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Home / Issues / № 2, 2014

IMPACT GRINDING ROCKS Problems and prospects
Ahlyustina N.V., Lyaptsev S.A.
 

The grinding process is widely used for the enrichment and reprocessing of materials in the mining, chemical and metallurgical industries. The smaller the size of the material, the better the beneficial agent is disclosed and the easier it will highlight it from the rock.

For grinding of a wide range of materials with initial (source) particle size of 8 (10) mm, various methods of destruction: the static load - crushing, splitting, fracture, abrasion and shearing pieces, and under dynamic loads - impact crushing and grinding. To reduce the size of the material disc attritors and vibratory mechanical mortar [1] dry milling is usually carried out by using disintegrants dismembrators and [2]. Shredders of different designs form a very large class of machines and are used in many fields of technology. They provide high chemical purity of samples and have a high durability.

Well established in the processing of solid crystalline structure or similar impact grinding method used in the disintegrator

       Lack of domestic manufacturers and designs, and consequently, the need to purchase imported shredders and quickly wear working bodies (rotors, fingers, CDs) was a stimulus for the development of design chopper closest analogue is a disintegrator.

Table 1

Characteristics of crushers and grinders [2]

Type Fashion

Feature boot

process

Hammermill small model

Inclined hopper

free kick

Hammer crusher with constricted blow

Vertical hopper

constricted kick

Reversible Hammermill

Vertical hopper

constricted kick

hammer Crusher

a movable wall

Inclined hopper

constricted and free kick

disintegrator

Inclined hopper

 

Flowing

Vertical hopper

 

 

Equipment selection is advantageously carried out by means of simulation, which gives reason to confirm or refute the accepted scheme without expensive experiments with real model installation. By varying the parameters within the specified limits may set the grinding efficiency, adding to the calculations for determining the dispersion and grinding performance. Calculations allow to rationalize the design of the boot node chopper. Integrating Writing equations to determine the relative velocity of the particles and the length of its trajectory to assess the method of grinding abrasion. With an increase in the angular velocity of the rotor increases, the collision energy of the particle with the hammer. On the other hand, increases (theory turbomachinery - linearly) the air flow in the passage, and hence the probability of passing debris through the unstressed external rows of rotor channels. For a particle size of 200 microns or less, this probability is already quite large. In addition, under the action of two opposing trends can be expected of an optimal rotor speed (for the design) granulometric composition of the product.

Tabl 2

wool-speed of spherical particles (m/s)

Particle diameter

, 10-6m

experiment

by Stokes' law

10

3,06·10-3

3,06·10-3

20

1,2·10-2

1,2·10-2

40

4,8·10-2

5,0·10-2

100

2,46·10-1

2,5·10-1

400

1,57

4,83

 

Table. 2 shows the experimental and calculated according to Stokes' law Withania velocities of particles of different sizes density of 1000 kg / m 3 in air at a temperature of 20 ° C and a pressure of 100 kPa [3]. Casts doubt on the validity of the experimental results for particles with a diameter of 400 microns.

  In steady motion of a particle when it falls in a serene environment, Withania speed can be calculated according to the formula proposed by Samsonov VT [4] = vB 0,0556ρchda2g / η-1, where ρch density of particle material, kg / m 3; VB Withania speed particles, m / s; g is the acceleration due to gravity, kg / m 2; η the viscosity of air, kg • s / m 2. The behavior of the ore particles in the forward moving air stream in the enrichment devices studied in [5].



References:
1. Kozin V.Z.Testing and control of technological processes of enrichment. Textbook for High Schools. - Moscow: Nedra, 1985, p. 295.

2. Sidenko PM Grinding in the chemical industry. , Chemistry, 1977, p.150.

3. Ostrich B. Industrial gas cleaning: Per. Translated from English. - M., Chemistry, 1981. 616 p.

4. Samsonov V.T. Universal cyclone. - URL: www.sam-vl.narod / ru / Universal, C / Universal Cw.htm.

5. Lyaptsev S.A., Potapov V.Ya. The mathematical description of the behavior of the ore particles in the air flow separation devices // Modern problems of science and education. - 2012. - № 1; URL: www.science-education.ru/101-5493.

6. Ahlyustina N.V., Lyaptsev S.A. Simulation of the motion of a particle in a shredder. - Proceedings of the universities, Mining Journal, № 8, 2007-s. 107-110.



Bibliographic reference

Ahlyustina N.V., Lyaptsev S.A. IMPACT GRINDING ROCKS Problems and prospects. International Journal Of Applied And Fundamental Research. – 2014. – № 2 –
URL: www.science-sd.com/457-24584 (10.12.2019).