JP2011185195A - Exhaust emission control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device giving no load to a power supply device for an ozone generation device. <P>SOLUTION: A pipe 4 and an air port 7 are each connected to the ozone generation device 5 at its opposite side to electrodes 8, 8, namely, so that electrodes 8, 8 are located between the pipe 4 and the air port 7. A inner diameter d<SB>1</SB>of the air port 7 at its connection portion to the ozone generation device 5 is smaller than an inner diameter d<SB>2</SB>of the pipe 4 at its connection portion to the ozone generation device 5. Thus, the opening area of the air port 7 at its connection portion to the ozone generation device 5 is smaller than the opening area of the pipe 4 at its connection portion to the ozone generation device 5. In the air port 7, a filter 12 is provided for removing dust from air introduced into the ozone generation device 5. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification apparatus for an internal combustion engine.

A urea SCR (Selective Catalytic Reduction) system has been developed to reduce nitrogen oxides (NOx) contained in exhaust gas from diesel engines. The urea SCR system is an oxidation catalyst for oxidizing nitric oxide (NO) to nitrogen dioxide (NO ₂ ), and a chemical reaction between ammonia and NOx generated from urea water provided downstream of the oxidation catalyst. The SCR catalyst for converting NOx into nitrogen and water, the urea addition system for adding urea water to the SCR catalyst, and the downstream side of the SCR catalyst are left without being consumed by the chemical reaction in the SCR catalyst. And an oxidation catalyst for oxidizing ammonia. When the temperature of the exhaust gas is low (200 ° C. or lower), the activity of the SCR catalyst is low, and at such a low temperature, an excellent purification performance is exhibited only when the NO / NO ₂ ratio is about 1. there were. Further, the activity of the oxidation catalyst is low at low temperatures, and there is a problem that it is necessary to increase the amount of platinum, palladium, etc., which are expensive noble metals, in order to increase the activity of the oxidation catalyst.

In order to solve these problems, NO is oxidized into higher-order NOx such as NO ₂ using ozone as an oxidant, and this is adsorbed by a NOx storage reduction catalyst to be reduced and decomposed, thereby generating exhaust gas. For example, Patent Document 1 discloses an exhaust gas purifying apparatus that removes NOx from a gas. This exhaust gas purification device includes a NOx storage catalyst provided in an exhaust pipe and an ozone generator having a pair of electrodes. One end of the ozone generator is provided in a pipe connected to the exhaust pipe on the upstream side of the NOx storage catalyst, and a suction pump is provided between the ozone generator and the exhaust pipe in the pipe. When the suction pump is driven, air is discharged from the inside of the ozone generator, and accordingly, air is sucked from an air port provided in the ozone generator. When a voltage is applied between the electrodes, a discharge is generated between the electrodes, and ozone is generated from oxygen in the sucked air.

JP 2008-163886 A

  However, when air is introduced into the ozone generation device, the pressure in the ozone generation device increases, and it becomes difficult for discharge to occur between the electrodes. Therefore, it is necessary to increase the voltage applied between the electrodes. There was a problem that a load was applied.

  This invention was made in order to solve such a problem, and it aims at providing the exhaust gas purification apparatus which does not apply a load to the power supply device of an ozone production | generation apparatus.

An exhaust gas purifying apparatus according to the present invention includes an exhaust gas purifying means provided in an exhaust pipe through which exhaust gas discharged from an internal combustion engine circulates, an ozone having an air inlet for introducing air and a pair of electrodes facing each other. An ozone generation device comprising: a generation device; a power supply device that applies a voltage between the electrodes; and an air introduction unit that introduces air into the ozone generation device through an air port by sucking air in the ozone generation device. Is communicated with the exhaust gas purification means via a pipe, the air introduction means is provided in the pipe between the ozone generation device and the exhaust gas purification means, and the opening area of the air port at the connection portion with the ozone generation device is the ozone It is smaller than the opening area of the pipe at the connecting portion with the generator. Since the resistance to air is greater when air is introduced into the ozone generator than when the air is discharged from the ozone generator to the piping, the pressure in the ozone generator is increased from the ozone generator. The decrease due to the exhaust of air is faster than the increase due to the introduction of air into the ozone generator via the air port, so that the pressure in the ozone generator is at atmospheric pressure. Smaller than.
Each of the piping and the air port may be connected to an ozone generator such that the electrodes are located between them.
A filter may be provided at the air port.

  According to this invention, since the opening area of the air port at the connection portion with the ozone generation device is smaller than the opening area of the piping at the connection portion with the ozone generation device, air is discharged from the ozone generation device to the piping. When the air is introduced into the ozone generating device through the air port, the resistance to the air is larger than the case where the air is discharged from the ozone generating device. Is faster than rising due to the introduction of air into the ozone generator through the air port, and as a result, the pressure in the ozone generator is lower than atmospheric pressure. Then, since it becomes easy to produce discharge between the electrodes in an ozone generator, the load concerning the power supply device of an ozone generator can be reduced.

1 is a schematic configuration diagram of an internal combustion engine provided with an exhaust gas purifying apparatus according to a first embodiment of the present invention. It is an ozone generating apparatus of the exhaust gas purification apparatus which concerns on 1st Embodiment, and the enlarged structure schematic diagram of its periphery. It is a structure schematic diagram of the internal combustion engine provided with the exhaust gas purification apparatus which concerns on 2nd Embodiment. It is a structure schematic diagram of the internal combustion engine provided with the exhaust gas purification apparatus which concerns on 3rd Embodiment.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
Embodiment 1 FIG.
FIG. 1 shows a schematic configuration diagram of an internal combustion engine equipped with an exhaust gas purifying apparatus according to Embodiment 1 of the present invention. An exhaust pipe 2 through which exhaust gas flows is connected to a diesel engine 1 that is an internal combustion engine. The exhaust pipe 2 is provided with a NOx storage catalyst 3 that is an exhaust gas purification means. On the upstream side of the NOx storage catalyst 3, a pipe 4 is connected to the exhaust pipe 2, and an ozone generator 5 is provided in the pipe 4. The ozone generator 5 communicates with the NOx storage catalyst 3 through the pipe 4. The piping 4 is provided with a suction pump 6 that is an air introduction means between the ozone generator 5 and the NOx storage catalyst 3. The ozone generating device 5 is provided with an air port 7 for introducing air from the atmosphere. The ozone generator 5 has a pair of electrodes 8, 8 provided to face each other with a gap therebetween, and each of the electrodes 8, 8 is connected to a power supply device 9 by an electric wire 11.

As shown in FIG. 2, the piping 4 and the air port 7 are respectively opposite to the electrodes 8 and 8, i.e., the electrodes 8 and 8 are positioned between the piping 4 and the air port 7. The generator 5 is connected. The inner diameter d ₁ of the air port 7 at the connection portion with the ozone generation device 5 is smaller than the inner diameter d ₂ of the pipe 4 at the connection portion with the ozone generation device 5. Thereby, the opening area of the air port 7 in the connection part with the ozone production | generation apparatus 5 is smaller than the opening area of the piping 4 in the connection part with the ozone production | generation apparatus 5. FIG. The air port 7 is provided with a filter 12 for removing dust and the like from the introduced air.

Next, the operation of the exhaust gas purifying apparatus according to Embodiment 1 will be described with reference to FIGS.
When the diesel engine 1 is started, since the temperature of the exhaust gas flowing through the exhaust pipe 2 is low and the catalytic activity of the NOx storage catalyst 3 is low, ozone is supplied from the ozone generator 5 in order to increase the NOx treatment capacity. When the suction pump 6 is activated, the air in the ozone generator 5 is sucked and discharged to the pipe 4. Accordingly, air is introduced from the atmosphere into the ozone generator 5 through the air port 7.

  Here, since the opening area of the air port 7 at the connection portion with the ozone generation device 5 is smaller than the opening area of the piping 4 at the connection portion with the ozone generation device 5, the piping 4 from the inside of the ozone generation device 5. The resistance to air is greater when air is introduced into the ozone generator 5 than when air is discharged. As a result, the pressure in the ozone generation device 5 is increased by the introduction of air into the ozone generation device 5 through the air port 7 when the pressure is reduced as the air is discharged from the ozone generation device 5. Therefore, the pressure in the ozone generator 5 is lower than the atmospheric pressure. The lower the pressure in the ozone generator 5, the easier the discharge occurs between the electrodes 8, 8, so that the voltage applied between the electrodes 8, 8 can be reduced and the load on the power supply device 9 becomes lighter.

  When a discharge occurs between the electrodes 8 and 8, a part of oxygen in the air introduced into the ozone generator 5 becomes ozone. Here, the piping 4 and the air port 7 are connected to the ozone generating device 5 so that the electrodes 8 and 8 are located between them, respectively, so that the inside of the ozone generating device 5 is connected via the air port 7. The introduced air is exposed to discharge from one end between the electrodes 8 and 8 to the other end between the electrodes 8 and 8 before reaching the pipe 4. As a result, since the air is exposed to the discharge for as long as possible, the ozone generation efficiency of the ozone generator 5 is improved.

The ozone generated by the ozone generator 5 is sucked by the suction pump 6 and flows through the pipe 4, mixed with the exhaust gas in the exhaust pipe 2, and flows into the NOx storage catalyst 3. In NOx storage catalyst 3, ozone is an oxidizing agent, the NO in the exhaust gas is oxidized to NO ₂ or the like, NO ₂ etc., is reduced and decomposed is adsorbed to the NOx storage catalyst 3.

  As described above, the opening area of the air port 7 at the connection portion with the ozone generation device 5 is smaller than the opening area of the piping 4 at the connection portion with the ozone generation device 5, so Since the resistance to air is greater when air is introduced into the ozone generator 5 through the air port 7 than when air is discharged, the pressure in the ozone generator 5 is As the air is exhausted from the air outlet 7, the air pressure is lowered faster than the air is introduced into the ozone generating device 5 through the air port 7. Pressure becomes smaller than atmospheric pressure. Then, since it becomes easy to produce discharge between the electrodes 8 and 8 in the ozone generator 5, the load concerning the power supply device 9 of the ozone generator 5 can be reduced. Moreover, since the filter 12 is provided in the air port 7, dust etc. can be removed from the introduced air.

Embodiment 2. FIG.
Next, an exhaust gas purification apparatus according to Embodiment 2 of the present invention will be described. In the following embodiments, the same reference numerals as those in FIGS. 1 and 2 are the same or similar components, and thus detailed description thereof is omitted.
The exhaust gas purification apparatus according to Embodiment 2 of the present invention is a modification of Embodiment 1 to a urea SCR catalyst as exhaust gas purification means.

  FIG. 3 shows a schematic configuration diagram of an exhaust gas purification apparatus according to Embodiment 2 of the present invention. An exhaust catalyst 2 through which exhaust gas discharged from the diesel engine 1 circulates is provided with an oxidation catalyst 23, an SCR catalyst 25 as exhaust gas purification means, and an oxidation catalyst 26. The exhaust pipe 2 is provided with an injection nozzle 27 for injecting urea water between the oxidation catalyst 23 and the SCR catalyst 25. The injection nozzle 27 communicates with a urea water tank 29 that stores urea water via a pipe 28. The piping 28 is provided with a urea water addition system 30 for supplying urea water in the urea water tank 29 to the injection nozzle 27. Further, between the oxidation catalyst 23 and the SCR catalyst 25, the ozone generator 5 communicates with the SCR catalyst 25 via the pipe 4. The piping 4 is provided with a suction pump 6 as air introduction means between the ozone generator 5 and the SCR catalyst 25. Other configurations are the same as those in the first embodiment.

Next, the operation of the exhaust gas purifying apparatus according to Embodiment 2 will be described.
When the diesel engine 1 is started, the temperature of the exhaust gas discharged from the diesel engine 1 is low. Therefore, even if exhaust gas flows through each of the oxidation catalyst 23, the SCR catalyst 25, and the oxidation catalyst 26, sufficient catalyst performance is achieved. The temperature does not rise to the temperature necessary to exert it. Therefore, ozone is supplied from the ozone generator 5 to the SCR catalyst 25 via the pipe 4 by the same operation as in the first embodiment. Then, using ozone as an oxidizing agent, NO in NOx is oxidized to NO ₂ and the NO / NO ₂ ratio approaches 1, so that the catalyst performance of the SCR catalyst 25 is sufficiently exhibited even at low temperatures. Become.

At an appropriate timing, the urea water addition system 30 supplies the urea water in the urea water tank 29 to the injection nozzle 27 via the pipe 28 and adds the urea water from the injection nozzle 27 to the SCR catalyst 25. The urea water added to the SCR catalyst 25 is hydrolyzed to become ammonia and carbon dioxide, and the produced ammonia reacts with NOx in the exhaust gas to become nitrogen and water. Ammonia remaining without being consumed in the SCR catalyst 25 is oxidized in the oxidation catalyst 26. Thereafter, when the diesel engine 1 is warmed up and the exhaust gas temperature is sufficiently increased, the catalytic performance of the oxidation catalyst 23 is sufficiently exerted, so the ozone generator 5 may be stopped.
Thus, even when the exhaust gas purifying apparatus according to the present invention is applied to the urea SCR system, the same effect as in the first embodiment can be obtained.

Embodiment 3 FIG.
Next, an exhaust gas purification apparatus according to Embodiment 3 of the present invention will be described. The exhaust gas purifying apparatus according to Embodiment 3 of the present invention is obtained by changing the exhaust gas purifying apparatus according to Embodiment 3 to a diesel particulate filter (DPF) as exhaust gas purifying means.
As shown in FIG. 4, the exhaust pipe 2 is provided with a DPF 40 as exhaust gas purification means. The DPF 40 is provided with a differential pressure gauge 41 that detects the differential pressure of the DPF 40. The ozone generator 5 communicates with the DPF 40 via the pipe 4 on the upstream side of the DPF 40. The piping 4 is provided with a suction pump 6 that is an air introduction means between the ozone generator 5 and the DPF 40. Other configurations are the same as those of the first embodiment.

If the differential pressure of the DPF 40 exceeds the preset upper limit value by the differential pressure gauge 41, ozone is supplied from the ozone generator 5 to the DPF 40 via the pipe 4 by the same operation as in the first embodiment. In the DPF 40, ozone oxidizes and removes particulate matter (PM) trapped in the DPF 40. When the trapped PM is oxidized and removed, and the differential pressure of the DPF 40 becomes equal to or lower than a preset lower limit value, the ozone generator 5 is stopped. It should be noted that ozone is not supplied to the DPF 40 only when the differential pressure of the DPF 40 is increased, but the operation of the diesel engine 1 is always performed from the ozone generator 5 to the DPF 40 while the diesel engine 1 is operating. Ozone may be supplied.
Thus, even when the DPF is applied as the purifying means, the same effect as in the first embodiment can be obtained.

  In the third embodiment, the ozone generator 5 is operated using the differential pressure gauge 41, but the present invention is not limited to this. A control device (ECU) for controlling the operation of the diesel engine 1 incorporates in advance a map representing the relationship between the operating state of the diesel engine 1 and the PM accumulation amount, and the PM accumulation amount is determined based on this map. The operation of the ozone generator 5 may be performed by estimation.

  DESCRIPTION OF SYMBOLS 1 Diesel engine (internal combustion engine), 2 exhaust pipe, 3 NOx occlusion catalyst (exhaust gas purification means), 4 piping, 5 ozone generation device, 6 suction pump (air introduction means), 7 air port, 8 electrode, 9 power supply device, 12 filters, 25 SCR catalyst (exhaust gas purification means), 40 DPF (exhaust gas purification means).

Claims (3)

Exhaust gas purification means provided in an exhaust pipe through which exhaust gas discharged from the internal combustion engine flows;
An ozone generator having an air inlet for introducing air and having a pair of electrodes facing each other;
A power supply device for applying a voltage between the electrodes;
Air introduction means for introducing air through the air port into the ozone generator by sucking air in the ozone generator;
The ozone generator communicates with the exhaust gas purification means via a pipe,
The air introduction means is provided in the pipe between the ozone generator and the exhaust gas purification means,
The exhaust gas purifying apparatus, wherein an opening area of the air port at a connection portion with the ozone generation device is smaller than an opening area of the pipe at a connection portion with the ozone generation device.   2. The exhaust gas purification device according to claim 1, wherein each of the pipe and the air port is connected to the ozone generation device such that the electrode is positioned between them.   The exhaust gas purification apparatus according to claim 1 or 2, wherein a filter is provided in the air port.

Images