JPH01304022A - Honeycobm-shape filter - Google Patents

Abstract

PURPOSE:To efficiently collect and remove fine particles contained in exhaust gas, by filling piercing holes opened at the end parts thereof on a gas inflow side with a ceramic fiber in a honeycomb-shape filter wherein the end parts of predetermined piercing holes are sealed. CONSTITUTION:The end parts of the predetermined piercing holes 1a, 1c of a honeycomb structure composed of a porous ceramic material are sealed with seal materials 2, 3. The piercing holes 1c opened at the end parts thereof on a gas inflow side are filled with a ceramic fiber or whisker. As a result, fine particles contained in exhaust gas can be efficiently collected and removed and this filter is reduced in pressure loss in long-term use and can be used stably.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a method for collecting and removing fine particles contained in gas, particularly fine particles such as carbon and unreacted fuel contained in automobile exhaust gas, thereby reducing exhaust gas.・Regarding a honeycomb-shaped filter for purification 6 [Problems to be solved by the prior art and the invention] For example, as shown in FIG. 5 and FIG. The sealing material 2 is filled and sealed in one end of the honeycomb structure, for example, in every vertical and horizontal direction, and the sealing material 3 is filled in the other end of the through hole adjacent to the sealed through hole. Ceramic honeycomb filters, which are made of porous partition walls filled and sealed, are known as exhaust gas purification devices that adsorb and purify fine particles contained in the exhaust gas of various combustion equipment, including automobile diesel engines. There is.

Normally, fine particles contained in exhaust gas are collected and accumulated on the surface of the partition walls of the ceramic honeycomb filter, so when used for a long period of time, clogging occurs and pressure loss increases. Conventionally, as a means to eliminate such drawbacks, the particulate collecting part of the filter, that is, the partition wall, has been combined with a heat-generating metal such as a nichrome wire heater and heated by electricity, heated air is supplied to the particulate collecting part, or fuel or Methods have been adopted to regenerate the filter by heating it using spark discharge, or by providing the filter itself with an electrode as a heater to generate heat, thereby burning and removing the fine particles. In addition, a method for regenerating fuel by increasing the combustion efficiency by using a catalyst or the like in combination with the above-mentioned means is also being used.

However, the fine particles or the fuel supplied to various combustors contain a considerable amount of metal compounds such as ash, and metal compounds such as ash are generated due to oxidation or wear of the components inside the combustor. Non-flammable fine particles such as metal fine powder or ash from sliding lubricating oil in automobile engines and the like are present. These non-combustible particles such as fine metal powder or ash are collected and accumulated on the surface of the partition wall together with combustible particles, but when the filter is regenerated, a chemical reaction occurs on the surface of the partition wall, and conversely -1 becomes strongly attached. The problem is that the filter becomes clogged, and when used for a long period of time, the pressure loss gradually increases, eventually making it impossible to regenerate the filter.

On the other hand, a ceramic skeleton structure obtained by impregnating a polymer foam material with ceramic slurry, causing the polymer foam material to disappear by heat treatment, and then firing it can be used for the exhaust gas filter. It is considered. However, even if the ceramic skeleton structure is used, the pressure drop is extremely low, but the collection efficiency is relatively low. Therefore, if there are extremely large pressure fluctuations on the exhaust gas inflow side of the filter, such as in cases where the filter is used for stray gas, the collected particulates may blow through, making it possible to efficiently and stably collect and remove particulates. It may be difficult to do so.

The present invention solves the above-mentioned problems, and provides a honeycomb that can efficiently collect and remove particulates contained in wandering gas, and can be used stably with low pressure loss even after long-term use. The purpose is to provide filters with similar properties.

[Means and effects for solving the problem] The honeycomb-shaped filter of the present invention is a honeycomb-shaped filter formed by sealing the ends of predetermined through holes of a honeycomb structure made of a porous ceramic material. It is characterized by filling ceramic fibers or whiskers into the through hole whose inflow end is open.

Hereinafter, the present invention will be explained in more detail based on the drawings.

FIG. 1 is a schematic vertical cross-sectional view of the honeycomb filter of the present invention.

That is, in the honeycomb filter of the present invention, one end of a predetermined through hole 1a among a large number of through holes connected in a honeycomb shape through a thin porous partition wall 1b is sealed with a sealing material 2, It is a honeycomb-shaped filter having a structure in which the other end of the through hole 1c except for the sealed through hole is sealed with a sealing material 3 so that exhaust gas passes through the partition wall 1b, and the end of the filter on the gas inflow side It has a structure in which ceramic fibers or whiskers are filled in a through hole 1c which is open at the end.

In other words, the non-flammable particles and combustible particles contained in the exhaust gas are mainly collected by the ceramic fibers or part of the whiskers, while the particles that have blown through without being collected by the ceramic fibers or whiskers are filtered through the honeycomb filter. This is a structure that attempts to collect the particles on the surface of the partition wall 1b. Therefore, when the collected particulates are regenerated by burning the filter by adding heated air, using fuel, or adding a catalyst to these methods, the remaining non-flammable particulates are It accumulates primarily in ceramic fibers or whiskers.

Therefore, the honeycomb-shaped filter of the present invention does not collect and remove particulates only by the partition wall 1b as in conventional filters, but has a two-stage filtration means of ceramic fibers or whiskers and the partition wall 1b. Therefore, the accumulation of nonflammable fine particles on the partition wall 1b can be suppressed to an extremely low level. If a large amount of nonflammable particles accumulate in the ceramic fibers etc. due to long-term use, the filter can be used again by replacing only the ceramic fibers etc.

The ceramic fibers and the like may be replaced by backwashing the honeycomb filter with pressure from the gas outflow side, and then filling the honeycomb filter with new fibers or whiskers.

According to the present invention, it is preferable that the ceramic fibers or whiskers have an average fiber diameter of 80 μm or less.

If the average fiber diameter is larger than 80 μm, the number of fibers that enter one through hole will be small, and the contact area with the exhaust gas will be small, making it impossible to efficiently remove particulates in the exhaust gas in this area. be.

Preferably, the ceramic fibers or whiskers are filled at least 1 ovol% with respect to the volume of the through hole having an opening on the gas inflow side.
This is because if the amount is less than 1%, efficient exhaust gas filtration will not be possible.

In order to perform more efficient filtration, it is preferable that the fiber diameter is small and that the fibers are intertwined in a complicated manner. Among them, fibers with a diameter of 0.5 to 10μm are preferably packed with a diameter of 20 to 30μm.
By vol% filling, pressure loss is small and fine particles in the exhaust gas can be removed with high efficiency, which is effective.

Furthermore, the average pore diameter formed by the above-mentioned fillers being intricately intertwined is 20 to 180 μm, and further 50 to 150 μm.
It is even more effective.

The ceramic fibers or whiskers include S i
C, 5x3N<, TiBx, ZrBz.

B, C, BN, ALa○3. Zro, Tyranno fiber, T
Preferably, the material is mainly composed of at least one compound selected from i0z and MgO.

Fibers or whiskers composed of these components are
It has excellent heat resistance and oxidation resistance against the heat generated during filter regeneration, that is, when burning and removing flammable particulates, and is extremely unlikely to melt or fuse and bond to the honeycomb matrix. from the beginning, especially S.
iC fiber, SiC whisker, S L3 N 4 whisker, A1□03 fiber, A1□03 whisker, and Tyranno fiber are excellent.

Furthermore, the open porosity of the honeycomb filter of the present invention is 5.
It is preferably 5 to 80 vol%.

If the open porosity is less than 55 vol%, the pressure loss within the filter will be high, and if it exceeds 80 vol%, the pressure loss will be small, but at the same time the thickness of the partition wall will be thin, so the mechanical strength of the filter will be reduced. There is a risk.

More preferably, it is 60 to 75 vol%. Further, in consideration of the above, the thickness of the partition wall is preferably 0.1 mm or more.

In addition, the honeycomb filter of the present invention has a through hole that is open at the end on the gas inflow side (hereinafter referred to as an "inflow side through hole" in some cases) and an open end on the gas outflow side. Through hole (hereinafter referred to as "outflow side through hole" in some cases)
) is preferably 1.1 to 2:1. The reason is that the inflow side through hole is filled with the above-mentioned material, so by increasing the volume of the inflow side through hole, the effective opening area on the inflow side and the outflow side becomes the same.
As a result, the gas flow rate can be made the same and the filtration efficiency increases. If the inflow side through-hole is smaller than 1.1 times the outflow side through-hole, or if it is more than 2 times larger than the outflow side through-hole, the effective gas passage area tends to decrease and the filtration pressure during use tends to increase. There is.

The honeycomb filter is made of powerful materials such as cordierite, muramet, and silicon carbide.

Although alumina and the like can be used, silicon carbide, which has excellent thermal conductivity, is particularly suitable.

Next, the present invention will be explained using examples.

Example 1 A honeycomb structure was manufactured by extrusion molding from powder consisting of 98% silicon carbide and 0.3% boron. A sealing material was manufactured using the same material as the honeycomb structure, and a sealing material was used to fill the through holes at predetermined positions. The ends were plugged. This honeycomb-like filter has a partition wall thickness of 0.4 mrn, an opening dimension, that is, a square cross-sectional shape of the through hole of 1.5 mm x 1.5 mm, an open porosity of 61.5 vol%, and an average pore diameter of the partition wall. 28% m, diameter 142 mm x length 150 mm.

The sealed state of the openings on the inflow side and the outflow side was such that the ratio of the through hole volume on the inflow side to the volume of the through hole on the outflow side was 1.2:1.Next, 99% of the opening on the inflow side was made of silicon carbide. 25 vol % of whiskers consisting of 1.8 μm in average fiber diameter and 85 in average aspect ratio were filled.

This filter was loaded into the exhaust gas treatment apparatus shown in FIG. 2, and diesel engine particulates generated at 100% engine load and 300 rpm were filtered.

At this time, the amount of particulates contained in the exhaust gas on the outflow side was sampled, the filtration efficiency was determined from the concentration and gas amount on the inflow side, and the initial pressure loss was also investigated.

The operation time was continued until the pressure loss reached 200 mmHg. Then, the filter itself was heated to 800°C in an oxidizing atmosphere.
The filter was regenerated by heating at ℃ to completely burn off the combustible particles.

Figures 3 and 4 show that the collection efficiency and initial pressure loss of the filter were investigated for each number of regenerations.

As is clear from Figure 3, the initial collection efficiency was 76% and 1
Even after repeated regeneration 00 times, the collection efficiency was 78%, with high collection efficiency and little variation.

Moreover, as is clear from FIG. 4, the initial pressure loss increased only slightly between the initial pressure loss and the 100th regeneration, and it was possible to obtain a high collection efficiency with a small pressure loss. After regenerating 100 times, the filter was backwashed under pressure at 2.5 kg/cm" to remove the filled whiskers, and the filter was filled with new whiskers in the same manner. When the pressure loss was measured, it was found to be 46 mmHg. It was found that there was almost no increase in the pressure loss of the filter.

Comparative Example 1 A honeycomb filter was manufactured using cordierite in the same manner as in Example 1 by filling a honeycomb structure with a sealing material. In this honeycomb structure, the thickness of the partition walls is 0.4 mm,
The cross-sectional shape of the through hole is a square of 1.5 x 1.5 mm, the open porosity is 61.9 vol%, and the average pore diameter of the partition wall is 26
μm, diameter 142 mm x length 150 mm. The ratio of the inflow side through hole volume to the outflow side through hole volume was 1:1. Particulate collection and pressure loss were measured in the same manner as in Example 1, and compared in FIGS. 3 and 4.

As is clear from FIG. 3, the collection efficiency was initially 65%, and as the number of regenerations increased, the collection efficiency tended to increase, and rose to 95% after 100 regenerations.

Also, as is clear from Figure 4, the initial pressure loss is 25
mmHg, but the initial pressure drop tends to increase as the number of regenerations increases, and after 100 regenerations, the initial pressure drop is 1O5mm.
Hg, and the amount of exhaust gas that could be treated each time the filter was regenerated gradually decreased. That is, it was found that the pores in the partition walls of the honeycomb filter gradually became clogged and did not become the same as the conventional pores even after the regeneration heat treatment.

Examples 2 to 8, Comparative Examples 2 to 5 Other than setting the open porosity of the honeycomb structure to 77.9%,
In the same case as in Example I (Example 2), in the same case as in Example 1 except that the open porosity of the honeycomb structure was 44.4 vol% (Comparative Example 2), the average fiber diameter was 5. !
In the same case as in Example 1 (Example 3) except that silicon carbide fibers with a thickness of 5 um and an average aspect ratio of 70 were used and the filling rate was 26 vol%, silicon carbide fibers with an average fiber diameter of 28 μm (stranded wire: average fiber diameter) were used. 5.5μm average aspect ratio 70
In Example 4), silicon carbide fibers with an average fiber diameter of 120 μm (stranded wire; average fiber) were used, except that the filling rate was 27 vol%. The same case as Example 1 (Comparative Example 3) except that the fibers were filled with fibers with a diameter of 5.5% and an average aspect ratio of 70 at a filling rate of 28 vol% and the open porosity was 61.9%. , the filling rate of silicon carbide whiskers is 35 vol.
% (Example 5), and the same case as Example 1 except that the silicon carbide whisker filling rate was 5 vol% and the open porosity was 61.9% (Example 5). Comparative Example 4) As a filler, Tyranno fibers with an average m-fiber diameter of 8.5 μm and an average aspect ratio of 60, or tyranno fibers with an average fiber diameter of 3.5 μm were used.
In the same case as in Example 1 (Example 6.7) except that 2□03 fibers were filled into the holes with a diameter of 0 μm and an average aspect ratio of 60, the volume ratio of the inflow side through hole and the outflow side through hole was set to 1.6: 1, except that the case was the same as Example 1 (Example 8), except that the volume ratio of the inflow side through hole and the outflow side through hole was 3:1, and the filling rate of silicon carbide fiber was 25 vol%. Honeycomb-shaped filters obtained in the same case as Comparative Example 4 (Comparative Example 5) were examined for particulate collection efficiency and pressure loss in the same manner as in Example 1, and are shown in the following table.

As is clear from the table, it can be seen that the honeycomb filter of the present invention has low pressure loss and maintains high collection efficiency over a long period of time.

[Effects of the Invention] As detailed above, in the honeycomb filter of the present invention, the through holes on the gas inflow side are filled with ceramic fibers or whiskers, so that fine particles contained in gases such as exhaust gas can be efficiently collected.・Removes the adhesion of non-flammable particulates to partition walls due to combustion treatment for filter regeneration.
Accumulation can be prevented, and even if the filter is used for a long period of time, high collection efficiency can be maintained without increasing pressure loss.

In addition, since the honeycomb filter of the present invention is filled with ceramic fibers and whiskers, it is also useful as a filter for filtering gas containing high-temperature adhesive particles used in high-temperature incinerators, high-temperature reactors, etc. It is.

[Brief explanation of the drawing]

FIG. 1 is a schematic vertical cross-sectional view showing a honeycomb filter of the present invention. FIG. 2 is a schematic diagram showing an exhaust gas treatment device used in Examples and Comparative Examples. 3 and 4 are diagrams showing the collection efficiency and initial pressure loss measured in Example 1 and Comparative Example 1. FIG. 5 is a front view for explaining a general honeycomb filter, and FIG. 6 is a schematic diagram showing gas inflow and outflow states. l - Honeycomb filter, 2.3 - Sealing material

Claims (1)

[Scope of Claims] 1. A honeycomb filter formed by sealing the ends of predetermined through holes of a honeycomb structure made of a porous ceramic material, the through holes having open ends on the gas inflow side. Inside the hole,
A honeycomb filter characterized by being filled with ceramic fibers or whiskers. 2. The open porosity of the honeycomb structure is 55 to 80 vo.
2. The honeycomb filter according to claim 1, wherein the content is 1%. 3. The honeycomb filter according to claim 1 or 2, wherein the average fiber diameter of the ceramic fibers or whiskers is 80 μm or less. 4. The honeycomb filter according to any one of claims 1 to 3, wherein the ceramic fibers or whiskers account for at least 10 vol% of the volume of the through holes. 5. The ceramic fiber or whisker is SiC,
Si_3N_4, TiB_2, ZrB_2, B_4C,
BN, Al_2O_3, ZrO_2, Tyranno fiber, Ti
The honeycomb-shaped filter according to any one of claims 1 to 4, comprising as a main component at least one selected from O_2 and MgO. 6. The volume ratio of the through hole with an open end on the gas inflow side and the through hole with an open end on the gas outflow side is 1.
The honeycomb-shaped filter according to any one of claims 1 to 5, wherein the ratio is 1 to 2:1.