Mind map

Filtration

Zulaikha Zulkifli English

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Filtration

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