JP2013087696A - Exhaust gas processing device and control method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust gas processing device for maintaining PM (particulate matter) concentration in an outlet of an exhaust gas processing device (DPF) within a specific value, even when the PM concentration is significantly increased at engine start-up or the like, as well as when the PM concentration in exhaust gas is low, and to provide a control method of the exhaust gas processing device.SOLUTION: This control method of the exhaust gas processing device includes the steps of: applying an AC current to a pre-stage electrode 2 and generating thermal non-equilibrium plasma between electrode plates 4 of the pre-stage electrode 2, to charge the particulate matter (PM); and executing first control for applying a DC current to a post-stage electrode 3 to cause the electrode plates 4 of the post-stage electrode 3 to attract the particulate matter, under a first condition, and executing second control for applying the AC current to the post-stage electrode 3 and generating the thermal non-equilibrium plasma between the electrode plates 4 of the rear stage electrode 3 to oxidize the particulate matter under a second condition.

Description

  The present invention relates to an exhaust gas processing apparatus for purifying exhaust gas of an internal combustion engine and a control method therefor.

  Conventionally, a diesel particulate filter (hereinafter referred to as DPF) has been used as an exhaust gas treatment device for internal combustion engines such as gasoline engines and diesel engines. The DPF includes a filter made of a ceramic honeycomb or a heat-resistant fiber, and can collect particulate matter (referred to as particulate matter or PM) in the exhaust gas. However, there is a problem that pressure loss increases due to clogging of the filter and the like.

  As a solution to the above problem, a DPF is disclosed in which PM in exhaust gas is charged and sucked, adsorbed and captured by an electrode to which a high voltage is applied (see, for example, Patent Document 1). The DPF described in Patent Document 1 has a configuration in which exhaust gas is passed between two electrodes and an alternating current is applied to the electrodes.

  Moreover, DPF provided with the scraper and the heating apparatus is disclosed (for example, refer patent document 2). With this scraper or the like, the DPF can remove PM adhering to the electrode. With this configuration, the PM adsorption performance of the DPF can be maintained.

  However, the above DPF has several problems. First, this DPF has a problem that PM cannot be sufficiently collected when the concentration of PM is high, such as when the engine is started. This is because the charged PM meanders between the two electrodes by the application of an alternating current.

  Secondly, this DPF has a problem that the cost of the DPF increases when a high-voltage AC power source capable of sufficiently collecting PM is used when the concentration of PM is high at the time of starting the engine. ing. Further, when the concentration of PM is low, this expensive AC power supply has a higher performance than necessary, and there is a problem that the cost effectiveness of the DPF is lowered.

  Thirdly, this DPF has a problem of low durability. This is because when the scraper removes PM adhering to the DPF, the filter is worn and damaged. Further, when PM is burned by a heating device or fuel spray, the filter becomes high temperature and the filter is damaged.

JP 2004-66063 A JP 2007-216193 A

The present invention has been made in view of the above problems, and its object is to dramatically increase the concentration of PM, such as when the engine is started, in addition to when the concentration of particulate matter (PM) in the exhaust gas is low. An object of the present invention is to provide an exhaust gas treatment device that can maintain the PM concentration at the outlet of the exhaust gas treatment device (DPF) at a predetermined value or less, and a control method therefor, even if it is high. It is another object of the present invention to provide a DPF that prevents the DPF from being damaged and realizes a long life of the DPF.

  In order to achieve the above object, a method for controlling an exhaust gas treatment apparatus according to the present invention includes two electrode plates and a power source for applying a voltage to the electrode plates, and the exhaust gas passes between the electrode plates. The exhaust gas treatment device that adsorbs the particulate matter contained in the exhaust gas treatment device, wherein the exhaust gas treatment device has a front electrode and a rear electrode, and the front electrode is configured to allow exhaust gas to pass between them. Two opposed electrode plates, an alternating current power source for applying an alternating current to the electrode plates, and the latter electrode configured to allow exhaust gas to pass therebetween, and the electrodes A control method for an exhaust gas treatment apparatus, comprising: an AC power source that applies an AC current to a plate; a DC power source that applies a DC current to the electrode plate; and a switch that switches between the AC power source and the DC power source. Interchange with electrode Applying a current to generate a non-thermal equilibrium plasma between the electrode plates of the front electrode to charge the particulate matter; and under a first condition, a direct current is applied to the rear electrode, The first control for adsorbing the particulate matter to the electrode plate is performed, and under the second condition, an AC current is applied to the rear electrode, and non-thermal equilibrium plasma is generated between the electrode plates of the rear electrode to generate the particles. A step of performing a second control for oxidizing the particulate material.

  With this configuration, the exhaust gas treatment device (DPF) is used when the amount of particulate matter (PM) contained in the exhaust gas is larger than a predetermined threshold (first condition), such as when the engine is started. However, it is possible to sufficiently adsorb PM and maintain the concentration of PM at the outlet of the exhaust gas treatment device below a certain value. Further, even when the amount of PM in the exhaust gas is smaller than a predetermined threshold (second condition), it is possible to regenerate the DPF while directly oxidizing the PM at the rear electrode.

  In order to achieve the above object, an exhaust gas treatment apparatus according to the present invention includes two electrode plates and a power source for applying a voltage to the electrode plates, and is included in the exhaust gas passing between the electrode plates. In the exhaust gas treatment apparatus that adsorbs particulate matter, the exhaust gas treatment apparatus has a front electrode and a rear electrode, and the front electrode is configured to pass two sheets of exhaust gas between them. An electrode plate and an AC power source for applying an AC current to the electrode plate, the back electrode being configured to allow exhaust gas to pass between, and two opposed electrode plates, and an AC to the electrode plate An AC power source for applying a current; a DC power source for applying a DC current to the electrode plate; and a switch for switching between the AC power source and the DC power source. An AC current is applied to the front electrode, and the front electrode Of the above A non-thermal equilibrium plasma is generated between the electrode plates to charge the particulate matter. Under a first condition, a direct current is applied to the latter electrode, and the particulate matter is adsorbed to the electrode plate of the latter electrode. 1 control is performed, and under the second condition, an AC current is applied to the rear electrode, and non-thermal equilibrium plasma is generated between the electrode plates of the rear electrode to perform second control to oxidize the particulate matter. It is characterized by comprising. With this configuration, the same effects as described above can be obtained.

  According to the exhaust gas treatment device of the present invention, the exhaust gas is exhausted not only when the concentration of particulate matter (PM) in the exhaust gas is low, but also when the concentration of PM is dramatically increased at the time of engine start. It is possible to provide an exhaust gas processing apparatus capable of maintaining the PM concentration at the outlet of the gas processing apparatus (DPF) at a certain value or less.

It is the figure which showed the outline of the exhaust-gas processing apparatus of embodiment which concerns on this invention. It is the figure which showed the outline of the exhaust-gas processing apparatus of embodiment which concerns on this invention. It is the figure which showed the outline of the exhaust gas processing apparatus of different embodiment which concerns on this invention. It is the figure which showed the outline of the exhaust gas processing apparatus of different embodiment which concerns on this invention.

  Hereinafter, an exhaust gas treatment device (DPF) according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of an exhaust gas processing apparatus (DPF) according to an embodiment of the present invention. The DPF 1 has a front electrode 2 and a rear electrode 3. The front electrode 2 has two opposing electrode plates 4 that allow exhaust gas to pass between them, and an AC power source 5 that applies an AC current to the electrode plates 4.

  The rear electrode 3 includes two opposed electrode plates 4 that allow exhaust gas to pass between them, an AC power source 5 that applies an AC current to the electrode plate 4, a DC power source 6 that applies a DC current to the electrode plate 4, and an AC current A switch 7 for switching between the power supply 5 and the DC power supply 6 is provided. Here, the interval between the two electrode plates 4 facing each other is, for example, about 1.0 mm to 3.0 mm.

  Next, the electrode plate 4 will be described. The electrode plate 4 includes, for example, an electric conductor 11 such as a metal plate, and a dielectric 12 such as alumina or ceramic disposed so as to sandwich the electric conductor 11 from both sides. At least one of the dielectrics 12 has a plurality of through holes 13. The electrode plate 4 is not limited to the above configuration as long as it is configured to generate non-thermal equilibrium plasma between the electrode plates 4.

  Next, the generation principle of non-thermal equilibrium plasma will be described. First, plasma is generated between the electrode plates 4 by dielectric barrier discharge. In this dielectric barrier discharge, at least one of the electrodes (electrical conductor 11) is covered with a dielectric 13, and electrons are accelerated by application of a high electric field to collide with neutral atoms in the space between the electrode plates 4, and electrons It is a discharge form that generates a large number of electrons and ions by avalanche. The electron population generated by this dielectric barrier discharge forms a streamer (fibrous discharge) that moves at high speed from the cathode side to the anode side, and a dielectric (insulator) 13 is formed on the surface of the electric conductor 11. Therefore, no current is injected from the electric conductor 11 into the plasma space, and arc discharge does not occur. When the change of the voltage applied to the electric conductor 11 is finished, the generation of the streamer is finished. When the direction of the electric field is reversed, avalanche in the reverse direction occurs. If the direction of the electric field is changed at high speed by a high-frequency power source, ions that are heavier than electrons can hardly move and only the electrons move. Therefore, low-temperature plasma (non-thermal equilibrium plasma) having only a high electron temperature can be generated.

  In addition, a white arrow shows the direction through which the exhaust gas discharged | emitted from an engine or a generator etc. flows, and PM has shown typically the particulate matter (PM) contained in exhaust gas. The symbol “+” or “−” attached to PM indicates that PM is charged. Further, the front-stage electrode 2 and the rear-stage electrode 3 can be configured by laminating a plurality of electrode plates 4.

  Next, the operation of the exhaust gas treatment device (DPF) 1 will be described. First, the first control (hereinafter referred to as adsorption control) performed when the engine or the like is started and the amount of PM contained in the exhaust gas is larger than a predetermined threshold value (first condition) will be described.

  An alternating current is applied to the front electrode 2 during the adsorption control of the DPF 1. Due to this alternating current, non-thermal equilibrium plasma is generated between the electrode plates 4 of the front electrode 2, and the PM is charged. As described above, the pre-stage electrode 2 is mainly charged with PM. In addition to the charging of PM, the front electrode 2 also performs adsorption of PM to the electrode plate 4 and oxidation of PM. In the former electrode 2, the charged PM proceeds while reversing the traveling direction between the two electrode plates 4 in accordance with the frequency cycle of the alternating current.

  On the other hand, in the adsorption control of the DPF 1, the electrode plate 4 and the DC power source 6 are connected by the switch 7, and a DC current is applied to the rear electrode 3. Due to this direct current, the rear electrode 3 adsorbs the PM passing between the electrode plates 4 to the electrode plate 4. In the subsequent electrode 3, the charged PM is attracted toward the corresponding electrode plate 4 without reversing the traveling direction.

  Next, the second control (hereinafter referred to as regeneration control) performed when the engine or the like shifts to steady operation and the amount of PM contained in the exhaust gas is smaller than a predetermined threshold (second condition). Will be described. FIG. 2 shows the state of the DPF 1 during regeneration control.

  In the regeneration control of the DPF 1, an alternating current is applied to the front electrode 2 as in the adsorption control. On the other hand, the electrode plate 4 and the AC power source 5 are connected by the switch 7, and an AC current is applied to the rear electrode 3. Due to this alternating current, the rear electrode 3 directly oxidizes the PM adsorbed on the electrode plate 4. That is, the PM of the rear electrode 3 is oxidized by the emission of electrons and removed from the DPF 1. From the above, the post-stage electrode 3 mainly oxidizes PM directly to regenerate the DPF 1 (the post-stage electrode 3). It should be noted that the post-stage electrode 3 in the regeneration control performs adsorption of PM in the exhaust gas in addition to PM oxidation.

  With the above configuration, the exhaust gas treatment device (DPF1) of the present invention can obtain the following effects. First, the DPF 1 maintains the amount of PM at the outlet of the DPF 1 below a certain amount even when the amount of PM contained in the exhaust gas is larger than a predetermined threshold, such as when the engine is started. be able to. This is because PM can be sufficiently adsorbed by the post-stage electrode 3 to which a direct current is applied (see FIG. 1).

  Secondly, since the DPF 1 can use the existing AC power supply 5 and DC power supply 6, the manufacturing cost is suppressed. Further, when the amount of PM in the exhaust gas is smaller than the threshold value, it is possible to adsorb PM while directly oxidizing the PM by applying an alternating current to the rear electrode 3. That is, the cost effectiveness of the DPF 1 can be improved.

  Thirdly, the DPF 1 can achieve a long life by applying an alternating current to the post-stage electrode 3 to directly oxidize PM. That is, it is not necessary to remove PM adhering to the DPF 1 with a scraper or a heating device that may damage the filter, so that the filter can be prevented from being damaged.

  FIG. 3 shows an outline of an exhaust gas processing apparatus (DPF 1a) according to another embodiment of the present invention. In the DPF 1a, the front-stage electrode 2 and the rear-stage electrode 3 are installed in a common casing 16a so as to be an integrated DPF. The front electrode 2 and the rear electrode 3 are formed by laminating a plurality of electrode plates 4. Here, 15 is the exhaust passage, and the white arrow indicates the traveling direction of the exhaust gas.

  FIG. 4 shows an outline of an exhaust gas processing apparatus (DPF 1b) according to another embodiment of the present invention. In the DPF 1b, unlike the example shown in FIG. 3, the front electrode 2 and the rear electrode 3 are installed in independent housings 16b. Further, the DPF 1 b is configured to install two rear electrodes 3 along the exhaust passage 15.

Next, the operation of the DPF 1b will be described. First, when the amount of PM contained in the exhaust gas is larger than a predetermined upper limit value, adsorption control for adsorbing PM is performed by applying a direct current to the two subsequent electrodes 3. When the amount of PM is between a predetermined upper limit value and lower limit value, continuous operation control is performed in which a direct current is applied to one of the two rear electrodes 3 and an alternating current is applied to the other. In addition, this continuous operation control includes the control which switches the back | latter stage electrode 3 which applied the direct current to alternating current, and switches the back | latter stage electrode 3 which has applied the alternating current to direct current after progress for a predetermined time. It is desirable. When the amount of PM falls below a predetermined lower limit value, an alternating current is applied to the two subsequent electrodes 3 to perform regeneration control of the DPF 1b. Note that one power source of the rear electrode 3 may be turned off.
With the above configuration, the exhaust gas treatment device (DPF 1b) of the present invention can obtain the following effects. First, even if the amount of PM in the exhaust gas is larger than a predetermined upper limit value, PM can be adsorbed by the two rear electrodes 3, so that the PM adsorption performance of the DPF 1b can be further increased. Can be improved.

  Secondly, even when the amount of PM in the exhaust gas is larger than a predetermined lower limit and the state continues for a long time, the PM adsorption performance of the DPF 1b can be maintained. This is because the two rear electrodes 3 alternately repeat the adsorption control and the regeneration control. In addition, you may install three or more back | latter stage electrodes 3 of DPF1b.

1, 1a, 1b Exhaust gas treatment equipment (DPF)
2 Front electrode 3 Rear electrode 4 Electrode plate 5 AC power source 6 DC power source 7 Switch PM Particulate matter (PM)

Claims (2)

An exhaust gas treatment apparatus having two electrode plates and a power source for applying a voltage to the electrode plates, and adsorbing particulate matter contained in exhaust gas passing between the electrode plates;
The exhaust gas treatment apparatus has a front electrode and a rear electrode, and the front electrode applies two alternating electrode plates configured to pass exhaust gas therebetween, and an alternating current is applied to the electrode plate. Has an AC power supply
Two opposing electrode plates configured to allow the exhaust gas to pass between the latter electrode, an AC power source that applies an AC current to the electrode plate, a DC power source that applies a DC current to the electrode plate, A control method for an exhaust gas treatment apparatus having a switch for switching between the AC power source and the DC power source,
Applying an alternating current to the front electrode, generating non-thermal equilibrium plasma between the electrode plates of the front electrode, and charging the particulate matter;
Under the first condition, a direct current is applied to the latter electrode, and a first control is performed to adsorb the particulate matter on the electrode plate of the latter electrode,
Under the second condition, there is provided a step of performing a second control in which an alternating current is applied to the latter electrode, non-thermal equilibrium plasma is generated between the electrode plates of the latter electrode, and the particulate matter is oxidized. Control method for exhaust gas treatment device. In an exhaust gas treatment apparatus that has two electrode plates and a power source that applies a voltage to the electrode plates, and adsorbs particulate matter contained in exhaust gas that passes between the electrode plates,
The exhaust gas treatment apparatus has a front electrode and a rear electrode, and the front electrode applies two alternating electrode plates configured to pass exhaust gas therebetween, and an alternating current is applied to the electrode plate. Has an AC power supply
Two opposing electrode plates configured to allow the exhaust gas to pass between the latter electrode, an AC power source that applies an AC current to the electrode plate, a DC power source that applies a DC current to the electrode plate, A switch for switching between the AC power source and the DC power source;
AC current is applied to the front electrode, non-thermal equilibrium plasma is generated between the electrode plates of the front electrode, and the particulate matter is charged,
Under the first condition, a direct current is applied to the latter electrode, and a first control is performed to adsorb the particulate matter on the electrode plate of the latter electrode,
Under the second condition, an AC current is applied to the rear electrode, and non-thermal equilibrium plasma is generated between the electrode plates of the rear electrode to perform second control for oxidizing the particulate matter. Exhaust gas treatment device.

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