RU2608142C2 - Vibration classifier - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: invention relates to mechanisms of loose materials classification by coarseness. Vibration classifier comprises base capable to vibration motion, on which supporting sieves with vertical parallel surfaces are fixed, separating alternating inner and outer channels with possibility of raw material feed into inner channels and separate fractions discharge from inner and outer channels. Inner channels have width of not more than triple nominal size of particles supplied for raw materials classification. Next to output from inner channels there are vertical lateral barriers with height of not less than one-third of sieves height attached to said base.

EFFECT: increasing classification efficiency, as well as reducing sieves clogging degree.

1 cl, 5 dwg

Description

The invention relates to devices intended for the classification of bulk materials by size, and can be used in the metallurgical, chemical, mining and processing industries and the construction industry, in particular, to obtain small commodity fractions in the production of crushed stone.

A vibration device is known for classifying granular material by particle size. This device is a set of sieves arranged one below the other, the mesh size of which is successively decreasing from the top to the bottom. During vibration, a portion of the material loaded on the upper sieve is distributed over the sieves in accordance with the particle size [1]. The disadvantages of this device include a relatively low productivity associated, in particular, with the clogging of the openings of the sieves.

Widely used in various industries, a vibrating screen, consisting of a box resting on elastic elements, vibration exciters and a work surface. As a working surface, for example, a sieve with a mesh size selected for the classification, which is the bottom of the box, is used. Bulk material moves along the sieve under the influence of vibration to the discharge end and is subjected to sifting - particles with a particle size less than a certain size pass through a sieve [2].

The disadvantage of the vibrating screen is the “clogging” of the screens, which is especially intense when sieving fine, wet or clay material; difficulties associated with ensuring a uniform layer when moving bulk material along a screening surface; limiting the speed of movement of bulk material along the screening surface, a large amount of occupied area at a given performance.

As a prototype, a vibrating screen was taken, containing vertical screens fixed on a common base, delimiting alternating internal and external channels [3]. The base makes helical vibrations, and the raw materials to be separated enter the internal channels. The resulting fractions are removed from the external and internal channels separately. The main disadvantage of this device is also a clogged sieve.

The objective of the invention was the creation of a vibration classifier, resistant to clogging sieves and having increased productivity per unit of working area of the production room.

The solution of this problem, taking into account these problems, is based on the use of the effect discovered by the authors, consisting in the fact that, with sufficient vibration intensity, the bulk material will acquire the properties of a gas and is sifted through holes located in inclined or vertical parts of the sifting surface due to the diffusion of, and sometimes more intensively than through openings located, as usual, in the bottom of a horizontal or slightly inclined longitudinal screen surface.

The specific task is solved by the proposed design and the selection of device parameters as follows.

The screen box includes a tray or a system of trays, the parallel side surfaces of which are vertically mounted screening surfaces. Between screens, alternating internal - of a certain width - and external channels are formed. The raw materials intended for classification are fed into the internal channels, the small fraction is screened out into the external channels, and the large fraction remains in the internal. Fractions are separated from internal and external channels separately. It was established experimentally that the distance between the side surfaces of the inner channel (tray width) should be no more than 3 nominal sizes of classified bulk material. With large values of the width of the tray, the process efficiency is significantly reduced. A barrier of a certain height is established at the discharge end of the tray between the side surfaces, which ensures that the volume of the tray is filled with bulk material, its circulation in it and thereby contributes to the intensification of the screening process.

In FIG. 1 presents a diagram of the proposed device; in FIG. 2 - screening surface of the proposed device; in FIG. 3 - general view of the classifier; in FIG. 4 - dependence of the operational efficiency of the proposed classifier E on the height of the barrier h; in FIG. 5 - dependence of the operational efficiency of the proposed classifier E on the width of the tray d.

The principle of operation of the device is illustrated in FIG. 1, which shows a top view. From the inner space of the loading hopper 1, the bulk material enters the inner channel 2, limited by parallel screens 3, and moves under the action of vibration in the horizontal direction. The vibration parameters are chosen so that the bulk material in the trays is in a state of boiling, accompanied by an increase in the volume of bulk material, intense chaotic interaction between particles, segregation of small particles to the side screening surfaces and passage through them. The fine fraction trapped in the outer channels moves horizontally under vibration and is discharged from edge 4. The remaining coarse fraction in the inner channel is discharged from edge 5. Intensive interaction between particles and intensification of the classification process are facilitated by limiting the width of the tray - not more than 3 nominal sizes particles of bulk material and the presence of a barrier with a height of at least 0.3 h, where h is the distance from the bottom of the tray to the upper edge of the screening surface (at a lower barrier height, the ktivnost sieving, since in this case the volume of the tray only partially filled with bulk material and only a part of the screening surface is contacted with the particulate material).

In FIG. 2 shows a side view from the side of one of the internal channels on the sieves 3, fixed on the base 7. Large particles that jumped over the barrier 6 move further to the edge 5. A side view of the classifier is shown in FIG. 3. The sieves fixed on a common base are placed inside the box 8, suspended on the springs 9 and 10, the lower ends of which are fixed on the fixed support 11. A fine fraction from the external channels pours out into the hopper 12, a large fraction from the internal channels enters the hopper 13. To generate vibrations the box used mechanical vibrational exciters of an unbalanced type 14, driven by electric motors 15, sitting on the same foundation 9. Vibration movements of the box occur in a plane perpendicular to the axes of the vibration exciters, i.e. parallel to the sieves.

To improve the efficiency of the classifier, experiments were conducted to find the optimal geometric parameters of the proposed device. The classified material was waste from the production of crushed stone with a particle size of less than 5 mm (the so-called "screening"). The sieves had square cells with a side of 2 mm, distributed over segments with a screening surface of 350 mm × 70 mm. The vibration angle to the horizontal plane was 75 °, the vibration amplitude was 4 mm, and the frequency was 16.6 Hz.

The dependence of the separation efficiency E (%) on the value of k, expressed as the ratio of the height of the barrier to the height of the screening surface of the sieves, is shown in FIG. 4. It is clearly seen that the greatest efficiency is achieved at k> 0.3, which corresponds to a barrier height of not less than a third of the sieve height.

The dependence of the separation efficiency E (%) on the ratio n, expressed as the quotient from the separation of the width of the internal channels d (FIG. 1) by the maximum (characteristic) size of the particles to be separated, is shown in FIG. 5. A significant drop in efficiency is noted for n> 3.

The compact arrangement of sieves in the form of a package, consisting of tens or even hundreds of pieces, can significantly increase the performance of the classifier per unit of production area.

The technical result of the invention is to significantly reduce the degree of clogging of sieves, record classification efficiency and high productivity per unit of production area associated with increased intensity of vibration during the classification process.

Information sources

1 P.A. Coase. Fundamentals of the analysis of the dispersed composition of industrial dusts and crushed materials // Leningrad: "Chemistry", 1987, p. 78-79.

2 Reference "Vibrations in technology", t. 4. - M .: Mechanical engineering, 1981, p. 349-352 - (prototype).

3 Copyright certificate No. 640766 of 05.05.75

Claims (1)

Vibration classifier having a vibration-capable base on which sieves with vertical parallel surfaces are fixed, delimiting alternating internal and external channels with the possibility of supplying raw materials to internal channels and separate removal of fractions from internal and external channels, characterized in that the internal channels have a width no more than three times the nominal particle size supplied to the classification of raw materials, and near the exit from the internal channels there are attached to the aforementioned at the base there are vertical transverse barriers not lower than a third of the height of the sieves.

Images