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

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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  1. CFD-Based Multiscale Modelling of Bubble-Particle Collision Rates and Efficiencies in a Flotation Cell Tom Liu, Peter Koh and Phil Schwarz CSIRO Minerals

  2. 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

  3. 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

  4. Background Information Froth flotation is a complex three phase physico-chemical processes Prediction of flotation kinetics has not been possible

  5. 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

  6. Jenkins et al.ICCS 2005, Atlanta Multiscale Modelling

  7. 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

  8. Koh et al.(2003) Current Modelling Methods For Flotation Processes • Correlation methods • First-principles methods • CFD methods

  9. Examples of Problems ? Nguyen & Kmet (1992)

  10. Examples of Problems Koh & Schwarz (2003)

  11. 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

  12. 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

  13. 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

  14. Bubble Rising Simulation A wavelet-based adaptive mesh scheme was embedded into CFX to track moving free surfaces

  15. Bubble-Particle Collisions

  16. Comparisons Between CFD Predicted Turbulent Collision Efficiencies and Laminar Collision Efficiencies

  17. Comparisons Between Drag Coefficients for Newtonian and Non-Newtonian Fluids

  18. 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

  19. 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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