DEN/VRH/DTEC/STCF/LGCI JP FERAUD ICONE15, Nagoya 2007 April 22-26 MODELING A FILTER PRESS ELECTROLYZER FOR THE WESTINGHOUSE HYBRID CYCLE USING TWO COUPLED

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DEN/VRH/DTEC/STCF/LGCI JP FERAUD ICONE15, Nagoya 2007 April 22-26

MODELING A FILTER PRESS ELECTROLYZER FOR THE WESTINGHOUSE HYBRID CYCLE USING TWO COUPLED CODESICONE15 -10639

Florent Jomard

Commissariat à l’Énergie Atomique

DEN/DTEC/STCF/LGCI

Site de Marcoule BP 17171

30207 Bagnols sur Cèze, France

Jean-Pierre Feraud

Commissariat à l’Énergie Atomique

DEN/DTEC/STCF/LGCI

Site de Marcoule BP 17171

30207 Bagnols sur Cèze, France

Jacques Morandini

Astek Rhone-Alpes

1 place du Verseau

38130 Echirolles, France

Yves Du Terrail Couvat

Laboratoire EPM, Madylam

1340 Rue de la Piscine

Domaine Universitaire

38400 Saint Martin d’Hères, FranceJean-Pierre Caire

LEPMI, ENSEEG

1130 Rue de la Piscine

38402 Saint Martin d’Hères, France

MODELING A FILTER PRESS ELECTROLYZER FOR THE WESTINGHOUSE HYBRID CYCLE USING TWO COUPLED CODES

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I. Introduction

II. The Westinghouse sulfur cycle

III. Modeling aim

IV. Coupling of physical phenomenawith Fluent® / Flux Expert® codes

V. Electrolyzer modeling, boundary conditions

VI. Software coupling results

VII. Conclusion, future prospect

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Global warming context requires decreasing world's greenhouse gas emission

I. Introduction

hydrogen

alternative solution to replace primary energy

Exemple :

Hydrogen + fuel cells can replace internal combustion engines

CEA / PSA Fuel cells : GENEPAC ( GENérateur Electrique de Pile A Combustible)

PSA hydrogen concept car (207 ePure)

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wide uses of energy = hydrogen mass production

High temperature cycles for hydrogen production

- 100% thermochemical : Bunsen Cycle…

- hybride cycle (Westinghouse sulfur cycle, Deacon cycle…)

- 100% electrochemical cycle (high temperature electrolysis of water)

I. Introduction

High temperature hydrogen production technologies could be provided by using :

- Gen. IV Nuclear power plants

- Thermal solar facilities…

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H2, product½ O2

by product

II. The Westinghouse sulfur cycle Hybrid Sulfur Process block

H2Ofeed

Thermalenergy

Filter press Electrolyzer (50 – 100°C)

Concentration

Évaporation

Décomposition

Absorption

300°C

Concentration 300°C

Thermal Decomposition 850°C

Evaporation 600°C

Thermalenergy

Thermalenergy

H2O + SO2 + ½ O2 H2SO4

Electrical energy

Compression H2SO4

partSO2

part

H2S

O4

SO2

Cooling

SO2

H2O

SO2

H2O

SO2

H2O

Absorption25°C

Westinghouse sulfur Westinghouse sulfur cyclecycle

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Process working conditions

-T°C : 50 - 100°C

- [H2SO4] : 20 - 60 % weight

- PSO2 1 bar

- Current density 200 mA/cm²

H+

H+

H+

H+

H+

H+

H+

H+

H+

e-

II. The Westinghouse sulfur cycle

membrane

Two compartment membrane electolysis cell :

AnodeAnode

++CathodeCathode

--SOSO22

HH22SOSO44

HH++

HH22

Anolyte : H2O-SO2- H2SO4 Catholyte: H2O – H2SO4

SO2 + 2H2O H2SO4 + 2H+ + 2e- 2H+ + 2e- H2

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Within the framework of the Westinghouse cycle studies

The aim of our works consists of modeling a filter press electrolyzer

for hydrogen production.

III. Modeling aim

Our studies have to take into account numerous physical interactions :

- electrokinetic (overpotential),

- thermal behaviour (Joule effect),

- fluid dynamics (forced convection),

- multiphasic flow (electrolyte + bubble plume).

We expect that the virtual filter press design will work as a real one

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IV. Coupling of physical phenomena with Fluent® / Flux Expert® codes

( )

( ) 0

( ) ( )p V S S

uu u g

t

ut

Tc u T k T Q Q

t

Physical phenomena :

- Thermohydraulics (Fluent, finite volume method)

Navier-Stokes continuity equations

Heat transfert equation

- CFD, Fluent model selected

- k-ε turbulence model so-called « realizable »- diphasic flow description : Euler-Euler - separate phase : disperse phases

n

ppqqqqqq mv

t 1

qqq

n

ppqpqqpqqqrqqqqqqqq FvmRgpvvv

t

1

momentum

Diphasic fluid dynamic

(1)(1)

(2)(2)

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0 =V)(-.

.V-j


Physical phenomena (continuation) :

- Electrokinetics (Flux-Expert, finite element method)

Charge Balance, Laplace equation :

Ohm's Law, primary current distribution (a):

RT

nF

RT

nF

eejj)1(

0

Secondary current distribution, Butler-Volmer's Law (b) :

Ele

ctr

od

e

Electrolyte

(j)

Pote

nti

al

(V)

Cell width

(a)

Inte

rface

gap

)j(f

j

n

nei

(1)(1)

(2)(2)

(b)

(a)

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Software coupling :

FLUENT® UDF Swap

functions

Main memory

Data files

FEcoupling.c UDF FEcoupling.c

Property operators : prxxxx.F

FLUX

EXPERT®

Main memory

Swap functions

Main memory

Main memory

Fluent®–Flux Expert® coupling flowchart

= message-passing function

physical phenomena can be solved by using different meshes (structured or unstructured)

Communication between the two codes : simple and robust message-passing library

algorithms developed are mainly location and interpolation algorithms

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FLUENT®

Solve the two phase Thermohydraulic problem

Calculation ofTemp. (K)

in all the domainu (flow velocity)

αg (hydrogen concentration)

FLUX EXPERT®

Solve the Electrokinetic

problem

Calculation of U : Potential (V)

J : current densities (A.m-2) Qs/Qv : Thermal Joule effect ( W.m-3 )

Thermal and current densitiesinputs

hydrogen concentrationTemperature


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The FM01-LC laboratory scale electrolyzer : :

0.16m

0.04m

0.013m

H++H2SO4

H2SO4

+ SO2

H2SO4

+ SO2

H2SO4

H2

+-

zx

y

Electrolyzer operating principle

With : cathode, hydrogen release area , catholyte, membrane, anolyte, anode..

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CA

TH

OL

YT

E

CA

TH

OD

E

mem

bran

AN

OL

YT

E

AN

OD

E

Overpotential Area

0 V

Y (mm)

Overpotential Area

Z (mm)

2000 A.m-2

CA

TH

OL

YT

E

CA

TH

OD

E

me

mb

ran

eA

NO

LY

TE

AN

OD

E

Flux-Expert

Hydrogen bubbles velocity : 0.01m.s-

1

bubble emission angle : 45°

Electrolyte uniform velocity profile

,,k,cp : temperature dependent

No thermal exchange with outsideHydrogen

area

160

mm

V= 0.07m.s-1 T=323K

V= 0.07m.s-1 T=323K

CA

TH

OL

YT

E

CA

TH

OD

E

me

mb

ran

e

AN

OL

YT

EA

NO

DE

0 1.5 6.5 6.6 11.2 13 mm

Fluent

Boundary conditions to produce 5 Nl.h-1 of hydrogen

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1 2 3

VI. Numerical results

Residuals continuity u residual sulphuric acid u residual hydrogen v residual sulphuric acid v residual hydrogen w residual sulphuric acid w residual hydrogen T1 residual sulphuric acid

T2 residual hydrogen

K residual sulphuric acid residual sulphuric acid (1–K) residual hydrogen

FLUENT iterations

Code Coupling Behavior

Interaction between the two codes is demonstrated by the convergence of the computational residuals with successive iterations

FLUX-EXPERT iterations

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T =323 Kυ = 0.069 m.s-1

T =323 Kυ = 0.069 m.s-10.16 m

0 m


0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

322 324 326

Anolyte Catholyte

Temperature (K)

Height (m) Thermal problem :

Graded colors scale

Temp. (K)

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3 mm


Cat

holy

te

Cat

hode

% H2 (vol.)

Cat

hode

Ano

de

membrane

Hydrogen plume area approx. 1 mm

Diphasic problem resolution :

Hydrogen volume fraction < 72%

Maximum concentation at 0.2 mm from cathode

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% H2 (vol.)

Cat

hode

Ano

de

Graded colors scale

0

10

20

30

40

50

60

70

80

0.0014 0.0019 0.0024 0.0029 0.0034distance from cathode (m)

hyd

rog

en c

on

cen

trat

ion

(%

)

h_0.15

h_0.08

h_0.01

height = 0.15m

height = 0.08m

height = 0.01m

Diphasic problem resolution :

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Anolyte


Fluid dynamic calculation :

Anolyte flow appearance:

Flat (uniform velocity) + wall effect on membrane and anode sides

Caracteristic of turbulent flow

Catholyte flow appearance :

Wall effect on membrane side,

High velocity increasing on cathode side (X4)

Characteristic of air lift effect

CatholyteFlow m.s-1

membrane

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Anodic overpotential = 70 % tension of cell

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 0.002 0.004 0.006 0.008 0.01 0.012 0.014Lenght (m)

Ele

ctr

ica

l p

ote

nti

al

(V)

0,73 V

cathodic over

potential

anodic over

potential0.47 V

Tension of cell : 0.73V

Goal :

Design a cell to obtain 0.6 V of total tension


Electrokinetics calculation :

Potential (V)V)

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Modeling with Flux-Expert / Fluent Codes

Performed with message-passing library

Only 24h of calculation on Pentium IV(F. Expert) + Core 2 Duo (Fluent) PC

CFD results

Electrolyte rising temperature : 4°C

Catholyte motion (x4), hydrogen bubbly effect

Electrokinetics calculation

Electrochemical irreversible process taken into account with Flux Expert®

Total cell tension obtained : 0.73V (in accordance with literature results)

VI. Conclusion, future prospect

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VI. Conclusion, future prospect

Calculation / Experiments

Experiments required to complete the lack of anodic overpotential law

Check Validity of diphasic flow behavior

development of specific physical operators

modelling a stack of cells before scaling-up

Optimization of the future electrochemical process with a design of numerical experiments

Jean-Pierre Caire

Je ne comprends pas bien:development of specific physical operators????

Documents

DEN/VRH/DTEC/STCF/LGCI JP FERAUD ICONE15, Nagoya 2007 April 22-26 MODELING A FILTER PRESS ELECTROLYZER FOR THE WESTINGHOUSE HYBRID CYCLE USING TWO COUPLED