Filtration

Filtration

1. 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

2. Filter media

   • Cake/Surface filtration
     • Bridging filtration
     • Complete blocking filtration
   • Depth filtration
     • Standard blocking filtration

3. Type of filtration

   • Gravity
   • Centrifugal
   • Pressure
     • Hydraulic
     • Mechanical
   • Vacuum

4. 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

5. 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

6. 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

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