JP2016186273A

JP2016186273A - Selective catalytic reduction device

Info

Publication number: JP2016186273A
Application number: JP2015066910A
Authority: JP
Inventors: 嘉久植田; Yoshihisa Ueda; 勝士長田; Katsushi Osada
Original assignee: Isuzu Motors Ltd
Current assignee: Isuzu Motors Ltd
Priority date: 2015-03-27
Filing date: 2015-03-27
Publication date: 2016-10-27

Abstract

PROBLEM TO BE SOLVED: To provide a selective catalytic reduction device capable of maintaining a ratio of nitrogen monoxide to nitrogen dioxide that are contained in exhaust gas at one to one even in operation transition and inhibiting deterioration of denitration efficiency in an SCR catalyst.SOLUTION: A selective catalytic reduction device 100 comprises: plural oxidation catalysts 125 that are arranged side by side on the exhaust upstream side of an SCR catalyst 104 and are different from each other in oxidation performance for oxidizing nitrogen monoxide into nitrogen dioxide; a manifold 127 that is arranged in the middle of an exhaust pipe 102 and has plural branch pipes 126 for making exhaust gas reach the SCR catalyst 104 through any one of the plural oxidation catalysts 125; plural regulating valves 128 regulating an exhaust flow rate distribution ratio in each of the plural branch pipes 126; and a control part 129 controlling a ratio of nitrogen monoxide to nitrogen dioxide, which are contained in exhaust gas, to one to one by adjusting openings of the plural regulating valves 128.SELECTED DRAWING: Figure 1

Description

本発明は、ディーゼル機関等の内燃機関から排気管を通じて排出される排気中に尿素水を噴射すると共に排気中で尿素水を加水分解させてアンモニアを生成し、そのアンモニアをＳＣＲ触媒に吸蔵させると共に排気中に含まれている窒素酸化物を窒素と水とに還元して無害化する選択触媒還元装置に関する。 The present invention injects urea water into exhaust discharged from an internal combustion engine such as a diesel engine through an exhaust pipe, hydrolyzes urea water in the exhaust to generate ammonia, and stores the ammonia in an SCR catalyst. The present invention relates to a selective catalytic reduction device for reducing nitrogen oxides contained in exhaust gas to nitrogen and water to make them harmless.

ディーゼル機関等の内燃機関が搭載されている自動車においては、内燃機関から排気管を通じて大気中に排出される排気を浄化する排気浄化装置として、排気中に尿素水［ＣＯ（ＮＨ₂）₂＋Ｈ₂Ｏ］を噴射すると共に排気中で尿素水を加水分解させてアンモニア［ＮＨ₃］を生成し、そのアンモニアをＳＣＲ触媒に吸蔵させると共に排気中に含まれている窒素酸化物（一酸化窒素［ＮＯ］と二酸化窒素［ＮＯ₂］）を窒素［Ｎ₂］と水［Ｈ₂Ｏ］とに還元して無害化する選択触媒還元（ＳＣＲ）装置が採用されている（例えば、特許文献１を参照）。 In an automobile equipped with an internal combustion engine such as a diesel engine, urea water [CO (NH ₂ ) ₂ + H ₂ is contained in the exhaust gas as an exhaust purification device that purifies exhaust gas discharged from the internal combustion engine into the atmosphere through an exhaust pipe. O] is injected and urea water is hydrolyzed in the exhaust gas to produce ammonia [NH ₃ ]. The ammonia is stored in the SCR catalyst and nitrogen oxide (nitrogen monoxide [NO] is contained in the exhaust gas. ] And nitrogen dioxide [NO ₂ ]) are reduced to nitrogen [N ₂ ] and water [H ₂ O], and a selective catalytic reduction (SCR) apparatus is employed (see, for example, Patent Document 1). ).

特開２０００−３０３８２６号公報JP 2000-303826 A

ところで、ＳＣＲ触媒におけるアンモニアと窒素酸化物との反応式は２ＮＨ₃＋ＮＯ＋ＮＯ₂→２Ｎ₂＋３Ｈ₂Ｏで表されることから、排気中に含まれている一酸化窒素と二酸化窒素との比率を一対一に維持することにより、ＳＣＲ触媒における脱硝効率を最大化することができるため、選択触媒還元装置においては、ＳＣＲ触媒の排気上流側に一酸化窒素を二酸化窒素に酸化する酸化触媒（ＤＯＣ）を配置し、排気中に含まれている一酸化窒素と二酸化窒素との比率を調整している。 By the way, since the reaction formula of ammonia and nitrogen oxide in the SCR catalyst is expressed by 2NH ₃ + NO + NO ₂ → 2N ₂ + 3H ₂ O, the ratio of nitrogen monoxide and nitrogen dioxide contained in the exhaust gas is expressed as a pair. Therefore, in the selective catalytic reduction device, an oxidation catalyst (DOC) that oxidizes nitrogen monoxide to nitrogen dioxide is disposed upstream of the SCR catalyst. It is arranged and the ratio of nitrogen monoxide and nitrogen dioxide contained in the exhaust is adjusted.

しかしながら、運転過渡時（例えば、加速時や減速時）においては、排気流量や排気温度の変動により、排気中に含まれている一酸化窒素と二酸化窒素との比率を一対一に維持することができないため、ＳＣＲ触媒における脱硝効率が低下するという課題がある。 However, at the time of operation transition (for example, at the time of acceleration or deceleration), the ratio of nitrogen monoxide and nitrogen dioxide contained in the exhaust gas can be maintained one-to-one due to fluctuations in the exhaust gas flow rate or the exhaust gas temperature. Since it cannot do, there exists a subject that the denitration efficiency in an SCR catalyst falls.

そこで、本発明の目的は、運転過渡時においても排気中に含まれている一酸化窒素と二酸化窒素との比率を一対一に維持することができ、ＳＣＲ触媒における脱硝効率の低下を抑制することが可能な選択触媒還元装置を提供することにある。 Accordingly, an object of the present invention is to maintain a one-to-one ratio of nitrogen monoxide and nitrogen dioxide contained in exhaust gas even during an operation transition, and suppress a decrease in denitration efficiency in the SCR catalyst. An object of the present invention is to provide a selective catalytic reduction device capable of achieving the above.

この目的を達成するために創案された本発明は、内燃機関から排気管を通じて排出される排気中に尿素水を噴射すると共に排気中で尿素水を加水分解させてアンモニアを生成し、そのアンモニアをＳＣＲ触媒に吸蔵させると共に排気中に含まれている窒素酸化物を窒素と水とに還元して無害化する選択触媒還元装置において、前記ＳＣＲ触媒の排気上流側に並列配置されていると共に一酸化窒素を二酸化窒素に酸化する酸化性能が相互に異なる複数の酸化触媒と、前記排気管の途中に設置されていると共に複数の前記酸化触媒の何れか一個を通じて排気を前記ＳＣＲ触媒に至らせる複数の支管を有している多岐管と、複数の前記支管の各々における排気流量分配比を調整する複数の調整弁と、複数の前記調整弁の開度を調整して排気中に含まれている一酸化窒素と二酸化窒素との比率を一対一に制御する制御部と、を備えている選択触媒還元装置である。 Invented to achieve this object, the present invention injects urea water into the exhaust gas discharged from the internal combustion engine through the exhaust pipe and hydrolyzes the urea water in the exhaust gas to produce ammonia. In a selective catalytic reduction device that absorbs nitrogen oxides contained in exhaust gas into nitrogen and water and detoxifies them while being stored in the SCR catalyst, it is arranged in parallel on the upstream side of the exhaust gas of the SCR catalyst and is oxidized A plurality of oxidation catalysts having different oxidation performances for oxidizing nitrogen into nitrogen dioxide, and a plurality of oxidation catalysts installed in the middle of the exhaust pipe and exhausted to the SCR catalyst through any one of the plurality of oxidation catalysts A manifold having a branch pipe, a plurality of adjusting valves for adjusting the exhaust flow rate distribution ratio in each of the plurality of branch pipes, and adjusting the opening of the plurality of adjusting valves to be included in the exhaust gas A control unit for controlling one-to-one ratio between nitrogen monoxide and nitrogen dioxide are a by which selective catalytic reduction device includes a.

本発明によれば、運転過渡時においても排気中に含まれている一酸化窒素と二酸化窒素との比率を一対一に維持することができ、ＳＣＲ触媒における脱硝効率の低下を抑制することが可能な選択触媒還元装置を提供することができる。 According to the present invention, it is possible to maintain a one-to-one ratio of nitrogen monoxide and nitrogen dioxide contained in the exhaust even during an operation transition, and it is possible to suppress a decrease in denitration efficiency in the SCR catalyst. A selective catalytic reduction apparatus can be provided.

本発明に係る選択触媒還元装置を示す概略図である。It is the schematic which shows the selective catalyst reduction apparatus which concerns on this invention.

以下、本発明の好適な実施の形態を添付図面に順って説明する。 DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the accompanying drawings.

図１に示すように、本発明の好適な実施の形態に係る選択触媒還元装置１００は、ディーゼル機関等の内燃機関１０１から排気管１０２を通じて大気中に排出される排気を浄化する排気浄化装置の一種であり、尿素水噴射制御装置（ＤＣＵ）１０３により自動車の走行時等にＳＣＲ触媒１０４の排気上流側に設置されている尿素水噴射器１０５から排気中に尿素水を噴射すると共に排気中で尿素水を加水分解させてアンモニアを生成し、そのアンモニアをＳＣＲ触媒１０４に吸蔵させると共に排気中に含まれている窒素酸化物を窒素と水とに還元して無害化する装置である。 As shown in FIG. 1, a selective catalytic reduction device 100 according to a preferred embodiment of the present invention is an exhaust purification device that purifies exhaust discharged into the atmosphere through an exhaust pipe 102 from an internal combustion engine 101 such as a diesel engine. This is a type of urea water injection control unit (DCU) 103 that injects urea water into the exhaust gas from urea water injector 105 installed upstream of the SCR catalyst 104 when the vehicle is running, etc. It is a device that hydrolyzes urea water to produce ammonia, occludes the ammonia in the SCR catalyst 104, and reduces nitrogen oxides contained in the exhaust gas to nitrogen and water for detoxification.

他にも、選択触媒還元装置１００は、尿素水が貯留されている尿素水貯留槽１０６と、尿素水配管１０７を通じて尿素水貯留槽１０６から尿素水噴射器１０５に尿素水を供給する尿素水供給ポンプ１０８を有している尿素水供給モジュール１０９と、を備えている。 In addition, the selective catalyst reduction device 100 includes a urea water storage tank 106 in which urea water is stored, and a urea water supply that supplies urea water from the urea water storage tank 106 to the urea water injector 105 through the urea water pipe 107. And a urea water supply module 109 having a pump 108.

また、ＳＣＲ触媒１０４の入口における排気温度を検出する排気温度検出器１１０と、ＳＣＲ触媒１０４の入口における窒素酸化物濃度を検出する前段窒素酸化物濃度検出器１１１と、がＳＣＲ触媒１０４の排気上流側に設置されており、ＳＣＲ触媒１０４の出口における窒素酸化物濃度を検出する後段窒素酸化物濃度検出器１１２がＳＣＲ触媒１０４の排気下流側に設置されている。 Further, an exhaust gas temperature detector 110 that detects the exhaust gas temperature at the inlet of the SCR catalyst 104 and a pre-stage nitrogen oxide concentration detector 111 that detects the nitrogen oxide concentration at the inlet of the SCR catalyst 104 are upstream of the exhaust gas of the SCR catalyst 104. A rear-stage nitrogen oxide concentration detector 112 that detects the nitrogen oxide concentration at the outlet of the SCR catalyst 104 is installed on the exhaust downstream side of the SCR catalyst 104.

更に、尿素水貯留槽１０６における尿素水残量を検出する尿素水残量検出器１１３と、尿素水貯留槽１０６における尿素水温度を検出する尿素水温度検出器１１４と、尿素水貯留槽１０６における尿素水品質（例えば、尿素水濃度や異物混入有無）を検出する尿素水品質検出器１１５と、を有しているＳＣＲセンサ１１６が尿素水貯留槽１０６に設置されている。 Further, the urea water remaining amount detector 113 that detects the urea water remaining amount in the urea water storage tank 106, the urea water temperature detector 114 that detects the urea water temperature in the urea water storage tank 106, and the urea water storage tank 106 An SCR sensor 116 having a urea water quality detector 115 that detects urea water quality (for example, urea water concentration and presence / absence of foreign matter) is installed in the urea water storage tank 106.

尿素水配管１０７は、尿素水貯留槽１０６と尿素水供給ポンプ１０８の吸込口とを接続する吸込流路１１７と、尿素水供給ポンプ１０８の吐出口と尿素水噴射器１０５とを接続する供給流路１１８と、尿素水供給ポンプ１０８の吐出口と尿素水貯留槽１０６とを接続する回収流路１１９と、を有している。 The urea water pipe 107 is a suction flow path 117 that connects the urea water storage tank 106 and the suction port of the urea water supply pump 108, and a supply flow that connects the discharge port of the urea water supply pump 108 and the urea water injector 105. It has a channel 118 and a recovery channel 119 connecting the discharge port of the urea water supply pump 108 and the urea water storage tank 106.

尿素水供給モジュール１０９は、吸込流路１１７を通じて尿素水貯留槽１０６から尿素水を吸い込むと共に供給流路１１８を通じて尿素水噴射器１０５に尿素水を供給する尿素水供給ポンプ１０８と、尿素水供給ポンプ１０８における温度を検出する温度検出器１２０と、尿素水供給ポンプ１０８の吐出口における尿素水圧力を検出する尿素水圧力検出器１２１と、供給流路１１８を通じて尿素水噴射器１０５に尿素水を供給する流路と回収流路１１９を通じて尿素水貯留槽１０６に尿素水を回収する流路とを切り替える切替弁１２２と、を有している。 The urea water supply module 109 sucks urea water from the urea water storage tank 106 through the suction flow path 117 and supplies urea water to the urea water injector 105 through the supply flow path 118, and a urea water supply pump. A temperature detector 120 that detects the temperature at 108, a urea water pressure detector 121 that detects the urea water pressure at the discharge port of the urea water supply pump 108, and urea water is supplied to the urea water injector 105 through the supply flow path 118. And a switching valve 122 that switches the urea water storage tank 106 to the flow path for recovering urea water through the recovery flow path 119.

図１は簡略化して描いているが、尿素水貯留槽１０６と尿素水噴射器１０５と尿素水供給ポンプ１０８と尿素水配管１０７とで構成されている尿素水供給経路に沿って内燃機関冷却水を循環させる循環流路１２３が配策されており、尿素水供給経路に沿って内燃機関冷却水を流すか否かを切り替える解凍出力調整弁１２４が循環流路１２３に設置されている。 Although FIG. 1 is illustrated in a simplified manner, the internal combustion engine cooling water is disposed along a urea water supply path including a urea water storage tank 106, a urea water injector 105, a urea water supply pump 108, and a urea water pipe 107. A circulatory flow path 123 is circulated, and a thawing output adjustment valve 124 for switching whether or not to flow the internal combustion engine cooling water along the urea water supply path is installed in the circulatory flow path 123.

なお、循環流路１２３は、解凍出力調整弁１２４の開閉に拘わらず、常時、尿素水噴射器１０５に内燃機関冷却水を供給しており、尿素水噴射器１０５に充填されている尿素水の変質固着等を防止している。 Note that the circulation flow path 123 always supplies the internal combustion engine cooling water to the urea water injector 105 regardless of whether the thawing output adjustment valve 124 is opened or closed, and the urea water filled in the urea water injector 105. Prevents alteration sticking.

さて、本発明の好適な実施の形態に係る選択触媒還元装置１００は、ＳＣＲ触媒１０４の排気上流側に並列配置されていると共に一酸化窒素を二酸化窒素に酸化する酸化性能が相互に異なる複数の酸化触媒１２５と、排気管１０２の途中に設置されていると共に複数の酸化触媒１２５の何れか一個を通じて排気をＳＣＲ触媒１０４に至らせる複数の支管１２６を有している多岐管１２７と、複数の支管１２６の各々における排気流量分配比を調整する複数の調整弁１２８と、複数の調整弁１２８の開度を調整して排気中に含まれている一酸化窒素と二酸化窒素との比率を一対一に制御する制御部１２９と、を備えている。 Now, the selective catalytic reduction apparatus 100 according to a preferred embodiment of the present invention is arranged in parallel on the exhaust upstream side of the SCR catalyst 104 and has a plurality of different oxidation performances for oxidizing nitric oxide into nitrogen dioxide. An oxidation catalyst 125, a manifold 127 that is installed in the middle of the exhaust pipe 102 and has a plurality of branch pipes 126 that lead exhaust to the SCR catalyst 104 through any one of the plurality of oxidation catalysts 125; A plurality of regulating valves 128 for adjusting the exhaust flow rate distribution ratio in each of the branch pipes 126, and the ratios of nitrogen monoxide and nitrogen dioxide contained in the exhaust by adjusting the opening degree of the plurality of regulating valves 128 one to one. And a control unit 129 for controlling the above.

なお、選択触媒還元装置１００は、ＳＣＲ触媒１０４の排気上流側であって尿素水噴射器１０５から排気中に噴射される尿素水の噴射先に設置されていると共に尿素水噴射器１０５から排気中に噴射される尿素水の加水分解を促進させる加水分解促進触媒１３０を備えていても構わない。 The selective catalyst reduction device 100 is installed on the upstream side of the exhaust gas from the SCR catalyst 104 and at the injection destination of urea water injected into the exhaust gas from the urea water injector 105 and is exhausted from the urea water injector 105. The catalyst may be provided with a hydrolysis promoting catalyst 130 that promotes hydrolysis of urea water injected into the tank.

制御部１２９は、制御回路等のハードウェアや制御プログラム等のソフトウェアとして尿素水噴射制御装置１０３に搭載されており、運転過渡時の排気流量や排気温度の変動に基づいて、即ち、内燃機関１０１の運転状態に基づいて、複数の調整弁１２８の開度を調整して排気中に含まれている一酸化窒素と二酸化窒素との比率を一対一に制御している。 The control unit 129 is installed in the urea water injection control apparatus 103 as hardware such as a control circuit and software such as a control program, and is based on the fluctuation of the exhaust flow rate and the exhaust temperature during the operation transition, that is, the internal combustion engine 101. Based on the operating state, the degree of opening of the plurality of regulating valves 128 is adjusted to control the ratio of nitrogen monoxide and nitrogen dioxide contained in the exhaust to one to one.

これにより、本発明の好適な実施の形態に係る選択触媒還元装置１００によれば、内燃機関１０１の運転状態に依らず常に排気中に含まれている一酸化窒素と二酸化窒素との比率を一対一にすることができるため、運転過渡時においても排気中に含まれている一酸化窒素と二酸化窒素との比率を一対一に維持することができ、ＳＣＲ触媒１０４における脱硝効率の低下を抑制することが可能となる。 Thus, according to the selective catalytic reduction device 100 according to the preferred embodiment of the present invention, the ratio of nitrogen monoxide and nitrogen dioxide that are always included in the exhaust gas regardless of the operating state of the internal combustion engine 101 is a pair. Therefore, the ratio of nitrogen monoxide and nitrogen dioxide contained in the exhaust gas can be maintained at a one-to-one ratio even during an operation transition, and the decrease in the denitration efficiency in the SCR catalyst 104 is suppressed. It becomes possible.

なお、制御部１２９は、運転状態に応じて単に複数の調整弁１２８の開閉を切り替えて排気が通過する酸化触媒１２５を一個だけ選択しても良いが（即ち、複数の調整弁１２８のうち一個のみを開とすると共にその他を閉とする）、運転状態に応じて複数の調整弁１２８の開度を調整して複数の支管１２６の各々における排気流量分配比を調整することにより、少ない酸化触媒１２５でより多くの運転状態に対して排気中に含まれている一酸化窒素と二酸化窒素との比率を一対一に制御することが可能となる。 The control unit 129 may select only one oxidation catalyst 125 through which exhaust gas passes by switching the opening and closing of the plurality of regulating valves 128 according to the operating state (that is, one of the plurality of regulating valves 128). Only the opening is opened and the others are closed), and by adjusting the exhaust flow rate distribution ratio in each of the plurality of branch pipes 126 by adjusting the opening degree of the plurality of regulating valves 128 according to the operating state, a small oxidation catalyst At 125, it becomes possible to control the ratio of nitrogen monoxide and nitrogen dioxide contained in the exhaust to one-to-one with respect to more operating states.

１００選択触媒還元装置
１０１内燃機関
１０２排気管
１０３尿素水噴射制御装置
１０４ＳＣＲ触媒
１０５尿素水噴射器
１０６尿素水貯留槽
１０７尿素水配管
１０８尿素水供給ポンプ
１０９尿素水供給モジュール
１１０排気温度検出器
１１１前段窒素酸化物濃度検出器
１１２後段窒素酸化物濃度検出器
１１３尿素水残量検出器
１１４尿素水温度検出器
１１５尿素水品質検出器
１１６ＳＣＲセンサ
１１７吸込流路
１１８供給流路
１１９回収流路
１２０温度検出器
１２１尿素水圧力検出器
１２２切替弁
１２３循環流路
１２４解凍出力調整弁
１２５酸化触媒
１２６支管
１２７多岐管
１２８調整弁
１２９制御部
１３０加水分解促進触媒 DESCRIPTION OF SYMBOLS 100 Selective catalyst reduction apparatus 101 Internal combustion engine 102 Exhaust pipe 103 Urea water injection control apparatus 104 SCR catalyst 105 Urea water injector 106 Urea water storage tank 107 Urea water piping 108 Urea water supply pump 109 Urea water supply module 110 Exhaust temperature detector 111 Pre-stage nitrogen oxide concentration detector 112 Post-stage nitrogen oxide concentration detector 113 Urea water remaining amount detector 114 Urea water temperature detector 115 Urea water quality detector 116 SCR sensor 117 Suction channel 118 Supply channel 119 Recovery channel 120 Temperature detector 121 Urea water pressure detector 122 Switching valve 123 Circulating flow path 124 Thaw output adjusting valve 125 Oxidation catalyst 126 Branch pipe 127 Manifold 128 Adjusting valve 129 Control unit 130 Hydrolysis promoting catalyst

Claims

内燃機関から排気管を通じて排出される排気中に尿素水を噴射すると共に排気中で尿素水を加水分解させてアンモニアを生成し、そのアンモニアをＳＣＲ触媒に吸蔵させると共に排気中に含まれている窒素酸化物を窒素と水とに還元して無害化する選択触媒還元装置において、
前記ＳＣＲ触媒の排気上流側に並列配置されていると共に一酸化窒素を二酸化窒素に酸化する酸化性能が相互に異なる複数の酸化触媒と、
前記排気管の途中に設置されていると共に複数の前記酸化触媒の何れか一個を通じて排気を前記ＳＣＲ触媒に至らせる複数の支管を有している多岐管と、
複数の前記支管の各々における排気流量分配比を調整する複数の調整弁と、
複数の前記調整弁の開度を調整して排気中に含まれている一酸化窒素と二酸化窒素との比率を一対一に制御する制御部と、
を備えていることを特徴とする選択触媒還元装置。 Injecting urea water into the exhaust gas discharged from the internal combustion engine through the exhaust pipe, hydrolyzing the urea water in the exhaust gas to generate ammonia, storing the ammonia in the SCR catalyst, and nitrogen contained in the exhaust gas In a selective catalytic reduction device that reduces oxides to nitrogen and water and renders them harmless,
A plurality of oxidation catalysts arranged in parallel on the exhaust upstream side of the SCR catalyst and having different oxidation performances for oxidizing nitric oxide into nitrogen dioxide;
A manifold having a plurality of branch pipes installed in the middle of the exhaust pipe and exhausting exhaust gas to the SCR catalyst through any one of the plurality of oxidation catalysts;
A plurality of adjusting valves for adjusting an exhaust flow rate distribution ratio in each of the plurality of branch pipes;
A control unit that controls the ratio of nitrogen monoxide and nitrogen dioxide contained in the exhaust gas in a one-to-one manner by adjusting the openings of the plurality of regulating valves;
A selective catalytic reduction device comprising: