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Numerical Study of the Self-ignition of

Tetrafluoroethylene in a 100-dm3-reactor

Fabio Ferrero , Robert Zeps, Martin Kluge

BAM Federal Institute for Materials Research and Testing

What is tetrafluoroethylene (TFE)?

• Tetrafluoroethylene (C2F4) is a colorless gas

INTRODUCTION

• TFE has a wide commercial relevance

• PTFE (Teflon®)

• PTFE Co-polymers

• TFE is a chemically unstable gas explosive decomposition

without oxidant (accidents in chemical plants*)

* Reza, A., Christiansen, E., A Case Study of a TFE Explosion in a PTFE Manufacturing Facility, Process Safety Progress, 26(1), 77-82 (2007)

• Focus: ignition of TFE caused by contact on hot surfaces

(self-ignition)

8442 FCc0.5FC

TFER molkJH 103

DIMERIZATION

REACTIONS

Main reactions

TFE at high pressure comes in contact with hot surfaces

TFE at high pressure comes in contact with hot surfaces

TFER molkJH 257

C(s)CFFC 442

8442 FCc0.5FC

TFER molkJH 103

DIMERIZATION

DECOMPOSITION

Main reactions

REACTIONS

2242 CFCFFC

26384 )()( CFeFCcFC

24263 )( CFFCcFC

)()( 6363 cFCeFC

4263284 )()( FCeFCCFcFC )(844242 cFCFCFC

42FC

2242 CFCFFC

26384 )()( CFeFCcFC

24263 )( CFFCcFC

)()( 6363 cFCeFC

4263284 )()( FCeFCCFcFC )(844242 cFCFCFC

42FC

*Bauer, S.H., Javanovic, S., The Pyrolysis of Octafluorocyclobutane - Revisited, International Journal of Chemical Kinetics, 30, 171-177 (1998)

Extended reaction net*

REACTIONS

100-dm³-autoclave

Properties: stainless steel 1200 kg 360° rotation 345 bar(a) at 20 °C

Measurements: temperature (up to 3 TC) pressure

EXPERIMENTS

100-dm³-autoclave

Properties: stainless steel 1200 kg 360° rotation 345 bar(a) at 20 °C

Measurements: temperature (up to 3 TC) pressure

EXPERIMENTS

Tests:

• p0 = 5, 10 and 20 bar(a)

• Twall,0 is varied

=> lowest Twall,0 with an ignition

100-dm³-autoclave

Properties: stainless steel 1200 kg 360° rotation 345 bar(a) at 20 °C

Measurements: temperature (up to 3 TC) pressure

EXPERIMENTS

Tests:

• p0 = 5, 10 and 20 bar(a)

• Twall,0 is varied

=> lowest Twall,0 with an ignition

Meshes (2D): only the TFE domain is computed

SIMULATIONS

Quality > 0.85

Fup=uut

u

2

Equations

0=ut

TPP STuρcTλ=t

Tρc

kCkkk

k SCuC=t

C

D

Tp sR/

SIMULATIONS

Chemical Engineering Module: - non-isothermal flow mode (chns)

- convection and conduction mode (chcc)

- convection and diffusion mode (chcd)

Momentum

Continuity

Mass transfer

Heat transfer

Ideal gas law

Horizontal Reactor

p0 = 11 bar(a)

T0 = 240 °C

Vertical Reactor

SIMULATIONS

p0 = 11 bar(a)

T0 = 240 °C

SIMULATIONS

T [°C] T [°C]

Horizontal Reactor

p0 = 11 bar(a)

T0 = 240 °C

t = 54 s

Vertical Reactor

p0 = 11 bar(a)

T0 = 240 °C

t = 54 s

MORE CRITICAL

Prediction accuracy of TFE ignition temperatures (MITD)

150 175 200 225 250 275 300

150

175

200

225

250

275

300

Vertical orientation

Horizontal orientation

+20%

MIT

D (

Ca

lcu

late

d)

[°C

]

MITD (Experimental) [°C]

-20%

Pressure range: 5-20 bar(a)

SIMULATIONS

• simulations of the self-ignition of TFE in a large scale vessel (100 dm³) were performed

• a good agreement with experimental data was observed

• in particular ignition temperatures of TFE were well predicted

• the model is considered validated for large geometries

CONCLUSIONS

QUESTIONS

Numerical Study of the Self-ignition of

Tetrafluoroethylene in a 100-dm3-reactor

Fabio Ferrero , Robert Zeps, Martin Kluge

BAM Federal Institute for Materials Research and Testing