Absorber Performance with Piperazine:Importance of Physical Liquid Film Mass Transfer

Darshan Sachde and Gary Rochelle

Importance of Physical Liquid Film Mass Transfer

Darshan Sachde and Gary Rochelle

Texas Carbon Management Program

The University of Texas at AustinThe University of Texas at Austin

PCCC3 Regina, Saskatchewan

9/8/20159/8/2015

Overview Modeling Background

Theoretical Basis : Film TheoryTheoretical Basis : Film Theory

Rate-based Parameter Sensitivityl f k k Relative Resistance of kL, kg, reaction rates

Evaluating uncertainty in kLEvaluating uncertainty in kL

Conclusions2

Modeling Framework: Rate Based Absorber Solvent Model :Thermo & Kinetic PZ Model

(“Independence”, Frailie 2014, Aspen Plus® )( p , , p )1. Thermo: e-NRTL regressed to fit experimental data

(amine volatility, VLE, heat capacity, speciation/NMR) y p y p2. Kinetics/Mass Transfer: Rate constants and diffusion

coefficients from wetted wall column data

Packing Mass Transfer Model (Tsai, Wang, Song)1. Regress pilot scale air-water column data 1. Regress pilot scale air water column data kL = f(uL/ap, packing geometry, μ)k = f(u /a packing geometry)kg f(uG/ap, packing geometry) ae = f(uL/ap, ρL, σ)

Aspen Plus® RateSep

Rate Parameter Sensitivity Analysis

Mass Transfer with Fast Chemical Rxn (Film Theory)B lk V Bulk LiquidBulk Vapor Bulk Liquid

PCO2,Bulk[Am] Bulk

[CO2]B lkVapor Film Rxn Film Liquid Film

[CO2]Bulk

Represents reaction kinetics;

Influenced by kL,Reactants 5

Rate Parameters via Film Theory

Coupled with

kL,Reactants

6

Film Theory (Pseudo-First Order)

At Pseudo-First order conditions (fast reactions, not ( ,instantaneous): kg” = kg’ (Total liquid film resistance) kg = kg (Total liquid film resistance) kL,Reactants & kL,Products are not limiting

E b b d f f (MEA PZ) Expect over most absorber conditions for fast amines (MEA, PZ) Explicit calculation of liquid film resistance 7

Rate Parameter Sensitivity: GOALS Identify Controlling Resistance As a function of position in columnAs a function of position in column For a wide range of operating conditions (CO2

sources L/G LLDG solvent systems etc )sources, L/G, LLDG, solvent systems, etc.)

Use results to validate model Are sensitivity results robust over expected y p

uncertainty in parameters?

Use results to guide absorber design choices Packing/Contacting type, solvent recycle, etc.

8

Scrubbed Flue Gas 

Rate Parameter Sensitivity: METHOD

Lean Amine1

For stages i = 1 to nFor parameters = k kFor parameters = kG, kL,

SMALL step size required to ensure n

SMALL step size required to ensure local linearity (+/-1%)

Result: Mass transfer resistance as f i f i i i b b

9

Gas In

Rich Amine

a function of position in absorber

Scrubbed Flue Gas 

Rate Parameter Sensitivity: METHOD

Lean Amine1 Coal-Fired Boiler (14.7% CO2)

8 m PZLLDG = 0.15 mols CO2/mols alk.

CO2 Removal = 90%2

No Intercooling1.2 *LMIN

n

1.2 LMIN

10

Gas In

Rich Amine

1.0011

0.80eter) kL

0.60

parame

0.40

x)/dln(

0.20

CO2Flux

k0.00dl

n(C kG

‐0.200 0.2 0.4 0.6 0.8 1

Z/ZtotalTOP BOTTOM

1.00Temperature Effects

12

0.80eter) kL

0.60

parame

0.40

x)/dln(

0.20

CO2Flux

k0.00dl

n(C kG

‐0.200 0.2 0.4 0.6 0.8 1

Z/ZtotalTOP BOTTOM

1.00Loading Effects Dominate (Steep VLE, incr. μ, depleted [Am])

13

0.80eter) kL

0.60

parame

0.40

x)/dln(

0.20

CO2Flux

k0.00dl

n(C kG

‐0.200 0.2 0.4 0.6 0.8 1

Z/ZtotalTOP BOTTOM

Rate Parameter Sensitivity: METHOD Bounding Cases R t L l l i t /b di Repeat Local analysis extreme/bounding

parameter values, e.g.:p g Reaction parameters: Reflect fastest/slowest

expected solvent systemexpected solvent system Mass transfer parameters (kL, kG): Alternate

contactor designs Uncertainty in parameters y p NOTE: Combination of parameters (reaction and

mass transfer) define approach to limitsmass transfer) define approach to limits

14

1 2E‐4MP250Y Wang, 2015

1 0E‐4

1.2E‐4

8 0E‐5

1.0E‐4

Wang (Air‐Water)6 0E‐5

8.0E‐5

(m/s) 

4 0E‐5

6.0E‐5

k L(

2 0E‐5

4.0E‐5L/ 0.5 * / 0.63 0.54

0 0E+0

2.0E‐5

15

0.0E+00 0.005 0.01 0.015 0.02

uL (m/s)

1 2E‐4Wang, 2015MP250Y

Bravo (1985)1 0E‐4

1.2E‐4

Wang8 0E‐5

1.0E‐4

Wang(Air‐Water)

6 0E‐5

8.0E‐5

(m/s) 

Hanley (2012)

4 0E‐5

6.0E‐5

k L(

2 0E‐5

4.0E‐5

0 0E+0

2.0E‐5

16

0.0E+00 0.005 0.01 0.015 0.02

uL (m/s)

1 2E‐4Wang, 2015MP250Y

Bravo (1985)1 0E‐4

1.2E‐4

8 0E‐5

1.0E‐4

Wang(Air‐Water)

6 0E‐5

8.0E‐5

(m/s) 

Hanley (2012)

4 0E‐5

6.0E‐5

k L(

2 0E‐5

4.0E‐5

Wang (8 m PZ)

0 0E+0

2.0E‐5

L/ 0.5 * / 0.63 0.54 µ/µo ‐0.5

17

0.0E+00 0.005 0.01 0.015 0.02

uL (m/s)

1 2E‐4Wang, 2015MP250Y

Bravo (1985)1 0E‐4

1.2E‐4

8 0E‐5

1.0E‐4

6 0E‐5

8.0E‐5

(m/s) 

kL (HIGH) ~ 5 x kL (BASE)

4 0E‐5

6.0E‐5

k L( ( ) ( )

2 0E‐5

4.0E‐5

Wang (8 m PZ)

0 0E+0

2.0E‐5

18

0.0E+00 0.005 0.01 0.015 0.02

uL (m/s)

1.00Coal‐Fired Boiler (14.7% CO2)LLDG = 0.15 mols CO2/mols alk.

CO Removal 90%

0.80

eter)

CO2 Removal = 90%1.2* LMIN

Comparison to 5* kL, BaseApproaching PFO Limit

0.60

parame

HIGH CASE

pp g

0.40x)/dln(

HIGH CASE

0 20CO2Flux kL

HIGH CASE

0.20

dln(C

kGHIGH CASE

0.000 0.2 0.4 0.6 0.8 1

‐0.20Z/Ztotal

1.00Coal‐Fired Boiler (14.7% CO2)LLDG = 0.15 mols CO2/mols alk.

0.80

eter)

CO2 Removal = 90%1.2* LMIN

Comparison to 5* kL, Base

0.60parame

HIGH CASE

0 40x)/dln(

0.40

CO2Flux BASE CASE

BASE CASE

0.20dln(C kL

HIGH CASE

0.00

HIGH CASE

0 0.2 0.4 0.6 0.8 1Z/Ztotal

Conclusions Liquid side physical mass transfer resistance dominant Liquid-side physical mass transfer resistance dominant

across most of absorberH ld ti diti f 8 PZ (L di Holds across operating conditions for 8 m PZ (Loading,

Intercooling, CO2 concentration)Diminishing benefits of enhancing kinetics aloneDiminishing benefits of enhancing kinetics alone

Bounding Case (5 x k ) approaches PFO Bounding Case (5 x kL) approaches PFO 80% of absorber is reaction controlledRi h d till hibit i ifi t k i tRich end still exhibits significant kL resistance

P D l t O t iti ith PZ Process Development Opportunities with PZReduce solvent viscosity (5 m PZ) – Pilot Plant Results

N l d i (hi h i i l l )Novel contactor design (high intensity e.g., solvent recycle)21

22

80

901.00

Liquid T70

800.80 Liet

er)

kL

Liquid T

50

600.60

quid Teparame

40

50

0 40

emperax)

/dln(

300.40 ture (C)CO

2Flux

10

200.20

)dln(C

Coal‐Fired Boiler (14.7% CO2)LLDG = 0.15 mols CO2/mols alk.

CO2 Removal = 90%1 2* LMIN (NO IC)

00.000 0 2 0 4 0 6 0 8 1

1.2* LMIN (NO IC)

0 0.2 0.4 0.6 0.8 1

Z/Ztotal

1.0023

0.80eter)

kL

0.60

parame

Coal‐Fired Boiler (14.7% CO2)LLDG = 0.15 mols CO2/mols alk.

8 m PZCO2 Removal = 90%

0.40

x)/dln( CO2 Removal = 90%

No Intercooling

0.20

CO2Flux

k0.00dl

n(C kG

‐0.200 0.2 0.4 0.6 0.8 1

Z/ZtotalTOP BOTTOM

7.5 0.220 RiConditionsCoal‐Fired Boiler (14 7% CO )

6.0 0.238

ich LoadCoal‐Fired Boiler (14.7% CO2)LLDG = 0.15 mols CO2/mols alk.

CO2 Removal = 90%

4.5l/mol)

No Intercooling  0.267

ding (m

4.5

/G (m

o 0.267

mols CO

3.0L/ 0.326

2 /mols1.05*LMIN

1.5 Isothermal (40°C) 0.501

alk.)

0.00 25 50 75 100 125

Total Packing Metal Area/G ( m2/mol/s) 24

7.5 0.220 RiConditionsCoal‐Fired Boiler (14 7% CO )

6.0 0.238

ich LoadCoal‐Fired Boiler (14.7% CO2)LLDG = 0.15 mols CO2/mols alk.

CO2 Removal = 90%

4.5l/mol)

No Intercooling  0.267

ding (m

4.5

/G (m

o 0.267

mols CO1.8*LMIN

3.0L/ 0.326

2 /mols

1.2*LMIN 1.05*LMIN

1.5 Isothermal (40°C) 0.501

alk.)

0.00 25 50 75 100 125

Total Packing Metal Area/G ( m2/mol/s) 25

1.00Conditions

Coal‐Fired Boiler (14.7% CO2)G 0 l CO / l lk

26

0.80

eter) kL 1.05*LMIN

LLDG = 0.15 mols CO2/mols alk.CO2 Removal = 90%

0.60parame

0 40x)/dln(

0.40

CO2Flux

0.20dln(C

1.05*LMIN

0.00

1.05 LMIN

0 0.2 0.4 0.6 0.8 1Z/ZtotalTOP BOTTOM

1.00Conditions

Coal‐Fired Boiler (14.7% CO2)G 0 l CO / l lk

27

0.80

eter) kL 1.05*LMIN

LLDG = 0.15 mols CO2/mols alk.CO2 Removal = 90%

0.60parame

1.2*LMIN

0 40x)/dln(

0.40

CO2Flux

0.20dln(C

1.2*LMIN

1.05*LMIN

0.00

1.05 LMIN

0 0.2 0.4 0.6 0.8 1Z/ZtotalTOP BOTTOM

1.00Conditions

Coal‐Fired Boiler (14.7% CO2)G 0 l CO / l lk

28

0.80

eter) kL 1.05*LMIN

LLDG = 0.15 mols CO2/mols alk.CO2 Removal = 90%

0.60parame

1.2*LMIN

0 40x)/dln(

1.8*LMIN

0.40

CO2Flux

1.8*LMIN

0.20dln(C

1.2*LMIN

1.05*LMIN

0.00

1.05 LMIN

0 0.2 0.4 0.6 0.8 1Z/ZtotalTOP BOTTOM

Rate Parameters via Film Theory

kL,ReactantsRepresents

reaction “film”

29

Pilot Plant Results: Solvent Viscosity EffectsEffects

5 m PZ vs. 8 m PZ: Absorber Performance

T t RPZ 

CSolvent R t

Gas R t

Lean Loading ( l

P*CO2@ 

Rich Loading ( l CO2Test Run Conc.

(molal)Rate(GPM)

Rate(ACFM)

(mol CO2/mol alk.)

@40°C(Pa)

(mol CO2/mol alk.)

2Removal

) )

19 5

14 5000.235 107 0.361 80%

14 8 0 236 85 0 342 75%14 8 0.236 85 0.342 75%

28 5

14 3500.238 114 0.352 96%

15 8 0.239 91 0.328 93%

33 5

10 2 3500.221 83 0.395 94%

3 10.2 35016 8 0.225 68 0.344 91%

5 PZ i ifi l f 8 PZ5 m PZ significantly outperforms 8 m PZ31

12Conditions

Coal Fired Boiler (14 7% CO )

9

Coal‐Fired Boiler (14.7% CO2)5 m PZ: LLDG = 0.18 mols CO2/mols alk.8 m PZ: LLDG = 0.20 mols CO2/mols alk

P*CO2 @ 40C = 0 04 kPa9

l/mol) P CO2 @ 40C = 0.04 kPa

CO2 Removal = 90%In‐and‐Out Intercooling

6

/G (m

oL/

5 m PZ

38 m PZ

00 20 40 60 80

Total Packing Metal Area/G ( m2/mol/s) 32

12

99

/mol)

6

G (m

ol/

l b dL/G

5 m PZEquilibrium Limited

Capacity 

38 m PZ

00 20 40 60 80

Total Packing Metal Area/G ( m2/mol/s) 33

12

9Mass Transfer Limited

C it9

/mol) Capacity 

6

G (m

ol/

L/G

5 m PZ

38 m PZ

00 20 40 60 80

Total Packing Metal Area/G ( m2/mol/s) 34

Conclusions: March 2015 Pilot Plant Campaign5 PZ i ifi l f d 8 PZ d i 5 m PZ significantly outperformed 8 m PZ during campaign Enhanced rates of 5 m PZ allowed for higher operating solvent

capacity despite inherently lower capacity of solvent

35

36

Rate Parameter Sensitivity: METHOD Base Case Conditions (8m PZ) : NGCC (4% CO ) Coal (13% CO ) Steel (27% NGCC (4% CO2), Coal (13% CO2), Steel (27%

CO2)

LLDG= 0.10 – 0.40 mol CO2/mol alkalinity

90% CO2 Removal

3 Configurations:3 Configurations: Adiabatic/No Intercooling (Worst-Case) Simple IntercoolingSimple Intercooling Isothermal @40°C (Ideal)

37

7.5 0.220 RiConditionsCoal‐Fired Boiler (14 7% CO )

6.0 0.238

ich LoadCoal‐Fired Boiler (14.7% CO2)LLDG = 0.15 mols CO2/mols alk.

CO2 Removal = 90%

4.5l/mol)

0.267

ding (m

4.5

/G (m

o

No Intercooling 

0.267

mols CO

3.0L/ 0.326

2 /mols1.2*LMIN

1.5 Isothermal (40°C) 0.501

alk.)

0.00 25 50 75 100 125

Total Packing Metal Area/G ( m2/mol/s) 38

1.039

0 6

0.8eter) kL

0 4

0.6

parame

NO IC  ‐‐‐‐‐‐

0.2

0.4

x)/∂ln(p

0.0

0.2

CO2Flux

C diti

‐0.2∂ln(C

kG

ConditionsCoal‐Fired Boiler (14.7% CO2)LLDG = 0.15 mols CO2/mols alk.

1.2*LMINCO R l 90%

‐0.4

G CO2 Removal = 90%1% Change in Parameters

0 0.2 0.4 0.6 0.8 1Z/ZtotalTOP BOTTOM

1.040

0 6

0.8eter) kL

0 4

0.6

parame

ISOTHERMAL ‐ ‐ ‐ ‐NO IC  ‐‐‐‐‐‐

0.2

0.4

x)/∂ln(p

0.0

0.2

CO2Flux

‐0.2∂ln(C

kG

ConditionsCoal‐Fired Boiler (14.7% CO2)LLDG = 0.15 mols CO2/mols alk.

1.2*LMIN

‐0.4

G MINCO2 Removal = 90%

1% Change in Parameters

0 0.2 0.4 0.6 0.8 1Z/ZtotalTOP BOTTOM

148m PZ

0

12

8

10

cP)

40°C

6

8

scosity

 (c 50°C

60°C

4

6

Vis

70°C

60 C

2

80°C

00.1 0.2 0.3 0.4 0.5

Loading (mol CO2/mol alk.)

4.0NGCC

Y, CO2 IN = 4 %3.5

MAL

, 28 m PZ

90% CO2 Removal "Infinite"Packing L

3.0

ISOTH

ERM "Infinite"Packing LMIN, NO IC

2.5

N/L

MIN, 

2.0L MIN

1.5

1.00.1 0.15 0.2 0.25 0.3 0.35

Lean Loading (mol CO2/mol alkalinity) 42

2.5 0.239 RiConditionsNGCC (4 1% CO )

2.0 0.253

ich LoadNGCC (4.1% CO2)

LLDG = 0.18 mols CO2/mols alk.CO2 Removal = 90%

1.5l/mol)

0.278

ding (m

1.5

/G (m

o No Intercooling 0.278

mols CO

1.0L/ 0.326

2 /mols

0.5Isothermal (40°C)

0.472

alk.)

0.00 20 40 60 80 100

Total Packing Metal Area/G ( m2/mol/s) 43

1.00Conditions

NGCC (4.1% CO2)G 0 8 l CO / l lk

0.80

eter) kL

1.05*LMIN

LLDG = 0.18 mols CO2/mols alk.CO2 Removal = 90%

0.60parame 1.05 LMIN

1.2*LMIN

1.8*LMIN

0 40x)/dln(

1.8*LMIN0.40

CO2Flux

1.2*LMIN

0.20dln(C

1.05*LMIN

0.000 0.2 0.4 0.6 0.8 1

Z/Ztotal 44