JPH06190236A - Gas cleaning method and device - Google Patents

Abstract

PURPOSE:To effectively purify gas against the contamination due to harmful gas by bringing the gas into contact with ozone generated from a ozonizer and bringing it into contact with a composite oxide catalyst having ozon resolution and harmful material adsorptivity. CONSTITUTION:A collecting decomposition part 6 of an air purifier 4 is constituted of an ozonizer 11 and a composite oxide catalyst 12 and tobacco odor components, etc., are removed here. The ozonizer 11 is of discharge type, etc., and a honeycomb manganese dioxide catalyst, etc., are used as the composite oxide catalyst 12. A fan is installed in a fan part 7 and sucks air to be treated 8 and discharges the treated purified air 10. Consequently gaseous harmful components are effectively treated by ozone and the composite oxide catalyst. And tobacco odor is removed by ozone.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a gas cleaning method and apparatus. INDUSTRIAL APPLICABILITY The cleaning method and apparatus of the present invention are used for air cleaning in offices, homes, hospitals, hotels, etc., sewage drainage, cleaning of exhaust gas in various industries such as a waste treatment plant, cleaning of atmosphere in a factory, underground parking lot and tunnel ventilation Cleaning,
Or clean room, clean booth, clean tunnel, clean bench, safety cabinet, bio clean box, aseptic room, pass box, storage of valuables in electronic industry, pharmaceutical industry, food industry, agriculture and forestry industry, medical care, precision machinery industry etc. ( It can be used for cleaning gases such as air, nitrogen and oxygen in a stocker), a transfer space, an air curtain, an air knife, a drying process, an apparatus for producing a gas supplied to a production line, and the like.

[0002]

2. Description of the Related Art For foul odor pollution by harmful gas in offices, acidic gas (eg, aldehyde, hydrogen sulfide, acetic acid,
There are compound odors that give off a bad odor by mixing fatty acids, mercaptans), alkaline gases (eg, ammonia, trimethylamine), and neutral gases (eg, sulfides), and more specifically, cigarette odors, toilet odors, and decay. There is odor and cooking odor.

Taking the tobacco odor as an example, the tobacco odor is
Remarkably various ingredients (It is said that more than 1,000 kinds)
It is a typical complex odor pollution consisting of, and its main components, such as aldehyde and nicotine, are carcinogenic or toxic. Therefore, it is required to collect and remove tar and fine particles (smoke). Is strong. For the removal of such tobacco odor, methods using various collecting / removing materials such as activated carbon and plant essential oils and fragrances aiming at the masking effect have been proposed. It does not meet the requirements for odor removal. For this reason,
There is a demand for an effective deodorizing method and device.

Next, regarding pollution by NOx, NO
Although x is a harmful gas and there has been a strong demand for removal from the past, there is no effective removal method to date. Regarding the pollution by harmful gas in the clean room of the semiconductor industry, the air cleaning methods of the conventional clean room or the apparatus therefor are roughly classified into (1) mechanical filtration method (for example, HEPA filter) (2) electrostatically collecting fine particles There are filtration methods using a high voltage for charging and a conductive filter (for example, HESA filter) for performing the above. All of these methods are intended to remove fine particles (particulate matter), and hydrocarbon (HC), NO
There is a drawback that it is not effective in removing gaseous pollutants (toxic components) such as x and NH ₃ .

H. 5 is a gaseous pollutant (hazardous component).
C. As a method for removing methane, combustion decomposition method, catalytic decomposition method, O ₃
The decomposition method and the like are known. However, these methods have a very low H.V. concentration in the air introduced into the clean room. C.
It has no effect on removal. In a clean room, H.O.
C. Also poses a problem as a pollutant. Further, various solvents (for example, alcohols, ketones, etc.) generated in the work in the clean room also pose a problem as contaminants.

Further, H. C. As harmful ingredients other than
There are NOx, NH _3, etc., and as a method for removing them, a method based on a neutralization reaction or an oxidation reaction using an appropriate alkaline substance or acidic substance is known. However, these methods are also less effective when the component concentration is an extremely low concentration such as contained in the air introduced into the clean room.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a gas cleaning method and apparatus effective against contamination by harmful gas, which can satisfy the various demands as described above.

[0008]

In order to solve the above-mentioned problems, the present invention provides a method for cleaning a gas containing a harmful gas, which has ozone decomposing ability and an ability to adsorb a harmful substance after the gas is brought into contact with ozone. This is to be brought into contact with the complex oxide catalyst. Further, according to the present invention, in the device for cleaning a gas containing harmful components, an ozone contact portion and a complex oxide catalyst layer are sequentially provided in the gas passage.

As ozone used in the present invention, ozone generated by a known ozone generator can be used. Any known method can be used for the ozone generator as long as it can effectively generate and supply ozone stably for a long time. For example, there are a discharge type and a radiation irradiation type. this house,
The discharge type is preferable because it can be stably supplied for a long time. Further, depending on the field of use, it is preferable to use an electric dust collector because both the dust collecting performance and the ozone generating performance can be used.

Although the action of decomposing and treating harmful gas by ozone is less than the action of ozone itself, it is an order of magnitude more active than the ozone generated when ozone is decomposed on the following complex oxide type catalysts (active oxygen active species (active For example, · OH, O ₂ ⁻ ·, HO ₂ such as oxygen atom or excited oxygen molecule
., (O)) is remarkably effective. Although the mechanism of harmful gas removal according to the present invention has not been fully clarified, it is considered as follows. That is, the generated oxygen active species is a coexisting harmful gas (for example, NH ₃ ,
₂ S, NOx, CH ₃ CHO) is activated to a state in which it is easily adsorbed by the catalyst, and is altered or decomposed on the composite oxide catalyst.

Any complex oxide catalyst used in the present invention can be used as long as it can be adsorbed and decomposed on the surface by passing ozone decomposing performance and a gas containing a harmful gas and oxygen active species. Good. As an example of such a complex oxide-based catalyst, a manganese dioxide-based catalyst such as MnO ₂ /
There are TiO ₂ —C and MnO ₂ / ZrO—C. The manganese dioxide-based catalyst can be obtained by sintering the powder into pellets, or pellets, a honeycomb-shaped molded product, or a catalyst supported on a honeycomb-shaped base material or a fibrous base material. Further, manganese dioxide to which an appropriate metal or metal compound is added can be used for suppressing deterioration, preventing performance deterioration in a low temperature range, and improving activity.

In addition to the above complex oxide-based catalyst, a well-known toxic gas trapping material, for example, a device to which the device is applied, a device type, a shape, a type and concentration of a target component, an effect, economical efficiency, etc.
Activated carbon, activated carbon fibers, zeolite, molecular sieves, silica gel, ion exchange fibers, filters and / or dehumidifying materials can be used in combination with appropriate preliminary tests. The present invention effectively decomposes and treats ozone and harmful gas by reacting active oxygen active species from ozone and harmful gas on a complex oxide catalyst.

The conversion of ozone to active oxygen active species is
Usually, it is carried out on a complex oxide-based catalyst, but when it is carried out by increasing the ozone concentration depending on the field of application or in the case of large-scale processing, oxygen activated species may be prepared in advance from a part of the ozone generated. This method includes utilizing electrons, light, high frequency, and heat. For example, for ozone decomposition by electrons, there is a method of Formula 1 using low-temperature plasma, (Formula 1) O ₃ + e → O ₂ + (O), and there is a method of using ultraviolet rays (254 nm) for ozone decomposition by light. Can be used.

In this regard, the field of application of the device, the scale,
Preliminary tests can be appropriately performed and determined depending on the generated ozone concentration, the harmful gas type, the concentration, and the like. Particularly, it is effective when the ozone concentration is increased. The ozone concentration with respect to the harmful gas concentration is 0.5 to 100 times as stoichiometric amount, preferably 1.0 to 20 times, and when the ozone concentration corresponding to the gas to be treated is included, the ozone is used. it can.

The ozone concentration relative to the concentration of harmful gas to be treated can be determined by conducting a preliminary test as appropriate according to the field of use, type of equipment, shape, target components, required performance and the like.
When the gas to be treated does not contain ozone, or when the coexisting ozone concentration is low, ozone generated from the ozone generator is added to the gas to be treated as in Examples 1 to 5 described later.

[0016]

In the present invention, the mechanism of removing harmful gas by using ozone and a complex oxide catalyst in combination to purify the gas has not been fully clarified, but it depends on the harmful gas and the generated oxygen active species. By the reaction and the adsorption / decomposition action on the surface of the complex oxide-based catalyst by passing the gas containing the harmful gas and the oxygen active species through the complex oxide-based catalyst, the harmful gas in the gas is effectively decomposed and removed, Be cleaned.

As described above, ozone is converted into an active substance and the outlet gas does not contain ozone. That is, in the cleaning method of the present invention, by combining an oxygen active species generation by ozone, ozone decomposition performance, and a composite oxide catalyst having both adsorption / decomposition performance for harmful gas,
The harmful components can be effectively removed.

[0018]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Example 1 FIG. 1 shows a schematic configuration diagram in which a gaseous harmful component removing device for deodorizing cigarette odor is installed in a waiting room of a doctor's office. In FIG. 1, cigarette smoke 3 is generated by smoking 2 in a waiting room 1, and an air purifying device 4 is installed to deodorize a cigarette odor. The device 4 is mainly composed of a pretreatment filter part 5, a tobacco odor component collecting / decomposing part 6 and a fan part 7. The treated air 8 containing the tobacco odor 3 flows through the device 4 in the direction of an arrow 9.
, And the deodorized clean air is discharged in the direction of arrow 10.

Each component will be described. The pretreatment filter unit 5 mainly collects and removes tar and particulate matter in cigarette smoke. As the constituent material of the filter portion 5, glass fiber, natural fiber, synthetic fiber filled in an appropriate shape, or paper-like material thereof, or woven cloth or paper thereof can be used. In this example, paper-shaped glass fibers are used in a corrugated shape. The outflow of tar and particulate matter to the rear deteriorates the constituent material of the rear collecting and decomposing section 6, and therefore it is preferable to reduce the amount as much as possible.

The collection / decomposition section 6 is composed of an ozone generator 11 and a complex oxide catalyst 12, and tobacco odor components are removed here. In this example, the ozone generator 11 is of a discharge type, and the composite oxide catalyst is a honeycomb manganese dioxide catalyst (MnO ₂ / TiO ₂ —C). A fan is installed in the fan unit 7, which sucks the air 8 to be treated and discharges the treated purified air. In this way, the ozone and the complex oxide catalyst effectively treat the gaseous harmful components as described above. Further, ozone has the effect of deodorizing the tobacco odor, gaseous harmful substances are removed, and deodorized clean air is obtained in the direction of arrow 10.

Embodiment 2 FIG. 2 shows a schematic configuration diagram in which an air purifying device is installed in a clean room to remove harmful gas. In FIG. 2, in the clean room 21 of class 10000 (> 0.1 μm), harmful gases such as NOx, NH ₃ , H ₂ S and fine particles 23 are generated by the work 22, and the air cleaning device 4 is installed. The harmful gas and fine particles are collected and removed. The device 4 is mainly composed of a pretreatment filter section 5, a fan section 7, a harmful gas decomposing section 6 and a particulate collection filter 13, and the air 8 to be treated containing the harmful gas is fed by the fan of the fan section 7. , Flows in the device 4 in the direction of arrow 9, and the treated clean air is discharged in the direction of arrow 10.

Each component will be described. The pretreatment filter unit 5 is filled with a coarse filter, and coarse particles in the suctioned air 8 are removed. Here, a filter mainly made of glass fiber having a low air resistance is used.
The noxious gas decomposing section 6 is composed of a discharge type ozone generator 11 and a complex oxide catalyst (MnO ₂ / TiO ₂ —C) 12 and generates noxious gas such as NOx, NH ₃ , H ₂ S and the like. And in air. C. Are removed by the action of the ozone generated from the ozone generator and the complex oxide catalyst.

Further, the particulate collection filter unit 13 has a U
The LPA filter is filled, and the fine particles in the suction air 8 and the fine particles (particulate matter) generated from the fan unit 7 or the harmful gas decomposition unit 6 are removed. In this way, the purified air 10 becomes class 10 or less by removing harmful gases and fine particles, and harmful gases such as NOx, NH ₃ , H ₂ S, and HC are 1/10 of the normal atmospheric concentration level. It has been removed up to: Since the harmful components (harmful gas and fine particles) are removed from the air as described above, surface contamination can be prevented by exposing the air to the wafer or the liquid crystal substrate.

This example is used for air cleaning in a semiconductor clean room. The position of each component in the first and second embodiments is not limited at all, and can be set at an appropriate position depending on the field of use, the scale of the device, the usage conditions of the component, the shape, and the like. The position of the fan unit 7 is the same as that of the second embodiment.
At least dust removal part (ULPA filter) when it is used for cleaning space in advanced industries such as semiconductors.
The front of is preferred. That is, in the advanced industry, fine particles generated by the operation of the fan are also targeted for removal.
Further, although the position of the ozone generator in Examples 1 and 2 is installed inside the air purifying device, it may be installed outside the device depending on the field of use, scale of the device, shape, etc. May be.

Example 3 FIG. 3 is a schematic diagram showing a case where activated carbon 16 is further installed behind the manganese dioxide-based catalyst in FIG. 2 of Example 2. Reference numerals other than 16 have the same meanings as in FIG. It is effective to provide an activated carbon layer when the generated harmful gas contains a large amount of neutral gas.

Embodiment 4 FIG. 4 is a schematic diagram showing a structure in which a low temperature plasma section 17 is installed behind the ozone generator in Embodiment 2. 1
Reference numerals other than 7 have the same meanings as in FIG. When performing high-concentration ozone generation or performing large-scale processing, it is effective to install a low temperature plasma part.

Example 5 Toxic gases (mainly NOx, H.
C. ) Is shown in FIG.
The tunnel ventilation exhaust gas 14 is processed by an exhaust gas processing device including a dust collector 18, an ozone generator 11, a harmful gas / ozone mixing section 19, a complex oxide-based catalyst 12, and a fan 7. can get. The dust collector 18 collects particulate matter in the exhaust gas, for example, carbonaceous wear tire fine powder, soil components, etc. by a filtration collection method. Next, harmful gas in the exhaust gas (mainly NOx, H.
C. ) Is mixed with ozone from the discharge type ozone generator 11 in the mixing section 19, and a mixed oxide catalyst (MnO ₂ / Ti) is mixed.
O ₂ -C) 12 with NOx and H. C. Are decomposed, removed and cleaned.

Sixth Embodiment FIG. 6 shows a case where the dust collector 18 also serves as the ozone generator 11 in FIG. 5 of the fifth embodiment. By using the electric dust collector 20, dust (carbons, etc.) is collected. It is a schematic block diagram of the cleaning apparatus which performs both and ozone generation. Reference numerals other than 20 have the same meanings as in FIG. Since the device becomes compact, it is preferable depending on the field of use and the scale of the device.

Example 7 The deodorizing effect using the harmful component removing apparatus of FIG. 1 is shown below. The ozone generator used is a discharge type, the generated ozone concentration is 8 to 10 ppm, and the complex oxide catalyst is a manganese dioxide catalyst, which is MnO ₂ / TiO ₂ —C. The volume of the waiting room 1 in which the air cleaning device 4 was installed was about 30 m ³ , and the air flow rate inside the device was 0.5 m ³ / min. When 10 cigarettes were smoked at a position of about 1 m just below the pretreatment filter 5, the odor concentration of the sample air collected at the position 8 immediately before the filter was 500 by sensory test (3-point comparison odor bag method).
Met. Moreover, when NH ₃ and NOx were measured, they were 5 ppm and 2 ppm, respectively.

When this air was cleaned by operating the air cleaning device, the odor concentration of the air at the position 10 immediately after the device outlet was 10 or less at the maximum in the sensory test. Further, no cigarette smoke was visually observed in the discharged air here. The NH ₃ and NOx concentrations are <0.1 ppm and <
It was 0.05 ppm. The fact that the cigarette odor with an odor concentration of 500 as described above becomes 10 or less at the maximum by the air purifying device is equivalent to that diluted by 50 times or more with odorless air, and this device is effective for removing cigarette odor and cigarette smoke. It turns out to be effective.

Example 8 An example in which the air cleaning apparatus shown in FIG. 2 is applied to cleaning the supply air of a drying apparatus in a liquid crystal factory will be described. The air purifier is installed in a class 10,000 room, and in the vicinity,
NH ₃ and NOx are generated by acid and alkali cleaning. The air purifier shown in FIG. 2 is installed to purify (clean) the air in such a clean room as the air to be supplied to the drying step of the liquid crystal manufacturing process. It was investigated by increasing the contact angle with the substrate.

The contact angle indicates the degree of contamination of the surface, and is represented by an angle representing the wettability of the surface. A high contact angle results in contamination, and a low contact angle results in contamination. Absent. ppm concentration levels of NH ₃ and NOx and indoor concentration levels of H.V. C. Results in an increased contact angle. Clean room: Class 10,000 (> 0.1μ)
m) Coarse filter: Glass fiber pretreatment filter Ozone generator and supply ozone concentration: Discharge type, 20-4
0 ppm

Complex Oxide Catalyst: Manganese Dioxide Catalyst (MnO ₂ / TiO ₂ -C) Air Cleaner Size: 30 × 30 × 40 cm Room NH ₃ and NOx Concentration (3 m from Source) NH
₃ : 10 ppm NOx: 5 ppm C. Concentration: 0.5 ~ as non-methane
The determination of the 0.8 ppm effect was performed by exposing the air at the outlet of the air purifier to a glass substrate and examining the increase in the contact angle on the substrate using a contact angle meter.

Results FIG. 7 shows the contact angle (circle) when the air treated according to the present invention was exposed to the glass substrate for 200 hours. In Figure 7,
For comparison, the one exposed to the air in the clean room as it is (marked with), or the one obtained by removing only the manganese dioxide-based catalyst from FIG. 7 (marked with Δ) is also shown. In addition, ↓ in FIG. 7 indicates a detection limit of 4 degrees or less.

Example 9 An example is shown in which the exhaust gas treatment apparatus shown in FIG. 5 is applied to the treatment of exhaust gas from tunnel ventilation. Ventilation exhaust gas from the tunnel containing NOx was flowed to the exhaust gas treatment device at 0.5 m ³ / min, and N
The removal performance of Ox was examined by a chemical type NOx measuring instrument. NOx concentration: 1-3 ppm Size of exhaust gas treatment device: 50 × 50 × 60 cm Complex oxide catalyst: MnO ₂ / TiO ₂ -C Ozone generator and supply ozone concentration: Discharge type, 10-3
0ppm dust collector: Filtration type

Result The NOx concentration at the outlet of the device was 0.1 to 0.2 ppm or less. The ozone concentration at the outlet of the apparatus was not detected (0.01 ppm or less). In the example, the case of treating harmful gas other than ozone was described,
It goes without saying that when the harmful gas is pure ozone, the ozone can be effectively treated by the above-mentioned catalyst, and the present invention can be effectively used for the exhaust ozone treatment. When ozone already coexists in the gas to be treated, the ozone can be used. In this case, ozone and harmful gases other than ozone can be treated.

[0037]

The present invention has the following effects. (1) In cleaning the gas, the gas is brought into contact with ozone and then passed through a complex oxide-based catalyst, so that (a) the harmful gas in the gas is caused by the oxygen active species from ozone and ozone. Effective treatment (removal) by reaction with the active substance, adsorption / decomposition reaction with complex oxide catalyst, decomposition reaction with oxygen active species on complex oxide catalyst, etc.
Was done. (B) From the above, it becomes a sterilized gas because it contains ozone and oxygen active species. (C) Ozone produces a gas that is deodorized. (D) An ultra-highly clean gas was obtained.

(2) When a discharge-type ozone generator is used as an ozone source, large-scale processing, such as industrial exhaust gas, tunnel exhaust gas, underground parking lot exhaust gas, and the like, can be performed at the destination where the amount of exhaust gas is large, and is practically used. And the field of application has expanded. (3) When ozone is contained in the gas to be treated, both ozone and harmful gas other than ozone can be treated at the same time, which is a practically effective treatment. (4) Depending on the field of application, it could also be used for waste ozone treatment.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an apparatus used in Example 1.

2 is a schematic configuration diagram of an apparatus used in Example 2. FIG.

FIG. 3 is a schematic configuration diagram of an apparatus used in Example 3.

FIG. 4 is a schematic configuration diagram of an apparatus used in Example 4.

5 is a schematic configuration diagram of an apparatus used in Example 5. FIG.

FIG. 6 is a schematic configuration diagram of an apparatus used in Example 6.

FIG. 7 is a graph showing the relationship between exposure time and contact angle.

[Explanation of symbols]

1: Waiting room, 2: Cigarette, 3: Cigarette smoke, 4: Air cleaning device, 5: Pretreatment filter part, 6: Collection / decomposition part, 7:
Fan part, 8, 14: Air to be treated, 9: Air flow, 1
0, 15: Clean air, 11: Ozone generator, 12: Complex oxide catalyst, 13: Fine particle collection filter, 16: Activated carbon layer, 17: Low temperature plasma part, 21: Clean room,
22: Work, 23: Hazardous gas, 18: Dust collector, 19: Mixing part of harmful gas and ozone, 20: Electrostatic precipitator

Claims (2)

[Claims] 1. A method for cleaning a gas containing a harmful gas, which comprises contacting the gas with ozone and then contacting a complex oxide catalyst having ozone decomposing ability and ability to adsorb harmful substances. Method. 2. A gas cleaning device comprising a harmful gas, wherein an ozone contact portion and a complex oxide catalyst layer are sequentially provided in the gas passage.