WO2010053404A1

WO2010053404A1 - Method for fractionating an air suspension and a rotoclone

Info

Publication number: WO2010053404A1
Application number: PCT/RU2009/000483
Authority: WO
Inventors: Илья Степанович РОЖКОВ
Original assignee: Rozhkov Ilya Stepanovich
Priority date: 2008-11-10
Filing date: 2009-09-22
Publication date: 2010-05-14
Also published as: UA100185C2; EA201100465A1; SK50332011A3; RU2385758C1

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

The method of separation of aerosuspension, rotoclone.

The technical field to which the invention relates.

The invention relates to a dry separation of aerosuspensions, in particular, to the separation of air from dust and smoke, in coal, engineering, construction and other industries.

The level of technology.

Aerosol suspensions are called aerosols, which are formed during the mechanical grinding of solids: crushing, abrasion, explosions. These include smoke generated by combustion. They are dispersed systems consisting of small solid particles suspended in a gaseous medium. Dispersibility can approach aerosuspenzy Yu- ^9m Also dispersibility, they are characterized by concentration. (Weight concentration - the number of dispersed phase per unit volume, concentration or partial - the number of particles per unit volume).

The formation of aerosuspensions is not the prerogative of human activity. In nature, processes constantly occur, the consequence of which it is, starting with dust storms and ending with pollen carried by the wind, spores of plants and simple living organisms. The release of air from suspended particles is necessary due to the explosiveness of its various ingredients (flour, coal, and other dusts), pollution of industrial products, and negative effects on the human body.

Methods based on filtering aerosuspensions through porous filters have gained widespread use in dry gas purification. One of the disadvantages of this kind of filters is the inconsistency of their operating parameters. It is noted that “... while the filter is partially not clogged with dust, it is not very effective in relation to small particles” (Brief Chemical Encyclopedia, M., 1961, v. 1, S.743-746).

A common apparatus for dry gas cleaning is a cyclone (ibid., Fig. 1), capable of removing particles from 5 * 10% or more in size from a gas stream. In this case, extraction from 30 to 86% of such particles is achieved by increasing the coefficient of hydraulic resistance from 60 to 180 (table 1). Battery cyclones were also used (Fig. 2, table 2).

In foreign practice, rotoclones have found application for trapping dry dust. Their action is based on the use of centrifugal force, which develops during the rotation of a special rotor inside the body into which the aerosuspension is fed. Dust particles are thrown to the walls of the housing by centrifugal force and are discharged to the outside, and the cleaned gas passes as intended. Their disadvantage is that the purified gas carries with it particles that have not settled on the walls of the body, i.e., the known rotoclones are comparable in efficiency with cyclones.

SUBSTITUTE SHEET (RULE 26) In patent RU 2 293761 of the author I. Rozhkov (RU) in paragraph 1 of the formula states that "along the outer perimeter of the circular ring at a small distance from the bottom edge, attach a cylindrical network." The circular ring is driven by an electric motor. The description indicates that with the selected parameters of the engine, mesh and steam flow rates, product droplets with a diameter greater than 6.2HO- ⁶ meters will not be able to pass into the cavity of the movable mesh, and for an equal diameter, the chance to slip through the mesh does not exceed 0.6% (prototype )

Dry separation of aerosuspensions is described in SU 919714 A (E. V. Karpov et al.) And SU 1755892 A1 (Samara regional center of HTT youth “Synthesis”). The first of them proposed the removal of a small fraction of dust from the filtering surface by periodically exposing it to a large fraction. The second proposes to remove dust from the surface of the filtering cloth of the drum (rotor) by means of a screw scraper and shaking, acting periodically.

In this prototype, we find a rotor of a special design, a housing, filtration through cells of a rotating mesh and the use of centrifugal force. However, it is used to separate airborne emulsions. Analogs are used to separate aerosuspensions, increase the productivity of devices, but exclude the possibility of reducing the size of the captured dust particles.

In general, it can be stated that the present level of dry gas purification methods and devices does not include a range of particle sizes from 10 ⁹ to 1Q- ⁶ meters, is characterized by a high value of hydraulic resistance and relatively low productivity.

A machine for compressing and supplying air under pressure is called a compressor. Known piston, centrifugal and centripetal compressors. In the direction of gas movement in the last two forms, we distinguish between axial (gas is moved parallel to the axis of rotation), radial (gas is moved in the direction perpendicular to the axis) and radial-axial centripetal compressors. In the latter case, the gas is pumped into the axial region by the action of the compressor blades, from which it moves parallel to the axis of rotation.

Disclosure of the invention.

The technical result of this group of inventions is to increase the efficiency of methods and machines for dry separation of aerosuspensions into purified gas and dust, shifting the dispersion border of the captured dust from micron to nanoscale, and reducing energy consumption.

1. The achievement of the specified technical result is provided by filtration through a moving mesh, using the action of centrifugal, centripetal forces, gravity and dust inertness, differences in the condensation conditions of the components of the aerosuspension. In this case, the flow of aerosuspension is directed parallel to the axis of rotation of the rotor from top to bottom. Purified gas

SUBSTITUTE SHEET (RULE 26) compress in the axial cavity of the rotor and output as intended. In the space near the grid create a rarefaction of gas.

2. The machine performing these actions is a rotoclone with a net. It includes a round cylindrical body, a rotor, aperture of distribution and separation of a suspension, a dust extraction cavity, nozzles for supplying an aerosuspension, a discharge of purified gas, dust and an engine, with an elongated shaft inserted into the separation cavity of the aerosuspension, where the rotor bottom is mounted on it disk and its cover in the form of a circular ring. Cavities of distribution, separation and retraction are reported by annular slots. In this case, the rotor shell is mesh-like, the blades of the radial-axial centripetal compressor are fixed between the bottom and the rotor cover, and dust is removed in the separation cavity by scrapers moved by the rim.

Brief explanations of the table and graphic materials.

The table shows the values of: the mean square velocity of the molecules (Q); average mean free path (/); the number of collisions of a molecule per unit time (v); and the size of the gas molecules (σ) found from the viscosity coefficient. It reproduces the data shown in table 2-54 of the first volume of “A brief physical and technical reference book)) edited by K. P. Yakovlev (State Publishing House, M ,, 1960, S.331). The need for the table is due to the mismatch of data in different sources (compare with the table by J. Kay and T. Labie “Tables of physical and chemical constants)), State Publishing House, 1962, p. 45), which can complicate the perception of examples.

The figure represents an axial section of a rotoclone with a grid. In addition to the generally accepted digital designations, the direction of movement of the aerosuspension and its components with arrows is used. Arrows: a) with round plumage indicate the direction of movement of the aerosuspension; b) without plumage - the direction of movement of the purified gas; c) with square plumage - the direction of dust movement.

The implementation of the group of inventions.

1. During chaotic motion, only a certain part of particles and molecules has a normal speed (perpendicular to the axis of rotation). By directing the aerosuspension normally to the axis of rotation of the rotor, we will have a probability of passage of the grid by a particle of a selected size equal to W _n . With the parallel movement of aerosuspension, the probability of its passage is equal to W _n . It is obvious that W _{n is} less than W _AND , which confirms the materiality of the corresponding distinguishing feature of claim 1 of the claims of the group of inventions.

The moment of direction of the flow of aerosuspension from top to bottom is also significant. Passing into the cavity of the rotor or being reflected by the grid, the particle by inertia in the cavity of the rotor will retain the tendency

SUBSTITUTE SHEET (RULE 26) movement to its bottom, as well as outside the rotor to the bottom of the cavity. As a result, its path increases and, accordingly, the probability of aggregation.

The rarefaction of gas in the space near the grid allows the potential of gas to expand to be realized. The compression of the gas in the axial cavity of the rotor, in a known part forming this potency, ensures the removal of the purified gas from the cavity of the rotor.

2. The figure shows an axial section of a rotoclone, including a housing 1 in the form of a round cylinder. The cavity of the housing is divided into an annular cavity 2 of the distribution of aerosuspension, a cavity 3 of separation of the aerosuspension, a cavity 4 of dust extraction and an engine 5 with an extension shaft 6.

The annular cavity of the aerosuspension distribution is formed by the inner surface of the body wall, its lid 7, the lid of the separation cavity 8, and the surface of the nozzle 9 cut into the lid 8 with a flange of the outlet of the purified gas. A nozzle 10 with a flange is inserted into the lid of the cavity to supply aerosuspension.

The separation cavity of the aerosuspension is formed by the walls of the body, the cover of the separation cavity and the bottom 11. The cover of this cavity and its bottom form annular slots along their perimeters with the body wall. The annular gap 12 of the lid of the cavity provides a uniform flow of aerosuspension from the distribution cavity to the separation cavity. An annular gap 13 of the bottom of the cavity allows the passage of dust deposited on the walls of the cavity during separation of the aerosuspension into the exhaust cavity.

The shaft extension by means of the bearing 14 is articulated with a pipe of the outlet of the cleaned gas and the bearing 15 with the bottom of the separation cavity. In the separation cavity on the motor shaft extension, a bottom 16 in the form of a disk and a rotor cover 17 in the form of a circular ring are fixed. Between them, the blades 18 of the radial-axial centripetal compressor are fixed. As the shell of the rotor, a fine-mesh mesh 19 is used. Dust removal from the walls of the separation cavity is carried out by a scraper of the rim 20 located in the groove of the top of the separation cavity. The rim is moved into the groove by a worm pair driven through a slot in the housing by an electric motor mounted outside the cavity. Dust removal from the exhaust cavity is carried out through a pipe with a flange 21.

3. The parameters characterizing both the grid and the aerosuspension influence the process of separation of aerosuspensions. One of these parameters for the grid is the linear velocity of its movement, which is determined from the formula:

Vs = 2trRn (1), where Vs is the linear velocity of the grid (m / s); R is the remoteness of the grid from the axis of rotation (m); p - the number of revolutions of the grid per unit time (vol./sec).

SUBSTITUTE SHEET (RULE 26) A significant parameter is the size of the mesh cell in the direction of rotation. Denote it by £. In addition to the size of the mesh cell, to assess its effectiveness, we need knowledge of the thickness (diameter) of the mesh wire, which we denote by d.

The flow of aerosuspension directed into the space between the grid and the wall of the housing is composed of particles of two kinds. First of all, these are gas molecules and evaporated solid particles. The size of the molecules is very small. For example, the diameter of nitrogen molecules is estimated at 3.5 ÷ 3.7 A (1 A = 10- ¹⁰ M), which allows to assume the size of the group of air particles smaller ^Yu-9 meters.

Both gas molecules and dust particles are in constant motion. The difference in the nature of their movement is due primarily to the difference in their masses. The larger the mass, the lower the average particle velocity of such a mass. Molecular velocities are temperature dependent and obey Maxwell's molecular velocity distribution. For example, under normal conditions (0 ⁰ C and 760 mm Hg), a carbon dioxide molecule has a mean square velocity of 390 m / s. A hydrogen molecule, under the same conditions - 1840 m / s. Speck size of 1 -10 ⁶ M has a mass several times greater than the weight of the hydrogen molecule and hence its velocity less than the velocity of the molecules, respectively any of the gases, if we assume it obeys the Maxwell distribution of speeds. For such particles at a density of 1000 Kr / m ³ and under normal conditions the mean square velocity is ³ -YU- 5 m / sec. Such a particle moves at a gas flow rate.

The second point that distinguishes the nature of the movement of dust particles and molecules is that the molecules collide elastically, while neutral or oppositely charged dust particles aggregate into larger ones during collisions.

Discarding dust particles by the action of the rotor to the walls of the rotoclone body, they increase their concentration at the walls. This contributes to an increase in the probability of collision, that is, an increase in the deposition rate. In this case, in the steady state, the concentration of dust in the space adjacent to the grid decreases, however, the random movement of molecules constantly introduces particles that did not have time to become larger. For this reason, the selection of gas directly from the space near the rotor is not effective enough. It is comparable to the efficiency of a cyclone, which implements a similar “sampling”.

When taking gas from the rotor cavity, it needs to go through a moving grid. The magnitude of the normal component of the velocity of the particles and molecules of the suspension u _P) must be such that the particle or molecule during the change of cell g has time to go a path equal to half the thickness of the wire mesh, i.e. 0.5d. Under the assumption that the wire is round, if it overcomes this distance, it will be discarded inside the rotor cavity, if not, it will be discarded to the wall of the housing. Therefore: r = 0.5d / u _p (2)

SUBSTITUTE SHEET (RULE 26) But m is equal to the quotient of dividing the grid cell size £ by its linear velocity v _s , which, taking into account equation (1), implies that: r = £ / 2πRn (3).

The identity of the left-hand sides of equations (2) and (3) allows us to write that

0.5d / Up =! 72trRn, whence: Up = tr -Rd -ri ^ - ¹ (4), where

Up- particle velocity (m / s); π is a constant number equal to 3.14 ...;

R is the radius of the rotor mesh (m); d is the diameter of the wire mesh (m); p - the number of revolutions of the rotor per unit time (r / s);

£ - mesh cell size (m).

Thus, for all components of aerosuspension, the normal component of their velocity is critical. If this speed is less than the following from equation (4), then the particle will not be able to overcome the grid with an arbitrarily small size.

Since all quantities characterize the rotor parameters on the right side of the equation, the ability to estimate the particle velocity sufficient to overcome the grid through their values seems significant. Moreover, assuming that the distribution of particles in space in front of the grid cell is statistically uniform, taking into account their size, their percentage that has passed through the grid can be estimated as a percentage. And finally, the Maxwell distribution includes a wide range of velocity values. That part of the spectrum whose velocities do not reach the values determined by equation (4) will be delayed.

Moreover, the direction of introducing aerosuspension into the space between the wall of the housing and the grid of the rotor of the device is also significant. Obviously, the advantage of its input in the axial direction. The result of its contact with the rotor grid is the acquisition of speed directed along the tangent to the path of the contact point. By the action of the gas flow, the resulting speed will be directed at an acute angle to the generatrix of the cylinder of the body, that is, 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 speed of molecules exceeds the speed of the grid. They either receive momentum in the same direction as the particles, or pass into the rotor cavity. Both of these processes reduce the concentration of molecules in the space near the grid, thereby increasing their mean free path.

Examples of evaluating the effectiveness of rotoclone.

4. We assume that rotoclone is used for gas purification of cement production with an aerosuspension volume of 10 m ³ / sec. With a mesh radius of 0.5 m and a height of 0.3 m, its area will be 0.94 m ² , and

SUBSTITUTE SHEET (RULE 26) aerosuspension flow rate should be of the order of 10.6 m / s. The dust velocity is approximately equal to the aerosuspension flow rate.

For driving the rotor in motion choose synchronous motor at a speed of 3000 rev / min, t. E. N = 50 rev / sec, the diameter of the wire mesh d = 5 ^Yu-4-m, and I- -YU- ³ m 2. Substituting in equation (4), we have u _p = 19.6 m / s. Obviously, not one of the particles having a speed of 10.6 m / s can penetrate into the rotor cavity. Of course, this conclusion is not unconditional for a number of reasons. Firstly, a speed of 10.6 m / s was found without taking into account the presence of a grid, which reduces the area and requires either an increase in the flow rate, or a decrease in the productivity of the device, or an increase in the height of the grid, etc. These "or" are easily taken into account in more detailed calculations.

5. There are moments that must be practiced empirically. For example, each molecule of nitrogen, oxygen and carbon dioxide under normal conditions experiences about 5-10 ⁸ collisions per second. Nothing interferes with such a molecule, given the directivity of the aerosuspension flow and its sparseness in the near-grid space, “pull” a 10 A particle into the mesh cell. The random nature of the motion of molecules determines the equiprobability of the presence of velocities in all possible directions, including normal. The probability of this kind of occurrence can be estimated by the weight concentration of particles in the aerosuspension and purified gas.

From equation (3), we can find the time of the period of the change of mesh cells (g), m = 1.3 -J- ⁵ sec or a frequency of 0.8-10 ⁵ . This frequency is comparable to the collision frequency of molecules. It can be changed by changing the parameters of the grid, as well as the frequency of collisions of molecules, by changing the temperature and the degree of rarefaction. The influence of these changes on the productivity of rotoclone, its selectivity is significant.

A review shows that a rotoclone with a grid cannot guarantee complete exclusion of the passage of nanoparticles. However, it can be assumed that a significant part of them, with sufficient experimental study, can be delayed.

In crowded places (entertainment, medical, educational institutions, metro, other vehicles), air purification by rotoclone may be recommended. For example, with a productivity of 10 m ³ / sec and human needs 1 liter / sec, the rotoclone considered in the fourth example can provide 10 thousand people with purified air.

SUBSTITUTE SHEET (RULE 26) Table

SUBSTITUTE SHEET (RULE 26)

Claims

Claim

1. The method of separation of aerosuspension using filtering by a moving mesh, the action of centrifugal, centripetal forces, gravity and dust inertness, differences in the condensation conditions of the components of the aerosuspension, characterized in that the flow of the aerosuspension is directed parallel to the axis of rotation of the rotor from top to bottom; the purified gas is compressed in the axial cavity of the rotor and removed as intended; create a rarefaction of gas in the space near the grid.

2. A rotoclone comprising a circular cylindrical body, a rotor, air suspension distribution and separation cavities, a dust extraction cavity, aerosuspension supply nozzles, purified gas and dust exhaust and an engine having an elongated shaft that is inserted into the aerosuspension separation cavity where the rotor rotates, characterized in that the rotor casing is mesh; between its bottom in the form of a disk and a lid in the form of a circular ring fix the blades of a radial-axial centripetal compressor; in the separation cavity, dust is removed by scrapers moved by the rim.