This document describes the principles, construction, and working of a semi-continuous centrifuge. It consists of a vertical perforated basket that rotates horizontally to separate solids from liquids in a slurry based on density differences. The solid cake builds up inside the basket until it reaches a certain thickness, at which point the slurry inlet stops. The cake is then washed, rotated for a period of time, and a hydraulic knife lifts to cut the cake but leaves a thin layer behind to act as a filter for the next cycle. This process allows for continuous and automated separation of solids from liquids in batches.

1. SEMI CONTINUOUS CENTRIFUGE

2. SEMI CONTINUOUS CENTRIFUGE
SHORT CYCLE AUTOMATIC BATCH CENTRIFUGE
Principle:-
❖Filtration centrifuge
❖The bowl contains a perforated side wall
❖The separation is through a perforated wall
based on the difference in densities of solid
and liquid phases

3. SEMI CONTINUOUS CENTRIFUGE
❖During centrifugation, the liquid phase passes
through the perforated wall, while solid phase
retains in the bowl
❖The solid is washed and removed by cutting
the sediment using a blade

4. SEMI CONTINUOUS CENTRIFUGE
Construction:-
❖It consists of a vertical perforated basket
❖The basket is supported from a horizontal
shaft driven by a motor
❖Slurry inlet and wash water pipes are
introduced from the side of the basket

5. SEMI CONTINUOUS CENTRIFUGE
❖The thickness of the feed depends on the
feeler which rides over the feed
❖The layer of the cake is removed by a chute
fitted with knife

6. SEMI CONTINUOUS CENTRIFUGE
❖The knife cuts down the cake within the basket
❖The knife-chute assembly is raised with the
help of a hydraulic apparatus

7. SEMI CONTINUOUS CENTRIFUGE
Working:-
❖The basket is rotated horizontally with a motor
❖The slurry is introduced through the pipe
❖During centrifugation slurry passes through
the perforated wall

8. SEMI CONTINUOUS CENTRIFUGE
❖The solids retained in the basket while filtrate
leaves the basket
❖Filtrate collected at outlet
❖The cake is washed with water. The washed
water escape from the basket through the
filtrate outlet

9. SEMI CONTINUOUS CENTRIFUGE
❖After achieving the desired thickness of the
cake the slurry inlet is stopped by a feeler-
diaphragm –valve assembly
❖The basket rotates predetermined time and
then the cake is washed with water again
rotated for another predetermined time

10. SEMI CONTINUOUS CENTRIFUGE
❖The hydraulic cylinder is actuated which lifts
the knife along with the discharge chute
❖The knife does not cut the cake completely but
leaves a layer of crystals that act as a filter
medium for further separation in the next cycle
❖The cake is collected through the chute

11. SEMI CONTINUOUS CENTRIFUGE
Advantage:-
❖Solids can be drained fast from the bowl
Disadvantages:-
❖Moving parts involved so construction and
functioning is complicated
❖During discharge breakage of cake occurs

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