Crushers product sizes

Crusher Product Sizes Table 20-10 relates product size to the discharge setting of the crusher in terms of the percent smaller than that size in the product. Size-distribution curves differ for various types of materials crushed, and a general set of curves is not vahd. 

Han (H3) and Han and Wilenitz (H4) have also presented steady-state models of fertilizer granulators based on population balance on the granules in the process loop operating in the snowballing mode. From the viewpoint of process control some interesting interrelationships between various recycle ratios, crusher speed, crusher product size, and the granule growth rate have been established. 

The work index may be round experimentally from laboratoiy crushing and grinding tests or from commercial miU operations. Some rules of thumb for extrapolating the work index to conditions different from those measured are that for dry grinding the index must be increased by a factor of 1.34 over that measured in wet grinding for open-circuit operations another factor of 1.34 is required over that measured in closed circuit if the product size Xp is extrapolated below 70 [Lm, an additional correction factor is (10.3 + Xp)/l.l45X . Also for a jaw or gyratory crusher the work index may be estimated from... 

TABLE 20-10 Relation of Product Size to Discharge Setting of Crusher ... 

Cone crushers can be operated in open circuit with capacities shown in Table 20-12, or in closed circuit in parallel with scalping screens for multistage size reduction, as Table 20-13 shows (the product sizes are not comparable). The feed should not contain more than... 

The objective of crusher control is usually to maximize crusher throughput at some specified product size, without overloading the crusher. Usually onlv three variables can be adjusted feed rate, crusher opening, and feed size in the case of a secondary crusher. Four modes of control for a crusher are (1) Setting overload control,... 

Feeding-rate control, for smooth operation. Setting control influences mainly product size and quality, while feed control determines capacity. Flow must also be synchronized with the feed requirements of downstream processes such as ball mills, and improved crusher efficiency can reduce the load on the more costly downstream grinding. 

Performance The dry pan is useful for crushing medium-hard and soft materials such as clays, shales, cinders, and soft minerals such as barites. Materials fed should normally be 7.5 cm (3 in) or smaller, and a product able to pass No. 4 to No. 16 sieves can be delivered, depending on the hardness of the material. High reduction ratios with low power and maintenance are features of pan crushers. Production rates can range from 1 to 54 Mg/h (1 to 60 tons/h) according to pan size and hardness of material as well as fineness of feed and product. 

These tertiary crushers employ smooth or toothed heavy-duty impact and abrasion-resistant steel-rimmed rolls. The rolls are mounted inline in a horizontal manner and turn toward each other at equal speeds to create a nip into which a friable feed material is introduced (Fig. 4). Heavy-duty compression springs with automatic reset are used to dampen crushing shock and to protect the crusher from tramp iron and oversize material. An adjustable screw that adjusts spring tension changes the crusher opening. A flywheel is used to even out pulses and economize on power consumption. These crushers have a theoretical maximum reduction ratio of 4 1 and will only crush materials to about 10 mesh. Roll crushers produce a controlled product size distribution without a lot of fines. The narrow particle size distribution is achieved by controlling a combination of variables including roll speed, gap measure, differential speed, feed rate, and roll surface. 

The main purpose of coarse comminution in sample preparation is to reduce the maximum particle size of samples to allow effective mixing prior to subsampling. The ratio of feed size before reduction to the product size after reduction is known as the reduction ratio, and for the first crushing or milling stage this ratio should be as large as possible (Smith James 1981). Ratios of 40/1 for coarse crushers and 15/1 for coarse milling equipment are useful minimum specifications for laboratory preparation of coarse contaminated soil samples of up to 2kg. 

The most common type of jaw crusher is the Blake crusher, illustrated in Fig. 29.2. In this machine an eccentric drives a pitman connected to two toggle plates, one of which is pinned to the frame and the other to the swinging jaw. The pivot point is at the top of the movable jaw or above the top of the jaws on the centerline of the jaw opening. Thp greatest amount of motion is at the bottom of the V, which means that there is little tendency for a crusher of this kind to choke. Some machines with a 1.8- by 2.4-m (72- by 96-in.) feed opening can accept rocks 1.8 m (6 ft) in diameter and crush 1200 ton/h to a maximum product size of 250 mm (10 in.). Smaller secondary crushers reduce the particle size of precrushed feed to 6 to 50 mm ( to 2 in.) at much lower rates of throughput. 

Fig. 6.1-13 is the block diagram of a typical compaction/granulation system. Right away it should be mentioned that the advantage of this technique of granulating powders is that any product size and distribution can be obtained. The final quality only depends on the crusher(s) and the sizing method(s) used. In this connection the discussion of Section 6.1 must be considered. A disadvantage is that always fines are also... 

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