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Types of grinding mill: ball mill, vertical mill, rod mill, AUTOGENOUS mill

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Types of grinding mill: ball mill, vertical mill, rod mill, AUTOGENOUS mill

May 4, 2023 nflg 0 Comments

Two main milling processes exist, those in which the product is ground as a dry powder and those in which the material to be ground is fed to the mill in the form of an aqueous slurry.

In cement grinding, the raw meal for kiln input can be ground either wet or dry, this being decided primarily by the moisture content of the quarried rock. If the rock is chalk based and have a high moisture content, it is more economical to wet grind whereas hard limestone rock is almost exclusively ground dry.

The final clinker grinding is obviously always carried out dry. Several other ancillary grinding processes are frequently located within a cement plant such as for coal grinding for kiln firing which is a dry process or sand grinding for silica additions which is normally carried out wet.

In case of iron ore preparation, either wet or dry grinding can be employed although most modern plants tend to be of the dry process, due to energy considerations. The preparation of non-ferrous metal ores always tend to be performed wet because of the nature of the subsequent separation process.

Grinding mill types

Four main types of grinding mill can be identified, each type having its own characteristic design variations.

a) ball mill : This consists of a rotating tube approximately one third filled with balls, the cascading action of the balls generating a grinding action.

b) ROD MILL: The principle is similar to that of a ball mill but the grinding media consists of a series of rods instead of balls. This process had certain limitations because of the minimum size of particle which can conveniently be produced by the action of rods.

c) AUTOGENOUS MILL: These are again of tubular design but the grinding action is produced by introducing large rocks and boulders into the mill feed which replace the ball or rod charge. In semi-autogenous practice a small quantity of balls are introduced and, therefore ball and rod mills are of semiautogenous type.

d) vertical mill : There are a series of alternative designs of vertical mills available where the principle of operation is to grind the feed material between a table and rotating rollers. The configuration of the rollers vary from manufacturer to manufacturer and can be a hollow roller tyre or even hollow balls up to 52 inches in diameter.

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