JP2011085060A - Device and method for controlling exhaust emission in internal combustion engine - Google Patents

Abstract

[PROBLEMS] To prevent a decrease in purification performance of a catalyst even when a low temperature range where the catalyst is difficult to activate continues for a long time.
A concentrating device concentrates at least a part of harmful components in exhaust from an internal combustion engine. The ozone addition valve 24 converts at least a part of harmful components concentrated by the concentrating device 14 into a highly reactive gas by adding ozone. The exhaust purification catalyst 16 purifies harmful components that are at least partially converted into highly reactive gas by the addition of ozone from the ozone addition valve 24.
[Selection] Figure 1

Description

  The present invention relates to an exhaust gas purification apparatus and method for an internal combustion engine for purifying harmful components in exhaust gas from the internal combustion engine.

  Conventionally, catalysts such as an oxidation catalyst, a reduction catalyst, and a three-way catalyst are used to purify harmful components such as hydrocarbons (HC) and nitrogen oxides (NOx) contained in exhaust gas from an internal combustion engine. . However, in a low temperature range where the catalyst is difficult to activate, such as immediately after the start of the internal combustion engine, hydrocarbons and nitrogen oxides, which are harmful components in the exhaust, are strongly adsorbed on the surface of the catalyst and inhibit the purification reaction of the harmful components ( Adsorption poisoning). For this reason, the catalyst tends to deteriorate the purification performance of harmful components, particularly in a low temperature range.

  In the following Patent Document 1, the HC adsorbent and the NOx adsorbent are provided at a position upstream of the lean NOx catalyst in the exhaust passage of the internal combustion engine. For example, in a low temperature range where the lean NOx catalyst is difficult to activate, such as immediately after starting the internal combustion engine, the HC adsorbent adsorbs HC in the exhaust from the internal combustion engine, and the NOx adsorbent adsorbs NOx in the exhaust from the internal combustion engine. Therefore, a reduction in purification performance due to adsorption of HC and NOx to the lean NOx catalyst is suppressed. After reaching the temperature range where the lean NOx catalyst is activated, HC and NOx adsorbed by the HC adsorbent and the NOx adsorbent are respectively released and purified by the lean NOx catalyst.

JP 2000-345832 A JP 2008-73625 A JP 2000-54833 A JP 2005-105925 A JP 2009-79540 A

  In Patent Document 1, it is possible to adsorb harmful components such as HC and NOx with an adsorbent until the adsorbent reaches a saturated state in a low temperature range where the catalyst is difficult to activate. After reaching, harmful components such as HC and NOx are released without being adsorbed by the adsorbent, and the purification performance is lowered by adsorbing to the catalyst. Therefore, when the low temperature range where the catalyst is difficult to activate continues for a long time, it is difficult to prevent the catalyst purification performance from being lowered.

  An object of the present invention is to prevent a reduction in the purification performance of a catalyst even when a low temperature range in which the catalyst is difficult to activate continues for a long time.

  The exhaust gas purification apparatus and method for an internal combustion engine according to the present invention employs the following means in order to achieve the above-described object.

  An exhaust purification device for an internal combustion engine according to the present invention is an exhaust purification device for an internal combustion engine for purifying harmful components in the exhaust from the internal combustion engine, and at least a part of the harmful components in the exhaust from the internal combustion engine. Concentrating device for concentration, conversion device for converting at least part of harmful components concentrated in the concentrating device into highly reactive gas, and purification of harmful components converted into highly reactive gas by the converting device The exhaust gas purifying catalyst is provided.

  In one embodiment of the present invention, the conversion device is a device that oxidizes at least a part of the harmful component and converts it into a highly reactive gas by adding an oxidizing agent to the harmful component concentrated by the concentrating device. Is preferred. In this aspect, it is preferable that the oxidizing agent is ozone. Furthermore, in this aspect, it is preferable to further include a water electrolysis device that generates ozone added to the harmful components concentrated by the concentration device by electrolysis of water. Furthermore, in this aspect, it is preferable to further include a hydrogen supply device that supplies hydrogen generated together with ozone in the water electrolysis device to the purification device.

  In one aspect of the present invention, the concentration device is preferably a device that concentrates by adsorbing at least a part of harmful components in the exhaust gas from the internal combustion engine with an adsorbent.

  In one embodiment of the present invention, the harmful component in the exhaust gas from the internal combustion engine preferably includes at least one of hydrocarbon and nitrogen oxide.

  An exhaust gas purification method for an internal combustion engine according to the present invention is an exhaust gas purification method for an internal combustion engine for purifying harmful components in the exhaust gas from the internal combustion engine, wherein at least one of the harmful components in the exhaust gas from the internal combustion engine. A process of concentrating a part with a concentrator, a process of converting at least a part of harmful components concentrated with a concentrator into a highly reactive gas with a converter, and a converter with at least a part of the gas being highly reactive The gist is to sequentially perform the process of purifying the converted harmful components with the exhaust purification catalyst.

  According to the present invention, even when a low temperature range where the exhaust purification catalyst is difficult to activate continues for a long time, the adsorption poisoning of the exhaust purification catalyst can be suppressed, and the inflow gas to the exhaust purification catalyst can be reduced to a highly reactive gas. Therefore, it is possible to prevent the exhaust purification catalyst from being deteriorated in purification performance.

1 is a diagram showing a schematic configuration of an exhaust gas purification apparatus for an internal combustion engine according to an embodiment of the present invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of an exhaust gas purification apparatus for an internal combustion engine according to an embodiment of the present invention. An internal combustion engine (engine) 10 generates power by burning fuel in a cylinder. The internal combustion engine 10 here may be a spark ignition engine such as a gasoline engine, or may be a compression ignition engine such as a diesel engine. Exhaust gas after combustion in the internal combustion engine 10 is discharged into the exhaust pipe 12. The exhaust discharged from the internal combustion engine 10 into the exhaust pipe 12 contains harmful components such as hydrocarbons (HC) and nitrogen oxides (NOx). In this embodiment, the exhaust from the internal combustion engine 10 In order to purify harmful components (for example, at least one of hydrocarbons and nitrogen oxides) in the exhaust, an exhaust purification catalyst 16 is provided in the exhaust pipe 12, and further, a concentrating device 14 purifies the exhaust in the exhaust pipe 12. It is provided at a position upstream of the catalyst 16 (position between the internal combustion engine 10 and the exhaust purification catalyst 16).

  The concentration device 14 concentrates at least a part of harmful components in the exhaust from the internal combustion engine 10. An adsorbent 14a is housed in the concentrator 14 and is concentrated by temporarily adsorbing hydrocarbons and nitrogen oxides (or at least a part thereof) in the exhaust gas with the adsorbent 14a. As the adsorbent 14a here, for example, zeolite or the like can be used, but any adsorbent may be used as long as it can adsorb harmful components (HC, NOx) in the exhaust gas.

In the present embodiment, at least a part of the harmful components concentrated by the concentration device 14 is converted into a highly reactive gas. As a conversion device for this purpose, an ozone addition valve 24 is provided at a position upstream of the concentrating device 14 in the exhaust pipe 12 (a position between the internal combustion engine 10 and the concentrating device 14). Ozone (O ₃ ) as an oxidant is injected from the ozone addition valve 24 toward the adsorbent 14a of the concentrator 14 so that it becomes a harmful component adsorbed by the adsorbent 14a (concentrated by the concentrator 14). Ozone is added. Due to the high oxidation activity of ozone, at least a part of the hydrocarbons and nitrogen oxides adsorbed by the adsorbent 14a is oxidized and converted into a highly reactive gas. For example, reactivity is increased by converting olefinic hydrocarbons into aldehydes among hydrocarbons, and nitrogen monoxide (NO) in nitrogen oxides is oxidized and converted into nitrogen dioxide (NO ₂ ). Increases nature. The harmful component which is at least partly converted into highly reactive gas by the addition of ozone is supplied to the exhaust purification catalyst 16 on the downstream side. Note that. The adsorbent 14a may have a function of oxidizing harmful components (HC, NOx), and thus can be efficiently converted into a highly reactive gas when ozone is added.

A water electrolysis device 18 is provided to generate ozone that is added to harmful components adsorbed by the adsorbent 14a (concentrated by the concentration device 14). The water electrolysis device 18 generates ozone by electrolysis of water. During the electrolysis of water, hydrogen (H ₂ ) is also generated along with ozone, and water is decomposed on the anode side separated by the cation exchange membrane to generate ozone, and the cation membrane is formed on the cathode side. Hydrogen gas is generated from the hydrogen ions that have passed. Ozone generated by the water electrolysis device 18 is injected from the ozone addition valve 24 toward the adsorbent 14a through the ozone conduit 20. The water used for electrolysis in the water electrolysis device 18 can be supplied from the outside, or the water in the exhaust can be recovered and supplied.

  The exhaust purification catalyst 16 provided at a position downstream of the concentrating device 14 in the exhaust pipe 12 removes harmful components at least partially converted into highly reactive gas by the ozone (oxidant) added by the ozone addition valve 24. Purify. The exhaust purification catalyst 16 here may be any catalyst that can purify harmful components in the exhaust, such as an oxidation catalyst, a three-way catalyst, a NOx storage reduction catalyst, a selective reduction catalyst, and the like. Can be used. A hydrogen addition valve 26 as a hydrogen supply device is provided at a position in the exhaust pipe 12 downstream of the concentration device 14 and upstream of the exhaust purification catalyst 16 (position between the concentration device 14 and the exhaust purification catalyst 16). ing. Hydrogen generated by the water electrolysis device 18 is injected from the hydrogen addition valve 26 toward the exhaust purification catalyst 16 through the hydrogen conduit 22, so that hydrogen is added to harmful components to be purified by the exhaust purification catalyst 16. Is done.

  For example, when the exhaust purification catalyst 16 is an oxidation catalyst, among the unburned hydrocarbons contained in the exhaust from the internal combustion engine 10, unsaturated hydrocarbons, aromatics, and higher hydrocarbons that are particularly catalyst poisoning components (Or at least a part thereof) is concentrated by selectively adsorbing with the adsorbent 14a. Subsequently, by addition of ozone from the ozone addition valve 24, it is converted into a partially reactive partial oxide such as alcohol, ketone, aldehyde, carboxylic acid or the like. Subsequently, it is oxidized to carbon dioxide and water with an oxidation catalyst. In that case, the oxidation reaction is promoted by adding hydrogen from the hydrogen addition valve 26 to the oxidation catalyst.

  Further, when the exhaust purification catalyst 16 is a selective reduction catalyst, among the unburned hydrocarbons contained in the exhaust from the internal combustion engine 10, unsaturated hydrocarbons, aromatics, and higher carbons that are particularly catalyst poisoning components. Hydrogen (or at least a part thereof) is concentrated by selectively adsorbing with the adsorbent 14a, and concentrated by adsorbing nitrogen monoxide contained in the exhaust gas with the adsorbent 14a. Subsequently, by adding ozone from the ozone addition valve 24, the concentrated hydrocarbon is converted into a highly reactive partial oxide such as alcohol, ketone, aldehyde, carboxylic acid, etc., and the concentrated nitric oxide is highly reactive. Convert to nitrogen dioxide. Subsequently, in the selective reduction catalyst, the partially oxidized hydrocarbon and nitrogen dioxide are reacted to purify carbon dioxide, water, and nitrogen. At that time, the reduction of nitrogen oxides is promoted by adding hydrogen from the hydrogen addition valve 26 to the selective reduction catalyst.

  For example, the exhaust purification catalyst 16 is often operated in a low temperature range where it is difficult to activate the internal combustion engine 10 immediately after the start, low load idle operation, frequent operation such as idling stop, or the like. When hydrocarbons and nitrogen oxides, which are harmful components in the exhaust from the internal combustion engine 10, are strongly adsorbed on the surface of the exhaust purification catalyst 16 in a low temperature range where the exhaust purification catalyst 16 is difficult to activate, the purification reaction of the harmful components is inhibited ( Adsorption poisoning). Therefore, the exhaust purification catalyst 16 is liable to deteriorate the purification performance of harmful components, particularly in a low temperature range.

  On the other hand, in the present embodiment, at least a part of the harmful components in the exhaust gas from the internal combustion engine 10 is concentrated by the concentrating device 14, and at least a part of the harmful components concentrated by the concentrating device 14 is ozonated. A process of converting to a highly reactive gas by adding ozone from 24, and a process of purifying by the exhaust purification catalyst 16 at least a harmful component converted to a highly reactive gas by adding ozone from the ozone addition valve 24; , In order. The harmful components in the exhaust gas supplied to the exhaust gas purification catalyst 16 by adsorbing and concentrating the harmful components (for example, hydrocarbons and nitrogen monoxide) in the exhaust gas by the concentrating device 14 provided in the preceding stage of the exhaust gas purification catalyst 16 Since the concentration can be lowered, poisoning due to adsorption of harmful components to the exhaust purification catalyst 16 can be suppressed in a low temperature range where the exhaust purification catalyst 16 is difficult to activate, and the purification performance of the exhaust purification catalyst 16 can be reduced. Decline can be prevented.

  Further, the harmful components concentrated in the concentrator 14 are supplied to the exhaust purification catalyst 16 after being converted to a highly reactive gas at any time or constantly by adding ozone. For example, hydrocarbons are partially oxidized and converted to partially oxidized hydrocarbons to increase the reactivity and then supplied to the exhaust purification catalyst 16. Nitric oxide is oxidized and converted to nitrogen dioxide to react. The exhaust gas is supplied to the exhaust purification catalyst 16 after the performance becomes high. At this time, the harmful component concentrated by the concentrating device 14 has a high concentration, and by adding ozone thereto, the reaction rate between the harmful component (for example, hydrocarbon or nitrogen monoxide) and ozone is improved. Even in a low temperature range, it can be efficiently converted into a highly reactive gas (for example, partially oxidized hydrocarbon or nitrogen dioxide). The harmful components flowing into the exhaust purification catalyst 16 are converted into highly reactive gas and activated, and thus are purified at a high purification rate even in a low temperature range where the exhaust purification catalyst 16 is difficult to activate. In addition, the harmful component concentrated in the concentrating device 14 is converted to a highly reactive gas as needed by adding ozone, and then supplied to the exhaust purification catalyst 16, so that the adsorbent 14a in the concentrating device 14 is saturated. It is possible to always concentrate harmful components.

  Therefore, according to the present embodiment described above, the adsorption poisoning of the exhaust purification catalyst 16 can be suppressed, and the inflow gas to the exhaust purification catalyst 16 is converted into a highly reactive gas and activated. Therefore, it is possible to prevent a reduction in the purification performance of the exhaust purification catalyst 16 in a wide temperature range from a low temperature to a high temperature.

  In Patent Document 2, by using an HC trap catalyst having an oxidation catalyst layer on the HC adsorbent layer having partial oxidation ability, HC adsorbed by the HC adsorbent layer is partially oxidized or reformed, Oxidized in the oxidation catalyst layer. However, in Patent Document 2, it is difficult to avoid HC poisoning of the oxidation catalyst layer, and the oxidation treatment is difficult at a temperature lower than the temperature at which the partial oxidation ability of the HC adsorbent layer is expressed, and low temperature purification is difficult. It becomes. Moreover, in patent document 3, light oil is partially oxidized with ozone, and NOx in exhaust gas is purified using the partial oxide as a reducing agent. However, in patent document 3, the partial oxidation temperature of light oil is as high as 350-400 degreeC, and there exists a possibility that ozone may decompose | disassemble at that temperature, and it becomes difficult to produce | generate a partial oxide efficiently. Further, in Patent Document 3, in order to purify NOx using a partial oxide as a reducing agent, a temperature of 300 ° C. or higher is necessary, and it becomes difficult to purify NOx in a low temperature range. In Patent Document 4, a part of saturated hydrocarbons in exhaust gas is reformed into unsaturated hydrocarbons using a discharge plasma apparatus, but the temperature that can be reformed by plasma is as high as 400 ° C. or higher. Reformation becomes difficult in the exhaust gas. On the other hand, in the present embodiment, the adsorption poisoning of the exhaust purification catalyst 16 can be suppressed and the inflow gas to the exhaust purification catalyst 16 even when the low temperature region where the exhaust purification catalyst 16 is difficult to activate continues for a long time. Therefore, it is possible to prevent a reduction in the purification performance of the exhaust purification catalyst 16.

  Further, in the present embodiment, ozone added to the harmful component concentrated by the concentration device 14 is generated by a water electrolysis method, thereby generating ozone having a high concentration and high purity as compared with the discharge method of Patent Document 5. As a result, the reactivity with harmful components is greatly improved, and the gas can be efficiently converted into a highly reactive gas. Further, in the water electrolysis method, ozone is generated from the anode side and hydrogen is generated from the cathode side, so that the purification performance in the exhaust purification catalyst 16 is greatly improved by supplying this hydrogen to the exhaust purification catalyst 16. Can do.

  In the present embodiment, when the temperature of the exhaust purification catalyst 16 is equal to or higher than the activation temperature, the exhaust purification catalyst 16 does not necessarily convert harmful components in the exhaust into highly reactive gases. It is possible to purify the components. Therefore, in the present embodiment, when the temperature of the exhaust purification catalyst 16 is equal to or higher than the activation temperature, ozone addition from the ozone addition valve 24 is not performed (the harmful component concentrated by the concentrating device 14 is converted into highly reactive gas). It is also possible not to convert.

  In the above description of the embodiment, the case where ozone and hydrogen are generated by the water electrolysis method has been described. However, ozone and hydrogen can also be generated by a method other than the water electrolysis method. However, when ozone and hydrogen are generated by the water electrolysis method, ozone and hydrogen having a high concentration and high purity can be generated with one apparatus, which is advantageous in terms of efficiency, cost, space, and the like. It is.

  As mentioned above, although the form for implementing this invention was demonstrated, this invention is not limited to such embodiment at all, and it can implement with a various form in the range which does not deviate from the summary of this invention. Of course.

  DESCRIPTION OF SYMBOLS 10 Internal combustion engine, 12 Exhaust pipe, 14 Concentrator, 14a Adsorbent, 16 Exhaust purification catalyst, 18 Water electrolyzer, 20 Ozone conduit, 22 Hydrogen conduit, 24 Ozone addition valve, 26 Hydrogen addition valve.

Claims (8)

An exhaust purification device for an internal combustion engine for purifying harmful components in exhaust from the internal combustion engine,
A concentrating device for concentrating at least a part of harmful components in exhaust from the internal combustion engine;
A conversion device for converting at least a part of the harmful components concentrated in the concentration device into a highly reactive gas;
An exhaust gas purification catalyst that purifies harmful components that have been converted into highly reactive gas at least partially in the converter;
An exhaust purification device for an internal combustion engine, comprising: An exhaust emission control device for an internal combustion engine according to claim 1,
The conversion device is an exhaust purification device for an internal combustion engine, which is a device that oxidizes at least a part of the harmful component and converts it into a highly reactive gas by adding an oxidizing agent to the harmful component concentrated by the concentrating device. . An exhaust emission control device for an internal combustion engine according to claim 2,
An exhaust gas purification apparatus for an internal combustion engine, wherein the oxidizing agent is ozone. An exhaust emission control device for an internal combustion engine according to claim 3,
An exhaust emission control device for an internal combustion engine, further comprising a water electrolysis device for generating ozone added to harmful components concentrated by the concentration device by electrolysis of water. An exhaust emission control device for an internal combustion engine according to claim 4,
An exhaust gas purification device for an internal combustion engine, further comprising a hydrogen supply device that supplies hydrogen generated together with ozone in the water electrolysis device to the purification device. An exhaust emission control device for an internal combustion engine according to any one of claims 1 to 5,
The concentrating device is an exhaust purifying device for an internal combustion engine, which is a device for concentrating at least a part of harmful components in exhaust from the internal combustion engine by adsorbing with an adsorbent. An exhaust emission control device for an internal combustion engine according to any one of claims 1 to 6,
The exhaust gas purification apparatus for an internal combustion engine, wherein the harmful component in the exhaust gas from the internal combustion engine includes at least one of hydrocarbon and nitrogen oxide. An internal combustion engine exhaust gas purification method for purifying harmful components in exhaust gas from an internal combustion engine,
A process of concentrating at least a part of harmful components in the exhaust gas from the internal combustion engine with a concentrator;
A process of converting at least a part of the harmful components concentrated in the concentrator into a highly reactive gas in the converter;
A process of purifying, with an exhaust purification catalyst, harmful components that have been at least partially converted into highly reactive gas in the conversion device;
The exhaust gas purification method for an internal combustion engine is executed in order.

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