KR20100077333A - Improved textile filter and method for manufacturing the same - Google Patents

Abstract

PURPOSE: An improved textile filter and a manufacturing method thereof are provided to improve collecting efficiency of fine particles by colleting the fine particles passing through a pore after protruding a part of whisker from a pore formed by filament of the filter. CONSTITUTION: A multi-layered textile filter(8) includes a plurality of filters(4) arranged at a constant interval and a fabric filter arranged on the rear part of a filter introduction part. Each filter is made of the textile filter. The fabric filter is arranged on the filter introduction part. A whisker is formed on each filament to collect fine particles passing through pores.

Description

Improved textile filter and its manufacturing method {IMPROVED TEXTILE FILTER AND METHOD FOR MANUFACTURING THE SAME}

The present invention relates to a filter, more specifically, a gas permeability and a structure capable of collecting small fine particles more efficiently, as well as improving the stability of the fine particle collecting structure, the life of the filter The present invention relates to a fabric filter and a method of manufacturing the same, which can be extended and can be used even in harsher environments.

Ceramic monolithic filters are used for the collection / removal of dust such as automobile fumes. In the ceramic monolithic filter, as the collection proceeds, particulate matter accumulates on the filter wall, thereby increasing the back pressure, which reduces the efficiency of the vehicle engine.

That is, as shown in Fig. 1, the conventional porous ceramic filter 1 has an irregular pore structure. Therefore, the particles 2 exhausted from the automobile accumulate in the section where the pore passage is small from the filter introduction portion, thereby accelerating the reduction of the gas permeability of the entire filter. In the case of the dust removal filter of automobile smoke, the decrease in the gas permeability of the filter increases the back pressure of the vehicle engine, which causes a problem of lowering the engine efficiency.

In addition, conventional porous ceramic filters expose a number of limitations to the capture of nanometer sized particles. That is, in the case of diesel cars, there are particles having a size of 10 to 20 nm among the fine particles discharged, which may cause respiratory diseases when inhaled. However, the conventional porous ceramic filter has a problem that can not collect the particles of this level.

In addition, the conventional ceramic filter is difficult to deform in various forms due to the characteristics of the material, it is accompanied by the hassle of having to change the design according to the application when applied to the filter.

On the other hand, in the case of a diesel engine aftertreatment device, a very high temperature is applied, and even if applied to the exhaust gas aftertreatment device of such a vehicle, there is also a need for a filter device that can withstand high temperatures while achieving the purpose of the filter. have.

In relation to such a conventional ceramic filter, the applicant of the present application has filed an invention that solves the above problem (Application No. 10-2008-101821). According to this fabric filter, the fabric filter is composed of a plurality of filters, the pore size of each filter is different, and silicon carbide whiskers are formed in each pore to increase specific surface area and form fine pore channels. In addition, it effectively collects the fine particles.

However, in the case of a filter for removing fine particles such as automobile fumes, as the combustion gas flows through the pores, irregular and instantaneously high pressures may locally occur in small pores. For example, in the case of the filter according to the patent application, a whisker 30 of several micrometers in diameter is formed in the pore wall of the filament 10 constituting the fabric filter, as shown in FIG. The cross-sectional shape of the pores may be, for example, a shape as shown in FIG. 10, and the pores of the porous base material are easily subjected to high pressure due to the flow of combustion gas. This results in a faster gas flow, which results in large and small particles that are evacuated and impinge on the walls of the pores. Whiskers 30 inside the pores are also exposed to these high speed / high pressure gases and particles in their flows, where very fine and thin whiskers 30 of several micrometers or less in diameter can be broken by such particles. Thus, the whiskers 30 cannot retain their original shape and the area that forms the bond between the whiskers and the pore walls is so small that the whiskers can be separated and removed from the pores of the base material. As a result, the whisker 30 provided to improve the fine particle collection efficiency does not exhibit its original function, and the collection efficiency is lowered, resulting in a decrease in the efficiency and life of the filter.

The present invention is to solve the problems of the prior art as described above, one object of the fabric filter having a structure that can effectively prevent the pore blockage by the fine particles, even when the collection of fine particles and its manufacture To provide a way.

It is another object of the present invention to provide a fabric filter having a structure capable of efficiently collecting fine particles of various sizes according to their size and increasing filtration efficiency and a method of manufacturing the same.

It is still another object of the present invention to provide a fabric filter and a method of manufacturing the same, which are capable of collecting fine particles of nanometer size level.

Still another object of the present invention is to provide a fabric filter and a method of manufacturing the same, which can be easily applied without special design changes with respect to the application to which the filter is applied.

Another object of the present invention is to provide a fabric filter and a method of manufacturing the same, which can prevent the whisker formed in the pores of the fabric filter from being broken or separated from the pore wall, thereby increasing the efficiency and life of the filter.

It is yet another object of the present invention to provide a fabric filter and a method of making the same that can be used even in harsh environments.

In order to achieve the above object, a multi-layer fabric filter is provided according to the present invention. The filter includes a plurality of filters disposed at regular intervals, each of the filters is made of a fabric filter, the pore formed by the filament constituting the fabric filter disposed in the filter inlet of the plurality of fabric filters The largest size, the pore size gradually decreases toward the fabric filter disposed at the rear end, and each filament constituting the fabric of the fabric filter disposed immediately opposite the filter inlet and the fabric filter immediately preceding it. Whiskers formed by a non-catalytic method or a catalyst method of forming a whisker using a separate catalyst are formed, a part of which protrudes into the pores between the filaments, fine particles that can pass through the pores Is configured to collect the filaments constituting the fabric of the fabric filter disposed at the rear end The size of the whiskers formed is smaller than the size of the whiskers formed on the filaments constituting the fabric of the fabric filter disposed immediately before the rear end, and the whiskers and the pore walls of the filaments on which the whiskers are formed are made of the same material as the whiskers. A protective layer is formed.

According to another aspect of the present invention, there is provided a method of manufacturing the multi-layer fabric filter, wherein the whisker is formed on each filament constituting the fabric of the fabric filter, and then the same as used in the process of forming the whisker. Supplying a carrier gas and a diluent gas to the reaction tube under a temperature and pressure condition at a ratio of about 1: 7 to form a protective layer of the same material as the whisker on the whisker and the pore wall. It features.

Preferably, the whiskers and the protective layer are made of silicon carbide.

In addition, according to the present invention, the whisker may be formed by a catalyst method using a non-catalytic method or a separate catalyst. When the whisker is formed by a catalyst method, a metal catalyst remaining on the tip of the whisker The process of forming the protective layer may be performed without performing a process of removing the protective layer.

According to the present invention, fabrication filters of various pore sizes are made by forming carbon fabrics of different pore sizes and also whiskers of different diameters on the carbon fabrics, and by placing them in an inclined form in the order of pore sizes, the gas permeability is reduced. Minimize, it is possible to obtain an effect that can efficiently collect the fine particles according to the size. Furthermore, a portion of the whisker is formed to protrude into the pores formed by the filament of the filter, and is configured to collect the fine particles passing through the pores, thereby further increasing the collecting efficiency of the fine particles.

Because of this, it is possible to minimize the back pressure due to the decrease in transmittance and to improve the nano dust collection efficiency has the advantage as a filter. The inclined functional filter according to the present invention also has no disadvantages of brittle fracture in ceramics, and the filter itself has the advantage of being less restricted in form as a fabric, and is widely used in construction equipment, vehicle soot filtration devices, ships, and power plants. It can be usefully used as various filter materials in the field. In addition, a protective layer of the same material as the whisker is formed on the whisker and the pore wall, so that the whisker is more stably fixed to the pore wall. Therefore, the whiskers are not damaged or separated from the pore walls even with the fast flowing gas, so that the life of the filter can be improved and the filter can be used even under more severe conditions.

Hereinafter, with reference to the accompanying drawings will be described a preferred embodiment of the present invention. In the following description, the description thereof is omitted for the parts that do not constitute the features of the present invention or for the components already known in the art. Even if this description is omitted, those skilled in the art will be able to easily understand the essential features of the present invention through the following description, and may implement the present invention without any particular difficulty.

As described in connection with the prior art, a conventional filter, in particular an automobile filter, is composed of a ceramic body, which limits the efficiency of the filter and makes it difficult to change the shape freely.

In connection with this prior art, the inventors first tried to filter the fine particles of various sizes by configuring the filter as multiple filters. That is, referring to FIG. 3, in which a structure of a multi-filter according to an embodiment of the present invention is schematically illustrated, the filter 8 according to the present invention comprises a plurality of filters 4, 5, 6, 7. . These filters are arranged at regular intervals to increase the gas permeation efficiency. In other words, rather than disposing the filters without gaps between the filters, by arranging the filters having different pore sizes at regular intervals, the permeation of gas through the filter is improved.

On the other hand, as shown, each filter is constituted like a sieve by filaments, preferably carbon cloth filaments, which form pore passages for filtering fine particles, for example. In addition, in the case of carbon fabric, it can be used even at a high temperature of 800 ° C. or higher, and the fabric filter of the present invention can be used in a vehicle exhaust gas aftertreatment device. Unlike conventional ceramic filters, it can be modified into various forms. Design changes can be made accordingly. At this time, in forming the pore passage, it is configured to filter the fine particles of various sizes by adjusting the arrangement between the filaments.

That is, the cloth filter 4 is a filter disposed at the filter introduction portion, and the size of the pores formed by the filaments constituting the filter is opposite to the cloth filter 4, that is, the cloth filter of the multilayer structure of the present invention. Is formed larger than the size of the pores formed by the filaments constituting the fabric filter (7) disposed at the far back end. That is, the fabric filter 8 is configured such that the pore size of the filter gradually decreases from the filter inlet to the rear end. The structure of this fabric filter can be more easily seen through FIG.

As shown in Fig. 4, in the fabric filter 8 of the present invention, each filter is sequentially arranged according to the pore size. That is, the size of the pore passage of the cloth filter 4 disposed in the filter introduction portion is the largest. When the fabric filter is constituted as described above, the particles can be sequentially collected according to the size of the particles, thereby minimizing the accumulation of particles from the filter introduction portion. That is, since the pore size of the filter disposed at the filter inlet is large, the smaller fine particles pass through the fabric filter 4 and are collected by the fabric filter arranged subordinately according to the size. Therefore, since the fine particles are collected in each fabric filter according to their size, it is possible to prevent the accumulation of fine particles at the filter inlet as time goes by, and to minimize the problem that the gas permeability of the filter as a whole decreases. I can do it.

As such, when the pore passage of each filter constituting the fabric filter 8 is formed in the micrometer unit to the nanometer unit, the nanometer-sized fine particles may be collected through the fabric filter 6 or 7 at the rear end. In addition, the micro-sized fine particles can be collected by the fabric filter of the filter inlet, thereby maximizing the collection efficiency. Therefore, compared to the conventional ceramic monolithic filter whose irregularities are in the form of pores, fine particles of various sizes can be collected more efficiently.

On the other hand, even if the filaments constituting the fabric filter (6, 7) arranged in the rear end close to each other to form a pore passage there is a limit in design to reduce the size of the pore passage. Therefore, fine particles are likely to pass through the cloth filter 7 having the smallest pore size.

In view of this point, the present inventor has devised a structure capable of collecting fine particles of a size passing through a fabric filter having a small pore size. Such an embodiment is shown in FIGS. 5 and 6.

As shown in FIG. 5, whiskers 9 and 10 are formed in the filaments constituting the fabric filters 6 and 7 arranged at the rear end of the fabric filter of the present invention, and a part of the pores between the filaments is formed. Is protruding into. In this way, when the whisker, preferably a whisker made of silicon carbide (SiC), protrudes into the pore passage, the particles are collected by the whisker even if the fine particles are small enough to pass through the pore passages between the filaments. Therefore, even if there is a limit to reducing the size of the pore passage due to the filament, the whisker can compensate for such a limit, so that finer particles of finer size can be filtered, thereby maximizing the efficiency of the filter. have.

On the other hand, as shown in Figs. 5 and 6, the size of the whisker is different. That is, the diameter of the silicon carbide whisker 10 (for example, the diameter of several hundred nanometers) formed in the filament of the fabric filter disposed at the rearmost end constitutes the filament constituting the fabric filter 6 disposed immediately in front of it. It is formed to be smaller than the diameter of the whiskers 9 (micrometer level diameter) formed in, and is configured to complement the pore passages formed between the filaments. As such, forming the whiskers with different sizes may be achieved by controlling various process conditions in fabric filament manufacturing. On the other hand, the technology itself for forming a whisker using a specific material, the technology itself for forming a whisker of different sizes through the control of process conditions, such as pressure control inside the reaction chamber does not constitute the gist of the present invention, known Since the technique can be implemented in various ways in the laboratory or manufacturing, the detailed description thereof will be omitted.

When the fabric filter of the above-described configuration is used under harsh environment such as automobile soot gas, the whiskers formed on the pore wall may be damaged by the fine particles of high flow rate. That is, whiskers collide with fine particles of high velocity flowing through the pores, the whiskers may be broken, or the whiskers may be separated from the pore walls, thereby degrading the life of the filter. Therefore, it is necessary to extend the life of the filter by stably fixing the whisker to the pore wall and exerting the original function of the whisker for a long time.

To this end, the inventors conducted a study on a method of increasing the stability of the whisker by forming a protective layer protecting the whisker on the whisker and the pore wall. Hereinafter, the characteristics of the present invention will be described in more detail with reference to specific experimental examples.

Experimental Example 1

11 is a schematic configuration diagram of a Low Pressure Chemical Vapor Deposition apparatus used for forming a whisker according to the present invention. How to form a whisker in the porous base material using such a device is as follows.

A porous base material, preferably a ceramic porous base material, is charged into the reaction tube 60 and heated at a constant heating rate. At this time, the reaction tube maintains the pressure in the reaction tube by a vacuum pump 64 to a vacuum of 10 torr or less using a bellows valve 63, the pressure of the reaction tube is indicated by reference numeral 62. It is displayed through one pressure display device 62. The carrier gas supplied from the gas source 51 is purified by the gas purification device 52 and then carries the sublimated or vaporized reactant by the evaporator 56 to the reaction tube 60. On the other hand, a dilution gas is introduced from the same gas source 51, and the dilution gas is purified by the gas purification device 52. The flow rate of the carrier gas and the dilution gas, which is distinguished according to the use, is controlled by the flow controllers 55 and 54, respectively, so that the ratio of the carrier gas and the dilution gas is adjusted. The diluent gas serves to dilute the reactant before the reactant carried by the carrier gas is introduced into the reaction tube 60. That is, the dilution gas serves to influence the reaction rate and the microstructure of the deposited material by controlling the density of the reactant gas lighter or thicker. On the other hand, the temperature in the reaction tube is preferably heated to maintain at a temperature of 1000 ~ 1400 ℃. Hydrogen is preferably used as the diluent gas, and the reactant sublimated or vaporized by the evaporator 56 is flowed into the reaction tube 60 while the diluent gas is flowed into the reaction tube. In the present invention, the reactant is preferably a material containing Si and C. Examples of such a material include methyltrichlorosilane (MTS, CH3SiCl3). The reactant is preferably kept constant through the thermostat (57). In addition, the carrier gas of the reactant may be the same as the diluent gas. The pressure of the evaporator 56 can be adjusted through the valve 59 and is preferably maintained at a constant pressure through the display device 58. The flow rate of the carrier gas was less than 50 cm / m ³ while the temperature in the reaction tube was maintained at a constant high temperature and a constant pressure, and the ratio of the evaporated reaction gas and the dilution / carrier gas was adjusted to 100 or more to provide the porous base material. When shed on the whisker is formed on the porous base material. Whisker formation time is less than 120 minutes.

The present inventors intend to form a protective layer on the whisker by forming a whisker in the porous base material and then reacting by flowing hydrogen gas and diluent gas at various flow rates. For example, after forming a whisker having a shape as shown in FIG. 7 in the porous base material, using a hydrogen gas as a carrier gas in the reaction tube at the same temperature and pressure conditions as the process performed at the time of whisker formation using 10 cm ³ / min It flowed into the reaction tube 60 at the flow volume of. At the same time, diluent gas was flowed into the porous base material on which whiskers were formed at a flow rate of 30 cm ³ / min. At this time, the protective layer for protecting the whisker is formed using the same material as the material used for whisker formation. This procedure was carried out for 10 minutes. As a result, as shown in Figure 8a, it was confirmed that the whisker shape is rather reduced, so that the deposition close to the thin film shape occurred. Accordingly, the inventors have concluded that the amount of diluent gas is too small to maintain whisker morphology in the process. On the other hand, when using a smaller amount of diluent gas than in Experimental Example 1, it can be easily predicted that the complete thin film deposition takes place and the whisker shape is further reduced.

Experimental Example 2

Except that the dilution gas was increased to a flow rate of 70 cm ³ / min was carried out the same procedure as in Experiment 1, the results are shown in Figure 8b. As shown in FIG. 8B, it can be seen that the protective layer 40 is uniformly formed on the whiskers 30 and the pore wall 20 under the controlled conditions, and the cross-sectional structure thereof is schematically represented. 9 is shown. This is another deposition phenomenon in the chemical vapor deposition system which was previously divided into a whisker or thin film deposit, which is a suitable result that meets the objectives of the present invention, such as improving the stability of the whisker. You can judge.

On the other hand, whisker formation can be divided into two methods, as in the present experimental example, a catalyst (VS (vapor-solid) mechanism) that can form a whisker without using a separate catalyst and Fe, Ni and There is a catalytic method (vapor-liquid-solid) mechanism (VLS) which is a method of forming a whisker by forming the same metal catalyst on a substrate in advance. In the case of the whisker formed by the catalytic method, unlike the non-catalytic whisker of the present embodiment, a round metal catalyst remains at the tip of the whisker after the process to act as an impurity and thus requires a separate removal process. . However, if the method of forming a protective layer on the whisker, which is a feature of the present invention, is applied to the whisker formed by the catalytic method, the protective layer can be formed covering the metal catalyst at the end of the whisker together with the whisker, thereby forming the catalyst at the end of the whisker. There is an advantage that does not need to remove separately. This not only improves the stability of the whisker formed by the catalytic method, but also has the advantage that the disadvantages caused by the remaining catalyst can be compensated by covering the remaining metal catalyst at the end of the catalytic whisker. This constitutes another important feature of the present invention.

Experimental Example 3

The same process as in Experiment 1 was carried out except that the dilution gas was increased to a flow rate of 110 cm ³ / min and the process time was 30 minutes. The results are shown in FIG. 8C. As shown in FIG. 8C, in spite of the deposition conditions in which the whiskers are grown, compared to Experimental Examples 1 and 2, although the deposition was performed for approximately three times as long, only the diameter of the whiskers was increased, and the pores were deposited on the walls. It was found that this is not done. That is, only the diameter of the whisker is increased so that the original function of the whisker cannot be exhibited properly, and the stability of the whisker cannot be improved. On the other hand, when using a larger amount of diluent gas than in Experimental Example 3, it can be easily predicted that the diameter of the whisker only continues to increase.

After the above-described series of chemical vapor deposition reactions, after the natural cooling in a hydrogen atmosphere to room temperature, it can be purged using a nitrogen gas, in the experimental example, nitrogen gas from the purge gas source 50 After purging for 10 minutes, the porous material was removed from the reaction tube. Reference numeral 53 is a device for adjusting the flow rate of the purge gas.

Through the above experimental example, the inventors carry out the same process with the same material as the whisker forming material under the environment used for the formation of the whiskers, and at a very limited condition, that is, the ratio of the carrier gas to the dilution gas is about 1: 7. When applied to, it has been found that the material is deposited in a form that surrounds the whiskers and the pore wall on which the whiskers are formed in a short time. In particular, the protective layer 40 not only protects the whiskers 30, but is formed over the entire pore wall 20, thereby further increasing the stability of the whiskers. Therefore, since the whisker 30 is more stably fixed to the pore wall 20, it is possible to further prevent a problem that the whisker is damaged or the whisker is separated from the pore wall by the gas flow of high velocity.

Although the present invention has been described above with reference to preferred embodiments, it should be noted that the present invention is not limited to the above-described embodiments. For example, although the fabric filter of the present invention has been described as being applied as a fabric filter for vehicle exhaust gas, the fabric filter of the present invention can be widely applied to other applications for collecting fine particles. That is, the present invention can be variously modified and modified within the scope of the following claims, all of which fall within the scope of the present invention. Accordingly, the invention is limited only by the constructions and equivalents described in the claims.

1 is a view showing a schematic configuration of a ceramic single filter according to the prior art.

FIG. 2 is a view schematically showing a form in which a whisker is formed on the pore wall of the filament.

3 is a view schematically showing the overall configuration of a multi-layer fabric filter according to an embodiment of the present invention.

4 is a schematic cross-sectional view of each filter of the multi-layer fabric filter according to an embodiment of the present invention.

5 is a view showing the structure of a woven whisker filter formed in accordance with an embodiment of the present invention.

6 is an image showing the appearance of whiskers of different sizes in accordance with an embodiment of the present invention.

7 is a view showing the shape of a whisker formed according to an embodiment of the present invention.

8A to 8C are views illustrating whether a protective layer is formed under different conditions.

FIG. 9 is a view schematically showing how the protective layer shown in FIG. 8B is formed on the whiskers and the pore wall.

10 is a view schematically showing the cross-sectional shape of FIG.

11 is a schematic structural diagram of a low pressure chemical vapor deposition apparatus used for forming a whisker according to the present invention.

Claims (4)

It includes a plurality of filters arranged at regular intervals, Each filter consists of a fabric filter, The largest size of pores formed by the filaments constituting the fabric filter disposed in the filter introduction portion of the plurality of fabric filters, the pore size gradually decreases toward the fabric filter disposed at the rear end, Catalytic method of forming a whisker by using a whisker formed by a catalyst or a separate catalyst in each of the filaments constituting the fabric of the fabric filter and the fabric filter immediately preceding the filter filter disposed on the opposite end of the filter inlet Whiskers are formed, a part of which is configured to protrude into pores between the filaments and to collect fine particles that can pass through the pores, The size of the whiskers formed in the filament constituting the fabric of the fabric filter disposed in the rear end is smaller than the size of the whiskers formed in the filament constituting the fabric of the fabric filter disposed in front of the rear end, And a protective layer of the same material as that of the whisker is formed on the whisker and the entire pore wall of the filament on which the whisker is formed. As a method of manufacturing a multi-layer fabric filter according to claim 1, After forming the whisker on each filament constituting the fabric of the fabric filter, under the same temperature and pressure conditions used in the whisker forming process, a carrier gas and a dilution gas were added to the reaction tube at a ratio of about 1: 7. Supplying to form a protective layer of the same material as the whisker on the whisker and the pore wall. The method of claim 2, wherein the whiskers and the protective layer are made of silicon carbide. The method according to claim 2, wherein the whisker is formed by a catalyst method using a non-catalyst method or a separate catalyst, and when the whisker is formed by a catalyst method, a step of removing the metal catalyst remaining on the tip of the whisker Performing the process of forming the protective layer without performing.

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