JP5282727B2 - Exhaust purification device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device capable of decomposing specific components contained in treated gas by efficiently utilizing high frequency energy with simple constitution, and excelling in mountability. <P>SOLUTION: The exhaust emission control device includes at least a high frequency oscillating means 30 oscillating a high frequency RF, and a waveguide 10 transmitting the high frequency RF oscillated from the high frequency generating means 30. The passage directions 11, 12 of exhaust passages through which treated exhaust flows, are made coincident with the transmitting direction of the waveguide 10 to interpose the waveguide 10 in the exhaust passages 11, 12. The treated exhaust permeates an inlet side opening of the waveguide 10 communicating with the before-treatment exhaust passage 11 through which exhaust before treated flows, and an outlet side opening of the waveguide 10 communicating with the treated exhaust passage 12 through which the treated exhaust flows. Gas permeable high frequency reflecting walls 20, 21 are provided for reflecting the high frequency RF oscillated from the high frequency generating means 30, and the waveguide 10 is set to such a length that the standing waves of the high frequency RF are formed between the gas permeable high frequency reflecting walls 20, 21 provided at both ends of the waveguide 10. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention decomposes specific components such as unburned fuel, particulate matter, NOx, SOF, and VOC contained in combustion exhaust discharged from an internal combustion engine, an incinerator, a combustion furnace, a thermal power generator, etc. by microwave plasma. The present invention relates to an exhaust purification device to be removed.

  Conventionally, a porous filter made of a honeycomb structure or a catalyst-carrying filter is disposed in a combustion exhaust passage of an internal combustion engine to adsorb harmful substances such as particulate matter and NOx contained in the combustion exhaust to the porous filter. Exhaust gas purification devices that are removed by decomposition with a catalyst are widely used.

  However, in a conventional exhaust gas purification device via a filter, there is a possibility that the exhaust gas purification capability may be reduced due to an increase in flow resistance due to clogging of the filter or due to aging of the catalyst.

  For such a problem, Patent Document 1 discloses a heating chamber provided in the middle of an exhaust pipe for exhausting exhaust gas from an internal combustion engine, and high-frequency generating means for generating and supplying high-frequency energy to the heating chamber. A high-frequency heating element that is housed in the heating chamber and generates heat by absorbing high-frequency energy, and is disposed behind the high-frequency heating element with respect to the flow of exhaust gas that is housed in the heating chamber and exhausted from the internal combustion engine, An exhaust gas purifying apparatus for an internal combustion engine is disclosed that includes a purification means for decomposing harmful substances contained in the exhaust gas heated by the heat of the exhaust gas and the heat generated by the high-frequency heating element.

  In Patent Document 2, when a ceramic or ceramic-lined reaction tube is interposed in a part of the exhaust passage, and a microwave electric field is applied to the exhaust gas flowing in the reaction tube from a waveguide or a cavity resonator orthogonal thereto, Promote the stable generation of microwave plasma by pre-ionizing the exhaust gas upstream of the waveguide or cavity resonator tube, and reacting exhaust particulates and unburned hydrocarbons with excess oxygen in the exhaust in this plasma Discloses a method of burning off internal combustion engine exhaust particulates.

  However, the high-frequency energy supplied from the high-frequency generating means as in Patent Document 1 is not directly used for decomposing harmful substances contained in the exhaust, but the high-frequency heating element absorbs the high-frequency energy and In an exhaust purification device that indirectly decomposes harmful substances in the exhaust by heat, the high frequency generating means requires a very high output, so when it is installed in an automobile with a limited power capacity, the energy that can be supplied is There is a risk that it will be insufficient and will not be able to demonstrate sufficient purification capacity.

  Further, in the exhaust gas purifying apparatus of Patent Document 1, the high frequency generated by the high frequency generating means is introduced into the exhaust pipe through the waveguide. At this time, an opening for blocking high frequency is provided on the inflow side of the exhaust gas, and an opening for supplying power to the high frequency heating element is provided on the downstream side. Since the high frequency cutoff means for preventing leakage is provided, not only the transmission direction of the high frequency introduced into the exhaust pipe is changed, but also the waveguide diameter and the exhaust pipe are greatly different, so that the resonance state is maintained. However, high frequency is dispersed and energy efficiency may be reduced.

  In addition, it is necessary to provide adjusting means such as a stub tuner or EH tuner in order to maintain the resonance state even if the high-frequency transmission direction changes, and the physique of the device becomes large, so that it can be used in a limited space such as a vehicle. May be difficult to mount.

  On the other hand, as described in Patent Document 2, when the exhaust gas is pre-ionized upstream of the waveguide or the cavity resonance tube to try to stably generate the microwave plasma, the pre-ionized exhaust gas is used as the cavity resonance tube. Depending on the distance to reach, the ionization state may not be maintained and the discharge energy may be wasted.

  Therefore, in view of such circumstances, the present invention has an object to provide an exhaust emission control device that can efficiently decompose high-frequency energy with a simple configuration and can decompose specific components contained in the gas to be processed, and has excellent mountability. .

The first aspect of the invention is an exhaust emission control device that irradiates and decomposes a specific component contained in the exhaust gas to be treated, and includes at least a high-frequency oscillation means that oscillates a high frequency, and a high-frequency wave oscillated from the high-frequency generation means A waveguide for transmitting the exhaust gas, the flow path direction of the exhaust flow path through which the exhaust to be treated flows matches the transmission direction of the waveguide, and the waveguide is interposed in the exhaust flow path, An inlet-side opening of the waveguide that communicates with the pre-treatment exhaust flow path through which the untreated exhaust flows, and an outlet-side opening of the waveguide that communicates with the treated exhaust flow path through which the treated exhaust flows. The gas-permeable high-frequency reflection is provided with a gas-permeable high-frequency reflection wall that transmits the exhaust to be treated and reflects the high-frequency wave oscillated from the high-frequency generating means, and the waveguide is provided at both ends of the waveguide. The length that the above high-frequency standing wave is formed between the walls With a constant, high voltage generating means for generating a high voltage, provided with a discharge means for performing discharge to the waveguide by applying a high voltage from the high voltage generating means, the said discharge means, said standing wave It is arranged so as to be able to discharge at a position where it becomes an antinode (claim 1).

According to the first invention, the high frequency generated from the high frequency generating means in the waveguide forms a standing wave, and the region corresponding to the antinode of the standing wave having a high electric field strength and the standing in which the electric field strength is low. A region corresponding to a wave node is formed at a constant period in the flow path direction, and the treated exhaust gas introduced from the pre-treatment exhaust flow channel into the waveguide always passes through the region where the electric field strength is high. The specific component contained in the exhaust to be treated directly absorbs the high frequency energy, is ionized and decomposes into a plasma state, and is discharged to the treated exhaust passage.
Further, since the high-frequency energy is directly and intensively applied to the specific component in the exhaust gas to be processed in the strong electric field region, the exhaust gas to be processed can be effectively purified.
In the present invention, not only high-frequency energy but also discharge energy is applied, so that the conversion of the specific component in the exhaust gas to be processed into plasma is more effectively promoted, and purification of the exhaust gas to be processed proceeds.
Further, due to the synergistic effect of the high frequency energy and the discharge energy, the energy supplied to each can be reduced as compared with the case where the energy is supplied alone in order to achieve the same effect.
At this time, since the high frequency energy and the discharge energy are simultaneously supplied to the specific component in the exhaust gas to be processed at a position where the electric field strength is high, the plasma conversion of the specific component in the exhaust gas to be processed is further effectively promoted, Purification of the exhaust to be treated proceeds.

  According to the third aspect of the invention, since the high frequency energy and the discharge energy are simultaneously supplied to the specific component in the exhaust gas to be processed at a position where the electric field strength is high, the plasma of the specific component in the exhaust gas to be processed is further effectively obtained. To promote the purification of exhaust gas to be treated.

In the second aspect of the invention, providing a plurality of said discharge means (claim 2).

According to the second invention, when the exhaust gas to be processed moves in the waveguide, not only the high frequency energy but also the discharge energy is repeatedly supplied over a plurality of times. Promoting the conversion of components into plasma and purifying the exhaust to be treated.

Specifically, as in the third aspect of the invention, an antenna that oscillates a high frequency from the high-frequency oscillation means to the waveguide is connected to a 1/4 wavelength or 3 / of the standing wave from the outlet side opening of the waveguide. 4 provided at a distance of a wavelength (claim 3).

According to the third aspect of the present invention, the high-frequency standing wave can be reliably formed in the waveguide, and the exhaust gas that effectively promotes the conversion of the specific component in the exhaust gas to be processed into plasma and purifies the exhaust gas to be processed. A purification device can be realized.

Specifically, as in the fourth invention, the high frequency is desirably a microwave 10GHz from the frequency 1 GHz (claim 4).

In the fifth invention, the exhaust to be treated is any one of an internal combustion engine, a firing furnace, an incinerator, a combustion furnace, and a combustion exhaust discharged from a thermal power generator, and the specific component is an unburned hydrocarbon, carbon , particulate matter (PM), soluble organic fraction (SOF), is either volatile organic compounds (VOC), nitrogen oxides (NOx) (claim 5).

According to the fifth invention, the flow resistance of the exhaust flow path does not change, and the specific component such as PM is converted into plasma or oxidized and rendered harmless without affecting the combustion efficiency of the internal combustion engine or the like. It can be discharged as treated exhaust.

The block diagram which shows the outline | summary of the exhaust gas purification apparatus in the 1st Embodiment of this invention. The mode of the standing wave which generate | occur | produces in the waveguide in the exhaust gas purification apparatus in the 1st Embodiment of this invention is shown, (a) is a top view which shows a magnetic field and an electric current, (b) is a magnetic field, an electric current, and (C) is a longitudinal sectional view showing the electric field, (d) is a transverse sectional view showing the electric field, (e) is a characteristic diagram showing the electric field distribution in the flow path direction, and (f) is The characteristic view which shows electric field distribution of a cross-sectional direction. The mode of the standing wave which generate | occur | produces in the waveguide in the exhaust gas purification apparatus in the 2nd Embodiment of this invention is shown, (a) is a top view which shows a magnetic field and an electric current, (b) is a longitudinal section which shows an electric field (C) is a characteristic diagram showing the state of a standing wave, (d) is a cross-sectional view showing an electric field and a magnetic field, and (e) is a cross-sectional view. The characteristic view which shows electric field distribution. The block diagram which shows the outline | summary of the exhaust gas purification apparatus in the 3rd Embodiment of invention.

  The present invention is any one of combustion exhaust discharged from an internal combustion engine, a firing furnace, an incinerator, a combustion furnace, and a thermal power generator as a treated exhaust, and a specific component contained in the treated exhaust is unburned carbonized. Exhaust flow in which combustion exhaust flows due to clogging when it is any of hydrogen, carbon, particulate matter (PM), soluble organic component (SOF), volatile organic compound (VOC), or nitrogen oxide (NOx) Since the flow resistance of the road does not change, specific components such as PM are converted into plasma or oxidized, rendered harmless and discharged as treated exhaust without affecting the combustion efficiency of the internal combustion engine, etc. The exhaust gas purification apparatus is particularly suitable for reducing PM and NOx in the exhaust gas at the start of the automobile engine.

With reference to FIG. 1, the outline | summary of the exhaust-air-treatment apparatus 1 in the 1st Embodiment of this invention is demonstrated.
The exhaust treatment apparatus 1 is an exhaust purification apparatus that irradiates a specific component such as PM contained in the exhaust gas to be treated with high frequency RF and decomposes the high frequency oscillation means 30 that oscillates high frequency RF such as microwaves, And a waveguide 10 that transmits the high-frequency RF oscillated from the oscillation means 30, and the exhaust flow paths 11 and 12 through which the exhaust gas to be treated flows and the transmission direction of the waveguide 10 are made to coincide with each other. An opening on the inlet side of the waveguide 10 that communicates with the pre-treatment exhaust flow path 11 in which the waveguides are interposed in the flow paths 11 and 12 and the unprocessed exhaust flows, and the processed exhaust in which the processed exhaust flows. Gas-permeable high-frequency reflection walls 20 and 21 that transmit the exhaust to be processed and reflect the high-frequency RF oscillated from the high-frequency oscillating means 30 are provided in the opening on the outlet side of the waveguide that communicates with the flow path 12. Gas with wave tube 10 provided at both ends of waveguide 10 It is set to a length that the standing wave of the high frequency RF between the over-soluble high-frequency reflection wall 20, 21 is formed.
Specifically, a magnetron that oscillates a microwave with a frequency of 1 GHz to 10 GHz, particularly a microwave with a frequency of 2.54 GHz is suitable as the high-frequency oscillation means 30. Moreover, the oscillation output of a magnetron can use the thing of 100W-300W, for example.
As the gas-permeable high-frequency reflecting walls 20 and 21, a punching metal, a wire net, or the like having an opening corresponding to the cutoff wavelength of the high-frequency RF to be used can be used.

The high frequency RF oscillated from the high frequency oscillating means 30 via the antenna 31 forms a standing wave in the waveguide 10, and a region corresponding to the antinode of the standing wave having a high electric field strength and the electric field strength. The region corresponding to the node of the standing wave having a low frequency is formed at a constant period in the flow path direction, and the treated exhaust gas introduced into the waveguide from the pre-treatment exhaust flow channel must pass through the region where the electric field strength is high. At this time, the specific component contained in the exhaust to be treated directly absorbs the high frequency energy, is ionized to be in a plasma state, decomposed, and discharged to the treated exhaust flow path.
Moreover, since the high frequency energy is directly and intensively applied to the specific component in the exhaust gas to be processed in the strong electric field region, the exhaust gas to be processed can be effectively purified.

Further, in the present embodiment, a high voltage generating unit 50 that generates a high voltage, and a discharging unit 40 that discharges in the waveguide 10 by applying a high voltage from the high voltage generating unit 50 are provided. In addition to the high-frequency energy, the discharge energy can be applied.
Further, it is desirable that the discharging means 40 is disposed so as to be able to discharge at a position where the antinode of the standing wave is present, and a plurality of discharging means are preferably provided for each half wavelength of the standing wave.

In the present invention, the specific configuration of the discharge means 40 is a discharge that is fixed to the wall surface of the waveguide 10 through at least the insulator 41 and can discharge into the waveguide 10 when a high voltage is applied. As long as the electrode 42 is provided, any type such as corona discharge, arc discharge, silent discharge, surface discharge, air discharge, plasma discharge and ion discharge may be used.
The high voltage generator 30 may be a device that applies a high voltage continuously or a device that applies a high voltage in pulses.
With such a configuration, the high frequency energy and the discharge energy are simultaneously supplied to the specific component in the exhaust to be processed at a position where the electric field strength is high, and furthermore, the exhaust to be processed is provided by providing a plurality of discharge means 40. When moving in the waveguide 10, not only high-frequency energy but also discharge energy is repeatedly supplied over a plurality of times, so that the specific component in the exhaust gas to be processed can be more reliably promoted to be processed, Exhaust purification proceeds.

Specifically, the antenna 31 that oscillates the high frequency RF from the high frequency oscillating means 30 to the waveguide 10 is ¼ wavelength or 3/3 of the standing wave formed by the change of the electric field from the outlet side opening of the waveguide 10. The length of the waveguide 10 is adjusted so that a standing wave node is generated at the positions of the gas permeable high-frequency reflection walls 20 and 21 at both ends of the waveguide 10. Yes.
By adopting such a configuration, it is possible to reliably form a high-frequency standing wave in the waveguide 10 and effectively promote the conversion of the specific component in the exhaust gas to be processed into plasma, thereby purifying the exhaust gas to be processed. An exhaust purification device that performs this can be realized.

  More specifically, the waveguide 10 is a rectangular waveguide in JEITA standards (formerly EIAJ standards) TT3001A to TT3011A issued by the Japan Electronics and Information Technology Industries Association (formerly the Japan Electronics Opportunity Industry Association). WRI-22, 26 (International Electrotechnical Commission IEC standard: equivalent to R22, 26), circular waveguide WCI-22, 25, 30 (IEC standard: equivalent to C22) and the like can be used as appropriate in accordance with the mode.

With reference to FIG. 2, the electromagnetic field distribution in the fundamental mode (H ₁₀ ) when a rectangular waveguide (WRI-26) is used as the waveguide 10 will be described.
This figure (a) is a top view which shows the magnetic field H and the electric current I, (b) is a side view which shows the magnetic field H and the electric current I, (c) is a longitudinal cross-sectional view which shows the electric field E, (d). Is a cross-sectional view showing the electric field E, (e) is a characteristic diagram showing the electric field distribution in the flow path direction and showing a standing wave, and (f) is a characteristic diagram showing the electric field distribution in the cross-sectional direction.

In this embodiment, the opening of the waveguide 10 is set to a = 86.4 mm and b = 43.2 mm.
For example, when the frequency of the high-frequency RF is a microwave of 2.45 GHz, the wavelength is about 122.4 mm. Therefore, the gas-permeable high-frequency reflection walls 20 and 21 have ½ wavelength, that is, an opening diameter of about A wire mesh having a grid with an opening diameter of less than 6 cm is provided.
In the present embodiment, the antenna 31 is provided at a position of 3/4 wavelength from the exit side opening, that is, about 91.8 mm.

The microwave oscillated from the antenna 31 propagates into the waveguide 10 and is reflected without passing through the gas-permeable high-frequency reflection walls 20 and 21 to form a standing wave in the waveguide 10.
At this time, the in-tube wavelength λ _g repeats a region having a high electric field strength and a region having a low electric field strength with a period of about 17.35 cm. In the figure, the electric field is represented by E, the magnetic field is represented by H, and the current is represented by I.
Cutoff wavelength: λ _c = 2a = 17.28 (cm)
Cutoff frequency: f _c = V _c /2a=17.36 ₍ GHz)
In-tube wavelength: λ _g = λ ₀ / √ {[1- (λ ₀ /1.728) ² ]}
= 17.35 cm
a: Waveguide long side (cm)
λ ₀ : Free space wavelength (cm)
Therefore, if the discharge means 40 is provided at intervals of about 17.35 cm so as to match the antinodes of the standing wave, the strong electric field region of the microwave and the discharge field are made to coincide with each other in the exhaust to be treated extremely efficiently. Specific components such as PM and NOx can be converted into plasma and decomposed.

  The exhaust to be treated containing specific components such as PM and Nox repeatedly passes through the region corresponding to the antinode of the standing wave having a high electric field strength when passing through the waveguide 10, so that the specific component is efficient during this period. It is well plasmad.

With reference to FIG. 3, the electromagnetic field distribution in the fundamental mode (H ₁₁ ) when the circular waveguide 10a (WCI 22) is used will be described as a second embodiment of the present invention. The H ₁₁ mode when the circular waveguide 10a is used corresponds to the H ₁₀ mode when the rectangular waveguide 10 is used. This figure (a) is a plan view showing the magnetic field H and the current I, (b) is a longitudinal sectional view showing the electric field E, (c) shows the electric field distribution in the flow path direction, standing wave state (D) is a cross-sectional view showing the electric field E and the magnetic field H, and (e) is a characteristic view showing the electric field distribution in the cross-sectional direction.

In the present embodiment, if the discharge means 40 is provided at intervals of about 18 cm, the strong electric field region of the microwave is matched with the discharge field, and specific components such as PM and NOx in the exhaust gas to be treated are extremely efficiently obtained. It can be turned into plasma and decomposed.
Cutoff wavelength: λ _c = 2a = 1.706d (cm)
Cutoff frequency: f _c = V _c /2a=17.59 ₍ GHz)
In-tube wavelength: λ _g = λ ₀ / √ {[1- (λ _{0 /} 1.706d) ² ]}
= 17.97 (cm)
d: Waveguide inner diameter (cm)
λ ₀ : Free space wavelength (cm)

  With reference to FIG. 4, an exhaust emission control device 1b according to a third embodiment of the present invention will be described. In the above embodiment, as the discharge means 40, when a high voltage is applied from the high voltage generator 50, discharge is performed between the discharge electrode 41 and the waveguide 10 or into the exhaust to be treated. However, it is also possible to use an electrode that discharges between the discharge electrode 41a and the ground electrode 41b facing the discharge electrode 41a as in the present embodiment.

  The shape of the discharge electrodes 41, 41a, 41b is not limited to a rod-like or needle-like shape as shown in FIGS. 1 and 4, but may be a flat plate shape or a spherical discharge at the tip of the shaft. It is also possible to use an arc discharge between a center electrode and a ground electrode facing each other via an insulator, such as those generally used as a spark plug, or a long-axis center electrode A plasma ignition plug in which a discharge space is defined inside the insulator by a cylindrical insulator covering the electrode and an annular ground electrode disposed concentrically may be used.

  Further, the present invention is not limited to the above-described embodiment, and a waveguide that transmits the exhaust to be processed and reflects the high frequency at both ends of a part of the exhaust flow path to be processed is provided with a gas-permeable high-frequency reflection wall. An antenna that emits a plurality of high frequencies can be appropriately changed without departing from the gist of the present invention, in which a high-frequency standing wave is formed in the waveguide and the specific component in the exhaust gas to be treated is turned into plasma. May be arranged side by side or arranged so that the axial directions of the two antennas are orthogonal to each other, the chance that the specific component in the exhaust gas to be treated is converted into plasma may be increased.

  Furthermore, although the exhaust purification apparatus of the present invention can exhibit the above-mentioned effects when used alone, it is provided on the upstream side or the downstream side of an exhaust purification apparatus using a conventional filter as an auxiliary exhaust purification apparatus. It may be used.

DESCRIPTION OF SYMBOLS 1 Exhaust purification apparatus 10 Waveguide 11 Pre-process exhaust flow path 12 Processed exhaust flow path 20 Inlet side high frequency reflective wall 21 Outlet side high frequency reflective wall 30 High frequency oscillation means (magnetron)
31 High-frequency oscillation antenna 40 Discharge means 41 Insulation part 42 Discharge part 50 High-voltage power supply

JP-A-6-2535 JP 2003-176710 A

Claims (5)

An exhaust purification device that irradiates and decomposes a specific component contained in the exhaust gas to be treated,
At least a high frequency oscillation means for oscillating a high frequency, and a waveguide for transmitting the high frequency oscillated from the high frequency oscillation means,
The flow path direction of the exhaust flow path through which the exhaust to be treated flows matches the transmission direction of the waveguide, and the waveguide is interposed in the exhaust flow path,
An inlet-side opening of the waveguide that communicates with the pre-treatment exhaust flow path through which the untreated exhaust flows, and an outlet-side opening of the waveguide that communicates with the treated exhaust flow path through which the treated exhaust flows. In addition, a gas-permeable high-frequency reflecting wall is provided that transmits the exhaust to be treated and reflects the high-frequency wave oscillated from the high-frequency oscillation means.
The waveguide is set to a length at which the high-frequency standing wave is formed between the gas-permeable high-frequency reflection walls provided at both ends of the waveguide , and
A high voltage generating means for generating a high voltage, and a discharging means for discharging into the waveguide by applying a high voltage from the high voltage generating means,
The exhaust gas purification apparatus according to claim 1, wherein the discharge means is disposed so as to be able to discharge at a position that is an antinode of the standing wave . The exhaust emission control device according to claim 1, wherein a plurality of the discharge means are provided . The antenna according to claim 1 or 2, wherein an antenna that oscillates a high frequency from the high-frequency oscillation means to the waveguide is provided at a distance of 1/4 wavelength or 3/4 wavelength of the standing wave from an opening on the exit side of the waveguide. The exhaust emission control device described. The exhaust emission control device according to any one of claims 1 to 3 , wherein the high frequency is a microwave having a frequency of 1 GHz to 10 GHz . The exhaust to be treated is any one of combustion exhaust discharged from an internal combustion engine, a firing furnace, an incinerator, a combustion furnace, a thermal power generator, and the specific component is unburned hydrocarbon, carbon, particulate matter, soluble The exhaust emission control device according to any one of claims 1 to 4, wherein the exhaust purification device is any one of an organic component (SOF), a volatile organic compound (VOC), and a nitrogen oxide (NOx) .

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