Numerical simulation of vitrification processes: glass homogeneity by gas bubbling study

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Numerical simulation of vitrification processes: glass

homogeneity by gas bubbling study

E. Sauvage

To cite this version:

E. Sauvage. Numerical simulation of vitrification processes: glass homogeneity by gas bubbling study.

Workshop on gases and bubbles in molten glasses from chemical engineering to geosciences, May 2016,

Paris, France. �cea-02400166�

Numerical simulation of vitrification

processes: glass homogeneity by

gas bubbling study

13 MAY 2016

Workshop on gases and bubbles in molten

glasses

|

E. Sauvage

Workshop on gases and bubbles in molten glasses | CEA | 13 MAY 2016 | PAGE 2

Modeling of air bubbling in molten glass

Summary

1- Vitrification technology presentation

2- Semi empirical approach

2-a Model

2-b Interaction with mechanical stirring

3- VOF simulation

Marcoule

(CEA)

Research center

La Hague

(AREVA)

Industrial plant

French Atomic Energy Commission (CEA)

Confinement Research Engineering Department

Waste Confinement and Vitrification Service

CEA / AREVA Joint Vitrification Laboratory (LCV)

Areva

Commercial and industrial operator of 3 vitrification plants

Current pilot of vitrification process

CEA Marcoule (inactive cell)

Cold Crucible

Melter

Workshop on gases and bubbles in molten glasses | CEA | 13 MAY 2016 | PAGE 4

VITRIFICATION PROCESS OPERATED

IN THE LA HAGUE PLANT

Solution fed to a rotary calciner (evaporating, drying and calcining functions)

Glass frit fed separately

Melter fed continuously / poured batchwise

Off-gas treatment unit (recycling of particulate material and purification of the gas streams)

4

Industrial French Vitrification Design / A two-step vitrification process

glass

frit

waste

solutions

CCIM

_IHMM

Calciner

Off-gas treatment

VITRIFICATION PROCESS OPERATED

IN THE LA HAGUE PLANT

Furnaces technology

Cold Crucible

Inductive Melter

Inductive Hot

Metallic Melter

Oxides Average composition of industrial glass (w %) SiO2 45,6 B2O3 14,1 Al2O3 4,7 Na2O 9,9 CaO 4 Fe2O3 1,1 NiO 0,1 Cr2O3 0,1 P2O5 0,2 Li2O 2 ZnO 2,5 Oxides (PF+Zr+actinides) + Suspension of fines Actinide oxides 17 SiO2+B2O3+Al2O3 64,4

Average chemical compositions for R7T7 glass produced in the industrial facilities at La Hague

Inside view in CCIM

Characteristics:

- Molten glass mass

400 kg

270 kg

- Max throughput

36 kg/h

25 kg/h

- Max temperature

>1400°C

1100°C

- Mechanical stirring

yes

yes

- Gas bubbling

yes

yes

- Approx. life time

>2 years

0.5 year

Workshop on gases and bubbles in molten glasses | CEA | 13 MAY 2016 | PAGE 6

- Oil with the same kinematic viscosity as glass (at a

given temperature)

- Explored parameters: liquid viscosity, air flow rate, hole

diameter of the injector...

2 Bubbling characterization and modelisation

Air bubbling overview

Experiment in hydraulic similirarity with silicon oil

R. RIVA (CEA / Grenoble)

Hot glass

Oil

30 to 60 cm

L L G G

g

ρ µ ρ µ σ

r

ρ µ

L

L

Modelisation

Model parameters

Characteristic parameters

2-a « One mesh » model

ε

Nomenclature : Q Gas flow rate (L/h) g Gravity (m/s2₎

d₀ Orifice diameter (m) V_g Gas velocity (m/s)

V_B Bubble rising velocity (m/s) d_e Equivalent diameter of bubble (m)

f_z Body force imposed in the fluid (N/m3₎

C_d Drag coefficient (-) V_ol Volume of a bubble (m3₎

p Liquid pressure (Pa)

ρ

L Liquid density (kg/m3)

µ_L Liquid viscosity (m2_/s)

ε

G Volume fraction of gas

Known parameters

es1

Diapositive 7

es1 The liquid is driven by the rising bubbles

This driving is modelise by a constant vertical body force in the liquid es210797; 22/08/2012

= f( , ) = choice of model

3

z

cuve

inj

z

f

z

H

H

h

D

d

f

ρ ε

g

N m

−

≈

−

≈





≈

_

_

= f( ) = experimental correlation

1, 23

f

e

d

=

d

2

3

e

B

Qd

V V

ε

=

2

4

(

1

)

3

e

B

d

d g

V

C

ε

+

=

2-a « One mesh » model

Snabre, P. & Magnifotcham, F. Recirculation flow induced by a bubble stream rising in a viscous liquid

The European Physical Journal B, 1998, 4, 379-38

Jamialahmadi, M. et al, Study of Bubble Formation Under Constant Flow

Workshop on gases and bubbles in molten glasses | CEA | 13 MAY 2016 | PAGE 9

Jamialahmadi, M. et al, Study of Bubble Formation Under Constant Flow

Conditions, Chemical Engineering Research and Design, 2001, 79, 523 - 532

2-a « One mesh » model

PIV measurement vs numerical simulation

-0.1 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 -300 -200 -100 0 100 200 300 Vz (m s -1) r (mm) Q100 Expt. Num. Q250 Expt. Num. Q500 Expt. Num. Q750 Expt. Num. Q1000 Expt. Num. -0.06 -0.05 -0.04 -0.03 -0.02 -0.01 0 0.01 0 50 100 150 200 250 300 350 400 450 Vz (m s -1 ) z (mm) Expt. Q100 Num. Expt. Q250 Num. Expt. Q500 Num. Expt. Q750 Num. Expt. Q1000 Num. 0 0.2 0.4 0.6 0.8 1 0 50 100 150 200 250 300 350 400 450 Vz (m s -1 ) z (mm) Expt. Q100 Num. Expt. Q250 Num. Expt. Q500 Num. Expt. Q750 Num. Expt. Q1000 Num.

1840 cSt

ν

=

Workshop on gases and bubbles in molten glasses | CEA | 13 MAY 2016 | PAGE 11

2-b Interaction with mechanical stirring

Effect of external flow induced by the mechanical stirring

Experimental set-up

PIV measurement

Deviation of the bubble train trajectory

Lagrangian equation for the trajectory :

Drag force

Added mass

Specific drag coefficient :

with

2

Re

18

24

D D p p

C

F

d

µ

ρ

=

(

) (

)

sup

p

p

D

p

p

g

du

F

u

u

F

dt

ρ

ρ

ρ

−

=

−

+

+

r

r

r

r

r

(

)

sup

1

2

_p p _p p _i

d

u

F

u

u

u

dt

dx

ρ

ρ

ρ

ρ

∂

=

−

+

r

_r

_r

_r

Re

ρ

d u

p p

u

µ

−

=

16

1

Re

Cd

= +

Trajectory of bubble train

Workshop on gases and bubbles in molten glasses | CEA | 13 MAY 2016 | PAGE 13

With one Air Bubler

Expt.

Num.

0 rpm

20 rpm

Stirring speed

60 rpm

40 rpm

Expt.

Num.

Stirring speed

Workshop on gases and bubbles in molten glasses | CEA | 13 MAY 2016 | PAGE 15

Results

A Semi empirical model, simple, validated in a specific range of bubbling, easy

to set up in global calculation of the process.

The interaction of mechanical stirrer is taken into account

Drawback : not predictive outside the range of validation.

This model is used in our project of optimisation or conception of new vitrification

furnace

Modeling the gas-liquid interface

Volume Of Fluid (VOF) model equations

- Volume fraction of one phase

- Momentum equation

(

) (

)

_







=

∇

+

∂

∂

0

.

1

L L L L L L

v

t

r

ρ

ε

ρ

ε

ρ

( ) ( )

v

v

v

p

[

(

v

v

)

]

g

t

T

r

r

r

r

r

r

ρ

µ

ρ

ρ

+

∇

=

−∇

+

∇

∇

+

∇

+

∂

∂

.

.

1

=

+

_G

L

ε

ε

G

G

L

L

ρ

ε

ρ

ε

ρ

=

+

µ

=

ε

L

µ

L

+

ε

G

µ

G

2-b Multiphase model

Workshop on gases and bubbles in molten glasses | CEA | 13 MAY 2016 | PAGE 17| PAGE 17

Air jet is a Rayleigh-Plateau

instability. This instability

should be numerically excited.

Problem :

No bubbles

are formed

Air inlet

With high

frequency

modulation of

the inlet air flow

(300 Hz and 4%

magnitude)

2-b Multiphase model

Time

A

ir

v

e

lo

c

it

y

Slow motion

(real time / 10)

Workshop on gases and bubbles in molten glasses | CEA | 13 MAY 2016 | PAGE 19

Good qualitative agreement – No more experimental-based correlations

Drawback : Highly time consuming (1 week of calculation for 1 second simulated)

Prospects : Multiphase model

VOF model, very accurate and allowing to simulate complex configuration.

Tool extremely useful to understand phenomena

Openfoam software

~2 millions mesh

Numerical Simulation of mixing molten glass with air bubbling is well

advanced :

1 -

A Semi empirical model, simple, validated in a specific range of

bubbling, easy to set up in global calculation of the process.

• The interaction of mechanical stirrer is taken into account

•

Drawback : not predictive outside the range of validation.

This model is used in our project of optimisation or conception of new

vitrification furnace

2 – A multiphase flow direct simulation (with VOF model) is used for

specifics studies involving very complex interface interaction

Prospects :

Include redox aspect

Workshop on gases and bubbles in molten glasses | CEA | 13 MAY 2016 | PAGE 21

Thank you for your attention

Any questions ?

| PAGE 22

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SCDV

Commissariat à l’énergie atomique et aux énergies alternatives Centre de Marcoule| 30207 Bagnols-sur-Cèze cedex

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| PAGE 22