CO 2 +.5N 2 4 Pure CO T / K

11 Evaluation of equations of state The Peng-Robinson Equation of State P RT = v b a v( v + b) + b( v b) Requires binary interaction parameters (k ij ) to describe mixtures. Temperature independent k ij Temperature dependent k ij (linear fit and Boltzmann fit for the H 2 -CO 2 pair) The GERG-24/GERG-28 Equation of State αα(δδ, ττ, xx ) = αα oo rr (ρρ, TT, xx ) + xx ii αα oooo NN ii=1 (δδ, ττ) + αα rr (δδ, ττ, xx ) For each binary pair, 4 adjustable parameters are required to calculate δ and τ. The departure functions need more adjustable parameters, e.g. The α r of the CO 2 -N 2 pair uses 4 adjustable parameters.

12 Evaluation of equations of state 8. (a) (a) p e / MPa (p c -p e )/MPa (p c -p e ) / p e CO 2 +. H (b) (c) T / K p e / MPa (p c -p e )/MPa (p c -p e ) / p e (b) (c). CO N 2 +. H T / K

13 Evaluation of equations of state VLE CO 2 + N 2 AARD % VLE CO 2 + H 2 VLE CO 2 + N 2 + H 2 A GERG-24 B PR with the linear fit C PR with the Boltzmann fit Density CO 2 + H 2 2.%.% 4.% 5.% 7.% 7.5%.1% 1.% 14.% Mole fraction of impurities

14 Solubility of H 2 O in CO 2 + N 2 (4 o C) Pure CO 2 5% CO 2 + 5% N 2 % CO 2 + 1% N 2 y H2O - mole fraction of H 2 O

15 Solubility of H 2 O in CO 2 + N 2 Pure CO 2 5% CO 2 + 5% N 2 c H2O (mol dm - ) % CO 2 + 1% N 2 c H2O molar concentration of H 2 O

16 Solubility of H 2 O in CO 2 + N 2 Equilibrium state C H2O = b +b 1 ρ +b 2 ρ 2 m m y H2O V C H2O y H2O ρ = f(t,p,x i ) m o C CO 2 L CO 2, N 2 Average of absolute relative deviations of y H2O Density / (mol/dm ) %CO 2 +5%N 2 5%CO 2 +1%N p / MPa N 25 o C N 4 o C CO % 5 4.% 5%CO2 + 5% N2 4.2% 7.% % CO2 + 1% N2 4.2% 7 4.5% All % 1 4.4% Dilute CO 2 + N 2 mixtures (y N2 <.1)

17 Conclusions New VLE data of binary/ternary mixtures of CO 2, N 2 and H 2. New water solubility data for impure CO 2 systems. H 2 and H 2 O are the key components in terms of understanding the thermodynamic properties of CO 2 mixtures relevant to CO 2 compression and transport. The presence of H 2 significantly increases the pressures required to form a homogeneous phase of impure CO 2. Permeant gases (e.g. N 2 ) decrease the solubility of H 2 O in CO 2 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 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 EPSRC TSB ETI National Grid PSE Our collaborators from the COZOC, MATTRAN and COOLTRANS projects