JPH10309438A - Exhaust gas purifying apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently purify exhaust gases by emitting and diffusing ultraviolet(UV) rays to the inside of a light transmissive catalyst carrier from an UV ray radiating means, efficiently radiate a photocatalyst deposited in the whole body of the catalyst carrier, and drawing the strongly oxidizing function of all of the photocatalyst while avoiding vain use. SOLUTION: A front catalyst converter 5 comprises a tubular body cover 11 with a widened diameter in a middle of an exhaust gas pipe 2 and a photocatalyst carrier 15 and three optical fibers 3 having one end parts supported by a heat resistant ring 12 and the carrier and the fibers are installed in the part with a widened diameter. The other end parts of the optical fibers 13 are connected with a light source part 14 provided with a UV ray radiating lamp in an engine room. The UV lamp is operated when the exhaust gas temperature is lower than a prescribed value at the time of starting the engine. The catalyst carrier 15 has a honeycomb structure cylindrical body and layers of a photocatalyst formed to be flat and having strongly oxidizing function by radiation of UV rays L on the surfaces of respective exhaust gas passing routes partitioned from one another by partitioning walls W. Except the front side, the outer circumferential part of the carrier 15 is treated for light reflection, so that UV rays L most efficiently enter the carrier and are diffused in the carrier and draw the strongly oxidizing function out of all of the photocatalyst and consequently, an exhaust gas is efficiently purified.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas purifying apparatus for purifying air and other various gases existing in a predetermined area, for example, exhaust gas of a vehicle by using a photocatalyst.

[0002]

2. Description of the Related Art Conventionally, purification of air and other various gases,
Photocatalysts are widely used for disinfection and deodorization. It is known that this photocatalyst contains titanium dioxide (TiO ₂ ) as a main component, and the internal electrons of the titanium dioxide are strongly vibrated by irradiation with light including ultraviolet rays (short wavelength light of about 0.8 μm). With the active displacement, various surrounding gases can be oxidized and purified by a strong oxidizing action, and can be used in a relatively low temperature (normal temperature) atmosphere.
Usually, when a photocatalyst is used, a catalyst carrier suitable for the use area is used, the photocatalyst is widely adhered to the surface on the catalyst carrier, and the entire surface area of the supported photocatalyst is irradiated with ultraviolet rays evenly, whereby The photocatalyst on the entire surface area flows by the strong oxidizing action and purifies various gases facing each other by oxidation and decomposition. Therefore, the photocatalyst on the catalyst carrier can exhibit a strong oxidizing action without waste as the surface area of the photocatalyst is large and the entire surface area can be evenly irradiated with ultraviolet rays.

Incidentally, since this photocatalyst exhibits a strong oxidizing effect in an atmosphere at a relatively low temperature (normal temperature), it has recently been proposed to use the photocatalyst in an exhaust gas purifying apparatus for a vehicle.
In particular, if the ambient temperature of the exhaust system of the vehicle is relatively low, the three-way catalyst and the like cannot be sufficiently activated, and if the photocatalyst is used in such an atmosphere, that is, if it is irradiated with ultraviolet light, Accordingly, the photocatalyst can purify the exhaust gas as an oxidation catalyst. An example in which such a photocatalyst is employed as an exhaust gas purifying device is disclosed in Japanese Patent Application Laid-Open No. Hei 4-30522.
No. 8 discloses this. Here, a bypass path provided with a photocatalyst is provided in a part of the exhaust path, and an ultraviolet irradiation lamp opposed to the photocatalyst is driven at a low temperature to purify exhaust gas passing through the bypass path.

[0004]

By the way, the above-mentioned photocatalyst is treated so as to be inseparable from the surface of a catalyst carrier having a shape suitable for the use area, and the surface of the photocatalyst receives ultraviolet rays from an ultraviolet irradiation lamp. Demonstrates a strong oxidizing effect, but depending on the surface shape and overall shape of the catalyst carrier, all the photocatalysts cannot receive ultraviolet light from the ultraviolet irradiation lamp uniformly, that is, the entire area of the used photocatalyst is efficiently treated by ultraviolet light. Irradiation cannot be performed well, and a region where the photocatalyst is wasted tends to occur.

For example, in a vehicle exhaust gas purifying apparatus disclosed in Japanese Patent Application Laid-Open No. 4-305228, a photocatalyst is attached to the surface of a honeycomb-shaped catalyst carrier. In this case, an ultraviolet irradiation lamp is provided on the side of the catalyst carrier that faces the inlet / outlet of the gas passage, whereby ultraviolet light is irradiated. However, even on the side where the ultraviolet irradiation lamp is not installed, or even on the side of the ultraviolet irradiation lamp, the photocatalyst attached to the shadowed portion due to the surface shape of the catalyst carrier does not receive ultraviolet rays and can exhibit a strong oxidizing effect. Without waste.

SUMMARY OF THE INVENTION It is an object of the present invention to diffuse and irradiate ultraviolet rays to the entire area of photocatalyst attached to catalyst carriers of various shapes to improve the irradiation efficiency so that all of the photocatalyst attached to the catalyst carrier is strong without waste. It is an object of the present invention to provide a gas purifying apparatus which exhibits an oxidizing action and can purify gas efficiently.

[0007]

According to the first aspect of the present invention, when the ultraviolet rays from the ultraviolet irradiation means are irradiated on the photocatalyst, the ultraviolet rays enter the light-transmissive catalyst carrier and diffuse, and the catalyst is dispersed. The photocatalyst attached to the entire area of the carrier is irradiated with ultraviolet rays with high efficiency, and the strong oxidizing action of all the photocatalysts attached to the catalyst carrier can be extracted without waste, and gas purification can be performed efficiently. Here, preferably, the outer peripheral wall of the catalyst carrier is subjected to a light reflecting surface treatment except for the incident path of ultraviolet rays. In this case, the incident ultraviolet light is reflected again inside without being diffused outside from the outer peripheral wall, and is efficiently diffused throughout the catalyst carrier acting as a light guide path, so that the photocatalyst in the entire catalyst carrier can efficiently purify gas. More preferably, light-transmitting fine particles are mixed into the photocatalyst attached to the catalyst carrier. In this case, the translucent fine particles can sufficiently diffuse the ultraviolet diffused light and irradiate the peripheral photocatalyst, and the photocatalyst can perform gas purification more efficiently.

According to the second aspect of the present invention, the ultraviolet irradiation means can be installed at a distance from the catalyst carrier, the catalyst carrier side can be miniaturized and the installation space can be easily secured. Maintenance can also be facilitated.

According to the third aspect of the present invention, since the light reflecting pieces diffuse and diffuse the ultraviolet light incident on the catalyst carrier acting as a light guide path from the ultraviolet irradiation means, the irradiation of the photocatalyst over the entire area of the catalyst carrier with high irradiation efficiency. Gas purification can be performed efficiently.

[0010]

1 and 2 show an automobile equipped with a gas purifying device as an embodiment of the present invention. The exhaust system of the vehicle includes an exhaust pipe 2 extending from the engine 1 to the rear end of the vehicle body.
It is arranged below the rear floor 4 through a downward recess 3 continuously formed from the side toward the center of the floor toward the front and rear.
In the vicinity of the engine 1 of the exhaust pipe 2, a front catalytic converter 5, which is a main part of the gas purification apparatus of the present invention, a rear catalytic converter 6 behind the exhaust catalytic converter 5, and a muffler 7 as a silencer behind the exhaust catalytic converter 5 are connected in series. Has been deployed.

Here, the rear catalytic converter 6 includes a well-known three-way catalyst, and effectively purifies harmful components such as HC, CO, and NOx in the exhaust gas G under an atmosphere at a predetermined activation temperature or higher. . The three-way catalyst is a Pt / Rh catalyst, and is obtained by using a cordierite carrier, alumina powder, and alumina sol as raw materials and passing through various steps such as immersion, blowing, drying, and calcination. As shown in FIGS. 2 and 3, the front catalytic converter 5 is fitted in a cover 11, which is a tubular body having an enlarged diameter and is provided in the middle of the exhaust pipe 2, and in an enlarged diameter portion 111 of the cover 11. , Photocatalyst 16 (FIG. 4)
(See (a)), a heat-resistant ring 12 abutted on the front end side of the catalyst support 15 and disposed in the step 112 of the cover 11, and an end supported by the heat-resistant ring 12. And three optical fibers 13 (only two are shown in FIG. 2).

Here, the optical fiber 13 is made of heat-resistant quartz glass, and the other end is connected to a light source section 14 provided in an engine room ER as shown in FIG. The light source unit 14 includes an ultraviolet irradiation lamp 141 and a fiber support member (not shown) for causing the ultraviolet light of the lamp to enter the end of the optical fiber 13.
41 is connected to the control unit 142. The control unit 142 takes in a key-on signal S, which is an engine drive signal, and an exhaust gas temperature signal Tg from an exhaust gas temperature sensor (not shown).
When the temperature is lower than 1 (set according to the activation determination temperature of the three-way catalyst), the control is performed such that the ultraviolet irradiation lamp 141 is driven.

Incidentally, instead of the ultraviolet irradiation lamp 141,
A halogen lamp that emits light containing ultraviolet light (short wavelength light in the vicinity of 0.8 μ) may be used. The light source unit 14, the control unit 142, and the three optical fibers 13 constitute an ultraviolet irradiation unit here. The optical fiber 13 on the side of the cover 11 is supported by the heat-resistant ring 12 in the step portion 112 without any deviation in the direction of the end, and is supported here in such a state that ultraviolet rays can be efficiently incident inside the catalyst carrier as described later. .

The catalyst carrier 15 is integrally formed of translucent quartz glass, and as shown in FIG. 3, the overall shape is a cylindrical body having a honeycomb structure. And each partition w is divided as shown in FIG.
A relatively flat layer of the photocatalyst 16 is formed on the surface of the photocatalyst. The photocatalyst 16 is capable of exhibiting a strong oxidizing action upon being irradiated with the ultraviolet light L, has titanium dioxide (TiO ₂ ) as a main component, and is subjected to various processes such as immersion, blowing, drying and firing. Thereby, it is formed in a layered manner on the surface of the partition wall w and cannot be separated.

As shown in FIG. 2, a thick tubular portion 151 is formed on the outer peripheral portion of the catalyst carrier 15. This tubular part 151
Is formed with an annular outer wall surface f and an annular inclined surface f1 at the front and rear ends thereof. In particular, a portion excluding the annular inclined surface f1 on the front side (the left side in FIG. 2) is subjected to aluminum coating treatment, that is, light reflecting surface treatment. You. Instead of the aluminum coating, a light reflection surface treatment may be performed by chrome plating. Furthermore, the cylindrical part 1
Instead of the annular outer wall surface 51 of the cover 51, the inner peripheral wall of the enlarged diameter portion 111 of the cover 11 which is in close contact with the same surface f may be subjected to a light reflection surface treatment by chrome plating. An end surface of the optical fiber 13 is opposed to the annular inclined surface f1 on the front side (the left side in FIG. 2) of the cylindrical portion 151.
It is appropriately set so that more ultraviolet rays can be diffused and incident on the entire inside of the catalyst carrier 15 most efficiently.

Here, as shown by the two-dot chain line in FIG. 2, the ultraviolet rays L incident on the thick cylindrical portion 151 from the front annular inclined surface f1 are repeatedly diffused by internal reflection, and particularly, the light reflection surface treatment. Is reflected to the inside on the side of the annular outer wall f. Moreover, since the inside of the cylindrical portion 151 is continuously formed of the same material as the many partition walls w, the diffused light L1 of the ultraviolet light guided by the cylindrical portion 151 is closer to the outside, that is, closer to the cylindrical portion 151 side. The light is incident on each partition w, and each partition w
Can be guided to the partition wall w at the center.

When an automobile equipped with such a gas purifying device is driven, exhaust gas G from the engine 1 is supplied to a front catalytic converter 5 and a rear catalytic converter 6 behind it.
And discharged through the muffler 7. At this time, the control unit 14
2 receives the key-on signal S and the exhaust gas temperature signal Tg,
When the exhaust gas temperature signal Tg is lower than the threshold value Tg1, the ultraviolet irradiation lamp 141 is driven, and the exhaust gas temperature signal Tg is set to the threshold value Tg.
When the value exceeds g1, the ultraviolet irradiation lamp 141 is turned off.

When the temperature of the exhaust gas G is low and the ultraviolet irradiation lamp 141 is on, the ultraviolet light L from the light source unit 14 is incident on the cylinder 151 via the optical fiber 13,
1, the inner surface reflection is repeatedly diffused. In particular, here, the light is reliably reflected inward at the light reflection processing portion on the annular outer wall surface f side, and the ultraviolet light is diffused from the cylindrical portion 151 to a large number of partition walls w and each exhaust gas passage r. The photocatalyst 16 attached to the partition w over the entire area of the catalyst support 15 is uniformly irradiated with ultraviolet light, that is, the ultraviolet light L can be efficiently irradiated, and the strong oxidation action of the photocatalyst 16 over the entire area of the catalyst support 15 is suppressed. I can pull it out. Thereby, even if the exhaust gas G is relatively low temperature, HC and CO are oxidized,
It can be made harmless and discharged.

The trace amount of NOx component in the relatively low-temperature exhaust gas G that has passed through the front catalytic converter 5 is further rendered harmless by the rear catalytic converter 6 and discharged.
When the exhaust gas temperature enters a high operating range, the ultraviolet irradiation lamp 141 is turned off and the front catalytic converter 5 enters a state where exhaust gas purification is not performed. In this case, the rear catalytic converter 6 on the rear side is activated, HC, CO, and NOx are all rendered harmless and discharged, and there is no problem. Further, in the front catalytic converter 5, since the light source unit 14 is separated, the front catalytic converter 5 side can be made relatively small, the installation space can be easily secured, and the light source unit 14 is mounted in the engine room ER. Therefore, maintenance such as replacement of the ultraviolet irradiation lamp 141 can be easily performed.

In the process described above, the partition w to which the photocatalyst 16 is attached is a thin plate as shown in FIG. 4A, and the photocatalyst 16 is attached in a layer on the surface of the partition w. In some cases, as shown in FIG. 4B, a partition wall w1 having a fine uneven portion b on the surface may be formed. In this case, the uneven portion b enhances the adhesion of the layered photocatalyst 16, and the uneven portion b receives the diffused light L1 passing through each exhaust gas passage r and the partition wall w1 and guides the diffused light L1 to the photocatalyst 16 in the vicinity thereof. The efficiency of irradiation of the photocatalyst 16 with ultraviolet rays can be improved. Further, instead of the partition w shown in FIG. 4A, a partition w2 containing the light reflecting piece d shown in FIG. 4C may be used. In this case, the light reflecting piece d may be an aluminum foil piece,
When the catalyst carrier 15 is formed, it is intensively mixed into the partition wall w. The ultraviolet light L incident on such a catalyst carrier 15 is guided as diffuse light L1 into each exhaust gas passage r and the partition wall w2,
The diffused light is diffusely reflected by the light reflecting piece d, and is radiated to the photocatalyst 16 with high irradiation efficiency, so that gas purification can be performed efficiently.

Further, instead of the photocatalyst 16 shown in FIG. 4A, a photocatalyst 16 containing light transmitting particles c shown in FIG. 4D may be used. In this case, the light transmitting particles c may be particles of quartz glass, and the partition wall w is immersed in the photocatalyst 16 liquid containing the light transmitting particles c, and then a process of forming a catalyst layer such as blowing off, drying and firing is performed. Photocatalyst 16 containing light transmitting particles c
Can be generated. In this case, the diffused light L1 that has passed through the partition wall w or the passage r is guided to the surrounding photocatalyst 16 by the light transmitting particles c, the irradiation efficiency of the photocatalyst 16 can be improved, and gas purification can be performed efficiently.

The catalyst carrier 15 of the front catalytic converter 5 shown in FIG. 1 has a thick cylindrical portion 151 on the outer peripheral portion. However, in some cases, the front catalytic converter 5a having the catalyst carrier 15a shown in FIG. Is also good. In this case, inside the translucent quartz glass bulging portion 20 composed of the front and rear short tubular portions 201 and the central bulging portion 202, the whole shape is a honeycomb structure and the translucent quartz glass bulging portion. Insert the core 21 and
The catalyst carrier 15a can be manufactured by integrating both. Here, the core portion 21 divides each exhaust gas passage r having a rectangular cross section by a partition wall w, and has the same configuration as the central portion of the catalyst carrier 15 in FIG.

In this case, the bulging portion 202 of the cylindrical bulging portion 20
The end of the optical fiber 13 is inserted into and supported by the front end of the optical fiber 13.
2 is repeatedly reflected between the inner surface of the core 2 and the outer peripheral surface of the core portion 21, and is uniformly irradiated on the outer peripheral surface of the core portion 21. And diffused ultraviolet light L1 into the photocatalyst 16 in the entire area of the core 21.
And the exhaust gas G can be efficiently purified.

In the automobile shown in FIG. 1, the gas purifying apparatus of the present invention is applied to the front catalytic converter 5, but instead of this, as shown in FIG. You may apply to converter 6A. In this case, the exhaust gas G from the engine 1 is discharged through a front catalytic converter 5A as a three-way catalyst, a rear catalytic converter 6A as a photocatalyst behind the catalytic converter 5A, and a muffler 7. In this case, the front catalytic converter 5A functioning as a three-way catalyst can be brought closer to the engine 1, and the front catalytic converter 5A can be easily maintained in the activation temperature range, and the activation range can be expanded. Catalytic converter 6A that is a photocatalyst
Can be reduced by thermal degradation.

FIG. 7 shows another embodiment of the present invention. The gas purification device here is applied as an air conditioner E for a vehicle. Here, the air-conditioning apparatus E is mounted in an airspace in a vehicle cabin surrounded by a dashboard 30 (see FIG. 1) and an instrument panel 31 of the vehicle, and an air conditioner unit 32 supported by the dashboard 30 and connected to the air conditioner unit 32. Left and right upper air ducts 33 and 34, left and right lower air ducts 35 and 36, and wind direction adjusting grills (not shown) provided at the outlets of these air ducts.

The air conditioner unit 32 includes an electric blower 37,
The air condition is adjusted by selectively operating a condenser and a heater (not shown) in a predetermined air-conditioning mode. The air is guided to the branch chamber 38, and is switched by the switching damper 39 of the branch chamber 38. Upper and lower chambers 40, 41
And is blown into the vehicle cabin by upper left and right air ducts 33 and 34 communicating with the upper chamber 40 or lower left and right air ducts 35 and 36 communicating with the lower chamber 41. Here, the branch room 38 and the upper and lower rooms 4 of the air conditioner unit 32
0, 41 partition h and each air duct 33, 34, 35,
36 are all formed of a translucent material such as acrylic, and the photocatalyst 16 is attached to the inner wall surface of these. And branch room 3
8 is provided with an ultraviolet irradiation lamp 141, which is connected to a power supply circuit (not shown).

When the air conditioner unit 32 is driven, when a power supply circuit (not shown) is turned on and the ultraviolet irradiation lamp 141 emits ultraviolet light, the light passes through the light transmitting partition h as well as the branch chamber 38 in the air conditioner unit 32. And the ultraviolet light L is applied to the upper and lower chambers 40, 41 and the air ducts 33, 34, 3
The ultraviolet light L can be diffused and radiated evenly to the photocatalyst 16 attached to the inner wall surfaces of the partition walls h and the air ducts. Molds, germs, and the like, which are likely to be formed on the inner wall surfaces of 33, 34, 35, and 36, can be removed by a strong oxidizing action, and a bad smell in the air blown out by the air conditioner can be eliminated.

[0028]

As described above, according to the first aspect of the present invention, ultraviolet rays are incident on the translucent catalyst carrier, diffused, and efficiently irradiate the photocatalyst attached to the entire area of the catalyst carrier with the ultraviolet rays. Irradiation makes it possible to extract the strong oxidizing action of all the photocatalysts attached to the catalyst carrier without waste, and gas can be efficiently purified.

According to the second aspect of the present invention, in particular, since the ultraviolet light from the light source is irradiated to the photocatalyst on the catalyst carrier via the optical fiber, the ultraviolet irradiation means can be divided, the catalyst carrier side can be made relatively small, and the installation space can be reduced. It is possible to facilitate the maintenance, and also to facilitate the maintenance of the ultraviolet irradiation means on the light source side.

According to the third aspect of the present invention, in particular, since the light reflecting piece diffuses and efficiently diffuses the ultraviolet light incident on the catalyst carrier acting as a light guide path from the ultraviolet irradiation means, the irradiation efficiency of the photocatalyst over the entire catalyst carrier can be reduced. Gas purification can be performed efficiently.

[Brief description of the drawings]

FIG. 1 is a schematic side view of a vehicle equipped with a gas purification device to which the present invention is applied.

FIG. 2 is a cross-sectional view of a front catalytic converter used in the gas purification device of FIG.

FIG. 3 is a sectional view taken along line AA of FIG. 1;

4A and 4B are explanatory diagrams of a partition and a photocatalyst in a front catalytic converter used in the gas purification device of FIG. 1; FIG. 4A shows the functions of the partition and photocatalyst of the gas purification device of FIG.
(C) and (d) show the functions of the partition wall and the photocatalyst of the other different gas purifying devices, respectively.

FIG. 5 is a cross-sectional view of a front catalytic converter used in place of the front catalytic converter used in the gas purification device of FIG.

FIG. 6 is a layout diagram of a gas purification device as another embodiment of the present invention.

FIG. 7 is a schematic layout diagram of a gas purification device as another embodiment of the present invention.

[Explanation of symbols]

 2 Exhaust pipe 13 Optical fiber 14 Light source section 141 Ultraviolet irradiation lamp 15 Catalyst carrier 16 Photocatalyst d Light reflection piece r Exhaust gas passage w Partition wall G Exhaust gas L Ultraviolet light

Claims (3)

[Claims] 1. A catalyst carrier provided in a passage of a gas to be treated, a photocatalyst carried on the catalyst carrier and purifying the gas to be treated by being irradiated with light containing ultraviolet rays, and irradiating the photocatalyst with ultraviolet rays. A gas purifier comprising: a catalyst carrier having a light-transmitting property. 2. The gas purifying apparatus according to claim 1, wherein said ultraviolet irradiation means irradiates light containing ultraviolet light from a light source to a photocatalyst on said catalyst carrier via an optical fiber. 3. The gas purifying apparatus according to claim 1, wherein said catalyst carrier is mixed with a light reflecting piece for irregularly reflecting light containing ultraviolet light transmitted through said catalyst carrier.