CFD Lagrangian Multiphase Simulation Applied to Dust Explosion

Characterization

Authors: Daniel Vizcaya, Carlos Murillo, Nathalie Bardin-Monnier,

Olivier Dufaud, Laurent Perrin, Nicolás Ratkovich & Felipe Muñoz

Contact: Daniel Vizcaya (dm.vizcaya62@uniandes.edu.co)

1

Speaker: Hugo Pineda

Content

1. Introduction to dust explosions

2. Explosivity Parameters and Equipment

3. Simulation

4. Results

5. Conclusiones and Future Work

2

1. Introduction to dust explosions: Imperial Sugar Case

Place: Port Wentworth, Georgia, USA

Date: February 7, 2008.

Process: Sugar refinery.

Combustible: Sugar.

Mean Particle size (m): 23

Pmax (bar): 7.5

MEC (g/m3): 95

Kst (bar m/s): 139

Impact:

• 14 fatalities.

• 36 injured.

• Process plant total destruction.3

Vorderbrueggen (2011)

1. Introduction to dust explosions

4

Eckhoff (2009)

1. Introduction to dust explosions

5

2. Explosivity parameters: Maximumpressure and maximum rate of pressure rise

6

Typical pressure profile of an explosion on the 20 L Sphere

Dahoe et al. (2001)

2. Explosivity parameters: MinimumExplosivity Concentration (MEC)

7

Eckhoff (2009)

Maize Starch Characterization

2. Explosivity parameters: Particle Size

8

Eckhoff (2009)

Aluminium Dust in Air

2. Explosivity parameters: Turbulence level

9Eckhoff (2009)

Lycopodium in Air

10

𝐾𝑠𝑡 =𝑑𝑃

𝑑𝑡𝑉1/3

Is a severity index developed from the maximum rate of

pressure rise and volume-invariant.

Risk Level Kst (bar m/s) Explosion Description

ST 1 1-200 Weak

ST 2 201-300 Strong

ST 3 > 300 Very Strong

2. Explosivity parameters: Deflagration Index

Table 1. Risk level associated to Deflagration Index

11

𝐾𝑠𝑡 =𝑑𝑃

𝑑𝑡𝑉1/3

Is a severity index developed from the maximum rate of

pressure rise and volume-invariant.

Material Mean ParticleSize

Concentration Kst (bar m/s)

Starch 10 105 189

Polyethylene 63 25 267

Phenolic Resin 40 50 165

2. Explosivity parameters: Deflagration Index

2. Dust explosion characterization equipment

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• MEC from nominal concentration.

• Maximum pressure (Pmax).

• Maximum rate of pressure rise (dP/dtmax).

20 L Sphere 1 m3 Vessel

𝐾𝑠𝑡 =𝑑𝑃

𝑑𝑡𝑉1/3

13

2. Deflagration Index

Dahoe et al. (2001)

[13] 14

20 L Sphere 1 m3 Vessel

Dust containerpressure (barg)

20 20

Ignition Time (ms) 60 200

Ignition Energy (kJ) 10 10

Type of nozzle Rebound Annular

Type of flammabledust

High densities All densities

Table 2. Comparison between dust explosion characterization equipments

2. Dust explosion characterization equipment: Comparative Table

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2. Experimental Studies

Dahoe et al. (2001)

• To develop a CFD multiphase flow to evaluate the dispersionphenomena of flammable dust within the 20 L Sphere understandard test conditions.

• To evaluate the dust concentration at ignition point on themoments previous to the explosion.

• To evaluate the turbulence level during the dispersion of thedust.

• To evaluate the particle distribution within the domain takinginto account the particle size.

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3. Objectives

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3. Simulation: General Geometry

Canister

Sphere

Igniters

Nozzle

Nozzle Vertical Cut

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3. Simulation: Mesh

Models:

• Polyhedral mesher

• Advancing Layer Mesher

• Surface Remesher

Principal Reference Values:

• Number prism layers: 2

• Prism Layer Thickness: 0.036 mm

• Minimum Surface Size: 0.2 mm

Mesh Results:

• Cells: 7,316,852

• Faces: 51,224,435

• Verts: 43,619,275

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3. Simulation: Mesh

Velref > 400 m/s

• Implicit Unsteady.– Time Step: 1 ms

– Temporal Discretization: 2nd Order

• Compressible Gas: Peng-Robinson

• Lagrangian Multiphase

• Detached Eddy Simulation

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3. Simulation: Principal Models

• Lagrangian Multiphase:– Material: Starch– Models:

• Constant density: = 610 kg/m3

• Drag Force• Material Particles• Pressure Gradient Force• Spherical Particles

• Injector:– Mass Flow Rate: 6 kg/s for t <

0.2 ms– Number of Parcels: 2.2e+06– Particle Size Distribution from

laser diffraction (Table 3)

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3. Simulation: Principal Models

Table 3. Particle Size Distribution from laser

diffraction

0

0.1

0.2

0.3

0.4

Mas

s Fr

acti

on

Particle Size (μm)

Particle Size Distribution

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3. Simulation: Initial Conditions

23

4. Results: Influence of iterations

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0 5 10 15 20

Pre

ssu

re (

bar

)

Time Step

Pressure profile

250 Iter

1000 Iter

Experimental results

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4. Results: Computational cost

0

50

100

150

200

0 5 10 15

Sim

ula

tio

n t

ime

(h

)

Time Step

Computational Cost

250 iter

1000 iter

• Windows Server 2008 – 64-bit

• Processor: Intel ® Xeon ® X5060 @ 2.67GHz

• RAM; 40 Gb

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4. Results: Particle flow

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4. Results: Particle flow

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4. Results: Particle diameter for 1000 iter

• STAR-CCM+® was used to developed a multiphase lagrangianflow in order to simulate the flammable dust dispersionwithin the 20 L sphere.

• The number of Maximum Inner Iterations has a significantimpact on the results as well as on the computational cost.

• The nozzle disperses correctly the dust within the domain.However, the smaller particles tends to the walls and thebigger ones to the center of the sphere.

• In order to model correctly the behavior of the flow, and dueto the geometry high complexity, it was necessary toimplement the DES turbulence model.

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5. Conclusions

• The Maximum Inner Iterations will be increased to 1500.

• The simulation time will be 120 ms in order to evaluate abetter ignition time for the standard test.

• The use of cohesion models to represent particlefragmentation and agglomeration will be added.

• Another types of nozzle will be simulated in order to evaluatethe dust homogeneity within the sphere.

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5. Future Work

CFD Lagrangian Multiphase Simulation Applied to Dust Explosion

Characterization

Authors: Daniel Vizcaya, Carlos Murillo, Nathalie Bardin-Monnier,

Olivier Dufaud, Laurent Perrin, Nicolás Ratkovich & Felipe Muñoz

Contact: Daniel Vizcaya (dm.vizcaya62@uniandes.edu.co)

30

Speaker: Hugo Pineda

7. BIBLIOGRAFHY

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brennbarer Stäube," Thesis, 1977.

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investigation," Process Safety Progress, vol. 30, pp. 66-81, 2011.

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7. BIBLIOGRAPHY