Size reduction is a process of reducing large solid unit masses - vegetables or chemical substances into small unit masses, coarse particles or fine particles.

1. Size Reduction
By Jagruti Marathe
Assistant Professor at
R.C.P.I.P.E.R ;shirpur

2. Size Reduction :
Size reduction is a process of reducing large solid unit masses - vegetables or chemical
substances into small unit masses, coarse particles or fine particles.
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3. Size reduction process is also termed as comminution or diminution or pulverisation
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Size reduction
Precipitation method Mechanical method

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Against
Drug degradation
Poor mixing
Contamination
For
Content uniformity:
Uniform flow:
Effective extraction of drugs:
Effective drying:
Improved physical:
Improved dissolution rate:
Improved rate of absorption:

5. Mechanism of size Reduction
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Modes of stress applied in size Reduction
• Cutter mill
Cutting
• Roller mill
Compression
• Hammer mii
• Ball mill
Impact
• Fluid
energy mill
Attrition

7. Classification of size Reduction Equipment
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Reduction Equipment
Crushers
Edge runner mill ,
end runner mill
Grinders
Impact mill Rolling-
compression Attrition mill
Tumbling mill
Ultrafine grinder
Cutting machine

8. Hammer mill
Principle: Impact
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Hammer mill
Principles: The hammer mill operates on the principle of impact between rapidly
moving hammers mounted moving hammer mounted on a rotor and the powder
material.
Construction:

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Hammer Mill
Working:
Allow to
continuous
motion(8000-
15000rpm)
Material is placed
in hopper ,which
flows vertically
down and then
horizontally
Hammers beat the
material to yield
smaller particles.
Then these
particles pass
through the
screen.

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Modes of stress applied in size Reduction
Uses:
Fine to moderate grinding powders may be obtained depending on the speed of
hammer.
10-400 mm
Merits and Demerits
1.It produces specified top size without the need for a closed-circuit crushing system.
2. It produces relatively numerous size distributions with a minimum of fines due to
self-classification.
3. It has a high reduction ratio and high capacity whether used for primary, secondary
or tertiary grinding.
4. Relatively reasonable energy requirements.
5. Brittle materials are best fractured by impact from blunt hammers.
6. It is capable of grinding many different types of materials
7. The machine is easy to install and operate and its operation is continuous.
8. It occupies small space
9. It is easy to maintain and clean.
10. It is inexpensive
11. Its ease of manufacture allows easier local construction

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Modes of stress applied in size Reduction
Demerits
1.Not recommended for the fine grinding of very hard and abrasive material due to
excessive wear.
2. Not suitable for low-melting sticky or plastic-like material due to heat generation in
the mill head as a result of mill fouling.
3. The mill may be choked if the feed rate is not controlled, leading to damage.
4. Presence of foreign materials like stone or metals which finds its way into the
material due to inadequate garbling process
5. There is a possibility of clogging of the screen

13. Ball mill
Principle: Impact and attrition
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Ball mill
Principles:
A ball mill is a type of grinder used to grind and blend bulk material into QDs/nanosize
using different sized balls. The working principle is simple; impact and attrition size
reduction take place as the ball drops from near the top of a rotating hollow cylindrical
shell.
Construction:

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Ball mill
Working :
The degree of milling in a ball mill is influenced by;
a. Residence time of the material in the mill chamber.
b. The size, density, and number of the balls.
c. The nature of the balls (hardness of the grinding material)
d. Feed rate and feed level in the vessel.
e. Rotation speed of the cylinder.

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Ball mill
1. The small and average capacity ball mills are used for the final grinding of drugs or
for grinding suspensions.
2. The maximum capacity ball mills are used for milling ores prior to manufacture of
pharmaceutical chemicals.

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Ball mill
Advantages of Ball Mills
1. It produces very fine powder (particle size less than or equal to 10 microns).
2. It is suitable for milling toxic materials since it can be used in a completely
enclosed form.
3. Has a wide application.
4. It can be used for continuous operation.
5. It is used in milling highly abrasive materials.

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Ball mill
Disadvantages of Ball Mills
1. Contamination of product may occur as a result of wear and tear which occurs
principally from the balls and partially from the casing.
2. High machine noise level especially if the hollow cylinder is made of metal, but
much less if rubber is used.
3. Relatively long milling time.
4. It is difficult to clean the machine after use.

19. Fluid energy mill
Principle: Impact and attrition
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Fluid energy mill
Principles:
Fluid energy mill operates on the principles of impact and attrition. In this equipment,
the feedstock is suspended within a high velocity air stream. Milling takes place
because of high velocity collisions between the suspended particles.
Construction:

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Fluid energy mill
The particle size and share are determined by;
a. The speed of air/inert gas
b. Feed rate and size
c. The configuration of the mill
d. Design of the classifier
e. The position of the nozzle
f. The impact between the feed and air

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Fluidized Energy mill
Advantages of Fluidized Energy mill
1. The machine has no moving parts and thus the tendency of contamination due to
wear of parts is minimized.
2. The equipment is easily sterilized.
3. Small particle size (between 2 and 10) is usually obtained at the end of milling.
4. Thermolabile materials can be milled with little degradation since the heat produced
by the process is nullified by the cooling effect of the expansion of the compressed
gas.

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Fluidized Energy mill
Disadvantages of Fluidized Energy mill
1. Tendency of forming aggregates or agglomerates after milling.
2. Generation of amorphous content due to high energy impact.
3. Formation of ultra-fine particles

24. Edge runner mill
Principle: compression
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Edge Runner Mill
Principles:
The size reduction is done by crushing(compression) due to heavy weight of stones.
Shearing force is also involved during the movement of the stones.
Construction:

26. End runner mill
Principle: compression
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End runner mill
Principles:
Fluid energy mill operates on the principles of impact and attrition. In this equipment,
the feedstock is suspended within a high velocity air stream. Milling takes place
because of high velocity collisions between the suspended particles.
Construction:

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