JP3632579B2 - Air purification device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an air purification device that removes dust, odor / hazardous gas components, suspended microorganisms and the like from air and exhaust gas.
[0002]
[Prior art]
In general, a gas removal method is known in which a gas is brought into a plasma state by discharge and an odor / hazardous gas component is decomposed by generated radical species. For example, Japanese Patent Laid-Open No. 2-52021 proposes an exhaust gas treatment apparatus of a type in which particles made of a ferroelectric material are arranged between a pair of electrodes to generate a discharge.
FIG. 4 is a side sectional view of a conventional exhaust gas treatment device (air purification device) disclosed in this publication.
In the figure, 1 is a cylindrical tube, 2 is an air inlet, 3 is an air outlet, 4 is an air passage, 5 and 6 are a pair of copper electrodes having air permeation holes, 7 is a partition wall, and 8 is a particle size of about 3 mm. This is a gas treatment layer filled with a large number of ferroelectric particles made of spherically processed barium titanate or the like. Reference numeral 9 denotes a reaction layer filled with an adsorbent such as activated carbon, and acts as a gas removal filter in cooperation with the gas treatment layer 8. Reference numeral 10 denotes a pulse generating means or an AC power source for applying a high voltage of about 5 kV between the pair of copper electrodes 5 and 6.
[0003]
In such a configuration, air containing an odor gas component is applied from the air inlet 2 of the cylindrical tube 1 to the air path of the cylindrical tube 1 by a blower such as a pump or a fan while a high voltage is applied between the copper electrodes 5 and 6. When introduced into 4, a part of the air is in a plasma state due to the discharge generated around the ferroelectric particles. As a result, surrounding water molecules, oxygen molecules, and the like are dissociated, and radical species with high chemical activity are generated. The radical species has an extremely strong oxidizing power, whereby the odorous gas component is decomposed into molecules having a simple structure and is not brominated. The odor gas component remaining without being decomposed is adsorbed and removed by the adsorbent filled in the reaction layer 9, and clean air from which the odor gas component is almost completely removed is discharged from the air outlet 3 of the cylindrical tube 1. Is done.
[0004]
[Problems to be solved by the invention]
Conventional air purifiers are configured as described above. When trying to purify air that contains dust or dust in addition to odors and harmful gas components, it is necessary to remove dust and dust first. It was necessary to dispose a filter or device for dust removal such as a HEPA filter or an electrostatic precipitator. For this reason, the entire apparatus becomes large, and it is difficult to make it compact.
[0005]
Further, ferroelectric particles having a particle size of about 3 mm are used. However, since the particles are large, the distance between the particles is large, and the discharge start voltage is high. In order to lower this discharge start voltage, a ferroelectric substance having a large dielectric constant is usually used, but conversely, the amount of generated nitrogen oxide increases, corrosion of the discharge electrode is accelerated, and the replacement cycle (life) is shortened. It was getting shorter.
[0006]
Also, the surface of activated carbon used as an adsorbent has a catalytic ability to accelerate the reaction between the adsorbed substance and radical species, but when nitrogen dioxide in nitrogen oxides is adsorbed on the surface, It reacted with water molecules adsorbed on the surface, generating nitrate ions at the reaction site, and deprived the catalytic activity from this site.
Therefore, when the nitrogen oxide increased, the catalytic ability gradually disappeared from the activated carbon surface, and as a result, the radical reaction of the whole activated carbon was lowered and the removal ability was also lowered.
[0007]
The present invention has been made to solve such problems, and simultaneously removes dust, odor / hazardous gas components, and suspended microorganisms, is compact and generates a small amount of nitrogen oxides. An object of the present invention is to provide an air purification device having a long activated carbon life.
[0008]
[Means for Solving the Problems]
An air purifying apparatus according to the present invention is provided with a conductive catalyst filter disposed in an air passage and facing the windward side of the catalyst filter, and a high voltage is applied between the catalyst filter and the air filter. Disposed between a discharge electrode and a ferroelectric filter disposed between the discharge electrode and the catalyst filter and having a ferroelectric as a constituent element. The ferroelectric filter is a ferroelectric fiber or a ferroelectric on the surface. It is made of an inorganic material to which particles are attached .
[0010]
The dielectric constant of the ferroelectric is set to be 50 or more and 3000 or less.
[0011]
Further, the discharge electrode or the catalyst filter is made of activated carbon fiber.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1
1 is a side sectional view of an air purification device according to Embodiment 1 of the present invention. Parts that are the same as or equivalent to those in the conventional example are denoted by the same reference numerals, and description thereof is omitted. Different parts will be described.
In the figure, 11 is a discharge electrode made of metal that is arranged on the air path in a direction orthogonal to the air flow, and is configured to allow air to pass through, and 12 is a direction downstream of the discharge electrode 11 and orthogonal to the air flow. A catalytic filter that is electrically conductive and air permeable and accelerates chemical reaction with radical species; 13 is a pulse generating means for applying a high voltage between the discharge electrode 11 and the catalytic filter 12 or an alternating current Power supply.
14 is a fiber made of a ferroelectric material such as zirconium having a wire diameter of about 10 μm (hereinafter referred to as a ferroelectric fiber) processed into a felt-like sheet having a thickness of about 1.5 mm, which is bent into a pleated shape, Is a ferroelectric filter configured to have a thickness of about 5 mm. Reference numeral 15 denotes a blower.
[0013]
The operation of the air purification apparatus configured as described above will be described with reference to FIG.
In the figure, contaminated air containing dust, odorous gas components, and floating microorganisms is sucked by a blower 15 disposed in the subsequent stage, and is guided from the air inlet 2 through the discharge electrode 11 to the ferroelectric filter 14.
[0014]
Here, a high voltage is applied between the discharge electrode 11 and the catalyst filter 12 by the AC power source 13, and a strong electric field is generated between the discharge electrode 11 where the ferroelectric filter 14 is installed and the catalyst filter 12. Yes. Due to this strong electric field, polarization occurs between the ferroelectric fibers constituting the ferroelectric filter 14, discharge occurs, and ion shower occurs. At the same time, a part of the surrounding air is in a plasma state to generate radical species.
[0015]
As a result, the contaminated air passing through the ferroelectric filter 14 is mixed with ion showers and radical species, and ions adhere to the contaminant, or a chemical reaction (oxidative decomposition) occurs between the contaminant and the radical species. . This point will be described.
[0016]
First, the dust is charged with ions attached by an ion shower. The charged dust adheres to the surface of the ferroelectric fiber by Coulomb force and is removed from the contaminated air. The dust adhering to the fiber is oxidized by radical species, and the residue that cannot be oxidized eventually remains as ash.
[0017]
Odor gas components are rapidly oxidized by radical species, decomposed into simple molecules, and are not brominated. At the same time, the odor gas component remaining without being decomposed is physically adsorbed by the catalyst filter 12 at the subsequent stage, and is oxidatively decomposed by a chemical reaction with the incoming radical species. This two-stage decomposition action removes almost all odorous gas components.
[0018]
Furthermore, the suspended microorganisms are on the order of microns, and like dust, are charged by an ion shower and captured by the ferroelectric filter 14 by Coulomb force. The trapped microorganisms are sterilized by destroying the cell wall by the oxidizing action of radical species. The impurities remaining as a result of the sterilization are oxidized by radical species, and the residue that cannot be oxidized eventually remains as ash in the ferroelectric filter 14.
[0019]
Note that the ash left after the dust and airborne microorganisms are oxidized needs to be removed by regular water washing or the like in order to reduce the removal ability.
[0020]
Thus, contaminants can be captured and oxidatively decomposed by ion shower and radical species caused by discharge, and an air purification device having three functions of dust removal, deodorization, and sterilization can be configured in a compact manner. In addition, it is possible to expect an apparatus having a larger removal capability and a longer life than removing the catalyst and activated carbon by a single apparatus.
[0021]
Embodiment 2
FIG. 2 shows an enlarged view of the main part of the ferroelectric filter of the air purifying apparatus according to Embodiment 2 of the present invention. The basic configuration is the same as in the first embodiment. The filter base material is different, and this point will be described.
In the figure, 16 is a fiber made of an inorganic material such as glass or ceramics, which is a substrate of a ferroelectric filter, and 17 is a ferroelectric particle made of barium titanate or the like attached to the surface of the fiber 16 made of an inorganic material. .
In the first embodiment, the discharge occurs between the ferroelectric fibers constituting the ferroelectric filter 14, whereas in the present embodiment, the discharge occurs between the ferroelectric particles 17 attached to the fibers 16 made of an inorganic material.
[0022]
Here, the relationship that holds between the dielectric constant and the amount of attachment of the ferroelectric, the discharge start voltage, and the amount of nitrogen oxide generated will be described based on the experimental results.
[0023]
Taking the barium titanate as a ferroelectric, the relationship between the dielectric constant, the discharge starting voltage, and the amount of nitrogen oxides generated was examined by experiments.
The results are shown in FIG. In the figure, the horizontal axis represents the dielectric constant, the vertical axis represents the discharge start voltage on the left, and the amount of nitrogen oxide generated on the right.
Here, the experimental conditions are that the size of the duct cross section is 10 cm × 10 cm, the thickness of the filter 12 is 10 mm, the basis weight of the ferroelectric is 10 g per square meter, and the flow rate is 1 m / s.
[0024]
As is apparent from the figure, the discharge start voltage increases rapidly as the dielectric constant decreases, and discharge is less likely to occur. On the other hand, the amount of nitrogen oxide generated increases substantially in proportion to the dielectric constant. Thus, the discharge start voltage and the amount of nitrogen oxide generated tend to contradict each other, and the dielectric constant is determined by the trade-off between the discharge start voltage and the amount of nitrogen oxide generated.
Therefore, if a standard that suppresses the discharge start voltage to 10 kV or less and the generation amount of nitrogen oxide to 1 ppm or less is set, 50 to 3000 is determined as the range of the dielectric constant.
[0025]
On the other hand, although not shown, the same tendency was observed for the relationship between the amount of deposition, the discharge start voltage, and the amount of nitrogen oxide generated.
That is, according to an experiment using barium titanate having a dielectric constant of 3000, the discharge starting voltage is 10 kV or more when the applied amount is 2 g or less per square meter, and the amount of nitrogen oxide generated rapidly increases when the applied amount is 20 g or more per square meter. As a result, it exceeded 1 ppm.
Therefore, if the discharge start voltage is suppressed to 10 kV or less and the generation amount of nitrogen oxide is suppressed to 1 ppm or less, 2 to 20 g is determined as the range of the amount of adhesion per square meter.
[0026]
Further, when the dielectric constant or the amount of attachment was within the above range, no difference was observed in the removal performance.
[0027]
In addition, the process of generating ion showers and radical species by discharge and thereby removing contaminants such as dust, odorous gas, and floating microorganisms is the same as that in the first embodiment, and therefore will be omitted.
[0028]
As described above, a ferroelectric particle such as barium titanate is attached to the surface of a fiber made of an inorganic material, and the discharge start voltage and nitrogen can be reduced without impairing the removal performance by selecting the dielectric constant and the attached amount from the above ranges. It is possible to obtain an air purification device that reduces the amount of oxide generation. Moreover, since the generation amount of nitrogen oxides is reduced, the lifespan of the discharge electrode and the activated carbon is extended, and the economy is improved.
[0029]
Furthermore, in Embodiment 1 or 2, activated carbon fiber may be used for the base material of the discharge electrode 11 or the catalyst filter 12.
Activated carbon fibers have a catalytic ability to accelerate the reaction with radical species, like activated carbon, but are far superior to activated carbon in terms of conductivity and adsorptivity.
For this reason, when the catalyst filter 12 is constituted by using activated carbon fibers as a base material, the undecomposed odor gas component reaching the subsequent catalyst filter 12 is almost completely physically adsorbed. The adsorbed odor gas component is oxidatively decomposed into simple, odorless and harmless molecules by the radical species coming in. Thereby, the activated carbon fiber is regenerated and can be prepared for the adsorption of the next odor gas component. In this way, the odorous gas component is completely removed.
[0030]
Moreover, when activated carbon fiber is used for the discharge electrode 11 as a base material, it not only functions as a normal discharge electrode but also removes and decomposes odorous gas components.
That is, a part of the odor gas component is adsorbed by the discharge electrode 11 based on activated carbon fiber when passing through the discharge electrode 11. The adsorbed odor gas component is oxidized and decomposed into simple, odorless and harmless molecules by radical species, and the activated carbon fiber is regenerated, which is the same as the case of the catalyst filter 12.
[0031]
In this way, by using activated carbon fibers having an extremely high adsorption capacity, highly toxic gas components that are hardly contained in the atmosphere and are difficult to remove, such as dioxins, PAH (polycyclic aromatic hydrocarbons). (Abbreviation of Hydrocarbons) and the like can be reliably captured. In addition, the substance captured in this manner is also oxidatively decomposed by the radical species that come in as described above, and is surely detoxified.
[0032]
Furthermore, a dust filter having heat resistance may be provided on the windward side of the discharge electrode 11 in the configuration of the first or second embodiment.
This is intended to purify high-temperature pollutant gas such as diesel exhaust gas, and the heat-resistant dust filter disposed on the windward side of the discharge electrode 11 functions as a pre-filter. Therefore, a dust filter having a coarser particle size than the ferroelectric filter, specifically, a medium dust removing ability of about 50% of the JIS colorimetric method is selected.
[0033]
Further, since exhaust gas such as diesel is at a high temperature, the discharge electrode 11 is made of a heat-resistant metal, and the ferroelectric filter is made of a heat-resistant ceramic fiber with a catalyst and ferroelectric particles, or a ferroelectric particle having catalytic ability. It has a configuration attached.
Further, since exhaust gas such as diesel contains a large amount of nitrogen oxides, the catalyst attached to the ceramic fiber of the ferroelectric filter 14 or the ferroelectric particles having catalytic ability and the catalyst filter are reduced. Having a catalytic ability.
[0034]
Exhaust gas such as diesel engine contains a large amount of dust, sulfur oxide, nitrogen oxide and the like. In the exhaust gas, dust having a large particle size is first removed by the dust removal filter and guided to the ferroelectric filter 14 through the discharge electrode 11. Here, the small particles that have not been removed by the dust filter are charged by the ion shower and adhere to the fiber by the Coulomb force.
Sulfur oxides, odors and harmful gas components are decomposed by radical species. Further, the nitrogen oxides are decomposed by the reducing catalyst constituting the ferroelectric filter 14 and the catalyst filter 12.
[0035]
As described above, in the configuration of the first embodiment, a medium performance dust removing filter having heat resistance is disposed on the windward side, and the heat resistant filter base material, reducing catalyst and ferroelectric particles, or reduction By using ferroelectric particles having a catalytic ability, a compact air purification device capable of purifying high-temperature exhaust gas such as diesel can be obtained.
[0036]
【The invention's effect】
Since the air purifying apparatus according to the present invention is configured as described above, the following effects can be obtained.
[0037]
A discharge electrode 11 having a air permeability, between the catalytic filter 12 having a air permeability and conductivity, ferroelectric filter formed by an inorganic material impregnated with ferroelectric fiber or ferroelectric particles, 14 is inserted and a high voltage is applied between the discharge electrode 11 and the catalyst filter 12 to generate ion showers and radical species, so that dust, odor / toxic gas components, suspended microorganisms, etc. can all be removed. A long-life and compact air purification device can be obtained.
[0038]
Further, since the ferroelectric filter 14 is made of an inorganic material , the flame retardance of the entire filter is improved, and a highly safe air purifying device can be obtained.
[0039]
In addition, since the dielectric constant of the ferroelectric material is 50 or more and 3000 or less, the discharge start voltage is low and the generation amount of nitrogen oxides is reduced without impairing the removal performance against dust, odor / hazardous gas components, and floating microorganisms. An air purification device is obtained.
Moreover, the lifetime of the discharge electrode 11 and activated carbon is extended by reducing the generation amount of nitrogen oxides, and an economical air purification device can be obtained.
[0040]
In addition, since the discharge electrode 11 or the catalyst filter 12 is made of activated carbon fiber, it can remove a highly toxic gas component that is hardly contained in the atmosphere and difficult to remove, and has high gas removal performance. The air purification apparatus which has is obtained.
[0041]
Furthermore, a dust filter with heat resistance, a discharge electrode, and a catalytic filter consisting of a reducing catalyst with conductivity are arranged in order from the upstream side, and a reducing substance with a ferroelectric as a component between the discharge electrode and the catalyst filter. Since a ferroelectric filter formed from fibers with catalytic ability was inserted and a high voltage was applied between the catalyst filter and the discharge electrode, dust, sulfur oxide, nitrogen oxide in high temperature exhaust gas Thus, a long-life and compact air purification device that can remove all of them can be obtained.
[Brief description of the drawings]
FIG. 1 is a side cross-sectional view of an air purification device according to Embodiment 1 of the present invention.
FIG. 2 is an enlarged view of a main part of a ferroelectric filter of an air purification device according to a second embodiment of the present invention.
FIG. 3 is a diagram showing a relationship between a dielectric constant, a discharge start voltage, and a nitrogen oxide generation amount according to Embodiment 2 of the present invention.
FIG. 4 is a side sectional view of a conventional exhaust gas treatment apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Cylindrical tube 2 Air inlet 3 Air outlet 4 Air path 5 Copper electrode 6 Copper electrode 7 Partition wall 8 Gas treatment layer 9 Reaction layer 10 AC power source 11 Discharge electrode 12 Catalytic filter 13 AC power source 14 Ferroelectric filter 15 Blower 16 Fiber 17 made of inorganic material Ferroelectric particles

Claims (3)

A conductive catalyst filter disposed in the air passage; a discharge electrode provided opposite to the windward side of the catalyst filter; and a high voltage applied between the catalyst filter; and the discharge electrode A ferroelectric filter disposed between the catalyst filter and a ferroelectric as a component; and
The air filter according to claim 1, wherein the ferroelectric filter is made of a ferroelectric fiber or an inorganic material having ferroelectric particles attached to the surface. The air purification apparatus according to claim 1, wherein the ferroelectric has a dielectric constant of 50 or more and 3000 or less. The air purification apparatus according to claim 1 or 2, wherein the discharge electrode or the catalyst filter is made of activated carbon fiber.

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