JPH05321632A - Exhaust emission control device - Google Patents

Abstract

PURPOSE:To provide an exhaust emission control device located in an exhaust passage in an internal combustion engine such as a Diesel-engine or the like, which has a less pressure loss in a gas stream. CONSTITUTION:Porous ceramic honeycomb members 2 and ceramic fiber filter elements 3 are stacked one upon another, and a heat generating element 5 is incorporated in each of the filter members 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying device arranged in an exhaust path of an internal combustion engine such as a diesel engine, and more particularly to an exhaust gas purifying device having a small gas flow pressure loss.

[0002]

2. Description of the Related Art Various purifiers for exhaust gas from internal combustion engines such as diesel engines have been studied. For example, Japanese Patent Laid-Open No. 56-129020 discloses a honeycomb formed of a porous cordierite sintered body. An exhaust gas purifying device having the above described filter is disclosed.

In this type of filter, one end face of each gas vent hole (cell) forming a honeycomb is provided in a checkered pattern so that either the gas supply side or the gas discharge side is sealed. Is introduced into the gas passage hole opened on the gas supply side and is discharged through the gas passage hole opened on the discharge side through the partition wall, so that the partition wall of the gas passage hole acts as a filtration membrane, and the exhaust gas is discharged. Soot and the like in the gas are collected in the partition wall, and the purified exhaust gas is discharged through the gas passage hole that is open to the discharge side.

However, the filter made of such a porous honeycomb structure has the following drawbacks. (1) Since the particulates such as soot are fine particles having a particle size of 1 μm or less, the partition walls of the gas passage holes must be formed in a size that does not allow the fine particles to pass therethrough. The pressure loss of is large. (2) As it is used as a purifying device, fine particles in exhaust gas that cannot pass through the partition wall are collected and the surface of the partition wall is covered with particulates, and as a result, exhaust gas becomes difficult to flow. (3) In the case of city gas, for example, the number of cells in the honeycomb is about 10,000 per set, and thus sealing both end faces of both is troublesome and enormous in cost. (4) When the particulates adhering to the partition walls are burned and removed for regeneration, the partition walls locally heat up due to the heat generation of the particulates, so that the partition walls are cracked or melted.

[0005]

The present invention has been completed as a result of various studies for solving the above-mentioned drawbacks, and the present invention has been completed. An object of the present invention is to provide an exhaust gas purifying apparatus that reduces loss, is highly trapped, and is easily regenerated.

[0006]

DISCLOSURE OF THE INVENTION The gist of the present invention is that a porous ceramic honeycomb member and a ceramic filter member are laminated and disposed, and a heating element is internally provided in the ceramic fiber filter member. It is a featured exhaust gas purification device.

That is, in the present invention, when the exhaust gas passes through the porous ceramic honeycomb member, a part of the particulates in the exhaust gas adheres to the cell wall and subsequently passes through the ceramic fiber filter member. During this process, the particulates in the exhaust gas adhere to and collect on the ceramic fiber filter. Increasing the number of layers of the porous ceramic honeycomb member and the ceramic fiber filter increases the collection efficiency of particulates in the exhaust gas, and the thickness of the porous ceramic honeycomb member and the ceramic fiber Increasing the thickness of the filter member also increases the collection efficiency.

The porous ceramic / honeycomb member in the present invention may be any one of cordierite, SiC, etc., and the honeycomb shape has a cell wall thickness of 0.1 to 0.6 m.
m is preferably about 0.3 mm, and the number of cells is about 100 to 400 per square inch, preferably 200.
The thickness of the honeycomb member is about 5 mm to 50 mm, preferably about 15 mm, and the porosity is 30% to 70%.
It is about 40%, preferably about 40%.

Further, the ceramic fiber filter member may be made of silica, mullite, alumina or the like, and may be string, sheet or board. The string is a string formed by bundling and twisting a plurality of long and short fibers of the ceramic fiber, and by inserting a nichrome wire in this manufacturing process,
A string with a nichrome wire is made, which is made into a spiral shape. The sheet-like shape means that the ceramic fiber is put into water, stirred and uniformly dispersed, and produced from the obtained dispersion by a paper making machine by the same operation as that of "paper making". Further, the board shape is a thicker and harder state than the above-mentioned "sheet shape", and the manufacturing method thereof is the same as that of the "sheet shape" or a blanket-shaped ceramic. A fiber is impregnated with a heat-resistant binder, dried and cured. Then, these ceramic fiber filter members can be improved in wind erosion resistance by using a heat resistant adhesive as required. These bulk density 0.05~0.5gr / cm ^3, preferably about a 0.1gr / cm ³ before and after its thickness is about 0.5 mm to 10 mm, preferably from to front and rear 3mm ..

This ceramic fiber filter
A nichrome wire for heating is enclosed therein, and the particulates trapped in the ceramic fiber filter are burned and regenerated. In the present invention, the ceramic fiber filter and the ceramic honeycomb portion are laminated. The number of layers is about 2 to 15 layers, preferably about 3 to 5 layers.

Next, the exhaust gas purifying apparatus of the present invention will be described with reference to the drawings. FIG. 1 is a sectional model view of an exhaust gas purifying apparatus according to the present invention. Porous ceramics in the metal case 1
The honeycomb members 2 and the ceramic fiber filter members 3 are arranged alternately. Cell 4 of honeycomb member
The direction of is matched with the direction of gas flow. Then, a nichrome wire 5 is provided inside the ceramic fiber filter member 3. A heat insulating material 6 is wound around the outer periphery of the ceramic fiber filter member 3 and the honeycomb member, and the heat insulating material 6 is integrally housed in a metal case and fixed by a fixing member 7. At that time, the ceramics / honeycomb members are fixed to the frontmost part and the rearmost part of the exhaust gas purifying apparatus.

In such an apparatus, the exhaust gas is introduced from the gas inlet, passes through the cells of the ceramic honeycomb member, is filtered by the fiber filter member, and is discharged from the gas outlet by repeating this process. The particulates in the exhaust gas are deposited on the cell surface of the ceramic honeycomb member or are collected by the filter member, and the collected particulates are burned by heating the nichrome wire to regenerate the device. Next, a more specific description will be given with reference to examples.

[0013]

EXAMPLE Exhaust gas is purified by using the exhaust gas device shown in FIG. It is introduced through the gas inlet and discharged through the gas outlet. The porous ceramic honeycomb member used in this example is shown in FIG. The honeycomb member has an outer diameter of 140 m
m, thickness 15 mm, pore diameter 15 μm, cell wall 0.3 m
m, 200 cells / square inch, Si with porosity of 45%
It is a honeycomb filter of C99.5%. On the other hand, a ceramic fiber filter member is shown in FIGS. The ceramic fiber filter member of FIG. 4 is provided at two locations on the exhaust gas introducing side, and the ceramic fiber filter member of FIG.
The filter member is arranged at one place on the exhaust gas discharge side. The ceramic fiber filter member of FIG. 4 has an outer diameter of 5 mm,
A ceramic cord having an average fiber diameter of 2.5 μm was formed into a spiral shape, and a nichrome wire was included in the center of the cord. The bulk density of this filter is 0.3 g / cm ³ and Al ₂
It is composed of a composition of 50% O _{3 and} 48% SiO ₂ . The ceramic fiber filter member shown in FIG. 4 was a disc having an average fiber diameter of 3 μm, an outer diameter of 140 mm and a thickness of 3 mm, and its bulk density was 0.1 g / cm ³ . Then, a nichrome wire was embedded in this filter.

When exhaust gas is passed through the exhaust gas purifying apparatus, particulates are collected on the string-shaped ceramic fiber filter member, and the amount of the collected particulates increases. It prevents the flow of exhaust gas from increasing and the pressure loss from rising. The most downstream sheet-shaped ceramic fiber filter member
When the nichrome wire was energized at 100 W for 10 minutes at the stage where the collection was approaching the limit, it was regenerated by burning away the particulates. The regeneration efficiency is 1
In order to make the temperature close to 00%, it is necessary to set a heater so that the temperature is not lower than 700 ° C and to make the air flow as uniform as possible.

[0015]

As a result of the above configuration, low pressure loss,
It was possible to provide an exhaust gas purifying device which has high collection and is easily regenerated. Conventionally, cracking or melting damage may occur in the filter member during regeneration, but the thickness of the honeycomb member should be thin, and the particulate collecting body should be the ceramic fiber member. It was completely solved by. Further, since the ceramic fiber filter member can collect and collect the particulates internally, the collection amount is high due to low pressure loss. Also, because the ceramic fiber filter member is lightweight and has high heat insulation performance,
This is an excellent exhaust gas purification device that can efficiently burn and remove PM by passing a small amount of current through the internally-provided heating element.

[0016]

[Brief description of drawings]

FIG. 1 is a sectional view of an exhaust gas purifying apparatus of the present invention.

FIG. 2 is a plan view of a porous ceramic honeycomb member used in the present invention.

FIG. 3 is a plan sectional view of a ceramic fiber filter used in the present invention.

FIG. 4 is a plan sectional view of another ceramic fiber filter used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal case 2 Ceramic honeycomb 3 Ceramic fiber-Filter-4 Vent hole (cell) 5 Nichrome wire 6 Thermal insulation 7 Fixing member

Claims (1)

[Claims] 1. An exhaust gas purifying apparatus characterized in that a porous ceramic honeycomb member and a ceramic fiber filter member are laminated and disposed, and a heating element is internally provided in the ceramic fiber filter member.