Transcript Particle size reduction and separation

Particle Size
Reduction & Separation
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KAUSAR AHMAD
KULLIYYAH OF PHARMACY
http://staff.iium.edu.my/akausar
PHM3133 Dosage Design 1 2011/12
Contents
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Particle size reduction
Particle size separation
 Fluid energy mill
 Cyclone
or jet mill
 Air classifier mill
 Others
 Crusher
 Grinder
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 Others
 Sieves
 Classifiers
 Membrane
filtration
Equipment & mechanism
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 Crusher – compression

E.g. crushing rolls (5 mm)
 Grinder – impact and attrition

E.g. hammer/ball millls, bowl grinder (100 m)
 Ultra-fine grinder – attrition
 E.g.
fluid-energy mills (5 m)
 Knife - cutting
 E.g.
carrot slicer ( 5 mm)
PHM3133 Dosage Design 1 2011/12
Choosing the equipment
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size of feed
particles
size-reduction ratio
• 5 mm & 100 m
• 100 to 5 m
hardness of feed
• Mohr’s scale: talc=1,diamond=10
processing rate
• 600 kg/hr
type of material
• abrasive, soft
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Step-by-step size reduction
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Feed material 10 cm
Crusher : 10x
Feed 1 cm
HOW MANY TIMES
REDUCTION?
Grinder: 100x
Feed 100 m
Fluid energy mill: 20x
Product ca. 5 m
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Attrition mills - principle
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 attrition - the act of wearing or grinding down by
friction
 hit the particles with high velocity air to fracture
them
 increasing the impact velocity or the energy
(increase temperature), produces smaller particles
 generate a greater amount of fines
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Types of attrition mills
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 Fluid energy mill

High pressure steam, high T

Compressed air, high T
 Air classifier mill

Air
 FEED into slightly negative pressure compartment!
 Q. But why?
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Classifier
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 Equipment that is used to narrow down the size
distribution of product
 Normally built-in design i.e. comes together with the mill
 Classifying ability depends on

Design and operation condition

Feed throughput

Air velocity
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Air classifier mill
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 Consists of:

Hammer mill


Hammer mill reduces the size
Classifier

Classifier determines the size distribution
 Size and distribution depends on

Design of mill and classifier

Operation conditions

Their speed of rotation

Feed throughput
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Air classifier mill (ACM)
PRODUCT ca. 100 m
(to Fluid Energy Mill)
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ROTATE
CLASSIFIER
FEED
ROTATE
ATMOSPHERIC AIR
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Fluid Energy Mill (FEM)
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FEED (from ACM)
Area enlarged
Superheated
compressed
Air/steam
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FEM: Design & Operation
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Size and distribution depends on
Design
1.

Air nozzles

Feed inlets

Grinding chamber
Operation conditions
2.

Air/steam at high pressure and temperature is introduced
into the chamber and reduces the size of particles

Feed throughput
PHM3133 Dosage Design 1 2011/12
FEM
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After size reduction
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Air/steam at high P, T
Size reduction & separation
CYCLONE
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FEED
into
FEM injector
CYCLONE
FEM
PRODUCT
HIGH
VELOCITY
HOT
AIR/STEAM
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PRODUCT
?
Cyclone
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 Equipment for separation

To separate product from air and/or fines
 Based on centrifugal force

Heavy particles settle down

Fine particles escape
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Cyclone
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FINES
OUTLET
FROM
FEM
INLET
PRODUCT
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Factors affecting extent of separation
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
Design of cyclone
 Diameter
 Height

Operation of cyclone
 Feed
throughput
 Velocity
at inlet
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Feed properties
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 Need to know size distribution of the feed stream.
 may lead to significant cost-reduction methods

such as pre-classifying the material to remove fines
before milling.
Thus, use air classifier mill first, followed by fluid
energy mill.
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Controlling feed/throughput
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 feeding the material into a mill, and handling the product
discharging from it, can pose a significant problem e.g.
FEM back-flow
 feed at a controlled rate is critical to optimizing the
performance of mills.
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Problems with poor feed-control
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overfilling the milling zone
• waste
retards exit of properly
sized particles &
• Fail QC, waste
subjecting them to further
size reduction and
excessive generation of
fines
• fail QC, waste
accelerate equipment wear
• maintenance
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Example of equipment wear
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Internal piping
CONSTRUCTION MATERIAL + FEED
FEM milling area
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Problems with FINE products
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 Highly charged, static
May produce sparks
 Possible explosion
 Need to earth equipment
 Very cohesive
 Stick to silos
 Form agglomerates
 Poor flow
 Add (pyrogenic) silica to allow free flow
 Health hazard……………..

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De-duster
Dust Filter
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http://www.pharmaceuticalonline.com/nl/347748/1849996
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Exercise
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 What do you do with so much air/steam in your
milled products?
 What is the difference between a fluid energy mill
and a fluidised bed dryer?

Function?

Operating principle?
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References
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Levin, M. (2002). Pharmaceutical process scale-up. New
York: Marcel Dekker. p 71, 120, 205, 224, 322, 417, 501,
503
PHM3133 Dosage Design 1 2011/12