Perforated Basket Centrifuge

Principle

• It is a filtration centrifuge.
The separation is through a perforated wall based on the difference in the
densities of solid and liquid phases

• The bowl contains a perforated
side wall

• The liquid phase passes through
the perforated wall, while solid phase is retained in the bowl

• The solid is removed after
cutting the sediment by a blade after stopping the centrifuge

Construction

It consists of a stainless steel
perforated basket (typically 1-2 m in diameter) lined with a filter cloth

The basket rotates at a speed which
is typically < 25 s-1, higher speeds tending to stress the basket
excessively

The product enters centrally and is
thrown outwards by centrifugal force and held against the filter cloth

The filtrate is forced through the
cloth and removed via the liquid outlet; the solid material is retained on the
cloth

The cake can be washed if required
by spraying water into the centrifuge

Working 

• The material is kept on a basket
when the basket is stationary

• The  amount 
of  material  should 
be  optimum,  otherwise, 
during  Centrifugation  it 
puts  a  great strain on the basket. The loading of
material done to give even distribution

• Power is applied to rotate the
basket and maximum speed must be attained quickly

• The basket runs at 1000
revolutions per minutes

• The power require for running is
small compared to the power require for starting and bringing it to the full
speed 

• During  Centrifugation,  the 
liquid  passes  through 
the  perforated  wall, 
while  the  solid 
phase retains in the basket • The liquid leaves the basket and is
collected at the outlet

• The cake is then spun to dry as
much as possible

• Sometimes higher speeds are used
so that the cake will be completely dried

• After  a 
definite  period  of 
time,  the  power 
is  turned  off. 
By applying a brake the Centrifuge is stopped

• The basket is brought to rest

• The solid cake is cut using a blade
and then unloaded manually

Uses 

1. Perforated basket Centrifuge is
extensively used for separating crystalline drugs (such as aspirin) from the
mother liquor is removed completely

2. It is also used for removing
unwanted solids from a liquid. For example, precipitated proteins are removed
from insulin

3. Sugar crystals are separated
using perforated basket centrifuge 

Advantages 

1. The Centrifuge is very compact
and it occupies very little floor space

2. It  can 
handle  slurries  with  a  high  proportion  of 
solid  and  even 
those  having  paste 
like consistency

3. 
The final product has a very low moisture content

4. 
In this method, the dissolved solids are separated from the cake 

5. 
The process is rapid

Disadvantages 

1. The entire cycle is complicated
resulting in considerable labour costs

 2. It is a batch process

3. If the machine is adapted for
prolonged operation, there is considerable were and tear of the equipment.  On prolonged operation, the solids may from
hard cake, due to the centrifugal force, which is difficult to remove
simultaneously.