JP2004011592A - Exhaust emission control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device for efficiently burning and eliminating particulate material (PM) included in exhaust from a diesel engine or the like. <P>SOLUTION: An electric discharge reactor 10 is disposed, and a diesel particulate filter 50 is disposed on a downstream side of an exhaust flow passage. In some cases, a PM burning medium is supported on a surface of the exhaust flow passage of the electric discharge reactor 15 and the diesel particulate filter 50. <P>COPYRIGHT: (C)2004,JPO

Description

【００３７】
【発明の効果】
本発明により、排気ガス上流に配置した放電リアクター内部の放電によって排気ガス成分が活性化され、活性酸素、オゾン、ＮＯｘ、酸素ラジカル、ＮＯｘラジカル等の酸化力の強いガス成分を発生させ、この酸化力の強いガス成分とＤＰＦにコートしたＰＭ酸化触媒との複合作用によって排気ガス中のＰＭを捕集し、かつ燃焼させるという考え方に基づくものであり、放電リアクターに電圧を印加することによりＰＭ燃焼除去の効率を著しく高めるという効果を有する。さらにＰＭ燃焼除去の効率が高まることによって、ＤＰＦの目詰まりが起こりにくくなり、エンジンへの負担が軽減し、燃費も向上するという効果も得られる。
【図面の簡単な説明】
【図１】本発明の一実施態様を表す概略図である。
【図２】本発明の放電リアクターで使用する電極の一例である網状電極を示す図である。ただし概念図であり目の大きさや数、形状は正確なものではない。
【図３】本発明の放電リアクターで使用する電極の一例である櫛状電極を示す図である。ただし概念図であり目の大きさや数、形状等は正確なものではない。
【符号の説明】
１０…放電リアクター
１５…リアクター本体
２０…放電電極
３０…放電電極
４０…電圧発生器
５０…ディーゼルパーティキュレートフィルター
７０…網状電極
８０…櫛状電極[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a device for purifying exhaust gas from an internal combustion engine or the like, and in particular, to purifying exhaust gas for removing particulate matter (particulate: hereinafter referred to as “PM”) discharged from a diesel engine. Equipment related.
[0002]
[Prior art]
2. Description of the Related Art Diesel engines are often used in automobiles, especially large vehicles. In recent years, it has been strongly desired to reduce PM emissions, particularly along with nitrogen oxides, carbon monoxide, and hydrocarbons in the exhaust gas. . Therefore, while technology development for essentially reducing PM by improving the engine or optimizing combustion conditions, etc., it is desired to establish a technology for efficiently removing PM in exhaust gas.
[0003]
As a method of removing PM from exhaust gas of a diesel engine, PM in the exhaust gas is removed by collecting the particulate matter with a filter called a diesel particulate filter (hereinafter, sometimes referred to as “DPF”), and the discharged PM is removed. Conventionally, a method for reducing the amount of A is known. As the DPF, a filter of a fiber type filter in which ceramics or metal is made into a fibrous form, a filter made of a ceramic honeycomb, a filter made of an alloy, and the like are known.
[0004]
However, these filters cause clogging of the filters due to the PM collected with the elapse of use time, and increase the airflow resistance, which places a burden on the engine. Further, the filter itself has the ability to trap PM, but does not itself burn PM. Therefore, in order to prevent clogging of the filter by the collected PM, it is necessary to regenerate the filter by burning the collected PM or backwashing with compressed air. The so-called continuous regeneration type filter that burns the collected PM has a catalyst that promotes PM combustion on the filter. To improve the speed of PM combustion, the filter temperature is increased to some extent. For example, when the vehicle is used in an automobile, there is a disadvantage that the PM combustion efficiency is deteriorated when the exhaust gas temperature is reduced when the automobile applies an engine brake. In order to improve this drawback, Japanese Patent Application Laid-Open No. 2001-280121 discloses a device in which a device for electrically heating is installed upstream of the exhaust gas flow of a DPF with a PM combustion catalyst when an engine braking operation of a vehicle is detected. Have been. This publication also discloses a device provided with a catalyst or plasma generator and an electric heating device upstream of a filter without a PM combustion catalyst. However, no detailed description of the plasma generator and a description of its PM removal effect are made, but PM combustion was not sufficient.
[0005]
On the other hand, regarding an exhaust gas purifying apparatus using plasma, for example, Japanese Patent Publication No. 63-500020 discloses that a non-equilibrium plasma is generated between electrodes by a voltage pulse, and harmful SOx and NOx are generated by radicals generated in the exhaust gas. SO ₂ , NO ₂ Although there is disclosed a method of purifying gas by converting to PM, it is not intended for PM combustion, there is no description of the effect of PM combustion, and there is no method capable of burning and removing PM. Japanese Patent Publication No. 7-293227 discloses that a discharge electrode having a mesh shape or the like and a metal cell-shaped receiving electrode carrying a catalyst are disposed to face each other, and the efficiency of removing nitrogen oxides and hydrocarbons, which are polluting molecules in exhaust gas, is reduced. Although an exhaust gas purifying device for the purpose of improvement is disclosed, also in this case, there is no description of PM combustion, and this alone cannot sufficiently perform PM combustion. Japanese Patent Application Laid-Open No. Hei 7-265652 discloses that NOx and SOx using ₂ , SO ₃ There is disclosed an exhaust gas purifying apparatus including a wire-type discharge electrode that oxidizes to an anode and a honeycomb-shaped counter electrode. However, this technique is not aimed at PM combustion removal, and does not describe the effect on PM combustion, nor is the effect capable of burning PM.
[0006]
[Problems to be solved by the invention]
That is, the conventionally known technique is extremely insufficient for removing and burning PM, and it is necessary to further increase the efficiency of removing and burning PM in exhaust gas discharged from a diesel engine or the like.
[0007]
[Means for Solving the Problems]
The present invention has been made in order to solve the above problems and realize high combustion efficiency of PM in exhaust gas, and includes a discharge reactor including an electrode for discharge and a reactor body that is an insulator. The present invention relates to an exhaust gas purification device including a diesel particulate filter disposed downstream of a discharge reactor in a flow direction of exhaust gas from a diesel engine.
[0008]
Further, according to a second aspect of the present invention, in the first aspect, the discharge reactor is a honeycomb structure to which a voltage can be applied, and a metal contact surface of the honeycomb structure with an exhaust gas is provided. An oxide and / or a metal oxide carrying one or more metals selected from transition metals and noble metals is coated, and a metal oxide and / or a metal oxide and / or Alternatively, the device according to claim 1, wherein the device is coated with a metal oxide carrying one or more metals selected from transition metals and noble metals.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
According to the present invention, a gas component having a strong oxidizing power such as active oxygen, ozone, NOx, oxygen radicals, and NOx radicals generated by activating an exhaust gas component by a discharge inside a discharge reactor disposed upstream in an exhaust gas flow direction is generated. The gas component having strong oxidizing power is oxidized by the gas component having strong oxidizing power, or the PM combustion catalyst is supported on the exhaust gas flow path surface of the discharge reactor as required, so that the gas component having strong oxidizing power and the PM burning catalyst are combined. Further, the combustion of PM is further promoted by the combined action of the above. In addition, a DPF is disposed downstream of the discharge reactor in the exhaust gas flow direction to remove the PM remaining after the combustion, or if necessary, coat the DPF with a PM oxidation catalyst. Then, by the combined action of the PM oxidation catalyst coated on the DPF and the gas component having a strong oxidizing power such as the ozone, It is based on the idea of removing by combustion of PM in the exhaust gas collected by PF.
[0010]
Hereinafter, the present invention will be described in detail with reference to FIG. 1, but FIG. 1 is a conceptual diagram of an apparatus constituting the present invention, and the present invention is not limited to the embodiment.
In FIG. 1, 10 is a discharge reactor, and 50 is a DPF. Exhaust gas containing PM flows from left to right in FIG. 1, first passes through the inside of the discharge reactor 10, and then passes through the inside of the DPF 50.
[0011]
An electrode 20 and an electrode 30 are arranged at the upstream entrance and the downstream exit of the exhaust gas flow of the discharge reactor 10, respectively, and a voltage is applied between both electrodes by a voltage generator 40. Downstream of the exhaust gas flow of the discharge reactor 10, a DPF 50 is disposed. The exhaust gas enters the discharge reactor 10, and inside the discharge reactor 10, gas components having strong oxidizing power such as active oxygen, ozone, NOx, oxygen radicals, and NOx radicals generated by electric energy are generated. The PM in the exhaust gas burns inside the discharge reactor 10 due to the strong oxidizing gas component. The strongly oxidizing gas component and the PM remaining after burning subsequently enter the DPF, and the PM remaining after burning is finally collected by the DPF. Here, when the DPF coated with the PM combustion catalyst is used, PM is more efficiently burned and removed by the combined action of the gas component having strong oxidizing power and the PM combustion catalyst coated on the DPF. .
[0012]
Hereinafter, each part constituting the present invention shown in FIG. 1 will be described more specifically.
In the discharge reactor 10 of the present invention, the exhaust gas passes through a structure disposed in the exhaust gas passage to generate a corona discharge by applying a voltage. The discharge reactor 10 generates the ozone or the like having a strong oxidizing power by discharge, thereby providing a place where PM is burned. The discharge reactor 10 includes an electrode 20 and an electrode 30 for discharging and a reactor body 15 which is an insulator. Corona discharge occurs inside the reactor body 15 due to the discharge between the electrode 20 and the electrode 30, and a highly oxidizing gas such as active oxygen, ozone, NOx, oxygen radicals, and NOx radicals is contained in the exhaust gas passing through the reactor 10. Ingredients are generated. The gas component having a strong oxidizing power and the PM in the exhaust gas come into contact in the reactor body 15 and the PM burns. That is, the reactor body 15 has an action of providing a place where a corona discharge occurs and a place where PM is burned by the strong oxidizing gas component generated by the corona discharge. Further, as described later, by supporting the PM combustion catalyst on the surface of the exhaust gas passage of the reactor body 15, it is possible to more efficiently burn and remove PM. A part of the strong oxidizing gas generated in the reactor 15 and the PM remaining after burning enter the DPF disposed further downstream of the exhaust gas.
[0013]
As the structure of the reactor body 15, any structure can be used as long as it is an insulator and a gas can pass through the inside, but a structure capable of increasing the contact area with the exhaust gas as much as possible, for example, a multilayer structure, a honeycomb structure, or the like is available. In particular, it is preferable to have a honeycomb structure in that a contact area between the reactor and the exhaust gas can be increased and resistance at the time of gas passage is small. As the insulator material constituting the reactor body 15, any material that is stable even under discharge conditions and has sufficient heat resistance to the exhaust gas temperature of a diesel engine can be used, but an insulating ceramic material is particularly preferable. . Specific examples include alumina, silica, zirconia, aluminum titanate, cordierite, etc., but cordierite is particularly preferred because it has excellent heat insulating properties and impact resistance. Thus, the most preferred reactor body 15 is a cordierite honeycomb.
[0014]
In the discharge reactor 10 of the present invention, when the surface of the exhaust gas flow path of the reactor body 15 is coated with a substance having a catalytic action capable of improving PM combustion efficiency, PM combustion can be further promoted. As the substance having the catalytic action, a metal oxide can be generally used, and specifically, for example, SiO 2 ₂ , Al ₂ O ₃ , CeO ₂ , TiO ₂ , ZrO ₂ Etc., especially TiO ₂ Is preferred from the viewpoint of promoting a radical reaction. These can be used alone or in combination of two or more. As a method of coating the metal oxide on the surface of the exhaust gas passage of the reactor body 15, a known method such as a wash coat can be used. The amount of the metal oxide to be coated can be arbitrarily selected within a coatable range. When a metal oxide is coated on the inner surface of the reactor by wash coating, it is preferable to further bake. As the firing conditions, those known by those skilled in the art can be used, and for example, 450 to 550 ° C. is preferable. When the metal oxide is coated and fired, the effect of improving the PM combustion efficiency is obtained as compared with the case where the metal oxide is not coated and fired.
[0015]
Further, a transition metal and / or a noble metal can be further supported on the metal oxide coated on the surface of the exhaust gas passage of the reactor. Specific examples of usable transition metals and / or noble metals include transition metals such as Fe, Mn, Ni, Co, and Cu, and noble metals such as Pt, Rh, Pd, and Ag. From the viewpoint of improving PM combustion efficiency, particularly preferred metals are Pt and Pd, and most preferably Pt. The amount of the metal to be supported is 0.1 to 10% by weight, particularly preferably 1 to 5% by weight, based on the metal oxide. These metals can be used alone or in combination, and one metal can be supported and then another metal can be supported to form a multilayer. The method of carrying the metal is specifically a method of carrying out water absorption carrying using the aqueous solution of the metal salt or the complex salt, followed by drying and firing. By supporting these transition metals and / or noble metals, an effect is obtained that the PM combustion efficiency is further improved as compared with the case where the metal oxide alone is coated.
[0016]
The discharge reactor 10 according to the present invention includes a discharge reactor body 15 and electrodes 20 and 30 for discharging. As shown in FIG. 1, it is particularly preferable that the electrode 20 and the electrode 30 are respectively disposed on an exhaust gas inlet surface and an exhaust gas outlet surface of the discharge reactor body 15. By doing so, corona discharge can be effectively generated inside the discharge reactor body 15.
[0017]
The electrode 20 and the electrode 30 can be arbitrarily used, such as a conductive material or a semiconductor, and a material capable of causing a discharge by applying a voltage, but a metal material is preferable, and specifically, Cu, W, Fe, Stainless steel and the like can be exemplified, and stainless steel is particularly preferable in terms of durability and cost.
In the present invention, the shape of the discharge electrode can be any shape as long as a discharge can be generated. 2 and 3 show preferred examples of electrodes of a discharge reactor that can be used when a honeycomb structure having a square cell structure is used as the discharge reactor body 15, but the present invention is not limited to this. Not something.
The mesh electrode 70 shown in FIG. 2 is an example in which the rectangular cells of the honeycomb structure are formed so that the electrode lines of the electrodes substantially overlap each other. The comb-like electrode 80 shown in FIG. Is formed so as to substantially overlap with each side in one direction of each square cell. Such a mesh electrode 70 or comb electrode 80 is preferable in that a uniform discharge can be generated inside the discharge reactor 10. That is, the shape of the discharge electrode of the present invention is particularly preferably a mesh electrode or a comb electrode that overlaps as much as possible with each cell on the surface of the honeycomb structure where the electrodes are arranged. Specifically, as in the above example, if the cell shape of the honeycomb structure is a quadrangle, the mesh is overlapped with each of the quadrangular cells arranged on the end face of the honeycomb structure. A comb-shaped electrode overlapping each side in one direction of the cell or an electrode having an intermediate shape thereof can be exemplified as a particularly preferable one.
[0018]
A voltage for discharging is applied to the electrodes by a voltage generator 40. As the voltage, a DC voltage, an AC voltage, a current having a periodic waveform, or the like can be used. In particular, it is preferable to apply a DC pulse voltage in order to favorably cause corona discharge. When a DC pulse voltage is used, the applied voltage, pulse width, and pulse period can be arbitrarily selected within a range in which corona discharge can occur, and may be subject to certain restrictions from the design of the apparatus and economy. A high voltage and a short pulse cycle are desirable from the viewpoint of generating corona discharge. As the applied voltage, a voltage of generally 10 kV or more, preferably 50 kV or more can be used. The pulse period is 10 ms or less, preferably 1 ms or less, and more preferably 0.1 ms or less. When a DC voltage is applied to the discharge reactor of the present invention, the electrode of the discharge reactor arranged on the upstream side of the exhaust gas flow path may be used as a cathode or an anode. It is particularly preferable that the electrode on the upstream side of the exhaust gas flow path is an anode. Further, one of the electrodes may be grounded.
[0019]
In the present invention, a diesel particulate filter (DPF) 50 is disposed downstream of the discharge reactor 10 in the exhaust gas flow path. As the DPF 50, a known DPF can be arbitrarily used. Specifically, a commercially available ceramic DPF, for example, a monolith honeycomb type wall flow type filter or a fiber type filter type filter made of ceramics or metal in a fibrous form may be used.
[0020]
In the present invention, the DPF is removed by filtering the PM remaining burned inside the discharge reactor 10 by filtration, and the DPF is coated with a substance having a PM combustion catalysis to add PM to the filtration of PM. Thus, the combustion of PM can be promoted, and the PM can be more efficiently removed to prevent clogging of the DPF.
That is, for PM combustion, it is preferable to coat the exhaust gas flow path surface of the DPF 50 that comes into contact with the exhaust gas with a substance having a catalytic action capable of improving the PM combustion efficiency. As the substance having the catalytic action, any substance known to act as a PM combustion catalyst can be used arbitrarily. In particular, metal oxides, specifically, for example, SiO 2 ₂ , Al ₂ O ₃ , CeO ₂ , TiO ₂ , ZrO ₂ Etc., among which CeO is particularly preferred in terms of promoting PM oxidation. ₂ Is preferred. These can be used alone or in combination of two or more. As a method for coating the metal oxide on the surface of the exhaust gas passage of the DPF 50, a known method such as wash coating can be used, for example. The amount of the metal oxide to be coated can be arbitrarily selected within a coatable range. When the metal oxide is coated on the inner surface of the DPF by wash coating, it is preferable to further bake. The firing conditions are preferably 450 to 550 ° C. When the metal oxide is coated and fired, the effect of improving the PM combustion efficiency is obtained as compared with the case where the metal oxide is not fired.
[0021]
Further, a transition metal and / or a noble metal can be further carried on the metal oxide coated on the exhaust gas flow path surface of the DPF. Specific examples of usable metals include transition metals such as Fe, Mn, Ni, Co, and Cu, and noble metals such as Pt, Rh, Pd, and Ag. Particularly preferred metals are Fe, Co, Mn, Pt, Pd, most preferably Pt. The amount of the metal to be supported is 0.1 to 10% by weight, particularly preferably 1 to 5% by weight, based on the metal oxide. These metals can be used alone or in combination, and one metal can be supported and then another metal can be supported to form a multilayer. The method of carrying the metal is specifically a method of carrying out water absorption carrying using the aqueous solution of the metal salt or the complex salt, followed by drying and firing. By supporting these metals, an effect is obtained that the PM combustion efficiency is further improved as compared with the case where the metal oxide alone is coated.
[0022]
Hereinafter, the present invention will be described based on examples, but the present invention is not limited thereto.
[0023]
【Example】
Production example (production of electrodes)
A copper plate having a thickness of 0.5 mm was punched out using a mold to form a reticulated electrode and a comb-like electrode corresponding to the shapes schematically shown in FIGS. 2 and 3. The aperture of the electrode is substantially the same as the cell shape of the cordierite honeycomb used below. For the mesh electrode, the aperture corresponds to the cell density of the cordierite honeycomb (200 cells / square inch). In the comb-like electrode, only the electrode wire in one direction of the mesh of the mesh-like electrode is left. In the following examples, these electrodes were used.
[0024]
Example 1
A comb-shaped electrode is attached to one end face of a cordierite honeycomb (cell shape: square, cell density: 200 cells / square inch) having a diameter of 30 mm and a length of 50 mm, and a reticulated electrode is attached to the other end face with a ceramics bond. And the discharge reactor of the present invention.
[0025]
On the other hand, a cordierite diesel particulate filter having a diameter of 30 mm and a length of 50 mm (cell shape: square, cell density 300 cells / square inch, porosity 60%) was added to CeO2. ₂ 4.0 g of the powder was wash-coated, and then calcined at 450 ° C. for 2 hours to obtain CeO. ₂ Was prepared, and this was used as a diesel particulate filter of the present invention.
[0026]
Example 2
Cordierite honeycomb (diameter: 30 mm, length: 50 mm) (cell shape: square, cell density: 200 cells / in 2) ₂ Wash coat 4.0 g of powder and then bake at 450 ° C. for 2 hours to obtain TiO 2 ₂ Was prepared. A comb-like electrode was attached to one end face of this honeycomb catalyst and a mesh-like electrode was attached to the other end face with a ceramics bond to obtain a discharge reactor of the present invention.
[0027]
On the other hand, a cordierite diesel particulate filter having a diameter of 30 mm and a length of 50 mm (cell shape: square, cell density 300 cells / square inch, porosity 60%) was added to CeO2. ₂ 4.0 g of the powder was wash-coated, and then calcined at 450 ° C. for 2 hours to obtain CeO. ₂ A coated honeycomb catalyst was prepared and used as a diesel particulate filter of the present invention.
[0028]
Example 3
The same discharge reactor as in Example 2 was used.
On the other hand, a cordierite diesel particulate filter having a diameter of 30 mm and a length of 50 mm (cell shape: square, cell density 300 cells / square inch, porosity 60%) was added to CeO2. ₂ 4.0 g of the powder was wash-coated and then calcined at 450 ° C. for 2 hours to obtain CeO. ₂ Coated. In addition to this, Fe (NO ₃ ) ₃ Fe was absorbed and supported using the aqueous solution. The supported Fe is CeO coated on DPF as Fe. ₂ It is 2% by weight based on the powder. This was further dried and then calcined at 450 ° C. for 2 hours to obtain a diesel particulate filter of the present invention.
[0029]
Example 4
The same discharge reactor as in Example 2 was used.
On the other hand, a cordierite diesel particulate filter having a diameter of 30 mm and a length of 50 mm (cell shape: square, cell density 300 cells / square inch, porosity 60%) was added to CeO2. ₂ 4.0 g of the powder was wash-coated and then calcined at 450 ° C. for 2 hours to obtain CeO. ₂ Coated. Further, Pt was absorbed and supported using an aqueous solution of dinitrodiammine platinum. The supported Pt is CeO coated on DPF as Pt. ₂ It is 2% by weight based on the powder. This was further dried and then calcined at 450 ° C. for 2 hours to obtain a diesel particulate filter of the present invention.
[0030]
Example 5
Cordierite honeycomb (diameter: 30 mm, length: 50 mm) (cell shape: square, cell density: 200 cells / in 2) ₂ Wash coat 4.0 g of powder and then bake at 450 ° C. for 2 hours to obtain TiO 2 ₂ Was coated. Further, Pt was absorbed and supported using an aqueous solution of dinitrodiammine platinum. The supported Pt is CeO coated on DPF as Pt. ₂ It is 2% by weight based on the powder. This was further dried and baked at 450 ° C. for 2 hours. A comb-shaped electrode was attached to one end face of the obtained catalyst-coated honeycomb with a ceramics bond on the other face, thereby forming a discharge reactor of the present invention.
[0031]
The same diesel particulate filter as used in Example 2 was used.
Example 6
The same discharge reactor as the discharge reactor of Example 5 was used.
The same diesel particulate filter as in Example 3 was used.
[0032]
Example 7
The same discharge reactor as the discharge reactor of Example 5 was used.
The same diesel particulate filter as in Example 4 was used.
Comparative example
For comparison, a cordierite honeycomb (cell shape: square, cell density 200 cells / square inch) having a diameter of 30 mm and a length of 50 mm, which is not coated with a catalyst and has no electrodes attached thereto, is a discharge reactor. Instead of On the other hand, a cordierite diesel particulate filter (cell shape: square, cell density: 300 cells / square inch, porosity: 60%) having a diameter of 30 mm and a length of 50 mm was used without coating with a catalyst.
[0033]
Performance evaluation for PM combustion
The discharge reactor and the diesel particulate filter described in Examples 1 to 8, and the honeycomb and the diesel particulate filter described in Comparative Example were each installed in a laboratory tube furnace. The installation was performed such that a discharge reactor was arranged upstream of the exhaust gas flow and a diesel particulate filter was arranged downstream. After installation, the tube furnace was heated to 300 ° C. Thereafter, a direct injection diesel engine with a displacement of 2000 cc was flowed through the tubular furnace at a rotation speed of 2,000 rpm and a load of 30 Nm for 1/13 of exhaust gas generated under operating conditions for 60 minutes. In addition, this test was performed under the same conditions as in the case where a DC voltage of 100 kV, a pulse width of 1 ms, and a repetition cycle of 200 Hz was applied to the discharge reactors of Examples 1 to 8 during the flow of exhaust gas. An experiment in which only application was not performed was also performed, and the effect of PM removal depending on the presence or absence of discharge was compared. The voltage was applied in an experiment in which the comb electrode was used as the anode, the mesh electrode was used as the cathode, and the comb electrodes were arranged on the upstream side of the exhaust gas flow.
[0034]
After the exhaust gas flows, the temperature of the tubular furnace is set to 700 ° C., and a mixed gas consisting of 80% by volume of nitrogen and 20% by volume of oxygen is passed through, thereby discharging CO. ₂ Concentration of CO ₂ Measurement using a CO ₂ From the time integrated value of the concentration, the amount of PM not burned and removed by the discharge reactor and the diesel particulate filter was calculated. The calculation is based on the released CO ₂ Was assumed to be derived from PM unburned carbon.
[0035]
Table 1 shows the results of the experiment. The table shows the type of catalyst coated on the discharge reactor and diesel particulate filter, the presence or absence of voltage application to the discharge reactor, and the amount of unburned PM. From this result, there is an effect that the amount of unburned PM is greatly reduced by applying a voltage to the discharge reactor.
[0036]
[Table 1]

[0037]
【The invention's effect】
According to the present invention, the exhaust gas components are activated by the discharge inside the discharge reactor disposed upstream of the exhaust gas, and generate highly oxidizing gas components such as active oxygen, ozone, NOx, oxygen radicals, and NOx radicals. It is based on the idea that PM in the exhaust gas is collected and burned by the combined action of a strong gas component and the PM oxidation catalyst coated on the DPF, and the PM is burned by applying a voltage to the discharge reactor. This has the effect of significantly increasing the efficiency of removal. Further, by increasing the efficiency of removing and burning PM, clogging of the DPF is less likely to occur, so that the load on the engine is reduced and the effect of improving fuel efficiency is obtained.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating one embodiment of the present invention.
FIG. 2 is a diagram showing a mesh electrode as an example of an electrode used in the discharge reactor of the present invention. However, it is a conceptual diagram and the size, number, and shape of the eyes are not accurate.
FIG. 3 is a view showing a comb-shaped electrode which is an example of an electrode used in the discharge reactor of the present invention. However, this is a conceptual diagram, and the size, number, shape, and the like of the eyes are not accurate.
[Explanation of symbols]
10. Discharge reactor
15 ... Reactor body
20 ... discharge electrode
30 ... discharge electrode
40 ... Voltage generator
50 ... Diesel particulate filter
70 ... reticulated electrode
80 ... Comb electrode

Claims (2)

An exhaust gas purifying apparatus including a discharge reactor including an electrode for discharge and a reactor body serving as an insulator, and a diesel particulate filter disposed downstream of the discharge reactor in a flow direction of exhaust gas from a diesel engine. The discharge reactor is a honeycomb structure to which a voltage can be applied, and at least one metal selected from a metal oxide and / or a transition metal and a noble metal is supported on a contact surface of the honeycomb structure with an exhaust gas. Metal oxide coated with at least one metal oxide and / or one or more metals selected from transition metals and noble metals on the exhaust gas flow path surface of the diesel particulate filter. 2. The device according to claim 1, wherein is coated.

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