Selection of amine solvents for CO2 capture from natural gas power plant - presentation by Jiafei Zhang in the Natural Gas CCS session at the UKCCSRC Cardiff Biannual Meeting, 10-11 September 2014

1. Selection of amine solvents for CO2 capture from natural gas power plant
Jiafei Zhang, Paul Fennell, Martin Trusler
Cardiff, 11th September 2014
Gas-FACTS project: Gas - Future Advanced Capture Technology Systems
UKCCSRC Biannual Meeting
Natural Gas CCS Technical Session

2. Outline
Introduction
•
Project overview
•
Solvents selection Process Evaluation
•
Conventional
•
Phase change Properties and Influence
•
VLE & CO2 capacity
•
Viscosity & Density
•
Heat capacity & Energy requirement
•
Surface tension Summary 2
Absorption
Desorption
Image Source: Siemens
Gas-specific solvents for CO2 capture
Thermophysical properties
VLE: Vapour-Liquid Equilibrium

3. Project overview
2.1 Gas-Specific Solvents 2.2 Flexible Capture Systems 2.3 Advanced Testing
Work packages 3
Consortium Members:
Natural Gas Combined Cycle + CO2 Capture & Storage
NGCC-CCS

4. PCC for gas-fired power plants
4
CO2 Emissions (kg/MWh)
w/o
w/ CCS
Coal-fired
800-1000
~100
Gas-fired
350-400
~40
After Combustion:
CO2
H2O
O2
N2
Ar
Coal-fired
13.53
15.17
2.40
68.08
0.82
Gas-fired
4.04
8.67
12.09
74.32
0.89

Natural gas becomes the new ‘coal’ for power generation…

burns much cleaner than coal

but...

Lower CO2 partial pressure

Reduce αCO2

Seeking specific solvents  reduce: solvent flow  column size  CapEx & OpEx

Higher O2 concentration

Enhanced solvent degradation

Seeking solvents resisting oxidation

Exhaust Gas Recycle (EGR)  CO2 ↑ & O2 ↓

w/o EGR: ~4% CO2, ~12% O2

w/ EGR: 6-8% CO2, 8-10% O2

5. Ideal solvent
The ideal chemical solvent for PCC

Fast reaction kinetics and mass transfer – reduce height requirements for the absorber and/or solvent circulation flow rates

High absorption capacity – directly influences solvent circulation flow rate requirements and equipment size

Good regenerability and reaction enthalpy – reduce energy consumption

High thermal stability and low solvent degradation – reduce solvent waste due to thermal and chemical degradations

Low solvent costs – easy and cheap to produce

No negative environmental impact

Technical feasibility
5
Process economic evaluation

6. Strategy for solvent selection 6
Gas-specific solvents
•
Monoethanlamine (MEA) as benchmark primary amine
•
2-Amino-2-methyl-1-propanol (AMP) sterically hindered
•
Dimethylaminoethanol (DMAE) tertiary
•
Diethylaminoethanol (DEAE) tertiary
•
Piperazine (PZ) as activator diamine
•
Piperazinyl ethylamine (PZEA) triamine
•
Blended amines – recommended
•
Solvent formulations
•
DEAE+PZ
•
AMP+PZ
•
etc.
NOHHONH2HNNHNOHNH2HO

High net CO2 loadings

Chemically stable
NNHH2N

Rapid reaction kinetics

Low energy consumption
Challenges

High O2

Low CO2

7. Processes
Conventional absorption
•
30wt% MEA solution
•
Activated MDEA
•
Other alkanolamines Liquid-Liquid phase change
•
DEAE+MAPA (NTNU)
•
Lipophilic amine, e.g.
•
DMX (IFP) Liquid-Solid phase change
•
KHCO3 solution
•
Concentrated AMP
7
NH2 N
Before regeneration
During regeneration
After regeneration NOHNHNH2HONH2NH2HOOHNOH

8. Conventional post-combustion capture process
8 Image Source: Sasol
Flue gas cooling & desulfurization
CO2 absorption Solvent regeneration
DCC = Direct Contact Cooler

9. Phase change capture process
9

10. Measurement & conditions
Density
•
25-80 °C
•
0.01% (uncertainty)
Viscosity
•
30-80 °C
•
1%
Heat capacity
•
30-120 °C, 1-40 bar
•
1.5%
Surface tension
•
25-60 °C
•
2%
VLE & composition analysis with GC
10
T2 Peltier Device Pump Bath T1 P
BPR
Feed flow
Column packings
Energy consumption
Packing wettability
(Sensible heat)
VLE + GC
Gap in the literature: few with CO2 loading

11. VLE: Experimental set-up
11
Process flow sheet
GSV
LSV

12. Validation with 30wt% MEA
30wt% DMAE, DMAE+PZ
30wt% DEAE
12
VLE: Results
1
10
100
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
pCO2 / kPa
α
This work
Tong 2012
Jou 1995
1
10
100
0
0.2
0.4
0.6
0.8
1
1.2
pCO2 / kPa
α
30wt% DMAE
25wt% DMAE + 5wt% PZ
20wt% DMAE + 10wt% PZ
30wt% DEAE
MEA
DEAE
40oC
120oC
120oC
40oC
NH2HONOHNOH
Solvent circulation

13. Net CO2 capacity
Δα for T between
40 and 120 oC at low pCO2
Higher Δα than for benchmarks
13
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
30% MEA
30% MDEA
30% AMP
25% AMP +
5% PZ
20% AMP +
10% PZ
30% DMAE
25% DMAE
+ 5% PZ
20% DMAE
+ 10% PZ
30% DEAE
Net CO2 loading
4 kPa
12 kPa
NH2HOOHNOH HONH2NOHNOHHNNH
Benchmarks
New solvents

14. Viscosity: Influence on absorption
Solvent viscosity (↑)
Electrical energy (↑) : e.g. pump power
Pressure drop (↑) in absorption column
Porosity of column packing (↑)
14
e.g.:
20%AMP+10%PZ
2.3 cP
4.1 cP

15. Viscosity: Validation
30wt% MEA solution Our studies on influences of
•
Concentration
•
Temperature
•
CO2 loading 15
NH2HO
0.5
1
1.5
2
2.5
3
3.5
4
0
0.1
0.2
0.3
0.4
0.5
η / mPa∙s
α
at 25 °C
at 30 °C
at 40 °C
at 50 °C
at 60 °C
at 70 °C
at 80 °CtK⋅=νρνη⋅=
Kinematic viscosity
Dynamic viscosity
Compared to Weiland’s (1998) correlation
Pump & Packing

16. Viscosity: Amine solutions
Correlations

Influence of T:

Influence of Cam:
16
TCaCaam2am1wamln⋅ +⋅=    ηη
(General Equation)
0
1
2
3
4
5
6
300
310
320
330
340
350
360
η / mPa∙s
T / K
Mod.15%wt
Mod.30%wt
Mod.45%wt
Exp.15%wt
Exp.30%wt
Exp.45%wt
0
1
2
3
4
5
6
300
310
320
330
340
350
360
η / mPa∙s
T / K
Exp.15%wt
Exp.30%wt
Exp.45%wt
Mod.15%wt
Mod.30%wt
Mod.45%wt
DMAE
DEAE
NOHNOH
AAD=2.4%
TBA+=     wln ηη
Cam mol/kg
T K

17. Viscosity: Effect of CO2 loading
Correlations

Influence of α:
17
TCCcCbCaCCcCbCaamCO2CO2am2amCO1CO1am1wam2222ln⋅⋅+⋅+⋅ +⋅⋅+⋅+⋅=    ηη
1
2
3
4
5
6
7
8
9
0
0.4
0.8
1.2
1.6
2
2.4
η / mPa∙s
CCO2 / (mol/kg)
303.15 K
313.15 K
323.15 K
333.15 K
Correlation
0
2
4
6
8
10
12
14
0
0.8
1.6
2.4
3.2
η / mPa∙s
CCO2 / (mol/kg)
303.15 K
313.15 K
323.15 K
333.15 K
Correlation
45% DEAE
45% DMAE
AAD=3%
Cam mol/kg
CCO2 mol/kg
T K

18. Density
Amine solutions

MEA

DMAE

DEAE

AMP

PZEA

Xam + PZ Influences
•
Concentration
•
Temperature
•
CO2 loading Plot: presented as ρ/ρw  suppress the T dependence
18
0.97
0.98
0.99
1
1.01
1.02
1.03
1.04
1.05
1.06
290
300
310
320
330
340
350
360
ρ/ρw
T / K
30% DMAE
w. α=0.26
w. α=0.43
w. 5%PZ
w. 10%PZ
Linear fits
+CO2
+PZ
NOH
Feed flow

19. Heat capacity: Influence on desorption
Energy consumption CO2 capture, transport, storage Solvent thermal regeneration: >50%; + blow + compression Sensible heat, reaction enthalpy, stripping energy, heat loss A lower Cp is preferred
19
TCFpsolΔ⋅⋅
Sensible heat
Reaction enthalpy
Stripping energy
Heat loss
Total
(ΔT=15)
30% MEA
0.9
(Δα=1.5 mol-CO2/kg-sol)
1.8
(ΔrH=80 kJ/mol-CO2)
1.1
(Reflux ratio ~2)
0.2
(ΔT=90 °C)
4.0
Unit:
MJ/kgCO2
~25%

20. Heat capacity: MEA
30wt% MEA solution Temperature CO2 loading Influence: T ↑  Cp ↑ α ↑  Cp ↓ (J/g/K) α ↑  ρCp ↑ (J/ml/K)
NH2HO
20
3.2
3.4
3.6
3.8
4
30% MEA
α=0.12
α=0.26
α=0.38
Cp / (J/g/K)
3.4
3.5
3.6
3.7
3.8
3.9
4
40
50
60
70
80
90
100
110
120
Cp / (J/g/K)
T / oC
α=0
α=0.12
α=0.26
α=0.38
Hilliard 2008, α=0
ρCp / (J/ml/K)
4.16
4.18
4.2
4.22
4.24
4.26
40
50
60
70
80
90
100
110
120
130
Cp / (J/g/K)
T / oC
This work
Manya 2011
IAPWS
AAD=0.2%
H2O
30% MEA
Sensible heat

21. Heat capacity: Other amines
Our studies:
DMAE, PZAE, DMAE+PZ, AMP+PZ…
21
3.7
3.8
3.9
4
4.1
4.2
4.3
40
50
60
70
80
90
100
110
120
130
Cp / (J/g/K)
T / oC
25% DMAE + 5% PZ
20% DMAE + 10% PZ
30% DMAE
30% DMAE (α=0.43)
4.06
4.08
4.1
4.12
4.14
4.16
4.18
4.2
40
50
60
70
80
90
100
110
120
130
Cp / (J/g/K)
T / oC
30% PZEA
20% AMP + 10% PZ
20% AMP + 10% PZ (α=0.33)
NNHH2NNOHHNNHHONH2
+CO2
+PZ

22. Energy requirement
Estimation of energy consumption
•
Sensible heat Qsen
•
Heat of reaction Qr
•
Stripping energy Qstr
•
Heat loss Qlos
How to reduce?
22
Qsen
Qr
Qstr
Qlos
Qsum
MEA
0.9
1.8
1.1
0.2
4.0
DMAE+ PZ
0.6
1.4
1.0
0.2
3.2
Target
0.5
1.2
0.6
0.1
2.4
TCFQpsolsenΔ⋅⋅= HFQrCOrΔ⋅= 2 vsteamstrLFQ⋅= ATQlos⋅Δ⋅=φ

23. Surface tension
Our tests:
30wt% MEA
AMP, AMP+PZ
Varying: T, Cam, α
Influences:
T ↑  γ ↓
Cam ↑  γ ↓ α ↑  γ ↑
Lower γ: better wettability
23
Wilhelmy plate
35
40
45
50
55
20
30
40
50
60
70
γ / (mN/m)
T / oC
15% AMP
30% AMP
45% AMP
20% AMP + 10% PZ
25% AMP + 5% PZ
62
64
66
68
70
72
74
-0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
γ / (mN/m)
α
This work
Jayarathna 2013
30% MEA
AAD=0.6%
HONH2HNNHNH2HO
Packing wettability

24. Summary
Highlight Measuring thermophysical properties of CO2 loaded amine solvents VLEHigh Δα  reduce solvent circulation Viscosity AMP > PZEA > DEAE > DMAE > MEA > H2O
•
Cam increase
•
T decrease
•
αCO2 increase
•
w. PZ increase Heat capacity H2O > PZAE > AMP > DMAE > MEA αCO2  decrease CP but increase ρCP Surface Tension T ↑ or αCO2 ↓  γ ↓ (better wettability)
24
Correlations

25. Summary
Evaluation
Cyclic loading 
ΔabH 
Reaction rate /
Base strength(pKb) 
Amine/Da 
Cost & availability 
Viscosity /
Volatility /
Thermal degradation 
Oxidative degradation 
Corrosivity 
HSE 
25
Comments
•
Recommendation of blended solvents
•
Viscosity ↑  porosity of packing ↑
•
Volatility preferable to degradation

26. Thank you for your attention!
26
Consortium Members:
Financial support

27. 27

28. Viscosity
Availability in literature Amine + Water

Varying Concentrations Many

Varying Temperatures Many (25-80 oC)

Varying CO2 loadings Few Influence of CO2 loading Weiland et al. MEA, DEA, MDEA, MEA+MDEA Fu et al. MDEA+DEA Svendsen et al. MEA Rochelle et al. PZ This work Single amine & blended solvent Influence of T, αCO2 and Cam.  Correlations 28
U-Tube capillary viscometer
tK⋅=νρνμ⋅=
kinematic viscosity
dynamic viscosity

29. Heat capacity
Flow calorimeter
29
Calorimeter cell
TmQCnetpΔ⋅ =   )(measuredbasenetQQbaQ−⋅+= )(21TTT−=Δρ⋅=Vm
T2 Peltier Device Pump Bath T1 P
BPR
Isocratic pump
Vacuum degasser
Power supplier
Data Acqu. Unit
Multimeter
Water or Oil Bath
4.16
4.18
4.2
4.22
4.24
4.26
40
50
60
70
80
90
100
110
120
130
Cp / (J/g/K)
T / oC
This work
Manya 2011
Water
AAD=0.2%