JP2002126428A - Electrothermally regenerated filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrothermally regenerated filter having high thermal impact resistance and high durability and for effectively removing graphite fine particles. SOLUTION: The electrothermally regenerated filter is formed by laminating 2 kinds of porous layers having different pore diameter form each other and has a three-layer structure of an inside layer 12 having the skeleton of the porous layer which is made of a heat resistant oxidation resistant material, an intermediate layer 14 formed on the outside periphery of the inside layer and made of a conductive material and an outside layer 16 formed on the outside peripheral surface of the intermediate layer and made of the heat resistant oxidation resistant material and the resistance of the filter is 0.01-200 Ω.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric heat regeneration filter used for an exhaust gas filter of a diesel vehicle or the like.

[0002]

2. Description of the Related Art Exhaust from diesel vehicles and the like
Black smoke fine particles (PM) are contained in a relatively large amount. For this reason, a diesel particulate filter (DPF) is used as an exhaust gas filter for preventing the PM from being released into the atmosphere. This filter is
As the usage time for collecting dust increases, the filter efficiency decreases due to the deposition of PM.

For this reason, PM deposited on the filter
And it is necessary to regenerate the filter, and various methods have been proposed.

When the DPF is used, the amount of the PM deposited on the filter increases with the operation of a diesel vehicle or the like, and the exhaust pressure loss at the filter increases. For this reason, in order to prevent a decrease in filter efficiency due to an increase in exhaust pressure loss, it is necessary to periodically burn the PM deposited on the filter to regenerate the DPF.

In this case, particularly in a diesel engine, since the exhaust gas temperature is relatively low, the temperature of the PM is raised to the ignition temperature by a heater incorporated in a filter for depositing the PM.

[0006]

[0005] A conventional DPF is formed by extruding a slurry of cordierite or the like to form a ceramic honeycomb, and then alternately plugging the through-holes constituting the honeycomb. is there. The PM deposited on this filter is burned by a catalyst and regenerated. However, the cordierite used in the DPF has a problem in durability due to poor maximum operating temperature and thermal conductivity, and the cordierite may be melted at a high temperature. In addition, if there is a large amount of black smoke particulates deposited on the filter, the temperature of the filter partially rises due to the progress of combustion, and the thermal shock generated by this temperature distribution sometimes exceeds the allowable stress of the filter, causing cracks in the filter. Sometimes.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above circumstances, and has as its object to provide an electrothermal regeneration filter which is resistant to thermal shock, has high durability, and can effectively remove black smoke fine particles.

[0008]

The invention of claim 1 is an electrothermal regeneration filter in which two types of porous layers having large and small pores are laminated, wherein the skeleton of both porous layers is made of a heat-resistant oxide. And a three-layer structure of an intermediate layer made of a conductive substance formed on the outer periphery of the inner layer and an outer layer made of a heat-resistant oxide formed on the outer peripheral surface of the intermediate layer. The present invention relates to an electrothermal regeneration filter having a resistance of 0.01 to 200Ω.

A second aspect of the present invention is characterized in that the inner layer, the intermediate layer and the outer layer in the first aspect are formed by a CVD or CVI method.

A third aspect of the present invention is characterized in that the central portion surrounded by the inner layer according to the first or second aspect is made of a hollow, carbonized or inorganic material.

A fourth aspect of the present invention is characterized in that the heat-resistant oxide according to any one of the first to third aspects is silicon carbide and the conductive substance is titanium nitride.

[0012]

Embodiments of the present invention will be described below. FIG. 1 is a cross-sectional view of an electrothermal regeneration filter according to one embodiment of the present invention, FIG. 2 is a schematic cross-sectional view showing a skeleton structure of the electrothermal regeneration filter according to one embodiment of the present invention, and FIG. It is a schematic sectional drawing which shows the skeleton structure of an electrothermal regeneration filter.

As shown in FIG. 1, an electrothermal regeneration filter F of the present invention has a porous layer F1 having a relatively large pore size.
And a small porous layer F2. A large pore size means that the pore size is coarse, and a small pore size means that the pore size is small. The average pore diameter of the porous layer F1 is 0.1 to 2 mm, the average pore diameter of the other porous layer F2 is 1 to 300 μm, and the porosity of the electrothermal regeneration filter is expressed by the following formulas (1) and (2). )
Usually, it is 0.2 to 0.85. Furthermore, the resistance value of the electrothermal regeneration filter F is 0.01 to 0.01 at a temperature of 15 to 20 ° C.
200Ω is preferred.

P = P ₀ × {1− (W ′ / D ′ + W ″ / D ″) / (S × _ds− W / D)} (1) P ₀ = 1− (W / (S × d _s ) / D) (2) where P: residual porosity P ₀ : initial porosity W ′: weight of the deposited heat-resistant oxide (g) D ′: true density of the deposited heat-resistant oxide (g) / Cm ³ ) W ″: weight of the deposited conductive substance (g) D ″: true density of the deposited conductive substance (g / cm ³ ) S: surface area of the substrate (cm ² ) d _s : thickness of the substrate (Cm) W: weight of substrate (g) D: true density of substrate (g / cm ³ )

The skeleton of the porous layers F1 and F2 is shown in FIG.
The inner layer 12 made of a heat-resistant and oxide-resistant material, the intermediate layer 14 made of a conductive substance formed on the outer periphery of the inner layer 12, and the outer peripheral surface of the intermediate layer 14 like the skeleton B1 of one embodiment shown in FIG. It has a three-layer structure with an outer layer 16 made of a heat-resistant oxide.

As the heat-resistant and oxidation-resistant substance constituting the inner layer 12, any substance having heat resistance and oxidation resistance may be used, and a substance containing any of silicon, chromium and aluminum, preferably silicon carbide, silicon nitride , Chromium carbide, or alumina, and silicon carbide, silicon nitride, and chromium carbide are particularly suitable because of their excellent heat resistance and oxidation resistance.

The inner layer 12 is formed by laminating two types of porous layer substrates having large and small pore diameters, and using a skeleton (fiber or the like) of the two porous layer substrates as a core material 11 to form a known CV on the surface of the core material 11.
It is formed by D or CVI method. The porous layer substrate from which the porous layers F1 and F2 are made is made of inorganic fiber, a material that is carbonized by heating, that is, an organic fiber, or a continuous resin foam impregnated with a thermosetting resin. And the like. Examples of the organic fibers include thermosetting resin fibers (melamine resin fibers, phenol resin fibers, and the like), pulp, absorbent cotton, and the like. Both porous layer substrates are not limited to those having a fixed shape from the beginning, such as woven fabric, nonwoven fabric, foam, etc., for example, one porous layer substrate is made of woven fabric, etc. The other porous layer substrate may be formed by applying a mixture of a fiber and a binder to one surface of the layer substrate and curing the mixture. The porous layer substrate used for the porous layer F1 having a coarse pore diameter has a porosity of 0.70 to 0.99 obtained by the above formula (2) and a fiber diameter of usually 1
0 to 300 μm is preferred. On the other hand, the porous layer substrate used for the porous layer F2 having a small pore diameter preferably has a porosity of 0.40 to 0.85 determined by the above formula (2). -10 μm is preferred. In addition,
When the core material 11 is made of a material that can be carbonized by heating,
Prior to the formation of the inner layer 12 by the D, CVI method, it is turned into a carbonized material by heating.

The conductive material constituting the intermediate layer 14 is a material containing at least titanium and carbon, preferably titanium nitride, titanium carbide, titanium boride, pyrolytic carbon, graphite, particularly preferably titanium nitride, carbon carbide. It is titanium. This intermediate layer 14 is formed on the outer periphery of the inner layer 12 by CVD or CVI.

The heat-resistant and oxidation-resistant substance constituting the outer layer 16 may be any substance having heat resistance and oxidation resistance as in the case of the inner layer 12, and may contain any element of silicon, chromium or aluminum, preferably carbonized. It is made of any one of silicon, silicon nitride, and chromium carbide, and is optimal because it has excellent heat resistance and oxidation resistance. The outer layer 16 is also formed on the outer peripheral surface of the intermediate layer 14 by a CVD or CVI method.

The skeleton B2 of the electrothermal regeneration filter in another embodiment shown in FIG. 3 comprises an inner layer 12A, an intermediate layer 14A, and an outer layer 16A as described above, and a central portion surrounded by the inner layer 12A is a hollow 11A. It is a thing. In this embodiment, the porous layer substrate is made of a material that can be carbonized by heating.
By heating when the intermediate layer or the outer layer is formed by the CVD or CVI method after the formation of A, the core material 11 previously surrounded by the inner layer 12A disappears and becomes a hollow 11A. Other configurations are the same as the skeleton B1 shown in FIG.

The production of the electrothermal regeneration filter F is carried out by laminating the porous layer substrate having two kinds of pore diameters, and if the porous layer substrate is made of a material which can be carbonized by heating, the core material is heated. 11 is carbonized, and when it is made of a non-carbonized material such as inorganic fiber, etc., it is not carbonized,
The inner layers 12, 12 are sequentially formed by a known CVD or CVI method.
A, by forming the intermediate layers 14, 14A and the outer layers 16, 16A. At this time, if the porous layer substrate is made of a material that can be carbonized by heating, the core material 11 may be used depending on the temperature at the time of forming the intermediate layer 14A or the outer layer 16A.
The part disappears and becomes hollow 11A.

Electrothermal regeneration filter F having the above structure
Is used for exhaust gas filters of diesel vehicles and the like. At this time, the electrothermal regeneration filter not only collects the black smoke fine particles, but also generates heat by being connected to a power supply and is energized, burns the collected black smoke fine particles, and regenerates the electrothermal regeneration filter itself. I do.

[0023]

EXAMPLES Example 1 Silica short fibers were applied to the surface of a silica layer which is a porous layer having a coarse pore diameter so as to be entangled, and then dried to form a two-layer porous layer substrate having a cubic shape of 10 cm on a side. . The porosity of the obtained two-layer porous layer substrate is obtained by the above-mentioned formulas (1) and (2). The coarse one is 0.9, and the fine one is 0.3.
Met.

The two-layer porous layer substrate was fixed in a quartz glass reaction vessel and housed in an electric furnace, and the inside of the reaction vessel was heated to 1,050 ° C. by the electric furnace. In addition, hydrogen gas (purity 99.9%) was passed through a methyltrichlorosilane saturator to pass primary methyltrichlorosilane (concentration 4
%), And after temporarily storing the primary methyltrichlorosilane mixed gas in the first reservoir tank, the 1,050
The reaction was carried out by supplying 250 ml into the reaction vessel at a temperature of ° C, and then the reaction vessel was evacuated. The process from supply of the primary methyltrichlorosilane mixed gas to evacuation was repeated for 16 hours. As a result, FIG.
Was formed.

Next, the two-layer porous layer substrate on which the inner layer 12 was formed was fixed and stored in the reaction vessel at 850 ° C. A mixed gas in which hydrogen (purity 99.9%) and nitrogen (purity 99.9%) were mixed at a ratio of 9: 1 was passed through a titanium chloride saturator to pass primary titanium chloride (concentration 2%). ) And the first-grade titanium chloride mixed gas
Temporarily stored in reservoir tank. Then, the first-grade titanium chloride mixed gas is introduced into the reactor at 850 ° C. for 250 m.
1 was supplied to cause a reaction, and then the chamber was evacuated. The steps from the supply of the primary titanium chloride mixed gas to the evacuation were repeated for 1.5 hours. Thus, the intermediate layer 14 in FIG. 2 was formed.

Further, the inside of the reaction vessel was heated to 1,150 ° C., and hydrogen gas (purity: 99.9%) was passed through a methyltrichlorosilane saturator to make primary methyltrichlorosilane (concentration: 4%). After temporarily storing the primary methyltrichlorosilane mixed gas in the first reservoir tank, 250 ml was supplied into the reaction vessel at 1,150 ° C. to cause a reaction, and then the reaction vessel was evacuated. The process from supply of the primary methyltrichlorosilane mixed gas to evacuation was repeated for 16 hours. Thereby, the outer layer 16 in FIG. 2 was formed, and the porosity was 0.8,
An electrothermal regeneration filter having an average pore diameter of 12 μm and a resistance value of 6Ω was obtained.

Example 2 A mixture of powdered filter paper and water paste at a ratio of 1: 4 was applied to absorbent cotton, which is a porous layer having a coarse pore diameter, and then dried, and two layers each having a cubic shape of 10 cm on a side. A porous layer substrate was formed. The porosity of the obtained two-layer porous layer substrate is
It was determined by the above equation (2), and the coarser one was 0.98 and the finer one was 0.3. This two-layer porous layer substrate is completely carbonized by being housed in a furnace at 1,000 ° C. for 5 hours in an argon gas atmosphere, and a carbonized two-layer porous layer substrate having a cubic shape of about 8 cm on a side is obtained. Obtained.

The carbonized two-layer porous layer substrate was fixed in a quartz glass reaction vessel and housed in an electric furnace, and the inside of the reaction vessel was heated to 1,050 ° C. by the electric furnace. Also, hydrogen gas (purity 99.9%) was passed through a methyltrichlorosilane saturator to make primary methyltrichlorosilane (concentration 4%), and this primary methyltrichlorosilane mixed gas was temporarily stored in a first reservoir tank. Thereafter, 250 ml was supplied into the reaction vessel at the temperature of 1,050 ° C. to cause a reaction, and then the reaction vessel was evacuated. The process from supply of the primary methyltrichlorosilane mixed gas to evacuation was repeated for 16 hours. Thereby, the inner layer 12A in FIG. 3 was formed.

Next, the two-layer porous layer substrate on which the inner layer 12A has been formed is oxidized. The oxidized two-layer porous body thus obtained was fixed and stored in the reaction vessel at 850 ° C. A mixed gas in which hydrogen (purity 99.9%) and nitrogen (purity 99.9%) were mixed at a ratio of 9: 1 was passed through a titanium chloride saturator to pass primary titanium chloride (concentration 2%). ) Was temporarily stored in the second reservoir tank. Then, the first-grade titanium chloride mixed gas is introduced into the reaction vessel at 850 ° C. for 25 minutes.
The reaction was performed by supplying 0 ml, and then the chamber was evacuated. The steps from the supply of the primary titanium chloride mixed gas to the evacuation were repeated for 1.5 hours. Thus, the intermediate layer 14A in FIG. 3 was formed.

Further, the inside of the reaction vessel was heated to 1,150 ° C., and hydrogen gas (purity: 99.9%) was passed through a methyltrichlorosilane saturator to obtain primary methyltrichlorosilane (concentration: 4%). After temporarily storing the primary methyltrichlorosilane mixed gas in the first reservoir tank, 250 ml was supplied into the reaction vessel at 1,150 ° C. to cause a reaction, and then the reaction vessel was evacuated. The process from supply of the primary methyltrichlorosilane mixed gas to evacuation was repeated for 16 hours. This forms the outer layer 16A in FIG.
8. An electrothermal regeneration filter having an average pore diameter of 12 μm and a resistance value of 6Ω was obtained.

[0031]

According to the electrothermal regeneration filter of the present invention, an inner layer made of a heat-resistant oxide, an intermediate layer made of a conductive substance formed on the outer periphery of the inner layer, and an outer layer formed on the outer surface of the intermediate layer are formed. Since it has a three-layer structure with an outer layer made of a heat-resistant oxide, not only the effect that the coefficient of linear expansion is small and the thermal shock resistance is excellent, but also the resistance value of the conductive material of the intermediate layer is 0.
Since the resistance is from 01 to 200Ω, it exhibits excellent performance as a heating resistor, and effectively removes the collected black smoke fine particles by combustion. Further, the inner layer, the intermediate layer and the outer layer may be formed by CVD or C
In the case of the film formed by the VI method, since the adhesion of each layer is strengthened, the layer is excellent in durability and has an effect that it is hardly melted by heat generated by burning of the collected black smoke fine particles. In addition, since it is formed by laminating two types of porous layers having large and small pore sizes, it is effective to collect black smoke fine particles of various diameters without clogging.

[Brief description of the drawings]

FIG. 1 is a sectional view of an electrothermal regeneration filter according to one embodiment of the present invention.

FIG. 2 is a schematic sectional view showing a skeletal structure of an electrothermal regeneration filter according to one embodiment of the present invention.

FIG. 3 is a schematic sectional view showing a skeletal structure of an electrothermal regeneration filter according to another embodiment.

[Explanation of symbols]

 F Electrothermal regeneration filter 11 Core material 11A Hollow 12, 12A Inner layer 14, 14A Intermediate layer 16, 16A Outer layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) F01N 3/02 341 F01N 3/02 341N (72) Inventor Kazuyasu Nakane Nakamura-ku, Nagoya-shi, Aichi Pref. No. 2-13-4 Inoac Corporation Inc. (72) Inventor Toshihiro Yamamoto No. 16-30, Millennial, Atsuta-ku, Nagoya-shi, Aichi F-term in Inoac Corporation Shipbuilding Office F-term (reference) 3G090 AA01 BA04 CA04 4D019 AA01 BA01 BB01 BC12 BC20 CA03 CB04 CB06 CB09 4K030 BA18 BA27 BA36 BA37 BA38 BA49 BB12 CA08 LA11

Claims (4)

[Claims] 1. An electrothermal regeneration filter in which two types of porous layers having large and small pores are laminated, wherein the skeleton of the porous layers is made of an inner layer made of a heat-resistant oxide and a conductive layer formed on the outer periphery of the inner layer. Having a three-layer structure of an intermediate layer made of a conductive material and an outer layer made of a heat-resistant and heat-resistant oxide formed on the outer peripheral surface of the intermediate layer, wherein the resistance value of the filter is 0.01 to 200Ω. Electrothermal regeneration filter. 2. The method according to claim 1, wherein the inner layer, the intermediate layer and the outer layer are formed by CVD or CV.
The electrothermal regeneration filter according to claim 1, wherein the filter is formed by Method I. 3. The electrothermal regeneration filter according to claim 1, wherein the central portion surrounded by the inner layer is formed of a hollow, carbonized or inorganic material. 4. The method according to claim 1, wherein the heat-resistant oxide constituting the inner layer and the outer layer is silicon carbide, and the conductive material constituting the intermediate layer is titanium nitride. Electric heat regeneration filter.