JP3738888B2

JP3738888B2 - FUEL CELL POWER GENERATION DEVICE HAVING RAW FUEL SWITCHING FACILITY AND METHOD

Info

Publication number: JP3738888B2
Application number: JP2000098487A
Authority: JP
Inventors: 仁人千田; 正小松
Original assignee: Fuji Electric Holdings Ltd
Current assignee: Fuji Electric Co Ltd
Priority date: 1999-05-11
Filing date: 2000-03-31
Publication date: 2006-01-25
Anticipated expiration: 2020-03-31
Also published as: JP2001028270A

Description

【０００１】
【発明の属する技術分野】
この発明は、複数の異なる組成の原燃料を運転中に切替えて使用するための原燃料切替設備を有する燃料電池発電装置とその運転方法に関する。
【０００２】
【従来の技術】
燃料電池は、天然ガス（都市ガス），ＬＰＧ，メタノール等の炭化水素改質原燃料を、水蒸気改質して得られた改質ガス中の水素と、空気中の酸素とを、燃料電池の燃料極および空気極にそれぞれ供給し、電気化学反応に基づいて発電を行うもので、原燃料を改質する改質装置としては、原燃料に水を加えて加熱し、水蒸気と原燃料を触媒を用いて水素リッチなガスに改質する水蒸気改質反応を利用したものがよく知られている。
【０００３】
近年、原燃料切替設備を有する燃料電池発電装置、例えば、都市ガスが遮断された場合でも備蓄してあるＬＰＧ等で燃料電池の運転を継続するシステム（特開平９−１０６８２５号公報参照）や、産業廃棄物，家庭用生ごみ，し尿処理等で発生した消化ガスを有効利用するために，この消化ガスと都市ガスとを交互に利用して燃料電池の連続運転を行う燃料切替えシステムの開発が進められている。
【０００４】
燃料電池の運転継続中、燃料の供給圧力低下検出等の燃料切替え信号により、不定期に燃料Ａから組成の異なる燃料Ｂに切替える場合、燃料Ｂの流量調節弁は燃料切替え時に備え、燃料Ｂへの切替え直後より一定の流量が流れるよう、燃料Ａでの運転中に常に開度保持しておく必要がある。
【０００５】
図９は、２系統の燃料を利用する従来の原燃料切替設備を有する燃料電池発電装置の概略構成を示す。図９において１は燃料Ａの遮断弁、２は燃料Ａの流量調節弁、３は燃料Ａの流量計、４は燃料Ｂの遮断弁、５は燃料Ｂの流量調節弁、６は燃料Ｂの流量計、７はスチームエゼクタ、８は脱硫器、９は改質器、１０はCO変成器、１１は燃料電池本体である。
【０００６】
上記従来装置の動作について、図５および前記図９に基づいて説明する。図５は、従来装置における各種弁の動作を模式的に示す図である。この例では、燃料ガスＡを都市ガス、燃料ガスＢをＬＰＧとして説明する。図５に示すように、切替え信号が時刻ｔ１で発生すると、都市ガス用の遮断弁が開から閉に切替わり、ＬＰＧ用の遮断弁が閉から開に切替わる。
【０００７】
一方、ＬＰＧ用の流量調節弁開度は、都市ガスでの運転中より都市ガス用の流量調節弁の開度×ｊ２で追従し、切替え信号の発生と同時に、一定時間この開度を保持する。ここで、都市ガス用の流量調節弁の開度×ｊ２で算出されるＬＰＧ流量調節弁の開度は、ＬＰＧのガス組成が考慮された、ＬＰＧにとって適正な最適流量（都市ガスの約半分の体積流量）が流れる開度である。
【０００８】
一定時間経過後の時刻ｔ２には、ＬＰＧの流量計に流量が立上るので、ＬＰＧの流量と電池電流によるＰＩ制御に入る。ここで、流量が立上がるとは、「流量計が、正しい流量を認識する」意味である。遮断弁開放直後は、流量計の値はゼロから始まり、直ちに流量計測値をＰＩ制御に用いると、調節弁の動作が不安定になるので、流量計の値が安定してから流量計測値をＰＩ制御に用いるようにする必要があり、この安定した状態を、前述のように流量が立上がった状態という。
【０００９】
なお、図５において、都市ガス流量調節弁の開度は、燃料ガスの再切替に備えて、ＬＰＧの流量調節弁×ｊ１の開度に調整され、都市ガス遮断弁の開放に伴って、都市ガスにとって定格運転において最適な流量（ＬＰＧガスの約２．２倍の体積流量）に相当する流量の供給開始ができるようにスタンバイする。
【００１０】
【発明が解決しようとする課題】
上述のとおり、燃料Ｂの調節弁開度は、切替え直後より燃料Ｂの組成に適したガス流量が流れるよう制御される。
【００１１】
一方、燃料調節弁から改質器の間には一定の容積（主に脱硫器の容積）が存在するため、切替え直後は切替え前の燃料Ａがこの容積中に充満している。この状態で、燃料Ｂへ燃料Ｂの通常の定格流量（燃料Ｂの組成上適切な流量）で切替えてしまうと、燃料調節弁から改質器間の容積中の燃料Ａを燃料Ｂで置換するまでの時間中、改質器には燃料Ａもしくは燃料Ａと燃料Ｂの混合ガスが燃料Ｂの流量で供給されるので、改質器により生成される改質ガス量ひいては燃料電池本体に供給される水素流量が大きく変動し、例えば、都市ガスからＬＰＧに切替える場合には水素不足が生じ、又逆にＬＰＧから都市ガスに切替える場合には、水素過剰，Ｓ／Ｃ異常などの不適正な運転状態となる問題がある。
【００１２】
上記問題について、燃料Ａを都市ガス，燃料ＢをＬＰＧとし、燃料Ａから燃料Ｂに切替える場合の例につき、以下に詳述する。
【００１３】
図４は、従来方式における改質器入口出口におけるガスの挙動を模式的に示す図で、改質器の入口における都市ガス濃度、ＬＰＧ濃度、改質器入口の燃料ガス流量および改質器の出口における改質ガス（水素リッチガス）流量の変化を模式的に示す。図５の弁動作に従い都市ガスからＬＰＧに切替えることにより、流量調節弁から改質器間に充満した都市ガスは、切替え直後よりＬＰＧの流量（都市ガスの約半分のボリューム）で改質器へ送出される。即ち、改質器入口ガス量は、その組成の都市ガス濃度が高い状態にもかかわらず流量が低下するため、改質器出口の改質ガス量は減少する。従って従来方式によれば、上記のように燃料電池において水素不足が生じ、装置の安定した運転に影響が生ずる問題があった。
【００１４】
この発明は、上記問題点を解消するためになされたもので、この発明の課題は、運転を停止することなく燃料Ａから、組成の異なる燃料Ｂへ燃料を切替える際に燃料電池における水素不足や水素過剰，およびＳ／Ｃ異常が生ずることのない安定した運転が可能な、原燃料切替設備を有する燃料電池発電装置とその運転方法を提供することにある。
【００１５】
【課題を解決するための手段】
前述の課題を解決するために、この発明は、燃料電池本体と、原燃料ガスを改質して水素リッチな改質ガスとして，この改質ガスを前記燃料電池本体に供給する改質器と、前記原燃料ガスとして，常時は一つの原燃料ガス（以下燃料Ａという。）を，燃料Ａ遮断弁，燃料Ａ流量計および燃料Ａ流量調節弁を介して前記改質器に供給する燃料Ａ供給装置と、前記燃料Ａ供給停止時には，前記原燃料として他の代替原燃料ガス（以下燃料Ｂという。）を，燃料Ｂ遮断弁，燃料Ｂ流量計および燃料Ｂ流量調節弁を介して前記改質器に供給する燃料Ｂ供給装置とを備えた原燃料切替設備を備えた燃料電池発電装置の運転方法において、前記原燃料ガスを燃料Ａから燃料Ｂに切替える際に、燃料Ｂの切替開始時の時間当たり体積流量（以下、単に流量ともいう。）を，切替前の燃料Ａの流量と同一流量となるようにし、その後は、燃料Ｂの供給流量を，前記改質器出口の改質ガス中の水素ガス量が切替前と同一となるように供給し、前記改質器出口部において燃料Ａの燃料Ｂによるガス置換が完了した後に、燃料Ｂの供給流量を，燃料Ｂの組成に適した最適流量に調節して，原燃料の切替を完了することとする（請求項１）。
【００１６】
上記のような、原燃料ガスの切替方法によれば、切替初期において、切替前の流量がそのまま継続され、ガス置換が完了した後には、切替え後の燃料ガス組成に適した原料ガスの供給が確保されるので、原燃料不足に伴う燃料電池における水素不足や水素過剰，Ｓ／Ｃ異常などが生ずることはなく、安定した燃料電池発電装置の運転が継続できる。
【００１７】
上記の運転方法を実施するための装置としては、請求項２の発明のように、燃料電池本体と、原燃料ガスを改質して水素リッチな改質ガスとして，この改質ガスを前記燃料電池本体に供給する改質器と、前記原燃料ガスとして，常時は一つの原燃料ガス（燃料Ａ）を，燃料Ａ遮断弁，燃料Ａ流量計および燃料Ａ流量調節弁を介して前記改質器に供給する燃料Ａ供給装置と、前記燃料Ａ供給停止時には，前記原燃料として他の代替原燃料ガス（燃料Ｂ）を，燃料Ｂ遮断弁，燃料Ｂ流量計および燃料Ｂ流量調節弁を介して前記改質器に供給する燃料Ｂ供給装置とを備えた原燃料切替設備を備えた燃料電池発電装置において、前記原燃料ガスの切替指令に基づき前記燃料Ａ遮断弁および燃料Ｂ遮断弁がそれぞれ所定の開閉操作をするための遮断弁駆動手段と、前記原燃料ガスを燃料Ａから燃料Ｂに切替える際に，燃料Ｂの切替開始時の流量を，切替前の燃料Ａの流量と同一流量となるようにし，その後は，燃料Ｂの供給流量を，前記改質器出口の改質ガス中の水素ガス量が切替前と同一となるように供給し，前記改質器出口部において燃料Ａの燃料Ｂによるガス置換が完了した後に，燃料Ｂの供給流量を，燃料Ｂの組成に適した最適流量に調節するための燃料Ｂ流量調節弁の開度制御手段と、前記原燃料ガスを燃料Ｂから燃料Ａに再度切替える場合に備えて，燃料Ａの流量を燃料Ｂの前記最適流量と同一流量で供給開始可能となるようにし，その後は，燃料Ａの供給流量を，前記改質器出口の改質ガス中の水素ガス量が切替前と同一となるように供給し，前記改質器出口部において燃料Ｂの燃料Ａによるガス置換が完了した後に，燃料Ａの供給流量を，燃料Ａの組成に適した最適流量に調節するための燃料Ａの流量調節弁の開度制御手段とを設けてなる原燃料切替制御装置を備えるものとする。
【００１８】
上記装置によれば、非常時にのみ原燃料を切替えて、一旦装置を停止することを前提とした燃料電池発電装置以外に、消化ガスを活用して都市ガスと交互に切替え使用するような連続的に切替える燃料電池発電装置にも対応できる。
【００１９】
さらに、上記請求項２に記載の装置において、前記燃料Ａ流量調節弁または燃料Ｂ流量調節弁の内の少なくとも一方は、複数個の流量調節弁を並列に接続してなるもの（請求項３）とするのが、制御上好適である。詳細は後述するが、上記構成によれば、例えば、通常運転時の最適流量として、比較的大流量の燃料Ａ(例えば都市ガス・消化ガス)から少流量の燃料Ｂ(例えばＬＰＧ)への切替時に、切替直後の燃料Ｂの初期流量を燃料Ａと同一としながらも、燃料切替完了後の燃料Ｂでの少流量の燃料による運転時の制御性を十分保ったまま運転を継続することが可能となる。
【００２０】
【発明の実施の形態】
図面に基づき、本発明の実施の形態について以下にのべる。
【００２１】
図１は、本発明の実施例を示す図であり、図９と同じ構成部材には同一の番号を付して説明を省略する。図１が図９と異なる点は、図１においては、原燃料切替制御装置１２を設けた点，およびこれに連携する計測制御信号線（図１における破線部）を設けた点である。上記原燃料切替制御装置１２は、図示しない下記の手段を備える。即ち、前述のように、原燃料ガスの切替指令に基づき前記燃料Ａ遮断弁および燃料Ｂ遮断弁がそれぞれ所定の開閉操作をするための遮断弁駆動手段と、前記原燃料ガスを燃料Ａから燃料Ｂに切替える際に，燃料Ｂの切替開始時の流量を，切替前の燃料Ａの流量と同一流量となるようにし，その後は，燃料Ｂの供給流量を，前記改質器出口の改質ガス中の水素ガス量が切替前と同一となるように供給し，前記改質器出口部において燃料Ａの燃料Ｂによるガス置換が完了した後に，燃料Ｂの供給流量を，燃料Ｂの組成に適した最適流量に調節するための燃料Ｂ流量調節弁の開度制御手段と、前記原燃料ガスを燃料Ｂから燃料Ａに再度切替える場合に備えて，燃料Ａの流量を燃料Ｂの前記最適流量と同一流量で供給開始可能となるようにし，その後は，燃料Ａの供給流量を，前記改質器出口の改質ガス中の水素ガス量が切替前と同一となるように供給し，前記改質器出口部において燃料Ｂの燃料Ａによるガス置換が完了した後に，燃料Ａの供給流量を，燃料Ａの組成に適した最適流量に調節するための燃料Ａの流量調節弁の開度制御手段とを備える。
【００２２】
原燃料ガスの切替指令は、従来の技術の項に記載のとおり、例えば原燃料の供給圧力低下検出に基づく燃料切替え信号による。原燃料を切替える事情によっては、マニュアル指令に基づく信号もあり得る。
【００２３】
次に、この発明の実施例の運転方法について、図２，図３に基づき説明する。図２は、従来の図４に対応するこの発明におけるガスの挙動を示し、図３は、図５に対応する各種弁の動作を示す。前述と同様に、燃料Ａを都市ガス，燃料ＢをＬＰＧとし、燃料Ａから燃料Ｂに切替える場合の例につき説明する。
【００２４】
図３に示すように、切替え信号が時刻ｔ１で発生すると、都市ガス用の遮断弁が開から閉に切替わり、ＬＰＧ用の遮断弁が閉から開に切替わる。一方、ＬＰＧ用の流量調節弁開度は都市ガスでの運転中より都市ガス用の流量調節弁開度×k2で算出される開度で追従し、切替え信号の発生（ｔ１）と同時に、開度変化曲線Ｓに沿って、切替え信号発生時（ｔ１）の都市ガス用の流量調節弁開度×ｊ２で算出される開度に向かわせる。ここで、都市ガス用の流量調節弁の開度×ｋ２で算出されるＬＰＧ流量調節弁の開度は、都市ガスと同一流量が流れる開度であり、都市ガス用の流量調節弁の開度×ｊ２で算出されるＬＰＧ流量調節弁の開度は、前述のようにＬＰＧのガス組成が考慮された、ＬＰＧにとって適正な最適流量（都市ガスの約半分の流量）が流れる開度である。この場合、従来でも同様であるが、エゼクタの吸引能力変化（ＬＰＧ燃料への切替えに伴う改質蒸気の流量増加制御によりエゼクタの吸引力が上昇すること）が考慮される。
【００２５】
図３における開度変化曲線Ｓは、燃料流量調節弁から改質器間の容積による燃料ガスのガス置換遅れを考慮した開度変化であり、改質器出口の改質ガス中の水素ガス量が切替前と略同一となるように，あらかじめシミュレーションにより求めた所定の演算値の変化曲線に基づき流量を変化させる。原燃料切替制御装置１２における燃料Ｂ流量調節弁の開度制御手段は、上記のような流量調節制御機能を備える。
【００２６】
一定時間経過後の時刻ｔ２には、ＬＰＧの流量計に流量が立上るので、ＬＰＧの流量と電池電流によるＰＩ制御に入る。なお、図３において、都市ガス流量調節弁の開度は、原燃料の再切替に備えて、ＬＰＧの流量調節弁×ｋ１の開度に調整され、都市ガス遮断弁の開放に伴って、ＬＰＧガスの最適流量と同一の都市ガス流量の供給開始ができるようにスタンバイする。
【００２７】
図２は、本発明による改質器の入口における都市ガス濃度、ＬＰＧ濃度、改質器入口の燃料ガス流量および改質器の出口における改質ガス流量の変化を模式的に示したものである。都市ガスとＬＰＧとでは改質ガスに含まれる水素の割合が厳密にいえば異なるので、前述のように、改質ガス中の水素ガス量が切替前と略同一となるようにすることは、図２のように改質ガス流量を一定としても、実現できないが、説明の便宜上、図２は、図４と同様に表示した。実際のシミュレーションは、水素ガス量ベースで行う。
【００２８】
上記のように、図２の方法で原燃料を切替えることにより、切替え初期のガス不足を防止することが可能となり、改質器出口の改質ガス量，水素ガス量の安定化が図れる。
【００２９】
ところで、上述のような燃料切替を実現するにあたり、特に切替る燃料が比較的大流量を要する燃料Ａ(例えば都市ガス・消化ガス)から比較的小流量で運転可能な燃料Ｂ(例えばＬＰＧ)に切替る場合、燃料Ｂの流量調節弁は燃料Ａの通常運転時と同流量の流量を確保する大きなCv値のバルブを選定する必要が生じる。ちなみに、通常運転時、同じ出力を得るために必要な燃料流量は、ＬＰＧを1.0としたとき、都市ガスは約2.2、消化ガス(メタン濃度60%)は約3.6である。
【００３０】
一方、燃料Ｂに切替完了後の運転では、燃料Ｂの流量調節弁は比較的小流量の燃料Ｂ(例えばＬＰＧ)を燃料電池発電装置の状態に応じて制御する必要がある。燃料電池発電装置にＬＰＧのような、少流量で運転可能、すなわち、高発熱量の燃料を適用する場合、特に出力変更時や燃料流量の少ない低出力時には、燃料流量のわずかな変動が燃料電池発電装置の状態に影響を与え、発電効率の低下や改質器の温度異常など、装置の異常停止を生じさせ、システムの運用に悪影響を及ぼすことが考えられる。このため、できるだけ少流量時のバルブの流量制御性を高い精度で保つ必要があるが、大きなCv値のバルブでは少流量時の制御性(分解能)は低下してしまう。
【００３１】
上述の問題を解決し、燃料切替時に安定した改質ガス(水素リッチガス)を供給しつつ、燃料切替り後の装置運転を安定させるためには、前記請求項３の発明を適用し、燃料Ｂ流量調節弁を、複数個の流量調節弁を並列に接続してなるものとするのが好適である。この実施例を図６に示す。
【００３２】
図６と図１との相違点は、燃料Ｂ流量調節弁の構成の相違である。図６においては、燃料Ｂの燃料流量調節弁を並列に並べた２個の燃料Ｂ流量調節弁１および２（５１および５２）で構成する。このような構成において、燃料Ａ(例えば都市ガス・消化ガス)から燃料Ｂ(例えばＬＰＧ)への切替時は、切替直後の燃料Ｂを切替前の燃料Ａと同じ流量を必要とするが、その時は燃料Ｂの複数の調節弁を同時に開とし、大流量を確保する。また、切替完了後の燃料Ｂでの運転時は、複数の調節弁のうち１つのバルブのみを使用することで、広い領域のバルブ開度での制御を可能とし、燃料流量の制御性を十分確保する。
【００３３】
次に、この実施例の弁動作について、図７および比較例としての図８に基づいて説明する。ここでは、燃料Ａを消化ガス、燃料ＢをＬＰＧとする。なお、通常運転時、同じ出力を得るために必要な燃料流量は、前述のように、ＬＰＧを1.0としたとき、消化ガス(メタン濃度60%)は約3.6である。説明の便宜上、この値と、概算した調節弁の開度を用いて、以下の説明を行う。
【００３４】
まず、燃料Ｂ燃料流量調節弁１個の場合の燃料切替自の弁動作を図８に示す。図８において、切替信号が時刻t1で発生すると、消化ガス用の遮断弁が開から閉に切替わり、ＬＰＧ用の遮断弁が閉から開に切替わる。一方、ＬＰＧ用の流量調節弁開度は、時刻t1以前より、ＬＰＧの流量が、運転中の消化ガス(3.6)と同じ流量(3.6)で流れるように算出される開度(90%)で追従しており、切替信号の発生t1と同時に、あらかじめ最適に計算された流量変化曲線Ｓに沿って、徐々に本来のＬＰＧの流量(1.0)になるように、流量調節弁の開度を25%に向けて変化させていく。
【００３５】
この切替方式の場合には、切替完了時t2以降、調節弁の開度は25%と低い値となる。この場合、燃料電池の低負荷時などにおいてさらに出力を下げる場合には、燃料流量の調節の制御性に問題が生じる恐れがある。
【００３６】
次に、この発明の図６の実施例における弁動作を図７に示す。図７において、切替信号が時刻t1で発生すると、消化ガス用の遮断弁が開から閉に切替わり、ＬＰＧ用の遮断弁が閉から開に切替わる。一方、ＬＰＧ用の流量調節弁１および流量調節弁２の開度は、時刻t1以前より、流量調節弁１と２を通過するＬＰＧの合計流量が、運転中の消化ガス(3.6)と同じ流量(3.6)で流れるように算出される開度で追従（この時流量調節弁１と２の開度の分配は等分、図中では90%、とする）し、切替信号の発生t1と同時に、あらかじめ最適に計算された流量変化曲線Ｓに沿って、徐々に本来のＬＰＧの流量(1.0)になるよう、流量調節弁１と２の開度を変化させていく。このとき、流量調節弁１の開度は切替時の開度を保ちつつ、流量調節弁２の開度のみを低下させ、流量調節弁２の開度が0%(閉)に至った段階t12で、直ちに流量調節弁１の開度調節を開始し、引き続き本来のＬＰＧの流量(1.0)になるよう制御を行い、切替完了時t2以降は流量調節弁１のみで、ＬＰＧでの運転に入る。
【００３７】
上記のように切替を行う場合には、切替完了時t2以降、調節弁の開度は50%程度となり、制御上適切な開度を保持することが可能となり、出力下降時等の燃料流量の調節の制御性は良好となる。
【００３８】
【発明の効果】
上記のとおり、この発明によれば、原燃料ガスを燃料Ａから燃料Ｂに切替える際に、燃料Ｂの切替開始時の時間当たり体積流量を，切替前の燃料Ａの流量と同一流量となるようにし、その後は、燃料Ｂの供給流量を，前記改質器出口の改質ガス中の水素ガス量が切替前と同一となるように供給し、前記改質器出口部において，燃料Ａの燃料Ｂによるガス置換が完了した後に、燃料Ｂの供給流量を，燃料Ｂの組成に適した最適流量に調節して，原燃料の切替を完了することとしたので、原燃料切替初期において、切替前の流量がそのまま継続され、ガス置換が完了した後には、切替え後の燃料ガス組成に適した原料ガスの供給が確保されるので、原燃料不足に伴う燃料電池における水素不足や水素過剰，Ｓ／Ｃ異常などが生ずることはなく、安定した燃料電池発電装置の運転が継続できる。
【図面の簡単な説明】
【図１】この発明の原燃料切替設備を有する燃料電池発電装置の実施例を示す図
【図２】この発明の実施例の改質器入口出口におけるガスの挙動を模式的に示す図
【図３】この発明の実施例の各種弁の動作を模式的に示す図
【図４】従来の燃料電池発電装置の改質器入口出口におけるガスの挙動を模式的に示す図
【図５】従来の燃料電池発電装置の各種弁の動作を模式的に示す図
【図６】この発明の図１とは異なる実施例を示す図
【図７】図６の実施例の各種弁の動作およびガス流量を模式的に示す図
【図８】各流量調節弁が１個の場合の図７に対応する弁動作およびガス流量の模式図
【図９】従来の原燃料切替設備を有する燃料電池発電装置の概略構成を示す図
【符号の説明】
１：燃料Ａ遮断弁、２：燃料Ａ流量調節弁、３：燃料Ａ流量計、４：燃料Ｂ遮断弁、５：燃料Ｂ流量調節弁、６：燃料Ｂ流量計、７：スチームエジェクタ、８：脱硫器、９：改質器、１０：ＣＯ変成器、１１：燃料電池本体、１２：原燃料切替制御装置、５１：燃料Ｂ流量調節弁１、５２：燃料Ｂ流量調節弁２。[0001]
BACKGROUND OF THE INVENTION
The present invention, a plurality of different compositions of the raw fuel operation during switching by fuel cell power plant that have a raw fuel switching equipment used and its operating method.
[0002]
[Prior art]
The fuel cell uses hydrogen in the reformed gas obtained by steam reforming a hydrocarbon reforming raw fuel such as natural gas (city gas), LPG, and methanol, and oxygen in the air. A reformer that supplies power to the fuel electrode and the air electrode and generates electricity based on an electrochemical reaction. As a reformer that reforms raw fuel, water is added to the raw fuel and heated, and steam and raw fuel are catalyzed. Those utilizing a steam reforming reaction for reforming to a hydrogen-rich gas by using hydrogen is well known.
[0003]
Recently, the raw fuel switching equipment fuel cell power plant that have a, for example, a system to continue operation of the fuel cell in LPG or the like that is stockpiled even when the city gas is shut off (JP-A-9-106825 JP-reference ), And the fuel switching system that operates the fuel cell continuously using the digested gas and city gas alternately in order to effectively use the digested gas generated in industrial waste, household garbage, human waste processing, etc. Development is underway.
[0004]
When the fuel cell operation is continued and the fuel switching signal such as detection of a decrease in the supply pressure of the fuel is used to switch the fuel A to the fuel B having a different composition irregularly, the flow control valve of the fuel B is provided at the time of fuel switching, and the fuel B It is necessary to always maintain the opening during the operation with the fuel A so that a constant flow rate flows immediately after the switching.
[0005]
Figure 9 shows a schematic configuration of a fuel cell power plant that have a conventional raw fuel switching equipment utilizing fuel two systems. In FIG. 9, 1 is a shutoff valve for fuel A, 2 is a flow control valve for fuel A, 3 is a flow meter for fuel A, 4 is a shutoff valve for fuel B, 5 is a flow control valve for fuel B, 6 is a flow control valve for fuel B, A flow meter, 7 is a steam ejector, 8 is a desulfurizer, 9 is a reformer, 10 is a CO converter, and 11 is a fuel cell body.
[0006]
The operation of the conventional apparatus will be described with reference to FIG. 5 and FIG. FIG. 5 is a diagram schematically showing the operation of various valves in the conventional apparatus. In this example, the fuel gas A is described as city gas, and the fuel gas B is described as LPG. As shown in FIG. 5, when the switching signal is generated at time t1, the city gas shut-off valve is switched from open to closed, and the LPG shut-off valve is switched from closed to open.
[0007]
On the other hand, the LPG flow control valve opening follows the city gas flow control valve opening xj2 during operation with city gas, and maintains this opening for a certain time simultaneously with the generation of the switching signal. . Here, the opening degree of the LPG flow rate regulating valve calculated by the opening degree of the flow regulating valve for city gas × j2 is the optimum flow rate suitable for LPG (about half of the city gas) considering the gas composition of LPG. (Volume flow rate) is the opening.
[0008]
At a time t2 after the elapse of a predetermined time, the flow rate rises in the LPG flow meter, and the PI control based on the LPG flow rate and the battery current starts. Here, the rise of the flow rate means “the flow meter recognizes the correct flow rate”. Immediately after the shut-off valve is opened, the flow meter value starts from zero. If the flow rate measurement value is immediately used for PI control, the operation of the control valve becomes unstable. It is necessary to use it for PI control, and this stable state is called the state where the flow rate has risen as described above.
[0009]
In FIG. 5, the opening of the city gas flow control valve is adjusted to the opening of the LPG flow control valve × j1 in preparation for fuel gas re-switching. It stands by so that supply of a flow rate corresponding to an optimal flow rate for gas at a rated operation (volume flow rate about 2.2 times that of LPG gas) can be started.
[0010]
[Problems to be solved by the invention]
As described above, the control valve opening degree of the fuel B is controlled so that a gas flow rate suitable for the composition of the fuel B flows immediately after switching.
[0011]
On the other hand, since there is a certain volume (mainly the volume of the desulfurizer) between the fuel control valve and the reformer, the volume of fuel A before switching is filled in this volume immediately after switching. In this state, when the fuel B is switched to the fuel B at the normal rated flow rate of the fuel B (a flow rate appropriate for the composition of the fuel B), the fuel A in the volume between the fuel control valve and the reformer is replaced with the fuel B. During this time, the reformer is supplied with fuel A or a mixed gas of fuel A and fuel B at the flow rate of fuel B, so that the amount of reformed gas generated by the reformer and thus the fuel cell body is supplied. For example, when switching from city gas to LPG, hydrogen shortage occurs, and conversely, when switching from LPG to city gas, inappropriate operation such as excessive hydrogen, S / C abnormality, etc. There is a problem that becomes a state.
[0012]
The above problem will be described in detail below with respect to an example in which fuel A is city gas, fuel B is LPG, and fuel A is switched to fuel B.
[0013]
FIG. 4 is a diagram schematically showing the behavior of gas at the reformer inlet / outlet in the conventional system. The city gas concentration, the LPG concentration at the reformer inlet, the fuel gas flow rate at the reformer inlet, and the reformer The change of the reformed gas (hydrogen rich gas) flow rate at the outlet is schematically shown. By switching from city gas to LPG in accordance with the valve operation of FIG. 5, the city gas filled between the flow control valve and the reformer enters the reformer at the LPG flow rate (about half the volume of city gas) immediately after switching. Sent out. That is, the flow rate of the reformer inlet gas decreases even though the city gas concentration of the composition is high, so the reformed gas amount at the reformer outlet decreases. Therefore, according to the conventional method, there has been a problem that hydrogen shortage occurs in the fuel cell as described above, which affects the stable operation of the apparatus.
[0014]
The present invention has been made to solve the above-mentioned problems. The object of the present invention is to reduce the amount of hydrogen in the fuel cell when the fuel is switched from the fuel A to the fuel B having a different composition without stopping the operation. It is an object of the present invention to provide a fuel cell power generation apparatus having a raw fuel switching facility and a method of operating the same, which can be stably operated without excessive hydrogen and S / C abnormality.
[0015]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention includes a fuel cell main body, a reformer that reforms the raw fuel gas to form a hydrogen-rich reformed gas, and supplies the reformed gas to the fuel cell main body. As the raw fuel gas, one raw fuel gas (hereinafter referred to as fuel A) is always supplied to the reformer through the fuel A shutoff valve, the fuel A flow meter and the fuel A flow control valve. When the supply of fuel A and the supply of fuel A is stopped, another alternative raw fuel gas (hereinafter referred to as fuel B) is supplied as the raw fuel via the fuel B cutoff valve, fuel B flow meter, and fuel B flow control valve. In a method of operating a fuel cell power generation apparatus having a raw fuel switching facility including a fuel B supply device that supplies fuel to a mass device, when the raw fuel gas is switched from fuel A to fuel B, when switching of fuel B starts Volumetric flow rate per hour (hereinafter simply referred to as flow rate) Refers.) Was to be the flow rate and the same flow rate of the fuel A before switching, then, the supply flow rate of fuel B, the reformer hydrogen gas amount in the reformed gas outlet before switching the same become so subjected sheet, after said gas replacement is completed by the fuel B in the fuel a in the reformer outlet, the supply flow rate of fuel B, adjusted to optimal flow suitable for the composition of the fuel B, The switching of the raw fuel is completed (claim 1).
[0016]
According to the raw fuel gas switching method as described above, at the initial stage of switching, the flow rate before switching is continued as it is, and after the gas replacement is completed , the supply of the raw material gas suitable for the fuel gas composition after switching is performed. Therefore, there is no hydrogen shortage, hydrogen excess, S / C abnormality, etc. in the fuel cell due to the shortage of raw fuel, and stable operation of the fuel cell power generator can be continued.
[0017]
As an apparatus for carrying out the above operation method, as in the invention of claim 2, the fuel cell main body and the raw fuel gas are reformed to form a hydrogen-rich reformed gas, and the reformed gas is used as the fuel. A reformer to be supplied to the battery body and the raw fuel gas is always one raw fuel gas (fuel A) through the fuel A shutoff valve, fuel A flow meter and fuel A flow control valve. When the fuel A supply is stopped, another alternative raw fuel gas (fuel B) is supplied as the raw fuel via a fuel B shutoff valve, a fuel B flow meter, and a fuel B flow control valve. In the fuel cell power generator having the raw fuel switching facility provided with the fuel B supply device for supplying to the reformer, the fuel A cutoff valve and the fuel B cutoff valve are each based on the raw fuel gas switching command. Shut-off valve drive for predetermined opening / closing operation And when the raw fuel gas is switched from the fuel A to the fuel B, the flow rate at the start of the switching of the fuel B is set to the same flow rate as the flow rate of the fuel A before the switching. the flow rate, after the amount of hydrogen gas in the reformed gas in the reformer outlet is subjected sheet such that the pre-switching and same, gas replacement is completed by the fuel B in the fuel a in the reformer outlet , the supply flow rate of fuel B, and opening control unit of the fuel B flow rate control valve for adjusting the optimal flow suitable for the composition of the fuel B, to switch the raw fuel gas again fuel B to fuel a The flow rate of fuel A can be started at the same flow rate as the optimum flow rate of fuel B. Thereafter, the supply flow rate of fuel A is changed to the amount of hydrogen gas in the reformed gas at the reformer outlet. There was subjected sheet so as to be switched before and same, fuel B in the reformer outlet After the gas replacement with fuel A is completed, the supply flow rate of the fuel A, fuel A fuel A raw fuel formed by providing a opening control means of the flow rate control valve for adjusting the optimal flow suitable for the composition of the A switching control device is provided.
[0018]
According to the above-mentioned device, in addition to the fuel cell power generation device on the premise that the raw fuel is switched only in an emergency and the device is temporarily stopped, continuous use such as switching to city gas alternately using digestion gas. It can also be applied to fuel cell power generators that switch to
[ 0019 ]
Furthermore, in the apparatus according to claim 2, at least one of the fuel A flow rate control valve or the fuel B flow rate control valve is made by connecting a plurality of flow control valve in parallel (claim 3 ) Is preferable in terms of control. Although details will be described later, according to the above configuration, for example, as an optimum flow rate during normal operation, switching from a relatively large flow rate of fuel A (for example, city gas / digested gas) to a low flow rate of fuel B (for example, LPG). Sometimes, the initial flow rate of the fuel B immediately after switching is the same as that of the fuel A, but it is possible to continue the operation while maintaining sufficient controllability at the time of the operation with the fuel B with a small flow rate after the fuel switching is completed. It becomes.
[ 0020 ]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below based on the drawings.
[ 0021 ]
FIG. 1 is a diagram showing an embodiment of the present invention. The same components as those in FIG. 1 differs from FIG. 9 in that a raw fuel switching control device 12 is provided in FIG. 1 and a measurement control signal line (broken line portion in FIG. 1) linked thereto is provided. The raw fuel switching control device 12 includes the following means (not shown). That is, as described above, the fuel A shutoff valve and the fuel B shutoff valve perform predetermined opening / closing operations based on the raw fuel gas switching command, and the raw fuel gas is supplied from the fuel A to the fuel. When switching to B, the flow rate at the start of switching of fuel B is set to the same flow rate as that of fuel A before switching, and then the supply flow rate of fuel B is changed to the reformed gas at the reformer outlet. hydrogen gas amount is subjected sheet so that before switching the same one in, after the gas replacement is completed by the fuel B in the fuel a in the reformer outlet, the supply flow rate of fuel B, the composition of the fuel B and opening control means of the fuel B flow rate control valve for adjusting the optimal flow suitable for, in case of switching the raw fuel gas again from the fuel B in fuel a, the flow rate of the fuel a fuel B Make it possible to start supplying at the same flow rate as the optimal flow rate, and then , The supply flow rate of the fuel A, the reformer hydrogen gas amount in the reformed gas outlet is provided sheet so as to be switched before and same, gas from the fuel A fuel B in the reformer outlet after the replacement has been completed, comprises a supply flow rate of the fuel a, the opening control means of the flow control valve of the fuel a for adjusting the optimal flow suitable for the composition of the fuel a.
[ 0022 ]
The raw fuel gas switching command is based on, for example, a fuel switching signal based on detection of a decrease in supply pressure of raw fuel, as described in the section of the related art. Depending on the circumstances of switching raw fuel, there may be a signal based on a manual command.
[ 0023 ]
Next, an operation method according to an embodiment of the present invention will be described with reference to FIGS. 2 shows the behavior of the gas in the present invention corresponding to the conventional FIG. 4, and FIG. 3 shows the operation of various valves corresponding to FIG. Similarly to the above, an example in which fuel A is city gas, fuel B is LPG, and fuel A is switched to fuel B will be described.
[ 0024 ]
As shown in FIG. 3, when the switching signal is generated at time t1, the city gas shut-off valve is switched from open to closed, and the LPG shut-off valve is switched from closed to open. On the other hand, the LPG flow control valve opening follows the opening calculated by the city gas flow control valve opening xk2 during operation with city gas, and opens simultaneously with the generation of the switching signal (t1). Along the degree change curve S, the opening is calculated as the opening calculated by the flow rate adjustment valve opening xj2 for city gas at the time of the switching signal generation (t1). Here, the opening of the LPG flow control valve calculated by the opening of the flow regulating valve for city gas × k2 is an opening through which the same flow as the city gas flows, and the opening of the flow regulating valve for city gas. The opening degree of the LPG flow rate control valve calculated by xj2 is an opening degree at which the optimum flow rate (approx. Half the flow rate of city gas) appropriate for LPG flows, considering the gas composition of LPG as described above. In this case, as in the conventional case, a change in the suction capacity of the ejector (increase in the suction power of the ejector due to the flow rate increase control of the reformed steam accompanying the switching to the LPG fuel) is considered.
[ 0025 ]
An opening change curve S in FIG. 3 is an opening change in consideration of a gas replacement delay of the fuel gas due to the volume between the fuel flow control valve and the reformer, and the amount of hydrogen gas in the reformed gas at the reformer outlet The flow rate is changed based on a change curve of a predetermined calculation value obtained in advance by simulation so that is substantially the same as before switching. The opening degree control means of the fuel B flow rate control valve in the raw fuel switching control device 12 has the above flow rate control function.
[ 0026 ]
At a time t2 after a lapse of a certain time, the flow rate rises in the LPG flow meter, and the PI control based on the LPG flow rate and the battery current starts. In FIG. 3, the opening of the city gas flow control valve is adjusted to the opening of the LPG flow control valve × k1 in preparation for the re-switching of the raw fuel. Stand-by so that the supply of the same city gas flow rate as the optimal gas flow rate can be started.
[ 0027 ]
FIG. 2 schematically shows changes in the city gas concentration, LPG concentration, fuel gas flow rate at the reformer inlet, and reformed gas flow rate at the reformer outlet according to the present invention. . Strictly speaking, the proportion of hydrogen contained in the reformed gas differs between city gas and LPG. As described above, the amount of hydrogen gas in the reformed gas is substantially the same as before switching. Although it cannot be realized even if the reformed gas flow rate is fixed as in FIG. 2, for convenience of explanation, FIG. 2 is displayed in the same manner as FIG. 4. The actual simulation is performed on a hydrogen gas amount basis.
[ 0028 ]
As described above, by switching the raw fuel by the method of FIG. 2, it becomes possible to prevent gas shortage at the initial stage of switching, and the amount of reformed gas and hydrogen gas at the reformer outlet can be stabilized.
[ 0029 ]
By the way, in realizing the fuel switching as described above, the fuel to be switched is changed from the fuel A (for example, city gas / digested gas) requiring a relatively large flow rate to the fuel B (for example, LPG) that can be operated at a relatively small flow rate. In the case of switching, it is necessary to select a valve with a large Cv value that secures the same flow rate as that during the normal operation of the fuel A as the flow control valve of the fuel B. Incidentally, during normal operation, the fuel flow rate required to obtain the same output is about 2.2 for city gas and about 3.6 for digestion gas (methane concentration 60%) when LPG is 1.0.
[ 0030 ]
On the other hand, in the operation after the switching to the fuel B is completed, the flow rate adjustment valve of the fuel B needs to control the fuel B (for example, LPG) having a relatively small flow rate according to the state of the fuel cell power generation device. When the fuel cell power generator can be operated at a low flow rate such as LPG, that is, when a fuel with a high calorific value is applied, especially when the output is changed or when the fuel flow is low and the output is low, a slight fluctuation in the fuel flow rate may occur. It may affect the state of the power generation device, causing an abnormal shutdown of the device, such as a decrease in power generation efficiency or a temperature abnormality of the reformer, and adversely affecting the operation of the system. For this reason, it is necessary to maintain the flow rate controllability of the valve at a low flow rate with high accuracy as much as possible. However, the controllability (resolution) at a low flow rate is lowered with a valve having a large Cv value.
[ 0031 ]
In order to solve the above-mentioned problem and to stabilize the operation of the apparatus after the fuel switching while supplying a stable reformed gas (hydrogen rich gas) at the time of fuel switching, the invention of claim 3 is applied and the fuel B It is preferable that the flow rate control valve is formed by connecting a plurality of flow rate control valves in parallel. This embodiment is shown in FIG.
[ 0032 ]
The difference between FIG. 6 and FIG. 1 is the difference in the configuration of the fuel B flow control valve. In FIG. 6, the fuel flow rate adjusting valve for fuel B is composed of two fuel B flow rate adjusting valves 1 and 2 (51 and 52) arranged in parallel. In such a configuration, when switching from fuel A (for example, city gas / digested gas) to fuel B (for example, LPG), fuel B immediately after switching requires the same flow rate as fuel A before switching. Opens a plurality of control valves for fuel B at the same time to ensure a large flow rate. In addition, when operating with fuel B after completion of switching, only one of the plurality of control valves is used, so that control over a wide range of valve opening is possible, and fuel flow controllability is sufficient. Secure.
[ 0033 ]
Next, the valve operation of this embodiment will be described based on FIG. 7 and FIG. 8 as a comparative example. Here, the fuel A is digestion gas and the fuel B is LPG. Note that the fuel flow rate required to obtain the same output during normal operation is about 3.6 for digestion gas (methane concentration 60%) when LPG is 1.0 as described above. For convenience of explanation, the following explanation is made using this value and the estimated opening of the control valve.
[ 0034 ]
First, FIG. 8 shows the valve operation of the fuel switching operation in the case of one fuel B fuel flow rate control valve. In FIG. 8, when the switching signal is generated at time t1, the digestion gas shutoff valve is switched from open to closed, and the LPG shutoff valve is switched from closed to open. On the other hand, the flow control valve opening for LPG is the opening (90%) calculated so that the flow of LPG flows at the same flow rate (3.6) as the digestion gas (3.6) during operation from time t1 or earlier. At the same time as the generation of the switching signal t1, the opening of the flow control valve is adjusted to 25 to gradually reach the original LPG flow rate (1.0) along the flow rate change curve S calculated optimally in advance. Change towards%.
[ 0035 ]
In the case of this switching method, the opening degree of the control valve becomes a low value of 25% after t2 when the switching is completed. In this case, when the output is further reduced when the fuel cell is under a low load, there is a possibility that a problem arises in the controllability of the fuel flow rate adjustment.
[ 0036 ]
Next, the valve operation in the embodiment of FIG. 6 according to the present invention is shown in FIG. In FIG. 7, when the switching signal is generated at time t1, the shut-off valve for digestion gas is switched from open to closed, and the shut-off valve for LPG is switched from closed to open. On the other hand, the opening degree of the flow control valve 1 and the flow control valve 2 for LPG is the same flow rate as the digestion gas (3.6) in operation since the total flow rate of LPG passing through the flow control valves 1 and 2 before time t1. Follows the opening calculated to flow in (3.6) (At this time, the distribution of the opening of the flow control valves 1 and 2 is equally divided, 90% in the figure), and at the same time as the generation of the switching signal t1 Then, along the flow rate change curve S calculated optimally in advance, the opening degree of the flow rate control valves 1 and 2 is gradually changed so as to gradually reach the original LPG flow rate (1.0). At this time, while the opening degree of the flow rate control valve 1 is maintained at the time of switching, only the opening degree of the flow rate control valve 2 is decreased and the opening degree of the flow rate control valve 2 reaches 0% (closed) t12 Then, the opening degree adjustment of the flow rate control valve 1 is started immediately, and the control is continued so that the flow rate of the original LPG is 1.0 (1.0). .
[ 0037 ]
When switching is performed as described above, the opening of the control valve is about 50% after t2 when the switching is completed, and it is possible to maintain an appropriate opening for control. The controllability of the adjustment is good.
[ 0038 ]
【The invention's effect】
As described above, according to the present invention, when the raw fuel gas is switched from the fuel A to the fuel B, the volume flow rate per hour at the start of the switching of the fuel B is set to the same flow rate as the flow rate of the fuel A before the switching. to, then, the supply flow rate of fuel B, the reformer hydrogen gas amount in the reformed gas outlet is provided sheet so as to be switched before and same, in the reformer outlet, the fuel a of after the gas replacement is completed by the fuel B, and the supply flow rate of the fuel B, and adjusted to optimal flow suitable for the composition of the fuel B, so it was decided to complete the switching of the raw fuel, in the raw fuel switching initial Since the flow rate before switching is continued and gas replacement is completed , supply of raw material gas suitable for the fuel gas composition after switching is ensured. , S / C abnormality does not occur and Operation of the fuel cell system can continue.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment of a fuel cell power generator having raw fuel switching equipment according to the present invention. FIG. 2 is a diagram schematically showing the behavior of gas at the reformer inlet / outlet of the embodiment of the present invention. 3 is a diagram schematically showing the operation of various valves according to an embodiment of the present invention. FIG. 4 is a diagram schematically showing the behavior of gas at the reformer inlet / outlet of a conventional fuel cell power generator. FIG. 6 is a diagram schematically showing the operation of various valves of the fuel cell power generator. FIG. 6 is a diagram showing an embodiment different from FIG. 1 of the present invention. FIG. 8 is a schematic diagram of valve operation and gas flow rate corresponding to FIG. 7 when there is one flow rate control valve. FIG. 9 is a schematic diagram of a conventional fuel cell power generator having raw fuel switching equipment. Diagram showing configuration 【Explanation of symbols】
1: Fuel A cutoff valve, 2: Fuel A flow rate adjustment valve, 3: Fuel A flow meter, 4: Fuel B cutoff valve, 5: Fuel B flow rate adjustment valve, 6: Fuel B flow meter, 7: Steam ejector, 8 : Desulfurizer, 9: reformer, 10: CO converter, 11: fuel cell main body, 12: raw fuel switching control device, 51: fuel B flow control valve 1, 52: fuel B flow control valve 2.

Claims

A fuel cell main body, a reformer that reforms the raw fuel gas to form a hydrogen-rich reformed gas, and supplies the reformed gas to the fuel cell main body, and the raw fuel gas is always one raw fuel. A fuel A supply device that supplies gas (hereinafter referred to as fuel A) to the reformer via a fuel A shutoff valve, a fuel A flow meter, and a fuel A flow control valve; and when the fuel A supply is stopped, A fuel B supply device for supplying another alternative raw fuel gas (hereinafter referred to as fuel B) as fuel to the reformer via a fuel B shutoff valve, a fuel B flow meter, and a fuel B flow control valve; In the operation method of the fuel cell power generation apparatus provided with the raw fuel switching facility, when the raw fuel gas is switched from the fuel A to the fuel B, the volumetric flow rate per hour at the start of the switching of the fuel B (hereinafter simply referred to as a flow rate). The same flow as the flow rate of fuel A before switching As a, then the supply flow rate of fuel B, the reformer hydrogen gas amount in the reformed gas outlet is provided sheet so as to be switched before and same, in the reformer outlet after the gas replacement is completed by the fuel B in the fuel a, the supply flow rate of fuel B, and adjusted to optimal flow suitable for the composition of the fuel B, raw fuel switching, characterized in that to complete the switching of the raw fuel A method of operating a fuel cell power generator having equipment.

A fuel cell main body, a reformer that reforms the raw fuel gas to form a hydrogen-rich reformed gas, and supplies the reformed gas to the fuel cell main body, and the raw fuel gas is always one raw fuel. A fuel A supply device that supplies gas (fuel A) to the reformer via a fuel A shutoff valve, a fuel A flow meter, and a fuel A flow rate control valve, and other fuel as the raw fuel when the fuel A supply is stopped A raw fuel switching facility comprising a fuel B supply device for supplying the alternative raw fuel gas (fuel B) to the reformer through a fuel B shut-off valve, a fuel B flow meter and a fuel B flow control valve In the fuel cell power generator, the fuel A shut-off valve and the fuel B shut-off valve respectively perform predetermined opening / closing operations based on the raw fuel gas switching command, and the raw fuel gas is supplied from the fuel A. When switching to fuel B, cut off fuel B The flow rate at the start, so the flow rate and the same flow rate of the fuel A before switching, then, the supply flow rate of fuel B, hydrogen gas amount in the reformed gas in the reformer outlet same as before the switching subjected sheet so as one, after said gas replacement with fuel B fuel a has been completed in the reformer outlet, the supply flow rate of fuel B, to adjust the optimal flow suitable for the composition of the fuel B The fuel B flow rate control valve opening control means and the supply of fuel A can be started at the same flow rate as the optimum flow rate of fuel B in preparation for switching the raw fuel gas from fuel B to fuel A again. so as to, after that, the supply flow rate of the fuel a, the amount of hydrogen gas in the reformed gas in the reformer outlet is subjected sheet such that the pre-switching and same fuel in the reformer outlet after the gas replacement is completed by the fuel a in B, and the supply flow rate of the fuel a, fuel a set Fuel cell power plant having a raw fuel switching equipment, characterized in that it comprises a raw fuel switching control device formed by providing a opening control means of the flow control valve of the fuel A for adjusting the optimal flow suitable for .

3. The apparatus according to claim 2, wherein at least one of the fuel A flow rate control valve and the fuel B flow rate control valve comprises a plurality of flow rate control valves connected in parallel. A fuel cell power generator.