carbon cullinane
TRANSCRIPT
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Solvent Development for AqueousAbsorption/Stripping of CO 2
The University of Texas at AustinJ. Tim Cullinane and Gary T. Rochelle
April 27, 2004
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Outline Overview Process Considerations Solvent Development
Experimental Methods
Development of Aqueous K +
/PZ Other UT Research Activities
Degradation
Process Modeling Pilot Plant/Packing Selection
Conclusions
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U.S. CO 2 Emissions from Fossil Fuel
Combustion by Sector Commercial
4.8%
Residential9.7% Power Plant - Petroleum
2.0%
Industrial31.8%
Power Plant - Coal47.1%
Power Plant - Natural Gas4.6%
Total U.S. Emissions = 3635.7 Tg CO 2 Eq.Excludes Transportation, EPA (1999)
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Advantages of Aqueous Absorption/Stripping
Near Commercial Technology Process used for treating H 2 & natural gas MEA demonstrated on small coal plants Promoted K 2CO 3 used for H 2 treating
Post-process Technology Development Lower cost and less risk to process Resolve problems in small pilot plants Demo Full-scale absorbers with 100 MW gas
Problems 20 - 40% energy use High capital cost
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Enhancing CO 2 Capture by Amines
1. Contactor Development Packing
2. Process Flowsheet Innovations Multi-pressure stripper
Inter-cooling3. Energy Integration Power plant specific
4. Engineering Development Large-scale equipment
5. Solvent Development
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CO2
Capture by Amines
Sour Gas10% CO 2
2-4 mol H 2O/mol CO 2Sweet Gas1% CO 2
Rich Amine Lean Amine Reboiler
Absorber T = 4060 oC
Stripper T = 100120 oC
Cooler
PCO2 * ~ 300 Pa
PCO2
* ~ 3000 Pa
H = 20-25 kcal/mol CO 2
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Solvent Development K +
/PZ1. Thermodynamics2. Rates of Absorption3. Degradation
4. System Modeling
5. Pilot Plant
Bench-Scale Work
Fundamental
Process Flowsheet
Large-Scale Work
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N NH H C
O
O
N NO
OH
N
+
N O
OH
H
N NO
O O
O
O
O OCO
O
O
H
H OO
OH
N NO
OH C
O
O
N NH H N+
NH
HH
N N O
O
H
CO2
Absorption by K +/Piperazine
+
+
+
Carbonate Species
Piperazine Species
2+
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PZ Speciation by 1H NMR
NH
CH2CH2
NHCH2
CH2
NCH2
CH2
NCH2
CH2
CO
CO
O
NHCH2
CH2
NCH2
CH2
CO
NH
CH2CH2
NHCH2
CH2
NCH2
CH2
NCH2
CH2
CO
OC
O
O
NHCH2
CH2
NCH2
CH2
CO
ONH
CH2
CH2
NCH2
CH2
CO
ONH
CH2
CH2
NCH2
CH2
CO
O
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Wetted-Wall Column
WWC(38 cm 2)
N2
CO 2
Flow Controllers(4 6 L/min)
Saturator
(25 110o
C)
Heater (25 110 oC) Solution Reservoir
(1000 cm 3)
Condenser
IR CO 2Analyzer
Sample Port
Pressure Control(35 60 psig)
Pump(2 4 cm 3/s)
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Model Parameter Summary
2037NMR, P CO2 *PZ, K +, CO 2, H 2O
4063aNMR, P CO2 *PZ, CO 2, H 2O
214UNIFACPZ, H 2O
1204P CO2 *KHCO 3, K 2CO 3, H 2O
6814Boiling pt. elev., P H2O *K 2CO 3, H 2O
Data
PointsParametersData TypesSystem
a. 6 parameters for equilibrium constants also regressed
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Loading (mol CO 2/mol PZ)
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
F r a c
t i o n o
f T o
t a l P Z
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
PZ
H+PZCOO -
PZH +
PZ(COO -)2PZCOO-
Total ReactiveSpecies
Speciation in 1.8 m PZ at 60 oC~300 Pa ~10000 Pa
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Loading (mol CO 2/(mol K+ + mol PZ)
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
F r a c
t i o n o
f T o
t a l P Z
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
PZ
H+PZCOO -
PZH +
PZ(COO-
)2
PZCOO -
Total ReactiveSpecies
Speciation in 5.0 m K +/2.5 m PZ at 60 oC~300 Pa ~10000 Pa
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Equilibrium in K +/PZ at 60 oC
[CO 2(aq)] Absorbed (m)
0 1 2 3 4
P C O 2
* ( P a
)
1
10
100
1000
10000
1 . 8 m
P Z
3 . 6 m
K + / 0
. 6 m
P Z
3 . 6
m K + / 1
. 8 m
P Z
5 . 0 m
K + / 2 .
5 m P Z
7 m ( 3 0
w t % ) M E A
6. 2 m
K + / 1
. 2 m
P Z
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Normalized Flux at 60 oC
P CO 2* (Pa)100 1000 10000
N o r m a
l i z e
d F l u x
( m o
l / P a - c m
2 - s
)
1e-10
5.0 M MEA
3.6 m K +/0.6 m PZ
3.6 m K +/1.8 m PZ
6.2 m K +/1.8 m PZ
3.6 m K +/3.6 m PZ
2.5 m K +/2.5 m PZ
5.0 m K +/2.5 m PZ
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Absorption Rate in 5.0 m K +/2.5 m PZ
P CO 2* (Pa)
100 1000 10000
N o r m a
l i z e
d F l u x
( m o
l / c m
2 - P a - s
)
1e-10
1e-9
40oC
80 oC
60 oC
100 oC
110 oC
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Research Activities at UT Bench-scale
Wetted-wall Column VLE, rates
NMR speciation Degradation Other solid solubility, transport properties
Modeling Thermodynamics Rate Process
Pilot Plant Contactor Testing
Solvent Testing
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Oxidative Degradation of MEA
OH CH 2 CH 2 NH
H?
O2
NH 3
Formaldehyde
Formate, Acetate
Rate is measured by NH 3 evolution from a sparged reactor vesselGas analysis is quick/liquid analysis requires long experimentsUncertainty in the stoichiometry of O 2 in the reaction
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Degradation Results
Conclusion: Mass Transfer Limited?
45.816.7Air w/Agitation
27.825.0Air
Goff and Rochelle
12.920.0Air Chi and Rochelle5.02.9Pure O 2Hofmeyer et al.
2.61.050% O 2Girdler
0.81.0Air Blachly and Ravner 0.40.006Air Rooney et al.
Max. Rate(mM/hr)
Gas Flow/Liq.Vol (min -1)
SpargeGas
Study
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Process Modeling Explore Optimum Operating Conditions
30
40
50
60
3 3.2 3.4 3.6 3.8 4 4.2 H e a
t r e q u
i r e m e n t
( k c a
l / g m o
l C O
2 )
lean loading (m)
10
5
2.5
P*CO2
1.25 kPa
optimumlean
OptimalMEA
40C Absorber 1.6 atm stripper
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Process Configuration Explore unique flowsheets
MultistageCompressor
W=7.4 kc/mol CO 2
CO 2130 atm
Q=20 kc/mol CO 2
118 C
113 C
Multipressure Stripper
Leanldg=0.34
Rich
ldg=0.46 115 C
4 atm
2.8 atm
2 atm
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Pilot Plant Operation NaOH/Air Screen packing areas
Packing areas based on 0.75 H 2O/ft, 5 gpm/ft 2
Solvent Simulation of absorber/stripper Quantify real solvent performance Includes impurities (Fe 2+, degradation, etc.)
Packing Wetted Area (ft 2 /ft 3)CMR 2, plastic 27
IMTP #40 44
CMR 2, metal 48Montz B1-250 64Montz B1-350 91
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Conclusions E-NRTL model describes speciation and VLE K + increases the amount of reactive species in
solution CO 32-/HCO 3- is an effective buffer Apparent carbamate stability is increased w/ K +
Solvent capacity increases with concentration andis comparable to MEA
Habs can be lower than other amine-basedsystems and depends on the ratio of K +:PZ
Absorption rate is 1.5 to 4 times faster than MEAor other amine-promoted K 2CO 3 solutions
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Acknowledgements
Texas Advanced Technology Program:
contract 003658-0534-2001 George Goff Degradation Tunde Oyenekan Process Modeling Dr. Ben Shoulders The University of
Texas at Austin, Department of Chemistry
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Questions?