SK50332011A3 - Method of separation aerosuspenzion - Google Patents

Abstract

The invention relates to the fractionation of air suspensions in the carbon sector, the construction sector and other sectors. The technical result consists in increasing the effectiveness of the methods and machines for fractionating air suspensions and shifting the dispersity range of suppressed dust from the micro to the nano scale. The method for fractionating an air suspension comprises the use of filtration with a moving screen, of centrifugal and centripetal forces, of forces of gravity and of inertia of the dust, and of the difference in the conditions for the condensation of the air suspension components. Furthermore, the flow of the air suspension is directed parallel to the axis of rotation of the rotor from the top to the bottom. The purified gas is compressed in a paraxial cavity of the rotor and is removed according to the intended use. Rarefaction of the gas is produced in the space near to the screen. The rotoclone comprises a circular-cylindrical body, a rotor, an air suspension distribution cavity and an air suspension fractionation cavity, a dust discharge cavity, an air suspension feed pipe, a purified gas and dust discharge pipe, and a drive having an elongated shaft, which is introduced into the air suspension fractionation cavity. A rotor is fixed to the shaft. The distribution, fractionation and dust discharge cavities communicate with one another by means of annular apertures. Furthermore, the rotor cowl is designed to be cellular, and blades of a radial/axial centripetal compressor are fixed between a base in the form of a disc and a cover in the form of a circular ring of the rotor. Scrapers moved by means of a hoop with a separate drive are used for removing the dust from the fractionation cavity.

Description

Method of separating aerosuspension, rotoclone

Technical field

The invention relates to dry separation of aerosol suspensions, in particular the separation of air from dust and smoke in the coal, engineering, construction and other sectors.

BACKGROUND OF THE INVENTION

Aerosuspensions are commonly referred to as aerosols that arise from mechanical crushing of solids: grinding, abrasion, explosions. These include the smoke produced by burning. They are dispersion systems consisting of fine solid particles suspended in a gaseous medium. Aerosuspenzií dispersity may be close to 10 ^-9 M. In addition to dispersity, concentration (mass concentration) is the amount of dispersion phase in a unit of volume, or the concentration of particles - the number of particles in a unit of volume.

The formation of aerosol suspensions is not a prerogative of human activity. In nature, there are ongoing processes that result in such creation, beginning with dust storms and ending with the drifting of pollen, plant spores and the simplest living organisms by the wind. Removal of suspended particles from the air is necessary due to the risk of explosion of these or other ingredients (flour, coal and other dust), contamination of the production of products, negative effects on the human organism.

In dry gas scrubbing, methods based on filtering aerosol suspensions through porous filters are widely used. One of the drawbacks of such filters is the volatility of their operating parameters. It is reported that, unless the filter is partially clogged with dust, it is less effective for fine particles. (Brief Chemical Encyclopedia, M., 1961, Volume 1, pages 743-740).

An advanced dry gas purification apparatus is a cyclone (ibid., Fig. 1), which is capable of removing particles from 5-10 ^-6 m or more from the gas stream. The removal of 30 to 88% of such particles is achieved by increasing the hydraulic resistance coefficient from 60 to 180 (Table 1). Battery cyclones are also used (Fig. 2, Table 2).

The use of rotoclones has been introduced in foreign practice to collect dry dust. Their operation is based on the use of centrifugal force, which is generated by the rotation of a special rotor inside the body to which the aerosol suspension is supplied. Dust particles are thrown by the centrifugal force on the walls of the body and vented out, and the cleaned gas is routed to its destination. Their deficiency lies in the fact that the purified gas also carries with it particles which have not settled on the walls of the body, i. from. that rotoclones comparable to cyclones are known for efficacy.

IS Rožkova (RU) patent RU 2 293 761 states that a cylindrical mesh is fastened down along the outer periphery of the ring at a small distance from the edge. The annular ring is rotated by an electric motor. The description states that at selected engine, mesh and vapor velocity parameters, product droplets with a diameter greater than 6.2-10 ^-6 meters cannot pass into the moving mesh area and at this average the chance of jumping through the mesh does not exceed 0.6% (prototype).

Dry separation of aerosol suspensions is described in SU 919714 (E. V. Karpov et al.) And in SU 1755892 A1 (Samarskaya District Youth Science Creativity Center Sintez). In the first one, it is recommended to remove the fine fraction of dust from the filter surface by periodically treating it with a coarse fraction. In the latter case, it is recommended to remove the dust from the filter screen of the drum (rotor) by using a spiral spatula and shaking performed periodically.

In said prototype there is a rotor of a special construction, a body, filtration through the meshes of a rotating mesh and the use of centrifugal force. However, it is used to separate aeroemulsions. The analogs used to separate aerosol suspensions increase the performance of the devices, but eliminate the possibility of reducing the dimensions of the dust particles collected.

Overall, it can be concluded that the existing level of methods and devices for dry gas cleaning does not include the range of particles from 10 ^{9-10 6} meters, it is characterized by high values of hydraulic resistance and relatively low power.

The machine for compressing and supplying air under pressure is called a compressor. Reciprocating, centrifugal and centripetal compressors are known. According to the direction of gas movement in the last two types we will distinguish axially (gas moves parallel to the axis of rotation), radial (gas moves in a direction perpendicular to the axis) and radial-axial centripetal compressors. In the latter case, the gas is forced by the compressor blades into the region along the axis, moving therefrom parallel to the axis of rotation.

SUMMARY OF THE INVENTION

The technical result of the inventions of a given group of efficiencies of methods and machines for dry separation of pensions for purified gas and dust, shifting the boundary of dust collection from micro-energy costs.

on nano-size is an increase ie aerosusdispersity reduction

1. The achievement of the above technical result shall be ensured by filtration through a moving mesh, using centrifugal, centripetal forces, gravitational forces and inertia of the dust, the difference in condensation conditions of the components of the aerosol suspension. The flow of the aerosol suspension is directed parallel to the axis of rotation of the rotor from top to bottom. The cleaned gas is compressed in the paraxial space at the rotor and the designated point is discharged. Gas underpressure is created in the space near the net.

2. The device that carries out the above activities shall be a rotoclean with a net. The apparatus comprises a circular cylindrical body, a rotor, aerosol distribution and separation spaces, a dust removal space, an aerosol injection line, a purge gas, a dust outlet and an engine, with an extended shaft introduced into the aerosol separation space where the rotor bottom is fixed in it. the shape of the disc and its lid in the form of a circular ring. The distribution, separation and drainage spaces are interconnected by annular slits. In this case, the rotor housing is realized as a mesh, blades of a radial-axial centrifugal compressor are fixed between the bottom and the rotor lid; In the separation area, dust is removed by squeegees moved through the hoop.

Explanatory notes to the table

The table gives the values of: average quadratic velocity of molecules (u); length of mean freeway (1); the number of impacts of the molecule per time unit (v); and the size of the gas molecules (σ) obtained from the viscosity coefficient. The table reproduces the data presented in Table 2-54 of Volume 1 of the 'Brief Physics and Technology Handbook' under the joint editions of K. P. Yakovlev (Gosizdat, Moscow, 1960, p. 331). The need for a table is conditioned by the mismatch of data in different sources (cf. Table G. Kay and T. Laby (Leby) Table Gosizdat, 1962, Examples).

physical and p. 45), which can make chemical constants difficult to understand

Implementation of a group of inventions

1. In a chaotic movement, only a fraction of the particles and molecules have a normal velocity (perpendicular to the axis of rotation). If we direct the aerosol suspension normally to the rotor rotation axis, we get a probability W _{H of} passing the particles of the selected size through the mesh. In the parallel movement of the aerosol suspension, the probability of passing it is equal to W _n . Obviously, W _n is less than W _H , confirming the importance of the respective distinguishing element of claim 1 of the inventive group.

The moment of orientation of the aerosol suspension flow from top to bottom is also significant. When the particle enters the rotor space or is reflected by the mesh, the particle retains its tendency to move towards the bottom as well as outside the rotor to the bottom due to inertia. As a result, its path and likelihood of aggregation increase.

Dilution of the gas in the vicinity of the mesh allows the gas to expand. Compressing the gas in the space near the rotor axis, which causes this capability to a certain extent, ensures the purge gas emerges from the rotor space.

2. The figure shows an axial section of a rotoclone comprising a body 7 ^{in the} form of a circular cylinder. The body space is divided into an annular aerosol distribution space 2, an aerosol suspension separation space 3, a dust removal space 4 and a shaft extension motor 5.

The annular space of distribution through the inner surface of the body wall, the aerosol suspension is formed by its lid 7, the separation chamber lid 8 as well as the surface embedded in the lid 8 of the pipe 9 with a flange for evacuating the cleaned gas. The annular space of the aerosol suspension is formed by the walls of the body and the bottom 11. The lid of this space and its bottom form annular slits along their perimeter with the body wall. The annular gap 12 of the lid of the space provides a uniform supply of aerosol suspension from the distribution space to the separation space over the entire length of the space. The annular gap 13 of the bottom of the space provides for the passage of dust deposited on the walls of the space when the aerosol suspension is separated into the exhaust space.

The shaft extension is connected by means of a bearing 14 to a line for evacuating the cleaned gas and by means of a bearing 15 to the bottom of the separation space. In the separation space, a disc-shaped bottom 16 and a rotor ring-shaped rotor cover 17 are fixed to the motor shaft extension. Blades 18 of the radial-axial centripetal compressor are mounted between them. A mesh 19 with small meshes is used as the rotor jacket. The dust removal from the walls of the separation space is carried out by the squeegee 20 which is located in the groove at the top of the separation space. The rim is moved in a groove by a helical gear which is moved through a cutout in the body by an electric motor mounted outside the space. Dust removal from the drainage area is performed via a flange 21.

3. The process of separating aerosol suspensions is influenced by the parameters that characterize both the mesh and the aerosol suspension. One such mesh-related parameter is the linear velocity of its movement, which is determined by the formula:

v _s = 2nRn (1), where v _s

R linear mesh speed distance of mesh from axis (m / s). rotation n - number of mesh revolutions per time unit (rpm)

An important parameter is the mesh size in the direction of rotation. Let's label it i. In addition to the mesh size of the mesh to evaluate its effectiveness, we will need to know the thickness (diameter) of the mesh wire. We denote this average d.

The aerosol suspension flow directed into the space between the mesh and the body wall consists of particles of two kinds. In particular, they are gas molecules and vaporized solid particles. The dimensions of the molecules are very small. For example, the diameter of the nitrogen molecule is estimated to be 3.5 e 3.7 Å (1 = = 10 ¹¹ m), which makes it possible to consider the size of this group of air particles to be less than 10 ⁹ meters.

Both the gas molecules and the dust particles are in constant motion. The differences in the nature of their movement are determined primarily by the differences in their weights. The greater the mass, the smaller the average velocity of movement of particles with such mass. The velocities of the molecules depend on the temperature and are subject to the Maxwell distribution of the molecules depending on the velocities. For example, under normal conditions (0 ° C and 760 mm of mercury) the carbon dioxide molecule has a mean quadratic velocity of 390 m / s. The hydrogen molecule has a velocity of 1840 m / s under the same conditions. Dust particles with dimensions of 110 ^'6 has a weight many times exceeding the weight of the hydrogen molecule, and therefore, the speed is correspondingly lower than the speed of any of the molecules of gases, assuming that the distribution of subjects by at Maxwell. For such a particle at a density of 1000 kg / m ³ and under normal conditions, the mean quadratic velocity is 5-10 ^-3 m / s. Such a particle moves with the gas flow rate.

The second moment, the different nature of the motion of the dust particles and molecules, is that the molecules collide elastically, while the neutral or differently charged dust particles merge into larger ones at impact.

Due to the fact that the dust particles are thrown to the walls of the rotoclone body by the action of the rotor, their concentration increases at the walls. This helps to increase the likelihood of impact, thus increasing the rate of settling. At steady-state mode, the dust concentration in the space near the mesh decreases, but the chaotic movement of the molecules constantly brings into it particles that have not been able to increase. For this reason, the removal of gas immediately from the space close to the rotor is not sufficiently effective. It is comparable to the efficiency of a cyclone in which analogous removal takes place.

When evacuating gas from the rotor space, the gas must pass through the movable mesh. The size of the normal velocity component of the particles and molecules of the suspension at _p must be such that the particle or molecule, over the time of eye change T, manages to travel a path equal to half the thickness of the wire of the mesh, ie 0.5 d. Assuming that the wire is circular, if the particle exceeds this distance, it will be thrown inside the rotor space and, if not, will be thrown against the body wall. thus:

T = 0.5 d / Up (2).

However, T is equal to the ratio obtained by dividing the mesh size by the net mesh speed in _s , taking into account equation (1), it follows that:

T = 1 / 2nRn (3).

Since the left sides of equations (2) and (3) are identical, we can write that

0.5 d / up = 1 / 2nRn, of which: u _p = nRd · nF ¹ (4), where u _p - particle velocity (m / s); n - constant, 3.14 ...;

R - rotor mesh radius (m);

d - mesh wire diameter (m) / n - number of rotor revolutions per unit of time (rpm), í - mesh size (m).

Thus, for all components of the aerosol suspension, the normal component of their rate is critical. If this velocity is less than the velocity resulting from equation (4), then the particle cannot cross the mesh regardless of its small size.

Since in the right part of the equation all values characterize the rotor parameters, then it proves to be a significant possibility, using the values of these parameters, to evaluate the particle velocity that is sufficient to overcome the mesh. Moreover, if we assume that the particle size distribution is statistically uniform in the area in front of the mesh eye, we can evaluate the percentage passing through the mesh in percent. Finally, Maxwell's distribution includes a wide range of velocity values. That part of the spectrum whose velocities do not reach the values defined by equation (4) shall be retained.

The direction of supply of the aerosol suspension into the space between the body wall and the rotor mesh of the device is also important. Obviously, the most preferred inlet is in the axial direction. Due to its contact with the rotor mesh, a velocity oriented tangential to the path of the contact point is obtained. Under the effect of the gas flow, the resulting velocity will be directed at an acute angle to the curve formed by the cylinder of the body, i.e. the path of the particle is greater than the distance of the contact point from the wall of the body, thereby increasing the likelihood of aggregation. The average velocity of the molecules is higher than that of the mesh. The molecules either receive a pulse in the same direction as the particles or pass into the rotor cavity. Both of these processes reduce the concentration of molecules in the area near the mesh, thereby increasing the length of their free path.

BRIEF DESCRIPTION OF THE DRAWINGS

The figure shows an axial section of a rotoclone with a mesh. In addition to commonly used numerical designations, an arrowhead indication of the direction of movement of the aerosol suspension and its components is used. The arrows: a) with circular operation indicate the direction of movement of the aerosol suspension, b) without operation - direction of movement of the cleaned gas, c) with square operation - direction of movement of dust.

Example

Examples of evaluation of rotoclone efficiency. Consider that rotoclone is used for gas purification in cement production with an aerosol suspension volume of 10 m ³ / s. At a mesh radius of 0.5 m and a height of 0.3 m, its surface will be 0.94 m ³ and the flow rate of the aerosol suspension should be of the order of 10.6 m / s. The dust velocity is approximately equal to the flow rate of the aerosol suspension.

To set the rotor in motion, choose a synchronous motor with a speed of 3000 rpm, or 50 rpm, the wire diameter d = 5-10 ' ⁴ mai = 2-10' ³ m. When we substitute into equation (4) we get u _p = 19.6 m / s. Obviously, none of the particles having a velocity of 10.6 m / s can penetrate the rotor cavity. It is understandable that this conclusion is not unconditional for many reasons. First, a speed of 10.6 m / s was determined without considering the presence of a mesh that reduces the area and requires or increase flow velocity, or reduce the performance of the device, or increase the height of the mesh and the like. These or can easily be taken into account by more detailed calculations.

5. There are moments that must be processed experimentally. For example, each molecule of nitrogen, oxygen, or carbon dioxide under normal conditions will perform about 5-10 ⁸ precipitation per second. Nothing interferes with such a molecule, taking into account the direction of flow of the aerosol suspension and its dilution in an area near the mesh to introduce a 10 particle into the mesh's mesh. The chaotic nature of the motion of the molecules predetermines the same probability of the existence of velocities in all possible directions, including the normal direction. The likelihood of realizing such phenomena can be evaluated by the mass concentration of the particles in the aerosol suspension in the cleaned gas.

From the equation (3) it is possible to determine the mesh change period of the mesh (T). T = 1.3-10 ^-5 s, or frequency 0.8-10 ⁵ . This frequency is comparable to the frequency of precipitation of molecules. It can be changed by changing the mesh parameters, as it is possible to change the precipitation frequency of the molecules by changing the temperature and the dilution level. The effect of these changes on rotoclone performance and selectivity is significant.

The analysis carried out shows that rotoclone with a mesh cannot guarantee complete elimination of the passage of nanoparticles. However, it suggests that a significant proportion of them may be retained with sufficient experimental processing.

In places with a mass gathering of people (auditoriums, medical, school facilities, metro, other means of transport) air purification with rotoclone may be recommended. For example, with an output of 10 m ³ / and a human consumption of 1 liter / s, the rotoclone shown in the fourth example can provide purified air for 10,000 people.

table

Gas molecule at m / s / m in s' ^{1 σ} π m nitrogen 490 9, 4 · 10 ^'10 5,0-10® 3.7 10 ¹⁰ argon 410 10, 1 · 10 ^'10 4,0-10® 3.5 · 1O ^'10 hydrogen 1840 ^17.8 · 10 ^_1 ° 10,0-10® 2, ^6-10 ” ¹⁰ helium 1310 28, 1 · 10 ' ^1θ 4,3-10® 2.3 · 1O ^'10 oxygen 460 10.2 · 10 ' ^1θ 4,4-10® 3, 6 · 1O ^'10 Carbon monoxide 490 9, 4 · 10 ^'10 4,7-10® 3.7 × 1O ^'10 Carbon dioxide 390 6, 1 · 10 ^'10 6, 0 -10® 4,4 1O ^'10

7? 5c VW f

Claims (2)

PATENT CLAIMS What is claimed is: 1. A method of separating an aerosol suspension by using a mesh filter, applying centrifugal, centripetal forces, gravitational forces, and inertia of the dust, a condensation condition of the aerosol suspension components, characterized in that the aerosol suspension flow is directed parallel to the rotor rotation axis; the cleaned gas is compressed in the space at the rotor axis and discharged to the designated location; a gas dilution is produced in the area near the net. 2. A rotoclone comprising a circular cylindrical body, a rotor, aerosol distribution and separation areas, a dust evacuation area, an aerosol injection conduit, a purge gas and dust evacuation and an engine having an elongated shaft which enters the aerosol suspension separation area where it rotates the rotor; characterized in that the rotor housing is implemented as a mesh; blades of a radial-axial centripetal compressor are fastened between its disc-shaped bottom and the ring-shaped lid; in the separation area, dust is removed with a trowel displaced by the tire.