1 iapws – cnc computer simulations of supercritical aqueous fluids and particle formation...
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IAPWS – CNC
Computer Simulations of Supercritical Aqueous Fluids and Particle Formation Processes
Lead Researcher:Svishchev, Igor (Trent University)
Co-investigators:Plugatyr, AndriyNahtigal, Istok
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Outline
1. Supercritical water research at Trent University experimental work - flow reactor computer modeling team expertise
2. Particle formation processes in supercritical water
3. CANDU SCWR chemistry project
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Supercritical Water Test Facility
Andriy Plugatyr and Igor M. Svishchev (Supercritical Water Research Lab, Trent University)
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Methodology – flow injection
“Hot” zone
A. Plugatyr and I. M. Svishchev, “Residence time distribution measurements and flow modeling in a supercritical water oxidation Reactor: Application of transfer function concept”, J. Supercrit. Fluids 44 (1), 31 (2008)
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Flow injection under SCW conditions
A. Plugatyr and I. M. Svishchev, J. Supercrit. Fluids, 44 (1), 31 (2008)
Impulse/response experiments:
Hydrodynamic behavior of flow-through reactor systems -Residence Time Distribution (RTD) measurements
Binary diffusion coefficients - Taylor dispersion technique
Kinetics measurements
,D192
duDD
12
20
20
12a
Taylor dispersion experiment
u - fluid velocity, d - diameter of diffusion tube and D12 - binary diffusion coefficient
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Experiments vs. Modeling
A. Plugatyr, “Molecular Dynamics simulations and flow injection studies of hydrothermal fluids”, Ph.D. Thesis (Queen’s U., 2009).
Binary diffusion coefficient of phenol in aqueous solution
T, K P, MPa
a, Pa s
Re Dexptl. × 109, m2/s
298.15 0.1 890.9 1.45 0.996 0.026
298.15 25 887.6 1.45 1.17 0.04
373.15 25 288.7 4.47 2.82 0.15
473.15 25 140.0 9.21 7.38 1.94
Flow parameters and measured diffusion coefficient of phenol
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Molecular Dynamics simulations
Molecular Dynamics simulation of ion pair formation in SCWSystem: 1000 H2O + 1 NaCl; T= 673 K and = 0.3 g/cm3
Nahtigal I., Zasetsky A.Y. and Svishchev I.M., J. Phys. Chem. B, 112, 7537-7543 (2008).
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Equation of state - simulations
Plugatyr A. and Svishchev I.M., Fluid Phase Equilibria 277, 145 (2009).
PT surface for the SPC/E water Red dots represent simulation results
Reference EOS by Wagner and Span
• Accurate short reference equation (16 coefficients)• Can be fitted to a restricted data set• Correct behavior of derivatives• Works for mixtures
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Equation of state - simulations
Plugatyr A. and Svishchev I.M., Fluid Phase Equilibria 277, 145 (2009).
Compressibility maximum of supercritical water
Gas-like fluid
Liquid-like fluid
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Particle formation in SCW
“Metastable” electrolyte solution
Amorphous salt hydrate particles Cluster-cluster fusions, 1 ns
“Critical” nuclei, 0.25 nsNucleation begins
Molecular Dynamics simulation of SrCl2 - H2O mixture at 673 K and 0.17 g/cm3
Svishchev I.M., Nahtigal I. and Zasetsky A.Y., J. Phys. Chem. C, 112, 20181-20189 (2008).
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Particle nucleation rate
Cluster growth – decay curves
System:NaCl-H2O (5.1 wt% salt)
T=673 K and =0.17 g/cm3
Critical NaCl clusterN* = 22
Particle nucleation rate J = 1.19 x 1028 cm-3s-1
Classical nucleation theoryJ = 1/t V
(delay time)
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Particle structure
Amorphous !
Post-critical NaCl cluster (salt hydrate particle)formed in supercritical water
Nahtigal I., Zasetsky A.Y. and Svishchev I.M., J. Phys. Chem. B, 112, 7537-7543 (2008).
Ion - ion separations
0.260
0.265
0.270
0.275
0.280
0.285
0 5 10 15 20 25 30 35 40 45 50 55 60 65
Number of ions (N)
Mea
n N
a -
Cl
sep
arat
ion
(n
m)
Charged clusters
Crystal
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Hydrolysis in SCW
Amorphous NaCl cluster formed in supercritical water
with hydroxide localized to subsurface regions
Nahtigal I. and Svishchev I.M., J. Phys. Chem. B, (in press).
Free acid (HCl) is in SCW phase
mNaCl(s) + nH2O HCl + (m-1)NaCl · NaOH(s) + (n-1)H2O
OH- HCl
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Quenched cluster products
Svishchev I.M. and Nahtigal I., J. Supercrit. Fluids (in press).
Plates and ridged plates
(NaCl)(NaCl)3232
(NaCl)(NaCl)99
(NaCl)(NaCl)1818
(NaCl)(NaCl)88
Rods
(NaCl)(NaCl)1010
CubesCubes
(NaCl)(NaCl)1616
Cubic morphology
Boron nitride morphology
Wurtzitemorphology
(NaCl)(NaCl)77
(NaCl)(NaCl)33
Non-cubic
Low temperature quench to T = 298 K and = 0.006 g/cm3
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Dynamics of clusters
Vibrational density of states
Shape control ?
0.0
0.2
0.4
0.6
0.8
1.0
50 100 150 200 250 300 350
Wavenumber (1/cm)
DO
S (
arb
.un
its)
64 Cube
64 PlateCube
Plate
(NaCl)(NaCl)3232
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CANDU SCWR Chemistry Project
DO consumption (O2 and H2O2 oxidation) rates for select DO scavengers, up to 25 MPa and 650°C – to develop chemistry control strategies under oxygenated supercritical conditions in a CANDU SCWR
Effect of H2O2 on corrosion and speciation in SCW
A kinetic model to estimate the residual levels of oxygen and the degradation by-products in the SCWR pressure tube and downstream of reactor core
Particle formation rates in a SCWR coolant (NaCl, Fe(OH)2, ZrO(OH)2, etc.) – to estimate potential particle (corrosion product) deposition on in-core and out-core surfaces
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