JP2006192013A - Air cleaning device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air cleaning device for efficiently decomposing a volatile organic substance included in air into carbon dioxide and efficiently removing the organic intermediate which can not be decomposed into carbon dioxide. <P>SOLUTION: The air cleaning device comprises a suction part for sucking air, an air cleaning part for cleaning the sucked air and an exhausting part for exhausting the clean air. The air cleaning part is characterized by a plasma discharge electrode having a micro-electrode element with a plurality of pointed projections on a dielectric thin film substrate and a capturing part for capturing a plasma-discharge-processed sol or gel substance included in air. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an air cleaning device, and more particularly to an air cleaning device capable of decomposing and removing volatile organic substances contained in the atmosphere.

In recent years, volatile organic substances generated from industrial materials and home building materials have become a major issue as contaminants in the semiconductor industry or as causative substances of sick house syndrome. Therefore, research and development of methods for effectively removing volatile organic substances present in the atmospheric environment are being actively conducted.
Conventionally, plasma discharge (Patent Document 1, Patent Document 4, Patent Document 5, Non-Patent Document 6) and corona discharge (Patent Document 2, Non-Patent Document 2, Non-Patent Document 3) are methods for removing volatile organic substances. Such as a discharge device, a physical device using electron beam generation (Patent Document 3), a chemical decomposition device using ozone generation (Non-Patent Document 1), a chemical decomposition device using a photocatalyst or an oxidation catalyst (Non-Patent Document 4, Non-Patent Document 4, Patent Document 5), a processing apparatus for burning an adsorbed volatile organic substance, and various processing apparatuses composed of a combination thereof are known.
The method of removing volatile organic substances by plasma or corona discharge is started by collision reaction between high energy electrons generated by discharge and organic compounds, and at the same time, carbon monoxide by reaction with oxygen active species generated from the atmosphere. It is estimated to be decomposed to carbon dioxide. However, the decomposition process includes various intermediates and some secondary products are generated as a result of discharge, and it is difficult to completely convert them into carbon dioxide or the like.

The method using ozone is a technique in which ozone generated from an ozone generator is thermally decomposed and oxidatively decomposed by reaction of chemically active oxygen atoms or hydroxy radicals with a volatile organic compound. In this case as well, it is difficult to decompose to carbon dioxide, and harmful oxides are also generated.
A method using a photocatalyst or an oxidation catalyst is a method in which the catalyst is activated by light irradiation or heat to accelerate the decomposition reaction of the volatile organic compound and remove it. Even by this method, a by-product that cannot be decomposed to carbon dioxide is generated.
As described above, there is no problem if the volatile organic compound is completely decomposed to carbon dioxide, but generally, the decomposition process of hydrocarbons and derivatives thereof includes active chemical species and reaction intermediates as intermediates. Chemical substances other than carbon dioxide are secondarily generated via these. Among them are aldehydes that are harmful to the human body. For example, when toluene is subjected to thermal ozone treatment, benzaldehyde, phenols, and the like are generated by the reaction of the intermediate with active oxygen atoms, hydroxy radicals, and the like (FIG. 6).
Therefore, an apparatus based on a combination of the above-described methods, for example, one in which a catalytic device is arranged after the discharge device to promote decomposition to carbon dioxide in a two-stage manner is also known. However, when a large amount of active species or intermediate reactants contained after discharge stays on the catalyst surface, the catalyst is deteriorated. In general, when a plurality of methods are combined, there is a problem that the apparatus becomes large. Moreover, when using a catalyst, thermal energy, etc. in addition to electric power, the maintenance burden is a major drawback.
JP 2000-279492 A JP 2001-62287 A JP 2003-144841 A JP 2004-283742 A JP 2004-290789 A JP 2004-105517 A JP 2004-215811 A Japanese Patent Application No. 2003-341192 G.Xiong, JAKoiel, J.Pawlisyn: J. Chromatography A, 1025, 57 (2004) W. Tanthapanichakoon, N. Sano, T. Charinpanitkul, N. Dhattavorn, S. Chaiyo, H. Tamon: J. Chem. Eng. Jpn, 36,946 (2003) D. Li, D. Yakushiji, S. Kanazawa, T. Ohkubo, Y. Nomoto: J. Electrostatics, 55, 311 (2002) Z. Pengyi, L. Fuyan, Y. Gang, C. Qing, Z. Wanpeng: J. Photochem. Photobio. A, Chem. 156, 189 (2003) K. Sekiguchi, A. Sanada, K. Sakamoto: Catalysis Commun. 4, 247 (2003) R. Rudolph, K.-P. Francke, H. Miessner: Plasma Chem Plasma Phys. 22, 401 (2002)

  The present invention relates to a sol-like or gel-like substance that is a by-product generated in the decomposition process in a processing apparatus that decomposes volatile organic substances in the atmosphere to carbon dioxide by high-energy electrons generated by plasma discharge. It is to provide a small apparatus that can easily remove chemically active species and reaction intermediates at normal temperature without using ozone, catalyst, or thermal energy.

In order to achieve the above object, the inventors of the present invention have intensively studied the treatment of a volatile organic substance by plasma discharge using a fine electrode element, particularly the decomposition of toluene, which is a typical volatile organic substance. As a result, toluene is efficiently decomposed to carbon dioxide as the main process, but some reaction intermediates are generated and rapidly condensed in the charged particle atmosphere generated simultaneously from the fine electrode elements. The presence of aerosolized particles was confirmed.
It has been confirmed that when these particle groups are present in the processing vessel as they are, an oxide is generated by a reaction with an oxidizing medium, for example, nascent oxygen or hydroxy radical generated by thermal decomposition or photolysis of ozone. .
On the other hand, the intermediates themselves, which are particles that are produced during processing by plasma discharge of volatile organic substances, are active and easily adsorbed on the surface of porous insulating materials such as paper and plastics, typically filter paper. And found to polymerize. The present invention has been made based on these findings in plasma discharge of volatile organic substances.

That is, the present invention is an air purifying device comprising a suction part for sucking air, an air purification part for purifying the sucked air, and an exhaust part for exhausting the purified air, wherein the air purification part is disposed on the dielectric thin film substrate. An air cleaning device comprising: a plasma discharge electrode having a fine electrode element having a plurality of pointed protrusions; and a trap for capturing a sol-like or gel-like substance in air subjected to plasma discharge treatment.
In the present invention, the plasma discharge electrode can be operated at 50 to 100 KHz and 3.0 to 5.0 KV.
Furthermore, in the present invention, the dielectric thin film substrate can be a mica, and a plate-like metal plate on which fine electrode elements are processed can be obtained. By doing in this way, a plasma discharge electrode can be made high output.
In addition, the present invention can also include an ion generator that charges a sol or gel substance in air that has been subjected to plasma discharge treatment. By doing in this way, a capture part can be charged to plus or minus, and the efficiency of a capture part can be raised further.
Furthermore, in the present invention, the capturing part can be a porous thin film.
Paper or plastics can be used as the porous thin film. In general, the surface of a porous thin film that is an insulator is positively or negatively charged, and in order to form a non-uniform electric field, the charged sol or gel substance can be electrostatically collected. And the collection efficiency can be improved.
Here, the porous thin film can take a different arrangement. In this case, since it becomes possible to increase the effective collection area in a collection part, collection efficiency can be improved.
Moreover, in this invention, it can be set as the structure which can replace the whole capture | acquisition part. By using inexpensive paper or plastic thin film as a replacement part, it is possible to easily and inexpensively dispose of the sol or gel substance.

  According to the present invention, a volatile organic substance can be efficiently converted into carbon dioxide, and active chemical species that are by-produced without being converted can be easily removed at room temperature without using ozone, catalyst, or thermal energy. Equipment can be provided.

Hereinafter, the present invention will be described in detail.
The main volatile organic substances in the atmosphere to be treated by the air cleaning apparatus of the present invention are volatile organic compounds (VOCs) such as hydrocarbons, alcohols, aldehydes, and organic acids.
The fine electrode element used in the air cleaning device of the present invention is obtained by connecting a plurality of pointed protrusions as discharge electrodes on a dielectric thin film substrate, and from a linear fine electrode circuit close to the pointed protrusions as a counter electrode. Is formed.
Such an electrode has already been developed and filed by the present inventors (Patent Document 8). Both electrodes are shielded by a dielectric thin film, and can emit high-energy electrons, ions, and radicals when a high voltage is applied.
The outline is shown in FIG. A fine electrode element 211 and a ground electrode 213 are provided on the electrode substrate 215, and are connected to a power source by a conducting wire 212 and a conducting wire 214, respectively.
The power source has a frequency of 50 to 100 KHz and a peak voltage of ± 3.0 to 5.0 KV. A typical example is a high-frequency power source using a piezoelectric transformer.
Here, when the frequency is 50 KHz or less or 3.0 KV or less, the decomposition efficiency is reduced, and when the frequency is 100 KHz or more and 5.0 KV or more, the electrode is deteriorated.
In the air cleaning apparatus of the present invention, air containing a volatile organic substance reaches the fine electrode element substrate and causes a collision reaction with high energy electrons, ions, and oxygen radicals, and is mostly decomposed to carbon dioxide. . However, at the same time, active chemical species containing ions produced as a by-product in the decomposition process are generated on the substrate and floated as a sol or gel substance, which circulates into an insulating material thin film for adsorption and polymerization. It is the apparatus characterized by the structure put in this way.

In particular, active chemical species are generated in the vicinity of the substrate that collides with high-energy electrons and ions, and these active chemical species other than carbon dioxide are associated and charged in the course of the pathway. To change. This reaction process depends on the flow rate of the atmosphere, but usually occurs up to 30 cm from the substrate. Therefore, in the present invention, it is possible to obtain an insulating thin film in which chemically active species charged within 30 cm from the substrate are efficiently adsorbed and converted to a stable resinous organic substance after adsorption and immobilized. The insulator thin film placed in the vicinity of the microelectrode element substrate may be a thin film made of paper or plastics. The insulating thin film is preferably porous, and filter paper is particularly preferably used.
Further, the arrangement is not limited to this, although it may be arranged in a step so as not to disturb the circulation of the atmosphere to be treated and so that the active chemical species floating can be captured effectively.
Furthermore, the ion generator for charging the sol or gel substance in the air subjected to the plasma discharge treatment can be shared with the plasma discharge electrode. Thus, the sol-like or gel-like substance in the air subjected to the plasma discharge treatment can be easily trapped by the trapping portion by being charged by positive or negative ions generated at the same time. At this time, the insulating thin film of the capturing part is preferably charged.

According to the present invention, an aerosol composed of an active intermediate that is a by-product other than carbon dioxide can be condensed and fixed on a filter paper or a plastic film, so that a large amount of air can flow. In addition, the amount of the resin immobilized from the aerosol substance is very small, and the insulating thin film can be used for a long time. Furthermore, it is preferable that the entire capturing portion is made of paper and has a structure that can be replaced as appropriate, since it can always be kept clean.
When the immobilization material is accumulated, the insulating thin film is easily replaced, and the used insulating thin film is an organic polymer resin and can be incinerated.
Further, the present invention generates high-energy electrons and oxygen radicals by discharge, efficiently decomposes volatile organic substances to carbon dioxide, and simultaneously captures active chemical species by-produced immediately after the generation. In order to perform the capturing process as close as possible, a fine electrode element in which a dielectric discharge circuit is miniaturized is used as a discharge body.

The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
Example 1
FIG. 2 shows an example of the air cleaning device of the present invention.
From the suction part 1, the atmosphere containing toluene is guided to the air cleaning part 2, and the atmosphere containing toluene is applied to the vicinity of the fine electrode element 221 of the plasma discharge electrode 2-1.
First, in order to obtain the decomposition rate in the closed space, an experiment was conducted by introducing the atmosphere containing toluene from the suction portion and then closing the inlet and outlet valves after a certain period of time. The microelectrode element 221 was driven at 67 KHz and 3.5 KV.
It is considered that the atmosphere containing toluene is decomposed in the air cleaning unit 2 and becomes an active intermediate that is carbon dioxide and a sol or gel substance.
Then, it passes through the insulating thin film (filter paper part) of the capturing part 3 and is discharged from the exhaust part.
It is desirable that the insulating thin film (filter paper portion) is disposed in the vicinity of the electrode element substrate so as not to significantly impede the flow of the atmosphere to be processed and to effectively capture the floating active chemical species.
FIG. 3 is a diagram showing the measurement results with a gas chromatograph mass spectrometer sampled before and after treatment in the treatment apparatus of the present invention in an atmosphere containing about 30 ppm of toluene. FIG. 4 is a graph showing the decomposition rate of toluene when a fine electrode element is operated for a certain period of time in a glass container having a capacity of 75 cm ^{3 with} the atmosphere closed containing about 30 ppm of toluene. It can be seen that by using the air purification element of the present invention, a decomposition rate of 99% or more is obtained by applying a voltage for about 30 minutes in a closed space.
A photograph of the plasma discharge electrode used here is shown in FIG. 7, and a photograph of the plasma discharge is shown in FIG.

Except for changing the amount of toluene, continuous decomposition of toluene mixed in air was performed under the same conditions as in Example 1.
FIG. 5 shows the processing apparatus according to the present invention, in which an atmosphere containing 1 to 100 ppm of toluene is circulated with a constant residence time, and the decomposition rate of toluene is calculated from measurements with a gas chromatograph mass spectrometer sampled before and after the treatment. It is a figure which shows the result.

(Comparative example)
FIG. 6 shows the results of measurement with a gas chromatograph mass spectrometer sampled in a state in which 10 to 20 ppm of ozone from an ozone generator was simply mixed in an atmospheric path containing about 20 ppm of toluene. It can be seen that a large amount of benzaldehyde and the like, which were hardly detected in FIG.

  The air purifying apparatus of the present invention can be widely used as a small air purifying apparatus capable of decomposing organic compounds present in the air by being installed indoors or in a factory. In addition, the maintenance is simple and the running cost can be reduced as compared with the conventional large-sized apparatus.

Plasma discharge electrode The schematic of the processing apparatus used in the Example. The chromatograph which shows the measurement result by the gas chromatograph mass spectrometer before use of this apparatus of the air containing toluene, and after a process. (1) is a chromatograph before treatment, and (2) is a chromatograph after treatment. The graph showing the toluene residual rate at the time of applying a fine electrode element within an airtight container. The graph which shows the ratio decomposed | disassembled when the atmosphere containing toluene is processed with the apparatus of this invention in a flow-type container. Chromatograph by gas chromatograph mass spectrometry measurement after ozone treatment of air containing toluene. (2) is an enlarged view in which the total ion intensity of (1) is increased 10 times. Real photo of plasma discharge electrode Real photo of plasma discharge electrode during plasma discharge

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Suction part 2 Air purification part 21 Plasma discharge electrode 211 Fine electrode element
212 conductor
213 Ground electrode 214 Conductor
215 Electrode substrate 3 exhaust part

Claims (9)

  An air purifier comprising a suction part for sucking air, an air purification part for purifying the sucked air, and an exhaust part for exhausting the purified air, wherein the air purification part has a plurality of pointed protrusions on the dielectric thin film substrate. An air cleaning apparatus comprising: a plasma discharge electrode having a fine electrode element and a trap for capturing a sol or gel substance in air subjected to plasma discharge treatment.   The air cleaning apparatus according to claim 1, wherein the plasma discharge electrode operates at 50 to 100 KHz and 3.0 to 5.0 KV.   The air cleaning device according to claim 1 or 2, wherein the dielectric thin film substrate is mica and is a plate-like metal plate on which fine electrodes are processed.   The air purifier according to any one of claims 1 to 3, further comprising an ion generator for charging a sol or gel substance in air subjected to plasma discharge treatment.   The air cleaning device according to any one of claims 1 to 4, wherein the trapping portion is a porous thin film.   The air cleaning apparatus according to claim 5, wherein the porous thin film is paper or plastics.   The air purifier according to claim 5, wherein the porous thin film has a stepped arrangement.   The air purifier according to any one of claims 1 to 7, wherein the entire capturing section is replaceable. The air cleaning device according to any one of claims 4 to 8, wherein the capturing unit is positively or negatively charged.