JP2014173503A - Exhaust gas treatment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust gas treatment device capable of suppressing temperature rise of a microwave generation source due to heat of exhaust gas.SOLUTION: The exhaust gas treatment device includes an exhaust pipe, the microwave generation source, a ridge waveguide, a retention metal pipe, and a fine particle collection filter. The ridge waveguide propagates microwave generated from the microwave generation source. The ridge waveguide includes a plurality of internal fins disposed along the propagation direction of the microwave and is made of metal. The retention metal pipe has an opening part connected with an emission part of the ridge waveguide on the lateral surface and is connected with an engine side exhaust pipe. The fine particle collection filter is retained on an inner part of the retention metal pipe and is made of a porous body which collects fine particles in exhaust gas flowing-in from the engine side exhaust pipe. The fine particles collected by the fine particle collection filter are thermally decomposed by the porous body which is heated by the microwave emitted from the emission part and are exhausted to an external part.

Description

  Embodiments described herein relate generally to an exhaust gas processing apparatus.

  It is required to purify exhaust gas from an engine or the like to reduce air pollution. In particular, exhaust gas regulations for diesel engines are becoming stricter.

When harmful substances such as unburned hydrocarbons, nitrogen oxides (NO _x ), carbon monoxide, and sulfate mixtures contained in the exhaust gas are thermally decomposed, they can be made harmless substances.

  For example, when the particulate collection filter is heated using a microwave heating apparatus, the deposited harmful substances can be decomposed in a short time.

  The particulate collection filter is provided in the exhaust pipe. For this reason, the heated air may pass through the inside of the waveguide, which is a microwave transmission path, and may deteriorate the electronic components that constitute the microwave generation source.

JP 2005-108449 A

  Provided is an exhaust gas processing apparatus capable of suppressing a temperature rise of a microwave generation source due to heat of exhaust gas.

  The exhaust gas treatment apparatus of the embodiment includes a microwave generation source, a ridge waveguide, a holding metal tube, and a particulate collection filter. The ridge waveguide propagates a microwave generated from a microwave source. The ridge waveguide is made of metal including a plurality of internal fins provided along the propagation direction of the microwave. The holding metal tube has an opening connected to the emission portion of the ridge waveguide on the side surface, and is connected to the engine side exhaust pipe. The particulate collection filter is held in the holding metal tube and is made of a porous body that collects particulates in the exhaust gas flowing in from the engine side exhaust pipe. The fine particles collected by the fine particle collection filter are thermally decomposed by the porous body heated by the microwave emitted from the emission part and discharged to the outside.

FIG. 1A is a schematic perspective view of an exhaust gas processing apparatus according to a first embodiment of the present invention, and FIG. 1B is a schematic cross-sectional view taken along the line AA. It is a schematic cross section of a particulate collection filter. It is a partial model perspective view of the exhaust-gas processing apparatus concerning a comparative example. FIG. 4A is a schematic cross-sectional view of a ridge waveguide of an exhaust gas processing apparatus according to the second embodiment, and FIG. 4B is a schematic cross-sectional view of a ridge waveguide of a modification of the second embodiment. . It is a schematic cross section of the ridge waveguide of the exhaust gas processing apparatus concerning 3rd Embodiment. It is a schematic cross section of the modification of a particulate collection filter.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1A is a schematic perspective view of an exhaust gas processing apparatus according to a first embodiment of the present invention, and FIG. 1B is a schematic cross-sectional view taken along the line AA.
As shown in FIG. 1A, the exhaust gas treatment device 10 includes a microwave generation source 22, a ridge waveguide 30, a holding metal tube 22, and a particulate collection filter 24.

  The exhaust gas F1 from the engine flows into one end portion of the holding metal tube 22 connected to the engine side exhaust tube 20. Further, the purified exhaust gas F2 is discharged from the muffler side exhaust pipe 26 to the outside.

  The microwave generation source 22 generates a microwave having a frequency (for example, near 0.9 GHz, near 2.45 GHz) assigned to the microwave heating apparatus. The generation source may be a semiconductor oscillator made of magnetron, klystron, GaN HEMT (High Electron Mobility Transistor), or the like.

  The ridge waveguide 30 has a ridge portion 32 including a plurality of internal fins made of metal in the vicinity of the central portion of the long side (width W) of the internal cross section, and the microwave generated from the microwave generation source 22. Is propagated to the load.

  An opening 22 a is provided on the side surface of the holding metal tube 22. The ridge waveguide 30 is connected to the side surface of the holding metal tube 22. The microwaves emitted from the emission portion 30a of the ridge waveguide 30 enter the holding metal tube 22 through the opening 22a.

  The particulate collection filter 24 is held inside the holding metal tube 22 and is made of a porous body that collects particulates in the exhaust gas F <b> 1 flowing from the exhaust pipe 20. The microwave incident from the opening 22a of the holding metal tube 22 irradiates the side surface of the porous body, and then is absorbed by the porous body while spreading and heats the porous body. That is, when the particle collection filter surrounded by the holding metal tube 22 is viewed from the emission portion 22a of the ridge waveguide 22, the microwave can efficiently heat the particle collection filter when operated like a resonator.

  Also, microwave blocking means 22a and 22b made of a metal mesh or the like are held between the particulate collection filter 24 and the engine side exhaust pipe 20 and between the particulate collection filter 24 and the muffler side exhaust pipe 26. 22 can be provided. When the microwave blocking means 22a and 22b are provided, leakage of the microwave to the outside is suppressed, and safety is ensured.

As shown in FIG. 1B, the ridge waveguide 30 has a ridge portion 32 composed of a plurality of internal fins. The internal fin includes a plurality of fins along the propagation direction of the microwave. Parallel to the propagation direction is more preferable because heat can be efficiently taken from the heated air. If the interval G between the internal fins is set to a quarter or less of the width W of the ridge waveguide 30, it functions as the ridge portion 32 without providing the connection plate 32a for the internal fins. FIG. 1 (b) represents the TE ₁₀ mode. The electric field is in the direction of the arrow, and its intensity E is maximum at the center.

The exhaust gas contains harmful substances composed of fine particles such as unburned hydrocarbons, nitrogen oxides (NO _x ), carbon monoxide, and sulfur oxides. These fine particles are collected when passing through the porous body. However, if the use is continued for a long time, the effect of collecting the porous material is lowered and the material is discharged to the outside as it is. For this reason, it is preferable to periodically remove harmful fine particles. For example, when these fine particles are set to 600 ° C. or higher, thermal decomposition efficiently occurs, and harmful substances can be rendered harmless in a short time.

  Even when heating by microwaves is not performed, the high-temperature exhaust gas passes through, so the porous body constituting the particulate collection filter 24 has a temperature of several hundred degrees Celsius or higher. The convection heat or radiant heat flows into the waveguide 30 from the opening 22 a of the holding metal tube 22 and raises the internal temperature of the microwave generation source 22. Since the microwave generation source 22 includes electronic components and the like, for example, the temperature is preferably 100 ° C. or lower.

  In the first embodiment, a ridge portion 32 is provided in the ridge waveguide 30. The plurality of internal fins constituting the ridge portion 32 take away convective heat or radiant heat and discharge it from the outer wall of the ridge waveguide 30 to the outside. For this reason, a cooling effect increases and the temperature rise of the microwave generation source 22 can be suppressed.

FIG. 2 is a schematic cross-sectional view of the particulate collection filter 24.
The porous body constituting the particulate collection filter 24 can be a material made of a composite oxide containing silicon carbide (SiC), carbon (C), metal, or the like, or a ceramic. These materials act as microwave absorbers. Note that the porous body includes a honeycomb structure. When the cross section of the particulate collection filter 24 is circular, the diameter D24 can be, for example, 3 to 10 cm.

  When the porous body is a honeycomb structure, a material such as alumina or zirconia can be used. The radio wave absorber may be an oxide such as zinc, copper, manganese, cobalt, or a composite oxide, and may be provided on the inner surface of the honeycomb structure.

  The size of the holding metal tube 22 can be appropriately selected so that the microwave emitted from the emission portion 30a of the ridge waveguide 30 is efficiently absorbed by the porous body.

  During normal engine operation, the particulate collection filter 24 is not irradiated with microwaves. However, the exhaust gas is hot even in the non-radiation state of the microwave except when the engine is started. If the exhaust gas blocking part 34 is provided between the emission part 30a of the ridge waveguide 30 and the ridge part 32, the inflow of high-temperature exhaust gas can be prevented.

FIG. 3 is a partial schematic perspective view of an exhaust gas treatment apparatus according to a comparative example.
The exhaust gas treatment apparatus includes a particulate collection filter 124, a microwave generation source 122, a waveguide 130, a cavity resonator 131, a holding metal tube 122, and a particulate collection filter 124. The cavity resonator 131 can control standing waves by the movable short-circuit plate 131a and the variable coupling window 131b.

  The particulate collection filter 124 is provided so as to penetrate the cavity resonator 131. The cavity resonator 131 and the microwave generation source 122 are connected by a waveguide 130. For this reason, the air (dot line) heated by the exhaust gas exposes the electronic components inside the microwave generation source 122 to a high temperature using the inside of the waveguide 130 as a flow path. For example, the heat-resistant temperature of the magnetron is as low as about 200 ° C., and the maximum rated temperature of the electronic components constituting the power circuit is as low as 200 ° C.

  By the way, a diesel engine that uses light oil that has high output and good fuel efficiency is used in automobiles, railcars, ships, and the like. The particulate component contained in the exhaust gas from the diesel engine is called diesel exhaust particulate (Diesel Particulate Matter: DPM), and becomes black smoke when the concentration is high. This component includes tufted carbon fine particles, a polymer hydrocarbon which is a soluble organic component, a mixture of sulfate (sulfate) oxidized with sulfur, and the like.

  If the diesel exhaust particulates adhere to cover the surface of the three-way catalyst used for exhaust gas treatment, the exhaust gas treatment performance deteriorates. For this reason, it is necessary to provide a filter for collecting diesel exhaust particulates in the exhaust flow path and perform cleaning more frequently than a gasoline engine filter.

  In the exhaust gas treatment device according to the comparative example, every time the diesel collection filter (Diesel Particulate Filter: DPF) is cleaned at a high frequency, the electronic components of the microwave generation source 122 are forced to operate at a high temperature. Easy to lower.

  In contrast, in the particulate collection filter 24 of the exhaust gas treatment apparatus of the first embodiment, the operating temperature of the electronic components of the microwave generation source 22 is kept low during the cleaning period. For this reason, even if cleaning is performed frequently, it is easy to keep the life of the exhaust gas treatment device long.

A three-way catalyst made of metal (platinum, palladium, rhodium) or a catalyst made of oxide (copper, manganese, cobalt) or the like can be provided on the inner surface of the porous body. When these catalysts are provided, harmful substances such as NO _x and carbon monoxide can be converted into nitrogen, carbon dioxide, water vapor and the like. That is, the exhaust gas from the gasoline engine can be purified.

FIG. 4A is a schematic cross-sectional view of a ridge waveguide of an exhaust gas processing apparatus according to the second embodiment, and FIG. 4B is a schematic cross-sectional view of a ridge waveguide of a modification of the second embodiment. .
The waveguide 30 may have a double ridge structure. As shown in FIG. 4A, the two ridge portions 32 a and 32 b are provided on the inner side of the ridge waveguide 30 on the sides facing each other. For this reason, the ridge portions 32a and 32b take convective heat and radiant heat, and release them from the outer wall of the ridge waveguide 30 to the outside from 30b and 30c, respectively. Since there are two heat radiation paths, the temperature rise of the microwave generation source 22 can be further reduced.

  Further, as shown in FIG. 4B, when the interval G between the internal fins is set to be equal to or less than a quarter of the width W of the internal long side of the ridge waveguide 30, the upper portions of the plurality of fins are connected in the horizontal direction. Even if not, it functions as the ridge portion 32. In this way, the structure can be simplified.

FIG. 5 is a schematic cross-sectional view of a ridge waveguide of the exhaust gas processing apparatus according to the third embodiment.
In the third embodiment, the external cooling fins 33 are respectively provided on the outer wall of the ridge waveguide 30. For this reason, the heat taken away by the internal fins is further dissipated from the external cooling fins 33 of the ridge waveguide 30. For this reason, the temperature of the microwave generation source 22 is further reduced.

FIG. 6 is a schematic cross-sectional view of a modified example of the particulate collection filter.
The particulate collection filter 25 includes a porous body 25a and a bulk portion 25b surrounding the porous portion 25a. Since the bulk part 25 is not porous, the outflow of exhaust gas can be suppressed. Since the exhaust gas does not flow into the microwave generation source 22 from the emission part 30a of the waveguide 30, the lifetime of the microwave generation source 22 can be kept long.

  The exhaust gas treatment apparatus according to the first to third embodiments can suppress the temperature rise of the microwave generation source due to the heat of the exhaust gas. For this reason, even if it uses a particulate collection filter with high frequency, the lifetime of the electronic components etc. which comprise a microwave generation source can be maintained long. As a result, for example, diesel particulates discharged from a diesel engine can be reliably collected and exhaust gas can be purified.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 10 Exhaust gas processing apparatus, 20 Engine side exhaust pipe, 22 Holding metal pipe, 22a Opening part, 24, 25 Particulate collection filter, 30 Ridge waveguide, 30a Output part, 32, 32a, 32b, 32c, 32d Ridge part , 33 External cooling fins, 34 Exhaust gas blocking part

Claims (7)

A microwave source;
A ridge waveguide for propagating microwaves generated from the microwave generation source, the ridge waveguide including a plurality of internal fins provided along the propagation direction of the microwaves and having a ridge portion made of metal. A wave tube,
An opening connected to the emission portion of the ridge waveguide is provided on a side surface, and a holding metal tube connected to the engine side exhaust pipe,
A particulate collection filter comprising a porous body that is retained inside the holding metal tube and collects particulates in the exhaust gas flowing from the engine side exhaust pipe;
With
The exhaust gas processing apparatus, wherein the fine particles collected by the fine particle collecting filter are thermally decomposed by the porous body heated by the microwave emitted from the emission part and discharged to the outside.   The exhaust gas processing apparatus according to claim 1, wherein the propagation direction of the microwave is parallel to the internal fin.   The exhaust gas processing apparatus according to claim 1, wherein the ridge waveguide has a double ridge structure.   The exhaust gas processing apparatus according to any one of claims 1 to 3, wherein a distance between the internal fins of the ridge portion is equal to or less than a quarter of a cross-sectional width of the ridge waveguide.   The exhaust gas processing apparatus according to any one of claims 1 to 4, wherein the particulate collection filter further includes a catalyst dispersed in the porous body.   The exhaust gas processing apparatus according to any one of claims 1 to 5, wherein the particulate collection filter further includes a radio wave absorber dispersed in the porous body.   The exhaust gas processing apparatus according to any one of claims 1 to 6, wherein the waveguide includes an exhaust gas blocking plate that blocks the exhaust gas but allows the microwave to pass therethrough.

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