JP6167935B2 - Exhaust gas treatment equipment - Google Patents

Description

  The present invention relates to an exhaust gas treatment apparatus that purifies exhaust gas from an internal combustion engine.

Various exhaust gas treatment apparatuses that purify nitrogen oxides (hereinafter referred to as “NOx” as appropriate) present in exhaust gas of internal combustion engines such as automobiles have been developed. These exhaust gas treatment apparatuses purify exhaust gas by reducing NOx in the exhaust gas and converting it into nitrogen.
However, nitrous oxide (N ₂ O) is produced when the combustion stroke of the engine or NOx in the exhaust gas is reduced, and this nitrous oxide may be discharged into the atmosphere. Since nitrous oxide has a high global warming potential, it is necessary to suppress its emission as much as possible. On the other hand, since nitrous oxide is decomposed into oxygen and nitrogen and the partial pressure of oxygen is increased to improve combustion, this is supplied to the combustion chamber of the internal combustion engine to improve combustion at the start-up of the internal combustion engine Has been proposed (Patent Document 1).

EP 1464831

  However, in the technique described in Patent Document 1, in order to supply nitrous oxide to the combustion chamber at a desired timing, it is necessary to temporarily store nitrous oxide generated from the exhaust gas in a tank. In this case, in order to store nitrous oxide in a gaseous state, a large volume of the tank is required, and there is a problem that the physique of the entire system is increased. In addition, it is conceivable to store nitrous oxide in a liquid state. In this case, however, it is necessary to maintain the storage tank at a high pressure, and a mechanism and energy for that purpose are required, and a cost problem remains.

  The present invention has been made in view of such a background, and intends to provide an exhaust gas treatment apparatus that contributes to improvement in combustion of an internal combustion engine and can realize downsizing, cost reduction, and high performance. It is.

The first aspect of the present invention is a separation means for adsorbing or occluding nitrogen oxides in exhaust gas discharged from a combustion chamber of an internal combustion engine and separating it from the exhaust gas;
Conversion means for generating nitrous oxide from the nitrogen oxides adsorbed or occluded by the separation means;
The conversion gas containing the nitrous oxide obtained by the conversion means have a, a recirculation means for recirculating into the combustion chamber,
In the exhaust gas treatment apparatus, an oxidation treatment unit for oxidizing nitrous oxide that may be present in the exhaust gas is provided between the combustion chamber and the separation means .
The second aspect of the present invention is a separation means for adsorbing or occluding nitrogen oxides in the exhaust gas discharged from the combustion chamber of the internal combustion engine and separating it from the exhaust gas;
Conversion means for generating nitrous oxide from the nitrogen oxides adsorbed or occluded by the separation means;
Reflux means for refluxing the conversion gas containing nitrous oxide obtained by the conversion means to the combustion chamber,
In the exhaust gas treatment apparatus, a reduction processing unit for reducing nitrous oxide that may be present in the exhaust gas is provided between the combustion chamber and the separation means.

  The exhaust gas treatment apparatus has the separation means, and adsorbs or occludes nitrogen oxides in the exhaust gas for separation. The nitrogen oxides separated from the exhaust gas are converted into nitrous oxide by the conversion means, and the conversion gas containing the nitrous oxide is returned to the combustion chamber by the reflux means. That is, the exhaust gas treatment apparatus can once adsorb or occlude nitrogen oxides in the separation means. The adsorbed or occluded nitrogen oxide can be discharged from the separation means at a desired timing, converted into nitrous oxide by the conversion means, and the nitrous oxide can be returned to the combustion chamber through the reflux means. Therefore, a tank or the like for storing the produced nitrous oxide is not required. As a result, the exhaust gas treatment device can be reduced in size and cost.

  As described above, since nitrous oxide can be returned to the combustion chamber through the return means at a desired timing, combustion of the internal combustion engine can be improved. Furthermore, in the conversion means, the nitrogen oxides are converted into nitrous oxide, and the exhaust gas can be purified by decomposing the nitrous oxide in the combustion chamber. That is, it is possible to improve the combustion of the internal combustion engine while purifying nitrogen oxides in the exhaust gas.

In the conversion means, nitrogen oxide (NOx) may be reduced to nitrous oxide (N ₂ O) without reducing nitrogen oxide (NOx) to nitrogen (N ₂ ). Therefore, compared with the case where nitrogen oxides are reduced to nitrogen, for example, a noble metal catalyst is not required and an inexpensive exhaust treatment device can be used, or a high-performance exhaust treatment device that can be applied in a wide temperature range that enables low-temperature activation of the catalyst. It can be done.

  As described above, according to the present invention, it is possible to provide an exhaust gas treatment apparatus that contributes to improvement in combustion of an internal combustion engine and can realize downsizing, cost reduction, and high performance.

Explanatory drawing of the waste gas processing apparatus in the reference example 1. FIG. Explanatory drawing of the waste gas processing apparatus in the reference example 2. FIG. Explanatory drawing of the waste gas processing apparatus which provided the two separation means connected in parallel in the reference example 3. FIG. Explanatory drawing of the waste gas processing apparatus which provided the two isolation | separation means connected in series in the reference example 3. FIG. In Example 1, illustration of an exhaust gas treatment apparatus. Explanatory drawing of the waste gas processing apparatus in the reference example 4. FIG. Explanatory drawing of the waste gas processing apparatus of the aspect which combined the reference example 2 and the reference example 3. FIG. Explanatory drawing of the other waste gas processing apparatus of the aspect which combined the reference example 2 and the reference example 3. FIG. Explanatory drawing of the waste gas processing apparatus of the aspect which combined the reference example 2 and Example 1. FIG. Explanatory drawing of the waste gas processing apparatus of the aspect which combined the reference example 2 and the reference example 4. FIG.

The exhaust gas treatment apparatus can be used for, for example, a diesel engine, a lean burn engine, or the like. In recent years, in order to reduce NOx in exhaust gas, an engine has been implemented to lower the combustion temperature, such as an exhaust gas recirculation device (EGR) or multistage injection. Such a device generally sacrifices improvement in fuel consumption as a contradiction to reduce NOx. On the other hand, by adopting the exhaust gas treatment device, it is possible to treat high-concentration nitrogen oxides and improve fuel efficiency in the engine combustion. In addition, the higher the NOx concentration in the exhaust gas, the greater the amount of heat and oxygen supplied by N ₂ O supplied to the combustion chamber when the exhaust gas is circulated and used, and the fuel efficiency can be further improved.

Moreover, the said waste gas processing apparatus may have a isolation | separation means and a conversion means as a separate process part, and may have as one process part.
In the former case, for example, the nitrogen oxides released from the separation means may be converted to the nitrous oxide by the conversion means. In this case, the separation means can separate the nitrogen oxide from the exhaust gas by adsorbing or occluding the nitrogen oxide in the exhaust gas. Then, the nitrogen oxide released from the separation means at a desired timing can be moved to the conversion means, and nitrous oxide can be generated from the nitrogen oxide by the conversion means.

  In the latter case, for example, it has a separation / conversion unit including the separation unit and the conversion unit, and the nitrogen oxide adsorbed or occluded in the separation / conversion unit is in the state of the nitrous oxide. You may comprise so that it may discharge | release from a separation conversion part. In this case, since the separation means and the conversion means can be concentrated in one place, it is easy to reduce the size and simplify the exhaust gas treatment apparatus.

( Reference Example 1 )
A reference example of the exhaust gas treatment apparatus will be described with reference to FIG.
The exhaust gas treatment apparatus 1 of this example includes a separation unit 2, a conversion unit 3, and a reflux unit 4. The separating means 2 adsorbs or occludes nitrogen oxide (NOx) in the exhaust gas discharged from the combustion chamber 7 of the internal combustion engine and separates it from the exhaust gas. The conversion means 3 generates nitrous oxide (N ₂ O) from the NOx adsorbed or occluded by the separation means 2. The reflux means 4 refluxes the conversion gas containing N ₂ O obtained by the conversion means 3 to the combustion chamber 7.

In this example, the NOx after being separated from the separation means 2 is converted to N ₂ O by the conversion means 3.

The separation means 2 is connected to the exhaust port 72 of the combustion chamber 7 via the first exhaust pipe 11. The separation means 2 is connected to a second exhaust pipe 12 that discharges the exhaust gas after separating NOx.
A branch pipe 13 is provided so as to connect the separating means 2 and the converting means 3. The conversion means 3 is connected to an intake port 71 of the combustion chamber 7 by a return pipe as the return means 4. Thereby, a recirculation path for recirculating a part of the exhaust gas from the separation means 2 to the combustion chamber 7 is formed. And in this example, the conversion means 3 is provided in the middle of this recirculation | reflux path | route.

  The separation means 2 is constituted by, for example, a catalyst device in which a NOx storage catalyst is supported on a porous body. Further, the separation means 2 uses an oxide having a high specific surface area such as alumina, zeolite, or silica that performs physical adsorption, or a substance such as Ba, K, or Ca that performs chemical adsorption as an adsorption or occlusion material. can do.

An example of the process of purifying the exhaust gas by the exhaust gas processing apparatus 1 of this example and returning a part of the exhaust gas to the combustion chamber 7 will be described below.
First, the exhaust gas discharged from the exhaust port 72 of the combustion chamber 7 reaches the separation means 2 via the first exhaust pipe 11. The exhaust gas discharged from the combustion chamber 7 contains nitrogen oxide (NOx), and NO (nitrogen monoxide) is particularly contained in NOx.

NO in the exhaust gas is adsorbed or occluded by the separation means 2. At this time, NO is adsorbed or occluded in the separation means 2 in the state of NO ₂ and NO ₃ . Thereby, NOx is separated and removed from the exhaust gas, and NOx is stored in the separation means 2. On the other hand, the exhaust gas from which NOx has been separated and removed is discharged through the second exhaust pipe 12.

NOx (NO ₂ , NO ₃ ) adsorbed or occluded by the separation means 2 can be separated from the separation means 2 at a desired timing. That is, for example, NOx is released from the separation means 2 at a timing when high torque is required in the internal combustion engine. That is, for example, when the rotational speed of the internal combustion engine is in a low rotational speed range equal to or lower than a predetermined rotational speed, NOx is released from the separation means 2.

At this time, a switching valve (not shown) is switched to connect the separation means 2 and the branch pipe 13 and to shut off the separation means 2 and the second exhaust pipe 12. In this state, NOx is released from the separation means 2 by temporarily supplying fuel to the separation means 2. For example, a nozzle for introducing additive gas and additive liquid is provided in the upper stage of the separating means 2 and the additive is charged at a desired timing. As additives, gas components such as HC gas, CO, H ₂ , and NH ₃ , and liquid components such as urea, water, and fuel are used. It should be noted that other means may be employed such as releasing NOx from the separation means 2 by temporarily increasing the temperature of the exhaust gas by rich lean control of combustion, for example.

Then, the exhaust gas containing NOx reaches the conversion means 3 through the branch pipe 13. In the conversion means 3, NOx is converted into nitrous oxide (N ₂ O) by a reduction reaction. As this reduction reaction, for example, an electrochemical method, a plasma reaction, a catalytic reaction, heating by electricity or microwave, ultraviolet irradiation, or the like can be used.

Further, the reflux gas containing N ₂ O generated in the conversion means 3 is supplied from the intake port 71 to the combustion chamber 7 via the reflux means 4. That is, N ₂ O is supplied to the combustion chamber 7 together with a new air-fuel mixture. The N ₂ O supplied to the combustion chamber 7 is decomposed by being exposed to a high temperature to generate heat, and active combustion is caused by supplying oxygen having an oxygen partial pressure or higher existing in the atmosphere. In addition to generating heat, supplying oxygen above the oxygen partial pressure present in the atmosphere causes active combustion. In this way, N ₂ O improves the combustion in the combustion chamber 7.

Next, the function and effect of this example will be described.
The exhaust gas treatment apparatus 1 has a separation means 2 and separates by adsorbing or occluding NOx in the exhaust gas. Then, NOx separated from the exhaust gas is converted into N ₂ O by the conversion means 3, and the conversion gas containing the N ₂ O is returned to the combustion chamber 7 by the reflux means 3. That is, the exhaust gas treatment device 1 can temporarily adsorb or occlude NOx in the separation means 2. Then, the adsorbed or occluded NOx can be released from the separation means 2 at a desired timing, converted into N ₂ O by the conversion means 3, and the N ₂ O can be returned to the combustion chamber 7 through the reflux means 4. Therefore, a tank or the like for storing the produced N ₂ O is not required. As a result, the exhaust gas treatment device 1 can achieve downsizing and cost reduction.

As described above, since N ₂ O can be recirculated to the combustion chamber 7 through the recirculation means 4 at a desired timing, combustion of the internal combustion engine can be improved. Furthermore, NOx in the exhaust gas can be purified by converting NOx into N ₂ O in the conversion means 3 and decomposing the N ₂ O in the combustion chamber 7. That is, it is possible to improve the combustion of the internal combustion engine while purifying NOx in the exhaust gas.

In the conversion means 3, without reducing the NOx to N _2, may be reduced to N ₂ O. Therefore, as compared with the case where NOx is reduced to N ₂ , for example, a noble metal catalyst is not required, and the low-temperature activation of the catalyst can be achieved. That is, when NOx is reduced to nitrogen, a noble metal such as platinum needs to be used as a catalyst. However, if NOx is reduced to N ₂ O, there are a wide range of catalyst options such as using a relatively inexpensive catalyst. . Alternatively, the reaction temperature of the catalyst can be lowered, and the exhaust gas treatment can be facilitated.

Further, the exhaust gas treatment device 1 is configured to recirculate the conversion gas to the combustion chamber 7 when the rotational speed of the internal combustion engine is in a low rotational speed range equal to or lower than a predetermined rotational speed. Thus, for example, when high torque is required, such as when the engine is started, N ₂ O can be returned to the combustion chamber 7 to improve combustion and increase combustion efficiency in the internal combustion engine.

  As described above, according to this example, it is possible to provide an exhaust gas treatment apparatus that contributes to improvement in combustion of an internal combustion engine and can realize downsizing, cost reduction, and high performance.

( Reference Example 2 )
As shown in FIG. 2, this example is an example of an exhaust gas treatment apparatus 1 having a separation conversion unit 5 in which the separation unit 2 and the conversion unit 3 are integrated in one place.
That is, the exhaust gas treatment apparatus 1 of this example includes a separation conversion unit 5 including a separation unit 2 and a conversion unit 3, and NOx adsorbed or occluded by the separation conversion unit 5 is in a state of N ₂ O. It is comprised so that it may discharge | release from a separation conversion part.

In this example, the separation conversion unit 5 can be configured by a catalyst device in which a NOx storage reduction catalyst is supported on a porous body, for example. Alternatively, the separation conversion unit 5 can be configured by a catalyst device in which a three-way catalyst is supported on a porous body.
Others are the same as in Reference Example 1 . Of the reference numerals used in this example or the drawings relating to this example, the same reference numerals as those used in Reference Example 1 represent the same components as in Reference Example 1 unless otherwise indicated.

In the case of this example, since the separation means 2 and the conversion means 3 can be consolidated in one place, the exhaust gas treatment device 1 can be easily downsized and simplified. In addition, the same effects as those of Reference Example 1 are obtained.

( Reference Example 3 )
As shown in FIG. 3, this example is an example of the exhaust gas treatment apparatus 1 provided with two separation means 2 and configured to be able to vary the release timing of nitrogen oxides from the two separation means 2 from each other. . That is, the exhaust gas treatment apparatus 1 of this example can adsorb or occlude NOx in the other separation means 2 while releasing NOx from the one separation means 2.

The two separation means 2 are connected in parallel between the first exhaust pipe 11 and the second exhaust pipe 12. And between the separation means 2 and the 2nd exhaust pipe 12 and the branch piping 13, it has the downstream switching piping part 14 provided with the switching valve 141 in the appropriate position. Further, between the two separating means 2 and the first exhaust pipe 11, there is an upstream side switching pipe section 15 provided with a switching valve 151 at an appropriate position. In accordance with the release of NOx from the two separation means 2, the switching valves 151, 141 are appropriately controlled to open and close to send NOx to the conversion means 3, convert it to N ₂ O, and burn through the reflux means 4 N ₂ O can be refluxed to the chamber 7. That is, NOx can be released from one separation means 2 and sent to the conversion means 3, while NOx can be adsorbed or occluded by the other separation means 2.

  Note that, by controlling the switching valves 151 and 141, the desorption of NOx from the separation means 2 can be performed at a desired timing according to the engine conditions, the adsorption amount or occlusion amount of NOx in each separation means 2, and the like. it can. Further, the desorption of NOx from the separation means 2 can be performed by rich lean control of combustion, addition of gas fuel or liquid fuel into the exhaust gas, and the like.

Others are the same as in Reference Example 1 . Of the reference numerals used in this example or the drawings relating to this example, the same reference numerals as those used in Reference Example 1 represent the same components as in Reference Example 1 unless otherwise indicated.

In the case of this example, the separation means 2 can continuously adsorb or occlude NOx and increase the amount of NOx to be stored. Thereby, the amount of N ₂ O that can be recirculated to the combustion chamber 7 and the degree of freedom of the recirculation timing can be improved.
In addition, the same effects as those of Reference Example 1 are obtained.

  In place of this example, as shown in FIG. 4, the two separating means 2 may be connected in series with each other and provided between the first exhaust pipe 11 and the second exhaust pipe 12. Alternatively, three or more separation means may be connected in parallel or in series.

( Example 1 )
This example is an example of the exhaust gas treatment apparatus 1 in which an oxidation treatment unit 61 that oxidizes N ₂ O that may exist in the exhaust gas is provided between the combustion chamber 7 and the separation means 2 as shown in FIG. is there.
That is, the exhaust gas treatment apparatus 1 is provided with an oxidation treatment unit 61 in the middle of the first exhaust pipe 11 that connects between the combustion chamber 7 and the separation means 2. The oxidation treatment unit 61 oxidizes N ₂ O that may be present in the exhaust gas and converts it into NO. As the oxidation treatment unit 61, for example, a heat treatment device, a catalyst device using a noble metal or a transition metal, a plasma treatment device, a UV irradiation device, a microwave irradiation device, or a device appropriately combining these devices can be used. .
Others are the same as in Reference Example 1 . Of the reference numerals used in this example or the drawings relating to this example, the same reference numerals as those used in Reference Example 1 represent the same components as in Reference Example 1 unless otherwise indicated.

In the case of this example, it is possible to reliably prevent N ₂ O from being discharged into the atmosphere together with the exhaust gas. That is, the exhaust gas treatment apparatus 1 having a conversion means 3, for those refluxing N ₂ O into the combustion chamber 7, a relatively large amount of N ₂ O is supplied to the combustion chamber 7. Therefore, it is assumed that a lot of N ₂ O remains in the combustion chamber 7 without being sufficiently decomposed and is discharged from the exhaust port 72 together with the exhaust gas. There is also a concern that the N ₂ O discharged in this way is released into the atmosphere without being separated from the exhaust gas in the separation means 2. Since N ₂ O is a gas with a high global warming potential, we want to avoid this situation. Therefore, assuming that N ₂ O can be contained in the exhaust gas discharged from the exhaust port 72, the oxidation treatment unit 61 is provided. Thereby, even if N ₂ O is discharged from the exhaust port 72, it is possible to prevent N ₂ O from being discharged into the atmosphere.
In addition, the same effects as those of Reference Example 1 are obtained.

In the above embodiment, instead of the oxidation treatment unit 61, a reduction treatment unit for reducing N ₂ O that may be present in the exhaust gas may be provided at the same position as the oxidation treatment unit 61 in FIG. In this case, the reduction processing unit reduces N ₂ O and converts it to N ₂ . This also prevents N ₂ O from being discharged into the atmosphere. As the reduction treatment unit, for example, a heat treatment device, a catalyst device using a noble metal or a transition metal, a plasma treatment device, a UV irradiation device, a microwave irradiation device, or a device appropriately combining these devices can be used.

( Reference Example 4 )
In this example, as shown in FIG. 6, the separation means 2 is connected to a discharge passage (second exhaust pipe 12) for discharging the exhaust gas from which NOx has been separated, and the exhaust passage is present in the exhaust gas. This is an example of the exhaust gas treatment apparatus 1 provided with a reduction treatment unit 62 for reducing the possible N ₂ O.
That is, the exhaust gas treatment apparatus 1 is provided with the reduction treatment unit 62 in the second exhaust pipe 12. The reduction processing unit 62 reduces N ₂ O that may be present in the exhaust gas and converts it into nitrogen (N ₂ ). As the reduction treatment unit 62, for example, a heat treatment device, a catalyst device using a noble metal or a transition metal, a plasma treatment device, a UV irradiation device, a microwave irradiation device, or a combination of these devices can be used.
Others are the same as in Reference Example 1 . Of the reference numerals used in this example or the drawings relating to this example, the same reference numerals as those used in Reference Example 1 represent the same components as in Reference Example 1 unless otherwise indicated.

This example also assumes that N ₂ O can be contained in the exhaust gas discharged from the exhaust port 72 as in the case of the first embodiment . Therefore, the exhaust gas treatment apparatus 1 of this example is provided with the reduction treatment unit 62 as described above. Thus, N ₂ O is discharged from the exhaust port 72, the N ₂ O is even flowing into the second exhaust pipe 12 passes through the separating means 2, for reducing the N ₂ O to nitrogen by the reducing unit 62 be able to. Thereby, it is possible to prevent N ₂ O from being discharged into the atmosphere.
In addition, the same effects as those of Reference Example 1 are obtained.

The present invention is not limited to the above embodiments. For example, the aspect which combined the reference example 2 and Example 1 can also be set. That is, as shown in FIG. 9 , the conversion means 3 can be incorporated in the separation means 2 in the first embodiment (FIG. 5) . In other words, it is possible to position the separating means 2 in the first embodiment, the separating means 2 and the conversion means 3 and the exhaust gas treatment apparatus 1 provided with a separate converting unit 5 that aggregates the. In this case, it can be set as the exhaust gas processing apparatus 1 which produces | generates the effect of Reference Example 2 and the effect of Example 1 synergistically.
In addition to the above, it is possible to appropriately combine the plurality of reference examples and Example 1, such as a combination of Reference Example 3 and Example 1 .
7 and 8 show a mode in which Reference Example 2 and Reference Example 3 are combined. FIG. 10 shows a mode in which Reference Example 2 and Reference Example 4 are combined.

DESCRIPTION OF SYMBOLS 1 Exhaust gas processing apparatus 2 Separation means 3 Conversion means 4 Reflux means 7 Combustion chamber

Claims (6)

Separation means (2) for adsorbing or storing nitrogen oxides in the exhaust gas discharged from the combustion chamber (7) of the internal combustion engine and separating it from the exhaust gas;
Conversion means (3) for generating nitrous oxide from the nitrogen oxides adsorbed or occluded by the separation means (2);
It possesses the converting means (3) converting the gas the combustion chamber containing the nitrous oxide obtained by the recirculation means for recirculating the (7) (4), a,
An exhaust gas treatment apparatus characterized in that an oxidation treatment section (61) for oxidizing nitrous oxide that may be present in the exhaust gas is provided between the combustion chamber (7) and the separation means (2). (1). Separation means (2) for adsorbing or storing nitrogen oxides in the exhaust gas discharged from the combustion chamber (7) of the internal combustion engine and separating it from the exhaust gas;
Conversion means (3) for generating nitrous oxide from the nitrogen oxides adsorbed or occluded by the separation means (2);
Reflux means (4) for refluxing the conversion gas containing nitrous oxide obtained by the conversion means (3) to the combustion chamber (7),
Between the combustion chamber (7) and the separation means (2), there is provided a reduction treatment unit for reducing nitrous oxide that may be present in the exhaust gas. . The separation conversion unit (5) including the separation unit (2) and the conversion unit (3) is provided, and the nitrogen oxide adsorbed or occluded in the separation conversion unit (5) is converted into the nitrous oxide. The exhaust gas treatment device (1) according to claim 1 or 2 , wherein the exhaust gas treatment device (1) is configured so as to be discharged from the separation / conversion unit (5) in the state described above. The nitrogen oxides after being released from the separating means (2), by the conversion means (3) according to claim 1 or 2, characterized in that are configured to convert the nitrous oxide Exhaust gas treatment device (1). A plurality of said separating means (2), according to claim 1 or 2, characterized in that are configured to be able to vary the release time of the nitrogen oxides from the plurality of separation means (2) to each other Exhaust gas treatment device (1). The separation means (2) is connected to a discharge passage for discharging the exhaust gas from which the nitrogen oxides have been separated, and a reduction treatment for reducing nitrous oxide that may be present in the exhaust gas is connected to the discharge passage. The exhaust gas treatment device (1) according to any one of claims 1 to 5, wherein a portion (62) is provided.

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