Crushers tertiary

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. 

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. 

Jaw crusher feed diameter 0.1 to 1.5 m reduction ratio 5 1 to 10 1 capacity 1 to 300 kg/s Mohs hardness <9 (reduction by compression). Gyratory crusher feed diameter 0.75 to 1.5 m reduction ratio 5 1 to 10 1, usually 8 1 capacity 140 to 1,000 kg/s Mohs hardness <9. More suitable for slabby feeds than jaw crusher (reduction by compression). Roll crusher feed diameter 1 cm reduction ratio 5 1 to 10 1 capacity 0.3 to 20 kg/s Mohs hardness <7.5. Suitable for softer, friable, and nonabrasive materials. OK for wet and sticky materials. Cone crusher and short head cone feed diameter <25 cm reduction ratio 5 1 to 10 1, usually 7 1 capacity 5 to 300 kg/s Mohs hardness <8. Usually secondary or tertiary crusher. Impact crusher pulverizers, shredders, or smooth roll feed diameter 1 cm with a reduction ratio of 7 1 to 10 1 capacity 0.3 to 50 kg/s. Mills, hammer, feed diameter 10 mm, reduction ratio 10 1 to 50 1, capacity 0.01 to 5 kg/s Mohs hardness <4.5. Maximum fines feed not hard or abrasive. Mills, ball, and rod feed diameter 0.5 mm with a reduction ratio of 10 1 to 50 1 Mohs hardness <9. Mills, autogenous, semiautogenous feed diameter 200 mm, reduction ratio 10 1 to 50 1 capacity 0.1 to 100 kg/s Mohs hardness <6. Mills, fluid energy feed diameter 50 pm reduction ratio 10 1 to 50 1 capacity <2 kg/s Mohs hardness <4.5. 

Before magnesite is calcined, it undergoes a third crushing step (tertiary), where it is generally reduced in size to less than 1 in. using short head cone crushers. 

Tertiary crushers are used to help balance the demand between sizes. By selecting primary and secondary crushers that produce more coarse material than is required on average, the amount of fines produced is kept to a minimum. Tertiary crushers are generally used to crush surplus quantities of larger products into the smaller sizes. 

Cone crushers are increasingly being used as secondary and tertiary crushers and are frequently operated in closed circuit (i.e. with over-sized particles being screened out and recycled to the crusher) to produce a well-defined top size, with minimum fines. They have similar reduction ratios to gyratory crushers (4 1 up to 6 1) and produce a more slabby product than impactors. 

Cone crusher and short head cone feed diameter < 25 cm reduction ratio 5 1 to 10 1 usually 7 1 capacity 5 to 300 kg/s Mohs hardness < 8. Usually secondary or tertiary crusher. 

Cone crusher selected as secondary and tertiary reducers power 0.9 to 5 MJ/Mg rpm 290-220. Breakup by compression, product diameter determined by the adjustment clearance between compressing plates. 

Quartz. A tertiary quartz sand was broken by jaw crushers and metallic ball mills at Dorentrup Sand and Clay Plant Ltd and sold under the name Ground Product No. 12 (in short DQ12), with a size distribution of <60 jim. A <5 jun size fraction was prepared from this material by centrifugal separation in air using the laboratory separator of Messrs. Walther-Staubtechnik of Cologne. This... 

Primary crushing may reduce as mined ore to less than 200 mm and then, in the conventional approach, it is further reduced in secondary and tertiary crushers followed by rod and ball mill grinding to the required particle size. Final sizing classification is usually achieved by operating the ball mill in closed circuit with hydrocyclones. 

Crushing the rocks is often achieved in two or three stages. The secondary and tertiary crushing machines resemble the machines used during primary crushing. They consist of vertical cone crushers or horizontal cylinder crushers. The former type is the most widespread. 

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