JP2009115022A - Exhaust emission control device - Google Patents

Exhaust emission control device Download PDF

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JP2009115022A
JP2009115022A JP2007290588A JP2007290588A JP2009115022A JP 2009115022 A JP2009115022 A JP 2009115022A JP 2007290588 A JP2007290588 A JP 2007290588A JP 2007290588 A JP2007290588 A JP 2007290588A JP 2009115022 A JP2009115022 A JP 2009115022A
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particulate filter
catalyst
exhaust gas
exhaust
oxidation catalyst
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Okitomo Matsunami
意知 松波
Jinichi Namikawa
仁一 南川
Rui Sano
類 佐野
Hiroshi Hirabayashi
浩 平林
Hisataka Michisaka
久貴 通阪
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Hino Motors Ltd
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    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02TCLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
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    • Y02T10/10Internal combustion engine [ICE] based vehicles
    • Y02T10/12Improving ICE efficiencies

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  • Exhaust Gas After Treatment (AREA)
  • Processes For Solid Components From Exhaust (AREA)
  • Filtering Of Dispersed Particles In Gases (AREA)
  • Exhaust Gas Treatment By Means Of Catalyst (AREA)
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Abstract

<P>PROBLEM TO BE SOLVED: To effectively reduce NOx by positively supplying a sufficient amount of HC gas for reducing and controlling NOx to a selective reduction type catalyst in an exhaust emission control device that reduces both of NOx and particulates by using both of a particulate filter and the selective reduction type catalyst. <P>SOLUTION: This exhaust emission control device includes, in mid-way of an exhaust pipe 9, the particulate filter 11 for collecting particulates in exhaust gas 7, an oxidation catalyst 12 for oxidizing unburned HC in the exhaust gas 7 at a further upstream side than the particulate filter 11, and an injector 14 (fuel addition device) for adding fuel to the exhaust gas 7 at a further upstream side than the oxidation catalyst 12. The selective reduction type catalyst 13 for selectively reacting NOx with HC even under coexistence of oxygen is interposed between the oxidation catalyst 12 and the particulate filter 11. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

本発明は、排気浄化装置に関するものである。   The present invention relates to an exhaust emission control device.

ディーゼルエンジンから排出されるパティキュレート(Particulate Matter:粒子状物質)は、炭素質から成る煤分と、高沸点炭化水素成分から成るSOF分(Soluble Organic Fraction:可溶性有機成分)とを主成分とし、更に微量のサルフェート(ミスト状硫酸成分)を含んだ組成を成すものであるが、この種のパティキュレートの低減対策としては、排気ガスが流通する排気管の途中に、パティキュレートフィルタを装備することが従来より行われている。   Particulate matter (particulate matter) discharged from a diesel engine is mainly composed of a soot fraction composed of carbon and a SOF fraction (Soluble Organic Fraction) composed of a high-boiling hydrocarbon component. Furthermore, the composition contains a small amount of sulfate (mist-like sulfuric acid component). As a measure to reduce this type of particulates, a particulate filter is installed in the middle of the exhaust pipe through which the exhaust gas flows. Has been performed conventionally.

前記パティキュレートフィルタは、コージェライト等のセラミックから成る多孔質のハニカム構造となっており、格子状に区画された各流路の入口が交互に目封じされ、入口が目封じされていない流路については、その出口が目封じされるようになっており、各流路を区画する多孔質薄壁を透過した排気ガスのみが下流側へ排出されるようにしてある。   The particulate filter has a porous honeycomb structure made of a ceramic such as cordierite, and the inlets of the respective channels partitioned in a lattice shape are alternately sealed, and the channels are not sealed. The outlet is sealed, and only the exhaust gas that has permeated through the porous thin wall that defines each flow path is discharged downstream.

そして、排気ガス中のパティキュレートは、前記多孔質薄壁の内側表面に捕集されて堆積するので、目詰まりにより排気抵抗が増加しないうちにパティキュレートを適宜に燃焼除去してパティキュレートフィルタの再生を図る必要があるが、通常のディーゼルエンジンの運転状態においては、パティキュレートが自己燃焼するほどの高い排気温度が得られる機会が少ない為、酸化触媒を一体的に担持させた触媒再生型のパティキュレートフィルタの採用が検討されている。   Then, the particulates in the exhaust gas are collected and deposited on the inner surface of the porous thin wall, so that the particulates are appropriately burned and removed before the exhaust resistance increases due to clogging. It is necessary to regenerate, but in normal diesel engine operation conditions, there are few opportunities to obtain exhaust temperatures that are high enough for particulates to self-combust, so a catalyst regeneration type that integrally supports an oxidation catalyst. Adoption of a particulate filter is being studied.

即ち、このような触媒再生型のパティキュレートフィルタを採用すれば、捕集されたパティキュレートの酸化反応が促進されて着火温度が低下し、従来より低い排気温度でもパティキュレートを燃焼除去することが可能となるのである。   That is, if such a catalyst regeneration type particulate filter is employed, the oxidation reaction of the collected particulates is promoted to lower the ignition temperature, and the particulates can be burned and removed even at an exhaust temperature lower than the conventional one. It becomes possible.

ただし、斯かる触媒再生型のパティキュレートフィルタを採用した場合であっても、排気温度の低い運転領域では、パティキュレートの処理量よりも捕集量が上まわってしまうので、このような低い排気温度での運転状態が続くと、パティキュレートフィルタの再生が良好に進まずに該パティキュレートフィルタが過捕集状態に陥る虞れがある。   However, even when such a catalyst regeneration type particulate filter is used, the trapped amount exceeds the particulate processing amount in the operation region where the exhaust temperature is low, so such a low exhaust gas. If the operation state at the temperature continues, there is a possibility that the particulate filter will fall into an over trapped state without the regeneration of the particulate filter proceeding well.

そこで、パティキュレートフィルタの前段に、フロースルー型の酸化触媒を別途配置し、パティキュレートの堆積量が増加してきた段階で前記酸化触媒より上流側の排気ガス中に燃料を添加してパティキュレートフィルタの強制再生を行うことが考えられている。   Therefore, a flow-through type oxidation catalyst is separately arranged in front of the particulate filter, and fuel is added to the exhaust gas upstream of the oxidation catalyst at the stage where the amount of particulate accumulation has increased. It is considered to perform forced regeneration.

つまり、パティキュレートフィルタより上流側で添加された燃料(HC)が前段の酸化触媒を通過する間に酸化反応し、その反応熱で昇温した排気ガスの流入により直後のパティキュレートフィルタの触媒床温度が上げられてパティキュレートが燃やし尽くされ、パティキュレートフィルタの再生化が図られることになる(例えば下記の特許文献1を参照)。   That is, the fuel (HC) added on the upstream side of the particulate filter undergoes an oxidation reaction while passing through the preceding oxidation catalyst, and the catalyst bed of the particulate filter immediately after the inflow of exhaust gas heated by the reaction heat. The temperature is raised, the particulates are burned out, and the particulate filter is regenerated (see, for example, Patent Document 1 below).

ただし、ディーゼルエンジンの排気浄化を図る場合、前述のように排気ガス中のパティキュレートを除去するだけでは十分ではなく、排気ガス中に含まれるNOx(窒素酸化物)についても除去する必要があるので、一般的には、排気系から抜き出した排気ガスの一部を吸気系へ戻し且つその吸気系に戻された排気ガスでエンジン内での燃料の燃焼を抑制させて燃焼温度を下げることによりNOx(窒素酸化物)の発生を低減するEGR装置(EGR:Exhaust Gas Recirculation)が併用されているが、近年における排ガス規制の強化に伴い、排気温度の低い運転状態でのNOx値を排気ガスの再循環だけで目標値まで低減するのが困難になってきている。   However, when purifying exhaust gas from a diesel engine, it is not sufficient to remove particulates in the exhaust gas as described above, and it is also necessary to remove NOx (nitrogen oxide) contained in the exhaust gas. In general, a part of the exhaust gas extracted from the exhaust system is returned to the intake system, and the exhaust gas returned to the intake system is used to suppress combustion of the fuel in the engine to lower the combustion temperature. An EGR device (EGR: Exhaust Gas Recirculation) that reduces the generation of (nitrogen oxides) is used together. However, in recent years, exhaust gas regulations have been strengthened. It has become difficult to reduce to the target value only by circulation.

このため、本発明者は、酸素共存下でも選択的にNOxをHCと反応せしめる選択還元型触媒をパティキュレートフィルタの直後に追加装備し、排気温度の低い運転状態で前記酸化触媒より上流側に添加した燃料の一部を未処理のまま前記選択還元型触媒まで導いてNOxを還元浄化することを創案するに到った。
特開2003−193824号公報
For this reason, the present inventor has additionally provided a selective reduction type catalyst that selectively reacts NOx with HC even in the presence of oxygen immediately after the particulate filter, and upstream of the oxidation catalyst in an operating state with a low exhaust temperature. The inventors have come up with the idea of reducing and purifying NOx by introducing a part of the added fuel to the selective catalytic reduction catalyst without any treatment.
JP 2003-193824 A

しかしながら、このように選択還元型触媒をパティキュレートフィルタの直後に追加装備した場合に、その上流側にNOxを還元浄化するための還元剤として燃料を添加しても、その添加燃料から生じたHCガスの大半が、前段の酸化触媒やパティキュレートフィルタを通過する間に消費されてしまうので、NOxを還元浄化するのに十分な量のHCガスを最終段の選択還元型触媒まで到達させるのが難しく、該選択還元型触媒を有効に活用することができないという問題があった。   However, when the selective reduction type catalyst is additionally provided immediately after the particulate filter in this way, even if fuel is added as a reducing agent for reducing and purifying NOx on the upstream side, HC generated from the added fuel Since most of the gas is consumed while passing through the preceding oxidation catalyst and particulate filter, a sufficient amount of HC gas to reduce and purify NOx reaches the final selective reduction catalyst. There is a problem that the selective catalytic reduction catalyst cannot be effectively used.

本発明は上述の実情に鑑みてなしたもので、パティキュレートフィルタと選択還元型触媒を併用してNOxとパティキュレートの同時低減化を図る排気浄化装置に関し、NOxを還元浄化するのに十分な量のHCガスを選択還元型触媒に対し確実に供給してNOxを効果的に低減し得るようにすることを目的としている。   The present invention has been made in view of the above-described circumstances, and relates to an exhaust emission control device that simultaneously reduces NOx and particulates by using a particulate filter and a selective reduction catalyst, and is sufficient to reduce and purify NOx. The object is to reliably supply an amount of HC gas to the selective catalytic reduction catalyst so that NOx can be effectively reduced.

本発明は、排気ガス中のパティキュレートを捕集するパティキュレートフィルタと、該パティキュレートフィルタより上流側で排気ガス中の未燃HCを酸化処理する酸化触媒と、該酸化触媒より上流側で排気ガス中に燃料を添加する燃料添加装置を排気管の途中に備えた排気浄化装置において、前記酸化触媒と前記パティキュレートフィルタとの間に、酸素共存下でも選択的にNOxをHCと反応せしめる選択還元型触媒を介装したことを特徴とするものである。   The present invention relates to a particulate filter that collects particulates in exhaust gas, an oxidation catalyst that oxidizes unburned HC in exhaust gas upstream of the particulate filter, and an exhaust gas upstream of the oxidation catalyst. In the exhaust gas purification apparatus provided with a fuel addition apparatus for adding fuel to the gas in the middle of the exhaust pipe, selection is made to selectively react NOx with HC even in the presence of oxygen between the oxidation catalyst and the particulate filter. It is characterized in that a reduced catalyst is interposed.

このようにすれば、燃料添加装置により排気ガス中に燃料を添加した際に、選択還元型触媒がパティキュレートフィルタに先行して配置されていることで該パティキュレートフィルタで消費されていた分のHCガスがそのまま選択還元型触媒に供給されることになり、パティキュレートフィルタの直後に選択還元型触媒を配置していた場合よりも該選択還元型触媒に供給されるHCガスの量が増加し、このHCガスを還元剤としてNOxを良好に還元浄化させることが可能となる。   In this way, when the fuel is added to the exhaust gas by the fuel addition device, the selective reduction catalyst is disposed in front of the particulate filter, so that the amount consumed by the particulate filter is reduced. HC gas is supplied as it is to the selective catalytic reduction catalyst, and the amount of HC gas supplied to the selective catalytic reduction catalyst is increased as compared with the case where the selective catalytic reduction catalyst is arranged immediately after the particulate filter. It becomes possible to satisfactorily reduce and purify NOx using this HC gas as a reducing agent.

他方、選択還元型触媒の直後のパティキュレートフィルタで排気ガス中のパティキュレートが捕集されていくため、パティキュレートとNOxの同時低減化が図られることになり、しかも、燃料添加装置により添加された燃料から生じたHCガスが前段の酸化触媒上で酸化反応し、その反応熱により昇温した排気ガスが流れ込むことにより後段のパティキュレートフィルタの触媒床温度が上げられ、内部に捕集されているパティキュレートが燃やし尽くされてパティキュレートフィルタの再生化が図られる。   On the other hand, the particulate filter in the exhaust gas is collected by the particulate filter immediately after the selective catalytic reduction catalyst, so that the particulate and NOx can be simultaneously reduced, and added by the fuel addition device. The HC gas generated from the burned fuel undergoes an oxidation reaction on the front stage oxidation catalyst, and the exhaust gas heated by the reaction heat flows in, so that the catalyst bed temperature of the rear stage particulate filter is raised and trapped inside. The particulate is burned out and the particulate filter is regenerated.

また、本発明においては、酸化触媒と選択還元型触媒とを同一担体上に担持させて一体化することが可能であり、このようにすれば、酸化触媒と選択還元型触媒とパティキュレートフィルタとを個別に三連配置する場合よりも装置全長が短くなって占有空間のコンパクト化が図られ、しかも、酸化触媒と選択還元型触媒をケーシング内で固定するための部品の点数も削減されることになる。   Further, in the present invention, the oxidation catalyst and the selective reduction catalyst can be supported and integrated on the same carrier, and in this way, the oxidation catalyst, the selective reduction catalyst, the particulate filter, The overall length of the device is shortened compared to the case where three are arranged individually, and the occupied space is made compact, and the number of parts for fixing the oxidation catalyst and the selective reduction catalyst in the casing is also reduced. become.

尚、酸素共存下でも選択的にNOxを還元剤と反応させる性質を持つ選択還元型触媒として知られている白金,パラジウム等の貴金属触媒は、パティキュレートフィルタの強制再生を図るための添加燃料を酸化処理する酸化触媒と成分的に近似するものであり、この酸化触媒と選択還元型触媒とを同一担体上に担持させて一体化することに特に技術的な支障はない。   In addition, noble metal catalysts such as platinum and palladium, which are known as selective reduction catalysts having the property of selectively reacting NOx with a reducing agent even in the presence of oxygen, use added fuel for forced regeneration of the particulate filter. The oxidation catalyst is similar in composition to the oxidation catalyst to be oxidized, and there is no particular technical problem in integrating the oxidation catalyst and the selective reduction catalyst on the same carrier.

ただし、選択還元型触媒としての十分な性能を発揮し得るように該選択還元型触媒をパティキュレートフィルタに担持させることは、該パティキュレートフィルタの目詰まりを招いてしまうため、選択還元型触媒とパティキュレートフィルタとを一体化させることは困難であり、選択還元型触媒をパティキュレートフィルタに先行して配置したからこそ酸化触媒と選択還元型触媒との一体化が実現されたものと言える。   However, carrying the selective reduction catalyst on the particulate filter so that sufficient performance as the selective reduction catalyst can be exerted causes clogging of the particulate filter. It is difficult to integrate the particulate filter with the particulate filter, and it can be said that the integration of the oxidation catalyst and the selective reduction catalyst is realized because the selective catalytic reduction catalyst is arranged in advance of the particulate filter.

上記した本発明の排気浄化装置によれば、下記の如き種々の優れた効果を奏し得る。   According to the exhaust emission control device of the present invention described above, various excellent effects as described below can be obtained.

(I)本発明の請求項1に記載の発明によれば、パティキュレートフィルタと選択還元型触媒を併用してNOxとパティキュレートの同時低減化を図る排気浄化装置に関し、NOxを還元浄化するのに十分な量のHCガスを選択還元型触媒に対し確実に供給してNOxを効果的に低減することができ、NOx浄化性能の向上や選択還元型触媒の容量削減によるコストダウンを実現することができる。   (I) According to the invention described in claim 1 of the present invention, it relates to an exhaust emission control device that simultaneously reduces NOx and particulates by using a particulate filter and a selective catalytic reduction catalyst. A sufficient amount of HC gas can be reliably supplied to the selective catalytic reduction catalyst to effectively reduce NOx, and the cost can be reduced by improving the NOx purification performance and reducing the capacity of the selective catalytic reduction catalyst. Can do.

(II)本発明の請求項2,3に記載の発明によれば、酸化触媒と選択還元型触媒とパティキュレートフィルタとを個別に三連配置する場合よりも装置全長を短くして占有空間のコンパクト化を図ることができるので、車両への搭載性を大幅に向上することができ、しかも、酸化触媒及び選択還元型触媒をケーシング内で固定するための部品の点数を削減することができて更なるコストダウンを実現することもできる。   (II) According to the second and third aspects of the present invention, the total length of the apparatus can be shortened compared to the case where the oxidation catalyst, the selective reduction catalyst, and the particulate filter are individually arranged in triplicate. Since downsizing can be achieved, the mountability to the vehicle can be greatly improved, and the number of parts for fixing the oxidation catalyst and the selective reduction catalyst in the casing can be reduced. Further cost reduction can be realized.

以下本発明の実施の形態を図面を参照しつつ説明する。   Embodiments of the present invention will be described below with reference to the drawings.

図1は本発明を実施する形態の一例を示すもので、図1中における1はターボチャージャ2を搭載したディーゼルエンジンを示しており、エアクリーナ3から導いた空気4が吸気管5を介し前記ターボチャージャ2のコンプレッサ2aへと送られ、該コンプレッサ2aで加圧された空気4が更にインタクーラ6へと送られて冷却され、該インタクーラ6から図示しないインテークマニホールドへと空気4が導かれてディーゼルエンジン1の各シリンダに導入されるようにしてある。   FIG. 1 shows an example of an embodiment for carrying out the present invention. In FIG. 1, reference numeral 1 denotes a diesel engine equipped with a turbocharger 2, and air 4 guided from an air cleaner 3 passes through the intake pipe 5 through the turbocharger. The air 4 sent to the compressor 2a of the charger 2 and pressurized by the compressor 2a is further sent to the intercooler 6 to be cooled, and the air 4 is led from the intercooler 6 to an intake manifold (not shown) to be a diesel engine. 1 is introduced into each cylinder.

また、このディーゼルエンジン1の各シリンダから排出された排気ガス7がエキゾーストマニホールド8を介し前記ターボチャージャ2のタービン2bへと送られ、該タービン2bを駆動した排気ガス7が排気管9を介し車外へ排出されるようにしてある。   Further, exhaust gas 7 discharged from each cylinder of the diesel engine 1 is sent to the turbine 2b of the turbocharger 2 through the exhaust manifold 8, and the exhaust gas 7 driving the turbine 2b passes through the exhaust pipe 9 to the outside of the vehicle. To be discharged.

この排気ガス7が流通する排気管9の途中には、マフラ外筒を成すケーシング10が備えられており、このケーシング10内における後段に、排気ガス7中のパティキュレートを捕集するパティキュレートフィルタ11が収容されていると共に、ケーシング10内における前段には、前記パティキュレートフィルタ11より上流側で排気ガス7中の未燃HCを酸化処理する酸化触媒12が備えられており、該酸化触媒12と前記パティキュレートフィルタ11との間に、酸素共存下でも選択的にNOxをHCと反応せしめる選択還元型触媒13が介装されている。   In the middle of the exhaust pipe 9 through which the exhaust gas 7 circulates, a casing 10 forming a muffler outer cylinder is provided, and a particulate filter that collects particulates in the exhaust gas 7 is provided in a subsequent stage in the casing 10. 11 is housed, and an oxidation catalyst 12 that oxidizes unburned HC in the exhaust gas 7 is provided upstream of the particulate filter 11 in the front stage in the casing 10. And the particulate filter 11 is provided with a selective reduction catalyst 13 that selectively reacts NOx with HC even in the presence of oxygen.

また、前記ケーシング10より上流側の排気管9には、排気ガス7中に還元剤として燃料(軽油等)を添加するインジェクタ14(燃料添加装置)が備えられており、該インジェクタ14により添加された燃料から生じたHCガスが酸化触媒12を通過する間に酸化反応し、その反応熱で昇温した排気ガス7の流入により最後段のパティキュレートフィルタ11の触媒床温度が上げられてパティキュレートが燃やし尽くされ、パティキュレートフィルタ11の再生化が図られるようになっており、また、その添加燃料の一部が未処理のまま前記選択還元型触媒13まで到達し、ここで添加燃料から生じたHCガスによりNOxが還元浄化されるようになっている。   Further, the exhaust pipe 9 upstream of the casing 10 is provided with an injector 14 (fuel addition device) for adding fuel (light oil or the like) as a reducing agent to the exhaust gas 7, and is added by the injector 14. The HC gas generated from the burned fuel undergoes an oxidation reaction while passing through the oxidation catalyst 12, and the catalyst bed temperature of the particulate filter 11 at the last stage is raised by the inflow of the exhaust gas 7 heated by the reaction heat, thereby causing the particulates The particulate filter 11 is regenerated, and part of the added fuel reaches the selective catalytic reduction catalyst 13 without being treated, and is generated from the added fuel. NOx is reduced and purified by the HC gas.

而して、このように排気浄化装置を構成すれば、インジェクタ14により排気ガス7中に燃料を添加した際に、選択還元型触媒13がパティキュレートフィルタ11に先行して配置されていることで該パティキュレートフィルタ11で消費されていた分のHCガスがそのまま選択還元型触媒13に供給されることになり、パティキュレートフィルタ11の直後に選択還元型触媒13を配置していた場合よりも該選択還元型触媒13に供給されるHCガスの量が増加し、このHCガスを還元剤としてNOxを良好に還元浄化させることが可能となる。   Thus, if the exhaust gas purification apparatus is configured in this way, when the fuel is added to the exhaust gas 7 by the injector 14, the selective catalytic reduction catalyst 13 is arranged ahead of the particulate filter 11. The amount of HC gas consumed by the particulate filter 11 is supplied to the selective catalytic reduction catalyst 13 as it is, and the selective catalytic reduction catalyst 13 is disposed immediately after the particulate filtering 11 compared with the case where the selective catalytic reduction catalyst 13 is arranged. The amount of HC gas supplied to the selective catalytic reduction catalyst 13 increases, and it becomes possible to satisfactorily reduce and purify NOx using this HC gas as a reducing agent.

他方、選択還元型触媒13の直後のパティキュレートフィルタ11で排気ガス7中のパティキュレートが捕集されていくため、パティキュレートとNOxの同時低減化が図られることになり、しかも、インジェクタ14により添加された燃料から生じたHCガスが前段の酸化触媒12上で酸化反応し、その反応熱により昇温した排気ガス7が流れ込むことにより後段のパティキュレートフィルタ11の触媒床温度が上げられ、内部に捕集されているパティキュレートが燃やし尽くされてパティキュレートフィルタ11の再生化が図られる。   On the other hand, since particulates in the exhaust gas 7 are collected by the particulate filter 11 immediately after the selective catalytic reduction catalyst 13, the particulates and NOx can be simultaneously reduced. The HC gas generated from the added fuel undergoes an oxidation reaction on the preceding oxidation catalyst 12, and the exhaust gas 7 heated by the reaction heat flows, whereby the catalyst bed temperature of the latter particulate filter 11 is raised, The particulates collected in the are burned out and the particulate filter 11 is regenerated.

従って、上記形態例によれば、パティキュレートフィルタ11と選択還元型触媒13を併用してNOxとパティキュレートの同時低減化を図る排気浄化装置に関し、NOxを還元浄化するのに十分な量のHCガスを選択還元型触媒13に対し確実に供給してNOxを効果的に低減することができ、NOx浄化性能の向上や選択還元型触媒13の容量削減によるコストダウンを実現することができる。   Therefore, according to the above-described embodiment, the exhaust purification device that simultaneously reduces the NOx and the particulates by using the particulate filter 11 and the selective reduction catalyst 13 in combination, an amount of HC sufficient to reduce and purify NOx. The gas can be reliably supplied to the selective reduction catalyst 13 to effectively reduce NOx, and the NOx purification performance can be improved and the cost can be reduced by reducing the capacity of the selective reduction catalyst 13.

また、図2は本発明の別の形態例を示すもので、酸化触媒12と選択還元型触媒13とを同一担体上に担持させて一体化するようにしており、このようにすれば、酸化触媒12と選択還元型触媒13とパティキュレートフィルタ11とを個別に三連配置する場合よりも装置全長が短くなって占有空間のコンパクト化が図られ、しかも、酸化触媒12と選択還元型触媒13をケーシング10内で固定するための部品の点数も削減されることになる。   FIG. 2 shows another embodiment of the present invention, in which the oxidation catalyst 12 and the selective catalytic reduction catalyst 13 are supported and integrated on the same carrier. The total length of the apparatus is shortened and the occupied space is made compact, compared to the case where the catalyst 12, the selective reduction catalyst 13 and the particulate filter 11 are individually arranged in triplicate. In addition, the oxidation catalyst 12 and the selective reduction catalyst 13 are reduced. The number of parts for fixing the inside of the casing 10 is also reduced.

尚、酸素共存下でも選択的にNOxを還元剤と反応させる性質を持つ選択還元型触媒13として知られている白金,パラジウム等の貴金属触媒は、パティキュレートフィルタ11の強制再生を図るための添加燃料を酸化処理する酸化触媒12と成分的に近似するものであり、この酸化触媒12と選択還元型触媒13とを同一担体上に担持させて一体化することに特に技術的な支障はない。   Incidentally, a noble metal catalyst such as platinum or palladium known as a selective reduction catalyst 13 having the property of selectively reacting NOx with a reducing agent even in the presence of oxygen is added for the purpose of forcibly regenerating the particulate filter 11. It is similar in composition to the oxidation catalyst 12 that oxidizes the fuel, and there is no particular technical problem in integrating the oxidation catalyst 12 and the selective catalytic reduction catalyst 13 on the same carrier.

ただし、選択還元型触媒13としての十分な性能を発揮し得るように該選択還元型触媒13をパティキュレートフィルタ11に担持させることは、該パティキュレートフィルタ11の目詰まりを招いてしまうため、選択還元型触媒13とパティキュレートフィルタ11とを一体化させることは困難であり、選択還元型触媒13をパティキュレートフィルタ11に先行して配置したからこそ酸化触媒12と選択還元型触媒13との一体化が実現されたものと言える。   However, since the selective filter 11 is supported on the particulate filter 11 so that sufficient performance as the selective catalytic reduction catalyst 13 can be exhibited, the particulate filter 11 is clogged. It is difficult to integrate the reduction catalyst 13 and the particulate filter 11, and the oxidation catalyst 12 and the selective reduction catalyst 13 are integrated because the selective reduction catalyst 13 is arranged in advance of the particulate filter 11. It can be said that realization has been realized.

従って、本形態例によれば、酸化触媒12と選択還元型触媒13とパティキュレートフィルタ11とを個別に三連配置する場合よりも装置全長を短くして占有空間のコンパクト化を図ることができるので、車両への搭載性を大幅に向上することができ、しかも、酸化触媒12及び選択還元型触媒13をケーシング10内で固定するための部品の点数を削減することができて更なるコストダウンを実現することもできる。   Therefore, according to the present embodiment, the total length of the apparatus can be shortened and the occupied space can be made compact compared to the case where the oxidation catalyst 12, the selective reduction catalyst 13 and the particulate filter 11 are individually arranged in triplicate. Therefore, the mounting property on the vehicle can be greatly improved, and the number of parts for fixing the oxidation catalyst 12 and the selective catalytic reduction catalyst 13 in the casing 10 can be reduced, thereby further reducing the cost. Can also be realized.

尚、本発明の排気浄化装置は、上述の形態例にのみ限定されるものではなく、本発明の要旨を逸脱しない範囲内において種々変更を加え得ることは勿論である。   Note that the exhaust emission control device of the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the gist of the present invention.

本発明を実施する形態の一例を示す概略図である。It is the schematic which shows an example of the form which implements this invention. 本発明の別の形態例を示す概略図である。It is the schematic which shows another form example of this invention.

符号の説明Explanation of symbols

7 排気ガス
9 排気管
11 パティキュレートフィルタ
12 酸化触媒
13 選択還元型触媒
14 インジェクタ(燃料添加装置)
7 Exhaust gas 9 Exhaust pipe 11 Particulate filter 12 Oxidation catalyst 13 Selective reduction catalyst 14 Injector (fuel addition device)

Claims (2)

排気ガス中のパティキュレートを捕集するパティキュレートフィルタと、該パティキュレートフィルタより上流側で排気ガス中の未燃HCを酸化処理する酸化触媒と、該酸化触媒より上流側で排気ガス中に燃料を添加する燃料添加装置を排気管の途中に備えた排気浄化装置において、前記酸化触媒と前記パティキュレートフィルタとの間に、酸素共存下でも選択的にNOxをHCと反応せしめる選択還元型触媒を介装したことを特徴とする排気浄化装置。   A particulate filter that collects particulates in the exhaust gas, an oxidation catalyst that oxidizes unburned HC in the exhaust gas upstream of the particulate filter, and a fuel in the exhaust gas upstream of the oxidation catalyst In the exhaust emission control device provided with a fuel addition device in the middle of the exhaust pipe, a selective reduction type catalyst that selectively reacts NOx with HC even in the presence of oxygen between the oxidation catalyst and the particulate filter. An exhaust purification device characterized by being interposed. 酸化触媒と選択還元型触媒とを同一担体上に担持させて一体化したことを特徴とする請求項1に記載の排気浄化装置。   2. The exhaust emission control device according to claim 1, wherein the oxidation catalyst and the selective reduction catalyst are supported and integrated on the same carrier.
JP2007290588A 2007-11-08 2007-11-08 Exhaust emission control device Pending JP2009115022A (en)

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