JP2001355432A - Exhaust emission control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a filter from being clogged with nonflammable particles in exhaust gas. SOLUTION: This exhaust emission control device equipped on the way of an exhaust pipe to eliminate particulates in the exhaust gas 2 is provided with the filter 10 disposed in a filter case disposed on the way of the exhaust pipe. The filter 10 is formed with coarse mesh of 0.7 mm to 2.0 mm in pore diameter by a support 11, carrying a catalyst so as to crush and burn inflammable particles of the particulates while allowing the nonflammable particles to flow downstream.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust emission control device applied to an internal combustion engine such as a diesel engine.

[0002]

2. Description of the Related Art Particulate matter (particulate matter) emitted from a diesel engine is:
Soot composed of carbonaceous material and SO composed of high-boiling hydrocarbon component
Combustible particles containing F (Soluble Organic Fraction: soluble organic component) as a main component. As a measure for reducing such particulates, exhaust gas 2 from a diesel engine 1 flows as shown in FIG. It is conceivable that an outer cylinder 4 is provided in the exhaust pipe 3 and a filter 5 is provided inside the outer cylinder 4.

[0003] The filter 5 has a porous honeycomb structure made of ceramic as shown in FIG. 9, and the inlets 7 of the flow paths 6 partitioned in a lattice are alternately plugged, and the inlets 7 are plugged. The outlet 8 of the channel 6 that is not
Are sealed, and only the exhaust gas 2 that has passed through the porous thin wall 9 that defines each flow path 6 is discharged to the downstream side.

Since the particulates in the exhaust gas 2 are collected and deposited on the inner surface of the porous thin wall 9, the particulates are appropriately burned and removed before the exhaust resistance increases due to clogging. It is necessary to regenerate the filter 5 in the normal operation of the diesel engine 1. However, in the normal operation state of the diesel engine 1, there is little chance that a high exhaust gas temperature at which the particulates self-combust can be obtained. It has been considered that active heating is performed by attaching such as.

[0005]

However, since the exhaust gas 2 contains ash, which is a wear substance of the diesel engine 1, calcium and phosphorus in oil, and flame-retardant particles such as rust, these exhaust gases 2 are difficult to use. There is a problem that the fuel particles adhere to the filter 5 and particulates such as soot also adhere to the filter layer to form a cake layer and clog the filter 5. At the same time, the cake layer clogging the filter 5 cannot be burned by an electric heater, a catalyst, or the like.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide an exhaust gas purifying apparatus that prevents a filter from being clogged by flame-retardant particles in exhaust gas.

[0007]

According to a first aspect of the present invention, there is provided an exhaust gas purifying apparatus which is provided in the middle of an exhaust pipe and removes particulates in exhaust gas. In order to crush and burn flammable particles of particulates,
The present invention relates to an exhaust gas purifying apparatus, which is provided with a filter that supports a catalyst and that has a coarse hole having a hole diameter of 0.7 mm to 2.0 mm formed by a pillar.

According to a second aspect of the present invention, in the first aspect, the filter may be either a metal foam filter or a ceramic foam filter.

According to a third aspect of the present invention, in the first aspect, the filter may be a metal wire filter.

[0010] According to a fourth aspect of the present invention, in the first aspect, the filter may be a metal fiber filter or an inorganic fiber filter.

According to a fifth aspect of the present invention, the catalyst of the filter may be an oxidation catalyst.

According to a sixth aspect of the present invention, in the first to fourth aspects, the catalyst of the filter may be a NOx catalyst.

According to a seventh aspect of the present invention, in the first to fourth aspects, the catalyst of the filter may be a NO ₂ generation catalyst.

When the exhaust gas flows into the filter case, the particulate combustible particles are 0.7 m
By colliding with columns forming a coarseness of m to 2.0 mm, they are broken into small particles and simultaneously burned by a catalyst. On the other hand, the flame-retardant particles flow downstream through the filter while colliding with the pillars constituting the coarseness of the filter.

As described above, the filter has a hole diameter of 0.7 mm.
To 2.0 mm, when the particulates in the exhaust gas pass through the filter, it is possible to prevent the combustible particles and the incombustible particles of the particulates from accumulating on the filter, and to reduce the coarseness of the filter. Since the combustible particles of the particulates are crushed and burned by the formed columns, and the flame-retardant particles are allowed to pass, clogging of the filter can be reliably prevented.

As described in the second aspect of the present invention, when the filter of the first aspect is a foamed metal filter or a foamed ceramic filter, the durability is improved. Can be filtered.

According to the third aspect of the present invention, if the filter of the first aspect is a metal wire filter, a desired metal wire can be collected to form a filter. can do.

According to a fourth aspect of the present invention, when the filter of the first aspect is a metal fiber filter or an inorganic fiber filter, the number of collisions with the particulates in the filter is increased, so that the flammability of the particulates is increased. The particles can be sufficiently burned.

According to the fifth aspect of the invention, when the catalyst of the filter according to the first, second, third or fourth aspect is an oxidation catalyst, the combustible particles of particulates can be efficiently burned.

As described in the sixth aspect of the present invention, when the catalyst of the filter according to the first, second, third or fourth aspect is a NOx catalyst, it reduces NOx to make it harmless and oxidizes the particulates. Curable combustible particles can be efficiently burned.

According to a seventh aspect of the present invention, when the catalyst of the filter according to the first, _{second, third} or fourth aspect is a NO ₂ generating catalyst, nitrogen oxides in the exhaust gas are converted into NO. _Since it is set to ₂ , the combustible particles of particulates can be efficiently burned by the NO ₂ .

[0022]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 show a filter of an exhaust gas purifying apparatus showing a first embodiment of the present invention. In the drawings, the portions denoted by the same reference numerals as those in FIGS. 8 and 9 represent the same components.

In the exhaust gas purifying apparatus of the first example, a metal foam filter is provided as a filter 10 in an outer cylindrical filter case in the middle of an exhaust pipe, and the metal foam filter has a rough porous material. It is manufactured with a structure and has a coarse hole diameter W
No. 1 is formed in a size from 0.7 mm to 2.0 mm by continuously sealing many bubbles inside.

The foamed metal filter carries an oxidation catalyst such as platinum and alumina.

The operation of the first embodiment of the present invention will be described below.

When the exhaust gas 2 flows into the filter case of the exhaust gas purification apparatus of the first example, the particulate combustible particles contained in the exhaust gas 2 are reduced from 0.7 mm to 2.0 mm of the expanded metal filter. By colliding with the pillars 11 constituting the rough surface, the particles are crushed into small particles, and at the same time, are burned by the oxidation catalyst, and finally become carbon dioxide and water.
The combustion using the oxidation catalyst may appropriately use a catalyst that releases oxygen, a fuel additive, or the like.

On the other hand, ash of engine wear substances contained in exhaust gas 2, calcium and phosphorus in oil,
Flame-retardant particles such as rust collide with the column 11 having a hole diameter W1 of 0.7 mm to 2.0 mm of the foamed metal filter, pass through the foamed metal filter, and flow downstream together with the exhaust gas 2.

Here, the table shown in FIG. 3 shows the filtering efficiency of combustible soot (filtering efficiency of combustible particles) and the passing efficiency of flame-retardant soot (passing efficiency of flame-retardant particles) with respect to the size of the filter eyes. The solid line in the table indicates the filtering efficiency of combustible soot (the filtering efficiency of combustible particles),
The dashed line indicates the passage efficiency of the flame-retardant soot (the passage efficiency of the flame-retardant particles). The filter used for the experiment was about 100 m long.
m, a cylindrical shape having a diameter of about 200 mm.

From this table, it can be seen that the filtering efficiency of combustible soot decreases as the size of the filter increases, and the passage efficiency of flame-retardant soot increases as the size of the filter increases to a predetermined value. A predetermined numerical value indicates that the value is substantially constant regardless of the size of the filter eyes.

Therefore, from the table, it can be seen that the pore diameter W
When 1 is 0.7 mm to 2.0 mm, the filtering efficiency of combustible soot and the passage efficiency of flame retardant soot are appropriate,
When the pore diameter W1 of the foamed metal filter is less than 0.7 mm, the passage efficiency of the flame-retardant soot is reduced and the possibility of clogging of the foamed metal filter increases, and the pore diameter W1 of the foamed metal filter is 2.0 mm. If it becomes larger, the filtering efficiency of combustible soot is reduced, and the filter does not function.

As described above, the pore size W1 of the foamed metal filter
From 0.7 mm to 2.0 mm, when particulates in the exhaust gas 2 pass through the foamed metal filter, it is possible to prevent the combustible particles and the flame-retardant particles of the particulates from depositing on the foamed metal filter. Further, since the combustible particles of the particulates in the exhaust gas 2 are crushed and burned by the pillars 11 forming the coarseness of the foamed metal filter and the flame-retardant particles are passed, the clogging of the foamed metal filter is reliably prevented. can do.

Here, the filter 10 of the exhaust gas purifying apparatus of the first example is a foamed metal filter, but the same effect can be obtained by a foamed ceramic filter.

When the filter 10 is a foamed metal filter or a foamed ceramic filter, the durability is improved, so that the exhaust gas 2 can be filtered for a long time without replacement.

Furthermore, when the catalyst of the filter 10 is an oxidation catalyst, the particulate combustible particles can be efficiently burned.

FIGS. 4 and 5 show an exhaust gas purifying apparatus according to a second embodiment of the present invention. The exhaust gas purifying apparatus according to the second embodiment is obtained by changing the filter of the first embodiment. is there.

The filter 12 provided in the exhaust gas purifying apparatus of the second example is a metal wire filter manufactured by collecting metals processed into fine-diameter fibers, and the metal wire filter is formed by a metal wire column 13. It is formed with a coarse size W2 from 0.7 mm to 2.0 mm.

The metal wire filter carries a NOx catalyst such as copper or zeolite. The NOx catalyst reduces NOx present in the exhaust gas 2 to nitrogen and reduces particulate matter in the exhaust gas 2. It has the activity of oxidizing combustion particles, carbon monoxide and hydrocarbons.

The operation of the second embodiment of the present invention will be described below.

When the exhaust gas 2 flows into the filter case of the exhaust gas purification apparatus of the second example, the particulate combustible particles contained in the exhaust gas 2 are reduced from 0.7 mm to 2.0 mm of the metal wire filter. By colliding with the metal wire columns 13 constituting the coarse size W2, the particles are crushed into small particles, and at the same time, oxidized by the NOx catalyst and burned,
The end result is carbon dioxide and water.

On the other hand, ash of engine wear substances contained in exhaust gas 2, calcium and phosphorus in oil,
Flame-retardant particles such as rust are deposited on a metal wire column 1 constituting a coarse size W2 of 0.7 mm to 2.0 mm of a metal wire filter.
3 and flows downstream along with the exhaust gas 2 through the metal wire filter while colliding with 3.

Here, the metal wire filter has substantially the same effect as the table shown in FIG. 3, so that when the hole diameter (eye size) W2 of the metal wire filter is 0.7 mm to 2.0 mm, the flammability is reduced. If the filtering efficiency of the particles and the passage efficiency of the flame-retardant particles are appropriate, and the hole diameter (eye size) W2 of the metal wire filter is less than 0.7 mm, the passage efficiency of the flame-retardant particles decreases and the metal wire The possibility of clogging of the filter increases, and the hole diameter (eye size) W of the metal wire filter
When 2 is larger than 2.0 mm, the filtering efficiency of combustible particles is reduced, and the filter does not function.

As described above, since the hole diameter (eye size) W2 of the metal wire filter is set to 0.7 mm to 2.0 mm, when the particulates in the exhaust gas 2 pass through the metal wire filter, Flammable particles and flame-retardant particles can be prevented from depositing on the metal wire filter.
Since the combustible particles of the particulates are crushed and burned by the pillars 13 forming the coarseness of the metal wire filter and the flame-retardant particles are allowed to pass, clogging of the metal wire filter can be reliably prevented.

If the filter 12 is a metal fiber filter, the filter 12 can be constructed by collecting desired metal wires, so that it is possible to perform filtering with an appropriate metal and to manufacture the filter at low cost.

Further, if the catalyst of the filter 12 is a NOx catalyst, NOx is reduced and rendered harmless and particulates are oxidized, so that combustible particles of the particulates can be efficiently burned.

FIGS. 6 and 7 show an exhaust gas purifying apparatus according to a third embodiment of the present invention. In the exhaust gas purifying apparatus according to the third embodiment, the filter of the first example is changed. is there.

The filter 14 installed in the exhaust gas purifying apparatus of the third example is a metal fiber filter manufactured by knitting a metal processed into a fine fiber into a knit shape. The metal fiber filter is a metal wire. The column 15 has a coarse size W3 of 0.7 mm to 2.0 mm.

The metal fiber filter carries a NO ₂ generating catalyst such as platinum or alumina. The NO ₂ generating catalyst has a high activity of oxidizing nitrogen oxides present in the exhaust gas 2 to NO _2. It has.

The operation of the third embodiment of the present invention will be described below.

When the exhaust gas 2 flows into the filter case of the exhaust gas purifying apparatus of the third example, the particulate combustible particles contained in the exhaust gas 2 are reduced from 0.7 mm to 2.0 mm of the metal fiber filter. By colliding with the metal wire column 15 constituting the coarse size of the coarse particles, the particles are crushed into small particles, and at the same time, oxidized by NO ₂ generated from nitrogen oxides in the exhaust gas 2 by the NO ₂ generation catalyst and burned,
The end result is carbon dioxide and water.

On the other hand, ash of engine wear substances contained in the exhaust gas 2, calcium and phosphorus in oil,
Flame-retardant particles such as rust pass through the metal fiber filter and flow downstream together with the exhaust gas 2 while colliding with the metal wire column 15 constituting a coarse size of 0.7 mm to 2.0 mm of the metal fiber filter. .

Since the metal fiber filter has substantially the same effect as the table shown in FIG. 3 similarly to the filter of the exhaust emission control device of the second example, the hole diameter (mesh size) W3 of the metal fiber filter is Is 0.7 mm to 2.0 mm, the filtering efficiency of combustible particles and the passage efficiency of flame-retardant particles are appropriate, and the pore size (size of the mesh) W of the metal fiber filter is
3 is less than 0.7 mm, the passage efficiency of the flame-retardant particles is reduced, and the possibility that the metal fiber filter is clogged is increased, and the hole diameter (eye size) W3 of the metal fiber filter is increased.
Is greater than 2.0 mm, the filtering efficiency of combustible particles is reduced, and the filter does not function.

As described above, since the hole diameter (mesh size) W3 of the metal fiber filter is set to 0.7 mm to 2.0 mm, when the particulates in the exhaust gas 2 pass through the metal fiber filter, The combustible particles and the flame-retardant particles can be prevented from accumulating on the metal fiber filter, and the particulate combustible particles are crushed and burned by the pillars 15 forming the coarseness of the metal fiber filter, and pass through the flame-retardant particles. Therefore, clogging of the metal fiber filter can be reliably prevented.

Here, the filter 14 of the exhaust emission control device of the third example is a metal fiber filter, but the same effect can be obtained by an inorganic fiber filter.

When the filter 14 is a metal fiber filter or an inorganic fiber filter, the number of collisions with the particulates in the filter 14 is increased, so that the combustible particles can be sufficiently burned.

Further, when the catalyst of the filter 14 is a NO ₂ generating catalyst, the nitrogen oxides in the exhaust gas 2 are converted into oxidizing NO ₂ , so that the NO ₂ efficiently converts the particulate combustible particles. Can be burned.

Note that the exhaust gas purifying apparatus of the present invention is not limited to the above-described embodiment, and may be configured such that a foamed metal filter or a foamed ceramic filter carries either a NOx catalyst or a NO ₂ generating catalyst. good thing, the metal wire filters, oxidation catalysts, it may carry either the NO ₂ reduction catalyst, the metal fiber filter or inorganic fibers filters,
It goes without saying that any one of the oxidation catalyst and the NOx catalyst may be supported, and that other various changes can be made without departing from the scope of the present invention.

[0058]

According to the exhaust gas purifying apparatus of the present invention described above, the following various excellent effects can be obtained.

(I) According to the first aspect of the present invention, since the filter has a hole diameter of 0.7 mm to 2.0 mm, when particulates in exhaust gas pass through the filter, Since particulate combustible particles and flame-retardant particles can be prevented from accumulating on the filter, and the combustible particles of the filter are crushed and burned by pillars forming coarseness of the filter, and the flame-retardant particles are passed. Clogging of the filter can be reliably prevented.

(II) When the filter is a foamed metal filter or a foamed ceramic filter as in the second aspect of the present invention, the durability is improved.
Exhaust gas can be filtered for a long time without replacement.

(III) If the filter is a metal wire filter as in the third aspect of the present invention, a desired metal wire can be collected to form a filter. Can be manufactured.

(IV) When the filter is made of either a metal fiber filter or an inorganic fiber filter, the number of collisions with the particulates in the filter is increased. Can be sufficiently burned.

(V) When the catalyst of the filter is an oxidation catalyst as in the invention of the fifth aspect of the present invention, the particulate combustible particles can be efficiently burned.

(VI) When the catalyst of the filter is a NOx catalyst as in the invention according to claim 6 of the present invention, NOx is reduced and rendered harmless, and the particulates are oxidized. Can be burned.

(VII) As described in the seventh aspect of the present invention, when the catalyst of the filter is a NO ₂ generating catalyst, the nitrogen oxides in the exhaust gas are converted into oxidizing NO _2. NO ₂ makes it possible to burn particulate combustible particles efficiently.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a filter of a first example of an embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing a part of the filter of the first example.

FIG. 3 is a table showing the filtering efficiency of combustible soot and the passage efficiency of flame-retardant soot with respect to the pore diameter of a filter.

FIG. 4 is a schematic diagram showing a filter of a second example of the embodiment of the present invention.

FIG. 5 is an enlarged sectional view showing a part of the filter of the second example.

FIG. 6 is a schematic diagram illustrating a filter of a third example of an embodiment of the present invention.

FIG. 7 is an enlarged sectional view showing a part of the filter of the third example.

FIG. 8 is a schematic diagram showing a state in which exhaust gas flows from the engine to the outer cylinder.

FIG. 9 is a sectional view showing details of a conventional particulate filter.

[Explanation of symbols]

2 Exhaust gas 10 Filter (foam metal filter, foam ceramic filter) 11 pillar 12 Filter (metal wire filter) 13 pillar 14 Filter (metal fiber filter, inorganic fiber filter) 15 pillar W1 Hole diameter W2 Hole diameter (mesh size) W3 Hole diameter ( Eye size)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B01D 39/20 B01D 39/20 AD 46/42 46/42 B 53/86 ZAB F01N 3/18 B 53 / 94 3/24 E F01N 3/18 3/28 301C 3/24 B01D 53/36 ZAB 3/28 301 103B 103C (72) Inventor Keiichi Dobashi 3-1-1, Hinodai, Hino City, Tokyo Hino Motors, Ltd. (72) Inventor Hiroaki Ito 3-1-1, Hinodai, Hino-shi, Tokyo Hino Motor Co., Ltd. (72) Inventor Tatsuoki 3-1-1, Hinodai, Hino-shi, Tokyo F-term in Hino Motor Co., Ltd. (Reference) 3G090 AA01 AA02 AA03 BA00 BA08 3G091 AA18 AB02 AB05 AB13 BA00 BA14 FB10 GA06 GA20 GB01W GB01X GB06W GB09W GB10W GB10X GB16W GB17X 4D019 AA01 BA02 BA05 BB02 BB07 BB13 BC07 BD01 CA03 4D048 AA06 AA13 AA14 AA18 AB01 AB03 BA03Y BA11Y BA30Y BA35Y BA41Y BB08 BB09 CA01 CC38 CC41 CD05 4D058 JA01 JA51 JB03 JB06 JB24 JB28 JB32 MA44 SA08 TA06

Claims (7)

[Claims] 1. An exhaust gas purifying apparatus provided in the middle of an exhaust pipe for removing particulates in exhaust gas, wherein the combustible particles of the particulates are crushed and burned in a filter case in the middle of the exhaust pipe. In order to flow the flame-retardant particles downstream, a catalyst is supported and the pore diameter is 0.7 mm to 2.0 mm.
An exhaust gas purifying apparatus, comprising a filter having a roughness of up to mm formed by columns. 2. The exhaust gas purifying apparatus according to claim 1, wherein the filter is a foam metal filter or a foam ceramic filter. 3. The exhaust gas purifying apparatus according to claim 1, wherein the filter is a metal wire filter. 4. The exhaust gas purifying apparatus according to claim 1, wherein the filter is one of a metal fiber filter and an inorganic fiber filter. 5. The exhaust gas purifying apparatus according to claim 1, wherein the catalyst of the filter is an oxidation catalyst. 6. The exhaust gas purifying apparatus according to claim 1, wherein the catalyst of the filter is a NOx catalyst. 7. The exhaust emission control device according to claim 1, wherein the catalyst of the filter is a NO ₂ generation catalyst.