mineral crushing device

In beneficiation plant, the types, sizes, and number of crushers employed in a complete reduction system will vary with such factors as the volume of ore to be processed, ore hardness, and the size of the feed and product.
GyratoryCrushers. Primary crushers are heavy-duty machines run in open circuit (sometimes in conjunction with scalping screens or grizzlies). They handle dry run-of-mine feed material as large as 1 m. There are two main types of primary crushers—gyratory crushers and jaw crushers. Gyratory crushers are the most common for new operations.
Secondary crushers are lighter-duty and include cone crushers, roll crushers, and impact crushers. Generally, the feed to these machines will be less than 15 cm, and secondary crushing is usually done on dry feed. Cone crushers are similar to gyratory crushers, but differ in that the shorter spindle of the cone is not suspended but is supported from below by a universal bearing. Also, the bowl does not flare as in a gyratory crusher. Cone crushers are generally the preferred type of secondary crusher because of their high reduction ratios and low wear rates. However, impact crushers are used successfully for relatively nonabrasive materials such as coal and limestone. Frequently, size reduction with secondary crushers is accomplished in closed circuit with vibrating screens for size separation.
The gyratory crusher is used as a primary and secondary stage crusher. The cone crusher is used as a secondary, tertiary, and quaternary crusher. The action of a typical gyratory-type crusher is illustrated in Figure 1. In gyratory crushers the crushing process comprises reduction by compression between two confining faces and a subsequent freeing movement during which the material settles by gravity until it is caught and subjected to further compression and again released. The particles are subjected to maximum breaking forces when they are on the side with the minimum gape.
Fig1.cutway of gyratory crusher
In the normal gyratory, the crushing stroke or travel of the head usually has an important bearing on the size of the finished product, although this factor is subject to modification when a parallel sizing zone is adopted. The movement of the head in the cone crusher is similar to that in the ordinary gyratory with an exception—toward the bottom of the cone, the head travels through a much greater distance and gyrates much faster (see cutaway in Figure2). The long movement changes the crushing stroke from slow compression to fast compression, and the increased clearance on the freeing stroke allows the material to fall away vertically after each impact.
Fig2. Cutaway of cone crusher
ImpactCrushers. Impact devices are often used for fine crushing. One type, a hammer mill, uses hammers rotating at high speed to break particles. Another type, an VSI impact crusher, accelerates particles with a rotor causing them to impact a curtain of falling particles (Figure 3). The latter has a significant advantage from a wear point of view.
FIG3. VSI crusher
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