RU179145U1 - Electrostatic air filter - Google Patents

Abstract

The utility model relates to electric air purifiers and can be used to trap dust, aerosols, fumes for ventilation systems, to clean technological gas-air emissions into the atmosphere. The technical objective of the claimed utility model is to simplify the design of the electrostatic filter, while maintaining a high degree of air purification, as well as reducing energy consumption and operating costs, increasing the efficiency of disposal of trapped particles. The problem is solved in that in a static filter containing an ionization chamber enclosed in a housing, consisting of sections including non-corona electrodes that are corona and parallel to the air flow, equidistant from the corona electrodes, and a precipitation chamber with filters consisting of plates located parallel to each other, the following changes have been made: - corona electrodes are made from a grid that is wound on the rod in the form of a brush; - non-corona electrodes have the shape of a cylinder; - filters of the precipitation chamber are made of plates of water oknistogo microporous insulating material disposed in the cassette, the distance between the cassettes is selected in the range of 50-200 mm.Krome addition, the device has entered a number izmeneniy.Zayavlyaemaya utility model has several advantages over the prior art, since it is structurally simple and compact and can trap dust of any composition, including oily, polymerizable compounds, paint, etc. Currently, based on the studies, technical documentation is being developed. 4 s.p. f-ly; 2 ill.

Description

The utility model relates to electric air purifiers and can be used to trap dust, aerosols, fumes for fresh air ventilation systems, to clean technological gas-air emissions into the atmosphere, and also as a fine cleaning step in air cleaning devices to protect against subsequent clogging of cleaning stages.

Most technological processes are accompanied by the emission of gases and dust into production facilities and the atmosphere. The intensification of production through the use of oxygen and natural gas has led to a sharp increase in the release to the atmosphere of process and ventilation gases contaminated with dust and harmful substances. Dust and harmful gases after release into the atmosphere change its composition, reducing the amount of oxygen necessary for the life of people and animals. Polluted air leads to a weakening of the human body, its resistance to infectious diseases and reduced performance. It also has a detrimental effect on the plant world, leading to its death, reduced yield; causes huge material damage due to corrosion of metals, destruction of building materials and structures.

The dust contained in the atmosphere absorbs light rays and traps the ultraviolet solar radiation necessary for life on Earth. Dust and acid fumes entering the atmosphere together with flue gases absorb water vapor from it, increasing the number of days with fogs. In most cases, process gases and ventilation air emitted into the atmosphere contain dust of ferrous and non-ferrous metals, valuable gaseous components that are irretrievably lost, so the release of such gases not only worsens the sanitary condition of the atmosphere, but also causes great material damage.

The importance of the problem of preserving the purity of atmospheric air and the danger of its increasing pollution are fairly well evaluated in all countries of the world. Reducing emissions of harmful substances into the atmosphere as a result of improving technological processes until the creation of waste-free technology, the creation of effective means of dust collection and purification of gases - these are ways to prevent air pollution.

Dry, wet and electrical methods are used to neutralize aerosols (dusts and mists). In addition, the apparatuses differ from each other both in design and in the principle of sedimentation of suspended particles. The basis of the dry apparatus are gravitational, inertial and centrifugal deposition mechanisms or filtration mechanisms. In wet dust collectors, dusty gases come into contact with a liquid. In this case, deposition occurs on drops, on the surface of gas bubbles or on a liquid film. In electrostatic precipitators, the separation of charged aerosol particles takes place on precipitation electrodes.

The choice of the cleaning method depends on many factors: the concentration of the extracted component in the exhaust gases, the volume and temperature of the gas, the content of impurities, the presence of chemisorbents, the possibility of using recovery products, the required degree of purification.

Cleaning air from dust can be coarse, medium or fine. During rough cleaning, only coarse dust with particle sizes of more than 50 microns is captured from the air, the degree of purification is relatively low - 70 ... 85%. With an average cleaning, dust with a particle size of up to 50 microns is retained, the degree of cleaning increases to 85 ... 95%. Fine cleaning allows you to capture dust with particle sizes less than 10 microns, the degree of purification with more than 95%. If the dust is not toxic, air after fine cleaning can be returned back to the room (air recirculation).

Under ordinary conditions, most of the gas molecules are neutral, i.e. It does not carry an electric charge of one or another sign. Due to the action of various physical factors, a gas always has a certain number of carriers of electric charges. Such factors include strong heating, radioactive radiation, friction, gas bombardment by fast moving electrons or ions, etc.

Ionization is the process or result of a process by which an electrically neutral atom or molecule acquires a positive or negative charge. When an atom absorbs excess energy, ionization occurs, a free electron and a positively charged atom are obtained. The term "air ions" in a broad sense refers to all particles of air that have an electric charge, whose motion depends on electric fields. Ionization is used for air purification, which is especially important in our time.

If a certain voltage is created between the electrodes in an electric field, then charge carriers, i.e. ions and electrons receive significant acceleration, and when they collide with molecules, the latter ionize. Ionization consists in the fact that one or more external electrons are knocked out of the orbit of a neutral molecule. As a result, neutral molecules are transformed into a positive ion and free electrons. This process is called impact ionization.

The ions and free electrons formed as a result of impact ionization under the action of the field also receive acceleration and ionize new molecules. Thus, the process is avalanche-like. However, as you move away from the corona electrode, the electric field is insufficient to maintain high speeds and the process of impact ionization gradually fades. Carriers of electric charges, moving under the influence of an electric field, as well as as a result of Brownian motion, collide with dust particles suspended in a gas stream passing through an electrostatic precipitator and transmit an electric charge to them.

The process of dedusting gas in an electrostatic precipitator consists of the following stages: dust particles passing an electric field with a gas stream receive a charge; charged particles move to the electrodes with the opposite sign; dust particles are deposited on these electrodes; dust deposited on the electrodes is removed. The main elements of the electrostatic precipitator are the corona and precipitation electrodes.

A two-zone electrostatic precipitator is known according to the patent of the Russian Federation No. 2144433, published on 30. 09.1998. The filter contains an ionizer enclosed in a housing, containing corona electrodes and plate non-corona electrodes mounted parallel to the air flow, a precipitator and a metal grid mounted perpendicular to the air flow, electrically connected to non-corona electrodes.

The disadvantage is the inconvenience of installing a metal mesh during the assembly and maintenance of the electrostatic precipitator.

In addition, in the known construction, submicron aerosol particles contained in the gas and generated by the corona discharge are not trapped by the precipitation electrodes and carried out with the purified gas to the outside; over time, the degree of purification in the dual-zone electrostatic precipitator decreases due to overgrowth of the plates of the precipitation electrodes.

A device is known (RF patent No. 94669, published: 05/27/2010 No. Bull. No. 15) for sanitary-hygienic processing of air, comprising an ionizer located in the channel for the flow of treated air, a dust filter, a catalytic filter with electrically conductive side plates, and in the channel a plasma torch installed in the form of a microwave resonator equipped with a system of sharp metal electrodes made of refractory material and installed in the region of the maximum electric field e line of field strength.

High-intensity electrostatic field and cold plasma provide effective bactericidal treatment of air flow. In the process of plasma generation, partial ionization of the air flow occurs, including the harmful impurities contained in it. As a result of this, molecules of harmful impurities receive a negative charge, which leads to their more active adsorption on the surface of the catalytic filter. Plasma-catalytic technology for purifying air from gaseous harmful substances is unique because it allows deep cleaning of the entire complex of toxic compounds to CO ₂ and H ₂ O, starting from low temperatures. In addition, cold plasma is unique in that, simultaneously with gas purification, the pathogenic air microflora are suppressed.

The proposed installation performs a full range of cleaning and deodorization of indoor air, including the additional effect of disinfection and decontamination of air, but it is very complex in design, energy-intensive and requires appropriate highly qualified staff

A device for air purification is known (RF Patent No. 2352382, published April 20, 2009 Bull. No. 11). The device comprises a mechanical coarse filter, a cylindrical capacitor consisting of an external grounded cylinder and a central corona wire electrode located along its axis, a coarse-flux electrostatic filter, a grounded cylindrical mesh, a photocatalytic filter, an activated carbon filter, a soft UV lamp, a cylindrical grounded body , a cylindrical high-voltage grid connected to a high-voltage source of positive voltage, m kroampermetr for measuring corona discharge current of a cylindrical condenser. The central corona wire electrode is made with a diameter of 100 to 200 μm and is connected to a high voltage voltage source.

As a result, highly effective air purification with its disinfection from pathogenic flora is achieved and the mass load of the dispersed phase on the catalyst and activated carbon is reduced, which supports the continuity of the filtration process.

The content of ozone and impurities of nitrogen oxides in the purified air does not exceed the MPC due to their adsorption by a carbon adsorbent.

The disadvantage is the complexity of the design, because it is required to have several sources of high-voltage power for corona and precipitation plates, as well as the use of activated carbon as a filter material, because clogging of pores of activated carbon by the filtrate of dispersed impurities, the use of high temperatures for reactivation of the adsorbent, and inefficient air purification from dispersed microcontaminations are not ruled out.

Closest to the claimed device is an electrostatic filter described in RF patent No. 61595 (published March 10, 2007 Bull. No. 7), which contains an ionization chamber enclosed in a housing, consisting of three or more ionization sections, including corona and installed parallel to the air plate non-corona electrodes, metal grids installed in the ionization chamber at the inlet and outlet perpendicular to the air flow and electrically connected to the non-corona electrodes, and measure, consisting of spaced parallel plates, wherein the discharge electrodes are located equidistant from the non-corona electrodes and grid. This arrangement of the corona electrodes ensures uniform formation of gas ions along the entire length of the corona electrode.

The settling chamber consists of plates with a conductive layer with alternating different or equal potential. The material for the precipitation plates can be an electrically conductive material, for example, an aluminum strip, an antistatic polymer with a specific surface resistance of not more than 10 ¹⁰ Ohms. The electrostatic filter operates as follows.

The cleaned gas enters the ionization chamber, where, passing between the corona electrodes, non-corona electrodes and grids, it acquires a charge. Then the charged dust particles enter the precipitation chamber, where, due to electrostatic forces, dust particles are deposited on the plates or in a porous conductive material having an electric potential.

The proposed design of the electrostatic filter allows us to solve the problem of increasing the efficiency of the electrostatic filter by increasing the active deposition area.

The disadvantage of the prototype is that the design of the electrostatic precipitator does not provide simplicity and convenience of removal and installation of metal grids at the inlet and outlet of the ionizer, which complicates the maintenance of the electrostatic precipitator.

In addition, a single-wire corona electrode is more prone to dust and aerosol overgrowth, which prevents the formation of ions.

The technical task of the claimed utility model is to simplify the design of the electrostatic filter while maintaining a high degree of air purification, as well as reducing energy consumption and operating costs, increasing the efficiency of disposal of trapped particles,

The problem is solved in that in an electrostatic filter containing an ionization chamber enclosed in a housing, consisting of sections including non-corona electrodes that are corona and parallel to the air flow, equidistant from the corona electrodes, and a precipitation chamber with filters consisting of plates located parallel to each other, are introduced changes, namely: the corona electrodes are made of a grid that is wound on the rod in the form of a brush;

- non-corona electrodes are in the form of a cylinder;

- filters precipitation chamber is made of one or more plates of fibrous microporous dielectric material placed in a cassette, and if there are several, then they are parallel with a distance between them equal to 50-200 mm

In addition, the filter material consists of thin fibers — it is either mineral wool (organosilicon fiber), or Dornit needle-punched material (polypropylene), or another thin dielectric fiber;

- the cassette can be made of any hard material, for example, of a coarse-mesh metal mesh with a mesh size of about 20-30 mm;

filters precipitation chamber can be made in the form of a cylinder with a diameter in the range of 100-300 mm

The corona electrode is made in the form of a brush, but from a metal mesh with a cell of about 0.5 mm, which is wound on a rod with a diameter of 6-8 mm (the brush of the corona electrode has a diameter of about 10-15 mm). Dust is easier to blow off the tip of the brush, so there is a greater reserve for dust absorption. The ionic wind that repels dust from the corona electrode is more uniform along the entire length of the brush. As a result, the deposition on the tip is less due to the presence of a more intense ionic wind, due to a more inhomogeneous electric field at the tip compared to the wire, which prevents the corona electrode from overgrowing.

The non-corona electrode is made in the form of a cylinder (diameter from 80 to 200 mm) for the following reasons. The ionizer is more compact, provided that the same ion density per unit m3 of air passing through the ionizer is created. Since the area of the deposition electrode in the cylinder is greater than in two parallel plates, therefore, the current densities will be higher. And accordingly, the concentration of ions with the same width and length of plate and cylindrical ionizers will be higher for a cylindrical one. And the higher the concentration of ions, the better the cleaning, while the greater the coagulation and the greater the potential that charges the filter cloth and the higher the electrostatic forces for trapping dust. And also, a more inhomogeneous electrostatic field around the charging fibers of the filter cloth and thereby higher the effect of polarization and dust collection in the inhomogeneous electrostatic field of the fibers of the filter cloth. The non-corona electrode is made in the form of a metal cylinder with a diameter of 100 mm for a voltage of about 15 kV. With increasing voltage of the power source, it is necessary to increase the diameter of the cylinder.

The filter material is placed in the cartridge and is located after the ionizer in the direction of air parallel to the air flow in one or more rows. In this case, the distance between the rows should be at least 50 mm, a maximum of 500 mm, if the distance between the cartridges is small, then the charged particle will not be able to go far between the cartridges, since the electrostatic forces will not allow.

As a result of lengthy studies conducted by the applicant with a standard pocket filter made of polypropylene, in which the filter cloth is made in the form of pockets and narrowed from the edge, it was found that in the narrowed region (about 50 mm) there was a breakthrough of model smoke. Therefore, with a distance of less than 50 mm, the degree of purification decreases, i.e. cleaning is not effective, and at more than 200 mm, the space of the filter unit is not rationally used, because the dimensions, and, consequently, the metal consumption of the installation increases.

The cassette can be made of any hard material, such as metal. It consists of two halves, consisting of corners around the perimeter, and inside a coarse mesh mesh with a mesh size of about 20-30 mm. Between these two halves is a filter cloth. The indicated mesh size is sufficient for the effective operation of the filter, and with greater filter stiffness decreases.

The filter material consists of thin fibers - it is either mineral wool (organosilicon fiber), or Dornit needle-punched material (polypropylene) - any thin dielectric fiber. It is important that this fibrous material is not in an electric field, but simply charged due to the charged dust (aerosols) absorbed by it. The formation of a layer of charged particles on the surface of the fibrous material, in contrast to uncharged particles, occurs in such a way that when the particles approach the layer and during deposition, the particles experience the repulsive effect of the particles already on the layer. Therefore, a loose layer is formed, which, unlike a non-loose layer, has less resistance and therefore the material will have a greater dust absorption.

It is known that ionized dust is captured by fiber filters significantly better than uncharged (Straus V. Industrial gas cleaning - M .: Chemistry, 1981.). So, Luvdgrey and Whiteby obtained empirical equations for the efficiency of the deposition of particles with a large electrostatic charge based on experiments with particles of methylene blue with a diameter of 1 μm. They found that the efficiency of a wool felt filter, which was 16% for uncharged particles, reached more than 99% when the particles acquired an elementary charge (p. 121, ibid.).

The filter of fibrous material can be made in the form of plates (s) or in the form of cylinders, but for cylindrical, air passage is required from the outside to the inside. According to our experimental data, when passing from inside to outside, the degree of purification is less.

The distance between the filter cloth and the ionizer can be any. The more, the even better, since the more time passes, the more the process of coagulation (coarsening) of dust. The area of the filter cloth should be such that the speed through it is in the range from 2 to 0, 1 m / s. In principle, these are standard speeds for filters. The lower the speed, the better the capture and the more dust the filter can catch due to the larger surface area of the filter cloth, however, in order to achieve a lower speed per unit area of the cloth, more surface area of the cloth is required, i.e. the increase in the dimensions of the precipitation chamber, which is impractical. The distance between the fibers, too, the smaller the more effective the cleaning.

The presence of the above characteristics allows us to solve the technical problem of the claimed utility model by changing the design of individual elements of the installation, reducing energy consumption by eliminating the electrical source for polarizing fiber filters, increasing the efficiency of the electrostatic filter by increasing the active deposition area, and reducing operating costs, because . does not require additional maintenance of fiber filters, they are simply disposed of and replaced with new ones, while a high (99%) degree of air purification is ensured.

The search in the patent and scientific and technical literature did not reveal a technical solution similar to that proposed in terms of the essential features, therefore, it corresponds to the “novelty” condition.

The essence of the utility model is illustrated by figures 1-2.

In FIG. Figure 1 shows the design of the main embodiment of the utility model. It shows an electrostatic filter for air purification, which contains a housing 1. comprising an ionization chamber 2 and a precipitation chamber 3. ionization chambers 2 include ionizers 4 (two ionizers 4 are shown, but depending on specific conditions, there may be more). Each ionizer contains a corona electrode 5, made in the form of a brush and non-corona electrodes 6, made in the form of a cylinder. The settling chamber contains plate fiber filters 7 located in cassettes 8 (Fig. 1 shows two parallel cassettes for each ionizer, but their number depends on the specific distance between the cassettes).

In FIG. 2 shows the design of an electrostatic filter, which differs from that shown in FIG. 1, only in that the fiber filter is made in the form of a cylinder 9.

In Figs. 1 and 2, it is shown that the ionizer electrodes are attached to the housing 1 through insulators 10. A source of high-voltage constant power supply (U), connected by a minus to the corona electrode and plus to the non-corona one, is conditionally shown. The voltage of the power source is 10-15 kV.

The number of sections may be larger, depending on the purpose of the electrostatic filter and the degree of contamination of the gas to be cleaned.

The following is a specific example of the implementation of the device and its operation.

Non-corona electrodes of the ionizer (4) are made of metal pipes with a diameter of 100 mm. The corona electrodes of the ionizer are made of a rod with a metal mesh wound on it with a diameter of 0.25 mm.

The corona 5 and non-corona 6 electrodes of the ionizer 4 should have a length in the range from 50 mm to 300 mm. In this case, the air flow rate must be at least 2 m / s through the ionizer. A speed of less than 2 m / s leads to rapid overgrowth of the ionizer electrodes. A flow of more than 2 m / s allows dust (aerosols) to slip through the ionizer without settling on the surface of the electrodes. The length of the ionizer electrodes of less than 50 mm does not allow creating the amount of charge necessary for effective cleaning on the surface of the filter sheets due to the low amount of ions in the air flow passing through the filter sheet, especially at high speeds of blowing the ionizer (more than 10 m / s). The length of the electrodes more than 300 mm does not lead to an increase in the number of ions in the air stream after the ionizer, provided that the air flow through the ionizer does not exceed more than 20 m / s. Exceeding air velocity of more than 20 m / s leads to a sharp increase in aerodynamic drag and the appearance of unwanted sound vibrations

The needle-punched material Dornit (polypropylene) was used as a filter material.

Air is supplied to the housing 1 by means of a fan (not shown in FIGS. 1 and 3).

Under the influence of forced ventilation, the cleaned air enters the ionization chamber 2. When a current is supplied from a constant electric current source (12 kV) to the corona 5 and non-corona 6 electrodes of the ionizers 4, an inhomogeneous electrostatic field is formed between the sharp edges of the brush and the inner surface of the cylinder of the non-corona electrode 6 under the action of which a corona gas discharge occurs at the tip of the brush. Particles contained in the cleaned air, passing through the corona discharge zone - the ionization zone of the cleaned air, acquire a positive electrical potential. Then air with ionized dust enters the precipitation chamber 3. During the passage of air from the ionizer to the cassettes 7 with a filter cloth, the ionized dust coagulates (coarsens) due to electrostatic forces. When passing through a filter dielectric cloth, dust is transferred from the dielectric fibers of the webs. It is important that this fibrous material is not located in a specially created electric field, but is simply charged due to the charged dust (aerosols) absorbed by it.

The formation of a layer of charged particles on the surface of the fibrous material, in contrast to uncharged particles, occurs in such a way that when the particles approach the layer and during deposition, the particles experience the repulsive effect of the particles already on the layer. Therefore, a loose layer is formed, which, unlike non-loose, has less resistance and therefore the material will have a greater dust absorption. Thus, the charge accumulated on the filter dielectric cloth, during charging with ionized dust, creates an electrostatic field that delays (filters) the dust entering the filter.

According to our data, the filter efficiency, which was 20% for uncharged particles of the welding aerosol, reaches more than 99% when the aerosol particles acquire an elementary charge.

The filter cloth is replaced by a signal from a standard differential pressure sensor, which is installed in a device (not shown). In this mechanical sensor, the so-called "dry contacts" of the relay are closed when a predetermined pressure drop is exceeded. As a rule, this value is in the range of 250-500Pa. The sensor closes the contacts and the lamp lights up or a signal is given to replace the filter sheets.

When using cylindrical cartridges 9, practically the principle of operation of the device does not change, but only, as noted above, the direction of the cleaned air (gas) flow changes.

When cleaning industrial gases, taking into account their specificity (metallic impurities and their size), coarse filters can be installed in front of the proposed fine filter: mechanical, magnetic or electric filters.

The advantages of the claimed utility model in comparison with the known ones include the fact that it is simple in design and more compact. To capture dust, for example, at an air flow rate of 1000 m ³ / h, a filter surface of about 0.5 m ² is required. To capture dust with a two-zone electrostatic precipitator, more than 5 m ^{2 of the} surface of the precipitation electrodes is required.

In addition, the device can pick up dust of any composition, including oily, polymerizable compounds, paint, etc. Since our filter material is disposable, it is not afraid of overgrowth of insoluble and difficult to wash out aerosols and smokes, in contrast to the need to forcibly clean plates at the electrostatic precipitator .

Currently, based on the studies, the development of technical documentation is ongoing.

Claims (5)

1. An electrostatic filter for air purification, comprising an ionization chamber enclosed in a housing, consisting of sections including non-corona electrodes corona and parallel to the air flow, equidistant from the corona electrodes, and a precipitation chamber with plate filters, characterized in that the corona electrodes are made of mesh , which is wound on the rod in the form of a brush, non-corona electrodes have the shape of a cylinder, and the filters of the precipitation chamber are made of fibrous microporous a dielectric material disposed in the cassette. 2. The electrostatic filter according to claim 1, characterized in that each lamellar fiber filter can be made of several parallel plates, and the distance between them is 50-200 mm 3. The electrostatic filter according to claim 1, characterized in that the filter material consists of thin fibers — it is either mineral wool — organosilicon fiber, or Dornit needle-punched material — polypropylene, or another thin dielectric fiber. 4. The electrostatic filter according to claim 1, characterized in that the cartridge can be made of any rigid material, for example, a coarse-mesh metal mesh with a mesh size of about 20-30 mm. 5. The electrostatic filter according to claim 1, characterized in that the fibrous filters of the precipitation chamber can be made in the form of a cylinder with a diameter in the range of 100-300 mm.

Images