JP3607343B2 - Diesel engine exhaust gas denitration equipment - Google Patents

Diesel engine exhaust gas denitration equipment Download PDF

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JP3607343B2
JP3607343B2 JP05654095A JP5654095A JP3607343B2 JP 3607343 B2 JP3607343 B2 JP 3607343B2 JP 05654095 A JP05654095 A JP 05654095A JP 5654095 A JP5654095 A JP 5654095A JP 3607343 B2 JP3607343 B2 JP 3607343B2
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exhaust gas
temperature
catalyst layer
fuel
cooling water
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JPH08226319A (en
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晃太郎 若本
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Komatsu Ltd
Japan Petroleum Energy Center JPEC
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Petroleum Energy Center PEC
Komatsu Ltd
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
    • F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
    • F01N3/2006—Periodically heating or cooling catalytic reactors, e.g. at cold starting or overheating
    • F01N3/2046—Periodically cooling catalytic reactors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
    • F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
    • F01N3/2066—Selective catalytic reduction [SCR]
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2240/00—Combination or association of two or more different exhaust treating devices, or of at least one such device with an auxiliary device, not covered by indexing codes F01N2230/00 or F01N2250/00, one of the devices being
    • F01N2240/02—Combination or association of two or more different exhaust treating devices, or of at least one such device with an auxiliary device, not covered by indexing codes F01N2230/00 or F01N2250/00, one of the devices being a heat exchanger
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2610/00—Adding substances to exhaust gases
    • F01N2610/03—Adding substances to exhaust gases the substance being hydrocarbons, e.g. engine fuel
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B3/00—Engines characterised by air compression and subsequent fuel addition
    • F02B3/06—Engines characterised by air compression and subsequent fuel addition with compression ignition
    • Y—GENERAL 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
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Exhaust Gas After Treatment (AREA)

Description

【０００１】
【産業上の利用分野】
本発明は、ディーゼルエンジンから排出される排気ガス中の窒素酸化物（ＮＯＸ ）を除去する装置に係り、特に排気ガス中に灯油などの燃料を還元剤として添加し、ＮＯＸ をＮ２ やＨ２ Ｏに還元して除去するディーゼルエンジンの排気ガス脱硝装置に関する。
【０００２】
【従来の技術】
従来、ディーゼルエンジンの排気ガス中からＮＯＸ を除去する場合、排気ガス温度を３００〜４００℃にして排気ガス中にＮＯＸ とほぼ等モルのアンモニアや尿素を加えた後、バナジウム／チタニア触媒やゼオライト触媒と接触させ、ＮＯＸ をＮ２ とＨ２ Ｏに還元分解する方法が採られていた。しかし、このアンモニアまたは尿素を添加してＮＯＸ を還元する方法は、アンモニアまたは尿素を別途用意する必要があり、また添加量が多すぎると環境の二次汚染を引き起こすおそれがある。そこで、このような問題を解決するために、排気ガス中の炭化水素を強制的に富化した後、銅／ゼオライト触媒を初めとする遷移金属担持メタロシリケート触媒や、銅／アルミナ触媒を初めとする遷移金属担持アルミナ系複合酸化物触媒と接触させ、排気ガス中のＮＯＸ を還元して除去する方法が開発された。
【０００３】
排気ガス中の炭化水素を富化させる方法として、エンジンの吸気管中に燃料を添加する方法（特開平４−３５８７１５号公報）、主燃料噴射時期に対してタイミングをずらして少量の燃料をエンジン筒内に別途噴射する方法（特開平３−２５３７１３号公報）、あるいは燃料や特別な炭化水素を排気管中に直接添加する方法がある。そして、排気管中に還元剤炭化水素を添加してＮＯＸ を除去する場合、特開平４−３５８７１６号公報に開示されているように、炭化水素を添加した排気ガスをそのまま触媒層に導いて還元する方法と、特開平５−４４４４５号公報に示されているように、還元剤炭化水素を添加した排気ガスを冷却して触媒層に導入する方法とがある。また、図３に示したように、排気ガス中に燃料を噴射して添加し、燃料を添加した排気ガスを冷却装置によって冷却したのち、触媒層に導入してＮＯＸ を還元する方法が考えられている。
【０００４】
すなわち、図３に示した装置は、ディーゼルエンジン１０の排気管１２に冷却器１４が設けてあって、冷却器１４を流れる冷却水１５によってディーゼルエンジン１０から排出された排気ガス１６を冷却できるようにしてある。また、排気管１２の冷却器１４の上流側には、燃料添加ノズル１８が取り付けてある。このノズル１８は、排気管１２を流れる排気ガス１６中に還元剤燃料を噴射するためのもので、還元剤燃料輸送管２０を介して燃料タンク２２に接続した還元剤燃料添加量調節器２４の吐出した燃料を排気管１２内に噴射する。
【０００５】
一方、排気管１２の冷却器１４の下流側には、遷移金属担持メタロシリケート触媒などによって構成した触媒層２６が設けてあり、通過する還元剤燃料の添加された排気ガス１６中のＮＯＸ を還元して除去するようにしてある。そして、触媒層２６には、温度センサ２８が設けてあり、この温度センサ２８の検出信号をコントローラ３０に入力し、コントローラ３０によって触媒層２６の温度を所定の温度となるようにしている。すなわち、コントローラ３０は、冷却器１４に冷却水１５を供給する入口管３２に設けた流量調節弁３４に接続してあり、温度センサ２８の検出信号に基づいて弁３４の開度を調節して冷却水１５の流量を制御し、触媒層２６に流入する排気ガス１６の温度が、触媒層２６の最適作用温度領域となるようにしている。
【０００６】
【発明が解決しようとする課題】
ところで、還元剤として炭化水素を用いて排気ガス中のＮＯＸ を還元浄化する触媒は、還元剤炭化水素の分子量（炭素数）に対するＮＯＸ 浄化温度特性が図４のようになっており、還元剤炭化水素の炭素数が小さくなればなるほど、大きな浄化率が得られる温度領域は高温側に移動する。このため、ほぼ同じぐらいのＮＯＸ 浄化率を得るためには、図５に示すように、炭素数が１４の場合には触媒層の温度は低いＡ温度、炭素数が９の場合には触媒層の温度は中位のＢ温度、および、炭素数が５の場合には触媒層の温度は高温のＣ温度というように触媒層の温度が異なる。このような特性をもつ触媒によって排気ガス中のＮＯＸ を効率的に還元除去するためには、触媒層において作用する還元剤炭化水素の炭素数を的確に把握するか、あるいは常に一定の炭素数分布をもった還元剤炭化水素が触媒層に導入されるように工夫するとともに、その炭素数あるいは炭素数分布のときに効率的なＮＯＸ の還元浄化ができるような排気ガスの温度（＝触媒層の温度）に制御する必要がある。
【０００７】
ところで、燃料等の高分子炭化水素は、酸素が共存する高温雰囲気において、図６に示したように容易に炭素数の小さな低級な炭化水素に分解されてしまう。しかも、この分解の程度は、温度や酸素分圧、さらにはＮＯＸ 等の他の共存ガス成分の存在など、雰囲気条件によって大きく異なる。例えば、雰囲気が高温度のＭ点では、炭素数はＥ点と小さく、雰囲気が低温度のＰ点では、炭素数はＦ点と大きくなる。このため、排気ガス温度により、ほぼ決まる還元剤炭化水素の炭素数（実線イ）と触媒層温度（点線ロ）は、図７に示すように変化し、最適な触媒層温度は交点付近の領域（Ｗ）となる。このため、上記した従来の燃料などの還元剤炭化水素を添加方する方法は、排気温度がディーゼルエンジンの使用条件により異なるとともに、炭素数も異なるためＮＯＸ の浄化を充分に行えないという問題があった。
【０００８】
すなわち、ディーゼルエンジンおよび排気ガスの温度は、ディーゼルエンジンが高速運転をしているか、低速運転をしているかなどのエンジンの運転状態によって大きく異なる。このため、従来のエンジン吸気管やエンジン筒内に還元剤燃料を噴射する方法、または排気管に炭化水素や還元剤燃料を添加する方法は、還元剤炭化水素の添加位置または添加位置から触媒層までの経路において分解の条件がディーゼルエンジンの運転状態によって変化し、還元剤炭化水素の炭素数分布が常に変化する。この結果、触媒層の温度と還元剤炭化水素の炭素数とがうまくマッチングしない場合を生じ、ＮＯＸ の浄化率が極端に低下する事態が発生する。
【０００９】
本発明は、前記従来技術の問題点を解消するためになされたもので、排気温度によりほぼ決まる炭素数に応じて、触媒層への排気ガス温度を変化させてエンジンの運転条件に関係なくＮＯＸ の浄化率をほぼ一定にできるディーゼルエンジンの排気ガス脱硝装置を提供することを目的としている。
【００１０】
【課題を解決するための手段】
上記の目的を達成するために、本発明に係るディーゼルエンジンの排気ガス脱硝装置は、灯油等のディーゼル燃料を還元剤として排気ガス中のＮＯＸ を還元浄化する触媒を用いてディーゼルエンジンの排気ＮＯＸ を還元浄化するディーゼルエンジンの排気ガス脱硝装置において、排気管路にて排気ガス中に燃料を還元剤として添加する還元剤燃料供給装置と、還元剤燃料が添加される排気管部の排気ガスの温度を検知する第１の温度センサと、触媒層の温度を検知する第２の温度センサと、排気管路中、触媒層と還元剤燃料添加部位との間に設けられた冷却水にて排気ガスを冷却する熱交換器と、熱交換器の冷却水入口部に設けられて冷却水量を制御する冷却水量調節弁と、前記の２つの温度センサからの検知温度により冷却水量調節弁の開度量を制御する指令を出力するコントローラとからなることを特徴とする。
【００１１】
前記コントローラから冷却水量調節弁への開度量の指令は、第１の温度センサから得られた排気ガス温度に対して、第２の温度センサから得られた触媒層の温度が予め定めた値となるようにフイードバックされることを特徴とする。
【００１２】
【作用】
上記のように構成した本発明は、還元剤用燃料が排気管中に添加する部位の排気ガスの温度を第１の温度センサによって検出してコントローラに与え、還元剤用燃料が触媒層までに到達するまでに熱分解される度合いをコントローラにて推定し、コントローラによって得られた炭素数に応じて最適な触媒層温度を決定する。次に、触媒層の温度が決定された最適温度になるように排気ガスを冷却する熱交換器の水量を調節する。また、触媒層の温度センサの出力がコントローラに入力され、温度が前記で求めた最適な触媒層温度よりも高い場合には、熱交換器の冷却水量調節弁の開度量を大きくし、触媒層の温度が常に、図７に示す適性温度範囲に入るように制御する。このように、熱交換器の冷却水量調節弁の開度量を適宜制御することにより、触媒層に応じた最適の触媒層温度に触媒層入口排ガス温度を制御する。このように温度を制御して、触媒層にて作用する還元剤炭化水素の成分分布をほぼ一定にする。この結果、エンジンの運転条件によらず図７の触媒特性を常に、ほぼ一定にでき、常時効率的な還元剤炭化水素の利用を図れる。
【００１３】
【実施例】
本発明に係るディーゼルエンジンの排気ガス脱硝装置の好ましい実施例を、添付図面に沿って詳細に説明する。
図１は、本発明の第１実施例に係る排気ガス脱硝装置の構成説明図である。
図１において、ディーゼルエンジン１０からの排気管１２には、排気ガス１６を冷却するための熱交換器の冷却器１４が設けてある。この冷却器１４は、排気ガス１６と熱交換をする冷媒である冷却水１５が入口管３２によって供給されるようになっており、排気ガス１６と熱交換をした冷却水１５が出口管３５を介してラジエータなどの熱交換部に戻される。そして、入口管３２には、コントローラ３０によって開度が制御される冷却水量調節弁３４が設けてあり、この冷却水量調節弁３４の開度量を変えることにより、冷却器１４を流れる冷却水１５の流量が変化し、冷却能力が変わるようになっている。
【００１４】
また、排気管１２には、冷却器１４の上流側（ディーゼルエンジン１０側）の適宜の位置に燃料添加ノズル１８が取り付けてある。このノズル１８は、燃料添加量調節装置２４の吐出した燃料を、排気管１２を流れる排気ガス１６に噴射して添加する。また、燃料添加ノズル１８を設けた付近の排気管１２には、第１の温度センサ４０が取り付けてあり、燃料を添加する位置の排気ガス１６の温度を検出してコントローラ３０に入力するようにしてある。そして、燃料を添加された排気ガス１６は、下流側に設けた触媒層２６を通過するようにしてあり、触媒層２６を通過する際に、ＮＯＸ が還元浄化されるようになっている。この触媒層２６には、触媒層２６の温度を検出してコントローラ３０に入力する第２の温度センサ２８が設けてある。
【００１５】
上記のごとく構成した実施例の作用は、次のとおりである。
燃料タンク２２内の燃料は、ディーゼルエンジン１０に供給されて燃焼され、排気ガス１６となってディーゼルエンジン１０から排気管１２に排出される。この排気ガス１６は、冷却器１４、触媒層２６を通過して外部に排出される。排気管１２に流入した排気ガス１６は、冷却器１４を通過する際に、冷却器１４を流れる冷却水１５と熱交換をして３００℃程度に冷却される。また、還元剤燃料添加量調節装置２４は、燃料輸送管２０を介して燃料タンク２２内の燃料を吸引し、燃料添加ノズル１８から排気管１２を流れる排気ガス１６中に噴霧して添加する。排気ガス１６に添加された還元剤燃料は、排気ガス１６の有する熱によって低級な炭化水素に分解され、還元剤炭化水素となって排気ガス１６とともに触媒層２６に流入する。そして、触媒層２６は、触媒作用によって排気ガス１６中のＮＯＸ を還元剤炭化水素と反応させ、ＮＯＸ をＮ２ やＨ２ Ｏに還元して浄化する。
【００１６】
他方、コントローラ３０は、第１の温度センサ４０と第２の温度センサ２８との検出信号を取り込み、冷却された排気ガス１６の温度と触媒層２６の温度とを監視している。そして、コントローラ３０は、第１の温度センサ４０からの信号に基づいて冷却器１４を流れる冷却水１５の流量を調節し、排気ガス１６の温度を予め定めた制御にするとともに、触媒層２６の温度を予め定めた温度に制御する。また、触媒層２６の温度を第２の温度センサ２８により検出して、予め定めた温度より外れているときには、冷却器１４を流れる冷却水１５の流量を調節し、予め定めた温度に制御する。
【００１７】
すなわち、ディーゼルエンジン１０の運転条件が変化することによって排気ガス１６の温度が変化し、例えばエンジンが高負荷運転となって排気ガス１６の温度が上昇すると、第１温度センサ４０の検出する排気ガス１６の温度が上がる。このため、排気ガス１６中に添加された燃料の分解条件が変化して還元剤炭化水素の炭素数分布が変化するとともに、触媒層２６の還元特性も変化するので、コントローラ３０は、第１の温度センサ４０の検出温度が高くなると、冷却水量調節弁３４に制御信号を出力して開度を大きくし、冷却水１５の流量を増加させて排気ガス１６の温度を低下させ、排気ガス１６、触媒層２６の温度が所定の温度となるようにする。
【００１８】
これにより、触媒層２６の温度を一定にできるため、排気ガス１６によって熱分解された還元剤炭化水素の炭素数分布をほぼ一定にすることが可能となる。また、触媒層２６は、温度がこの炭素数分布においてＮＯＸ を還元するのに適した温度に維持されるため、図２に示したように、従来に比較してＮＯＸ の浄化率を大幅に向上することができる。
【００１９】
【発明の効果】
以上に説明したように、本発明によれば、排気管に設けた冷却器より上流側に燃料添加ノズルを取り付けるとともに、このノズルから還元剤用燃料を添加する位置の排気ガスの温度を第１の温度センサによって検出してコントローラに与え、コントローラによって冷却器の冷却能力（冷媒流量）を変えて燃料添加位置から触媒層までの還元剤用燃料が触媒層までに到達するまでに熱分解される度合いを所定値にできるようにしているため、エンジンの運転状態に関係なく触媒層に流入する排気ガス中の還元剤炭化水素の炭素数分布をほぼ一定にすることが可能となり、触媒層の大きな浄化能力が得られる炭素数の分布にすることができる。また、予めコントローラにて求めた触媒層の温度に対して、触媒層の温度を測定し、触媒層の温度を再度制御しているため、触媒層の温度が所定の温度になり、浄化率が向上する。
【図面の簡単な説明】
【図１】本発明の実施例に係るディーゼルエンジンの排気ガス脱硝装置の説明図である。
【図２】実施例に係る排気ガス脱硝装置と従来の排気ガス脱硝装置とのＮＯＸ 浄化率を比較する図である。
【図３】従来のディーゼルエンジンの排気ガス脱硝装置の説明図である。
【図４】排気ガスに含まれる還元剤炭化水素とＮＯＸ 浄化率との関係を示す図である。
【図５】触媒層温度と還元剤炭化水素の炭素数とＮＯＸ 浄化率との関係を示す図である。
【図６】酸素共存下における雰囲気温度において高分子炭化水素が分解されたときに生ずる炭化水素の炭素数を示す図である。
【図７】排気ガス温度と分解された還元剤炭化水素の炭素数および最適触媒層温度の関係を示す図である。
【符号の説明】
１０…ディーゼルエンジン、 ２６…触媒層、
１２…排気管、 ２８…第２の温度センサ、
１４…熱交換器の冷却器、 ３０…コントローラ、
１６…排気ガス、 ３４…冷却水量調節弁、
１８…燃料添加ノズル、 ４０…第１の温度センサ。[0001]
[Industrial application fields]
The present invention relates to an apparatus for removing nitrogen oxides (NO x ) in exhaust gas discharged from a diesel engine, and in particular, a fuel such as kerosene is added to the exhaust gas as a reducing agent, and NO x is added to N 2 or The present invention relates to an exhaust gas denitration device for a diesel engine that is reduced to H 2 O and removed.
[0002]
[Prior art]
Conventionally, when NO X is removed from exhaust gas of a diesel engine, the exhaust gas temperature is set to 300 to 400 ° C., and NO x is almost equimolarly added to the exhaust gas, followed by adding vanadium / titania catalyst. A method has been employed in which NO X is reduced and decomposed into N 2 and H 2 O by contacting with a zeolite catalyst. However, a method for reducing the NO X by the addition of ammonia or urea, it is necessary to prepare the ammonia or urea otherwise, also the amount is too large may cause secondary pollution of the environment. Therefore, in order to solve such problems, after forcibly enriching the hydrocarbons in the exhaust gas, transition metal-supported metallosilicate catalysts such as copper / zeolite catalysts and copper / alumina catalysts are first used. transition metal supported alumina is contacted with the composite oxide catalyst, a method of removing by reducing NO X in the exhaust gas have been developed.
[0003]
As a method for enriching the hydrocarbons in the exhaust gas, a method of adding fuel into the intake pipe of the engine (Japanese Patent Laid-Open No. 4-358715), a small amount of fuel is shifted from the main fuel injection timing to the engine. There is a method of injecting separately into the cylinder (Japanese Patent Laid-Open No. 3-253713) or a method of directly adding fuel or special hydrocarbons into the exhaust pipe. Then, when removing added to NO X reducing agent hydrocarbon into the exhaust pipe, as disclosed in JP-A-4-358716, the exhaust gas added with the hydrocarbon as it is led to the catalyst layer There are a method of reducing and a method of cooling the exhaust gas to which the reducing agent hydrocarbon is added and introducing it into the catalyst layer as disclosed in JP-A-5-44445. Further, as shown in FIG. 3, it was added by injecting fuel into the exhaust gas, after the exhaust gas added fuel was cooled by the cooling device, considered a method of reducing NO X is introduced into the catalyst layer It has been.
[0004]
That is, the apparatus shown in FIG. 3 is provided with a cooler 14 in the exhaust pipe 12 of the diesel engine 10 so that the exhaust gas 16 discharged from the diesel engine 10 can be cooled by the cooling water 15 flowing through the cooler 14. It is. A fuel addition nozzle 18 is attached to the exhaust pipe 12 upstream of the cooler 14. The nozzle 18 is for injecting the reducing agent fuel into the exhaust gas 16 flowing through the exhaust pipe 12. The reducing agent fuel addition amount regulator 24 connected to the fuel tank 22 through the reducing agent fuel transport pipe 20 is provided in the nozzle 18. The discharged fuel is injected into the exhaust pipe 12.
[0005]
On the other hand, on the downstream side of the cooler 14 of the exhaust pipe 12, a catalyst layer 26 constituted by a transition metal-supported metallosilicate catalyst or the like is provided, and NO X in the exhaust gas 16 to which the reducing agent fuel is added is passed. It is reduced and removed. The catalyst layer 26 is provided with a temperature sensor 28. A detection signal from the temperature sensor 28 is input to the controller 30, and the controller 30 sets the temperature of the catalyst layer 26 to a predetermined temperature. That is, the controller 30 is connected to a flow rate adjustment valve 34 provided in the inlet pipe 32 that supplies the cooling water 15 to the cooler 14, and adjusts the opening degree of the valve 34 based on the detection signal of the temperature sensor 28. The flow rate of the cooling water 15 is controlled so that the temperature of the exhaust gas 16 flowing into the catalyst layer 26 falls within the optimum operating temperature region of the catalyst layer 26.
[0006]
[Problems to be solved by the invention]
By the way, the catalyst for reducing and purifying NO X in the exhaust gas using hydrocarbon as the reducing agent has NO X purification temperature characteristics with respect to the molecular weight (carbon number) of the reducing agent hydrocarbon as shown in FIG. The smaller the carbon number of the agent hydrocarbon, the higher the temperature range where a high purification rate can be obtained. Therefore, in order to obtain the NO X purification rate of about approximately the same, as shown in FIG. 5, lower A temperature is the temperature of the catalyst layer in the case of carbon number 14, the catalyst when the number of carbon atoms is 9 The temperature of the catalyst layer is different such that the temperature of the layer is an intermediate B temperature, and when the number of carbon atoms is 5, the temperature of the catalyst layer is a high C temperature. Such a characteristic by a catalyst with the NO X in the exhaust gas in order to efficiently reduce and remove the accurately understand the number of carbon atoms in the reductant hydrocarbon that acts in the catalyst layer, or a constant and the number of carbon atoms The reducing agent hydrocarbon having a distribution is devised so as to be introduced into the catalyst layer, and the temperature of the exhaust gas (= catalyst) that can efficiently reduce and purify NO x when the carbon number or the carbon number distribution is present. It is necessary to control the temperature of the layer).
[0007]
By the way, polymer hydrocarbons such as fuel are easily decomposed into lower hydrocarbons having a small number of carbon atoms as shown in FIG. 6 in a high temperature atmosphere in which oxygen coexists. Moreover, the extent of this decomposition, the temperature and oxygen partial pressure, more like the presence of other coexisting gas components such as NO X, varies greatly depending ambient conditions. For example, the carbon number is as small as the E point at the M point where the atmosphere is high temperature, and the carbon number is as large as the F point at the P point where the atmosphere is low temperature. For this reason, the carbon number of the reducing agent hydrocarbon (solid line a) and the catalyst layer temperature (dotted line b), which are substantially determined by the exhaust gas temperature, change as shown in FIG. 7, and the optimum catalyst layer temperature is a region near the intersection. (W). For this reason, the above-described conventional method of adding a reducing agent hydrocarbon such as fuel has a problem in that exhaust gas temperature differs depending on the use conditions of the diesel engine, and the number of carbon atoms also varies, so that NO X purification cannot be sufficiently performed. there were.
[0008]
That is, the temperatures of the diesel engine and the exhaust gas vary greatly depending on the operating state of the engine, such as whether the diesel engine is operating at high speed or operating at low speed. For this reason, the conventional method of injecting the reducing agent fuel into the engine intake pipe or the engine cylinder, or the method of adding hydrocarbon or reducing agent fuel to the exhaust pipe is the catalyst layer from the addition position or addition position of the reducing agent hydrocarbon. In the route up to this point, the cracking conditions change depending on the operating state of the diesel engine, and the carbon number distribution of the reducing agent hydrocarbon always changes. As a result, there is a case where the temperature of the catalyst layer and the carbon number of the reducing agent hydrocarbon do not match well, and a situation in which the NO X purification rate is extremely lowered occurs.
[0009]
The present invention has been made to solve the above-described problems of the prior art, and changes the exhaust gas temperature to the catalyst layer in accordance with the number of carbons that is substantially determined by the exhaust temperature, so that NO can be obtained regardless of the engine operating conditions. An object of the present invention is to provide an exhaust gas denitration device for a diesel engine capable of making the purification rate of X substantially constant.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, an exhaust gas denitration device for a diesel engine according to the present invention uses a catalyst for reducing and purifying NO X in exhaust gas using diesel fuel such as kerosene as a reducing agent. In a diesel engine exhaust gas denitration device that reduces and purifies X , a reducing agent fuel supply device that adds fuel as a reducing agent to exhaust gas in an exhaust pipe, and an exhaust gas in an exhaust pipe portion to which reducing agent fuel is added A first temperature sensor for detecting the temperature of the catalyst, a second temperature sensor for detecting the temperature of the catalyst layer, and cooling water provided between the catalyst layer and the reducing agent fuel addition site in the exhaust pipe. A heat exchanger that cools the exhaust gas, a cooling water amount adjusting valve that is provided at a cooling water inlet of the heat exchanger and controls the amount of cooling water, and a cooling water amount adjusting valve that is detected by the two temperature sensors. Characterized in that comprising a controller for outputting a command for controlling the metric.
[0011]
The opening degree command from the controller to the cooling water amount adjusting valve is such that the temperature of the catalyst layer obtained from the second temperature sensor is a predetermined value with respect to the exhaust gas temperature obtained from the first temperature sensor. It is fed back as follows.
[0012]
[Action]
In the present invention configured as described above, the temperature of the exhaust gas at the site where the reducing agent fuel is added to the exhaust pipe is detected by the first temperature sensor and supplied to the controller. The degree of thermal decomposition until reaching the temperature is estimated by the controller, and the optimum catalyst layer temperature is determined according to the number of carbons obtained by the controller. Next, the amount of water in the heat exchanger that cools the exhaust gas is adjusted so that the temperature of the catalyst layer becomes the determined optimum temperature. Further, when the output of the temperature sensor of the catalyst layer is input to the controller and the temperature is higher than the optimum catalyst layer temperature obtained above, the opening amount of the cooling water amount control valve of the heat exchanger is increased, and the catalyst layer The temperature is always controlled so as to fall within the appropriate temperature range shown in FIG. Thus, the catalyst layer inlet exhaust gas temperature is controlled to the optimum catalyst layer temperature according to the catalyst layer by appropriately controlling the opening amount of the cooling water amount adjusting valve of the heat exchanger. By controlling the temperature in this way, the component distribution of the reducing agent hydrocarbon acting in the catalyst layer is made substantially constant. As a result, the catalyst characteristics shown in FIG. 7 can always be made substantially constant regardless of the operating conditions of the engine, so that efficient use of reducing agent hydrocarbons can be achieved at all times.
[0013]
【Example】
A preferred embodiment of an exhaust gas denitration device for a diesel engine according to the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is an explanatory diagram of a configuration of an exhaust gas denitration apparatus according to a first embodiment of the present invention.
In FIG. 1, a heat exchanger cooler 14 for cooling an exhaust gas 16 is provided in an exhaust pipe 12 from a diesel engine 10. In this cooler 14, cooling water 15 that is a refrigerant that exchanges heat with the exhaust gas 16 is supplied by the inlet pipe 32, and the cooling water 15 that exchanges heat with the exhaust gas 16 passes through the outlet pipe 35. To the heat exchanger such as a radiator. The inlet pipe 32 is provided with a cooling water amount adjusting valve 34 whose opening degree is controlled by the controller 30, and the cooling water 15 flowing through the cooler 14 is changed by changing the opening amount of the cooling water amount adjusting valve 34. The flow rate changes and the cooling capacity changes.
[0014]
A fuel addition nozzle 18 is attached to the exhaust pipe 12 at an appropriate position on the upstream side (diesel engine 10 side) of the cooler 14. The nozzle 18 injects and adds the fuel discharged from the fuel addition amount adjusting device 24 to the exhaust gas 16 flowing through the exhaust pipe 12. Further, a first temperature sensor 40 is attached to the exhaust pipe 12 near the fuel addition nozzle 18 so that the temperature of the exhaust gas 16 at the position where the fuel is added is detected and input to the controller 30. It is. The exhaust gas 16 to which fuel is added passes through the catalyst layer 26 provided on the downstream side, and NO X is reduced and purified when passing through the catalyst layer 26. The catalyst layer 26 is provided with a second temperature sensor 28 that detects the temperature of the catalyst layer 26 and inputs the detected temperature to the controller 30.
[0015]
The operation of the embodiment configured as described above is as follows.
The fuel in the fuel tank 22 is supplied to the diesel engine 10 and burned to become exhaust gas 16 and is discharged from the diesel engine 10 to the exhaust pipe 12. The exhaust gas 16 passes through the cooler 14 and the catalyst layer 26 and is discharged to the outside. When passing through the cooler 14, the exhaust gas 16 flowing into the exhaust pipe 12 is cooled to about 300 ° C. by exchanging heat with the cooling water 15 flowing through the cooler 14. The reducing agent fuel addition amount adjusting device 24 sucks the fuel in the fuel tank 22 through the fuel transport pipe 20 and sprays and adds it to the exhaust gas 16 flowing through the exhaust pipe 12 from the fuel addition nozzle 18. The reducing agent fuel added to the exhaust gas 16 is decomposed into lower hydrocarbons by the heat of the exhaust gas 16 and flows into the catalyst layer 26 together with the exhaust gas 16 as reducing agent hydrocarbons. Then, the catalyst layer 26 catalyzes NO X in the exhaust gas 16 to react with the reducing agent hydrocarbon, and reduces the NO X to N 2 or H 2 O for purification.
[0016]
On the other hand, the controller 30 captures detection signals from the first temperature sensor 40 and the second temperature sensor 28 and monitors the temperature of the cooled exhaust gas 16 and the temperature of the catalyst layer 26. Then, the controller 30 adjusts the flow rate of the cooling water 15 flowing through the cooler 14 based on the signal from the first temperature sensor 40 to set the temperature of the exhaust gas 16 to a predetermined control, and The temperature is controlled to a predetermined temperature. Further, when the temperature of the catalyst layer 26 is detected by the second temperature sensor 28 and deviates from a predetermined temperature, the flow rate of the cooling water 15 flowing through the cooler 14 is adjusted and controlled to a predetermined temperature. .
[0017]
That is, when the operating conditions of the diesel engine 10 change, the temperature of the exhaust gas 16 changes. For example, when the temperature of the exhaust gas 16 rises due to high engine operation, the exhaust gas detected by the first temperature sensor 40. The temperature of 16 goes up. For this reason, the decomposition conditions of the fuel added to the exhaust gas 16 change, the carbon number distribution of the reducing agent hydrocarbons changes, and the reduction characteristics of the catalyst layer 26 also change. When the temperature detected by the temperature sensor 40 increases, a control signal is output to the cooling water amount adjusting valve 34 to increase the opening, increase the flow rate of the cooling water 15 to decrease the temperature of the exhaust gas 16, The temperature of the catalyst layer 26 is set to a predetermined temperature.
[0018]
Thereby, since the temperature of the catalyst layer 26 can be made constant, the carbon number distribution of the reducing agent hydrocarbon pyrolyzed by the exhaust gas 16 can be made almost constant. Further, the catalyst layer 26, since the temperature is maintained at a temperature suitable for the reduction of NO X in the carbon number distribution, as shown in FIG. 2, significant purification rate of the NO X compared to conventional Can be improved.
[0019]
【The invention's effect】
As described above, according to the present invention, the fuel addition nozzle is attached upstream of the cooler provided in the exhaust pipe, and the temperature of the exhaust gas at the position where the reducing agent fuel is added from the nozzle is set to the first temperature. This is detected by the temperature sensor and supplied to the controller, and the controller changes the cooling capacity (refrigerant flow rate) of the cooler and thermally decomposes the fuel for the reducing agent from the fuel addition position to the catalyst layer until it reaches the catalyst layer. Since the degree can be set to a predetermined value, the carbon number distribution of the reducing agent hydrocarbon in the exhaust gas flowing into the catalyst layer can be made almost constant regardless of the operating state of the engine. It is possible to obtain a distribution of the number of carbons capable of obtaining a purification capacity. In addition, since the temperature of the catalyst layer is measured and the temperature of the catalyst layer is controlled again with respect to the temperature of the catalyst layer obtained in advance by the controller, the temperature of the catalyst layer becomes a predetermined temperature, and the purification rate is improves.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of an exhaust gas denitration device for a diesel engine according to an embodiment of the present invention.
2 is a diagram comparing the NO X purification rate of the exhaust gas denitration apparatus of the conventional exhaust gas denitration apparatus according to the embodiment.
FIG. 3 is an explanatory view of an exhaust gas denitration device of a conventional diesel engine.
4 is a diagram showing the relationship between contained in exhaust gas reducing agent hydrocarbon and NO X purification rate.
5 is a diagram showing the relationship between carbon number and the NO X purification rate of the catalyst layer temperature with a reducing agent hydrocarbon.
FIG. 6 is a graph showing the number of carbon atoms of hydrocarbons produced when polymer hydrocarbons are decomposed at an atmospheric temperature in the presence of oxygen.
FIG. 7 is a graph showing the relationship between the exhaust gas temperature, the carbon number of the decomposed reducing agent hydrocarbon, and the optimum catalyst layer temperature.
[Explanation of symbols]
10 ... diesel engine, 26 ... catalyst layer,
12 ... Exhaust pipe, 28 ... Second temperature sensor,
14 ... cooler of heat exchanger, 30 ... controller,
16 ... exhaust gas, 34 ... cooling water control valve,
18 ... Fuel addition nozzle, 40 ... First temperature sensor.

Claims (2)

灯油等のディーゼル燃料を還元剤として排気ガス中のＮＯＸ を還元浄化する触媒を用いてディーゼルエンジンの排気ＮＯＸ を還元浄化するディーゼルエンジンの排気ガス脱硝装置において、排気管路にて排気ガス中に燃料を還元剤として添加する還元剤燃料供給装置と、還元剤燃料が添加される排気管部の排気ガスの温度を検知する第１の温度センサと、触媒層の温度を検知する第２の温度センサと、排気管路中、還元剤燃料添加部位と触媒層との間に設けられた冷却水にて排気ガスを冷却する熱交換器と、熱交換器の冷却水入口部に設けられて冷却水量を制御する冷却水量調節弁と、前記の２つの温度センサからの検知温度により冷却水量調節弁の開度量を制御する指令を出力するコントローラとからなることを特徴とするディーゼルエンジンの排気ガス脱硝装置。In the exhaust gas denitration apparatus of a diesel engine to reduce and purify the exhaust NO X of the diesel engine using a catalyst that reduces and purifies NO X in the exhaust gas as a reducing agent diesel fuel such as kerosene, exhaust gas at the exhaust pipe A reductant fuel supply device for adding fuel as a reductant, a first temperature sensor for detecting the temperature of exhaust gas in the exhaust pipe portion to which the reductant fuel is added, and a second temperature sensor for detecting the temperature of the catalyst layer. A temperature sensor, a heat exchanger for cooling the exhaust gas with cooling water provided between the reducing agent fuel addition site and the catalyst layer in the exhaust pipe, and a cooling water inlet of the heat exchanger. A diesel engine comprising: a cooling water amount adjusting valve that controls the cooling water amount; and a controller that outputs a command for controlling the opening amount of the cooling water amount adjusting valve based on the detected temperature from the two temperature sensors. Jin exhaust gas denitration device. 前記コントローラから冷却水量調節弁への開度量の指令は、第１の温度センサから得られた排気ガス温度に対して、第２の温度センサから得られた触媒層の温度が予め定めた値となるようにフイードバックされることを特徴とする請求項１に記載のディーゼルエンジンの排気ガス脱硝装置。The opening degree command from the controller to the cooling water amount adjusting valve is such that the temperature of the catalyst layer obtained from the second temperature sensor is a predetermined value with respect to the exhaust gas temperature obtained from the first temperature sensor. The exhaust gas denitration device for a diesel engine according to claim 1, wherein the exhaust gas denitration device is fed back.
JP05654095A 1995-02-20 1995-02-20 Diesel engine exhaust gas denitration equipment Expired - Fee Related JP3607343B2 (en)

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GB2337710B (en) * 1998-05-15 2002-11-13 Arvin Ind Inc Exhaust system
KR100375523B1 (en) * 2000-12-13 2003-03-10 주식회사 경동보일러 Waste gas purification device for condensing boiler
US6871489B2 (en) * 2003-04-16 2005-03-29 Arvin Technologies, Inc. Thermal management of exhaust systems
CN107989680A (en) * 2017-12-27 2018-05-04 广西玉柴机器股份有限公司 Catalyst temperature sensitivity test equipment

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