Tumbling mills types

Tumbling mills are commonly used in industry for grinding large quantities. There are three distinct types, each with different application areas ... 

In a review of milling, it was stated that ball milling was the most commonly used type of tumbling mill in pharmacy (Parrot 1974). Indeed, it is probably used most often at the preformulation stage to reduce the particle size of small amounts of a compound, especially for the preparation formulations to be administered to animals. At the lead optimization (LO) stage, however, only small quantities (e.g., 50 mg) will be available to administer to a test animal. For a review of high purity applications of ball milling, such as pharmaceuticals, see Vernon (1994). 

The term grinder describes a variety of size-reduction machines for intermediate duty. The product from a crusher is often fed to a grinder, in which it is reduced to powder. The chief types of commercial grinders described in this section are hammer mills and impactors, rolling-compression machines, attrition mills, and tumbling mills. 

The diversity of designs of the above-described machinery implies that their operating variables differ quite considerably. While energy requirements are generally governed by the comminution laws previously discussed, as illustrated in Example 4.1, some other features such as capacity and rotational velocity are particular for each imit and may be related, in some way, to the predominant force performing the reduction action. Two types of equipment with critical particularities of operation would be roller mills and tumbling mills. 

Tumbling mills operated with grinding media are usually of the type called tube mills. 

The mills used for coal grinding and drying are either tumbling mills or roller mills. Some commonly employed types of mill will now be briefly described, without laying claim to completeness. 

Figure 12.5. Jaw, roll, impact, and tumbling equipment for size reduction, (a) Blake-type jaw crusher operates at 200-300 strokes/min (Allis-Chalmers Co.), (b) Smooth roll crusher, for which operating data are in Table 12.8(b). (c) Swing hammer mill operating data in Table 12.7(a). (d) View of a conical ball mill, showing distributions of balls and material and crusting ranges data in Table 12.6(b) (Hardinge Co.). (e) Tube mill with three compartments, length to diameter ratio 3-5. (f) Rod mill in a cylindrical tumbler, LID = 1.2-1.6 data in Table 12.6(d).

Another type of miU commonly used in studies of mechanochemical processing is the planetary mUl. As implied by the name, the milling container is rotated about two separate paraUel axes in a manner analogous to the rotation of a planet around the sun. The miUing action of a planetary mill is similar to that of a conventional horizontal tumbling mUl. However, the velocity of the grinding media is not limited by centrifugal forces. 

You have seen polished stones of hematite, quartz, etc. These are obtained by tumbling in the same type of mill— the particle size is just bigger. The biggest ball mill is the seashore, where pebbles are eventually changed into sand. 

Various types of mills are used for mechanochemical treatment, commonly vibratory, attrition, planetary, and tumbling ball mill. The final product depends on the milling conditions, hence, different types of mill or the alteration of milhng parameters may result in diverse reaction paths for mechanochemical reaction. Besides, the milling time necessary to reach desired structure... 

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