KR100389125B1 - Cross flow type heat-resistant ceramic filter and method for preparing thereof - Google Patents

Abstract

PURPOSE: Provided are a cross flow type heat-resistant ceramic filter, which has a large filtering area per unit volume and good mechanical strength and thermal-stability, and a method for preparing thereof, which is able to mass-produce the ceramic filter by simplifying the process and easily produces a flow path having a desired shape. CONSTITUTION: The method comprises steps of (a) molding a ceramic slip including a plasticizer and ceramic powder into a ceramic sheet; (b) compressing the ceramic sheet by using a compressing means where a fixed pattern is formed to form a flow path on the ceramic sheet; and (c) after laminating the flow path formed ceramic sheet, sintering it, wherein the content of the plasticizer is about 5-18 wt.% of based on the ceramic slip.

Description

Cross flow type heat resistant ceramic filter using plastic ceramic sheet and its manufacturing method

The present invention relates to a cross-flow heat-resistant ceramic filter using a plastic sheet and a method of manufacturing the same. More specifically, a plastic sheet is formed by using a slip mixed with a large amount of a plasticizer and ceramic powder. The present invention relates to manufacturing a heat-resistant cruciform ceramic filter by manufacturing and then compressing the same, processing a flow path having a desired shape on the ceramic sheet, and laminating the same.

In general, honeycomb filters, cross flow filters, cartridge filters, and the like are mainly used to purify particulate matter contained in the gas. Among them, the cross-type filter has many advantages compared to other filters because of the following advantages, and the present invention also relates to such cross-type filter.

First, unlike honeycomb filters, the gas is introduced into the filter plane in parallel with the filter surface, which causes a stress and causes turbulence, causing particles to accumulate evenly within the filter. It can reduce the phenomenon of surface fouling.

Second, the filtration efficiency remains relatively constant and the rate of increase in back pressure due to the accumulation of particles is low.

Third, the conventional honeycomb filter is circular, whereas the cross-flow filter is a hexahedron and is stacked with bricks without a separate mounting case to reduce the cost and space required for the device, and each flow is flow-through. As a result, it is possible to design various playback systems.

Fourth, when applied to the diesel particulate filter, uniform regeneration occurs during the regeneration of the filter, thereby reducing the breakage of the filter due to heat, thereby allowing the regeneration to occur relatively completely, reducing the concentration polarization phenomenon and reducing the inflow gas Self-cleaning is caused by its own flow rate, which reduces the surface clogging phenomenon.

Conventional techniques for a cross-flow filter having such an advantage and a manufacturing method thereof are disclosed in Japanese Patent Application Laid-Open Nos. 4-100508 and 4-114710, and the cross-flow filter disclosed herein is shown in FIG. As shown in Fig. 1, in order to produce a filter of such a shape in which the flow crosses crosswise, the structure having a hole cut as shown in (A) of FIG. 1 is extruded and bonded to the ceramic dough with a predetermined gap such as the dotted line of FIG. Each of the extruded unit structures thus manufactured was fabricated using a method of sintering or heat treatment to make the work easier, and then bonding the extruded unit structures to a suitable ceramic adhesive.

However, the cross-flow filter described above has a problem in that a manufacturing process is complicated and difficult and a binder must be used to give a constant gap in lamination.

In addition, since the conventional cross-flow filter has a much smaller filtration area per unit volume than a honeycomb type filter, at the same time, a larger amount of filter is required for filtration of a unit volume of gas, which takes up a large space in practical applications. there was.

Accordingly, an object of the present invention is to manufacture a plastic sheet having a plasticity by using a slip mixed with a large amount of plasticizer and ceramic powder in order to solve the above problems, and then compressed to form a flow path of a desired shape on the ceramic sheet The present invention provides a method of manufacturing a cross-flow heat-resistant ceramic filter that can be mass-produced, can be freely made, and can easily change the size of a filter by simplifying a process and stacking them.

It is still another object of the present invention to provide a heat resistant cruciform heat resistant ceramic filter which is manufactured by the above method and has a very large filtration area per unit volume and is excellent in mechanical strength and thermal stability.

Method for producing a cross-flow heat-resistant ceramic filter of the present invention for achieving the above object comprises the steps of: a) molding a ceramic slip mixed with a plasticizer and a ceramic powder into a plastic ceramic sheet; b) pressing the ceramic sheet to form a flow path in the ceramic sheet by using a pressing means having a predetermined pattern; And c) laminating and sintering a ceramic sheet on which a flow path is formed.

On the other hand, the cross-flow ceramic filter of the present invention is characterized in that the ceramic sheet formed with the inlet portion and the ceramic sheet formed with the outlet portion are stacked alternately in the vertical direction.

Hereinafter, the cross-type heat resistant ceramic filter of the present invention and a manufacturing method thereof will be described in more detail with reference to the accompanying drawings.

As described above, the conventional cross-flow ceramic filter extrudes the life-saving structure and gives it a certain gap with ceramic dough to sinter or heat-treat each extruded unit structure manufactured by making it easy to work. It was then fabricated using the method of bonding with a suitable ceramic adhesive. However, this method has a problem in that a manufacturing process is complicated and difficult and a binder must be used to give a constant gap in lamination. In addition, other conventional cross-flow filters also have a much smaller filtration area per unit volume than honeycomb filters, and at the same time, require a larger amount of filters for filtration of a unit volume of gas, thus occupying a large space in practical applications. There was this.

The present inventors have conducted a number of studies to solve this problem, as a result of manufacturing a plastic ceramic sheet using a slip mixed with a large amount of a plasticizer and a ceramic powder, and then crimped to form a desired flow path on the ceramic sheet By simplifying the process and laminating it, a method of manufacturing a cross-flow heat-resistant ceramic filter according to the present invention can be simplified and mass-produced, a desired shape of the flow path can be freely made, and the size of the filter can be easily changed.

In short, the method for producing a cross-flow heat resistant ceramic filter of the present invention comprises the steps of: molding a ceramic slip mixed with a plasticizer and a ceramic powder into a plastic ceramic sheet; Pressing the ceramic sheet to form a flow path in the ceramic sheet by using a pressing means having a predetermined pattern; And laminating and sintering the ceramic sheet on which the flow path is formed.

(A)-(d) of FIG. 2 is a front view of the pattern of the roller and die used for crimping a ceramic sheet in this invention, and FIG. 3 is a manufacturing process drawing of a cross-type ceramic filter which concerns on this invention.

According to FIG. 3, the present invention adopts a tape casting method for forming a ceramic slip into a sheet having a predetermined thickness in order to manufacture the ceramic sheet, and the filter manufacturing process using the tape casting method is largely made of slip manufacturing, casting and drying. It is divided into green sheet processing, sheet lamination, firing and finishing processes.

On the other hand, a doctor blade tape casting method using ceramic slips is used to produce plastic ceramic sheets in the manufacturing process of the cross-flow multilayer ceramic filter of the present invention. First of all, the selection and composition of raw materials is important for the manufacture of ceramic slips.In the selection of raw powders, it is desirable to select high purity powders in consideration of average particle size distribution, specific surface area, particle shape, moisture content, chemical purity, etc. Do. In this case, the average particle size of the raw material affects the pore size, strength, and pore distribution of the final product, and also has a great influence on the drying rate, crack, thickness variation, and workability of the green sheet. Thus, the optimum powder selection is dependent on the relative mixing ratio of the powder and the desired physical properties, and also on processability and sinterability. In addition, proper formulation and selection of the powder directly affects the physical properties of the filter and is a key condition. Therefore, the raw powder may be selectively used depending on the desired material and the physical properties of the final product. The ceramic powder in the present invention is cordierite and usually has a composition in the range of about 9-20% by weight MgO, about 30-50% by weight Al ₂ O ₃ , and about 41-56.5% by weight SiO ₂ .

Unlike a general ceramic substrate manufacturing process that uses less plasticizer, the present invention is characterized in that the plasticizer is added in an excessive amount to increase the plasticity of the ceramic sheet and the bonding strength after sintering the laminated ceramic. The plastic sheet should be pressed into the groove of the roller to have enough plasticity to be filled and the plasticizer should be used in excess in order to increase the lamination adhesion of the laminated sheets during sintering. , Octyl phthalate or the like is preferably used. The amount of plasticizer used is preferably in the range of about 5 to 18% by weight based on the total weight. When the amount of the plasticizer is less than 5% by weight, the plasticity of the ceramic sheet is significantly reduced after drying, and the amount used is more than 18% by weight. In this case, the increase of plasticity is insignificant and excessive addition causes large sintering shrinkage during sintering, which causes the breakage of the filter.

On the other hand, the binder is usually used in the range that there is no problem in the manufacture of the ceramic sheet using the ceramic slip and the strength of the dry sheet later, but the use of polyvinyl butyral, polyvinyl alcohol, polyvinylacetate, etc. desirable. The amount of the binder is suitably about 10% by weight or less relative to the total weight, and in the case of polyvinyl butyral, when the amount is added 11% by weight or more, the plasticity is decreased. It is desirable to minimize the amount of the binder used because it reduces the plasticity of the ceramic sheet and is expensive. The composition for producing a plastic ceramic sheet is as shown in Table 1 below.

The ceramic sheet prepared in the above-described composition is cut out of a portion whose thickness is not constant, and then cut to a suitable length, and processed using a pressing roller having a desired pattern. When the pattern is processed, ceramic sheets with a certain width are continuously supplied. At this time, if the width of the sheet is about 140 mm to be cut later, the width of the roller is cut to a width of about 150 mm and the width of the roller is the width of the supplied sheet. Make a pattern 10mm wider than wide. This is to prevent the distortion of the sheet due to the asymmetry of the pattern when the sheet is supplied to the roller or the unbalance of pressure applied to the ceramic sheet.

The above rollers have a variety of patterns, and care must be taken when manufacturing these patterns that the depth of the groove, that is, the height of the desired flow path, cannot be changed as desired. Generally, the depth of the groove is limited to about 20-150% of the thickness of the ceramic sheet. An example of a pattern of patterns is shown in FIG. The line marked in FIG. 2 becomes a groove having a constant thickness and depth as shown in (d) of FIG. 2. The ceramic sheet having a constant thickness is pushed into the groove under a certain pressure. In addition, the inlet portion of the groove must be curved to remove the fragile portion of the machined sheet.

After compressing the ceramic sheet and processing the flow path, it is cut into a desired size with a cutter in consideration of sintering shrinkage, etc., and the lamination method is changed according to the shape of the pattern. Filters with different back pressures can be produced.

In case of (b) of FIG. 2, sheets should be laminated by turning 180 °, in which case they have flow characteristics similar to those of general wall flow honeycomb and have a very large specific surface area. In other words, the inlet part has a staggered inlet shape and an outlet shape in the form of a western chess board, and a honeycomb requires a process to prevent lifesaving from staggering, whereas such a step is omitted when laminating using a ceramic sheet of (b). can do.

As shown in (c) of FIG. 2, when the sheets are stacked while rotating in the 180 ° direction, the input stage and the output stage are alternately opened and closed to form a filter. Filters can be fabricated with alternating holes from the bottom to the top, and when the sheets are stacked while rotating in the order of 0 °, 90 °, 0 °, 90 ° ... Can be produced. When stacking ceramic sheets with uniform patterns, parallel sheets and sheets 90 ° or 180 ° are 1: 1, 2: 1, 2: 2, 3: 1, 1: 3, 2: 3, 3 : 2, 3: 3, ... can be laminated, and depending on the stacking combination, the filter has very different flow characteristics and structural characteristics. As described above, when all the sheets of the pattern of FIG. 2 are stacked with different combination ratios, the flow characteristics, structural characteristics, structural characteristics, and pressure changes of the filter are affected, and as the combination ratio increases, the flow tends to be suppressed. . Combinations of these can be made in any combination and for any sheet of pattern.

On the other hand, when sintering the laminated ceramic sheet is preferably performed for 3 hours or more in the temperature range of about 1350 ~ 1450 ℃.

4A and 4B are schematic views of one embodiment of a cross flow filter manufactured according to the method of the present invention, in which 11 is an inlet, 12 is an outlet, 14 is a suction flow, and 15 is a discharge Flow.

As shown in (a) and (b) of FIG. 4, the cross-flow heat resistant ceramic filter according to the present invention is obtained by stacking a sheet having an inlet portion 11 and a sheet having an outlet portion 12 alternately stacked vertically. It is characterized by Optionally, the filter is repeatedly laminated with one or more parallel sheets and one or more sheets rotated therein in a 90 ° or 180 ° direction.

Although the effects of the present invention are described in more detail with reference to the following examples, the scope of the present invention is not limited to the following examples.

Example 1

The plasticity change with the change of the kind and addition amount of a plasticizer and a binder was performed using the constant powder, and the composition used is as Table 2 below.

The change in plasticity according to the type and amount of the binder and the plasticizer added to the composition is shown in Table 3 below.

The degree of plasticity is indicated by the symbol

×: no deformation occurs even under pressure, only slight traces remain on the surface or breakage of the ceramic sheet

(Triangle | delta): A deformation | transformation generate | occur | produces when pressure is applied, but deformation | transformation enough to fill a groove | channel does not occur. Excessive pressure causes breakage

○: deformation enough to fill the groove of the pattern

Example 2

Examples of filters in which ceramic sheets pressed by using rollers having a pattern as shown in FIG. 2A are alternately stacked in the vertical direction are shown in FIGS. 4A and 4B. In this case, it is a typical cross-flow filter with two input stages and two output stages.

Example 3

There are various methods of laminating ceramic sheets, and an example of lamination using a ceramic sheet pressed with a roller having a pattern as shown in FIG. (A) of FIG. 5 is an example of repeating alternately stacking the previous ceramic sheet in the vertical direction, and (B) of FIG. 5 is to stack the two ceramic sheets first in the same direction, An example of repeating the lamination of one sheet in the ° direction, (C) is an example of repeating the process of laminating two sheets of ceramic sheets in the same direction first and then laminating two sheets in the 90 ° direction. A comparison of the filtration area and the open area of (a), (b) and (c) of FIG. 5 is shown in Table 4 below.

Therefore, in the present invention, since the flow path is manufactured directly on the plastic sheet having a plasticity, and the lamination does not use an adhesive for laminating adhesion between the ceramic sheets, the process of applying the adhesive is omitted and the manufacturing process is shortened compared to the existing process. It is a suitable process for production, and it is possible to change the size of the filter only by changing the size of the cutting process and the stacking height of the stacking process, and thus there is an advantage that no additional equipment is required when producing filters of various sizes. In addition, the tensile stress in consideration of the mechanical or thermal tensile stress caused by the failure of the ceramic due to the mutually compressive stress of the filter by sintering in both directions during sintering by stacking each ceramic sheet in different directions Since the compressive stress is canceled, the mechanical strength is excellent, and there is an advantage in that a filter widely used in a filter medium and a catalyst carrier of a strong particulate matter that well resists thermal shock can be manufactured.

(A) and (b) of FIG. 1 are schematic views of one embodiment of a conventional cross-flow filter,

(A) to (d) of FIG. 2 are front views of patterns of rollers and dies used for pressing ceramic sheets in the present invention;

3 is a manufacturing process diagram of the cross flow ceramic filter according to the present invention,

4A and 4B are schematic views of one embodiment of a cross flow filter manufactured according to the method of the present invention,

(A)-(c) of FIG. 5 is a partial view of a cross-flow filter showing an example when the lamination combination is different when laminating ceramic sheets in accordance with the method of the present invention.

Explanation of symbols on the main parts of the drawings

1, 11: entrance 2, 12: exit

3: porous wall 14: suction flow

15: discharge flow

Claims (12)

a) molding a ceramic slip comprising a plasticizer and ceramic powder into a plastic ceramic sheet; b) pressing the ceramic sheet to form a flow path in the ceramic sheet by using a pressing means having a predetermined pattern; And c) laminating and sintering the ceramic sheet having the flow path formed thereon; And the content of the plasticizer is about 5 to 18% by weight based on the ceramic slip. The method of claim 1, wherein the plasticizer is selected from the group consisting of polyethylene glycol, dibutyl phthalate, glycerin, and octyl phthalate. The method of claim 1 wherein the ceramic powder is cordierite, based on the weight of the ceramic powder of about 9 to 20% by weight of MgO, about 30 to 50% by weight of Al ₂ O ₃ , and about 41 to 56.5% by weight Method for producing a cross-flow heat-resistant ceramic filter, characterized in that consisting of SiO ₂ . The method of claim 1, wherein the forming process is performed by a tape casting process. The method of manufacturing a cross flow heat resistant ceramic filter according to claim 1, wherein the crimping means is a roller. The method of claim 1, wherein the laminating of the ceramic sheet is performed by rotating the ceramic sheet in a predetermined direction in a 90 ° or 180 ° direction. The method of claim 1, wherein the laminating of the ceramic sheet is performed by repeatedly laminating one or two or more sheets in the same direction, and then laminating one or more sheets in the same direction in a 90 ° or 180 ° direction. Method for producing a cross-flow heat resistant ceramic filter, characterized in that. The method of claim 1, wherein the sintering temperature of the laminated ceramic sheet is about 1350 to 1450 ° C. The method of claim 1, wherein the ceramic slip further comprises a binder. The method of claim 9, wherein the binder is included in an amount of about 10 wt% or less based on the weight of the ceramic slip. 10. The method of claim 9, wherein the binder is selected from the group consisting of polyvinyl butyral, polyvinyl alcohol, and polyvinylacetate. The method of claim 6, wherein the ceramic filter is formed by stacking a ceramic sheet having an inlet portion and a ceramic sheet having an outlet portion alternately stacked in a vertical direction.