SU865430A1 - Apparatus for aerodynamic classification of loose materials - Google Patents

Description

(54) DEVICE FOR AERODYNAMIC CLASSIFICATION OF BULK MATERIALS

I

The invention relates to the processing of powdered materials and can be used in the building materials industry in the preparation of finely dispersed fillers, abrasive materials, etc., in the chemical industry and other branches of the national economy, in which it is necessary to classify the product by size.

A device is known that includes its classification chamber, a fan, a precipitation chamber, loading and unloading devices 1.

A device for the aerodynamic classification of granular materials not larger than 1 mm in a transverse laminar flow is known, comprising a classification chamber, receiving chambers for the fine and coarse fraction, an air blower, a material metering device, and a dispenser in the form of a metering unit and a particle insertion system in the form of a rotating disk. , from the periphery of which particles of the material under the action of centrifugal force are introduced into the classification chamber with some initial velocity at an angle close to direct 2.

However, in the known device of dispersion of particles (the destruction of agglomerates, the separation of small particles from large ones) and their classification by size occurs simultaneously from the moment the particles enter the stream in the classification chamber, which reduces the severity of classification and makes it difficult to classify easily agglomerated materials (powders). In addition, as the practice of similar devices shows, the input system allows the supply and, therefore, Q. and classification of materials with a size of the main fraction of several tens of microns, which does not allow the classification of finely dispersed powders.

The purpose of the invention is to improve the quality of classification.

The goal is achieved by the fact that the device

15 is equipped with a pneumatic material supply system consisting of an accelerating line, at the inlet of which an ejector is installed, and at the exit - a diffuser head and a return line connecting the diffuser 20 nozzle to the ejector, the diffuser nozzle consists of a diffuser and an intermediate insert, internal size which is smaller than the size of the outlet of the diffuser, and the boot device is installed at the inlet of the accelerating line.

The drawing shows the proposed device.

The device includes a classification chamber 1 provided with guide vanes 2, rotating blades 3 and confusor nozzle 4 at the entrance, and receiving chambers 5 for individual fractions at the exit, with a separate receiving chamber 6 for the coarse fraction. For entering the classified material into the classification chamber There is a pneumatic powder supply system which includes an accelerating line 8, at the exit of which a diffuser nozzle is installed, including a diffuser nozzle chamber 9, a diffuser 10 with an opening angle O - 10 and the intermediate piece 11, and the output - an ejector 12. The ejector 12 and the diffuser nozzle is connected to highway 13 return. A movable plate 14 is installed to adjust the size of the coarse fraction.

The main stream in the classification chamber 1 is created by a gas blower, which can be used as a fan or gas blower. Elements 2 and 3 are not indispensable for the device, but are useful for creating a flux-free flow structure. In addition, by means of the rotary blades 3, a linear flow velocity profile can be formed with a maximum in the material introduction zone, which allows to reduce the required flow rate of the main gas.

For the pneumatic system for injecting powder into the classification chamber, both an independent gas blower and a part of the gas from the main blower can be used. The material to be classified is dispensed by the dispenser 7 into the accelerating line 8, into which the carrier gas is injected through the ejector 12. Dispersed and accelerating in the main section of the accelerating line 8, the powdery material passes further through the short diffuser 10 and further through the intermediate insert AND is introduced into the classification chamber, where it is distributed across its cross section in accordance with the particle size, with the larger and therefore more inertial particles entering receivers more distant from the point of entry. Part of the mixture of powder and gas through the gap between the diffuser 10 and the intermediate insert 11 enters the chamber of the diffuser nozzle 9, from where it is sucked off via the return line 13 to the ejector chamber 12 and returns to the classification again. The mixture of gas and fractionated material from the receiving chambers 5 is directed, depending on the size, into separate cyclones and filters for each fraction.

From the point of view of classification efficiency, the best cross-sectional shape of the accelerating line and the diffuser nozzle is round, but in order to increase productivity with some loss of sharpness of classification they can be made with a rectangular cross-section

5 bases approximately equal to the width of the body of the classification chamber.

In the case of a pneumatic system for introducing material into the classification chamber, dispersion occurs in the accelerating line 8

.. and during the acceleration of the material by the gas supplied through the pipe. The powder is distributed in the gas volume, and the distance between the material particles, determined by the ratio between the material consumption and the carrier gas consumption, can be

5 is chosen large enough so that the particles do not interfere with and agglomerate. In addition, there is an additional destruction of the agglomerates upon their impact on the surface of the accelerating line 8 and mutual collisions. Due to the efficiency of deagglomeration processes and the possibility of distributing material particles in an arbitrarily large predetermined volume, the pneumatic injection system is also suitable for classifying

5 tend to agglomerate powders.

Simultaneously with the material dispersion, the gas flow of the accelerating line 8 accelerates the particles of the material to speeds that ensure their effective classification.

 The use of a pneumatic material injection system reduces the lower marginal size of the classification to a value not less than 5 microns, and the lower marginal size is determined by

5 instructive and regime parameters of particle size remaining in the jet of injected gas and not separating from it. It decreases with increasing levels of velocity of the injected gas and main stream and decreasing the size of the outlet

0 holes enter the mixture of gas and powder. The upper boundary size is limited by technical and economic considerations and is about 100 microns. In the speed range for both streams 5-100 m / s

. possible classification of materials in the range of boundary sizes 5-100 microns, with a lower boundary size correspond to higher flow rates.

High degree of dispersion and uniformity of the velocity field of particles in the system with

0 by pneumatic injection allows the installation of additional receiving chambers to classify the material not only into fine and coarse, but also into intermediate fractions.

When used directly as a pipe 8 or a channel of another cross section, a portion of the material particles located near the channel surface have a disordered sex velocity structure, which to a certain extent aggravates the severity of the classification. Elimination of such particles from the classification can be achieved by installing a diffuser nozzle of the same cross sectional profile as the main section of the accelerating line, but several smaller sizes, in front of the point of entry of particles into the classification chamber.

In addition, the lagging of the particle velocities from the gas velocity characteristic of a two-phase flow in the channel leads to a slight increase in the lower boundary size of the classification. The ideal system for eliminating this effect would be a system that, without violating the structure of the movement of particles formed in the accelerating line, would remove the carrier gas. A further reduction in the carrier gas flow rate injected with the material particles into the main flow, while maintaining a virtually unchanged pattern of particle motion, can be achieved by installing a short diffuser 10 at the end of the main section of the accelerating line 8.

Claims (3)

1. A device for aerodynamic classification of bulk materials, including its classification chamber, air blower, loading and unloading devices, characterized in that, in order to improve the quality of the classification, the device is equipped with a pneumatic supply system consisting of an accelerating line, at the entrance of which an ejector is installed, and a diffuser is installed at the outlet on the cage and return line connecting the diffuser nozzle to the ejector. 2. A device according to claim 1, characterized in that the diffuser nozzle consists of a diffuser and an intermediate insert, the internal size of which is smaller than the size of the outlet opening of the diffuser. 3. The device according to claim 1, characterized in that the loading device is installed at the inlet of the accelerating line. Information sources, 0 taken into account in the examination 1. USSR Author's Certificate No. 215152, cl. On 07 May 4/08, 1966. 2. US patent number 3520407, cl. 209-139, published. 1970 (prototype). yes ff, 5 No . tsss - dusty gas  - napouiMofpaiHkiu material III lir II  . D