hi water vle modelling ppt
TRANSCRIPT
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Thermodynamics modeling of theHIx part of the Iodine Sulfur
thermocycle
M. K. Hadj-Kali, V. Gerbaud,
P. Floquet, X. Joulia
J.M. Borgard,
P. Carles, G. Moutiers
November 4 -9, 2007Salt Palace Convention CenterSalt Lake City, Utah
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P. Carles / Thermodynamic modeling of HIx part of the Iodine Sulfur thermocycleNovember 4 -9, 2007Salt Palace Convention CenterSalt Lake City, Utah
H2SO4
Decomposition
H2SO4
Concentration
HI
Decomposition
HIVaporization
Bunsen Reaction
H2O
H2O2
2 HI H2 + I2
[330 C]
I2 + SO2 + 2 H2O H2SO4 + 2 HI
[120 C]
SO2 + H2O + O2
[850 C]
H2SO4
I2SO2
Iodine sulfur thermocycle for hydrogen production
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P. Carles / Thermodynamic modeling of HIx part of the Iodine Sulfur thermocycleNovember 4 -9, 2007Salt Palace Convention CenterSalt Lake City, Utah
Multiphase behavior (vapor liquid liquid solid),
H2O I2 : highly immiscible liquid liquid equilibrium system,
HI I2 : solid liquid equilibrium system,
H2O HI
Maximum boiling / low pressure azeotrope,
Strong electrolytic system,
Liquid liquid equilibrium,
The ternary mixture has two separate liquid liquid regions,
Solvation reactions occur as well as poly-iodides formation in the solution.
Thermodynamics challenges of HIx system
The sulfuric acid decomposition section of this process can be simulated accurately, but other
sections (acid generation and hydrogen iodide decomposition) illustrate the difficulty of modeling phase
behavior, particularly liquid-phase immiscibility, in complex electrolyte systems.
(Mathias 2005, Fluid Phase Equilibria)
HIx = HI/H2O/I2 (nominal : HI / 5 H2O / 4 I2)
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P. Carles / Thermodynamic modeling of HIx part of the Iodine Sulfur thermocycleNovember 4 -9, 2007Salt Palace Convention CenterSalt Lake City, Utah
Outline
Iodine-Suldure thermochemical cycle for hydrogen production
HIx modeling Challenges
Proposed model and identification methodology
Validation vs experimental literature data
Conclusions and perspectives
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P. Carles / Thermodynamic modeling of HIx part of the Iodine Sulfur thermocycleNovember 4 -9, 2007Salt Palace Convention CenterSalt Lake City, Utah
UNIQUAC
Homogeneous model-
Equation of State PR Boston Mathias
Mixture rules
ComplexStandardModel
Symmetric convention
Electrolytes
MHV2
HIx modeling
Engels Solvation
Non- Electrolytes
Heterogeneous model -
liquid Phase
Ideal gas
ModelAsymmetric convention
NRTL + Pitzer
vapor Phase
Equation of StateModel
Symmetric convention
Electrolytes
Engels Solvation Wilson
NRTL Neumann
Electrolytes
Neumann : Engels + NRTL
Mathias et al. : electrolyte
Literature models:
Non- Electrolytes
UNIQUAC Solvation (UQSolv)
New models:
Ideal
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P. Carles / Thermodynamic modeling of HIx part of the Iodine Sulfur thermocycleNovember 4 -9, 2007Salt Palace Convention CenterSalt Lake City, Utah
Advantages of the model
- approach:
No extrapolation of the vapor pressure law above critical points
Correct handling of mixture phase behavior above HI critical point (TC=423K)
Equation of state: Peng Robinson w/ Boston Mathias function
Accurate behavior of pure components above critical points
Mixing rule: MHV2 including non ideal liquid phase behavior via a Gex model
Activity coefficient model: Engels solvation
Electrolytic model but with symmetric convention so as to span the whole composition range
Introduces solvation complexes with several solvents
Activity coefficient model: UNIQUAC vs NRTL:
Combinatorial term handles steric effect
Residual term accounts for non ideal liquid phase behavior (as NRTL)
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P. Carles / Thermodynamic modeling of HIx part of the Iodine Sulfur thermocycleNovember 4 -9, 2007Salt Palace Convention CenterSalt Lake City, Utah
Simulis Thermodynamics component
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P. Carles / Thermodynamic modeling of HIx part of the Iodine Sulfur thermocycleNovember 4 -9, 2007Salt Palace Convention CenterSalt Lake City, Utah
Model parameter identification procedure
Three binary mixtures
H2O I2: only UNIQUAC binary interaction parameters
HI I2: only UNIQUAC binary interaction parameters
H2O HI:
HI solvation by H2O equilibrium constant and solvation number
m H2O + HI 2C
UNIQUAC binary interaction parameters for H2O, HI and the solvation complex C
Ternary mixture
H2O HI I2: refined parameter values
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P. Carles / Thermodynamic modeling of HIx part of the Iodine Sulfur thermocycleNovember 4 -9, 2007Salt Palace Convention CenterSalt Lake City, Utah
Available experimental data
Haase (1963)21 P = f(T,x,y)VLE
LLE
VLE
LSE
LSE
LLE
LLE
H
VLE
VLE
Data
Neumann (1986)280 P = f(T,x)H2O HI I2
Vanderzee & Gier (1974)13
Norman (1984)12
Wster (1979)80 P = f(T,x)
Pascal (1926)38 T = f(P,x,y)
H2O HI
Okeefe & Norman (1982)5 T = f(x)HI I2
Haase (1963) / Norman (1985)6 T = f(x)
Kracek (1932)10 T = f(x)
Kracek (1932)10 T = f(x)H2O I2
Data sourcesData number
Fitting data validation
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P. Carles / Thermodynamic modeling of HIx part of the Iodine Sulfur thermocycleNovember 4 -9, 2007Salt Palace Convention CenterSalt Lake City, Utah
Model prediction of iodinesolubility in aqueous solution
H2O I2 identification results
Iodine phase
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P. Carles / Thermodynamic modeling of HIx part of the Iodine Sulfur thermocycleNovember 4 -9, 2007Salt Palace Convention CenterSalt Lake City, Utah
Iodine
melting point
Neumann Model
(wI2 > 100)
HI I2 identification results
0
20
40
60
80
100
0 20 40 60 80 100 120
Temperature (C)
Masscompositionofiodine(%)
exp (O'Keefe et Norman, 1982)
Ideal UNIQUAC
Neumann
UQSolv
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P. Carles / Thermodynamic modeling of HIx part of the Iodine Sulfur thermocycleNovember 4 -9, 2007Salt Palace Convention CenterSalt Lake City, Utah
Good agreement up to the azeotrope
H2O HI identification results 1/2
azeotrope0,1
1
10
100
0 0,1 0,2 0,3 0,4 0,5 0,6 0,7
HI mass fraction
Press
ure(bar)
T=90C
T=130C
T=170C
T=190C
T=230C
Wster Correlations (1979)
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P. Carles / Thermodynamic modeling of HIx part of the Iodine Sulfur thermocycleNovember 4 -9, 2007Salt Palace Convention CenterSalt Lake City, Utah
H2O HI identification results 2/2
H20 - HI liquid - vapor equilibrium curve at atmospheric pressure
-60
-40
-20
0
20
40
60
80
100
120
140
0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1
HI molar fraction
Temperature(C)
exp bubble points (Pascal, 1926)
exp dew points (Pascal, 1926)
UQSolv bubble curve
UQSolv dew curve
Model prediction of LVE curve at atmospheric pressure
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P. Carles / Thermodynamic modeling of HIx part of the Iodine Sulfur thermocycleNovember 4 -9, 2007Salt Palace Convention CenterSalt Lake City, Utah
Engels experimental data
(0,017 < xHI < 0,159)
Ternary system H2O HI I2
Liquid liquid equilibrium data
(Norman, 1984)
HI I2
H2O
For regression For validation
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P. Carles / Thermodynamic modeling of HIx part of the Iodine Sulfur thermocycleNovember 4 -9, 2007Salt Palace Convention CenterSalt Lake City, Utah
6.5062.249.53
3.7344.838.18UQSolv
Neumann
criterionMax error (%)Average error (%)
2
=
Np exp
calexpP
PPCriterion
Liquid liquid equilibrium (H2O I2)
Solid liquid equilibrium (HI I2)
Vapor liquid equilibrium (H2O HI) with solvation (m H2O + HI 2C)
Keeping identified parameters for :
H2O HI I2 identification results 1/2
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P. Carles / Thermodynamic modeling of HIx part of the Iodine Sulfur thermocycleNovember 4 -9, 2007Salt Palace Convention CenterSalt Lake City, Utah
H2O HI I2 identification results 2/2
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P. Carles / Thermodynamic modeling of HIx part of the Iodine Sulfur thermocycleNovember 4 -9, 2007Salt Palace Convention CenterSalt Lake City, Utah
Conclusion and perspectives
HIx non ideal and electrolytic system is modeled by an equation of state (EOS)
approach with complex mixing rules including GEX models.
The EOS approach is well suited with expected process T and P conditions that may be
higher than the HI critical point.
The liquid phase non ideal behavior is modelled combining Engels solvation equations
suitable for any electrolyte composition and activity coefficient UNIQUAC equation.
The resulting UQsolv model predict accurately most of the experimental data available
and accurate, incl. LLE, LSE and LLVE for each binary and ternary system.
Largest discrepancy is found for high HI concentration mixtures where experimental
data is lacking or is uncertain.
Improvements are under investigation:
Polyiodide ion formation
HI decomposition in I2 and H2 for the vapor phase rich in HI