• 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

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

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 ?

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

Molecular Simulation:Molecular Simulation: liquid water

Computer Experiment

Simulated PVT database: Simulated PVT database: water and steam

SvishchevHarringtonGuissaniMountain

Outcome

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

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

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

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)

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

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

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

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

Thank YouThank You

Acknowledgements: NSERC

T. Hayward

A. Plugatyr