Transcript Modeling a filter press electrolyzer

Modeling a filter press electrolyzer By using two coupled codes within nuclear Gen. IV hydrogen production
Modeling a filter press electrolyzer
by using two coupled codes within nuclear Gen. IV
hydrogen production.
Jean-Pierre Feraud, Florent Jomard, Denis Ode, Jean Duhamet
Commissariat à l’Énergie Atomique
DEN/DTEC/SGCS/LGCI
Site de Marcoule BP 17171
30207 Bagnols sur Cèze, France
Jacques Morandini
Jean-Pierre Caire
Yves du Terrail Couvat
Astek Rhône-Alpes
LEPMI, ENSEEG
Laboratoire EPM, Madylam
1 place du Verseau
1130 Rue de la Piscine
1340 Rue de la Piscine
38130 Echirolles, France
38402 Saint Martin d’Hères, France
Domaine Universitaire
38400 Saint Martin d’Hères, France
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Modeling a filter press electrolyzer By using two coupled codes within nuclear Gen. IV hydrogen production
I.
Introduction
II.
The Westinghouse sulfur cycle
III. Modeling objective
IV. Coupling of physical phenomena
with Fluent® / Flux Expert® codes
V.
Electrolyzer modeling, boundary conditions
VI. Software coupling results
VII. Conclusion – Future prospects
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Modeling a filter press electrolyzer By using two coupled codes within nuclear Gen. IV hydrogen production
I. Introduction
Extensive use of energy = hydrogen mass production
High-temperature hydrogen production technologies
could be provided by using:
- Gen. IV nuclear power plants
- Thermal solar facilities…
High-temperature cycles for hydrogen production
- 100% thermochemical: Bunsen Cycle…
- Hybrid cycle: Westinghouse sulfur cycle, Deacon cycle…
- 100% electrochemical cycle: high-temperature electrolysis of water
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Modeling a filter press electrolyzer By using two coupled codes within nuclear Gen. IV hydrogen production
II. The Westinghouse sulfur cycle
Hybrid Sulfur Process block
½ O2
by-product
H2O
feed
H2, product
Westinghouse sulfur
cycle
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Modeling a filter press electrolyzer By using two coupled codes within nuclear Gen. IV hydrogen production
II. The Westinghouse sulfur cycle
Hybrid Sulfur Process block
½ O2
by-product
H2, product
H2O
feed
Absorption
Absorption
25°C
SO2
H2O
Compression
SO2
Filter press
Electrolyzer
(50 – 100°C)
Electrical energy
SO2
side
300°C
SO2
H2O
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Concentration
300°C
Concentration
Thermal
energy
Evaporation
Evaporation
600°C
Thermal
energy
H2SO4
side
H2O
Cooling
H2SO4
SO2
H2O + SO2 + ½ O2 H2SO4
Thermal
decomposition 850°C
Decomposition
Thermal
energy
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Modeling a filter press electrolyzer By using two coupled codes within nuclear Gen. IV hydrogen production
III. Modeling objective
Within the framework of the Westinghouse cycle studies
The aim of our works consists of modeling a filter press electrolyzer
for hydrogen production.
Our studies have to take into account numerous physical interactions:
- electrokinetics (overpotential),
- thermal behavior (Joule effect),
- fluid dynamics (forced convection),
- multiphase flow (electrolyte + bubble plume).
We expect that the virtual filter press design will work as a real one
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Modeling a filter press electrolyzer By using two coupled codes within nuclear Gen. IV hydrogen production
IV. Coupling of physical phenomena
with realizable Fluent® / Flux Expert® codes
Physical phenomena:
- Thermohydraulics solved with Fluent®

u
  (u  )u       g
t
Navier-Stokes continuity equations

   ( u)  0
t
T
 cp (
 u  T )    (k T )  QV  QS  S
t
Heat transfer equation
- CFD, Fluent model selected
Two-phase fluid dynamics
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- so-called “realizable” k-ε turbulence model
- two-phase flow description: Euler-Euler
- separate phase: disperse phases
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Modeling a filter press electrolyzer By using two coupled codes within nuclear Gen. IV hydrogen production
IV. Coupling of physical phenomena with
Fluent® / Flux Expert® codes
Physical phenomena :
- Electrokinetics solved with Flux-Expert®


.(- V) = 0


j  - .V
Ohm’s law, primary current distribution (a)
Secondary current distribution, Butler-Volmer Law (b)
 ei
j
 n
 f ( jn )
gap
(a)
(j)
(a)
(b)
Interface
(2)
Electrolyte
Potential (V)
(1)
 (1  ) nF
 nF

RT
RT


j  j0 e
e





Electrode
Charge balance, Laplace equation
Cell width
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Modeling a filter press electrolyzer By using two coupled codes within nuclear Gen. IV hydrogen production
IV. Coupling of physical phenomena with
Fluent® / Flux Expert® codes
Software coupling:
= message-passing function
Main
memory
Main
memory
UDF
Swap
functions
FEcoupling.c UDF
FEcoupling.c
®
FLUENT
 Physical phenomena can be
solved by using different meshes
(structured or unstructured)
Data
files
 Communication between the two
codes: simple and robust
message-passing library
FLUX
®
EXPERT
 Algorithms developed are mainly
location and interpolation
algorithms
Proprietary
operators :
prxxxx.F
Swap
functions
Main
memory
Main
memory
Fluent®–Flux Expert® coupling flowchart
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Modeling a filter press electrolyzer By using two coupled codes within nuclear Gen. IV hydrogen production
V.
Electrolyzer modeling, boundary conditions
H2SO4
The FM01-LC laboratory scale electrolyzer:
H2SO4
+ SO2
H2
 
  
0.16m
+
 cathode
 hydrogen release area
 catholyte
 membrane
z
 anolyte
 anode

0.04m
x
y
H++H2SO4
H2SO4
+ SO2
0.013m
Electrolyzer operating principle
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Modeling a filter press electrolyzer By using two coupled codes within nuclear Gen. IV hydrogen production
Electrolyzer modeling, boundary conditions
V = 0.07 m·s-1 T = 323 K
Overpotential
area
Overpotential Area
0V
160 mm
ANODE
membrane
CATHODE
CATHOLYTE
Hydrogen bubble velocity: 0.01 m·s-1
ANODE
ANODE
ANOLYTE
ANOLYTE
membrane
membrane
CATHODE
CATHODE
CATHOLYTE
CATHOLYTE
2000
A.m-2
ANOLYTE
V.
Hydrogen
area
Bubble emission angle: 45°
Uniform electrolyte velocity profile
,,k,cp: temperature-dependent
No heat exchange with outside
Z (mm)
0 1.5 6.5 6.6 11.2 13 mm
Y (mm)
Flux-Expert
V = 0.07 m·s-1 T = 323 K
Fluent
Boundary conditions to produce 5 NL·h-1 of hydrogen
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Modeling a filter press electrolyzer By using two coupled codes within nuclear Gen. IV hydrogen production
VI. Numerical results
Code Coupling Behavior
Interaction between the two codes is demonstrated by the convergence of the
computational residuals with successive iterations
FLUX-EXPERT iterations
1
2
3
 Residual 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
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Modeling a filter press electrolyzer By using two coupled codes within nuclear Gen. IV hydrogen production
VI. Numerical results
Thermal problem:
Graded color
scale
T =323 K
Height (m)
υ = 0.069 m.s-
0.16 m
1
0.16
0.14
0.12
0.1
Anolyte
Catholyte
0.08
0.06
0.04
0.02
0
322
326
Temperature (K)
0m
Temp. (K)
324
T =323 K
υ = 0.069 m.s-1
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Modeling a filter press electrolyzer By using two coupled codes within nuclear Gen. IV hydrogen production
VI. Numerical results
Two-phase problem resolution:
Anode
Cathode
Catholyte
Cathode
3 mm
Hydrogen plume area
approx. 1 mm
 Maximum concentration 0.2 mm from cathode
 Hydrogen volume fraction < 72%
H2 (vol.%)
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Modeling a filter press electrolyzer By using two coupled codes within nuclear Gen. IV hydrogen production
VI. Numerical results
Two-phase problem resolution:
Graded color
scale
height =
0.15m
80
Anode
Cathode
height =
0.08m
hydrogen concentration (%)
70
60
h_0.15
h_0.08
50
h_0.01
40
30
20
10
0
height =
0.01m
0.0014
0.0019
0.0024
0.0029
0.0034
distance from cathode (m)
H2 (vol.%)
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Modeling a filter press electrolyzer By using two coupled codes within nuclear Gen. IV hydrogen production
VI. Numerical results
Fluid dynamic calculation:
Anolyte flow appearance:
Anolyte
Flat (uniform velocity) + wall effect
on membrane and anode sides
 Characteristic of turbulent flow
Catholyte flow appearance:
Wall effect on membrane side,
Increasing velocity on cathode side
(×4)
 Characteristic of air lift effect
Catholyte
Flow rate
(m·s-1)
Membrane
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Modeling a filter press electrolyzer By using two coupled codes within nuclear Gen. IV hydrogen production
VI. Numerical results
Electrokinetics calculation:
Electrical potential (V)
0.8
0.7 0,73 V
0.6
anodic over
potential
0.47 V
0.5
0.4
0.3
cathodic over
potential
0.03 V
0.2
0.1
Cell potential: 0.73V
Goal:
improve cell designing
to obreach 0.6 V of total
potential
0
0
0
0
0.01 0.01 0.01 0.01 0.01
Length (m)
Potential (V)
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Anodic overpotential = 70% of cell potential
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Modeling a filter press electrolyzer By using two coupled codes within nuclear Gen. IV hydrogen production
VI. Conclusion – Future prospects
Modeling with Flux-Expert / Fluent Codes
 Performed with message-passing library
 Only 24 h of computing on Pentium IV (Flux Expert) + Core 2 Duo (Fluent) PCs
CFD results
 Electrolyte temperature rise: 4°C
 Catholyte motion (×4), hydrogen bubbling effect
Electrokinetics calculation
 Electrochemical irreversible process taken into account with Flux Expert®
 Total cell voltage obtained: 0.73 V (in accordance with published results)
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Modeling a filter press electrolyzer By using two coupled codes within nuclear Gen. IV hydrogen production
VI. Conclusion – Future prospects
Calculation / Experiments
 Experiments required to complete the lack of anodic overpotential law
 Check the validity of two-phase flow behavior
 Model a stack of cells before scaling up
 Optimize the future electrochemical process by designing numerical
experiments
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