The third lecture in the module Particle Technology, delivered to second year students who have already studied basic fluid mechanics. Hindered systems is mainly about sedimentation of concentrated suspensions. The way concentrated dispersions behave is also covered: buoyancy correction and viscosity for Newtonian suspensions. Industrial thickener design is included, based on incompressible settling behaviour.

1. Hindered Systems &Thickening Chapter 6 in Fundamentals Watch this lecture at http://www.vimeo.com/10201270 Visit http://www.midlandit.co.uk/particletechnology.htm for further resources. Professor Richard Holdich R.G.Holdich@Lboro.ac.uk

3. Porosity/voidage

5. Viscosity correction – p61

6. Hindered settling relations – p55

7. Zones in batch sedimentation – p57

8. Kynch's analysis – p60

10. When a body is wholly, or partially, immersed in a fluid it experiences an upthrust equal to the weight of fluid displaced.

13. NOT appropriate for sedimentation and filtration of a homogeneous suspension.

14. Krieger’s equation:Kis crowding factor 1/CMAX, and equal to 1.56 for spheres eta is intrinsic viscosity, which is 2.5 for spheres

15. Viscosity correction

17. Zones in batch sedimentation Height Zones: Supernatant Original concentration Co Variable concentration Sediment Concentration

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23. Batch flux curveCU

31. Particles of given size settle fastest in free settling

32. Increasing concentration slows particles - hindered settling

33. If a PSD then smaller particles dragged down by the larger ones