Title
Ball Milling
Objective
To reduce the coarse salt into fine salt by using ball milling and get the
particle size distribution by sieving.
Date of Experiment
30th September 2014
Introduction
Ball milling is a type
of grinder used to grind materials into fine powder.
Ball mills rotate around a horizontal axis, partially filled with the coarse
salt to be ground plus the grinding medium. There are many types of grinding
media suitable for use in a ball mill, each material having its own specific
properties and advantages.
Common in some applications are stainless
steel balls. Stainless steel balls are also used in this practical. This is
because stainless steel balls are usually very effective due to their high
density and low contamination of the material being processed. Speed of the
ball milling is adjusted to produce a uniform grind of the coarse salt. Ball
milling method is working on the principle of critical speed. The critical
speed can be understood as that speed after which the steel balls start
rotating along the direction of the cylindrical device, thus causing no further
grinding.
Apparatus
Weighing balance, ball mill, sieve nest
Material
Coarse salt, stainless steel ball
Procedure
1. 300g-500g of coarse salt was weighed by using the weighing balance.
2.Different sizes of stainless steel balls were put into the mill.
3.Coarse salt was then inserted into the mill.
4.Milling process was started with suitable speed and this process was lasted for 15-20 minutes.
5.Product obtained from the milling is weighed after the ball milling process.
6.The product obtained is sieved by using sieve nest method.
7.The particle size distribution obtained from the sieve nest method is plotted with histogram.
1. 300g-500g of coarse salt was weighed by using the weighing balance.
2.Different sizes of stainless steel balls were put into the mill.
3.Coarse salt was then inserted into the mill.
4.Milling process was started with suitable speed and this process was lasted for 15-20 minutes.
5.Product obtained from the milling is weighed after the ball milling process.
6.The product obtained is sieved by using sieve nest method.
7.The particle size distribution obtained from the sieve nest method is plotted with histogram.
Result
Original weight: 325g
Final weight : 320.1g
Sieve nest size (micrometer)
|
Weight of the salt (g)
|
500
|
35.0
|
350
|
10.3
|
250
|
3.6
|
150
|
0
|
Discussion
Ball milling is a method
of grinding and mixing of materials, with or without liquid in a rotating
cylinder or conical mill partially filled with grinding media. It is a ball
milling process where a powder mixture placed in the ball mill is subjected to
high-energy collision from the balls. ball milling machines enable very precise
milling, in porcelain jars, even for relatively tough materials, wet or dry.It
was found that this method, termed mechanical alloying, could successfully
produce fine, uniform dispersion of oxide particles.
This ball mill is horizontal type and tubular
running device. Ball mills consist of a hollow cylinder mounted such that it
can be rotated on its horizontal longitudinal axis. Commonly, stainless steel ball is used as grinding media in the
ball milling method. Stainless steel ball is chosen because it low
contamination of the material being processed and contains high density.
Different specification steel balls are installed on the scale board in the
ball mill, when the barrel body rotates and
produces centrifugal force ,at this time , the steel ball is carried to
some height and falls to make the material grinding and striking. The speed of
rotation is the greatest important factor in the operation of the ball mill.
Thus, speed also important for the ball milling process to be carried out
successfully. Appropriate speed must be adjusted by hearing the sound of the
grinding when the ball milling process is carried out. This is because this
ball milling method is working on the principle of critical speed.
In this practical, 325g
of coarse salt is grinded with numerous numbers of stainless steel balls with
the speed of 5. The grinding process produced a total weight of 320.1g of
product. All of the products are sieved by using sieve nest method which will
produce 150 micrometer of particle size, 250 micrometer of particle size, 350
micrometer of particle size, 500 micrometer of particle size and coarse salt
that cannot sieve by 500 micrometer sieve nest. The least salt produced is
150 micrometer particle size of salt while the mostly salt produced is 500
micron of salt.
Questions
- What are the factors that will influence the
particle size reduction process (milling)?
The factors that will influence the particle size
reduction process (milling) are nature of raw materials , nature of the
finished product (Particle size: Moderately coarse powders may be obtained from
various impact mill. If very fine particles like micronized particles of
griseofulvin may be obtained from fluid energy mill.Ease of sterilization: When
preparations are intended for parenteral (injection) purpose and ophthalmic
uses, size reduction must be conducted in a sterile environment. Mills should
be sterilized by steam before use.Contamination of milled materials: In case of
potent drugs and low dose products, contamination of the products should be
avoided),the toughness and surface hardness of the solid, the roll speed, the
milling time, the particle mixture and the size of milling ball.
2. What are the apparatus that can be used to
reduce particle size?
The apparatus that can be used to reduce particle
size are mortar and pestle, cutter mill ,end-runner ,and edge-runner mill,
vibration mill,hammer mill, roller mill , ball mill and fluid energy mill.
- What are the factors that will influence the
selection of certain apparatus for particle size reduction?
The size reduction range required, the cost of size reduction, properties of
the powder particles, the available of equipment will influence the selection of apparatus for particle size reduction
Conclusion
Ball milling is a method
used in reduction of particle size to a smaller size or fine particles.
References
1. http://www.ncsu.edu/project/feedmill/presentations/CFIA%20Corn%20Symp%20Particle%20Size-Pellet.pdf
2. http://books.google.com.my/bookshl=en&lr=&id=jlR12Zz2SfoC&oi=fnd&pg=PP2&dq=factor+influence+selection+of+apparatus+for+particle+size+reduction&ots=Zo0KI5zKU&sig=ptk3LPkUzTNNOR2KLR_sXoTc0bg&redir_esc=y#v=onepage&q&f=false
3. http://www.powdertechnologyinc.com/toll-processing-services/toll-processing-capabilities/?gclid=COvs1uj5ycECFZcmvQoduxsA1g
4. Michael E.Aulton (2007).
Aulton’s Pharmaceutics The Design and Manufacture of Medicines, 3rd
edition,Churchill LivingStone.
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