JP4961682B2 - Fuel cell power generation apparatus and operation stop method - Google Patents

Fuel cell power generation apparatus and operation stop method Download PDF

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JP4961682B2
JP4961682B2 JP2005115828A JP2005115828A JP4961682B2 JP 4961682 B2 JP4961682 B2 JP 4961682B2 JP 2005115828 A JP2005115828 A JP 2005115828A JP 2005115828 A JP2005115828 A JP 2005115828A JP 4961682 B2 JP4961682 B2 JP 4961682B2
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fuel
fuel cell
gas
electrode layer
power generation
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JP2006294508A (en
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順 秋草
範壽 千歳
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Kansai Electric Power Co Inc
Mitsubishi Materials Corp
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Kansai Electric Power Co Inc
Mitsubishi Materials Corp
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Priority to EP06714166A priority patent/EP1852930B1/en
Priority to EP09164506A priority patent/EP2101371A3/en
Priority to EP10194752A priority patent/EP2287954A3/en
Priority to AT06714166T priority patent/ATE542255T1/en
Priority to PCT/JP2006/303026 priority patent/WO2006090685A1/en
Priority to US11/884,785 priority patent/US20110076573A1/en
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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

本発明は、燃料電池の出力電力に基づいて反応用ガスの供給量を制御する燃料電池の運転停止方法に関するものである。   The present invention relates to a fuel cell operation stop method for controlling a supply amount of a reaction gas based on output power of a fuel cell.

酸化物イオン導電体から成る固体電解質層を両側から空気極層（カソード）と燃料極層（アノード）で挟み込んだ構造を有する燃料電池は、燃料の有する化学エネルギーを直接電気エネルギーに変換する高効率、且つクリーンな発電装置として注目されている。固体酸化物形燃料電池では、空気極層側に酸化剤ガス（酸素) が供給され、燃料極層側に燃料ガス (Ｈ2 、ＣＯ、ＣＨ4 等) が供給される。 A fuel cell with a structure in which a solid electrolyte layer made of an oxide ion conductor is sandwiched between the air electrode layer (cathode) and the fuel electrode layer (anode) from both sides is highly efficient in converting the chemical energy of the fuel directly into electrical energy And it is attracting attention as a clean power generation device. In the solid oxide fuel cell, an oxidant gas (oxygen) is supplied to the air electrode layer side, and a fuel gas (H 2 , CO, CH 4, etc.) is supplied to the fuel electrode layer side.

空気極層側に供給された酸素は、空気極層内の気孔を通って固体電解質層との界面近傍に到達し、この部分で空気極層から電子を受け取って酸化物イオン（Ｏ2-）にイオン化される。この酸化物イオンは、燃料極層に向かって固体電解質層内を拡散移動する。燃料極層との界面近傍に到達した酸化物イオンは、この部分で、燃料ガスと反応して反応生成物（Ｈ2Ｏ、ＣＯ2等）を生じ、燃料極層に電子を放出する。電極反応で生じた電子は、別ルートの外部負荷にて起電力として取り出すことができる。 Oxygen supplied to the air electrode layer passes through the pores in the air electrode layer and reaches the vicinity of the interface with the solid electrolyte layer, and receives electrons from the air electrode layer at this portion to form oxide ions (O2−). Ionized. The oxide ions diffuse and move in the solid electrolyte layer toward the fuel electrode layer. Oxide ions that have reached the vicinity of the interface with the fuel electrode layer react with the fuel gas at this portion to generate reaction products (H 2 O, CO 2, etc.), and discharge electrons to the fuel electrode layer. Electrons generated by the electrode reaction can be taken out as an electromotive force at an external load on another route.

ところで、係る燃料電池の運転を停止する場合、従来では、燃料極層側への燃料ガスの供給と、空気極層側への酸化剤ガスの供給を停止し、その後、燃料電池に不活性ガス（例えば窒素）を供給して燃料電池の内部を不活性ガスで置換する、所謂、パージを行っていた（例えば、特許文献１参照）。
これは、運転停止後の高温状態において、燃料電池の内部に残留する酸化剤ガス中の酸素によって燃料極層が酸化され、発電性能が極端に低下してしまうためであって、仮に運転開始時に酸化された燃料極層が燃料ガス（水素）によって再度還元されたとしても、酸化前の発電性能を回復することは殆どないことが知られている。 By the way, when stopping the operation of the fuel cell, conventionally, the supply of the fuel gas to the fuel electrode layer side and the supply of the oxidant gas to the air electrode layer side are stopped, and then the inert gas is supplied to the fuel cell. A so-called purge is performed in which the inside of the fuel cell is replaced with an inert gas by supplying (for example, nitrogen) (see, for example, Patent Document 1).
This is because the fuel electrode layer is oxidized by oxygen in the oxidant gas remaining inside the fuel cell in a high temperature state after the operation is stopped, and the power generation performance is extremely lowered. It is known that even if the oxidized fuel electrode layer is reduced again by the fuel gas (hydrogen), the power generation performance before oxidation is hardly recovered.

特に、固体酸化物形燃料電池は、作動温度が６００〜１０００℃と極めて高いため、運転停止後の降温過程において短時間で温度を下げることは不可能であり、且つ、発電セルの外周部にガス漏れ防止シールを設けないシールレス構造を採用した場合は、電池内圧力の低下により外部（燃料電池モジュール内）の酸素含有ガスが電池内部に侵入し易くなっており、よって、運転停止時には大量のパージが必要であり、且つ、燃料電池が大型化するに連れてパージのための不活性ガスの使用量も比例的に増加する傾向であった。
特開平２−２４４５５９号公報 In particular, since the solid oxide fuel cell has an extremely high operating temperature of 600 to 1000 ° C., it is impossible to lower the temperature in a short time in the temperature lowering process after the operation is stopped, and in the outer periphery of the power generation cell. When a sealless structure that does not have a gas leak prevention seal is adopted, the oxygen-containing gas outside (in the fuel cell module) easily enters the inside of the battery due to a decrease in the pressure inside the battery. The amount of inert gas used for purging tended to increase proportionally as the fuel cell size increased.
JP-A-2-244559

ところが、不活性ガスによるパージを行う場合、反応用ガスとしての燃料ガスや酸化剤ガスの他にパージ用の不活性ガスを用意する必要があり、一般的には、ガスボンベを装備して燃料ガス供給経路にパージ用の不活性ガスを供給する構成としている。このため、ガスボンベや不活性ガスの供給経路を含め、燃料電池全体の重量や容積が増大すると共に、メンテナンス作業も煩雑化するという問題があった。   However, when purging with an inert gas, it is necessary to prepare an inert gas for purging in addition to a fuel gas or an oxidant gas as a reaction gas. Generally, a fuel gas is provided with a gas cylinder. A purge inert gas is supplied to the supply path. For this reason, there is a problem that the weight and volume of the entire fuel cell including the gas cylinder and the inert gas supply path increase, and the maintenance work becomes complicated.

本発明は、このような問題に鑑みてなされたもので、別途パージ用ガスの供給系を設けることなくパージを行うことができる燃料電池発電装置および運転停止方法を提供することを目的としている。   The present invention has been made in view of such a problem, and an object of the present invention is to provide a fuel cell power generation apparatus and an operation stop method that can perform a purge without providing a separate purge gas supply system.

すなわち、請求項１に記載の本発明は、燃料極層側へ燃料ガスを供給し、空気極層側へ酸化剤ガスを供給して発電反応を生じさせる燃料電池スタックを備えた燃料電池の運転停止方法であって、発電停止の際に、前記空気極層側への上記酸化剤ガスの供給を維持するとともに、上記燃料電池スタックの温度が３００℃に低下するまで前記燃料電池スタックのセル電圧が０．５Ｖ以上となるように上記燃料ガスである水素の流量または改質されて上記燃料ガスとなる水素リッチなガスを生成させる水および炭化水素系燃料の流量を減少させながら上記燃料極層側へ上記燃料ガスを供給することにより、上記燃料極層側を還元状態に保持しつつ、上記燃料電池スタックの温度を低下させることを特徴としている。
この方法は、発電停止以降も少量の水と燃料ガスの供給を継続しつつ、燃料電池の熱容量を利用して水蒸気を生成し、改質ガスと水蒸気の混合ガスを燃料極に供給することにより還元性を保持するものである。 That is, the present invention according to claim 1 is an operation of a fuel cell including a fuel cell stack that supplies a fuel gas to the fuel electrode layer side and supplies an oxidant gas to the air electrode layer side to cause a power generation reaction. A stopping method, wherein when the power generation is stopped, the supply of the oxidant gas to the air electrode layer side is maintained, and the cell voltage of the fuel cell stack is decreased until the temperature of the fuel cell stack decreases to 300 ° C. The fuel electrode layer while reducing the flow rate of hydrogen , which is the fuel gas, or the flow rate of water and hydrocarbon-based fuel that is reformed to produce a hydrogen-rich gas that becomes the fuel gas so as to be 0.5 V or higher By supplying the fuel gas to the side, the temperature of the fuel cell stack is lowered while maintaining the fuel electrode layer side in a reduced state.
In this method, a small amount of water and fuel gas are continuously supplied even after power generation is stopped, steam is generated using the heat capacity of the fuel cell, and a mixed gas of reformed gas and steam is supplied to the fuel electrode. It retains reducibility.

また、上記燃料電池スタックの温度が３００℃以上で燃料ガスの供給を停止すると、燃料極層側が酸化され、劣化してしまう虞があるが、上記燃料電池スタックの温度が３００℃程度に低下するまではセル電圧が０．５Ｖを下回らないように燃料ガスを徐々に減少していくことにより、燃料極層側を還元状態に保持しておくことができる。 Further, when the temperature of the fuel cell stack to stop the supply of fuel gas at 300 ° C. or higher, the fuel electrode layer side is oxidized, there is a risk that degraded, lowering the temperature of the fuel cell stack to about 300 ° C. Until this is done, the fuel electrode layer side can be kept in the reduced state by gradually reducing the fuel gas so that the cell voltage does not fall below 0.5V.

また、請求項２に記載の本発明は、請求項１に記載の燃料電池の運転停止方法において、前記燃料電池スタックにおいて、改質する上記炭化水素系燃料への上記水の供給停止時に、当該水による水蒸気温度が２００℃以上であるように水の供給量を減少させることを特徴としている。
水の供給を停止した時に水蒸気温度が２００℃以下であると、水蒸気の温度は一気に１００℃まで低下し、水蒸気の連続的な発生が難しくなる。その結果、セル内に液体水が供給され、セルの劣化や割れが発生する虞がある。このため、水の供給停止時の水蒸気温度は２００℃以上とする必要がある。 Further, the invention of claim 2 is the fuel shutdown method of a battery according to claim 1, in the fuel cell stack, when the supply stop of the water into the hydrocarbon-based fuel to the reforming, the The water supply amount is decreased so that the water vapor temperature is 200 ° C. or higher.
If the water vapor temperature is 200 ° C. or lower when the supply of water is stopped, the temperature of the water vapor drops to 100 ° C. all at once, making it difficult to continuously generate water vapor. As a result, liquid water is supplied into the cell, and the cell may be deteriorated or cracked. For this reason, the water vapor temperature at the time of stopping the supply of water needs to be 200 ° C. or higher.

また、請求項３に記載の本発明は、燃料ガス供給量と酸化剤ガス供給量に応じて電力を出力する燃料電池スタックと、当該燃料電池スタックに燃料ガスを供給する燃料供給系、酸化剤ガスを供給する酸化剤ガス供給系および水を供給する水供給系と、これら各系を制御する制御部とを備え、上記制御部は、発電停止の際に、上記空気極層側への上記酸化剤ガスの供給を維持するとともに、少なくとも上記燃料電池スタックの温度が３００℃に低下するまで上記燃料ガスである水素の流量または改質されて上記燃料ガスとなる水素リッチなガスを生成させる水および炭化水素系燃料の流量を減少させながら上記燃料極層側へ上記燃料ガスを供給することにより、上記発電反応を生じさせた状態で、上記燃料極層側を還元状態に保持しつつ上記燃料電池スタックの温度を低下させるように、上記燃料供給系、酸化剤ガス供給系および水供給系を制御することを特徴としている。 According to a third aspect of the present invention, there is provided a fuel cell stack that outputs electric power according to a fuel gas supply amount and an oxidant gas supply amount, a fuel supply system that supplies fuel gas to the fuel cell stack, an oxidant An oxidant gas supply system that supplies gas, a water supply system that supplies water, and a control unit that controls each of the systems, and the control unit supplies the air to the air electrode layer when power generation is stopped. Water that maintains the supply of the oxidant gas and generates hydrogen-rich gas that becomes the fuel gas by the flow rate or reforming of the hydrogen that is the fuel gas until at least the temperature of the fuel cell stack is lowered to 300 ° C. And by supplying the fuel gas to the fuel electrode layer side while reducing the flow rate of the hydrocarbon-based fuel, the fuel electrode layer side is maintained in the reduced state while the power generation reaction is caused. As lowering the temperature of the cell stack, the fuel supply system is characterized by controlling the oxidant gas supply system and water supply system.

また、請求項４に記載の本発明は、請求項３に記載の燃料電池発電装置において、前記燃料電池スタックは、発電反応に使用されなかった残余のガスを発電セルの外周部より放出するシールレス構造の固体酸化物形燃料電池であることを特徴としている。 According to a fourth aspect of the present invention, there is provided the fuel cell power generator according to the third aspect , wherein the fuel cell stack is a seal that discharges residual gas that has not been used for power generation reaction from the outer peripheral portion of the power generation cell. It is a solid oxide fuel cell having a loess structure.

本発明によれば、発電停止の際に、燃料電池に水、および水素または炭化水素系燃料の流量を減少させて供給することにより、燃料極層の還元性を保持することができ、これにより、昇降温サイクルにおける発電セルの酸化やそれに伴う発電セルの性能劣化が防止でき、高寿命化が図れる。
加えて、従来の不活性ガスによるパージは不要であるから、不活性ガスボンベ（例えば、窒素ボンベ）を含むパージ用ガス供給系を設ける必要が無くなり、メンテナンス作業を簡略化できると共に、装置自体を小型化できる。 According to the present invention, when the power generation is stopped, the reducing property of the fuel electrode layer can be maintained by supplying the fuel cell with a reduced flow rate of water and hydrogen or hydrocarbon fuel. In addition, the oxidation of the power generation cell and the accompanying performance deterioration of the power generation cell in the heating / cooling cycle can be prevented, and the life can be extended.
In addition, since purging with a conventional inert gas is unnecessary, there is no need to provide a purge gas supply system including an inert gas cylinder (for example, a nitrogen cylinder), which simplifies maintenance work and reduces the size of the apparatus itself. Can be

以下、図面に基づいて本発明の実施形態を説明する。
図１は本発明が適用された燃料電池発電装置の概略構成を示し、図２は当燃料電池発電装置で用いる燃料電池スタックの構成を示し、図３は本発明の運転停止制御形態を示している。 Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a schematic configuration of a fuel cell power generator to which the present invention is applied, FIG. 2 shows a configuration of a fuel cell stack used in the fuel cell power generator, and FIG. 3 shows an operation stop control mode of the present invention. Yes.

本実施形態の燃料電池発電装置は、図１に示すように、燃料ガス供給量と空気供給量に応じて直流出力を発生する固体酸化物形燃料電池１（燃料電池スタック１）、燃料ガス（例えば、メタンガス、都市ガス）と水蒸気の混合ガスを水素リッチなガスに改質して燃料電池スタック１に供給する燃料改質器１５等を断熱ハウジング内に収納して構成した燃料電池モジュール１０、および、この燃料電池モジュール１０の周辺に配設され、燃料ガスブロア２１や脱硫器２３や各燃料ガス供給配管等で構成されて燃料改質器１５に燃料ガスを導入する燃料供給系４０、空気ブロアや空気供給配管等で構成されて燃料電池スタック１に酸化剤ガス（空気）を供給する空気供給系３０、給水ポンプ２５や水供給管から構成されて燃料電池モジュール内に水（尚、この水は燃料電池モジュール内において図示しない水蒸気発生器により水蒸気となる）を導入する水供給系５０、燃料電池スタック１からの直流出力を交流出力に変換して交流電力Ｐａを外部負荷（図示せず）に供給するインバータ２４、上記した空気供給系３０、燃料供給系４０、水供給系５０の各系の流量を制御する制御部２０等で構成されている。   As shown in FIG. 1, the fuel cell power generator of this embodiment includes a solid oxide fuel cell 1 (fuel cell stack 1) that generates a direct current output in accordance with a fuel gas supply amount and an air supply amount, a fuel gas ( For example, a fuel cell module 10 configured by housing a fuel reformer 15 or the like that reforms a mixed gas of methane gas, city gas) and water vapor into a hydrogen rich gas and supplies the fuel cell stack 1 in a heat insulating housing, And a fuel supply system 40 that is disposed around the fuel cell module 10 and that includes a fuel gas blower 21, a desulfurizer 23, each fuel gas supply pipe, and the like, and introduces fuel gas into the fuel reformer 15, and an air blower Or an air supply pipe or the like, and an air supply system 30 for supplying an oxidant gas (air) to the fuel cell stack 1, a water supply pump 25, and a water supply pipe. (Note that this water is converted into water vapor by a water vapor generator (not shown) in the fuel cell module), the DC output from the fuel cell stack 1 is converted into AC output, and AC power Pa is externally loaded. It comprises an inverter 24 supplied to (not shown), a control unit 20 for controlling the flow rate of each of the air supply system 30, the fuel supply system 40, and the water supply system 50 described above.

また、この制御部２０には、燃料電池発電装置内の適所に配設された各検出器（図示せず）から送出される、セル電圧情報Ｖ、スタック温度情報Ｔ１、水蒸気温度情報Ｔ２、出力電力情報Ｐａ等の各種検知情報が入力されるようになっている。   Further, the control unit 20 sends cell voltage information V, stack temperature information T1, water vapor temperature information T2, and outputs sent from detectors (not shown) disposed at appropriate positions in the fuel cell power generator. Various detection information such as power information Pa is input.

ここで、上記燃料電池スタック１は、図２に示すように、固体電解質層２の両面に燃料極層３と空気極層４を配した発電セル５と、燃料極層３の外側に配した燃料極集電体６と、空気極層４の外側に配した空気極集電体７と、各集電体６、７の外側に配したセパレータ８とで構成した単セル９を縦方向に多数積層してスタック化したものである。   Here, as shown in FIG. 2, the fuel cell stack 1 is disposed outside the fuel electrode layer 3, and a power generation cell 5 in which the fuel electrode layer 3 and the air electrode layer 4 are disposed on both surfaces of the solid electrolyte layer 2. A single cell 9 composed of a fuel electrode current collector 6, an air electrode current collector 7 arranged outside the air electrode layer 4, and a separator 8 arranged outside each current collector 6, 7 is vertically arranged. Many are stacked to form a stack.

単セル９の構成要素の内、固体電解質層２はイットリアを添加した安定化ジルコニア（ＹＳＺ）等で構成され、燃料極層３はＮｉ、Ｃｏ等の金属またはＮｉ−ＹＳＺ、Ｃｏ−ＹＳＺ等のサーメットで構成され、空気極層４はＬａＭｎＯ3 、ＬａＣｏＯ3 等で構成され、燃料極集電体６はＮｉ基合金等のスポンジ状の多孔質焼結金属板で構成され、空気極集電体７はＡｇ基合金等のスポンジ状の多孔質焼結金属板で構成され、セパレータ８はステンレス等で構成されている。 Among the constituent elements of the unit cell 9, the solid electrolyte layer 2 is made of stabilized zirconia (YSZ) or the like to which yttria is added, and the fuel electrode layer 3 is made of a metal such as Ni or Co or Ni-YSZ or Co-YSZ. It is composed of cermet, the air electrode layer 4 is composed of LaMnO 3 , LaCoO 3, etc., and the fuel electrode current collector 6 is composed of a sponge-like porous sintered metal plate such as a Ni-based alloy. 7 is composed of a sponge-like porous sintered metal plate such as an Ag-based alloy, and the separator 8 is composed of stainless steel or the like.

セパレータ８は、発電セル５間を電気的に接続すると共に、発電セル５に対して反応用ガスを供給する機能を有するもので、燃料ガスをセパレータ８の外周面から導入してセパレータ８の燃料極集電体６に対向する面のほぼ中央部１１ａから吐出する燃料ガス通路１１と、酸化剤ガスをセパレータ８の外周面から導入してセパレータ８の空気極集電体７に対向する面のほぼ中央部１２ａから吐出する酸化剤ガス通路１２を備えている。   The separator 8 has a function of electrically connecting the power generation cells 5 and supplying a reaction gas to the power generation cells 5. The fuel of the separator 8 is introduced by introducing fuel gas from the outer peripheral surface of the separator 8. The fuel gas passage 11 discharged from the substantially central portion 11a of the surface facing the electrode current collector 6 and the surface of the surface of the separator 8 facing the air electrode current collector 7 by introducing oxidant gas from the outer peripheral surface of the separator 8 An oxidant gas passage 12 that is discharged from the substantially central portion 12a is provided.

燃料電池スタック１内には、積層方向に延びる燃料ガス用のマニホールド１７と酸化剤ガス用のマニホールド１８が設けられており、マニホールド１７には改質された燃料ガスが流通し、マニホールド１８には外部から供給される空気が流通し、各ガスがマニホールド１７、１８より各セパレータ８の各ガス通路１１、１２に導入され、各ガス吐出口１１ａ、１２ａより吐出して各発電セルの各電極に分配・供給されるようになっている。燃料電池スタック１の両端には、ステンレス等で成る一対の端板８ａ、８ｂが配設されており、燃料電池スタック１の発電電力は、この端板８ａ、８ｂを介して取り出すことができるようになっている。   A fuel gas manifold 17 and an oxidant gas manifold 18 extending in the stacking direction are provided in the fuel cell stack 1, and the reformed fuel gas flows through the manifold 17. Air supplied from the outside flows, and each gas is introduced into each gas passage 11 and 12 of each separator 8 from the manifolds 17 and 18 and discharged from each gas discharge port 11a and 12a to each electrode of each power generation cell. Distributed and supplied. A pair of end plates 8a, 8b made of stainless steel or the like are disposed at both ends of the fuel cell stack 1, and the generated power of the fuel cell stack 1 can be taken out through the end plates 8a, 8b. It has become.

また、この燃料電池スタック１は、発電セル５の外周部にガス漏れ防止シールを敢えて設けないシールレス構造を採用しており、運転時には、発電反応で消費されなかった余剰ガス（高温排ガス）を発電セル５の外周部からハウジング内に自由に放出するようになっている。尚、ハウジングの内部空間に放出された高温度の排ガスは上部排気穴よりモジュール外に排出されるようになっている。   In addition, the fuel cell stack 1 employs a sealless structure in which a gas leakage prevention seal is not provided on the outer periphery of the power generation cell 5, and surplus gas (high temperature exhaust gas) that has not been consumed in the power generation reaction during operation is used. It is discharged freely from the outer periphery of the power generation cell 5 into the housing. Note that the high-temperature exhaust gas discharged into the internal space of the housing is discharged out of the module through the upper exhaust hole.

次ぎに、図３を参照して、上記構成の燃料電池発電装置の運転停止制御を説明する。当運転停止制御は、上記した各種検出器から入力された各種検知情報（Ｖ、Ｐａ、Ｔ１、Ｔ２等）に基づいて上記制御部２０により行われる。   Next, operation stop control of the fuel cell power generation device having the above configuration will be described with reference to FIG. The operation stop control is performed by the control unit 20 based on various detection information (V, Pa, T1, T2, etc.) input from the various detectors described above.

図３に示す運転停止制御は、燃料電池スタック１に供給される空気流量を一定流量に維持した状態で行われる。図３において、左縦軸は燃料ガス（メタン）の供給量および水蒸気源となる水の供給量を示し、右縦軸はスタック温度および電池出力を示し、横軸は経過時間を示している。   The operation stop control shown in FIG. 3 is performed in a state where the flow rate of air supplied to the fuel cell stack 1 is maintained at a constant flow rate. In FIG. 3, the left vertical axis indicates the supply amount of fuel gas (methane) and the supply amount of water serving as a water vapor source, the right vertical axis indicates the stack temperature and the battery output, and the horizontal axis indicates the elapsed time.

図３に示すように、定格発電期間（出力１ｋＷ、スタック温度７５０℃）において、運転停止操作が成されると、燃料電池モジュール１０に供給するメタンおよび水のそれぞれの流量を減少させながら、約４時間で電池出力を１ｋＷから０Ｗにまで低下させる（出力低下期間）と共に、その後、約１５時間でスタック温度を約７００℃から３００℃以下に低下させていく（降温期間）。本発明は、この運転停止操作後の出力低下期間〜降温期間における高温雰囲気下において、燃料極層側を還元状態に保持することにより燃料極層の酸化現象を回避するパージ処理である。
すなわち、本実施形態の運転停止制御は、発電停止時にあっても、燃料電池モジュール１０に少量のメタンと水を供給し続け、燃料電池モジュール１０の熱容量を利用して水蒸気を発生させると共に、改質反応により水素を生成して水蒸気との混合ガスを燃料極層側に供給することにより、燃料極層の還元性を保持するようにしたものである。 As shown in FIG. 3, in the rated power generation period (output 1 kW, stack temperature 750 ° C.), when the operation stop operation is performed, the respective flow rates of methane and water supplied to the fuel cell module 10 are reduced, and about The battery output is reduced from 1 kW to 0 W in 4 hours (output reduction period), and then the stack temperature is reduced from about 700 ° C. to 300 ° C. or less in about 15 hours (temperature reduction period). The present invention is a purge process for avoiding an oxidation phenomenon of the fuel electrode layer by maintaining the fuel electrode layer side in a reduced state in a high temperature atmosphere during the output reduction period to the temperature falling period after the operation stop operation.
That is, the operation stop control of the present embodiment continues to supply a small amount of methane and water to the fuel cell module 10 even when power generation is stopped, generates steam using the heat capacity of the fuel cell module 10, and The reducibility of the fuel electrode layer is maintained by generating hydrogen by a quality reaction and supplying a gas mixture with water vapor to the fuel electrode layer side.

尚、上記運転停止制御において、メタンや水の流量を変化させるには、制御部２０により燃料ガスブロア２１（制御弁でも良い）や給水ポンプ２５（制御弁でも良い）の動作を制御することにより行うことができる。   In the operation stop control, the flow rate of methane or water is changed by controlling the operation of the fuel gas blower 21 (which may be a control valve) or the water supply pump 25 (which may be a control valve) by the control unit 20. be able to.

上記運転停止制御において、メタンの流量については、スタック温度Ｔ1が３００℃の時にセル電圧Ｖが０．５Ｖ以上を維持しているようにメタンの供給量を減少させていく必要がある。
これは、スタック温度Ｔ1が３００℃以上の時にメタンの供給を停止すると、その熱によりＮｉを主成分とする燃料極層が酸化され、ＮｉＯが生成されてしまう虞があるからであり、このような燃料極層の酸化還元反応は発電セルの性能を著しく低下させるものである。従って、スタック温度Ｔ1が３００℃程度に低下するまでは、図３に示すように、セル電圧Ｖが０．５Ｖを下回らないよう、メタンの流量を徐々に減少していく必要がある。これにより、燃料極層側を還元状態に保持しておくことができる。尚、メタン流量の制御においては、セル電圧Ｖの代わりにスタック電圧を監視するようにしても良い。 In the above-described operation stop control, regarding the flow rate of methane, it is necessary to decrease the supply amount of methane so that the cell voltage V is maintained at 0.5 V or higher when the stack temperature T1 is 300 ° C.
This is because if the supply of methane is stopped when the stack temperature T1 is 300 ° C. or higher, the fuel electrode layer containing Ni as a main component may be oxidized by the heat and NiO may be generated. The redox reaction in the fuel electrode layer significantly reduces the performance of the power generation cell. Therefore, until the stack temperature T1 is lowered to about 300 ° C., it is necessary to gradually decrease the flow rate of methane so that the cell voltage V does not fall below 0.5V, as shown in FIG. Thereby, the fuel electrode layer side can be kept in a reduced state. In the control of the methane flow rate, the stack voltage may be monitored instead of the cell voltage V.

一方、水の流量については、給水停止時に、水蒸気の温度が２００℃以上を維持するように、水の供給量を減少させていく必要がある。これは、水蒸気温度が２００℃以下になると、水蒸気の温度は一気に１００℃まで低下し、水蒸気の連続的な発生が難しくなるためであり、その結果、セル内に水蒸気ではなく液体水が供給されることになり、これにより、セルの劣化や割れが発生する虞があるためである。   On the other hand, with respect to the flow rate of water, it is necessary to reduce the amount of water supplied so that the temperature of water vapor is maintained at 200 ° C. or higher when water supply is stopped. This is because when the water vapor temperature is 200 ° C. or lower, the temperature of the water vapor drops to 100 ° C. at a stretch, making it difficult to continuously generate water vapor. As a result, liquid water is supplied into the cell instead of water vapor. This is because there is a possibility that the cell is deteriorated or cracked.

以上のように、本発明では、発電停止の際に、燃料電池に水、および燃料ガスの流量を減少させながら供給することにより、発電停止後の高温雰囲気にあって燃料極層側の還元性を保持することができ、これにより、昇降温サイクルにおける発電セルの酸化やそれに伴う発電セルの性能劣化を防止でき、高寿命化が図れるようになる。
加えて、この運転停止方法では、従来の不活性ガスによるパージは不要であるから、不活性ガスボンベ（例えば、窒素ボンベ）を含むパージ用ガス供給系を設ける必要が一切無くなり、メンテナンス作業を簡略化できると共に、装置自体を小型化できる。 As described above, in the present invention, when power generation is stopped, the fuel cell is supplied while reducing the flow rates of water and fuel gas, so that the reducing property on the fuel electrode layer side in a high-temperature atmosphere after power generation is stopped. As a result, it is possible to prevent oxidation of the power generation cell in the temperature increasing / decreasing cycle and deterioration of the performance of the power generation cell associated therewith, thereby extending the life.
In addition, this operation stop method does not require purging with a conventional inert gas, so there is no need to provide a purge gas supply system including an inert gas cylinder (for example, a nitrogen cylinder), and the maintenance work is simplified. In addition, the device itself can be downsized.

特に、固体酸化物形燃料電池では、作動温度が６００〜１０００℃と高いため、降温期間において金属やセラミック等のモジュールの熱容量が大きく、短時間でスタック温度を下げることは不可能であり、その間、高温雰囲気が継続されること、シールレス構造では、電池内圧力の低下により外部（燃料電池モジュール内）の酸素含有ガスが電池内部に侵入し易いこと、等の理由により、運転停止時には確実なパージ処理が要求されるが、不活性ガスによるパージを必要としない本発明の運転停止方法は、このような、高温作動型の燃料電池に対して極めて有効である。   In particular, in the solid oxide fuel cell, since the operating temperature is as high as 600 to 1000 ° C., the heat capacity of the module such as metal or ceramic is large during the cooling period, and it is impossible to lower the stack temperature in a short time. In a sealless structure, the oxygen-containing gas outside (in the fuel cell module) tends to enter the battery due to a decrease in the pressure inside the battery. The operation stop method of the present invention, which requires a purge process but does not require a purge with an inert gas, is extremely effective for such a high temperature operation type fuel cell.

本発明が適用された燃料電池発電装置の概略構成を示す図。The figure which shows schematic structure of the fuel cell power generator to which this invention was applied. 図１の燃料電池発電装置に用いる固体酸化物形燃料電池スタックの構成を示す図。The figure which shows the structure of the solid oxide fuel cell stack used for the fuel cell power generation device of FIG. 本発明による運転停止制御形態を示す図。The figure which shows the driving | operation stop control form by this invention.

符号の説明Explanation of symbols

１ 燃料電池（燃料電池スタック）
３ 燃料極層
４ 空気極層
２０ 制御部
３０ 酸化剤ガス供給系
４０ 燃料供給系
５０ 水供給系 1 Fuel cell (fuel cell stack)
3 Fuel electrode layer 4 Air electrode layer 20 Control unit 30 Oxidant gas supply system 40 Fuel supply system 50 Water supply system

Claims (4)

燃料極層側へ燃料ガスを供給し、空気極層側へ酸化剤ガスを供給して発電反応を生じさせる燃料電池スタックを備えた燃料電池の運転停止方法であって、
発電停止の際に、前記空気極層側への上記酸化剤ガスの供給を維持するとともに、上記燃料電池スタックの温度が３００℃に低下するまで前記燃料電池スタックのセル電圧が０．５Ｖ以上となるように上記燃料ガスである水素の流量または改質されて上記燃料ガスとなる水素リッチなガスを生成させる水および炭化水素系燃料の流量を減少させながら上記燃料極層側へ上記燃料ガスを供給することにより、上記燃料極層側を還元状態に保持しつつ、上記燃料電池スタックの温度を低下させることを特徴とする燃料電池の運転停止方法。 A fuel cell shutdown method comprising a fuel cell stack for supplying a fuel gas to the fuel electrode layer side and supplying an oxidant gas to the air electrode layer side to cause a power generation reaction,
When power generation is stopped, the supply of the oxidant gas to the air electrode layer side is maintained, and the cell voltage of the fuel cell stack is 0.5 V or more until the temperature of the fuel cell stack is reduced to 300 ° C. The fuel gas is supplied to the fuel electrode layer side while reducing the flow rate of hydrogen as the fuel gas or the flow rate of water and hydrocarbon-based fuel that is reformed to generate hydrogen-rich gas that becomes the fuel gas. A method of stopping the operation of a fuel cell, characterized in that the temperature of the fuel cell stack is lowered by supplying the fuel electrode layer while maintaining the fuel electrode layer side in a reduced state. 前記燃料電池スタックにおいて、改質する上記炭化水素系燃料への上記水の供給停止時に、当該水による水蒸気温度が２００℃以上であるように上記水の供給量を減少させることを特徴とする請求項１に記載の燃料電池の運転停止方法。 In the fuel cell stack, when the supply stop of the water into the hydrocarbon-based fuel to the reforming, wherein the water vapor temperature by the water, characterized in that to reduce the supply amount of the water such that 200 ° C. or higher Item 6. A fuel cell operation stop method according to Item 1. 燃料ガス供給量と酸化剤ガス供給量に応じて電力を出力する燃料電池スタックと、当該燃料電池スタックに燃料ガスを供給する燃料供給系、酸化剤ガスを供給する酸化剤ガス供給系および水を供給する水供給系と、これら各系を制御する制御部とを備え、
上記制御部は、発電停止の際に、上記空気極層側への上記酸化剤ガスの供給を維持するとともに、少なくとも上記燃料電池スタックの温度が３００℃に低下するまで上記燃料ガスである水素の流量または改質されて上記燃料ガスとなる水素リッチなガスを生成させる水および炭化水素系燃料の流量を減少させながら上記燃料極層側へ上記燃料ガスを供給することにより、上記発電反応を生じさせた状態で、上記燃料極層側を還元状態に保持しつつ上記燃料電池スタックの温度を低下させるように、上記燃料供給系、酸化剤ガス供給系および水供給系を制御することを特徴とする燃料電池発電装置。 A fuel cell stack that outputs electric power according to a fuel gas supply amount and an oxidant gas supply amount; a fuel supply system that supplies fuel gas to the fuel cell stack; an oxidant gas supply system that supplies oxidant gas; and water A water supply system to supply and a control unit for controlling each of these systems;
The control unit, when the power generation is stopped, while maintaining the supply of the oxidant gas to the air electrode layer side, the hydrogen is the fuel gas to a temperature of at least the fuel cell stack is reduced to 300 ° C. The power generation reaction is caused by supplying the fuel gas to the fuel electrode layer side while reducing the flow rate of water and hydrocarbon-based fuel that generates a hydrogen-rich gas that is flow rate or reformed to become the fuel gas. And controlling the fuel supply system, the oxidant gas supply system, and the water supply system so as to lower the temperature of the fuel cell stack while maintaining the fuel electrode layer side in a reduced state. Fuel cell power generator. 前記燃料電池スタックは、発電反応に使用されなかった残余のガスを発電セルの外周部より放出するシールレス構造の固体酸化物形燃料電池であることを特徴とする請求項３に記載の燃料電池発電装置。   4. The fuel cell according to claim 3, wherein the fuel cell stack is a solid oxide fuel cell having a sealless structure that discharges residual gas that has not been used in a power generation reaction from an outer peripheral portion of the power generation cell. Power generation device.
JP2005115828A 2005-02-22 2005-04-13 Fuel cell power generation apparatus and operation stop method Expired - Fee Related JP4961682B2 (en)

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EP10194752A EP2287954A3 (en) 2005-02-22 2006-02-21 Solid oxide type fuel cell and operating method thereof
AT06714166T ATE542255T1 (en) 2005-02-22 2006-02-21 SOLID OXIDE FUEL CELL AND OPERATING METHOD THEREOF
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