1. DEN/VRH/DTEC/SGCS/LGCIDenis ODEGLOBAL 2007 – Boise USA September 9-13 Modeling a filter press electrolyzer By using two coupled codes within nuclear Gen. IV hydrogen production 1/19 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 Yves du Terrail Couvat Laboratoire EPM, Madylam 1340 Rue de la Piscine Domaine Universitaire 38400 Saint Martin d’Hères, France Jean-Pierre Caire LEPMI, ENSEEG 1130 Rue de la Piscine 38402 Saint Martin d’Hères, France Modeling a filter press electrolyzer by using two coupled codes within nuclear Gen. IV hydrogen production. Jacques Morandini Astek Rhône-Alpes 1 place du Verseau 38130 Echirolles, France

2. DEN/VRH/DTEC/SGCS/LGCIDenis ODEGLOBAL 2007 – Boise USA September 9-13 Modeling a filter press electrolyzer By using two coupled codes within nuclear Gen. IV hydrogen production 2/19 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

3. DEN/VRH/DTEC/SGCS/LGCIDenis ODEGLOBAL 2007 – Boise USA September 9-13 Modeling a filter press electrolyzer By using two coupled codes within nuclear Gen. IV hydrogen production 3/19 Extensive use of energy = hydrogen mass production 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 I. Introduction High-temperature hydrogen production technologies could be provided by using: - Gen. IV nuclear power plants - Thermal solar facilities…

4. DEN/VRH/DTEC/SGCS/LGCIDenis ODEGLOBAL 2007 – Boise USA September 9-13 Modeling a filter press electrolyzer By using two coupled codes within nuclear Gen. IV hydrogen production 4/19 H 2, product ½ O 2 by-product II. The Westinghouse sulfur cycle Hybrid Sulfur Process block H 2 O feed Westinghouse sulfur cycle

5. DEN/VRH/DTEC/SGCS/LGCIDenis ODEGLOBAL 2007 – Boise USA September 9-13 Modeling a filter press electrolyzer By using two coupled codes within nuclear Gen. IV hydrogen production 5/19 H 2, product ½ O 2 by-product II. The Westinghouse sulfur cycle Hybrid Sulfur Process block H 2 O feed Thermal energy Filter press Electrolyzer (50 – 100°C) Concentration Evaporation Decomposition Absorption 300°C Concentration 300°C Thermal decomposition 850°C Evaporation 600°C Thermal energy H 2 O + SO 2 + ½ O 2  H 2 SO 4 Electrical energy Compression H 2 SO 4 side SO 2 side H 2 SO 4 SO 2 Cooling SO 2 H 2 O SO 2 H 2 O SO 2 H 2 O Absorption 25°C

6. DEN/VRH/DTEC/SGCS/LGCIDenis ODEGLOBAL 2007 – Boise USA September 9-13 Modeling a filter press electrolyzer By using two coupled codes within nuclear Gen. IV hydrogen production 6/19 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 objective 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

7. DEN/VRH/DTEC/SGCS/LGCIDenis ODEGLOBAL 2007 – Boise USA September 9-13 Modeling a filter press electrolyzer By using two coupled codes within nuclear Gen. IV hydrogen production 7/19 IV. Coupling of physical phenomena with realizable Fluent® / Flux Expert® codes Physical phenomena: - Thermohydraulics solved with Fluent® Navier-Stokes continuity equations Heat transfer equation - CFD, Fluent model selected - so-called “realizable” k-ε turbulence model - two-phase flow description: Euler-Euler - separate phase: disperse phases Two-phase fluid dynamics

8. DEN/VRH/DTEC/SGCS/LGCIDenis ODEGLOBAL 2007 – Boise USA September 9-13 Modeling a filter press electrolyzer By using two coupled codes within nuclear Gen. IV hydrogen production 8/19 IV. Coupling of physical phenomena with Fluent® / Flux Expert® codes Physical phenomena : - Electrokinetics solved with Flux-Expert® Charge balance, Laplace equation Ohm’s law, primary current distribution (a) Secondary current distribution, Butler-Volmer Law (b) Electrode Electrolyte  (j) Potential (V) Cell width (a) Interface gap  (1) (2) (b) (a)

9. DEN/VRH/DTEC/SGCS/LGCIDenis ODEGLOBAL 2007 – Boise USA September 9-13 Modeling a filter press electrolyzer By using two coupled codes within nuclear Gen. IV hydrogen production 9/19 IV. Coupling of physical phenomena with Fluent® / Flux Expert® codes Software coupling: 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

10. DEN/VRH/DTEC/SGCS/LGCIDenis ODEGLOBAL 2007 – Boise USA September 9-13 Modeling a filter press electrolyzer By using two coupled codes within nuclear Gen. IV hydrogen production 10/19 V. Electrolyzer modeling, boundary conditions : The FM01-LC laboratory scale electrolyzer:  0.16m 0.04m 0.013m H + +H 2 SO 4 H 2 SO 4 +  SO 2 H 2 SO 4 + SO 2 H 2 SO 4 H2H2 + -     z x y Electrolyzer operating principle  cathode  hydrogen release area  catholyte  membrane  anolyte  anode

11. DEN/VRH/DTEC/SGCS/LGCIDenis ODEGLOBAL 2007 – Boise USA September 9-13 Modeling a filter press electrolyzer By using two coupled codes within nuclear Gen. IV hydrogen production 11/19 V. Electrolyzer modeling, boundary conditions CATHOLYTE CATHODE membrane ANOLYTE ANODE Overpotential Area 0 V Y (mm) Overpotential area Z (mm) 2000 A.m -2 CATHOLYTE CATHODE membrane ANOLYTE ANODE Flux-Expert Hydrogen bubble velocity: 0.01 m·s -1 Bubble emission angle: 45° Uniform electrolyte velocity profile , ,k,c p : temperature-dependent No heat exchange with outside Hydrogen area 160 mm V = 0.07 m·s -1 T = 323 K CATHOLYTE CATHODE membrane ANOLYTE ANODE 0 1.5 6.5 6.6 11.2 13 mm Fluent Boundary conditions to produce 5 NL·h -1 of hydrogen

12. DEN/VRH/DTEC/SGCS/LGCIDenis ODEGLOBAL 2007 – Boise USA September 9-13 Modeling a filter press electrolyzer By using two coupled codes within nuclear Gen. IV hydrogen production 12/19 123 VI. Numerical results  Residual continuity  u residual sulphuric acid  u residual hydrogen  v residual sulphuric acid  v residual hydrogen  w residual sulphuric acid  w residual hydrogen  T 1 residual sulphuric acid  T 2 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

13. DEN/VRH/DTEC/SGCS/LGCIDenis ODEGLOBAL 2007 – Boise USA September 9-13 Modeling a filter press electrolyzer By using two coupled codes within nuclear Gen. IV hydrogen production 13/19 T =323 K υ = 0.069 m.s -1 T =323 K υ = 0.069 m.s - 1 0.16 m 0 m VI. Numerical results Thermal problem: Graded color scale Temp. (K)

14. DEN/VRH/DTEC/SGCS/LGCIDenis ODEGLOBAL 2007 – Boise USA September 9-13 Modeling a filter press electrolyzer By using two coupled codes within nuclear Gen. IV hydrogen production 14/19 3 mm VI. Numerical results Catholyte Cathode H 2 (vol.%) Cathode Anode membrane Hydrogen plume area approx. 1 mm Two-phase problem resolution:  Maximum concentration 0.2 mm from cathode  Hydrogen volume fraction < 72%

15. DEN/VRH/DTEC/SGCS/LGCIDenis ODEGLOBAL 2007 – Boise USA September 9-13 Modeling a filter press electrolyzer By using two coupled codes within nuclear Gen. IV hydrogen production 15/19 VI. Numerical results H 2 (vol.%) Cathode Anode Graded color scale height = 0.15m height = 0.08m height = 0.01m Two-phase problem resolution:

16. DEN/VRH/DTEC/SGCS/LGCIDenis ODEGLOBAL 2007 – Boise USA September 9-13 Modeling a filter press electrolyzer By using two coupled codes within nuclear Gen. IV hydrogen production 16/19 Anolyte VI. Numerical results Fluid dynamic calculation: Anolyte flow appearance: 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

17. DEN/VRH/DTEC/SGCS/LGCIDenis ODEGLOBAL 2007 – Boise USA September 9-13 Modeling a filter press electrolyzer By using two coupled codes within nuclear Gen. IV hydrogen production 17/19 Anodic overpotential = 70% of cell potential Cell potential: 0.73V Goal: improve cell designing to obreach 0.6 V of total potential VI. Numerical results Electrokinetics calculation: V) Potential (V)

18. DEN/VRH/DTEC/SGCS/LGCIDenis ODEGLOBAL 2007 – Boise USA September 9-13 Modeling a filter press electrolyzer By using two coupled codes within nuclear Gen. IV hydrogen production 18/19 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) VI. Conclusion – Future prospects

19. DEN/VRH/DTEC/SGCS/LGCIDenis ODEGLOBAL 2007 – Boise USA September 9-13 Modeling a filter press electrolyzer By using two coupled codes within nuclear Gen. IV hydrogen production 19/19 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