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