JPH11267461A - Method of purifying polluted gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable producing the device with simple construction and at a low cost, to reduce its running cost, and moreover, to decrease the frequency of its periodic inspection. SOLUTION: When a blower of an air purifier 12 is driven, polluted air discharged from a car C is sucked in from an air intake 22 and passes through a tubular body 26, a ventilated air merging point 36, a lower space, and a supporting member 38 is fed to a soil bed 30 and reaches the surface from the bottom part of the soil bed 30 through the soil bed 30, thereby purifying it to release the purified air in the air. When a guide rail 16 or the inner surface of a sound insulation wall 18 is coated with titanium oxide, or when titanium oxide is applied to at least one place of the air supply path and ultraviolet rays are irradiated by irradiating means 45, carbon monoxide in the polluted air is converted into carbon dioxide, which is then fed to the soil bed 30.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for purifying contaminated air.

[0002]

2. Description of the Related Art In a method of purifying contaminated air using soil, the removal capability of nitrogen oxides (NOx) is such that NO ₂ is stably at 90% or more, while NO is as low as about 15%, and the performance is low. Not enough. In order to improve the NO removing ability, the present applicant has filed Japanese Patent Application Nos. 6-06573 and 8-069.
No. 016 proposed a pretreatment method for oxidizing NO to NO ₂ using ozone, and improved the NO removal rate to 90% or more.

[0003]

However, the above-mentioned ozone pretreatment method has the following problems. (1) The initial cost is high. In the case of full-scale application, the cost of equipment such as an ozone generator, an ozone control system, and an ozone leak detection system is 10% of the total construction cost. (2) High running cost. In the case of full-scale application, the power consumption related to ozone pretreatment is 8% of the power consumption of the entire system. Also, the maintenance cost of the ozone pretreatment system is 20% of the operation cost of the whole system. (3) The system is complicated and requires frequent periodic inspections. The present invention relates to the improvement of such prior application, and an object of the present invention is to reduce the number of regular inspections by reducing the number of periodic inspections because the manufacturing cost can be reduced, the running cost can be reduced, and the number of regular inspections can be reduced. It is to provide a purification method.

[0004]

In order to achieve the above object, the present invention provides a method for purifying contaminated air, wherein the contaminated air is purified by passing the air through a soil layer. The contaminated air is passed through a portion on which a photocatalyst that exerts an oxidation function by receiving light is applied, and nitric oxide in the contaminated air is changed to nitrogen dioxide by the oxidation function of the photocatalyst. . Further, the present invention is characterized in that the location where the photocatalyst is applied is a location where sunlight is received. Further, the present invention is characterized in that an irradiating means for irradiating light is provided on a portion where the photocatalyst is applied. Further, according to the present invention, the contaminated air is supplied to the soil layer from an air supply path by an air flowing means, the air supply path has an intake of the contaminated air, and the air is allowed to flow through the intake. A foreign matter intrusion prevention means such as a wire net or a louver for preventing intrusion of foreign matter is attached, the foreign matter intrusion prevention means is disposed at a place where sunlight is received, and the photocatalyst is applied to the foreign matter intrusion prevention means. Features. Further, according to the present invention, the contaminated air is supplied to the soil layer from an air supply path by an air flowing means, and the air supply path has an intake of the contaminated air facing a guide rail on a side of a roadway, The photocatalyst is applied to a surface of a guide rail. Further, in the present invention, the contaminated air is supplied to the soil layer from an air supply path by an air flowing means, and the air supply path has an intake port for the contaminated air that opens to a sound insulating wall on a side portion of the roadway and faces the roadway. The photocatalyst is applied to a surface where the sound insulation wall near the intake faces the roadway. Further, according to the present invention, the contaminated air is supplied to the soil layer from an air supply path by an air flowing means, the air supply path has an intake for the contaminated air, and the intake has a space formed therein. The photocatalyst is applied to the inner surface of the case, and irradiation means for irradiating light to the portion where the photocatalyst is applied is provided. Further, according to the present invention, the contaminated air is supplied to the soil layer from an air supply path by an air flowing unit, and the air flowing unit includes a case, a fan disposed inside the case, and a fan driving unit. A photocatalyst is applied to the inner surface of the case, and an irradiating unit that irradiates light to a portion where the photocatalyst is applied is provided. Further, according to the present invention, the contaminated air is supplied to the soil layer from an air supply path by an air flowing unit, and the air flowing unit includes a case, a fan disposed inside the case, and a fan driving unit. A photocatalyst is applied to a surface of the fan, and irradiation means for irradiating the fan with light is provided. Further, in the present invention, the contaminated air is supplied to the soil layer from an air supply path by an air flowing means, the air supply path includes a tube, the photocatalyst is applied to a wall surface of the tube, and the photocatalyst is applied. Irradiation means for irradiating light to the formed pipe portion is provided. Further, in the present invention, the soil layer is provided on a plate-shaped support member having a large number of voids that allow air to flow, a lower space is provided below the support member, and the contaminated air is provided. Is supplied from the lower space to the lower part of the soil layer through the gap of the support member by air flow means, the photocatalyst is applied to the support member, and irradiation means for irradiating the support member with light is provided. It is characterized by. Further, the present invention is characterized in that the photocatalyst is titanium dioxide or vanadium oxide. Further, the present invention is characterized in that the photocatalyst is titanium dioxide or vanadium oxide, and the light irradiated by the irradiation means is ultraviolet light.

According to the present invention, since the oxidizing action of the photocatalyst is utilized, NO having a low removal ability in soil is converted into NO ₂ having a high removal ability without increasing the cost, thereby removing nitrogen oxides (NOx). Performance can be improved.

[0006]

Next, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows a schematic diagram of an apparatus for carrying out the method of the invention. A contaminated air purification device 12 for purifying contaminated air is installed on the side of a roadway (or highway) 14. A guide rail 16 extends on a side portion of the roadway 14, and a sound insulating wall 18 is erected outside the guide rail 16, and the guide rail 16 and the sound insulating wall 18 are provided at locations where ultraviolet rays in sunlight are received. . The contaminated air purification device 12 includes a contaminated air intake 22, a blower 24, a pipe 26, a lower space 28, a soil layer 30, and the like.

Openings 1802 are formed at a plurality of locations below the sound insulation wall 18 at intervals in the direction in which the roadway 14 extends, so as to reach the outside of the guide rail 16.
The inlet 22 is formed to include the inlet 802.
The intake port 22 includes a box-shaped case 32 having a space therein, and an opening of the case 32 and the opening 180.
A case 32 is installed on the sound insulation wall 18 so as to match the two. The opening 1802 is provided with a foreign matter entry preventing means 34 such as a wire mesh or a louver that allows air to flow and prevents foreign matter from entering.

The blower 24 is connected to a portion of the case 32 facing the opening 1802. As shown in FIGS. 2A and 2B, the blower 24 includes a cylindrical case 2402, a fan 2404 disposed on the center axis of the case 2402, and a fan 2404 supported in the case 2402. A motor 2406 that rotates and the like is provided, and the fan 2404 is rotated by driving the motor 2406, so that the contaminated air is sucked in from the air intake port 22 and supplied to the soil layer 30. The tube 26
Is connected to the air discharge port of the case 2402 of the blower 24, is buried in the ground, and extends below the soil layer 30. Then, the contaminated air sucked from the air intake ports 22 at a plurality of locations below the sound insulating wall 18 by the respective blowers 24 is supplied from the pipe 26 to the lower space 28 via the ventilation room 36.

The lower space 28 is provided below the soil layer 30 and has an area substantially equal to the area of the soil layer 30 when viewed in plan. The lower space 28 has a bottom and a periphery partitioned by wall surfaces, and a plate-like support member 38 having a large number of voids such as a porous plate through which air can flow is provided above the lower space 28. The soil layer 30 is provided on the support member 38. The soil layer 30 is laminated so that air can flow, and a plant 40 is planted in the soil layer 30.

In such an air purifying apparatus 12, when the blower 24 is driven, the contaminated air discharged from the car C is sucked through the air intake port 22, and the pipe 26, the ventilation room 36, the lower space 28, the support member 38, the air is supplied to the soil layer 30, reaches from the bottom to the surface of the soil layer 30, passes through the soil layer 30, and the purified air is released to the atmosphere. In this case, when titanium dioxide (TiO ₂ ) is applied as a photocatalyst to 16 guide rails located near the air intake and the inner surface (surface facing the roadway) of the sound insulating wall 18, these portions are exposed to sunlight. Because it is a place that receives ultraviolet rays, the photocatalytic action of titanium dioxide is exhibited,
After the nitrogen monoxide in the contaminated air is changed to nitrogen dioxide, it is sucked into the air intake 22 and supplied to the soil layer 30.

Alternatively, the case 3 of the air intake 22
2, the inner surface of the case 2402 of the blower 24, the surface of the fan 2404, the inner surface of the tube 26, the wall surface forming the ventilation space 36, or the wall surface forming the lower space 28, At least one portion of the surface of the member 38 is coated with titanium dioxide as a photocatalyst, and since these portions are locations where ultraviolet rays in sunlight do not reach, irradiation means (ultraviolet lamp) 45 is provided to irradiate the ultraviolet rays. In the same manner as described above, the photocatalytic action of titanium dioxide is exerted, and nitrogen monoxide in the contaminated air is changed to nitrogen dioxide, and then supplied to the soil layer 30.

Titanium dioxide is excited by light (ultraviolet light) in a wavelength range of 390 nm or less, and generates a photocatalyst that generates strong active oxygen species such as O ₂ and OH radicals shown in reaction formulas (1) and (2). It is. O ₂ + e ⁻ → O ₂ ⁻ (1) H ₂ O + h ⁺ → H ⁺ + OH (2) Titanium dioxide, vanadium oxide and the like are known as photocatalysts, but unlike catalysts such as Pt used in thermochemical reactions. There are notable points such as the catalyst function is exhibited at normal temperature and normal pressure, and the reaction proceeds sufficiently even when the light intensity is low. The application of photocatalyst to polluted air purification technology is to convert NO and NO ₂ to NO ₃
^- to oxidize, it is a method of adsorbing to the carrier for holding the photocatalyst body or photocatalytic. Adsorbed NO ₃ ^- is lost and adsorptivity reaches breakthrough, NO ₃ by washing with water ^- it is necessary to remove. However, the photocatalyst even after reaching the breakthrough point continues to function, to oxidize NO to NO _2, NO _2, which is oxidized is released to the atmosphere without being adsorbed. The present invention focuses on the NO oxidation function of the photocatalyst. The photocatalyst used in the present invention is not limited to titanium dioxide or vanadium oxide. In short, any photocatalyst that exhibits an oxidizing function by receiving light may be used.

That is, in the conventional method of purifying contaminated air using soil, the NO ₂ removal rate is high and the NO removal rate is low as described above. Since nitrogen oxide is supplied to the soil layer 30 after being changed to nitrogen dioxide, the removal rate of NO can be increased. The above effect can be obtained by applying titanium dioxide to the guide rail 16, the sound insulating wall 18, or the foreign matter mixing preventing means 34, so that the equipment cost and the running cost can be reduced. Further, the inner surface of the case 32 of the air inlet 22, the inner surface of the case 2402 of the blower 24, the surface of the fan 2404, the inner surface of the tube 26, the wall surface forming the ventilation room 36, or the lower space Even in the case where titanium dioxide is applied to a place where ultraviolet rays in sunlight do not reach, such as a wall surface forming the portion 28, the above effects can be obtained by providing the irradiation means 45 and irradiating the ultraviolet rays. Also in this case, the equipment cost and the running cost can be reduced. In addition, since the structure is simple, the number of periodic inspections can be reduced. In comparison with the cost of the present invention and the processing method using ozone, which was previously filed by the present applicant, it was found that the initial cost was about 1/3 and the running cost was about half. Inspections and the like have become extremely easy because complicated controls such as pretreatment for ozone oxidation and an ozone leak alarm system have been eliminated. The only replacement part was an ultraviolet light.

Next, an experimental example will be described. FIG. 3 is a schematic diagram of an experimental device of the contaminated air purification system. Reference numeral 50 denotes a soil column which is formed in a cylindrical shape having an inner diameter of 36 cm and a height of 80 cm. For the soil 52, perlite and peat moss are mixed at a volume ratio of 3: 3: 1 to secure air permeability.
The soil column 50 is packed with a layer thickness of 40 cm.
The soil 52 is supported by a porous plate 54. Air chambers 56 and 58 were provided above and below the soil 52. The upper chamber 56 has an exhaust port 60 for exhausting the processing air. The lower chamber 58 is provided for the photocatalyst pretreatment tank 6.
2 and a tube 64, and the photocatalyst pretreatment tank 62 is formed of a tube having an inner diameter of 8 cm and a length of 1.4 m, and its inner wall is coated with titanium dioxide. The photocatalyst pretreatment tank 62 communicates with the blower 66 by a pipe 68, a flow meter 70 is connected to the pipe 68, and the blower 66 is connected to the inverter 7.
2, the frequency is changed, and the air volume is controlled to be constant.

Nitrogen monoxide (NO) was supplied from a nitrogen gas cylinder 74 to the pipe 68 by controlling the flow rate of the nitrogen monoxide by a mass flow controller 76 to produce artificially contaminated air having a constant NO concentration. The nitrogen oxide concentration measuring method is as follows. The contaminated air before the pretreatment is collected from the pipe 68 and the Teflon tube 78
A was introduced into the high-sensitivity NOx meter 80A via A and measured. Similarly, the contaminated air after the pretreatment is collected from the lower chamber 58 and is supplied through the Teflon tube 78B to the high-sensitivity NOx analyzer 8.
It was introduced at 0B and measured. The purified air is supplied from the air chamber 56 through the Teflon tube 78C with high sensitivity NOx.
It was introduced into a total of 80C and measured.

As shown in FIG. 4, a 40 W black light 82 is installed inside the photocatalyst pretreatment tank 62, and near ultraviolet light having a peak wavelength of 352 nm is emitted by a fluorescent lamp stabilizing device 84. As a method of applying titanium dioxide to the inner wall of the photocatalyst pretreatment tank 62, for example, a method of applying an aqueous paint 86 as shown in FIG. Can be The experimental conditions were as follows: the amount of ventilation air was 0.12 m ³ / min, and the set nitrogen oxide concentration was NO = 1.0 ppm. After the air volume and the NO concentration were stabilized under the above experimental conditions, three high-sensitivity NOx analyzers were used without turning on the black light.
Nitrogen oxides were measured in A to C. After 6 hours, lighting of the black light was started, and nitrogen oxides were measured for 72 hours thereafter.

FIG. 6 shows a graph of the experimental results. FIG.
(A), (B) and (C) each show a high-sensitivity NOx meter 80
A, high-sensitivity NOx meter 80B, and high-sensitivity NOx meter 80C
5 is a graph of the simultaneous measurement data of FIG. The graph of FIG. 6A shows the nitrogen oxide concentration in the air at the entrance of the photocatalyst pretreatment tank,
The NO concentration is stable at 1 ppm and the NO ₂ concentration is almost 0 ppm. The graph in FIG. 6 (B) is the concentration of nitrogen oxides in the air after passing through the photocatalyst pretreatment tank. Until 6 hours from the start of the experiment, the black light was not turned on.
m, NO ₂ concentration becomes 0 ppm, and there is no change from the inlet concentration.
The NO concentration sharply decreased immediately after the black light was turned on,
Conversely, the NO ₂ concentration increases to almost 1 ppm. Thereafter, the NO oxidation rate was stabilized at about 95% or more. FIG.
(C) is the concentration of oxides in the atmosphere after passing through the soil 2. The NO concentration was about 0.8 ppm before lighting the black light, but decreased to about 0.01 ppm or less after lighting. As is clear from these results, the method for purifying contaminated air of the present invention is extremely advantageous in improving the NO removing ability.

[0018]

As is clear from the above description, the present invention
In the method for purifying contaminated air, in which the contaminated air is purified by passing through the soil layer, a photocatalyst that exerts an oxidizing function by receiving light from the contaminated air before being passed through the soil layer is applied. Through the site, the oxidation function of the photocatalyst was used to convert nitrogen monoxide in the contaminated air to nitrogen dioxide. Therefore, since the nitrogen monoxide is converted into nitrogen dioxide and then supplied to the soil layer, the NO removal rate can be increased. The above effects can be obtained by applying a photocatalyst to an appropriate place or by irradiating light with an irradiating means, so that equipment costs and running costs can be reduced, and the number of periodic inspections can be reduced. Becomes possible.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an apparatus for performing the method of the present invention.

FIG. 2A is a front view of a blower, and FIG. 2B is a cross-sectional side view of the blower.

FIG. 3 is an explanatory view of an experimental facility.

FIG. 4 is a sectional side view of a photocatalyst pretreatment tank.

FIG. 5 is a sectional front view of a photocatalyst pretreatment tank.

FIGS. 6A, 6B, and 6C are diagrams showing experimental results.

[Explanation of symbols]

 12 Contaminated air purification device 16 Guide rail 18 Sound insulation wall 22 Inlet 24 Blower 26 Tube 28 Lower space 30 Soil layer 45 Irradiation means

Continuation of the front page (72) Inventor Hideki Satake 4-6-15 Sendagaya, Shibuya-ku, Tokyo Inside Fujita Co., Ltd. (72) Inventor Katsuya Nagata 2-3-16 Jujo Nakahara Kita-ku, Tokyo

Claims (13)

[Claims] 1. A method for purifying contaminated air, wherein the contaminated air is purified by passing the air through a soil layer, wherein the contaminated air receives light before passing through the soil layer to exhibit an oxidizing function. A method for purifying contaminated air, characterized in that nitric oxide in contaminated air is changed to nitrogen dioxide by a photocatalyst applied portion through an oxidation function of the photocatalyst. 2. The method according to claim 1, wherein the location where the photocatalyst is applied is a location where sunlight is received. 3. The method for purifying contaminated air according to claim 1, wherein an irradiation means for irradiating light is provided at a position where the photocatalyst is applied. 4. The contaminated air is supplied to the soil layer from an air supply channel by an air flow means, the air supply channel has an intake port for the contaminated air, allows air to flow through the intake port, and removes foreign matter. A foreign matter intrusion prevention means such as a wire mesh or a louver for preventing intrusion of light is attached, the foreign matter intrusion prevention means is disposed at a place where sunlight is received, and the photocatalyst is applied to the foreign matter intrusion prevention means. The method for purifying contaminated air according to claim 1. 5. The contaminated air is supplied to the soil layer from an air supply path by an air flowing means, wherein the air supply path has an intake for contaminated air facing a guide rail on a side of a roadway, and The method for purifying contaminated air according to claim 1, wherein the photocatalyst is applied to a surface of a rail. 6. The contaminated air is supplied to the soil layer from an air supply path by an air flowing means, and the air supply path has an intake port for the contaminated air that opens to a sound insulating wall on a side of a roadway and faces the roadway, The method for purifying contaminated air according to claim 1, wherein the photocatalyst is applied to a surface of the sound insulation wall near the intake opening facing a roadway. 7. The contaminated air is supplied to the soil layer from an air supply path by an air flowing means, the air supply path has an intake for the contaminated air, and the intake has a space formed therein. The contaminated air according to claim 1, wherein the photocatalyst is applied to an inner surface of the case, and irradiation means for irradiating light to a portion where the photocatalyst is applied is provided. Purification method. 8. The contaminated air is supplied to the soil layer from an air supply path by an air flowing means, wherein the air flowing means comprises a case, a fan disposed inside the case, and a fan driving means for the fan. 2. A method for purifying contaminated air according to claim 1, wherein a photocatalyst is applied to an inner surface of the case, and irradiation means for irradiating light to a portion where the photocatalyst is applied is provided. 9. The contaminated air is supplied to the soil layer from an air supply path by an air flowing means, wherein the air flowing means comprises a case, a fan disposed inside the case, and a fan driving means for driving the fan. 2. A method for purifying contaminated air according to claim 1, wherein a photocatalyst is applied to the surface of the fan, and irradiation means for irradiating the fan with light is provided. 10. The contaminated air is supplied to the soil layer from an air supply path by an air flow means, the air supply path includes a tube, the photocatalyst is applied to a wall surface of the tube, and the photocatalyst is applied. 2. The method for purifying contaminated air according to claim 1, further comprising an irradiating means for irradiating the pipe portion with light. 11. The soil layer is provided on a plate-shaped support member having a large number of voids that allow air to flow,
A lower space is provided below the support member, and the contaminated air is supplied from the lower space to the lower part of the soil layer through the gap of the support member by the air flow means, and the photocatalyst is applied to the support member, The method for purifying contaminated air according to claim 1, wherein irradiation means for irradiating the support member with light is provided. 12. The method according to claim 1, wherein the photocatalyst is titanium dioxide or vanadium oxide. 13. The method according to claim 3, wherein the photocatalyst is titanium dioxide or vanadium oxide, and the light irradiated by the irradiation means is ultraviolet light.
The method for purifying contaminated air according to any one of items 10 and 11.