JP4100876B2

JP4100876B2 - Carbon monoxide removal method, fuel reforming system operation method using the same, and iron poisoning prevention method

Info

Publication number: JP4100876B2
Application number: JP2001091761A
Authority: JP
Inventors: 満秋越後; 健田畑; 修山▲崎▼
Original assignee: Osaka Gas Co Ltd
Current assignee: Osaka Gas Co Ltd
Priority date: 2001-03-28
Filing date: 2001-03-28
Publication date: 2008-06-11
Anticipated expiration: 2021-03-28
Also published as: JP2002284505A

Description

【０００１】
【発明の属する技術分野】
本発明は、天然ガス、ナフサ、灯油等の炭化水素類又はメタノール等のアルコール類を改質（水蒸気改質、部分燃焼改質など）して得られる改質ガスのように、主成分として水素（Ｈ₂）を含み、夾雑物として一酸化炭素（ＣＯ）を含む混合ガス中の一酸化炭素を除去する一酸化炭素除去触媒から構成される触媒層をその筐体内に形成した一酸化炭素除去器に、前記混合ガスに酸化剤を添加した反応ガスを導入する導入工程と、前記一酸化炭素除去触媒上で前記酸化剤と前記混合ガスとを反応させて一酸化炭素を除去する除去工程とを有する一酸化炭素除去方法、及びこれを用いた燃料改質システムの運転方法、並びに鉄被毒防止方法に関するものである。
【０００２】
【従来の技術】
従来、天然ガス等の化石燃料を原燃料として、水素と一酸化炭素を含む改質ガス（水素を４０体積％以上含むガス（ドライベース））を製造する燃料改質システムにあっては、前記原燃料を、連設した脱硫器、燃料改質装置で、脱硫、水蒸気改質（場合によっては部分燃焼改質、もしくは水蒸気改質と部分燃焼改質の組み合わせ）して、水素を主成分とし一酸化炭素、二酸化炭素（ＣＯ₂）、水分（Ｈ₂Ｏ）等を含む改質ガスを得ていた。又、前記アルコール類、例えばメタノールを原燃料とする燃料改質システムは、メタノール改質触媒を内装した燃料改質装置を備え、メタノールから、水素を主成分とし、一酸化炭素（ＣＯ）、二酸化炭素、水分等を含む改質ガスを得ていた。
【０００３】
ここで、リン酸型燃料電池に供する改質ガスを製造する燃料改質システムにあっては、一酸化炭素の存在によって、燃料電池の電極触媒が被毒することが知られており、前記水素を主成分とする改質ガスを一酸化炭素変成器に導入し、一酸化炭素変成反応によって、前記一酸化炭素を二酸化炭素に変換し、ガス中の一酸化炭素濃度を所定値以下（例えば、０．５％）とした改質ガスを得ていた。
しかし、固体高分子型燃料電池に供する改質ガスを製造する燃料改質システムにあっては、固体高分子型燃料電池が約８０℃という低温で作動することから、微量の一酸化炭素によっても電極触媒が被毒されてしまうために、更に前記一酸化炭素を低減する必要があり、前記一酸化炭素変成器の下流に、一酸化炭素を除去する一酸化炭素除去触媒を収容した一酸化炭素除去器を設けて、前記一酸化炭素変成器で処理された前記改質ガスに、空気等の酸化剤を添加してこれに導入し、この一酸化炭素除去触媒の存在下で、一酸化炭素を二酸化炭素に酸化し、一酸化炭素濃度を所定濃度以下（例えば、１００ｐｐｍ以下）にまで低減した改質ガスを得ていた。又、固体高分子型燃料電池のより高い性能や耐久性を確保するために、一酸化炭素濃度を１０ｐｐｍ以下にまで低減した改質ガスを得ていた。
【０００４】
前記一酸化炭素除去器は、筐体に、ルテニウム（Ｒｕ）、ロジウム（Ｒｈ）、白金（Ｐｔ）、パラジウム（Ｐｄ）等をアルミナ等の担体に担持した一酸化炭素除去触媒から構成される触媒層を収容してあって、ガス流入口より前記触媒層に前記改質ガスに空気などの酸化剤を添加したガス（反応ガス）を導入して、前記一酸化炭素除去触媒と接触させ、これによって、前記改質ガス中の一酸化炭素を二酸化炭素に酸化して除去していた。そして、前記触媒層を通過して一酸化炭素濃度が減少した前記反応ガスを、前記筐体に設けられたガス流出口から排出していた。又、前記一酸化炭素除去触媒は、前記触媒層の温度が８０〜２００℃程度のときに、一酸化炭素を酸化する反応が進行し易くなるので、ヒータや冷却器などを備えた温度調節手段を前記筐体に付設して、前記触媒層の温度がその温度域になるように保持されていた。
【０００５】
尚、従来、前記燃料改質装置を構成する部材としては、耐侯性、耐熱性、強度、加工性、コストなどの諸事情を勘案して、含鉄材料であるステンレス鋼が主として用いられていた。
【０００６】
【発明が解決しようとする課題】
ところが、前記一酸化炭素除去器を、前記一酸化炭素除去触媒の作用に適した温度域で運転しても、使用条件によっては、長期間に亘って運転すると徐々に前記一酸化炭素除去器から排出される前記反応ガス中の一酸化炭素濃度が高まって数十ｐｐｍに達し、前記固体高分子型燃料電池の燃料として供するには一酸化炭素濃度が高くなりすぎるという問題が発生することを、本願発明者らは見出した。
このような前記一酸化炭素除去触媒の性能劣化の原因は、従来判明しておらず、本願発明者らの新知見である。
【０００７】
従って、本発明の目的は、上記欠点に鑑み、前記一酸化炭素除去器や前記燃料改質システムを運転するに際して、長期間に亘って安定して一酸化炭素を除去する方法、及び前記燃料改質システムの運転方法、並びに鉄被毒防止方法を提供することにある。
【０００８】
【課題を解決するための手段】
この目的を達成するための本発明の一酸化炭素除去方法の第１特徴手段は、請求項１に記載されているように、固体高分子型燃料電池に供する燃料ガスを得るために、原燃料を改質して得た水素と一酸化炭素を含む混合ガス中の一酸化炭素を除去するルテニウム、白金、ロジウム、又はパラジウムを含む一酸化炭素除去触媒から構成される触媒層をその筐体内に形成した一酸化炭素除去器に、前記混合ガスに酸化剤を添加した反応ガスを導入する導入工程と、前記一酸化炭素除去触媒上で前記酸化剤と前記混合ガスとを反応させて一酸化炭素を除去する除去工程とを有する一酸化炭素除去方法において、前記導入工程において、１００℃以下の前記反応ガスを、前記一酸化炭素除去器に導入するに、前記一酸化炭素除去器の入口に接続される配管に、当該配管内を流通する前記混合ガス又は前記反応ガスを冷却する熱交換器とドレントラップとを設けて、当該配管を流通する前記反応ガス中の水蒸気を凝縮させることで、前記一酸化炭素除去器の入口に導入される前記反応ガスの露点を、プロセス圧力において４０℃以下とする点にある。
更に、上記第１特徴手段において、請求項２に記載してあるように、前記導入工程において、８０℃以下の前記反応ガスを、前記一酸化炭素除去器に導入することが好ましい。
【０００９】
又、この目的を達成するための本発明の一酸化炭素除方法の第２特徴手段は、請求項３に記載されているように、固体高分子型燃料電池に供する燃料ガスを得るために、原燃料を改質して得た水素と一酸化炭素を含む混合ガス中の一酸化炭素を除去するルテニウム、白金、ロジウム、又はパラジウムを含む一酸化炭素除去触媒から構成される触媒層をその筐体内に形成した一酸化炭素除去器に、前記混合ガスに酸化剤を添加した反応ガスを導入する導入工程と、前記一酸化炭素除去触媒上で酸化剤と前記混合ガスとを反応させて一酸化炭素を除去する除去工程とを有する一酸化炭素除去方法において、前記除去工程において、前記触媒層の最高温度を１３０℃以上１８０℃以下に保持するに、前記一酸化炭素除去器の入口に接続される配管に、当該配管内を流通する前記混合ガス又は前記反応ガスを冷却する熱交換器とドレントラップとを設けて、当該配管を流通する前記反応ガス中の水蒸気を凝縮させることで、前記一酸化炭素除去器の入口に導入される前記反応ガスの露点を、プロセス圧力において４０℃以下とする点にある。
【００１０】
更に、上記第２特徴手段において、請求項４に記載してあるように、前記触媒層の最高温度が、１５０℃以上１８０℃以下であることが好ましい。
【００１１】
又、この目的を達成するための本発明の一酸化炭素除去方法の第３特徴手段は、請求項５に記載されているように、固体高分子型燃料電池に供する燃料ガスを得るために、原燃料を改質して得た水素と一酸化炭素を含む混合ガス中の一酸化炭素を除去するルテニウム、白金、ロジウム、又はパラジウムを含む一酸化炭素除去触媒から構成される触媒層をその筐体内に形成した一酸化炭素除去器に、前記混合ガスに酸化剤を添加した反応ガスを導入する導入工程と、前記一酸化炭素除去触媒上で酸化剤と前記混合ガスとを反応させて一酸化炭素を除去する除去工程とを有する一酸化炭素除去方法において、前記導入工程において、１００℃以下の前記反応ガスを、前記一酸化炭素除去器に導入し、前記除去工程において、前記触媒層の最高温度を１３０℃以上１８０℃以下に保持するに、前記一酸化炭素除去器の入口に接続される配管に、当該配管内を流通する前記混合ガス又は前記反応ガスを冷却する熱交換器とドレントラップとを設けて、当該配管を流通する前記反応ガス中の水蒸気を凝縮させることで、前記一酸化炭素除去器の入口に導入される前記反応ガスの露点を、プロセス圧力において４０℃以下とする点にある。
【００１２】
更に、上記第１〜第３特徴手段において、請求項６に記載してあるように、前記混合ガスが炭化水素類又はアルコール類を改質して得られる改質ガスであることが好ましく、
請求項７に記載してあるように、前記一酸化炭素除去触媒がルテニウムを含む触媒であることが好ましく、
請求項８に記載してあるように、前記導入工程を行う前に、前記一酸化炭素除去触媒から構成される前記触媒層を水素と窒素とを混合したガス気流中で前処理することが好ましい。
【００１３】
又、この目的を達成するための本発明の燃料改質システムの運転方法の第１特徴手段は、請求項９に記載されているように、原燃料と水蒸気とを含むガス中の前記原燃料を水素と一酸化炭素を含む混合ガスに改質する改質触媒を収容した改質器と、前記混合ガス中の一酸化炭素を変成する一酸化炭素変成触媒を収容した一酸化炭素変成器と、前記一酸化炭素変成器から排出された前記混合ガスに酸化剤を添加した反応ガス中の一酸化炭素を除去するルテニウム、白金、ロジウム、又はパラジウムを含む一酸化炭素除去触媒を収容した一酸化炭素除去器とを記載順に気体流通可能に配管で連結し、前記一酸化炭素変成器と前記一酸化炭素除去器とを連結する配管内を流通する前記混合ガス又は前記反応ガスに対して熱交換可能に伝熱媒体が流通する熱交換器を設けた固体高分子型燃料電池システムに供する燃料改質システムの運転方法において、前記配管内を流通する前記混合ガス又は前記反応ガスと前記熱交換器内を流通する前記伝熱媒体との熱交換によって、前記熱交換器が設けられた部位より下流側の配管内を流通する前記反応ガスを１００℃以下に保持して前記一酸化炭素除去器に導入するに、前記一酸化炭素除去器の入口に接続される配管に、当該配管内を流通する前記混合ガス又は前記反応ガスを冷却する熱交換器とドレントラップとを設けて、当該配管を流通する前記反応ガス中の水蒸気を凝縮させることで、前記一酸化炭素除去器の入口に導入される前記反応ガスの露点を、プロセス圧力において４０℃以下とする点にある。
ここで、請求項１０に記載されているように、前記一酸化炭素除去器へ前記反応ガスを導入する前に、前記一酸化炭素除去触媒から構成される前記触媒層を水素と窒素とを混合したガス気流中で前処理することが好ましい。
さらに、この目的を達成するための本発明の鉄被毒防止方法の第１特徴手段は、請求項１１に記載されているように、固体高分子型燃料電池に供する燃料ガスを得るために、原燃料を改質して得た水素と一酸化炭素を含む混合ガス中の一酸化炭素を除去するルテニウム、白金、ロジウム、又はパラジウムを含む一酸化炭素除去触媒から構成される触媒層をその筐体内に形成した一酸化炭素除去器に、前記混合ガスに酸化剤を添加した反応ガスを導入する導入工程と、前記一酸化炭素除去触媒上で前記酸化剤と前記混合ガスとを反応させて一酸化炭素を除去する除去工程とを有する一酸化炭素除去方法を実行するに際し、前記導入工程において、１００℃以下の前記反応ガスを、前記一酸化炭素除去器に導入するに、前記一酸化炭素除去器の入口に接続される配管に、当該配管内を流通する前記混合ガス又は前記反応ガスを冷却する熱交換器とドレントラップとを設けて、当該配管を流通する前記反応ガス中の水蒸気を凝縮させることで、前記一酸化炭素除去器の入口に導入される前記反応ガスの露点を、プロセス圧力において４０℃以下として、前記一酸化炭素除去触媒から構成される触媒層の鉄被毒を防止する点にある。
ここで、請求項１２に記載されているように、前記導入工程を行う前に、前記一酸化炭素除去触媒から構成される前記触媒層を水素と窒素とを混合したガス気流中で前処理することが好ましい。
そして、これらの作用効果は、以下の通りである。
【００１４】
本発明において提案する一酸化炭素除去方法及びこれを用いた燃料改質システムの運転方法は、この一酸化炭素除去器に収容した一酸化炭素除去触媒が、鉄又は鉄化合物によって被毒（鉄被毒）されるという新知見に基づくものである。
【００１５】
発明者らは、前記一酸化炭素除去器による一酸化炭素除去率が徐々に低下する（劣化する）原因を解明すべく、鋭意研究を進めた結果、前記劣化した触媒の表面の状態を電子プローブ微量分析（ＥＰＭＡ）により解析することによって、その表面に何らかの形態で鉄原子が存在していることを確認した。又、発明者らは、劣化していない触媒の表面にほとんど鉄原子が存在しないことも同時に確認しており、前記触媒の劣化に、前記鉄又は鉄化合物、或いは前記鉄及び鉄化合物双方の存在が深く関与していると考えた。
【００１６】
そこで、更に、前記劣化した触媒に存在する鉄又は鉄化合物の由来について検討した結果、前記燃料改質装置を構成する部品（例えば、ステンレス鋼製の反応器や配管、熱交換器など）に含まれる鉄又は鉄化合物が、前記改質ガスに混入して、前記一酸化炭素除去器に内装した前記触媒に付着して活性点を塞いで、活性が低下する虞れがあることが分かった。
これまで、一酸化炭素除去器を通常の条件で使用するにあたって、一酸化炭素除去触媒が鉄被毒を受けるとは考えられていなかったが、鉄や鉄化合物が前記改質ガスに混入し、一酸化炭素除去触媒が鉄被毒され得る原因について考察してみると、可能性の一つとして、以下の様なプロセスが推測される。
先ず、前記一酸化炭素変成器を通過して一酸化炭素濃度を低減した改質ガス（例えば、代表的な組成としては、水素６５％、二酸化炭素１９％、一酸化炭素０．５％、水蒸気１５．５％）は、前記一酸化炭素変成器の出口温度（約２００℃程度）と同程度の温度で、前記一酸化炭素変成器から排出されるわけであるが、後続する前記一酸化炭素除去器の運転温度は、これより低い（８０〜２００℃程度）ため、前記一酸化炭素除去器に導入する前に、前記一酸化炭素変成器と前記一酸化炭素除去器とを接続する反応器や配管、熱交換器中などで放熱して、その温度が下がる。このとき、前記改質ガスは、水素の濃度が高く、又、前記配管や熱交換器などを構成するステンレス鋼材等には鉄、ニッケルが存在しているので、鉄と一酸化炭素とが結合することによって鉄カルボニル（Ｆｅ（ＣＯ）₅）のような形態を取って遊離し易い条件となっている。従って、鉄が前記改質ガスと共に移動して、前記一酸化炭素除去器に流入して、前記一酸化炭素除去触媒に付着することによって、被毒するものと考えられる。
又、前記一酸化炭素変成器と前記一酸化炭素除去器との間で一酸化炭素を除去するために添加する酸化剤や、前記一酸化炭素変成器と前記一酸化炭素除去器との間で結露する水等も前記鉄被毒のプロセスに関与している可能性がある。
【００１７】
ここで、前記筐体がステンレス鋼からなるものであったとしても、前記触媒部周辺の一酸化炭素濃度が触媒反応によって低下するので、前記鉄カルボニルの発生は、前記一酸化炭素除去器の上流域からの流入と比べて、少ないものと考えられる。
【００１８】
そこで、発明者らは、前記一酸化炭素触媒を用いた前記混合ガスからの一酸化炭素の除去方法について鋭意研究の結果、鉄によって前記酸化炭素除去触媒が被毒されにくい一酸化炭素除去方法があることを見出し、本発明を完成するに至った。
【００１９】
ここで、請求項１に記載されているように、固体高分子型燃料電池に供する燃料ガスを得るために、原燃料を改質して得た水素と一酸化炭素を含む混合ガス中の一酸化炭素を除去するルテニウム、白金、ロジウム、又はパラジウムを含む一酸化炭素除去触媒から構成される触媒層をその筐体内に形成した一酸化炭素除去器に、前記混合ガスに酸化剤を添加した反応ガスを導入する導入工程と、前記一酸化炭素除去触媒上で前記酸化剤と前記混合ガスとを反応させて一酸化炭素を除去する除去工程とを有する一酸化炭素除去方法において、前記導入工程において、１００℃以下の前記反応ガスを、前記一酸化炭素除去器に導入するに、前記一酸化炭素除去器の入口に接続される配管に、当該配管内を流通する前記混合ガス又は前記反応ガスを冷却する熱交換器とドレントラップとを設けて、当該配管を流通する前記反応ガス中の水蒸気を凝縮させることで、前記一酸化炭素除去器の入口に導入される前記反応ガスの露点を、プロセス圧力において４０℃以下とすると、前記配管等を構成する鉄分と一酸化炭素との結合が起こりにくくなって鉄カルボニルの生成が抑制されると考えられる。又、前記鉄カルボニルが生成したとしても、その沸点が１０３℃であるので、前記反応ガスの温度を１００℃以下に保つことで気化が抑制され、前記配管の下流にある前記一酸化炭素除去器内への流入を抑制することができると考えられる。
尚、前記反応ガスの冷却は０℃以上とすると、空気や水等の媒体を用いて簡便な冷却手段を用いることができる。
【００２０】
【００２１】
また、前記一酸化炭素除去器に導入する反応ガスに多量の水分が含まれていると、前記一酸化炭素除去器入口に導入される前記反応ガスの温度を１００℃以下に下げたときに前記配管内や前記一酸化炭素除去器内で水分が凝集して結露し、これにより、前記配管内や前記一酸化炭素除去器内における前記反応ガスの通路の断面積や容積がランダムに変化し、前記一酸化炭素除去器に供給される前記反応ガスの流量がランダムに変動したり、前記一酸化炭素除去器に収容された前記一酸化炭素除去触媒が凝集水に濡れて活性が低下したりする虞がある。そこで、前記一酸化炭素除去器入口に導入される前記反応ガスの温度を下げると同時に、前記反応ガス中の露点がプロセス圧力において４０℃以下になるように前記反応ガスに含まれる水蒸気を前記一酸化炭素除去器に導入する前に凝縮分離しておくと、前記一酸化炭素除去触媒が濡れ難くなるので活性が低下し難くなり、又、前記配管内や一酸化炭素除去器内における前記反応ガスの流量の変動幅を非常に小さく抑えることができる。又、負荷変動時等に前記改質器におけるＳ／Ｃ（蒸気と前記原燃料に含まれる炭素のモル比）が変動して、前記反応ガス中の水蒸気量が多くなった場合にも、前記配管や一酸化炭素除去器に導入される前記反応ガスの水蒸気量を調整することで、安定して一酸化炭素を除去することができる。
【００２２】
そして、前記反応ガスの露点が、プロセス圧力において４０℃以下であると、前記反応ガス中の水分の結露を充分に抑制でき、又、前記一酸化炭素除去触媒によって前記反応ガス中の一酸化炭素除去触媒を１０ｐｐｍ以下にまで除去できる温度範囲（特に低温での温度範囲）が広くなり、低温の前記反応ガスを前記一酸化炭素除去器に導入しても一酸化炭素除去反応を開始しやすい。
尚、上記第１特徴手段において、請求項２に記載してあるように、前記導入工程において、前記一酸化炭素除去器に導入する前記反応ガスの温度を８０℃以下とすると、前記鉄カルボニルの生成速度を充分低く抑えることができる上に、前記触媒層の最高温度も制御しやすくなるので好ましい。
【００２３】
一方、前記鉄カルボニルは高温で分解したり、重合したりすることが知られている。そこで、請求項５に記載されているように、固体高分子型燃料電池に供する燃料ガスを得るために、原燃料を改質して得た水素と一酸化炭素を含む混合ガス中の一酸化炭素を除去するルテニウム、白金、ロジウム、又はパラジウムを含む一酸化炭素除去触媒から構成される触媒層をその筐体内に形成した一酸化炭素除去器に、前記混合ガスに酸化剤を添加した反応ガスを導入する導入工程と、前記一酸化炭素除去触媒上で酸化剤と前記混合ガスとを反応させて一酸化炭素を除去する除去工程とを有する一酸化炭素除去方法において、前記除去工程における前記触媒層の最高温度を１３０℃以上に保持することによって、前記一酸化炭素除去器に鉄カルボニルが流入した場合であっても、分解することによって前記一酸化炭素除去触媒への付着状態を制御することができ、或いは前記鉄カルボニルの重合によって付着点を実質的に減少させることができると考えられる。
尚、前記触媒層の温度が高くなりすぎると二酸化炭素のメタン化反応が起こり易くなり、前記混合ガスに含まれる水素が消費され収量が減少するばかりでなく、反応熱によって温度の制御が困難になるので、１８０℃以下に前記触媒層の最高温度を保持することが好ましい。
また、この一酸化炭素除去方法においても、前記一酸化炭素除去器の入口に接続される配管に、当該配管内を流通する前記混合ガス又は前記反応ガスを冷却する熱交換器とドレントラップとを設けて、当該配管を流通する前記反応ガス中の水蒸気を凝縮させることで、前記一酸化炭素除去器の入口に導入される前記反応ガスの露点を、プロセス圧力において４０℃以下とする。
【００２４】
ここで、請求項４に記載してあるように、前記触媒層の最高温度を１５０℃以上１８０℃以下とすることで、更に、前記一酸化炭素除去触媒の長寿命化を図ることができる（実施例参照）。
【００２５】
更に、請求項５に記載されているように、固体高分子型燃料電池に供する燃料ガスを得るために、原燃料を改質して得た水素と一酸化炭素を含む混合ガス中の一酸化炭素を除去するルテニウム、白金、ロジウム、又はパラジウムを含む一酸化炭素除去触媒から構成される触媒層をその筐体内に形成した一酸化炭素除去器に、前記混合ガスに酸化剤を添加した反応ガスを導入する導入工程と、前記一酸化炭素除去触媒上で酸化剤と前記混合ガスとを反応させて一酸化炭素を除去する除去工程とを有する一酸化炭素除去方法において、前記導入工程における前記反応ガスの温度を１００℃以下として前記一酸化炭素除去器に導入することで、前記触媒層への前記鉄カルボニルの流入を抑制することと、前記除去工程において、前記触媒層の最高温度を１３０℃以上１８０℃以下に保持して前記一酸化炭素除去触媒への前記鉄カルボニルの付着を抑制することの相乗効果によって、前記一酸化炭素除去触媒の被毒が更に抑制されて、前記反応ガス中の前記一酸化炭素を非常に高い率で除去することができる。
尚、この一酸化炭素除去方法においても、前記一酸化炭素除去器の入口に接続される配管に、当該配管内を流通する前記混合ガス又は前記反応ガスを冷却する熱交換器とドレントラップとを設けて、当該配管を流通する前記反応ガス中の水蒸気を凝縮させることで、前記一酸化炭素除去器の入口に導入される前記反応ガスの露点を、プロセス圧力において４０℃以下とする。
【００２６】
更に、請求項６に記載してあるように、前記混合ガスが炭化水素類又はアルコール類を改質して得られる改質ガスである場合に、請求項１〜５に記載した方法により一酸化炭素を除去すると、長期間に亘って一酸化炭素を除去できるので好ましい。
【００２７】
更に、本願発明者らは、前記一酸化炭素除去触媒がルテニウムを含む触媒である場合に、前記鉄被毒による活性低下や寿命短縮といった影響が大きいことを見出したので、請求項７に記載してあるように、前記一酸化炭素除去触媒がルテニウムを含む触媒である場合に、本法を適用すると有効である。
【００２８】
ここで、原燃料と水蒸気とを含むガス中の前記原燃料を水素と一酸化炭素を含む混合ガスに改質する改質触媒を収容した改質器と、前記混合ガス中の一酸化炭素を変成する一酸化炭素変成触媒を収容した一酸化炭素変成器と、前記一酸化炭素変成器から排出された前記混合ガスに酸化剤を添加した反応ガス中の一酸化炭素を除去するルテニウム、白金、ロジウム、又はパラジウムを含む一酸化炭素除去触媒を収容した一酸化炭素除去器とを記載順に気体流通可能に配管で連結し、前記一酸化炭素変成器と前記一酸化炭素除去器とを連結する配管内を流通する前記混合ガス又は前記反応ガスに対して熱交換可能に伝熱媒体が流通する熱交換器を設けた固体高分子型燃料電池システムに供する燃料改質システムを運転するにあたって、請求項９に記載されているように、前記配管内を流通する前記混合ガス又は前記反応ガスと前記熱交換器内を流通する前記伝熱媒体との熱交換によって、前記熱交換器が設けられた部位より下流側の配管内を流通する前記反応ガスを１００℃以下に保持することによって、前記配管内で前記鉄カルボニルが発生することを抑制することができる。従って、このようにして温度を調整した反応ガスを前記一酸化炭素除去器に導入することで前記触媒層への前記鉄カルボニルの流入を抑制することができ、前記一酸化炭素除去触媒の鉄被毒を軽減して長期間に亘って、前記一酸化炭素除去触媒による一酸化炭素除去活性を高く保持することができる。
尚、この燃料改質システムの運転方法においては、前記一酸化炭素除去器の入口に接続される配管に、当該配管内を流通する前記混合ガス又は前記反応ガスを冷却する熱交換器とドレントラップとを設けて、当該配管を流通する前記反応ガス中の水蒸気を凝縮させることで、前記一酸化炭素除去器の入口に導入される前記反応ガスの露点を、プロセス圧力において４０℃以下とする。
【００２９】
【発明の実施の形態】
以下に本発明の実施の形態を図面に基づいて説明する。
図１は、本発明に係る一酸化炭素除去方法を実施可能な燃料改質システムを示す。この燃料改質システムは、天然ガス（都市ガス）を原燃料として、固体高分子型燃料電池に供する水素を主成分とする改質ガスを製造するものであって、前記原燃料を供給する原燃料供給系１、脱硫触媒を収容した脱硫器２、改質触媒を収容した改質器４、一酸化炭素変成触媒を収容した一酸化炭素変成器５及び前記一酸化炭素除去触媒を収容した一酸化炭素除去器６が配管を通じて連接されている。これらを通過して改質された改質ガス（燃料ガス）は、固体高分子型燃料電池７に供給される。
前記原燃料供給系１に貯えられた天然ガスは、前記脱硫器２を通過する際に、前記脱硫触媒と接触して硫黄分が除去される。そして、水蒸気発生器３から供給される水蒸気と混合された後に、前記改質器４に搬送されて、ここで、前記改質触媒と接触して、前記天然ガス中のメタンが主に水素、そして副生物としての一酸化炭素に改質される。このようにして得られた改質ガスは、水素に富むものの、副生成物としての一酸化炭素を十数％含むので、前記固体高分子型燃料電池７に直接供給することができない。そこで、前記一酸化炭素変成器５において、銅−亜鉛系触媒のような一酸化炭素変成触媒と接触させて、一酸化炭素を二酸化炭素に変成させ、０．５〜１％にまで一酸化炭素濃度を下げる。
【００３０】
更に、一酸化炭素濃度を０．５〜１％に低減した前記改質ガスは、酸化剤供給器９から供給される空気（酸素が酸化剤として作用する）と混合された後に、反応ガスとして、前記配管を通じて前記一酸化炭素除去器６に導入される。
この一酸化炭素除去器６は、一酸化炭素除去触媒から構成される触媒層をその筐体内に形成し、前記反応ガスが前記触媒層を通過するよう構成したものである。前記一酸化炭素除去触媒は、例えば、ルテニウム、白金、ロジウム、パラジウム等の貴金属をアルミナ球等の担体に担持したものが用いられる。
一酸化炭素濃度を０．５〜１％に低減した前記改質ガスは、前記酸化剤と共に前記一酸化炭素除去器６の筐体内に流入すると、ここに形成された前記触媒層に接触する。前記触媒層には前記一酸化炭素除去触媒が収容されていて、ここで前記一酸化炭素除去触媒の触媒反応によって、主として、一酸化炭素が酸素と反応して酸化され二酸化炭素となる。このようにして、前記改質ガス中の一酸化炭素濃度は除去され、最終的には、前記固体高分子型燃料電池７に供給される。
【００３１】
前記一酸化炭素除去器６は、前記触媒層が約８０〜１８０℃となるように運転するので、この範囲に前記筐体の温度を調節するための温度調節手段８を備えている。この温度調節手段８は、前記筐体を加熱するためのヒータ又は熱源並びに前記筐体を冷却するための冷却器を備えている。
【００３２】
そして、前記触媒層内に流入した鉄カルボニル等の含鉄化合物や金属鉄が前記一酸化炭素除去触媒表面に付着して活性を低下させることを抑制し、又、一酸化炭素のメタン化などの副反応を抑制するために、前記触媒層の最高温度が１３０〜１８０℃、好ましくは、１５０〜１８０℃になるように、前記温度調節手段８で調整する。
【００３３】
又、前記一酸化炭素変成器５と前記一酸化炭素除去器６とを連結する配管の一部又は全部の外壁面には熱交換器８１が沿設されていて、前記熱交換器内を前記配管の壁面を介して前記混合ガスや前記反応ガスと熱交換可能に伝熱媒体（例えば、空気や水等）が流通する。前記熱交換器８１を設ける位置は、図１に示すように前記酸化剤が前記混合ガスに添加されるより前の段階であってもよく、或いは、前記混合ガスに前記酸化剤が添加されて前記反応ガスとして流通している部位であってもよい。前記熱交換器８１内を流れる前記伝熱媒体と前記配管内を流れる前記混合ガス又は前記反応ガスとの間で熱交換が起こることによって、前記混合ガス又は前記反応ガスは冷却されるので、前記配管に流入する前記混合ガス又は前記反応ガスの流量、温度等を予め測定して前記伝熱媒体の流量等を適切に調整する、或いは所定の流量等で前記伝熱媒体を流通することによって、前記熱交換器８１が設けられた部位より下流側の配管内を流れるガスの温度を１００℃以下、好ましくは、負荷変動等を考慮して８０℃以下に調整する。尚、前記一酸化炭素除去器６の設置環境や使用する前記熱媒体の温度等の要因に基づいて、前記反応ガスの温度（下限）は定まる。
【００３４】
前述したように、前記触媒層の温度を１３０℃以上１８０℃以下に調整するか、前記一酸化炭素除去器の上流に接する前記配管の温度を１００℃以下に調整するかの何れか少なくとも一方を実施することで前記一酸化炭素除去触媒の鉄被毒を大幅に抑制して、前記一酸化炭素除去触媒の長寿命化及び活性改善を図ることができるが、両方を実施することで相乗効果が得られて、更に前記一酸化炭素除去触媒の長寿命化し活性を改善することができる。
【００３５】
更には、前記配管にドレントラップを設けて、前記一酸化炭素除去器６に導入する前記反応ガス中の水蒸気を凝縮させ、前記反応ガスの露点をプロセス圧力において６０℃以下、好ましくは、４０℃以下にすると、前記配管や前記一酸化炭素除去器内で結露することを防ぐことができる。
【００３６】
【実施例】
以下、本発明に係る一酸化炭素除去方法の効果を実証するための試験について説明する。
【００３７】
直径２〜４ｍｍの球状のγ−アルミナ担体を三塩化ルテニウム水溶液に浸漬し、含浸法よりルテニウムを担持させた。これを乾燥させた後、炭酸ナトリウム水溶液に浸漬して前記担体に前記ルテニウムを固定化して、水洗、乾燥し、前駆体を得た。この前駆体をヒドラジン溶液に浸漬して前記前駆体表面のルテニウムを還元し、再度水洗し、１０５℃で乾燥させてＲｕ／アルミナ触媒を得た。得られたＲｕ／アルミナ触媒中のルテニウム濃度は０．９８重量％、平均細孔径は７．４ｎｍであった。
尚、以下の実施例１、２においては、得られたＲｕ／アルミナ触媒を反応管に充填した後、５体積％の水素を含む水素と窒素とを混合したガス気流中で２２０℃、１．５時間保持した（前処理）。この前処理は、前記Ｒｕ／アルミナ触媒の低温にける初期活性を高めるための処理である。
【００３８】
（実施例１）
上記Ｒｕ／アルミナ触媒（一酸化炭素除去触媒）８ｃｃを、内部に外径６ｍｍの熱電対挿入用鞘管を有する内径２１．２ｍｍのステンレス鋼製の反応管（筐体）に充填して触媒層を形成した後、前記前処理を施して、２つのマイクロリアクター（一酸化炭素除去器）を作製した。この一酸化炭素除去器の入口から筐体内部に導入された反応模擬ガスは、前記触媒層を通過して、前記出口から筐体外に放出される。又、この一酸化炭素除去器は、前記反応管を外部からヒータにより加熱することによって、前記反応管の温度を制御可能に構成してある。
【００３９】
前記一酸化炭素除去器の上流側には、ステンレス鋼製の配管が接続されていて、この配管から前記反応模擬ガスが前記一酸化炭素除去器に対して供給される。
【００４０】
前記反応模擬ガスとしては、前記一酸化炭素変成器の出口ガスに、酸素／一酸化炭素モル比（［Ｏ₂］／［ＣＯ］）が１．５となるように、空気を混合したものに相当する組成のガス（一酸化炭素０．５％、メタン０．５％、二酸化炭素２０．９％、酸素０．７５％、窒素３．０％、水素でバランスの混合ガス１０００Ｎｍｌ／分に湿りガス中の水蒸気濃度が５％（露点３３℃相当）になるように水蒸気を添加した反応模擬ガス）を用いた。尚、この時の空間速度（ＧＨＳＶ）は７，５００／時間（ドライベース）となっている。
【００４１】
８０℃に加熱した前記反応模擬ガスと、１４０℃に加熱した前記反応模擬ガスとを、前記配管の夫々に供給し、夫々の前記配管に接続された前記一酸化炭素除去器の前記筐体内の最高温度を９０℃に調整して一酸化炭素除去を行なった。尚、前記触媒層の最高温度は１１０℃になっていた。このとき、前記筐体の出口（流出口）において前記反応模擬ガス（出口ガス）を経時的に採取し、前記出口ガス中の一酸化炭素濃度（ドライベース）を、熱伝導度検出器（ＴＣＤ）及び水素炎イオン化検出器（ＦＩＤ）を搭載したガスクロマトグラフ装置を用いて測定した。この測定結果を、図２に示す。尚、前記ガスクロマトグラフ装置による一酸化炭素の検出下限は、１ｐｐｍである。
【００４２】
１４０℃のガスを前記配管に供給した一酸化炭素除去器では、運転開始直後から前記出口ガスの一酸化炭素濃度が上昇し始め、運転開始から１００時間後には、１０ｐｐｍを超えた。一方、８０℃のガスを前記配管に供給した一酸化炭素除去器の前記出口ガスの一酸化炭素濃度は、他方の一酸化炭素除去器と比べて運転開始時より低く、運転開始から約１００時間経過しても、前記出口ガス中の一酸化炭素濃度は２ｐｐｍ程度であった。
【００４３】
ここで、活性が低下した前記一酸化炭素除去触媒を、前記反応管より取り出し、前記ＥＰＭＡにより前記一酸化炭素除去触媒の表面における原子分布を調べたところ、その表面に鉄が存在することを明らかにした。一方、高い活性を維持していた一酸化炭素除去触媒の表面ではＥＰＭＡで表面の原子分布を調べても鉄は検出限界以下であった。
【００４４】
従って、前記一酸化炭素除去器に導入する前記反応ガスの温度を１００℃以下に保つことで、前記一酸化炭素除去器への鉄分の流入を抑制し、これによって、前記一酸化炭素除去触媒の活性が高く保たれていると考えられる。
【００４５】
（実施例２）
前記触媒層の前段に直径２〜４ｍｍの球状のγ−アルミナ（アルミナ球）を８ｃｃ充填した以外は、前記実施例１に係る一酸化炭素除去器と同じ構成の一酸化炭素除去器を３つ作製して、実施例１で用いた反応ガスと同組成のガスを１４０℃に加熱して、前記配管の夫々に供給した。これら３種の一酸化炭素除去器の筐体の温度を、夫々１００、１２０、１４０℃に保持し、前記触媒層の最高温度が１２０、１４０、１６０℃となるようにしたときの前記出口ガス中の一酸化炭素濃度（ドライベース）を図３に示す。
【００４６】
図３に示すように、前記一酸化炭素変成器の出口ガスを模した反応模擬ガスを、前記鉄カルボニルが生成し易い温度域である１４０℃に加熱して前記配管内を通過させた前記一酸化炭素除去器のうち、前記触媒層の最高温度が１２０℃付近にあるものは、連続運転開始から夫々数百時間後には一酸化炭素除去能が低下し始め、長期運転に適していないことが明らかになった。
【００４７】
一方、前記筐体の温度を１２０、１４０℃、即ち、前記触媒層の最高温度を１４０〜１６０℃付近とした一酸化炭素除去器では、１０００時間を越えても前記出口ガスの一酸化炭素濃度が４ｐｐｍ以下という、高い一酸化炭素除去能を保持し続けた。特に、前記筐体内の温度を１４０℃、即ち、前記触媒層の最高温度を１６０℃付近とした一酸化炭素除去器では、２５００時間を越えても前記出口ガスの一酸化炭素濃度が４ｐｐｍ以下という高い一酸化炭素除去能を保持し続けた。このような結果は、前記筐体内の温度を１６０℃、即ち、前記触媒層の最高温度を１８０℃付近とした一酸化炭素除去器でも同様に得られた。
【００４８】
ここで、前記反応管から夫々の触媒を取り出して前記ＥＰＭＡにより前記一酸化炭素除去触媒の表面における原子分布を調べたところ、３種類の触媒及び前段に充填したアルミナ球の一部の表面に鉄が存在することを明らかにした。このため、一酸化炭素除去器の入口温度が１４０℃という鉄化合物が流入しやすい温度であっても、前記触媒層の最高温度を変化させることで，前記一酸化炭素除去触媒の寿命を延長させることができることがわかった。
【００４９】
従って、前記一酸化炭素除去器の前記触媒層の最高温度を１３０〜１８０℃に保つことで、前記一酸化炭素除去触媒表面への鉄の付着状態を制御し、これによって、前記一酸化炭素除去触媒の活性が長期間に亘って保たれていると考えられる。
【００５０】
〔別実施形態〕
以下に別実施形態を説明する。
（イ）本発明に係る一酸化炭素除去器は、その上流に設けられる器材を、特に選ばない。従って、前記燃料改質システムで用いる脱硫触媒、改質触媒、一酸化炭素変成触媒は、その種類を限定する必要はなく、公知のものを使用することができる。また、前記改質方法としては、水蒸気改質に限らず、部分燃焼法を採用することもでき、これにより生じた一酸化炭素を除去するために使用することが出来る。
（ロ）本発明に係る一酸化炭素除去器及びこれを備えた燃料改質システムは、メタノール、ナフサなどの炭化水素を改質することにより得られた改質ガスの一酸化炭素除去にも使用することができる。
（ハ）本発明に係る一酸化炭素除去方法は、前記一酸化炭素除去触媒を空間速度（ＧＨＳＶ）が好ましくは５００〜５０，０００／時間、更に好ましくは１，００〜３０，０００／時間で使用することができる。
【図面の簡単な説明】
【図１】本発明を実施可能な燃料改質装置を表わす概念図
【図２】一酸化炭素除去器に導入されるガスの温度と一酸化炭素酸化除去活性との相関関係を表わすグラフ
【図３】一酸化炭素除去器の触媒層最高温度と一酸化炭素酸化除去活性との相関関係を表わすグラフ
【符号の説明】
５一酸化炭素変成器
６一酸化炭素除去器
７固体高分子型燃料電池
８温度調節手段[0001]
BACKGROUND OF THE INVENTION
  The present invention uses hydrogen as a main component, such as reformed gas obtained by reforming hydrocarbons such as natural gas, naphtha and kerosene, or alcohols such as methanol (steam reforming, partial combustion reforming, etc.). (H₂A carbon monoxide remover in which a catalyst layer composed of a carbon monoxide removal catalyst that removes carbon monoxide in a mixed gas containing carbon monoxide (CO) as a contaminant is formed in the casing, And an introduction step of introducing a reaction gas obtained by adding an oxidant to the mixed gas, and a removal step of removing the carbon monoxide by reacting the oxidant with the mixed gas on the carbon monoxide removal catalyst. The present invention relates to a method for removing carbon oxide, a method for operating a fuel reforming system using the same, and a method for preventing iron poisoning.
[0002]
[Prior art]
  Conventionally, in a fuel reforming system for producing reformed gas containing hydrogen and carbon monoxide (gas containing 40% by volume or more of hydrogen (dry base)) using fossil fuel such as natural gas as raw fuel, The raw fuel is desulfurized and steam reformed (in some cases, partial combustion reforming or a combination of steam reforming and partial combustion reforming) with a continuous desulfurizer and fuel reformer, and hydrogen as the main component. Carbon monoxide, carbon dioxide (CO₂), Moisture (H₂A reformed gas containing O) was obtained. Further, the fuel reforming system using alcohols such as methanol as a raw fuel includes a fuel reforming device having a methanol reforming catalyst incorporated therein, and is mainly composed of hydrogen from methanol, carbon monoxide (CO), carbon dioxide. A reformed gas containing carbon, moisture and the like was obtained.
[0003]
  Here, in a fuel reforming system that produces reformed gas for use in a phosphoric acid fuel cell, it is known that the electrode catalyst of the fuel cell is poisoned by the presence of carbon monoxide. Is introduced into a carbon monoxide converter, the carbon monoxide is converted into carbon dioxide by a carbon monoxide conversion reaction, and the concentration of carbon monoxide in the gas is equal to or lower than a predetermined value (for example, A reformed gas of 0.5%) was obtained.
  However, in a fuel reforming system that produces reformed gas for use in a polymer electrolyte fuel cell, the polymer electrolyte fuel cell operates at a low temperature of about 80 ° C. Since the electrode catalyst is poisoned, it is necessary to further reduce the carbon monoxide, and carbon monoxide containing a carbon monoxide removal catalyst for removing carbon monoxide downstream of the carbon monoxide converter. An oxidizer such as air is added to the reformed gas treated by the carbon monoxide converter by introducing a remover, and introduced into the reformed gas. In the presence of the carbon monoxide removal catalyst, carbon monoxide Was oxidized to carbon dioxide, and a reformed gas having a carbon monoxide concentration reduced to a predetermined concentration or lower (for example, 100 ppm or lower) was obtained. Further, in order to ensure higher performance and durability of the polymer electrolyte fuel cell, a reformed gas having a carbon monoxide concentration reduced to 10 ppm or less has been obtained.
[0004]
  The carbon monoxide remover is a catalyst composed of a carbon monoxide removal catalyst in which ruthenium (Ru), rhodium (Rh), platinum (Pt), palladium (Pd) or the like is supported on a carrier such as alumina in a casing. And a gas (reaction gas) in which an oxidizing agent such as air is added to the reformed gas is introduced into the catalyst layer from a gas inlet and brought into contact with the carbon monoxide removal catalyst. Thus, carbon monoxide in the reformed gas was oxidized and removed to carbon dioxide. And the said reaction gas which the carbon monoxide density | concentration decreased through the said catalyst layer was discharged | emitted from the gas outlet provided in the said housing | casing. In addition, the carbon monoxide removal catalyst has a heater, a cooler, etc., since the reaction for oxidizing carbon monoxide easily proceeds when the temperature of the catalyst layer is about 80 to 200 ° C. Is attached to the casing, and the temperature of the catalyst layer is maintained in the temperature range.
[0005]
  Conventionally, stainless steel, which is an iron-containing material, has been mainly used as a member constituting the fuel reformer in consideration of various circumstances such as weather resistance, heat resistance, strength, workability, and cost.
[0006]
[Problems to be solved by the invention]
  However, even if the carbon monoxide remover is operated in a temperature range suitable for the action of the carbon monoxide removal catalyst, depending on use conditions, the carbon monoxide remover is gradually removed from the carbon monoxide remover. The concentration of carbon monoxide in the discharged reaction gas increases to reach several tens of ppm, and the problem that the concentration of carbon monoxide becomes too high to serve as the fuel for the polymer electrolyte fuel cell occurs. The present inventors have found out.
  The cause of the performance deterioration of the carbon monoxide removal catalyst has not been clarified so far, and is a new finding of the present inventors.
[0007]
  Accordingly, an object of the present invention is to provide a method for stably removing carbon monoxide over a long period of time when operating the carbon monoxide remover and the fuel reforming system in view of the above drawbacks, and the fuel modification. It is to provide a method for operating a quality system and a method for preventing iron poisoning.
[0008]
[Means for Solving the Problems]
  In order to achieve this object, the first characteristic means of the carbon monoxide removal method of the present invention is as described in claim 1,Obtained by reforming raw fuel to obtain fuel gas for use in polymer electrolyte fuel cellsRemove carbon monoxide in gas mixture containing hydrogen and carbon monoxideContains ruthenium, platinum, rhodium, or palladiumAn introduction step of introducing a reaction gas obtained by adding an oxidizing agent to the mixed gas into a carbon monoxide remover in which a catalyst layer composed of a carbon monoxide removal catalyst is formed in the housing; and on the carbon monoxide removal catalyst And removing the carbon monoxide by reacting the oxidant with the mixed gas to remove the carbon monoxide in the introduction step. A pipe connected to the inlet of the carbon monoxide remover is provided with a heat exchanger and a drain trap for cooling the mixed gas or the reaction gas flowing through the pipe, and the pipe By condensing water vapor in the reaction gas flowing through the reaction gas, the dew point of the reaction gas introduced into the inlet of the carbon monoxide remover is 40 ° C. or less at the process pressure.
  Further, in the first feature means, as described in claim 2, it is preferable that the reaction gas at 80 ° C. or less is introduced into the carbon monoxide remover in the introduction step.
[0009]
  Further, the second characteristic means of the carbon monoxide removal method of the present invention for achieving this object is as described in claim 3,Obtained by reforming raw fuel to obtain fuel gas for use in polymer electrolyte fuel cellsRemove carbon monoxide in gas mixture containing hydrogen and carbon monoxideContains ruthenium, platinum, rhodium, or palladiumAn introduction step of introducing a reaction gas obtained by adding an oxidizing agent to the mixed gas into a carbon monoxide remover in which a catalyst layer composed of a carbon monoxide removal catalyst is formed in the housing; and on the carbon monoxide removal catalyst And a removal step of removing carbon monoxide by reacting the oxidant with the mixed gas to maintain the maximum temperature of the catalyst layer at 130 ° C. or more and 180 ° C. or less in the removal step. In addition, a pipe connected to the inlet of the carbon monoxide remover is provided with a heat exchanger and a drain trap for cooling the mixed gas or the reaction gas flowing through the pipe, and flows through the pipe. By condensing water vapor in the reaction gas, the dew point of the reaction gas introduced into the inlet of the carbon monoxide remover is 40 ° C. or less at the process pressure.
[0010]
  Furthermore, in the second characteristic means, as described in claim 4, it is preferable that the maximum temperature of the catalyst layer is 150 ° C. or higher and 180 ° C. or lower.
[0011]
  The third feature means of the carbon monoxide removal method of the present invention for achieving this object is as described in claim 5,Obtained by reforming raw fuel to obtain fuel gas for use in polymer electrolyte fuel cellsRemove carbon monoxide in gas mixture containing hydrogen and carbon monoxideContains ruthenium, platinum, rhodium, or palladiumAn introduction step of introducing a reaction gas obtained by adding an oxidizing agent to the mixed gas into a carbon monoxide remover in which a catalyst layer composed of a carbon monoxide removal catalyst is formed in the housing; and on the carbon monoxide removal catalyst And removing the carbon monoxide by reacting the oxidant with the mixed gas in the step of removing carbon monoxide from the reaction gas at 100 ° C. or less in the introduction step. In the removal step, in the removal step, in order to keep the maximum temperature of the catalyst layer at 130 ° C. or more and 180 ° C. or less, the mixing that flows through the piping to the piping connected to the inlet of the carbon monoxide removing device. A heat exchanger for cooling the gas or the reaction gas and a drain trap are provided to condense the water vapor in the reaction gas flowing through the pipe, thereby introducing the gas monoxide remover into the inlet. The dew point of the reaction gas, there in the process pressure points to 40 ° C. or less.
[0012]
  Furthermore, in the first to third characteristic means, as described in claim 6, the mixed gas is preferably a reformed gas obtained by reforming hydrocarbons or alcohols,
  As described in claim 7, it is preferable that the carbon monoxide removal catalyst is a catalyst containing ruthenium,
  As described in claim 8, before performing the introducing step, it is preferable to pre-treat the catalyst layer composed of the carbon monoxide removal catalyst in a gas stream in which hydrogen and nitrogen are mixed. BetterYes.
[0013]
  Moreover, the first characteristic means of the operation method of the fuel reforming system of the present invention for achieving this object is as follows.9A reformer containing a reforming catalyst for reforming the raw fuel in a gas containing raw fuel and water vapor into a mixed gas containing hydrogen and carbon monoxide, and in the mixed gas A carbon monoxide converter containing a carbon monoxide conversion catalyst that converts carbon monoxide, and carbon monoxide in the reaction gas obtained by adding an oxidizing agent to the mixed gas discharged from the carbon monoxide converter DoContains ruthenium, platinum, rhodium, or palladiumThe carbon monoxide remover containing the carbon monoxide removal catalyst is connected by a pipe so that gas can flow in the order described, and the mixture that flows in the pipe connecting the carbon monoxide converter and the carbon monoxide remover A heat exchanger in which a heat transfer medium circulates so as to exchange heat with the gas or the reaction gas is provided.Used for polymer electrolyte fuel cell systemIn the operation method of the fuel reforming system, the portion where the heat exchanger is provided by heat exchange between the mixed gas or the reaction gas flowing in the pipe and the heat transfer medium flowing in the heat exchanger In order to introduce the reaction gas flowing in the downstream pipe into the carbon monoxide remover while maintaining the reaction gas at 100 ° C. or less, the pipe is connected to the inlet of the carbon monoxide remover. A heat exchanger and a drain trap for cooling the mixed gas or the reaction gas that is circulated are provided, and water vapor in the reaction gas that circulates through the piping is condensed to be introduced into the inlet of the carbon monoxide remover. The reaction gas has a dew point of 40 ° C. or less at the process pressure.
  Where the claim10Before introducing the reaction gas into the carbon monoxide remover, the catalyst layer composed of the carbon monoxide removal catalyst is pretreated in a gas stream in which hydrogen and nitrogen are mixed. Preferably to handleYes.
  Furthermore, the first characteristic means of the iron poisoning prevention method of the present invention for achieving this object is as follows:11As described inObtained by reforming raw fuel to obtain fuel gas for use in polymer electrolyte fuel cellsRemove carbon monoxide in gas mixture containing hydrogen and carbon monoxideContains ruthenium, platinum, rhodium, or palladiumAn introduction step of introducing a reaction gas obtained by adding an oxidizing agent to the mixed gas into a carbon monoxide remover in which a catalyst layer composed of a carbon monoxide removal catalyst is formed in the housing; and on the carbon monoxide removal catalyst In performing the carbon monoxide removal method including the removal step of removing the carbon monoxide by reacting the oxidizing agent with the mixed gas in the step, the reaction gas at 100 ° C. or less is added to the one gas in the introduction step. Introduced into carbon oxide removerIn addition, a pipe connected to the inlet of the carbon monoxide remover is provided with a heat exchanger and a drain trap for cooling the mixed gas or the reaction gas flowing through the pipe, and flows through the pipe. By condensing water vapor in the reaction gasThe dew point of the reaction gas introduced into the inlet of the carbon monoxide remover is set to 40 ° C. or less at the process pressure to prevent iron poisoning of the catalyst layer composed of the carbon monoxide removal catalyst. .
  Where the claim12It is preferable to pre-treat the catalyst layer composed of the carbon monoxide removal catalyst in a gas stream mixed with hydrogen and nitrogen before performing the introduction step.Yes.
  These functions and effects are as follows.
[0014]
  The carbon monoxide removal method proposed in the present invention and the operation method of the fuel reforming system using the carbon monoxide removal method are such that the carbon monoxide removal catalyst accommodated in the carbon monoxide remover is poisoned by iron or an iron compound. It is based on new knowledge that it is poisoned.
[0015]
  The inventors of the present invention have made extensive studies to elucidate the reason why the carbon monoxide removal rate by the carbon monoxide remover gradually decreases (deteriorates). As a result, the state of the surface of the deteriorated catalyst is determined by an electron probe. Analysis by microanalysis (EPMA) confirmed the presence of iron atoms in some form on the surface. The inventors have also confirmed that there are almost no iron atoms on the surface of the catalyst that has not deteriorated, and that the deterioration of the catalyst includes the presence of the iron or iron compound, or both the iron and iron compound. Thought deeply involved.
[0016]
  Therefore, as a result of further study on the origin of iron or iron compounds present in the deteriorated catalyst, it is included in the components (for example, stainless steel reactors and piping, heat exchangers, etc.) constituting the fuel reformer. It was found that the iron or iron compound to be mixed into the reformed gas adheres to the catalyst built in the carbon monoxide remover, blocks the active site, and the activity may decrease.
  Until now, when using a carbon monoxide remover under normal conditions, it was not thought that the carbon monoxide removal catalyst would be subjected to iron poisoning, but iron and iron compounds were mixed in the reformed gas, Considering the reason why the carbon monoxide removal catalyst may be poisoned with iron, one of the possibilities is as follows.
  First, a reformed gas that has passed through the carbon monoxide transformer and has reduced the concentration of carbon monoxide (for example, typical compositions include 65% hydrogen, 19% carbon dioxide, 0.5% carbon monoxide, steam, 15.5%) is discharged from the carbon monoxide converter at the same temperature as the outlet temperature of the carbon monoxide converter (about 200 ° C.). Since the operating temperature of the remover is lower than this (about 80 to 200 ° C.), the reactor for connecting the carbon monoxide converter and the carbon monoxide remover before introduction into the carbon monoxide remover. Radiates heat in the pipes, heat exchangers, etc., and the temperature drops. At this time, the reformed gas has a high hydrogen concentration, and since iron and nickel are present in the stainless steel material and the like constituting the pipe and heat exchanger, the iron and carbon monoxide are combined. Iron carbonyl (Fe (CO)_Five) Is easy to release. Therefore, iron is considered to be poisoned by moving together with the reformed gas, flowing into the carbon monoxide remover, and adhering to the carbon monoxide removal catalyst.
  Further, an oxidant added to remove carbon monoxide between the carbon monoxide converter and the carbon monoxide remover, or between the carbon monoxide transformer and the carbon monoxide remover. Condensed water may also be involved in the iron poisoning process.
[0017]
  Here, even if the casing is made of stainless steel, the carbon monoxide concentration around the catalyst portion is lowered by a catalytic reaction, so that the generation of the iron carbonyl is caused by the top of the carbon monoxide remover. Compared with inflow from the basin, it is considered to be less.
[0018]
  Thus, as a result of intensive studies on a method for removing carbon monoxide from the mixed gas using the carbon monoxide catalyst, the inventors have found a method for removing carbon monoxide that is difficult to poison the carbon oxide removal catalyst by iron. As a result, the present invention has been completed.
[0019]
  Here, as described in claim 1,Obtained by reforming raw fuel to obtain fuel gas for use in polymer electrolyte fuel cellsRemove carbon monoxide in gas mixture containing hydrogen and carbon monoxideContains ruthenium, platinum, rhodium, or palladiumAn introduction step of introducing a reaction gas obtained by adding an oxidizing agent to the mixed gas into a carbon monoxide remover in which a catalyst layer composed of a carbon monoxide removal catalyst is formed in the housing; and on the carbon monoxide removal catalyst And removing the carbon monoxide by reacting the oxidant with the mixed gas to remove the carbon monoxide in the introduction step. A pipe connected to the inlet of the carbon monoxide remover is provided with a heat exchanger and a drain trap for cooling the mixed gas or the reaction gas flowing through the pipe, and the pipe If the dew point of the reaction gas introduced into the inlet of the carbon monoxide remover is 40 ° C. or less at the process pressure by condensing water vapor in the reaction gas flowing through Considered the generation of iron carbonyl can be suppressed less likely to occur the bond between iron and carbon monoxide that constitute. Further, even if the iron carbonyl is generated, the boiling point thereof is 103 ° C., and therefore the vaporization is suppressed by keeping the temperature of the reaction gas at 100 ° C. or less, and the carbon monoxide remover located downstream of the pipe It is thought that the inflow to the inside can be suppressed.
  If the reaction gas is cooled to 0 ° C. or higher, a simple cooling means can be used using a medium such as air or water.
[0020]
[0021]
  Further, when a large amount of water is contained in the reaction gas introduced into the carbon monoxide remover, the temperature of the reaction gas introduced into the carbon monoxide remover inlet is reduced to 100 ° C. or less. Moisture is condensed and condensed in the pipe and the carbon monoxide remover, whereby the cross-sectional area and volume of the reaction gas passage in the pipe and the carbon monoxide remover change randomly, The flow rate of the reaction gas supplied to the carbon monoxide remover fluctuates randomly, or the carbon monoxide removal catalyst housed in the carbon monoxide remover gets wet with the condensed water and the activity decreases. There is a fear. Accordingly, the temperature of the reaction gas introduced into the carbon monoxide remover inlet is lowered, and at the same time, the water vapor contained in the reaction gas is reduced so that the dew point in the reaction gas is 40 ° C. or less at the process pressure. If it is condensed and separated before being introduced into the carbon oxide remover, the carbon monoxide removal catalyst becomes difficult to wet, so that the activity is difficult to decrease, and the reaction gas in the pipe and the carbon monoxide remover The fluctuation range of the flow rate can be kept very small. Also, when the S / C (molar ratio of steam and carbon contained in the raw fuel) fluctuates when the load fluctuates or the like, the amount of water vapor in the reaction gas increases. By adjusting the amount of water vapor of the reaction gas introduced into the pipe or the carbon monoxide remover, carbon monoxide can be stably removed.
[0022]
  When the dew point of the reaction gas is 40 ° C. or less at the process pressure, it is possible to sufficiently suppress the dew condensation of moisture in the reaction gas, and the carbon monoxide removal catalyst can reduce the carbon monoxide in the reaction gas. The temperature range (especially the temperature range at a low temperature) at which the removal catalyst can be removed to 10 ppm or less is widened, and the carbon monoxide removal reaction is easily started even if the low-temperature reaction gas is introduced into the carbon monoxide remover.
  In the first feature means, as described in claim 2, in the introduction step, when the temperature of the reaction gas introduced into the carbon monoxide remover is 80 ° C. or less, the iron carbonyl It is preferable because the generation rate can be suppressed sufficiently low and the maximum temperature of the catalyst layer can be easily controlled.
[0023]
  On the other hand, the iron carbonyl is known to decompose or polymerize at high temperatures. Therefore, as described in claim 5,Obtained by reforming raw fuel to obtain fuel gas for use in polymer electrolyte fuel cellsRemove carbon monoxide in gas mixture containing hydrogen and carbon monoxideContains ruthenium, platinum, rhodium, or palladiumAn introduction step of introducing a reaction gas obtained by adding an oxidizing agent to the mixed gas into a carbon monoxide remover in which a catalyst layer composed of a carbon monoxide removal catalyst is formed in the housing; and on the carbon monoxide removal catalyst In the carbon monoxide removal method having a removal step of removing carbon monoxide by reacting the oxidant with the mixed gas in the above step, by keeping the maximum temperature of the catalyst layer in the removal step at 130 ° C. or higher, Even when iron carbonyl flows into the carbon monoxide remover, the state of attachment to the carbon monoxide removal catalyst can be controlled by decomposition, or the attachment point can be substantially controlled by polymerization of the iron carbonyl. Can be reduced.
  If the temperature of the catalyst layer becomes too high, the methanation reaction of carbon dioxide tends to occur, and not only the hydrogen contained in the mixed gas is consumed and the yield is reduced, but also the control of the temperature is difficult due to the reaction heat. Therefore, it is preferable to keep the maximum temperature of the catalyst layer at 180 ° C. or lower.
  Also in this carbon monoxide removal method, a pipe connected to the inlet of the carbon monoxide remover is provided with a heat exchanger for cooling the mixed gas or the reaction gas flowing through the pipe and a drain trap. By providing and condensing water vapor in the reaction gas flowing through the pipe, the dew point of the reaction gas introduced into the inlet of the carbon monoxide remover is set to 40 ° C. or less at the process pressure.
[0024]
  Here, as described in claim 4, by setting the maximum temperature of the catalyst layer to 150 ° C. or more and 180 ° C. or less, it is possible to further extend the life of the carbon monoxide removal catalyst ( See Examples).
[0025]
  Furthermore, as described in claim 5,Obtained by reforming raw fuel to obtain fuel gas for use in polymer electrolyte fuel cellsRemove carbon monoxide in gas mixture containing hydrogen and carbon monoxideContains ruthenium, platinum, rhodium, or palladiumAn introduction step of introducing a reaction gas obtained by adding an oxidizing agent to the mixed gas into a carbon monoxide remover in which a catalyst layer composed of a carbon monoxide removal catalyst is formed in the housing; and on the carbon monoxide removal catalyst And removing the carbon monoxide by reacting the oxidant with the mixed gas in the carbon monoxide removing method, wherein the temperature of the reaction gas in the introducing step is 100 ° C. or less. The carbon monoxide removal catalyst by suppressing the inflow of the iron carbonyl to the catalyst layer and maintaining the maximum temperature of the catalyst layer at 130 ° C. or higher and 180 ° C. or lower in the removing step. By the synergistic effect of suppressing the adhesion of the iron carbonyl to the carbon, the poisoning of the carbon monoxide removal catalyst is further suppressed, and the carbon monoxide in the reaction gas is very high in rate. It can be removed.
  In this carbon monoxide removal method, a heat exchanger and a drain trap for cooling the mixed gas or the reaction gas flowing through the pipe are connected to the pipe connected to the inlet of the carbon monoxide remover. By providing and condensing water vapor in the reaction gas flowing through the pipe, the dew point of the reaction gas introduced into the inlet of the carbon monoxide remover is set to 40 ° C. or less at the process pressure.
[0026]
  Furthermore, as described in claim 6, when the mixed gas is a reformed gas obtained by reforming hydrocarbons or alcohols, monoxide is oxidized by the method described in claims 1-5. It is preferable to remove carbon because carbon monoxide can be removed over a long period of time.
[0027]
  Furthermore, the present inventors have found that when the carbon monoxide removal catalyst is a catalyst containing ruthenium, it has been found that there is a great influence such as a decrease in activity and a shortened life due to the iron poisoning. As described above, this method is effective when the carbon monoxide removal catalyst is a catalyst containing ruthenium.
[0028]
  Here, a reformer containing a reforming catalyst that reforms the raw fuel in the gas containing raw fuel and water vapor into a mixed gas containing hydrogen and carbon monoxide, and carbon monoxide in the mixed gas. A carbon monoxide converter containing a carbon monoxide conversion catalyst to be converted, and carbon monoxide in the reaction gas obtained by adding an oxidant to the mixed gas discharged from the carbon monoxide converter is removed.Contains ruthenium, platinum, rhodium, or palladiumThe carbon monoxide remover containing the carbon monoxide removal catalyst is connected by a pipe so that gas can flow in the order described, and the mixture that flows in the pipe connecting the carbon monoxide converter and the carbon monoxide remover A heat exchanger in which a heat transfer medium circulates so as to exchange heat with the gas or the reaction gas is provided.Used for polymer electrolyte fuel cell systemClaims when operating a fuel reforming system9As described in the above, by heat exchange between the mixed gas or the reaction gas flowing through the pipe and the heat transfer medium flowing through the heat exchanger, the portion where the heat exchanger is provided By maintaining the reaction gas flowing in the downstream pipe at 100 ° C. or less, the iron carbonyl can be prevented from being generated in the pipe. Accordingly, by introducing the reaction gas whose temperature has been adjusted in this way into the carbon monoxide remover, the inflow of the iron carbonyl into the catalyst layer can be suppressed, and the iron coating of the carbon monoxide removal catalyst can be suppressed. Poisoning can be reduced and the carbon monoxide removal activity of the carbon monoxide removal catalyst can be kept high over a long period of time.
  In this fuel reforming system operation method, a heat exchanger and a drain trap for cooling the mixed gas or the reaction gas flowing in the pipe are connected to a pipe connected to the inlet of the carbon monoxide remover. And condensing water vapor in the reaction gas flowing through the pipe, thereby setting the dew point of the reaction gas introduced into the inlet of the carbon monoxide remover to 40 ° C. or less at the process pressure.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
  Embodiments of the present invention will be described below with reference to the drawings.
  FIG. 1 shows a fuel reforming system capable of implementing the carbon monoxide removing method according to the present invention. This fuel reforming system uses a natural gas (city gas) as a raw fuel to produce a reformed gas containing hydrogen as a main component for use in a polymer electrolyte fuel cell, and supplies the raw fuel. A fuel supply system 1, a desulfurizer 2 containing a desulfurization catalyst, a reformer 4 containing a reforming catalyst, a carbon monoxide converter 5 containing a carbon monoxide conversion catalyst, and a one containing the carbon monoxide removal catalyst A carbon oxide remover 6 is connected through a pipe. The reformed gas (fuel gas) reformed by passing through these is supplied to the polymer electrolyte fuel cell 7.
  When the natural gas stored in the raw fuel supply system 1 passes through the desulfurizer 2, it comes into contact with the desulfurization catalyst to remove sulfur. And after being mixed with the steam supplied from the steam generator 3, it is transported to the reformer 4, where it comes into contact with the reforming catalyst, and methane in the natural gas is mainly hydrogen, And it is reformed to carbon monoxide as a by-product. Although the reformed gas thus obtained is rich in hydrogen, it contains tens of percent of carbon monoxide as a by-product, and therefore cannot be directly supplied to the polymer electrolyte fuel cell 7. Therefore, in the carbon monoxide converter 5, the carbon monoxide is converted into carbon dioxide by contacting with a carbon monoxide conversion catalyst such as a copper-zinc catalyst, and the carbon monoxide is reduced to 0.5 to 1%. Reduce concentration.
[0030]
  Further, the reformed gas whose carbon monoxide concentration is reduced to 0.5 to 1% is mixed with air (oxygen acts as an oxidant) supplied from the oxidant supplier 9, and then as a reaction gas. The carbon monoxide remover 6 is introduced through the pipe.
  The carbon monoxide remover 6 is configured such that a catalyst layer composed of a carbon monoxide removal catalyst is formed in the casing, and the reaction gas passes through the catalyst layer. As the carbon monoxide removal catalyst, for example, a catalyst in which a noble metal such as ruthenium, platinum, rhodium or palladium is supported on a support such as an alumina sphere is used.
  When the reformed gas whose carbon monoxide concentration is reduced to 0.5 to 1% flows into the casing of the carbon monoxide remover 6 together with the oxidant, the reformed gas comes into contact with the catalyst layer formed here. The carbon monoxide removal catalyst is accommodated in the catalyst layer, and carbon monoxide mainly reacts with oxygen by the catalytic reaction of the carbon monoxide removal catalyst to be oxidized into carbon dioxide. In this way, the carbon monoxide concentration in the reformed gas is removed and finally supplied to the polymer electrolyte fuel cell 7.
[0031]
  Since the carbon monoxide remover 6 operates so that the catalyst layer has a temperature of about 80 to 180 ° C., the temperature adjusting means 8 for adjusting the temperature of the casing is provided in this range. The temperature adjusting means 8 includes a heater or a heat source for heating the casing and a cooler for cooling the casing.
[0032]
  Then, iron-containing compounds such as iron carbonyl and metallic iron that have flowed into the catalyst layer are prevented from adhering to the surface of the carbon monoxide removal catalyst and reducing the activity, and carbon monoxide is methanated. In order to suppress the reaction, the temperature is adjusted by the temperature adjusting means 8 so that the maximum temperature of the catalyst layer is 130 to 180 ° C, preferably 150 to 180 ° C.
[0033]
  In addition, a heat exchanger 81 is provided along a part or all of the outer wall surface of a pipe connecting the carbon monoxide transformer 5 and the carbon monoxide remover 6, and the heat exchanger includes the inside of the heat exchanger. A heat transfer medium (for example, air or water) circulates through the wall surface of the pipe so as to be able to exchange heat with the mixed gas or the reaction gas. The position where the heat exchanger 81 is provided may be a stage before the oxidizing agent is added to the mixed gas as shown in FIG. 1, or the oxidizing agent is added to the mixed gas. The site | part currently distribute | circulating as the said reactive gas may be sufficient. Since the heat exchange occurs between the heat transfer medium flowing in the heat exchanger 81 and the mixed gas or the reactive gas flowing in the pipe, the mixed gas or the reactive gas is cooled. By measuring the flow rate, temperature, etc. of the mixed gas or the reaction gas flowing into the piping in advance and appropriately adjusting the flow rate of the heat transfer medium, or by circulating the heat transfer medium at a predetermined flow rate, etc. The temperature of the gas flowing in the pipe on the downstream side of the portion where the heat exchanger 81 is provided is adjusted to 100 ° C. or lower, preferably 80 ° C. or lower in consideration of load fluctuations. The temperature (lower limit) of the reaction gas is determined based on factors such as the installation environment of the carbon monoxide remover 6 and the temperature of the heat medium to be used.
[0034]
  As described above, at least one of either adjusting the temperature of the catalyst layer to 130 ° C. or higher and 180 ° C. or lower, or adjusting the temperature of the pipe contacting the upstream of the carbon monoxide remover to 100 ° C. or lower. By implementing it, it is possible to significantly suppress iron poisoning of the carbon monoxide removal catalyst and to extend the life and improve the activity of the carbon monoxide removal catalyst. As a result, the life of the carbon monoxide removal catalyst can be extended and the activity can be improved.
[0035]
  Further, a drain trap is provided in the pipe to condense water vapor in the reaction gas introduced into the carbon monoxide remover 6, and the dew point of the reaction gas is 60 ° C. or less, preferably 40 ° C. at the process pressure. If it makes below, it can prevent dew condensation in the said piping and the said carbon monoxide remover.
[0036]
【Example】
  Hereinafter, the test for demonstrating the effect of the carbon monoxide removal method which concerns on this invention is demonstrated.
[0037]
  A spherical γ-alumina carrier having a diameter of 2 to 4 mm was immersed in an aqueous ruthenium trichloride solution, and ruthenium was supported by an impregnation method. After drying this, it was immersed in an aqueous sodium carbonate solution to immobilize the ruthenium on the carrier, washed with water and dried to obtain a precursor. This precursor was immersed in a hydrazine solution to reduce ruthenium on the surface of the precursor, washed again with water, and dried at 105 ° C. to obtain a Ru / alumina catalyst. The ruthenium concentration in the obtained Ru / alumina catalyst was 0.98% by weight, and the average pore diameter was 7.4 nm.
  In Examples 1 and 2 below, the reaction tube was filled with the obtained Ru / alumina catalyst, and then at 220 ° C. in a gas stream in which hydrogen containing 5% by volume of hydrogen and nitrogen were mixed. Hold for 5 hours (pretreatment). This pretreatment is a treatment for increasing the initial activity of the Ru / alumina catalyst at a low temperature.
[0038]
Example 1
  8 cc of the Ru / alumina catalyst (carbon monoxide removal catalyst) is filled into a 21.2 mm stainless steel reaction tube (housing) having a thermocouple insertion sheath tube having an outer diameter of 6 mm inside to form a catalyst layer. Then, the above pretreatment was performed to produce two microreactors (carbon monoxide removers). The reaction simulation gas introduced into the casing from the inlet of the carbon monoxide remover passes through the catalyst layer and is discharged from the outlet to the outside of the casing. The carbon monoxide remover is configured such that the temperature of the reaction tube can be controlled by heating the reaction tube from the outside with a heater.
[0039]
  A stainless steel pipe is connected to the upstream side of the carbon monoxide remover, and the reaction simulation gas is supplied from the pipe to the carbon monoxide remover.
[0040]
  As the reaction simulation gas, the oxygen / carbon monoxide molar ratio ([O₂] / [CO]) having a composition corresponding to a mixture of air (carbon monoxide 0.5%, methane 0.5%, carbon dioxide 20.9%, oxygen 0 .75%, nitrogen 3.0%, hydrogen balance mixed gas 1000 Nml / min, a reaction simulated gas in which water vapor is added so that the water vapor concentration in the wet gas is 5% (corresponding to a dew point of 33 ° C.). . The space velocity (GHSV) at this time is 7,500 / hour (dry base).
[0041]
  The reaction simulation gas heated to 80 ° C. and the reaction simulation gas heated to 140 ° C. are supplied to each of the pipes, and the inside of the casing of the carbon monoxide remover connected to each of the pipes Carbon monoxide was removed by adjusting the maximum temperature to 90 ° C. The maximum temperature of the catalyst layer was 110 ° C. At this time, the reaction simulation gas (outlet gas) is sampled over time at the outlet (outlet) of the casing, and the carbon monoxide concentration (dry base) in the outlet gas is measured with a thermal conductivity detector (TCD). ) And a flame ionization detector (FID). The measurement results are shown in FIG. In addition, the detection lower limit of the carbon monoxide by the said gas chromatograph apparatus is 1 ppm.
[0042]
  In the carbon monoxide remover in which a 140 ° C. gas was supplied to the pipe, the carbon monoxide concentration of the outlet gas started to increase immediately after the start of operation, and exceeded 10 ppm after 100 hours from the start of operation. On the other hand, the concentration of carbon monoxide in the outlet gas of the carbon monoxide remover supplied with 80 ° C. gas to the pipe is lower than that at the start of operation compared to the other carbon monoxide remover, and is about 100 hours from the start of operation. Even after the lapse of time, the carbon monoxide concentration in the outlet gas was about 2 ppm.
[0043]
  Here, when the carbon monoxide removal catalyst having reduced activity was taken out from the reaction tube and the atomic distribution on the surface of the carbon monoxide removal catalyst was examined by the EPMA, it was found that iron was present on the surface. I made it. On the other hand, on the surface of the carbon monoxide removal catalyst that maintained high activity, even if the atomic distribution on the surface was examined with EPMA, iron was below the detection limit.
[0044]
  Therefore, by keeping the temperature of the reaction gas introduced into the carbon monoxide remover at 100 ° C. or lower, the inflow of iron into the carbon monoxide remover is suppressed, and thereby the carbon monoxide removal catalyst It is thought that the activity is kept high.
[0045]
(Example 2)
  Three carbon monoxide removers having the same configuration as the carbon monoxide remover according to Example 1 except that 8 cc of spherical γ-alumina (alumina spheres) having a diameter of 2 to 4 mm is filled in the previous stage of the catalyst layer. The gas having the same composition as the reaction gas used in Example 1 was heated to 140 ° C. and supplied to each of the pipes. The outlet gas when the casings of these three types of carbon monoxide removers are held at 100, 120, and 140 ° C., respectively, and the maximum temperature of the catalyst layer is 120, 140, and 160 ° C. The concentration of carbon monoxide (dry base) is shown in FIG.
[0046]
  As shown in FIG. 3, the reaction simulated gas imitating the outlet gas of the carbon monoxide converter is heated to 140 ° C., which is a temperature range in which the iron carbonyl is easily generated, and passed through the pipe. Among the carbon oxide removers, those having a maximum temperature of the catalyst layer near 120 ° C. may not be suitable for long-term operation because the carbon monoxide removal ability starts to decrease after several hundred hours from the start of continuous operation. It was revealed.
[0047]
  On the other hand, in the carbon monoxide remover in which the temperature of the casing is 120 to 140 ° C., that is, the maximum temperature of the catalyst layer is around 140 to 160 ° C., the concentration of carbon monoxide in the outlet gas is over 1000 hours. The carbon monoxide removal ability of 4 ppm or less continued to be maintained. In particular, in the carbon monoxide remover in which the temperature in the casing is 140 ° C., that is, the maximum temperature of the catalyst layer is around 160 ° C., the carbon monoxide concentration of the outlet gas is 4 ppm or less even after 2500 hours. High carbon monoxide removal ability continued to be maintained. Such a result was also obtained with a carbon monoxide remover in which the temperature in the casing was 160 ° C., that is, the maximum temperature of the catalyst layer was around 180 ° C.
[0048]
  Here, each catalyst was taken out from the reaction tube, and the atomic distribution on the surface of the carbon monoxide removal catalyst was examined by the EPMA. As a result, three types of catalysts and iron on the surface of a part of the alumina sphere packed in the previous stage were obtained. Clarified that there exists. For this reason, even if the inlet temperature of the carbon monoxide remover is 140 ° C. at which the iron compound easily flows, the lifetime of the carbon monoxide removal catalyst is extended by changing the maximum temperature of the catalyst layer. I found out that I could do it.
[0049]
  Therefore, by maintaining the maximum temperature of the catalyst layer of the carbon monoxide remover at 130 to 180 ° C., the iron adhesion state on the carbon monoxide removal catalyst surface is controlled, thereby removing the carbon monoxide. It is considered that the activity of the catalyst is maintained for a long period.
[0050]
    [Another embodiment]
  Another embodiment will be described below.
(A) The carbon monoxide remover according to the present invention is not particularly selected from equipment provided upstream thereof. Accordingly, the desulfurization catalyst, reforming catalyst, and carbon monoxide conversion catalyst used in the fuel reforming system need not be limited in their types, and known ones can be used. Further, the reforming method is not limited to steam reforming, and a partial combustion method can also be adopted, and it can be used to remove carbon monoxide generated thereby.
(B) The carbon monoxide remover according to the present invention and the fuel reforming system equipped with the carbon monoxide remover are also used for removing carbon monoxide from the reformed gas obtained by reforming hydrocarbons such as methanol and naphtha. can do.
(C) In the carbon monoxide removal method according to the present invention, the space velocity (GHSV) of the carbon monoxide removal catalyst is preferably 500 to 50,000 / hour, more preferably 1,000 to 30,000 / hour. Can be used.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram showing a fuel reformer that can implement the present invention.
FIG. 2 is a graph showing the correlation between the temperature of the gas introduced into the carbon monoxide remover and the carbon monoxide removal activity.
FIG. 3 is a graph showing the correlation between the maximum catalyst layer temperature of the carbon monoxide remover and the carbon monoxide oxidation removal activity.
[Explanation of symbols]
5 Carbon monoxide transformer
6 Carbon monoxide remover
7 Polymer electrolyte fuel cell
8 Temperature control means

Claims

In order to obtain a fuel gas for use in a polymer electrolyte fuel cell, ruthenium, platinum, rhodium, or palladium is used to remove carbon monoxide in a mixed gas containing hydrogen and carbon monoxide obtained by reforming the raw fuel. An introduction step of introducing a reaction gas obtained by adding an oxidant to the mixed gas into a carbon monoxide remover in which a catalyst layer including a carbon monoxide removal catalyst is formed in the housing; and the carbon monoxide removal catalyst In the carbon monoxide removal method comprising the removal step of removing the carbon monoxide by reacting the oxidizing agent and the mixed gas above.
In the introduction step, the reaction gas at 100 ° C. or lower is introduced into the carbon monoxide remover.
The reaction gas that flows through the pipe by providing the pipe connected to the inlet of the carbon monoxide remover with a heat exchanger and a drain trap for cooling the mixed gas or the reaction gas flowing through the pipe. A carbon monoxide removal method in which the dew point of the reaction gas introduced into the inlet of the carbon monoxide remover is 40 ° C. or less at a process pressure by condensing water vapor therein.

The carbon monoxide removal method according to claim 1, wherein in the introduction step, the reaction gas of 80 ° C. or less is introduced into the carbon monoxide remover.

In order to obtain a fuel gas for use in a polymer electrolyte fuel cell, ruthenium, platinum, rhodium, or palladium is used to remove carbon monoxide in a mixed gas containing hydrogen and carbon monoxide obtained by reforming the raw fuel. An introduction step of introducing a reaction gas obtained by adding an oxidant to the mixed gas into a carbon monoxide remover in which a catalyst layer including a carbon monoxide removal catalyst is formed in the housing; and the carbon monoxide removal catalyst In the carbon monoxide removal method comprising the removal step of removing the carbon monoxide by reacting the oxidant with the mixed gas above,
In the removing step, to maintain the maximum temperature of the catalyst layer at 130 ° C. or higher and 180 ° C. or lower,
The reaction gas that flows through the pipe by providing the pipe connected to the inlet of the carbon monoxide remover with a heat exchanger and a drain trap for cooling the mixed gas or the reaction gas flowing through the pipe. A carbon monoxide removal method in which the dew point of the reaction gas introduced into the inlet of the carbon monoxide remover is 40 ° C. or less at a process pressure by condensing water vapor therein.

The method for removing carbon monoxide according to claim 3, wherein the maximum temperature of the catalyst layer is 150 ° C or higher and 180 ° C or lower.

In order to obtain a fuel gas for use in a polymer electrolyte fuel cell, ruthenium, platinum, rhodium, or palladium is used to remove carbon monoxide in a mixed gas containing hydrogen and carbon monoxide obtained by reforming the raw fuel. An introduction step of introducing a reaction gas obtained by adding an oxidant to the mixed gas into a carbon monoxide remover in which a catalyst layer including a carbon monoxide removal catalyst is formed in the housing; and the carbon monoxide removal catalyst In the carbon monoxide removal method comprising the removal step of removing the carbon monoxide by reacting the oxidant with the mixed gas above,
In the introduction step, the reaction gas at 100 ° C. or less is introduced into the carbon monoxide remover,
In the removing step, to maintain the maximum temperature of the catalyst layer at 130 ° C. or higher and 180 ° C. or lower,
The reaction gas that flows through the pipe by providing the pipe connected to the inlet of the carbon monoxide remover with a heat exchanger and a drain trap for cooling the mixed gas or the reaction gas flowing through the pipe. A carbon monoxide removal method in which the dew point of the reaction gas introduced into the inlet of the carbon monoxide remover is 40 ° C. or less at a process pressure by condensing water vapor therein.

The method for removing carbon monoxide according to any one of claims 1 to 5, wherein the mixed gas is a reformed gas obtained by reforming hydrocarbons or alcohols.

The carbon monoxide removal catalyst according to any one of claims 1 to 6, wherein the carbon monoxide removal catalyst is a catalyst containing ruthenium.

8. The process according to claim 1, wherein the catalyst layer including the carbon monoxide removal catalyst is pretreated in a gas stream in which hydrogen and nitrogen are mixed before the introduction step. Carbon oxide removal method.

A reformer containing a reforming catalyst for reforming the raw fuel in the gas containing raw fuel and water vapor into a mixed gas containing hydrogen and carbon monoxide, and one for modifying the carbon monoxide in the mixed gas A carbon monoxide converter containing a carbon oxide conversion catalyst, and ruthenium, platinum, rhodium for removing carbon monoxide in the reaction gas obtained by adding an oxidizing agent to the mixed gas discharged from the carbon monoxide converter , or A carbon monoxide remover containing a carbon monoxide removal catalyst containing palladium is connected by a pipe so that gas can flow in the order described, and the inside of the pipe connecting the carbon monoxide converter and the carbon monoxide remover is circulated. In a method for operating a fuel reforming system provided in a polymer electrolyte fuel cell system provided with a heat exchanger through which a heat transfer medium flows so that heat exchange can be performed with respect to the mixed gas or the reaction gas.
By the heat exchange between the mixed gas or the reaction gas flowing through the pipe and the heat transfer medium flowing through the heat exchanger, the gas flows through the pipe downstream from the portion where the heat exchanger is provided. In order to introduce the reaction gas into the carbon monoxide remover while maintaining the reaction gas at 100 ° C. or lower,
The reaction gas that flows through the pipe by providing the pipe connected to the inlet of the carbon monoxide remover with a heat exchanger and a drain trap for cooling the mixed gas or the reaction gas flowing through the pipe. A method for operating a fuel reforming system in which a dew point of the reaction gas introduced into an inlet of the carbon monoxide remover is set to 40 ° C. or less at a process pressure by condensing water vapor therein.

10. The catalyst layer according to claim 9 , wherein the catalyst layer including the carbon monoxide removal catalyst is pretreated in a gas stream in which hydrogen and nitrogen are mixed before introducing the reaction gas into the carbon monoxide remover. Operation method of fuel reforming system.

In order to obtain a fuel gas for use in a polymer electrolyte fuel cell, ruthenium, platinum, rhodium, or palladium is used to remove carbon monoxide in a mixed gas containing hydrogen and carbon monoxide obtained by reforming the raw fuel. An introduction step of introducing a reaction gas obtained by adding an oxidant to the mixed gas into a carbon monoxide remover in which a catalyst layer including a carbon monoxide removal catalyst is formed in the housing; and the carbon monoxide removal catalyst In performing the carbon monoxide removal method having the removal step of reacting the oxidizing agent and the mixed gas to remove carbon monoxide above,
In the introduction step, the reaction gas at 100 ° C. or lower is introduced into the carbon monoxide remover.
The reaction gas that flows through the pipe by providing the pipe connected to the inlet of the carbon monoxide remover with a heat exchanger and a drain trap for cooling the mixed gas or the reaction gas flowing through the pipe. By condensing the water vapor therein, the dew point of the reaction gas introduced into the inlet of the carbon monoxide remover is set to 40 ° C. or less at the process pressure, and the iron in the catalyst layer composed of the carbon monoxide removal catalyst Iron poisoning prevention method to prevent poisoning.

The iron poisoning prevention method according to claim 11 , wherein the catalyst layer composed of the carbon monoxide removal catalyst is pretreated in a gas stream in which hydrogen and nitrogen are mixed before the introduction step.