This document discusses size reduction and roller mills. It introduces size reduction as reducing large solid masses into smaller particles through comminution, and that it can be achieved through precipitation or mechanical processes. The objectives of size reduction are then outlined, such as improving appearance, increasing surface area, and facilitating absorption. It also discusses different modes of size reduction like cutting, compression, impact and attrition. Finally, the document describes how a roller mill works through stress and attrition between two cylindrical rollers, with one driven by a motor and the other running freely, in order to crush and crack materials like seeds before oil extraction.
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ROllER MILL.pptx
1. TOPIC: Mechanism of SIZE Reduction & Roller Mill
PHARMACEUTICAL ENGINEERING
Prepared by kashish Wilson
Assistant Professor,
MM College of Pharmacy,
MM(DU),Mullana Ambala
2. SIZE REDUCTION:
INTRODUCTION:
Size reduction is a process of reducing large solid unit masses into small unit
masses, coarse particles or fine particles.
Size reduction process also termed as comminution or diminution or pulverisation.
Size reduction may be achieved by TWO methods
Precipitation process
Mechanical process
3. OBJECTIVE OF SIZE REDUCTION :
It improves appearance.
It increases surface area.
It facilitate absorption and bioavailability.
It improves the stability.
It facilitate extraction.
It facilitate mixing.
In aerosol and inhalation preparation.
Parental suspension.
It facilitate drying.
Ophthalmic suspension.
Increase in viscosity.
4. Modes of size reduction:
Cutting: The material is cut by means of a sharp blades
Eg : cutter mill
Compression:
In this mode material is crushed between roller by the application of
pressure Eg : roller mill
Impact:
This involve the operation of hammer/bars at high speeds.
When a lump of material strikes the rotating hammers, the material splits
apart. Eg : fluid energy mill
Attrition: breaking down by the rubbing action between two surfaces.
Eg : fluid energy mill, ball mill
5. Roller mill :
Principle: stress&attrition(rubbing action)
Construction: it consists of two cylindrical
rollers made of stone or metal
Rollers are capable of rotating on their
longitudinal axes.
One roller is driven directly using a motor,
while second one runs freely.
The gap between the rollers can be controlled
to obtain the desired particle size.
Uses: used for crushing and cracking of seeds
before extraction of fixed oils.