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1. Solid-liquid separation, Removal of solids relies on the density…

- - - - Disc centrifuge
        
        Consists of several disc - separate the bowl into setting zones
        
        Stack of discs is placed on a vertical spindle
        
        It rotates inside a stationary housing
        
        Feed/slurry is fed through a central tube
        
        Clarified fluid moves upwards
        
        Solids settle at the lower surface
      - Scroll centrifuge or decanter
        
        Composed of a rotating horizontal bowl tapered at one end
        
        Used to concentrate fluids
        
        Solids are deposited on the wall of the bowl
        
        The solids can scrap and removed form the barrow end
      - Tubular bowl centrifuge
        
        Small in size
        
        Commonly used in pilot plants
        
        Can run at high speed
        
        Can use both batch & continuous fermentation
        
        Working:
        
        Feed added to spinning bowl
        
        Sedimentation of particles occurs in centrifuge field
        
        Separation happens if sedimentation velocity is high enough for particle to reach side of bowl within residence time
        
        Large particles hv higher setting velocities
      - Multi-chamber centrifuge
        
        A modification of tubular bowl type
        
        Consists of several chamber
        
        The chambers connected in such a way that the feed flows in a zigzag fashion
        
        The force is much higher in the peripheral chambers
        
        Resulting smallest particles settle down int he outermost chamber
  - - - Vacuum filters
        
        Used for clarification of fermentation broths
        
        Uses for 10-40% is solids and particle size range is 0.5-10 micrometer
        
        Easy to operate
        
        Low cost
        
        Example: Rotary drum vacuum filters
        
        Used for filtration of filamentous fungi and yeast cells
        
        Clarify large volumes of liquid with automatic solids discharge
        
        Simple with low power consumption and easy to operate
        
        Small agent to coagulating is added to the broth before it is pumped into the filter
        
        Filtration unit consist of a rotating drum partially immersed in a tank of broth
        
        As the drum rotate, picks up the biomass which gets deposited as a cake on the drum surface
        
        Filter cake can be easily removed
      - Filter press
        
        Build of a sequence of holed plates alternating with hollow frames
        
        Plates are covered with suitable filter medium - cloth
        
        Filter medium create a series of chambers through which the slurry can be forced
        
        Solids are retained in the chambers
        
        Filtrate discharges into the hollows on the plate surface and drain out
      - Plate and frame filters
        
        Principles:
        
        The slurry enters the frame by pressure & flows through filter membrane
        
        The filtrate is collected on the plates and send to outlet
        
        Several frames and plates are used so that surface area increases and consequently larger volumes of slurry can be processed.
        
        Cheap & versatile
        
        Surface area can be adjusted by varying the number of plates
        Not suitable for removal of large quantities of solids - plates to be dismantled
        
        Polishing devices to filter out low residual solids