JP3924407B2

JP3924407B2 - Fuel reformer and fuel cell system

Info

Publication number: JP3924407B2
Application number: JP29108499A
Authority: JP
Inventors: 重徳光島; 賢史山賀; 甚一今橋; 友一加茂
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 1999-10-13
Filing date: 1999-10-13
Publication date: 2007-06-06
Anticipated expiration: 2019-10-13
Also published as: JP2001114502A

Description

【０００１】
【発明の属する技術分野】
本発明は、炭化水素、空気、水から水素を含むガスを製造する燃料改質器及びその燃料改質器を具備する燃料電池システムに関する。
【０００２】
【従来の技術】
高分子固体電解質型燃料電池（ＰＥＦＣ）は、他の燃料電池と比較して、室温起動が可能で、高出力密度が得られるという特長を有し、電気自動車用電源、あるいは家庭用、ビル用の小型のコジェネレーションシステムとして開発されている。しかし、燃料として、一次エネルギーとして産出されず、貯蔵や輸送に高い技術を要する水素を供給する必要があるという欠点も有している。
【０００３】
ＰＥＦＣを電気自動車用電源として用いる場合、水素の高圧ボンベ搭載、水素吸蔵合金タンク搭載、液化水素タンク搭載等の方法で水素を直接搭載する方法も考えられているが、それぞれ低体積エネルギー密度、低重量エネルギー密度、蒸発による損失等の問題があること、並びに水素インフラの整備等の課題がある。電気自動車用の原燃料としては、体積エネルギー密度、重量エネルギー密度ともに高い液体燃料であることが望まれる。液体燃料の例としては、比較的低い温度で水素を製造できるメタノールを改質器により水素濃度の高いガスとする方法が特開平９−２６６００６号公報、特開平１１−９２１０２公報等に開示されている。
【０００４】
燃料電池用の改質器は、電気自動車用、小型コジェネレーション用を問わず、電力あるいは温水等の熱の負荷に対して燃料電池システムが追随するために、高い負荷応答性が要求される。燃料電池システムが追従できない負荷変動に対しては２次電池システムや蓄熱システムを具備することによって対応できるが、システムの大きさ、重量、価格ともに上昇要因となるため、改質器の応答性を高めることが要求される。
【０００５】
特開平９−２６６００６号公報に開示されている改質器では、メタノール等の原燃料と水蒸気を反応させて水蒸気改質を行う改質室内に原燃料の燃焼バーナー及び燃料電池排ガスの触媒燃焼器を配置した単位改質器を並列配置し、単位改質器の入口に設けた開閉弁により、原燃料及び燃焼器用燃料を供給する単位改質器を選択することにより改質器の体積を変化させる方法、平板の改質室と、触媒燃焼室を交互に積層して挿入棒あるいは回転棒を用いて原料及び燃焼器用燃料を供給する改質室及び触媒燃焼室を選択して改質器の体積を変化させる方法が開示されている。この方法では、改質器の体積を変化させることにより、水素製造量に関らず反応ガスの線速を一定にして負荷変動に対する応答性を高めている。
【０００６】
特開平１１−９２１０２号公報には、原燃料、水蒸気及び空気を反応させる改質器について、改質器内の温度分布が適正となる構造、並びに原燃料、水蒸気及び空気の供給方法が開示されている。この方法は、発熱反応である部分酸化反応と吸熱反応である水蒸気改質反応をバランスさせることが特徴である。この改質反応器は、応答速度が燃焼器から反応器への熱伝導速度に依存しないため負荷応答性が高くなっている。
【０００７】
【発明が解決しようとする課題】
しかしながら、特開平９−２６６００６号公報に開示された方法においては、応答速度が燃焼器から反応器への熱伝導速度に依存すること、改質器の体積を制限して運転する場合において、休止状態の改質室の温度を維持する方法等については改良すべき点がある。
【０００８】
特開平１１−９２１０２号公報に開示された方法においては、水素製造量が少ないときに、反応器内の反応ガスの線速が遅くなるため、たとえば最大水素製造量に対して１０％の製造量から２０％の製造量に負荷追従させるというような運転モードにおける応答速度が遅くなる問題点を有する。
【０００９】
本発明は、このような従来技術の問題点に鑑み、熱伝導速度に依存せず、水素製造量の変動に対して反応器内の反応ガスの線速変動を抑制し、かつ休止状態の改質室温度を所定の温度範囲に維持できる燃料改質器及びその燃料改質器を組み込んだ燃料電池システムを提供することを目的とする。
【００１０】
【課題を解決するための手段】
本発明の燃料改質器は炭化水素と水蒸気及び空気のうち、炭化水素を含む２成分以上からなる原料を反応させて水素を主成分とする改質ガスを製造する。炭化水素としてメタノールを用いた場合、主に次の反応式で水素を主成分とする改質ガスを製造する。
【００１１】
CH₃OH(g)＋H₂O(g)→3H₂(g)＋CO₂(g)−61kJ/mol （１）
CH₃OH(g)＋1/2 O₂→2H₂(g)＋CO₂(g)＋184kJ/mol （２）
H₂O(g)＋CO(g)←→H₂(g)＋CO₂(g)＋39kJ/mol （３）
【００１２】
上記（１）式は水蒸気改質反応と呼ばれる吸熱反応、（２）式は部分酸化反応と呼ばれる発熱反応、（３）式はシフト反応と呼ばれる発熱反応であり、燃料改質器内の改質反応器内において同時に進行させる。燃料改質器には改質反応器に熱を供給するための燃焼器が配置され、燃料電池から排出される低濃度水素含有ガス等の可燃性排ガスや原料の炭化水素を燃焼させて、改質反応器に熱を供給する。改質反応器内では、上記（１）〜（３）の反応の反応熱、燃焼器から供給される熱、改質反応器からの放熱等の熱損失、及び必要に応じて液体で供給される炭化水素及び水の気化熱及び反応温度まで昇温するための顕熱をバランスさせて一定温度で運転する。運転温度は触媒が動作する温度で決定され、炭化水素として例えばメタノールを用いる場合には２００〜４００℃、ＬＮＧ等を用いる場合には７００〜９００℃で運転する。温度の制御は、炭化水素、水及び空気の比率を調節して、部分酸化反応と水蒸気改質反応の比率を調節することにより行う。
【００１３】
本発明の燃料改質器は、負荷変動に対する応答性を高めるために、実効的な改質反応器の体積を変化させ、負荷が変動した時、反応器内を流れる反応ガスの線速の変動が小さくなる構造を有する。即ち、負荷変動にかかわらず炭化水素、水及び空気が供給されるベース反応器と、負荷に応じて炭化水素、水及び空気が供給される負荷応答反応器とを具備する。負荷応答反応器への炭化水素、水及び空気の供給は分配器により制御される。負荷が小さい時、炭化水素、水及び空気が供給されない負荷応答反応器は、燃焼器、ベース反応器、及び炭化水素、水及び空気が供給されている負荷応答反応器からの伝熱により触媒動作温度に保たれた状態で休止する。
【００１４】
休止中の負荷応答反応器温度を触媒動作温度に保つためには、負荷応答反応器が燃焼器及びベース反応器から効率的に熱の供給を受ける構造が望ましい。一方、負荷が変動した時、反応ガスの線速の変動を抑制するためには、ベース反応器の体積よりも負荷応答反応器の体積の総和が大きく、かつ負荷応答反応器が複数であることが望ましい。線速の変動を抑制するためには、１本のベース反応器に対して、３本以上、好ましくは６本の負荷応答反応器をベース反応器から等距離に配置することが望ましい。ベース反応器から等距離に負荷応答反応器を配置するためには、幾何学的に３本以上の負荷応答反応器が必要である。負荷応答反応器の本数が増えると反応器内の線速を一定にして運転しても、動作させる負荷応答反応器の本数分の段数でステップ状に水素製造量を変化させることができるので、負荷応答速度を犠牲にしないで追従できる。しかし、負荷応答反応器の本数をあまりに増やすとガス分配器の構造が複雑になる等の問題もあり、６本程度が適当である。
【００１５】
ベース反応器の大きさは負荷応答反応器の触媒温度を触媒作動温度に保つのに必要な最低限であることが、負荷応答範囲を広くするための必要条件であるので、１本の負荷応答反応器の断面積はベース反応器の断面積より大きい方が負荷応答範囲を広く取ることができる。
【００１６】
燃焼器は、例えばベース反応器と負荷応答反応器の間のように改質反応器間に配置し、燃焼器で発生する熱を効率的かつ均等に改質反応器に供給することが望ましい。燃焼器の配置の方法としては、ベース反応器及び２本の負荷応答管と接する部分に配置する方法、ベース反応器を２重管の内管とし、外管を燃焼器とする方法、ベース反応器及び負荷応答反応器を燃焼器内に配置する方法等がある。
【００１７】
炭化水素、水及び空気は、負荷応答反応器に対して、負荷量に応じて分配器により供給／停止を行わなければならない。このための構造としては、分配器と負荷応答反応器の接続部分にそれぞれ開閉弁を設け、各々の負荷応答反応器の出口に逆止弁を配置した後、ベース反応器及び各々の負荷応答反応器で製造された改質ガスを合流させる構造が比較的簡便な構造である。
【００１８】
休止状態の負荷応答反応器の触媒温度を動作温度に保つためには開閉弁の動作手順が重要である。すなわち、ベース反応器に対して対称性が高くなる順序で開閉動作を行うことにより、なるべく休止中の負荷応答反応器同士が隣接するのを避け、燃料改質器全体の温度分布が小さくなるように動作させる。開閉弁の構造としては、負荷応答反応器に対して１対１に接続される電磁弁のような開閉弁の他に、回転弁の形をとって、１つの回転弁の回転角度を調節することで接続される負荷応答反応器の開閉を行うようにすることもできる。
【００１９】
ベース反応器及び負荷応答反応器に充填する触媒は、反応器の上流側に貴金属の燃焼触媒、例えばアルミナ担持白金触媒を配置し、下流側に銅−亜鉛系触媒、ニッケル系触媒等の改質触媒を配置することが望ましい。反応器上流側に燃焼触媒を具備することにより、コールドスタート時に低温での着火性に優れ、かつ運転時に水蒸気改質反応速度が速い反応器が得られる。改質触媒としては、メタノールには銅−亜鉛系触媒、メタン等の炭素と水素からなる炭化水素にはニッケル系触媒が適する。
【００２０】
燃料電池では、改質ガス中に含まれるＣＯが触媒を被毒してセル電圧を低下させることが知られている。りん酸を電解質とするりん酸型燃料電池ではＣＯ濃度を数vol％以下、高分子を電解質とする高分子固体電解質型燃料電池では１００ｐｐｍ以下程度にＣＯ濃度を低下させなければならない。一方、燃料改質器では前記（３）の反応がほぼ平衡となっているため、炭化水素の部分酸化及び水蒸気改質反応が終了した後で、（３）のシフト反応の速度が速い触媒下、例えば銅−亜鉛系触媒下で２００℃程度にすることにより、（３）の反応が右側に進行し、ＣＯ濃度を１vol％程度まで低下させることができる。燃料改質器にこのシフト反応器の機能を付与するためには、改質反応器、即ちベース反応器及び負荷応答反応器の長さを燃焼器より長くし、改質反応器の下流側が空冷されるようにする。さらに、改質反応器の空冷部分のうち、上流側に熱交換器を設け、空冷部分の温度が２００℃程度になるようにするとよい。熱交換器内の熱媒体として改質反応器に供給する空気を用いると、改質反応器に供給する空気の予熱も兼ねることができる。
【００２１】
以上のような構成の燃料改質器は、特に起動・停止や負荷変動が比較的激しい用途に適する。したがって、水蒸気改質反応温度が低いメタノールのような燃料を用いることが望ましい。
【００２２】
次に、本発明の燃料改質器を組み込んだ燃料電池システムについて説明する。本発明の燃料改質器で製造した改質ガス中のＣＯを選択的に燃焼させる選択酸化器により、改質ガスを脱ＣＯする。選択酸化器はアルミナ担持白金ルテニウム触媒等の触媒を充填した反応器で、改質ガスとＣＯ流量に応じた空気を供給し、可燃成分であるＨ₂とＣＯの内、ＣＯを選択的に燃焼する反応器である。選択酸化器により、改質ガス中のＣＯ濃度を１００ｐｐｍ以下とすることができる。脱ＣＯした改質ガスを燃料電池、例えば高分子固体電解質型燃料電池の燃料として供給する。燃料電池では改質ガス中のＨ₂のうち、約８０％を反応消費し、電力、水及び熱を発生する。燃料電池からはＨ₂が５〜１０vol％程度の濃度となった改質ガスが排出され、これを本発明の燃料改質器内の燃焼器で燃焼し、改質反応器の熱源とする。
【００２３】
燃料改質器の温度を触媒作動温度に保つためには、燃料電池から排出される排ガスを燃焼させた時の熱量及び燃料改質器の温度を検出し、負荷要求に対して適正な炭化水素、水及び空気の量をコントローラで算出し、制御を行う。熱量を求めるためには排ガスの水素濃度及び流量を検出すればよい。熱量が高い時及び燃料改質器の温度が高い時には、水蒸気改質反応の比率を高める。即ち、水の流量を高く、炭化水素及び空気の量を低く設定する。逆に、熱量が低い時及び燃料改質器の温度が低い時には、部分酸化反応の比率を高める。即ち、水の流量を低く、炭化水素及び空気の量を高く設定する。コントローラーでは上記の制御を適当な時間間隔毎に、例えばＰＤＩ制御のような方式により制御し、燃料改質器を動作温度に保ちながら、水素負荷の変動に追従させる。
【００２４】
このようなシステムを、停止、負荷変動が頻繁であり、エネルギー密度の高い炭化水素が用いられる電気自動車の様な移動体電源に用いる場合は、炭化水素としてメタノールを用いることが望ましい。一方、コジェネレーションの様な定置型のシステムでは、都市ガス、プロパンガス等の流通が容易な天然ガス系の炭化水素を用いることが望ましく、本発明の燃料改質器では炭化水素を用いる場合と比較して、起動停止の速度は遅くなるが天然ガス系の炭化水素を用いることもできる。
【００２５】
以上述べたように、本発明による燃料改質器は、炭化水素と水蒸気及び空気のうち炭化水素を含む２成分あるいは３成分からなる原料を反応させて水素を主成分とする改質ガスを製造する改質反応器と、可燃ガスを燃焼させて改質反応器に熱を供給する燃焼器とを含む燃料改質器において、改質反応器は、燃料改質器運転時に常に原料が供給されるベース反応器と、水素製造量に応じて原料が供給される複数の負荷応答反応器とからなり、ベース反応器と負荷応答反応器に原料を分配する分配器を具備することを特徴とする。
【００２６】
ベース反応器に直近の反応器を負荷応答反応器とし、１つのベース反応器に直近の負荷応答反応器は３個以上であることが望ましい。また、原料流の方向と直交する方向の負荷応答反応器の断面積がベース反応器の断面積以上であることが望ましい。改質反応器間に燃焼器を配置するのが好ましく、燃焼器は例えばベース反応器と２本の負荷応答反応器と接するように配置することができる。ベース反応器と燃焼器とは内側にベース反応器が配置され外側に燃焼器が配置された二重管構造としてもよいし、ベース反応器及び負荷応答反応器を一つの燃焼器内に配置してもよい。
【００２７】
分配器は負荷応答反応器に接続される部分にそれぞれ開閉弁を具備し、水素製造量に応じて各開閉弁を開閉制御することができる。また、分配器は回転位置に応じて各負荷応答反応器への原料供給及び遮断を並列的に行う回転弁を備え、水素製造量に応じて回転弁の回転位置を制御するように構成することもできる。分配器の弁の制御は、改質ガスを製造する負荷応答反応器のベース反応器に対する配置が対称に近くなる順序で行うのが好ましい。
【００２８】
改質反応器の原料入口側に貴金属触媒を配置し、出口側に銅及び亜鉛を含む改質触媒を配置することができる。また、改質反応器の原料入口側に貴金属触媒を配置し、出口側にニッケルを含む改質触媒を配置することができる。
【００２９】
改質反応器の長さが前記燃焼器より長く、改質反応器内の銅亜鉛触媒を配置した銅亜鉛触媒層中に熱交換器を設けた構造とし、熱交換器の上流側で主に炭化水素を反応させて改質ガスを製造し、熱交換器の下流側で改質ガス中の一酸化炭素と水蒸気を水素と二酸化炭素に変換する反応を行うようにすることができる。このとき、熱交換器の熱媒体を空気とし、熱交換器により改質ガスの温度を低下させるとともに、原料中の空気を予熱するのが好ましい。
【００３０】
炭化水素はメタノールとすることができる。また、ベース反応器とベース反応器直近の負荷応答反応器と燃焼器を基本単位として、複数個の基本単位から燃料改質器を構成してもよい。
【００３１】
本発明による燃料電池システムは、炭化水素と水蒸気及び空気のうち炭化水素を含む２成分あるいは３成分からなる原料を反応させて水素を主成分とする改質ガスを製造する改質反応器及び改質反応器に熱を供給する燃焼器とを備える燃料改質器と、燃料改質器で製造された改質ガス中の一酸化炭素を選択的に燃焼する選択酸化器と、イオン伝導体である電解質膜の両側に電極を配置し、一方に選択酸化器で一酸化炭素を除去した改質ガスを、もう一方に加湿空気を供給し、電気化学的に改質ガス中の水素を酸化して電力と水とを発生する燃料電池とを含む燃料電池システムにおいて、燃料改質器として前述の燃料改質器を用い、燃料電池から排出される低水素濃度になった改質ガスを燃料改質器の燃焼器に供給することを特徴とする。
【００３２】
この燃料電池システムは、燃料電池から排出される低水素濃度になった改質ガスの燃焼熱を算出する手段と、燃料改質器の温度を測定する手段と、燃料電池に対する電力負荷要求と燃焼熱と燃料改質器の温度をもとに燃料改質器に供給する原料の組成、流量及び前記分配器の動作を決定する制御器とを備える。
本発明の燃料電池システムは、モーターを搭載した電気自動車の燃料電池システムとして好適である。このとき、炭化水素としてはメタノールを用いる。
【００３３】
炭化水素として天然ガスを用いた本発明の燃料電池システムは、コジェネレーションシステムに適用することができ、そのとき、燃料改質器と選択酸化器の間に改質ガスを冷却する水冷式の熱交換器を具備し、熱交換器から排出される水を給湯に使用する構成をとることができる。
【００３４】
【発明の実施の形態】
以下、本発明の実施の形態について、図面を参照して説明する。以下の図において、同じ機能部分には同じ符号を付し、重複する説明を省略する。
図１は本発明による燃料改質器の一例を示す構成図であり、図１（ｂ）は側面図、図１（ａ）はそのＡＡ′断面図である。この燃料改質器は、１本のベース反応器１の周囲に等距離、等間隔で６本の負荷応答反応器２〜７を配置し、バース反応器１と負荷応答反応器２〜７の間に、それぞれ２本の負荷応答反応器とベース反応器１と接するようにして６本の燃焼器８を配置した構造を有する。７本に分岐された空気配管９にブロワを用いて空気を供給し、負荷応答反応器２〜７につながる配管部分にそれぞれ電磁式の開閉弁１０を配置した。炭化水素としてはメタノールを用い、メタノールは空気配管と同様の構造の配管で供給した。メタノールは７本に分岐されている配管１１にポンプにて供給し、負荷応答反応器２〜７につながる配管部分に電磁式開閉弁１２を配置した。水の供給も同様に７本に分岐されている配管１３を用いてポンプで行い、負荷応答反応器につながる配管部分に電磁式開閉弁１４を配置した。ベース反応器１及び負荷応答反応器２〜７の出口にはクラッキング圧０．０７ｋｇ／ｃｍ²の逆止弁１６を取り付け、配管１５に合流させた。
【００３５】
ベース反応器１及び負荷応答反応器２〜７の直径は４０ｍｍ、長さは３００ｍｍとし、上流の４０ｍｍにアルミナ担持白金触媒、残りの２６０ｍｍに銅−亜鉛系触媒を充填した。両者とも触媒は直径３ｍｍ、高さ３ｍｍの円柱状ペレットである。ハニカム形状の触媒を使用することもできるが、その場合には口径の選定等を行い、並列に接続されるベース反応器１及び負荷応答反応器２〜７のガス分配が適切に行われるように、定格運転時のベース反応器及び負荷応答用反応器の圧力損失が０．２〜０．４ｋｇ／ｃｍ²程度になるように反応器直径及び触媒構造を選定することが望ましい。
【００３６】
燃焼器８への燃焼ガス及び空気の配管は図では省略したが、低濃度水素ガスと空気の混合ガスをそれぞれの燃焼器８に分配して供給した。燃焼器８へのガス供給は図中下から上、即ちベース反応器１及び負荷応答反応器２〜７でのガス流れと対向させた。ベース反応器１及び負荷応答反応器２〜７内では水蒸気改質反応と比較して部分改質反応の方が反応速度が速いため、上流側で発熱量が多く、下流側で吸熱量が多くなるので、燃焼器からの熱供給を下流側が優先するようにし、温度分布を小さくするためである。燃焼器８の直径は２０ｍｍ、長さは２００ｍｍとした。燃焼器８へ充填する燃焼触媒は、３ｍｍペレットのアルミナ担持白金触媒とした。燃焼触媒もハニカム状触媒とすることもできる。改質ガス中のＣＯ濃度を低下させるために、燃焼器８の長さを改質反応器１〜７の長さより短くし、改質反応器の下流側が空冷される構造にして、前記（３）のシフト反応が右側に進行するようにした。
【００３７】
ベース反応器１は常に作動状態にあるが、負荷応答反応器２〜７は、開閉弁１０，１２，１４を開閉することにより、作動状態になったり休止状態になったりする。負荷応答反応器２〜７が休止状態にある時でも、その触媒はベース反応器１及び燃焼器８からの熱伝導で作動温度に維持されている。ベース反応器１及び燃焼器８からの熱伝導で休止中の負荷応答反応器２〜７の触媒温度が作動温度にある状態から、負荷量に応じて負荷応答反応器２，３，４，５，６，７の順で電磁式開閉弁１０，１２，１４を開にして、ベース反応器１に対して対称性が高くなる順番で負荷応答反応器を作動状態にする。
【００３８】
図１には、空気配管９を介した負荷応答反応器２〜７への空気の供給・遮断をそれぞれの負荷応答反応器２〜７に対応して設けた電磁式開閉弁１０により行い、炭化水素用配管１１を介した負荷応答反応器２〜７への炭化水素の供給・遮断をそれぞれの負荷応答反応器２〜７に対応して設けた電磁式開閉弁１２により行い、水用配管１３を介した負荷応答反応器２〜７への水の供給・遮断をそれぞれの負荷応答反応器２〜７に対応して設けた電磁式開閉弁１４により行う例を説明した。しかし、負荷応答反応器２〜７への空気、炭化水素、水の供給・遮断の制御は、電磁式開閉弁１０，１２，１４以外の手段で行うことも可能である。その一例として、図２により、配管９（１１，１３）と電磁式開閉弁１０（１２，１４）を一体化した回転弁式ガス分配器について説明する。図２（ｂ）は回転式開閉弁３０の側面図、図２（ａ）はそのＡＡ′断面図である。回転弁ハウジング１７内に、回転弁１８が納められている。図２（ａ）に図示した回転弁１８の黒い放射状の部分は連通部分である。従って、図２（ａ）の状態は、すべての負荷応答反応器２〜７に炭化水素、水あるいは空気を供給する状態を図示している。回転式開閉弁３０はステップモーターを内蔵しており、回転弁１８を左回りに８°ずつ回転させることにより、負荷応答反応器２〜７を７，６，５，４，３，２の順で休止状態にする。負荷応答反応器２〜７を休止状態から作動状態にするためには、休止状態にする時と逆に回転弁１８を右回りに８°ずつ回転させる。なお、回転式開閉弁３０はベース反応器１に対しては常に開状態にある。
【００３９】
図３は本発明による燃料改質器の他の例を示す構成図であり、図３（ｂ）は燃料改質器の側面図、図３（ａ）はそのＡＡ′断面図である。この例では、燃焼器８′をベース反応器１との２重管構造とした。２重管の内管の直径を４０ｍｍ、外管の直径を６０ｍｍとした。ベース反応器１、負荷応答反応器２〜７、及び燃焼器８の長さは図１に示した燃料改質器と同様に、反応器１〜７は３００ｍｍ、燃焼器８は２００ｍｍとした。
【００４０】
図４は本発明による燃料改質器の他の例を示す構成図であり、図４（ｂ）は燃料改質器の側面図、図４（ｂ）はそのＡＡ′断面図である。この例の燃料改質器は、ベース反応器１及び負荷応答反応器２〜７を燃焼器８″内に納めた構造とした。ベース反応器１及び負荷応答反応器２〜７の外径は４０ｍｍ、燃焼器８″の内径は１２０ｍｍとした。ベース反応器１、負荷応答反応器２〜７、及び燃焼器８の長さは、図１に示した燃料改質器と同様に反応器１〜７は３００ｍｍ、燃焼器８は２００ｍｍとした。
【００４１】
以上、ベース反応器１及び負荷応答反応器２〜７の反応器７本から構成される３種類の燃料改質器に反応器１本あたり、メタノールを７．７ｃｃ／ｍｉｎ、水を１．４ｃｃ／ｍｉｎ、空気を９．１Ｌ／ｍｉｎ供給して運転したところ、燃焼器８には燃焼ガスを供給せずに熱的に自立し、反応器１本あたり９．７ＬのＨ₂が製造できた。この時のＨ₂濃度は４０vol％、ＣＯ濃度は３vol％であった。ベース反応器１のみを動作させた時と比較して、ベース反応器１及び負荷応答反応器２〜７の全てを作動させた時の方が、相対的に放熱量が小さくなるため温度が１５℃上昇した。
【００４２】
反応器１本あたり、メタノールを６．２ｃｃ／ｍｉｎ、水を２．５ｃｃ／ｍｉｎ、空気を２．８Ｌ／ｍｉｎ供給して運転し、燃焼器８には燃焼ガスを供給して反応器温度を３００℃に保った時、反応器１本あたり８．９ＬのＨ₂が製造できた。この時のＨ₂濃度は５０vol％、ＣＯ濃度は４vol％であった。ベース反応器１のみを動作させた時と比較して、ベース反応器１及び負荷応答反応器２〜７の全てを作動させた時の方が、相対的に放熱量が小さくなるため、燃焼器８への燃焼ガス供給量は５％少なかった。
【００４３】
図５は本発明による燃料改質器の他の例を示す構成図であり、図５（ａ）は燃料改質器の側面図、図５（ｂ）はそのＡＡ′断面図である。この燃料改質器は、熱交換機２０を備え、空気配管９が改質ガス用配管１５側から入り、改質反応器内のシフト反応部内の空気配管１９、改質器内の熱交換器２０、改質反応器内の改質反応部の空気配管２１を通して反応器に導かれる。改質反応器内のシフト反応部内の空気配管１９に導かれた空気は、図５（ｂ）に示すように、熱交換器２０の空気流入部２４から熱交換器２０内に流入し、改質ガス流路２２の間の空気流路２３を通って空気排出部２５から改質反応器内の改質反応部の空気配管２１に導かれる。つまり、改質器内の熱交換器２０で改質ガスを冷却し、空気を予熱する構成となっていて、図１、図３及び図４に示した燃料改質器より改質反応器内のシフト反応部内の改質ガス温度が低い。このため、シフト反応部で前記（３）のシフト反応を右側に進めて改質ガス中のＣＯ濃度を１vol％に低下させることができた。
【００４４】
図６は、負荷応答反応器２〜７に原料を供給する分配器に設けた開閉弁の構成例を示す図である。図６（ａ）は、図１、図３〜図５に示したように、原料供給管にそれぞれ開閉弁を設ける構成である。図６（ｂ）は、開閉弁を一つ省略した構成である。炭化水素としてメタノールの様に液体を用いる場合には図６（ｂ）の構成で炭化水素と水の開閉弁を共用することができ、炭化水素として天然ガスのように気体を用いる場合には炭化水素と空気の開閉弁を共用できる。液体同士あるいは気体同士で開閉弁を共用する場合には燃料改質器の応答性を犠牲にすることはないが、気体と液体に対して開閉弁を共用すると反応器に導かれる炭化水素、水、空気の組成が一時的に不安定になるので、好ましくない。
【００４５】
図７は、本発明による燃料改質器の断面図である。これまで示した燃料改質器ではベース反応器１と負荷応答反応器２〜７の直径が等しく、ベース反応器１に対して負荷応答反応器２〜７が６本の構成であったが、図７に示すように、ベース反応器１の直径を小さくしてもよい。ベース反応器１及び燃焼器８を動作させて負荷反応器２〜７が動作温度を保てる大きさがあればよい。また、図７（ｃ）はベース反応器１に対して負荷応答反応器が４本の構成であり、負荷応答反応器を３本、５本、あるいはその他の本数とする構成も可能である。
【００４６】
図８は、ベース反応器１及び負荷応答反応器２〜７を一つの構成単位のブロックＢ１，Ｂ２，Ｂ３，‥‥とし、４個のブロックＢ１〜Ｂ４を並列配置した燃料改質器を示す断面図である。図８（ａ）は、ブロックとブロックの境界部分で３つの負荷応答反応器に囲まれる部分にも燃焼器８を配置した構成例である。図８（ｂ）は、単純にブロックＢ１〜Ｂ４を４つ並列させた構成例である。図を見やすくするために、ベース反応器１にハッチングを付けて示した。いずれの方式でも、部分負荷時に休止中の負荷応答反応器２〜７を触媒動作温度に保つことができる。なお、単位ブロックＢ１，Ｂ２，Ｂ３，‥‥に含まれる負荷応答反応器の数は６個に限られるわけではなく、また、ブロックＢ１，Ｂ２，Ｂ３，‥‥の並列数は４個に限られるわけでもない。ブロックＢ１，Ｂ２，Ｂ３，‥‥を基本単位として複数個並列させることにより、燃料改質器の大容量化が可能である。
【００４７】
図１、図３〜図８に示した燃料改質器の反応管や燃焼器の構造はパイプを束ねた構造に限るものではない。例えば、アルミニウムのブロックを機械加工により削り出して作製したり、鋳造により一体化した部品を作製することもできる。燃料改質器内の温度分布を小さくするためには、ベース反応器１、負荷応答反応器２〜７、燃焼器８間の熱伝導が高い方が望ましいので、むしろ図１、図３〜図８に示した構造を機械加工、鋳造等の方法により一体成形する方が良い。一方、軽量化や材料費削減に主眼を置く場合には、パイプを束ねた構造が望ましい。反応器の形状は円筒形に限らず、熱伝導に優れ、体積効率の高い構造が望ましい。パイプを束ねた構造とする場合には、多角形のパイプを使用したり、改質反応器間のスペースをそのまま燃焼器として使用する方法もある。
【００４８】
図９は、本発明の燃料改質器を組み込んだ燃料電池システムの一例を示す構成図である。燃料は燃料ポンプ１０１、水は水ポンプ１０２、空気は空気ブロワ１０３により、気化器１０４を通じて本発明の燃料改質器の反応器１０５に供給される。燃料として、例えば都市ガス或はＬＰＧの様に加圧ガスを用いる場合には、燃料ポンプ１０１の代わりに流量コントローラを用いる。気化器１０４は燃料改質器と別途に設けることも可能であるが、燃料改質器の反応器１０５に水及び液体燃料を供給して内部で気化させることも可能である。
【００４９】
燃料改質器の反応器１０５で生成された改質ガスはＣＯ除去器１０６でＣＯを酸化してＣＯ₂とする。ＣＯ酸化の酸化剤は空気であり、ＣＯ除去器用空気ブロワ１０７から供給される。ＣＯ除去器１０６は可燃成分のＨ₂及びＣＯの内、ＣＯを選択的に酸化する触媒を充填した反応器である。ＣＯ除去した改質ガスは燃料ガス用加湿器１０８で加湿されて燃料電池１１０に供給される。燃料電池１１０は図１０に示したように、イオン伝導体１１０Ｅの両側に燃料極１１０Ａ、空気極１１０Ｃを配置した電極−電解質接合体を、ガス流路を具備した電子伝導体であるセパレータ１１０Ｓで保持した構成が基本単位のセルとなり、セルを積層した構成である。燃料ガス用加湿器１０８には燃料加湿用水ポンプ１０９で水が供給される。燃料電池１１０の空気極１１０Ｃには、空気極用空気ブロワ２０１から空気極用加湿器２０３を介して加湿された空気が供給される。空気極用加湿器には空気極加湿用水ポンプ２０２より水が供給される。
【００５０】
燃料電池１１０から排出される燃料ガスは燃焼器用ブロワ１１１から供給される空気と混合されて燃焼器１１２で燃焼して、改質器の改質反応器１０５の熱源となる。燃料電池１１０から排出される空気は気水分離器２０４で気水分離し、水は水ポンプ１０２、１０９、２０２に供給され、気体は排ガスとなる。燃料電池１１０の冷却のためには、冷却水循環用水ポンプ２７１、燃料電池１１０内熱交換器２７２、及び熱負荷２７３から構成される冷却系が具備されている。また、燃料改質器１０５に供給する炭化水素原料として天然ガスを用いる場合には燃料改質器の改質反応器１０５から排出される改質ガスは高温になるため、改質反応器１０５と選択酸化器１０６の間に冷却水循環用水ポンプ２８１、熱交換器２８２及び熱負荷２８３からなる改質ガス冷却系が設けられる。
【００５１】
燃料改質器の改質反応器１０５へ供給する燃料、空気、及び水の量は負荷要求、温度計３０２の測定値、及びセンサ３０１で測定した水素流量をもとにコントローラ３０３で決定される。負荷要求は、電力負荷要求量や水素要求量という形でコントローラ３０２にもたらされる。次に、コントローラ３０３での燃料、空気、及び水の量の決定方法について簡単に説明する。ここでは、基本的な考え方を説明するために改質器内の反応が前記（１）式の水蒸気改質と（２）式の部分酸化のみの場合を取り上げて説明するが、実際には（３）式のシフト反応等も起こる。水蒸気改質と部分酸化の比率をｘ：１−ｘとすると、前記（１）式と（２）式より次の（４）式が成り立つ。
CH₃OH(g)+xH₂O(g)+(1-x)/2 O₂→(2+x)H₂(g)+CO₂(g)+(184-248x)kJ/mol （４）
【００５２】
例えば、１分間にｙモルの水素を発生させる時の熱収支は、次の（５）式で表される。
（１８４−２４８ｘ）ｙ／（２＋ｘ）＋Ｗ＋σΔＴ＝０（５）
ここで、Ｗ（ｋＪ／ｍｉｎ）は燃焼器の発熱量であり、センサ３０１で測定した水素流量をもとに算出される。σ（ｋＪ／ｍｉｎ・℃）は熱損失の係数、ΔＴ（℃）は外気と反応器の温度差である。従って、要求される水素量に対する燃料、空気、及び水の量は（５）式及び（４）式より求まる。制御方法の一例としては、負荷要求や燃焼器の発熱量Ｗが急激に変動した時には（５）式及び（４）式により燃料、空気、及び水の量を急激に変動させ、定常状態では温度計３０２の測定値が触媒作動のために適正な値となるように、フィードバックをかけながら水蒸気改質の比率ｘを調節する方法がある。
【００５３】
改質反応器１０５一本あたりの最大水素製造量は水蒸気改質の比率ｘの関数となる。前記（１）式の水蒸気改質反応の速度と（２）式の部分酸化反応の速度が異なるためである。従って、ベース反応器１と負荷応答反応器２〜７の反応器体積が等しい時の開閉弁１２を開とする本数Ｎは次式（６）となる。
Ｎ＝Floor(Ｆ／ｖ(ｘ)) （６）
ここで、Floor(ｚ)は小数点以下切り捨ての関数、Ｆは要求される水素量、ｖ(ｘ)は反応器一本あたりの最大水素製造量である。（６）式で小数点以下を切り捨てるのはベース反応器１が常に開の状態となっているためである。
【００５４】
燃料電池１１０の電気出力は燃料電池用直交変換器２５１を介して交流負荷２５２に接続される。交流負荷２５２に対して、燃料電池用直交変換器２５１と並列に電力貯蔵手段用直交変換器２５４を介して電力貯蔵手段２５３が接続される。
【００５５】
例えば、図１１に示した電気自動車Ｃ２では、燃料電池システムＣ１の交流負荷２５２が電気自動車Ｃ２を駆動するためのモーターとなる。燃料電池システムＣ１には、燃料タンク４０１から燃料が供給される。この場合は、電力負荷が主体で、負荷変動が激しいので、電力貯蔵手段２５３及び電力貯蔵手段用直交変換器２５４を具備することが望ましく、熱負荷２７３は例えばラジエータの様な冷却装置となる。本発明の燃料改質器を用いることにより、燃料電池１１０の負荷応答性を高めることが可能となり、電力貯蔵手段２５３に貯える電力が少ないシステムの設計が可能となる。
【００５６】
図１２に示した小型コジェネレーションシステムＣ３のように系統電源４０２に接続器４０３を介して接続される用途においては、電力貯蔵手段２５３及び電力貯蔵手段用直交変換器２５４を具備する必要はない。この場合は、交流負荷２５２として、照明等の電気機器は接続器４０３を介して接続される。また、燃料電池システムＣ１への燃料は系統ガス配管４０４、水は水道４０５から供給される構成となる。この時は熱負荷２７３を給湯用４０６や暖房機器４０７の熱源として動作させる。また、燃料改質器１０５に供給する炭化水素原料として天然ガスを用いる場合には燃料改質器の改質反応器１０５から排出される改質ガスは高温となる。従って、改質反応器１０５と選択酸化器１０６の間に改質ガスを冷却する水冷式の熱交換器２８２を具備し、熱交換器２８２から排出される水を給湯に使用するとよい。系統電源に接続されるコジェネレーションシステムにおいては電力負荷に応答して動作させる方法と熱負荷に応答して動作させる方法があるが、電力系統で接続される系全体のエネルギー効率を考えると、熱負荷に応答させて動作させる方がエネルギー効率が高くなる。本発明の燃料改質器を用いることにより、熱負荷２７３に対する燃料電池システムの応答性が高まり、蓄熱槽等の蓄熱手段を具備する必要が無くなる。
【００５７】
【発明の効果】
本発明によると、休止中の負荷応答反応器の触媒温度を常に作動可能温度に保つことができ、燃料改質器の負荷応答性を高めることができる。
【図面の簡単な説明】
【図１】本発明による燃料改質器の一例を示す構成図。
【図２】回転弁式ガス分配器の例を示す構成図。
【図３】本発明による燃料改質器の他の例を示す構成図。
【図４】本発明による燃料改質器の他の例を示す構成図。
【図５】本発明による燃料改質器の他の例を示す構成図。
【図６】負荷応答反応器に原料を供給する分配器に設けた開閉弁の構成例を示す図。
【図７】本発明による燃料改質器の断面図。
【図８】燃料改質器集合体の構成例を示す断面図。
【図９】本発明の燃料改質器を用いた燃料電池システムの例を示す構成図。
【図１０】燃料電池の構成を示す模式図。
【図１１】電気自動車の模式図。
【図１２】コジェネレーションシステムの模式図。
【符号の説明】
１…ベース反応器、２〜７…負荷応答反応器、８…燃焼器、９…空気配管、１０…空気用開閉弁、１１…炭化水素用配管、１２…炭化水素用開閉弁、１３…水用配管、１４…水用開閉弁、１５…改質ガス用配管、１６…逆止弁、１７…回転弁ハウジング、１８…回転弁、１９…改質反応器内のシフト反応部内の空気配管、２０…改質反応器内の熱交換器、２１…改質反応器内の改質反応部内の空気配管、２２…熱交換器内の改質ガス流路、２３…熱交換器内の空気流路、２４…熱交換器内の空気流入部、２５…熱交換器内の空気排出部、３０…回転式開閉弁、１０１…燃料ポンプ、１０２…水ポンプ、１０３…空気ブロワ、１０４…気化器、１０５…燃料改質器の改質反応器、１０６…ＣＯ除去器、１０７…ＣＯ除去器用空気ブロワ、１０８…燃料ガス用加湿器、１０９…燃料加湿用水ポンプ、１１０…燃料電池、１１１…燃焼器用ブロワ、１１２…燃焼器、２０１…空気極用空気ブロワ、２０２…空気極加湿用水ポンプ、２０３…空気極用加湿器、２０４…気水分離器、２５１…燃料電池用直交変換器、２５２…交流負荷、２５１…電力貯蔵手段、２５３…電力貯蔵手段用直交変換器、２７１…冷却水循環用水ポンプ、２７２…燃料電池内熱交換器、２７３…熱負荷、２８１…冷却水循環用水ポンプ、２８２…熱交換器、２８３…熱負荷、３０１…センサ、３０２…温度計、３０３…コントローラ、４０１…燃料タンク、４０２…系統電源、４０３…接続器、４０４…系統ガス配管、４０５…水道、４０６…給湯、４０７…暖房機器、Ｂ１〜Ｂ４…基本単位反応器、Ｃ１…燃料電池システム、Ｃ２…電気自動車、Ｃ３…コジェネレーションシステム[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel reformer that produces a gas containing hydrogen from hydrocarbons, air, and water, and a fuel cell system including the fuel reformer.
[0002]
[Prior art]
Compared with other fuel cells, polymer solid oxide fuel cells (PEFC) have the features that they can be started at room temperature and have a high output density. It has been developed as a small cogeneration system. However, there is a disadvantage that it is necessary to supply hydrogen which is not produced as primary energy as fuel and requires high technology for storage and transportation.
[0003]
When using PEFC as a power source for electric vehicles, it is also possible to mount hydrogen directly by installing a high-pressure hydrogen cylinder, a hydrogen storage alloy tank, or a liquefied hydrogen tank. There are problems such as weight energy density, loss due to evaporation, and problems such as development of hydrogen infrastructure. The raw fuel for electric vehicles is desired to be a liquid fuel having a high volumetric energy density and high weight energy density. As an example of liquid fuel, a method in which methanol capable of producing hydrogen at a relatively low temperature is converted into a gas having a high hydrogen concentration by a reformer is disclosed in JP-A-9-266006 and JP-A-11-92102. Yes.
[0004]
A reformer for a fuel cell is required to have a high load responsiveness because the fuel cell system follows a load of heat such as electric power or hot water regardless of whether it is for electric vehicles or small cogeneration. Load fluctuations that cannot be followed by the fuel cell system can be dealt with by providing a secondary battery system or a heat storage system. However, since the size, weight, and price of the system increase, the responsiveness of the reformer is reduced. It is required to increase.
[0005]
In a reformer disclosed in Japanese Patent Laid-Open No. 9-266006, a raw fuel combustion burner and a fuel cell exhaust gas catalytic combustor in a reforming chamber in which steam is reformed by reacting raw fuel such as methanol with steam. Unit reformers arranged in parallel are arranged, and the volume of the reformer is changed by selecting the unit reformer that supplies raw fuel and combustor fuel by the on-off valve provided at the inlet of the unit reformer A reforming chamber and a catalytic combustion chamber in which flat plate reforming chambers and catalytic combustion chambers are alternately stacked and a raw material and a combustor fuel are supplied using insertion rods or rotating rods. A method for changing the volume is disclosed. In this method, by changing the volume of the reformer, the linearity of the reaction gas is kept constant regardless of the amount of hydrogen produced, and the responsiveness to load fluctuations is enhanced.
[0006]
Japanese Patent Application Laid-Open No. 11-92102 discloses a structure in which the temperature distribution in the reformer is appropriate for a reformer that reacts raw fuel, steam, and air, and a method for supplying raw fuel, steam, and air. ing. This method is characterized by balancing a partial oxidation reaction that is an exothermic reaction and a steam reforming reaction that is an endothermic reaction. This reforming reactor has a high load response because the response speed does not depend on the heat conduction speed from the combustor to the reactor.
[0007]
[Problems to be solved by the invention]
However, in the method disclosed in Japanese Patent Application Laid-Open No. 9-266006, the response speed depends on the heat conduction speed from the combustor to the reactor. There is a point which should be improved about the method etc. which maintain the temperature of the reforming chamber of a state.
[0008]
In the method disclosed in Japanese Patent Application Laid-Open No. 11-92102, when the amount of hydrogen production is small, the linear velocity of the reaction gas in the reactor becomes slow. For example, the production amount is 10% of the maximum hydrogen production amount. Therefore, there is a problem that the response speed in the operation mode in which the load is made to follow the manufacturing amount of 20% becomes slow.
[0009]
In view of such a problem of the prior art, the present invention suppresses fluctuations in the linear velocity of the reaction gas in the reactor with respect to fluctuations in the amount of hydrogen production and does not depend on the heat conduction speed, and improves the resting state. It is an object of the present invention to provide a fuel reformer that can maintain the temperature in the temperature chamber within a predetermined temperature range and a fuel cell system incorporating the fuel reformer.
[0010]
[Means for Solving the Problems]
The fuel reformer of the present invention produces a reformed gas containing hydrogen as a main component by reacting a raw material composed of two or more components including hydrocarbons among hydrocarbon, steam and air. When methanol is used as the hydrocarbon, a reformed gas mainly containing hydrogen is produced mainly by the following reaction formula.
[0011]
CH _Three OH (g) + H ₂ O (g) → 3H ₂ (g) + CO ₂ (g) -61kJ / mol (1)
CH _Three OH (g) +1/2 O ₂ → 2H ₂ (g) + CO ₂ (g) + 184kJ / mol (2)
H ₂ O (g) + CO (g) ← → H ₂ (g) + CO ₂ (g) + 39kJ / mol (3)
[0012]
Equation (1) is an endothermic reaction called a steam reforming reaction, Equation (2) is an exothermic reaction called a partial oxidation reaction, and Equation (3) is an exothermic reaction called a shift reaction. Proceed simultaneously in the reactor. The fuel reformer is equipped with a combustor for supplying heat to the reforming reactor, and combustible exhaust gas such as low-concentration hydrogen-containing gas exhausted from the fuel cell and raw material hydrocarbons are combusted for modification. Heat is supplied to the quality reactor. In the reforming reactor, reaction heat of the reactions (1) to (3) above, heat supplied from the combustor, heat loss such as heat radiation from the reforming reactor, and liquid supplied as necessary. The hydrocarbon and water vaporization heat and the sensible heat for raising the temperature to the reaction temperature are balanced to operate at a constant temperature. The operation temperature is determined by the temperature at which the catalyst operates. For example, when methanol is used as the hydrocarbon, operation is performed at 200 to 400 ° C., and when LNG or the like is used, operation is performed at 700 to 900 ° C. The temperature is controlled by adjusting the ratio of the partial oxidation reaction and the steam reforming reaction by adjusting the ratio of hydrocarbon, water and air.
[0013]
The fuel reformer of the present invention changes the effective reforming reactor volume in order to increase the responsiveness to load fluctuations, and when the load fluctuates, fluctuations in the linear velocity of the reaction gas flowing in the reactor It has a structure where becomes small. That is, it comprises a base reactor to which hydrocarbons, water and air are supplied regardless of load fluctuations, and a load response reactor to which hydrocarbons, water and air are supplied according to the load. The feed of hydrocarbons, water and air to the load responsive reactor is controlled by a distributor. When the load is small, load response reactors that are not supplied with hydrocarbons, water and air are catalyzed by heat transfer from the combustor, base reactor, and load response reactors supplied with hydrocarbons, water and air. Pause while maintaining temperature.
[0014]
In order to maintain the load-responsive reactor temperature during the rest at the catalyst operating temperature, it is desirable that the load-responsive reactor be efficiently supplied with heat from the combustor and the base reactor. On the other hand, when the load fluctuates, in order to suppress fluctuations in the reaction gas linear velocity, the sum of the volume of the load response reactor is larger than the volume of the base reactor, and there are a plurality of load response reactors. Is desirable. In order to suppress the fluctuation of the linear velocity, it is desirable to arrange three or more, preferably six load response reactors at an equal distance from the base reactor with respect to one base reactor. In order to place load response reactors equidistant from the base reactor, geometrically more than two load response reactors are required. As the number of load response reactors increases, the amount of hydrogen produced can be changed in steps with the number of stages corresponding to the number of load response reactors to be operated, even if the linear speed in the reactor is kept constant. It can follow without sacrificing load response speed. However, if the number of load response reactors is increased too much, there is a problem that the structure of the gas distributor becomes complicated, and about six is appropriate.
[0015]
Since the size of the base reactor is the minimum necessary to keep the catalyst temperature of the load response reactor at the catalyst operating temperature, it is a necessary condition for widening the load response range, so that one load response A larger load response range can be obtained if the cross-sectional area of the reactor is larger than the cross-sectional area of the base reactor.
[0016]
It is desirable that the combustor is disposed between the reforming reactors, for example, between the base reactor and the load responsive reactor, and heat generated in the combustor is efficiently and evenly supplied to the reforming reactor. As a method of disposing the combustor, a method of disposing the base reactor and a portion in contact with the two load response tubes, a method of using the base reactor as an inner tube of a double tube, and a method of using an outer tube as a combustor, base reaction And a method of arranging the reactor and the load response reactor in the combustor.
[0017]
Hydrocarbon, water and air must be supplied / stopped to the load responsive reactor by a distributor depending on the load. As a structure for this purpose, an open / close valve is provided at the connection between the distributor and the load response reactor, and a check valve is arranged at the outlet of each load response reactor, and then the base reactor and each load response reaction are arranged. The structure for joining the reformed gas produced in the vessel is a relatively simple structure.
[0018]
The operation procedure of the on-off valve is important in order to keep the catalyst temperature of the resting load response reactor at the operating temperature. That is, by performing opening and closing operations in the order of increasing symmetry with respect to the base reactor, it is possible to avoid adjacent load response reactors as close as possible and to reduce the temperature distribution of the entire fuel reformer. To work. As the structure of the on-off valve, in addition to the on-off valve such as an electromagnetic valve connected to the load response reactor on a one-to-one basis, it takes the form of a rotary valve and adjusts the rotation angle of one rotary valve. Thus, the connected load response reactor can be opened and closed.
[0019]
The catalyst charged in the base reactor and the load response reactor is a precious metal combustion catalyst such as an alumina-supported platinum catalyst on the upstream side of the reactor, and reforming of a copper-zinc catalyst, nickel catalyst, etc. on the downstream side. It is desirable to place a catalyst. By providing the combustion catalyst on the upstream side of the reactor, a reactor having excellent ignitability at a low temperature during cold start and a high steam reforming reaction rate during operation can be obtained. As the reforming catalyst, a copper-zinc based catalyst is suitable for methanol, and a nickel based catalyst is suitable for hydrocarbons composed of carbon and hydrogen such as methane.
[0020]
In fuel cells, it is known that CO contained in the reformed gas poisons the catalyst and lowers the cell voltage. In a phosphoric acid fuel cell using phosphoric acid as an electrolyte, the CO concentration must be lowered to several vol% or less, and in a polymer solid electrolyte fuel cell using a polymer as an electrolyte, the CO concentration must be reduced to about 100 ppm or less. On the other hand, in the fuel reformer, since the reaction (3) is almost in equilibrium, after the partial oxidation of hydrocarbon and the steam reforming reaction are completed, the shift reaction (3) has a fast reaction rate. For example, by setting the temperature to about 200 ° C. under a copper-zinc catalyst, the reaction (3) proceeds to the right, and the CO concentration can be reduced to about 1 vol%. In order to add the shift reactor function to the fuel reformer, the length of the reforming reactor, that is, the base reactor and the load response reactor is made longer than that of the combustor, and the downstream side of the reforming reactor is air-cooled. To be. Furthermore, it is preferable to provide a heat exchanger on the upstream side of the air-cooled portion of the reforming reactor so that the temperature of the air-cooled portion is about 200 ° C. When air supplied to the reforming reactor is used as a heat medium in the heat exchanger, the air supplied to the reforming reactor can also be preheated.
[0021]
The fuel reformer configured as described above is particularly suitable for applications in which start / stop and load fluctuations are relatively severe. Therefore, it is desirable to use a fuel such as methanol having a low steam reforming reaction temperature.
[0022]
Next, a fuel cell system incorporating the fuel reformer of the present invention will be described. The reformed gas is de-CO 2 by a selective oxidizer that selectively burns CO in the reformed gas produced by the fuel reformer of the present invention. The selective oxidizer is a reactor filled with a catalyst such as platinum-supported ruthenium catalyst on alumina, supplying reformed gas and air according to the CO flow rate, and is a combustible component H ₂ It is a reactor that selectively burns CO out of CO. The selective oxidizer can reduce the CO concentration in the reformed gas to 100 ppm or less. The degassed reformed gas is supplied as fuel for a fuel cell, for example, a polymer solid oxide fuel cell. In fuel cells, H in the reformed gas ₂ About 80% of the reaction is consumed, generating electricity, water and heat. H from the fuel cell ₂ The reformed gas having a concentration of about 5 to 10 vol% is discharged and burned in the combustor in the fuel reformer of the present invention to be used as a heat source for the reforming reactor.
[0023]
In order to keep the temperature of the fuel reformer at the catalyst operating temperature, the amount of heat when the exhaust gas discharged from the fuel cell is burned and the temperature of the fuel reformer are detected, and the hydrocarbon is appropriate for the load demand. The amount of water and air is calculated by the controller and controlled. In order to determine the amount of heat, the hydrogen concentration and flow rate of the exhaust gas may be detected. When the amount of heat is high and when the temperature of the fuel reformer is high, the ratio of the steam reforming reaction is increased. That is, the flow rate of water is set high, and the amount of hydrocarbons and air is set low. Conversely, when the amount of heat is low and the temperature of the fuel reformer is low, the ratio of the partial oxidation reaction is increased. That is, the flow rate of water is set low, and the amount of hydrocarbon and air is set high. The controller controls the above control at appropriate time intervals, for example, by a method such as PDI control, and follows the fluctuation of the hydrogen load while keeping the fuel reformer at the operating temperature.
[0024]
When such a system is used for a mobile power source such as an electric vehicle in which a hydrocarbon having a high energy density is frequently used because of frequent stoppages and load fluctuations, it is desirable to use methanol as the hydrocarbon. On the other hand, in stationary systems such as cogeneration, it is desirable to use natural gas-based hydrocarbons that allow easy circulation of city gas, propane gas, etc., and the fuel reformer of the present invention uses hydrocarbons. In comparison, the start / stop speed is slow, but natural gas hydrocarbons can also be used.
[0025]
As described above, the fuel reformer according to the present invention produces a reformed gas mainly composed of hydrogen by reacting a raw material composed of two or three components including hydrocarbon, steam and air. In a fuel reformer including a reforming reactor that performs combustion and a combustor that burns combustible gas and supplies heat to the reforming reactor, the reforming reactor is always supplied with raw materials when the fuel reformer is in operation. And a distributor for distributing the raw material to the base reactor and the load responsive reactor. .
[0026]
It is desirable that the reactor closest to the base reactor is a load response reactor, and that there are three or more load response reactors closest to one base reactor. Moreover, it is desirable that the cross-sectional area of the load-responsive reactor in the direction orthogonal to the direction of the raw material flow is greater than or equal to the cross-sectional area of the base reactor. A combustor is preferably disposed between the reforming reactors, and the combustor can be disposed, for example, in contact with the base reactor and the two load response reactors. The base reactor and the combustor may have a double tube structure in which the base reactor is disposed inside and the combustor is disposed outside, or the base reactor and the load response reactor are disposed in one combustor. May be.
[0027]
Each distributor is provided with an on / off valve at a portion connected to the load response reactor, and the on / off valve can be controlled to open / close according to the amount of hydrogen produced. Further, the distributor is provided with a rotary valve that performs parallel supply and shutoff of the raw materials to each load response reactor according to the rotational position, and is configured to control the rotational position of the rotary valve according to the amount of hydrogen production. You can also. It is preferable to control the valves of the distributor in the order in which the load response reactor for producing the reformed gas is arranged symmetrically with respect to the base reactor.
[0028]
A noble metal catalyst can be arranged on the raw material inlet side of the reforming reactor, and a reforming catalyst containing copper and zinc can be arranged on the outlet side. Further, a noble metal catalyst can be disposed on the raw material inlet side of the reforming reactor, and a reforming catalyst containing nickel can be disposed on the outlet side.
[0029]
The length of the reforming reactor is longer than that of the combustor, and a structure in which a heat exchanger is provided in a copper zinc catalyst layer in which the copper zinc catalyst in the reforming reactor is disposed, and mainly on the upstream side of the heat exchanger. A reformed gas can be produced by reacting hydrocarbons, and a reaction for converting carbon monoxide and water vapor in the reformed gas into hydrogen and carbon dioxide can be performed downstream of the heat exchanger. At this time, it is preferable that the heat medium of the heat exchanger is air, the temperature of the reformed gas is lowered by the heat exchanger, and the air in the raw material is preheated.
[0030]
The hydrocarbon can be methanol. In addition, the fuel reformer may be configured from a plurality of basic units, with the base reactor and the load response reactor and the combustor in the immediate vicinity of the base reactor as basic units.
[0031]
The fuel cell system according to the present invention includes a reforming reactor and a modified reactor for producing a reformed gas mainly composed of hydrogen by reacting a raw material comprising two or three components of hydrocarbon, steam and air. A fuel reformer including a combustor that supplies heat to the quality reactor, a selective oxidizer that selectively burns carbon monoxide in the reformed gas produced by the fuel reformer, and an ion conductor Electrodes are arranged on both sides of an electrolyte membrane, one side is supplied with a reformed gas from which carbon monoxide has been removed by a selective oxidizer, and the other is supplied with humidified air to electrochemically oxidize hydrogen in the reformed gas. In a fuel cell system including a fuel cell that generates electricity and water, the above-described fuel reformer is used as a fuel reformer, and the reformed gas having a low hydrogen concentration discharged from the fuel cell is fuel-modified. It supplies to the combustor of a mass device.
[0032]
This fuel cell system includes a means for calculating the combustion heat of the reformed gas having a low hydrogen concentration discharged from the fuel cell, a means for measuring the temperature of the fuel reformer, a power load requirement for the fuel cell, and a combustion And a controller for determining the composition, flow rate and operation of the distributor to be supplied to the fuel reformer based on the heat and the temperature of the fuel reformer.
The fuel cell system of the present invention is suitable as a fuel cell system for an electric vehicle equipped with a motor. At this time, methanol is used as the hydrocarbon.
[0033]
The fuel cell system of the present invention using natural gas as a hydrocarbon can be applied to a cogeneration system. At that time, a water-cooled heat for cooling the reformed gas between the fuel reformer and the selective oxidizer. It can comprise the exchanger and can take the composition which uses the water discharged from the heat exchanger for hot water supply.
[0034]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. In the following drawings, the same functional parts are denoted by the same reference numerals, and redundant description is omitted.
FIG. 1 is a block diagram showing an example of a fuel reformer according to the present invention, FIG. 1 (b) is a side view, and FIG. 1 (a) is an AA 'sectional view thereof. In this fuel reformer, six load response reactors 2 to 7 are arranged at equal distances and at equal intervals around one base reactor 1, and the berth reactor 1 and the load response reactors 2 to 7 are arranged. Between the two load response reactors and the base reactor 1, six combustors 8 are arranged in between. Air was supplied to the air piping 9 branched into seven using a blower, and the electromagnetic on-off valves 10 were respectively arranged in the piping portions connected to the load response reactors 2 to 7. Methanol was used as the hydrocarbon, and methanol was supplied through a pipe having the same structure as the air pipe. Methanol was supplied to a pipe 11 branched into seven by a pump, and an electromagnetic on-off valve 12 was arranged in a pipe portion connected to the load response reactors 2 to 7. Similarly, water was supplied by a pump using a pipe 13 branched into seven, and an electromagnetic on-off valve 14 was arranged in a pipe portion connected to a load response reactor. Cracking pressure 0.07 kg / cm at the outlets of the base reactor 1 and load response reactors 2-7 ² The check valve 16 was attached and joined to the pipe 15.
[0035]
The base reactor 1 and the load response reactors 2 to 7 had a diameter of 40 mm and a length of 300 mm, and the upstream 40 mm was filled with an alumina-supported platinum catalyst and the remaining 260 mm was filled with a copper-zinc catalyst. In both cases, the catalyst is a cylindrical pellet having a diameter of 3 mm and a height of 3 mm. A honeycomb-shaped catalyst can also be used, but in that case, the diameter is selected so that gas distribution between the base reactor 1 and the load-responsive reactors 2 to 7 connected in parallel is performed appropriately. The pressure loss of the base reactor and the load response reactor during rated operation is 0.2 to 0.4 kg / cm. ² It is desirable to select the reactor diameter and the catalyst structure so as to be approximately.
[0036]
Although piping of the combustion gas and air to the combustor 8 is omitted in the drawing, a mixed gas of low-concentration hydrogen gas and air is distributed and supplied to each combustor 8. The gas supply to the combustor 8 was made to face the gas flow in the base reactor 1 and the load response reactors 2 to 7 from the bottom in the figure. In the base reactor 1 and the load response reactors 2 to 7, the partial reforming reaction has a higher reaction rate than the steam reforming reaction, so that the heat generation amount is higher on the upstream side and the heat absorption amount is higher on the downstream side. Therefore, the downstream side has priority over the heat supply from the combustor, and the temperature distribution is reduced. The diameter of the combustor 8 was 20 mm, and the length was 200 mm. The combustion catalyst charged into the combustor 8 was an alumina-supported platinum catalyst with 3 mm pellets. The combustion catalyst can also be a honeycomb catalyst. In order to reduce the CO concentration in the reformed gas, the length of the combustor 8 is made shorter than the length of the reforming reactors 1 to 7, and the downstream side of the reforming reactor is structured to be air-cooled. ) Shift reaction to the right.
[0037]
Although the base reactor 1 is always in an operating state, the load response reactors 2 to 7 are in an operating state or in a resting state by opening and closing the on-off valves 10, 12, and 14. Even when the load responsive reactors 2-7 are at rest, the catalyst is maintained at operating temperature by heat conduction from the base reactor 1 and the combustor 8. From the state in which the catalyst temperature of the load-responsive reactors 2 to 7 that are not operating due to heat conduction from the base reactor 1 and the combustor 8 is at the operating temperature, the load-responsive reactors 2, 3, 4, and 5 according to the load amount. , 6 and 7, the electromagnetic on-off valves 10, 12, and 14 are opened, and the load response reactors are operated in the order of increasing symmetry with respect to the base reactor 1.
[0038]
In FIG. 1, supply / shutoff of air to the load response reactors 2 to 7 through the air pipe 9 is performed by the electromagnetic on-off valves 10 provided corresponding to the load response reactors 2 to 7, and carbonization is performed. Supply and shut-off of hydrocarbons to the load response reactors 2 to 7 through the hydrogen pipe 11 are performed by the electromagnetic on-off valves 12 provided corresponding to the load response reactors 2 to 7, respectively. The example which performs supply and interruption | blocking of the water to the load response reactors 2-7 via 1 by the electromagnetic on-off valve 14 provided corresponding to each load response reactor 2-7 was demonstrated. However, the supply / shutoff control of air, hydrocarbons, and water to the load response reactors 2 to 7 can be performed by means other than the electromagnetic on-off valves 10, 12, and 14. As an example, a rotary valve type gas distributor in which the piping 9 (11, 13) and the electromagnetic on-off valve 10 (12, 14) are integrated will be described with reference to FIG. FIG. 2B is a side view of the rotary on-off valve 30, and FIG. A rotary valve 18 is housed in the rotary valve housing 17. A black radial portion of the rotary valve 18 illustrated in FIG. 2A is a communication portion. Accordingly, the state of FIG. 2A illustrates a state in which hydrocarbons, water, or air is supplied to all the load response reactors 2 to 7. The rotary on-off valve 30 has a built-in step motor. By rotating the rotary valve 18 by 8 degrees counterclockwise, the load response reactors 2 to 7 are moved in the order of 7, 6, 5, 4, 3, 2. To pause. In order to change the load response reactors 2 to 7 from the resting state to the operating state, the rotary valve 18 is rotated clockwise by 8 °, contrary to the resting state. The rotary on-off valve 30 is always open with respect to the base reactor 1.
[0039]
FIG. 3 is a block diagram showing another example of the fuel reformer according to the present invention, FIG. 3 (b) is a side view of the fuel reformer, and FIG. 3 (a) is an AA 'sectional view thereof. In this example, the combustor 8 ′ has a double tube structure with the base reactor 1. The diameter of the inner tube of the double tube was 40 mm, and the diameter of the outer tube was 60 mm. The lengths of the base reactor 1, the load response reactors 2 to 7, and the combustor 8 are 300 mm for the reactors 1 to 7 and 200 mm for the combustor 8 as in the fuel reformer shown in FIG.
[0040]
FIG. 4 is a block diagram showing another example of the fuel reformer according to the present invention, FIG. 4 (b) is a side view of the fuel reformer, and FIG. 4 (b) is an AA 'sectional view thereof. The fuel reformer in this example has a structure in which the base reactor 1 and the load response reactors 2 to 7 are accommodated in the combustor 8 ″. The outer diameters of the base reactor 1 and the load response reactors 2 to 7 are The inner diameter of 40 mm and the combustor 8 ″ was 120 mm. The lengths of the base reactor 1, the load response reactors 2 to 7, and the combustor 8 were 300 mm for the reactors 1 to 7 and 200 mm for the combustor 8 as in the fuel reformer shown in FIG.
[0041]
As described above, three types of fuel reformers composed of the base reactor 1 and the seven reactors of the load response reactors 2 to 7 are combined with 7.7 cc / min of methanol and 1.4 cc of water per reactor. When 9.1 L / min of air was supplied for operation, the combustor 8 was thermally independent without supplying combustion gas, and 9.7 L of H per reactor ₂ Could be manufactured. H at this time ₂ The concentration was 40 vol% and the CO concentration was 3 vol%. Compared with the case where only the base reactor 1 is operated, when the base reactor 1 and all of the load response reactors 2 to 7 are operated, the heat radiation amount is relatively small, so the temperature is 15 The temperature rose.
[0042]
Each reactor is operated with methanol of 6.2 cc / min, water of 2.5 cc / min, and air of 2.8 L / min. Combustor 8 is supplied with combustion gas to adjust the reactor temperature. When kept at 300 ° C., 8.9 L of H / reactor ₂ Could be manufactured. H at this time ₂ The concentration was 50 vol%, and the CO concentration was 4 vol%. Compared with the case where only the base reactor 1 is operated, when the base reactor 1 and all of the load response reactors 2 to 7 are operated, the amount of heat radiation becomes relatively small. The amount of combustion gas supplied to 8 was 5% less.
[0043]
FIG. 5 is a block diagram showing another example of the fuel reformer according to the present invention. FIG. 5 (a) is a side view of the fuel reformer, and FIG. 5 (b) is an AA 'sectional view thereof. This fuel reformer includes a heat exchanger 20, an air pipe 9 enters from the reformed gas pipe 15 side, an air pipe 19 in a shift reaction section in the reforming reactor, and a heat exchanger 20 in the reformer. Then, it is led to the reactor through the air pipe 21 of the reforming reaction section in the reforming reactor. The air led to the air pipe 19 in the shift reaction section in the reforming reactor flows into the heat exchanger 20 from the air inflow section 24 of the heat exchanger 20 as shown in FIG. Through the air flow path 23 between the quality gas flow paths 22, the air is discharged from the air discharge part 25 to the air pipe 21 of the reforming reaction part in the reforming reactor. That is, the reformed gas is cooled by the heat exchanger 20 in the reformer, and the air is preheated. The fuel reformer shown in FIG. 1, FIG. 3 and FIG. The reformed gas temperature in the shift reaction part is low. For this reason, the shift reaction of (3) was advanced to the right side in the shift reaction part, and the CO concentration in the reformed gas could be reduced to 1 vol%.
[0044]
FIG. 6 is a diagram illustrating a configuration example of an on-off valve provided in a distributor that supplies raw materials to the load response reactors 2 to 7. FIG. 6A shows a configuration in which an open / close valve is provided in each raw material supply pipe as shown in FIGS. 1 and 3 to 5. FIG. 6B shows a configuration in which one on-off valve is omitted. When a liquid such as methanol is used as the hydrocarbon, the on-off valve of the hydrocarbon and water can be shared in the configuration of FIG. 6B, and when a gas such as natural gas is used as the hydrocarbon, carbonization is performed. Hydrogen and air on-off valves can be shared. When the on-off valve is shared between liquids or between gases, the responsiveness of the fuel reformer is not sacrificed. However, if the on-off valve is shared for gas and liquid, hydrocarbons and water introduced to the reactor This is not preferable because the composition of air temporarily becomes unstable.
[0045]
FIG. 7 is a cross-sectional view of a fuel reformer according to the present invention. In the fuel reformer shown so far, the diameters of the base reactor 1 and the load response reactors 2 to 7 are equal, and the load reaction reactors 2 to 7 are configured to be six with respect to the base reactor 1. As shown in FIG. 7, the diameter of the base reactor 1 may be reduced. The base reactor 1 and the combustor 8 may be operated so long as the load reactors 2 to 7 can maintain the operating temperature. FIG. 7C shows a configuration in which four load response reactors are provided for the base reactor 1, and three, five, or other numbers of load response reactors are possible.
[0046]
FIG. 8 shows a fuel reformer in which the base reactor 1 and the load response reactors 2 to 7 are formed as one block B1, B2, B3,... And four blocks B1 to B4 are arranged in parallel. It is sectional drawing. FIG. 8A shows a configuration example in which the combustor 8 is also arranged in a portion surrounded by three load response reactors at the boundary between the blocks. FIG. 8B is a configuration example in which four blocks B1 to B4 are simply arranged in parallel. In order to make the figure easy to see, the base reactor 1 is shown hatched. In any system, it is possible to keep the load-responsive reactors 2 to 7 that are at rest during partial load at the catalyst operating temperature. The number of load response reactors included in the unit blocks B1, B2, B3,... Is not limited to six, and the number of parallel blocks B1, B2, B3,. It is not possible. The capacity of the fuel reformer can be increased by arranging a plurality of blocks B1, B2, B3,.
[0047]
The structure of the reaction tube and the combustor of the fuel reformer shown in FIGS. 1 and 3 to 8 is not limited to a structure in which pipes are bundled. For example, an aluminum block can be produced by machining, or an integrated part can be produced by casting. In order to reduce the temperature distribution in the fuel reformer, it is desirable that the heat conduction among the base reactor 1, the load response reactors 2 to 7, and the combustor 8 is high. It is better to integrally form the structure shown in FIG. 8 by a method such as machining or casting. On the other hand, when focusing on weight reduction and material cost reduction, a structure in which pipes are bundled is desirable. The shape of the reactor is not limited to a cylindrical shape, and a structure with excellent heat conduction and high volumetric efficiency is desirable. In the case of a structure in which pipes are bundled, there are also methods in which polygonal pipes are used or the space between the reforming reactors is used as it is as a combustor.
[0048]
FIG. 9 is a block diagram showing an example of a fuel cell system incorporating the fuel reformer of the present invention. Fuel is supplied to the reactor 105 of the fuel reformer of the present invention through the vaporizer 104 by the fuel pump 101, water by the water pump 102, and air by the air blower 103. For example, when a pressurized gas such as city gas or LPG is used as the fuel, a flow rate controller is used instead of the fuel pump 101. The vaporizer 104 can be provided separately from the fuel reformer, but it is also possible to supply water and liquid fuel to the reactor 105 of the fuel reformer and vaporize it inside.
[0049]
The reformed gas produced in the reactor 105 of the fuel reformer oxidizes the CO in the CO remover 106 to produce CO. ₂ And The oxidizing agent for CO oxidation is air, which is supplied from the CO blower air blower 107. The CO remover 106 is a combustible component H ₂ And a reactor filled with a catalyst that selectively oxidizes CO among CO. The reformed gas from which CO has been removed is humidified by the fuel gas humidifier 108 and supplied to the fuel cell 110. As shown in FIG. 10, the fuel cell 110 includes an electrode-electrolyte assembly in which a fuel electrode 110A and an air electrode 110C are arranged on both sides of an ion conductor 110E, and a separator 110S that is an electronic conductor having a gas flow path. The held configuration becomes a basic unit cell, and the cells are stacked. Water is supplied to the fuel gas humidifier 108 by a fuel humidification water pump 109. Humidified air is supplied from the air electrode air blower 201 via the air electrode humidifier 203 to the air electrode 110C of the fuel cell 110. Water is supplied from the air electrode humidification water pump 202 to the air electrode humidifier.
[0050]
The fuel gas discharged from the fuel cell 110 is mixed with the air supplied from the combustor blower 111 and burned in the combustor 112 to be a heat source for the reforming reactor 105 of the reformer. The air discharged from the fuel cell 110 is separated into air and water by the air / water separator 204, the water is supplied to the water pumps 102, 109, and 202, and the gas becomes exhaust gas. In order to cool the fuel cell 110, a cooling system including a cooling water circulation water pump 271, a heat exchanger 272 in the fuel cell 110, and a heat load 273 is provided. Further, when natural gas is used as the hydrocarbon raw material to be supplied to the fuel reformer 105, the reformed gas discharged from the reforming reactor 105 of the fuel reformer becomes high temperature. A reformed gas cooling system including a cooling water circulation water pump 281, a heat exchanger 282, and a heat load 283 is provided between the selective oxidizers 106.
[0051]
The amount of fuel, air, and water supplied to the reforming reactor 105 of the fuel reformer is determined by the controller 303 based on the load demand, the measured value of the thermometer 302, and the hydrogen flow rate measured by the sensor 301. . The load request is provided to the controller 302 in the form of a power load request amount or a hydrogen request amount. Next, a method for determining the amount of fuel, air, and water in the controller 303 will be briefly described. Here, in order to explain the basic concept, the case where the reaction in the reformer is only the steam reforming of the formula (1) and the partial oxidation of the formula (2) will be described. 3) The shift reaction of the formula also occurs. When the ratio of steam reforming and partial oxidation is x: 1−x, the following equation (4) is established from the above equations (1) and (2).
CH _Three OH (g) + xH ₂ O (g) + (1-x) / 2 O ₂ → (2 + x) H ₂ (g) + CO ₂ (g) + (184-248x) kJ / mol (4)
[0052]
For example, the heat balance when generating y moles of hydrogen per minute is expressed by the following equation (5).
(184-248x) y / (2 + x) + W + σΔT = 0 (5)
Here, W (kJ / min) is the calorific value of the combustor, and is calculated based on the hydrogen flow rate measured by the sensor 301. σ (kJ / min · ° C.) is a coefficient of heat loss, and ΔT (° C.) is a temperature difference between the outside air and the reactor. Therefore, the amount of fuel, air, and water with respect to the required amount of hydrogen can be obtained from equations (5) and (4). As an example of the control method, when the load requirement or the calorific value W of the combustor suddenly fluctuates, the amount of fuel, air, and water is abruptly varied according to the equations (5) and (4), and the temperature in the steady state There is a method of adjusting the steam reforming ratio x while applying feedback so that the measured value of the total 302 becomes an appropriate value for the catalyst operation.
[0053]
The maximum amount of hydrogen produced per reforming reactor 105 is a function of the steam reforming ratio x. This is because the speed of the steam reforming reaction of the formula (1) is different from the speed of the partial oxidation reaction of the formula (2). Therefore, the number N for opening the on-off valve 12 when the reactor volumes of the base reactor 1 and the load response reactors 2 to 7 are equal is expressed by the following equation (6).
N = Floor (F / v (x)) (6)
Here, Floor (z) is a function of rounding down the decimal point, F is a required amount of hydrogen, and v (x) is a maximum hydrogen production amount per reactor. The reason why the decimal part is rounded down in the equation (6) is that the base reactor 1 is always open.
[0054]
The electric output of the fuel cell 110 is connected to an AC load 252 via a fuel cell orthogonal transformer 251. A power storage means 253 is connected to the AC load 252 via a power storage means orthogonal converter 254 in parallel with the fuel cell orthogonal converter 251.
[0055]
For example, in the electric vehicle C2 shown in FIG. 11, the AC load 252 of the fuel cell system C1 serves as a motor for driving the electric vehicle C2. Fuel is supplied from the fuel tank 401 to the fuel cell system C1. In this case, since the power load is the main component and the load fluctuation is severe, it is desirable to include the power storage means 253 and the power storage means orthogonal converter 254, and the thermal load 273 is a cooling device such as a radiator. By using the fuel reformer of the present invention, it becomes possible to improve the load responsiveness of the fuel cell 110 and to design a system with less power stored in the power storage means 253.
[0056]
In an application connected to the system power supply 402 via the connector 403 like the small cogeneration system C3 shown in FIG. 12, it is not necessary to include the power storage means 253 and the power storage means orthogonal transformer 254. In this case, as an AC load 252, an electric device such as a lighting is connected via the connector 403. Further, the fuel to the fuel cell system C1 is supplied from the system gas pipe 404 and the water is supplied from the water supply 405. At this time, the heat load 273 is operated as a heat source for the hot water supply 406 and the heating device 407. Further, when natural gas is used as the hydrocarbon raw material supplied to the fuel reformer 105, the reformed gas discharged from the reforming reactor 105 of the fuel reformer becomes high temperature. Therefore, a water-cooled heat exchanger 282 that cools the reformed gas is provided between the reforming reactor 105 and the selective oxidizer 106, and water discharged from the heat exchanger 282 may be used for hot water supply. In a cogeneration system connected to a grid power supply, there are a method of operating in response to an electric power load and a method of operating in response to a thermal load, but considering the energy efficiency of the entire system connected in the electric power system, It is more energy efficient to operate in response to a load. By using the fuel reformer of the present invention, the responsiveness of the fuel cell system to the heat load 273 is increased, and it is not necessary to provide heat storage means such as a heat storage tank.
[0057]
【The invention's effect】
According to the present invention, the catalyst temperature of the resting load response reactor can always be kept at an operable temperature, and the load responsiveness of the fuel reformer can be improved.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing an example of a fuel reformer according to the present invention.
FIG. 2 is a configuration diagram showing an example of a rotary valve type gas distributor.
FIG. 3 is a block diagram showing another example of a fuel reformer according to the present invention.
FIG. 4 is a configuration diagram showing another example of a fuel reformer according to the present invention.
FIG. 5 is a configuration diagram showing another example of a fuel reformer according to the present invention.
FIG. 6 is a diagram showing a configuration example of an on-off valve provided in a distributor that supplies a raw material to a load response reactor.
FIG. 7 is a cross-sectional view of a fuel reformer according to the present invention.
FIG. 8 is a cross-sectional view showing a configuration example of a fuel reformer assembly.
FIG. 9 is a configuration diagram showing an example of a fuel cell system using the fuel reformer of the present invention.
FIG. 10 is a schematic diagram showing the configuration of a fuel cell.
FIG. 11 is a schematic diagram of an electric vehicle.
FIG. 12 is a schematic diagram of a cogeneration system.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Base reactor, 2-7 ... Load response reactor, 8 ... Combustor, 9 ... Air piping, 10 ... Air on-off valve, 11 ... Hydrocarbon piping, 12 ... Hydrocarbon on-off valve, 13 ... Water Piping for water, 14 on-off valve for water, 15 ... piping for reformed gas, 16 ... check valve, 17 ... rotary valve housing, 18 ... rotary valve, 19 ... air piping in shift reaction section in reforming reactor, DESCRIPTION OF SYMBOLS 20 ... Heat exchanger in reforming reactor, 21 ... Air piping in reforming reaction part in reforming reactor, 22 ... Reformed gas flow path in heat exchanger, 23 ... Air flow in heat exchanger 24, air inflow part in the heat exchanger, 25 ... air discharge part in the heat exchanger, 30 ... rotary on-off valve, 101 ... fuel pump, 102 ... water pump, 103 ... air blower, 104 ... vaporizer 105 ... Reforming reactor of fuel reformer, 106 ... CO remover, 107 ... CO blower air blower, 108 Humidifier for fuel gas, 109 ... Water pump for fuel humidification, 110 ... Fuel cell, 111 ... Blower for combustor, 112 ... Combustor, 201 ... Air blower for air electrode, 202 ... Water pump for humidification of air electrode, 203 ... For air electrode Humidifier, 204 ... Steam separator, 251 ... Fuel cell orthogonal converter, 252 ... AC load, 251 ... Electric power storage means, 253 ... Electric power storage means orthogonal converter, 271 ... Cooling water circulation water pump, 272 ... Fuel In-battery heat exchanger, 273 ... heat load, 281 ... cooling water circulation water pump, 282 ... heat exchanger, 283 ... heat load, 301 ... sensor, 302 ... thermometer, 303 ... controller, 401 ... fuel tank, 402 ... system Power supply, 403 ... Connector, 404 ... System gas piping, 405 ... Water supply, 406 ... Hot water supply, 407 ... Heating equipment, B1-B4 ... Basic unit reactor, C1 ... Fuel electricity System, C2 ... electric car, C3 ... cogeneration system

Claims

A reforming reactor for producing a reformed gas mainly composed of hydrogen by reacting a hydrocarbon, water vapor, and air containing two or three components of the raw material containing hydrocarbon, and combusting the combustible gas to improve the reforming gas. comprising a combustor for supplying heat to the quality reactor, a distributor for distributing the feed to the reforming reactor, and a controller,
The reforming reactor is composed of a base reactor and three or more load response reactors arranged at equal distances and at equal intervals around the base reactor,
The controller controls the distributor to reduce the number of the load-responsive reactors that are operated while resting part of the load-responsive reactor when the load is small, and to operate when the load is large Control is performed to increase the number of response reactors, and the raw material is always supplied to the base reactor during operation of the fuel reformer, and reformed gas is supplied to the plurality of load response reactors according to the amount of hydrogen produced. A fuel reformer characterized by supplying the raw materials in an order in which the load response reactor to be manufactured is arranged symmetrically with respect to the base reactor.

2. The fuel reformer according to claim 1 , wherein a cross-sectional area of one of the load-responsive reactors in a direction orthogonal to a direction of a raw material flow is equal to or larger than a cross-sectional area of the base reactor. vessel.

3. The fuel reformer according to claim 1, wherein the combustor is disposed between the reforming reactors.

4. The fuel reformer according to claim 3, wherein the combustor is in contact with the base reactor and the two load response reactors.

3. The fuel reformer according to claim 1, wherein the base reactor and the combustor have a double pipe structure in which the base reactor is disposed inside and the combustor is disposed outside. A featured fuel reformer.

3. The fuel reformer according to claim 1, wherein the base reactor and the load response reactor are arranged in one combustor.

The fuel reformer according to any one of claims 1 to 6, wherein each of the distributors is provided with an on-off valve in a portion connected to the load response reactor, and the controller is controlled according to a hydrogen production amount. A fuel reformer characterized in that each on-off valve is controlled to open and close below.

The fuel reformer according to any one of claims 1 to 6, wherein the distributor includes a rotary valve that supplies and shuts off the raw material in parallel to each load response reactor according to a rotational position, and produces hydrogen. A fuel reformer that controls the rotational position of the rotary valve under the control of the controller according to the amount.

The fuel reformer according to any one of claims 1 to 8, wherein a noble metal catalyst is disposed on a raw material inlet side of the reforming reactor, and a reforming catalyst containing copper and zinc is disposed on an outlet side. A featured fuel reformer.

The fuel reformer according to any one of claims 1 to 8, wherein a noble metal catalyst is arranged on a raw material inlet side of the reforming reactor, and a reforming catalyst containing nickel is arranged on an outlet side. Fuel reformer.

10. The fuel reformer according to claim 9, wherein a length of the reforming reactor is longer than that of the combustor, and a heat exchanger is disposed in a copper zinc catalyst layer in which the copper zinc catalyst in the reforming reactor is disposed. The reformed gas is produced mainly by reacting the hydrocarbons upstream of the heat exchanger, and carbon monoxide and water vapor in the reformed gas are converted into hydrogen and dioxide on the downstream side of the heat exchanger. A fuel reformer characterized by performing a reaction to convert to carbon.

12. The fuel reformer according to claim 11, wherein the heat medium of the heat exchanger is air, the temperature of the reformed gas is lowered by the heat exchanger, and the air in the raw material is preheated. A fuel reformer.

The fuel reformer according to any one of claims 1 to 12, wherein the hydrocarbon is methanol.

The fuel reformer according to any one of claims 1 to 13, wherein the base reactor, the load response reactor in the immediate vicinity of the base reactor, and the combustor are basic units, and the fuel reformer includes a plurality of basic units. The fuel reformer characterized by the above-mentioned.

A reforming reactor for producing a reformed gas containing hydrogen as a main component by reacting a hydrocarbon, steam and air containing two or three raw materials containing hydrocarbon, and supplying heat to the reforming reactor A fuel reformer including a combustor, a selective oxidizer that selectively burns carbon monoxide in the reformed gas produced by the fuel reformer, and both sides of an electrolyte membrane that is an ionic conductor. An electrode is disposed, the reformed gas from which carbon monoxide has been removed by the selective oxidizer is supplied to one side, and humidified air is supplied to the other side, and the hydrogen in the reformed gas is electrochemically oxidized to generate power. In a fuel cell system including a fuel cell that generates water,
The fuel reformer according to any one of claims 1 to 14 is used as the fuel reformer, and the reformed gas having a low hydrogen concentration discharged from the fuel cell is combusted in the fuel reformer. A fuel cell system, wherein the fuel cell system is supplied to a vessel.

16. The fuel cell system according to claim 15, wherein means for calculating combustion heat of the reformed gas having a low hydrogen concentration discharged from the fuel cell, means for measuring the temperature of the fuel reformer, fuel A controller for determining a composition, a flow rate of the raw material to be supplied to the fuel reformer and an operation of the distributor based on a power load requirement for the battery, the combustion heat, and a temperature of the fuel reformer; A fuel cell system.

17. The fuel cell system according to claim 15 or 16, wherein the hydrocarbon is methanol.

An electric vehicle equipped with a motor, comprising the fuel cell system according to any one of claims 15 to 17.

The fuel cell system according to claim 15 or 16, wherein the hydrocarbon is natural gas.

20. The fuel cell system according to claim 15, 16 or 19, and a water-cooled heat exchanger that cools the reformed gas between the fuel reformer and the selective oxidizer, and is discharged from the heat exchanger. Cogeneration system characterized by using water to be used for hot water supply.