PARK HYEONG-JUNG (KR)
KIM KI-HO (KR)
PARK HYEONG-JUNG (KR)
JPH11333226A | 1999-12-07 | |||
KR20030007302A | 2003-01-23 | |||
JP2002219319A | 2002-08-06 | |||
JPH09206524A | 1997-08-12 | |||
US6080219A | 2000-06-27 |
1. | A method for preparing a multilayered ceramic filter, which comprises the steps of : a) mixing i) 25 to 60 parts by weight of ceramic powder selected from the group consisting of silicon carbide, alumina, sillimanite, kaolin, silica, titania, and siliceous earth; ii) 10 to 40 parts by weight of clay ; iii) 5 to 40 parts by weight of poreforming material; iv) 1 to 20 parts by weight of a binder; and v) 20 to 60 parts by weight of a dispersion to prepare a slurry ; b) supporting the slurry prepared in step a) on a support to prepare a molded article ; c) drying the molded article prepared in step b) ; d) further coating inside or outside of the molded article dried in step c) a slurry comprising: i) 40 to 80 parts by weight of ceramic powder selected from the group consisting of silicon carbide, alumina, sillimanite, kaolin, silica, titania and siliceous earth; ii) 10 to 40 parts by weigh of a poreforming material ; iii) 7 to 30 parts by weight of a binder; iv) 10 to 50 parts by weight of a dispersion; e) drying the molded article further coated in step d); and f) sintering the molded article dried in step e). |
2. | A method for preparing a multilayered ceramic filter, which comprises the steps of : a) mixing i) 25 to 60 parts by weight of ceramic powder selected from the group consisting of silicon carbide, alumina, sillimanite, kaolin, silica, titania, and siliceous earth; ii) 10 to 40 parts by weight of clay ; iii) 5 to 40 parts by weight of poreforming material ; iv) 1 to 20 parts by weight of a binder ; and v) 20 to 60 parts by weight of a dispersion to prepare a slurry ; b) supporting the slurry prepared in step a) on a support to prepare a molded article ; c) drying the molded article prepared in step b); d) sintering the molded article dried in step c) ; e) further coating inside or outside of the molded article sintered in step d) a slurry comprising: i) 40 to 80 parts by weight of ceramic powder selected from the group consisting of silicon carbide, alumina, sillimanite, kaolin, silica, titania and siliceous earth; ii) 10 to 40 parts by weigh of a poreforming material ; iii) 7 to 30 parts by weight of a binder; iv) 10 to 50 parts by weight of a dispersion; f) drying the molded article further coated in step e); and g) secondary sintering the molded article dried in step f). |
3. | The method for preparing a multilayered ceramic filter according to claim 1 or 2, further comprising the step of molding the support on which the slurry is supported into a determined shape, before or after the step of b) supporting. |
4. | The method for preparing a multilayered ceramic filter according to claim 1 or 2, wherein the a) i) ceramic powder is alumina, silicon carbide or a mixture thereof. |
5. | The method for preparing a multilayered ceramic filter according to claim 1 or 2, wherein the a) iii) a poreforming material is selected from the group consisting of carbon, active carbon, woodbased powder, salt, naphthalene, and talc. |
6. | The method for preparing a multilayered ceramic filter according to claim 1 or 2, wherein the a) iv) binder is an inorganic binder selected from the group consisting of frit, barium carbonate (BaCOs), or an organic binder selected from the group consisting of MAP (mono aluminum phosphate), water binder, polyvinyl butyral, polyvinyl alcohol and polyvinyl acetate. |
7. | The method for preparing a multilayered ceramic filter according to claim 1 or 2, wherein the b) support is nonwoven fabric, wovenfabric or sponge having pores on which the slurry of a) is supported. |
8. | The method for preparing a multilayered ceramic filter according to claim 7, wherein the nonwoven fabric is selected from the group consisting of polyester, aramide, polyphenylene sulfide, homeacryl, polyimide, PTFE, viscose, natural fiber, glass fiber, ceramic fiber and metal fiber having pores. |
9. | The method for preparing a multilayered ceramic filter according to claim 1 or 2, wherein the b) molded article is of circular tube, radial curved tube, or rectangular tube shape. |
10. | The method for preparing a multilayered ceramic filter according to claim 1 or 2, wherein the step b) comprises bonding a release film on a molding and then bonding the molded article with the support. |
11. | The method for preparing a multilayered ceramic filter according to claim 1 or 2, wherein the slurry further comprises v) 10 to 40 parts by weight of clay. |
12. | The method for preparing a multilayered ceramic filter according to claim 1 or 2, wherein the sintering step comprises elevating temperature at a rate of 0.5 to 1 °C/min from 150450 °C. |
13. | A ceramic filter prepared by the method of anyone of claims 1 to 12. |
14. | The ceramic filter according to claim 13, wherein the ceramic filter has two layers consisting of a sintered layer of a supported material and a sintered layer of a further coated material. |
15. | The ceramic filter according to claim 13, wherein the ceramic filter is of circular, rectangular or radial curved tube shape. |
16. | The ceramic filter according to claim 13, wherein the ceramic filter is used for a dusting apparatus for an incinerator or crematory, an apparatus for dusting engine exhaust gas, a support of automobile exhaust gas, or an apparatus for removing volatile organic compounds. |
(b) Description of the Related Art With the development of industries, damages from hazardous material such as dust, smoke, waste gas, fume, volatile organic chemicals (VOC's), etc. have increased. Therefore, in order to prevent release of such pollutants, a polymer filter is used. However, the polymer filter has problems of inferior heat resistance, chemical resistance, abrasion resistance and flame retardation. Specifically, polyester shrinks at 150toc, and even PTFE (Teflon) has maximum heat resistance of approximately 250°C. Since various waste gases and moisture are simultaneously generated under conditions for process using an industrial filter, if the surface of a non-woven fabric filter made of polymers such as polyester, polypropylene, acryl, polyamide, polyimide, glass fiber, etc. is dust off, dust falls down to seriously abrade a filter surface, thereby damaging a filter and shortening life cycle of a filter. In addition, sparks generated during firing process may be attached to
a filter to cause fire or make a hole in the filter, which may expose waste gas in the air in case filters are used for a waste incinerator, a boiler, a coal steam power plant, a coal gasification complex plant, and this is against recent environmental regulation.
Therefore, in order to solve these problems, a ceramic filter has been developed, which has superior heat resistance, chemical resistance, abrasion resistance to a polymer filter, and does not require a separate cooling apparatus in an exhauster due to superior heat resistance to reduce installation and maintenance costs.
However, the existing ceramic filters are generally prepared by vacuum molding or extrusion molding of ceramic fiber into a tube shape.
Although such ceramic filters have relatively superior filtering efficiency and pressure property, the production cost is high, durability of a filter decreases due to deterioration of ceramic fiber thereby decreasing filtering efficiency if used for a long time, compressed air is reverse-sprayed during regeneration of a filter and thus ceramic fiber is damaged when dusting off the external wall, the damaged ceramic fiber is included in and discharged as exhaust gas to cause secondary pollution, and since whole ceramic filter has the same porosity, dust inside of a filter may cause eye-blocking thereby causing pressure loss and increasing pressure.
In addition, in a vacuum molding, a lot of cost is required for preparing vacuum chambers and vacuum pumps, the size of ceramic filter that can be manufactured is limited according to the size limitation of a vacuum chamber and thus a large-sized filter cannot be manufactured, and a mold should be replaced at an interval of certain productions due to serious abrasion of ceramic material and thus production cost is high.
In addition to the vacuum molding, an extrusion molding, a press molding, a hydrostatic pressure molding, etc. are employed. However, since these also require preparation of molding and pressurizing apparatus, production cost increases, preparation is not easy, shape modification is not easy due to determined molding, and a large-sized filter cannot be prepared.
And, since these molding methods employ pressurization, porosity is low and ventilation decreases, and pressure loss increases during passage of the filter.
SUMMARY OF THE INVENTION In order to solve the problems of the prior art, it is an object of the present invention to provide a ceramic filter having light weight, which has superior abrasion resistance and heat resistance, comparatively broad porosity control range.
It is another object of the present invention to provide a method for preparing a ceramic filter, wherein production cost is low, preparation is easy, and modification of shape and production of a large-sized filter are easy.
It is another object of the present invention to provide a method for preparing a ceramic filter that can collect surface dusts to prevent eye- blocking, decrease pressure loss, and remarkably improve ventilation and dusting efficiency.
It is another object of the present invention to provide a ceramic filter that can maximize filtering area by shape modification in a certain space to maximize dusting efficiency.
In order to achieve these objects, the present invention provides a method for preparing a multi-layered ceramic filter, which comprises the steps of:
a) mixing i) 25 to 60 parts by weight of ceramic powder selected from the group consisting of silicon carbide, alumina, sillimanite, kaolin, silica, titania, and siliceous earth ; ii) 10 to 40 parts by weight of clay ; iii) 5 to 40 parts by weight of pore-forming material ; iv) 1 to 20 parts by weight of a binder; and v) 20 to 60 parts by weight of a dispersion to prepare a slurry ; b) supporting the slurry prepared in step a) on a support to prepare a molded article ; c) drying the molded article prepared in step b); d) further coating inside or outside of the molded article dried in step c) a slurry comprising i) 40 to 80 parts by weight of ceramic powder selected from the group consisting of silicon carbide, alumina, sillimanite, kaolin, silica, titania and siliceous earth; ii) 10 to 40 parts by weigh of a pore-forming material ; iii) 7 to 30 parts by weight of a binder ; iv) 10 to 50 parts by weight of a dispersion; e) drying the molded article further coated in step d); and f) sintering the molded article dried in step e).
The present invention also provides a method for preparing a multi- layered ceramic filter, which comprises the steps of : a) mixing i) 25 to 60 parts by weight of ceramic powder selected from the group
consisting of silicon carbide, alumina, sillimanite, kaolin, silica, titania, and siliceous earth ; ii) 10 to 40 parts by weight of clay ; iii) 5 to 40 parts by weight of pore-forming material ; iv) 1 to 20 parts by weight of a binder; and v) 20 to 60 parts by weight of a dispersion to prepare a slurry ; b) supporting the slurry prepared in step a) on a support to prepare a molded article ; c) drying the molded article prepared in step b) ; d) sintering the molded article dried in step c); e) further coating inside or outside of the molded article sintered in step d) a slurry comprising i) 40 to 80 parts by weight of ceramic powder selected from the group consisting of silicon carbide, alumina, sillimanite, kaolin, silica, titania and siliceous earth ; ii) 10 to 40 parts by weigh of a pore-forming material ; iii) 7 to 30 parts by weight of a binder ; iv) 10 to 50 parts by weight of a dispersion; f) drying the molded article further coated in step e) ; and g) secondary sintering the molded article dried in step f).
The present invention also provides a multi-layered ceramic filter prepared by the above methods.
BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows a cross-sectional view of one embodiment of a mold used in the preparation method of a multi-layered ceramic filter of the present
invention.
Fig. 2 is a photograph of a circular tube shaped ceramic filter prepared by the preparation method of the present invention.
Fig. 3 is a photograph of a radial curbed tube shaped ceramic filter prepared by the preparation method of the present invention.
Fig. 4 is a photograph of various kinds of ceramic filters prepared by the preparation methods of the present invention.
Fig. 5 is a photograph of a ceramic filter in which the upper and the lower caps are assembled, prepared by the preparation method of the present invention.
Fig. 6 is a Scanning Electron Microscope picture of the further coated area of a ceramic filter prepared by the preparation method of the present invention.
Fig. 7 is a Scanning Electron Microscope picture of a support containing an area of a ceramic filter prepared by the preparation method of the present invention.
Fig. 8 is a Scanning Electron Microscope picture of the upper part of a support containing area and further coated area of a ceramic filter prepared by the preparation method of the present invention.
Fig. 9 is a photograph of an extended ceramic filter prepared by the preparation method of the present invention.
Fig. 10 is a photograph of a multi-layered ceramic filter installed in a dusting apparatus, prepared by the preparation method of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be explained in more detail.
In one aspect of the present invention, the ceramic filter of the present invention is prepared by a first method comprising the steps of mixing ceramic powder selected from the group consisting of silicon carbide, alumina, sillimanite, kaolin, titania and siliceous earth, clay, pore-forming material, a binder and a dispersion to prepare a slurry ; supporting the slurry on a support to prepare a molded article; drying the molded article ; further coating inside or outside of the dried molded article ceramic a slurry comprising ceramic powder, a pore-forming material, a binder and a dispersion; drying; and sintering. In another aspect of the present invention, the ceramic filter of the present invention is prepared by a second method comprising the steps of mixing ceramic powder selected from the group consisting of silicon carbide, alumina, sillimanite, kaolin, silica, titania and siliceous earth, clay, a pore-forming material, a binder and a dispersion to prepare a slurry; supporting the slurry on a support to prepare a molded article ; drying and sintering the molded article ; further coating inside or outside of the sintered molded article a slurry comprising ceramic powder, a pore-forming material, a binder and a dispersion ; and drying and sintering.
The first method will be explained in detail. a) Preparation of a slurry This step is to mix i) 25 to 60 parts by weight of ceramic powder selected from the group consisting of silicon carbide, alumina, sillimanite, kaolin, silica, titania and siliceous earth, ii) 10 to 40 parts by weight of clay, iii) 5 to 40 parts by weight of a pore-forming material, iv) 1 to 20 parts by weight of a binder, and v) 20 to 60 parts by weight of a dispersion.
The i) ceramic powder, which constitutes a basic structure of the ceramic filter after sintering, functions as a support of a ceramic filter.
Ceramic powder of various kinds commonly used in the art can be used. Preferably, silicon carbide, alumina, sillimanite group (AI20s SiO2), kaolin group (AI203 2Si02 2H20), silica (SiO2), titania or siliceous earth can be used, and more preferably, alumina, silicon carbide or a mixture thereof is used.
As the ceramic powder, various kinds of material having various particle sizes, specific kinds of material having the same particle diameter, or one kinds of material having different particle sizes can be used. The particle size is preferably 0. 001 um to 1 mm. If the particle size of the ceramic powder falls within the above range, pore formation and mechanical strength of a ceramic filter can be improved.
The ceramic powder preferably is comprised in the slurry composition in an amount of 25 to 60 parts by weight, more preferably in an amount of 30 to 50 parts by weight. If the content falls within the above range, physical strength, shape of a ceramic filter can be maintained, filtering efficiency can be remarkably improved, twisting and cracks can be prevented during sintering, and abrasion resistance of a ceramic filter can increase.
The ii) clay, which constitutes a basic structure of a ceramic filter after sintering, facilitates bonding between ceramic particles during sintering.
As the clay, various kinds of material having various particle sizes, specific kinds of material having the same particle size, or one kind of material having different particle sizes can be used. The particle size is preferably 0. 001, um to 1 mm. If the particle size of the clay falls within the above range, pore formation and mechanical strength of a ceramic filter can be improved.
The clay is preferably comprised in the slurry composition in an
amount of 10 to 40 parts by weight, more preferably in an amount of 15 to 25 parts by weight. If the content falls within the above range, physical strength and shape of a ceramic filter can be maintained, filtering efficiency can be remarkably improved, twisting and cracks can be prevented during sintering, and abrasion resistance of a ceramic filter can increase.
The iii) pore forming material forms pores in a ceramic filter.
As the pore forming material, carbon, active carbon, wood-based powder, sawdust, salt, naphthalene or talc can be used.
As the pore forming material, those having various particle sizes can be used. The particle size is preferably 0. 001, um to 1 mm. If the particle size of the pore forming material falls within the above range, pores with appropriate size can form and mechanical strength of a ceramic filter can be improved.
The pore forming material burns to disappear during sintering process thereby forming pores in a ceramic filter. The pore forming material is preferably comprised in the slurry composition in an amount of 5 to. 40 parts by weight, and more preferably 10 to 25 parts by weight. If the content falls within the above range, the pore forming material completely burns during sintering to efficiently form pores in a ceramic filter.
The iv) binder functions for binding the slurry with the support.
As the binder, an organic binder, an inorganic binder, or a mixture thereof can be used, preferably a mixture of an inorganic binder and an organic binder is used.
Specifically, the binder includes an inorganic binder such as frit or barium carbonate (BaCOs), and an organic binder such as MAP (monoaluminum phosphate), water binder, polyvinylbutyral, polyvinylalcohol
or polyvinyl acetate, etc. , and preferably a mixture of frit and a water binder is used.
The binder is preferably composed in the slurry composition in an amount of 1 to 20 parts by weight, preferably in an amount of 5 to 10 parts by weight. If the content falls within the above range, the slurry and the support can be efficiently bound.
The v) dispersion may be varied according to the kinds of the binder, and preferably water or alcohol is used.
The dispersion is preferably composed in the slurry composition in an amount of 20 to 60 parts by weight, preferably in an amount of 20 to 30 parts by weight. If the content falls within the above range, each component can be efficiently mixed, and the slurry can maintain appropriate viscosity to efficiently bind to the support.
The ceramic powder, clay, pore-forming material and a binder can be simultaneously introduced into the dispersion, or sequentially separately introduced at a specific interval. It is preferable to mix ceramic powder, clay, pore forming material and an inorganic binder (mixed in case an inorganic binder is used) with the dispersion and then mix an organic binder with the mixture in order for convenience of mixing.
The mixing is preferably conducted for 1 to 10 hours.
The mixed slurry is preferably aged for 1 hour or more. b) Supporting This step is to support the slurry prepared in step a) on a support to prepare a molded article.
The size of the support may be varied according to the size of a ceramic filter to be prepared.
The support may include those having porous structure capable of supporting a slurry, and preferably non-woven fabric, woven-fabric or sponge, etc. is used in terms of facility of application.
The non-woven fabric is prepared by binding short staple to a web or sheet type fiber aggregate using an adhesive, adhering fibers using thermoplastic fiber, or entangling fibers by needle punching, sewing, etc.
Preferably, polyester, aramide, polyphenylenesulfide, home-acrylic, polyimide, polytetrafluoroethylene (PTFE), viscose, natural fiber, glass fiber, ceramic fiber or metal fiber, etc. is used.
The woven-fabric is prepared by spinning, weaving, cotton weaving, etc. Preferably, it is loosely woven to contain sufficient pores for supporting the slurry.
This step is conducted by coating the slurry on the support, immersing the support in the slurry, or spraying the slurry on the support. And, before supporting the slurry, the support may be made into a shape of a ceramic filter to be prepared by adhesion, fusion, sewing, bonding or molding with a mold.
Preferably, a process of immersing the support in a slurry solution and squeezing is repeated 2-3 times so that sufficient amount of a ceramic mixture can be safely arrived on the support. And, it is more preferable to repeat a process of coating or spraying the slurry on the support and squeezing 2-3 times so that sufficient amount of the slurry solution can be supported on the support.
In case the slurry is supported on the support after cutting or molding the support to a specific size, drying may be immediately conducted. And, in case the support is not cut or molded to a specific size, a step of molding
to a suitable shape can be further conducted to prepare a molded article with a specific shape.
The support on which the slurry is supported can be molded into various shapes according to its purposes. Specifically, the support is closely adhered and bound to a mold of circular tube shape, radial curved tube shape, or rectangular tube shape, and they are fixed with a clamp, etc. to mold into circular tube, radial tube or rectangular tube shape. In case a ceramic filter of radial curved tube shape is prepared using a mold of radial curved tube shape as shown in Fig. 1, it can be applied to those that a circular tube is applied to, while maximizing filtering area to increase filtering efficiency.
In addition, in case a support is closely adhered to a mold, a release film can be added between the support and the mold in order to facilitate separation of the mold and the support. As the release film, resin film made of rubber, urethane resin, or epoxy resin, or a paper film such as kraft paper can be used. c) Drying This step is to dry the molded article prepared in step b). It allows safe sintering and prevents modification of a shape of the molded article during sintering preparation process and sintering process.
It can be conducted by natural drying, hot wind, sunlight, or shade.
Preferably, drying is conducted by infrared rays so as to reduce drying time and prevent modification of a molded article and cracks. d) Further coating This step is to further coat inside or outside of the molded article dried in step c) a slurry comprising i) 40 to 80 parts by weight of ceramic powder, ii)
10 to 40 parts by weight of pore forming material, iii) 7 to 30 parts by weight of a binder and iv) 10 to 50 parts by weight of a dispersion.
The i) ceramic powder may be identical to that used in step a).
The ceramic powder is preferably comprised in the slurry composition in an amount of 40 to 80 parts by weight. If the content falls within the above range, fine pores form inside or outside of the molded article to prevent eye-blocking and recycling of the filter is easy.
The ii) pore forming material may be identical to that used in step a).
The pore forming material is preferably comprised in the slurry composition in an amount of 10 to 40 parts by weight. If the content falls within the above range, the pore forming material completely burns during sintering to efficiently form pores.
The iii) binder may be identical to that used in step a).
The binder is preferably comprised in the slurry composition in an amount of 7 o 30 parts by weight. If the content falls within the above range, the slurry can be effectively bound to the molded article.
The iv) dispersion may be identical to that used in step a).
The dispersion is preferably comprised in the slurry composition in an amount of 10 to 50 parts by weight. If the content falls within the above range, each component can be effectively mixed and slurry can maintain appropriate viscosity to effectively bind to the molded article.
The slurry for further coating may, if necessary, further comprise v) clay.
The clay may be identical to that used in step a), and it is preferably comprised in the slurry in an amount of 10 to 40 parts by weight.
The slurry is further coated inside or outside of the molded article dried in step c), and the further coating can be repeated twice or more times
according to requirements and purposes of a ceramic filter. In addition, the content and thickness of the slurry may varied in order to differing in porosity, strength and functions of a surface layer according to the purpose of a ceramic filter The further coating can be conducted by addition painting with a brush, immersing a molded article in a slurry, or spraying.
According to the further coating, a dense sintered layer that does not comprise a support forms on a surface to improve strength of a ceramic filter.
And, since pores can be controlled only by pore forming material or binder, a surface layer having fine pores forms to allow dusting to be conducted mainly on a surface thereby reducing eye-blocking. Therefore, recycling of a filter becomes easy, the filter can be applied at high temperature high pressure, and surface roughness improves compared to sintered layer of an area including a support to facilitate subsequent coating. e) drying This step is to dry the molded article further coated in step d), wherein the drying may be conducted by the same method as in step c). f) sintering This step is to sinter the molded article dried in step e).
The sintering is conducted by removing a mold from the dried molded article and introducing it into a sintering furnace and then elevating the temperature of the furnace to a sintering temperature.
And, the sintering may be conducted after further conducting a processing step for cutting the molded article into a size of a ceramic filter to prepare body of the filter ; and an assembling step of manufacturing a lower cap fitted to an outer diameter of the body and an upper cap having wings by
supporting a slurry on a support and drying, and assembling the upper and lower caps using a ceramic bond so that lower part is closed and an upper part is opened.
The sintering temperature may be set according to components and compositional ratio of the slurry. In order to prevent modification, shrinkage and damage of the molded article during temperature elevation, it is preferable to elevate temperature at a speed of 0. 5-3"C/min from room temperature to 500°C. And, it is more preferable to elevate at a speed of 0. 5-1°C/min between 150-450°C, and to finally elevate to 900-1300°C according to composition of a ceramic powder and maintain the temperature for 2-48 hours to complete sintering.
The second method of the present invention will be explained. a) Preparation of slurry This step can be conducted by the same method as in step a) of the first method. b) Supporting This step can be conducted by the same method as in step b) of the first method. c) drying This step can be conducted by the same method as in step c). d) sintering This step can be conducted by the same method as in step d). e) Further coating This step is to further coat inside or outside of the molded article dried in step d) a slurry comprising i) 50 to 80 parts by weight of ceramic powder, ii) 10 to 40 parts by weight of pore forming material, iii) 7 to 30 parts by
weight of a binder, and iv) 10 to 30 parts by weight of a dispersion.
This step can be conducted by the same method as in step d) of the first method. f) Drying This step is to dry the molded article further coated in step d), and can be conducted by the same method as the above step c). g) Sintering This step is to sinter the molded article dried in step f), and can be conducted by the same method as in step f) of the first method.
The second method wherein further coating is conducted after sintering can be applied where further coating is conducted before sintering according to the first method, as well as where further coating is not conducted before sintering.
The finally prepared ceramic filter can be made into various shapes as shown in Figs. 2 to 5, and it can be manufactured into a structure having high porosity for an area including a support and dense porosity for further coated layer as shown in Figs. 6 to 8. And, as shown in Fig. 9,2 or more ceramic filters can be adhered using an adhesive to use extended ceramic filter, wherein a pipe with a size smaller than inner diameter of a ceramic filter can be introduced between the ceramic filters.
The adhesive can be commonly used adhesive, and ceramic adhesive is preferable.
In addition, the method of the present invention, in order to improve functionality of a ceramic filter, may further comprise the steps of further coating functional material insider or outside of a ceramic filter dried in step c), one further coated and dried, one sintered in step d), one sintered, and then
further coated and dried, one sintered, and then further coated, dried and sintered; and then drying. The coating of the functional material can be conducted by known methods capable of appropriately bonding ceramic filter with functional material. And, after coating the functional material and drying, sintering step can be further conducted.
As the functional material, zeolite, platinum, palladium, silver, Ti02, or ZnO can be used alone or in combination.
The inside and outside of the ceramic filter can be coated with the same or different material.
According to the first and second methods of the present invention, production cost is low, preparation is easy, modification of a shape and production of a large-sized filter are easy, abrasion resistance and heat resistance are superior, and porosity control range broadens. In addition, the method of the present invention can form dense sintered layer inside or outside surface to improve strength of a ceramic filter, form a surface layer having fine pores to reduce eye-blocking thus enabling recycling of a filter, prepare ceramic filter applicable at high temperature high pressure, improves roughness thus making further coating easy.
The present invention also provides a ceramic filter prepared by the above method. The ceramic filter of the present invention can be used for a post treating apparatus in various industries, a dusting filter of various dusting equipment as shown in Fig. 10, an incinerator, a dusting apparatus for a crematory, a dusting apparatus for engine exhaust gas, an air purifier for automobile exhaust gas, or an apparatus for removing volatile organic compounds by photo-catalytic activity in an air purifier.
The present invention will be explained in more detail with reference to
the following Examples. However, these are to illustrate the present invention and the present invention is not limited to them.
EXAMPLES Example 1 To 50 parts by weight of water, 40 parts by weight of alumina (Al203), 25 parts by weight of clay, 25 parts by weight of active carbon and 5 parts by weigh of an inorganic binder of frit (VA950, Duklim material) were added and mixed in a mixer. And, 5 parts by weight of an organic binder of water binder was added to the mixture and then they were mixed for 2 hours in a mixer to prepare a primary slurry solution.
The primary slurry solution was coated on non-woven fabric with size of 1000mm x 1500mm x 2 mm so as to be sufficiently supported thereon.
Then, a mold with a circular tube shape was manufactured from PVC, a release film is bound to the mold surface, and then the non-woven fabric immersed in the slurry solution was wound along with the shape of the mold to prepare a molded article, which was dried by hot wind at 30-90 °C for 1 hour.
Then, to 25 parts by weight of water, 70 parts by weight of alumina (Al203), 25 parts by weight of active carbon, and as a binder, 5 parts by weight of frit (VA950, Duklim material) and 10 parts by weight of a water binder were added and they were uniformly mixed to prepare a slurry solution for further coating. The slurry solution was further coated inside and outside of the dried molded article by painting with a brush, and dried by the same method as mentioned above.
The mold and the release film were removed from the dried molded article, and then the molded article was put in an electric furnace, which was
elevated at a speed of 3°C/min from room temperature to 150°C, slowly elevated at a speed of 0. 5~1°C/min from 150 to 450°C, and maintained at 900-1300°C for 2 hours to complete sintering thereby preparing a ceramic filter having 2 layers with different pore sizes.
Fig. 6 is Scan Electronic Microscope (SEM) picture of further coated pore layer, and Fig. 7 is SEM picture of an area including a support, and Fig.
8 is SEM picture of a ceramic filter having 2 layers with pores of different sizes.
Example 2 A ceramic filter having 2 layers with pores of different sizes was prepared by the same method as in Example 1, except that the slurry solution was further coated only inside of the molded article.
Example 3 A ceramic filter having 2 layers with pores of different sizes was prepared by the same method as in Example 1, except that the slurry solution was further coated only outside of the molded article.
Example 4 A ceramic filter having 2 layers with pores of different sizes was prepared by the same method as in Example 1, except that silicon carbide was used instead of alumina in the slurry solution.
Example 5 A ceramic filter having 2 layers with pores of different sizes was prepared by the same method as in Example 1, except that 25 parts by weight of alumina and 25 parts by weight of silicon carbide were used together instead of alumina in the slurry solution.
Example 6
A ceramic filter having 2 layers with pores of different sizes (Fig. 3) was prepared by the same method as in Example 1, except that a radial curved tube shaped mold (Fig. 1) was used instead of the circular tube shaped mold to mold a non-woven fabric supporting the slurry solution.
Example 7 A ceramic filter having 2 layers with pores of different sizes was prepared by the same method as in Example 1, except that a rectangular tube shaped mold was used instead of the circular tube shaped mold to mold a non-woven fabric supporting the slurry solution.
Example 8 A non-woven fabric immersed in a slurry solution was molded and dried by hot wind by the same method as in Example 1, except using a mold of radial curved tube shape.
Then, the dried mold was cut to manufacture a body of a filter, and a lower cap fitted to an outer diameter of the body and an upper cap having wings were manufactured by immersing or coating the non-woven fabric with the slurry solution and drying. The body and the upper and lower caps were assembled so that the lower part is closed and the upper part is opened as the wing shape.
Then, the same process as in Example 1 was conducted to manufacture a ceramic filter having 2 layers having different pore sizes as shown in Fig. 5.
Example 9 A ceramic filter having different pore sizes was prepared by the same method as in Example 1, except that a slurry solution for further coating was primarily coated and dried, and then secondary coating and drying was
conducted on the primarily coated surface.
Example 10 50 parts by weight of water, 40 parts by weight of alumina (Al203), 25 parts by weight of clay, 25 parts by weight of active carbon, and 5 parts by weight of an inorganic binder of frit (VA950, Duklim material) were mixed in a mixer. To the mixture, 5 parts by weight of an organic binder of water binder was added, and mixed in a mixer for 2 hours to prepare a primary slurry solution.
The primary slurry solution was coated on a non-woven fabric of 1000m x 1500mm x 8mm so as to be sufficiently supported.
Then, a mold of a circular tube shape was manufactured from PVC, a release film was bound to the mold surface, and then the non-woven fabric immersed in the slurry solution was rolled along the shape of the mold, and dried by hot wind at 30~90 °C for 1 hour.
From the dried mold, a mold and a release film were removed, and then the mold was put in an electric furnace, of which temperature was elevated at a speed of 3°C/min from room temperature to 150°C, slowly elevated at a speed of 0. 5~1°C/min, and maintained at 900-1300'C for 2 hours to complete sintering.
Then, 20 parts by weight of water, 70 parts by weight of alumina (Al203), 25 parts by weight of active carbon and 5 parts by weight of a binder of frit (VA950, Duklim material) and 10 parts by weight of water binder were uniformly mixed in a mixer to prepare a slurry solution for further coating, which was coated inside and outside of the sintered molded article by painting with a brush.
Drying and sintering were conducted as the above to manufacture a
ceramic filter having 2 layers with different pore sizes.
Example 11 A ceramic filter having 2 layers with different pore sizes was manufactured by the same method as in Example 10, except that a slurry solution for further coating was coated only inside of the mold.
Example 12 A ceramic filter having 2 layers with different pore sizes was manufactured by the same method as in Example 10, except that the slurry solution for further coating was coated only outside of the mold.
Example 13 A ceramic filter having 2 layers with different pore sizes was manufactured by the same method as in Example 10, except that silicon carbide (SiC) was used instead of alumina in the primary slurry solution.
Example 14 A ceramic filter having 2 layers with different pore sizes was manufactured by the same method as in Example 10, except that 25 parts by weight of alumina and 25 parts by weight of silicon carbide were used instead of alumina (Al203).
Example 15 A ceramic filter having 2 layers with different pore sizes was manufactured by the same method as in Example 10, except that a mold of a radial curved tube shape (Fig. 1) was used instead of the circular tube shaped mold.
Example 16 A ceramic filter having 2 layers with different pore sizes was manufactured by the same method as in Example 10, except that a
rectangular tube shaped mold is used instead of the circular tube shaped mold.
Example 17 A non-woven fabric immersed in a slurry solution was mold and dried by the same process as described in Example 10, except that a radial curved tube shaped mold was used.
Then, the dried mold was cut to make a body of a filter, and a lower cap fitted to an outer diameter of a body and an upper cap having wings were manufactured by immersing or coating the non-woven fabric with the slurry solution and drying. The body and the lower and upper caps were assembled with a ceramic adhesive so that the lower part is closed and the upper part is opened as a wing shape.
Then, a ceramic filter having 2 layers with different pore sizes was manufactured by the same process as in Example 10.
Example 18 A ceramic filter having 2 layers with different pore sizes was manufactured by the same method as in Example 10, except that a slurry solution for further coating was primarily coated and then secondary coating was conducted on the primarily coated surface.
A large-sized ceramic filters having diameter of 100mm or more and length of 1 m or more can be manufactured by Examples 1 to 18, which has high porosity of 40% or more and superior heat resistance up to 1000°C.
According to the method of the present invention, a separate preparation of an expensive mold is not required, a pressurizing device or vacuum device is not required, and thus production cost of a ceramic filter is low, preparation is easy, modification of a shape is easy, and a large-sized
filter can be produced as long as the size of a sintering furnace allows. And, porosity control range can be comparatively broad because pressurization or vacuum process is not needed, pore size can be selected within the range of 0. 001-5 mm according to the density of a support, the size and content of pore forming material to control pore size with small variation, high porosity of 40% or more can be achieved, and a light-weighted porous filter can be prepared.
In addition, the present invention can prepare a ceramic filter that can maximize filtering area within a specific space because modification of a shape and production of a complicated shape are easy.
In addition, since the ceramic filter of the present invention has a pore structure wherein surface is dense and inside is sparse, the surface of the ceramic filter has superior heat resistance and abrasion resistance thus can be used at high temperature high pressure. And, total weight is reduced because a filtering layer has dense structure while a back side has sparse structure, dusts are collected at surface to prevent eye-blocking inside of a ceramic filter, the ceramic filter has low pressure loss and high ventilation and dusting efficiency, and the ceramic filter can be easily recycled by heating it at high temperature to burn and remove dusts.
In addition, the ceramic filter of the present invention does not require a heat-exchange device for cooling liquid at high temperature, is very light because of porous structure with pores of 40% or more, dusting efficiency is 99.8% or more, dusting can be conducted with more rapid filtering speed than the existing dusting filter, deterioration or damage of a filter does not occur even at high temperature, high pressure, and it can be easily applied for a waste incinerator, a crematory, a boiler, a cement preparation process, a coal steam power plant, a coal gasification complex power equipment because there is no concern about a fire due to sparks.