Centrifugation

CENTRIFUGATION
by
Ms.Suchita Gokhale
Assistant professor
IDEAL COLLEGE OF PHARMACY AND RESEARCH, Kalyan

CONTENT
• Definition
• What exactly basic concept behind centrifugation
• Application
• Instrument
• Construction
• Working
Suchita Gokhale , Assistant professor IDEAL COLLEGE OF PHARMACY AND RESEARCH, Kalyan

Centrifugationis a technique used for the
separation of particles from a solution
according to their size, shape,
density, viscosity of the medium and
rotor speed. The particles are
suspended in a liquid medium and
placed in a centrifuge tube.
It works by causing denser
substances and particles to move
outward in the radial direction.
Suchita Gokhale , Assistant professor IDEAL COLLEGE OF PHARMACY AND RESEARCH,Kalyan

CENTRIFUGE
• Separation of milk into
skimmed milk and
cream is done with a
centrifuge

APPLICATIONS
• Production of bulk drug
eg: Crystalline form of aspirin
separated from mother liquor
• Production of Biological products
such as Proteinaceous and
colloidal substances e.g.
Separation Blood cells from blood
• Biopharmaceutical analysis of
drugs: Drug present in the blood,
tissue fluids, urine are normally
present in the colloidal dispersion
form, to separate the drug from
body fluids.
• Biopharmaceutical analysis of drugs:
Separation of drug for the Pharmacokinetic
and bioequivalence studies.
• Evaluation of suspension and emulsion:
Normally creaming is slow process in emulsion
so can be fastened using centrifuge, stable
emulsion should be stable at 2000-3000
revolutions of centrifuge.
• Determination of molecular weight of colloids:
Normally determination of molecular weight
of polymer not possible, but by
ultracentrifugation molecular weight of
sample like Serum albumin, insulin can be
done and degree of homogeneity can be
determined e.g.insulin is a monodispersed
protein composed of polypeptide chains

THOERY OF CENTRIFUGATION
In colloidal dispersion, the dispersed phase may be
either solid or liquid. Particles having size above 5
mm sediment at the bottom due to gravitational
force. In such cases separation of solids is possible
by simple filtration. If particles are less than 5mm
they under go Brownian movement. Hence they do
not sediment due to gravity strong force is required
to separate them. The sedimentation depends upon
the densities of dispersed phase and dispersion
medium.

SLUDGE THICKENING AND DEWATERING
In wastewater treatment, sludge is produced from a number
of operations such as primary settling, coagulation and
flocculation, and biological activated sludge processes. ·The
sludge produced in these processes may vary greatly in
concentration, but it is typically of the order of 1%. · Sludge
concentration, typically conducted in stages, is a common
way to reduce the amount of sludge to be eventually
disposed of. Thickening and dewatering are common
operations to concentrate sludges.

TYPES OF CENTRIFUGES
• A centrifuge machine can be described as a machine with a rapidly rotating
container that applies centrifugal force to its contents.
• There are multiple types of centrifuge, which can be classified by intended
use or by rotor design:
• Types by rotor design:
• Fixed-angle centrifuges are designed to hold the sample containers at a
constant angle relative to the central axis.
• Swinging head (or swinging bucket) centrifuges, in contrast to fixed-angle
centrifuges, have a hinge where the sample containers are attached to the
central rotor. This allows all of the samples to swing outwards as the
centrifuge is spun.
• Continuous tubular centrifuges do not have individual sample vessels and are
used for high volume applications.

THE RATE OF SEPARATION IN A SUSPENSION OF PARTICLES BY WAY OF
GRAVITATIONAL FORCE MAINLY DEPENDS ON THE PARTICLE SIZE AND
DENSITY. PARTICLES OF HIGHER DENSITY OR LARGER SIZE TYPICALLY
TRAVEL AT A FASTER RATE AND AT SOME POINT WILL BE SEPARATED
FROM PARTICLES LESS DENSE OR SMALLER. THIS SEDIMENTATION OF
PARTICLES, INCLUDING CELLS, CAN BE EXPLAINED BY THE STOKES
EQUATION, WHICH DESCRIBES THE MOVEMENT OF A SPHERE IN A
GRAVITATIONAL FIELD. EQUATION (1) CALCULATES THE VELOCITY OF
SEDIMENTATION UTILIZING FIVE PARAMETERS
v = sedimentation rate or velocity of the sphere
d = diameter of the sphere
p = particle density
L = medium density
n = viscosity of medium
g = gravitational force

SEDIMENTATION
CENTRIFUGES
• Solid two different densities
two or more phases of the
mixture.
• Efficiency depends on the
velocity of rotation which
the mixture is subjected.
• ULTRACENTRIFUGATION :
When extremely fine solid is
to be separated e.g:
colloidal solutions
• Is the centrifuge solid is
passed through porous
medium based on difference in
the densities of liquid and
solid phase.
FILTRATION CETRIFUGE
CLASSIFICATION BASED ON MECHANISM

CLASSIFICATION BASED ON SCALE OF USE
• Laboratory scale
• Horizontal Spinning rotation
arms
• Angle of Centrifuge 45 to 50
• High speed centrifuge 1000
RPM
• Ultracentrifuge 85000 rpm
• Commercial type
• Batch type: perforated basket
centrifuge
• Semi continuous scale: Short
cycle batch centrifuge
• Continuous centrifuge: Super
centrifuge

PERFORATED BASKET CENTRIFUGE
• Perforated Basket Centrifuge · This type of centrifuge is
provided with a rotating perforated basket, which
allows a cake of solids to build inside the basket while
allowing the liquid to pass through the cylindrical wall
of the basket (centrifugal filtration) · The clarified liquid
is continuously removed as it emerges from the basket
• The solid is intermittently removed with a knife (not
rotating with the basket) placed inside the basket, and
collected in a vertical chute · Drier cakes are obtained
with this type of centrifuge than with other types.
Therefore this type of centrifuge is used when the
recovery of solids is desirable

CONSTRUCTION :The basket is
suspended on vertical shaft driven by
motor with power system such as belt
pulleys, water turbine and electric
motors, Basket require 5kg of powder at
starting and 2kg of power for running.
Surrounding basket casing is provided
which collects the filtrate and
discharges.
WORKING
The material kept in basket when the
basket is stationary. The amount of
material should be optimum otherwise
during centrifugation it puts a great
strain on the basket.. Loading of material
should be even. Power supplied and
maximum speed must be attained. The
During centrifugation liquid passes
through the perforated wall and solid
phase retain in the basket. Liquid
leaves basket and is collected at the
outlet. Cake obtained is spun to dry as
much as possible. Some condition high
speed is used so that cake will be dried
completely After sometime power is off
and basket brought to rest. The solid
cake is cut using a blade and then
unloaded manually.

NON PERFORATED BASKET
CENTRIFUGE
Construction: basket made up of steel as
suitable metal, suspended on vertical shaft
working; solid phase is retained on the sides
;liquid remains on the top. Liquid removes
by wire and using scrapper. Solids are
scraped of by hand or using a scrapper
blade.
Uses: when deposited solids offer high
resistance to the flow of the liquid.
Applications: (i) Non-perforated basket centrifuge is
useful when the deposited solids offer high resistance
to the flow of liquid. (ii) It allows avoiding the
This is a sedimentation centrifuge. This type of
centrifuge is used when resistance to flow of
liquid offered by cake is high. The non-
perforated basket centrifuge is used in
separation of suspension whose solid content
is higher. The principle involved in separation
of solid Pharmaceutical Engineering
Centrifugation 10.8 particles in this machine is
density difference as they move away from
axis of rotation. It consists of a simple drum-
shaped basket or bowl, usually rotating
around a vertical axis. The solids accumulate
and compress as effect of the centrifugal force,
but they are not dewatered. The residual liquid
is drained out when the rotation of the bowl is
stopped. The layer of solids is removed
manually by scraping. Unloading can be

Semi-Continuous Centrifuge /short cycle centrifuge
Semi-continuous centrifuge is a
filtration centrifuge. The
separation is done on the basis of
difference in the densities of the
solid and liquid. This separation
occurs through a perforated wall.
The bowl contains a perforated
side-wall, 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. Suchita Gokhale , Assistant professor IDEAL COLLEGE OF PHARMACY AND RESEARCH,Kalyan

SEMI-CONTINUOUS CENTRIFUGE /SHORT
CYCLE CENTRIFUGE
• Construction: It consists of a rotating basket
placed on a horizontal shaft and driven by a
motor from side. The side of the basket is
perforated. Surrounding the basket is a
stationary casing that collects the filtrate.
Slurry is introduced through a pipe that
enters the basket through the center. To
wash the crystal the wash-pipe is also
introduced through the center of the
basket. The layer of cake is removed by a
cut fitted with a knife. The knife cuts down
the cake within the basket. The knife-cut
assembly is raised with the help of a
hydraulic apparatus.
• Working: The basket is rotated
horizontally by a motor. The slurry is
introduced through the slurry entry
pipe. The liquid passes out through
the perforated side. The crystals
remain within the basket. When the
cake height is about 2 - 3 inches the
slurry entry is stopped by a "feeler-
diaphragm valve assembly". The
basket rotates at a predetermined
time then the cake is washed with
water. The basket is rotated for
another predetermined time. After
that the hydraulic apparatus raise the
knife-chute assembly to cut the cake.

• Advantages: (i) It is a short-cycle
centrifuge. (ii) It work
automatically reducing labor cost.
(iii) It can be batch operated when
solids can be drained fast from
the bowl.
• Disadvantage: (i) It has problems
during drain discharge. (ii) Its high
speed considerably breaks
crystals. (iii) Many moving parts
are involved making the
construction and functioning
more complicated.
• Applications: The semi-
continuous type
centrifuge has following
applications : (i) Crystals
can be separated from
mother-liquor. (ii) Liquids
can be clarified by
removing unwanted solid
dirt from oils. (iii) It is used
to purify mononuclear
cells from human
peripheral blood.

SUPER CENTRIFUGE
Principle: It is a solid bowl type
continuous centrifuge used for
separating two immiscible liquid
phases. It is a sedimentation type of
centrifuge in which during
centrifugation the heavier liquid is
thrown against the wall of the bowl
while the lighter liquid remains as
an inner layer. The two layers are
simultaneously separated.

• Construction: It consists of a long, hollow,
cylindrical bowl with a diameter between
15 - 50 cm which rotates at highspeed to
generate a settling acceleration of up to
about 18,000 g (where, g is the
acceleration due to gravity) for industrial
models and 65,000 g for laboratory
models. The bowl is suspended from a
flexible spindle at the top and the bottom
is fitted loosely in a bush, Fig. 10.6. It is
rotated on its vertical axis. Feed is
introduced through the bottom through a
nozzle. Two liquid outlets are provided at
different heights. Inside the bowl there
are three baffles (not shown in the figure)
to catch the liquid and force it to travel at
the same speed of rotation as the
• Working: The centrifuge is allowed to
rotate on its vertical axis at about 2000
r.p.m. The feed is introduced at the
bottom through the bowl neck using a
nozzle under pressure. A distributor
disperses the feed to prevent travel too
far along the bowl length. During
centrifugation, two liquid phases
separate based on their densities. The
heavier liquid moves towards periphery
and the lighter liquid forms an inner
layer. Both the liquids climb-up to the
top of the vertical bowl. These two
layers are simultaneously separated and
removed from different heights through
modified outlets. The concentrate
discharges from the top of the bowl by

THANK YOU

Centrifugation

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