JP2004169665A - Exhaust emission control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To use anion clathrate crystal as oxidation catalyst under a state where combustion gas is continuously introduced. <P>SOLUTION: Exhaust passages 2A and 2B for exhausting combustion gas are provided with a catalyst apparatus 4 constituted of catalyst carriers 6A-6E including the anion clathrate crystal 7. The anion clathrate crystal 7 is provided with a microwave generator 10 for radiating micro wave to the anion clathrate crystal 7, and temperature control means 16 and 20 control temperature of the catalyst apparatus 4 to a regeneration temperature zone where active oxygen is regenerated in a crystal lattice of the anion clathrate crystal 7. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an exhaust purification system for purifying combustion gas exhausted from an engine used as a power source of a power generator, a ship, a vehicle, or the like, or a boiler (hereinafter referred to as an engine) provided in a power plant, an industrial plant, or the like. Regarding the device, in particular, the reactive oxygen species (O₂ ⁻Ion radical and O⁻Anion inclusion crystals (12CaO · 7Al) that contain high concentrations of ion radicals (hereinafter simply referred to as active oxygen)₂O₃Compound) as a catalyst in an exhaust gas purification device.
[0002]
[Prior art]
In recent years, attention has been focused on anion clathrate crystals capable of generating a very large amount of active oxygen. The anion clathrate crystal has a cage-like crystal lattice structure (cage) composed of Ca, Al and O, and encloses active oxygen in this crystal lattice. In addition, the anion clathrate crystal has a characteristic of releasing active oxygen wrapped in the crystal lattice in a temperature range of 650 ° C. or more, and regenerating active oxygen in the crystal lattice in a temperature range of about 500 ° C. is there.
[0003]
Patent Literature 1 discloses a method for producing an anion clathrate crystal having such characteristics, and also mentions a suitable use thereof. An application of the anion clathrate crystal disclosed in Patent Document 1 is an oxidation catalyst, which utilizes the oxidizing action of active oxygen.
[0004]
[Patent Document 1]
JP-A-2002-3218
[0005]
[Problems to be solved by the invention]
However, although the anion clathrate crystal has a function as an excellent oxidation catalyst, when the anion clathrate crystal is used in an exhaust gas purification device for purifying combustion gas generated in an engine or the like, the anion clathrate crystal is directly placed in the exhaust passage. Sufficient effects cannot be obtained simply by arranging inclusion crystals. Since the combustion gas is continuously exhausted in an engine or the like, the exhaust purification device is required to have a continuous purification ability. However, the anion clathrate crystal oxidizes harmful substances [CO, HC, PM (particulate matter) etc.] in the combustion gas by releasing active oxygen wrapped in the crystal lattice, When all the active oxygen in the lattice is released, the oxidizing ability is lost, and the lattice no longer functions as an exhaust gas purification device.
[0006]
Therefore, in a situation in which the combustion gas is continuously introduced, such as an exhaust gas purification device provided in an exhaust passage of an engine or the like, some device for maintaining or recovering the function of the anion clathrate crystal as an oxidation catalyst is used. Is required.
The present invention has been made in view of such a problem, and an object of the present invention is to provide an exhaust gas purification device that can use an anion clathrate crystal as an oxidation catalyst in a situation where combustion gas is continuously introduced. And
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the first exhaust purification device of the present invention is provided with a catalyst device comprising a catalyst carrier containing an anion inclusion crystal in an exhaust passage for exhausting combustion gas. A microwave generator for irradiating microwaves to the anion clathrate crystal is provided, and the temperature of the catalyst device is controlled to a regeneration temperature range in which active oxygen is regenerated in the crystal lattice of the anion clathrate crystal by the temperature control means. It is characterized by doing so.
[0008]
According to this, active oxygen in a cage (crystal lattice) is vibrated by microwave irradiation, the cage is expanded by frictional heat between the active oxygen and the cage, and active oxygen is released from the cage to purify combustion gas. be able to. In addition, since the catalyst device is controlled to the regeneration temperature range by the temperature control means, when the release proceeds and the active oxygen in the anion clathrate decreases, the microwave irradiation is stopped to activate the catalyst in the crystal lattice. Since the oxygen is regenerated, it can be continuously used without losing the function of the anion clathrate as an oxidation catalyst even in a situation where the combustion gas is continuously introduced. In addition, by using a catalyst carrier containing not only the anion clathrate crystal itself but also the anion clathrate crystal, during the regeneration of the active oxygen, the anion clathrate crystal can cause another composition of the catalyst carrier to purify the combustion gas. Therefore, purification of the combustion gas can be performed continuously.
[0009]
When the temperature of the combustion gas is high and the catalyst device exceeds the regeneration temperature range in a natural state, means for forcibly lowering the catalyst temperature to the regeneration temperature range may be provided as the temperature control means. Conversely, when the temperature of the combustion gas is low and the catalyst device is below the regeneration temperature range in a natural state, a means for forcibly increasing the catalyst temperature to the regeneration temperature range may be provided as a temperature control means.
[0010]
As means for forcibly reducing the catalyst temperature, fresh air introduction means for introducing fresh air into the exhaust passage, cooling the catalyst device with the fresh air, and lowering the temperature of the catalyst device to the regeneration temperature range is preferable. The introduction of fresh air lowers the temperature of the combustion gas to cool the catalyst device. In addition, steam in the combustion gas is converted into OH by reaction with active oxygen.⁻To reduce free oxygen, which hinders the regeneration of active oxygen in the anion clathrate crystal.However, fresh air has a smaller amount of steam than combustion gas, so the introduction of fresh air reduces the partial pressure of steam. As a result, the regeneration of active oxygen in the anion inclusion crystal can be promoted.
[0011]
As means for forcibly raising the temperature of the catalyst, heating means for heating the combustion gas introduced into the catalyst device to raise the temperature of the catalyst device to the regeneration temperature range, or heating the catalyst device itself, Heating means for raising the temperature to the regeneration temperature range is preferred. By providing such a heating means, even when the temperature of the combustion gas is low, it can function as an oxidation catalyst for anion inclusion crystals. More preferably, the above-described heating means is provided, and the catalyst device is surrounded by a heat insulating material to keep the temperature.
[0012]
In order to achieve the above object, the second exhaust gas purification apparatus of the present invention is provided with a catalyst device comprising a catalyst carrier containing an anion inclusion crystal in an exhaust passage for exhausting combustion gas. A microwave generator for irradiating microwaves to the anion clathrate crystal is provided, and a plasma generator is provided on the upstream side of the catalyst device, and the operating state of the microwave generator and the plasma generator is controlled by the control means by the catalyst. It is characterized in that control is performed according to the temperature of the device.
[0013]
Since the release rate of active oxygen from the anion clathrate crystal and the regeneration rate of active oxygen in the crystal change with the temperature of the catalyst device, the operating state of the microwave generator is changed according to the temperature of the catalyst device as described above. By controlling, the amount of active oxygen released from the anion clathrate crystal can be adjusted appropriately. Further, according to the plasma generator, active oxygen can be generated in the air by plasma discharge, and therefore, by controlling the operation state of the plasma generator according to the temperature of the catalyst device, it is possible to generate the active oxygen from the anion clathrate crystal. It is possible to compensate for a decrease in the amount of active oxygen released, and to suppress a decrease in the purification efficiency of the combustion gas.
[0014]
As the control method by the control means, specifically, the following control method can be adopted. First, the temperature of the combustion gas upstream of the catalyst device is detected by a temperature sensor. Then, based on the detected information, when the combustion gas temperature is lower than the first predetermined temperature which is the lower limit of the active oxygen release temperature range of the anion clathrate crystal, the microwave generator is controlled. When the combustion gas temperature is lower than the first predetermined temperature and lower than the second predetermined temperature which is the lower limit of the regeneration temperature range of the anion clathrate crystal, the plasma generator is further controlled.
[0015]
When the combustion gas temperature is equal to or higher than the first predetermined temperature, active oxygen is spontaneously released from the anion clathrate regardless of the microwave generator, and the combustion gas is purified. When the temperature is lower than the first predetermined temperature, by controlling the microwave generator, active oxygen can be forcibly released from the inside of the anion clathrate crystal to purify the combustion gas. Further, when the temperature is lower than the second predetermined temperature, by controlling the plasma generator, active oxygen can be generated by plasma discharge to purify the combustion gas, and the amount of active oxygen released from the anion clathrate crystal decreases. Can be supplemented.
[0016]
In this case, more preferably, when the combustion gas temperature is lower than the second predetermined temperature, the microwave generator is controlled so as to suppress the release of active oxygen from the anion clathrate crystal. Thereby, the function of the anion clathrate crystal as an oxidation catalyst can be maintained. As a control method for suppressing the release of active oxygen from the anion clathrate crystal, a control method in which the microwave irradiation time is shortened and the microwave irradiation is performed intermittently, or a current or voltage is controlled. And controlling at least one of them to suppress the wattage.
[0017]
In the first exhaust gas purification device and the second exhaust gas purification device described above, preferably, the catalyst device is composed of a plurality of catalyst carriers divided in the flow direction of the combustion gas, and the catalyst device is provided upstream of each catalyst carrier. An anion clathrate crystal is arranged for each. Active oxygen has high reactivity, so active oxygen will not reach if it is far from the anion clathrate crystal.However, a plurality of catalyst carriers are arranged in the flow direction of the combustion gas, and an anion clathrate crystal is included on each upstream side By doing so, active oxygen can be supplied to the entire inside of the catalyst device, and high purification efficiency can be obtained.
[0018]
In this case, more preferably, in the catalyst device, the upstream-side catalyst carrier is of a type without plugging, and the downstreammost catalyst carrier is of a type with plugging. By making the lowermost catalyst carrier a plugged type, PM that could not be purified by the upstream catalyst carrier can be finally collected and purified by active oxygen.
It is also preferable to dispose electromagnetic shielding members that shield electromagnetic waves and allow the passage of combustion gas, respectively, on the upstream side of the most upstream catalyst carrier and on the downstream side of the most downstream catalyst carrier. According to this, it is possible to prevent the electromagnetic wave from leaking outside without obstructing the flow of the combustion gas.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(A) First embodiment
FIG. 1 is a diagram showing a system configuration of the exhaust gas purification device according to the first embodiment of the present invention. As shown in FIG. 1, the exhaust gas purification device according to the present embodiment includes a catalyst device 4 disposed in exhaust pipes 2A and 2B. The exhaust pipes 2A and 2B are connected to an exhaust port (not shown) of an engine or the like, and serve as a passage (exhaust passage) for combustion gas (hereinafter, referred to as exhaust gas) exhausted from the engine or the like. In the present embodiment, it is assumed that the temperature of the exhaust gas is relatively low and the temperature when flowing into the catalyst device 4 is less than 500 ° C. The catalyst device 4 has a cylindrical metal case 8 interposed in the middle of the exhaust pipes 2A and 2B. In the case 8, a plurality of catalyst carriers 6A to 6E are provided along the flow direction of the exhaust gas. Are located. On the upstream side of each of the catalyst supports 6A to 6E, an anion clathrate crystal (12CaO.7Al₂O₃Compound 7) is provided. Of these catalyst carriers 6A to 6E, the most downstream catalyst carrier 6E is of a plugged type, and the other upstream catalyst carriers 6A to 6D are of a non-plugged type. Hereinafter, only when each catalyst carrier is distinguished from the others, it is indicated by reference numerals 6A to 6E, and when each catalyst carrier is not distinguished, it is simply indicated by reference numeral 6.
[0020]
Further, the catalyst device 4 includes a magnetron 10 that generates a microwave by applying a high voltage, and a high voltage generator 11 that applies a high voltage to the magnetron 10. The magnetron 10 and the high-voltage generator 11 constitute a microwave generator according to the present invention. The magnetron 10 is provided separately from the case 8 in order to prevent a decrease in efficiency due to an increase in temperature, and the magnetron 10 and the case 8 are connected by a waveguide 9 for guiding microwaves. The connection portion of the waveguide 9 to the case 8 is provided close to the surface of each catalyst carrier 6 on which the anion inclusion crystal layer 7 is provided. A punching metal (electromagnetic shielding member) 5 is provided on the upstream side of the most upstream catalyst carrier 6A and on the downstream side of the most downstream catalyst carrier 6E so as to sandwich the catalyst carrier 6 in the case 8. I have. The punching metal 5 is provided with a large number of small-diameter holes through which electromagnetic waves cannot pass. The electromagnetic waves are shielded by the punching metal 5, while the exhaust gas flows through the holes of the punching metal 5 into the case 8. It has become.
[0021]
Further, a heating device 16 such as a heater is attached to the exhaust pipe 2A on the upstream side. The heating device 16 indirectly raises the internal temperature of the catalyst device 4 by heating and increasing the temperature of the exhaust gas flowing through the exhaust pipe 2A.
The control of the high-voltage generator 11 and the heating device 16 is performed by the control device 20 constituting the exhaust gas purification device according to the present embodiment. FIG. 2A is a time chart showing the control contents of the high voltage generator 11 by the control device 20. As shown in FIG. 2A, the control device 20 alternately repeats the application (ON) of the voltage to the magnetron 10 by the high voltage generator 11 and the stop (OFF) of the application of the voltage. The magnetron 10 generates the microwave by applying the voltage, and the magnetron 10 stops generating the microwave by stopping the application of the voltage.
[0022]
FIG. 2B is a graph showing a temperature change of the internal temperature of the catalyst carrier 6 and the anion clathrate crystal layer 7 (hereinafter referred to as catalyst temperature). The control device 20 controls the heating device 16 to adjust the temperature of the exhaust gas flowing into the case 8 so that the catalyst temperature is always around 500 ° C. In a steady state where changes in the flow rate and temperature of the exhaust gas are small, it can be considered that the internal temperatures of the catalyst support 6 and the anion inclusion crystal layer 7 are substantially equal to the temperature in the case 8. Although not shown in FIG. 1, when the temperature of the exhaust gas is not constant but is changing, a temperature sensor is provided upstream of the heating device 16, and the temperature of the heating device 16 is changed according to the temperature of the exhaust gas. The heating temperature can be adjusted. In the present embodiment, the heating device 16 and the control device 20 constitute a temperature control unit according to the present invention.
[0023]
When the above control is performed, the crystals in the anion clathrate crystal 7 show the following reaction. FIG. 3 is a diagram schematically showing a reaction represented by the anion clathrate crystal 7. First, as an initial state, the anion clathrate 7 contains active oxygen (O 2) in a crystal lattice (cage).₂ ⁻). At this time, when the voltage is applied to operate the magnetron 10 to generate a microwave, the microwave is introduced into the case 8 through the waveguide 9, and the microwave introduced into the case 8 is converted into a metal case. The light travels through the case 8 while being reflected by the inner surface 8 and the punching metal 5. When the microwave is applied to the anion clathrate crystal 7, the active oxygen in the cage vibrates according to the change in the polarity of the microwave, and the electric energy of the microwave is consumed for the vibration of the active oxygen. Then, friction occurs between the active oxygen and the cage due to the vibration of the active oxygen, and the cage expands due to the frictional heat.
[0024]
Since the thermal expansion of the cage allows oxygen molecules to pass through the bottleneck of the cage, a high voltage is applied to the magnetron 10 by the high voltage generator 11 while the microwave is irradiated on the anion clathrate 7 Active oxygen is continuously released from the anion clathrate crystal 7 to the outside. The released active oxygen reacts with harmful substances (CO, HC, PM, etc.) in the exhaust gas. For example, when reacting with PM, PM is oxidized and burned, and CO_XConvert to Alternatively, NO in the exhaust gas generated by combustion is oxidized to NO.₂And this NO₂Reacts indirectly with harmful substances as an oxidant.
[0025]
The release of active oxygen from the anion clathrate crystal 7 is stopped when the generation of microwaves by the magnetron 10 is stopped. When the temperature of the anion clathrate crystal 7 is maintained at around 500 ° C., the anion clathrate crystal 7 takes in oxygen from the outside and regenerates active oxygen in the crystal lattice.
In the present embodiment, as shown in FIG. 2B, the catalyst temperature is always kept in a temperature range around 500 ° C. (regeneration temperature range) in which active oxygen is regenerated in the crystal lattice of the anion clathrate crystal 7. I have. Therefore, as shown in FIG. 2A, the application of the voltage is repeated ON / OFF to periodically irradiate the microwave to the anion clathrate crystal 7 so that the active oxygen from the anion clathrate crystal 7 at the time of ON is turned on. The discharge and the regeneration of the active oxygen in the anion clathrate crystal 7 at the time of OFF are alternately repeated.
[0026]
Since the number of crystal lattices of the anion clathrate 7 is finite, the active oxygen in the anion clathrate 7 is saturated when the catalyst temperature is maintained in the regeneration temperature range around 500 ° C. Similarly, if the microwave irradiation continues, the active oxygen in the anion clathrate crystal 7 is eventually lost. Therefore, during the ON time (microwave generation time) T2 during which the control device 20 applies the voltage to the high voltage generator 11, the release of active oxygen from the anion clathrate crystal 7 starts with the irradiation of the microwave from the magnetron 10. The time is set in consideration of the time until active oxygen in the anion clathrate crystal 7 is lost. The ON / OFF control cycle (microwave generation ON / OFF cycle) T1 of the high voltage generator 11 by the control device 20 is the ON time T2 and the voltage in the anion clathrate crystal after stopping the application of the voltage. The time is set in consideration of the time until active oxygen becomes saturated.
[0027]
With the above configuration, according to the exhaust gas purification apparatus of the present embodiment, the release of active oxygen from the anion clathrate crystal 7 and the regeneration of active oxygen in the anion clathrate crystal 7 are alternately repeated. In addition, even when exhaust gas is continuously introduced, the anion clathrate 7 can be continuously used without losing its function as an oxidation catalyst. Further, by providing the anion clathrate crystal 7 as a part of the catalyst carrier 6, the catalyst carrier 6 can purify the exhaust gas during regeneration of the active oxygen by the anion clathrate crystal 7. Purification of exhaust gas can be continuously performed regardless of the state of release / regeneration of the crystal 7.
[0028]
Further, active oxygen has high reactivity, so that the active oxygen becomes more difficult to reach as the distance from the anion clathrate crystal 7 increases, but a plurality of anion clathrate crystals 7 are arranged in the flow direction of the combustion gas as in the present embodiment. By doing so, active oxygen can be supplied to the entire inside of the case 8. Further, an anion clathrate crystal 7 is arranged on the upstream side of each of the divided catalyst carriers 6, and a waveguide 9 is connected at each location to guide microwaves, thereby converting the microwaves into anion clathrate crystals. 7 can be efficiently irradiated, and the efficiency of heating the anion clathrate crystal 7 by microwaves can be increased. Furthermore, by using the plugged type of the lowermost catalyst carrier 6E as in the present embodiment, PM that could not be purified by the upper catalyst carriers 6A to 6D is finally collected by the lowermost catalyst carrier 6E. Then, it can be oxidized by the active oxygen supplied from the anion clathrate crystal 7. Therefore, according to the exhaust gas purification apparatus of the present embodiment, the reaction efficiency between the harmful substances such as PM flowing into the case 8 and the active oxygen can be increased, and high purification efficiency can be obtained.
[0029]
In the present embodiment, the anion clathrate crystal 7 is indirectly heated by the heated exhaust gas to raise the temperature. However, a heating unit such as a heater is provided in the catalyst device 4 to directly anion clathrate 7. The tangent crystal 7 may be heated. Further, the anion clathrate crystal 7 may be heated by burning the additional fuel on the oxidation catalyst provided upstream of the catalyst device 4 to increase the temperature of the anion clathrate crystal 7.
[0030]
(B) Second embodiment
FIG. 4 is a diagram illustrating a system configuration of an exhaust emission control device according to a second embodiment of the present invention. In the present embodiment, it is assumed that the temperature of the exhaust gas is relatively high, and when the exhaust gas flows into the catalyst device 4 as it is, the catalyst temperature exceeds a regeneration temperature range around 500 ° C.
[0031]
As shown in FIG. 4, in this embodiment, a secondary air introduction pipe 26 is attached to the exhaust pipe 2A on the upstream side. The secondary air introduction pipe 26 has a front end opening inside the exhaust pipe 2 </ b> A, and a rear end connected to the compressor 22. The compressor 22 takes in fresh air (outside air), compresses it, and sends it out to the secondary air introduction pipe 26 as secondary air. An electromagnetic valve 24 is interposed in the middle of the secondary air introduction pipe 26 so that the amount of secondary air introduced from the compressor 22 into the exhaust pipe 2A can be controlled by duty control of the electromagnetic valve 24. It has become.
[0032]
The secondary air introduced into the exhaust pipe 2A from the secondary air introduction pipe 26 is mixed with the exhaust gas and introduced into the catalyst device 4. At this time, the temperature of the mixed gas becomes lower than the temperature of the exhaust gas itself, because the temperature of the secondary air, which is fresh air, is lower than the temperature of the exhaust gas itself. The mixed gas having a lower temperature than the exhaust gas acts as cooling air for cooling the catalyst support 6 and the anion clathrate crystal 7 heated by the exhaust gas. The temperature decrease width of the mixed gas with respect to the exhaust gas can be controlled by the amount of secondary air introduced, and this can be controlled by the duty ratio of the solenoid valve 24.
[0033]
The control of the electromagnetic valve 24 is performed by the control device 30 that constitutes the exhaust gas purification device according to the present embodiment. As in the first embodiment, the control device 30 controls the solenoid valve 24 to adjust the amount of secondary air introduced so that the catalyst temperature is always around 500 ° C., and controls the amount of exhaust gas flowing into the case 8. Adjusting the temperature. Although not shown in FIG. 4, when the temperature of the exhaust gas is not constant but is changing, a temperature sensor is provided upstream of the secondary air introduction pipe 26, and the electromagnetic sensor is provided in accordance with the temperature of the exhaust gas. The duty ratio of the valve 24 can also be adjusted. In the present embodiment, the compressor 22, the electromagnetic valve 24, the secondary air introduction pipe 26, and the control device 30 constitute a temperature control unit according to the present invention. Further, the control device 30 also controls the high voltage generator 14, and as in the first embodiment, the high voltage generator 14 applies a high voltage between the inner and outer electrodes 10 and 12 (ON) and applies a voltage. (OFF) is alternately repeated.
[0034]
With the configuration as described above, according to the exhaust purification device of the present embodiment, the catalyst temperature can be maintained in the regeneration temperature range around 500 ° C. even when the temperature of the exhaust gas is high. Therefore, similarly to the first embodiment, the release of active oxygen from the anion clathrate 7 and the regeneration of active oxygen in the anion clathrate 7 are alternately repeated by ON / OFF control of the high voltage generator 14. Therefore, even when exhaust gas is continuously introduced, the anion clathrate 7 can be continuously used without losing its function as an oxidation catalyst.
[0035]
Further, a large amount of water vapor is contained in the exhaust gas.⁻Is formed, and free oxygen required for regeneration of active oxygen in the anion clathrate crystal 7 is reduced. Therefore, even if the catalyst temperature is simply maintained in the regeneration temperature range, the regeneration of active oxygen may not proceed in the exhaust gas atmosphere. In response to such a fear, according to the exhaust gas purification apparatus of the present embodiment, fresh air (outside air) having a smaller amount of water vapor than the exhaust gas is introduced as the secondary air for cooling. Thereby, the partial pressure of water vapor in the atmosphere surrounding the anion clathrate crystal 7 can be reduced, and the regeneration of active oxygen in the anion clathrate crystal 7 can be promoted. As a method for further reducing the amount of water vapor of fresh air, for example, silica gel (SiO 2) is provided between the compressor 22 and the solenoid valve 24.₂・ 2H₂A drying / dehydrating agent such as O) may be provided.
[0036]
(C) Third embodiment
FIG. 5 is a diagram illustrating a system configuration of an exhaust emission control device according to a third embodiment of the present invention. As shown in FIG. 5, in the present embodiment, a temperature sensor 32 for detecting the temperature of exhaust gas is used instead of having a temperature control means such as a heating device or a secondary air introduction device as in the first and second embodiments. Is attached to the exhaust pipe 2A on the upstream side.
[0037]
In the present embodiment, the catalyst support 6 and the anion clathrate crystal 7 are arranged in four sets along the flow direction of the exhaust gas, and the first set of catalyst devices is formed by the two sets on the upstream side and the two sets on the downstream side. The sets form a second group of catalyst devices. A pair of upper and lower punching metals 5 and 5 are provided so as to sandwich the upstream first group of catalyst devices. Similarly, a pair of upper and downstream punching metals 5 and 5 are provided so as to sandwich the downstream second group of catalyst devices. 5 are provided. The connection between the waveguide 9 and the case 8 is provided between the respective punching metals 5 and 5. As for the catalyst carriers 6 belonging to each group, only the most downstream catalyst carrier 6E of the second group is of the plugged type, and the other catalyst carriers 6A, 6B, 6D are of the unplugged type.
[0038]
An inner electrode (anode) 12 having a large number of discharge plates is arranged upstream of the catalyst devices of each group, that is, upstream of the most upstream punching metal 5 and between the two central punching metals 5 and 5, respectively. I have. A cylindrical outer electrode (cathode) 13 is disposed on the inner peripheral surface of the case 8 so as to surround each inner electrode 12. A high voltage generator 14 is connected to the inner electrode 12 and the outer electrode 13. When a high voltage is applied between the inner and outer electrodes 12 and 13 by the high voltage generator 14, a discharge occurs between the inner and outer electrodes 12 and 13, and the energy of the discharge causes the exhaust gas in the case 8 to be in a plasma state and active oxygen Is generated. Although microwaves are introduced from the waveguide 9 into the case 8, the inner and outer electrodes 12, 13 are arranged outside the space defined by the punching metals 5, 5, so that the inner and outer electrodes 12, The discharge between 13 is not affected by the microwave.
[0039]
A high voltage generator (hereinafter, a high voltage generator for plasma) 14 is controlled by a control device 40 together with a high voltage generator (hereinafter, a high voltage generator for microwave) 11 for applying a high voltage to the magnetron 10. Is done. The control device 40 estimates the internal temperature (catalyst temperature) of the catalyst device of each group, more specifically, the internal temperature of the anion clathrate crystal 7 from the temperature of the exhaust gas detected by the temperature sensor 32, and according to the catalyst temperature. The operating state of each of the high voltage generators 11 and 14 is controlled.
[0040]
For example, it is assumed that the temperature change range of the exhaust gas is wide and the catalyst temperature changes from a temperature range higher than the regeneration temperature range around 500 ° C. to a temperature range lower than the regeneration temperature range. When the catalyst temperature is in the regeneration temperature range, specifically, it is lower than the first predetermined temperature which is the lower limit of the release temperature range, and is the second predetermined temperature which is the lower limit of the regeneration temperature range (the second predetermined temperature <the first predetermined temperature). When the temperature is equal to or higher than the temperature, since the active oxygen is being regenerated in the anion clathrate 7, the control device 40 sets the microwave generation time T2 with respect to the ON / OFF cycle T1 of the microwave high-voltage generator 11 to T1. Is set high to promote the release of active oxygen.
[0041]
On the other hand, when the catalyst temperature is lower than the second predetermined temperature, the regeneration rate of active oxygen in the anion clathrate crystal 7 is greatly reduced. Therefore, the control device 40 sets a small ratio of the microwave generation time T2 to the ON / OFF cycle T1 of the microwave high voltage generator 11 so that all the active oxygen in the anion clathrate crystal is not consumed. Thus, the release of active oxygen from the anion clathrate crystal is suppressed. At the same time, the high-voltage generator for plasma 14 is operated to apply a high voltage between the inner and outer electrodes 12 and 13, thereby turning the exhaust gas in the case 8 into a plasma state and generating active oxygen.
[0042]
When the catalyst temperature is higher than the first predetermined temperature and equal to or higher than 650 ° C., the anion clathrate crystal 7 naturally releases active oxygen without irradiation with microwaves. Therefore, the control device 40 stops the application of the high voltage to the magnetron by the high voltage generator 14 and leaves the release of active oxygen from the anion clathrate crystal 7 to the spontaneous release accompanying the temperature rise.
[0043]
By controlling the operating state of the microwave high-voltage generator 11 in accordance with the temperature of the exhaust gas, the amount of active oxygen released from the anion clathrate crystal 7 can be controlled. The function as an oxidation catalyst of the anion clathrate crystal 7 can be maintained even under a situation where the value of the anion inclusion crystal 7 greatly changes. In addition, the operating state of the high voltage generator for plasma 14 is controlled in accordance with the temperature of the exhaust gas, and active oxygen is generated by plasma discharge, thereby compensating for a decrease in the amount of active oxygen released from the anion clathrate crystal 7. Therefore, it is possible to suppress a decrease in exhaust gas purification efficiency.
[0044]
Here, two threshold values (a first predetermined temperature and a second predetermined temperature) are set, and when the catalyst temperature is in the regeneration temperature range, in the lower temperature range, and in the higher temperature range. Although the cases are divided into three cases, the operating state of each of the high voltage generators 11 and 14 may be controlled more finely by dividing the temperature range of the catalyst temperature into smaller cases. In addition, when the device that discharges the exhaust gas is a vehicle engine, the catalyst temperature can be estimated based on the history of the engine torque and the engine rotation speed from the start of operation.
[0045]
In this embodiment, the amount of active oxygen released from the anion clathrate crystal 7 is controlled by the microwave irradiation time. However, the control of the wattage supplied to the magnetron 10, that is, at least one of the current and the voltage is controlled. By controlling, the amount of active oxygen released from the anion clathrate crystal 7 can also be controlled.
(D) Other
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and can be implemented with various modifications without departing from the spirit of the present invention.
[0046]
For example, the operation method of the exhaust gas purification device according to the first and second embodiments is not limited to the above example. For example, instead of heating the exhaust gas or introducing secondary air so that the catalyst temperature is always in the regeneration temperature range around 500 ° C., heating or introducing secondary air should be performed when the active oxygen is released by discharge. The exhaust gas may be heated or the secondary air may be introduced only when the active oxygen is regenerated after the discharge is stopped. At the end of the previous operation, active oxygen was stored in the anion clathrate crystal. After the operation was started, the active oxygen stored in the anion clathrate crystal was used. An operation method in which the catalyst temperature is raised or lowered to a nearby regeneration temperature range to regenerate active oxygen in the anion clathrate crystal is also possible.
[0047]
【The invention's effect】
As described above in detail, according to the exhaust gas purification apparatus (first exhaust gas purification apparatus) of the present invention, active oxygen is released from within the crystal lattice of the anion clathrate crystal by microwave irradiation to purify the combustion gas. When the active oxygen in the crystal lattice decreases as the release progresses and the irradiation of microwaves is stopped, the active oxygen is regenerated in the crystal lattice by stopping the microwave irradiation, so that the combustion gas is continuously introduced. There is an advantage that it can be continuously used without losing the function of the anion clathrate crystal as an oxidation catalyst even below.
[0048]
According to the exhaust gas purification device (second exhaust gas purification device) of the present invention, the amount of active oxygen released from the anion clathrate crystal can be reduced by controlling the operation state of the microwave generator in accordance with the temperature of the catalyst device. It can be adjusted appropriately, and by controlling the operating state of the plasma generator in accordance with the temperature of the catalyst device, it is possible to compensate for the decrease in the amount of active oxygen released from the anion clathrate crystal, It is possible to suppress a decrease in purification efficiency.
[Brief description of the drawings]
FIG. 1 is a diagram showing a system configuration of an exhaust gas purification device according to a first embodiment of the present invention.
2 (a) is a time chart showing control contents of a high voltage generating circuit by the control device of FIG. 1, and FIG. 2 (b) is a graph showing a change in catalyst temperature.
FIG. 3 is a diagram schematically showing a reaction exhibited by an anion clathrate crystal.
FIG. 4 is a diagram showing a system configuration of an exhaust gas purification device according to a second embodiment of the present invention.
FIG. 5 is a diagram showing a system configuration of an exhaust gas purification device according to a third embodiment of the present invention.
[Explanation of symbols]
2A, 2B exhaust pipe
4 Catalyst device
5 punching metal
6,6A-6E catalyst carrier
7 Anion clathrate crystals
8 cases
9 Waveguide
10 magnetron
11 High voltage generator
12. Inner electrode (anode)
13 outer electrode (cathode)
14 High voltage generator
16 Heating device
20, 30, 40 control device
22 Compressor
24 Solenoid valve
26 Secondary air inlet pipe
32 temperature sensor

Claims (7)

A catalyst device provided in an exhaust passage for exhausting combustion gas, comprising a catalyst carrier containing anion inclusion crystals;
A microwave generator for irradiating the anion clathrate with microwaves,
An exhaust gas purification apparatus comprising: a temperature control means for controlling a temperature of the catalyst device in a regeneration temperature range in which active oxygen is regenerated in a crystal lattice of the anion clathrate crystal. A catalyst device provided in an exhaust passage for exhausting combustion gas, comprising a catalyst carrier containing anion inclusion crystals;
A microwave generator for irradiating the anion clathrate with microwaves,
A plasma generator provided on the upstream side of the catalyst device,
An exhaust emission control device comprising: a control unit that controls an operation state of the microwave generation device and the plasma generation device according to a temperature of the catalyst device. The control means includes a temperature sensor that detects a temperature of a combustion gas upstream of the catalyst device,
The control means controls the microwave generator based on the detection information of the temperature sensor when the combustion gas temperature is lower than a first predetermined temperature which is the lower limit of the active oxygen release temperature range of the anion clathrate crystal. And controlling the plasma generator when the combustion gas temperature is lower than the first predetermined temperature and lower than a second predetermined temperature which is the lower limit of the regeneration temperature range of the anion clathrate crystal. An exhaust purification device according to claim 2. The control means controls the microwave generator so as to suppress the release of active oxygen from the anion clathrate when the combustion gas temperature is lower than the second predetermined temperature. Item 4. An exhaust gas purification apparatus according to Item 3. 3. The catalyst device according to claim 1, wherein the catalyst device includes a plurality of catalyst carriers divided in a flow direction of the combustion gas, and an anion clathrate crystal is disposed on an upstream side of each catalyst carrier. 4. Exhaust purification equipment. 6. The exhaust gas purifying apparatus according to claim 5, wherein in the catalyst device, an upstream-side catalyst carrier is a non-sealing type, and a most downstream catalyst carrier is a sealing type. The catalyst device according to claim 1, further comprising an electromagnetic shielding member that shields electromagnetic waves and allows combustion gas to pass therethrough, on an upstream side of the most upstream catalyst carrier and on a downstream side of the most downstream catalyst carrier. An exhaust gas purification apparatus according to claim 5.

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