JP2006342699A - Exhaust emission control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device capable of efficiently oxidizing particles even in a low operation region of the exhaust temperature, while enhancing a collection rate and durability by using a plate-like dielectric filter. <P>SOLUTION: A flow passage 3 of exhaust gas 2 is partitioned and formed by juxtaposing the plate-like dielectric filter 1 to be multiply laminated at a required interval. An inlet of each flow passage 3 is alternately sealed for a mesh by a plug body 4, and an outlet of the flow passage 3 of not sealing the inlet for the mesh is sealed for the mesh by a plug body 5, and only the exhaust gas 2 passing through the dielectric filter 1 for partitioning the respective flow passages 3 is exhausted to the downstream side. An electric conductor 6 capable of passing the exhaust gas 2 is arranged on a dielectric filter 1 surface on the flow passage 3 side of sealing the inlet for the mesh, and an electrode 8 covered with a dielectric barrier 7 is arranged in the flow passage 3 of not sealing the inlet for the mesh, and creeping discharge is generated on the dielectric filter 1 surface on the flow passage 3 side of not sealing the inlet for the mesh. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an exhaust emission control device.

  Particulate matter (particulate matter) discharged from a diesel engine is mainly composed of soot made of carbonaceous matter and SOF content (Soluble Organic Fraction) made of high-boiling hydrocarbon components. The composition contains a small amount of sulfate (mist-like sulfuric acid component). As a measure to reduce this type of particulates, a particulate filter is installed in the middle of the exhaust pipe through which the exhaust gas flows. It has been done conventionally.

  This type of particulate filter has a porous honeycomb structure made of ceramics such as cordierite, and the inlets of each flow path partitioned in a lattice pattern are alternately sealed, and the inlets are not sealed. About the flow path, the exit is sealed, and only the exhaust gas which permeate | transmitted the porous thin wall which divides each flow path is discharged | emitted downstream.

  Particulates in the exhaust gas are collected and deposited on the inner surface of the porous thin wall, and are spontaneously combusted and removed when the exhaust gas moves to an operating region. For example, in a vehicle that travels only on a congested road, such as a route bus in Tokyo, the accumulated amount is higher than the processing amount of particulates because operation at a predetermined temperature or higher does not continue for a long time. There is a possibility that the particulate filter may be clogged.

  For this reason, plasma-assisted exhaust purification systems are being developed so that particulates can be burned and removed (oxidized) well even in operating regions where the exhaust temperature is low. If plasma is generated by discharge, the exhaust gas is excited to generate active radicals such as O radical and OH radical, and it becomes possible to satisfactorily oxidize the particulates even in the operation region where the exhaust temperature is low. .

For example, in Patent Document 1 and Patent Document 2 below, ceramic pellets forming a dielectric material are filled between an outer electrode and an inner electrode made of cylindrical stainless steel that has been perforated, and a packed layer of the pellet is formed. A plasma-assisted exhaust purification system is proposed in which exhaust gas is allowed to flow and particulates in the exhaust gas are collected, while plasma is generated by discharging between the outer electrode and the inner electrode. Has been.
Japanese translation of PCT publication No. 2002-501813 Japanese translation of PCT publication No. 2002-511332

  However, in the plasma assist type exhaust purification device that has been proposed in the past, as shown in the above-mentioned Patent Document 1 and Patent Document 2, an outer electrode and an inner electrode made of perforated cylindrical stainless steel are provided. A ceramic pellet forming a dielectric is filled between the electrode and an exhaust gas is allowed to flow through the packed layer of the pellet to collect particulates in the exhaust gas. It is common to generate plasma by discharging between the two, but when mounting on an automobile, ceramic pellets may rub against each other due to running vibration and wear in a short time However, there are still issues regarding durability. In addition, it has been difficult to increase the collection rate with pellets.

  In view of such circumstances, the present invention can improve the collection rate and durability by using a flat dielectric filter, and can purify particulates efficiently even in an operating region where the exhaust temperature is low. The device is to be provided.

In the present invention, exhaust gas flow paths are partitioned by arranging a large number of flat plate-like dielectric filters so as to be stacked at a required interval, and the inlets of the partitioned flow paths are plugged. Sealed alternately, the outlets of the channels not sealed at the inlet were sealed with plugs, and only the exhaust gas that permeated through the dielectric filter partitioning each channel was discharged downstream. An exhaust purification device,
A conductive material that allows exhaust gas to pass through is disposed on the surface of the dielectric filter on the flow path side where the inlet is sealed, and an electrode covered with a dielectric barrier is placed in the flow path where the inlet is not sealed. The present invention relates to an exhaust emission control device that is configured to generate a creeping discharge on the surface of a dielectric filter on the flow path side that is disposed and whose inlet is not sealed.

  In the exhaust emission control device, a voltage necessary for creeping discharge can be applied between the electrode and the conductor.

  In the exhaust purification apparatus, a voltage necessary for creeping discharge may be applied between the electrodes.

  According to the above means, the following operation can be obtained.

  The exhaust gas flows through the flat dielectric filter and the conductor from the flow path where the inlet is not sealed, and the particulates in the exhaust gas are collected when passing through the dielectric filter. However, if creeping discharge is generated on the surface of the dielectric filter on the flow path side where the inlet is not sealed as required, the particulates are efficiently oxidized.

  In addition, since a flat dielectric filter is used, when mounted in an automobile, ceramic pellets rub against each other due to running vibration as in a plasma-assisted exhaust purification device that has been proposed in the past. Durability is not increased, durability can be increased, and a higher collection rate, which was difficult with pellets, can be achieved.

  According to the exhaust emission control device of the present invention, when creeping discharge is used, particulates on the filter surface can be efficiently oxidized, so that the collection rate and durability can be increased using a flat dielectric filter. The particulates can be efficiently oxidized even in the operation region where the exhaust gas temperature is low.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  1 to 3 show an example of an embodiment of the present invention. A large number of flat dielectric filters 1 made of ceramics such as cordierite (preferably a surface filtration type are preferable) are stacked at a required interval. The flow passages 3 of the exhaust gas 2 are partitioned by arranging them side by side, and the inlets of the partitioned flow passages 3 are alternately sealed by the plugs 4 so that the inlets are not sealed. The outlet of the passage 3 is sealed with a plug 5 so that only the exhaust gas 2 that has permeated through the dielectric filter 1 partitioning each passage 3 is discharged downstream, and the inlet is sealed. A conductor 6 such as a metal mesh through which the exhaust gas 2 can pass is disposed on the surface of the dielectric filter 1 on the third side, and the channel 3 whose inlet is not sealed is covered with a dielectric barrier 7. Exhaust the rod-shaped electrode 8 extending in the flow direction of the exhaust gas 2 Scan 2 to flow direction and the direction perpendicular spaced predetermined intervals arranged, in which the inlet is configured to generate surface discharge in the dielectric filter 1 surface of the flow path 3 side, which is not sealed.

  In the case of the illustrated example, a power source 9 capable of applying a high voltage (AC high voltage, AC pulse high voltage, DC pulse high voltage, etc.) is connected to the electrode 8 and the conductor 6, and the electrode 8 and the conductor are connected. 6, a voltage necessary for creeping discharge is applied.

  As shown in FIG. 3, the power source 9 is connected to the downstream end of the electrode 8 in the flow direction of the exhaust gas 2 and the upstream end of the conductor 6 in the flow direction of the exhaust gas 2.

  Next, the operation of the illustrated example will be described.

  The exhaust gas 2 flows through the flat dielectric filter 1 and the conductor 6 from the flow path 3 whose inlet is not sealed, and the particulates in the exhaust gas 2 pass through the dielectric filter 1. If necessary, when the power supply 9 is turned on and a high voltage is applied between the electrode 8 and the conductor 6, the dielectric filter on the channel 3 side where the inlet is not sealed is collected. Creeping discharge is generated on one surface, and the particulates are efficiently oxidized.

  Here, as shown in FIG. 3, the power source 9 is connected to the downstream end side in the exhaust gas 2 flow direction of the electrode 8 and the upstream end side of the conductor 6 in the exhaust gas 2 flow direction. This is more effective in generating creeping discharge over the entire surface of the dielectric filter 1 on the side of the flow path 3 that is not sealed. Needless to say, the power source 9 may be connected to the upstream end of the electrode 8 in the flow direction of the exhaust gas 2 and the downstream end of the conductor 6 in the flow direction of the exhaust gas 2.

  Further, since the flat dielectric filter 1 is used, when mounted on an automobile, the ceramic pellets rub against each other due to running vibration as in a conventionally proposed plasma-assisted exhaust purification device, and for a short period of time. It is possible to improve durability without being worn.

  Thus, the flat dielectric filter 1 can be used to increase the collection rate and durability, and the particulates can be efficiently oxidized even in the operation region where the exhaust temperature is low.

  4 and 5 show another example of the embodiment of the present invention. In the figure, the same reference numerals as those in FIGS. 1 to 3 denote the same components, and the basic configuration is shown in FIG. 1 to FIG. 3, but the feature of the illustrated example is that, as shown in FIGS. 4 and 5, a high voltage (AC high voltage, AC pulse high voltage, or A power source 9 to which a DC pulse high voltage or the like can be applied is connected, and a voltage necessary for creeping discharge is applied between the electrodes 8.

  For the power source 9, as shown in FIG. 5, one of the electrodes 8 adjacent to each other at an interval in a direction perpendicular to the exhaust gas 2 flow direction is upstream of the exhaust gas 2 flow direction of one electrode 8. The end side is connected to the downstream end side in the exhaust gas 2 flow direction of the other electrode 8.

  In the example shown in FIGS. 4 and 5, the exhaust gas 2 flows through the flat dielectric filter 1 and the conductor 6 from the flow path 3 whose inlet is not sealed, and flows through the dielectric filter 1. Particulates in the exhaust gas 2 are collected during passage, but if necessary, when the power supply 9 is turned on and a high voltage is applied between the electrodes 8, the flow path 3 in which the inlet is not sealed. A creeping discharge is generated on the surface of the dielectric filter 1 on the side, and the particulates are efficiently oxidized.

  Here, as shown in FIG. 5, with respect to the power source 9, one of the electrodes 8 adjacent to each other with a required interval in a direction perpendicular to the direction in which the exhaust gas 2 flows, the upstream end of one electrode 8 in the direction in which the exhaust gas 2 flows Since the first electrode 8 is connected to the downstream end of the other electrode 8 in the exhaust gas 2 flow direction, creeping discharge is generated over the entire surface of the dielectric filter 1 on the flow path 3 side where the inlet is not sealed. It has become more effective.

  In the example shown in FIGS. 1 to 3, since a high voltage is applied between the electrode 8 and the conductor 6, the dielectric filter 1 on the flow path 3 side where the inlet is not sealed. Since creeping discharge occurs only around the electrodes 8 on the surface (about several millimeters), the number of electrodes 8 must be increased and they must be arranged relatively densely. In the example shown in FIG. 5, since a high voltage is applied between the electrodes 8, the plasma of creeping discharge generated around each electrode 8 is connected by the potential difference between the adjacent electrodes 8. The range of creeping discharge can be expanded.

  Also, in the examples shown in FIGS. 4 and 5, as in the examples shown in FIGS. 1 to 3, since the flat dielectric filter 1 is used, the plasma assist conventionally proposed when mounted on an automobile is used. As in the case of the exhaust gas purification device, ceramic pellets are not rubbed with each other due to running vibration and are not worn in a short period of time, and it is possible to improve durability. A collection can also be achieved.

  Thus, in the case of the example shown in FIGS. 4 and 5, as in the case of the example shown in FIGS. 1 to 3, the collection rate and the durability can be increased using the flat dielectric filter 1, and Particulates can be oxidized efficiently even in an operating region where the exhaust temperature is low.

  It should be noted that the exhaust emission control device of the present invention is not limited to the illustrated examples described above, and it is needless to say that various modifications can be made without departing from the scope of the present invention.

It is the schematic which shows an example of the form which implements this invention. It is II-II sectional drawing of FIG. It is a perspective view which shows an example of the form which implements this invention. It is the schematic which shows the other example of the form which implements this invention. It is a perspective view which shows the other example of the form which implements this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dielectric filter 2 Exhaust gas 3 Flow path 4 Plug body 5 Plug body 6 Conductor 7 Dielectric barrier 8 Electrode 9 Power supply

Claims (3)

By arranging a large number of flat dielectric filters in parallel so as to be stacked at a required interval, the exhaust gas flow paths are partitioned, and the inlets of the partitioned flow paths are alternately sealed with plugs. And an exhaust purification device in which only the exhaust gas that has passed through the dielectric filter partitioning each flow path is discharged to the downstream side by sealing the outlet of the flow path whose inlet is not sealed with a plug. There,
A conductive material that allows exhaust gas to pass through is disposed on the surface of the dielectric filter on the flow path side where the inlet is sealed, and an electrode covered with a dielectric barrier is placed in the flow path where the inlet is not sealed. An exhaust emission control device configured to generate creeping discharge on a surface of a dielectric filter on a flow path side that is disposed and whose inlet is not sealed.   The exhaust emission control device according to claim 1, wherein a voltage necessary for creeping discharge is applied between the electrode and the conductor.   The exhaust emission control device according to claim 1, wherein a voltage necessary for creeping discharge is applied between the electrodes.

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