Reverse Electrodialysis process with seawater and concentrated brines: a COMSOL model for equipment design
Dipartimento di Ingegneria Chimica,
Gestionale, Informatica, Meccanica (DICGIM)
Michele Tedesco
Carmelo Scavuzzo, Andrea Cipollina, Alessandro Tamburini, Giorgio Micale
1. Introduction
4. Conclusions
2. Modelling
3. Results
Outline
RED process with seawater and concentrated brines – COMSOL Conference Rotterdam 2013 2/12
1. Introduction • Reverse Electrodialysis process • Modelling goals
2. Model development • System definition • Governing equations • Model calibration
3. Results
• Concentration profiles inside channels • Electric potential through the stack • Salt fluxes through membranes
4. Conclusions
1. Introduction
4. Conclusions
2. Modelling
3. Results
Reverse Electrodialysis Technology
RED process with seawater and concentrated brines – COMSOL Conference Rotterdam 2013 3/12
1. Introduction
CATHODE
ANODE
e-
e-
ELECTRODE RINSE
C D C
+ + - -
I, J+
1. Introduction
4. Conclusions
2. Modelling
3. Results
Investigated physics
Modelling goals
RED process with seawater and concentrated brines – COMSOL Conference Rotterdam 2013 4/12
1. Introduction
Mass transport through membranes
Transport of electrolytes
Electrochemical reaction
Fluid dynamics
1. Introduction
4. Conclusions
2. Modelling
3. Results
Model assumptions:
System definition and model assumptions
RED process with seawater and concentrated brines – COMSOL Conference Rotterdam 2013 5/12
2. Modelling
• Empty channels
• NaCl aqueous solutions
• Negligible solvent flux through membranes
• Adopting Nernst-Planck equation
• Activity coefficients equal to unity
• Adopting Einstein relation for ion diffusion coefficient
1. Introduction
4. Conclusions
2. Modelling
3. Results
Governing equations
RED process with seawater and concentrated brines – COMSOL Conference Rotterdam 2013 6/12
2. Modelling
• Laminar flow for Newtonian fluid:
• Transport equation through solutions (Nernst-Planck model):
• Electrode kinetics (Butler-Volmer theory):
1. Introduction
4. Conclusions
2. Modelling
3. Results
0.0
1.0
2.0
3.0
4.0
5.0
0 50 100 150 200
Po
we
r d
en
sit
y (
W/m
2c
ell
pa
ir)
current density, i (A/m2)
0.1 M
0.3 M
0.5 M
diluateconcentration
0.0
0.5
1.0
1.5
2.0
0.0 0.5 1.0 1.5 2.0
Cell
pair
Res
ista
nc
e, R
cell
( 1
03Ω
*m2)
Co-ion permeability coefficient, DCou
( 1010 m2/s)
experimental
model
Model tuning/validation
RED process with seawater and concentrated brines – COMSOL Conference Rotterdam 2013 7/12
2. Modelling
Experimental data collected with a 50 cell pairs stack, Fujifilm membranes, Deukum 270 µm spacers. Brine: 5 M NaCl. T=20°C. Fluid velocity: 1 cm/s.
0
20
40
60
80
100
120
0 20 40 60 80 100
Op
en
Cir
cu
it V
olt
ag
e, O
CV
(mV
)
Permeability coeff ratio, Dcounter/Dcou (-)
experimental
model
Model tuning
on OCV
Model validation
Model tuning
on cell resistance
1. Introduction
4. Conclusions
2. Modelling
3. Results
Concentration profiles along channels
RED process with seawater and concentrated brines – COMSOL Conference Rotterdam 2013 8/12
3. Results
1. Introduction
4. Conclusions
2. Modelling
3. Results
Electric potential through the stack
RED process with seawater and concentrated brines – COMSOL Conference Rotterdam 2013 9/12
3. Results
1. Introduction
4. Conclusions
2. Modelling
3. Results
Salt fluxes through membranes
RED process with seawater and concentrated brines – COMSOL Conference Rotterdam 2013 10/12
3. Results
1. Introduction
4. Conclusions
2. Modelling
3. Results
Next steps
Conclusions
RED process with seawater and concentrated brines – COMSOL Conference Rotterdam 2013 11/12
4. Conclusions
Model validated on experimental data under different conditions
Simplified approach to simulate both fluid dynamics/electrochemical
phenomena
• Activity coefficients evaluation
• Mechanical analysis on membranes
• Description of Donnan Potentials across membranes
1. Introduction
4. Conclusions
2. Modelling
3. Results
Acknowledgments
RED process with seawater and concentrated brines – COMSOL Conference Rotterdam 2013 12/12
www.reapower.eu
Project title: Reverse Electrodialysis Alternative Power Production
Call identifier: FP7-ENERGY-2010-FET
(Future Emerging Technologies for Energy Applications)
Dipartimento di Ingegneria Chimica,
Gestionale, Informatica, Meccanica (DICGIM)
Thank you for your attention
Michele Tedesco
