1

IAPWS – CNC  

Computer Simulations of Supercritical Aqueous Fluids and Particle Formation Processes

Lead Researcher:Svishchev, Igor (Trent University)

Co-investigators:Plugatyr, AndriyNahtigal, Istok

2

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

3

Supercritical Water Test Facility

Andriy Plugatyr and Igor M. Svishchev (Supercritical Water Research Lab, Trent University)

4

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)

5

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

6

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

7

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).

8

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

9

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

10

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).

11

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)

12

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

13

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

14

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

15

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

16

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