Solid minerals, construction materials, chemical raw material, abrasive materials, solid recyclable materials, some kinds of vegetable raw materials are subject to crushing. Among all kinds of raw materials subject to crushing, the dominating ones are the ferrous and nonferrous ores and non-metallic mineral resources (coal, granites, limestones). Roughly, about 2.5-3 bln. t of solid raw materials are subject to crushing in the world annually.
It is obvious that the solid raw materials crushing is necessary to produce smaller grain-size pieces as compared to initial material, as from the very beginning this material, for example, the ore extracted from the pit, can be rather large, i.e. the pieces of up to 1-1.5 m.
The crushing operations are, as a rule, used together with the particle size processes (screening) of solid raw materials.
The crushing operations like the other disintegration methods are mainly used for solving the following tasks:
- For successive particle size reduction of minerals to 3-15 mm before fine grinding and enrichment of minerals.
- For production of the raw materials of the same size that is required for direct consumers, for example, in production of the crushed stone, abrasive materials, as well as preparation of solid fuel and components of metallurgical feed .
- For preparation of solid industrial and domestic wastes for their advanced processing for secondary products.
- Crushing is performed with the use of special machines - crushers. The material is destroyed in crushers by the forces of compression, shift, impact, or their combination.
Jaw crushers
One of the oldest types of crushers used until now are the jaw crushers (JC). They ensure crushing primarily by compression. The JC design is simple and reliable in operation. The JC crushing unit consists of immovable and moving plates (jaws). The latter makes reciprocating motion (oscillations) in the space getting narrow downwards. A bit more complicated modification of jaw crushers are the single-toggle crushers (STC) that combine reciprocating and elliptical vibrations, thus simplifying the material transportation downwards the crushing chamber and, in addition, ensuring application of combined compression and impact forces to the crushed material by improving the energy efficiency of the crushing process.
Cone crushers
The other common type of crushers are the cone crushers (CC). Crushing in the CC is performed by application of compression and partially shift forces generated in the cone-shaped crushing chamber inside which the crushing cone suspended in its top point and driven by eccentric mechanism located under the lower edge of the crushing cone ensures the space rolling.
In mining, over 90% of all the crushers used are jaw and cone crushers. The key feature of crushing in the JC and CC are their limited opportunities by reduction of particle size of the crushed material. Sometimes, the degree of reduction does not exceed 4-5 in them. That’s why in the conventional ore preparation schemes, three and sometimes four successive crushing stages are used.
Disintegration in the KID range cone vibrating (inert) crushers and high pressure grinding rollers is relatively new energy efficient crushing principles of minerals implementing the principles of material destruction due to shift and partially compression forces. Such crushers may ensure the reduction in material size by 5-10 times. Therefore, sometimes it is possible to replace two crushing stages or a crushing stage and a grinding stage with one process operation or significantly to reduce the average size of the fine crushed material.
Hammer crushers
To crush less strong material than the massive crude ore or to crush non-homogeneous material, the rotor crushers are used. The most common type of high-speed rotor crushers are the hammer crushers (HC) which crushing elements are the plate-type bars (hammers) made of impact-resistant steel that are freely suspended on the horizontal shaft. The HC are used for crushing relatively soft rocks, i.e. plaster-stone, limestone, or for crushing of different types of solid domestic waste. The low-speed rotor crushers are mainly represented by gear machines used for destruction, for example, of reinforced concrete or old auto-tyre casing waste fragments.
Crushing the solid raw material, particularly, the minerals, is rather energy-consuming. Besides, the worn metal lining and crushing elements of the crushers need to be regularly replaced in the course of operation.
References
- V.A. Perov, E.E. Andreev, L.F. Bilenko Crushing, grinding and screening of minerals. - M.: Nedra, 1990. - 300 p.
- L.A. Vaisberg, L.P. Zarogatsky, V.Y. Turkin Vibrating crushers. Basis for calculation, design and technological use / Editor L.A. Vaisberg SPb.: VSEGEI. 2004. - 306 p. ISNB 93761-061-X
- L.A. Vaisberg, A.N. Kartavy, A.N. Korovnikov Screening surfaces of screens. - SPb: VSEGEI. 2005. - 252 p. ISNB 5-8198-0074-5
- K.V. Fedotov, N.I. Nikolskaya Designing of processing plant. - M.: Gornaya Kniga, 2012. - 366 p. ISBN 978-5-98672-282-5
- I.I. Blekhman Theory of vibrational processes and devices. – SPb, ID “Ruda i Metally”, 2013. – 640 p. ISBN 978-5-98191-074-6
- L.A. Vaisberg, I.D. Ustinov Industrial and laboratory equipment for enrichment of natural and technogenic raw materials // Ore Enrichment (Obogashcheniye rud), 2010, No. 5, P. 25-28. ISSN 0202-3776