Filtration

Membrane filtration
1. Benefit
  1. Can take place while temperatures are low
    1. Treatment for heat-sensitive matter such as food production
  2. Low energy cost
    1. Only use to pump liquids through the membrane
  3. Can be operated in two process
    1. Conventional - Death end
      1. Flows perpendicularly towards the filter media
        Easily cause fouling, flux rate decreases rapidly.
    2. Cross-flow - (TFF)
      1. Flows parallel or tangentially to the membrane surface.
        What Can TFF Do?
        Not cause fouling.
      2. Process Variable in TFF
        Crossflow Velocity (CF)
        Rate of solution flow the feed channel & across membrane
        sweep aways larger molecules and aggregates retained on membrane surface
        Transmembrane pressure (TMP)
        F drives fluid through membrane, carrying along & across permeable membrane
        Pressure Drop
        regulate the CF and TMP
      3. How to choose TFF system for application
        Step 1
        Define the purpose of TFF process
        Step 2
        Choose the membrane MWCO
    3. Can be easily be expanded or scale-up
2. Concentration
  1. Remove H2O to retaiin solute
  2. Choose membrane with lower MWCO than the solute
    1. 3 to 6 lower
      1. complete retention
      2. Choose whether
        Higher flow rate
        maximum recovery
3. Diafiltration
  1. Continous
    1. Volume Constant
      1. Flow rate constant
        Less filtrate volume
        fast salt removal
  2. Discontinous
    1. Sequential Dilution
      1. Diluted first
        Concentrated then
    2. Volume reduction
      1. Concentrated first
        Diluted then
Filter media
1. Cake/Surface filtration
  1. Bridging filtration
  2. Complete blocking filtration
2. Depth filtration
  1. Standard blocking filtration
Type of filtration
1. Gravity
2. Centrifugal
3. Pressure
  1. Hydraulic
  2. Mechanical
4. Vacuum
Filter aids
1. Objectives
  1. Protect basic medium
    1. PRECOAT
  2. Improve flow rate
2. What it is all about?
  1. Powdered solid
    1. Improve operation
  2. Use when filtering
    1. Bacteria
    2. Gelatinous suspension
  3. Forms a porous layer
  4. KIESELGUHR
3. How?
  1. Added directly to feed
    1. PREMIXING
  2. Applied to filtration equipment
    1. PRECOAT
Theory
1. Constant flow rate , Q
  1. dV/dt = (1/y) [(A.P)/µ.L]]
  2. Q = flow rate of filtration (m3) A = filtration area (m2) L = thickness of filter material (m) P = pressure drop across the cake (N/m2) µ = viscosity of the slurry (Ns/m2) y = cake porosity V = volume of filtrate (L)
  3. Constant flow rate, Q = incerease in pressure
2. Constant Pressure
  1. t(A/V) = [(yµw)/(2P)] (V/A) + (K2/P)
  2. Pressure constant = decrease in flow rate , Q
Membrane technology
1. Advantage
  1. Work without addition of chemicals
  2. Low energy use
  3. Easy and well arranged process
2. Principle
  1. Semi- permeable membrane
  2. Acts as specific filter
  3. Methods to enable substances penetrate
    1. High pressure
    2. Maintenance of concentration gradient
    3. Introduction of electric potential
  4. Occupy through selective wall
  5. Alternative for
    1. Flocculation
    2. Sediment purification
    3. Adsorption
    4. Extraction
    5. Distillation

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Filtration

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	Created by Zulaikha Zulkifli about 7 years ago