Conical Disc Centrifuge / De laval Clarifier - Pharmaceutical Engineering B. Pharm Third Semester PDF Notes

Conical Disc Centrifuge / De laval Clarifier 

Conical Disc Centrifuge 

As it is a clarified, solids or immiscible liquids are present in low concentration in the feed complete clarification of the feed is possible by centrifugal means

Principle

• It is a sedimentation centrifuge

• The separation is based on the difference in the densities between the phases under the influence of centrifugal force

• In this, a number of cone shaped plates are attached to a central shaft (which has the provision for feed) at different elevations

• During centrifugation, the dense solids are thrown outwards to the underside of the cone shaped casing, while the lighter clarified liquid passes over the bowl and recovered from the top of the cone

Construction 

• The construction of a conical disc centrifuge is shown in figure

  It  construction  of  a  shallow  form  of  bowl  contacting  a  series of conical disc are made up of a thin sheet of metal or plastic separated by narrow spaces

• Matching  hole  in  the  disc  (above  half  way  between  the  axis and  the  wall  of  the  bowl)  from  channel  through  which  the liquid passes

  A  concentric  tube  is  placed  surrounding  the  central  drive shaft

Working

• Centrifuge is allowed to rotate. 

• Low speed and short time of centrifugation is sufficient to give high degree of clarification

• The feed is introduced through the concentric tube surrounding the shafts

• The feed flow down and enters in to the space between the discs (show by the narrows)

• During centrifugation, the liquid flow in to the channel (holes at the centre of disc) and upward past the discs

• These substances move along the surfaces of the discs to the limits of the inner and outer layers

• The solids and heavy liquids are thrown outward and move underside of the discs

• Then the solids deposit at the bottom of the cone, which is removed intermittently

• The lighter liquid moves to the upper side of the discs

• The liquid raises to the top and escapes from the outlet

Uses 

• Two  immiscible  liquids  can  be  easily  separated  by  a  continuous  process  after liquid/liquid extraction as in case of manufacture of antibiotics 

• Suspensions containing low concentration of solids can be separated quickly. Solids  that  are  gelatinous  are  slimy  can  be  separated  by  disc  cone  centrifuge. Such substances may plug the filter in the other methods

• Starch is collected after washing and purification stages 

• In  the  manufacture  of  insulin,  the  liquor  is  clarified  to  remove  the  precipitated proteins

• Concentration  of  one  fluid  phase  is  possible  as  in  the  separation  of  cream  from milk,  concentration  of  rubber  latex,  removing  solids  from  lubricating  oils,  inks and beverages

Advantages

• Conical disk centrifuges are compact occupying a very small space

• The separating efficiency is very high, so that the particle are deposited very rapidly. It is suitable, if the sediment is a fluid deposit or sludge

• By controlling the speed of rotation and rate of flow, particle are separated intotwo size fractions

Disadvantages

• The construction of a conical disc centrifuge is complicated

• Its capacity is limited

• It is not suitable if the sediment of solid forms a hard cake

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