Size Reduction
Contents of this
session
• Introduction to size reduction
• Applications of size reduction
• Factors affecting size reduction
• Mechanism of size reduction
• Laws governing size reduction
• Classification of mills
• Ball mill
• Fluid Energy mill
• Hammer mill
• Edge runner mill
• End runner mill
Learning objectives
At the end of this lecture student will be able to:
• Explain various applications of size reduction
• Discuss the factors affecting size reduction
• Discuss various mechanisms of size reduction
• Explain the laws governing size reduction
• Discuss on the construction and working of a ball mill
• Discuss the process of Fluid energy mill and Hammer mill
operation
• Explain the construction and working of Edge runner and
End runner mill
Summary
• Size reduction is the process of reducing the particle
size of a substance to a finer state
• The factors that affect size reduction process are
hardness, toughness, stickiness, moisture content, ratio of feed to product
ratio etc.
• Moh’s scale is used to quantify the hardness of a
substance
• The applications of size reduction include efficient
mixing of different ingredients, increased drying and improved absorption
• Different mechanisms of size reduction includes cutting,
compression, impact and attrition
• Laws governing size reduction include Kick’s Law,
Rittinger’s Law, and Bond’s Law
• Ball mill mechanism of operation include both impact and
attrition
• Optimum speed of ball mill operation at which maximum efficiency of size
reduction obtained is termed as Critical speed
• Fluid energy mill utilizes both impact and attrition
mechanism of size reduction
• The feed to the Fluid energy mill should be pre size
reduced
• It is used
for size reduction
of thermolabile substances
like antibiotics, vitamins etc..
• Hammer mill utilizes impact as the mechanism of size
reduction process
• Optimum speed of ball mill operation at which maximum
efficiency of size reduction obtained is termed as Critical speed
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