E a
Py  x  P
sat
Py  x  P
K 
H  1 1  k  Ae RT
ln  2   

R T2 T1 
 K1 
 H 
CP  

Q
 T P
S 
sat
Habs
K 
H  1 1   P

ln  2   
    1/T
R
R T2 T1 
 K1 
dU   q   w
dU   q   w
CO2
S 
Q
T
 H 
CP  

 T P
G  U TS  PV
H  U  PV
PV  nRT
 G 

 Ni T ,P ,N j i
Habs
P

 1/T
R
Py  x  P
T
G  U TS  PV
dQ  dU  PdV
 G 
i  

 Ni T ,P ,N j i
E a
k  Ae RT
k  Ae RT
sat
 H 

 T P
dU   q   w
Q
T
H  U  PV
 G 

 Ni T ,P ,N j i
K 
H  1 1 
ln  2   

R T2 T1 
 K1 
Py  x  P sat
 P CO
2
Habs
R
dU   q   w
S 
Q
T
E a
k  Ae RT
 H 

 T P
1 1
  
T2 T1 
Q
S 
T
E a
k  Ae RT
G  U TS  PV
 G 
i  

 Ni T ,P ,N j i
T
E a
E a
k  Ae RT
 G 
i  

 Ni T ,P ,N j i
2
Habs
 P CO

 1/T
R
Q
S 
T
2
E a
PV  nRT
 G 
i  

 Ni T ,P ,N j
k  Ae RT
 H 

 T P
 H 

 T P
H  U  PV
CP  
G  U TS  PV
G  U TS  PV
H  U  PV
H  U  PV
PV  nRT
PV  nRT
 G 

 Ni T ,P ,N j i
2
i  
Habs
P

 1/T
R
K 
H
ln  2   
K
R
 1
Py  x  P sat
Habs
 P CO

 1/T
R
Q
S 
T
2
k  Ae RT
Py  x  P sat
PV  nRT
 1 1  Py  x  P sat
  
T2 T1  dU   q   w
K 
H
ln  2   
K
R
 1
Py  x  P sat
Habs
 P CO2
 K2 
H  1 1 

ln    


1/
T
R
R T2 T1 
 K1 
dU   q   w
dU   q   w
S 
By
Q
S 
T
dQ  dU  PdV
E a
 H 

 T P
Q
T
G  U TS  PV
dQ  dU  PdV
 G 

 Ni T ,P ,N j i
i  
 H 

 T P
Habs
 P CO

 1/T
R
Q
S 
T
CP  
2
G  U TS  PV
Gary T. Rochelle
G  U TS  PV
H  U  PV
H  U  PV
The
University
of
Texas
at
Austin

H


PV  nRT
PV  nRT

 T P
PV  nRT
Py  x  P sat
K 
H  1 1 
ln  2   
   dU   q   w
i  
 G 
i  

 Ni T ,P ,N j i
P
K 
H  1
ln  2   
 
 G 

 Ni T ,P ,N j i
CO2

Habs
 H 

 T P
H  U  PV
CP  
 H 

 T P
CP  
PV  nRT
sat
1  Py  x  P

i
Habs
P

 1/T
R
CO2
E a
k  Ae RT
CP  
T
2
1 1
E a
   k  Ae RT
T
T
 2
1
 H 
CP  

 T P
k  Ae RT
E a
k  Ae RT
Q
S 
Habs
 P CO

 1/T
R
Q
S 
T
PV  nRT
 G 
i  

 Ni T ,P ,N j
 H 

 T P
CP  
 G 

 Ni T ,P ,N j i
i  
CO2
Habs
 P CO

 1/T
R
 H 

 T P
CP  
i
 G 
i  

 Ni T ,P ,N j i
E a
k  Ae RT
CP  
G  U TS  PV
Marcus Hilliard
CP  
G  U TS  PV
2
K 
H
ln  2   
K
R
 1
PV  nRT
G  U TS  PV
Habs
 P CO

 1/T
R
dU   q   w
H  U  PV
CP  
 G 
i  

 Ni T ,P ,N j i
PV  nRT
Py  x  P sat
Habs
 P CO

 1/T
R
Q
S 
T
CP  
PV  nRT
CP  
i  
E a
H  U  PV
 H 

 T P
PV  nRT
dQ  dU  PdV
 H 

 T P
2
G  U TS  PV
dQ  dU  PdV
k  Ae RT
Habs
 P CO

 1/T
R
Q
S 
T
CP  

K 
H  1 1 
ln  2   
    1/T
R T2 T1 
 K1 
S 
sat
A Predictive Thermodynamic Model for
an Aqueous Blend of Potassium
Carbonate, Piperazine, and
Monoethanolamine for Carbon Dioxide
Capture from Flue Gas
E a
CO2
k  Ae
Py  x  P sat
RT
k  Ae RT
a
K 
H  1 1 
RT
ln  2   
   k  Ae
R T2 T1 
 K1 
 H 
Q
CP  

S 
 T P
Py  x  P
 K2 
H  1 1  CO2
Habs
ln    
 P
R T2 T1  1/T   R
 K1 
dU   q   w
dU   q   w
Q
Q
S 
S 
T
T
dQ  dU  PdV
dQ  dU  PdV
E a
E a
Q
S 
dQ  dU  PdV
i  
T
E
Py  x  P sat
E a
k  Ae RT
Py  x  P sat
Habs
 P CO

 1/T
R
Q
S 
T
2
 H 

 T P
H  U  PV
CP  
PV  nRT
 G 
i  

 Ni T ,P ,N j
P
CO2

i
Habs
background – carbon capture technologies
• This research addresses the use of carbon
capture from coal fired power plants to
reduce factors contributing to global warming
• Our aim is to understand the fundamental
thermodynamic behavior associated with the
post-combustion chemical absorption process
• Chemical Solvents
– Monoethanolamine (MEA)
– Increase in capacity, faster rates, robustness
• MEA/Piperazine (PZ)
• K2CO3/PZ
Cooler
2-4 mol H2O/mol CO2
process - aqueous absorption
Clean Gas
1% CO2
Absorber
40–60oC
1 atm
Flue Gas
10% CO2
Stripper
100–120oC
1-2 atm
Rich Solvent
Lean Solvent
Reboiler
needs for thermodynamics
Mass Transfer
• Driving force CO
P as f  T,ldg 
• Capacity
• Speciation
[amine]  kinetics
2
Calorimetry
• Cp
• Habs
Volatility
• Amine P*
…with solvent characterization through rigorous modeling
research objective
Development of a rigorous thermodynamic model for
the H2O-K2CO3-MEA-PZ-CO2 sub-component base
systems
H2OK2CO3
Cullinane (2005)
H2OKHCO3
H2O-K2CO3PZ-CO2
UNIFAC
Tosh et al. (1959)
H2O-K2CO3CO2
H2O-K2CO3MEA-CO2
H2O-K2CO3-MEAPZ-CO2
H2OMEA
H2O-PZ
H2O-MEACO2
H2O-PZ-CO2
Bishnoi (2000)
Perez-Salado Kamps et al. (2003)
Numerous
Authors
H2O-MEA-PZCO2
Derks et al. (2005)
Dang (2001) and Okoye (2005)
Jou et al. (1995)
aqueous chemistry
CO2 Solubility
2
HCO
abs
Complex Mass Transfer with
Chemical Reactions
Vapor Phase
H 2O
H 2O
CO2
CO2
Amine Volatility
MEA
MEA
Liquid Phase
2H2O  H3O  OH 
NMR Speciation
2H2O  CO2  H3O  HCO3
H2O  HCO3  H3O  CO32
H2O  MEAH   H3O  MEA l 
H2O  MEACOO  MEAl   HCO3
Specific Heat
aspen plus 2006.5 framework
Gm*  xw  w*   xk k   x j ln x j  Gm* E
k
Enthalpy
C p ,m
Gm*
  ln K i
RT
j
ln Ki  f T 
   Gm / RT  
Hm
 T 

RT
T

P
 H 
 m 
 T  P
   nGmE / RT  

ln  i  
ni

 P ,T ,n
i
Phase Equilibrium
─ Aqueous Chemistry
Gmo G0o  H 0o H 0o 1 CPo
CPo dT
 ln Ki 


 
dT  
RT
RT0
RT T T0 R
R T
T0
T
T
elecNRTL model
• Activity coefficient model in Aspen Plus 2006.5
E
G
G
G
G
NRTL  



RT
RT
RT
RT
E
E
PDH
E
Born
• Rigorously represents liquid and vapor phases
• Reference state convention:
– Inf. Dil. Aqu. phase for molecular solutes (i.e. CO2) and ions
– Pure liquid for molecular solvents (i.e. H2O and MEA)
• By adjusting binary interaction parameters
• Through sequential non-linear regressions with
multiple, independent data sets
international collaboration
• Apparatus at NTNU
– High P CO2 Solubility (100 – 120 oC)
2
oC)
– Calorimeter  HCO
(40
–
120
abs
• Measured by Inna Kim (NTNU)
• Apparatus at UT
– ATM P Reactor (30 – 70 oC)
(multi-component vapor phase analysis reactor)
– Differential Scanning Calorimeter:
• Specific Heat Capacity & PZ Solubility
– NMR Speciation (Chem dept.)
• Measured by Steve Sorey and Jim Wallin
– X-ray Diffraction (Chem dept.)
• Crystallization Identification
• Measured by Vince Lynch
experimental design - overall
K+
5.0
52 Systems
9,757 data points
3.6
0.9
2 2.5
3.6
5.0
PZ
MEA
7
11
3.5
sequential regression
System
H2O
MEA
PZ
H2O-MEA
Number of
Sources Parameters AARD (%)
4
2
1.3
6
2
2.3
2
3
2.7
10
6
2.6
H2O-PZ
3
4
5.8
H2O-MEA-PZ*
1
10
4.3
H2O-MEA-N2O
4
3
3.5
H2O-K2CO3-CO2
6
23
3.9
H2O-MEA-CO2
8
35
24.8
H2O-PZ-CO3
H2O-K2CO3-PZ-CO2
4
3
35
33
10.6
15.5
H2O-MEA-PZ-CO2
4
(26)
37.9
H2O-K2CO3-MEA-CO2
H2O-K2CO3-MEA-PZ-CO2
1
1
57
(12)
194
41.9
108.7
19.0
Overall
CO2 Solubility in 7m MEA at 40 oC
10000
1000
CO2 Partial Pressure (kPa)
Austgen (1989)
100
Freguia (2002)
10
1
Jou et al. (1995)
0.1
This work
0.01
Lee et al. (1976) - corrected
0.001
0.0001
0
0.1
0.2
0.3
0.4
0.5
0.6
Loading (mol CO2/mol MEA)
0.7
0.8
0.9
1
CO2 Solubility in 2 and 5 m PZ at 40 - 60 oC
CO2 Partial Pressure (kPa)
100
10
60 oC
1
40 oC
0.1
Solid Pt & Curves : 2 m PZ
Open Pt & Curves : 5 m PZ
0.01
0.1
0.15
0.2
0.25
0.3
0.35
Loading (mol CO2/2∙mol PZ)
0.4
0.45
0.5
CO2 Solubility in 5 m K+/2.5 m PZ
Partial Pressure of CO2 [kPa]
100
Hilliard (2005)
60
10
40 oC
1
80 oC
Cullinane (2005)
60
0.1
40
0.01
NTNU (80 oC)
UT (40 & 60 oC)
0.001
0.4
0.45
0.5
0.55
0.6
0.65
Loading (mol CO2/mol K+ + mol PZ)
0.7
0.75
0.8
MEA Volatility in 7 m MEA at 40oC
MEA Partial Pressure (kPa)
0.1
0.01
64 ppmv
0.001
Austgen (1989)
This work
0.0001
0.00001
0
0.1
0.2
0.3
0.4
Loading (mol CO2/mol MEA)
0.5
0.6
0.7
MEA Volatility at 40oC
0.01
~15 %
MEA Partial Pressure (kPa)
5 m K+ + 7 m MEA
~50 ppmv
7 m MEA + 2 m PZ
7 m MEA
0.001
5 m K+ + 7 m MEA + 2 m PZ
0.0001
0.001
0.01
0.1
1
CO2 Partial Pressure (kPa)
10
100
PZ Volatility in 2 m PZ at 40oC
0.1
PZ Partial Pressure (kPa)
Hilliard (2005)
0.01
25 ppmv
0.001
This work
0.0001
0.00001
0
0.05
0.1
0.15
0.2
0.25
0.3
Loading (mol CO2/2∙mol PZ)
0.35
0.4
0.45
0.5
PZ Volatility at 40oC
PZ Partial Pressure (kPa)
0.01
~30 %
0.001
2 m PZ
~20 ppmv
5 m K+ + 2 m PZ
7 m MEA + 2 m PZ
5 m K+ + 7 m MEA + 2 m PZ
0.0001
0.001
0.01
0.1
1
CO2 Partial Pressure (kPa)
10
100
CO2 Solubility in 7m MEA at 60oC
100000
10000
CO2 Partial Pressure (kPa)
Austgen (1989)
1000
100
Freguia (2002)
10
Jou et al. (1995)
1
Differential
Capacity
0.1
This work
Lee et al. (1976) - corrected
0.01
0.001
0
0.1
0.2
0.3
0.4
0.5
0.6
Loading (mol CO2/mol MEA)
0.7
0.8
0.9
1
Differential Capacity wrt PCO2 (0.01 – 1.0 kPa) at 60oC
Differential Capacity (mol CO2/kg-H2O)
4
3.5
H2O-MEA-CO2
3
H2O-MEA-PZ-CO2
2.5
2
H2O-K2CO3-MEA-PZ-CO2
1.5
H2O-K2CO3-PZ-CO2
1
H2O-K2CO3-MEA-CO2
0.5
H2O-PZ-CO2
0
0
2
4
6
8
10
12
Total Alkalinity (m)
14
16
18
20
C13 NMR Speciation for 7 m MEA at 40oC
mole/kg-H2O of Species i
10
MEA + MEAH+
1
MEACOO-1
MEA
0.1
HCO3-1 + CO3-2
0.01
Solid Pt: Poplsteinovo (2004)
Open Pt: This work
Solid Curves: This work
0.001
0
0.1
0.2
0.3
0.4
0.5
0.6
Loading (mol CO2/mol MEA)
0.7
0.8
0.9
1
H1 NMR Speciation for 1.5 m PZ at 40oC
10
PZ + PZH+1
mole/kg-H2O of Species i
1
H+1PZCOO-1 + PZCOO-1
PZ
0.1
PZ(COO-1)2
0.01
Points: Ermatchkov et al. (2003)
Curves: This work
0.001
0
0.05
0.1
0.15
0.2
0.25
0.3
Loading (mol CO2/2∙mol PZ)
0.35
0.4
0.45
0.5
Enthalpy of CO2 Absorption in 7 m MEA at 40 and 120oC
140
120oC
Differential -HCO2 (kJ/mol-CO2)
120
Kim and Svendsen (2007)
100
80
40oC
60
This Work
40
20
0
0
0.1
0.2
0.3
0.4
0.5
Loading (mol CO2/mol MEA)
0.6
0.7
0.8
Enthalpy of CO2 Absorption in 2.4 m PZ at 40 and 120oC
120
120oC
Kim (2007)
Differential -HCO2 (kJ/mol-CO2)
100
80
40oC
This Work
60
40
20
0
0
0.1
0.2
0.3
Loading (mol CO2/2∙mol PZ)
0.4
0.5
Enthalpy of CO2 Absorption Predictions at 40 and 120oC
140
Differential -Habs (kJ/mol-CO2)
120
100
7 m MEA
2.4 m PZ
80
60
6 m K+ + 1.2 m PZ
40
5 m K+ + 2.5 m PZ
20
0.00001
0.0001
0.001
0.01
0.1
1
CO2 Partial Pressure (kPa) at 40 oC
10
100
1000
Specific Heat Capacity Results for loaded 7 m MEA
4.4
4.2
H 2O
4.0
a = 0.0
Cp (kJ/kg-K)
3.8
3.6
a = 0.139
3.4
3.2
a = 0.358
a = 0.541
3.0
2.8
2.6
MEA
120
Tem
100
per
atu 80 60
re ( o
C)
40
20
0.6
0.5
0.4
0.3
0.2
L
0.0
)
MEA
l
o
/m
O
ol C 2
m
(
ng
oadi
0.7
0.1
Specific Heat Capacity Refinement for loaded 7 m MEA
Specific Heat Cpacity (kJ/kg(H2O+MEA)-K)
4.3
H2O
4.1
a = 0.541
3.9
a = 0.139
3.7
3.5
3.3
MEA
3.1
2.9
2.7
20
40
60
80
Temperature (oC)
100
120
140
Specific Heat Capacity Refinement for loaded 2 m PZ
4.5
H2O
CP (kJ/(kgH2O+kgPZ)-K)
4
a = 0.000
a = 0.269
3.5
3
2.5
PZ
2
20
40
60
80
Temperature (oC)
100
120
140
SLE Results for Mixtures of H2O-PZ using DSC
120
110
Solubility Temperature (oC)
100
90
Liquid Solution
80
Bishnoi (2002)
70
60
10 m PZ
50
PZ (s)
40
25 m PZ
30
This work
20
20 m PZ
10
PZ∙6H2O (s)
0
0
0.1
0.2
0.3
0.4
0.5
0.6
Piperazine (weight fraction)
0.7
0.8
0.9
1
unit cell of K2PZ(COO)2
COO- complex
SEM image
PZ
K
Crystal Size: 0.43 x 0.33 x 0.08 mm
SLE Results for K+ + PZ Solutions
55
50
45
o
Temperature ( C)
KHCO3 (s)
40
35
5m
K+
K2PZ(COO)2 (s)
+ 3.6 m PZ
30
5 m K+ + 2.5 m PZ
6 m K+ + 1.2 m PZ
25
2
K+ 3
/P Z
Ra 4
tio
5
6
0.30
0.35
0.40
g (mo
L o a d in
0.45
0.50
0.55
0.60
+ 2m o
K
l
o
/m
l CO 2
+
0.65
l PZ)
Systems Exhibiting SLE Behavior for K+ + PZ Solutions
7
6
Systems which may exhibit solid
phase precipitation
6 m K+ + 1.2 m PZ
5 m K+ + 3.6 m PZ
5
K+ (m)
5 m K+ + 2.5 m PZ
4
3
2
1
0
0
0.5
1
1.5
2
2.5
PZ (m)
3
3.5
4
4.5
5
• In this work:
– Developed a new VLE apparatus = PCO2, PAmine, PH2O
– At typical lean absorber conditions:
PMEA = 64 ppmv PPZ = 25 ppmv
– Amine blends illustrate an enhanced capacity over MEA
– Enthalpy of CO2 absorption increased in temperature
summary
– Successfully measured Cp in loaded solutions between 40 and
120oC  Cp of CO2 may be negligible in loaded MEA and PZ
– Inferred a possible operating region for CO2 capture utilizing
aqueous PZ. Identified and determine the solubility of
K2PZ(COO)2 present in K+/PZ solutions
– Created a consistent rigorous thermodynamic model that
adequately predicts solubility, volatility, speciation, and
calorimetry in the base sub-component H2O-K2CO3-MEA-PZCO2 systems within Aspen Plus® 2006.5
This concludes my presentation…
Thank you for your
attention.