i. molecular simulations of water and steam ii. hazardous waste treatment: supercritical water...
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• I. Molecular Simulations of Water I. Molecular Simulations of Water and Steam and Steam
II. Hazardous Waste Treatment: II. Hazardous Waste Treatment: Supercritical Water OxidationSupercritical Water Oxidation
Igor SvishchevTrent University, Peterborough, ON
IAPWS-CNC 2003IAPWS-CNC 2003
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Key applications:Thermal properties of aqueous fluids under extreme conditionsNucleation rates in metastable steamSolubilities of salts at elevated temperatures and pressuresPartition coefficients
Advantages:Cost and time savings over laboratory measurementsReplaces empirical extrapolations and fits
IAPWS Simulation Task Group:Promotes modeling of aqueous fluids relevant to power cycles and other industrial applications, and provides an international forum for exchange of results of research (PVT databases, analytical fits, computer programs).
Molecular Simulation: Molecular Simulation: Industry ConnectionsIndustry Connections
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Properties of Working Fluids:Properties of Working Fluids:
“Releases provide carefully evaluated, internationally agreed-upon formulations of properties for which measurement of high quality exist over a wide range of states”.
“Guidelines are carefully evaluated, internationally agreed-upon formulations of properties for which measurement of high quality do not exist over a wide range of states or can not be made”.
International Association for the Properties of Water and Steam, 1994
IAPWS Releases and Guidelines
Real Fluid Simulated Fluid
?
Where do the standards come from ?
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Molecular Models:Molecular Models: water and oxygen
Simple Point Charge (SPC/E ) potentialBerendsen, 1987
Polarizable Point Charge (PPC) potentialSvishchev and Kusalik, 1996
Point charge potentialZassetsky and Svishchev, 2001 WaterOxygen
Starting point
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Molecular Simulation:Molecular Simulation: liquid water
Computer Experiment
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Simulated PVT database: Simulated PVT database: water and steam
SvishchevHarringtonGuissaniMountain
Outcome
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Equation of State:Equation of State: Pitzer-Sterner EOS
P
RT= ρ + c1ρ
2− ρ 2
c3 + 2 c4 ρ + 3c5ρ2 + 4 c6 ρ 3
( )
c2 + c3 ρ + c4 ρ2 +c5 ρ 3 + c6 ρ 4
( )2
⎡
⎣
⎢ ⎢ ⎢ ⎢
⎤
⎦
⎥ ⎥ ⎥ ⎥
+ c7 ρ2
(exp −c8 ρ ) +
+ c9 ρ 2(exp −c10 ρ )
ci = ci ,1T−4
+ ci ,2 T−2
+ ci ,3T−1
+ ci , 4 + ci ,5 T + ci , 6T2
Critical Point for Water: Tc, K Pc, bar ρc, g/cm3
IAPWS Release, 1992 647.1 220.6 0.322
Pitzer-Sterner EOS, 1994 647.2 220.8 0.322
Analytical fit
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Analytical fit:Analytical fit: PVT surface for simulated water
0.02 0.04 0.06
Density, molêcm3
300
400500
600700
Temperature,K- 2000
0
2000
4000
6000
Pressure,bar
0.02 0.04 0.06
Density,molêcm3
Pressure, bar
Best fit
Pitzer-Sterner EOS27 fitting coefficientsSvishchev and Hayward, 2001
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Water-Oxygen Mixtures:Water-Oxygen Mixtures: Simulations and EOS
• Analytical fits for simulated PVT data
- EOS for the mixture () has the same form as for pure solvent, water (component ),
- Mixture parameters are derived from the parameters of the single-component EOS
c1() = x2() c1 () +x2() c1() + x() x() [c1() + c1()] (1-k), x - mole fraction of O2
c2-10() = x() c2-10(
PRT =ρ + c1ρ
2−ρ2 c3 +2c 4ρ+3c5ρ
2 +4c 6ρ3 ⎛
⎝ ⎜ ⎞ ⎠ ⎟
c2 +c3ρ +c4ρ2 +c5ρ
3 +c6ρ4 ⎛
⎝ ⎜
⎞
⎠ ⎟2
⎡
⎣
⎢ ⎢ ⎢ ⎢ ⎢
⎤
⎦
⎥ ⎥ ⎥ ⎥ ⎥+ c7ρ
2exp(−c 8 ρ ) + c 9 ρ
2exp (−c10 ρ )
Note : k is the only “coupling” parameter, independent of T and ρ
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Water-Oxygen Mixtures:Water-Oxygen Mixtures: results
0.90.80.70.60.50.40.30.20.10.00
500
1000
1500
2000
2500
MD data
MD data
EOS, validity rangeEOS, extrapolation
EOS, validity rangeEOS, extrapolation
PVT data at 643 K
Density, g/cm^3
Pressure, bars
O2-H2O
H2O
• Comparison with Experiment (6 % O2, T=645 K, ρ =0.32 g/cm3)
Exp., Franck, 1985 Simulated EOS P ~ 300 bar P = 296 bar
• Simulated EOS (water + 5% O2)
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Phase diagram for waterPhase diagram for water
Supercritical Water Oxidation:Supercritical Water Oxidation: basics
Supercritical Water
OxidationP>221 bar,
T > 647K
Wet Air OxidationP~ 200 barT=400-550K
Purpose:Total destruction of organic wastes by chemical oxidation in supercritical water
Features:- rapid and effective process- environmentally safe- eliminates residual salts (radioactivity)
Customers:- chemical plants, paper mills- power utilities- military facilities
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Oxidation reactionOxidation reactionss in supercritical water in supercritical water
Dioxin
O
OCl
Cl Cl
Cl
+ 22 H2O2 12 CO2 + 22 H2O + 4 HCl
NO2
NO2O2N
CH3
2 + 21 H2O2 14 CO2 + 26 H2O + 3 N2
Cl
H2C
CH2
Cl
H2C
CH2
S+ 14 H2O2 4 CO2 + 16 H2O + 2 HCl + H2SO4
ClCl
Cl
Cl Cl
Cl Cl
Cl
ClCl
+ 22 H2O2 12 CO2 + 14 H2O + 10 HCl
ClCl
+ 13 H2O2 6 CO2 + 14 H2O + 2 HCl
TNT
Nerve Agent HD
PCBo-Dichlorobenzene
(2,3,4,5,6,2',3',4',5',6'-Decachloro-biphenyl)
(2,3,7,8-Tetrachloro-dibenzo[1,4]dioxine)
Supercritical Water Oxidation: Supercritical Water Oxidation: reactionsreactions
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SCWO process
Reactor SchematicReactor Schematic
Reactor:Stainless Steel 316 V = 3.74 cm3
P = 450 barP = 450 bar
2.4 ml/min
0.6 ml/min
3.0 ml/mintr = 75 s
Reagents:Aqueous dichlorobenzene
Oxidizer:Aqueous H2O2
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Supercritical Water Oxidation: Supercritical Water Oxidation: resultsresults
94.96
99.02 98.96 99.06
99.93
93.00
94.00
95.00
96.00
97.00
98.00
99.00
100.00
523 648 693 753 773
Temperature, K
Degradation efficiency, %
chlorophenoldichlorophenol
Temperature effect on degradation efficiency at 450 barTemperature effect on degradation efficiency at 450 bar
3.6 ppm
0.87 ppm
1.14 ppm
1.03 ppm
0.09 ppm
Wet airWet air Supercritical waterSupercritical water
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Thank YouThank You
Acknowledgements: NSERC
T. Hayward
A. Plugatyr