JP2012026331A - Exhaust gas post treatment system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust gas post treatment system that can accurately detect an amount of ozone added to an exhaust gas.SOLUTION: An SCR catalyst 3 and an oxidation catalyst 4 are arranged at an exhaust pipe 2 of a diesel engine 1, and a muffler 5 is connected to the downstream side of the oxidation catalyst 4. Furthermore, an ozone generation reactor 12 which generates ozone from a raw-material gas is connected to the upstream side of the SCR catalyst 3 via an ozone supply pipe 11. A semiconductor ozone sensor 17 for detecting an amount of ozone generated by the ozone generation reactor 12 is arranged in the ozone supply pipe 11. Immediately ahead of the muffler 5, there is arranged a semiconductor ozone sensor 18 for detecting an amount of ozone contained in the exhaust gas which has passed the SCR catalyst 3 and the oxidation catalyst 4. A generation amount of ozone generated by the ozone generation reactor 12 is controlled on the basis of amounts of ozone detected by the semiconductor ozone sensors 17, 18.

Description

  The present invention relates to an exhaust gas aftertreatment system that purifies exhaust gas from a diesel engine, and more particularly, to a configuration of an exhaust gas aftertreatment system that uses ozone as an oxidizing agent.

A urea selective reduction system (urea SCR system) is an example of an exhaust gas aftertreatment system that purifies particulate matter (PM) and nitrogen oxides (NOx) contained in exhaust gas from a diesel engine. For example, as described in Patent Document 1, the urea SCR system supplies an SCR catalyst provided in an exhaust pipe, an injector that injects urea water into the exhaust pipe, and urea water stored in a tank to the injector. A pump is provided. The injector is configured to add urea water to the exhaust gas upstream of the SCR catalyst, and ammonia (NH ₃ ) is generated by the hydrolysis of the urea water added to the exhaust gas. The SCR catalyst reacts the produced ammonia with NOx in the exhaust gas and reduces it to harmless nitrogen (N ₂ ) and water (H ₂ O).

Here, the SCR catalyst has a problem that the activity at low temperature is low, and NOx purification cannot be performed unless the ratio of nitric oxide (NO) to nitrogen dioxide (NO ₂ ) is 1: 1 at low temperature. ing. Moreover, since the amount of nitrogen monoxide contained in the exhaust gas is usually larger than the amount of nitrogen dioxide, it is common to provide an oxidation catalyst upstream of the SCR catalyst and oxidize the nitric oxide to form nitrogen dioxide. . However, since the activity of the oxidation catalyst itself is low at low temperatures, and it is necessary to support expensive noble metals such as platinum (Pt) and palladium (Pd) in order to increase the activity, ozone is not contained in the exhaust gas instead of providing an oxidation catalyst. It has been proposed to oxidize NO with ozone by adding (O ₃ ).

JP 2006-105014 A

  When ozone is used as the oxidant in the exhaust gas aftertreatment system, it is necessary to supply an amount of ozone corresponding to the amount of NOx and PM contained in the exhaust gas. That is, if the amount of ozone supplied is small relative to the amount of NOx and PM, NOx and PM that could not be purified will be released into the atmosphere. Conversely, if the amount of ozone supplied is large, surplus ozone will be released into the atmosphere without being reacted. In addition, an ozone generation reactor that applies a high voltage while flowing a raw material gas such as air between a pair of electrodes is generally used to generate ozone added to exhaust gas. The amount of produced differs depending on the temperature, humidity, pressure and the like of the raw material gas. Therefore, in order to supply an appropriate amount of ozone, it is necessary to accurately detect the amount of generated ozone.

  Here, in order to accurately detect the amount of ozone, it is desirable to use an ozone sensor, particularly a semiconductor ozone sensor. A semiconductor ozone sensor detects the amount of ozone based on a change in electrical resistance when ozone comes into contact with a semiconductor thin film. For example, a small amount of ozone can be detected compared to an optical ozone sensor or the like. It has become. However, the electrode part of the semiconductor ozone sensor has low heat resistance, and cannot be provided at a portion where the temperature is high in the exhaust passage. That is, the amount of ozone cannot be directly measured inside the exhaust passage, and it is difficult to accurately detect the amount of ozone.

  The present invention has been made to solve such problems, and an object of the present invention is to provide an exhaust gas aftertreatment system that realizes accurate detection of the amount of ozone added to exhaust gas.

  An exhaust gas aftertreatment system according to the present invention includes an exhaust pipe through which exhaust gas discharged from an internal combustion engine flows, a muffler that is connected to the exhaust pipe and reduces exhaust noise when the exhaust gas is released into the atmosphere, and an exhaust pipe A purification device that purifies the exhaust gas, an ozone generation reactor that generates ozone, and an ozone supply pipe that connects the ozone generation reactor and the exhaust pipe upstream of the purification device in the direction in which the exhaust gas flows. In the exhaust gas aftertreatment system for supplying ozone generated by the ozone generation reactor to the inside of the exhaust pipe through the ozone supply pipe, the ozone sensor further includes an ozone sensor for detecting the amount of ozone. And at least one immediately before the muffler.

  When the ozone sensor is arranged inside the ozone supply pipe, the ozone supply pipe is not a path through which the exhaust gas flows, and therefore does not become as high as inside the exhaust pipe. Therefore, a semiconductor ozone sensor having low heat resistance but capable of detecting a small amount of ozone can be used as the ozone sensor, and the amount of ozone generated by the ozone generation reactor is accurately detected. On the other hand, when the ozone sensor is disposed immediately before the muffler, the exhaust gas that has passed through the purification device is usually cooled while flowing through the exhaust pipe, and the temperature at which the semiconductor ozone sensor can be used before reaching the muffler. It becomes. Therefore, a semiconductor ozone sensor can be used as the ozone sensor, and the amount of ozone remaining unreacted can be accurately detected. Therefore, the amount of ozone can be accurately detected in the exhaust gas aftertreatment system.

  The ozone sensor may be provided both inside the ozone supply pipe and immediately before the muffler. NOx contained in the exhaust gas is controlled by controlling the amount of ozone added to the exhaust gas based on the amount of ozone generated inside the ozone supply pipe and the residual amount of ozone detected immediately before the muffler. It is possible to generate ozone in accordance with the amount of PM. Further, even if one ozone sensor fails, the amount of ozone can be detected by the other ozone sensor, so that reliability can be improved.

  The purification device includes a urea selective reduction catalyst that purifies nitrogen oxides contained in the exhaust gas using ammonia as a reducing agent, temporary storage of nitrogen oxides contained in the exhaust gas, and purification of the stored nitrogen oxides. It may be at least one of a NOx occlusion reduction catalyst performed according to fuel consumption and a diesel particulate filter that collects particulate matter contained in the exhaust gas. When the purification device is a urea selective reduction catalyst, NOx purification efficiency is improved by oxidizing nitrogen monoxide in exhaust gas with ozone to form nitrogen dioxide. When the purification device is a NOx occlusion reduction catalyst, NOx occlusion efficiency by the NOx occlusion reduction catalyst is improved by oxidizing NOx in the exhaust gas into higher order nitrogen oxides. Further, when the catalyst device is a diesel particulate filter, the collected PM can be oxidized with ozone, and therefore PM can be removed regardless of the temperature of the exhaust gas or the temperature of the diesel particulate filter.

According to this invention, in the exhaust gas aftertreatment system using ozone as an oxidant, the amount of ozone added to the exhaust gas is accurately detected.
It is possible to supply ozone without excess or deficiency with respect to the amounts of NOx and PM.

It is the schematic which shows the structure of the exhaust gas aftertreatment system which concerns on Embodiment 1 of this invention. It is the schematic which shows the structure of the exhaust gas aftertreatment system which concerns on Embodiment 2 of this invention.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
Embodiment 1 FIG.
In FIG. 1, the structure of the diesel engine provided with the exhaust gas aftertreatment system which concerns on this Embodiment 1 is shown roughly. An exhaust pipe 2 is connected to the diesel engine 1 which is an internal combustion engine, and exhaust gas discharged from the diesel engine 1 flows in the direction indicated by the arrow A through the exhaust pipe 2. In the middle of the exhaust pipe 2, a urea selective reduction catalyst 3 (hereinafter referred to as SCR catalyst 3) as a purification device is provided, and an oxidation catalyst 4 is disposed downstream of the SCR catalyst 3 in the direction indicated by the arrow A. Is provided. Further, on the downstream side of the oxidation catalyst 4, a muffler 5 is connected to the end portion of the exhaust pipe 2, and exhaust gas that has passed through the SCR catalyst 3 and the oxidation catalyst 4 in sequence is reduced in exhaust sound inside the muffler 5. Since then, it has been released into the atmosphere.

  An injection nozzle 6 for injecting urea water into the exhaust pipe 2 is provided upstream of the SCR catalyst 3, and a urea water tank 7 for storing urea water is connected to the injection nozzle 6. It is connected via a tube 8. Further, a urea water addition system 9 for supplying urea water in the urea water tank 7 to the injection nozzle 6 is provided in the middle of the connecting pipe 8. The urea water addition system 9 is electrically connected to the ECU 10 which is a control device for the diesel engine 1 and the exhaust gas aftertreatment system, and is based on a signal output from the ECU 10 to the urea water addition system 9 by the injection nozzle 6. The injection of urea water is controlled.

One end of an ozone supply pipe 11 is connected to the upstream side of the SCR catalyst 3, and the other end of the ozone supply pipe 11 is an ozone generation reactor 12 that generates ozone (O ₃ ) from air that is a raw material gas. Is connected. The ozone generation reactor 12 includes a generation unit 13 having a pair of electrodes 13a and 13b therein, a power supply unit 14 that applies a high voltage between the electrodes 13a and 13b, and an air pump that supplies air into the generation unit 13 15 is provided. The ozone supply pipe 11 is provided with an on-off valve 16 that switches between communication and blocking between the ozone supply pipe 11 and the exhaust pipe 2. The power supply unit 14, the air pump 15, and the on-off valve 16 are electrically connected to the ECU 10, and their operations are controlled based on the output from the ECU 10.

  In the exhaust gas aftertreatment system configured as described above, the amount of ozone generated by the ozone generation reactor 12 is detected immediately after the ozone generation reactor 12, that is, upstream of the on-off valve 16 inside the ozone supply pipe 11. A semiconductor ozone sensor 17 is provided as the ozone sensor. The semiconductor ozone sensor 17 is electrically connected to the ECU 10. The semiconductor ozone sensor 17 detects the amount of ozone based on a change in electrical resistance when ozone contacts the semiconductor thin film. In general, such a semiconductor ozone sensor has a low heat resistance of the electrode portion and cannot be disposed at a high temperature inside the exhaust pipe 2. However, for example, when an optical ozone sensor is used Compared with the case where an oxygen sensor is used, a very small amount of ozone can be detected. Here, since the exhaust gas does not flow through the inside of the ozone supply pipe 11, it does not become high temperature due to the exhaust gas unlike the inside of the exhaust pipe 2. Therefore, it is possible to use the semiconductor ozone sensor 17 having low heat resistance but capable of detecting a very small amount of ozone as the ozone sensor.

  Further, an ozone sensor for detecting the amount of ozone that has passed through the inside of the exhaust pipe 2 and passed through the SCR catalyst 3 and the oxidation catalyst 4 is located in the exhaust pipe 2 at a position immediately before the muffler 5. A semiconductor ozone sensor 18 similar to the semiconductor ozone sensor 17 is provided. The semiconductor ozone sensor 18 is electrically connected to the ECU 10. Here, the term “immediately before the muffler” includes a range from the connection portion 5a between the exhaust pipe 2 and the muffler 5 to a portion where the temperature of the exhaust gas becomes 300 ° C. or lower on the upstream side of the connection portion 5a. Normally, the exhaust gas that has passed through the SCR catalyst 3 and the oxidation catalyst 4 is cooled while flowing through the exhaust pipe 2, and is 300 ° C. or less, which is a temperature at which the semiconductor ozone sensor 18 can be used before reaching the muffler 5. It becomes.

Inside the exhaust pipe 2, a NOx sensor 19 for detecting the concentration of NOx discharged from the diesel engine 1 is provided, and the NOx sensor 19 and the ECU 10 are electrically connected. Further, the diesel engine 1 has a sensor (not shown) that detects an operation state such as the engine speed and outputs it to the ECU 10. The ECU 10 can estimate the amount of NOx contained in the exhaust gas and the ratio of nitrogen monoxide and nitrogen dioxide in the NOx based on the concentration of NOx detected by the NOx sensor 19 and the operating state of the diesel engine 1. ing. The amount of NOx contained in the exhaust gas and the ratio of nitrogen monoxide (NO) and nitrogen dioxide (NO ₂ ) in NOx are maps corresponding to the engine speed, engine torque and fuel injection amount of the diesel engine 1. Can be stored in advance in the ECU 10, and in this case, the NOx sensor 19 can be omitted.

Next, the operation of the exhaust gas aftertreatment system according to Embodiment 1 of the present invention will be described.
As shown in FIG. 1, when the operation of the diesel engine 1 is started, the ECU 10 operates the power supply unit 14 and the air pump 15 of the ozone generation reactor 12. When the air pump 15 is activated, air is supplied to the inside of the generator 13 and flows between the electrodes 13a and 13b. Further, by the power supply unit 14 applies a high voltage between the electrodes 13a and the electrodes 13b, oxygen molecules contained in the air flowing between the (O ₂₎ is decomposed into two oxygen atoms (O) The The decomposed oxygen atoms are combined with other oxygen molecules to generate ozone, and the generated ozone circulates inside the ozone supply pipe 11. The semiconductor ozone sensor 17 detects the amount of ozone flowing through the ozone supply pipe 11, that is, the amount of ozone generated by the ozone generation reactor 12 and outputs the detected amount to the ECU 10.

  The ECU 10 outputs a valve opening command to the on-off valve 16, and the exhaust pipe 2 and the ozone supply pipe 11 are in communication with each other. Therefore, the ozone generated by the ozone generation reactor 12 is supplied to the exhaust pipe 2 through the ozone supply pipe 11 and added to the exhaust gas flowing through the exhaust pipe 2. The added ozone oxidizes nitric oxide in NOx contained in the exhaust gas to form nitrogen dioxide, whereby the ratio of nitric oxide and nitrogen dioxide in the exhaust gas gradually becomes 1: 1. The ratio of nitrogen monoxide and nitrogen dioxide in the exhaust gas is estimated by the ECU 10 based on the operation state of the diesel engine 1 such as the engine speed, the engine torque, and the fuel injection amount and the output from the NOx sensor 19. . The ECU 10 determines the amount of ozone generated based on this estimation result, and controls the operation of the ozone generation reactor 12.

When the operation of the diesel engine 1 is started, the ECU 10 operates the urea water addition system 9. The urea water in the urea water tank 7 is supplied to the injection nozzle 6 by the urea water addition system 9 and is injected into the exhaust pipe 2 from the injection nozzle 6. The injected urea water is hydrolyzed inside the exhaust pipe 2 to produce ammonia (NH ₃ ). The SCR catalyst 3 purifies NOx in exhaust gas by reacting ammonia with NOx and reducing it to nitrogen (N ₂ ) and water (H ₂ O). Here, NOx in the exhaust gas has a ratio of nitric oxide to nitrogen dioxide of 1: 1 because ozone has oxidized nitric oxide. Normally, NOx purification by the SCR catalyst 3 can be efficiently performed from a low temperature when the ratio of nitric oxide to nitrogen dioxide is 1: 1, so that ozone is not added to the exhaust gas. In comparison, the NOx purification efficiency by the SCR catalyst 3 is improved.

  Next, the exhaust gas whose NOx has been purified by the SCR catalyst 3 passes through the oxidation catalyst 4. The oxidation catalyst 4 becomes a surplus during the reduction of NOx by the SCR catalyst 3, and oxidizes and removes the ammonia that has remained unreacted. The exhaust gas purified in this way is cooled to a temperature of 300 ° C. or less while flowing through the exhaust pipe 2. The cooled exhaust gas passes through a semiconductor ozone sensor 18 provided immediately before the muffler 5 and is discharged into the atmosphere after exhaust noise is reduced inside the muffler 5. The semiconductor ozone sensor 18 detects the amount of ozone contained in the passing exhaust gas, that is, the amount of ozone remaining unreacted and outputs it to the ECU 10.

  Here, the amount of ozone generated by the ozone generation reactor 12 varies depending on the temperature, humidity, pressure, etc. of the air that is the raw material gas, so the amount of ozone added to the amount of NOx contained in the exhaust gas is excessive or insufficient. May occur. In order to eliminate such excess and deficiency of ozone, the ECU 10 compares the ozone generation amount detected by the semiconductor ozone sensor 17 with the residual ozone amount detected by the semiconductor ozone sensor 18, and uses the ozone generation reactor 12. The generation amount of ozone is controlled.

  Further, the ECU 10 generates ozone so that a small amount of ozone is detected by the semiconductor ozone sensor 18 on the muffler 5 side, that is, the exhaust gas flows into the muffler 5 in a state containing a small amount of ozone. Is controlling. By supplying a small amount of ozone to the inside of the muffler 5, it is possible to oxidize and remove the PM remaining in the muffler 5, thereby further purifying the exhaust gas. Note that since all of the ozone supplied into the muffler 5 is consumed to oxidize PM, excess ozone is not released into the atmosphere without being reacted.

  That is, the amount of ozone determined based on the operating state of the diesel engine 1 such as the engine speed, the engine torque, and the fuel injection amount and the output from the NOx sensor 19 is detected by the semiconductor ozone sensor 17, and the semiconductor ozone When the sensor 18 does not detect ozone, the ECU 10 determines that the amount of ozone generated is insufficient, and controls the ozone generation reactor 12 so that the semiconductor ozone sensor 18 detects a small amount of ozone. Increase the amount of production. On the other hand, if the amount of ozone detected by the semiconductor ozone sensor 18 exceeds a predetermined amount, the ECU 10 determines that the amount of ozone generated is too large, and outputs a valve closing command to the on-off valve 16 to supply the exhaust pipe 2 and ozone. By blocking communication with the tube 11, the amount of ozone added to the exhaust gas is reduced.

  As described above, when the ozone sensor is arranged inside the ozone supply pipe 11, the ozone supply pipe 11 is not a path through which the exhaust gas flows, and thus does not reach a high temperature unlike the inside of the exhaust pipe 2. Therefore, it is possible to use the semiconductor ozone sensor 17 that has low heat resistance but can detect a very small amount of ozone, and the amount of ozone generated by the ozone generation reactor 12 is accurately detected. When an ozone sensor is disposed immediately before the muffler 5, the exhaust gas that has passed through the SCR catalyst 3 and the oxidation catalyst 4 is usually cooled while flowing through the exhaust pipe 2, and before reaching the muffler 5, the semiconductor This is a temperature at which the ozone sensor 18 can be used. Therefore, the semiconductor ozone sensor 18 can be used as the ozone sensor, and the amount of ozone remaining unreacted is accurately detected. Therefore, the amount of ozone can be accurately detected in the exhaust gas aftertreatment system.

Further, semiconductor ozone sensors 17 and 18 are provided both inside the ozone supply pipe 11 and immediately before the muffler 5, respectively, and the amount of ozone detected inside the ozone supply pipe 11 and detected immediately before the muffler 5. Since the amount of ozone added to the exhaust gas is controlled based on the residual amount of ozone, it is possible to generate ozone according to the amount of NOx contained in the exhaust gas. Further, even if one semiconductor ozone sensor fails, the amount of ozone can be detected by the other semiconductor ozone sensor, so that reliability can be improved.
Since the SCR catalyst 3 that purifies NOx contained in the exhaust gas using ammonia as a reducing agent is used as the purification device, NOx purification efficiency is obtained by oxidizing nitrogen monoxide in the exhaust gas with ozone to form nitrogen dioxide. Will improve.

Embodiment 2. FIG.
Next, an exhaust gas aftertreatment system according to Embodiment 2 of the present invention will be described with reference to FIG. The exhaust gas aftertreatment system according to the second embodiment uses a NOx occlusion reduction catalyst and a diesel particulate filter, which will be described below, as a purifier for the first embodiment. In the following embodiments, the same reference numerals as those in FIG. 1 are the same or similar components, and thus detailed description thereof is omitted.

  As shown in FIG. 2, a NOx occlusion reduction catalyst 23 (hereinafter referred to as NSR catalyst 23) for purifying NOx in the exhaust gas is provided in the middle of the exhaust pipe 2. Further, on the downstream side of the NSR catalyst 23 in the direction indicated by the arrow A, a diesel particulate filter 33 (hereinafter referred to as DPF 33) for collecting particulate matter (PM) contained in the exhaust gas is provided. Yes. Further, the on-off valve 16 and the NOx sensor 19 used in the first embodiment are omitted, and the ECU 10 detects the exhaust gas based on the operating state of the diesel engine 1 such as the engine speed, the engine torque, and the fuel injection amount. The amount of NOx contained in is estimated from a map stored in advance. Other configurations are the same as those in the first embodiment.

Next, the operation of the exhaust gas aftertreatment system according to Embodiment 2 of the present invention will be described.
As shown in FIG. 2, when the operation of the diesel engine 1 is started, the ozone generation reactor 12 generates ozone based on a command from the ECU 10 as in the first embodiment. The generated ozone is supplied into the exhaust pipe via the ozone supply pipe 11 and added to the exhaust gas. The semiconductor ozone sensor 17 in the ozone supply pipe 11 detects the amount of ozone generated by the ozone generation reactor 12 and outputs it to the ECU 10.

  The NSR catalyst 23 temporarily stores NOx contained in the exhaust gas in an oxidizing atmosphere in which the air-fuel ratio of the exhaust gas is lean, that is, the air concentration in the exhaust gas is high. Here, NOx in the exhaust gas becomes higher-order NOx by being oxidized into the added ozone. Further, the NOx occlusion efficiency by the NSR catalyst 23 usually increases as the NOx becomes higher, so that a larger amount of NOx can be occluded in the NSR catalyst 23 than in the case where ozone is not added to the exhaust gas. It has become. On the other hand, when it becomes a reducing atmosphere where the air-fuel ratio of the exhaust gas is rich, that is, the air concentration in the exhaust gas is low, the NSR catalyst 23 uses NOx with carbon monoxide, hydrogen, hydrocarbons, etc. contained in the exhaust gas as a reducing agent. Reduce to nitrogen.

  When the exhaust gas that has passed through the NSR catalyst 23 passes through the DPF 33, PM contained in the exhaust gas is collected in the DPF 33. The collected PM is oxidized and removed by ozone that has passed through the NSR catalyst 23. Here, oxidation of PM collected by the DPF is usually performed using an oxidation catalyst supported on the DPF, but the oxidation catalyst has low activity at a low temperature. Expensive noble metals are required. That is, by using ozone to oxidize PM, it is possible to oxidize PM at low cost and at low temperatures.

  The exhaust gas that has passed through the DPF 33 is cooled to a temperature of 300 ° C. or less while flowing through the exhaust pipe 2. The cooled exhaust gas passes through the semiconductor ozone sensor 18 immediately before the muffler 5 and is discharged into the atmosphere after the exhaust noise is reduced inside the muffler 5. The semiconductor ozone sensor 18 detects the amount of ozone contained in the passing exhaust gas and outputs it to the ECU 10. The ECU 10 compares the generated amount of ozone detected by the semiconductor ozone sensor 17 with the residual amount of ozone detected by the semiconductor ozone sensor 18 so that the exhaust gas passing through the DPF 33 contains a small amount of ozone. 12 power supply units 14 are controlled.

  As described above, even when the NSR catalyst 23 and the DPF 33 are used as a purification device, the ozone amount is accurately detected and the amounts of NOx and PM contained in the exhaust gas are determined as in the first embodiment. It is possible to generate ozone. Further, since the NSR catalyst 23 and the DPF 33 are used as the purification catalyst, NOx in the exhaust gas is oxidized into ozone to become higher-order NOx, and the NOx occlusion efficiency of the NSR catalyst 23 is improved and the PM collected by the DPF 33 Can be removed at low cost regardless of the temperature of the DPF 33.

As the purification device, the SCR catalyst 3 is used in the first embodiment and the NSR catalyst 23 and the DPF 33 are used in the second embodiment. However, the configuration of the purification device is not limited to these. If ozone can be used as an oxidizing agent, it is possible to use a catalyst or the like other than these as the purifying device, and in that case, the number and arrangement order of the purifying devices can be appropriately changed.
In the first and second embodiments, the two semiconductor ozone sensors 17 and 18 are used, but even if only one of them is provided, it is possible to accurately detect the amount of ozone. is there.

  DESCRIPTION OF SYMBOLS 1 Internal combustion engine, 2 exhaust pipe, 3 SCR catalyst (urea selective reduction catalyst, purification device), 5 muffler, 11 ozone supply pipe, 12 ozone generation reactor, 17 semiconductor ozone sensor (ozone sensor), 18 semiconductor ozone sensor (ozone sensor) ), 23 NSR catalyst (NOx storage reduction catalyst, purification device), 33 DPF (diesel particulate filter, purification device).

Claims (3)

An exhaust pipe through which exhaust gas discharged from the internal combustion engine flows;
A muffler connected to the exhaust pipe and reducing exhaust noise when the exhaust gas is released into the atmosphere;
A purification device provided in the exhaust pipe for purifying the exhaust gas;
An ozone generation reactor for generating ozone;
An ozone supply pipe connecting the ozone generation reactor and the exhaust pipe on the upstream side of the purification device in a direction in which the exhaust gas flows, and the ozone generated by the ozone generation reactor is supplied to the ozone supply pipe In the exhaust gas aftertreatment system that supplies the exhaust pipe through
An ozone sensor for detecting the amount of ozone;
The exhaust gas aftertreatment system, wherein the ozone sensor is disposed in at least one of the inside of the ozone supply pipe and immediately before the muffler.   The exhaust gas post-processing system according to claim 1, wherein the ozone sensor is provided both inside the ozone supply pipe and immediately before the muffler. The purification device comprises:
A urea selective reduction catalyst that purifies nitrogen oxides contained in the exhaust gas using ammonia as a reducing agent;
A NOx occlusion reduction catalyst for temporarily storing nitrogen oxides contained in the exhaust gas and purifying the stored nitrogen oxides according to the air fuel consumption of the exhaust gas;
The exhaust gas aftertreatment system according to claim 1 or 2, wherein the exhaust gas aftertreatment system is at least one of a diesel particulate filter that collects particulate matter contained in the exhaust gas.

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