Study of adsorption-based CCS systems under wet conditions · Measurement of dry excess sorption....

Study of adsorption-based CCS systems under wet conditions

Dorian Marxa, Ronny Pinib, Marco Mazzottia

a Institute of Process Engineering, ETH Zurich, Switzerlandb Department of Energy Resources Engineering, Stanford University, USA

TCCS-6, 15 June 2011, Trondheim

Motivation

Adsorption processes used in CO2 capture and storage have to deal with the presence of moisture in the system. These include:

Flue gases

Gasification products

Coal seams used for ECBM

28 June 2011 Dorian Marx / [email protected] 2

Therefore it is important that we deal with wet sorbents.

Measurement of dry excess sorption

Dry adsorption-based separation systems are increasingly well studied


CO2

CH4

N2

Methods for measurement

are reliable and consistent

Plot on the left shows data

from two separate

laboratories

CSIRO

ETHZ

coalT = 55°C

Sakurovs et al., Energ. Fuel. 21 (2007) 992-997Mazzotti et al., J. Supercrit. Fluids 47 (2009) 619-627

Measurement of dry excess sorption

Excess sorption is the truly measurable quantity


CO2

CH4

N2

At high gas densities, the

adsorbed phase

experiences a buoyancy

coalT = 55°C

ex a a bn n V ρ= −

Sakurovs et al., Energ. Fuel. 21 (2007) 992-997Mazzotti et al., J. Supercrit. Fluids 47 (2009) 619-627

Modeling dry gas adsorption on AC and coal


0 0.2 0.4 0.6 0.80

0.1

0.2

0.3

0.4

0.5Adsorption of CO

2 on activated carbon

bulk phase density [g/cm3]

CO

2 ads

orbe

d [g

/g]

Langmuir model max 11

ex b b

b a

N knkρ ρρ ρ

= − +

0 0.2 0.4 0.6 0.80

0.05

0.1

0.15Adsorption of CO

2 on Sulcis coal


CO

2 ads

orbe

d [g

/g]

25°C

45°C65°C

45°C

60°C

Research on wet sorbents


AC Zeolites Silica coalETHZ This work

CSIRO Day et al. 2008

Okla. State University Fitzgerald et al. 2005

RWTH Aachen Kroos et al. 2002Monash Li et al. 2009

Univ. of Maine Brandani et al. 2004

Univ. of Queensland Do et al. 2009

Univ. of Illinois Qi et al. 2000

Vanderbilt University Qi et al. 2005

Univ. of Porto Ribeiro et al. 2008

Univ. of Stuttgart Gorbach et al. 2004

Univ. de Mons Billemont et al. 2011

CO2 on wet sorbent

water

CO2














CO2 on wet sorbent

water

CO2

0 0.2 0.4 0.6 0.8 10

5

10

15

20

25Water adsorption on activated carbon

relative humidity (Pw

/Psat

)

adso

rbed

wat

er [m

ol/k

g]


Pure water data and isotherm on activated carbon

Sources: Barton et al., Carbon 22 (1984) 265-272Rudisill et al., Ind. Eng. Chem. Res. 31 (1992) 1122-30

298.15 K / Barton et al. (ads/des)

Rudisill et al (ads only)


Pure water data and isotherm on activated carbon

0 0.2 0.4 0.6 0.8 10

90

180

270

360

450Water adsorption on activated carbon

relative humidity (Pw

/Psat

)

adso

rbed

wat

er [c

m3 /k

g]

298.15 K 0

1/21+expw

w

sat sat

VV

P PkP P

=

−

where:Vw – pore volume filled with

water [cm3/kg sorbent]V0 – specific pore volume

[cm3/kg sorbent]Psat – saturation pressure of

waterPw – partial pressure of water

k, P1/2 – model parameters

Sources: (data) Rudisill et al., Ind. Eng. Chem. Res. 31 (1992) 1122-30(model) Qi et al. J. Env. Eng. 126. (2000) 267-271














CO2 on wet sorbent

water

CO2


Data from Li et al. on activated silica

CO2 adsorption described by Langmuir model

Water adsorption described by modified BET model

Li et al. Langmuir 25 (2009) 10666-10675

Pure water isotherms

Temp

273K

CO2, N2 isotherms

303K


Data from Li et al. for CO2/water isotherm

For a good description, it is necessary to fit parameters for the interaction of water and CO2

298 K1 atm

Li et al. Langmuir 25 (2009) 10666-10675

Binary H2O + CO2

Single H2O














CO2 on wet sorbent

water

CO2

ETHZCSIRO

0 0.2 0.4 0.6 0.8 10

0.02

0.04

0.06

0.08

0.1

0.12Water adsorption on Sulcis coal

relative humidity (Pw/Psat)

adso

rbed

wat

er [g

/g]

Work on coal – CSIRO and ETHZ


Day et al., Int. J. Coal Geol. 74 (2008) 203-214

Pure water adsorption data, described by the Guggenheim-Anderson-de Boer model (GAB)

Pw/Psat

Model for adsorption of water on coal

Adsortion of pure water vapor onto coal has been described using the

Guggenheim-Anderson-de Boer (GAB) model.


model parametersWm [g/g] 0.032CG [-] 6.43K [-] 0.55

( )1 1 1

wm G

sat

w wG

sat sat

PW CPW

P PK C KP P

= − + −

0 0.2 0.4 0.6 0.8 10

0.02

0.04

0.06

0.08

0.1


relative humidity (Pw/Psat)

adso

rbed

wat

er [g

/g]


Measurements of sorption on wet coal

H2O/salt “Humidifier”Beaker

H2O/saltH2O/salt “Humidifier”Beaker

Saturated salt solutions used to controlrelative humidity.

Beaker with saturated salt solution inserted atthe bottom of the cell.

Coal sample let saturate under a constanthumidity atmosphere for 2 days.

Coal sample exposed to the high pressureCO2.

MSB slightly modified to ensure constant humidity during the adsorption experiments.

Procedure:


Interpretation of the results

Total excess sorption (CO2 and water) with respect to dry sample

total sorption

total volume increase due to adsorption2

* aCO= + wm m m

*V∆

eas b b 0 b met coal1 1 0

* b *

( , ) ( , ) ( )

m T M T M V Vm V

ρ ρ ρ

ρ

= − + +

= − ∆


Interpretation of the results

Total excess sorption (CO2 and water) with respect to dry sample

total sorption

total volume increase due to adsorption

CO2 excess sorption

*V∆

eas b b 0 b met coal1 1 0

* b *

( , ) ( , ) ( )

m T M T M V Vm V

ρ ρ ρ

ρ

= − + +

= − ∆

w2

2

eas b b 0 b met coalCO 1 1 0

a b *CO

( , ) ( , ) ( ) ( )

ρ ρ ρ

ρ

= − + + +

= − ∆

m T M T M m V V

m V

is constant

2

* aCO= + wm m m

wm

ETHZ

0 0.2 0.4 0.6 0.8-0.1

-0.05

0

0.05

0.1Excess CO2 on wet Sulcis coal


exce

ss C

O2 [g

/g]

CO2 adsorption on wet coal


salt NaCl MgCl2 LiClr.H. [%] 75 30 11

moisture [%] 10.3 5.5 2.7

318 K

excess calculated with respect to dry sample

ETHZ

0 0.2 0.4 0.6 0.8-0.1

-0.05

0

0.05



exce

ss C

O2 [g

/g]




moisture [%] 10.3 5.5 2.7

318 K

CSIRO

Increasing moisture

328 K


excess calculated with respect to dry sample

excess calculated with respect to wet sample

ETHZ

0 0.2 0.4 0.6 0.8-0.1

-0.05

0

0.05



exce

ss C

O2 [g

/g]




moisture [%] 10.3 5.5 2.7

318 K

CSIRO

Increasing moisture

328 K


Separate model parameters fit to each moisture level

Proposed modeling approach


0 0.2 0.4 0.6 0.8 10

0.05

0.1

0.15

0.2


relative humidity (P/Psat

)

adso

rbed

wat

er v

olum

e [c

m3 /g]

( )1 1 1

wm G

satw

w wG w

sat sat

PW CPV

P PK C KP P

ρ= − + −

Specific pore volume of sorbent



0 0.2 0.4 0.6 0.8 10

0.05

0.1

0.15

0.2



)

adso

rbed

wat

er v

olum

e [c

m3 /g]


pore space available for adsorption

2 2

2

2

, 1+CO CO

CO LCO

N kn

kρρ

=

( )1 1 1

wm G

satw

w wG w

sat sat

PW CPV

P PK C KP P

ρ= − + −



22(aq)CO ( )dissH COC k T = = f

0 0.2 0.4 0.6 0.8 10

0.05

0.1

0.15

0.2



)

adso

rbed

wat

er v

olum

e [c

m3 /g]



Water available for dissolution

2 2

2

2

, 1+CO CO

CO LCO

N kn

kρρ

=

( )1 1 1

wm G

satw

w wG w

sat sat

PW CPV

P PK C KP P

ρ= − + −



22(aq)CO ( )dissH COC k T = = f

0 0.2 0.4 0.6 0.8 10

0.05

0.1

0.15

0.2



)

adso

rbed

wat

er v

olum

e [c

m3 /g]



Water available for dissolution

2 2

0,

0

diss wCO w CO L

V Vn V C n

V −

= +

2 2

2

2

, 1+CO CO

CO LCO

N kn

kρρ

=

( )1 1 1

wm G

satw

w wG w

sat sat

PW CPV

P PK C KP P

ρ= − + −

0 0.2 0.4 0.6 0.8-0.1

-0.05

0

0.05

0.1

0.15

0.2total adsorbed excess on wet Sulcis coal


tota

l exc

ess

adso

rbed

[g/g

]

0 0.2 0.4 0.6 0.8-0.1

-0.05

0

0.05

0.1

0.15

0.2CO2 adsorbed excess on wet Sulcis coal


exce

ss C

O2 a

dsor

bed

[g/g

]

Results of the proposed model


2CO

eas a a b awm m m Vρ= + −

2CO

eas a b am m Vρ= −

Conclusions

Proposed model delivers encouraging results Extension to other adsorbent materials

Model is simple enough to have low computational requirements Use in simulation software for separation columns

Water/gas interactions still need to be better understood

Assumption of constant water content needs testing Modified experimental procedure Monitoring of gas phase composition


Study of adsorption-based CCS systems under wet conditions · Measurement of dry excess sorption....

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