THE UNIVERSITY OF TEXAS AT AUSTIN
THE UNIVERSITY OF TEXAS AT AUSTIN
Texas Carbon Management Program
Texas Carbon Management Program
Research needs and opportunities for
amine scrubbing for gas combustion
Gary T. Rochelle
Department of Chemical Engineering
WORKSHOP ON
TECHNOLOGY PATHWAYS FORWARD FOR
CCS ON NATURAL GAS POWER SYSTEMS
Washington, DC 20004
April 22, 2014
THE UNIVERSITY OF TEXAS AT AUSTIN
Texas Carbon Management Program
Messages
 Bellingham demonstrated technical feasibility
 Advanced processes improve economics, but need D & Demo
 Better solvents
 Better processes
 Bigger & Better equipment
 Environmental issues need preemptive resolution
 Oxidation, Nitrosation, Amine reclaiming, Amine aerosols
Better Second Generation Solvents
Properties at natural gas conditions, PCO2*= 0.1/1 kPa
Solvent
(m)
kg’avg x1e7
(mol/s∙Pa∙m2)
ΔCµ
(mol/kg)
-ΔHABS
(kJ/mol)
Tmax
7 MEA
12
0.70
77
121
11 MEA
8 PZ
5 PZ
7 MDEA/2 PZ
4 AMP/2 PZ
12
31
36
19
41
0.82
0.93
0.90
0.70
1.24
77
71
71
72
77
116
163
163
138
128
3
(°C)
Scrubbed
Flue Gas to
Atmosphere
DCC not needed
for water
Advanced
Absorber
for NGCC
Less Packing, Richer Solvent
No Prescubbing or DCC
Lean Amine
RECYCLE INTERCOOLING
to Cool Gas
Wet/Dry ??
HOT Flue Gas In
RECYCLE INTERCOOLING
TO Replace DCC
Rich Amine
Advanced flash stripper reduces Weq
8 m PZ at 0.25 lean loading
6 bar/150oC reduces compressor cost
CO2
Wpump= 4.4 kWh/tonne
Wcomp= 67.6
Wreb= 155.3
WEQ= 227.3
20K LMTD
Cold Rich BPS
9%
6.2 bar
Warm Rich BPS
30% 127 oC (BP)
Qreb=2.3 GJ/tonne
Rich Solvent
0.36 Ldg
Lean
Solvent
0.25 Ldg
Flash
Avg DT=5 K
150 oC
5
270
Gas takes 10% more energy than coal
WEQ (kWh / tonne CO2)
260
Simple Stripper
(NG, Rldg=0.36)
250
240
230
Advanced Flash Stripper
(NG, Rldg=0.36)
Simple Stripper
(Coal, Rldg=0.40)
220
210
200
0.20
Advanced Flash Stripper
(Coal, Rldg=0.40)
0.22
0.24
0.26
0.28
0.30
0.32
Lean loading (mol CO2 / mol alkalinity)
0.34
6
THE UNIVERSITY OF TEXAS AT AUSTIN
Texas Carbon Management Program
Bigger and better Equipment needs D & D
 Absorber - Single Vessel for 250 MW gas = 19 m
 Square, concrete, low DP packing
 Stripper - 7.5 m for 2 bar, 5 m for 8 bar
 Reboiler/convective steam heater
 Multiple, larger plate and frame exchangers
 Materials Selection/Corrosion – CS, SS, Concrete, polymer?
 Effective heat integration with NGCC
 Optimum design/controls for peaking load operation
7
THE UNIVERSITY OF TEXAS AT AUSTIN
Texas Carbon Management Program
Oxidation
 Amine Oxidation will be more significant with gas than with coal
 O2/CO2 = 5 for gas vs 0.4 for coal
 MEA makeup at Bellingham = 3 lbs/ton CO2
 Economically acceptable C= 2-3 $/ton CO2
 Environmentally questionable : NH3, aldehydes, et al.
 Advances in Understanding, gained mostly with air/CO2:
 catalysts/inhibitors; O2 mass transfer, thermal cycling
 Identified mitigation options need to developed and demonstrated
 N2 stripping, Inhibitors, Solvent Selection
8
THE UNIVERSITY OF TEXAS AT AUSTIN
Texas Carbon Management Program
Nitrosation
 Secondary amines react quantitatively with NO2 to make carcinogenic
nitrosamines, R2N-N=O
 Nitrosation will be more significant with gas
 NOx/CO2 = 10 ppm/3% > 10 ppm/12%
 Because of degradation all solvents will nitrosate
 Identified mitigation options need development & demonstration




Thermal decomposition at 150oC
Prescrubbing to remove NO2
Reclaiming to concentrate and remove
Water Wash to avoid gas emissions
9
THE UNIVERSITY OF TEXAS AT AUSTIN
Texas Carbon Management Program
Solvent Reclaiming
 Required for degradation products, RNNO, sulfate, nitrate, metals
 Effective reclaiming eliminates need for gas prescrubbing
 Thermal reclaiming of nonvolatile impurities
 Bellingham demonstrated1G thermal reclaiming w gas impurities
 2G thermal reclaiming will reduce amine losses
 Less attractive alternatives – required for nonvolatile solvents
 Ion exchange, Electrodialysis, Precipitation
 Volatiles processing to remove NH3, aldehydes, et al.
 All need development & demonstration with long term operation
10
THE UNIVERSITY OF TEXAS AT AUSTIN
Texas Carbon Management Program
Amine Aerosols / Water Wash
 Amine aerosol growth degrades water wash performance
 Amine aerosols will be less significant with gas
 No SO3 or fly ash
 However ambient particulate & SO2 may be problematic
 Needs science and monitoring on variable gas sources
11
THE international meeting on CCS
Austin Convention Center
Hosted by UT with IEAGHG
Rochelle – co-chair of Steering
1500+ participants
Sponsorship opportunities:
contribute $10k, 25k, or 50k
Exhibitor: $5k
www.GHGT.info
October 5 - 9, 2014 | AUSTIN, TX - USA
PCO2, OUT ≈ 0.3 kPa
PCO2, OUT ≈ 1.2 kPa
NATURAL GAS TURBINE vs.
COAL BOILER (8m PZ)
CO2 to
Compression
P*CO2, LEAN ≈ 0.1 kPa
P*CO2, LEAN ≈ 0.4 kPa
Absorber
Stripper
Main Cross
Exchanger
Reboiler
Flue Gas
In
PCO2, IN ≈ 3 kPa
PCO2, IN ≈ 12 kPa
P*CO2, RICH ≈ 1 kPa
P*CO2, RICH ≈ 4 kPa
Opportunities: Natural Gas Turbine vs. Coal Boiler
 Benefits of leaner loading range
1) Higher CO2 absorption rate constant
 Increased free amine
N CO 
 ~2x coal reaction rate
2
D CO 2 k 2  Am 
LMPD
H CO 2
2) Improved Operating Solvent Capacity
 Flat VLE curve in NG loading range
 ~20% increase in CO2 capacity per kg solvent circulated
 Recycle intercooling to cool gas
 Cool gas in absorber to reduce overall column temperatures
14
Challenges: Natural Gas Turbine vs. Coal Boiler
 Lower flue gas CO2 concentration => Smaller driving force
 Coal: ~3.2 kPa LMPD; NG: ~0.8 kPa LMPD
 Lower CO2 pressure in stripper (leaner loading range => reduced
PCO2)
 More mechanical compression
 More H2O vapor per mole of CO2 (irreversible losses in condensation)
15
 Larger gas volume
 Column diameter increases
 Blower size increases
Reddy et al., 2003
Chapel et al., 1999
Sander & Mariz, 1992
Bellingham, NGCC, 1991-2005
98.5% on stream in 2004
14 tonne/hr
Air Cooled
1.5-2 bar
40 MW Slipstrm
13 % O2
3 % CO2
7? % H2O
150? oC
16
110-1200C
4.2 GJ/t (?)
30-50 psig
Kettle
3 lbs MEA/t CO2 makeup (?)
Bellingham, NGCC, Fluor
Stripper
3x40 m
Sander and Mariz, 1992
Absorber
7.5x55 m
DCC
8.4x21m
17
Case Studies
 Combined cycle gas turbine
 3 – 4.5% CO2; 6 – 8% H2O
 8m PZ solvent
 LLDG = 0.25 mols CO2/mols alkalinity
 NEW ABSORBER CONCEPTS
 Recycle Intercooling
 Removing Direct Contact Cooler
18
Scrubbed
Flue Gas to
Atmosphere
No Intercooling
Lean Amine
Gas In
Flue Gas IN
DCC
Rich Amine
L/G (mol/mol)
0.279
4.0
0.287
No Intercooling
3.0
0.299
2.0
0.323
Conditions
NGCC (4.1% CO2)
LLDG = 0.25 mols CO2/mols alk.
CO2 Removal = 90%
1.0
0.396
0.0
0
50
100
Total Packing Metal Area/G ( m2/mol)
150
Rich Loading (mols CO2/mols alk.)
5.0
Simple Intercooling
Recycle Intercooling
5.0
L/G (mol/mol)
4.0
0.279
0.287
No Intercooling
3.0
0.299
Simple Intercooling
2.0
0.323
1.0
Recycle
Intercooling
( LRecycle/G = 3)
0.0
0
50
100
Total Packing Metal Area/G ( m2/mol)
0.396
150
Rich Loading (mols CO2/mols alk.)
Conditions
NGCC (4.1% CO2)
LLDG = 0.25 mols CO2/mols alk.
CO2 Removal = 90%
Removing the Direct Contact Cooler
24
Scrubbed
Flue Gas to
Atmosphere
BASE CASE WITH DCC
RECYCLE
INTERCOOLING
Gas In
Flue Gas IN
DCC
Rich Amine
70
65
Temperature (°C)
60
WITH DCC
4.E-06
3.E-06
55
50
Molar Flux CO2
MAX T = 47.1° C
2.E-06
Liquid T
45
Molar Flux (kmol CO2/s/m2)
90% Removal
Lean α = 0.250 mols CO2/mols alkalinity
Rich α = 0. 358 mols CO2/mols alkalinity
Interfacial Area (1000 m2) : 289
L/G = (1.2*Lmin) = 1.106 mol/mol
TLiquid in : 40°C
TFlue gas in : 40°C
5.E-06
1.E-06
40
Vapor T
35
0.E+00
0
26
Top
0.2
0.4
0.6
Z/ZTOTAL
0.8
1
Bottom
Scrubbed
Flue Gas to
Atmosphere
NEW DESIGN NO DCC
Lean Amine
RECYCLE
INTERCOOLING
RECYCLE TO
REPLACE DCC
HOT Flue Gas In
Rich Amine
70
65
Temperature (°C)
60
55
4.E-06
3.E-06
Vapor T
Molar Flux CO2
MAX T = 47.7° C
50
NO DCC
2.E-06
45
Liquid T
1.E-06
40
TGAS, MIN = 41.2° C
35
0.E+00
0
28
Top
0.2
0.4
0.6
Z/ZTOTAL
0.8
1
Bottom
Molar Flux (kmol CO2/s/m2)
90% Removal
Lean α = 0.250 mols CO2/mols alkalinity
Rich α = 0.355 mols CO2/mols alkalinity
Interfacial Area (1000 m2 ): 286
L/G = (1.2*Lmin) = 1.134 mol/mol
TLiquid in : 40°C
TFlue gas in : 121°C
5.E-06
THE UNIVERSITY OF TEXAS AT AUSTIN
Texas Carbon Management Program
No DCC vs. DCC
 Nearly identical absorber packing requirement & rich loading
 Performance & profiles without DCC replicate DCC case
 Trade-off: Additional intercooling loop vs. cost of DCC
 Operational risk: reliability of wet-dry interface
Simple Stripper using 8 m PZ
6 bar/150oC reduces compressor cost
Condenser
CO2
150 bar
6~12 bar
Compressor
Cross
exchanger
CO2 Rich Solvent
~140 oC
Stripper
1 bar
150 oC
Pump
Trim cooler
CO2 Lean Solvent
Reboiler
30
Reboiler duty (GJ/tonne CO2)
Reboiler duty (GJ / tonne CO2)
3.0
Simple Stripper
(NG, Rldg=0.36)
2.8
2.6
Advanced Flash Stripper
(NG, Rldg=0.36)
Simple Stripper
(Coal, Rldg=0.40)
2.4
2.2
Advanced Flash Stripper
(Coal, Rldg=0.40)
2.0
0.20
0.22
0.24
0.26
0.28
0.30
Lean loading (mol CO2 / mol alkalinity)
0.32
0.34
31
THE UNIVERSITY OF TEXAS AT AUSTIN
Energy Analysis
Texas Carbon Management Program
Estimated Total Equivalent Work
12% CO2, 90% Removal, 150 bar, 40 °C
W (kWh/tonne CO2)
500
W equiv  0 . 75 Q
400
300
Tstm  Tsink
Tstm
 W comp  W pump
MEA
1.08 GJ/t
PZ
200
0.72 GJ/t
100
0
2000
Minimum Work = 109 kWh/tonne = 0.39 GJ/t
CO2 Separation = 46 kWh/tonne = 0.17 GJ/t
Compression = 63 kWh/tonne = 0.23 GJ/t
2004
Year
2008
32