JP4325270B2 - Operation control method of fuel cell power generator - Google Patents

Operation control method of fuel cell power generator Download PDF

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JP4325270B2
JP4325270B2 JP2003127304A JP2003127304A JP4325270B2 JP 4325270 B2 JP4325270 B2 JP 4325270B2 JP 2003127304 A JP2003127304 A JP 2003127304A JP 2003127304 A JP2003127304 A JP 2003127304A JP 4325270 B2 JP4325270 B2 JP 4325270B2
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raw fuel
reformer
flow rate
value
fuel cell
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JP2004047438A (en
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正 小松
誠 三上
英幸 三輪
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Fuji Electric Co Ltd
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Fuji Electric Holdings Ltd
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Description

【０００１】
【発明の属する技術分野】
この発明は、燃料電池発電装置の運転制御方法に関し、特に、原燃料組成が変動する場合の原燃料流量や改質用蒸気流量等の制御方法に関する。
【０００２】
【従来の技術】
燃料電池発電装置は、燃料ガスと酸化剤ガスとの電気化学的反応によって電気を取り出す装置である。そして、燃料電池の電気化学的反応に必要な燃料ガスと酸化剤ガスの量は、燃料電池から取り出す電流に比例する。
【０００３】
前記電気化学的反応に水素ガスを使用するリン酸型燃料電池や固体高分子型燃料電池においては、例えば、原燃料として使用される都市ガスやメタン発酵ガスなどの炭化水素ガスと水蒸気とを反応させて、水素リッチガスに改質して燃料電池に供給する。燃料電池発電装置は、炭化水素ガスから水素リッチガスに改質する改質器を備え、この改質器は改質反応を継続するために高温にコントロールされてる。
【０００４】
なお、改質器における炭化水素ガスと水蒸気の反応は、吸熱反応であるため、燃料電池には、電気化学的反応で消費する水素量より多めの改質ガスを供給し、燃料電池からのオフガスを改質器に還流して燃焼させ、改質器における熱源とするのが一般的である。
【０００５】
改質器の温度コントロールは、改質器に還流して燃焼させる水素量の増減が大きく影響するので、改質器に供給する原燃料流量は、燃料電池で電気化学的反応で消費する水素量に相当する流量と改質器温度制御分に相当する流量との和を、電池電流に比例させて供給する。
【０００６】
特許文献１には、前述のように、燃料電池の出力電流の測定値に基いて、改質器への供給原燃料流量を流量制御弁により制御する燃料電池発電装置の一例が開示されている。図９は、前記公報の図１に記載されたシステム系統図であり、その説明として、前記公報には、下記のとおり記載されている。
【０００７】
即ち、「原料燃料ガスは燃料供給装置２７から改質器２２に送られ、ここで水蒸気改質され、改質ガスは改質器２２から燃料電池２１に供給される。改質器２２には、改質反応に必要な温度まで昇温させるバーナ２３が設置されている。燃料電池２１では、水素を含む改質ガスと空気とを用いて発電を行う。また、酸化剤の空気は、空気供給装置２４から供給される。燃料電池２１から排出された空気は、空気側水回収器２５で外気により冷却され、凝縮水を発生する。得られた凝縮水は水タンク２６に蓄えられる。回収された水は、燃料側水ポンプ４１により改質器２２に送られ、燃料改質に利用される。燃料電池２１では電気とともに熱が生じるために、冷却水を送る冷却用ポンプ４２と、発生した熱を外部へ放出する冷却用放熱器４３を備えている。
【０００８】
また、燃料電池２１には、出力電流を計測する電流計３０が設置されている。原料燃料ガス流路には、原料燃料ガス量の流量制御を行う原料燃料流量制御弁３２が設置されている。改質器２２、バーナ２３、燃料側水ポンプ４１、燃料供給装置２７、原燃料流量制御弁３２とで水素発生装置２８が構成されている。原料燃料供給手段は、燃料供給装置２７と原料燃料流量制御弁３２とで構成される。
【０００９】
改質器２２内部では、原料となる原料燃料ガスと燃料側水ポンプ４１から送り込まれる水を混合し、水蒸気改質が行われている。これにより得られる水素を含む改質ガスを燃料電池２１に供給している。燃料電池では水素をすべて消費することができないため、供給水素の２０％〜３０％が排出される。この水素はバーナ２３に送られて燃焼し、改質に必要な熱となる。排出される水素を燃焼に利用するとエネルギーの回収にはなるが、改質ガスの発生量が増加し改質器の負荷を大きくする。これにより、全体の発電効率も低下する。
【００１０】
一方、燃料電池２１で消費される水素量は、燃料電池２１から出力される電流値に比例する。そこで、電流計３０により得られた電流値を用いて、第１の制御器３１で必要水素量を推定し、それに応じて原料燃料ガス量の流量を原料燃料流量制御弁３２で制御する。こうすれば、発電に必要最低量の水素を生成できる。
【００１１】
以上のように、本実施の形態の効果として、原料燃料流量制御弁３２の動作によって必要最低量の水素を生成させることにより、改質器の効率を保つことが可能となり、高い発電効率が得られる。」旨、記載されている。
【００１２】
なお、前記図９において、前記改質器２２への原燃料供給ライン上の原燃料流量制御弁３２の前段に、図示しない原燃料流量計を設け、この原燃料流量計の流量計測値と前記第１の制御器３１で設定した改質器への供給原燃料設定値との比較演算に基づく制御出力（ＰＩＤ制御出力）により、前記原燃料流量制御弁の開度制御を行なって、前記改質器への供給原燃料の制御を行う場合もある。
【００１３】
ところで、前述のような燃料電池発電装置においては、原燃料を改質して得られる水素の量は炭化水素の組成によって異なるために、使用する原燃料の種類によって、原燃料流量の設定値を決める必要がある。また、特に前記メタン発酵ガス（バイオガス）を原燃料とする場合等においては、原燃料の組成が変動するため、供給されるバイオガス中のメタンガス成分の濃度を検出し、このメタンガス検出濃度に応じて、原燃料としてのバイオガス供給流量を調整する必要がある。この種の、原燃料にバイオガスを用いる燃料電池発電装置の構成は、例えば、特許文献２や特許文献３に開示されている。
【００１４】
図１０は、前記特許文献２における図１として（図１０においては、部番を一部変更）記載された燃料電池発電設備のシステム構成図である。図１０の構成について、同公報の記載を概ね引用して、以下に述べる。
【００１５】
即ち、図１０に示す燃料電池発電設備は、下水汚泥からメタン発酵処理により得られる消化ガスを導く原燃料供給配管１ａと、この原燃料供給配管１ａを通して供給される消化ガス中に含まれる硫黄成分を除去する脱硫器６４と、この脱硫器６４により硫黄成分が除去された消化ガスを例えば水蒸気で触媒反応させることにより一酸化炭素と水素ガスに改質する改質器２２と、この改質器２２から出力される一酸化炭素および水素ガスのうち、被毒ガス成分となる一酸化炭素を二酸化炭素に変成するために、当該一酸化炭素を例えば水蒸気などで触媒反応させて二酸化炭素と水素ガスに変成する変成器６６と、燃料電池本体２１とが設けられている。
【００１６】
前記原燃料供給配管１ａには消化ガス中のガス濃度を検出する検出器６ａが設置されている。また、原燃料供給配管１ａの所要とする位置に燃料ガス入口遮断弁７ａおよび燃料ガス流量調整弁３２が介在され、さらに前記改質器２２の入力側に触媒を反応させるために例えば水蒸気を供給する水蒸気供給ライン９ａが設けられ、この水蒸気供給ライン９ａには水蒸気の流量を調整供給するための改質用蒸気流量調整弁１０ａが設置されている。
【００１７】
さらに、検出器６ａの出力側には消化ガスに含まれる所要のガス濃度を評価演算するガス濃度評価演算部１１ａが設けられている。このガス濃度評価演算部１１ａは、検出器６ａの出力である各種のガス濃度データを収集するガス濃度収集手段１２ａと、ガス濃度収集手段１２ａにより収集された消化ガス中のメタン系炭化水素の成分濃度から総発電量を算出し、この総発電量から必要となる燃料ガス流量を決定し、燃料ガス流量調整弁３２を調整する燃料流量演算手段１３ａと、この燃料流量演算手段１３ａによって決定される燃料ガス流量から改質用蒸気流量を決定し、改質用蒸気流量調整弁１０ａを調整する改質用蒸気流量演算手段１４ａと、被毒成分である一酸化炭素、硫黄、窒素、塩類、酸素等のうち少なくとも１つ以上の被毒成分濃度が許容範囲を越えたとき、燃料電池発電設備を構成する機器のうち必要な機器を停止させる設備停止手段１５ａとによって構成されている。
【００１８】
また、図１０において、６０は水蒸気分離器であって、水から蒸気を分離し水蒸気供給ライン９に供給する。この蒸気を得る手段は、水蒸気分離器６０である必要はなく、従来周知の種々の方法によって得ることができる。１７ａは燃料電池本体５を構成する空気極から出力される排気を水に熱交換する熱交換機、１８ａはタンク、１９ａはポンプである。
【００１９】
以上は概ね、前記特許文献２に記載された図１０の説明であるが、燃料電池の水回収装置や純水装置など一部の系統は省略されており、また、燃料電池の冷却系統や排熱回収系統等、システムの細部構成については、種々の変形例がある。なお、前記改質用蒸気供給流量は、通常、原燃料供給量と所定のＳ／Ｃ（原燃料中の炭素原子に対する水蒸気のモル数比）とに基づき決定されバイオガスの場合、メタンガスが主であるので、２．５〜４．０である。
【００２０】
【特許文献１】
特開２００１−１５８６０４号公報
【特許文献２】
特開平１１−１２６６２９号公報
【００２１】
【特許文献３】
特開２０００−９０９５３号公報
【００２２】
【発明が解決しようとする課題】
前記図１０に示す装置のように、原燃料組成の変動を検知し、この変動を制御系にフィードバックしない場合の問題点について、種々のケースについて整理すると、下記のとおりである。
【００２３】
例えば、メタン発酵ガスのメタン濃度が下がって、原燃料の発熱量が低下した場合、この組成変動を制御系にフィードバックしない場合には、改質器から燃料電池に供給される水素量が少なくなり、燃料電池における水素不足、所謂、ガス欠が発生する危険性がある。ガス欠が生じると燃料電池セルに電気化学的反応分の水素が供給されず、セルに損傷を与える。また、燃料電池で水素を消費したオフガス水素は改質器に戻し、燃焼させて改質に必要な熱となるが、水素不足で、この熱量が低下するので、改質器の温度が低下し改質反応を維持できなくなる。
【００２４】
次に、上記ケースとは逆に、メタン発酵ガスのメタン濃度が高くなって、原燃料の発熱量が増加した場合、この組成変動を制御系にフィードバックしない場合には、改質器から燃料電池に過剰に水素が供給され、この水素は発電に使われないので無駄となり発電効率が低下する。また、燃料電池で水素を消費したオフガスは改質器に戻し、燃焼して改質に必要な熱になるが、水素過剰で、この熱量が増加し改質器の温度が上昇して、改質反応を適温に維持できなくなる。
【００２５】
通常、改質器の温度制御は、改質器触媒と燃料電池を経由する原燃料系の流量を増減して改質器に戻るオフガス量が増減することで行われるが、オフガス水素を燃焼するには空気が必要なので、燃料用空気ブロアの空気供給能力の上限で制限される原燃料の増加量の上限値と、燃料電池における水素不足が発生しない最低流量の下限値で決まる原燃料流量の増減幅がある。従って、前記原燃料の組成変動を制御系にフィードバックしない装置において、原燃料の組成変動が大きい場合には、この制御幅を超える発熱量の変動となり、改質器の温度制御ができなくなる。
【００２６】
また、改質器の別の温度制御方法として、改質器燃焼炉に直接、原燃料を助燃焼ガスとして供給する方法があるが、改質器触媒と燃料電池を経由する原燃料系の流量を増減する方式と同じ理由で、燃焼炉に直接供給する原燃料流量の上限値があり原燃料の組成変動が大きいと改質器の温度制御ができなくなる。
【００２７】
さらに、燃焼用空気量は、原燃料１Nm3/hを燃焼させるに必要な酸素流量と原燃料流量、即ち燃料電池の発電電流相当分で決まるので、原燃料組成が変わると、原燃料１Nm3/hを燃焼させるに必要な酸素量が変わるので、原燃料組成が判らないと最適な燃焼用空気量の制御が行えず、空気不足のため不完全燃焼が発生したり、余剰の空気供給のため動力損失が大きくなる問題が生じる。
【００２８】
さらにまた、改質器では、前述のように、スチームと原燃料を反応させて水素リッチなガスに改質するが、スチームと原燃料のカーボン比（Ｓ／Ｃ）が最適でないと、改質ガス組成が悪くなったり、改質器触媒に炭素が析出することがある。スチーム流量は、原燃料組成から算出される原燃料１Nm3当りに必要なスチーム量と設定Ｓ／Ｃで決まるので、原燃料組成が判らないと最適なスチーム流量が算出できない。
【００２９】
また、燃料電池の発電負荷が変動する場合、例えば、燃料電池の発電負荷を低減する場合、発電負荷低減に伴う改質器の負荷減少のために改質器の温度制御系が原燃料流量を低減させ改質器の温度を下げる方向の制御が働くので、原燃料流量が少なすぎることが無いように原燃料流量の下限値を設定する必要がある。この原燃料下限流量は、発電電池電流と原燃料組成から決まる改質後の水素量から算出される。
【００３０】
従って、原燃料組成が変動し、この組成変動を制御系にフィードバックしない場合には、発電負荷低減時に原燃料流量が少なすぎて、燃料電池における水素不足、所謂、ガス欠が発生する危険性がある。ガス欠が生ずると燃料電池セルに電気化学的反応分の水素が供給されず、セルに損傷を与える。
【００３１】
上記諸理由により、原燃料の組成を測定・分析し、その結果をフィードバックして改質器への供給原燃料と燃焼用空気量を定め、燃料電池における水素不足防止と、燃料の有効利用による発電効率の向上と、改質器の適正な温度制御と、改質器燃焼炉におけるオフガスの適正な燃焼をおこなうことが望ましい。しかしながら、原燃料の組成を、随時測定・分析する装置はコストが高く、また、校正を定期的に行う必要がありメンテナンスコストが嵩む等の問題があり、さらに、分析計の信頼性もあって、実用上問題が多い。
【００３２】
また、前記図９の説明で述べたように、改質器への原燃料供給ライン上に原燃料流量計および原燃料流量制御弁を設け、前記原燃料流量計の流量計測値と前記改質器への供給原燃料設定値との比較演算に基づく制御出力（ＰＩＤ制御出力）により、前記原燃料流量制御弁の開度制御を行なって、前記改質器への供給原燃料の制御を行う場合、通常の原燃料流量計を用いた場合、原燃料ガスのガス組成の変化に伴う比重変化により、原燃料流量計の流量計測値に誤差が生じ、所望のＰＩＤ制御ができない問題が発生する。
【００３３】
さらに、原燃料のガス組成が変化した場合、前述のように供給原燃料を増減する必要が生じるが、このうち原燃料のガス濃度が希薄側に変化した場合には、原燃料ガス供給量を増大する必要があるが、増大に伴い、原燃料配管や改質ガス系配管及び弁を含む各種機器の圧力損失も増大する。そのため、原燃料制御弁の開度を次第に増大していくこととなるが、ついには、原燃料制御弁が全開となって、それ以降は、燃料電池の電流に見合ったガス供給量を確保できなくなる問題がある。
【００３４】
また、上記に対応するため、低濃度にあわせ原燃料配管や改質ガス系配管及び機器の圧力損失が少ない設計を採用する場合には、装置が大型化しコストも増大する。さらに、原燃料制御弁の径を大きくしたとしても、反対に低流量の制御が安定してできなくなる問題が生じ、原燃料高濃度側で低負荷時に制御性を損なう問題がある。
【００３５】
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、原燃料の組成変動があっても、原燃料の随時組成分析を行なうことなく、最適な原燃料供給，燃焼用空気供給，スチームの供給等の制御を行うことが可能であって、かつ、原燃料濃度が希薄となっても制御性が確保可能な燃料電池発電装置の運転制御方法を提供することにある。
【００３６】
【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、原燃料を改質して水素リッチな改質ガスを生成する改質器と、前記改質器の温度を検出する改質器温度検出器と、前記改質器温度検出器が検出した値を基に改質器温度を上方向または下方向に変動させる指令値を出力する改質器温度調節器と、前記改質ガスと酸化剤ガスとを電気化学的に反応させて発電する燃料電池とを備えた燃料電池発電装置の運転制御方法において、
起動時においては、予め使用する原燃料に応じて定めた原燃料流量と出力電流の比（原燃料換算比Ａ）と、予め使用する原燃料組成に応じて定めた原燃料濃度定数（Ｂ）との比（Ａ／Ｂ）に、前記燃料電池の出力電流値を乗じて原燃料流量を算出し、この算出値を改質器への供給原燃料流量として設定し、
定常発電状態においては、前記改質器の温度調節器からの指令値が温度を下げる方向に変動した場合前記原燃料濃度定数を上昇させ、前記改質器の温度調節器からの指令値が温度を上げる方向に変動した場合前記原燃料濃度定数を減少させて、前記比を変更し、この変更された比に燃料電池の出力電流値を乗じて原燃料流量を算出し、この算出値を改質器への供給原燃料流量として設定して、改質器への供給原燃料流量を制御することとする（請求項１の発明）。
【００３７】
本発明において、原燃料濃度とは、メタン発酵ガスなど主成分がメタンガスと炭酸ガスの場合はメタンガス濃度を示し、天然ガスなどメタンガスにエタンガスが混入している場合は、原燃料ガス中の可燃ガスを全て改質した場合の水素濃度と同濃度の水素を生成するメタンガス濃度に換算して表示することとする。
【００３８】
前記請求項１の発明による運転制御方法によれば、原燃料濃度が低下すれば、改質器での改質ガス水素濃度が下がり、改質器に戻る電池オフガス中の水素が減るので改質器は温度が低下する方向になり、改質器の温度調節器は温度を上げる方向に指令値が動き、反対に原燃料濃度が増加すれば改質器の温度調節器は温度を下げる方向に指令値が動くので、温度調節器の指令値によって原燃料濃度を推定することが可能であり、実質的に、原燃料組成変動を制御系にフィードバックした制御系とすることができる。
【００３９】
また、負荷変動時に好適な制御を行なうためには、下記請求項２の発明が好ましい。即ち、請求項１に記載の運転制御方法において、負荷低減時または負荷上昇時においては、前記改質器の温度調節器からの指令値が温度を下げる方向に変動した場合には上昇し、前記改質器の温度調節器からの指令値が温度を上げる方向に変動した場合には減少する定常発電状態での原燃料濃度定数を、ホールド回路にメモリーしておき、このメモリーした原燃料濃度定数に基づいて、前記比を算出し、この比に負荷低減時および負荷上昇時の燃料電池の出力電流値を乗じて原燃料流量を算出し、この算出値を改質器への供給原燃料流量として設定して、改質器への供給原燃料流量を制御することとする。
【００４０】
発電装置の負荷を上昇するときは、改質に必要な熱が多く必要となるので改質器の温度調節器は温度を上げる方向に指令値が動き、逆に負荷を下げる時は改質器の温度調節器は温度を下げる方向に指令値が動く。この負荷変動時の改質器温度変化は大きく改質器の温度調節器の指令値の上・下限値幅まで変動するが、この変動は原燃料組成変動による改質器の温度調節器の指令値変化ではないので、改質器の温度調節器の指令値によって変更された定常発電状態での原燃料濃度定数をホールド回路にメモリーしておくことにより、適正な供給原燃料流量の制御が可能となる。
【００４１】
さらに、前記請求項１または２の発明の実施態様としては、下記請求項３ないし７の発明が好ましい。即ち、請求項１または２に記載の運転制御方法において、前記原燃料濃度定数の変更は、前記改質器の温度調節器からの指令値の変動が、所定の変動率の上限値または下限値以上において所定時間継続した際に、行なうこととする（請求項３の発明）。詳細は後述するが、例えば、変動率５％が少なくとも１分（最大１０分）継続後に前記原燃料濃度定数の変更を行なう。燃料電池発電装置が負荷変動しない定常時では、外気温の変動で燃焼用空気温度や改質器の放熱量が変化し、改質器の温度変動となり改質器の温度調節器が働くので、原燃料の組成変動を適正に把握するために、上記のような制御を行い、変動率または継続時間が前記より小の場合は、組成変動とは見なさない制御とする。
【００４２】
また、前記請求項１ないし３のいずれかに記載の運転制御方法において、前記原燃料濃度定数の変更はステップ状に行い、そのステップ幅は、前記使用する原燃料組成に応じて定めた原燃料濃度定数の０．１〜１％とする（請求項４の発明）ことにより、原燃料流量の変動幅を小さくし安定した制御とすることができる。
【００４３】
さらに、負荷変動時にメモリする原燃料濃度定数は、改質器温度指令値により補正することが望ましい。例えば、発電負荷を下げると、改質器での吸熱反応熱量の減少から改質器の温度は下げる方向に制御しなければならないが、定常状態において改質器温度指令値が、改質器の温度を下げる方向、即ち０％近くにある場合は、改質器温度調節器からの指令値が０％飽和になり温度を下げるため原燃料を減少させることができない。負荷を上げる場合は逆のことが言える。
【００４４】
この観点から、下記請求項５の発明が好ましい。即ち、請求項２に記載の運転制御方法において、前記ホールド回路にメモリーする原燃料濃度定数を、改質器温度調節器からの指令値に基づき、指令値の大または小に応じて、所定値減少または増加する補正を行なう。例えば、改質器温度調節器からの指令値の中間点（５０％）を基準にして、補正を行なう。詳細は後述する。
【００４５】
また、改質器の燃焼用空気流量やスチーム流量の制御は、下記請求項６ないし７のようにして行うことが好ましい。即ち、前記請求項１または２に記載の運転制御方法において、前記改質器は、燃料電池オフガスを燃焼用空気とともに燃焼させるバーナを有するものとし、前記燃焼用空気流量設定値は、前記改質器の温度調節器からの指令値が温度を下げる方向に変動した場合には上昇し、前記改質器の温度調節器からの指令値が温度を上げる方向に変動した場合には減少する原燃料濃度定数から計算された単位原燃料当りの燃焼空気量換算値に、前記原燃料濃度定数に基づく原燃料流量設定値を乗じて求めた空気量から、燃料電池電流に空気消費量換算値を乗じて求めた空気量を減算し、所定の空燃比を乗じて求める（請求項６の発明）。
【００４６】
さらに、前記請求項１または２に記載の運転制御方法において、前記改質器は、原燃料を水蒸気（スチーム）と混合して改質するものとし、前記スチーム流量設定値は、前記改質器の温度調節器からの指令値が温度を下げる方向に変動した場合には上昇し、前記改質器の温度調節器からの指令値が温度を上げる方向に変動した場合には減少する原燃料濃度定数を基に単位原燃料当りのスチーム量を計算し、前記単位原燃料あたりのスチーム量から設定されたＳ／Ｃ比（原燃料中の炭素原子に対するスチームのモル数比）に、前記原燃料濃度定数に基づく原燃料流量設定値を乗じて求める（請求項７の発明）。
【００４７】
また、前記請求項１に記載の運転制御方法において、前記改質器への原燃料供給ライン上に原燃料流量計および原燃料流量制御弁を設け、前記原燃料流量計の流量計測値と前記改質器への供給原燃料設定値との比較演算に基づく制御出力（ＰＩＤ制御出力）により、前記原燃料流量制御弁の開度制御を行なって、前記改質器への供給原燃料の制御を行い、さらに、前記原燃料流量計の流量計測値は、前記原燃料濃度定数に基づいて補正し、この補正値に基づいて前記比較演算を行なう（請求項８の発明）。これにより、原燃料ガスのガス組成の変化に伴う流量制御誤差の問題を解消したＰＩＤ制御が可能となる。
【００４８】
さらに、前記ＰＩＤ制御は、前記原燃料流量制御のみならず燃焼空気流量およびスチーム流量の制御にも適用することが好ましく、この観点から、下記請求項９ないし１０の発明が好ましい。即ち、前記請求項６に記載の運転制御方法において、前記燃焼用空気流量設定値は、前記原燃料流量設定値に代えて、前記請求項８に記載のＰＩＤ制御出力によって制御された原燃料流量値に基づいて演算して求める（請求項９の発明）。また、前記請求項７に記載の運転制御方法において、前記スチーム流量設定値は、前記原燃料流量設定値に代えて、前記請求項８に記載のＰＩＤ制御出力によって制御された原燃料流量値に基づいて演算して求める（請求項１０の発明）。
【００４９】
さらにまた、原燃料濃度が希薄となっても制御性を確保する観点から、下記請求項１１あるいは１２の発明が好ましい。即ち、前記請求項１に記載の運転制御方法において、前記改質器への原燃料供給ライン上に原燃料流量制御弁を設け、前記原燃料流量制御弁の開度が、原燃料濃度が希薄であって所定の上限開度に到達した際に、前記燃料電池の出力を所定値まで低減する（請求項１１の発明）。
【００５０】
また、前記請求項１に記載の運転制御方法において、前記燃料電池は、原燃料濃度が希薄となった際に燃料電池の出力を所定値まで低減する出力上限リミッタを有し、前記出力上限リミッタにおける出力上限値は、前記原燃料濃度が希薄である程小となるように、前記原燃料濃度定数に基づいて設定する（請求項１２の発明）。前記請求項１１あるいは１２の発明の具体的な内容およびその作用効果に関しては、後述する。
【００５１】
【発明の実施の形態】
図面に基づき、本発明の実施例について以下にのべる。
【００５２】
図１は、本発明の実施例の燃料電池発電装置の運転制御方法に関わるシステム系統図を示す。図１において、図９および図１０に示した部材と同一機能を有する部材には、同一番号を付して詳細説明を省略する。図１は、運転制御方法を説明する観点から、後に、図２および図３の制御ブロック線図により詳述する制御量、即ち、原燃料流量６，燃焼用空気流量１８およびスチーム流量５２をブロックで示し、これらの諸量は、制御信号によって設定される。なお、図１において、６２は、原燃料とスチームを混合して改質器２２に供給するためのエゼクタを示し、５８は、燃料電池空気流量を示す。
【００５３】
図２は原燃料流量６および燃焼用空気流量１８に関わる制御ブロック線図、図３はスチーム流量５２に関わる制御ブロック線図を示す。前記図１ないし図３に基づき、本発明の運転制御方法の実施例について以下に述べる。
【００５４】
発電装置の起動時は、図１には図示しない助燃ラインを介して改質器に直接原燃料を供給して、改質器の温度を上げ、各機器の温度が上昇しスタンバイ状態になった時点で、図１に示す原燃料供給ラインに原燃料２７を供給し発電を始める。
【００５５】
この起動発電時は、図２に示すように、予め測定し制御装置に入力された起動時の原燃料濃度定数入力値１を使って制御するが、改質器の温度は発電後、３０分〜１時間で整定するので、図示しないタイマーにより起動時セレクタ２を切り替え、通常発電時の原燃料濃度定数を入力する。
【００５６】
次に、原燃料濃度定数は上下限リミッタ３で異常値をカットし、原燃料流量演算器４で電池電流１Ａ当りの原燃料量に換算される。原燃料流量演算器４は、電流１Ａ当りの原燃料量を演算する機能を有する。この演算は、即ち、予め使用する原燃料に応じて定めた原燃料流量と出力電流の比（原燃料換算比Ａ）と、予め使用する原燃料組成に応じて定めた原燃料濃度定数（Ｂ）との比（Ａ／Ｂ）の演算であり、原燃料濃度が低下すれば、電流１Ａ当りの原燃料量は多く設定される。
【００５７】
次に、原燃料流量演算器４の出力値に乗算器５で燃料電池電流１３を乗算し、原燃料流量を算出する。なお、この原燃料流量に、好ましくは通常、従来の技術の項において述べたように、改質器温度制御加算原燃料流量８を加えて、原燃料流量設定値６とし、図１に示す原燃料流量制御弁３２をコントロールする。また、図２に図示してはいないが、乗算器５の入力の燃料電池電流１３に補正ブロックを入れて、燃焼用空気ブロアに余裕がある発電負荷が小さい時は、計算に使う燃料電池電流を多めに設定して、原燃料流量設定値６を多めにしても良く、この場合は、起動時の原燃料濃度定数１は予め測定した値でなく、計画値を入力しても良い。
【００５８】
なお、前述のように、改質器温度制御用に原燃料を加算する各種の方法とその特徴等について、以下に補足して述べる。前記改質器の温度制御方法としては、(1)図１には図示しない、改質器に直接原燃料を供給する助燃ラインに、改質器の温度調節器出力に応じた原燃料量を供給し温度制御をする方法、(2)改質器燃焼炉に供給する、電池オフガスの燃焼に必要な燃焼用空気量に、改質器の温度調節器出力に応じた燃焼空気量を加算して改質器の温度制御をする方法、(3)図２の実施例に示すように、改質器経由で燃料電池に至る原燃料ラインに対して、燃料電池で必要な原燃料に、改質器の温度調節器出力に応じた原燃料量を加算して供給し、温度制御をする方法等がある。
【００５９】
いずれも、原燃料組成が変化すると改質器の熱バランスの変化によって改質器温度調節器からの出力が変化するので、原燃料組成の補正として使用できるが、前記(3)の方法は、(1)の方法に比べて、改質器の温度制御のために加算された原燃料により、結果として燃料電池が必要とする水素より過剰な水素が燃料電池に供給されることとなり、燃料電池出口の水素濃度が高くなることによって発電効率が高くなる利点がある。
【００６０】
(2)の燃焼用空気を増減する方法は、原燃料は過剰に供給し改質器の熱が余っている状態で、燃焼用空気の増減によって改質器を冷却制御する方法であり、過剰に供給する原燃料ロスによる発電効率の低下と、燃焼用空気量が多くなることによる燃焼用ブロア動力の増加によって発電効率が低下する欠点がある。
【００６１】
従って、改質器の温度制御は、前記(3)の方法が発電効率の点から望ましく、また、改質器の温度制御のために燃料電池に過剰に水素が供給されるので、燃料電池が水素欠をおこす可能性が低くなる利点がある。
【００６２】
次に、燃焼空気流量の設定について述べる。燃焼用空気は、原燃料濃度定数から燃焼空気流量演算器１５で原燃料１Nm3当りの燃焼用空気量を計算し、原燃料流量設定値６との積から原燃料を燃焼させるに必要な空気量を計算する。また、燃料電池電流１３と空気消費量換算値１４から燃料電池で消費した水素に相当する空気量を計算する。この、原燃料を燃焼させるに必要な空気量と燃料電池で消費した水素に相当する空気量の差に空燃比１７を乗じて燃焼用空気流量設定値１８とし、燃焼用空気ブロアを制御する。
【００６３】
次に、スチーム流量は図３の制御ブロック線図に示すとおり、原燃料濃度から、スチーム流量演算器５９で原燃料１Nm3当りのスチーム量を計算し、設定するＳ／Ｃ定数５０と原燃料流量設定値とから、乗算器５１によりスチーム流量を計算しスチーム流量設定値５２とし、改質用蒸気流量調整弁１０ａをコントロールする。
【００６４】
次に、原燃料濃度定数の変更や負荷変動時の制御等の詳細について、図２に基づき以下に述べる。通常発電時の原燃料濃度定数は、負荷変動セレクタ１２により起動直後は定常時になっている。定常時は原燃料濃度補正器１０により、改質器温度調節器からの指令値７が、例えば５％を継続して、リセットタイマ１１で設定された所定時間、例えば１分以上経過した際、０．５％原燃料濃度を上昇させる補正を行い、改質器温度調節器からの指令値７が９５％を継続して、１分以上経過した際には、０．５％原燃料濃度を減少させる補正を行う。
【００６５】
原燃料濃度を上昇させる補正を行なうと、原燃料流量演算器４の出力、燃料電池電流１Ａ当りの原燃料量が少なくなるので、原燃料流量設定値６が小さくなり、結果として改質器の温度が低下し、改質器温度調節器からの指令値７は温度を上げる方向、即ち５％より大きい方向になり、改質器の温度調節の指令幅が広がる。原燃料濃度を減少させる補正を行なうと、逆の動作となる。この原燃料濃度の補正により、供給される実原燃料の組成が変化しても、改質器の温度を制御することが可能となる。
【００６６】
次に、請求項８ないし１０に関わるＰＩＤ制御について、図４および図５に基づいて述べる。図４および図５は、図１および図２に対して、前記ＰＩＤ制御関連部材を追加した系統図を示す。図４は、図１に対して、原燃料流量調節器（ＰＩＤ）は図示を省略しているものの、ＰＩＤ制御関連部材として、原燃料流量計７１および原燃料流量測定値７２を追加し、さらに後述する燃料電池負荷指令７０を追加して示す。図５は、図２に対して、前記原燃料流量調節器（ＰＩＤ）７５と原燃料流量測定値７２を示し、かつ、ＰＩＤ出力としての原燃料制御バルブ指令値７３を示す。さらに、原燃料濃度変化に伴って流量計測値を補正するための、後述する分子変化分補正演算器７６を示す。
【００６７】
ＰＩＤ制御に関しては公知であるので、その詳細説明は省略するが、前述のように、原燃料供給流量制御にＰＩＤ制御を適用する場合、図４に示す原燃料流量計７１にガスの比重変化により誤差が生じるタイプの流量計を使用した場合には、原燃料供給量の計測値と実際値との間に誤差を生ずる。この問題を解消するために、あらかじめ定まっている原燃料流量計７１のガス組成の分子量と原燃料濃度定数（ここではバイオガスを使用するものとしメタン濃度に換算した値を使用する）とに基づき、メタン濃度が変化した場合の分子量を求め、この分子量変化分を補正計算する分子量変化分補正演算器７６を、図５に示すように設けることにより、測定誤差なく原燃料流量計測を行うことができる。なお、メタン濃度の変化に対応して変化するガスは、バイオガス使用の場合、二酸化炭素ガスである。
【００６８】
次に、負荷変動時の制御について述べる。負荷変動は、発電装置の操作盤からの手動入力、または、遠隔操作による負荷変化指令を入力することで行われ、この負荷変化指令により、図２に示す負荷変動セレクタ１２は、定常時側から負荷変動時側に切替わる。負荷変動時の原燃料濃度定数は、負荷変化前の原燃料濃度定数に補正係数９の乗算補正が行われ、本実施例では、改質器温度調節器からの指令値７の５０％を基準にして、指令値が小さい場合は改質器温度調節器からの指令値７の１０％に対し、原燃料濃度定数＋０．５％の補正が行われ、指令値が大きい場合には、改質器温度調節器からの指令値７の１０％に対し、原燃料濃度定数−０．５％の補正が行われ、負荷変動セレクタ１２のホールド回路にメモリさせ、このメモリされた原燃料濃度定数が負荷変動セレクタ１２の出力となる。負荷変動セレクタ１２は、図示しないタイマにより、負荷変化が終了して改質器温度が整定する１時間後に定常値側に切り替わる。
【００６９】
次に、請求項１１または１２に関わり、原燃料濃度が希薄となった場合の燃料電池の負荷変動対策（出力低減対策）の実施例について述べる。まず、請求項１１に関わる実施例について、図６に示す原燃料濃度の変化に伴う燃料電池の負荷変動の変化の模式的説明図に基づいて述べる。図６（ａ）は原燃料メタン濃度（％）の時間変化を、図６（ｂ）は原燃料制御バルブ（弁）の開度（％）の時間変化を、図６（ｃ）は負荷指令（％）の時間変化の一例を、それぞれ模式的に示す。
【００７０】
通常、図４に示す燃料電池２１の負荷指令変化は、図示しない発電装置操作盤からの手動入力、または遠隔操作による負荷変化指令により行われ、図４に示す燃料電池負荷指令７０により発電装置の負荷を決めて運転を行っている。ここで例えば、図６（ａ）に示すように、原燃料のメタン濃度が希薄側に変化し、メタンガス濃度が６５％から４５％に変化したとすると、本発明の前記請求項１の適用により、ガス濃度が変化しても、とりあえずは運転継続が可能となり、原燃料流量中同量のメタンガスが供給できるように制御されるが、全ガスの供給量としては1.5倍に変化してしまうため、前述のように、低濃度の程度によっては、原燃料制御バルブが全開となり制御不能となってしまう。
【００７１】
そこで、例えば、図６（ｂ）に示すように、バルブ開度が一段目の上限設定値１０１として示すようにバルブ開度が９３％となった時、燃料電池負荷指令７０を、図６（ｃ）に示すように、５％低下させる。そして、さらに濃度低下により、バルブ開度が二段目の上限設定値１０２（バルブ開度９５％）となった時、さらに燃料電池負荷指令値７０を５％低下させる制御を行う。
【００７２】
上記のような制御によれば、原燃料濃度が希薄となっても原燃料供給量の制御性が確保できる。上記制御性は、前記請求項１２の発明によっても確保できる。かかる実施例について、図７および図８により以下に述べる。図７は負荷指令上限制御に関する制御ブロック図、図８は負荷指令上限値と原燃料濃度定数との関係の模式的説明図である。
【００７３】
原燃料濃度が希薄となった場合に、原燃料濃度定数の制御信号に基づいて、燃料電池の出力（負荷）を低減することは、前記実施例と同様であるので、詳細説明は省略するが、請求項１２の発明の実施例の場合には、図７に示すように、燃料電池負荷指令７０に負荷指令上限リミッタ７９を設け、その結果として上限リミッタ後燃料電池負荷指令７７に基づき、燃料電池の負荷制御を行うようにする。
【００７４】
また、図８に示すように、原燃料濃度定数に対応した負荷指令上限値７８の関係を制御に組み込み、原燃料濃度定数が希薄側に変化した場合は、例えば、５０％濃度から上限値を濃度１％あたり１％減らすように制御する。これにより、前記請求項１１の発明の実施例と同様に、原燃料濃度が希薄となっても原燃料供給量の制御性が確保できる。
【００７５】
以上のような各実施例によれば、改質器の温度調節器の指令値から原燃料組成を示す原燃料濃度を補正するようにし、この補正された原燃料濃度から原燃料流量，燃焼用空気流量，スチーム流量等の設定値を算出して制御するようにしたので、起動時に設定した原燃料組成と運転中の原燃料組成が違っても、原燃料の随時分析を行うことなく、原燃料流量と燃焼空気流量が適正に制御され、燃料電池における水素不足によるセル損傷を防止でき、また、燃料の無駄な消費による発電効率の低下が防止できる。さらに、改質器の適正な温度制御ができ、改質器バーナにおけるオフガスの適正な燃焼が行われ不完全燃焼や過剰空気供給によるブロア動力損失が防止できる。また、適正な原燃料とスチームの比を確保することによって安定が改質ガス組成が得られ、ガス組成悪化による発電効率の低下や改質器触媒への炭素析出による改質器閉塞などのトラブルを防止できる。
【００７６】
また、原燃料濃度が低下し必要ガス量が供給不能になる前に、燃料電池の負荷指令を原燃料バルブの開度または原燃料濃度定数に基づき制御することにより、発電装置の運転を継続することができる。
【００７７】
【発明の効果】
上記のとおり、この発明によれば、起動時においては、予め使用する原燃料に応じて定めた原燃料流量と出力電流の比（原燃料換算比Ａ）と、予め使用する原燃料組成に応じて定めた原燃料濃度定数（Ｂ）との比（Ａ／Ｂ）に、前記燃料電池の出力電流値を乗じて原燃料流量を算出し、この算出値を改質器への供給原燃料流量として設定し、定常発電状態においては、前記改質器の温度調節器からの指令値が温度を下げる方向に変動した場合前記原燃料濃度定数を上昇させ、前記改質器の温度調節器からの指令値が温度を上げる方向に変動した場合前記原燃料濃度定数を減少させて、前記比を変更し、この変更された比に燃料電池の出力電流値を乗じて原燃料流量を算出し、この算出値を改質器への供給原燃料流量として設定して、改質器への供給原燃料流量を制御すること（請求項１）とし、また、ＰＩＤ制御を行う場合には、前述のように原燃料流量計の流量計測値を原燃料濃度定数に基づいて補正すること（請求項８）とし、
さらに、負荷低減時または負荷上昇時においては、前記改質器の温度調節器からの指令値が温度を下げる方向に変動した場合には上昇し、前記改質器の温度調節器からの指令値が温度を上げる方向に変動した場合には減少する定常発電状態での原燃料濃度定数を、ホールド回路にメモリーしておき、このメモリーした原燃料濃度定数に基づいて、前記比を算出し、この比に負荷低減時および負荷上昇時の燃料電池の出力電流値を乗じて原燃料流量を算出し、この算出値を改質器への供給原燃料流量として設定して、改質器への供給原燃料流量を制御すること（請求項２）とし、
さらにまた、改質器の燃焼用空気流量やスチーム流量の制御は、前記請求項６ないし７、あるいは請求項９ないし１０のようにして行うこととしたので、
原燃料の組成変動があっても、原燃料の随時組成分析を行なうことなく、最適な原燃料供給，燃焼用空気供給，スチームの供給等の制御を行うことが可能な燃料電池発電装置の運転制御方法を提供することができる。
【００７８】
また、原燃料濃度が低下しても、請求項１１ないし請求項１２のように燃料電池の負荷制御を行うようにしたので、必要ガス量が供給不能になることなく運転継続可能な燃料電池発電装置の運転制御方法を提供することができる。
【図面の簡単な説明】
【図１】 この発明の燃料電池発電装置の運転制御方法の実施例を示すシステム系統図
【図２】 図１の実施例の制御ブロック線図
【図３】 図１の実施例のスチーム流量に関する制御ブロック線図
【図４】 図１とは異なる運転制御方法の実施例を示すシステム系統図
【図５】 図４の実施例の制御ブロック線図
【図６】 請求項１１の発明に関わり、原燃料濃度の変化に伴う燃料電池の負荷変動の変化の模式的説明図
【図７】 請求項１２の発明に関わる負荷指令上限制御に関する制御ブロック図
【図８】 図７における負荷指令上限値と原燃料濃度定数との関係の模式的説明図
【図９】 従来の燃料電池発電装置の一例のシステム系統図
【図１０】 従来の燃料電池発電装置の図９とは異なるシステム系統図
【符号の説明】
１：起動時の原燃料濃度定数入力値、２：起動状態セレクタ、３：上下限リミッタ、４：原燃料流量演算器、５，１６，５１：乗算器、６：原燃料流量設定値、７：改質器温度調節器からの指令値、８：改質器温度制御加算原燃料流量、９：補正係数、１０：原燃料濃度補正器、１１：リセットタイマ、１２：負荷変動セレクタ、１３：燃料電池電流、１４：空気消費量換算値、１５：燃焼空気流量演算器、１７：空燃比設定器、１８：燃焼用空気流量設定値、２１：燃料電池、２２：改質器、２３：バーナ、３２：原燃料流量制御弁、５９：スチーム流量演算器、５０:Ｓ/Ｃ係数乗算器、５２：スチーム流量設定値、６０：水蒸気分離器、６２：エゼクタ、６４：脱硫器、６６：ＣＯ変成器、７０：燃料電池負荷指令、７１：原燃料流量計、７２：原燃料流量計測値、７３：原燃料制御バルブ指令値、７５：原燃料流量調節器（PID）、７６：分子量変化分補正演算器、７７：上限リミッタ後燃料電池負荷指令、７８：負荷指令上限値、７９：上限リミッタ。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an operation control method for a fuel cell power generator, and more particularly to a control method for a raw fuel flow rate, a reforming steam flow rate, and the like when the raw fuel composition varies.
[0002]
[Prior art]
A fuel cell power generator is a device that extracts electricity by an electrochemical reaction between a fuel gas and an oxidant gas. The amount of fuel gas and oxidant gas required for the electrochemical reaction of the fuel cell is proportional to the current taken from the fuel cell.
[0003]
In phosphoric acid fuel cells and solid polymer fuel cells that use hydrogen gas for the electrochemical reaction, for example, a gas such as city gas or methane fermentation gas used as raw fuel reacts with water vapor. Then, it is reformed into a hydrogen-rich gas and supplied to the fuel cell. The fuel cell power generator includes a reformer that reforms hydrocarbon gas into hydrogen-rich gas, and this reformer is controlled to a high temperature in order to continue the reforming reaction.
[0004]
Since the reaction between the hydrocarbon gas and the water vapor in the reformer is an endothermic reaction, the reformed gas is supplied to the fuel cell with more reformed gas than the amount of hydrogen consumed in the electrochemical reaction, and the off-gas from the fuel cell is supplied. In general, the gas is recirculated to the reformer and burned to become a heat source in the reformer.
[0005]
The temperature control of the reformer is greatly affected by the increase or decrease in the amount of hydrogen that flows back to the reformer and burns. Therefore, the flow rate of raw fuel supplied to the reformer is the amount of hydrogen consumed by the electrochemical reaction in the fuel cell. And the sum of the flow rate corresponding to the reformer temperature control is supplied in proportion to the battery current.
[0006]
As described above, Patent Document 1 discloses an example of a fuel cell power generator that controls the flow rate of raw fuel supplied to a reformer using a flow control valve based on a measured value of the output current of the fuel cell. . FIG. 9 is a system diagram of the system described in FIG. 1 of the publication, and as an explanation thereof, the publication describes as follows.
[0007]
That is, “the raw material fuel gas is sent from the fuel supply device 27 to the reformer 22 where it is steam reformed, and the reformed gas is supplied from the reformer 22 to the fuel cell 21. A burner 23 is installed to raise the temperature to a temperature required for the reforming reaction, and the fuel cell 21 generates power using reformed gas containing hydrogen and air. Supplied from the supply device 24. The air discharged from the fuel cell 21 is cooled by the outside air in the air-side water recovery unit 25 to generate condensed water, and the obtained condensed water is stored in the water tank 26. Recovery The water thus supplied is sent to the reformer 22 by the fuel-side water pump 41 and used for fuel reforming.In the fuel cell 21, heat is generated together with electricity, so that a cooling pump 42 for sending cooling water is generated. Cooling radiator 43 that releases the heat generated outside It is provided.
[0008]
The fuel cell 21 is provided with an ammeter 30 for measuring the output current. In the raw material fuel gas flow path, a raw material fuel flow rate control valve 32 for controlling the flow rate of the raw material fuel gas amount is installed. The reformer 22, the burner 23, the fuel-side water pump 41, the fuel supply device 27, and the raw fuel flow rate control valve 32 constitute a hydrogen generator 28. The raw material fuel supply means includes a fuel supply device 27 and a raw material fuel flow control valve 32.
[0009]
Inside the reformer 22, the raw material fuel gas and the fuel side water pump as raw materials 41 Water reforming is performed by mixing the water fed from. The reformed gas containing hydrogen thus obtained is supplied to the fuel cell 21. Since the fuel cell cannot consume all hydrogen, 20% to 30% of the supplied hydrogen is discharged. This hydrogen is sent to the burner 23 and burned, and becomes heat necessary for reforming. When the discharged hydrogen is used for combustion, energy is recovered, but the amount of reformed gas generated increases and the load on the reformer increases. This also reduces the overall power generation efficiency.
[0010]
On the other hand, the amount of hydrogen consumed by the fuel cell 21 is proportional to the current value output from the fuel cell 21. Therefore, the required hydrogen amount is estimated by the first controller 31 using the current value obtained by the ammeter 30, and the flow rate of the raw material fuel gas amount is controlled by the raw material fuel flow rate control valve 32 accordingly. In this way, the minimum amount of hydrogen required for power generation can be generated.
[0011]
As described above, as an effect of the present embodiment, it is possible to maintain the efficiency of the reformer by generating the minimum amount of hydrogen by the operation of the raw fuel flow control valve 32, and high power generation efficiency is obtained. It is done. Is written.
[0012]
In FIG. 9, a raw fuel flow meter (not shown) is provided upstream of the raw fuel flow control valve 32 on the raw fuel supply line to the reformer 22, and the flow rate measurement value of the raw fuel flow meter and the first The degree of opening of the raw fuel flow rate control valve is controlled by a control output (PID control output) based on a comparison calculation with the raw fuel set value supplied to the reformer set by the controller 31 of the reformer, and the reformer In some cases, the raw fuel supplied to the vehicle is controlled.
[0013]
By the way, in the fuel cell power generator as described above, since the amount of hydrogen obtained by reforming the raw fuel differs depending on the composition of the hydrocarbon, the set value of the raw fuel flow rate is set depending on the type of raw fuel used. It is necessary to decide. In particular, when the methane fermentation gas (biogas) is used as a raw fuel, the composition of the raw fuel fluctuates. Therefore, the concentration of the methane gas component in the supplied biogas is detected, and this detected methane gas concentration is detected. Accordingly, it is necessary to adjust the supply flow rate of biogas as raw fuel. The configuration of this type of fuel cell power generation apparatus using biogas as raw fuel is disclosed in, for example, Patent Document 2 and Patent Document 3.
[0014]
FIG. 10 is a system configuration diagram of the fuel cell power generation facility described as FIG. 1 in the above-mentioned Patent Document 2 (part numbers are partially changed in FIG. 10). The configuration of FIG. 10 will be described below with reference to the description in the publication.
[0015]
That is, the fuel cell power generation facility shown in FIG. 10 includes a raw fuel supply pipe 1a that guides a digested gas obtained from sewage sludge by methane fermentation, and a sulfur component contained in the digested gas supplied through the raw fuel supply pipe 1a. A desulfurizer 64 that removes sulfur, a reformer 22 that reforms the digestion gas from which the sulfur component has been removed by the desulfurizer 64 with, for example, steam, to carbon monoxide and hydrogen gas, and the reformer In order to convert carbon monoxide, which is a poisoning gas component, into carbon dioxide from the carbon monoxide and hydrogen gas output from the carbon dioxide, the carbon monoxide is catalytically reacted with, for example, water vapor to form carbon dioxide and hydrogen gas. A transformer 66 for transformation and a fuel cell main body 21 are provided.
[0016]
The raw fuel supply pipe 1a is provided with a detector 6a for detecting the gas concentration in the digestion gas. Further, a fuel gas inlet shut-off valve 7a and a fuel gas flow rate adjusting valve 32 are interposed at a required position of the raw fuel supply pipe 1a, and further, for example, steam is supplied to react the catalyst on the input side of the reformer 22. A steam supply line 9a is provided, and a steam flow rate adjusting valve 10a for reforming for adjusting and supplying the flow rate of water vapor is installed in the steam supply line 9a.
[0017]
Furthermore, a gas concentration evaluation calculation unit 11a for evaluating and calculating a required gas concentration contained in the digestion gas is provided on the output side of the detector 6a. The gas concentration evaluation calculation unit 11a includes a gas concentration collecting unit 12a that collects various gas concentration data that is an output of the detector 6a, and a methane-based hydrocarbon component in digestion gas collected by the gas concentration collecting unit 12a. The total power generation amount is calculated from the concentration, the required fuel gas flow rate is determined from the total power generation amount, and the fuel flow rate calculation means 13a for adjusting the fuel gas flow rate adjustment valve 32 is determined by the fuel flow rate calculation unit 13a. A reforming steam flow rate calculating means 14a for determining the reforming steam flow rate from the fuel gas flow rate and adjusting the reforming steam flow rate adjusting valve 10a, and carbon monoxide, sulfur, nitrogen, salts, oxygen as poisonous components Etc., when the concentration of at least one poisoning component exceeds an allowable range, a facility stop means 15a for stopping a required device among the devices constituting the fuel cell power generation facility. It is.
[0018]
In FIG. 10, 60 is a steam separator, which separates steam from water and supplies it to the steam supply line 9. The means for obtaining the steam does not need to be the steam separator 60, and can be obtained by various conventionally known methods. 17a is a heat exchanger for exchanging heat of the exhaust gas output from the air electrode constituting the fuel cell main body 5 with water, 18a is a tank, and 19a is a pump.
[0019]
The above is generally the description of FIG. 10 described in Patent Document 2, but some systems such as the fuel cell water recovery device and the pure water device are omitted, and the fuel cell cooling system and exhaust system are omitted. There are various modifications of the detailed configuration of the system such as the heat recovery system. The reforming steam supply flow rate is usually determined based on the raw fuel supply amount and a predetermined S / C (ratio of the number of moles of water vapor to carbon atoms in the raw fuel). In the case of biogas, methane gas is mainly used. Therefore, it is 2.5 to 4.0.
[0020]
[Patent Document 1]
JP 2001-158604 A
[Patent Document 2]
Japanese Patent Laid-Open No. 11-126629
[0021]
[Patent Document 3]
JP 2000-90953 A
[0022]
[Problems to be solved by the invention]
As in the case of the apparatus shown in FIG. 10, when the fluctuation of the raw fuel composition is detected and this fluctuation is not fed back to the control system, various cases are summarized as follows.
[0023]
For example, if the methane concentration of the methane fermentation gas decreases and the calorific value of the raw fuel decreases, the amount of hydrogen supplied from the reformer to the fuel cell decreases if this composition variation is not fed back to the control system. In addition, there is a risk of hydrogen shortage in the fuel cell, so-called gas shortage. When the gas runs out, hydrogen for the electrochemical reaction is not supplied to the fuel cell, and the cell is damaged. In addition, off-gas hydrogen that has consumed hydrogen in the fuel cell is returned to the reformer and burned to become the heat required for reforming. However, due to the lack of hydrogen, the amount of heat decreases, so the temperature of the reformer decreases. The reforming reaction cannot be maintained.
[0024]
Next, contrary to the above case, when the methane concentration of the methane fermentation gas increases and the calorific value of the raw fuel increases, if this composition variation is not fed back to the control system, the fuel cell Hydrogen is supplied excessively, and since this hydrogen is not used for power generation, it is wasted and power generation efficiency is reduced. In addition, the off-gas that has consumed hydrogen in the fuel cell returns to the reformer and burns to become the heat required for reforming.However, excessive hydrogen increases the amount of heat and raises the temperature of the reformer. The quality reaction cannot be maintained at an appropriate temperature.
[0025]
Normally, the temperature control of the reformer is performed by increasing or decreasing the flow rate of the raw fuel system passing through the reformer catalyst and the fuel cell to increase or decrease the amount of off-gas returning to the reformer, but burn off-gas hydrogen. Since air is required for fuel, the upper limit of the increase in raw fuel, which is limited by the upper limit of the air supply capacity of the fuel air blower, and the lower limit of the minimum flow rate at which hydrogen shortage does not occur in the fuel cell There is a range of increase and decrease. Therefore, if the composition variation of the raw fuel is large in an apparatus that does not feed back the composition variation of the raw fuel to the control system, the amount of generated heat exceeds the control width, and the reformer temperature cannot be controlled.
[0026]
As another temperature control method for the reformer, there is a method in which raw fuel is directly supplied to the reformer combustion furnace as auxiliary combustion gas. However, the flow rate of the raw fuel system via the reformer catalyst and the fuel cell is known. For the same reason as the method of increasing / decreasing the ratio, there is an upper limit value of the flow rate of the raw fuel directly supplied to the combustion furnace.
[0027]
Furthermore, the amount of combustion air is 1Nm of raw fuel. Three is determined by the oxygen flow rate and raw fuel flow rate required to burn / h, that is, the fuel cell power generation current equivalent, so if the raw fuel composition changes, the raw fuel 1Nm Three Since the amount of oxygen required to burn / h changes, the optimal amount of combustion air cannot be controlled unless the raw fuel composition is known, resulting in incomplete combustion due to lack of air, or excess air supply. Therefore, the problem that power loss becomes large arises.
[0028]
Furthermore, in the reformer, as described above, steam and raw fuel are reacted to reform into a hydrogen-rich gas. However, if the carbon ratio (S / C) of steam and raw fuel is not optimal, reforming is performed. The gas composition may deteriorate or carbon may deposit on the reformer catalyst. Steam flow is 1Nm of raw fuel calculated from raw fuel composition Three Since it is determined by the amount of steam required per hit and the set S / C, the optimum steam flow rate cannot be calculated unless the raw fuel composition is known.
[0029]
Further, when the power generation load of the fuel cell fluctuates, for example, when the power generation load of the fuel cell is reduced, the reformer temperature control system reduces the raw fuel flow rate in order to reduce the load on the reformer accompanying the power generation load reduction. Since the control in the direction to reduce the temperature of the reformer works, it is necessary to set the lower limit value of the raw fuel flow rate so that the raw fuel flow rate is not too small. The raw fuel lower limit flow rate is calculated from the reformed hydrogen amount determined from the power generation cell current and the raw fuel composition.
[0030]
Therefore, when the raw fuel composition fluctuates and this composition fluctuation is not fed back to the control system, the flow rate of the raw fuel is too small when the power generation load is reduced, and there is a risk that a shortage of hydrogen in the fuel cell, a so-called gas shortage may occur. is there. When the gas runs out, hydrogen for the electrochemical reaction is not supplied to the fuel cell, causing damage to the cell.
[0031]
For the reasons described above, the composition of the raw fuel is measured and analyzed, and the results are fed back to determine the raw fuel and combustion air amount to be supplied to the reformer, to prevent hydrogen shortage in the fuel cell and to effectively use the fuel. It is desirable to improve the power generation efficiency, to control the temperature of the reformer properly, and to properly burn off gas in the reformer combustion furnace. However, a device that measures and analyzes the composition of raw fuel as needed is expensive, has problems such as the need for regular calibration and increased maintenance costs, and the reliability of the analyzer. There are many practical problems.
[0032]
Further, as described in the explanation of FIG. 9, a raw fuel flow meter and a raw fuel flow rate control valve are provided on the raw fuel supply line to the reformer, and the flow rate measurement value of the raw fuel flow meter and the reformer are provided. The opening of the raw fuel flow rate control valve is controlled by a control output (PID control output) based on a comparison operation with the set value of the raw fuel supplied to the reactor, and the raw fuel supplied to the reformer is controlled. In this case, when a normal raw fuel flow meter is used, an error occurs in the flow rate measurement value of the raw fuel flow meter due to a change in specific gravity accompanying a change in the gas composition of the raw fuel gas, resulting in a problem that desired PID control cannot be performed. .
[0033]
Furthermore, when the gas composition of the raw fuel changes, it is necessary to increase or decrease the supply raw fuel as described above. However, when the gas concentration of the raw fuel changes to a lean side, the supply amount of the raw fuel gas is reduced. Although it is necessary to increase, the pressure loss of various apparatuses including raw fuel piping, reformed gas piping and valves increases with the increase. As a result, the opening of the raw fuel control valve will gradually increase, but eventually the raw fuel control valve will be fully opened, and after that, a gas supply amount commensurate with the current of the fuel cell can be secured. There is a problem that disappears.
[0034]
Further, in order to cope with the above, when adopting a design in which the pressure loss of the raw fuel pipe, the reformed gas system pipe, and the equipment is reduced in accordance with the low concentration, the apparatus becomes larger and the cost increases. Furthermore, even if the diameter of the raw fuel control valve is increased, there arises a problem that the control of the low flow rate cannot be stably performed, and there is a problem that the controllability is impaired at a low load on the raw fuel high concentration side.
[0035]
The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to provide an optimal raw fuel supply without performing an analysis of the raw fuel composition at any time, even if the raw fuel composition varies. To provide an operation control method for a fuel cell power generator capable of controlling the supply of combustion air, the supply of steam, etc., and capable of ensuring controllability even when the raw fuel concentration is low. is there.
[0036]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention includes a reformer that reforms raw fuel to generate a hydrogen-rich reformed gas; A reformer temperature detector for detecting the temperature of the reformer and a command value for outputting a command value for changing the reformer temperature upward or downward based on the value detected by the reformer temperature detector. Temperature controller, and In an operation control method of a fuel cell power generation device including a fuel cell that generates electricity by electrochemically reacting a reformed gas and an oxidant gas,
At start-up, the ratio of the raw fuel flow rate to the output current (raw fuel conversion ratio A) determined according to the raw fuel used in advance and the raw fuel concentration constant (B) determined according to the raw fuel composition used in advance. The raw fuel flow rate is calculated by multiplying the ratio (A / B) with the output current value of the fuel cell, and this calculated value is set as the feed raw fuel flow rate to the reformer,
In the steady power generation state, the reformer temperature controller From Command value When the temperature fluctuates in the direction of lowering the temperature, the raw fuel concentration constant is increased, and when the command value from the reformer temperature controller fluctuates in the direction of increasing the temperature, the raw fuel concentration constant is decreased. , Changing the ratio, multiplying the changed ratio by the output current value of the fuel cell to calculate the raw fuel flow rate, and setting this calculated value as the feed raw fuel flow rate to the reformer, The flow rate of the raw fuel supplied to the vehicle is controlled (the invention of claim 1).
[0037]
In the present invention, the raw fuel concentration indicates the methane gas concentration when the main components such as methane fermentation gas are methane gas and carbon dioxide gas, and when ethane gas is mixed in methane gas such as natural gas, the combustible gas in the raw fuel gas Is converted into a methane gas concentration that produces hydrogen at the same concentration as the hydrogen concentration when all of the gas is reformed.
[0038]
According to the operation control method of the first aspect of the present invention, if the raw fuel concentration is lowered, the reformed gas hydrogen concentration in the reformer is lowered, and the hydrogen in the battery off-gas returning to the reformer is reduced. The temperature of the reformer decreases, the temperature controller of the reformer moves the command value in the direction of increasing the temperature, and conversely, if the raw fuel concentration increases, the temperature controller of the reformer decreases the temperature. Since the command value moves, it is possible to estimate the raw fuel concentration based on the command value of the temperature regulator, and it is possible to make a control system that substantially feeds back the raw fuel composition variation to the control system.
[0039]
In order to perform suitable control when the load fluctuates, the invention of the following claim 2 is preferable. That is, in the operation control method according to claim 1, when the load is reduced or the load is increased, the temperature regulator of the reformer is used. From Command value Increases when the temperature fluctuates in the direction of decreasing the temperature, and decreases when the command value from the temperature controller of the reformer fluctuates in the direction of increasing the temperature. The raw fuel concentration constant in the steady power generation state is stored in the hold circuit, and the ratio is calculated based on the stored raw fuel concentration constant, and the ratio of the fuel cell at the time of load reduction and load increase is calculated based on this ratio. The raw fuel flow rate is calculated by multiplying the output current value, and this calculated value is set as the supply raw fuel flow rate to the reformer to control the supply raw fuel flow rate to the reformer.
[0040]
When increasing the load on the power generator, a lot of heat is required for reforming, so the temperature controller of the reformer moves the command value in the direction of increasing the temperature, and conversely when reducing the load, the reformer In the temperature controller, the command value moves in the direction of decreasing the temperature. The temperature change of the reformer at the time of this load fluctuation largely fluctuates up to the upper and lower limits of the command value of the reformer temperature controller, but this fluctuation is the command value of the reformer temperature controller due to the fluctuation of raw fuel composition Since this is not a change, by storing the raw fuel concentration constant in the steady power generation state changed by the command value of the reformer temperature controller in the hold circuit, it is possible to control the appropriate supply raw fuel flow rate. Become.
[0041]
Further, as an embodiment of the invention of claim 1 or 2, the inventions of claims 3 to 7 below are preferable. That is, in the operation control method according to claim 1 or 2, the change of the raw fuel concentration constant is performed by a temperature regulator of the reformer. From When the command value fluctuates for a predetermined time at an upper limit value or a lower limit value of a predetermined fluctuation rate, the change is performed (invention of claim 3). Although details will be described later, for example, the raw fuel concentration constant is changed after a fluctuation rate of 5% continues for at least 1 minute (maximum 10 minutes). In the steady state when the load of the fuel cell generator does not fluctuate, the temperature of the combustion air and the amount of heat dissipated by the reformer change due to fluctuations in the outside air temperature. In order to properly grasp the composition variation of the raw fuel, the above-described control is performed. When the variation rate or the duration time is smaller than the above, the control is not regarded as the composition variation.
[0042]
Further, in the operation control method according to any one of claims 1 to 3, the change in the raw fuel concentration constant is performed in steps, and the step width is determined according to the raw fuel composition to be used. By setting the concentration constant to 0.1 to 1% (invention of claim 4), the fluctuation range of the raw fuel flow rate can be reduced to achieve stable control.
[0043]
Further, it is desirable to correct the raw fuel concentration constant stored at the time of load fluctuation by the reformer temperature command value. For example, when the power generation load is reduced, the reformer temperature must be controlled to decrease due to a decrease in the endothermic reaction heat amount in the reformer, but the reformer temperature command value in the steady state is If the temperature decreases, i.e., near 0%, the reformer temperature controller From Since the command value becomes 0% saturation and the temperature is lowered, the raw fuel cannot be reduced. The opposite is true when increasing the load.
[0044]
From this viewpoint, the invention of claim 5 below is preferable. That is, in the operation control method according to claim 2, the raw fuel concentration constant stored in the hold circuit is set as a reformer temperature controller. From Based on the command value, a correction to decrease or increase a predetermined value according to the magnitude of the command value is performed. For example, reformer temperature controller From Correction is performed with reference to the midpoint (50%) of the command value. Details will be described later.
[0045]
The combustion air flow rate and steam flow rate of the reformer are preferably controlled as described in claims 6 to 7 below. That is, in the operation control method according to claim 1 or 2, the reformer includes a burner that burns fuel cell off gas together with combustion air, and the combustion air flow rate setting value is the reforming value. Temperature controller From Command value Increases when the temperature fluctuates in the direction of decreasing the temperature, and decreases when the command value from the temperature controller of the reformer fluctuates in the direction of increasing the temperature. Raw fuel concentration constant Calculated from Combustion air conversion value per unit raw fuel Is subtracted from the air amount obtained by multiplying the raw fuel flow rate set value based on the raw fuel concentration constant by the air consumption amount converted value by the fuel cell current. , Predetermined air-fuel ratio Multiplied by Obtained (Invention of Claim 6).
[0046]
Furthermore, in the operation control method according to claim 1 or 2, the reformer reforms by mixing raw fuel with steam (steam), and the steam flow rate set value is the reformer. Temperature controller From Command value Increases when the temperature fluctuates in the direction of decreasing the temperature, and decreases when the command value from the temperature controller of the reformer fluctuates in the direction of increasing the temperature. Raw fuel concentration constant The steam amount per unit raw fuel was calculated based on the above, and the steam amount per unit raw fuel was set. S / C ratio (ratio of moles of steam to carbon atoms in raw fuel) Multiplied by the raw fuel flow rate setting value based on the raw fuel concentration constant. Obtained (Invention of Claim 7).
[0047]
In the operation control method according to claim 1, a raw fuel flow meter and a raw fuel flow control valve are provided on a raw fuel supply line to the reformer, and a flow measurement value of the raw fuel flow meter Control of opening of the raw fuel flow rate control valve is performed by a control output (PID control output) based on a comparison calculation with a set value of the raw fuel supplied to the reformer to control the raw fuel supplied to the reformer. Further, the flow rate measurement value of the raw fuel flow meter is corrected based on the raw fuel concentration constant, and the comparison operation is performed based on the correction value (invention of claim 8). As a result, PID control that eliminates the problem of flow rate control errors associated with changes in the gas composition of the raw fuel gas becomes possible.
[0048]
Further, the PID control is preferably applied not only to the raw fuel flow rate control but also to the control of the combustion air flow rate and the steam flow rate. From this viewpoint, the inventions of the following claims 9 to 10 are preferred. That is, in the operation control method according to claim 6, the combustion air flow rate setting value is replaced by the raw fuel flow rate setting value, and the raw fuel flow rate controlled by the PID control output according to claim 8. It calculates and calculates based on a value (invention of Claim 9). Further, in the operation control method according to claim 7, the steam flow rate setting value is changed to the raw fuel flow rate value controlled by the PID control output according to claim 8, instead of the raw fuel flow rate setting value. The calculation is made based on the above (invention of claim 10).
[0049]
Furthermore, from the viewpoint of ensuring controllability even when the raw fuel concentration becomes lean, the invention of claim 11 or 12 is preferable. That is, in the operation control method according to claim 1, a raw fuel flow rate control valve is provided on a raw fuel supply line to the reformer, and an opening degree of the raw fuel flow rate control valve is set so that a raw fuel concentration is low. When the predetermined upper limit opening is reached, the output of the fuel cell is reduced to a predetermined value (invention of claim 11).
[0050]
The operation control method according to claim 1, wherein the fuel cell includes an output upper limiter that reduces the output of the fuel cell to a predetermined value when the raw fuel concentration becomes lean, and the output upper limiter. Is set based on the raw fuel concentration constant so that the lower the raw fuel concentration, the smaller the output upper limit value. Specific contents and operational effects of the invention of claim 11 or 12 will be described later.
[0051]
DETAILED DESCRIPTION OF THE INVENTION
Examples of the present invention will be described below with reference to the drawings.
[0052]
FIG. 1 is a system diagram related to an operation control method for a fuel cell power generator according to an embodiment of the present invention. In FIG. 1, members having the same functions as those shown in FIGS. 9 and 10 are given the same reference numerals, and detailed description thereof is omitted. From the viewpoint of explaining the operation control method, FIG. 1 blocks the control amounts, that is, the raw fuel flow rate 6, the combustion air flow rate 18 and the steam flow rate 52, which will be described in detail later with reference to the control block diagrams of FIGS. These quantities are set by control signals. In FIG. 1, 62 indicates an ejector for mixing raw fuel and steam and supplying them to the reformer 22, and 58 indicates a fuel cell air flow rate.
[0053]
FIG. 2 is a control block diagram related to the raw fuel flow rate 6 and the combustion air flow rate 18, and FIG. 3 is a control block diagram related to the steam flow rate 52. An embodiment of the operation control method of the present invention will be described below with reference to FIGS.
[0054]
When starting up the power generation device, the raw fuel was directly supplied to the reformer via an auxiliary combustion line (not shown in FIG. 1), the temperature of the reformer was raised, and the temperature of each device rose to a standby state. At the time, the raw fuel 27 is supplied to the raw fuel supply line shown in FIG.
[0055]
As shown in FIG. 2, the start-up power generation is controlled by using the raw fuel concentration constant input value 1 at the time of start-up that is measured in advance and input to the control device. The reformer temperature is 30 minutes after the power generation. Since the settling time is ˜1 hour, the startup selector 2 is switched by a timer (not shown), and the raw fuel concentration constant during normal power generation is input.
[0056]
Next, the raw fuel concentration constant is cut into an abnormal value by the upper / lower limiter 3 and converted to a raw fuel amount per 1 A of battery current by the raw fuel flow rate calculator 4. The raw fuel flow rate calculator 4 has a function of calculating the raw fuel amount per 1 A of current. In other words, this calculation is performed by the ratio of the raw fuel flow rate to the output current (raw fuel conversion ratio A) determined according to the raw fuel used in advance, and the raw fuel concentration constant (B) determined according to the raw fuel composition used in advance. ) And the ratio (A / B), and if the raw fuel concentration decreases, the amount of raw fuel per 1 A of current is set large.
[0057]
Next, the output value of the raw fuel flow rate calculator 4 is multiplied by the fuel cell current 13 by the multiplier 5 to calculate the raw fuel flow rate. In addition, normally, as described in the section of the prior art, the reformer temperature control addition raw fuel flow rate 8 is usually added to the raw fuel flow rate to obtain a raw fuel flow rate set value 6, which is shown in FIG. The fuel flow control valve 32 is controlled. Although not shown in FIG. 2, when a correction block is inserted into the fuel cell current 13 input to the multiplier 5 and the power generation load with a margin in the combustion air blower is small, the fuel cell current used for calculation May be set to a larger value and the raw fuel flow rate set value 6 may be increased. In this case, the starting raw fuel concentration constant 1 may be a planned value instead of a previously measured value.
[0058]
As described above, various methods for adding the raw fuel for reformer temperature control, characteristics thereof, and the like will be supplementarily described below. As a temperature control method of the reformer, (1) A method for controlling the temperature by supplying the amount of raw fuel corresponding to the output of the temperature regulator of the reformer to an auxiliary combustion line that supplies raw fuel directly to the reformer, not shown in FIG. (2) A method for controlling the temperature of the reformer by adding the amount of combustion air corresponding to the output of the temperature regulator of the reformer to the amount of combustion air required for the combustion of the battery off gas supplied to the reformer combustion furnace; (3) As shown in the embodiment of FIG. 2, for the raw fuel line that reaches the fuel cell via the reformer, the amount of raw fuel corresponding to the output of the temperature controller of the reformer is added to the raw fuel necessary for the fuel cell. There is a method in which the temperature is controlled by adding and supplying.
[0059]
In both cases, when the raw fuel composition changes, the reformer temperature controller is adjusted by the change in the heat balance of the reformer. From Can be used as a correction for the raw fuel composition. (3) The method is (1) Compared with the above method, the raw fuel added for the temperature control of the reformer results in the hydrogen being supplied to the fuel cell in excess of the hydrogen required by the fuel cell. There is an advantage that the power generation efficiency is increased by increasing the concentration.
[0060]
(2) The method of increasing / decreasing the combustion air is a method in which the reformer is cooled and controlled by increasing / decreasing the combustion air in a state where the raw fuel is excessively supplied and the heat of the reformer is surplus, and excessively supplied. There are drawbacks in that power generation efficiency is reduced due to a decrease in power generation efficiency due to raw fuel loss and an increase in combustion blower power due to an increase in the amount of combustion air.
[0061]
Therefore, the temperature control of the reformer (3) This method is desirable from the viewpoint of power generation efficiency, and since excessive hydrogen is supplied to the fuel cell for the temperature control of the reformer, there is an advantage that the possibility that the fuel cell runs out of hydrogen is reduced.
[0062]
Next, setting of the combustion air flow rate will be described. Combustion air is 1 Nm of raw fuel from the raw fuel concentration constant by the combustion air flow rate calculator 15. Three The amount of air for combustion is calculated, and the amount of air necessary for burning the raw fuel is calculated from the product with the raw fuel flow rate setting value 6. Further, an air amount corresponding to hydrogen consumed by the fuel cell is calculated from the fuel cell current 13 and the air consumption converted value 14. The difference between the amount of air necessary for burning the raw fuel and the amount of air corresponding to hydrogen consumed by the fuel cell is multiplied by the air-fuel ratio 17 to obtain a combustion air flow rate set value 18 to control the combustion air blower.
[0063]
Next, as shown in the control block diagram of FIG. 3, the steam flow rate is determined from the raw fuel concentration by the steam flow rate calculator 59 to 1 Nm of raw fuel. Three The steam flow per unit is calculated, the steam flow is calculated by the multiplier 51 from the S / C constant 50 to be set and the raw fuel flow set value, and set to the steam flow set value 52, and the reforming steam flow control valve 10a is controlled. To do.
[0064]
Next, details of the change of the raw fuel concentration constant and the control when the load fluctuates will be described below with reference to FIG. The raw fuel concentration constant during normal power generation is a steady state immediately after startup by the load variation selector 12. At regular times, the reformer temperature controller is adjusted by the raw fuel concentration corrector from When the command value 7 continues for 5%, for example, when a predetermined time set by the reset timer 11, for example, 1 minute or more elapses, a correction for increasing the 0.5% raw fuel concentration is performed to adjust the reformer temperature. vessel from When the command value 7 continues to be 95% and 1 minute or more has passed, correction is performed to decrease the raw fuel concentration by 0.5%.
[0065]
When the correction for increasing the raw fuel concentration is performed, the output of the raw fuel flow rate calculator 4 and the raw fuel amount per 1 A of the fuel cell current are reduced, so that the raw fuel flow rate set value 6 is reduced, and as a result, the reformer Temperature drop, reformer temperature controller From Command value 7 Increases the temperature, that is, in a direction larger than 5%, and the command range for temperature adjustment of the reformer widens. When correction for reducing the raw fuel concentration is performed, the reverse operation is performed. By correcting the raw fuel concentration, the temperature of the reformer can be controlled even if the composition of the actual raw fuel supplied changes.
[0066]
Next, PID control according to claims 8 to 10 will be described with reference to FIGS. 4 and 5 show system diagrams in which the PID control related members are added to FIGS. 1 and 2. Although FIG. 4 does not show the raw fuel flow rate regulator (PID) in FIG. 1, a raw fuel flow meter 71 and a raw fuel flow rate measurement value 72 are added as PID control-related members, A fuel cell load command 70 described later is additionally shown. FIG. 5 shows the raw fuel flow rate regulator (PID) 75 and the raw fuel flow rate measurement value 72, and the raw fuel control valve command value 73 as the PID output with respect to FIG. Furthermore, a molecular change correction calculator 76, which will be described later, for correcting the flow rate measurement value in accordance with the change in the raw fuel concentration is shown.
[0067]
Since PID control is well known, detailed description thereof will be omitted. As described above, when PID control is applied to raw fuel supply flow rate control, the raw fuel flow meter 71 shown in FIG. When a flow meter that causes an error is used, an error occurs between the measured value of the raw fuel supply amount and the actual value. In order to solve this problem, based on the molecular weight of the gas composition of the raw fuel flow meter 71 and the raw fuel concentration constant (in this case, biogas is used and the value converted to the methane concentration is used). By providing a molecular weight change correction computing unit 76 for obtaining the molecular weight when the methane concentration is changed and correcting the molecular weight change as shown in FIG. 5, the raw fuel flow rate can be measured without a measurement error. it can. Note that the gas that changes in response to the change in methane concentration is carbon dioxide gas when using biogas.
[0068]
Next, control at the time of load fluctuation will be described. The load fluctuation is performed by inputting a manual input from the operation panel of the power generator or a load change command by remote operation. By this load change command, the load fluctuation selector 12 shown in FIG. Switch to the load fluctuation side. The raw fuel concentration constant at the time of load change is corrected by multiplying the raw fuel concentration constant before the load change by a correction coefficient 9, and in this embodiment, the reformer temperature controller from If the command value is small with reference to 50% of the command value 7, the reformer temperature controller from A correction of the raw fuel concentration constant + 0.5% is performed for 10% of the command value 7, and if the command value is large, the reformer temperature controller from The raw fuel concentration constant is corrected to -0.5% with respect to 10% of the command value 7 and is stored in the hold circuit of the load fluctuation selector 12, and the stored raw fuel concentration constant is output from the load fluctuation selector 12. It becomes. The load change selector 12 is switched to the steady value side by an unillustrated timer one hour after the load change is completed and the reformer temperature is settled.
[0069]
Next, an embodiment of measures against load fluctuation (output reduction measures) of the fuel cell when the raw fuel concentration becomes lean will be described. First, an embodiment related to claim 11 will be described based on a schematic explanatory view of a change in load variation of a fuel cell accompanying a change in raw fuel concentration shown in FIG. 6A shows the change over time in the raw fuel methane concentration (%), FIG. 6B shows the change over time in the opening degree (%) of the raw fuel control valve (valve), and FIG. 6C shows the load command. An example of the time change of (%) is schematically shown.
[0070]
Normally, the load command change of the fuel cell 21 shown in FIG. 4 is performed by a manual input from a power generator operation panel (not shown) or a load change command by remote operation, and the fuel cell load command 70 shown in FIG. Driving with a determined load. Here, for example, as shown in FIG. 6A, if the methane concentration of the raw fuel is changed to a lean side and the methane gas concentration is changed from 65% to 45%, the application of claim 1 of the present invention Even if the gas concentration changes, the operation can be continued for the time being, and it is controlled so that the same amount of methane gas can be supplied in the raw fuel flow rate, but the total gas supply amount changes by a factor of 1.5. As described above, depending on the degree of the low concentration, the raw fuel control valve is fully opened and cannot be controlled.
[0071]
Therefore, for example, as shown in FIG. 6B, when the valve opening becomes 93% as shown by the upper limit set value 101 of the first stage, the fuel cell load command 70 is set as shown in FIG. Reduce by 5% as shown in c). Then, when the valve opening reaches the second upper limit set value 102 (valve opening 95%) due to further concentration reduction, control is performed to further reduce the fuel cell load command value 70 by 5%.
[0072]
According to the control as described above, the controllability of the raw fuel supply amount can be ensured even if the raw fuel concentration becomes lean. The controllability can also be ensured by the invention of claim 12. Such an embodiment will be described below with reference to FIGS. FIG. 7 is a control block diagram regarding the load command upper limit control, and FIG. 8 is a schematic explanatory diagram of the relationship between the load command upper limit value and the raw fuel concentration constant.
[0073]
Since the output (load) of the fuel cell is reduced based on the control signal of the raw fuel concentration constant when the raw fuel concentration becomes lean, the detailed description is omitted because it is the same as the above embodiment. In the embodiment of the twelfth aspect of the present invention, as shown in FIG. 7, a load command upper limiter 79 is provided in the fuel cell load command 70, and as a result, based on the fuel cell load command 77 after the upper limit limit, Perform battery load control.
[0074]
Further, as shown in FIG. 8, when the relation of the load command upper limit 78 corresponding to the raw fuel concentration constant is incorporated in the control and the raw fuel concentration constant changes to a lean side, for example, the upper limit value is changed from 50% concentration. Control to reduce 1% per 1% concentration. Thereby, as in the embodiment of the invention of claim 11, controllability of the raw fuel supply amount can be ensured even if the raw fuel concentration becomes lean.
[0075]
According to each embodiment as described above, the raw fuel concentration indicating the raw fuel composition is corrected from the command value of the temperature controller of the reformer, and the raw fuel flow rate, the combustion Since setting values such as air flow rate and steam flow rate are calculated and controlled, even if the raw fuel composition set at start-up differs from the raw fuel composition during operation, the raw fuel is not analyzed at any time. The fuel flow rate and the combustion air flow rate are appropriately controlled, so that cell damage due to hydrogen shortage in the fuel cell can be prevented, and reduction in power generation efficiency due to wasteful consumption of fuel can be prevented. Furthermore, proper temperature control of the reformer can be performed, and proper combustion of off-gas in the reformer burner is performed, and blower power loss due to incomplete combustion and excess air supply can be prevented. In addition, by ensuring an appropriate ratio of raw fuel and steam, a stable reformed gas composition can be obtained, and troubles such as reduction in power generation efficiency due to gas composition deterioration and reformer clogging due to carbon deposition on the reformer catalyst. Can be prevented.
[0076]
Further, before the raw fuel concentration decreases and the required gas amount cannot be supplied, the operation of the power generator is continued by controlling the load command of the fuel cell based on the opening degree of the raw fuel valve or the raw fuel concentration constant. be able to.
[0077]
【The invention's effect】
As described above, according to the present invention, at the time of start-up, the ratio of the raw fuel flow rate to the output current (raw fuel conversion ratio A) determined according to the raw fuel used in advance and the raw fuel composition used in advance are determined. The raw fuel flow rate is calculated by multiplying the ratio (A / B) with the raw fuel concentration constant (B) determined in advance by the output current value of the fuel cell, and this calculated value is supplied to the reformer. In the steady power generation state, the reformer temperature controller From Command value When the temperature fluctuates in the direction of lowering the temperature, the raw fuel concentration constant is increased, and when the command value from the reformer temperature controller fluctuates in the direction of increasing the temperature, the raw fuel concentration constant is decreased. , Changing the ratio, multiplying the changed ratio by the output current value of the fuel cell to calculate the raw fuel flow rate, and setting this calculated value as the feed raw fuel flow rate to the reformer, The raw fuel flow rate supplied to the vehicle is controlled (Claim 1), and when the PID control is performed, the flow rate measurement value of the raw fuel flow meter is corrected based on the raw fuel concentration constant as described above. (Claim 8)
Further, when the load is reduced or the load is increased, the temperature regulator of the reformer From Command value Increases when the temperature fluctuates in the direction of decreasing the temperature, and decreases when the command value from the temperature controller of the reformer fluctuates in the direction of increasing the temperature. The raw fuel concentration constant in the steady power generation state is stored in the hold circuit, and the ratio is calculated based on the stored raw fuel concentration constant, and the ratio of the fuel cell at the time of load reduction and load increase is calculated based on this ratio. The raw fuel flow rate is calculated by multiplying the output current value, and this calculated value is set as the feed raw fuel flow rate to the reformer to control the feed raw fuel flow rate to the reformer (Claim 2). ,
Furthermore, since the control of the combustion air flow rate and the steam flow rate of the reformer is performed as in the sixth to seventh or ninth to tenth aspects,
Operation of a fuel cell power generator capable of controlling optimal raw fuel supply, combustion air supply, steam supply, etc., without performing composition analysis of the raw fuel as needed, even if there are fluctuations in the composition of the raw fuel A control method can be provided.
[0078]
Further, even if the concentration of the raw fuel is lowered, the load control of the fuel cell is performed as in claims 11 to 12, so that the fuel cell power generation that can continue the operation without making the necessary gas amount unusable A method for controlling the operation of the apparatus can be provided.
[Brief description of the drawings]
FIG. 1 is a system diagram showing an embodiment of an operation control method for a fuel cell power generator according to the present invention.
FIG. 2 is a control block diagram of the embodiment of FIG.
FIG. 3 is a control block diagram relating to steam flow in the embodiment of FIG. 1;
FIG. 4 is a system diagram showing an embodiment of an operation control method different from FIG.
FIG. 5 is a control block diagram of the embodiment of FIG.
FIG. 6 is a schematic explanatory view of a change in a load variation of a fuel cell associated with a change in raw fuel concentration in relation to the invention of claim 11.
FIG. 7 is a control block diagram relating to load command upper limit control according to the invention of claim 12;
8 is a schematic explanatory diagram of the relationship between the load command upper limit value and the raw fuel concentration constant in FIG. 7;
FIG. 9 is a system diagram of an example of a conventional fuel cell power generator.
10 is a system diagram different from FIG. 9 of a conventional fuel cell power generator.
[Explanation of symbols]
1: raw fuel concentration constant input value at start-up, 2: start-up state selector, 3: upper / lower limiter, 4: raw fuel flow rate calculator, 5, 16, 51: multiplier, 6: raw fuel flow rate set value, 7 : Reformer temperature controller from Command value, 8: reformer temperature control addition raw fuel flow rate, 9: correction coefficient, 10: raw fuel concentration corrector, 11: reset timer, 12: load fluctuation selector, 13: fuel cell current, 14: air consumption Conversion value, 15: Combustion air flow rate calculator, 17: Air-fuel ratio setting device, 18: Combustion air flow rate setting value, 21: Fuel cell, 22: Reformer, 23: Burner, 32: Raw fuel flow rate control valve, 59: Steam flow calculator, 50: S / C coefficient multiplier, 52: Steam flow set value, 60: Steam separator, 62: Ejector, 64: Desulfurizer, 66: CO converter, 70: Fuel cell load command 71: Raw fuel flow meter, 72: Raw fuel flow rate measurement value, 73: Raw fuel control valve command value, 75: Raw fuel flow rate controller (PID), 76: Molecular weight change correction calculator, 77: After upper limiter Fuel cell load command, 78: on load command Value, 79: upper limit limiter.

Claims (12)

原燃料を改質して水素リッチな改質ガスを生成する改質器と、前記改質器の温度を検出する改質器温度検出器と、前記改質器温度検出器が検出した値を基に改質器温度を上方向または下方向に変動させる指令値を出力する改質器温度調節器と、前記改質ガスと酸化剤ガスとを電気化学的に反応させて発電する燃料電池とを備えた燃料電池発電装置の運転制御方法において、
起動時においては、予め使用する原燃料に応じて定めた原燃料流量と出力電流の比（原燃料換算比Ａ）と、予め使用する原燃料組成に応じて定めた原燃料濃度定数（Ｂ）との比（Ａ／Ｂ）に、前記燃料電池の出力電流値を乗じて原燃料流量を算出し、この算出値を改質器への供給原燃料流量として設定し、
定常発電状態においては、前記改質器の温度調節器からの指令値が温度を下げる方向に変動した場合前記原燃料濃度定数を上昇させ、前記改質器の温度調節器からの指令値が温度を上げる方向に変動した場合前記原燃料濃度定数を減少させて、前記比を変更し、この変更された比に燃料電池の出力電流値を乗じて原燃料流量を算出し、この算出値を改質器への供給原燃料流量として設定して、改質器への供給原燃料流量を制御することを特徴とする燃料電池発電装置の運転制御方法。A reformer that reforms the raw fuel to produce a hydrogen-rich reformed gas, a reformer temperature detector that detects the temperature of the reformer, and a value detected by the reformer temperature detector A reformer temperature controller that outputs a command value for changing the reformer temperature upward or downward, and a fuel cell that generates electricity by electrochemically reacting the reformed gas with an oxidant gas; In an operation control method of a fuel cell power generation device comprising
At start-up, the ratio of the raw fuel flow rate to the output current (raw fuel conversion ratio A) determined according to the raw fuel used in advance and the raw fuel concentration constant (B) determined according to the raw fuel composition used in advance. The raw fuel flow rate is calculated by multiplying the ratio (A / B) with the output current value of the fuel cell, and this calculated value is set as the feed raw fuel flow rate to the reformer,
In the steady power generation state, when the command value from the temperature controller of the reformer fluctuates in the direction of decreasing the temperature, the raw fuel concentration constant is increased, and the command value from the temperature controller of the reformer is The raw fuel concentration constant is decreased , the ratio is changed, the changed ratio is multiplied by the output current value of the fuel cell to calculate the raw fuel flow rate, and the calculated value is revised. An operation control method for a fuel cell power generation apparatus, characterized in that the flow rate of raw fuel supplied to a reformer is controlled by setting the flow rate of raw fuel supplied to a mass device. 請求項１に記載の運転制御方法において、負荷低減時または負荷上昇時においては、前記改質器の温度調節器からの指令値が温度を下げる方向に変動した場合には上昇し、前記改質器の温度調節器からの指令値が温度を上げる方向に変動した場合には減少する定常発電状態での原燃料濃度定数を、ホールド回路にメモリーしておき、このメモリーした原燃料濃度定数に基づいて、前記比を算出し、この比に負荷低減時および負荷上昇時の燃料電池の出力電流値を乗じて原燃料流量を算出し、この算出値を改質器への供給原燃料流量として設定して、改質器への供給原燃料流量を制御することを特徴とする燃料電池発電装置の運転制御方法。The operation control method according to claim 1, wherein when the load is reduced or the load is increased, the command value from the temperature regulator of the reformer increases when the temperature fluctuates in a direction of decreasing the temperature, and the reforming is performed. When the command value from the temperature controller of the generator fluctuates in the direction of increasing the temperature , the raw fuel concentration constant in the steady power generation state that decreases is stored in the hold circuit, and based on this stored raw fuel concentration constant. The ratio is calculated, and this ratio is multiplied by the output current value of the fuel cell when the load is reduced and when the load is increased to calculate the raw fuel flow rate, and this calculated value is set as the supply raw fuel flow rate to the reformer. And controlling the flow rate of the raw fuel supplied to the reformer. 請求項１または２に記載の運転制御方法において、前記原燃料濃度定数の変更は、前記改質器の温度調節器の指令値からの変動が、所定の変動率の上限値または下限値以上において所定時間継続した際に、行なうことを特徴とする燃料電池発電装置の運転制御方法。3. The operation control method according to claim 1, wherein the change in the raw fuel concentration constant is such that a change from a command value of a temperature regulator of the reformer is greater than or equal to an upper limit value or a lower limit value of a predetermined fluctuation rate. An operation control method for a fuel cell power generator, which is performed when the fuel cell power generator is continued for a predetermined time. 請求項１ないし３のいずれかに記載の運転制御方法において、前記原燃料濃度定数の変更はステップ状に行い、そのステップ幅は、前記使用する原燃料組成に応じて定めた原燃料濃度定数の０．１〜１％とすることを特徴とする燃料電池発電装置の運転制御方法。4. The operation control method according to claim 1, wherein the change in the raw fuel concentration constant is performed in a step-like manner, and the step width is a raw fuel concentration constant determined according to the raw fuel composition to be used. An operation control method for a fuel cell power generator, characterized by being 0.1 to 1%. 請求項２に記載の運転制御方法において、前記ホールド回路にメモリーする原燃料濃度定数を、改質器温度調節器からの指令値に基づき、指令値の大または小に応じて、所定値減少または増加する補正を行なうことを特徴とする燃料電池発電装置の運転制御方法。3. The operation control method according to claim 2, wherein the raw fuel concentration constant stored in the hold circuit is reduced by a predetermined value based on a command value from a reformer temperature controller, according to a large or small command value. An operation control method for a fuel cell power generator characterized by performing an increasing correction. 請求項１または２に記載の運転制御方法において、前記改質器は、燃料電池オフガスを燃焼用空気とともに燃焼させるバーナを有するものとし、前記燃焼用空気流量設定値は、前記改質器の温度調節器からの指令値が温度を下げる方向に変動した場合には上昇し、前記改質器の温度調節器からの指令値が温度を上げる方向に変動した場合には減少する原燃料濃度定数から計算された単位原燃料当りの燃焼空気量換算値に、前記原燃料濃度定数に基づく原燃料流量設定値を乗じて求めた空気量から、燃料電池電流に空気消費量換算値を乗じて求めた空気量を減算し、所定の空燃比を乗じて求めることを特徴とする燃料電池発電装置の運転制御方法。3. The operation control method according to claim 1, wherein the reformer includes a burner that burns fuel cell off gas together with combustion air, and the combustion air flow rate setting value is a temperature of the reformer. rises if the command value from the controller has changed in a direction to lower the temperature, the raw fuel concentration constant decreases when the command value from the temperature controller of the reformer is varied in the direction of raising the temperature Calculated by multiplying the calculated amount of combustion air per unit raw fuel by the raw fuel flow rate set value based on the raw fuel concentration constant and multiplying the fuel cell current by the air consumption converted value. A method for controlling the operation of a fuel cell power generator, comprising subtracting the amount of air and multiplying by a predetermined air-fuel ratio. 請求項１または２に記載の運転制御方法において、前記改質器は、原燃料を水蒸気（スチーム）と混合して改質するものとし、前記スチーム流量設定値は、前記改質器の温度調節器からの指令値が温度を下げる方向に変動した場合には上昇し、前記改質器の温度調節器からの指令値が温度を上げる方向に変動した場合には減少する原燃料濃度定数を基に単位原燃料当りのスチーム量を計算し、前記単位原燃料あたりのスチーム量から設定されたＳ／Ｃ比（原燃料中の炭素原子に対するスチームのモル数比）に、前記原燃料濃度定数に基づく原燃料流量設定値を乗じて求めることを特徴とする燃料電池発電装置の運転制御方法。3. The operation control method according to claim 1, wherein the reformer reforms by mixing raw fuel with steam (steam), and the steam flow rate setting value is a temperature adjustment of the reformer. command value from vessel rises in the case of change in the direction of lowering the temperature, based on the raw fuel concentration constant command value from the temperature controller of the reformer is decreased when varied in the direction of raising the temperature The steam amount per unit raw fuel is calculated, and the S / C ratio (ratio of moles of steam to carbon atoms in the raw fuel ) set from the steam amount per unit raw fuel is set to the raw fuel concentration constant. An operation control method for a fuel cell power generation apparatus, characterized in that it is obtained by multiplying a raw fuel flow rate setting value based thereon. 請求項１に記載の運転制御方法において、前記改質器への原燃料供給ライン上に原燃料流量計および原燃料流量制御弁を設け、前記原燃料流量計の流量計測値と前記改質器への供給原燃料設定値との比較演算に基づく制御出力（ＰＩＤ制御出力）により、前記原燃料流量制御弁の開度制御を行なって、前記改質器への供給原燃料の制御を行い、さらに、前記原燃料流量計の流量計測値は、前記原燃料濃度定数に基づいて補正し、この補正値に基づいて前記比較演算を行なうことを特徴とする燃料電池発電装置の運転制御方法。2. The operation control method according to claim 1, wherein a raw fuel flow meter and a raw fuel flow control valve are provided on a raw fuel supply line to the reformer, and a flow rate measurement value of the raw fuel flow meter and the reformer are provided. By controlling the opening of the raw fuel flow rate control valve by a control output (PID control output) based on a comparison calculation with the supply raw fuel set value to control the raw fuel supplied to the reformer, Furthermore, the flow rate measurement value of the raw fuel flow meter is corrected based on the raw fuel concentration constant, and the comparison calculation is performed based on the correction value. 請求項６に記載の運転制御方法において、前記燃焼用空気流量設定値は、前記原燃料流量設定値に代えて、前記請求項８に記載のＰＩＤ制御出力によって制御された原燃料流量値に基づいて演算して求めることを特徴とする燃料電池発電装置の運転制御方法。The operation control method according to claim 6, wherein the combustion air flow rate set value is based on a raw fuel flow rate value controlled by a PID control output according to claim 8, instead of the raw fuel flow rate set value. An operation control method for a fuel cell power generator, characterized in that 請求項７に記載の運転制御方法において、前記スチーム流量設定値は、前記原燃料流量設定値に代えて、前記請求項８に記載のＰＩＤ制御出力によって制御された原燃料流量値に基づいて演算して求めることを特徴とする燃料電池発電装置の運転制御方法。8. The operation control method according to claim 7, wherein the steam flow rate setting value is calculated based on a raw fuel flow rate value controlled by a PID control output according to claim 8, instead of the raw fuel flow rate setting value. A method for controlling the operation of a fuel cell power generator, characterized in that 請求項１に記載の運転制御方法において、前記改質器への原燃料供給ライン上に原燃料流量制御弁を設け、前記原燃料流量制御弁の開度が、原燃料濃度が希薄であって所定の上限開度に到達した際に、前記燃料電池の出力を所定値まで低減することを特徴とする燃料電池発電装置の運転制御方法。2. The operation control method according to claim 1, wherein a raw fuel flow control valve is provided on a raw fuel supply line to the reformer, and the opening of the raw fuel flow control valve has a lean raw fuel concentration. An operation control method for a fuel cell power generator, wherein the output of the fuel cell is reduced to a predetermined value when a predetermined upper limit opening is reached. 請求項１に記載の運転制御方法において、前記燃料電池は、原燃料濃度が希薄となった際に燃料電池の出力を所定値まで低減する出力上限リミッタを有し、前記出力上限リミッタにおける出力上限値は、前記原燃料濃度が希薄である程小となるように、前記原燃料濃度定数に基づいて設定することを特徴とする燃料電池発電装置の運転制御方法。2. The operation control method according to claim 1, wherein the fuel cell has an output upper limiter that reduces the output of the fuel cell to a predetermined value when the raw fuel concentration becomes lean, and an output upper limit in the output upper limiter. The value is set based on the raw fuel concentration constant so that the value becomes smaller as the raw fuel concentration becomes leaner.
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