carbon cullinane

8/13/2019 Carbon Cullinane

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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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