Roll crusher

Impact Crushers One type of impact crusher is the hammer mill. This consists of swinging hammers rotating at high speed on either a vertical or horizontal axis inside of a lined crushing chamber. Ore is broken by impact with the hammers and breakage plates that reside on the periphery of the crusher. Reduction ratios as high as 40 1 can be obtained however, because of their very high reduction ratios, they have a tendency to produce more fines than other crushers. 

Roll crushers are comprised of two counterrotating rolls. This actions draws material into a nip zone between the rolls, producing high compression forces that fracture the ore. Reduction ratios of only 4 1 are obtainable, with a low production of fines. 

Frame Connecting Rods Side Piste Frame Bolt 

Toggle Seat Plate Toggle Seat Tension Rod Toggle Plate 

Toothed rolls such as those of Table 12.8(b) can handle relatively large lumps, for example, 14 in. maximum with 24 in. rolls according to the table. To smooth rolls, the feed size is limited by the angle of nip which depends on the surface conditions but often is approximately 16° or arccos 0.961. Accordingly the relation between the diameters of the roll dr and feed df and the gap d0 between the rolls is given by 

For example, with df = lin. and d0 = 0.25 in., the roll diameter is figured as 18 in. Table 12.8(b) lists 16 in. as the smallest size suitable for this service, which appears to be somewhat marginal in comparison with the calculated result. According to the formula, 1 in. lumps could be nipped by 16 in. rolls with a spacing of 0.34 in. It is not possible to state who is smarter, the formula or the manufacturer. 

Material Work Index w, Material Work Index w, 

Cement clinker is to be reduced from an initial ds0 = 1500 jum to a final dso of 75, um. From Table 12.2 the work index is 1VJ = 13.49. Substituting into Eq. (12.3), 

This equipment is particularly suited to crushing of soft, friable materials to cube-shaped products with small proportions of fines. For fibrous materials, the screen is provided with cutting edges. Some data are in Table 12.7(c). A list of materials that are handled in hammer mills is in Table 12.5(a), and other products are referred to in Table 12.10. 

lumps could be nipped by 16 in. rolls with a spacing of 0.34 in. It is not possible to state who is smarter, the formula or the manufacturer. 

TABLE 12.3. Operating Ranges for Commonly Used Size Reduction Equipment 

Material Work Index W, Material Work Index W, 

---

Roll Crushers. Traditional roU emshers effect size reduction by cmshing single particles between two counterrotating roUs hence they are emshed between the two surfaces. The roUs can either be smooth or profiled to aid feeding of coarser materials. Figure 6 shows a particle of diameter x being reduced between two roUs of diameter D. For smooth roUs D/x > 17 is usually selected, whereas for profiled roUs this can be varied to D/x < 10. The feed size-to-gap width ratio is essentially limited to approximately 4. 

Q Capacity of roll crusher cmVmin ftVmin of coarse fractions ... 

The capacity of roll crushers is calculated from the ribbon theory, according to the following formula ... 

A novel comminution device, the roll press, has achieved commercial success [Schoenert, International J. Mineral Processing, 22, 401-412 (1988)]. It is used for fine crushing, replacing the function of a coarse-baU mill or of tertiary crushers. Unlike ordinary roll crushers which crush individual particles, the roll press is choke fed and acts on a thick stream or ribbon of feed. Particles are crushed mostly against other particles, so wear is veiy low. Energy efficiency is also greater than in ball mills. 

Operating experience (Wuestner et al., loc. cit.) has shown that roll diameters about 1 m are preferred, as a compromise between production rate and stress on the equipment. The press must be operated choke fed, with a substantial depth of feed in the hopper otherwise it will act like an ordinary roll crusher. 

Penn.sylvania Cru.sher Corp. offers a variety of impactor types granulators, Bradford breakers, roll crushers, and jaw crushers. (See Table 20-15.)... 

Prater Industries, Inc., offers a double roll with heavy-duty teeth as a precrusher feeder. The Mikro roll crusher (Hosokawa Micron... 

Primaiy crushers used are jaw, gyratoiy, impact, and toothed roll crushers. Impact mills are hmited to hmestone and softer stone. With rocks containing more than 5 percent quartz, maintenance of hammers may become prohibitive. Gyratoiy and cone crushers dominate the field for secondaiy crushing of hard and tough stone. Rod mills have been employed to manufacture stone sand when natural sands are not available. 

Hydraulic piston-type compactors for collection vehicles, on-site compactors, and transfer-station compactors roll crushers used to fracture brittle materials and to crush tin and aluminum cans and other ductile materials... 

Equipment used to reduce the size of solid waste including hammer mills, shredders, roll crushers, grinders, chippers, jaw crushers, rasp mills, and hydropulpers briquettes... 

Walzen-glas, n. cylinder glass, -gldttwerk, n. Paper) calender, -kessel, m. cylinder boiler, cylindrical boiler, -lager, m. roller bearing, -muhle, /. roller mill, roll crusher, -satz, m. 

Roll crushers are made either smooth or with teeth. A 24 in. toothed roll can accept lumps 14 in. dia. Smooth roiis effect reduction ratios up to about 4. Speeds are 50-900 rpm. Capacity is about 25% of the maximum corresponding to a continuous ribbon of materiai passing through the roiis. 

There are several crushers referred to as secondary crushers. Examples of these (shown in Figure 2.7) are the cone crusher, the roll crusher, and the hammer mill. 

Roll crusher Typical roll speed = 50- 100 rpm Typical capacity —10-25 ton/hr (6 mm particles) [31]... 

Other coarse crushers Hammer mill Single roll crusher Pin mill Symons disc crusher Griffin mill Ring roller mill (Lopulco) Ball mill Tube mill Hardinge mill Babcock mill... 

The single roll crusher shown in Figure 2.13 consists of a toothed crushing roll which rotates close to a breaker plate. Figure 2.14 is an illustration of an industrial model. The material is crushed by compression and shearing between the two surfaces. It is used extensively for crushing coal. 

Asbestos and mica roll crushers, hammer, and jet mills... 

Cement gyratory, jaw and roll crushers, roller, and ball mills... 

Coal roll crushers, pulverizers, ball, ring-roller, and bowl mills... 

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).

The material aggregate is fed from the mixer via a connecting shaft to the cooler (5) and then to the crusher (6) wherein it is crushed preliminarily (by a single-roll crusher unit) and finally (by a toothed-disc mill). 

In industrial and laboratory settings the subdivision process more commonly involves the comminution of large particles or aggregates into smaller sizes, either dry with subsequent dispersion (size reduction to the order of a few pm) or directly in a slurry (size reduction to as small as a few tenths of pm). Examples of comminution machines include agitator ball mills, colloid mills, cutting mills, disk mills, homogenizers, jet mills, mechanical impact mills, ring-roller mills, and roll crushers. 

---