Filtration: SolidLiquid Separation

1
Filtration Solid-Liquid Separation
Cake, or Deposit, or Residue
Feed, or Suspension, or Slurry
Filtrate, or Permeate
Clarification
Cake filtration
Cross-flow filtration
2
Filtration Applications

• Recovery of crystalline solids (cake filtration)
• Separation of catalysts (cake filtration)
• Recovery of cells from fermentation medium (cake
  filtration, cross-flow filtration)
• Clarification of liquids (clarification)
• Removal of particles from gases (clarification)
• Sterilisation of liquids (clarification)

3
Mechanisms of Filtration
Surface filtration
Depth filtration

• Surface interception or sieving
• Cake formation

• Direct interception
• Inertial impaction
• Diffusional interception

4
Filter medium Barrier for solid material

• Filter paper
• Woven material (e.g. cheese cloth, woven polymer
  fibre, woven glass fibre)
• Sintered and perforated glass
• Sintered and perforated metal
• Ceramic
• Synthetic membranes

In cake filtration, the cake itself acts as a
barrier.
5
Driving force in filtration
Pressure
Vacuum
Filtrate
Filtrate
6
Theory of filtration
Medium resistance
Cake resistance