KR20050100098A - A diesel particulate trap using porous pellets coated with catalysts - Google Patents

Abstract

The present invention relates to a soot filtration device using catalytically coated porous pellets. The present invention is a soot filtration device which is installed in the exhaust gas discharge portion of the vehicle to filter the exhaust gas discharged from the vehicle, comprising at least one filter unit consisting of a plurality of pellets (pelts) through which the exhaust gas, the pellet is porous It is characterized in that the catalyst is coated on the inner and outer surfaces. Through the present invention, it is possible to greatly improve particulate matter collecting performance and back pressure characteristics of the soot filtration device.

Description

Soot filtration system using catalytically coated porous pellets {A DIESEL PARTICULATE TRAP USING POROUS PELLETS COATED WITH CATALYSTS}

The present invention relates to a soot filtration device, and more particularly to a soot filtration device using a catalytic coated porous pellet.

With the development of modern society, as the amount of people's movement increases, the utilization of transportation including cars is exploding. As the traffic volume increases, various problems are emerging. Among them, the air pollution problem caused by the use of fossil fuels is particularly important in large cities. Carbon dioxide, sulfides and nitrides (NOx, NOx) generated by the combustion of fossil fuels used as fuels for automobiles are becoming the main culprit of environmental pollution. In particular, significant environmental pollution occurs due to ozone layer destruction by Freon, N ₂ O gas, and acid rain by SO _x and NO _x components. In addition, the human body mainly affects the respiratory and neurological disorders. In particular, ozone generation due to photochemical reaction between HC and NO _x and PM (particulate matter) have recently been found to be the cause of lung cancer. There is a growing interest in the effects on the human body. Therefore, research and development to reduce this have been conducted.

In order to reduce harmful emissions due to the combustion of fossil fuels, technologies for reducing pollutants in the engine itself, that is, engine technology and pretreatment technology, have been developed. There are limitations to satisfying regulations alone, making it necessary to apply aftertreatment technology to treat exhaust gases already burned in engines.

Examples of after-treatment technologies for diesel vehicles include oxidation catalysts, NO _x catalysts, and soot filters. Among them, diesel particulate filter traps (DPFs) are the most efficient and practical approaches. This device is a technology that collects particulate matter and soot discharged from diesel engine in filter, burns it, recycles it, and collects particulate matter and continues to use it. And economics are acting as obstacles to practical use.

The soot filtration device basically consists of three parts: filter, regeneration device and control device. Among them, a regeneration apparatus is required to remove particulate matter and to continue using the filter after collecting particulate matter and soot into the filter. The regeneration method of the regeneration device is a technology that burns and regenerates the trapped material, and collects and reuses the particulate material, and continues to use it. It can be divided into two types: passive regeneration type, in which regeneration is performed only by exhaust gas without supply.

In the forced regeneration method, the collected particulate matter is heated with an external heat source up to an ignition temperature of 550 ° C. to 600 ° C., and in the natural regeneration method, the ignition temperature of the particulate material is reduced by using a catalyst or an additive and continuously burned with the engine exhaust gas. In the forced regeneration method, the particulate filter is collected by the capture filter and then burned to induce regeneration by supplying an auxiliary heat source.Therefore, frequent regeneration causes severe failures and shortens the life. It is likely to cause damage to the filter. Therefore, a natural regeneration method with a simple structure and few failures is currently being developed. However, when driving at a low temperature for a long time, particulate matter in the vehicle exhaust gas does not burn and accumulates inside the filter, thereby damaging the filter or making the vehicle impossible to operate. can do.

Therefore, a passive and active combination has been developed that uses a forced regeneration device as a natural regeneration method. In this case, electric heaters are used a lot as auxiliary heat sources, but most of them are installed outside the filter, and the method of increasing the temperature of the exhaust gas by adding energy of the electric heater to the exhaust gas, and radiant heat of the electric heater are collected inside the filter. The method of regenerating particulate matter by direct delivery to the particulate matter is applied.

However, when this method is used in a soot filtration apparatus, when particulate matter is collected and the pressure before and after the soot filtration apparatus is above a certain value, the collected particulate matter is forcibly regenerated by using a heating wire, so the regeneration process is continuously performed. There is a problem that cannot be supported.

Ceramic cordierite filters are most commonly used for soot filtration, and silicon carbide filters (SiC), ceramic integrated filters, and metal powder filters are also used. The ceramic filter or silicon carbide filter has a circular or oval cylindrical cross section, and a small triangular or square exhaust channel having a diameter of several mm in the axial direction has a honeycomb shape. The honeycomb super honeycomb evenly distributes the torsion in six directions to smooth the air flow.

Patent application publication No. 1996-0038063 describes a conventional honeycomb type filter. Here, a ceramic honeycomb filter is used to remove particulate matter from diesel vehicles, and a portion of the center of the filter is blocked to form a clogged portion to remove particulate matter from exhaust gas emitted from the diesel vehicle and to improve durability. In addition, the honeycomb filter is characterized in that the shape of the circle, ellipse, triangle, square or hexagon.

Such honeycomb type filters are manufactured in an extruded form, plugged at one inlet to prevent plugging, and filtered by passing exhaust gas through a porous wall. Therefore, the plugging process for blocking each hole is difficult and not only easy to automate, but also has to be sintered several times. Therefore, the manufacturing process is complicated and the manufacturing cost increases. In addition, in the case of the filter of the honeycomb structure, the hole is so small that it is difficult to install the heater therein.

The present invention solves the filter breakdown caused by the abnormal combustion phenomena generated in the conventional soot filtration device, and efficiently collects particulate matter of a small size which is naturally regenerated and harmful to human body even at low exhaust gas operating conditions. An object of the present invention is to provide a soot filtration device of a continuous regeneration method.

The present invention is a soot filtration device which is installed in the exhaust gas discharge portion of the vehicle to filter the exhaust gas discharged from the vehicle, comprising at least one filter unit consisting of a plurality of pellets (pelts) through which the exhaust gas, the pellet is porous It is characterized in that the catalyst is coated on the inner and outer surfaces.

Here, the catalyst is preferably at least one catalyst selected from platinum and rhodium.

In addition, an electric heater is provided between one or more filter units, and the electric heater may be formed by overlapping coils.

And an electric heater may be installed in front of the filter unit in which the exhaust gas is introduced for the first time.

Here, the diameters of the plurality of pellets may be substantially the same.

The pellet also includes a plurality of first pellets and a plurality of second pellets, the diameter of the first pellets being greater than the diameter of the second pellets, and the number of first pellets and the number of second pellets may be substantially the same. have.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 and 2. These embodiments of the present invention are merely for illustrating the present invention, but the present invention is not limited thereto.

1 is a schematic diagram of a soot filtration device 100 according to a first embodiment of the present invention. As shown in FIG. 1, the soot filtration device 100 according to the first embodiment of the present invention includes a catalyst coated porous pellet 19, a leaf spring 16, an electric heater 17, and a controller 15. It includes. The soot filtration device 100 is installed at the exhaust gas outlet of the vehicle to filter the exhaust gas discharged from the vehicle. That is, the filter unit composed of a plurality of porous pellets 19 is discharged from the diesel engine 11 of the vehicle and the exhaust gas flowing along the exhaust passage 13 is filtered and then discharged to the atmosphere. The exhaust gas is filtered while passing through a filter section made of a plurality of porous pellets 19.

The leaf spring 16 is installed to fix the plurality of porous pellets 19 and prevents friction due to the flow of the porous pellets 19 during operation. In addition, the leaf spring 16 helps the smooth inflow of the exhaust gas.

The electric heater 17 is provided between one or more filter parts and overlaps the coil. In addition, the electric heater 17 may be installed at the front end of the filter unit in which the exhaust gas flows for the first time. The electric heater 17 serves to maintain the regeneration reaction temperature of the particulate matter so that the particulate matter is burned and regenerated and the particulate matter is collected and used again. The controller 15 is connected to the electric heater 17 to supply an appropriate current to the electric heater 17 according to the operating state of the diesel engine 11.

In the first embodiment of the present invention, the plurality of porous pellets 19 forming the filter portion are porous spherical ceramics, and the catalyst is coated on the inside and outside thereof. Here, ceramics are particularly heat resistant and therefore suitable as pellets, and the catalyst consists of one or more materials selected from platinum and rhodium.

Porous pellets are coated with one or more materials selected from platinum and rhodium. That is, noble metals such as platinum and rhodium are mixed with the washcoat and applied to the porous pellets, followed by sintering. The performance of the catalyst is influenced by the loading ratio of the precious metal, the loading amount and the washcoat material.

Thereby, the NO component contained in the exhaust gas which passes inside and outside the porous pellet can be easily oxidized to the NO ₂ component. As shown in the enlarged source of FIG. 1, the exhaust gas is included in the exhaust gas while the pores 191 inside the passage pass through the porous pellet 19 connected to each other by an open channel 192. The particulate matter 30 comes into contact with the inside as well as the outside thereof. In particular, in the present invention, since not only the outside but also the inside of the porous pellet 19 is coated with a catalyst, the NO component in the exhaust gas permeating into the porous pellet 19 can be easily oxidized to the NO ₂ component. And since the porosity can be up to 80%, the back pressure is considerably less than that of ceramic beads of the same size with 0% porosity.

The catalyst serves to lower the regeneration temperature of particulate matter. The particulate matter is combusted at 650 ° C. or higher under normal conditions, but oxidation is promoted due to the catalyst, and in the case of NO ₂ atmosphere, combustion may occur at 260 ° C. to 370 ° C. to lower the combustion temperature by about 300 ° C. to 400 ° C. Therefore, there is an advantage that can filter the soot even at a relatively low temperature.

2 is a schematic diagram of a soot filtration device 200 according to a second embodiment of the present invention. The soot filtration device 200 according to the second embodiment of the present invention shown in FIG. 2 is the same as the soot filtration device according to the first embodiment of the present invention except for the shape of the porous pellets 28 and 29. The description is omitted.

The soot filtration device 200 according to the second embodiment of the present invention shown in FIG. 2 includes a plurality of first pellets 28 and a plurality of second pellets 29, the diameter of the first pellets 28. Is larger than the diameter of the second pellets 29, and the number of the first pellets 28 and the number of the second pellets 29 are substantially the same. The smaller the size of the pellet, the higher the collection rate of the particulate matter, while the lower the back pressure characteristic. On the contrary, the larger the size of the pellet, the lower the collection rate of the particulate matter, while the back pressure characteristic is improved. In view of this, in the second embodiment of the present invention, the particulate matter is mixed by mixing a plurality of first pellets 28 and a plurality of second pellets 29 having different diameters, and making the number thereof substantially the same. Excellent soot filtration device is obtained in terms of both collection rate and back pressure characteristics.

In the particulate filter of the present invention, since the pellets are porous, there is an advantage that the back pressure performance is greatly improved. In addition, since the inside and outside surfaces of the porous pellets are coated with a catalyst, soot can be filtered at a relatively low temperature, thereby reducing the electrical energy consumption during regeneration. In addition to the relatively large sized particulate matter, it is possible to capture and recycle small sized particulate matter that is harmful to the human body.

In addition, the use of one or more catalysts selected from platinum and rhodium makes it easier to filter soot at low temperatures.

In addition, since the electric heater made of overlapping coils is installed between the filter parts made of porous pellets and used at the same time, the particulate material can be continuously and smoothly reproduced even under the low operating temperature of the exhaust gas, and the material cost is low.

On the other hand, by installing an electric heater in front of the filter unit in which the exhaust gas flows for the first time to increase the temperature of the particulate matter it is possible to more efficiently capture and regeneration.

In the present invention, the production cost of the pellets can be reduced by making the diameters of the plurality of pellets substantially the same.

Further, by using two kinds of pellets having different diameters and the same number, excellent results can be obtained in terms of both the collection rate and the back pressure characteristics of the particulate matter.

Although the present invention has been described above, it will be readily understood by those skilled in the art that various modifications and variations are possible without departing from the spirit and scope of the claims set out below.

1 is a schematic diagram of a soot filtration device according to a first embodiment of the present invention.

2 is a schematic diagram of a soot filtration device according to a second embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

11. Diesel Engine 13. Exhaust Channel

19, 28, 29. Porous pellets 16. Leaf spring

17. Electric heater 15. Controller

30. Particulate Matter

Claims (6)

A soot filtration device installed in the exhaust gas discharge part of a vehicle and filtering exhaust gas emitted from the vehicle, And at least one filter part comprising a plurality of pellets through which the exhaust gas passes, wherein the pellets are porous and the catalyst is coated on the inner and outer surfaces thereof. In claim 1, Said catalyst is at least one catalyst selected from platinum and rhodium. In claim 1, An electric heater is provided between the at least one filter unit, and the electric heater is configured to overlap coils. In claim 1, A soot filtration device in which an electric heater is installed in front of the filter part to which the exhaust gas is first introduced. In claim 1, A soot filtration device having a diameter of the plurality of pellets substantially the same. In claim 1, The pellet comprises a plurality of first pellets and a plurality of second pellets, the diameter of the first pellets being greater than the diameter of the second pellets, the number of the first pellets and the number of the second pellets being substantially Same soot filtration device.