The edge runner mill is also called a roller stone mill and is a mechanized form of mortar and pestle-type compression comminution. It crushes the materials into fine powders by rotating stones. The edge runner mill consists of two large rotating grinding wheels or stones turning slowly in a large bowl. In this mill, the material can be crushed or ground in a continuous operation.
Principle of Edge Runner Mill:
The
edge runner mill mainly works on the attrition and impaction by which the
crushing or grinding of the powder material takes place. The principle of size
reduction by this mill is crushing due to the heavyweight of the stones or
metal and shearing force. The movement of stones or metal causes size
reduction. The Edge-runner mill has the pastel equivalent mounted horizontally
and rotating against a bed of powders.
Construction of Edge Runner Mill:
The
basic parts of this mill consist of two heavy rollers and a bed made of stones
or granite which is used for the grinding of the materials, Fig.1. The rollers
are mounted on the central horizontal shaft and move around the bed in a
shallow circular pan.
Working of Edge Runner Mill:
The
material to be milled is fed into the center of the pan and is worked outwards
by the action of the wheels. Scrapers are employed in scraping the material
constantly from the bottom of the wheel vessel after which it is fed to the
wheel where it gets crushed to powders. The material is ground for a definite
period and then it is passed through the sieves to get the powder of the
required size. An electric motor in the basement provides power for the mill to
start the device as used in flour mills. This mill is used for crushing or
grinding various materials without the danger of clogging or jamming the
machine by the accumulation of the ore with greater efficiency and in high
comparative quantities. The crushed powder is discharged through the outlet at
the bottom.
Fig.1: Edge Runner Mill (a) Schematic (b) Industrial Mill Used In Practice |
Uses of Edge Runner Mill:
- This mill is used for grinding most of the drugs to a very fine powder.
- It is used to crush or grind all types of drugs.
- It is most preferred for size reduction of non-sticky materials.
Advantages of Edge Runner Mill:
- Very fine particle-sized materials can be obtained by this edge runner mill.
- It has a simple design.
- The major advantage of this mill is that it requires less attention during operation.
- The combinations of various elements in this machine make it operate with greater efficiency.
- Utilizes less power, and does not require frequent clean-up and particular adjustment.
Disadvantages of Edge Runner Mill:
- It requires more floor space than the other commonly used mills.
- It is not suitable for sticky materials.
- This mill produces a lot of noise pollution.
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