Post on 18-Jun-2020
transcript
INVESTIGATION OF REVERSE ELECTRODIALYSIS
UNITS BY MULTIPHYSICAL MODELLING
G. Battaglia, L. Gurreri, F. Santoro, A. Cipollina, A. Tamburini, G. Micale, M. Ciofalo
giuseppe.battaglia91@gmail.com
Scuola PolitecnicaDipartimento dell’innovazione Industriale e
digitale (DIID) Ingegneria Chimica, Gestionale, Informatica e Meccanica,
viale delle Scienze (Ed.6), 90128 Palermo, Italy
CONTENTS
1. INTRODUCTION• REVERSE ELECTRODIALYSIS
• RED STACK
3. RESULTS• FLUID DYNAMICS
• ELECTROCHEMICAL TRASPORT
PHENOMENA
• SENSITIVITY ANALYSIS
4. CONCLUSIONS
2. MODELLING• COMPUTATIONAL DOMAIN
• MODEL EQUATIONS
• BOUNDARY CONDITIONS
• GEOMETRIES
INVESTIGATION OF REVERSE ELECTRODIALYSIS UNITS BY MULTIPHYSICAL MODELLING
REVERSE ELECTRODIALYSIS
o Reverse electrodialysis (RED) is
a technology to produce electrical
energy from the salinity difference
between two salt solutions.
1. INTRODUCTION 2. NUMERICAL MODELLING 3. RESULTS 4. CONCLUSIONS
Dilute solution
INVESTIGATION OF REVERSE ELECTRODIALYSIS UNITS BY MULTIPHYSICAL MODELLING
o Reverse electrodialysis uses ion-
exchange membranes. These
present fixed charges in their
polymeric structure that allows
selectivity transport of ions with
opposite charge through the
membranes.
RED STACK
1. INTRODUCTION 2. NUMERICAL MODELLING 3. RESULTS 4. CONCLUSIONS
INVESTIGATION OF REVERSE ELECTRODIALYSIS UNITS BY MULTIPHYSICAL MODELLING
Consists of:
• Concentrate flow compartment
• Dilute flow compartment
• Redox solutions compartment
• Anionic exchange membrane
• Cationic exchange membrane
RED STACK
1. INTRODUCTION 2. NUMERICAL MODELLING 3. RESULTS 4. CONCLUSIONS
INVESTIGATION OF REVERSE ELECTRODIALYSIS UNITS BY MULTIPHYSICAL MODELLING
Consists of:
• Concentrate flow compartment
• Dilute flow compartment
• Redox solutions compartment
• Anionic exchange membrane
• Cationic exchange membrane
RED STACK
1. INTRODUCTION 2. NUMERICAL MODELLING 3. RESULTS 4. CONCLUSIONS
INVESTIGATION OF REVERSE ELECTRODIALYSIS UNITS BY MULTIPHYSICAL MODELLING
Consists of:
• Concentrate flow compartment
• Dilute flow compartment
• Redox solutions compartment
• Anionic exchange membrane
• Cationic exchange membrane
RED STACK
1. INTRODUCTION 2. NUMERICAL MODELLING 3. RESULTS 4. CONCLUSIONS
INVESTIGATION OF REVERSE ELECTRODIALYSIS UNITS BY MULTIPHYSICAL MODELLING
Consists of:
• Concentrate flow compartment
• Dilute flow compartment
• Redox solutions compartment
• Anionic exchange membrane
• Cationic exchange membrane
RED STACK
1. INTRODUCTION 2. NUMERICAL MODELLING 3. RESULTS 4. CONCLUSIONS
INVESTIGATION OF REVERSE ELECTRODIALYSIS UNITS BY MULTIPHYSICAL MODELLING
Consists of:
• Concentrate flow compartment
• Dilute flow compartment
• Redox solutions compartment
• Anionic exchange membrane
• Cationic exchange membrane
RED STACK
1. INTRODUCTION 2. NUMERICAL MODELLING 3. RESULTS 4. CONCLUSIONS
INVESTIGATION OF REVERSE ELECTRODIALYSIS UNITS BY MULTIPHYSICAL MODELLING
Consists of:
• Concentrate flow compartment
• Dilute flow compartment
• Redox solutions compartment
• Anionic exchange membrane
• Cationic exchange membrane
RED STACK
1. INTRODUCTION 2. NUMERICAL MODELLING 3. RESULTS 4. CONCLUSIONS
INVESTIGATION OF REVERSE ELECTRODIALYSIS UNITS BY MULTIPHYSICAL MODELLING
River
Water
CELL PAIR
1. INTRODUCTION 2. NUMERICAL MODELLING 3. RESULTS 4. CONCLUSIONS
RED STACK
INVESTIGATION OF REVERSE ELECTRODIALYSIS UNITS BY MULTIPHYSICAL MODELLING
RED STACK
MODELLING
1. INTRODUCTION 2. NUMERICAL MODELLING 3. RESULTS 4. CONCLUSIONS
INVESTIGATION OF REVERSE ELECTRODIALYSIS UNITS BY MULTIPHYSICAL MODELLING
o 2-D simulations
o Consists of:
o Half anionic membrane
o Concentrate flow compartment
o Cationic membrane
o Dilute flow compartment
o Half anionic membrane
o Cell pair of 1.2 mm instead of 10 cm
o Pure NaCl solutions
COMPUTATIONAL DOMAIN
CELL PAIR
1. INTRODUCTION 2. NUMERICAL MODELLING 3. RESULTS 4. CONCLUSIONS
CONCETRATE
CHANNEL
DILUTE
CHANNEL
1.2
mm
0.27 0.0620.125 0.062 mm0.27
INVESTIGATION OF REVERSE ELECTRODIALYSIS UNITS BY MULTIPHYSICAL MODELLING
MODEL EQUATIONS
o Current density:
𝒊 = 𝐹∑𝑧𝑖 −𝐷𝑖𝛻𝑐𝑖 − 𝑧𝑖𝑢𝑚𝑖𝐹𝑐𝑖𝛻𝛷𝑖
o Donnan Potential:
𝛷𝐷𝑜𝑛𝑛𝑎𝑛 = 𝛷𝑀𝑒𝑚𝑏𝑟𝑎𝑛𝑒 − 𝛷𝑆𝑜𝑙𝑢𝑡𝑖𝑜𝑛 =𝑅𝑇
𝑍𝐹𝑙𝑛
𝑎𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛𝑎𝑚𝑒𝑚𝑏𝑟𝑎𝑛𝑒
o Absorption equilibrium at solution-membrane interface:
𝐶𝐶𝑜−𝑖𝑜𝑛,𝑚𝑒𝑚 =1
2𝐶𝑓𝑖𝑥,𝑚𝑒𝑚2 + 4𝐶𝑐𝑜𝑢𝑛𝑡𝑒𝑟−𝑖𝑜𝑛,𝑠𝑜𝑙𝑢𝐶𝐶𝑜−𝑖𝑜𝑛,𝑠𝑜𝑙𝑢 − 𝐶𝑓𝑖𝑥,𝑚𝑒𝑚 + 𝛼𝐶𝑓𝑖𝑥,𝑚𝑒𝑚
1. INTRODUCTION 2. NUMERICAL MODELLING 3. RESULTS 4. CONCLUSIONS
INVESTIGATION OF REVERSE ELECTRODIALYSIS UNITS BY MULTIPHYSICAL MODELLING
o Continuum equation:
𝜌𝛻(𝒖) = 0
o Navier-Stokes:
𝜌𝛿𝒖
𝛿𝑡+ 𝜌 𝒖𝛻 𝒖 = 𝛻[−𝑝𝐼 + µ 𝛻𝒖 + 𝛻𝒖 𝑇 +F
o Nernst-Plank :
𝑵𝑖 = −𝐷𝑖𝛻𝑐𝑖 − 𝑧𝑖𝑢𝑚𝑖𝐹𝑐𝑖𝛻𝛷𝑖 + 𝒖𝑐𝑖
o Electro-neutrality:
∑𝑧𝑖𝑐𝑖 = 0
o Cell pair electric potential:
𝐸𝑐𝑝 = 𝛷𝐴𝐸𝑀_𝑟𝑖𝑔ℎ𝑡 − 𝛷𝐴𝐸𝑀_𝑙𝑒𝑓𝑡
o External current:
𝐼 =𝑁 𝐸𝑐𝑝
(𝑅𝑏𝑙𝑎𝑛𝑐𝑘+𝑅𝑒𝑥𝑡)
o Stack electric potential:
𝐸𝑠𝑡𝑎𝑐𝑘 = 𝐼𝑅𝑒𝑥𝑡o Total cell pair resistance:
𝑅𝑐𝑝 =(𝐸𝑂𝐶𝑉,𝑐𝑝 − 𝐸𝑐𝑝)
𝐼o Gross power density:
PGross = Estack ∗ j
o Pumping power density:
Ppump=(ΔPdil ∗ Qdil+ΔPconc ∗ Qconc)
Amembrane
o Net power density:
PNe𝑡 = PGross − PPump
EQUIVALENT ELECTRICAL CIRCUIT
A=9.6*9.6 cm2 and N=10
1. INTRODUCTION 2. NUMERICAL MODELLING 3. RESULTS 4. CONCLUSIONS
INVESTIGATION OF REVERSE ELECTRODIALYSIS UNITS BY MULTIPHYSICAL MODELLING
BOUNDARY CONDITIONS
1. INTRODUCTION 2. NUMERICAL MODELLING 3. RESULTS 4. CONCLUSIONS
P=1atm
o Outlet Pressure
INVESTIGATION OF REVERSE ELECTRODIALYSIS UNITS BY MULTIPHYSICAL MODELLING
BOUNDARY CONDITIONS
1. INTRODUCTION 2. NUMERICAL MODELLING 3. RESULTS 4. CONCLUSIONS
P=1atm
o Outlet Pressure
v=0.3-5 cm/s
o Inlet Velocity
INVESTIGATION OF REVERSE ELECTRODIALYSIS UNITS BY MULTIPHYSICAL MODELLING
BOUNDARY CONDITIONS
1. INTRODUCTION 2. NUMERICAL MODELLING 3. RESULTS 4. CONCLUSIONS
P=1atm
o Outlet Pressure
o No slip condition
at membranes
surfaces
v=0.3-5 cm/s
o Inlet Velocity
INVESTIGATION OF REVERSE ELECTRODIALYSIS UNITS BY MULTIPHYSICAL MODELLING
o No slip condition at
membranes
surfaces
o Periodic concentration at
external boundaries of domain
1. INTRODUCTION 2. NUMERICAL MODELLING 3. RESULTS 4. CONCLUSIONS
P=1atm
o Outlet Pressure
o Inlet Velocity
v=0.3-5 cm/s
o Current density at
external boundaries of
domain
cAEM,left=cAEM,right
ileft=iright
BOUNDARY CONDITIONS
INVESTIGATION OF REVERSE ELECTRODIALYSIS UNITS BY MULTIPHYSICAL MODELLING
o No slip condition at
membranes
surfaces
o Periodic concentration at
external boundaries of domain
1. INTRODUCTION 2. NUMERICAL MODELLING 3. RESULTS 4. CONCLUSIONS
P=1atm
o Outlet Pressure
o Inlet Velocity
v=0.3-5 cm/s
o Current density at
external boundaries of
domain
o Absorption equilibrium,
Donnan potential and
continuity of current density
at solutions-membranes
interfaces
cAEM,left=cAEM,right
ileft=iright
Absorption equilibrium
Donnan
Current density
BOUNDARY CONDITIONS
INVESTIGATION OF REVERSE ELECTRODIALYSIS UNITS BY MULTIPHYSICAL MODELLING
Empty channel
Non conductive square spacers
Non conductive round spacers
Profiled Membranes
GEOMETRIES
1. INTRODUCTION 2. NUMERICAL MODELLING 3. RESULTS 4. CONCLUSIONS
INVESTIGATION OF REVERSE ELECTRODIALYSIS UNITS BY MULTIPHYSICAL MODELLING
Empty channel
Non conductive square spacers
Non conductive round spacers
Profiled Membranes
GEOMETRIES
1. INTRODUCTION 2. NUMERICAL MODELLING 3. RESULTS 4. CONCLUSIONS
INVESTIGATION OF REVERSE ELECTRODIALYSIS UNITS BY MULTIPHYSICAL MODELLING
RESULTS
1. INTRODUCTION 2. NUMERICAL MODELLING 3. RESULTS 4. CONCLUSIONS
INVESTIGATION OF REVERSE ELECTRODIALYSIS UNITS BY MULTIPHYSICAL MODELLING
VELOCITY MAPS
Velocity maps:
o Parabolic profile in
empty channel
o Dead pocket
1. INTRODUCTION 2. NUMERICAL MODELLING 3. RESULTS 4. CONCLUSIONS
INVESTIGATION OF REVERSE ELECTRODIALYSIS UNITS BY MULTIPHYSICAL MODELLING
Concentrate Ch. CEMAEM AEMDiluate Ch.
ELECTRIC POTENTIAL
ELECTRIC POTENTIAL:
• OPEN CIRCUIT
• MAX GROSS POWER DENSITY
• SHORTCUT
1. INTRODUCTION 2. NUMERICAL MODELLING 3. RESULTS 4. CONCLUSIONS
CONCETRATE
CHANNEL
DILUTE
CHANNEL
INVESTIGATION OF REVERSE ELECTRODIALYSIS UNITS BY MULTIPHYSICAL MODELLING
C_con_4M and C_dil_0.5M
Concentrate Ch. CEMAEM AEMDiluate Ch.
CONCENTRATION PROFILES
Concentration
Polarisation
1. INTRODUCTION 2. NUMERICAL MODELLING 3. RESULTS 4. CONCLUSIONS
CONCETRATE
CHANNEL
DILUTE
CHANNEL
INVESTIGATION OF REVERSE ELECTRODIALYSIS UNITS BY MULTIPHYSICAL MODELLING
Concentrate Ch. CEMAEM AEMDiluate Ch.
Concentration
profiles in
membranes
1. INTRODUCTION 2. NUMERICAL MODELLING 3. RESULTS 4. CONCLUSIONS
CONCETRATE
CHANNEL
DILUTE
CHANNEL
CONCENTRATION PROFILES
INVESTIGATION OF REVERSE ELECTRODIALYSIS UNITS BY MULTIPHYSICAL MODELLING
1. INTRODUCTION 2. NUMERICAL MODELLING 3. RESULTS 4. CONCLUSIONS
A sensitivity analysis was performed in order to investigate the produced
Net Power Density studying:
• Previously presented geometries of cell pair:
• Velocity of solutions between 0.3-5 cm/s
• Five dilute solutions:
- 0.5M
- 0.1M
- 0.05M
- 0.01M
- 0.005M
SENSITIVITY ANALYSIS C_CON=4M
INVESTIGATION OF REVERSE ELECTRODIALYSIS UNITS BY MULTIPHYSICAL MODELLING
1. INTRODUCTION 2. NUMERICAL MODELLING 3. RESULTS 4. CONCLUSIONS
0
1
2
3
4
5
6
7
Diluito AEM CEM
Conductivity
[S/m
]
Conductivity [S/m]
C_dil_0.005M
C_dil_0.01M
C_dil_0.05M
C_dil_0.1M
C_dil_0.5M
Diluite
• Less concentrated
dilute solutions have
less conductivity
• Membranes have
higher conductivy
than dilute solutions
at 0.005-0.01M
SENSITIVITY ANALYSIS C_CON=4M
INVESTIGATION OF REVERSE ELECTRODIALYSIS UNITS BY MULTIPHYSICAL MODELLING
1. INTRODUCTION 2. NUMERICAL MODELLING 3. RESULTS 4. CONCLUSIONS
As dilute concentration
decreases, the current
density flows preferentially
through membrane profiles
instead of flowing through the
solution, due to their higher
conductivity.
CURRENT DENSITY MAPSC_dil_0.5M C_dil_0.1M
SENSITIVITY ANALYSIS C_CON=4M
INVESTIGATION OF REVERSE ELECTRODIALYSIS UNITS BY MULTIPHYSICAL MODELLING
C_dil_0.05M C_dil_0.01M
• At C_dil_0.01M and
C_dil_0.005M
profiled membranes
give the lowest
resistance
• At higher
concentrations the
empty channel
gives the lowest
resistance
• Non conductive
spacers give always
the highest
resistance
1. INTRODUCTION 2. NUMERICAL MODELLING 3. RESULTS 4. CONCLUSIONS
SENSITIVITY ANALYSIS C_CON=4M
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
Re
sis
tan
ce
[Ω
]
Resistance
C_dil_0.005M
C_dil_0.01M
C_dil_0.05M
C_dil_0.1M
C_dil_0.5M
INVESTIGATION OF REVERSE ELECTRODIALYSIS UNITS BY MULTIPHYSICAL MODELLING
Ne
t P
ow
er
De
nsity
[W/m
2]
Net Power Density
C_dil_0.005M
C_dil_0.01M
C_dil_0.05M
C_dil_0.1M
C_dil_0.5M
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
• The profiled
membrane gives
the highest net
power density with
a value of 4.38
W/m2 at dilute
solution of 0.01M
• Empty channel
gives higher power
density for all other
more concentrated
diluite solutions
1. INTRODUCTION 2. NUMERICAL MODELLING 3. RESULTS 4. CONCLUSIONS
SENSITIVITY ANALYSIS C_CON=4M
INVESTIGATION OF REVERSE ELECTRODIALYSIS UNITS BY MULTIPHYSICAL MODELLING
Conclusions
o The model allows:
• to analyze stacks with different configurations;
• to study different electric current conditions;
• to describe the concentration profiles in the membranes.
o The model has shown that profiled membranes less resistive than diluite solution are able to increase Net power density of RED Units.
o 4M-0.01M solutions, with profiled membranes, give the highest net power density with a value of 4.38W/m2.
o Even if C_dil_0.005M gives the highest driving force to the process, its high dilute solution resistance gives rise to high ohmic losses with less Net power Density production.
1. INTRODUCTION 2. NUMERICAL MODELLING 3. RESULTS 4. CONCLUSIONS
INVESTIGATION OF REVERSE ELECTRODIALYSIS UNITS BY MULTIPHYSICAL MODELLING
THANK YOU FOR YOUR ATTENTION
Giuseppe Battaglia
PhD Student
giuseppe.battaglia91@gmail.com