Crushers secondary

Cement plants Quarrying primary crusher, secondary crusher, conveying, storage Particulates (dust) Wetting exhaust systems with fabric filters... 

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,... 

Smooth jaws produce more numerous flaky pieces than corrugated jaws. Curved jaws produce less fines but more numerous flaky particles. Crusher speed has little effect. The presence of material too small to be crushed has a deleterious effect on the shape of products. Secondary crushers with a small reduction ratio can improve the shape of primaiy crushed material, but secondaiy crushers are not inherently different from primaiy crushers. Slotted screens can remove flaky particles from the product. Impact crushers produce fewer flaky particles than any other type. 

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. 

Beneficiation. Iron ore coming from the mine must be properly sized. A gyratory crusher is normally used for primary crushing down to approximately 300 mm (see Size reduction). Secondary crushing down to 25 mm can be done in a cone crusher. Fine grinding can be done by rod mills followed by either ball or pebble mills. In some cases, autogenous grinding can be used to replace the cone cmsher and rod mills. 

In a suspended bed or entrained flow reactor technology, the coal is crushed, dried, and then pulverized to fine powder in a crusher and mill. As Table 9.1 shows, the coal particles used in entrained flow reactors are very small. The pulverized coal is transported with air to the furnace (primary air), and secondary air is heated and fed into the combustor to ensure complete combustion. The residence time of the coal in the furnace is typically around 1-2 s, which usually suffices for complete combustion. However, not all coal burns completely, and fly ash will be generated (see Table 9.1). 

For standard, or reduction, types with nonchoking concaves. Single-toggle jaw product, on screened feed, will approximate that of gyratory-type secondary crushers with nonchoking concaves. 

Conventionally, in talc milling, rock taken from the mines is crushed in primary and then in secondary crushers to at least 1.25 cm (fo in) and frequently as fine as 0.16 cm (We in). 

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

In preliminary crushers the route of the material to be crushed from entry to exit point is as direct as possible. In secondary reducing machines the route is long so as to afford the fragments the opportunity to come under the influence of the haphazard... 

Primaiy crushers have a steep cone angle and a small reduction ratio. Secondaity crushers have a wider cone angle this allows the finer product to be spread over a larger passage area and also spreads the wear over a wider area. Wear occurs to the greatest extent in the lower, fine-crushing zone. These features are further extended in cone crushers therefore secondary gyratories are much less popular than crushers, but they can be used as primaries when... 

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