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CFD-Based Multiscale Modelling of Bubble-Particle Collision Rates and Efficiencies in a Flotation Cell PowerPoint PPT Presentation


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CFD-Based Multiscale Modelling of Bubble-Particle Collision Rates and Efficiencies in a Flotation Cell. Tom Liu, Peter Koh and Phil Schwarz CSIRO Minerals. Multiscale Modelling in Industrial Systems . Team Members: Phil Schwarz, CM (Project leader) Nick Stokes, CMIS Murray Rudman, CMIT

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CFD-Based Multiscale Modelling of Bubble-Particle Collision Rates and Efficiencies in a Flotation Cell

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CFD-Based Multiscale Modelling of Bubble-Particle Collision Rates and Efficiencies in a Flotation Cell

Tom Liu, Peter Koh and Phil Schwarz

CSIRO Minerals


Multiscale Modelling in Industrial Systems

Team Members:

Phil Schwarz, CM (Project leader)

Nick Stokes, CMIS

Murray Rudman, CMIT

Alf Uhlherr, CMS

Peter Witt, CM

Paul Cleary, CMIS

Tom Liu, CM


Outline

  • Background information

  • Brief introduction to multiscale modelling

  • Brief introduction to the modelling of flotation processes

  • CFD-based multiscale modelling strategy for a flotation cell

  • Some simulation results and future works

  • Conclusions


Background Information

Froth flotation is a complex three phase physico-chemical processes

Prediction of flotation kinetics has not been possible


Life Is Not Simple

The extension of direct free-surface modelling techniques to resolve every bubble and particle in a industrial-scale vessel would require far more computational power than will be available


Jenkins et al.ICCS 2005, Atlanta

Multiscale Modelling


Jenkins et al., ICCS 2005, Atlanta

Continuum model

Molecular model

Multiscale Modelling Methods

  • Domain decomposition method

  • Process decomposition method

Jenkins et al.ICCS 2005, Atlanta


Koh et al.(2003)

Current Modelling Methods For Flotation Processes

  • Correlation methods

  • First-principles methods

  • CFD methods


Examples of Problems

?

Nguyen & Kmet (1992)


Examples of Problems

Koh & Schwarz (2003)


Prediction formula:

Quiescent condition

Bubble size

Bubble rising velocity

Bubble Re

Collision efficiency

Flotation cell:

Turbulent condition

Stirring speed, cell structure, gas flow rate, … Bubble size, bubble velocity, bubble Re

Collision efficiency

Examples of Problems


Five different types of computational experiments are defined to calculate:

(1)Bubble-particle collision frequencies

(2)Bubble-particle collision efficiencies

(3)Bubble-particle attachment and detachment rates

(4)Drag coefficients for bubbles

(5)Bubble coalescence and break-up rates

CFD Model with time averaged RANS and multifluid techniques through suitable microscale closure relations

Structure Of CFD-based Multiscale Flotation Modelling


Some Results

  • A wavelet-based adaptive mesh scheme to track moving free surfaces

  • 2D CFD turbulent collision model

  • 3D CFD model for Non-Newtonian drag coefficients


Bubble Rising Simulation

A wavelet-based adaptive mesh scheme was embedded into CFX to track moving free surfaces


Bubble-Particle Collisions


Comparisons Between CFD Predicted Turbulent Collision Efficiencies and Laminar Collision Efficiencies


Comparisons Between Drag Coefficients for Newtonian and Non-Newtonian Fluids


Further works

  • 3D CFD turbulent collision model

  • LES of bubble-particle collision

  • 2D CFD turbulent collision frequency model

  • CFD bubble coalescence/breakup model

  • Coupling macroscale model to microscale models


Conclusions

  • Multiscale modelling strategy for a flotation cell

  • Wavelet-based adaptive moving mesh scheme

  • CFD-based numerical experiments for turbulent bubble-particle collisions and Non-Newtonian drag coefficients

  • Further works


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