JP2004239098A - Nox adsorbing device and nox purifying system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an NOx adsorbing device and an NOx purifying system for adsorbing and desorbing NOx by using discharge. <P>SOLUTION: Respective adsorbing parts 12 and 13 are used by either of an adsorbing mode or a desorbing mode. In the adsorbing mode, only an upstream side earth electrode 32 is grounded, and the discharge is generated in an upstream side discharge division DCA1. The NOx oxidized by the discharge is adsorbed by an adsorbent 24 of a downstream side discharge division DCA2. In the desorbing mode, the discharge is generated in both of the respective discharge divisions DCA1 and DCA2. The desorbed NOx is reduced by recirculating in a combustion chamber of an engine together with desorbed gas (outside air or exhaust gas). The adsorbing function and the discharge function are built in the respective adsorbing parts 12 and 13, and since a discharge generating part can be switched according to a use mode, a structure of the whole device can be simplified and compactly formed. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a NOx adsorption device and a NOx purification system that purify exhaust gas by removing NOx (nitrogen compound) in exhaust gas discharged from, for example, a diesel engine or a gasoline engine.
[0002]
[Prior art]
Various methods are known as a method of reducing NOx emitted from various engines and the like. One of the methods is to adsorb NOx on an adsorbent, desorb the adsorbed NOx, regenerate the adsorbent, and regenerate the adsorbent. There is known an adsorption method for reusing urea.
[0003]
As a first prior art, at the time of adsorption, the temperature of the exhaust gas is lowered and then guided to the adsorbent, so that NOx in the exhaust gas is adsorbed by the adsorbent, while at the time of regeneration, high-temperature exhaust gas is introduced into the adsorbent. There is known a device that desorbs and collects NOx that has been adsorbed (for example, see Patent Document 1).
[0004]
Further, as a second conventional technique, an adsorbent whose adsorbability increases under plasma is used. When the temperature is lower than the operating temperature of the catalyst, plasma is generated to adsorb NOx, and at high temperature, the plasma is stopped to stop NOx. Is known, and is purified by a catalyst arranged on the downstream side (for example, see Patent Document 2).
[0005]
Further, as a third conventional technique, there is known a technique in which a non-thermal plasma is applied to an adsorbent to desorb the adsorbed exhaust gas, and the desorbed exhaust gas is decomposed by the non-thermal plasma (for example, see, for example, Japanese Patent Application Laid-Open No. H11-157556). And Patent Document 3).
[0006]
[Patent Document 1]
JP-A-6-233915
[0007]
[Patent Document 2]
JP 2001-182525 A
[0008]
[Patent Document 3]
JP-A-11-114351
[0009]
[Problems to be solved by the invention]
In the first prior art, NOx is desorbed by utilizing the temperature difference of the exhaust gas. However, for example, in the case of an engine or the like, the structure is such that the exhaust gas flows directly into the adsorbent. It is difficult to obtain a temperature difference between time and desorption. Therefore, in the case of a structure in which exhaust gas is directly introduced into the adsorbent, it is difficult to use.
[0010]
In the second conventional technique, it is necessary to provide a separate catalyst for purifying NOx desorbed by plasma.
[0011]
In the third conventional technique, a gas is desorbed by using plasma. However, nitrogen monoxide (NO), which is largely contained in exhaust gas, has a property that it is generally difficult to be adsorbed as it is. Therefore, nitrogen dioxide (NO ₂ A separate device for oxidizing is required, and the structure becomes complicated.
[0012]
The present invention has been made in view of the above-described various problems, and an object of the present invention is to provide a NOx adsorption device and a NOx purification system that can adsorb and desorb NOx using discharge. . Another object of the present invention is to provide a NOx adsorbing apparatus and a NOx purifying system which can switch a portion of the adsorbent to be discharged in the adsorbent according to a use mode and can form the whole compact. Further objects of the present invention will become clear from the description of the embodiments described later.
[0013]
[Means for Solving the Problems]
In order to solve the above problem, a NOx adsorbing device of the present invention includes an adsorbent for adsorbing NOx, a first discharge unit provided on one side of the adsorbent for oxidizing NOx, And a second discharge unit provided on the side for desorbing NOx adsorbed by the adsorbent.
[0014]
The adsorbent is mainly composed of NOx, especially nitrogen dioxide (NO ₂ ) Is formed from a material capable of adsorbing zeolite, for example, zeolite, alumina, activated carbon and the like can be used. The adsorbent has a property of adsorbing NOx in a non-discharge state and desorbing NOx in a discharge state. A first discharge section and a second discharge section are provided on one side and the other side of the adsorbent, respectively. The first discharge unit is for oxidizing NOx flowing into the adsorbent by discharge, and the second discharge unit is for desorbing NOx adsorbed on the adsorbent by discharge. Thus, a first discharge section is formed on one side (upstream side) of the adsorbent, and a second discharge section is formed on the other side (downstream side) of the adsorbent. That is, two discharge sections are integrally provided on one adsorbent, and each discharge section is selected and discharged at a predetermined time, thereby obtaining a compact NOx adsorption apparatus as a whole.
[0015]
For example, a NOx adsorbing device is provided with an insulated cylindrical casing having an inlet and an outlet for fluid on one side and the other side, and provided in the casing, adsorbing NOx under no discharge and discharging under NOx. An adsorbent for desorbing NOx and a discharge unit provided in the casing, wherein the discharge unit is disposed in the casing in the axial direction, and an internal electrode (center electrode, high-voltage electrode) to which a predetermined high voltage is applied And two external electrodes (ground electrodes) provided adjacent to the inner surface of the casing in the axial direction so as to face the internal electrode with the adsorbent interposed therebetween, and grounded at a predetermined time. Can be configured.
[0016]
In a preferred embodiment, there is provided a control unit for selecting and discharging one or both of the first discharge unit and the second discharge unit. When the control unit is used in the adsorption mode, the control unit transmits the first discharge unit or the second discharge unit. In a case where NOx is adsorbed on the adsorbent by discharging and used in the desorption mode, at least the second discharge unit is discharged to desorb the NOx adsorbed on the adsorbent.
[0017]
In the adsorption mode, discharge is performed by the first discharge unit, whereby the inflowing NOx is oxidized (NO → NO). ₂ ), Adsorbed by the adsorbent. Next, in the desorption mode in which the adsorbed NOx is discharged and regenerated, discharge is performed from the second discharge unit that has not discharged in the adsorption mode. As a result, NOx is desorbed on the other side of the adsorbent provided with the second discharge unit. That is, in the adsorption mode, the discharge is performed only in a part of the adsorbent, and in the desorption mode, the discharge is performed from the part that is not discharged in the adsorption mode.
[0018]
In addition, the part to be discharged can be controlled according to the type of fluid used for desorption. For example, when a fluid having a low NOx content (for example, outside air) is used, only the first discharge unit is discharged in the adsorption mode, and both the first discharge unit and the second discharge unit are discharged in the desorption mode. . On the other hand, when a fluid having a relatively high NOx content (eg, exhaust gas) is used, only the first discharge unit is discharged in the adsorption mode, and only the second discharge unit is discharged in the desorption mode.
[0019]
A NOx purifying system according to the present invention includes a NOx adsorbing device and a recirculation unit that recirculates NOx released from the NOx adsorbing device to a combustion chamber of an engine. The NOx adsorbing device includes an adsorbent for adsorbing NOx, and an adsorbent. A first discharge unit provided on one side of the NOx for oxidizing NOx, and a second discharge unit provided on the other side of the adsorbent for desorbing NOx adsorbed on the adsorbent It becomes.
[0020]
That is, as described above, the NOx adsorption device is configured by providing the first discharge unit and the second discharge unit on one side and the other side of the adsorbent, and can be formed compact as a whole. . Then, the NOx desorbed from the NOx adsorbing device is returned to the combustion chamber of the engine by the recirculating means. The recirculated NOx is decomposed and purified by combustion.
[0021]
In a preferred embodiment, the recirculation means is configured to recirculate NOx desorbed from the adsorbent to the combustion chamber by using either the outside air or exhaust gas from the engine.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0023]
1. First embodiment
[0024]
A first embodiment will be described with reference to FIGS. FIG. 1 is an overall configuration diagram in the case where a NOx purification system is applied to, for example, an automobile engine device.
[0025]
The engine 1 is mounted on, for example, a passenger car and is configured as a four-cycle gasoline engine. However, the present invention is not limited to this, and can be applied to other types of engines such as a diesel engine and a two-stroke engine.
[0026]
A plurality of cylinders 2 such as two, four, six, etc. are formed in a cylinder block of the engine 1, and a piston 3 is slidably provided in each cylinder 2 (description). Only one cylinder is shown for convenience). The opening of each cylinder 2 is gas-liquid tightly covered by a cylinder head 4, and a combustion chamber 5 is formed on the upper surface of the piston 3. An intake valve 6 is provided at a connection between the combustion chamber 5 and the intake manifold 8, and an exhaust valve 7 is provided between the combustion chamber 5 and the exhaust manifold 9 so as to be opened and closed.
[0027]
An intake passage L1 for introducing outside air is connected to the intake manifold 8, and an exhaust passage L2 for releasing exhaust gas to the atmosphere is connected to the exhaust manifold 9. Further, a NOx adsorbing device 10 described later is provided midway between the intake passage L1 and the exhaust passage L2. For convenience of description, the intake passage L1 is denoted by L1 (1), L1 (2), L1 (3) in order from the upstream side, and the exhaust passage L2 is L2 in order from the upstream side. (1) and L2 (2).
[0028]
The NOx adsorption device 10 includes a first switching valve 11, a first adsorption unit 12, a second adsorption unit 13, a second switching valve 14, a high-voltage power supply 15, an electrode switching switch 16, and a control unit 17 as described later. It is provided with.
[0029]
The first switching valve 11 and the second switching valve 14 can be expressed as a first switching unit and a second switching unit, respectively, and are configured as, for example, four-port two-position solenoid valves. Each of the switching valves 11 and 14 has two switching positions (a) and (b), and switches the positions in synchronization with each other according to a control signal from the control unit 17. Note that each of the switching valves 11 and 14 may have a transient position where each port is not connected to anywhere, and in this case, a four-port three-position solenoid valve. Further, the invention is not limited to the electromagnetic valve, and another switching mechanism such as a pneumatic valve may be employed.
[0030]
Between the first switching valve 11 and the second switching valve 14, a first suction unit 12 and a second suction unit 13 are provided in parallel. The first suction part 12 is connected to the first switching valve 11 and the second switching valve 14 via the first branch passage L21, and the second suction part 13 performs the first switching via the second branch passage L22. It is connected to the valve 11 and the second switching valve 14. The detailed structure of each of the adsorbing portions 12 and 13 will be described later with reference to FIG. 2. For example, the adsorbing portions 12 and 13 each include an electrode for generating a plasma discharge in an adsorbent such as alumina, zeolite, or activated carbon, and a fluid flows therein. An independent discharge section is formed on the upstream side and on the downstream side where the fluid flows out. The adsorbent 24 may be divided into an upstream section and a downstream section in accordance with each discharge section. However, no member or the like for partitioning each section is provided inside the adsorbent.
[0031]
Here, it should be noted that each of the adsorbing units 12 and 13 performs switching between oxidizing NOx by discharging and adsorbing oxidized NOx and desorbing (desorbing) NOx by discharging. It is a point that has become. That is, NOx is adsorbed and desorbed inside each of the adsorbing sections 12 and 13 by controlling the portion to be discharged, so that the entire adsorbing section can be formed compactly.
[0032]
When each of the switching valves 11 and 14 is at the first position (a), the upstream side of the first suction unit 12 is connected to the exhaust passage L2 (1) connected to the exhaust manifold 9 via the first switching valve 11. The downstream side of the first adsorption unit 12 is connected to an exhaust passage L2 (2) opened to the atmosphere via the second switching valve 14. On the other hand, the upstream side of the second adsorption unit 13 is connected to the intake passage L1 (1) opened to the atmosphere via the first switching valve 11, and the downstream side of the second adsorption unit 13 is connected to the intake passage L2. Is done.
[0033]
When each of the switching valves 11 and 14 is at the first position (a), the first adsorption unit 12 is in the adsorption mode, and the exhaust gas in the combustion chamber 5 flows into the first adsorption unit 12, and the first adsorption unit 12 The exhaust gas from which NOx has been removed is discharged into the atmosphere (S1). On the other hand, the second adsorption unit 13 is in the desorption mode, and outside air at atmospheric pressure flows into the second adsorption unit 13, and NOx desorbed from the adsorbent by the plasma discharge (S2) becomes a mixed gas mixed with the outside air. Then, it flows into the combustion chamber 5 through the intake passages L1 (2) and L1 (3) (S3). The NOx flowing into the combustion chamber 5 is burned and reduced in the combustion chamber 5 (S4). In this specification, the terms “upstream” and “downstream” respectively indicate upstream and downstream in the flow direction of a fluid (exhaust gas, reducing agent, outside air).
[0034]
Next, when each of the switching valves 11 and 14 switches from the first position (a) to the second position (b), on the contrary, the first adsorbing section 12 is in the desorption mode, and outside air flows in. The desorbed NOx flows from the first adsorption section 12 into the combustion chamber 5 via the switching valve 14 and the intake passage L1. On the other hand, the second adsorption unit 13 is in the adsorption mode, and the exhaust gas flowing into the second adsorption unit 13 is discharged to the atmosphere after NOx is adsorbed and removed.
[0035]
As shown in the time chart 17A on the lower side in FIG. 1, by alternately switching the use mode of each of the adsorption sections 12, 13, NOx is desorbed from the other adsorption section while adsorbing NOx in one adsorption section. Thus, it is possible to continuously adsorb and purify NOx in the exhaust gas. In the embodiment, the case where two suction units 12 and 13 are provided is illustrated, but the present invention is not limited to this, and a configuration in which three or more suction units are switched and used may be adopted.
[0036]
The high-voltage power supply 15 applies a predetermined voltage and a high frequency of a predetermined frequency to each of the suction units 12 and 13. As long as the high-voltage power supply 15 is operating, the high voltage from the high-voltage power supply 15 is constantly applied to the high-voltage electrodes of the suction units 12 and 13. The electrode switch 16 is for grounding one of the ground electrodes forming the discharge section (DCA2 in FIG. 2) on the downstream side of each of the adsorption sections 12 and 13. Plasma discharge is generated between the high-voltage electrode and the ground electrode grounded by the electrode switch 16. It should be noted that the upstream ground electrodes of the suction sections 12 and 13 are always grounded.
[0037]
The control unit 17 controls the operation of each of the switching valves 11 and 14 as shown in a time chart 17A. Further, the control unit 17 controls the operation of the electrode changeover switch 16 according to each of the adsorption mode and the desorption mode. Specifically, the control unit 17 controls the electrode changeover switch 16 so that the downstream ground electrode of the suction unit used in the desorption mode is not grounded and the downstream ground electrode of the suction unit used in the desorption mode is grounded. Control the operation. As described above, the control unit 17 outputs a control signal to each of the switching valves 11 and 14 and the electrode switching switch 16 at an appropriate time, and switches the positions of the switching valves 11 and 14 and the electrode switching switch 16. The control unit 17 can be configured as a microcomputer system, or can be configured as a hardware circuit such as an electromagnetic relay. Further, the control unit 17 can be realized as a part of an engine control unit (ECU). The control unit 17 can also control the operation of the high-voltage power supply 15, for example, generation and stop of the high voltage.
[0038]
Next, an example of the structure of each of the suction units 12 and 13 will be described with reference to FIG. Since the suction sections 12 and 13 have the same structure, the first suction section 12 will be mainly described.
[0039]
As described later, the first adsorbing section 12 includes a casing 21 having an inlet 22 and an outlet 23 formed therein, an adsorbent 24 provided in the casing 21, and a discharge electrode 30 provided in the casing 21. It has.
[0040]
The casing 21 is, for example, formed in a cylindrical shape from an insulating material such as ceramics, and has an inlet 22 through which exhaust gas or outside air flows in on one side (the left side in the figure), and the other side ( An outlet 23 from which exhaust gas or outside air flows out is provided on the right side in the figure).
[0041]
The inside of the casing 21 is filled with, for example, an adsorbent 24 formed in a pellet shape or a honeycomb shape from alumina, zeolite, activated carbon, or the like. The adsorbent 24 is fixed in the casing 21 by, for example, a ring member (not shown).
[0042]
The discharge electrode 30 includes a high-voltage electrode 31, an upstream ground electrode 32, a downstream ground electrode 33, and an insulating part. For example, the high-voltage electrode 31 formed in a rod shape is disposed along the axis of the casing 21 and is connected to the output terminal of the high-voltage power supply 15 via the electric wire W1.
[0043]
For example, the upstream ground electrode 32 and the downstream ground electrode 33 formed in a cylindrical shape are provided so as to cover the outer peripheral surface of the casing 21. The ground electrodes 32 and 33 are adjacent to each other in the axial direction of the casing 21 via an insulating portion 34, and the ground electrodes 32 and 33 are electrically separated by the insulating portion 34. The insulating portion 34 is formed by, for example, a gap or an insulating member. The insulating portion 34 is provided so that the ground electrode on the outer peripheral surface of the casing is partially grounded according to the use mode, and partial discharge can be performed in the casing 21. Therefore, for example, even when a cylindrical or tubular net-like ground electrode formed integrally (continuously) is employed, if partial discharge is possible by changing the ground position, the insulating portion 34 is not necessarily required. is not.
[0044]
The upstream-side ground electrode 32 is grounded via a wire W2, and the downstream-side ground electrode 33 is connected via a wire W4 (the downstream ground electrode 33 of the second suction portion 13 is a wire W5) and the electrode switch 16. It is grounded at a predetermined time.
[0045]
More specifically, for example, in the single-pole double-throw electrode switch 16, the common contact 16 </ b> C is grounded via the electric wire W <b> 3, and the make contact 16 </ b> A The break contact 16B is connected via a wire W5 to the downstream ground electrode 33 of the first suction unit 12 via an electric wire W4. Therefore, the upstream ground electrode 32 of each of the suction units 12 and 13 is always grounded via the electric wire W2, and the downstream ground electrode 33 of each of the suction units 12 and 13 is set in accordance with the switching position of the electrode switch 16. Either one is selectively grounded. Note that the downstream ground electrode 33 of the first suction part 12 may be connected to the make contact 16A, and the downstream ground electrode 33 of the second suction part 13 may be connected to the break contact 16B. Further, the structure of the electrode changeover switch 16 is not limited to the single pole double throw type, and two single pole single throw type switches may be used.
[0046]
Here, an upstream discharge section DCA1 (or a first discharge section) is formed on the upstream side of the adsorbent 24 (or on the upstream side of the casing 21) by the upstream ground electrode 32, and the downstream ground electrode is formed. 33, a downstream discharge section DCA2 (or a second discharge section) is formed on the downstream side of the adsorbent 24. The discharge sections DCA1 and DCA2 are formed corresponding to the ground electrodes 32 and 33, respectively. The axial length of each of the discharge sections DCA1 and DCA2 is determined by the axial length of the ground electrodes 32 and 33. . The upstream discharge section DCA1 mainly oxidizes nitrogen monoxide (NO) in the exhaust gas that has flowed in, and converts the nitrogen oxide (NO) ₂ The downstream discharge section DCA2 mainly desorbs nitrogen dioxide from the adsorbent 24 in the section.
[0047]
Accordingly, the upstream discharge section DCA1 responsible for oxidation by discharge is formed to have a shorter axial length than the downstream discharge section DCA2 responsible for adsorption and desorption. In other words, of the entire length of the adsorbent 24, the upstream discharge section DCA1 only needs to have a length necessary for oxidizing the NOx that has flowed in, and the remaining discharge section DCA2 is used as the downstream discharge section DCA2. Can be used effectively. However, in some cases, the length of each of the discharge sections DCA1 and DCA2 may be set to be the same. That is, the length of the upstream discharge section DCA1 is set to 50% or less of the entire length (of the casing or the adsorbent), and is preferably set to 10 to 30% of the entire length.
[0048]
Next, the operation of the present embodiment will be described with reference to FIG.
[0049]
FIG. 3A shows a case where the first adsorption unit 12 is used in the adsorption mode to adsorb NOx, and the second adsorption unit 13 is used in the desorption mode to desorb NOx. Exhaust gas from the combustion chamber 5 flows into the first adsorption section 12 via the exhaust manifold 9, the exhaust passage L2 (1), and the first switching valve 11.
[0050]
In the case of the suction mode, only the upstream ground electrode 32 is grounded, so that in the first suction section 12, plasma discharge occurs only in the upstream discharge section DCA1. Nitric oxide, which occupies most of the NOx flowing into the first adsorption section 12, is oxidized by plasma discharge while passing through the upstream discharge section DCA1, and becomes nitrogen dioxide. This nitrogen dioxide moves to the downstream discharge section DCA2 with the flow of the exhaust stream, and is adsorbed by the adsorbent 24 in the downstream discharge section DCA2. Part of the nitrogen dioxide is immediately adsorbed on the adsorbent 24 in the upstream discharge section DCA1. However, since the plasma discharge has an action of desorbing the adsorbed nitrogen dioxide, not much nitrogen dioxide is adsorbed by the adsorbent 24 in the upstream discharge section DCA1. This is because in the adsorbent 24 in the upstream discharge section DCA1, as the amount of adsorbed nitrogen dioxide increases, the amount of desorbed nitrogen dioxide from the adsorbent also increases.
[0051]
The nitrogen dioxide not adsorbed in the upstream discharge section DCA1 is adsorbed by the adsorbent 24 in the downstream discharge section DCA2. Since the downstream side ground electrode 33 is not grounded and no plasma discharge is generated, the desorbing action of nitrogen dioxide does not work, and the flowing nitrogen dioxide is adsorbed by the adsorbent 24. Although depending on the type of the adsorbent, the adsorbent 24 also adsorbs some nitrogen monoxide. The exhaust gas from which NOx has been removed by adsorption is discharged from the second switching valve 14 to the atmosphere via the exhaust passage L2 (2).
[0052]
On the other hand, in FIG. 3A, turning to the second adsorbing section 13 used in the desorption mode, the second adsorbing section 13 that has already adsorbed NOx is connected to the first adsorbing section L1 (1) through the first intake passage L1 (1). Outside air as a desorption gas is supplied via the switching valve 11. In addition, the ground electrodes 32 and 33 of the second suction unit 13 are both grounded, whereby a plasma discharge is generated over the entire area of the suction unit 13. The plasma discharge has an action of desorbing NOx (mainly nitrogen dioxide) adsorbed on the adsorbent 24. The outside air used as the desorbed gas does not substantially contain NOx, and the difference in NOx concentration between the adsorbent 24 and the desorbed gas is large. This NOx concentration difference also contributes to NOx desorption. The NOx desorbed from the adsorbent 24 by the plasma discharge is mixed with the inflowing outside air, flows into the intake passage L1 (2) from the second switching valve 14, and is returned to the combustion chamber 5 from the intake passage L1 (3). Then, in the combustion chamber 5, NOx is decomposed and reduced using the fuel as a reducing agent.
[0053]
Next, as shown in FIG. 3B, when each of the switching valves 11 and 14 and the electrode switch 16 are switched, the first suction unit 12 is used in the desorption mode and the second suction is performed. The unit 13 is used in a suction mode.
[0054]
As described in detail above, according to the present embodiment, the discharge electrodes 30 are provided so as to form the discharge sections DCA1 and DCA2 on the upstream side and the downstream side of the adsorbent 24, respectively. The discharge generation site can be appropriately switched in the suction units 12 and 13. Therefore, the oxidizing function by electric discharge, the adsorbing function, and the desorbing function by electric discharge can be realized in each of the adsorbing sections 12 and 13, and an oxidation catalyst and a discharge device separate from the adsorbing section are not required. Can be formed into a compact overall configuration, and the manufacturing cost of the entire apparatus can be reduced.
[0055]
2. Second embodiment
[0056]
Next, a second embodiment of the present invention will be described with reference to FIG. The feature of this embodiment resides in that a part of the exhaust gas is used as the desorbed gas.
[0057]
The NOx adsorption device 40 according to the present embodiment includes two adsorption units 12 and 13, a high-voltage power supply 15, and a control unit 17, similarly to the NOx adsorption device 10 described in the above embodiment.
[0058]
However, in the present NOx adsorption device 40, the first switching valve 11 is eliminated, and the exhaust gas from the exhaust manifold 9 is supplied from the exhaust passage L2 (1) to the first branch passage L21 and the second branch passage L22, respectively. It has become. Further, one outflow port of the second switching valve 14 is connected in the middle of the intake passage L1 by a recirculation passage L3, and the other outflow port is connected to an exhaust passage L2 (2) that is open to the atmosphere. .
[0059]
A throttle portion 41 is provided in the return passage L3. The throttle section 41 is for restricting the flow rate of the exhaust gas flowing into the reflux passage L3. The throttle section 41 reduces the flow rate of the exhaust gas flowing into the adsorption section used in the desorption mode by the adsorption mode used in the adsorption mode. The flow rate is set to be smaller than the flow rate of the exhaust gas flowing into the section. That is, more exhaust gas flows into the adsorption section used in the adsorption mode to adsorb NOx, and part of the exhaust gas flows into the adsorption section used in the desorption mode to act as a desorption gas. Not limited to the throttle section 41, any member or mechanism that can adjust the flow rate of the exhaust gas flowing into each of the adsorption sections 12, 13 may be used.
[0060]
The structure of the electric circuit is also different from that of the first embodiment. In the present embodiment, only one of the upstream ground electrode 32 and the downstream ground electrode 33 is grounded by the electrode switch 42. That is, in the present embodiment, when used in the adsorption mode, only the upstream ground electrode 32 is grounded to generate plasma discharge only in the upstream discharge section DCA1, and when used in the desorption mode, the downstream ground electrode is used. Only 33 is grounded to generate plasma discharge only in the downstream discharge section DCA2.
[0061]
For example, the double-pole double-throw electrode switch 42 has substantially two built-in single-pole double-throw switches 42A and 42B, and one switch 42A is connected to the ground electrodes 32 and 33 of the first suction unit 12. And the other switch 42 </ b> B is connected to the ground electrodes 32 and 33 of the second suction unit 13. In one switch 42A, the common contact is grounded, the make contact is connected to the downstream ground electrode 33, and the break contact is connected to the upstream ground electrode 32. The other switch 42B is similar in that the common contact is grounded, but the make contact is connected to the upstream ground electrode 32 and the break contact is connected to the downstream ground electrode 33. Therefore, while the discharge is being performed in the upstream discharge section DCA1 of one suction section, the discharge is also generated in the downstream discharge section of the other suction section, and both discharge sections DCA1 and DCA2 are both in the same suction section. It does not discharge.
[0062]
The exhaust gas from which NOx has been removed by the adsorption unit used in the adsorption mode is discharged into the atmosphere via the exhaust passage L2 (2). NOx desorbed from the adsorption section used in the desorption mode is mixed with the exhaust gas used as the desorption gas, returned to the combustion chamber 5 via the intake passage L1, and reduced.
[0063]
The process in the case of using in the adsorption mode will be described. As in the above embodiment, nitrogen dioxide is generated by discharging the upstream discharge section DCA1, and the generated nitrogen dioxide is mainly used as the adsorbent 24 in the downstream discharge section DCA2. To be absorbed.
[0064]
When used in the desorption mode, exhaust gas is used as the desorption gas. However, the flow rate of the exhaust gas used as the desorption gas is limited by the throttle section 41, and is smaller than the flow rate flowing into the adsorption section in the adsorption mode. In the desorption mode, discharge occurs only in the downstream discharge section DCA2. Here, even when the discharge is performed while the exhaust gas is flowing, the desorption action by the plasma discharge works, and the adsorbed NOx is desorbed from the adsorbent 24. This is because the adsorbent 24 in the downstream discharge section DCA2 has already adsorbed a large amount of NOx, so that the amount of desorption by discharge exceeds the amount of new adsorption by discharge. As the desorption proceeds and the amount of NOx adsorbed on the adsorbent 24 decreases, the desorption amount due to the discharge gradually decreases and eventually reaches an equilibrium state. It is considered that the equilibrium concentration in this case is lower than the equilibrium concentration of the downstream discharge section DCA2 in the adsorption mode at least by the desorption effect due to the plasma discharge, and only by the equilibrium concentration difference between the two. Is desorbed.
[0065]
In the present embodiment configured as described above, the same effects as in the first embodiment can be obtained. In addition, since the exhaust gas is used as the desorbing gas, it is possible to prevent the temperature of the adsorbing portions 12 and 13 from decreasing, and to exhibit a higher desorbing effect than when the temperature of the desorbing gas is low. In addition, since the temperature change of each of the suction portions 12 and 13 can be suppressed, deterioration or damage due to the temperature change can be prevented, and the life of the suction portions 12 and 13 can be extended.
[0066]
3. Third embodiment
[0067]
FIG. 5 shows a third embodiment of the present invention. The feature of this embodiment is that outside air is used as the desorbed gas, and the desorbed gas containing NOx is returned to the middle of the intake passage L1 and recirculated into the combustion chamber 5.
[0068]
That is, the NOx adsorption device 10 according to the present embodiment employs the same configuration as that described in the first embodiment, but the outside air as the desorbed gas is supplied to an outside air introduction passage L4 different from the intake passage L1. The mixed gas of NOx and the outside air desorbed from the adsorbing section flows through the recirculation passage L3 into the intake passage L1 and is returned to the combustion chamber 5 through the flow path. ing.
[0069]
It should be noted that those skilled in the art can make various additions and changes within the scope of the present invention described in each embodiment. For example, those skilled in the art can appropriately combine the above embodiments.
[0070]
For example, a configuration in which a conventional reduction catalyst, a three-way catalyst, and the like are further added to the NOx adsorption device of the present invention is also possible.
[0071]
Further, the present invention can be applied not only to engines for passenger cars but also to various engines such as engines for construction machines, engines for ships, engines for agricultural machines, and engines for power generation.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of a NOx purification system according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view illustrating a structure of each suction unit.
3A and 3B are explanatory diagrams illustrating a switching operation of each adsorption unit, wherein FIG. 3A illustrates a state where NOx is adsorbed by a first adsorption unit and NOx is desorbed by a second adsorption unit, and FIG. Shows a state in which NOx is desorbed and NOx is adsorbed by the second adsorption section.
FIG. 4 is an overall configuration diagram of a NOx purification system according to a second embodiment of the present invention.
FIG. 5 is an overall configuration diagram of a NOx adsorption device according to a third embodiment of the present invention.
[Explanation of symbols]
1 engine
2 cylinder
5 Combustion chamber
8 Intake manifold
9 Exhaust manifold
10 NOx adsorption device
11 1st switching valve
12 First suction unit
13 Second suction unit
14 Second switching valve
15 High voltage power supply
16 Electrode selector switch
17 Control part
21 Casing
22 Inlet
23 Outflow
24 Adsorbent
30 Discharge electrode
31 High voltage electrode
32 upstream ground electrode
33 Downstream ground electrode
34 insulation
40 NOx adsorption device
41 Aperture
42 Electrode changeover switch
L1 intake passage
L2 exhaust passage
L3 return path
L4 Outside air introduction passage
L21 1st branch passage
L22 Second branch passage
DCA1 Upstream discharge section
DCA2 Downstream discharge section

Claims (4)

An adsorbent (24) for adsorbing NOx;
A first discharge unit (1, 32) provided on one side of the adsorbent (24) for oxidizing NOx;
A second discharge unit (1, 33) provided on the other side of the adsorbent (24) for desorbing NOx adsorbed on the adsorbent (24). Suction device. A control unit (17) for selecting and discharging one or both of the first discharge unit (1, 32) and the second discharge unit (1, 33);
The control unit (17) discharges from the first discharging unit (1, 32) to adsorb NOx on the adsorbent (24) when used in the adsorption mode, and when used in the desorption mode. A NOx adsorbing device for discharging the NOx adsorbed to the adsorbent (24) by discharging at least from the second discharge section (1, 33). A NOx adsorption device (10, 40);
Recirculation means (L1, L3) for recirculating NOx released from the NOx adsorption device (10, 40) to the combustion chamber (5) of the engine (1);
The NOx adsorption devices (10, 40)
An adsorbent (24) for adsorbing NOx;
A first discharge unit (1, 32) provided on one side of the adsorbent (24) for oxidizing NOx;
A second discharge unit (1, 33) provided on the other side of the adsorbent (24) for desorbing NOx adsorbed by the adsorbent (24). NOx purification system. 4. The recirculation means (L <b> 1, L <b> 3) recirculates NOx desorbed from the adsorbent to the combustion chamber using one of outside air and exhaust gas from the engine. 5. NOx purification system.

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