Stirring and Mixing For Chemists and Chemical Engineers

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Stirring and Mixing For Chemists and Chemical Engineers

  1. 1. Colloids2010 - 84 th Colloid Symposium, June 20 –23, 2010, Akron, OH Stirring and Mixing for Chemists and Chemical Engineers Ingo H. Leubner, Ph.D. Crystallization Consulting [email_address]
  2. 2. Stirring and Mixing <ul><li>The ‘Ying - Yang’ Problem of Chemists and Chemical Engineer s </li></ul><ul><li>Although closely related - Stirring and Mixing - are not the same for Reaction Control </li></ul><ul><li>Stirring moves the content of the reactor with a turnover rate of Τ (min) </li></ul><ul><ul><li>Frequently, the flow is laminar which does not efficiently mix material with the reactor content </li></ul></ul><ul><li>Mixing provides stirring plus intimate combination of reactant with reactor content </li></ul><ul><ul><li>Efficiently combines added material with the reactor content </li></ul></ul><ul><ul><li>Efficiently combines all added materials </li></ul></ul>© Copyright I. H. Leubner www.CrystallizationConsulting.com
  3. 3. Mixing / Stirring <ul><li>Stirring </li></ul><ul><li>Pumping of Reaction Mixture </li></ul><ul><li>Reaction Volume: V r (liter) </li></ul><ul><li>Pumping Rate of Turbine, R (ltr/min) </li></ul><ul><li>Turn-over of Reaction Mixture </li></ul><ul><li>Residence Time τ = V r /R [min] </li></ul><ul><li>Mixing Combining Reactants + Reaction Mixture </li></ul><ul><li>Reactant Addition Rate (mole/min) </li></ul><ul><li>+ Solvent Pumping Rate (ltr/min) </li></ul><ul><li>+ Stirring Rate </li></ul><ul><li>Residence Time, τ </li></ul>© Copyright I. H. Leubner www.CrystallizationConsulting.com
  4. 4. Stirrers / Mixers Copied from: http://www.neutecgroup.com <ul><li>‘ Marine’ Propeller </li></ul><ul><li>Shrouded Turbine </li></ul>© Copyright I. H. Leubner www.CrystallizationConsulting.com ‘ Shroud’
  5. 5. Stirrer © Copyright I. H. Leubner www.CrystallizationConsulting.com Stirring Laminar Flow
  6. 6. Stirring <ul><li>τ = Residence / Turn-over Time </li></ul><ul><li>V r = Reaction Volume [ltr] </li></ul><ul><li>F r = Pumping Rate [ltr/min] </li></ul><ul><li>= k S * RPM </li></ul>© Copyright I. H. Leubner www.CrystallizationConsulting.com
  7. 7. Mixer - Scheme: Counter acting double shrouded Turbine © Copyright I. H. Leubner www.CrystallizationConsulting.com For Mixer: Both on same Shaft
  8. 8. Mixer Counter Acting Double Shrouded Turbine © Copyright I. H. Leubner www.CrystallizationConsulting.com Reactant A Reactant B Dilution A Dilution B Mixing Turbulent Flow Stirring Laminar Flow
  9. 9. Mixing <ul><li>τ = Residence or Turn-over Time [min] </li></ul><ul><li>R A , R B = [mole/min], Reactant Addition Rate </li></ul><ul><li>F A , F B = [ltr/min], Reactant Flow Rate </li></ul><ul><li>F A,R , F B,R = [ltr/min], Dilution Flow Rate ~ Pumping Rate [ltr/min] = k S * RPM </li></ul><ul><li>RPM = Stirring Rate </li></ul>© Copyright I. H. Leubner www.CrystallizationConsulting.com
  10. 10. Summary <ul><li>Stirring: Turn-over time in Reactor e.g., magnetic stirring bar, ‘marine propeller’ </li></ul><ul><li>Mixing: Intimate combination of Reaction Mixture with Reactants e.g., counter-acting double shrouded turbine </li></ul>© Copyright I. H. Leubner www.CrystallizationConsulting.com
  11. 11. Thank You for Your Attention Ingo H. Leubner Crystallization Consulting www.CrystallizationConsulting.com

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