JP4525442B2

JP4525442B2 - Exhaust gas purification device for internal combustion engine

Info

Publication number: JP4525442B2
Application number: JP2005123601A
Authority: JP
Inventors: 優一祖父江; 一伸石橋; 宏幸松原; 真由子大▲崎▼
Original assignee: Toyota Motor Corp
Current assignee: Toyota Motor Corp
Priority date: 2005-04-21
Filing date: 2005-04-21
Publication date: 2010-08-18
Anticipated expiration: 2025-04-21
Also published as: JP2006299960A

Description

本発明は内燃機関の排気浄化装置に関する。 The present invention relates to an exhaust emission control device for an internal combustion engine.

機関から排出された排気ガスを水で満たされたバブリング槽内に噴出させてバブリング槽内の水にＮＯｘを溶解させ、多数の電極板を備えた中和槽内にＮＯｘが溶解している水を送り込んでこの水内に含まれるＮＯｘを電解作用により可溶性物質に変換し、この水を排出することによりＮＯｘを除去するようにした排気ガス浄化装置が公知である（例えば特許文献１参照）。
特開２００３−３０１７１４号公報 Water in which NOx is dissolved in a neutralization tank equipped with a large number of electrode plates by discharging exhaust gas discharged from the engine into a bubbling tank filled with water to dissolve NOx in the water in the bubbling tank. There is known an exhaust gas purifying device in which NOx contained in the water is converted into a soluble substance by electrolysis and NOx is removed by discharging the water (see, for example, Patent Document 1).
JP 2003-301714 A

しかしながら上述の排気ガス浄化装置では電極板は消耗品であり、従って電極板をしばしば交換しなければならないという問題がある。 However, in the above-described exhaust gas purification apparatus, the electrode plate is a consumable item, and therefore there is a problem that the electrode plate must be frequently replaced.

上記問題点を解決するために本発明によれば、機関排気通路内にＮＯｘを浄化しうる触媒を配置し、この触媒下流の機関排気通路内に排気ガス中のＮＯｘを水又は水溶液内に吸収させるＮＯｘ吸収部を設け、ＮＯｘを吸収した水又は水溶液を触媒上流の機関排気通路内に供給するための供給装置を具備し、機関始動後触媒が活性化するまでは機関から排出されたＮＯｘはＮＯｘ吸収部において水又は水溶液内に吸収され、ＮＯｘを吸収した水又は水溶液は触媒が活性化しているときに供給装置から機関排気通路内に供給され、このとき供給された水又は水溶液中に含まれるＮＯｘは触媒において浄化される。 In order to solve the above problems, according to the present invention, a catalyst capable of purifying NOx is disposed in the engine exhaust passage, and NOx in the exhaust gas is absorbed in water or an aqueous solution in the engine exhaust passage downstream of the catalyst. Provided with a supply device for supplying NOx absorbed water or an aqueous solution into the engine exhaust passage upstream of the catalyst, and NOx discharged from the engine until the catalyst is activated after the engine is started The water or aqueous solution absorbed in the water or aqueous solution in the NOx absorption section and absorbed NOx is supplied from the supply device into the engine exhaust passage when the catalyst is activated, and is included in the supplied water or aqueous solution. NOx is purified in the catalyst.

しばしば交換を必要とするような消耗品を用いることなく機関始動時から排気ガス中のＮＯｘを除去することができる。 NOx in the exhaust gas can be removed from the start of the engine without using consumables that often need replacement.

図１を参照すると、１はガソリンエンジン又はディーゼルエンジン、２はエンジン１の排気通路、３は排気通路２内に配置されたＮＯｘを浄化しうる触媒３を示す。この触媒３としては、三元触媒、又は炭化水素の存在のもとで排気ガス中のＮＯｘを浄化するＮＯｘ浄化触媒、又は排気ガス中のＮＯｘを吸収するＮＯｘ還元型三元触媒のいずれかが用いられる。 Referring to FIG. 1, 1 is a gasoline engine or diesel engine, 2 is an exhaust passage of the engine 1, and 3 is a catalyst 3 that can purify NOx disposed in the exhaust passage 2. The catalyst 3 is either a three-way catalyst, a NOx purification catalyst that purifies NOx in exhaust gas in the presence of hydrocarbons, or a NOx reduction type three-way catalyst that absorbs NOx in exhaust gas. Used.

触媒３下流の排気通路２内には排気ガス中のＮＯｘを水又は水溶液内に吸収させるためのＮＯｘ吸収部４が設けられており、このＮＯｘ吸収部４下流の排気通路２内には排気ガス中に含まれる水分を捕集するための水捕集部５が配置されている。一方、ＮＯｘ吸収部４においてＮＯｘを吸収した水又は水溶液を貯蔵するためのＮＯｘ吸収水タンク６が設けられており、更にＮＯｘを吸収した水又は水溶液を触媒３上流の排気通路２内に供給するための供給装置７が設けられている。 A NOx absorption part 4 for absorbing NOx in the exhaust gas into water or an aqueous solution is provided in the exhaust passage 2 downstream of the catalyst 3. The exhaust gas is exhausted in the exhaust passage 2 downstream of the NOx absorption part 4. A water collecting part 5 for collecting moisture contained therein is arranged. On the other hand, a NOx absorption water tank 6 for storing water or an aqueous solution that has absorbed NOx in the NOx absorption section 4 is provided, and further water or an aqueous solution that has absorbed NOx is supplied into the exhaust passage 2 upstream of the catalyst 3. A supply device 7 is provided.

この供給装置７は具体的に言うと、ＮＯｘ吸収水タンク６内に貯蔵されたＮＯｘを含有した水又は水溶液を排気通路２内に噴霧するためのインジェクタ８と、ＮＯｘ吸収水タンク６内に貯蔵されたＮＯｘを含有した水又は水溶液をインジェクタ８に送り込むための供給ポンプ９からなる。また、本発明による実施例では、水捕集部５において捕集された水分を貯蔵するための水タンク１０が設けられている。 More specifically, the supply device 7 stores the NOx-containing water or aqueous solution stored in the NOx absorption water tank 6 in the exhaust passage 2 and the NOx absorption water tank 6. It comprises a supply pump 9 for feeding water or an aqueous solution containing the NOx thus produced into the injector 8. Moreover, in the Example by this invention, the water tank 10 for storing the water | moisture content collected in the water collection part 5 is provided.

本発明による実施例では機関始動時および機関始動後少くとも触媒３が活性化するまでの間、エンジン１の燃焼室内における空燃比が理論空燃比又はリーンとされる。無論この場合、機関の始動から機関が停止されるまでの全ての運転期間に亘って燃焼室内における空燃比をリーンとすることもできる。 In the embodiment according to the present invention, the air-fuel ratio in the combustion chamber of the engine 1 is made the stoichiometric air-fuel ratio or lean at the time of engine start and until at least the catalyst 3 is activated after engine start. Of course, in this case, the air-fuel ratio in the combustion chamber can be made lean over the entire operation period from the start of the engine to the stop of the engine.

さて、燃焼室内における空燃比がリーンにされると酸素が過剰なために未燃ＨＣ，ＣＯはあまり発生しないが多量のＮＯｘが発生する。従って、機関の運転が開始されてから触媒３が活性化するまでの間、燃焼室内における空燃比がリーンにされるとこの間、多量のＮＯｘが排気通路２内に排出されることになる。一方、触媒３は活性化するまではＮＯｘを浄化する能力はなく、従って機関の運転が開始されてから触媒３が活性化するまでの間、排気ガス中に含まれる多量のＮＯｘは触媒３において浄化されることなく触媒３を素通りすることになる。 When the air-fuel ratio in the combustion chamber is made lean, oxygen is excessive, so that unburned HC and CO are not generated much, but a large amount of NOx is generated. Therefore, when the air-fuel ratio in the combustion chamber is made lean between the start of engine operation and the activation of the catalyst 3, a large amount of NOx is discharged into the exhaust passage 2 during this period. On the other hand, the catalyst 3 does not have the ability to purify NOx until it is activated. Therefore, a large amount of NOx contained in the exhaust gas is not generated in the catalyst 3 until the catalyst 3 is activated after the operation of the engine is started. The catalyst 3 passes through without being purified.

このことは燃焼室内の空燃比をほぼ理論空燃比に維持するようにした場合も同様である。即ち、この場合には、燃焼室内の空燃比がややリッチになっても未燃ＨＣ，ＣＯはさほど増大せず、燃焼室内の空燃比がややリーンになると多量のＮＯｘが発生する。従って、機関の運転が開始されてから触媒３が活性化するまでの間、燃焼室内の空燃比がほぼ理論空燃比に維持されると多量のＮＯｘが排気通路２内に排出されることになる。このとき上述したように触媒３はＮＯｘを浄化する能力を有さず、従ってこの場合も同様に機関の運転が開始されてから触媒３が活性化するまでの間、排気ガス中に含まれる多量のＮＯｘは触媒３において浄化されることなく触媒３を素通りすることになる。 The same applies to the case where the air-fuel ratio in the combustion chamber is maintained substantially at the stoichiometric air-fuel ratio. That is, in this case, even if the air-fuel ratio in the combustion chamber becomes slightly rich, unburned HC and CO do not increase so much, and when the air-fuel ratio in the combustion chamber becomes slightly lean, a large amount of NOx is generated. Therefore, a large amount of NOx is discharged into the exhaust passage 2 when the air-fuel ratio in the combustion chamber is maintained at approximately the stoichiometric air-fuel ratio between the start of engine operation and the activation of the catalyst 3. . At this time, as described above, the catalyst 3 does not have the ability to purify NOx. Therefore, in this case as well, a large amount contained in the exhaust gas from the start of the operation of the engine until the activation of the catalyst 3 is similarly performed. The NOx passes through the catalyst 3 without being purified in the catalyst 3.

本発明ではこのように機関の運転が開始されてから触媒３が活性化するまでの間、触媒３を素通りしたＮＯｘ、即ちエンジン１から排出されたＮＯｘは、ＮＯｘ吸収部４において水又は水溶液内に吸収される。具体的に言うと、このＮＯｘ吸収部４では、排気ガスに水又は水溶液を噴霧することにより排気ガス中に含まれるＮＯｘが水又は水溶液内に溶解せしめられるか、或いは排ガスを水又は水溶液内を通過させることにより排気ガス中に含まれるＮＯｘが水又は水溶液内に溶解せしめられる。ＮＯｘが溶解せしめられた水又は水溶液はＮＯｘ吸収水タンク６に送り込まれる。 In the present invention, the NOx passing through the catalyst 3, that is, the NOx discharged from the engine 1 during the period from the start of the operation of the engine to the activation of the catalyst 3, that is, NOx discharged from the engine 1 is contained in water or an aqueous solution in the NOx absorption section 4. To be absorbed. More specifically, in this NOx absorption section 4, NOx contained in the exhaust gas is dissolved in the water or the aqueous solution by spraying water or an aqueous solution on the exhaust gas, or the exhaust gas is passed through the water or the aqueous solution. By passing it, NOx contained in the exhaust gas is dissolved in water or an aqueous solution. The water or aqueous solution in which NOx is dissolved is fed into the NOx absorption water tank 6.

一方、ＮＯｘ吸収部４においては排気ガス中のＮＯｘを吸収するための水および水溶液として、水タンク１０内に貯蔵されている水又は水溶液、即ち水捕集部５において捕集された水分が使用される。このようにＮＯｘ吸収部４においてＮＯｘを吸収するために使用される水又は水溶液は排気ガス中から捕集されるので外部から水又は水溶液を特に補充する必要はない。 On the other hand, in the NOx absorption unit 4, water or an aqueous solution stored in the water tank 10, that is, water collected in the water collection unit 5 is used as water and an aqueous solution for absorbing NOx in the exhaust gas. Is done. Thus, since the water or aqueous solution used for absorbing NOx in the NOx absorption part 4 is collected from the exhaust gas, it is not necessary to replenish water or the aqueous solution from the outside.

さて、触媒３が活性化すると排気ガス中のＮＯｘは触媒３において浄化することができる。そこで本発明では、ＮＯｘ吸収部４においてＮＯｘを吸収した水又は水溶液は触媒３が活性化しているときに供給装置７から排気通路２内に供給され、このとき供給された水又は水溶液中に含まれるＮＯｘが触媒３において浄化せしめられる。具体的に言うと、触媒３が活性化したとき、又は触媒３が活性化してから暫らくした後にＮＯｘ吸収水タンク６内のＮＯｘを含有した水又は水溶液が供給ポンプ９によってインジェクタ８から排気通路２内に予め定められた期間に亘って噴霧され、噴霧内に含まれるＮＯｘは触媒３において浄化される。 When the catalyst 3 is activated, NOx in the exhaust gas can be purified by the catalyst 3. Therefore, in the present invention, the water or aqueous solution that has absorbed NOx in the NOx absorbing portion 4 is supplied into the exhaust passage 2 from the supply device 7 when the catalyst 3 is activated, and is included in the supplied water or aqueous solution. NOx is purified in the catalyst 3. Specifically, when the catalyst 3 is activated or after a while after the catalyst 3 is activated, water or an aqueous solution containing NOx in the NOx absorption water tank 6 is discharged from the injector 8 by the supply pump 9 from the injector 8. 2 is sprayed over a predetermined period, and NOx contained in the spray is purified by the catalyst 3.

触媒３が活性化した後も燃焼室内の空燃比がリーンにされる場合には、触媒３として前述した炭化水素の存在のもとで排気ガス中のＮＯｘを浄化するＮＯｘ浄化触媒、又は排気ガス中のＮＯｘを吸収するＮＯｘ還元型三元触媒が用いられる。なお、このＮＯｘ浄化触媒３は例えばＣｕゼオライトからなり、排気ガスの空燃比がリーンのもとでＮＯｘの還元作用が行われる。一方、ＮＯｘ吸蔵還元型三元触媒３は例えばアルカリ金属やアルカリ土類金属からなるＮＯｘ吸収剤を担持しており、ＮＯｘ吸蔵還元型三元触媒３に流入する排気ガスの空燃比がリーンのときに排気ガス中のＮＯｘがＮＯｘ吸収剤に吸収される。この場合、ＮＯｘ吸蔵還元型三元触媒３内に流入する排気ガスの空燃比を一時的にリッチにするとＮＯｘ吸収剤に吸収されていたＮＯｘがＮＯｘ吸収剤から放出して還元される。 When the air-fuel ratio in the combustion chamber is made lean even after the catalyst 3 is activated, the NOx purifying catalyst for purifying NOx in the exhaust gas in the presence of the hydrocarbon described above as the catalyst 3, or the exhaust gas A NOx reduction type three-way catalyst that absorbs NOx therein is used. The NOx purification catalyst 3 is made of, for example, Cu zeolite, and NOx is reduced when the air-fuel ratio of the exhaust gas is lean. On the other hand, the NOx occlusion reduction type three-way catalyst 3 carries a NOx absorbent made of, for example, alkali metal or alkaline earth metal, and the exhaust gas flowing into the NOx occlusion reduction type three way catalyst 3 is lean. NOx in the exhaust gas is absorbed by the NOx absorbent. In this case, when the air-fuel ratio of the exhaust gas flowing into the NOx occlusion reduction type three-way catalyst 3 is temporarily made rich, the NOx absorbed in the NOx absorbent is released from the NOx absorbent and reduced.

一方、触媒３が活性化した後は燃焼室内の空燃比がほぼ理論空燃比に維持される場合には触媒３として三元触媒が使用される。三元触媒３を用い、燃焼室内の空燃比がほぼ理論空燃比に維持されると排気ガス中のＮＯｘばかりでなく、未燃ＨＣ，ＣＯも同様に除去される。 On the other hand, a three-way catalyst is used as the catalyst 3 when the air-fuel ratio in the combustion chamber is substantially maintained at the stoichiometric air-fuel ratio after the catalyst 3 is activated. When the three-way catalyst 3 is used and the air-fuel ratio in the combustion chamber is maintained substantially at the stoichiometric air-fuel ratio, not only NOx in the exhaust gas but also unburned HC and CO are similarly removed.

図２に別の実施例を示す。この実施例ではＮＯｘ吸収部４において排気ガス中のＮＯｘを吸収するために使用される水又は水溶液内にオゾンを添加するためにオゾン供給部１１が設けられている。なお、図２に示す例でオゾンはオゾン供給部１１から、水タンク１０内に貯蔵されている水又は水溶液内に添加される。このように水又は水溶液内にオゾンを添加すると水又は水溶液によるＮＯｘの吸収能力が向上し、斯くしてＮＯｘの排出量を低減することができる。 FIG. 2 shows another embodiment. In this embodiment, an ozone supply unit 11 is provided to add ozone into water or an aqueous solution used to absorb NOx in the exhaust gas in the NOx absorption unit 4. In the example shown in FIG. 2, ozone is added from the ozone supply unit 11 to water or an aqueous solution stored in the water tank 10. When ozone is added to water or an aqueous solution in this way, the ability to absorb NOx by the water or aqueous solution is improved, and thus the amount of NOx discharged can be reduced.

オゾン供給部１１では例えばオゾネータを用いて空気中の酸素からオゾンが生成される。従って図２に示される実施例ではＮＯｘを吸収するための水も、水に添加されるオゾンも外部から補充する必要はない。 In the ozone supply unit 11, ozone is generated from oxygen in the air using, for example, an ozonator. Therefore, in the embodiment shown in FIG. 2, it is not necessary to replenish water for absorbing NOx and ozone added to water from the outside.

図１および図２に示される実施例ではＮＯｘ吸収部４におけるＮＯｘの吸収作用は機関の運転が開始されてから触媒３が活性化するまで行われ、この間に吸収されたＮＯｘが触媒３の活性化後にインジェクタ８から排気通路２内に噴霧される。しかしながら機関の運転が開始されてから機関の運転が停止されるまで継続的にＮＯｘ吸収部４においてＮＯｘが吸収され続け、これらＮＯｘを含んだ水又は水溶液を触媒３の活性化後、継続的にインジェクタ８から排気通路２内に供給し続けることもできる。 In the embodiment shown in FIGS. 1 and 2, the NOx absorption action in the NOx absorption unit 4 is performed from the start of engine operation until the catalyst 3 is activated, and the NOx absorbed during this time is the activity of the catalyst 3. After the conversion, the fuel is sprayed from the injector 8 into the exhaust passage 2. However, NOx is continuously absorbed in the NOx absorption unit 4 from the start of the engine operation until the engine operation is stopped, and after the activation of the catalyst 3, the NOx-containing water or aqueous solution is continuously absorbed. The supply from the injector 8 into the exhaust passage 2 can be continued.

排気浄化装置の全体図である。1 is an overall view of an exhaust purification device. 排気浄化装置の別の実施例を示す全体図である。It is a general view which shows another Example of an exhaust gas purification apparatus.

Explanation of symbols

１エンジン
２排気通路
３触媒
４ＮＯｘ吸収部
５水捕集部
６ＮＯｘ吸収水タンク
７供給装置
８インジェクタ
９供給ポンプ
１０水タンク
１１オゾン供給部 DESCRIPTION OF SYMBOLS 1 Engine 2 Exhaust passage 3 Catalyst 4 NOx absorption part 5 Water collection part 6 NOx absorption water tank 7 Supply apparatus 8 Injector 9 Supply pump 10 Water tank 11 Ozone supply part

Claims

A catalyst capable of purifying NOx is disposed in the engine exhaust passage, and a NOx absorption part for absorbing NOx in the exhaust gas into water or an aqueous solution is provided in the engine exhaust passage downstream of the catalyst, and the water or aqueous solution that has absorbed NOx. Is supplied into the engine exhaust passage upstream of the catalyst, and after the engine is started, the NOx discharged from the engine is absorbed in water or an aqueous solution in the NOx absorption section until the catalyst is activated, The water or aqueous solution that has absorbed NOx is supplied from the supply device into the engine exhaust passage when the catalyst is activated, and the NOx contained in the supplied water or aqueous solution is purified by the catalyst. Engine exhaust purification system.

2. The catalyst according to claim 1, wherein the catalyst is a three-way catalyst, a NOx purification catalyst that purifies NOx in exhaust gas in the presence of hydrocarbons, or a NOx reduction type three-way catalyst that absorbs NOx in exhaust gas. Exhaust gas purification device for internal combustion engine.

2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the air-fuel ratio in the engine combustion chamber is set to the stoichiometric air-fuel ratio or lean from the time of starting the engine until the catalyst is activated at least.

2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the NOx absorption unit dissolves NOx contained in the exhaust gas in the water or the aqueous solution by spraying water or an aqueous solution on the exhaust gas.

2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the NOx absorption unit dissolves NOx contained in the exhaust gas in the water or the aqueous solution by allowing the exhaust gas to pass through the water or the aqueous solution.

The exhaust purification device for an internal combustion engine according to claim 1, further comprising a NOx absorption water tank for storing water or an aqueous solution that has absorbed NOx in the NOx absorption section.

The exhaust purification device for an internal combustion engine according to claim 6, wherein the supply device includes an injector for spraying water or an aqueous solution containing NOx stored in a NOx absorption water tank into the engine exhaust passage.

A water collecting unit for collecting moisture contained in the exhaust gas is disposed in the engine exhaust passage downstream of the NOx absorbing unit, and water and an aqueous solution for absorbing NOx in the exhaust gas in the NOx absorbing unit. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein moisture collected in the water collecting part is used.

The exhaust gas purification apparatus for an internal combustion engine according to claim 8, further comprising a water tank for storing the water collected in the water collecting section.

The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein ozone is added to water or an aqueous solution used for absorbing NOx in the exhaust gas in the NOx absorption section.

The exhaust emission control device for an internal combustion engine according to claim 10, wherein the ozone is generated using oxygen in the air.