Amino Acid Solvents1st Post Combustion Capture Conference

Abu Dhabi, United Arab Emirates. May 18th, 2011

Le Li, Gary Rochelle

University of Texas at AustinLuminant Carbon Management Program

Overview Introduction Amino Acid Solvents Experimental Methods

Data Analysis

Experimental Results K+ based solvents

Rate CO2 solubility Heat of Absorption

Na+ based solvent Summary

Conclusions Amino Acid Solvents for Natural Gas Application

1 5/18/2011

Introduction - Amino Acid Solvents

Amino Acid Solvents

Intrinsic Characteristics Nonvolatile Biodegradable Stable for oxidative degradation*

Precipitation with CO2 loading Activate amino group for reaction with

CO2 with equi-molar base (KOH, NaOH) Activated amino group react with CO2

same as amines

Amino Carboxylic Acid

Amino Sulfonic Acid

Low Environmental Impact

* Rochelle Group, 3rd Quarterly Report 2010, Alex Voice

3 5/18/2011

Amino acid Structure MW Solubility Previous Work

Glycine 75Precipitate @ 6m,

P*CO2 = 0.5kPa

reaction rate/kinetics, CO2

solubility, physical parameter

Sarcosine 89Soluble @ 6m

with CO2 loadingphysical parameters,

CO2 solubility

Taurine 125Precipitates @

5m, P*CO2 = 0.05 kPa

reaction rate/kinetics, CO2

solubility, physical parameter

Homo -taurine

139Soluble @ 6m

with CO2 loadingN/A

β -Alanine

89Precipitates @

6.5 m P*CO2=6kPaphysical parameters,

Solid solubility

Proline 115 Soluble at 8mWWC rate and solubility,

physical parameters

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Introduction- Experimental Methods

WWC Set Up

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CO2 flux

kg’ PCO2*

'

111

ggg kkK+=

)( *,, 222 lCOgcoGco PPKN −=

Data Analysis Rate (kg’)

CO2 Solubility (PCO2*): function of T and loading (α)

Heat of Absorption: function of loading (α) only

Calculate: kg’avg and cyclic capacity

2* //)ln(2

ααα ⋅+⋅+⋅++= eTdcTbaPCO

( )α⋅+−=−=∆ dbRTd

PdRH Abs )/1(

ln

Directly Measured

),][,,,('222 etcAmDHkfk iCOCOg =

NCO2= kl ([CO2]i-[CO2]b)= kg’ (Pco2i – PCO2

*)

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Operation Lean & Rich Loadings

Cyclic Capacity = mol CO2/kg solution=

kg’avg =

)/( solutionkgAlkmol⋅∆α

Solvent

12% CO2@ 1 atm

PCO2=12kPa

PCO2=1.2kPa1.2% CO2@ 1 atm

PCO2* =0.5kPa@ αlean

αrich @PCO2* = 5kPa

Coal Flue Gas

90%Removal

LMCOgasCO

LMCO

PP

Flux

)( *,

,

22

2

−

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Flue gas change = loadings change

Coal Fired Plants GT Natural Gas

Absorber(@ 1atm)

Flue Gas PCO2 (kPa)

PCO2* @ 40 C(kPa)

Flue GasPCO2 (kPa)

PCO2* @40 C(kPa)

Bottom(rich) 12 5 3 1

Top(lean) 1.2 0.5 0.3 0.1

kPaPkPaP COCO 5.05 22 == −=∆ ααα kPaPkPaP COCO 1.01 22 == −=∆ ααα

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Experimental Results:K+ based solvents

Absorption Rates for 6.5m beta-AlaK

1.E-07

1.E-06

1.E-05

5 50 500 5000

k g' (

mol

/s∙P

a∙m

2 )

P*CO2 @ 40•C (Pa)

40°C

60°C

80°C

100°C

7m MEA @ 40°C

8m PZ @ 40°C

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2

2

CO

b2CO'

H

[Am]kD≈gk COAL

NATURAL GAS

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0.001

0.01

0.1

1

10

100

0.3 0.35 0.4 0.45 0.5 0.55 0.6

P* C

O2

(kPa

)

CO2 loading (mol CO2/mol Alk)

7m MEA40 C

40 C

60 C

80 C

100 C

7m MEA @ 100 C

CO2 Solubility of 6.5m beta AlaK

5/18/201113

0.001

0.01

0.1

1

10

100

0.3 0.35 0.4 0.45 0.5 0.55 0.6

P* C

O2

(kPa

)

CO2 loading (mol CO2/mol Alk)

7m MEA40 C

40 C

Solvent Capacity for 6.5m beta AlaK

5 kPa

0.5 kPa

CoalCapacity0.25 mol

CO2/mol alk

GasCapacity0.28 mol

CO2/mol alk

MEA Capacity= 0.5 mol CO2/mol alk)/( solutionkgAlkmol

Capacity

⋅∆= α

40

50

60

70

80

90

0.001

0.01

0.1

1

10

100

1000

0.3 0.35 0.4 0.45 0.5 0.55 0.6

Hab

s(k

J/mol

)

P* C

O2

(kP

a)

CO2 loading (mol CO2/mol alk)

Habs β-AlaK

Habs 7m MEA

Heat of Absorption

( )α⋅+−=−=∆ dbRTd

PdRH Abs )/1(

ln

2//)ln( ααα ⋅+⋅+⋅++= eTdcTbaP

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40 C

60 C

80 C

100 C

Summary of Results

AminoAcid(m)

CO2 Capacity (mol CO2/kg

Solution)

kg’avg (@40 C)(x 10-7 mol CO2/s

Pa m2)

Mid ∆Habs(kJ/mol)

PCO2=1.5kPa

PCO2=0.5kPa

Coal Gas Coal Gas Coal Gas

GlyK (3.55) 0.25 0.25 3 10 6469

GlyK (6) 0.35* 0.35 0.2* 3.2 64*

SarK (6) 0.22 0.24 5 19 57 64

Tau/Htau (3/5) 0.2* 0.23 2.2* 10 75* 80

βAlaK (6.5) 0.25* 0.29 2* 7 64* 67

MEA (7m, Dugas) 0.47 0.55 4.3 12 70 75X3

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~ 50% 7m MEA

Experimental Results:Na+ Solvent

4.5m SarNa

AminoAcid(m)

CO2 Capacity (mol CO2/kg

Solution)

kg’avg (@40 C)(x 10-7 mol CO2/s

Pa m2)

Mid ∆Habs(kJ/mol)

PCO2=1.5kPa

PCO2=0.5kPa

Coal Gas Coal Gas Coal Gas

GlyK (3.55) 0.25 0.25 3 10 6469

GlyK (6) 0.35* 0.35 0.2* 3.2 64*

SarK (6) 0.22 0.24 5 19 57 64

Tau/Htau (3/5) 0.2* 0.23 2.2* 10 75* 80

βAlaK (6.5) 0.25* 0.29 2* 7.4 64* 67

MEA (7m, Dugas) 0.47 0.55 4.3 12 70 75

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CO2 Solubility of Sarcosine

5/18/201118

0.01

0.1

1

10

100

1000

0 0.2 0.4 0.6 0.8 1

PC

O2*

(kP

a)

CO2 Loading (mol CO2/mol alk)

40°C

120°C

60°C80°C

100°C

CH3 NH

O-

O

Empty Square: SarK (Arnu NTNU)Filled Square: 6 m SarK (WWC)Asterisk (*): 4.5 m SarNa (WWC)

Result 4.5m SarNa

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PropertyOperation condition

SarNa4.5 m

SarK6 m

MEA 7 m(Dugas, 2009)

kg'avg(• 107 mol/s∙Pa∙m2)

Coal 4.5* 5 4.3

Gas 11 19 12

Capacity(mol CO2/kg solvent)

Coal 0.31* 0.35 0.47

Gas 0.31 0.35 0.55

∆Habs(kJ/mol)

Coal(@P*CO2=1500)

54* 70

Gas(@P*CO2=500)

62 75

CH3 NH

O-

O

Rate vs. Capacity (Coal)

0

2

4

6

8

10

0 0.2 0.4 0.6 0.8 1 1.2

k g' av

g@

40

C (

x107

mol

/pa∙

s∙m

2 )

CO2 Capacity (mol CO2/kg solvent)

5/5 MDEA/PZ

Primary Amine

PZ Derivative

PZ based solvents

Hindered Amines

Amino Acids

SarK

2-PE

PZ

2MPZ

MEA

EDA

)/( solutionkgAlkmolCapacity ⋅∆= α

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Limitations

Intrinsic low capacity 0.2-0.3mol CO2/kg solvent (50% 7m MEA)

Solubility limits alkalinity in solution Base (Na+ / K+)increase solvent masskg solution = (amino acid + H2O + base+)

Precipitation at rich loadings

)/( solutionkgAlkmolCapacity ⋅∆= α

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Amino Acids for Natural Gas Applications

Solvent Criteria for Natural Gas (vs. Coal) Lower CO2 content (Gas: 3 vol%, Coal: 12%) Operate at leaner loading regions Amino Acids Advantage, Amines Advantage

Higher O2 content (Gas:15 vol%, Coal: 8%) Effect of oxidative degradation more important (12X) Amino Acids ? , Amines ?

Higher total gas rate (Gas = 2 X Coal) Solvent volatility more important, capacity less

important Amino Acids Advantage, Amines Disadvantage

Low Environmental Impact Amino Acids Advantage, Amines Disadvantage

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Conclusions

5/18/201125

6m SarK has competitive rates against 7m MEA K+ salt of amino acids are more soluble than Na+ salt Base choice (K+/Na+) does not change CO2 solubility Two limitations of amino acid solvents Low capacity (~50% 7m MEA) Rich loading solid precipitations

Amino acids not competitive at coal conditions Low rates Low heat of absorption Except: Tau/Htau blend

Environmental advantage

Appropriate for natural gas applications

leli@che.utexas.edu

Thank You!

26 5/18/2011

Neutralization

Activate amino group for reaction with CO2 with equi-molar base (KOH, NaOH, K2CO3, etc)

NH3+– R – COO- + KOH • NH2 – R – COO-K+ + H2O

Activated amino group react with CO2 like amines

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Reactions with CO2

Deprotonated amino acids behave like amines Primary / Secondary amino acid

Tertiary amino acid [AminoAcid] + [CO2] + [H2O] [AminoAcid+] + [HCO3

-]

k f← → kr

B-H+

(Termolecular Mechanism)

Bicarbonate formation

Carbamate formation

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1.00E-07

1.00E-06

1.00E-05

10 100 1000 10000

k g' @

40•

C (

mol

/s∙Pa∙m

2 )

P*CO2 @ 40•C (Pa)

8m PZ

Tau/HtauK3/5m

GlyK 3.55m

SarK 6m

MEA 7m

ProK8m

β AlaK6.5m

Rate (kg’) for Amino Acids (K+) at 40 C

TauK 5m COALNATURAL GAS

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2

2

CO

b2CO'

H

[Am]kD≈gk

Heat of Absorption (coal range)

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Rates of 4.5 m SarNa

5/18/201131

1.E-07

1.E-06

1.E-05

5 50 500 5000

k g' (

mol

/s∙P

a∙m

2 )

PCO2* @ 40°C (Pa)

40°C60°C

80°C

100°C

7m MEA @ 40°C

8m PZ @ 40°C

6 m SarK@ 40°C

CH3 NH

O-

O

Natural Gas Flue Gas Properties

21% O279% N2

100-200%Excess

CH4

Natural Gas Coal

Flue Gas Rate (400MW) 2.5 x 106 m3/hr 1.5 x 106 m3/hr

CO2 3% 12%

O2 15% 5-8%

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