SU1745370A1 - Pneumatic classifier - Google Patents

Abstract

Usage: industry of building materials and mineral fertilizers, mining, coal, chemical industry, pneumatic classification of various bulk materials at a grain size of 0.1-5.0 mm. The classifier includes a housing 1 with a lid 10, a grill 9 mounted obliquely inside the housing 1, a loading device 2 located at the upper end of the grille 9, a pipe 4 supplying air under the grille 9 communicated with the housing 1 and vertically mounted on the side opposite to the loading device 2 re

Description

The invention relates to the field of building materials industry, mining, coal, chemical, mineral fertilizers and can be used in the pneumatic classification of various bulk materials on the border of 0.1-5.0 mm.

A pneumatic classifier is known, including a rectangular section housing with an inclined and gas distribution grille made of a set of inclined plate shelves, loading and unloading nozzles, and air inlet and exhaust nozzles. From the source material entering the first shelf, a part of the fine fractions is separated by the transverse air flow; the half-finished product of the large product formed in this way is poured onto the second shelf, once again blown off by an air stream, and some more fine fractions are separated from it. etc. The process continues to the extent necessary to remove the coarse product.

However, in this apparatus, unlike a coarse product, the fine product does not undergo repeated cleaning, which is reflected in the separation efficiency in an unfavorable manner. The classification efficiency of such devices does not exceed 60% according to Eder-Meier,

The closest in technical essence and the achieved result to the proposed is a pneumatic classifier that includes a housing with a grille cover. Installed obliquely inside the housing, a loading device located at the upper end of the grille, an air inlet pipe under the grille installed in the end wall of the housing - a vertical settling chamber with a discharging common with the case; - a device and a device for exhausting the dust-air mixture located respectively in the lower and upper its parts

This unit is a three product.

The disadvantage of it is the low classification efficiency due to the contamination by fine particles of the discharge product of the precipitation chamber.

If the particles of the material being separated have the same density, then the design of the settling chamber will not ensure the production of an unblown dust-free product in its unloading. In sedative

part of the small particles, hitting the near-wall region, fall down along the walls, since the air flow velocity (in the vertical direction) in this region is close to 0. The discharge product is precipitated

The chamber contains particles with a particle size of 0-0.3 mm, i.e. dust is not effective.

The aim of the invention is to improve the classification efficiency by organizing the process of multiple cleaning of both large and small products. The goal is achieved by the fact that the pneumatic classifier, which includes a housing with a lid, a grating mounted obliquely inside the housing, a loading

a device located at the upper end of the lattice, a pipe for supplying air under the lattice in communication with the body and vertically mounted on the side opposite to the loading device.

a cleaning chamber with devices for removal of coarse fraction and dust-air mixture, located respectively in the lower and upper parts of the cleaning chamber, is equipped with strings stretched between

housing cover and grille, and inclined perforated pouring shelves, cantilever mounted on the end wall of the vertical cleaning list

camera in front of her place of communication with the body.

The cleaning chamber is made in the form of a truncated cone with large bases facing upwards with ring elements and flow splitters, the flow dividers are located in the lower part of the ring elements coaxially to the cleaning chamber, and the device for removing the air-dust mixture is made of axially and tangentially connected pipes.

It is known that the dependence of the classification efficiency on the regime and design parameters for the classifiers of the claimed type can be represented by:

Pb (1-e) h g / sin a

E - to

-t)

(D

where E is the classification efficiency according to the Hankok-Luyken criterion, the proportion of units;

D - the mass fraction of the little things in the source material, the share of units;

p is the density of the dispersed phase, kg / m3;

e is the volume fraction of air in the layer of material located on the distribution grid, the fraction of units;

h - the height of the layer of material on the grid, m;

t is the residence time of the material on the lattice, s;

ft — consumption concentration of the material, kg / m;

Wan - air flow rate in the cross section of the separation zone of the apparatus, m / s;

a is the angle of inclination of the lattice to the horizontal, degrees;

RM - the amount of large material trapped in a small product, the share of units

As can be seen from formula (1) with increasing m, the efficiency of classification E increases. The organization of the process of cleaning up a small product reduces RM and increases E. When installing additional elements on the distribution grid, it is not possible to significantly increase the thickness of the material layer h on it, since this leads to a decrease in the efficiency of classification.

The presence in the classifier of a cleaning chamber with a tangentially installed pipe for exhausting the dust-air mixture ensures the flow of the twist, which increases the residence time of the material in the apparatus. By installing a cleaning chamber equipped with ring elements, flow breakers and inclined perforated pouring shelves, more efficient

to clean the small product. This allows also increasing the size of the material blown out of the layer, i.e. increase the air flow rate (Wan in formula 1), without changing the separation boundary, since this material then undergoes efficient cleaning, the largest particles can be separated from the main gas flow in the cleaning chamber,

Inclined perforated pouring shelves, cantilever-mounted on the end wall of the vertical cleaning chamber opposite to the place of its communication with the body, are used for additional cleaning of the small product.

The strings stretched between the grille and the top cover of the classifier housing change the trajectory of the particles of the material being divided. The fine fraction of the material carried by the air flow, 5 passing through the distribution grid and the layer of material moving on it, is subjected to repeated cleaning when striking the strings. Large particles of material, striking the strings, slow down

10, the speed of its movement along the distribution lattice, as a result of which the residence time of the particles in the apparatus and the degree of dust removal increase.

FIG. 1 depicts a pneumatic

15 classifier, general view; Fig. 2 is a diagram of the installation for the pneumatic classification of granular materials.

The pneumatic classifier includes a body 1 of a rectangular cross section.

20, equipped with a pipe 2 material loading, pipe 4 supply air flow. Inside the device there is an inclined distribution grid 9. Between the upper lid of the device 10 and the distribution grid 9, there are tensioned strings 11. A vertical cleaning chamber 12 is connected to the body of the device 1 with devices 3 for draining a large fraction and a dust-air mixture: tangential 5,

30 axial 6; discharging device 8 The cleaning chamber 12 is equipped with perforated pouring shelves 15, which are cantilever-mounted opposite the cleaning chamber communicating with the housing

35 of the apparatus, ring elements 13 and flow splitters 14. The ring elements 13 are connected to each other with a gap, and the outer diameter of each subsequent ring is equal to the inner diameter

40 of the previous ring, the diameter of the lower ring is equal to half the diameter of the clean-up chamber. The diameter of the upper ring is less than the diameter of the clean-out chamber in this

section into two thicknesses of the ring, the Chisel is 12 chamber has two splitters 14 flows in the form of conjugate cones. The diameter of the base of the cone is equal to no more than 1/3 of the diameter of the cleaning chamber in this section. The cross-sectional area of the upper part of the cleaning cell 12 is advisable to be set equal to the cross-sectional area of the apparatus:

NR -I & Han ban - -d-

where Nal is the height of the apparatus;

Shaft - the width of the apparatus;

D is the diameter of the cross section of the upper part of the list cell.

This is due to the fact that the air flow rate in the cross section of the separation zone of the apparatus must correspond to the soaring speed of particles equal to the separation boundary. That is, the relative air flow rate in the cross section of the separation zone of the apparatus and in the upper cross section of the cleaning chamber must be equal.

The area of the lower part of the cleaning cell 12 is set equal to 0.5-0.6 of the cross-sectional area of the separation zone of the apparatus,

0.5-0.6 Nap d - diameter of the cross section of the lower part of the clean-up chamber.

For the lower part of the cleaning cell, the cross-section is made smaller than the cross-section of the separation zone of the apparatus, since particles that are 2-3 times larger than the separation boundary are carried away into the cleaning chamber. It is necessary to separate and return only particles larger than the separation boundary to discharge from the cleaning chamber, therefore the relative air velocity in the lower cross section of the cleaning cell is not greater than that in the separation zone of the apparatus. This is due to the fact that, unlike the prototype, which uses concentrated input of the dust-air mixture into the precipitation chamber, the input classifier in the proposed classifier is distributed over the height of the cleaner cell.

Since the flow is rotated in the lower part of the cleaning chamber, this results in additional separation of particles larger than the separation boundary from the main gas flow, which in the lower part of the cleaning chamber move along the walls of this chamber.

The angle of inclination of the distribution grid 9 is chosen from the conditions for ensuring the transportation of material through it. The optimum angle of inclination of the lattice to the horizontal is 25-60 °.

When the angle of inclination of the distribution grid is less than 25 ° possible violation

transporting the largest pieces of material through it,

When the angle of inclination of the distribution grid is greater than 6Q °, the speed of the material moving along it increases sharply, which leads to a decrease in the residence time of the material on the grid and the incomplete dedusting of a large product.

Installation for pneumatic classification {FIG. 2) includes a fan

16, an apparatus 17 for wet gas cleaning, a conveyor 18 for supplying a material to be separated, a dust collector 19 with counter-swirling flows, a classifier 1 and air ducts with flaps a, b, c, d, d.

The installation works as follows.

The fan 16 creates the movement of the air and the cuts of the apparatus 1; with the help of the dampers on the air ducts a, b, c, d, e they set

the air velocity in the apparatus 1, the dust-gas path, and the necessary ratio of air returned to the apparatus 1 and emitted into the atmosphere

through the apparatus 17 wet gas cleaning.

The source material by the conveyor 18 and the loading device 7 through the loading pipe 2 of the classifier 1 is fed to the distribution grid 9. Passage

along the sloped distribution grid 9 of the classifier, the material is intensively loosened by jets of air escaping through the slots of the distribution grid 9. Fine fractions of the material are carried by the air flow from the layer of material flowing in the distribution grid 9 of the apparatus 1. 12, the largest particles, striking the strings 11, the ring elements 13 and the flow dividers 14, lose their speed and are poured into a suspended layer of material on the grid and on inclined pouring shelves 15, and where there is an additional dedusting material ssypayuschegos then into the discharge pipe 3.

The dusty flow coming out of the nozzles 5 and 6 of the cleaning chamber of the apparatus 12 is cleaned of solid particles in a dust collector with counter-swirling flows 19. The fine fraction of material M caught in the dust collector 19 is one of the products of the classification. The coarse fraction of the material (the dust-free material) K is discharged from the apparatus through the discharge device 8.

Most of the air after the dry cleaning stage in the dust collector 19 is returned to the classifier 1 through the air inlet 4, the rest of the air is equal to the number of leaks in the system, is subjected to additional treatment in the gas cleaning unit 17 and is discharged into the atmosphere. Thus, the installation operates in an air-closed loop, which is widely practiced in such processes.

In the proposed classifier, the separation process is carried out in a stream of air at a constant speed of movement, and in it it is possible to effectively divide the material into two size classes.

Tests of the pneumatic classifier with an estimated capacity of 4 t / h were carried out in a package with experimental installations of the Uralkali software.

FIG. 1 shows a pneumatic classifier; in fig. 2 - installation, general view.

The angle of inclination of the distribution grid to the horizontal was 40 °, its width was 200 mm, and the length was 700 mm. The air flow rate in the cross section of apparatus 1 was 3.2–3.8 m / s.

The separation of crushed sylvinite ore with an initial moisture content of 0.2% achieved a classification efficiency of 71.7% according to the Eder-Mayerap criterion with a classifier productivity of 4 t / h, a separation margin of 0.39 mm and a fine product yield of 12.0 %

The results of the separation of sylvinite ore in the claimed classifier are presented in the table.

The proposed classifier will be used for dedusting potash

RUDIS the use of the proposed apparatus will improve the efficiency of classification of granular materials by more than 10%.

Claims (2)

1. Pneumatic classifier, including a housing with a lid, a grill mounted obliquely inside the housing, a loading device located at the upper end of the grille, an air inlet pipe under the grill connected to the housing and vertically mounted on the side opposite to the loading device, cleanup chamber with devices for removal of the coarse fraction and the dust-air mixture, located respectively in the lower and upper parts of the clean-up chamber, is distinguished by the fact that, in order to increase the effect NOSTA classification, it is provided with strings tensioned between the housing cover and the lattice and the perforated sloping shelves and mixing cantilevered fixed on the end wall of the vertical chamber opposite the recleaning its communication with the enclosure. 2. A classifier according to claim 1, characterized in that the cleaning chamber is made in the form of a truncated cone with a large base facing upwards with ring elements and flow dividers, the flow dividers being located in the lower part of the ring elements coaxially with the cleaner cell, and the device for removal of dust and air the mixture is made of axial and tangential nozzles % s h "5 U s to $ -U71 L -L h g CHA  / Cvj and