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By: Mohsen Karimi Co-authors : Guven Akdogan Kiran Dellimore Steven Bradshaw

Comparison of different drag coefficient correlations in the CFD modelling of a laboratory-scale Rushton-turbine flotation tank. By: Mohsen Karimi Co-authors : Guven Akdogan Kiran Dellimore Steven Bradshaw. Outline. Single-phase modelling Gas-liquid modelling Sparger designs

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By: Mohsen Karimi Co-authors : Guven Akdogan Kiran Dellimore Steven Bradshaw

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  1. Comparison of different drag coefficient correlations in the CFD modelling of a laboratory-scale Rushton-turbine flotation tank By: Mohsen Karimi Co-authors: GuvenAkdogan KiranDellimore Steven Bradshaw

  2. Outline • Single-phase modelling • Gas-liquid modelling • Sparger designs • Gas holdup prediction • Different drag coefficients • Bubbles size predictions • Flotation modelling • Flotation kinetics • Sub-processes

  3. Single-phase • Impeller modelling • Comparing Multiple Reference Frame (MRF) & Sliding Mesh (SM) • Turbulence models • Computational Domain Representation • Two types of stirred tanks • Grid resolution • Periodicity

  4. Single Phase Modelling • Unbaffled six-bladed tank & Rushton-turbine flotation tank

  5. Single Phase Modelling • Rushton-turbine flotation tank

  6. Single-Phase Modelling • Flow Pattern

  7. Gas-Liquid Modelling • Motivation Is there a need to compare different drag coefficient correlations? • Available solver’s options • Slip velocity between air bubbles and the surrounding liquid

  8. Motivation • Where does it affect? Interfacial force

  9. Gas-Liquid Modelling • Interfacial force • Different equations for CD have been implemented into the CFD solverfor different flow regimes.

  10. Gas-Liquid Modelling • Simulation Matrix

  11. Numerical Approach

  12. Numerical Approach • Mesh

  13. Gas-Liquid Modelling: Numerical Approach • Different sparger configurations • Disk and Ring in different locations with respect to the impeller

  14. Results

  15. Results

  16. Results • Gas distribution around the impeller

  17. Results Lane Bakker Schiller-Naumann

  18. Gas-Liquid Modelling • Air bubbles streamlines

  19. Gas-Liquid Modelling • Bubble size predictions • Additional PDE in order to account for the coalescence and breakup

  20. Flotation Modelling • Two types of PDE to include all sub-processes

  21. Flotation modelling • Parametric study of bubble particle collision rate • Angular velocity (350 – 800rpm) • Solid % (5 -25) • Particle diameter (8 - 90mm) • Bubble diameter (0.8 – 1.9mm) • Gas velocity (0.1 - 0.55 cm/s) 350rpm 800rpm Contour plot of collision rate

  22. Conclusion

  23. Acknowledgements • Prof. G. Akdogan • Prof. S.M. Bradshaw • OUTOTEC (Western Cape Branch)

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