Modeling CO2 Capture Using Concentrated PZ - · PDF file2 Capture Using Concentrated PZ ... Rate-based calculations for 5 m packed columns RadFrac with rate- based calculation of H&M

Modeling CO2 Capture Using Concentrated PZ

Jorge M. Plaza, David H. Van Wagener, Peter Frailie, Eric Chen, Gary T. RochelleLuminant Carbon Management Program

Department of Chemical EngineeringThe University of Texas at Austin

1st Post Combustion Capture ConferenceAbu Dhabi, United Arab Emirates , May 18, 2011

Outline

Concentrated PZ

Model Framework

5deMayo and Guy Fawkes

Pilot Plant Campaigns

Intercooling & Interheating

Conclusions and Future Work

18/05/2011 The University of Texas at Austin 2

8m Piperazine


Benefits of 8 m PZ

Double MEA CO2 absorption rate & capacity

Thermally stable to 150 °C

Negligible oxidative degradation


NN HH

NN+

HH

HNNH

O-

OPZ

PZH+ PZCOO-

Model Framework


Model Characteristics

Rigurous independent absorber/ stripper models Built in Aspen Plus® RateSepTM

Model integration matching loadings and solvent rate

Thermodynamics Regressions in Aspen Plus® for Cp, VLE, PZ volatility Guy Fawkes model – Absorber 5deMayo – Stripper

Activity – based kinetics WWC data by Dugas (2009) Fitted by adjusting k2 and diffusivity of CO2 and amine species

Transport properties Density and viscosity using FORTRAN subroutines Diffusivity implemented using Dugas (2009) and FORTRAN subroutine


Pilot Plant Campaigns


CO2 Capture Pilot Plant

Column ID = 0.43 m (16.8 in)

Packed height – 6.1 m in 2

beds (3.05 m each)

12mol% CO2 Synthetic flue

gas

Equiv to 0.1-0.2 MW

3-6 tons CO2/day

18/05/2011 8The University of Texas at Austin

8 m PZ Pilot Plant Flowsheet

Gas Acc

Condenser

Liq Acc

Feed Tank

Blower

Stripper

CrossExchanger

Trim Cooler

Air

CO2 Makeup

GasOut

Recycled CO2

Lean AmineRich Amine

20-60 psia

Intercooling

12% CO2


Absorber Intercooling Process Flowsheet


Campaign Conditions

Campaign November ‘08 September ‘10

PZ (m) 5, 8, 9 8

Gas rate (ACFM) 350 350 -750

Liquid Rate (gpm) 12, 15, 18 8 – 26

Absorber Packing Mellapak 2X RSP 250

Stripper Packing Mellapak 2X Mellapak 2X

Intercooling No Yes/No

Runs 14 13


Pilot Plant Modeling


PP Absorber model

1 packing section (30 segments) Mellapak 2X

3 packing sections:

1st & 3rd : 3.05 m RSP-250 (15 segments)

2nd reduced to min. mass transfer

Intercooling using pump around 2nd section

Fortran subroutines for:

Interfacial area (Wang) based on Tsai (2010)

kL & kG (Wang) for RSP-250


CO2 lean flue gas

Rich solvent

Lean solvent

CO2

H2O

N2O2

CO2

H2OPZ

Inlet Gas

Liquid intercooling

PP Absorber model validation


LoadingFlow

T, P

TemperatureFlow

yCO2, yH2OFlow

Match removal by changing lean loading

Loading

T, P

0.E+00

2.E-08

4.E-08

6.E-08

8.E-08

1.E-07

30

40

50

60

70

0 0.5 1

CO

2M

ass

Tran

sfer

(km

ol/s

)

T (o

C)

Z/ZTotal

T and mass transfer for L/G= 2.9350 ACFM


RSP- 250Removal = 91%• Lean=0.21/0.22• Rich=0.37/0.38yCO2-out =0.011/0.010

0.E+00

2.E-08

4.E-08

6.E-08

8.E-08

1.E-07

30

40

50

60

70

0.0 0.2 0.4 0.6 0.8 1.0

CO

2M

ass

Tran

sfer

(km

ol/s

)

T (o

C)

Z/ZTotal

T and mass transfer for L/G= 2.9350 ACFM -Intercooled


RSP- 250Removal = 90%• Lean=0.22/0.25• Rich=0.38/0.41yCO2-out =0.013/0.012

PP Absorber Simulations


Variable Average Adjustment

Campaign 2008 (Mellapak 2X) 2010 (RSP-250)

Removal Matched (NTU)

LLDG 0.01 (±0.01) 0.02 (±0.01)

MLDG ----- -0.01 (±0.04)

RLDG 0.02 (±0.01) 0.02 (±0.01)

TG-out -1.0 oC (±0.3) -1.0 oC (±0.5)

TL-out 0.2 oC (±0.3) 0.2 oC (±0.3)

Stripper Calculations Rate-based calculations for 5 m packed columns RadFrac with rate-based calculation of H&M transfer Reactions assumed to reach equilibrium - high T In-house correlation for packing area (Tsai, 2010)

Equilibrium calculations for other units Flash tanks Heaters/cross exchangers Pumps

Equivalent work: electric capacity used for capture

comppumprebeq WWWW ++=

+−+

=KT

KKTQW

reb

rebreb 5

3135750.


8 m PZ Pilot Plant Example

Condensate

CO2

Lean

Rich48.0 °C0.365 ldg1.23 kg/s

52.0 °C0.287 ldg / 0.286 ldg1.21 kg/s / 1.18 kg/s

106.8 °C / 111.7 °C0.033 kg/s / 0.035 kg/s

131.9 kW

27.1 kW

272.3 kPa

122.3 °C / 122.2 °C

2010 - Run 1


PP Stripper Simulations


Variable Average Adjustment

Campaign 2008 (Mellapak 2X) 2010 (Mellapak 2X)

Lean flow -0.5% (±0.5%) 0.7% (±3.9%)

LLDG 2.8 % (±1.8%) -1.2% (±3.5%)

Overhead T -9.0oC(±4.7) -3.2oC (±2.5)

CO2 rate -7.8% (±7.1%) -2.6% (±3.9%)

Reboiler T 2.1 oC (±1.9) 0.2oC (±1.1)


1E+1

1E+2

1E+3

1E+4

1E+5

1E+6

1E+7

0.2 0.3 0.4 0.5

PC

O2 (P

a)

CO2 Loading (moles/equiv. PZ)

CO2 Solubility in 0.9-12 m PZ

Solid lines: Aspen Plus®

Dashed lines: Empirical model Fawkes Model, 8m PZ


1E+1

1E+2

1E+3

1E+4

0.2 0.3

PC

O2 (P

a)





40oC

60oC

80oC


1E+1

1E+2

1E+3

1E+4

1E+5

1E+6

1E+7

0.2 0.3 0.4 0.5

PC

O2 (P

a)






1E+3

1E+4

1E+5

0.35 0.4 0.45 0.5

PC

O2 (P

a)





40oC

60oC

80oC


1E+1

1E+2

1E+3

1E+4

1E+5

1E+6

1E+7

0.2 0.3 0.4 0.5

PC

O2 (P

a)






1E+5

1E+6

1E+7

0.35 0.4 0.45

PC

O2 (P

a)



120oC

140oC

160oC

Process Configurations


Water for reflux

CO2 Multistage compressor

Lean

Rich

Stripper

Water knockout

Simple Stripper (SS)150 bar

Pumping for gravity and P drop

5 m IMTP#40 packing

5°C approach

Isothermal (variable P) at maximum allowable T

150°C

Rich loading assumed constant:

5 kPa CO2 @ 40°C


2-Stage Flash (2SF)

Water for reflux


Lean

Rich


Equal vapor production per stage

Interheated Column (IH)

Water for reflux


Lean

Rich

Stripper

Liquid drawoff


Benefit of interheated column

30

32

34

36

38

40

42

44

0.20 0.25 0.30 0.35

Equi

vale

nt W

ork

(kJ/

mol

CO

2)

Lean Loading (mol CO2/equiv. PZ)

8 m PZ0.40 rich loading

150°C in reboiler(s)

0.31 lean

loading

2-Stage Flash

Simple Stripper

Interheated Column


Intercooling +

Interheating


Case Conditions

1100 MW plant – 90% Removal (1/3 gas flow)

Absorber and stripper modeled separately Solvent flow rate based on 1.1 Lmin for absorber

Stripper optimum based on Minimum Weq

Complete system model: Optimum stripper loadings fed to absorber

Absorber loadings adjusted based PP results

Resulting ldgs fedback to stripper and Weq recalculated

Compared to 9m MEA using Plaza et al. 2010


8 m PZ Flowsheet

Stripper

CrossExchanger

Trim Cooler

GasOut

Lean AmineRich Amine

CO2 to Compression

Intercooling

Flue Gas

Interheating


Optimum - Absorber

Variable Units Value

Solvent ------ 8m PZ 9m MEA

yCO2 mol frac 0.15

Gas flow m3/s (actual) 286

Gas T °C 40

L/G mol/mol 6.2 9.2 (48%)

Lean ldg mol CO2/mol alk 0.300 0.390

Rich ldg mol CO2/mol alk 0.391 0.492

Packing Type ----- RSP-250

Packing per kmolCO2 removed/hr

Characteristic m2 83 145 (74%)


Optimum - Stripper

Variable Units Value

Solvent 8m PZ 9m MEA

Stripper P bar 8.71 5.1

Stripper T °C 150 120

Packing type -------- IMTP - 40

Pump work kJ/mol CO2 1.5 2.2

Compression work to 15MPa

kJ/mol CO2 9.3 11.5

Heat work kJ/mol CO2 21.2 21.5

Equivalent work kJ/mol CO2 32.0 36.2 (13.1%)18/05/2011 The University of Texas at Austin 36

Conclusions


Conclusions

38

PP absorber performance can be adequately matched using PZ model and correlations by Wang (2010).

Temperature profiles require revision Location of the thermocouples in the absorber Effect of kL and kG in water transfer Thermal inertia

Ldgs required adjustments possibly due to VLE fit. Larger deviation for intercooled cases and lean ldg Minimum adjustment in the stripper (high T fit)

18/05/2011 The University of Texas at Austin

Conclusions

39

An absorber/stripper system for 90% for 1/3 gas flow of a 1100 Mw unit has been designed.

Interheating and intercooling can improve capture performance (6% reduction of Weq)

It is possible to integrate separate rigorous absorber and stripper to generate an optimized capture unit

8 m PZ optimum system requires: 74% more packing (83 m2 per kmol CO2/hr removed)

48% less solvent ( L/G = 6.2 mol/mol)

13% less work requirement (32 kJ/mol CO2)

18/05/2011 The University of Texas at Austin

Luminant Carbon Management ProgramPSTC staff

Thank you!18/05/2011 The University of Texas at Austin 40

Questions?

Jorge M. [email protected]


Documents

Modeling CO2 Capture Using Concentrated PZ - · PDF file2 Capture Using Concentrated PZ ... Rate-based calculations for 5 m packed columns RadFrac with rate- based calculation of H&M