Ball mill; an example of grinder is an efficient tool for size reduction of solid through grinding for many applications e.g. in chemical industry. Grinding means sub dividing the solids to a finer product than crushing.
Principle; Ball mill works on the principle of impact that is the size reduction of the solids is done by the impact.
Construction; a ball mill consists of a hollow cylindrical shell that rotates about its axis, this axis can be either horizontal or at a small angle to the horizontal. This horizontally shell is filled with balls; the grinding media. The grinding media that is ball can be made up of steel, stainless steel or rubber. The inner surface of the hollow cylindrical shell is usually lined with an abrasion resistance material such as manganese steel or rubber.
The balls occupy about 30 to 50 percent of the volume of the ball mill. As the cylindrical shell rotates with the material to be ground, the ball are lifted up on the rising side of the shell and then they cascade down or drop down from near to top of the cell, in doing so, the solid particles in between the balls are ground and reduced in size by impact. The ball mil may be operated in batch or continuous fashion, wet or dry.
Importance of size reduction through grinding (Ball Mill)
Size reduction refers to an operation where the solid particles are broken down into smaller pieces, it (necessity of size reduction) is very important in application; and this process is carried out
- To increase the surface in order to increase the rate of physical and chemical process.
- To meet the stringent specification regarding the size of commercial products.
- To accomplish intimate mixing of solids in solid-solid operations since the mixing is more prominent when size is small.
- To improve dissolution rate.
- To improve solubility.
- To improve binding strength.
- To improve dispersion properties.