Size reduction equipment crushers

Principles of Comminution Computer Simulation of Milling Operations Size-Reduction Equipment Crushers Grinders... 

Control of Crushers Lower-grade raw materials, higher energy costs, larger-scale operations, and more complex, capital-intensive plants make automatic control of size-reduction equipment more important (Suominen, 21st International Symposium—Applications of Computers and Operations Research in the Mineral Industry, 1011-1018). Benefits are increased productivity, process stability and safety, improved recoveiy of mineral values, and reduced costs [Horst and Enochs, Engineering Mining J., 181(6), 69-171 (1980)]. 

Fig. 1 The four basic types of size reduction equipment used to produce fine solid particles (A) crushers and shredders (B) hammermills (C) colloid mills and (D) fluid energy mills.

Taggart proposed a rule-of-thumb that a jaw crusher would be the economically preferred size reduction equipment if the required throughput in tons per hour was less than the square of the crusher gap in inches. Depending on size, jaw crushers can handle up to a 48-in. size feed and create product smaller than half an inch. Jaw crushers are available in a variety of sizes up to about 1000 ton/hr and can be stationary, portable, or skid mounted. 

The size distribution of products from various types of size-reduction equipment can be predicted by a computer simulation of the comminution process. This makes use of two basic concepts, that of a grinding-rate function S and a breakage function A5 a. The material in a mill or crusher at any time is made up of partides of many different sizes, and they all interact with one another during the size-reduction process, but for purposes of computer simulation the material is imagined to be divided into a number of discrete fractions (such as the ones retained on the various standard screens) and that particle breakage occurs in each fraction more or less independently of the other fractions. 

Size reduction equipment Gyratoiy crushers Feed rate. W, ton/hr 25-1,200 ton/hr C, = 8,300 Includes motor and drive... 

Introduction and classification. Size-reduction equipment may be classified according to the way the forces are applied as follows between two surfaces, as in crushing and shearing at one solid surface, as in impact and by action of the surrounding medium, as in a colloid mill. A more practical classification is to divide the equipment into crushers, grinders, fine grinders, and cutters. 

Figure 14.5-3. Types of size-reduction equipment (o) gyratory crusher, b) roll crusher.

Crushers and Roller Mills. In this equipment group, stress is applied by either cmshing single particles or a bed of particles between two sohd surfaces. In general, most machines are used for coarse and medium-size reduction, with the exception of the high pressure roUer mill which can achieve extremely fine particle distributions. 

The selection guides given by Lowrison (1974) and Marshall (1974), which are reproduced in Tables 10.12 (see p. 465) and 10.13, can be used to make a preliminary selection based on particle size and material hardness. Descriptions of most of the equipment listed in these tables are given in Volume 2, Chapter 2 or can be found in the literature Perry et al. (1997), Hioms (1970), Lowrison (1974). The most commonly used equipment for coarse size reduction are jaw crushers and rotary crushers and for grinding, ball mills or their variants pebble, roll and tube mills. 

The apparent efficiency of the size reduction operation depends on the type of equipment used. Thus, for instance, a ball mill is rather less efficient than a drop weight type of crusher because of the ineffective collisions that take place in the ball mill. 

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.,... 

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).

BatteUe personnel contacted manufacturers and vendors of these types of crushers to determine the applicability of the equipment types to the specific requirements for the explosives-contaminated debris. Toothed-roll crushers would be unable to achieve the required size reduction. This type of equipment was not recommended by the manufacturers and/or vendors. 

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