JP3956208B2

JP3956208B2 - Fuel cell power generation system and operation method thereof

Info

Publication number: JP3956208B2
Application number: JP2002266419A
Authority: JP
Inventors: 仁人千田
Original assignee: Fuji Electric Holdings Ltd
Current assignee: Fuji Electric Co Ltd
Priority date: 2002-09-12
Filing date: 2002-09-12
Publication date: 2007-08-08
Anticipated expiration: 2022-09-12
Also published as: JP2004103487A

Description

【０００１】
【発明の属する技術分野】
この発明は、炭化水素系原燃料を水蒸気改質して得られた燃料ガスと酸化剤ガス（空気）との電気化学反応に基づいて電気および熱エネルギーを発生する燃料電池と、前記熱エネルギーの一部を温水として貯える貯湯槽とを備える燃料電池発電システムとその運転方法に関する。
【０００２】
【従来の技術】
燃料電池発電装置に組み込まれる燃料電池としては、電解質の種類、改質原料の種類等によって異なる種々のタイプがあるが、例えば、固体高分子膜を電解質として用い、その運転温度が約８０℃と比較的低いタイプの燃料電池として、固体高分子電解質型燃料電池がよく知られている。
【０００３】
この固体高分子電解質型燃料電池は、リン酸型燃料電池と同様に、例えばメタンガス（都市ガス）等の炭化水素系原燃料を水蒸気改質して得られた燃料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ある。
【０００４】
また、原燃料を燃料ガスへ改質するに際しては、原燃料に水蒸気を加え燃料改質器で触媒により改質を促進する方法が採られているが、改質を定常的に行なうには所要の水蒸気量を定常的に補給する必要があり、水蒸気の供給装置には、これに対応した水を常時補給する必要がある。なお、使用する水は高純度の水であることが必要であり、イオン交換式の水処理装置で不純物を除去したイオン交換水が用いられるのが通例である。
【０００５】
一方、燃料電池の電気化学反応では発電生成水が生じ、また燃料改質器では吸熱反応である水蒸気改質反応を定常的に行なうための触媒加熱用の燃焼に伴い燃焼生成水が生じるが、これらの生成水は通常の水道水に比べて不純物が少なく、これらの生成水を原水として用いれば、水処理装置の負荷を軽減することができるため、回収水タンクおよび排ガス冷却器を付加して、これらの生成水を回収して改質水蒸気発生用の供給水とする方法が、通常採用されている。
【０００６】
また、燃料電池の電気化学反応では反応に伴って熱が発生し、この排熱エネルギーの一部は、貯湯槽に温水として貯え、給湯もしくは暖房に供される。
【０００７】
図２は、従来の固体高分子電解質型燃料電池発電システムの一例を示す系統図である。この系統図について説明する前に、貯湯槽を備えた小容量の燃料電池発電システムの効率に関して先に述べ、この効率の問題との関わりを含めて後述する。
【０００８】
小容量固体高分子型燃料電池発電装置は、家庭や小規模事業所への設置が想定されているが、本装置の目標効率は電気出力である送電端発電効率が約40%(LHV)、熱出力である温水の目標排熱効率が約40%(LHV)であり、総合熱効率の目標値は約80%(LHV)に達するが、約20%(LHV)の熱は装置からの排気および放熱として大気に捨てられている。ここで、前記LHVとは、Lower Heat Valueの略記であり、前記効率は、凝縮潜熱を含めない低位発熱量ベースで算出した効率であることを示す。
【０００９】
さらに、温水として給湯等に用いられる約40%(LHV)の熱出力について着目すると、給湯の負荷(需要)が低い状態が継続する場合には、貯湯槽の温度が上限値である例えば約70℃に達した場合、それ以降は熱出力である温水の熱エネルギーを、後述する温水冷却器によって大気に放熱する必要が生じるため、この場合の総合熱効率は、送電端発電効率である40%(LHV)まで低下してしまう。
【００１０】
これらの理由を、前記図２の系統図により説明する。図２において、３０で示した一点鎖線の範囲内は、固体高分子形燃料電池発電装置のパッケージ内部を示す。パッケージ３０の内部には図２の部番１〜１６以外にも多数の機器が存在するが、ここではこれらを省略している。
【００１１】
１は燃料電池本体である。1aは燃料極、1bは空気極、1cは電池冷却水が通過する冷却板であり、これらが複数枚積層され燃料電池本体１を構成している。燃料電池発電時は、1aに水素リッチガスが、1bに反応空気ブロワ７から空気が供給され、直流電力と共に熱を発生する。1aに供給される水素リッチガスは、原燃料(メタンガス、プロパンガス、ブタンガス、およびこれらのガス組成からなる都市ガス等の炭化水素系気体、灯油、軽油等の炭化水素系液体等が適用可能)をパッケージ３０に導入し、脱硫器２により脱硫した後、改質用水ポンプ１５にて送出され水処理装置１４により純化された改質用水と合流し、改質器３にて吸熱反応である水蒸気改質反応を行うことにより得ることができる。
【００１２】
ここで得られる水素リッチガスには、燃料電池本体の触媒を被毒する一酸化炭素(CO)が含まれているため、さらに後段のCO変成器４、CO除去器５により一酸化炭素の濃度レベルを10ppm以下に低減した後に燃料電池燃料極1aに供給し、燃料電池本体１の発電に伴い水素の一部が消費される。1aにて消費されなかった残余の水素は改質器３のバーナ部にて燃焼し改質反応の熱源となる。
【００１３】
改質器３の燃焼排ガスと燃料電池本体１の空気極1bを通過した空気は、排ガス冷却器１０により冷却されて水が回収される。この水回収量が不足すると、排ガス冷却器１０の水位レベルが維持できなくなり、補給水用電磁弁１６を開として市水の補給を行う必要が生じる。市水の補給が行なわれた場合、改質用水中にシリカSiOの混入を防ぐために設けている水処理装置14の寿命が極端に短くなってしまう。
【００１４】
これを防止するためには、排ガス冷却器１０で良好な水回収を行うべく、回収水温度検出器１３に基づき、回収水冷却器１１のファンと回収水循環ポンプ１２とを駆動し、回収水冷却器１１による適切な冷却を行なうことが必要となる。回収水冷却器１１による回収水の冷却は、通常、大気と熱交換することで行われるため、冷却用空気の熱は、利用できない熱として継続的に大気に放出される。
【００１５】
また、燃料電池本体１は、発電と同時に比較的高温の排熱を発生する。固体高分子型燃料電池の場合には、その発生熱効率は約40%(LHV)であり、温度レベルは約80℃である。この排熱は、電池冷却水ポンプ８および電池冷却水冷却器９の電池冷却水系機器を介して、温水循環ポンプ２０により送出される温水により、貯湯槽21に蓄熱される。
【００１６】
蓄熱が継続し、貯湯槽の温度レベルが一定値以上に達したことを温水温度検出器１９が検知すると、温水冷却器１８が作動する。これは、電池冷却水の温度を燃料電池冷却水冷却器９で調節し、燃料電池本体１の運転温度を一定にした安定運転を継続するためである。従って、ユーザー給湯設備２２の給湯需要よりも燃料電池本体１の排熱量が上回る状態が継続すると、約40%(LHV)の熱出力は、温水冷却器１８を介して大気に放熱せざるを得なくなる。
【００１７】
上記のように、従来の燃料電池を用いたコージェネレーションシステムにおいては、燃料電池発電装置からの放熱および排熱の蓄熱手段である貯湯槽の蓄熱量が上限に達した以降に出力される燃料電池本体からの比較的高温の排熱は、有効に利用されてはいなかった。
【００１８】
一方、固体高分子型燃料電池発電装置の導入先として考えられている家庭や小規模事業所には、エアコンが冷房・暖房機器として導入されているのが一般的である。エアコンは、夏季は室内の熱を室外機から放熱する冷凍サイクルに、冬季は外気の熱をくみ上げて室内に放熱するヒートポンプサイクルとして用いられる。
【００１９】
図３は、ヒートポンプ式エアコンにおけるヒートポンプモードの模式的系統図を示す。図３において、５０は室内用熱交換器、５１は室外用熱交換器、５２は圧縮機、５３は膨張弁である。ヒートポンプは外気の熱を熱源としているため、厳冬期および寒冷地では、利用しようとする温度(室内温度)に対する吸熱温度(外気温度)の差が大きくなりヒートポンプの運転に必要な動力が大きくなってしまう問題がある。
【００２０】
そこで、燃料電池の排熱を、室外用熱交換器に導入して、暖房時の効率を高める熱供給システムが提案されている（例えば、特許文献１参照）。
【００２１】
特許文献１に記載された熱供給システムは、同公報によれば、「少なくとも室外熱交換器及び室内熱交換器を有し、室外の熱を室内へ汲み上げるヒートポンプサイクルを行う空調装置と、燃料ガスを空気中の酸素と反応させて発生させた電気エネルギーを前記空調装置へ供給すると共に、反応熱により昇温された反応後の高温空気を排出する燃料電池装置と、前記高温空気との間で熱交換して昇温された水を蓄える給湯装置と、前記空調装置が暖房運転を行っている時には前記燃料電池装置から排出された高温空気を前記室外熱交換器へ導き、前記空調装置が暖房を行っていない時には前記燃料電池装置から排出された高温空気を前記給湯装置へ導く排気切換手段と、を有するもの」であり、
「上記構成の熱供給システムによれば、空調装置による暖房運転時には排気切換手段が燃料電池装置から排出された高温空気を空調装置の室外熱交換器へ導くことにより、燃料電池から排出された高温空気から空調装置の室外熱交換器により熱回収でき、この高温空気からの回収熱により熱交換の効率を高めることができるので、熱交換器の容量を増大することなく実質的な暖房能力を高めることができる。この結果、外気温の低下に伴って暖房能力が低下することを防止でき、かつ一定の暖房状態を維持するために必要となる電力コストを低減できる。また空調装置が暖房運転を行っていない時には排気切換手段が燃料電池装置から排出された高温空気を給湯装置へ導くことにより、燃料電池から排出された高温空気から給湯装置により熱回収でき、この高温空気からの回収熱により水を昇温して温水として外部へ供給できるので、水を昇温するために必要となるエネルギーコストを抑制又は不要にできる。」とされている。
【００２２】
【特許文献１】
特開平１１−２８１０７２号公報（第２−４頁、図１）
【００２３】
【発明が解決しようとする課題】
ところで、前述のような従来の燃料電池発電システムにおいても、下記のような問題点があった。
【００２４】
上述の特許文献１に記載のシステムにおいては、反応熱により昇温された反応後の高温空気、即ち、燃料電池の空気極排ガスを、暖房時に、空調装置の室外熱交換器へ導くが、この場合、燃料電池の空気極排ガス中に含まれる水分が、大気中に放出されるため、燃料電池における反応生成水が有効に回収されず、燃料電池発電装置の水自立運転（外部からの補給水を受けいれることなく運転を継続する状態）が不可能となり、水処理を含むシステム運転上、全体として経済的ではない問題がある。また、特許文献１に記載のシステムの場合、上記のように水分を含んだ多湿の空気を、空調装置の室外熱交換器へ導入することとなるので、室外熱交換器が腐食し易い問題もある。
【００２５】
この発明は、上記問題点に鑑みてなされたもので、この発明の課題は、燃料電池の排空気中の水を回収する装置と、燃料電池の排熱を貯える貯湯槽を有するシステムにおいて、なおかつ余剰となる熱を、前記排空気中の水分を放出することなく、有効に暖房の熱源に利用することが可能な燃料電池発電システムとその運転方法を提供することにある。
【００２６】
【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、この発明においては、炭化水素系原燃料を水蒸気改質して得られた燃料ガスと酸化剤ガスとしての空気との電気化学反応に基づいて電気および熱エネルギーを発生する燃料電池本体と、燃料改質系機器と、燃料電池の冷却水系機器と、燃料電池の排空気および燃料改質器の燃焼排ガス中の水を回収する回収水系機器と、前記熱エネルギーの一部を温水として貯える貯湯槽とを有し、さらに、前記回収水系機器は排ガス冷却器と回収水冷却器とを備え、かつ前記貯湯槽は過昇温防止用の温水冷却器を備えた燃料電池発電システムの運転方法において、
前記燃料電池発電システムは、少なくとも室外の熱を室内へ汲み上げるヒート
ポンプによる暖房運転が可能な室外用熱交換器と室内用熱交換器とを有する空調装置を備え、前記回収水冷却器および温水冷却器の少なくとも一方の作動を検知することにより、当該回収水冷却器および温水冷却器の少なくとも一方の排熱を前記空調装置の室外用熱交換器に導入して、前記ヒートポンプの暖房用熱源として利用することとする（請求項１の発明）。
【００２７】
上記運転方法によれば、ヒートポンプの熱源として、空気極排ガスならびに改質器の燃焼排ガスからの水回収時に発生する熱（回収水冷却器からの熱）と、貯湯槽の貯液熱容量がいっぱいになった場合に生じる温水の余剰熱（温水冷却器からの熱）を用いるため、水の回収性能に影響を与えることなく室外用熱交換器を予熱することができ、また室外用熱交換器の腐食の問題も解消できる。
【００２８】
前記請求項１の発明の方法を実施するためのシステムとしては、下記請求項２ないし３の発明が好ましい。即ち、前記請求項１記載の運転方法を実施するための燃料電池発電システムであって、前記排熱を室外用熱交換器に導入する排熱回収用水循環回路と、この循環回路上に設けた暖房熱源水循環ポンプと、前記回収水冷却器および温水冷却器の少なくとも一方の作動を検知することにより前記暖房熱源水循環ポンプを駆動する排熱利用暖房運転制御装置とを備え、前記排熱回収用水循環回路は、前記回収水冷却器および温水冷却器にそれぞれ設けた排熱回収用水循環熱交換器と、前記室外用熱交換器に設けた受熱用水循環熱交換器と、前記排熱回収用および受熱用水循環熱交換器とを接続して閉ループを形成する配管とからなるものとする（請求項２の発明）。
【００２９】
前記請求項２の発明において、前記回収水冷却器および温水冷却器の少なくとも一方の作動が停止し、他方が作動している場合には、前記排熱回収用水循環回路は、作動している側の排熱回収用水循環熱交換器内の水のみを、受熱用水循環熱交換器に通流するように、電磁弁による切替バイパス回路を構成することができる。
【００３０】
前記切替回路を設けず、構成をシンプルとするためには、多少の熱ロスは伴うものの、下記請求項３の発明が好適である。即ち、請求項２記載の燃料電池発電システムにおいて、前記回収水冷却器および温水冷却器に設けた排熱回収用水循環熱交換器は、それぞれ直列に接続して前記排熱回収用水循環回路を形成し、かつ回収水冷却器用の排熱回収用水循環熱交換器を上流側に配設する。
【００３１】
上記構成によれば、前記回収水冷却器および温水冷却器の両方が作動する場合、温水冷却器に設けた排熱回収用水循環熱交換器の方が、回収水冷却器用のそれより作動温度レベルが高いので、熱ロスが抑制できる。
【００３２】
【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。
【００３３】
図１は、この発明に関わる実施例を示す系統図であり、図２および図３と同じ機能を有する部材には同一の番号を付して詳細説明を省略する。また、図１においては、図２における発電装置パッケージ３０内の大部分の機器、ならびに温水冷却器１８前後の蓄熱槽２１関連機器等については、省略して示す。
【００３４】
図１において、図２と異なる点は、ヒートポンプ運転が可能な室外用熱交換器５１と室内用熱交換器５０とを有する空調装置を備え、回収水冷却器１１および温水冷却器１８の少なくとも一方の作動を検知することにより、当該回収水冷却器および温水冷却器の少なくとも一方の排熱を前記空調装置の室外用熱交換器５１に導入して、ヒートポンプの暖房用熱源として利用するように構成した点である。
【００３５】
また、図１においては、前記排熱を室外用熱交換器５１に導入する排熱回収用水循環回路４２と、この循環回路上に設けた暖房熱源水循環ポンプ４５と、回収水冷却器１１および温水冷却器１８の少なくとも一方の作動を検知することにより前記暖房熱源水循環ポンプ４５を駆動する排熱利用暖房運転制御装置４０とを備える。さらに、前記排熱回収用水循環回路４２は、回収水冷却器１１および温水冷却器１８にそれぞれ設けた排熱回収用水循環熱交換器（１１ａおよび１８ａ）と、前記室外用熱交換器５１に設けた受熱用水循環熱交換器５１ａと、前記排熱回収用および受熱用水循環熱交換器とを接続して閉ループを形成する配管４２ａとからなる。なお、前記排熱利用暖房運転制御装置４０は、空調装置のヒートポンプモードのアンサーバック信号に基づき、前記暖房熱源水循環ポンプ４５を駆動する。
【００３６】
さらにまた、図１の構成は、前記請求項３に記載のように、回収水冷却器１１および温水冷却器１８に設けた排熱回収用水循環熱交換器（１１ａおよび１８ａ）をそれぞれ直列に接続し、かつ回収水冷却器用の排熱回収用水循環熱交換器１１ａを、１８ａの上流側に配設する構成を示している。
【００３７】
前記構成により、従来は大気に放熱せざるを得なかった回収水冷却器１１からの熱エネルギーおよび貯湯槽２１の熱容量が飽和している場合に温水冷却器１８から大気に放熱されていた熱エネルギーを、既設エアコンの暖房熱源に有効に用いるとともに、暖房時の電力使用量を削減することで、小容量固体高分子型燃料電池発電装置を導入したユーザーの省エネルギーメリットを拡大することが可能となる。
【００３８】
【発明の効果】
上記のとおり、この発明によれば、炭化水素系原燃料を水蒸気改質して得られた燃料ガスと酸化剤ガスとしての空気との電気化学反応に基づいて電気および熱エネルギーを発生する燃料電池本体と、燃料改質系機器と、燃料電池の冷却水系機器と、燃料電池の排空気および燃料改質器の燃焼排ガス中の水を回収する回収水系機器と、前記熱エネルギーの一部を温水として貯える貯湯槽とを有し、さらに、前記回収水系機器は排ガス冷却器と回収水冷却器とを備え、かつ前記貯湯槽は過昇温防止用の温水冷却器を備えた燃料電池発電システムおよびその運転方法において、前記燃料電池発電システムは、少なくとも室外の熱を室内へ汲み上げるヒートポンプによる暖房運転が可能な室外用熱交換器と室内用熱交換器とを有する空調装置を備え、前記回収水冷却器および温水冷却器の少なくとも一方の作動を検知することにより、当該回収水冷却器および温水冷却器の少なくとも一方の排熱を前記空調装置の室外用熱交換器に導入して、前記ヒートポンプの暖房用熱源として利用するようにしたので、
燃料電池の排空気中の水を回収する装置と、燃料電池の排熱を貯える貯湯槽を有するシステムにおいて、なおかつ余剰となる熱を、有効に暖房の熱源に利用することを可能とし、また、前記排空気中の水分を放出することなく、前記空調装置の室外用熱交換器の腐食を抑制可能な燃料電池発電システムとその運転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システムの実施例を示す系統図
【図２】従来の燃料電池発電システムの一例を示す系統図
【図３】ヒートポンプ式エアコンにおけるヒートポンプモードの模式的系統図
【符号の説明】
１：燃料電池本体、３：改質器、１０：排ガス冷却器、１１：回収水冷却器、１１ａ，１８ａ：排熱回収用水循環熱交換器、１４：水処理装置、１８：温水冷却器、２１：貯湯槽、４０：排熱利用暖房運転制御装置、４２：排熱回収用水循環回路、４２ａ：閉ループを形成する配管、４５：暖房熱源水循環ポンプ、５０：室内用熱交換器、５１：室外用熱交換器、５１ａ：受熱用水循環熱交換器。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel cell that generates electricity and thermal energy based on an electrochemical reaction between a fuel gas obtained by steam reforming a hydrocarbon-based raw fuel and an oxidant gas (air), The present invention relates to a fuel cell power generation system including a hot water storage tank that stores a part of it as hot water, and an operation method thereof.
[0002]
[Prior art]
There are various types of fuel cells incorporated in the fuel cell power generator, depending on the type of electrolyte, the type of reforming raw material, and the like. A solid polymer electrolyte fuel cell is well known as a relatively low type fuel cell.
[0003]
This solid polymer electrolyte fuel cell is similar to a phosphoric acid fuel cell, for example, in hydrogen and air in a fuel gas obtained by steam reforming a hydrocarbon-based raw fuel such as methane gas (city gas). Oxygen is supplied to the fuel electrode and the air electrode of the fuel cell, respectively, and electricity is generated based on the electrochemical reaction.
[0004]
In addition, when reforming raw fuel into fuel gas, a method is adopted in which steam is added to the raw fuel and reforming is promoted by a catalyst in a fuel reformer. It is necessary to constantly replenish the amount of water vapor, and it is necessary to constantly replenish the water vapor supply device with water corresponding thereto. The water to be used needs to be high-purity water, and ion-exchanged water from which impurities have been removed by an ion-exchange type water treatment device is usually used.
[0005]
On the other hand, in the electrochemical reaction of the fuel cell, power generation product water is generated, and in the fuel reformer, combustion product water is generated with combustion for catalyst heating for performing a steam reforming reaction which is an endothermic reaction constantly. These generated waters have fewer impurities than normal tap water, and if these generated waters are used as raw water, the load on the water treatment device can be reduced. Therefore, a recovery water tank and an exhaust gas cooler are added. A method of recovering these generated waters to obtain supply water for generating reformed steam is usually employed.
[0006]
Further, in the electrochemical reaction of the fuel cell, heat is generated along with the reaction, and a part of the exhaust heat energy is stored as hot water in a hot water storage tank and supplied for hot water supply or heating.
[0007]
FIG. 2 is a system diagram showing an example of a conventional solid polymer electrolyte fuel cell power generation system. Before describing this system diagram, the efficiency of a small-capacity fuel cell power generation system equipped with a hot water tank will be described first, and will be described later, including the relationship with this efficiency problem.
[0008]
Small-capacity polymer electrolyte fuel cell power generators are expected to be installed in homes and small-scale offices, but the target efficiency of this equipment is about 40% (LHV) power generation efficiency at the transmission end, which is electrical output. The target exhaust heat efficiency of hot water, which is the heat output, is about 40% (LHV), and the target value of total heat efficiency reaches about 80% (LHV), but about 20% (LHV) heat is exhausted and released from the equipment. As abandoned in the atmosphere. Here, the LHV is an abbreviation for Lower Heat Value, and the efficiency is an efficiency calculated on the basis of a lower heating value not including latent heat of condensation.
[0009]
Furthermore, when focusing on the heat output of about 40% (LHV) used for hot water as warm water, when the state of low load (demand) of hot water continues, the temperature of the hot water tank is the upper limit, for example, about 70 When the temperature reaches ℃, after that, it is necessary to dissipate the thermal energy of the hot water, which is the heat output, to the atmosphere by the hot water cooler described later, so the total thermal efficiency in this case is 40% ( LHV).
[0010]
These reasons will be described with reference to the system diagram of FIG. In FIG. 2, the area within the alternate long and short dash line indicated by 30 indicates the inside of the package of the polymer electrolyte fuel cell power generator. In the package 30, there are many devices other than the part numbers 1 to 16 in FIG. 2, but these are omitted here.
[0011]
Reference numeral 1 denotes a fuel cell main body. 1a is a fuel electrode, 1b is an air electrode, and 1c is a cooling plate through which battery cooling water passes. A plurality of these are laminated to constitute the fuel cell main body 1. At the time of fuel cell power generation, hydrogen rich gas is supplied to 1a and air is supplied from the reaction air blower 7 to 1b to generate heat together with DC power. The hydrogen-rich gas supplied to 1a is a raw fuel (a methane gas, a propane gas, a butane gas, a hydrocarbon gas such as city gas composed of these gas compositions, or a hydrocarbon liquid such as kerosene or light oil). After being introduced into the package 30 and desulfurized by the desulfurizer 2, it is combined with the reforming water sent out by the reforming water pump 15 and purified by the water treatment device 14, and the reformer 3 performs steam reforming which is an endothermic reaction. It can be obtained by conducting a quality reaction.
[0012]
Since the hydrogen-rich gas obtained here contains carbon monoxide (CO) that poisons the catalyst of the fuel cell main body, the concentration level of carbon monoxide is further increased by the CO converter 4 and the CO remover 5 in the subsequent stage. After being reduced to 10 ppm or less, the fuel cell is supplied to the fuel electrode 1a, and part of the hydrogen is consumed as the fuel cell body 1 generates power. The remaining hydrogen not consumed in 1a is burned in the burner portion of the reformer 3 and becomes a heat source for the reforming reaction.
[0013]
The combustion exhaust gas from the reformer 3 and the air that has passed through the air electrode 1b of the fuel cell body 1 are cooled by the exhaust gas cooler 10 to recover water. If this water recovery amount is insufficient, the water level of the exhaust gas cooler 10 cannot be maintained, and it becomes necessary to replenish city water by opening the electromagnetic valve 16 for makeup water. When city water is replenished, the life of the water treatment apparatus 14 provided to prevent the silica SiO from being mixed into the reforming water is extremely shortened.
[0014]
In order to prevent this, the exhaust gas cooler 10 drives the fan of the recovered water cooler 11 and the recovered water circulation pump 12 based on the recovered water temperature detector 13 to recover the recovered water. Appropriate cooling by the vessel 11 is required. Since the recovered water is cooled by the recovered water cooler 11 by exchanging heat with the atmosphere, the heat of the cooling air is continuously released to the atmosphere as unusable heat.
[0015]
Further, the fuel cell main body 1 generates relatively high-temperature exhaust heat simultaneously with power generation. In the case of a polymer electrolyte fuel cell, the generated heat efficiency is about 40% (LHV), and the temperature level is about 80 ° C. This exhaust heat is stored in the hot water storage tank 21 by the hot water sent out by the hot water circulation pump 20 through the battery cooling water system equipment of the battery cooling water pump 8 and the battery cooling water cooler 9.
[0016]
When the hot water temperature detector 19 detects that the heat storage has continued and the temperature level of the hot water tank has reached a certain value or more, the hot water cooler 18 is activated. This is because the temperature of the battery cooling water is adjusted by the fuel cell cooling water cooler 9 and the stable operation in which the operation temperature of the fuel cell main body 1 is kept constant is continued. Therefore, if the exhaust heat quantity of the fuel cell main body 1 exceeds the hot water supply demand of the user hot water supply facility 22, the heat output of about 40% (LHV) must be radiated to the atmosphere via the hot water cooler 18. Disappear.
[0017]
As described above, in a cogeneration system using a conventional fuel cell, a fuel cell that is output after the amount of heat stored in the hot water storage tank, which is a heat storage means for heat dissipation and exhaust heat from the fuel cell power generator, reaches an upper limit. The relatively high temperature exhaust heat from the main body has not been effectively utilized.
[0018]
On the other hand, an air conditioner is generally introduced as a cooling / heating device in homes and small-scale offices that are considered as installation destinations of polymer electrolyte fuel cell power generation devices. The air conditioner is used as a refrigeration cycle that radiates indoor heat from the outdoor unit in summer, and as a heat pump cycle that radiates heat from outside air in the winter.
[0019]
FIG. 3 shows a schematic system diagram of the heat pump mode in the heat pump type air conditioner. In FIG. 3, 50 is an indoor heat exchanger, 51 is an outdoor heat exchanger, 52 is a compressor, and 53 is an expansion valve. Since heat pumps use the heat of the outside air as the heat source, in severe winter and cold regions, the difference in the endothermic temperature (outside air temperature) with respect to the temperature to be used (indoor temperature) increases and the power required to operate the heat pump increases. There is a problem.
[0020]
Thus, a heat supply system has been proposed in which the exhaust heat of the fuel cell is introduced into an outdoor heat exchanger to increase the efficiency during heating (see, for example, Patent Document 1).
[0021]
According to the publication, the heat supply system described in Patent Document 1 is “an air conditioner that has at least an outdoor heat exchanger and an indoor heat exchanger, performs a heat pump cycle that pumps outdoor heat indoors, and a fuel gas. Between the high-temperature air and the fuel cell device for supplying the electric energy generated by reacting oxygen with oxygen in the air to the air-conditioning apparatus and discharging the high-temperature air after the reaction that has been heated by the reaction heat. A hot water supply device that stores water heated by heat exchange, and when the air conditioner is performing a heating operation, the high-temperature air discharged from the fuel cell device is guided to the outdoor heat exchanger, and the air conditioner is heated. And an exhaust switching means for guiding the high-temperature air discharged from the fuel cell device to the hot water supply device when not performing the operation "
“According to the heat supply system having the above-described configuration, the high temperature air discharged from the fuel cell is generated by the exhaust gas switching unit guiding the high temperature air discharged from the fuel cell device to the outdoor heat exchanger of the air conditioner during the heating operation by the air conditioner. Heat can be recovered from the air by the outdoor heat exchanger of the air conditioner, and the efficiency of heat exchange can be increased by the recovered heat from the high-temperature air, so that the substantial heating capacity is increased without increasing the capacity of the heat exchanger. As a result, it is possible to prevent the heating capacity from being lowered with a decrease in the outside air temperature, and to reduce the power cost necessary for maintaining a constant heating state. If not, the exhaust gas switching means guides the hot air discharged from the fuel cell device to the hot water supply device, so that the hot water from the high temperature air discharged from the fuel cell is heated by the hot water supply device. Can yield, can be supplied to the outside as hot water by heating the water by collecting heat from the hot air, water and energy costs necessary for raising the temperature can be suppressed or eliminated. There is a ".
[0022]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-281072 (page 2-4, FIG. 1)
[0023]
[Problems to be solved by the invention]
Incidentally, the conventional fuel cell power generation system as described above also has the following problems.
[0024]
In the system described in Patent Document 1, the high-temperature air after the reaction heated by the reaction heat, that is, the air electrode exhaust gas of the fuel cell is led to the outdoor heat exchanger of the air conditioner during heating. In this case, since the water contained in the fuel cell air exhaust gas is released into the atmosphere, the reaction product water in the fuel cell is not effectively recovered, and the water self-sustained operation of the fuel cell power generator (replenishment water from the outside) In such a situation, the system operation including water treatment is not economical as a whole. In addition, in the case of the system described in Patent Document 1, humid air containing moisture is introduced into the outdoor heat exchanger of the air conditioner as described above, so that the outdoor heat exchanger is likely to corrode. is there.
[0025]
The present invention has been made in view of the above problems, and an object of the present invention is to provide a system having a device for recovering water in exhaust air of a fuel cell and a hot water storage tank for storing exhaust heat of the fuel cell, and An object of the present invention is to provide a fuel cell power generation system capable of effectively using surplus heat as a heat source for heating without releasing moisture in the exhaust air, and an operation method thereof.
[0026]
[Means for Solving the Problems]
In order to solve the above-described problems, in the present invention, electric and thermal energy is generated based on an electrochemical reaction between a fuel gas obtained by steam reforming a hydrocarbon-based raw fuel and air as an oxidant gas. A generated fuel cell main body, a fuel reforming system device, a cooling water system device for the fuel cell, a recovered water system device for recovering water in the exhaust air of the fuel cell and the combustion exhaust gas of the fuel reformer, and the thermal energy A hot water storage tank for storing a part of it as hot water, the recovered water system device further comprising an exhaust gas cooler and a recovered water cooler, and the hot water storage tank is provided with a hot water cooler for preventing overheating In the operation method of the battery power generation system,
The fuel cell power generation system includes an air conditioner having an outdoor heat exchanger capable of performing a heating operation by a heat pump that pumps at least outdoor heat indoors, and an indoor heat exchanger, and the recovered water cooler and the hot water cooler by detecting at least one of the actuation of at least one of the exhaust heat of the recovery water condenser and warm the cooler is introduced into the outdoor heat exchanger of the air conditioning system, utilized as a heat source for heating of the heat pump (Invention of claim 1).
[0027]
According to the above operating method, the heat generated by the heat recovery from the air exhaust gas and the reformer combustion exhaust gas (heat from the recovered water cooler) and the storage heat capacity of the hot water tank are filled as heat sources for the heat pump. The surplus heat of the hot water (heat from the hot water cooler) that is generated in the event of using the heat exchanger can be used, so that the outdoor heat exchanger can be preheated without affecting the water recovery performance. Corrosion problems can also be eliminated.
[0028]
As a system for carrying out the method of the invention of claim 1, the inventions of claims 2 to 3 below are preferable. That is, a fuel cell power generation system for carrying out the operation method according to claim 1, wherein the exhaust heat recovery water circulation circuit introduces the exhaust heat into an outdoor heat exchanger, and is provided on the circulation circuit. A heating heat source water circulation pump; and a waste heat utilization heating operation control device that drives the heating heat source water circulation pump by detecting an operation of at least one of the recovered water cooler and the hot water cooler, and the exhaust heat recovery water circulation The circuit includes a water circulation heat exchanger for exhaust heat recovery provided in the recovered water cooler and the hot water cooler, a water circulation heat exchanger for heat reception provided in the outdoor heat exchanger, and the waste heat recovery and heat reception, respectively. It shall consist of piping which connects with a water circulation heat exchanger, and forms a closed loop (invention of Claim 2).
[0029]
In the invention of claim 2, when the operation of at least one of the recovered water cooler and the hot water cooler is stopped and the other is operated, the exhaust heat recovery water circulation circuit is operated. The switching bypass circuit by the solenoid valve can be configured so that only the water in the exhaust heat recovery water circulation heat exchanger passes through the heat reception water circulation heat exchanger.
[0030]
In order to simplify the configuration without providing the switching circuit, the invention of claim 3 below is preferable, although some heat loss is involved. That is, in the fuel cell power generation system according to claim 2, the exhaust heat recovery water circulation heat exchanger provided in the recovered water cooler and the hot water cooler is connected in series to form the exhaust heat recovery water circulation circuit. In addition, an exhaust heat recovery water circulation heat exchanger for the recovered water cooler is disposed on the upstream side.
[0031]
According to the above configuration, when both the recovered water cooler and the hot water cooler operate, the exhaust heat recovery water circulation heat exchanger provided in the hot water cooler operates at an operating temperature level than that for the recovered water cooler. Therefore, heat loss can be suppressed.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
Examples of the present invention will be described below with reference to the drawings.
[0033]
FIG. 1 is a system diagram showing an embodiment relating to the present invention. Members having the same functions as those in FIGS. 2 and 3 are denoted by the same reference numerals, and detailed description thereof is omitted. Further, in FIG. 1, most of the devices in the power generation device package 30 in FIG. 2 and the devices related to the heat storage tank 21 around the hot water cooler 18 are omitted.
[0034]
1 is different from FIG. 2 in that an air conditioner having an outdoor heat exchanger 51 and an indoor heat exchanger 50 capable of heat pump operation is provided, and at least one of the recovered water cooler 11 and the hot water cooler 18 is provided. The exhaust heat of at least one of the recovered water cooler and the hot water cooler is introduced into the outdoor heat exchanger 51 of the air conditioner and used as a heat source for heating of the heat pump. This is the point.
[0035]
1, the exhaust heat recovery water circulation circuit 42 for introducing the exhaust heat into the outdoor heat exchanger 51, the heating heat source water circulation pump 45 provided on the circulation circuit, the recovered water cooler 11, and the hot water The exhaust heat utilization heating operation control device 40 that drives the heating heat source water circulation pump 45 by detecting the operation of at least one of the coolers 18 is provided. Further, the exhaust heat recovery water circulation circuit 42 is provided in the exhaust heat recovery water circulation heat exchanger (11a and 18a) provided in the recovery water cooler 11 and the hot water cooler 18, respectively, and in the outdoor heat exchanger 51. The heat receiving water circulation heat exchanger 51a and a pipe 42a that connects the exhaust heat recovery and heat receiving water circulation heat exchanger to form a closed loop. In addition, the said waste heat utilization heating operation control apparatus 40 drives the said heating heat source water circulation pump 45 based on the answer back signal of the heat pump mode of an air conditioner.
[0036]
Furthermore, in the configuration of FIG. 1, the exhaust water recovery water circulation heat exchangers (11 a and 18 a) provided in the recovered water cooler 11 and the hot water cooler 18 are connected in series as described in claim 3. And the structure which arrange | positions the water circulation heat exchanger 11a for waste heat recovery for recovery water coolers in the upstream of 18a is shown.
[0037]
With the above configuration, the heat energy from the recovered water cooler 11 that has been conventionally radiated to the atmosphere and the heat energy that has been radiated from the hot water cooler 18 to the atmosphere when the heat capacity of the hot water storage tank 21 is saturated. Can be used effectively as a heating heat source for existing air conditioners, and by reducing the amount of power used during heating, it is possible to expand the energy saving benefits of users who have introduced small-capacity polymer electrolyte fuel cell power generators. .
[0038]
【The invention's effect】
As described above, according to the present invention, a fuel cell that generates electricity and thermal energy based on an electrochemical reaction between a fuel gas obtained by steam reforming a hydrocarbon-based raw fuel and air as an oxidant gas. A main body, a fuel reforming system device, a cooling water system device for a fuel cell, a recovery water system device for recovering water in the exhaust air of the fuel cell and the combustion exhaust gas of the fuel reformer, and a part of the thermal energy in hot water As a fuel cell power generation system, wherein the recovered water system device includes an exhaust gas cooler and a recovered water cooler, and the hot water tank includes a hot water cooler for preventing overheating. in operation method thereof, the fuel cell power generation system includes an air conditioning apparatus having at least a heating operation by the heat pump for pumping up the outdoor heat into the room capable outdoor heat exchanger and an indoor heat exchanger, By detecting at least one of the operation of the serial recovered water condenser and warm water cooler, and at least one of the exhaust heat of the recovery water condenser and warm water condenser was introduced into the outdoor heat exchanger of the air conditioning system, Since it was used as a heat source for heating the heat pump,
In a system having a device for collecting water in the exhaust air of the fuel cell and a hot water storage tank for storing the exhaust heat of the fuel cell, it is possible to effectively use surplus heat as a heat source for heating, and A fuel cell power generation system capable of suppressing corrosion of an outdoor heat exchanger of the air conditioner without releasing moisture in the exhaust air and an operation method thereof can be provided.
[Brief description of the drawings]
FIG. 1 is a system diagram showing an embodiment of a fuel cell power generation system of the present invention. FIG. 2 is a system diagram showing an example of a conventional fuel cell power generation system. FIG. 3 is a schematic system diagram of a heat pump mode in a heat pump type air conditioner. Explanation of symbols]
1: fuel cell body, 3: reformer, 10: exhaust gas cooler, 11: recovered water cooler, 11a, 18a: water circulation heat exchanger for exhaust heat recovery, 14: water treatment device, 18: hot water cooler, 21: Hot water storage tank, 40: Waste heat utilization heating operation control device, 42: Waste heat recovery water circulation circuit, 42a: Piping forming a closed loop, 45: Heating heat source water circulation pump, 50: Indoor heat exchanger, 51: Outdoor Heat exchanger, 51a: a water circulation heat exchanger for receiving heat.

Claims

A fuel cell body that generates electricity and thermal energy based on an electrochemical reaction between a fuel gas obtained by steam reforming a hydrocarbon-based raw fuel and air as an oxidant gas, a fuel reforming system device, A cooling water system device for the fuel cell, a recovery water system device for recovering water in the exhaust air of the fuel cell and the combustion exhaust gas of the fuel reformer, and a hot water storage tank for storing a part of the thermal energy as hot water, In the operation method of the fuel cell power generation system, the recovered water system device includes an exhaust gas cooler and a recovered water cooler, and the hot water storage tank includes a hot water cooler for preventing excessive temperature rise.
The fuel cell power generation system includes an air conditioner having an outdoor heat exchanger capable of performing a heating operation by a heat pump that pumps at least outdoor heat indoors, and an indoor heat exchanger, the recovered water cooler and the hot water cooler by detecting at least one of the actuation of at least one of the exhaust heat of the recovery water condenser and warm the cooler is introduced into the outdoor heat exchanger of the air conditioning system, utilized as a heat source for heating of the heat pump A method for operating a fuel cell power generation system.

A fuel cell power generation system for carrying out the operation method according to claim 1, wherein the exhaust heat recovery water circulation circuit introduces the exhaust heat into an outdoor heat exchanger, and a heating heat source water circulation provided on the circulation circuit. A pump and a waste heat utilization heating operation control device that drives the heating heat source water circulation pump by detecting an operation of at least one of the recovered water cooler and the hot water cooler, and the exhaust heat recovery water circulation circuit includes: The exhaust heat recovery water circulation heat exchanger provided in the recovered water cooler and the hot water cooler, the heat receiving water circulation heat exchanger provided in the outdoor heat exchanger, and the exhaust heat recovery and heat receiving water circulation heat, respectively. A fuel cell power generation system comprising a pipe connected to an exchanger to form a closed loop.

The fuel cell power generation system according to claim 2, wherein the exhaust heat recovery water circulation heat exchanger provided in the recovered water cooler and the hot water cooler is connected in series to form the exhaust heat recovery water circulation circuit, respectively. In addition, the fuel cell power generation system is characterized in that an exhaust heat recovery water circulation heat exchanger for the recovered water cooler is disposed upstream.