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The ball mill works on the principle of impact between the rapidly moving balls and the materials .Both the balls and the sample are enclosed in a hollow cylinder. At low speeds the ball rolled over each other and attrition takes place.1,2 At critical speed the centrifugal force just occurs as a result the balls are picked up by the mill wall and carried nearly the top where that break contact with the wall and fall to the bottom to be picked up. In this manner impact stress will also be induced and the size reduction made effective.
Aim: The aim of the experiment was to achieve size reduction of the given granular material using a ball mill.
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Apparatus: Ball mill
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Kept 100 gm of rice and charge it to series of sieves to get pregrinding size distribution. Continuous sieving for 10 minutes. Weigh the mass of rice retained on each sieve. Load the rice into ball mill along with metal balls. Run the ball mill for 30 minutes at a speed of 1 rpm. After 30 minutes take out rice powder from the ball mill. Fill the rice powder to a new set of sieve of smaller sizes. Weigh the mass of rice powder retained on each sieve.
Observation and calculation
|Nominal mesh aperture size,ᶯm
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Size of the given rice sample is reduced and after reduction mass of the rice powder weighed.
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- Subrahmanyam CVS, Setty JT, Suresh S. Laboratory manual of pharmaceutical engineering (Unit operations). Delhi Vallabh Publications.
- Pharmaceutical Engineering by Sanbamurty K. (New Age International, New Delhi)