JP2002371823A - Exhaust emission control device for diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily remove particle, make ceramic fiber composing a filter difficult to be bent and to shorten refreshing time. SOLUTION: In this exhaust emission control device, an exhaust gas passage 10 and a purified gas passage 11 are separated by a planar filter 9. A gas inflow port 10a is provided on an upper part of the exhaust gas passage 10 and a gas outflow port 11a is provided on a lower part of the purified gas passage 11. The filter 9 is made to have a multi-layer structure or a filter layer single layer structure of a base part 31 and a filter part 32. The base part 31 is formed by SiC fiber woven fabric or unwoven fabric 33, and the filter part 32 is made of SiC fiber unwoven fabric 34 and extremely short carbon fiber 35 filled into a cavity 36 of at least unwoven fabric 34 or extremely short carbon fiber 35 and SiC fiber. A SiC coating layer 37 by a CVD method is formed on the surface of the fiber. A material adhered to the filter 9 is burned by energizing electrodes 13 and 14 fitted on the filter 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diesel engine exhaust gas purifying apparatus for purifying exhaust gas discharged from a diesel engine.

[0002]

2. Description of the Related Art Conventionally, as a filter applied to a diesel engine exhaust gas purifying apparatus, a honeycomb filter made of sintered silicon carbide or a bellows filter made of silicon carbide fiber is known.

[0003]

However, the honeycomb filter made of sintered silicon carbide has the following problems: (a) it is liable to crack, there are restrictions on the conditions under which it can be used, and (b) it is necessary to stop exhaust gas during regeneration. Two sets of filters are required, resulting in high cost, (c) long time required for regeneration,
(D) the price is expensive, (e) the filter directly,
There were problems such as the inability to attach a catalyst.

A bellows filter made of silicon carbide fiber is
(A) it is difficult to remove fine particles, (b) broken silicon carbide fibers are released into the atmosphere, (c) the time required for regeneration is long, and (d) catalyst is directly applied to the filter. There was a problem that it could not be attached and (e) the price was expensive.

The present invention has been made in view of such conventional problems, and has as its object to facilitate the removal of fine particles, to prevent the ceramic fibers constituting the filter from breaking, and to improve the reproduction. An object of the present invention is to provide a diesel engine exhaust gas purifying apparatus that requires a short time.

[0006]

Means for Solving the Problems In order to solve the above problems, the present invention is configured as follows.

That is, (1) an exhaust gas purifying apparatus for purifying exhaust gas of a diesel engine, which has an exhaust gas path and a clean gas path alternately separated by a plate-like filter, and a gas flow passing through the exhaust gas path. An inlet is provided on the upstream side, a gas outlet communicating with the clean gas passage is provided on the downstream side, and the filter has a multilayer structure of a base portion and a filtration portion or a single-layer structure of a filtration layer, and the base portion has The filtration part is formed of a woven or non-woven fabric made of silicon carbide fiber, and the filtration unit is made of a non-woven fabric made of silicon carbide fiber, and a very short carbon fiber or a very short carbon fiber filled with at least pores of the non-woven fabric and silicon carbide. A coating layer of silicon carbide formed by a vapor deposition method on the surface of the fibers constituting the base portion and the filtration portion. Attaching an electrode for use, by heating the filter by energizing the said filter, a diesel engine exhaust gas purification apparatus characterized by incinerating the material adhering to the filter.

(2) A diesel engine according to (1), wherein ceramics or metal particles are impregnated into pores of the filter part constituting the filter part, and at least the particle surface is coated with ceramics. It is an exhaust gas purification device.

(3) The specific resistance of the plate filter is 1 × 1
The exhaust gas purifying apparatus for a diesel engine according to (1) or (2), wherein the exhaust gas purifying apparatus has a value of 0 ^{-2 to} 3 Ω-cm.

(4) The diesel engine according to (1) or (2), wherein the silicon carbide coating layer covering the surface of the fiber has a specific resistance of 10 ⁵ Ω-cm or less and a film thickness of 50 μm or less. It is an exhaust gas purification device.

(5) An oxidation catalyst is attached to the surface of the fiber constituting the filter portion or the surface of the coating film deposited on the surface of the fiber constituting the filtration portion ( A diesel engine exhaust gas purifying apparatus according to (1), (2), (3) or (4).

(6) An electrode is brought into contact with a plate-like filter via a conductive paste (1).
(2), (3), (4) or (5).

Here, it is desirable to apply any one of the following as the filtering section.

(B) Paper, mat, or felt (b) Paper, mat, or felt having short fibers in pores or short fibers in pores and surfaces (c) Paper or mat in outermost layer Or having felt, and having short fibers in the holes, or having short fibers in the holes and the surface, paper, mat, or felt.Fibers to be filled in the holes are paper, mat,
Alternatively, a fiber having a diameter smaller than the diameter of the felt fiber and penetrating into the pores of the paper, mat, or felt is preferable.

[0015] The particles filled in the pores are preferably ceramics or metals.

The coating material for the particles is preferably a ceramic paint, a ceramic adhesive, or silicon carbide deposited by a vapor deposition method.

In addition, a spacer formed of a porous ceramic, a metal mesh, or the like, which supports a differential pressure acting on the plate filter, is provided between the plate filters serving as the clean gas passage, through which the clean gas flows. Is preferred.

[0018]

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

In FIG. 1, 1 is a diesel engine,
2 is an exhaust pipe connected to the diesel engine 1, 3 is a hollow case provided in the middle of the exhaust pipe 2, 4 is an exhaust gas purifying device set in the hollow case 3, 5 is connected to the exhaust gas purifying device 4. A timer type switch or a differential pressure switch which can be energized at predetermined time intervals, 6 is a storage battery, 7 is an alternator (generator), and the exhaust gas a discharged from the diesel engine 2 is purified by the exhaust gas purifying device 4 to be purified. Gas a 'is discharged into the atmosphere.

As shown in FIG. 3, the exhaust gas purifying apparatus 4 comprises:
A plurality (6 in the figure) of the hollow box 8 is spaced at a predetermined interval.
Plate filters 9 are provided in parallel, an exhaust gas passage 10 is formed on one side, and a clean gas passage 11 is formed on the other side. In other words, the exhaust gas path 10 and the clean gas path 1
1 are provided alternately via a plate-shaped filter 9.

The plate-like filter 9 includes the first spacer 1
2 and an electrode 1 serving also as a lid or shielding plate provided at the upstream end thereof
3. First spacer 12
Is formed in a hollow thick plate shape by a gas permeable material such as a porous material or a mesh, and also serves as a clean gas passage 11. Further, the downstream end of the exhaust gas path 10
It is shielded by the electrode 14 which also serves as a lid or a shielding plate. The upstream end of the exhaust gas passage 10 is located at the gas inlet 1
0a, and the downstream end of the first spacer 12 is a gas outlet 11a.

Reference numeral 15 denotes a second spacer provided so as to cross the first spacer 12. The second spacer 15 allows the electrodes 13 and 14 and the filter 9 to be in contact with each other via a conductive paste. Has become.

As shown in FIG. 3, the left and right heat insulators 16 and 17 located on both sides of the spacer group 120 composed of the plurality of first spacers 12 are reinforced by iron plates 18, respectively. However, the heat insulating material 17 on the left side of the figure is not fixed to the box 8, and when a bolt 20 screwed to a nut 19 fixed to the side surface of the box 8 is tightened, the heat insulating material 17 for movement is interposed. Thus, the pressing force of the second spacer 15 is increased. The filter 9 and the iron plate 18 are insulated by an insulating material (not shown).

The box 8 has a gas inlet 21 at its upstream end and a gas outlet 22 at its downstream end.
Portions other than the gas inlet 21 and the gas outlet 22 are covered with a heat insulating material 23.

Reference numeral 24 denotes an electric wire connected to the electrode 13;
Is an electric wire connected to the electrode 14, the electric wire 24 is connected to the positive pole of the storage battery, and the electric wire 25 is connected to the negative pole of the storage battery.

As shown in FIG. 2, the heat insulating materials 26 and 27 mounted on the upper and lower sides of the box 8 have grooves 2 inside thereof.
The first spacer 12 and the plate-like filter 9 are inserted into upper and lower grooves 28, 28 facing each other.

As shown in FIG. 4, the plate-like filter 9 is
It has a multilayer structure of a base part 31 and a filtration part 32,
The base portion 31 is formed of a plain woven fabric 33 made of silicon carbide fiber, and the filtration portion 32 is formed of a nonwoven fabric (paper) 34 made of silicon carbide fiber and a fiber (carbon fiber) 35 having an extremely short fiber length. As shown in FIG. 5, the fibers (carbon fibers) 35 having an extremely short fiber length have holes 36 existing between the silicon carbide fibers 34 a forming the paper 34.
And is deposited in a layer on the surface of the paper 34.

The surface of the fibers 33a, 34a and 35 constituting the base portion 31 and the filtration portion 32 is coated with a silicon carbide coating layer 37 by a vapor deposition method (CVD method).
Are precipitated (see FIG. 6).

The plate-like filter 9 is provided with an electrode 1 which also serves as a cover or a shielding plate, so that the filtering portion 32 is on the exhaust gas passage 10 side.
Attached to 3,14. The specific resistance of the plate-like filter 9 is preferably in the range of 1 × 10 ^{-2 to} 3Ω-cm.
The specific resistance of the coating layer 37 is 10 ⁵ Ω-cm.
Or less, and the film thickness is preferably 50 μm or less.

Next, the operation of the exhaust gas purifying apparatus will be described.

As shown in FIG. 7, the exhaust gas a flowing into the exhaust gas passage 10 from the gas inlets 21 and 10a of the exhaust gas purifying device 4 passes through the plate-shaped filter 9 as shown by the arrow, and is cleaned. 11 flows. At that time, the particulate matter contained in the exhaust gas a is collected by the filtering part (not shown) of the plate-shaped filter 9. When the differential pressure of the filter 9 reaches a predetermined value, the plate-shaped filter 9 is energized, the filter 9 is heated to a predetermined temperature, and the particles collected by the plate-shaped filter 9 burn. Oxygen for burning the collected particles is supplied by a method of supplying electricity while flowing exhaust gas or a method of stopping the flow of exhaust gas and supplying fresh air. Clean gas a 'from which particulate matter has been removed
Is discharged from the gas outlets 11a and 22 into the atmosphere via the exhaust pipe 2.

If desired, the plate-shaped filter 9 is impregnated with ceramics or metal particles, so that the filter layer 32
It is possible to easily adjust the size of the pores existing between the fibers forming the fibers. As a method for coating the particles with the ceramic, a vapor deposition method, a ceramic adhesive coating method, a thermal spraying method, or the like can be applied.

Further, if desired, an oxidation catalyst can be attached to the surface of the fiber constituting the plate-shaped filter 9 or the surface of the coating film deposited on the surface of the fiber constituting the filtration layer. .

Thus, in the case of diesel exhaust gas having a high temperature, the particulate matter collected by the filtration layer 32 can be catalytically burned. In the case of low-temperature diesel exhaust gas, by energizing the plate-shaped filter 9 directly and heating it to a temperature at which the oxidation catalyst is activated, the collected particulate matter can be catalyzed and burned. Can be handled.

Next, the present invention will be described in more detail with reference to examples.

[0036]

EXAMPLES (Example) (1) Exhaust gas removing device (a) Configuration: One plain woven cloth made of silicon carbide fiber (Tyranno Lo)
xM) /0.3 mm thick SiC paper (fiber length 6 m)
m, composed of 15 μm thick SiC fiber) / milled carbon fiber (7 μm thick, 300 μm fiber length, 500 g / m ² )
/ SiC coating (vapor phase deposition method) (b) Molding / deposition of filter (a) Silicon carbide fiber (Tyranno LoxM (fiber diameter 11 μm
The following fiber binder is impregnated into a plain woven cloth (weight per unit area: 150 g / m ² ). Fiber binder: phenol resin diluted with carbon tetrachloride (weight concentration: 20%) (b) Paper made of silicon carbide fiber (fiber A slurry (dispersed in ethanol) of milled fiber of carbon fiber (Treca T300 (diameter: 7 μm, fiber length: 300 μm)) was applied to one surface of a diameter of 15 μm, a fiber length of 6 mm, and a basis weight of 20 g / cm ² . Forming a 5 mm nonwoven fabric (c) Impregnating the above (b) with the fiber binder of the above (b) (d) Laminating the above (c) on the above (a) to form a plate (e) Release cloth And a cotton-like cloth for impregnating excess resin is stuck on the surface, covered with a plastic film, and the fiber binder is cured in an autoclave. (F) The above molded article is mineralized in argon gas at 800 ° C. The average film thickness 10μ at the surface 50 places the silicon carbide coating (flat woven by a chemical vapor deposition)
m).

The specific resistance of the SiC film measured in the air at 26 ° C. and a relative humidity of 50% (four-terminal method) is 2.1.
× 10 ^-2 Ω-cm (c) Filter dimensions and structure ・ Plate filter: width 100 mm, length 200 mm, thickness 1 mm ・ Number of sheets: 20 ・ Filter interval: 5 mm ・ Contact surface between electrode and filter: silver Paste application ・ Electrode: SUS304 ・ External dimensions: 250 mm x 150 mm in cross section, 400 mm in length ・ Seal at both ends: Formation of exhaust gas passage and clean gas passage every other in heat-resistant alloy lid with flat honeycomb insertion groove (with filtration layer (Exhaust gas to passage) (d) Wiring ・ Connect to two electric double layer capacitors with 40V and rated current of 250A (10 cards / unit) ・ Built-in timer that can be energized at predetermined time intervals (2) Characteristics (a) 1993 Replaced with a truck muffler with a loading capacity of 4.5 tons for production, and traveled for 8 hours in and around urban areas.

(B) Regeneration conditions: 2 minutes / 1 time, 1 time / 1 hour running (c) Filter pressure loss During operation: 1350 (initial value and after 2 minutes energization) to 193
0 mmH ₂ O (highest value after running for 1 hour) (d) Dust collection rate: 94.6% (e) Median diameter of passing particles: 0.30 μm

[0039]

As described above, since the exhaust gas purifying apparatus of the present invention has a very simple structure, it is easy to manufacture and the cost can be reduced.

Further, the plate filter of the present invention has a multilayer structure of a base portion and a filtering portion or a single layer structure of a filtering portion, and the base portion is formed of a woven or non-woven fabric made of silicon carbide fiber, The filtration unit, a non-woven fabric made of silicon carbide fiber, at least a very short carbon fiber filled into the pores of the non-woven fabric, or a very short carbon fiber and silicon carbide fiber, and the base unit and Since a coating layer of silicon carbide is formed by a vapor deposition method on the surface of the fiber constituting the filtration section, the collection rate of the particulate matter contained in the exhaust gas is improved, and Deterioration of the plate filter due to combustion of the soot-like substance (soot) was reduced. Further, since the plate filter is formed of ceramic fibers such as silicon carbide fibers and carbon fibers, it has high strength and has toughness, so that it is difficult to break.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an exhaust gas system of a diesel engine having an exhaust gas purifying apparatus according to the present invention.

FIG. 2 is a cross-sectional view of the exhaust gas purifying apparatus according to the present invention.

FIG. 3 is a sectional view taken along line AA ′ of FIG. 2;

FIG. 4 is an enlarged sectional view of a plate filter.

FIG. 5 is an enlarged view of a portion B in FIG. 4;

FIG. 6 is an enlarged sectional view of a fiber.

FIG. 7 is a diagram illustrating the operation of the exhaust gas purifying apparatus according to the present invention.

[Explanation of symbols]

 a Exhaust gas 1 Diesel engine 4 Exhaust gas purifier 9 Plate filter 10 Exhaust gas path 10a Gas inlet port leading to the exhaust gas path 11 Clean gas path 11a Gas outlet port leading to the clean gas path 13, 14 Electrode 31 Base part 32 Filtration part 33 Weaving Cloth 34 Non-woven fabric 35 Very short fiber 36 Void 37 Coating layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) F01N 3/02 F01N 3/02 341N B01D 39/00 B01D 39/00 D 39/06 39/06 39/08 39/08 AZ 39/14 39/14 BC 39/20 39/20 AD 53/86 ZAB 46/42 B 53/94 53/36 103C // B01D 46/42 ZAB F term (reference) 3G090 AA01 BA04 CB11 DA07 4D019 AA01 BA01 BA02 BA03 BA05 BB02 BB03 BB04 BB05 BB10 BB13 BB18 BC07 BC15 BD01 BD06 CA10 CB04 CB09 DA01 4D048 AA14 AB02 BA06X BA45X BB08 CC04 CC08 CC38 CC41 CC53 CC63 CD05 EA02 MA03 J04 MA03 J04 MA04

Claims (6)

[Claims] An exhaust gas purifying apparatus for purifying exhaust gas of a diesel engine, comprising an exhaust gas passage and a clean gas passage alternately separated by a plate-like filter,
A gas inlet leading to the exhaust gas path is provided on the upstream side, a gas outlet leading to the clean gas path is provided on the downstream side, and
The filter has a multilayer structure of a base portion and a filtration portion or a single-layer structure of a filtration layer, the base portion is formed of a woven or nonwoven fabric made of silicon carbide fibers, and the filtration portion is a nonwoven fabric of silicon carbide fibers. And at least a very short carbon fiber filled into the pores of the nonwoven fabric or a very short carbon fiber and a silicon carbide fiber, and the surface of the fiber constituting the base portion and the filtration portion has air. Forming a coating layer of silicon carbide by a phase deposition method, further attaching an electrode for energization and heating to the filter, energizing the filter to generate heat, thereby incinerating a substance attached to the filter. Diesel engine exhaust gas purifier. 2. A method for impregnating ceramic or metal particles into pores of a filtration part constituting a filter part,
The exhaust gas purifying apparatus for a diesel engine according to claim 1, wherein at least a surface of the particles is coated with a ceramic. 3. A plate-shaped filter having a specific resistance of 1 × 10 ^-2 or ^less .
The diesel engine exhaust gas purifying apparatus according to claim 1 or 2, wherein the pressure is 3 Ω-cm. 4. The diesel engine exhaust gas purifying apparatus according to claim 1, wherein the silicon carbide coating layer covering the surface of the fiber has a specific resistance of 10 ⁵ Ω-cm or less and a film thickness of 50 μm or less. . 5. An oxidation catalyst is attached to a surface of a fiber constituting a filter portion or a surface of a coating film deposited on a surface of a fiber constituting a filtration portion. 5. The diesel engine exhaust gas purifying apparatus according to 2, 3, or 4. 6. An electrode is brought into contact with a plate-shaped filter via a conductive paste.
The diesel engine exhaust gas purifying apparatus according to 3, 4, or 5.