modelling of slurry absorber for biomimetic co2...

MODELLING OF SLURRY ABSORBER

FOR BIOMIMETIC CO2 CAPTURE

Maria Elena Russo, Piero Bareschino, Giuseppe Diglio, Giuseppe

Olivieri, Riccardo Chirone, Piero Salatino, Antonio Marzocchella

13TH INTERNATIONAL CONFERENCE MULTIPHASE FLOW IN INDUSTRIAL

PLANTS SESTRI LEVANTE (GENOVA), ITALY - 17-19 SEPTEMBER 2014

Introduction: biomimetic CO2 capture

The biomimetic approach is the adoption of Carbonic anhydrase as industrial biocatalyst for the

enhancement of CO2 absorption rate in aq. solutions

2 2

2 2

2 2

2 2

[ ] [ ]* [ ]

[ ]* [ ]

[ ] [ ]* [ ]

e e

H O H O

OH OH

r k CA CO CO

r k CO CO

r k OH CO CO

- -

2 3CO + OH HCO

- +

2 2 3CO + H O HCO + H

Parallel reactions in aq. phase

Catalysed by

carbonic anhydrase



Introduction: bioreactor design

Technical solutions for the adoption of CA as industrial biocatalyst (Russo

et al. 2013, Sep Pur Technol)

•Random and structured packing columns (Fradette and Ceperkovic, 2008 Patent

n° US2008/0148939)

•Spray columns (Fradette, 2004 Patent n°WO2004/056455A1, Bhattacharya, et al.

2004 Biotechnol Bioeng)

•Membrane systems (Trachtenberg et al. 2001 Energy Proc.)

•Monolith in Taylor regime (Iliuta and Larachi, 2012 Sep Pur Technol)



Main issues related with selection of a reactor configuration

Counter-current gas-liquid flows

Maximization gas-liquid interface

Enzyme immobilization/entrapment on/in solid phase

Optimization of heterogeneous catalysis in chemical absorption:

Enzyme catalysis close to the g-l interface



Introduction: bioreactor design

Aim of the work

Development of a theoretical model for the assessment of performances of

heterogeneous biocatalyst based on immobilized CA in the enhancement

of CO2 absorption under typical CCS operating conditions

Development of a mathematical model of slurry absorber for biomimetic

CO2 capture

Selection of reactor configuration: staged bubble column

Model computation

Comparison of different reactor configurations and biocatalyst types



Model assumptions and equations

Staged Counter-current gas-liquid flows

Bubble

Column

Slurry

Zahradnik, J. (2001) in Multiphase Bioreactor Design. Ed.

Cabrai, J. M. S., Mota, M., Tramper J. CRC Press 1-23

ID= 0.29 m

H=2m

6 stages

(perforated plates)

Stage height 0.3 m

Enzyme immobilization/entrapment

on/in solid fine particles

Optimization of heterogeneous

catalysis in chemical absorption

Maximization gas-liquid interface




Gas IN

yIN

Gas OUT

yOUT

Liq IN

Liq OUT ith stage

Sta

ge

d S

lurr

y B

ub

ble

Co

lum

n




Liquid phase

KHCO3/K2CO3 sol

(K2CO3 20%wt)

L=2.6 10-4 m3/s

Gas phase

CO2 10%vol

N2 90%vol

G=1.7 10-3 m3/s

Isothermal operation @ 25°C

Total volume V=1.32 10-2 m3

Homogeneous catalysis by

free carbonic anhydrase

Heterogeneous catalysis by slurry

immobilized carbonic anhydrase

Sta

ge

d S

lurr

y B

ub

ble

Co

lum

n

Stable and uniform gas distribution for the particular plate geometry

kL= 5.1 – 4.6 m/s a= 194 – 108 m-1 eg= 0.28 – 0.16

Bubble diameter 0.7 10-3<db<1.1 10-2 m Zahradnik, J. (2001)



Overall stoichiometry 2

2 3 2 32CO CO H O HCO

Chemical reactions occurring in liquid phase

2 2 3CO H O HCO H

2 3CO OH HCO

Spontaneous CO2 hydration

and catalysed by

free enzyme

slurry immobilized enzyme

CO2 hydroxylation

Bicarbonate dissociation

Solvent dissociation


Kinetic models

1 1

1

d i i

i i i i

w hr c w h k c

K

, ,

2

3

3

i

i

i

i

i

CO c

HCO w

CO z

H h

OH oh

2

2 2

1

H Od

i i i i i i

Kr c w oh k c oh w

K

, ,

equilibrium

1

d i i

e i i i e i

w hr c w h k CA c

K

, ,

1

d i i

e imm i i i s s e iimm

w hr c w h k CA c

Ke

_

, ,

ith stage



2

3 3CO H HCO

2H O OH H




1 1 1 10

i i i i i i i i

PGY Y L C C L W W L Z Z

RT

Overall carbon balance

Equations at each column stage

Liq

uid

(slu

rry)

bulk

L

iqu

id (

slu

rry)

bo

un

da

ry la

ye

r

2

2

1 220, , , , , ,i

CO i i i i i i e i i i

d cD r c w h r c w oh r c w h

dx

23 3

2 2

1 22 20, , , , , ,i i

i i i i i i e i i iHCO CO

d w d zD D r c w h r c w oh r c w h

dx dx

0 0 1

ii i

i

YPx c x c C

He Y

( ) ( )

2[ ]i i i i

h K w z oh

2i i

i

z hK

w

2H O i iK oh h

2 1 1 2

0, , , , , ,iCO i i SL i i i i i i e i i i

x

dcVaD L C C Va r C W H r C W OH r C W H

dx

e

23 3

1 1 1 2 0, , , , , ,i ii i i i SL i i i i i i e i i iHCO CO

x x

dw dzVaD L W W VaD L Z Z Va r C W H r C W OH r C W H

dx dx

e

2[ ]i i i i

H K W Z OH

2i i

i

Z HK

W

2H O i iK OH H

CO2 mass balances

3

0

0 ii iHCO

x

dwD w W

dx

( )

HCO3/CO3 mass balances Electroneutrality condition Chemical equilibrium

conditions

The system of algebraic/differential equation

was computed using the commercial software

package Comsol Multiphisycs®



Fink, D. J (1973). Biotechnology & Bioengineering

Model results

i) pure solvent 20% wt K2CO3;

ii) solvent 20% wt K2CO3 plus free CA;

iii) solvent 20% wt K2CO3 plus immobilized CA.

CA solubility limit 100 mg/L

Wide spectrum of immobilized CA

• non-porous solid particles

• porous solid particles

• cross-linked enzyme aggregates

Preliminary assessment of

effectiveness factor for

heterogeneous biocatalyst

Cases

iii

CO2

concentration

mol/m3

ked=kcat/KM

m3/mol s

[CA]imm

mg/g es

s

kg/m3

rp

m DCO2/Deff

A

5 10-2

105 80 0.08

1200 10-6 10

0.2

B 50 0.02

0.4

C 5 104 50 0.5

D

104

80 0.08 0.4

E 50 0.02

0.8

F 1 0.9

Porous solid particles 10-6m

Irreversible M&M kinetics

Biocatalyst properties according to

Russo et al 2013 Chem Eng Transact

Model results



Concentration profiles in the Slurry Staged Bubble column

Case free CA

% captured CO2

73% 86%



Model results Concentration profiles in the Slurry Staged Bubble column

Case slurry biocatalyst

% captured CO2

51% 87%



Model results Concentration profiles in liquid boundary layer

Stage 1

Stage 6

Inert slurry Slurry biocatalyst



Conclusion and …

Theoretical results confirmed the beneficial effect of free CA catalysis on CO2

absorption in staged bubble column at CA concentration consistent with enzyme

solubility limit (100 mg/L).

The slurry biocatalyst considered provided the same CO2 capture %

obtained with homogeneous free enzyme catalysis

Detailed modelling of chemical absorption catalysed by free or immobilized

CA is required since the process can be classified as moderately fast chemical

absorption(2>Ha>4)

… next steps

Study of different reactor configurations (changing kL and gas hold-up)

Development of single particle model to assess effectiveness factor:

non linear enzyme kinetics, porous/non porous biocatalyst

Design of operating conditions of 60 L staged bubble column (national research

project PON 03 PE 00157 ‘Smart Generation’ )



Thank you

modelling of slurry absorber for biomimetic co2...

Documents