This document discusses different types of centrifugation used in industrial processes. It describes tubular bowl centrifuges and disc-stack bowl centrifuges. Tubular bowl centrifuges can generate high centrifugal forces and are widely used in food and pharmaceutical industries. Disc-stack bowl centrifuges are common in bioprocesses and can generate forces between 5000-15000 G, separating particles as small as 5 microns. The document also discusses how disc-stack centrifuges work continuously to separate solids and liquids using extremely high rotational speeds.

1. Dr. N. Banu, Associate Professor
Vels University

2. • use of the centrifugal force for the separation
of mixtures
• More-dense components migrate away from
the axis of the centrifuge
• less-dense components migrate towards the
axis.

3. 3
Centrifugation is used to separate materials of different
density when a force greater than gravity is desired
The type of industrial centrifugation unit:
• Tubular bowl centrifuge (Narrow tubular bowl centrifuge or
ultracentrifuge, decanter centrifuge, etc). Simple and widely
applied in food and pharmaceutical industry. Operates at
13000-16000 G, 105-106 G for ultracentrifuge
• Disc-stack bowl centrifuge. This type is common in
bioprocess. The developed forces is 5000-15000 G with
minimal density difference between solid and liquid is 0.01-
0.03 kg/m3. The minimum particle diameter is 5 µm

4. Tubular bowl Chamber Disc

5.  Tube
◦ High centrifugal force
◦ Good dewatering
◦ Easy to clean
 Chamber
◦ Large solids capacity
◦ Good dewatering
◦ Bowl cooling possible
 Disc type
◦ Solids discharge
◦ No foaming
◦ Bowl cooling possible
◦ Limited solids capacity
◦ Foams
◦ Difficult to recover
protein
◦ No solids discharge
◦ Cleaning difficult
◦ Solids recovery difficult
◦ Poor dewatering
◦ Difficult to clean

6.  Bacteria
◦ Small cell size
◦ Resilient
 Yeast cells
◦ Large cells
◦ Resilient
 Filamentous fungi
◦ Mycelial
◦ Resilient
 Cultured animal cells
◦ Large cells
◦ Very fragile
◦ High speed required
◦ Low cell damage
◦ Lower speed required
◦ Low cell damage
◦ Lower speed required
◦ High water retention in
pellet
◦ Very susceptible to
damage

7. a key role in many industrial processes, including the
production of insulin, is to separate liquid phases and
solids from each other
centrifugation can be utilized to separate the cellular debris
from the released protein
purpose of the centrifugation

8. decanter centrifuge
disk stack centrifuge

9. properties of the disk stack
centrifugation
ideal for a wide range
of separation tasks
that involve
particle (biomass) size – 1.5 microns
biomass percentage – 0.6%
total solid percentage - 5.54%
process!
•lower solids
concentrations
•smaller particle sizes

10. how a disk stack centrifuge works
• separates solids and liquid phases in a continuous process
• uses extremely high centrifugal forces
• denser solids are forced outwards against the solid bowl
wall
• less dense liquid phases form concentric inner layers
• inserting special plates provides additional surface settling
area

11. how a disk stack centrifuge works

12. parts of the disk stack centrifuge
inlet zone
• reduces shear forces and amount of
foaming
• increases and avoids disturbances of the
separation processes occurring in the bowl
liquid discharge section
• important that oxygen pick-up is kept to a
minimum
• temperature increases in the liquid must be
avoided to prevent problems later in the
process
solids discharge section
• remove solids by continuous solids discharge, intermittent solids discharge
or manual removal

13. parts of the disk stack centrifuge
disk stack area
•heart of the centrifuge
•key to good separation
performance lies in the efficiency
of the disk stack
•layout and design of the
distribution holes ensure that the
process flow is evenly spread
among all the disks

14. design considerations
efficiency depends on
•solids volume fraction
•sedimentation area
•rotational speed
efficiency can be improved if
•particle diameter is increased (coagulation,
flocculation)
•residence time
•distance for sedimentation

15. gDu p
fp
g
2
18
 

rDu p
fp
c
22
18


 

15
The terminal velocity during gravity settling of a small
spherical particle in dilute suspension is given by Stoke’s law:
Where ug is sedimentation velocity under gravity, ρp is particle
density, ρf is liquid density, µ is liquid viscosity, Dp is
diameter of the particle, and g is gravitational acceleration.
In the centrifuge:
uc is particle velocity in the centrifuge, ω is angular velocity
in rad/s, and r is radius of the centrifuge drum.

16.   3
1
3
2
2
tan3
12
rr
g
N





 2
1
2
2
2
3
2
rr
g
b


16
Disc-stack bowl centrifuge
N is number of disc, θ is half-cone angle of the disc.
The r1 and r2 are inner and outer radius of the disc, respectively.
Tubular-bowl centrifuge
b is length of the bowl, r1 and r2 are inner and outer radius of
the wall of the bowl.