Jorge M. PlazaThe University of Texas at Austin

January 10-11, 2008

OutlinePrevious Work

Intercooling effect

Conclusions

Future Work

Modeling K+/PZCullinane K+/PZ (2005)

e-NRTL to predict VLE and speciation

Equilibrium and interactions regressed in FORTRAN

Experimental rate constants and diffusion coefficients

Hilliard K+ /PZ(2005)

Thermodynamics into ASPEN Plus ®

Chen

Pilot plant testing (2004 – 2006)

4 Campaigns 5m/2.5m, 6.4m/1.6m K+/PZ and 7m MEA

Absorber Model developed for K+/PZ (2006)

System ModelingFreguia MEA (2002) - Ratefrac

Aspen Plus® rate-based model based on Dang (2001)

Equilibrium by Jou et al. (1995)

Intercooling for MEA absorber

Ziaii MEA (2006) - RateSepTM

Developed rate-based model for MEA in Aspen Plus ® based on Freguia (2002), Hikita (1977) and Aboudheir (2002)

Plaza K +/PZ(2006 – 2007)Activity based kinetics for 4.5m/4.5m K+/PZ

Intercooling with split feed

Approaches to Absorber modeling

Lj-1

Lj

Gj

Gj+1

Lj-1

Lj

Gj

Gj+1

Lj-1

Lj

Gj

Gj+1

Lj-1

Lj

Gj

Gj+1

Lj-1

Lj

Gj

Gj+1

Rate-based ApproachReaction equilibrium

Rate-based ApproachReaction KineticsEnhancement Factor

Rate-based ApproachReaction KineticsFilm Reactions

Equilibrium ApproachReaction Equilibrium

Equilibrium ApproachReaction Kinetics

Reaction

Mass Transfer

Enh

R RR

Kenig et al. Reactive Absorption: Optimal Process Design Via Optimal Modeling. Chem. Eng. Sci. 2001, 56, 343-350.

Rate BasedReaction equilibrium

Rate BasedReaction kineticsEnhancement factor

Rate BasedReaction kineticsFilm Reactions

EquilibriumReaction equilibrium

EquilibriumReaction kinetics

Gas Film

PG

Pi = H[CO2]i

P*i P*B

[CO2]*i [CO2]*B

Bulk Gas Bulk LiquidInterface

Rxn Film Liquid Film

Film Discretization

Absorber ReactionsPZCOO-

PZ(COO-)2

b= OH-, H2O, PZ, CO3-2, PZCOO-

HCO3-

b=PZ, PZCOO-, OH-

bHPZCOObCOPZ 2

2 2PZCOO CO b PZ COO bH

bHHCObCO 32

Effect of Intercooling for 4.5m K+/4.5m PZ

Gas Out

Q

Lean

Rich5.48 kmol/s

H=15 m D=9.8 m

CMR-MTL metal NO-2P

5% V. Liquid Hold up

90% removal

12.7% mol CO2

(500 MW Plant)

Gas in

Variable ldg & flow

Intercooling with 4.5m K+/ 4.5 m PZ

Rich loading vs. lean loading. 4.5m K+/ 4.5 m PZ

T and CO2 rate profiles 4.5m/4.5 m K+/ PZ . Loading = 0.44

No Intercooling

T and CO2 rate with intercooling 4.5m/4.5 m K+/ PZ. Loading=0.44

T and CO2 rate profiles. 4.5m/4.5 m K+/ PZ. Loading = 0.21

No Intercooling

T and CO2 rate with intercooling. 4.5m/4.5 m K+/ PZ Loading=0.21

T and CO2 rate profiles. 4.5 m K+/ 4.5 m PZ. Loading=0.315

No Intercooling

T and CO2 rate with intercooling. 4.5m/4.5 m K+/ PZ Loading=0.315

Effect of Intercooling for 11m MEA

Gas Out

Q

Lean

Rich5.48 kmol/s

H=15 m D=10.6 m

CMR-MTL metal NO-2P

1% V. Liquid Hold up

Variable removal

12.7% mol CO2

(500 MW Plant)

Gas in

0.40

Semi Lean

Q

0.46

T and CO2 rate profiles for no intercooling. 11 m MEA.

85% Removal85% Removal

T and CO2 rate profiles with intercooled semilean feed. 11 m MEA.

92.3% Removal92.3% Removal

T and CO2 rate profiles with intercooled semilean feed & intercooling. 11 m MEA.

93.0% Removal93.0% Removal

CO2 removal results for MEA absorber with split feed

Intercooling CO2 Removal (%)

None 85.0

Single 92.3

Double 93.0

Conclusions

Optimum intercooling is related with T bulge position

Tbulge = pinch then intercooling efficientTbulge = pinch then intercooling efficient

Tbulge away from pinch then not much Tbulge away from pinch then not much

improvementimprovement

ConclusionsFor a simple absorber system intercooling allows

increase in solvent capacity as high as 45%. Intercooling improves performance for MEA split

feed as high as 10% Intercooling offers a benefit in energy

consumption in the stripper thanks higher rich solvent loading

Intercooling is most effective for operations in the range of 0.27 to 0.40 loading for the lean feed.

Future WorkSubstitute new Hilliard (2007) thermodynamics

Model Aboudheir laminar jet to extract kinetics with

RateSepTM

Fix ASPEN to represent physical properties : ρ, D, H

Regress MEA pilot plant data to validate model