Accurate Screening of Candidate Solvents by the Wetted Wall Column

Xi Chen, Ross Dugas, Fred Closmann, Shan Zhou, Gary T. Rochelley

The University of Texas at Austin

12th MEETING of the INTERNATIONAL POST‐COMBUSTION CO2 CAPTURE NETWORK

Sep 29, 2009p

Regina, Canada

Outline• Background

• Research needs• Research needs• Literature review

• Apparatus• Apparatus• Wetted Wall Column (WWC)

• Results:• Results:• CO2 solubility, CO2 capacity, Heat of absorption• Absorption/Desorption Rates• Absorption/Desorption Rates

• Conclusions

Research Needs• Previous amine capacity & kinetics studies:

– Low amine concentration (< 3 M)

– Zero or very lean CO2 loading

– Narrow temperature range (25~60 oC) 

• Typical industrial conditions for CO2 capture

– Absorber: 40‐60 oC

St i 80 120 oC– Stripper: 80‐120 oC

– 12% CO2 in flue gas at 1atm and 90% removal: CO2‐loaded amine solvent (P*CO2 lean=0.5 kPa and P*CO2 rich=5 kPa)amine solvent (P CO2,lean 0.5 kPa and P CO2,rich 5 kPa) 

• Previous amine screening efforts

– Simple gas sparging: Absorption rate affected by solution property (density, viscosity & surface tension etc.)

– CO2 capacity for industrial conditions not available 

Why WWC for Screening?Why WWC for Screening?

• More representative of commercial packingMore representative of commercial packing than laminar jet or stirred cell.

• More accurate VLE and mass transfer rate in• More accurate VLE and mass transfer rate in loaded solution. 

Ad f d i f b b d i• Adequate for design of absorber and stripper.

[Amine]

Previous work with WWC

Literature Solvents[Amine]max

(molality)

Dugas 2009 MEA/PZ 13

/Cullinane 2005 K+/ PZ 4

Al‐Juaied 2004 DGA / Morpholine 18Al Juaied 2004 DGA / Morpholine 18

Bishnoi 2000 MDEA/PZ 8

Pacheco 1998 MDEA/ DGA 12

Mashewa 1995 MDEA/DEA 9

Viscosity@

Scope of this work

Conc. (m)

Viscosity@40oC&P*CO2

=5kPa (cP)( )

PrimaryA i

Ethanolamine (MEA) 7 2.5

Ethylenediamine (EDA) 12 14Amines

Diglycolamine® (DGA®) 10 n/a

Piperazine (PZ) 8 10Piperazine & derivatives

p ( )

N‐(2‐hydroxyethyl)piperazine(HEP) 7.7 17

1‐(2‐Aminoethyl)piperazine (AEP) 6 231 (2 Aminoethyl)piperazine (AEP) 6 23

Hindered Amines

2‐amino‐2‐methyl‐1‐propanol (AMP) 4.8 4

2‐piperidineethanol (2‐PE) 8 242‐piperidineethanol (2‐PE) 8 24

PromotedTertiary Amine

Methyldiethanolamine (MDEA)/Piperazine (PZ)

7/2 8

Wetted Wall Column

kR 1

1 = 022CO

EkH

R = CO

COP

kR

][1 *

032

∂

∂=

gk lEk TPRODl COk ][ 2, ∂

'2

*

00

11][

111 22

ggT

CO

PRODll

CO

gG kkCOP

kEkH

kK+=

∂

∂++=

2, ][ ggTPRODllgG

)( lCOgCOgCO PPKN −=

22

222

)(

)(

,,'

,,

lCOiCOg

lCOgCOgCO

PPk

PPKN

−=

22

2

,,

'

lCOiCO

COg PP

Nk

−=⇒

2

22

][2

,,

bCO

lCOiCO

HAmkD

≈2COH

10m DGA® @ 60°C, CO2 ldg= 0.4 mol/mol alka

2.5 x 10-7

1.3 x 10-7

m2 ))

E lib i i t (P * 2670 P )

0-3000 -1500 0 1500 3000m

ol/(s

*c Equlibrium point (Pco2*=2670 Pa)

-1.3 x 10-7

3000 500 0 500 3000

Flux

(m

2 5 x 10-7-2.5 x 10

Driving force (PCO2,g

- P*CO2,l

) (Pa)

PIPERAZINE DERIVATIVESPIPERAZINE DERIVATIVES

CO2 Solubility 7 7m HEP

N

NH

OH

100

7.7m HEP2//ln ααα ⋅+⋅+⋅++= eTdcTbaP

NH

10100 °C5kPa

1

P* (k

Pa)

80 °C

0.5kPa

0.1

P

60 °CCapacity=0.68mol CO2/kg

0.01

40 °Cmol CO2/kg (H2O+HEP)

0 0.05 0.1 0.15 0.2 0.25 0.3

CO2 Loading (mol/mol alkalinity)

6m AEP N

NH

NH2

100100

ol))/1(

)(lnTdPdRHabs −=Δ

NH

8010

n (kJ/mo)/1( Td

5kPa

40

60

0 1

1

sorption

P* (k

Pa)

80 °C

100 °C

0.5kPa

20

40

0.01

0.1

at of a

bsP

60 °C

0.66

0

20

0.001

0.01

Hea

40 °Cmol CO2/kg Solv.

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4

CO2 Loading (mol/mol alkalinity)

HINDERED AMINEHINDERED AMINE

8m 2‐PE NH

OH

100

10

80 °C

100 °CPZ@100 °C

5kPa

1

* (kPa)

60 °C

80  C5kPa

0.1

P*

40 °C

0.5kPa 1.23mol CO2/kg Solv.

0.01

PZ@40 °C (Hilliard & Dugas)

0.01

0.1 0.2 0.3 0.4 0.5 0.6 0.7

CO2 Loading (mol/mol alkalinity)

PRIMARY AMINEPRIMARY AMINE

12m EDA

NH

NH2

100NH2

10 MEA@100°C (Hilliard & Dugas)

MEA@40°C

5

0 1

1

P* (k

Pa)

100 °C

MEA@40°C

0.5

0.01

0.1P

80 °C0.78mol CO2/kg Solv

0.001

0.01

40 °C60 °C

Solv.

0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55

CO2 Loading (mol/mol alkalinity)

PROMOTED TERTIARY AMINEPROMOTED TERTIARY AMINE

7m MDEA/2m PZ  NHNHOH

NOH

CH3

100

PZ@100 °C

10100 °C

P* (k

Pa)

80 °C

° ( ll d )

5

1

P

60 °C

PZ@40 °C (Hilliard & Dugas)

0.5

0.1

40 °C0.71mol CO2/kg Solv.

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35

CO2 Loading (mol/mol alkalinity)

CO2 Capacity for 5kPa Rich Solution

8m PZ

8 2 PE

1.0mol/kg 

ne))

8m 2‐PE

1.0

pacity (m

er+amin

7m MEA

CO2cap

(wate

7.7m HEP

0.1

5 50 500 50005 50 500 5000

Lean Partial Pressure of CO2 (Pa)

1 4

1.2

1.4/kg 

2-PE

0.8

1

mol CO

2/mine))

PZMDEA/PZ EDA

AMP

0.6

pacity (m

H2O

+am MDEA/PZ

HEPAEP

MEA

0.2

0.4

CO2 ca (

DGA

0

0 0.2 0.4 0.6 0.8 1 1.2

Rich CO2 loading (mol CO2/mol amine)

Enthalpy of CO2 Absorption84

J/mol)

7m MEA

76

80

ption (kJ

8m 2‐PE4.8m AMP 12m EDA

72

O2ab

sor

7.7m HEP

68

py of C

O 7.7m HEP8m PZ

60

64

Enthal

7m MDEA/2m PZ

0.1 0.2 0.3 0.4 0.5 0.6 0.7

CO2 Loading (mol/mol alkalinity)

1E-05

22' ][ CODAmk

2

22' ][

CO

COg H

DAmkk ≈

1E 06ol/s

. Pa.

m2 )

40˚C1E-06

k g' (

mo

100˚C80˚C60˚C

0 C

Filled Points – 2, 5, 8, 12 m PZEmpty Points – 7, 9, 11, 13 m MEA

1E-070.01 0.1 1 10

Empty Points 7, 9, 11, 13 m MEA

(by Ross Dugas)

P*CO2 @ 40C (kPa)

Absorption/Desorption rates for 7.7m HEP

5E-06

bCOiCO

COg PP

Nk

,,

'

22

2

−=

m2 )

7 m MEA@40°C8 m PZ@40°C

,, 22

5E-07

ol/s

. Pa.

m

HEP@100°C

HEP@80°C

k g' (

mo HEP@80°C

HEP@40°CNOH

5E 08

HEP@60°C

NH

5E-080.01 0.1 1 10

P*CO2 @ 40C (kPa)

8m 2‐PE 

40°C

m2 )

7 m MEA@40°C8 m PZ@40°C

80°C

60°C

40 C

1E-06

ol/s

. Pa.

m

100°C

80°C

k g' (

mo

NH

OH

1E 071E-070.01 0.1 1 10

P*CO2 @ 40C (kPa)

12m EDA m

2 )

8 m PZ@40°C80°C

1E-06

ol/s

. Pa.

m 7 m MEA@40°C

100°C

k g' (

mo

60°C40°CNH2

1E 07

NH2

1E-070.01 0.1 1 10

P*CO2 @ 40C (kPa)

7m MDEA/2m PZ m

2 )

7 m MEA@40°C8 m PZ@40°C

80°C60°C40°C

1E-06

ol/s

. Pa.

m

100°C

k g' (

mo

NHNHN

CH3

1E 07

NHNHOH

NOH

1E-0710 100 1000 10000

P*CO2 @ 40C (Pa)

5E-06

7m MDEA/2 PZ

m2 ) 8m PZ

7mMEA

5E-07

ol/s

. Pa.

m 7m MEA

k g' (

mo

7.7m HEP8m 2‐PE

5E 085E-0850 500 5000 50000

P*CO2 @ 40C (Pa)

Apparent second order reaction rate of amine with CO

Amine k2 (m3/mol·s) Source

of amine with CO2

PZ 54 (Bishnoi and Rochelle 2000)

AEP 30 (Bishnoi 2000)( )

HEP 12 (Bishnoi 2000)

EDA 8.8 (Sada et al. 1977)

MEA 5.9 (Blauwhoff et al. 1984)

DGA 5.1 (Pacheco 1998)

AMP 0.7 (Saha and Bandyopadhyay 1995)

2-PE 0.6 (Xu et al. 1993)

MDEA 0.005 (Versteeg and Van Swaaij 1988)

5

6

PZ

MDEA/PZ

4

s∙Pa

∙m2 )

MEA3

107 m

ol/s

HEP

AEP

MEA

DGAAMP

1

2

kg' (×1

AEP

EDA2-PE

AMP

0

0 10 20 30 40 50 600 10 20 30 40 50 60

k2 (m3/mol∙s)

Conclusions

Fast solvents

Conc

CO2 Capacity@PCO2,lean=0.5kPa

kg’ @PCO2=5kPa

∆Habs@PCO2=1.5kPa

Amine Conc(m) (mol/kg

(water+amine))

(×107mol/s·Pa·m2) (kJ/mol)

MDEA/PZ 7/2 0.71 5.7 67PZ 8 0.79 5.3 70

MEA 7 0 47 3 1 82MEA 7 0.47 3.1 82MEA 11 0.52 2.5 84

CO2 Capacity@P 0 5kP

kg’ @PCO25kP

∆Habs@PCO21 5kP

Slow solvents

Amine Conc.(m)

PCO2,lean=0.5kPa =5kPa =1.5kPa

(mol/kg (water+amine))

(×107mol/s·Pa·m2) (kJ/mol)( ))

MEA 7 0.47 3.1 82HEP 7.7 0.68 2.9 69

DGA® 10 0.38 2.4 81AEP 6 0.66 2.3 722 PE 8 1 23 2 732-PE 8 1.23 2 73AMP 4.8 0.96 1.7 73EDA 12 0.78 1.6 80

AcknowledgementAcknowledgement

• Luminant Carbon Management ProgramLuminant Carbon Management Program

• Industrial Associates Program for CO2 Capture by Aqueous Absorptionby Aqueous Absorption

Accurate Screening of Candidate Solvents by the Wetted WallSolvents by the Wetted Wall

Column

Xi Chenxi@che.utexas.edu