Size reduction equipment attrition mills

Forces commonly used in food processes for particle size reduction are compressive, impact, attrition (or shear), and cutting forces. More than one force usually participates in the comminution operation in industrial size-reduction equipment. In particular, crushing rolls use mainly compressive forces, hammer mills are based on impact, disc mills cause particle attrition through shear force application, and rotary knife cutters use cutting forces. 

The second class of grinding equipment is used to prepare dispersions. Typical of this class are baU and pebble mills, ultrasonic mills, and attrition mills. SoHds, eg, sulfur, antioxidants, accelerators, and zinc oxide, are generaUy ground on this equipment (see Size reduction). BaU mill action is assisted in some mills by a combination of dispersion circulation by an external pump and mechanical osciUation of an otherwise fixed nonrotary mill chamber. Where baU mill chambers are rotated it is necessary to experimentally estabHsh an optimum speed of rotation, the size and weight of the baU charge, and ensure the mills do not overheat during the grinding period. 

Comminution, or particle size reduction of solids, is considerably different from that of the breakup of one liquid by dispersal as small droplets in another. Particle size reduction is generally achieved by one of four mechanisms (1) compression, (2) impact, (3) attrition and (4) cutting or shear. Equipment for particle size reduction or milling includes crushers (which operate by compression, e.g., crushing rolls), grinders (which operate principally by impact and attrition, although some compression may be involved, e.g.,... 

Another way that milling processes can be categorized is by the mechanism used to break the particles. Compression, impact and attrition, and cutting or shear are usually listed as the main methods of accomplishing size reduction. Note that for a particular piece of milling equipment, multiple mechanisms may be involved. 

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