CA1193206A - Exhaust gas filter - Google Patents
Exhaust gas filterInfo
- Publication number
- CA1193206A CA1193206A CA000406998A CA406998A CA1193206A CA 1193206 A CA1193206 A CA 1193206A CA 000406998 A CA000406998 A CA 000406998A CA 406998 A CA406998 A CA 406998A CA 1193206 A CA1193206 A CA 1193206A
- Authority
- CA
- Canada
- Prior art keywords
- exhaust gas
- filter
- compartment
- ceramic fiber
- container
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Abstract
Abstract of the Disclosure Filtering operation of an exhaust gas contain-ing particulate is improved in a small initial pressure-drop, a small increasing rate of the pressure drop and a high durability against regeneration process, by use of a novel ceramic filter comprising a sintered ceramic fiber board composite made of a ceramic fiber such as alumina fiber, alumina-silica fiber or silica fiber and of a binding agent of alumina-silica clay. The ceramic fiber composite boards are arranged in a corrugated shape (of accordion-pleats cross-section), in a container so as to part the space in the container by the corrugated shape filter into an upstream compartment and a downstream compartment.
Description
P4696 ~32~6 ,,~ 1 Title of the Invention Exhaust gas filter Background of the lnvention 1. Field of the Invention:
______________________ The present invention relates generally to the art of preventing environmental pollution` attributable to exhaust gas of internal combustion engines. Particularly, it is concerned with filter for removing particulates such as soot, which is inevitably contained in the exhaust gas of diesel engine due to the gas component~
Such soot has recently been reported to be carcinogenic and is extremely harmul to human health.
A legislative regulation on emission of such particulates is now being contemplated in order to fight against the air pollution.
______________________ The present invention relates generally to the art of preventing environmental pollution` attributable to exhaust gas of internal combustion engines. Particularly, it is concerned with filter for removing particulates such as soot, which is inevitably contained in the exhaust gas of diesel engine due to the gas component~
Such soot has recently been reported to be carcinogenic and is extremely harmul to human health.
A legislative regulation on emission of such particulates is now being contemplated in order to fight against the air pollution.
2. Descri~tion of_the Prior Axt:
Although considerable improvement has been made on the engine or other combustion apparatus itself, the very source, which emits such particulates, has hitherto been made and is still in progress, for the present time, it is considered to be the best way for preventing the environment from pullution to trap the particulates by a filter thereon and then to burn the particulates-carryir.g filter to oxidize the particulates into carbon dioxide. And a variety of concrete systems for accomplishing this object , r~7 ''~:,"
~3~
have been proposed.
The known proposals include the use of metal mesh or ceramic fiber packed and sealed in a container, and that of a porous~ceramic foam or a monolithic ceramic honey comb structure. An apparatus of the container wherein the metal mesh or ceramic fiber is randomly filled to be sealed is not suited for the purpose because the filter may frequently offset during the service to create channels of too large size for the particulates-containing ~xhaust gas and there occurs a blow-off phenomenon for the soot or an attrition phenomenon of the fiber. The metal mesh may encounter a problem of melting-down during a process for reyenerating the filtering function wherein the trapped particulates should be burn-t. The ceramic foa~ and monolithic ceramic structured body have insuf-ficient heat shock resistant property to cause a crack during the regeneration process. Particularly, the mono-lithic ceramic structural body has another drawback that it has an insufficient gas permeability which amounts to a large pressure drop, because it cannot be structured to have a large porosity.
Summar~ of the Invention ~he present invention has for its object the provision of an exhaust gas filter which obviates the drawbacks inherent to the above described known filters almost completely. The exhaust gas filter built in accordance witb the present invention can treat large quantities of exhaust gas containing particulates with a high particulates collection efficiency, a small initial 5- pressure drop and a small increasing rate of the pressure drop~
The present inventors have found that a sintered board of ceramic fiber composite, which is made of the ceramic fiber and a binding agent of fire clay of silica~alumina is excellent for the filter element and able to be embodied in a structure of a large filtering area by being put together in a container to have a corrugated s~ape of accordion pleats cross-section and completed the present in~ention.
Namely, according to the present invention, there is provided an exhaust gas filter to be placed in a path for the exhaust gas containing particulates which comprises:
a container having a side wall partitioned by a filter element into first and second compartments; the Eirst compartment forming an inlet compartment having an inlet conduit for introducing the exhaust gas therein, and the second compartment forming an outlet compartment having an outlet conduit Eor withdrawing the treated exhaust gas therefrom, wherein said filter element has a generally corrugated cross-section and an edge, and is made of sintered ceramic fiber composite board of heat-resistant ~3~
ceramic fiber and a binding agent of fire clay o~ alumina-silica the entire edge of said container is supported by the side wall of said container, said sintered ceramic fiber composite board having numerous minute pores in the direction of its thickness for permitting passage of gas component of the inflowing exhaust gas therethrough and for trapping solid component of the inElowing exhaust gas therein, to filter the exhaust gas which is introduced into the inlet compartment ~hrough the inlet conduit and is to be withdrawn from the outlet compartment through the outlet conduit.
The structural and functional features of the filter element is that; numerous minute pores are provided therein in the direction of its thickness for permitting passage of gas component of the inflowing exhaust gas there~hrough and for trapping solid component of the inflowing exhaust gas therein, so that the exhaust gas introduced into the inlet compartment through the inlet conduit is withdrawn from the outlet compartment through the outlet conduit after said gas is removed of its particulates.-Although novel features which are believed to be char-acteristic of the present invention are pointed out in the appended claims, the invention itsel:E, as to its objects and advantages, and the manner in which it may be carried out, may be better understood by reference to the follow--ing detailed description taken in connection with the acco!npanying drawings.
al ~3~
- 4a -Brief Exp].anat on of the Drawin~
FIG. 1 is a schematic iLlustration representing a scanning electron microphotograph of the ceramic fiber composite to be used as the filter element of the exhaust gas filter of the present invention.
FIG. 2~a) is a persepctive view of one embodiment of the exhaust gas filter.
~3~6 FIG. 2(b) is a cross-section of the e~bodiment shown in FIG. 2ta).
FIG. 3 is a graph showing a curve which repre-sents pressure drop/operating time characteristics of the embodiment.
Description of the Preferred ~mbodiments The filter element to be used in the exhaust gas filter of the present invention is preferably a sintered ceramic fiber composite board made of the ~0 ceramic fibe~ and a fire clay of silica-alumina as the binding agent. The ceramic fiber is at least one selected from the group consisting of alumina fiber, alumina-silica fiber and silica fiber.
The preparing process of the sintered board of ceramic fiber composite generally includes the follow~
ing steps. Firstly, the ceramic fiber (mean diameter:
2 ~m) such as alumina fiber, alumina-silica fiber or silica fiber is cut by a chopper into short yarns (or staple) of 0.1 mm - 10 mm lengthes, and the chopped fiber is dispersed in water. Then, powdery clay prepared by blending a fire clay of silica-alumina, such as ball clay or china clay, with coarse particle powder material such as petalite, is added to the dispersion at a ratio ranging from 4 to ~0 w-t ~ of the total weight to give a slurry.
After being stirred well, the slurry is combined with an aqueous solution of starch to be ayylu-ti.nated, and then placed in a forming die, where it is dehydrated and molded. A paper mill may suitabl~ be used to give a sheet-like material. Af-ter being dried, the molded material is baked at a temperature of 900C or above to give a sintered ceramic fiber composite board, as illus-trated in FIG. 1.
In general, the larger the effective filtering surface of a filter becomes, the smaller become the initial pressure drop as well as its increasing rate.
Accordingl~, the disclosed corrugated ~accordion-pleats shaped) arrangement of the multiplicity of the ceramic fiber composite boards means a filteriny surface area of as large as possible.
Furthermore, the V-shape cross-section of the flow paths formed between the ceramic fiber composite boards makes inflowing or withdrawing pressure drop small.
The ceramic fiber composite board used in the filter of the present invention has a thickness of 2 mrn, a pressure drop of below 20 cm Aq at flow path velocity of room temperature air of 10 cm/sec and a heat shock resisti~ity of 1000C or above.
Furthermore, it is found that the very small increasiny rate of pressure drop is attributable to its ability of taking the dust therein, as is the case of a fibrous
Although considerable improvement has been made on the engine or other combustion apparatus itself, the very source, which emits such particulates, has hitherto been made and is still in progress, for the present time, it is considered to be the best way for preventing the environment from pullution to trap the particulates by a filter thereon and then to burn the particulates-carryir.g filter to oxidize the particulates into carbon dioxide. And a variety of concrete systems for accomplishing this object , r~7 ''~:,"
~3~
have been proposed.
The known proposals include the use of metal mesh or ceramic fiber packed and sealed in a container, and that of a porous~ceramic foam or a monolithic ceramic honey comb structure. An apparatus of the container wherein the metal mesh or ceramic fiber is randomly filled to be sealed is not suited for the purpose because the filter may frequently offset during the service to create channels of too large size for the particulates-containing ~xhaust gas and there occurs a blow-off phenomenon for the soot or an attrition phenomenon of the fiber. The metal mesh may encounter a problem of melting-down during a process for reyenerating the filtering function wherein the trapped particulates should be burn-t. The ceramic foa~ and monolithic ceramic structured body have insuf-ficient heat shock resistant property to cause a crack during the regeneration process. Particularly, the mono-lithic ceramic structural body has another drawback that it has an insufficient gas permeability which amounts to a large pressure drop, because it cannot be structured to have a large porosity.
Summar~ of the Invention ~he present invention has for its object the provision of an exhaust gas filter which obviates the drawbacks inherent to the above described known filters almost completely. The exhaust gas filter built in accordance witb the present invention can treat large quantities of exhaust gas containing particulates with a high particulates collection efficiency, a small initial 5- pressure drop and a small increasing rate of the pressure drop~
The present inventors have found that a sintered board of ceramic fiber composite, which is made of the ceramic fiber and a binding agent of fire clay of silica~alumina is excellent for the filter element and able to be embodied in a structure of a large filtering area by being put together in a container to have a corrugated s~ape of accordion pleats cross-section and completed the present in~ention.
Namely, according to the present invention, there is provided an exhaust gas filter to be placed in a path for the exhaust gas containing particulates which comprises:
a container having a side wall partitioned by a filter element into first and second compartments; the Eirst compartment forming an inlet compartment having an inlet conduit for introducing the exhaust gas therein, and the second compartment forming an outlet compartment having an outlet conduit Eor withdrawing the treated exhaust gas therefrom, wherein said filter element has a generally corrugated cross-section and an edge, and is made of sintered ceramic fiber composite board of heat-resistant ~3~
ceramic fiber and a binding agent of fire clay o~ alumina-silica the entire edge of said container is supported by the side wall of said container, said sintered ceramic fiber composite board having numerous minute pores in the direction of its thickness for permitting passage of gas component of the inflowing exhaust gas therethrough and for trapping solid component of the inElowing exhaust gas therein, to filter the exhaust gas which is introduced into the inlet compartment ~hrough the inlet conduit and is to be withdrawn from the outlet compartment through the outlet conduit.
The structural and functional features of the filter element is that; numerous minute pores are provided therein in the direction of its thickness for permitting passage of gas component of the inflowing exhaust gas there~hrough and for trapping solid component of the inflowing exhaust gas therein, so that the exhaust gas introduced into the inlet compartment through the inlet conduit is withdrawn from the outlet compartment through the outlet conduit after said gas is removed of its particulates.-Although novel features which are believed to be char-acteristic of the present invention are pointed out in the appended claims, the invention itsel:E, as to its objects and advantages, and the manner in which it may be carried out, may be better understood by reference to the follow--ing detailed description taken in connection with the acco!npanying drawings.
al ~3~
- 4a -Brief Exp].anat on of the Drawin~
FIG. 1 is a schematic iLlustration representing a scanning electron microphotograph of the ceramic fiber composite to be used as the filter element of the exhaust gas filter of the present invention.
FIG. 2~a) is a persepctive view of one embodiment of the exhaust gas filter.
~3~6 FIG. 2(b) is a cross-section of the e~bodiment shown in FIG. 2ta).
FIG. 3 is a graph showing a curve which repre-sents pressure drop/operating time characteristics of the embodiment.
Description of the Preferred ~mbodiments The filter element to be used in the exhaust gas filter of the present invention is preferably a sintered ceramic fiber composite board made of the ~0 ceramic fibe~ and a fire clay of silica-alumina as the binding agent. The ceramic fiber is at least one selected from the group consisting of alumina fiber, alumina-silica fiber and silica fiber.
The preparing process of the sintered board of ceramic fiber composite generally includes the follow~
ing steps. Firstly, the ceramic fiber (mean diameter:
2 ~m) such as alumina fiber, alumina-silica fiber or silica fiber is cut by a chopper into short yarns (or staple) of 0.1 mm - 10 mm lengthes, and the chopped fiber is dispersed in water. Then, powdery clay prepared by blending a fire clay of silica-alumina, such as ball clay or china clay, with coarse particle powder material such as petalite, is added to the dispersion at a ratio ranging from 4 to ~0 w-t ~ of the total weight to give a slurry.
After being stirred well, the slurry is combined with an aqueous solution of starch to be ayylu-ti.nated, and then placed in a forming die, where it is dehydrated and molded. A paper mill may suitabl~ be used to give a sheet-like material. Af-ter being dried, the molded material is baked at a temperature of 900C or above to give a sintered ceramic fiber composite board, as illus-trated in FIG. 1.
In general, the larger the effective filtering surface of a filter becomes, the smaller become the initial pressure drop as well as its increasing rate.
Accordingl~, the disclosed corrugated ~accordion-pleats shaped) arrangement of the multiplicity of the ceramic fiber composite boards means a filteriny surface area of as large as possible.
Furthermore, the V-shape cross-section of the flow paths formed between the ceramic fiber composite boards makes inflowing or withdrawing pressure drop small.
The ceramic fiber composite board used in the filter of the present invention has a thickness of 2 mrn, a pressure drop of below 20 cm Aq at flow path velocity of room temperature air of 10 cm/sec and a heat shock resisti~ity of 1000C or above.
Furthermore, it is found that the very small increasiny rate of pressure drop is attributable to its ability of taking the dust therein, as is the case of a fibrous
3~
filter of container packed with metal mesh or ceramic fiber.
The improved performance of the filter is also attributable to its manner of partitioning the container whereby both of the inlet compartment and the outlet compartment have gradually widening cross-sections toward their inlet and outlet openings, respectively.
Example 1. Preparation of the filter element:
Ceramic fiber of alumina-silica (500 g) which has a mean diameter of approximately 2 ~m was cut by a chopper into short yarns (staple) of 0.1 - 10 mm lengthes and the chopped fiber was dispersed in water (about 50 ~) together with a small quantity of a surfactant. The dispersion, after being added with 150 g of a fire clay of silica~alumina, prepared by blending ball clay and china clay in 1:3 ratio, was moderately stirred to give an intimate admixture. Then an aqueous solution of starch was added to the admixture of ceramic fiber/clay system to be agglutinated. This was~ poured into another 100 ~ of water to be diluted to give a slurry 3~6 and was formed into a sheet of 1 m2 area and 2 mm thick-ness by a paper mill equipped with a screen of 60 mesh.
After being dried in the air at 120C for abou-t 30 minu-tes, the sheet was baked in an electric furnace at 1200C in the presence of air to give a sintered ceramic fiber composi-te board, which is illustrated by EIG. 1.
2. Assembly of the fi]ter:
The ceramic fiber composite board was cut into 90 rectangular boards of 120 mm width and 90 mm length.
The rectangular boards were arranged in a corrugated shape of 90 accordion-pleats cross-section with 4 mm intervals as a filter element 1 in the container 2 and abutting edges of the boards were bonded by a known ceramic bonding agent, so that they form a multiplicity of flow pathes of V-shaped cross-section by being supported and sealed by the side walls of the container 2 at their respective side edges. As a modified example, the accordior~shaped filter is made by molding the belt-shaped material of half-dried sheet of the filter material in a mold of accordion form. The upper side surfaces of the multiplicity o~ the filter elements 1 face an inlet gas chamber 3 which is connected to an inlet conduit 4, and the lower side surfaces face an outlet gas chamber 5 which is connected to an outle-t conduit 6. Accordingly, the multiplicity of upper flow pathes form an inflowincJ
~32Q~
path 7 and those of the lower flow pathes form a withdra~
ing path. The effec-tive surface area of the composite ceramic board of this embodiment, throuyh which the exhaust gas passes and on which the particulates contained in the exhaust gas is trapped, amounts to 0.86 m2.
In FIG. 2(b), an arrow ~1 designates the direction of the exhaust gas inflow through the inlet conduit 4, arroT"s 31 represent the manner whereby the gas inflow is intro-duced into the multiplicity of the flow pathes 7.
Arrows 91 represent the manner whereby the gas removed of its particulates is withdrawn from the flow pathes 8 through the filter element, and an arrow 61 designates the direction of the exhaust gas out~low through the outlet conduit 6.
FIG. 3 is a graph showing a curve which represents the pressure drop/operating time characteristics obtained as a result of experiment wherein the filter constructed as described above was connected to a diesel engine which emits an exhaust gas containing particulates at 0.1 g/m3 at a rate of 3.1 m3/min. In this experiment, the particulate collection efficiency E defined in SAE standard as:
quantity of soot in the exhaust gas~
~- 1 (after beinq trapped by -the filter rwhole quantity of soot exhausted lwith being trapped the value E is approximately 75 %.
filter of container packed with metal mesh or ceramic fiber.
The improved performance of the filter is also attributable to its manner of partitioning the container whereby both of the inlet compartment and the outlet compartment have gradually widening cross-sections toward their inlet and outlet openings, respectively.
Example 1. Preparation of the filter element:
Ceramic fiber of alumina-silica (500 g) which has a mean diameter of approximately 2 ~m was cut by a chopper into short yarns (staple) of 0.1 - 10 mm lengthes and the chopped fiber was dispersed in water (about 50 ~) together with a small quantity of a surfactant. The dispersion, after being added with 150 g of a fire clay of silica~alumina, prepared by blending ball clay and china clay in 1:3 ratio, was moderately stirred to give an intimate admixture. Then an aqueous solution of starch was added to the admixture of ceramic fiber/clay system to be agglutinated. This was~ poured into another 100 ~ of water to be diluted to give a slurry 3~6 and was formed into a sheet of 1 m2 area and 2 mm thick-ness by a paper mill equipped with a screen of 60 mesh.
After being dried in the air at 120C for abou-t 30 minu-tes, the sheet was baked in an electric furnace at 1200C in the presence of air to give a sintered ceramic fiber composi-te board, which is illustrated by EIG. 1.
2. Assembly of the fi]ter:
The ceramic fiber composite board was cut into 90 rectangular boards of 120 mm width and 90 mm length.
The rectangular boards were arranged in a corrugated shape of 90 accordion-pleats cross-section with 4 mm intervals as a filter element 1 in the container 2 and abutting edges of the boards were bonded by a known ceramic bonding agent, so that they form a multiplicity of flow pathes of V-shaped cross-section by being supported and sealed by the side walls of the container 2 at their respective side edges. As a modified example, the accordior~shaped filter is made by molding the belt-shaped material of half-dried sheet of the filter material in a mold of accordion form. The upper side surfaces of the multiplicity o~ the filter elements 1 face an inlet gas chamber 3 which is connected to an inlet conduit 4, and the lower side surfaces face an outlet gas chamber 5 which is connected to an outle-t conduit 6. Accordingly, the multiplicity of upper flow pathes form an inflowincJ
~32Q~
path 7 and those of the lower flow pathes form a withdra~
ing path. The effec-tive surface area of the composite ceramic board of this embodiment, throuyh which the exhaust gas passes and on which the particulates contained in the exhaust gas is trapped, amounts to 0.86 m2.
In FIG. 2(b), an arrow ~1 designates the direction of the exhaust gas inflow through the inlet conduit 4, arroT"s 31 represent the manner whereby the gas inflow is intro-duced into the multiplicity of the flow pathes 7.
Arrows 91 represent the manner whereby the gas removed of its particulates is withdrawn from the flow pathes 8 through the filter element, and an arrow 61 designates the direction of the exhaust gas out~low through the outlet conduit 6.
FIG. 3 is a graph showing a curve which represents the pressure drop/operating time characteristics obtained as a result of experiment wherein the filter constructed as described above was connected to a diesel engine which emits an exhaust gas containing particulates at 0.1 g/m3 at a rate of 3.1 m3/min. In this experiment, the particulate collection efficiency E defined in SAE standard as:
quantity of soot in the exhaust gas~
~- 1 (after beinq trapped by -the filter rwhole quantity of soot exhausted lwith being trapped the value E is approximately 75 %.
Claims
1. An exhaust gas filter to be placed in a path for the exhaust gas containing particulates which comprises:
a container having a side wall partitioned by a filter element into first and second compartments; the first compartment forming an inlet compartment having an inlet conduit for introducing the exhaust gas therein, and the second compartment forming an outlet compartment having an outlet conduit for withdrawing the treated exhaust gas therefrom, wherein said filter element has a generally corrugated cross-section and an edge, and is made of sintered ceramic fiber composite board of heat-resistant ceramic fiber and a binding agent of fire clay of alumina-silica the entire edge of said container is supported by the side wall of said container, said sintered ceramic fiber composite board having numerous minute pores in the direction of its thickness for permitting passage of gas component of the inflowing exhaust gas therethrough and for trapping solid component of the inflowing exhaust gas therein, to filter the exhaust gas which is introduced into the inlet compartment through the inlet conduit and is to be withdrawn from the outlet compartment through the outlet conduit.
a container having a side wall partitioned by a filter element into first and second compartments; the first compartment forming an inlet compartment having an inlet conduit for introducing the exhaust gas therein, and the second compartment forming an outlet compartment having an outlet conduit for withdrawing the treated exhaust gas therefrom, wherein said filter element has a generally corrugated cross-section and an edge, and is made of sintered ceramic fiber composite board of heat-resistant ceramic fiber and a binding agent of fire clay of alumina-silica the entire edge of said container is supported by the side wall of said container, said sintered ceramic fiber composite board having numerous minute pores in the direction of its thickness for permitting passage of gas component of the inflowing exhaust gas therethrough and for trapping solid component of the inflowing exhaust gas therein, to filter the exhaust gas which is introduced into the inlet compartment through the inlet conduit and is to be withdrawn from the outlet compartment through the outlet conduit.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000406998A CA1193206A (en) | 1982-07-09 | 1982-07-09 | Exhaust gas filter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000406998A CA1193206A (en) | 1982-07-09 | 1982-07-09 | Exhaust gas filter |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1193206A true CA1193206A (en) | 1985-09-10 |
Family
ID=4123188
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000406998A Expired CA1193206A (en) | 1982-07-09 | 1982-07-09 | Exhaust gas filter |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1193206A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4923487A (en) * | 1988-10-17 | 1990-05-08 | The Duriron Company, Inc. | Cross flow diesel particulate trap |
| CN112374818A (en) * | 2020-11-27 | 2021-02-19 | 山东鲁阳节能材料股份有限公司 | High-density ceramic fiber board with use temperature of more than 1100 ℃ and preparation method thereof |
-
1982
- 1982-07-09 CA CA000406998A patent/CA1193206A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4923487A (en) * | 1988-10-17 | 1990-05-08 | The Duriron Company, Inc. | Cross flow diesel particulate trap |
| CN112374818A (en) * | 2020-11-27 | 2021-02-19 | 山东鲁阳节能材料股份有限公司 | High-density ceramic fiber board with use temperature of more than 1100 ℃ and preparation method thereof |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |