Size Separation: Objectives, applications & mechanism of size separation, official standards of powders, sieves, size separation Principles, construction, working, uses, merits and demerits of Sieve shaker, cyclone separator, Air separator, Bag filter & elutriation tank.

1. Topic cover
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Size Separation: Objectives, applications & mechanism of size separation, official
standards of powders, sieves, size separation Principles, construction, working, uses,
merits and demerits of Sieve shaker, cyclone separator, Air separator, Bag filter &
elutriation tank.
Presented by : Jagruti Marathe
assistant professor at R.C.P.I.P.E.R

2. Size seperation
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Size separation is a unit operation that involves the separation of a mixture of
various size particles into two or more portions by means of screening
surfaces.
Size separation is also known as sieving, sifting, screening.

3. Size seperation Objective/Application:
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To determine particle size for the production of tablets and capsules.
To improve mixing of powders.
To improve the solubility and stability of particles during production.
To optimize feed rate, agitation, screening during production.
Quality control of raw materials.
Useful in production of tablets, capsules, suspension, emulsion, ophthalmic
preparations, ointments, creams, etc.

4. Mechanism of size separation
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Oscillation Vibration Gyration

5. Mechanism of size separation
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Sieve arrangement:
•Descending order or sieve of large size is at the top and smallest is at the bottom.
•Materials displaced in the uppermost sieve.
•Mechanism of action of sieving involved:
• Agitation (oscillation, vibration, gyration)
• brushing
• Centrifugal
Advantage of sieving method: Rapid process with the requirement of little skill

6. Official standards of powders
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Sr.No Grade of powder all particles must pass through Sieve
No. /Nominal mesh aperture
Sieve through which 40% of the
particles pass/ Nominal mesh
aperture
1 Coarse powder 10 /(1700 µm) 44 /(355 µm)
2 Moderately coarse
powder
22 /(710 µm) 60/ (250 µm)
3 Moderately fine
powder
44/(355 µm) 85/(180 µm)
4 Fine powder 85/(180 µm) Not specified
5 Very fine powder 120/(125 µm) Not specified
Coarse or fineness of powder is expressed by Reference to the nominal mesh
aperture size of the sieve through which powder is able to pass.
•Indian pharmacopoeia- 5 grade of powder

7. Official standards of powders
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Sr. No. Grade of powder Comparison of powder size
1 Coarse powder 1
2
Moderately coarse powder
1/6
3 Moderately fine powder 1/24
4 Fine powder 1/90
5 Very fine powder
1/2000
Comparison of Powder size by Grade of Powder
Note: 1.70 mm=1700 µm

8. Official standards of powders
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(Coarse)
All the particles of
which pass through a
sieve with nominal
mesh aperture of
1.70 mm/1700
µm(Sieve No.10)
not more than 40%
pass through
nominal mesh
aperture of 355 µm
(Sieve No. 44)
(Moderately
Coarse)
All the particles of
which pass through
a sieve with
nominal mesh
aperture of 710 µm
(Sieve No. 22)
not more than 40%
pass through
nominal mesh
aperture of 250 µm
(Sieve No. 60) (Moderately
Fine)
All the particles of
which pass through
a sieve with
nominal mesh
aperture of 355 µm
(Sieve No. 44)
not more than 40%
pass through
nominal mesh
aperture of 180 µm
(Sieve No. 85)
(Fine
Powder)
(Microfine
powder)
All the particles
of which pass
through a sieve
with nominal
mesh aperture of
180 µm (Sieve
No. 85)
All the particles
of which pass
through a sieve
with nominal
mesh aperture
of 125 µm (Sieve
No. 120)

9. Method of size separation:
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Method Cyclone
separator
Sieving hods
Air separator
Sedimentation Tank
Elutriation

10. Sieve shaker
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Principal : The powdered drug is separated according to its particles size a number of
sieves in a nest. These are subjected to difference type of agitation, so that size
separation is rapid.
Contraction:

11. Sieve shaker
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Working:
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• Sieves are arranged in a nest with
coarsest at top and fine at last.(50g)
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• Place the powder on the top sieve
3
• This sieves set is fix in sieve shaker
4
• And allow to shake for the certain time
period(20 minutes )

12. Sieve shaker
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 Advantage:
1. It is inexpensive and rapid with reproducible results.
 Disadvantage:
1. Lower limit of particles size is 50mm
2. If powder is not dry, apertures get clogged with particles , leading to improper
sieving.
3. During shaking, attrition occurs causing size reduction of particles. This lead to
error in estimation.

13. Cyclone separator
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Principle: centrifugal force is used to separate solid form fluidized in air.(separation
depends on particle size and density)
Solids are suspended in air and Force air introduced tangentially at Higher velocity so
that Rotary movement take place.
Contraction:

14. Cyclone separator
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Working:
Separated solid is suspended in stream in gas
(Air)
Such a feed is introduced tangentially at very
high velocity
Rotary movement take place within
vessel.
Centrifugal force and vertexing throws the solids on
wall.
As the speed of air diminishes, the particles fall to the
conical base and are discharged through the solid outlet.
Air is escape through the outlet.

15. Cyclone separator
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16. Cyclone separator
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Uses:
It is used to separate the solids from gases.
It is also used for size separation of solids in liquids.
It is used for separating the heavy or coarse fraction from fine dust.
Variants: Cyclone separators are also used for size separation of solids suspended in
liquid such as water. Such separators are known as wet or liquid cyclone.one such
apparatus used for this purpose is Dorrclone.

17. Air separator
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Principle: In air separator ,centrifugal force is used to separate solids. The air
environment is obtained by means of rotating disc and blades. To improve the
separation, stationary blades are used. By controlling these blades and the speed of
the rotation, it is possible to vary the size at which separation occurs.
Contraction

18. Air separator
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Working:
Disc and blades are allowed to rotate by means of motor
These produce a current of air
The sample is introduced through the feed inlet. And allow to rotating
the disc.
The fine particles are picked up and carried into space, where air
velocity is sufficiently reduced.
The fine particles are dropped and are ultimately collected at outlet
meant for the fine particles.& heavy particles fall down wards are
removed at outlet.

19. Bag filter
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Principle : In a bag filter , size separation of fines from the milled powder is achieved
into 2 steps.
Step:1 Powder is passed through a bag filter by applying the suction on the opposite
side of the feed entry.
Step:2 pressure is applied in order to shake the bags so that powder adhering to the
bag falls off, which is collected from the conical base.
Construction:

20. Bag filter
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Construction:

21. Bag filter
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Working: The working of the bag filter consists of two steps.
•Feed is separated from air by passing through the cloth bags.
Step 1
•In the subsequent step, the bags are shaken to collect the fines that are adhered to the bags.
•These two steps flow in succession and are controlled at different intervals with the help of a bell crank lever
arrangement.
Step 2

22. Bag filter
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Step Mechanism Movement of damper
Contact
between
Contact
between bags
and
atmosphere
Filtering period Cam does not
press the bell
crank lever
Opens Closes
Shaking period Cam presses
the bell crank
lever
Closes Open

23. Bag filter
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Advantages :
Bag filter is extremely useful for removing fines, which cannot be separated by other
methods.
These can be used even to remove dust. The ordinary household vacuum cleaner is a
simple bag filter.
Disadvantages:
Bag filter is not size separation equipment as such.

24. Elutriation tank
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• Elutriation is a method of separation of particles in powder based on the low
density of fine particles and high density of the coarse particles using fluid flow.
• Elutriation and sedimentation are different in one respect .
• In case of sedimentation , particles move in the direction on gravitational force,
while in elutriation , some particles move against the gravitational force.
• In elutriation , fluid flows in opposite direction of the settling movement. The
upward velocity of fluid is less than the settling velocity of the particles . Hence ,
time is an important factor. In particle, particles can be seen to rise with the fluid
and then to move outwards to the tube- wall, where the velocity is lower and these
start to fall.

25. Elutriation tank
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Uses:
These technique is applicable to insoluble solids such as kaolin, or chalk, which is
subjected to wet grinding following by sedimentation or elutriation.
Advantage:
It is a continuous process.
Separation of size fraction is quick as compare to other methods.
The apparatus is more compact than that are used in sedimentation methods,
Depending on the number of fractions required the same number of tubes of different
area of cross-section can be connected.
Disadvantage:
The suspension s diluted which may be desirable in certain cases.

26. Elutriation tank
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Thank you