JP4619753B2

JP4619753B2 - Fuel cell operation control method and system therefor

Info

Publication number: JP4619753B2
Application number: JP2004330779A
Authority: JP
Inventors: 久孝矢加部; 輝浩桜井
Original assignee: Tokyo Gas Co Ltd
Current assignee: Tokyo Gas Co Ltd
Priority date: 2004-11-15
Filing date: 2004-11-15
Publication date: 2011-01-26
Anticipated expiration: 2024-11-15
Also published as: JP2006140103A

Description

本発明は、燃料電池の運転制御方法及びそのためのシステムに関し、より詳しくは、燃料電池で利用する原燃料の組成が未知であっても、あるいは燃料電池で利用する原燃料の組成が未知で、しかも変動しても、燃料電池を安全且つ安定して燃料利用率が適正ないし最大になるように運転制御する方法及びそのためのシステムに関する。 The present invention relates to a fuel cell operation control method and a system therefor, and more particularly, even if the composition of the raw fuel used in the fuel cell is unknown or the composition of the raw fuel used in the fuel cell is unknown, In addition, the present invention relates to a method and a system for controlling operation of a fuel cell so that the fuel utilization rate is appropriate or maximized safely and stably even if it fluctuates.

燃料電池にはイオン伝導体すなわち電解質に利用される物質の違いにより固体電解質形燃料電池（ＳＯＦＣ）、溶融炭酸塩形燃料電池（ＭＣＦＣ）、固体高分子形燃料電池（ＰＥＦＣ）、リン酸形燃料電池（ＰＡＦＣ）、その他各種あるが、これらは原理的には同じである。その電解質として、ＳＯＦＣでは固体電解質（通常固体酸化物）が用いられ、ＭＣＦＣでは溶融炭酸塩が用いられ、ＰＥＦＣでは固体高分子電解質が用いられ、ＰＡＦＣではリン酸が用いられる。 Fuel cells include solid electrolyte fuel cells (SOFCs), molten carbonate fuel cells (MCFCs), polymer electrolyte fuel cells (PEFCs), and phosphoric acid fuels, depending on the difference in the materials used for the ionic conductor or electrolyte. There are various types of batteries (PAFC) and others, but these are the same in principle. As the electrolyte, a solid electrolyte (usually a solid oxide) is used in SOFC, a molten carbonate is used in MCFC, a solid polymer electrolyte is used in PEFC, and phosphoric acid is used in PAFC.

以下、適宜、主としてＳＯＦＣを例にして説明するが、他の燃料電池についても同様である。ＳＯＦＣは、固体電解質を挟んでアノード（燃料極）とカソード（空気極または酸素極）の両電極を配置して構成される。ＳＯＦＣは、一般的には作動温度が８００〜１０００℃程度と高いが、６００〜８００℃程度、例えば７５０℃程度の作動温度のものも開発されつつある。 Hereinafter, description will be given mainly using SOFC as an example, but the same applies to other fuel cells. The SOFC is configured by arranging both an anode (fuel electrode) and a cathode (air electrode or oxygen electrode) with a solid electrolyte interposed therebetween. The SOFC generally has an operating temperature as high as about 800 to 1000 ° C., but an operating temperature of about 600 to 800 ° C., for example, about 750 ° C. is being developed.

ＳＯＦＣでは、その運転時に、アノード側に水素、一酸化炭素または両者を含む燃料を供給し、カソード側に酸化剤ガスとして空気、酸素富化空気、あるいは酸素を供給して電気化学反応を起こさせることで電力が取り出される。カソード側に供給される空気中の酸素はカソードで酸化物イオン（Ｏ^2-）となり、電解質を通ってアノードに至る。ここで、アノード側に導入される燃料と反応して電子を放出し、電気と反応生成物（Ｈ₂ＯやＣＯ₂）を生成する。電解質を通るイオンは、ＭＣＦＣでは炭酸イオン（ＣＯ₃ ^2-）であり、ＰＥＦＣ及びＰＡＦＣでは水素イオン（Ｈ⁺）である。 In SOFC, during operation, fuel containing hydrogen, carbon monoxide, or both is supplied to the anode side, and air, oxygen-enriched air, or oxygen is supplied to the cathode side as an oxidant gas to cause an electrochemical reaction. Thus, electric power is taken out. Oxygen in the air supplied to the cathode side becomes oxide ions (O ²⁻ ) at the cathode and passes through the electrolyte to the anode. Here, it reacts with the fuel introduced to the anode side to release electrons, and generates electricity and reaction products (H ₂ O and CO ₂ ). The ions passing through the electrolyte are carbonate ions (CO ₃ ²⁻ ) in MCFC and hydrogen ions (H ⁺ ) in PEFC and PAFC.

ＳＯＦＣにおいては、水素と一酸化炭素が燃料となるが、炭化水素のうちメタンは、アノードの構成成分である金属、例えばニッケルの触媒作用により水蒸気改質されて水素と一酸化炭素になる。このため、ＳＯＦＣでは、水素、一酸化炭素、メタン、あるいはそれらの２種以上からなる燃料であればそのままアノードへ導入すればよいが、燃料にメタン以外のエタン、エチレン、プロパン、ブタン等の炭素数Ｃ₂以上の炭化水素が含まれていると、ＳＯＦＣへの配管、特にアノードへの燃料導入管やアノードに炭素を生成し、これが電気化学反応を阻害して電池性能を劣化させてしまう。 In the SOFC, hydrogen and carbon monoxide are used as fuel. Of the hydrocarbons, methane is steam-reformed by the catalytic action of a metal that is a constituent component of the anode, such as nickel, to become hydrogen and carbon monoxide. For this reason, in SOFC, hydrogen, carbon monoxide, methane, or a fuel composed of two or more thereof may be introduced as it is to the anode, but the fuel is carbon such as ethane other than methane, ethylene, propane, butane, etc. If hydrocarbons of several C ₂ or more are contained, carbon is generated in the SOFC piping, particularly the fuel introduction tube to the anode and the anode, which inhibits the electrochemical reaction and degrades the battery performance.

ＳＯＦＣにより需要に応じた必要電力を得る上では、一般的にはメタンのほか炭素数Ｃ₂以上の炭化水素を含む都市ガスなどを原燃料とし、これを改質した燃料を用いることが想定されている。例えば１３Ａといわれる都市ガスの組成は、一例としてメタン＝８７．８％（容量％、以下同じ）、エタン＝５．９％、プロパン、ブタン等＝６．３％である。これに付臭剤として数ｐｐｍレベルのジメチルサルファイドやターシャリーブチルメルカプタン、あるいはテトラヒドロチオフェンなどの硫黄化合物が添加されている。また、天然ガスの場合、メタンを主成分とするが、特に石油系天然ガスや構造性天然ガスではメタンより重質の炭化水素が含まれ、産地等の如何によりそれぞれ組成が異なる。 In order to obtain the required power corresponding to the demand by the SOFC, generally a raw fuel such as city gas containing other carbon number C ₂ or more hydrocarbons methane, it is assumed to use a fuel that has modified this ing. For example, the composition of city gas called 13A is methane = 87.8% (volume%, the same applies hereinafter), ethane = 5.9%, propane, butane, etc. = 6.3% as an example. As an odorant, sulfur compounds such as dimethyl sulfide, tertiary butyl mercaptan, or tetrahydrothiophene are added at a level of several ppm. In the case of natural gas, methane is the main component. In particular, petroleum-based natural gas and structural natural gas contain hydrocarbons that are heavier than methane and have different compositions depending on the production area.

このため、炭素数Ｃ₂以上の炭化水素を含む原燃料の場合は、水蒸気改質法や部分酸化法で予備改質して水素、一酸化炭素及びメタンを含む予備改質ガスに変えられる。予備改質に代えて、メタンも改質して水素、一酸化炭素を含む改質ガスに変えてもよい。水蒸気改質法で原燃料を改質する場合、メタン換算スチーム（モル）比（Ｓ／Ｃ比）は２以上（完全水蒸気改質に必要な水蒸気量の２倍以上）、好ましくは３以上とされる。 Therefore, if the raw fuel comprising a hydrocarbon number C ₂ or more carbon atoms, pre reformed hydrogen is changed to the pre-reforming gas containing carbon monoxide and methane steam reforming process or a partial oxidation process. Instead of the preliminary reforming, methane may be reformed to be a reformed gas containing hydrogen and carbon monoxide. When the raw fuel is reformed by the steam reforming method, the methane conversion steam (mole) ratio (S / C ratio) is 2 or more (more than twice the amount of steam required for complete steam reforming), preferably 3 or more. Is done.

ここで、本明細書及び特許請求の範囲において、そのように、予備改質または改質する前の燃料を“原燃料”と言い、その原燃料を水蒸気改質法や部分酸化法で予備改質または改質して燃料電池のアノードへ導入する予備改質済みの燃料（水素、一酸化炭素、メタン、あるいはそれらの２種以上を含む燃料）及び改質済みの燃料（水素、一酸化炭素のうちの一方または両者を含む燃料）を単に“燃料”と言う。 In this specification and claims, the fuel before the preliminary reforming or reforming is referred to as “raw fuel”, and the raw fuel is preliminarily modified by the steam reforming method or the partial oxidation method. Pre-reformed fuel (hydrogen, carbon monoxide, methane, or a fuel containing two or more thereof) and reformed fuel (hydrogen, carbon monoxide) introduced into the anode of the fuel cell after quality or reforming The fuel containing one or both of them is simply called “fuel”.

図１は、原燃料として都市ガスを使用して水蒸気改質法で予備改質し、ＳＯＦＣスタックからのアノードオフガスを燃料及び空気の予熱に利用するとともに、コージェネレーションシステムなどにおける給湯システムに利用する従来のＳＯＦＣシステムを示している。図１のとおり、原燃料である都市ガスは、昇圧機、脱硫器を経て予備改質器に供給され、エタン、プロパン、ブタン等を水蒸気で予備改質して水素、一酸化炭素及びメタンを含む予備改質ガスに変えられる。 In FIG. 1, city gas is used as a raw fuel and is preliminarily reformed by a steam reforming method. The anode off-gas from the SOFC stack is used for preheating fuel and air, and also used for a hot water supply system in a cogeneration system or the like. 1 shows a conventional SOFC system. As shown in FIG. 1, city gas, which is a raw fuel, is supplied to a pre-reformer via a booster and a desulfurizer, and ethane, propane, butane, etc. are pre-reformed with steam to produce hydrogen, carbon monoxide and methane. It is converted into a pre-reformed gas containing.

予備改質ガスは、熱交換器２で予熱された後、燃料としてＳＯＦＣスタックのアノードに導入され、カソードからの酸素との電気化学反応により発電する。一方、空気は、ブロワを経て熱交換器１で予熱された後、ＳＯＦＣスタックのカソードに供給される。なお、ＳＯＦＣスタックで得られた電力は必要に応じてインバータで交流電流に変えられる。ＳＯＦＣスタックからのアノードオフガスは燃焼器（図１中オフガス燃焼器）でカソードオフガスと混合し、燃焼する。燃焼ガスは、順次、熱交換器１、熱交換器２に通され、それぞれ空気、予備改質ガスの予熱に利用された後、さらに熱交換器３に通される。ここで給湯システムでの水の加熱に利用された後、排気として放出される。 The pre-reformed gas is preheated by the heat exchanger 2 and then introduced into the anode of the SOFC stack as fuel, and generates electricity by an electrochemical reaction with oxygen from the cathode. On the other hand, the air is preheated by the heat exchanger 1 through the blower and then supplied to the cathode of the SOFC stack. In addition, the electric power obtained by the SOFC stack is converted into an alternating current by an inverter as necessary. The anode offgas from the SOFC stack is mixed with the cathode offgas in a combustor (offgas combustor in FIG. 1) and burned. The combustion gas is sequentially passed through the heat exchanger 1 and the heat exchanger 2 and used for preheating air and the pre-reformed gas, respectively, and then further passed through the heat exchanger 3. Here, after being used for heating water in the hot water supply system, it is discharged as exhaust gas.

ところで、例えば、そのようなＳＯＦＣシステムにおいては、適量の燃料をアノードへ供給するために原燃料の流量を制御する必要があるが、その制御は一般的には次のように行うことができる。ＳＯＦＣの効率を決める一つの要因として燃料利用率がある。燃料利用率とは、アノードへの導入する燃料量に対する実際に発電に寄与する燃料量の比率であり、アノードへ導入する燃料のうちどれだけ発電に利用されるかを示す比率である。したがって、燃料利用率が高いほど発電効率が高くなるので、一般的には、できる限り燃料利用率を高めるような工夫をし、できる限り高い燃料利用率で運転する。 By the way, for example, in such an SOFC system, it is necessary to control the flow rate of the raw fuel in order to supply an appropriate amount of fuel to the anode, but the control can be generally performed as follows. One factor that determines SOFC efficiency is fuel utilization. The fuel utilization rate is a ratio of the amount of fuel that actually contributes to power generation with respect to the amount of fuel introduced into the anode, and is a ratio that indicates how much of the fuel introduced into the anode is used for power generation. Therefore, the higher the fuel utilization rate, the higher the power generation efficiency. In general, the device is designed to increase the fuel utilization rate as much as possible, and is operated at the highest fuel utilization rate.

しかし、燃料利用率には理論上、そして実用上も上限がある。図２はその事実を説明する図で、ＳＯＦＣにおいて、電流密度（＝０．２Ａ/ｃｍ²）を一定にして、燃料利用率を高めた場合のＳＯＦＣセル中における燃料出口付近のセル電圧の変化を示している。図２のとおり、ＳＯＦＣでの燃料利用率が高くなるにつれてセル電圧が漸次低下する。そして、燃料利用率が９０％程度を超えると急激にセル電圧が落ち込む。このようにセル電圧が落ちてくる現象は、アノード部分（アノード側）での酸素分圧の増加を意味しており、酸素分圧がある一定値以上に増加すると、アノード中のＮｉが酸化してＮｉＯに変化し、Ｎｉの酸化に伴って起こる格子膨張によりアノードが破損し、安全性を損なってしまう。 However, there is a theoretical and practical upper limit on the fuel utilization rate. FIG. 2 is a diagram for explaining the fact. In the SOFC, when the current density (= 0.2 A / cm ² ) is kept constant and the fuel utilization is increased, the change in the cell voltage near the fuel outlet in the SOFC cell. Is shown. As shown in FIG. 2, the cell voltage gradually decreases as the fuel utilization rate in the SOFC increases. When the fuel utilization rate exceeds about 90%, the cell voltage suddenly drops. The phenomenon in which the cell voltage decreases in this way means an increase in the oxygen partial pressure at the anode part (anode side). When the oxygen partial pressure increases above a certain value, Ni in the anode is oxidized. Then, it changes to NiO, and the anode is damaged by the lattice expansion caused by the oxidation of Ni, and the safety is impaired.

そのように電池に十分な燃料が行き渡らず、発電を損なうことを燃料枯れと呼ぶ。ＳＯＦＣに導入された燃料は順次消費されていくので、燃料枯れは、単セルでも複数のセルを電気的に直列に配置したスタックでも、通常、燃料の出口側で起こる。加えて、実際のＳＯＦＣセルあるいはスタックの場合には、若干の燃料リークや、電極内部のガス拡散が律速（支配的）となる。これらに起因して、燃料利用率は８５％程度が限度となる。 Such a case where sufficient fuel does not reach the battery and impairs power generation is called fuel exhaustion. Since the fuel introduced into the SOFC is consumed sequentially, fuel depletion usually occurs on the fuel outlet side in either a single cell or a stack in which a plurality of cells are electrically arranged in series. In addition, in the case of an actual SOFC cell or stack, some fuel leakage and gas diffusion inside the electrode become rate-limiting (dominant). Due to these reasons, the fuel utilization rate is limited to about 85%.

そこで、図３に示すように、アノードが酸化されないようなセル電位、例えば０．６Ｖ程度の下限電位、すなわち限界電圧をセットする。そして、セル電圧が限界電圧を下回らないようにリミッタをかけながら、すなわちセル電圧が限界電圧を下回らないようにしながら、燃料利用率を所定値、つまり限界電圧に対応する限界燃料利用率に安全性の幅をもたせた範囲、すなわち限界燃料利用率に安全性のマージンを加味した範囲に制御する方式がとられる。 Therefore, as shown in FIG. 3, a cell potential at which the anode is not oxidized, for example, a lower limit potential of about 0.6 V, that is, a limit voltage is set. Then, while applying a limiter so that the cell voltage does not fall below the limit voltage, that is, while keeping the cell voltage below the limit voltage, the fuel utilization rate is set to a predetermined value, that is, the limit fuel utilization rate corresponding to the limit voltage. In other words, a method is adopted in which the control is performed in a range with a width of 1, that is, a range in which a margin of safety is added to the limit fuel utilization rate.

上記のような燃料利用率の所定値への制御としては、セル電圧が限界電圧を下回らないように原燃料の供給量を制御することが考えられる。例えば、所定の燃料利用率を８０％として、電流値をモニタし（すなわち電流値を計測して監視し）、その計測電流値から算出した所定量の原燃料を供給し、これに合わせて、予備改質用ないし改質用の水蒸気量、空気量も制御して、燃料利用率が常に８０％程度になるように制御する。 As a control of the fuel utilization rate to a predetermined value as described above, it is conceivable to control the supply amount of the raw fuel so that the cell voltage does not fall below the limit voltage. For example, with a predetermined fuel utilization rate of 80%, the current value is monitored (that is, the current value is measured and monitored), and a predetermined amount of raw fuel calculated from the measured current value is supplied. The amount of steam and air for preliminary reforming or reforming are also controlled so that the fuel utilization rate is always about 80%.

図４はその制御態様例を示す図である。例えば、燃料利用率を８０％（限界電圧、すなわち図３の例で言えば、セル電圧０．６Ｖに対応する燃料利用率）と設定する。そして発電時に、ＳＯＦＣスタックからの電流値を経時的にモニタし、燃料利用率が常に８０％になるように、その計測電流値から算出した所定の原燃料量を供給するよう制御し、これに合わせて改質用水蒸気量、カソードへの空気量も制御する。これらの制御は、記憶装置、入出力装置を伴う中央処理装置（ＣＰＵ）により行う。 FIG. 4 is a diagram showing an example of the control mode. For example, the fuel usage rate is set to 80% (limit voltage, that is, the fuel usage rate corresponding to the cell voltage of 0.6 V in the example of FIG. 3). Then, during power generation, the current value from the SOFC stack is monitored over time, and control is performed to supply a predetermined raw fuel amount calculated from the measured current value so that the fuel utilization rate is always 80%. At the same time, the amount of steam for reforming and the amount of air to the cathode are also controlled. These controls are performed by a central processing unit (CPU) with a storage device and an input / output device.

その制御に際し、原燃料の組成（＝原燃料の成分、その量比）があらかじめ分かっている場合には、それに対応して予備改質ガスあるいは改質ガス、すなわち燃料の組成（＝燃料の成分、その量比）が分かるので、原燃料の増減量は一義的ないしほぼ一義的に制御することができる。これをアノードへ導入する燃料の側から言えば、予備改質ガスあるいは改質ガスである燃料中の組成は原燃料の増減量により一義的ないしほぼ一義的に制御される。 In the control, if the composition of the raw fuel (= component of the raw fuel, the amount ratio) is known in advance, the pre-reformed gas or the reformed gas, that is, the composition of the fuel (= the component of the fuel) Therefore, the increase / decrease amount of the raw fuel can be controlled uniquely or almost uniquely. Speaking from the side of the fuel introduced into the anode, the composition in the fuel that is the pre-reformed gas or reformed gas is uniquely or almost uniquely controlled by the amount of increase or decrease in the raw fuel.

ところで、都市ガスは、その組成にある程度の自由度があり（すなわち、都市ガスの燃焼性については、燃焼速度ＭＣＰは３５≦ＭＣＰ≦４７の範囲、ウォッペ指数ＷＩは５２．７≦ＷＩ≦５７．８の範囲と規定されており、その範囲内では変動する）、また、例えばＬＮＧを原料とする都市ガスの場合、通常ＬＰＧを添加して組成調整をして送出される。しかし、原料費削減への要請などから、ＬＰＧ添加量を低減させ、あるいはその組成調整をせずに送出することも検討されており、この場合、ＬＮＧの組成はその産地等の如何により変動することから、供給基地の場所、時間によっても変動する場合がある。 By the way, city gas has a certain degree of freedom in its composition (that is, regarding the flammability of city gas, the combustion rate MCP is in the range of 35 ≦ MCP ≦ 47, and the Wappe index WI is 52.7 ≦ WI ≦ 57. In the case of city gas using LNG as a raw material, for example, LPG is usually added to adjust the composition and sent out. However, due to demands for reducing raw material costs, etc., it is also considered to reduce the amount of LPG added or to send it without adjusting its composition. In this case, the composition of LNG varies depending on the production area and the like. Therefore, it may vary depending on the location and time of the supply base.

また、ＳＣＦＣの原燃料には多様性があり、その原燃料として各種気体燃料、炭化水素系液体燃料、エーテル系液体燃料、アルコール系液体燃料が使用でき、それらの２種以上
の燃料を混合して利用することも可能である。そのうち気体燃料としては、木材チップなどのガス化によるバイオマス燃料なども利用可能であり、また、下水汚泥、し尿、生ごみ、家畜糞尿、食品系廃棄物などの有機性廃棄物からメタン発酵などにより発生する消化ガス、すなわちバイオガスを利用することも提案されている（特開２００３−２２１２０４号公報）。これらの原燃料は、組成があらかじめ分かっているものとは限らず、組成が未知のもの、組成が未知でしかも変動するものもあり、また、それら燃料の２種以上を混合して利用する場合には未知でしかも変動する場合が多い。 In addition, SCFC raw fuels are diverse, and various gaseous fuels, hydrocarbon liquid fuels, ether liquid fuels, alcohol liquid fuels can be used as raw fuels. Can also be used. Among them, gas fuel such as wood chips and other biomass fuels can be used, and methane fermentation from organic waste such as sewage sludge, human waste, garbage, livestock manure, and food waste It has also been proposed to use generated digestive gas, that is, biogas (Japanese Patent Laid-Open No. 2003-221204). These raw fuels are not necessarily those whose compositions are known in advance, those whose compositions are unknown and those whose compositions are unknown and fluctuate, and when two or more of these fuels are used in combination Are often unknown and fluctuate.

特開２００３−２２１２０４号公報JP 2003-221204 A

ＳＯＦＣを運転制御する場合、前述のとおり、原燃料の組成が既知であれば、その組成とＳＯＦＣ運転時の負荷量から、供給すべき原燃料の量を算出し、燃料利用率が一定になるように原燃料の供給量を調整、制御することができる。しかし、原燃料の組成が（既知であっても）変動する場合、原燃料の組成が未知の場合、あるいは未知でしかも変動する場合には、供給する原燃料の流量を算出することが困難になる。上記のようにＳＯＦＣへ供給する原燃料が多様化すると、原燃料の組成は地理的、また時間的にも大きく変動することが想定される。 When controlling the operation of the SOFC, as described above, if the composition of the raw fuel is known, the amount of the raw fuel to be supplied is calculated from the composition and the load amount during the SOFC operation, and the fuel utilization rate becomes constant. In this way, the supply amount of the raw fuel can be adjusted and controlled. However, if the composition of the raw fuel fluctuates (even if it is known), or if the composition of the raw fuel is unknown or unknown and fluctuates, it is difficult to calculate the flow rate of the raw fuel to be supplied. Become. When the raw fuel supplied to the SOFC is diversified as described above, the composition of the raw fuel is expected to vary greatly both geographically and temporally.

本発明は、燃料電池に供給する原燃料の組成が未知であっても、また、それが未知で変動しても、燃料電池を安全且つ安定して燃料利用率が適正ないし最大になるように運転制御する方法及びそのためのシステムを提供することを目的とするものである。 Even if the composition of the raw fuel supplied to the fuel cell is unknown or even if it is unknown or fluctuated, the fuel cell can be used safely and stably so that the fuel utilization rate is appropriate or maximized. An object of the present invention is to provide a method for controlling operation and a system therefor.

本発明は、（１）原燃料を改質した燃料を用いる燃料電池の運転制御方法であって、燃料電池のアノードへの燃料導入部に酸素センサを配置してアノードへ導入する燃料中の酸素分圧を測定し、その酸素分圧値から燃料組成を予測して燃料利用率が適正ないし最適になるように原燃料の流量を制御することを特徴とする燃料電池の運転制御方法及びそのためのシステムを提供する。
より詳しくは、本発明は、（１）原燃料を改質した燃料を用いる燃料電池の運転制御方法及びそのためのシステムであって、燃料電池のアノードへの燃料導入部に酸素センサを配置してアノードへ導入する原燃料を改質した燃料である燃料中の酸素分圧を測定し、その酸素分圧値から原燃料を改質した燃料である燃料中のＣ成分、Ｈ成分のモル数を求め、そのモル数から実効燃料量Ｑを算出し、当該実効燃料量Ｑを基に燃料電池での燃料利用率が適正ないし最適になるように原燃料の流量を制御することを特徴とする燃料電池の運転制御方法及びそのためのシステムを提供する。 The present invention is (1) a method for controlling the operation of a fuel cell using fuel obtained by reforming raw fuel, wherein an oxygen sensor is disposed in a fuel introduction part to the anode of the fuel cell, and oxygen in the fuel introduced to the anode. A fuel cell operation control method characterized by measuring a partial pressure, predicting a fuel composition from the oxygen partial pressure value, and controlling a flow rate of the raw fuel so that a fuel utilization rate is appropriate or optimal, and for the same Provide a system.
More specifically, the present invention relates to (1) a fuel cell operation control method using a fuel obtained by reforming raw fuel, and a system therefor, in which an oxygen sensor is arranged at a fuel introduction part to the anode of the fuel cell. Measure the oxygen partial pressure in the fuel that is a reformed raw fuel to be introduced into the anode, and determine the number of moles of C component and H component in the fuel that is the reformed raw fuel from the oxygen partial pressure value. And calculating an effective fuel amount Q from the number of moles, and controlling the flow rate of the raw fuel based on the effective fuel amount Q so that the fuel utilization rate in the fuel cell is appropriate or optimal. A battery operation control method and a system therefor are provided.

本発明は、（２）原燃料を改質した燃料を用いる燃料電池の運転制御方法であって、燃料電池の電流値を計測し、その計測電流値から原燃料の流量を制御するに際して、燃料電池のアノードへの燃料導入部に酸素センサを配置してアノードへ導入する燃料中の酸素分圧を測定して燃料組成を予測し、その予測燃料組成を基に燃料利用率が適正ないし最適になるように原燃料の流量を制御することを特徴とする燃料電池の運転制御方法及びそのためのシステムを提供する。
より詳しくは、本発明は、（２）原燃料を改質した燃料を用いる燃料電池の運転制御方法及びそのためのシステムであって、燃料電池の電流値を計測し、その計測電流値から原燃料の流量を制御するに際して、燃料電池のアノードへの燃料導入部に酸素センサを配置してアノードへ導入する原燃料を改質した燃料である燃料中の酸素分圧を測定し、その酸素分圧値から原燃料を改質した燃料である燃料中のＣ成分、Ｈ成分のモル数を求め、そのモル数から実効燃料量Ｑを算出し、当該実効燃料量Ｑを基に燃料電池での燃料利用率が適正ないし最適になるように原燃料の流量を制御することを特徴とする燃料電池の運転制御方法及びそのためのシステムを提供する。 The present invention relates to (2) a fuel cell operation control method using fuel obtained by reforming raw fuel, and measures the current value of the fuel cell and controls the flow rate of the raw fuel from the measured current value. An oxygen sensor is placed at the fuel inlet to the anode of the battery and the fuel composition is predicted by measuring the oxygen partial pressure in the fuel introduced to the anode, and the fuel utilization is appropriate or optimal based on the predicted fuel composition. Provided is a fuel cell operation control method and a system therefor characterized by controlling the flow rate of raw fuel.
More specifically, the present invention relates to (2) a fuel cell operation control method using a fuel obtained by reforming raw fuel, and a system therefor, which measures the current value of the fuel cell and uses the measured current value as a raw fuel. When controlling the flow rate of the fuel cell, an oxygen sensor is arranged at the fuel introduction part to the anode of the fuel cell, and the partial pressure of oxygen in the fuel, which is a reformed raw fuel introduced to the anode, is measured. The number of moles of the C component and H component in the fuel, which is the fuel obtained by reforming the raw fuel, is calculated from the value, the effective fuel amount Q is calculated from the number of moles, and the fuel in the fuel cell is calculated based on the effective fuel amount Q. Provided is a fuel cell operation control method and a system therefor, characterized by controlling the flow rate of raw fuel so that the utilization rate is appropriate or optimal.

本発明は、（３）原燃料を改質した燃料を用いる燃料電池の運転制御方法であって、燃料電池のアノードへの燃料供給管から分岐した分岐管に酸素センサを配置し、分岐燃料に水蒸気を添加して分岐燃料の酸素分圧を測定することでアノードへ導入する燃料中の酸素分圧を測定し、その酸素分圧値から燃料組成を予測して燃料利用率が適正ないし最適になるように原燃料の流量を制御することを特徴とする燃料電池の運転制御方法及びそのためのシステムを提供する。
より詳しくは、本発明は、（３）原燃料を改質した燃料を用いる燃料電池の運転制御方法及びそのためのシステムであって、燃料電池のアノードへの燃料供給管から分岐した分岐管に酸素センサを配置し、分岐燃料に水蒸気を添加して分岐燃料の酸素分圧を測定することでアノードへ導入する原燃料を改質した燃料である燃料中の酸素分圧を測定し、その酸素分圧値から原燃料を改質した燃料である燃料中のＣ成分、Ｈ成分のモル数を求め、そのモル数から実効燃料量Ｑを算出し、当該実効燃料量Ｑを基に燃料電池での燃料利用率が適正ないし最適になるように原燃料の流量を制御することを特徴とする燃料電池の運転制御方法及びそのためのシステムを提供する。 The present invention is (3) a fuel cell operation control method using fuel obtained by reforming raw fuel, wherein an oxygen sensor is arranged in a branch pipe branched from a fuel supply pipe to the anode of the fuel cell, The oxygen partial pressure in the fuel introduced to the anode is measured by adding water vapor and measuring the oxygen partial pressure of the branched fuel, and the fuel composition is predicted from the oxygen partial pressure value so that the fuel utilization rate is appropriate or optimal. Provided is a fuel cell operation control method and a system therefor characterized by controlling the flow rate of raw fuel.
More specifically, the present invention relates to (3) a fuel cell operation control method using a fuel obtained by reforming raw fuel and a system therefor, in which oxygen is supplied to a branch pipe branched from a fuel supply pipe to the anode of the fuel cell. A sensor is installed, and the partial pressure of oxygen in the fuel, which is the reformed raw fuel introduced into the anode, is measured by adding water vapor to the branched fuel and measuring the oxygen partial pressure of the branched fuel. The number of moles of the C component and H component in the fuel, which is the fuel obtained by reforming the raw fuel, is calculated from the pressure value, the effective fuel amount Q is calculated from the number of moles, and the fuel cell based on the effective fuel amount Q is calculated. Provided is a fuel cell operation control method and a system therefor, characterized in that the flow rate of raw fuel is controlled so that the fuel utilization rate is appropriate or optimal.

本発明によれば、燃料電池を運転するに際して、燃料電池に供給する原燃料の組成が未知であっても、あるいは燃料電池で利用する原燃料の組成が未知で、しかも変動しても、燃料電池を安全且つ安定して燃料利用率が適正ないし最大になるように制御することができる。これにより、燃料電池を安全且つ安定して燃料利用率が適正ないし最大になるように制御できることから、アノード中のＮｉの酸化に伴って起こるアノードの破損を防止し、燃料電池を安全に運転することができる。 According to the present invention, when the fuel cell is operated, even if the composition of the raw fuel supplied to the fuel cell is unknown or the composition of the raw fuel used in the fuel cell is unknown and fluctuates, The battery can be controlled safely and stably so that the fuel utilization rate is appropriate or maximized. As a result, the fuel cell can be controlled safely and stably so that the fuel utilization rate is appropriate or maximized. Therefore, damage to the anode caused by oxidation of Ni in the anode is prevented, and the fuel cell is operated safely. be able to.

また、本発明は、燃料電池の運転中のほか、起動時においても適用可能である。さらに、本発明は、原燃料の組成が既知である場合やそれがある程度の自由度で変動する場合にも適用できる。この場合には、例えば前述図４のような原燃料の組成が既知の場合の制御に加えて、本発明の制御を補足的に適用してもよく、例えば前述図４のような原燃料の組成が既知の場合の制御に代えて、本発明の制御を適用してもよい。 Further, the present invention can be applied not only during operation of the fuel cell but also at startup. Furthermore, the present invention can be applied to a case where the composition of the raw fuel is known or a case where it varies with a certain degree of freedom. In this case, for example, in addition to the control in the case where the composition of the raw fuel as shown in FIG. 4 is known, the control of the present invention may be supplementarily applied. Instead of the control when the composition is known, the control of the present invention may be applied.

本発明（１）は、原燃料を改質した燃料を用いる燃料電池の運転制御方法及びそのためのシステムである。そして、燃料電池のアノードへの燃料導入部に酸素センサを配置してアノードへ導入する燃料中の酸素分圧を測定し、その酸素分圧値から燃料組成を予測して燃料利用率が適正ないし最適になるように原燃料の流量を制御することを特徴とする。
より詳しくは、本発明（１）は、原燃料を改質した燃料を用いる燃料電池の運転制御方法及びそのためのシステムである。そして、燃料電池のアノードへの燃料導入部に酸素センサを配置してアノードへ導入する原燃料を改質した燃料である燃料中の酸素分圧を測定し、その酸素分圧値から原燃料を改質した燃料である燃料中のＣ成分、Ｈ成分のモル数を求め、そのモル数から実効燃料量Ｑを算出し、当該実効燃料量Ｑを基に燃料電池での燃料利用率が適正ないし最適になるように原燃料の流量を制御することを特徴とする。 The present invention (1) is a fuel cell operation control method using a fuel obtained by reforming raw fuel and a system therefor. Then, an oxygen sensor is arranged at the fuel introduction part to the anode of the fuel cell, the oxygen partial pressure in the fuel introduced to the anode is measured, the fuel composition is predicted from the oxygen partial pressure value, and the fuel utilization rate is not appropriate. It is characterized by controlling the flow rate of raw fuel so as to be optimized.
More specifically, the present invention (1) is a fuel cell operation control method using a fuel obtained by reforming raw fuel and a system therefor. Then, an oxygen sensor is disposed at the fuel introduction portion to the anode of the fuel cell, and the oxygen partial pressure in the fuel, which is a reformed raw fuel introduced into the anode, is measured, and the raw fuel is determined from the oxygen partial pressure value. The number of moles of the C component and H component in the fuel that is the reformed fuel is obtained, the effective fuel amount Q is calculated from the number of moles, and the fuel utilization rate in the fuel cell is appropriate based on the effective fuel amount Q. It is characterized by controlling the flow rate of raw fuel so as to be optimized.

本発明（２）は、原燃料を改質した燃料を用いる燃料電池の運転制御方法及びそのためのシステムである。そして、燃料電池の電流値を計測し、その計測電流値から原燃料の流量を制御するに際して、燃料電池のアノードへの燃料導入部に酸素センサを配置してアノードへ導入する燃料中の酸素分圧を測定して燃料組成を予測し、その予測燃料組成を基に燃料利用率が適正ないし最適になるように原燃料の流量を制御することを特徴とする。
より詳しくは、本発明（２）は、原燃料を改質した燃料を用いる燃料電池の運転制御方法及びそのためのシステムである。そして、燃料電池の電流値を計測し、その計測電流値から原燃料の流量を制御するに際して、燃料電池のアノードへの燃料導入部に酸素センサを配置してアノードへ導入する原燃料を改質した燃料である燃料中の酸素分圧を測定し、その酸素分圧値から原燃料を改質した燃料である燃料中のＣ成分、Ｈ成分のモル数を求め、そのモル数から実効燃料量Ｑを算出し、当該実効燃料量Ｑを基に燃料電池での燃料利用率が適正ないし最適になるように原燃料の流量を制御することを特徴とする。 The present invention (2) is a fuel cell operation control method using a fuel obtained by reforming raw fuel and a system therefor. Then, when measuring the current value of the fuel cell and controlling the flow rate of the raw fuel from the measured current value, an oxygen sensor is arranged at the fuel introduction part to the anode of the fuel cell and the oxygen content in the fuel introduced to the anode is measured. The fuel composition is predicted by measuring the pressure, and the flow rate of the raw fuel is controlled based on the predicted fuel composition so that the fuel utilization rate is appropriate or optimal.
More specifically, the present invention (2) is a fuel cell operation control method using a fuel obtained by reforming raw fuel and a system therefor. Then, when measuring the current value of the fuel cell and controlling the flow rate of the raw fuel from the measured current value, an oxygen sensor is disposed in the fuel introduction portion to the anode of the fuel cell to reform the raw fuel introduced to the anode. Measure the partial pressure of oxygen in the fuel, the obtained fuel, determine the number of moles of the C component and H component in the fuel that is the reformed raw fuel from the oxygen partial pressure value, and calculate the effective fuel amount from the number of moles Q is calculated, and the flow rate of the raw fuel is controlled based on the effective fuel amount Q so that the fuel utilization rate in the fuel cell is appropriate or optimal.

本発明（３）は、原燃料を改質した燃料を用いる燃料電池の運転制御方法及びそのためのシステムである。そして、燃料電池のアノードへの燃料供給管から分岐した分岐管に酸素センサを配置し、分岐燃料に水蒸気を添加して分岐燃料の酸素分圧を測定することでアノードへ導入する燃料中の酸素分圧を測定し、その酸素分圧値から燃料組成を予測して燃料利用率が適正ないし最適になるように原燃料の流量を制御することを特徴とする。
より詳しくは、本発明は、（３）原燃料を改質した燃料を用いる燃料電池の運転制御方法及びそのためのシステムである。そして、燃料電池のアノードへの燃料供給管から分岐した分岐管に酸素センサを配置し、分岐燃料に水蒸気を添加して分岐燃料の酸素分圧を測定することでアノードへ導入する原燃料を改質した燃料である燃料中の酸素分圧を測定し、その酸素分圧値から原燃料を改質した燃料である燃料中のＣ成分、Ｈ成分のモル数を求め、そのモル数から実効燃料量Ｑを算出し、当該実効燃料量Ｑを基に燃料電池での燃料利用率が適正ないし最適になるように原燃料の流量を制御することを特徴とする。
The present invention (3) is a fuel cell operation control method using a fuel obtained by reforming raw fuel and a system therefor. Then, an oxygen sensor is arranged in the branch pipe branched from the fuel supply pipe to the anode of the fuel cell, and the oxygen in the fuel introduced into the anode is measured by adding water vapor to the branched fuel and measuring the oxygen partial pressure of the branched fuel. The partial pressure is measured, the fuel composition is predicted from the oxygen partial pressure value, and the flow rate of the raw fuel is controlled so that the fuel utilization rate is appropriate or optimal.
More specifically, the present invention is (3) a fuel cell operation control method using a fuel obtained by reforming raw fuel and a system therefor. Then, an oxygen sensor is arranged in the branch pipe branched from the fuel supply pipe to the anode of the fuel cell, and the raw fuel introduced into the anode is modified by adding water vapor to the branched fuel and measuring the oxygen partial pressure of the branched fuel. The partial pressure of oxygen in the fuel, which is a refined fuel, is measured, the number of moles of the C component and H component in the fuel, which is the reformed raw fuel, is obtained from the partial pressure of oxygen, and the effective fuel is determined from the number of moles. The quantity Q is calculated, and the flow rate of the raw fuel is controlled based on the effective fuel quantity Q so that the fuel utilization rate in the fuel cell is appropriate or optimal.

本発明における原燃料としては、水素、一酸化炭素、メタン、エタン、エチレン、プロパン、ブタン等の炭化水素、これらの二種以上の混合ガス、都市ガス、天然ガス、石油ガス、石炭ガス、発生炉ガス、水性ガス、高炉ガス、石油分解ガスなどの気体燃料、ガソリン、軽油、灯油、ディーゼル油などの炭化水素系液体燃料、ジメチルエーテルなどのエーテル系液体燃料、メタノールやエタノールなどのアルコール系液体燃料、各種有機性廃棄物のメタン発酵や木材チップなどのガス化により得られるバイオマス燃料のほか、それら気体燃料、液体燃料の二種以上の混合燃料、すなわち二種以上の気体燃料の混合燃料、二種以上の液体燃料の混合燃料、少なくとも一種の気体燃料と少なくとも一種の液体燃料の混合燃料も用いられる。 As raw fuel in the present invention, hydrogen, carbon monoxide, methane, ethane, ethylene, propane, butane and other hydrocarbons, mixed gas of these two or more, city gas, natural gas, petroleum gas, coal gas, generation Gas fuel such as furnace gas, water gas, blast furnace gas, petroleum cracking gas, hydrocarbon liquid fuel such as gasoline, light oil, kerosene, diesel oil, ether liquid fuel such as dimethyl ether, alcohol liquid fuel such as methanol and ethanol In addition to biomass fuel obtained by gasification of various organic wastes such as methane fermentation and wood chips, two or more mixed fuels of these gaseous fuels and liquid fuels, that is, mixed fuels of two or more gaseous fuels, two A mixed fuel of at least one liquid fuel, a mixed fuel of at least one gas fuel and at least one liquid fuel may also be used.

ＳＯＦＣの燃料は水素、一酸化炭素及びメタンであるが、ＭＣＦＣの燃料としては水素が用いられ、一酸化炭素はＭＣＦＣのアノードでのシフト反応により水素になるのでＭＣＦＣの燃料として用いられる。ＰＥＦＣ及びＰＡＦＣの燃料としては水素が用いられる。本発明においては、ＳＯＦＣ、ＭＣＦＣでは、上記のような各種原燃料のうち炭化水素、エーテル類、あるいはアルコール類を含む原燃料は予備改質または改質して燃料として用いられ、水素、一酸化炭素及びメタン（それらの混合ガスを含む）はそのまま燃料として用いられる。また、ＰＥＦＣ、ＰＡＦＣでは、上記のような各種原燃料のうち炭化水素、エーテル類、あるいはアルコール類を含む原燃料は改質し、改質ガス中の一酸化炭素は水素に変成して燃料として用いられる。水素はそのまま燃料として用いられるが、一酸化炭素または石炭ガス等の一酸化炭素を含む気体燃料はその一酸化炭素を水素に変成して燃料として用いられる。 The fuel of SOFC is hydrogen, carbon monoxide and methane, but hydrogen is used as the fuel of MCFC, and carbon monoxide is used as the fuel of MCFC because it becomes hydrogen by the shift reaction at the anode of MCFC. Hydrogen is used as the fuel for PEFC and PAFC. In the present invention, in SOFC and MCFC, raw fuel containing hydrocarbons, ethers, or alcohols among the above various raw fuels is pre-reformed or reformed and used as fuel. Carbon and methane (including mixed gases thereof) are used as fuels as they are. Also, in PEFC and PAFC, raw fuels containing hydrocarbons, ethers, or alcohols are reformed among the above various raw fuels, and carbon monoxide in the reformed gas is converted to hydrogen to serve as fuel. Used. Hydrogen is used as fuel as it is, but gaseous fuel containing carbon monoxide such as carbon monoxide or coal gas is used as fuel by converting the carbon monoxide into hydrogen.

本発明においては、前記のような各種原燃料、また各原燃料の二種以上の混合燃料（これも原燃料である）の予備改質または改質した燃料を燃料電池のアノードに導入するが、これら予備改質または改質には水蒸気改質法を適用してもよく、部分酸化法を適用してもよい。ここで、ＳＯＦＣの場合には、水素、一酸化炭素のほか、メタンも燃料となるので、それら改質法により、Ｃ₂以上の炭化水素を予備改質レベルの改質ガスにして燃料としてもよいが、メタンをも改質した改質レベルの改質ガスにして燃料としてもよい。 In the present invention, the above-mentioned various raw fuels, or a pre-reformed or reformed fuel of two or more mixed fuels (also raw fuels) of each raw fuel are introduced into the anode of the fuel cell. In this preliminary reforming or reforming, a steam reforming method or a partial oxidation method may be applied. Here, in the case of SOFC, in addition to hydrogen and carbon monoxide, methane is also used as a fuel. Therefore, by these reforming methods, hydrocarbons of C ₂ or higher can be used as a reformed gas at a pre-reforming level and used as fuel. However, methane may also be used as a reformed gas having a reforming level.

以下、本発明に係る、原燃料を改質した燃料を用いる燃料電池の運転制御方法及びそのためのシステムの態様について、その原理、メカニズム（機序）などを含めて順次説明する。本発明は各種変形態様が可能であり以下に述べる態様例に限定されないことはもちろんである。またここでは、主としてＳＯＦＣ（一部、ＰＥＦＣを含む）を例に説明するが、ＭＣＦＣ、ＰＥＦＣ、あるいはＰＡＦＣなどの燃料電池についても同様である。 Hereinafter, a fuel cell operation control method using a fuel obtained by reforming raw fuel according to the present invention and an aspect of a system therefor will be sequentially described including its principle, mechanism (mechanism), and the like. The present invention can be modified in various ways and is not limited to the following embodiments. In addition, here, description will be given mainly using SOFC (partly including PEFC) as an example, but the same applies to fuel cells such as MCFC, PEFC, or PAFC.

《本発明の態様例１：水蒸気改質法による改質の場合》
本態様例１は、ＳＯＦＣに組み込まれた酸素センサからの酸素分圧信号を利用して燃料中の実効燃料量を算出、決定し、別途計測する電流モニタによる電流値から、その電流値に相当する燃料量を算出して、原燃料量、改質用水蒸気量、カソードへ供給する空気量を決定し、それら流量を制御する態様である。 << Aspect Example 1 of the Present Invention: Case of Modification by Steam Reforming Method >>
In this embodiment example 1, the effective fuel amount in the fuel is calculated and determined using the oxygen partial pressure signal from the oxygen sensor incorporated in the SOFC, and the current value is obtained from a current value measured separately by a current monitor. This is a mode in which the amount of fuel to be calculated is determined, the amount of raw fuel, the amount of steam for reforming, and the amount of air supplied to the cathode are determined, and their flow rates are controlled.

ここで、本明細書中“実効燃料量”とは、燃料電池の運転中、実際に発電に寄与可能な燃料量の意味である。すなわち、その実効燃料量を燃料電池のアノードに導入すると、その燃料量のうち燃料利用率、例えば８０％（限界電圧、すなわち図３の例で言えば、セル電圧０．６Ｖに対応する燃料利用率）に相当する量が発電に寄与して消費され、残りの未利用燃料２０％を含む利用済み燃料がアノードオフガスとして排出されることになる。 Here, “effective fuel amount” in this specification means the amount of fuel that can actually contribute to power generation during operation of the fuel cell. That is, when the effective fuel amount is introduced into the anode of the fuel cell, the fuel utilization rate, for example, 80% of the fuel amount (the limit voltage, that is, the fuel utilization corresponding to the cell voltage 0.6V in the example of FIG. 3). The amount corresponding to the rate) is consumed to contribute to power generation, and the used fuel including the remaining 20% of unused fuel is discharged as the anode off-gas.

図５は本態様例１を説明する図である。図５のとおり、ＳＯＦＣスタックのアノードへの燃料導入部に酸素センサを配置するとともに、ＳＯＦＣスタックに電流計を配置する。ここで、燃料導入部とは改質器からのガスの出口（＝予備改質ガスまたは改質ガスの出口）からアノードの直前までの間を指し、酸素センサはその間に配置する。そして、発電時に、酸素センサにより燃料の酸素分圧を測定し、これを基にアノードに導入している実効燃料量を決定する。一方、ＳＯＦＣスタックで発電している電流値を電流計でモニタし（すなわち、その電流値を経時的ないし所定間隔を置いて計測し）、その電流値に相当する燃料量を算出し、その算出燃料量を、例えば８０％の燃料利用率（限界電圧、すなわち図３の例で言えばセル電圧０．６Ｖに対応する燃料利用率）に相当する燃料量と比較する。 FIG. 5 is a diagram for explaining the first embodiment. As shown in FIG. 5, an oxygen sensor is arranged at the fuel introduction part to the anode of the SOFC stack, and an ammeter is arranged in the SOFC stack. Here, the fuel introduction portion refers to a period from the gas outlet (= preliminary reformed gas or reformed gas outlet) from the reformer to immediately before the anode, and the oxygen sensor is disposed therebetween. Then, during power generation, the oxygen partial pressure of the fuel is measured by an oxygen sensor, and the effective fuel amount introduced into the anode is determined based on this. On the other hand, the current value generated by the SOFC stack is monitored with an ammeter (that is, the current value is measured over time or at predetermined intervals), and the fuel amount corresponding to the current value is calculated, and the calculation is performed. The fuel amount is compared with a fuel amount corresponding to, for example, a fuel usage rate of 80% (a limit voltage, that is, a fuel usage rate corresponding to a cell voltage of 0.6 V in the example of FIG. 3).

そして、その比較により、その算出燃料量が燃料利用率８０％に相当する燃料量以下であれば、供給原燃料量を増加させるが、その原燃料の増加量の程度を実効燃料量を基に算定して行う。また、算出燃料量が燃料利用率８０％に相当する燃料量以上であれば、供給原燃料量を減少させるが、その原燃料の減少量の程度を実効燃料量を基に算定して行う。こうして、アノードに導入している燃料の実効燃料量から、供給すべき原燃料量、これに対応した改質器に供給する水蒸気量、ＳＯＦＣスタックのカソードに供給する空気量を決定し、それらの決定量に応じてそれらの各流量をそれぞれ流量調整弁Ｖ１〜Ｖ３により制御する。以上の計算、制御は、記憶装置、入出力装置を伴う中央処理装置（ＣＰＵ）により行われる。 As a result of the comparison, if the calculated fuel amount is equal to or less than the fuel amount corresponding to the fuel utilization rate of 80%, the supply raw fuel amount is increased, but the extent of the increase in the raw fuel is determined based on the effective fuel amount. Calculate and do. Further, if the calculated fuel amount is equal to or greater than the fuel amount corresponding to the fuel utilization rate of 80%, the supplied raw fuel amount is decreased, and the degree of the decrease in the raw fuel is calculated based on the effective fuel amount. Thus, the amount of raw fuel to be supplied, the amount of water vapor to be supplied to the reformer corresponding to this, and the amount of air to be supplied to the cathode of the SOFC stack are determined from the effective amount of fuel introduced into the anode. The respective flow rates are controlled by the flow rate adjusting valves V1 to V3 according to the determined amounts. The above calculation and control are performed by a central processing unit (CPU) with a storage device and an input / output device.

そのように、本発明においては、アノードに導入している燃料の実効燃料量Ｑを酸素センサにより測定される酸素分圧により決定する。Ｃ₂〜Ｃ₄の飽和炭化水素の水蒸気改質は下記反応式（１）〜（４）で表される。これらの反応式における生成系のＣＯ、Ｈ₂はいわゆる“反応素過程”を経て生成している。なお、Ｃ₂〜Ｃ₄の不飽和炭化水素やＣ₅以上の炭素を含む炭化水素（飽和炭化水素のほか、不飽和炭化水素を含む）についても同様である。

Thus, in the present invention, the effective fuel amount Q of the fuel introduced into the anode is determined by the oxygen partial pressure measured by the oxygen sensor. Steam reforming of C _{2 to} C ₄ saturated hydrocarbons is represented by the following reaction formulas (1) to (4). In these reaction formulas, CO and H ₂ in the production system are produced through a so-called “reactor process”. The same applies to C _{2 to} C ₄ unsaturated hydrocarbons and hydrocarbons containing C ₅ or more carbons (including unsaturated hydrocarbons as well as saturated hydrocarbons).

こうして炭化水素の水蒸気改質反応によって、完全に改質した場合のガス組成は、水素と一酸化炭素のほか、水蒸気（余剰水蒸気）と二酸化炭素の４種の成分の混合ガスとなる。このうち二酸化炭素は一酸化炭素と水蒸気の反応成分である。このように、改質ガスはＣＯ、Ｈ₂、Ｈ₂Ｏ及びＣＯ₂を含む系であるが、厳密にはそれら各ガスの構成原子はラジカルやイオンの状態で混在して相互に解離、反応を繰り返しており、ＣＯやＨ₂との反応には酸素が関与している。 In this way, the gas composition when completely reformed by the steam reforming reaction of hydrocarbon is a mixed gas of four kinds of components of water vapor (excess water vapor) and carbon dioxide in addition to hydrogen and carbon monoxide. Of these, carbon dioxide is a reaction component of carbon monoxide and water vapor. As described above, the reformed gas is a system containing CO, H ₂ , H ₂ O and CO _2. Strictly speaking, the constituent atoms of each gas are mixed in the state of radicals or ions and dissociated and reacted with each other. And oxygen is involved in the reaction with CO and H ₂ .

これをＨ₂とＣＯについて見れば、以下の反応式（５）及び（６）のように、それぞれ、１/２モル（１/２Ｏ₂）の酸素が反応してＨ₂ＯとＣＯ₂になる。

Looking at this with respect to H ₂ and CO, as shown in the following reaction formulas (5) and (6), 1/2 mole ( _1/2 O ₂ ) of oxygen reacts to form H ₂ O and CO ₂ , respectively. Become.

ここで、平衡定数Ｋは、それぞれの気体の分圧Ｐで示される。例えば（５）式の反応の場合、分母に（５）式の左辺すなわち原系のガスの分圧積を置き、分子に右辺すなわち生成系のガスの分圧積を置くことで記述される。そこで、例えば温度７５０℃における（５）式における平衡定数をＫ₁、（６）式における平衡定数をＫ₂とすると、Ｋ₁及びＫ₂は下記式（７）、（８）から、それぞれＫ₁＝６．０×１０⁹、Ｋ₂＝７．６×１０⁹となり、平衡定数Ｋ₁及びＫ₂はともに非常に大きな値である。

Here, the equilibrium constant K is indicated by the partial pressure P of each gas. For example, the reaction of equation (5) is described by placing the left side of equation (5), ie, the partial pressure product of the original gas, in the denominator, and placing the right side, ie, the partial pressure product of the generating gas, in the numerator. Thus, for example, assuming that the equilibrium constant in the equation (5) at a temperature of 750 ° C. is K ₁ and the equilibrium constant in the equation (6) is K ₂ , K ₁ and K ₂ can be calculated from the following equations (7) and (8), respectively. ₁ = 6.0 × 10 ⁹ and K ₂ = 7.6 × 10 ⁹ , and the equilibrium constants K ₁ and K ₂ are both very large values.

（５）式と（６）式はそれぞれ独立に満たされるべき平衡式であるが、改質ガスでは通常（５）式と（６）式が同時に成り立っているので、下記式（９）のシフト反応式が成立する。これは（５）式から（６）式を引くことで自然に導かれる。このためＳＯＦＣのアノードにはＣＯ、Ｈ₂Ｏ、Ｈ₂及びＣＯ₂を含む混合ガスが導入されることになるが、厳密にはそれら成分のほか（５）式及び（６）式で示されるように酸素も含むことになる。

Equations (5) and (6) are equilibrium equations that must be satisfied independently. However, in reformed gas, since Equations (5) and (6) usually hold simultaneously, the shift of Equation (9) below The reaction formula holds. This is naturally derived by subtracting (6) from (5). For this reason, a mixed gas containing CO, H ₂ O, H ₂ and CO ₂ is introduced into the anode of the SOFC. Strictly speaking, in addition to these components, the gas is expressed by equations (5) and (6). Thus, oxygen is also included.

そして、（９）式の平衡定数Ｋ₃は、上記（７）及び（８）式から下記式（１０）のとおりとなる。

Then, the following (9) The equilibrium constant K ₃ of formula, (7) and (8) the following equation from the equation (10).

上記のとおり、炭化水素の水蒸気改質反応によって、完全に改質した場合のガス組成は、原系である水素及び一酸化炭素と、生成系である水蒸気及び二酸化炭素の４種の成分の混合ガスとなる。ここで、反応式（５）（Ｋ₁＝６．０×１０⁹）及び（６）（Ｋ₂＝７．６×１０⁹）のように、水素もしくは一酸化炭素の平衡が著しく水蒸気もしくは二酸化炭素側に偏っているために、混合ガスに酸素ガスが混入しても、混入酸素は即座に水素もしくは一酸化炭素と反応して、混合ガスには酸素は僅かしか存在しないが、それでも（７）式及び（８）式から明らかなとおり、酸素が分圧１０^-20程度のオーダで存在している。 As described above, the gas composition when completely reformed by the steam reforming reaction of hydrocarbon is a mixture of four components of hydrogen and carbon monoxide as the original system and steam and carbon dioxide as the production system. It becomes gas. Here, as shown in the reaction formulas (5) (K ₁ = 6.0 × 10 ⁹ ) and (6) (K ₂ = 7.6 × 10 ⁹ ), the equilibrium of hydrogen or carbon monoxide is remarkably high. Since the gas is biased toward the carbon side, even if oxygen gas is mixed in the mixed gas, the mixed oxygen reacts immediately with hydrogen or carbon monoxide, and there is little oxygen in the mixed gas. As is clear from the equations (8) and (8), oxygen is present on the order of a partial pressure of about 10 ⁻²⁰ .

ところで、（９）式のシフト反応は、実際上、速度論的に非常に速い反応であり、触媒反応などの過程では殆ど成立する。また、このシフト反応は等モル反応であるので、シフト平衡を満たすように反応が進んでも、ＣＯとＨ₂の総量すなわちＣＯとＨ₂の両者を合わせたモル量は変わらず、初期のガス組成が決定されていれば、ＳＯＦＣの運転中に発電に寄与可能な燃料量（＝実効燃料量）Ｑ、すなわち発電可能量も一意的に決定される。そして、実効燃料量Ｑは、以下のようにして燃料中の酸素分圧を測定し、決定することができる。実効燃料量Ｑは、その全量のうち燃料利用率例えば８０％に相当する量が発電に寄与して消費され、未利用燃料はアノードオフガスとして排出される。 By the way, the shift reaction of the equation (9) is actually a very fast reaction in terms of kinetics, and is almost established in a process such as a catalytic reaction. Further, since the shift reaction is an equimolar reaction, also the reaction so as to satisfy the shift equilibrium proceeds, the molar amount of the combined both total i.e. CO and H ₂ in CO and H ₂ is not changed, the initial gas composition Is determined, the fuel amount (= effective fuel amount) Q that can contribute to power generation during operation of the SOFC, that is, the power generation possible amount is also uniquely determined. The effective fuel amount Q can be determined by measuring the oxygen partial pressure in the fuel as follows. Of the total amount of the effective fuel amount Q, an amount corresponding to a fuel utilization rate, for example, 80% is consumed by contributing to power generation, and unused fuel is discharged as anode offgas.

〈酸素センサの原理、構造、機能について〉
ガス中の酸素濃度を測定する方法として酸素センサがある。酸素センサには原理的には幾つかの種類があるが、そのうち固体電解質酸素センサは、基本的には、電解質として安定化ジルコニア〔イットリア（Ｙ₂Ｏ₃）ドープのジルコニアやカルシア（ＣａＯ）ドープのジルコニアなど〕をベースとし、安定化ジルコニアを挟む電極間の酸素分圧差を電力に変えて測定するものである。 <Principle, structure and function of oxygen sensor>
There is an oxygen sensor as a method for measuring the oxygen concentration in gas. Although there are several types of oxygen sensors in principle, solid electrolyte oxygen sensors are basically stabilized zirconia [yttria (Y ₂ O ₃ ) -doped zirconia or calcia (CaO) as an electrolyte. Zirconia, etc.) as a base, and the measurement is performed by changing the oxygen partial pressure difference between the electrodes sandwiching the stabilized zirconia to electric power.

固体電解質酸素センサは、いわゆるＳＯＦＣの原理を応用しており、ガス中の僅かな酸素濃度でも高精度で正確に測定することができる。特に、低濃度の酸素分圧を測定するには、カソード側に空気を供給し、カソード側の酸素分圧を空気分圧としてレファレンス（すなわち照合ガスないし基準ガス）に使用するタイプが適当である。図６はその酸素センサの原理、構造、機能について説明する図である。 The solid electrolyte oxygen sensor applies the so-called SOFC principle and can accurately measure even a slight oxygen concentration in a gas. In particular, in order to measure a low concentration oxygen partial pressure, a type in which air is supplied to the cathode side and the oxygen partial pressure on the cathode side is used as a reference (ie, reference gas or reference gas) as an air partial pressure is appropriate. . FIG. 6 is a diagram for explaining the principle, structure, and function of the oxygen sensor.

図６のとおり、電極保護層としての多孔質セラミック層間に安定化ジルコニアが配置され、両多孔質セラミック層のうち一方側にカソードが、他方側にアノードが設けられる。両電極材料としては好ましくはＰｔ電極が用いられる。そして、カソード側に空気を流通させ、アノード側に被測定ガスを流通させる。これにより両電極間の起電力Ｅを開回路状態で測定することで、被測定ガス中の酸素分圧を知ることができる。 As shown in FIG. 6, stabilized zirconia is disposed between porous ceramic layers as electrode protective layers, and a cathode is provided on one side and an anode on the other side of both porous ceramic layers. Pt electrodes are preferably used as both electrode materials. Then, air is circulated on the cathode side, and a measurement gas is circulated on the anode side. Thus, by measuring the electromotive force E between both electrodes in an open circuit state, it is possible to know the partial pressure of oxygen in the gas to be measured.

酸素センサの出力すなわち起電力Ｅは、ＳＯＦＣの場合と同様、下記ネルンスト（Nernst）の式（１１）で表される。式（１１）中、Ｐｏ₂（ｃ）はカソード側（空気側）の酸素分圧、Ｐｏ₂（ａ）はアノード側（低酸素濃度の被測定ガス側）の酸素分圧、Ｆはファラデー定数、Ｒは気体定数、Ｔは酸素センサ温度（Ｋ）である。Ｐｏ₂（ｃ）は、空気をレファレンスとして用いる場合には０．２０９４８になる。 The output of the oxygen sensor, that is, the electromotive force E is expressed by the following Nernst equation (11), as in the case of SOFC. In formula (11), Po ₂ (c) is the oxygen partial pressure on the cathode side (air side), Po ₂ (a) is the oxygen partial pressure on the anode side (the gas to be measured with low oxygen concentration), and F is the Faraday constant. , R is a gas constant, and T is an oxygen sensor temperature (K). Po ₂ (c) is 0.20948 when air is used as a reference.

空気の酸素濃度（酸素＝２０．９４８ｖｏｌ％）は一定であるので、酸素濃度が低いもう一方の側の酸素濃度の測定ができる。酸素センサでは、センサ起電力Ｅから、式（１１）を用いて計算し低酸素濃度の被測定ガスの酸素分圧を同定する。本発明においては、例えばこのような酸素センサを使用して燃料中の酸素分圧を測定する。なお、図６中下部に、Ｐｏ₂（ａ）を常用対数で求める場合の式（Ｚ）を示している。

Since the oxygen concentration of oxygen (oxygen = 20.948 vol%) is constant, it is possible to measure the oxygen concentration on the other side where the oxygen concentration is low. In the oxygen sensor, the oxygen partial pressure of the gas to be measured having a low oxygen concentration is identified by calculating from the sensor electromotive force E using the equation (11). In the present invention, for example, such an oxygen sensor is used to measure the partial pressure of oxygen in the fuel. In the lower part of FIG. 6, Formula (Z) in the case where Po ₂ (a) is obtained by a common logarithm is shown.

図７〜８は上記原理に基づく固体電解質酸素センサの構成例を模式的に示す図である。図７は二室式の酸素センサで、アルミナチューブの先端内周内に安定化ジルコニアペレットが配置され、アルミナチューブ内に空気導入管が配置されている。ジルコニアペレットの外面に外部電極が配置され、ジルコニアペレットの内面に内部電極が配置されている。これら部材を囲って被測定ガス流通孔を有する保護シールドが配置され、またジルコニアペレットの上面には温度測定用の熱電対が配置される。流通する被測定ガス中にアルミナチューブの保護シールド側を臨ませ、空気導入管から空気を導入流通させながら、両電極間の起電力Ｅを測定し、併せて熱電対により温度Ｔを測定する。その測定値を式（１１）に代入ことで被測定ガス中の酸素分圧Ｐｏ₂（ａ）が得られる。 7 to 8 are diagrams schematically showing examples of the configuration of the solid electrolyte oxygen sensor based on the above principle. FIG. 7 shows a two-chamber oxygen sensor, in which a stabilized zirconia pellet is disposed in the inner periphery of the tip of an alumina tube, and an air introduction tube is disposed in the alumina tube. An external electrode is disposed on the outer surface of the zirconia pellet, and an internal electrode is disposed on the inner surface of the zirconia pellet. A protective shield having a gas flow hole to be measured is disposed so as to surround these members, and a thermocouple for temperature measurement is disposed on the upper surface of the zirconia pellet. The protective shield side of the alumina tube is exposed to the gas to be measured, and the electromotive force E between the two electrodes is measured while introducing and circulating air from the air introduction tube, and the temperature T is measured with a thermocouple. By substituting the measured value into equation (11), the oxygen partial pressure Po ₂ (a) in the gas to be measured is obtained.

図８は他の形式の酸素センサで、多孔質安定化ジルコニアを挟んでカソード及びアノードが配置され、カソードを囲って空気導入孔を有する蓋が配置されている。カソード側に空気を導入し、アノード側に被測定ガスを流通させながら開回路状態で測定した両電極間のセンサ起電力Ｅの値を式（１１）に代入ことで被測定ガス中の酸素分圧Ｐｏ₂（ａ）が得られる。本発明で用いる酸素センサは、燃料中の低濃度酸素の分圧を測定できる酸素センサであれば特に限定はないが、例えば図７〜８のような酸素センサを用いる。 FIG. 8 shows another type of oxygen sensor in which a cathode and an anode are disposed with a porous stabilized zirconia in between, and a lid having an air introduction hole is disposed around the cathode. By introducing the value of the sensor electromotive force E between the two electrodes measured in an open circuit state while introducing air to the cathode side and flowing the gas to be measured to the anode side, the oxygen content in the gas to be measured is substituted. A pressure Po ₂ (a) is obtained. The oxygen sensor used in the present invention is not particularly limited as long as it is an oxygen sensor that can measure the partial pressure of low-concentration oxygen in the fuel. For example, oxygen sensors as shown in FIGS.

〈燃料中の酸素分圧測定値による実効燃料量Ｑの算出、決定〉
そのように酸素センサで測定した燃料中の酸素分圧値を基にして実効燃料量Ｑを算出、決定する。その実効燃料量Ｑは以下のようにして算出、決定することができる。ここで、燃料電池のアノードに導入する燃料に含まれるＣ成分、Ｈ成分及び添加するＨ₂Ｏの初期のモル量を、それぞれ、Ｃ：ｃモル、Ｈ：ａモル、Ｈ₂Ｏ：Ｂモルとする。 <Calculation and determination of effective fuel quantity Q based on measured oxygen partial pressure in fuel>
The effective fuel amount Q is calculated and determined based on the oxygen partial pressure value in the fuel measured by the oxygen sensor. The effective fuel amount Q can be calculated and determined as follows. Here, the initial molar amounts of the C component, H component and H ₂ O added to the fuel introduced into the anode of the fuel cell are respectively determined as C: c mol, H: a mol, H ₂ O: B mol. And

例えば、原燃料が１モルのＣＨ₄と１モルのＣ₂Ｈ₆で構成され、メタン換算スチーム比Ｓ／Ｃ＝２（完全水蒸気改質に必要な水蒸気モル量の２倍）のＨ₂Ｏを添加するとすると、（１）式及び（２）式から、ｃ＝１＋２＝３モル、ａ＝４＋６＝１０モル、Ｂ＝（１＋２）×２＝６モルとなる。このとき、完全水蒸気改質後のガス組成は、Ｈ₂：ａ/２＋ｃ＝８モル、ＣＯ：ｃ＝３モル、Ｈ₂Ｏ：Ｂ−ｃ＝３モル、ＣＯ₂：０モルとなる。 For example, the raw fuel is composed of 1 mole of CH ₄ and 1 mole of C ₂ H ₆ , and H ₂ O with a methane equivalent steam ratio S / C = 2 (twice the molar amount of steam required for complete steam reforming). Is added, from formulas (1) and (2), c = 1 + 2 = 3 mol, a = 4 + 6 = 10 mol, and B = (1 + 2) × 2 = 6 mol. At this time, the gas composition after complete steam reforming is H ₂ : a / 2 + c = 8 mol, CO: c = 3 mol, H ₂ O: Bc = 3 mol, and CO ₂ : 0 mol.

ここで、（９）式のシフト反応により、組成がｘモルだけ変化したとすると、シフト反応後の組成は、Ｈ₂：ａ/２＋ｃ＋ｘ＝８＋ｘモル、ＣＯ：ｃ−ｘ＝３−ｘモル、Ｈ₂Ｏ：Ｂ−ｃ−ｘ＝３−ｘモル、ＣＯ₂：ｘモルとなる。 Here, if the composition is changed by x mol by the shift reaction of the formula (9), the composition after the shift reaction is H ₂ : a / 2 + c + x = 8 + x mol, CO: c−x = 3−x mol, _{H 2 O: B-c-} x = 3-x moles, CO _2: a x mol.

そこで、上記シフト反応後の組成について、（５）式：Ｈ₂＋１/２Ｏ₂→Ｈ₂Ｏの平衡反応を考慮すると、平衡定数をＫ₁、酸素分圧をＰｏ₂として、下記式（１２）が成立する。

Therefore, considering the equilibrium reaction of the formula (5): H ₂ + 1 / 2O ₂ → H ₂ O with respect to the composition after the shift reaction, the following formula (12) is assumed, where the equilibrium constant is K ₁ and the oxygen partial pressure is Po _2. ) Holds.

同じく、上記シフト反応後の組成について、（６）式：ＣＯ＋１/２Ｏ₂→ＣＯ₂の平衡反応を考慮すると、平衡定数をＫ₂、酸素分圧をＰｏ₂として、下記式（１３）が成立する。ここで（１３）式をｘについて整理すると下記式（１４）となる。

Similarly, regarding the composition after the shift reaction, considering the equilibrium reaction of the equation (6): CO + 1 / 2O ₂ → CO ₂ , the following equation (13) is established, assuming that the equilibrium constant is K ₂ and the oxygen partial pressure is Po _2. To do. Here, when the equation (13) is arranged with respect to x, the following equation (14) is obtained.

そして、（１２）式に（１３）式のｘ、すなわち（１４）式を代入して整理すると下記式（１５）のとおり記述される。

Then, by substituting x in the expression (13), that is, the expression (14), into the expression (12), the following expression (15) is obtained.

〈原燃料が炭化水素だけの場合〉
ところで、炭化水素の水蒸気改質を行う場合に、添加する水蒸気量を増加させていくと、結果として（９）式が満たされるように平衡組成が変化し、その結果、その系内の酸素分圧も変化する。このとき、（５）式及び（６）式の各成分は同じ系内にあるので、正確には（９）のシフト平衡式が満たされるように変化することになる。 <When raw fuel is only hydrocarbon>
By the way, when performing steam reforming of hydrocarbons, if the amount of steam to be added is increased, as a result, the equilibrium composition changes so that the formula (9) is satisfied, and as a result, the oxygen content in the system is changed. The pressure also changes. At this time, since each component of the formulas (5) and (6) is in the same system, the shift equilibrium formula of (9) is accurately changed.

したがって、添加水蒸気量を変化させて、それぞれの系内の酸素分圧を測定すれば、その添加水蒸気量に応じたＨ及びＣの組成を計算することができる。原燃料が炭化水素だけの場合、成分の数（変数）はＨとＣの２種であるので、変化させる水蒸気量の数（すなわち異ならせる水蒸気量の数）は二つすなわち２条件“２点”が必要である。 Therefore, the composition of H and C according to the amount of added water vapor can be calculated by changing the amount of added water vapor and measuring the oxygen partial pressure in each system. When the raw fuel is only hydrocarbons, the number of components (variables) is two types, H and C. Therefore, the number of water vapors to be changed (that is, the number of water vapors to be different) is two, that is, two conditions “2 points” "is required.

なお、後述の、原燃料中に炭化水素のほか、一酸化炭素も含まれている場合や一酸化炭素、二酸化炭素、あるいは水蒸気などに含まれるＯを含む場合などに関連するが、異ならせる水蒸気量の数（条件）は、そのように原燃料中における成分の数（変数）に対応した数とすればよい。しかし、原燃料として例えば前述バイオマス燃料や混合燃料を使用するときには、原燃料中の成分数があらかじめ予測される数より多いこともあり得る。このような場合には、異ならせる水蒸気量の数（条件）を予測される成分数より多くすることで、その組成をより確実に計算することができる。 In addition, although it is related to the case where carbon monoxide is contained in the raw fuel, which will be described later, or carbon monoxide, carbon dioxide, or O contained in water vapor, etc. The number (condition) of the quantity may be a number corresponding to the number (variable) of components in the raw fuel. However, when, for example, the aforementioned biomass fuel or mixed fuel is used as the raw fuel, the number of components in the raw fuel may be larger than the number predicted in advance. In such a case, the composition can be calculated more reliably by increasing the number (condition) of the amount of water vapor to be varied from the number of components to be predicted.

ここで、水蒸気量が水素組成に与える影響について、一例として１モルの水素に、水蒸気を１モル加えた平衡組成と１０モル加えた平衡組成を考える。前述のとおり、実は（５）式：Ｈ₂＋１/２Ｏ₂→Ｈ₂Ｏの平衡定数がＫ₁＝６．０×１０⁹と非常に大きいために、水蒸気を１モル加えようが、１０モル加えようが、水素の平衡組成は、加えた水蒸気量からは殆ど変化せず（ただし、酸素分圧は変化する）、１モルのままである。これは、多少水蒸気を多く加えても、ガス中の水素組成は殆ど変わらずに、元のガス組成を保つことを表しており、このことを利用して、元のガス中の水素濃度を判定できることになる。同様に、（６）式：ＣＯ＋１/２Ｏ₂→ＣＯ₂の平衡も、（９）式を通じて平衡組成が決定され、元のガス中のＣＯ濃度が判定できる。 Here, as an example of the influence of the amount of water vapor on the hydrogen composition, an equilibrium composition obtained by adding 1 mol of water vapor to 1 mol of hydrogen and an equilibrium composition obtained by adding 10 mol of water vapor are considered. As described above, the equilibrium constant of the formula (5): H ₂ + 1 / 2O ₂ → H ₂ O is very large as K ₁ = 6.0 × 10 ^9. In addition, the equilibrium composition of hydrogen hardly changes from the amount of water vapor added (however, the oxygen partial pressure changes) and remains at 1 mole. This shows that even if a lot of water vapor is added, the hydrogen composition in the gas remains almost unchanged, and the original gas composition is maintained. This is used to determine the hydrogen concentration in the original gas. It will be possible. Similarly, the equilibrium composition of the equation (6): CO + 1 / 2O ₂ → CO ₂ is determined through the equation (9), and the CO concentration in the original gas can be determined.

そこで、Ｈ₂Ｏのモル量Ｂを２種類すなわち“２条件（２点）”設定し、それぞれをＢ（１）、Ｂ（２）とし、それぞれに対応する平衡酸素分圧をＰｏ₂（１）、Ｐｏ₂（２）として、（１５）式を書き下すと下記式（１６）のとおり記述される。

Therefore, two types of molar amounts B of H ₂ O, that is, “2 conditions (2 points)” are set, and each is set to B (1) and B (2), and the equilibrium oxygen partial pressure corresponding to each is set to Po ₂ (1 ), Po ₂ (2), the expression (15) is written as the following expression (16).

そして、（１６）式を解いてａ（Ｈ：ａモル）を求めると下記式（１７）のとおりとなる。

Then, when the equation (16) is solved to obtain a (H: a mol), the following equation (17) is obtained.

同じく、（１６）式を解いてｃ（Ｃ：ｃモル）を求めると下記式（１８）のとおりとなる。

Similarly, when c (C: c mol) is obtained by solving the equation (16), the following equation (18) is obtained.

こうして、原燃料の水蒸気改質に際して添加する水蒸気量Ｂを“２条件（２点）”変化させて、それぞれ酸素分圧を測定し、（１７）式及び（１８）式に代入することにより、燃料中のａ（Ｈ：ａモル）及びｃ（Ｃ：ｃモル）の値を特定することができる。その結果として、燃料電池の運転中の実効燃料量Ｑ＝ａ／２＋２ｃは下記式（１９）で決定される。本発明においては、原燃料が炭化水素だけの場合、このようにして“燃料電池のアノードへの燃料導入部に酸素センサを配置してアノードへ導入する燃料中の酸素分圧を測定し、その酸素分圧値から燃料組成を予測”するものである。

Thus, by changing the amount of steam B added during steam reforming of the raw fuel by “2 conditions (2 points)”, and measuring the oxygen partial pressures respectively, substituting them into the equations (17) and (18), The values of a (H: a mol) and c (C: c mol) in the fuel can be specified. As a result, the effective fuel amount Q = a / 2 + 2c during operation of the fuel cell is determined by the following equation (19). In the present invention, when the raw fuel is only hydrocarbon, the oxygen partial pressure in the fuel introduced to the anode is measured by arranging an oxygen sensor in the fuel introduction portion to the anode of the fuel cell in this way. The fuel composition is predicted from the oxygen partial pressure value.

図９（ａ）はその操作態様を説明する図である。条件１の添加量の水蒸気を供給しながら、所定の安定時間（例えば１０〜２０分間）保持した時点で酸素センサにより出力すなわち起電力Ｅをモニタし、式（１１）により酸素分圧値を計算する。引き続き、条件２の添加量の水蒸気を供給しながら、所定の安定時間（例えば１０〜２０分間）保持した時点で酸素センサにより起電力Ｅをモニタし、同じく酸素分圧値を計算する。そして、それら酸素分圧値を（１９）式に代入することで実効燃料量Ｑが得られる。それら２条件（２点）への水蒸気添加量の調整は図５で言えば流量調整弁Ｖ２により行う。図５の態様の場合、流量調整弁Ｖ２により流量調整された水は加熱交換器により加熱され水蒸気として供給される。 FIG. 9A is a diagram for explaining the operation mode. While supplying the amount of water vapor added under condition 1, the output, that is, the electromotive force E is monitored by the oxygen sensor when the predetermined stable time (for example, 10 to 20 minutes) is maintained, and the oxygen partial pressure value is calculated by the equation (11). To do. Subsequently, the electromotive force E is monitored by the oxygen sensor at the time when a predetermined stable time (for example, 10 to 20 minutes) is maintained while supplying the added amount of water vapor of the condition 2, and the oxygen partial pressure value is similarly calculated. The effective fuel amount Q is obtained by substituting these oxygen partial pressure values into the equation (19). Adjustment of the amount of steam added to these two conditions (two points) is performed by the flow rate adjusting valve V2 in FIG. In the case of the embodiment of FIG. 5, the water whose flow rate is adjusted by the flow rate adjusting valve V2 is heated by the heat exchanger and supplied as water vapor.

得られた実効燃料量Ｑは、アノードに導入している燃料の組成、すなわち水素及び一酸化炭素の全量を示すものであることから、これにより原燃料の組成を一義的に推定することができる。すなわち、実効燃料量Ｑにより燃料の組成（＝燃料の成分、その量比）が分かるので、原燃料の組成があらかじめ分かっている場合と同様、原燃料の増減量は一義的ないしほぼ一義的に制御することができる。これをアノードへ導入する燃料の側から言えば、燃料中の組成は原燃料の増減量により一義的ないしほぼ一義的に制御できる。このため本発明は、例えば都市ガスのように原燃料の組成が既知の場合にも適用することができる。この場合には、前述図４のような原燃料の組成が既知の場合の制御に代えて適用してもよく、原燃料の組成が既知の場合の制御に加え、本発明を補足的に適用してもよい。この点、本発明の他の態様の場合も同様である。 The obtained effective fuel amount Q indicates the composition of the fuel introduced into the anode, that is, the total amount of hydrogen and carbon monoxide, so that the composition of the raw fuel can be uniquely estimated. . That is, since the fuel composition (= fuel component, amount ratio thereof) is known from the effective fuel amount Q, the amount of increase / decrease in the raw fuel is unambiguous or almost unambiguous, as in the case where the composition of the raw fuel is known in advance. Can be controlled. Speaking from the side of the fuel introduced to the anode, the composition in the fuel can be uniquely or almost uniquely controlled by the amount of increase or decrease in the raw fuel. For this reason, this invention is applicable also when the composition of raw fuel is known like city gas, for example. In this case, the control may be applied in place of the control when the composition of the raw fuel as shown in FIG. 4 is known, and the present invention is applied in addition to the control when the composition of the raw fuel is known. May be. This also applies to other embodiments of the present invention.

本発明は、燃料電池を運転制御するに際して、燃料電池に供給する原燃料の組成が未知である場合や、それが未知で変動する場合に、そのようにして燃料の実効燃料量Ｑを算出、決定し、これを基に原燃料の増減量を制御する。そして、燃料の実効燃料量Ｑにより原燃料の増減量を制御すること以外は、原燃料の組成があらかじめ分かっている場合の制御と同様であり、燃料電池を運転制御するに際して、原燃料の増減量を制御する運転技術の全部に適用される。 The present invention calculates the effective fuel amount Q of the fuel when the composition of the raw fuel supplied to the fuel cell is unknown or when it is unknown and fluctuates when operating the fuel cell. Decide and control the amount of increase or decrease in raw fuel based on this. The control is the same as the control when the composition of the raw fuel is known in advance, except that the increase / decrease amount of the raw fuel is controlled by the effective fuel amount Q of the fuel. Applies to all driving techniques that control quantity.

図５は、そのうちの燃料利用率により行う態様例を示している。例えば、図３に示すように、アノードが酸化されないようなセル電位、例えば０．６Ｖ程度の下限電位、すなわち限界電圧をセットし、セル電圧が限界電圧を下回らないようにしながら、電流計でモニタする。そして、測定電流値に相当する燃料量が燃料利用率、例えば８０％を基にあらかじめセットされた必要燃料量に対して不足する場合には、原燃料の供給量を増加させるが、その増加の程度を実効燃料量Ｑを基に制御し、これに合わせて水蒸気量、空気量を決定し、それらの決定量に応じて各流量を制御する。 FIG. 5 shows an example of an embodiment performed based on the fuel utilization rate. For example, as shown in FIG. 3, a cell potential at which the anode is not oxidized, for example, a lower limit potential of about 0.6 V, that is, a limit voltage is set, and the cell voltage is monitored by an ammeter while preventing the cell voltage from falling below the limit voltage. To do. When the fuel amount corresponding to the measured current value is insufficient with respect to the required fuel amount set in advance based on the fuel utilization rate, for example, 80%, the supply amount of the raw fuel is increased. The degree is controlled based on the effective fuel amount Q, the amount of water vapor and the amount of air are determined according to this, and each flow rate is controlled according to the determined amount.

それとは逆に、測定電流値に相当する燃料量が燃料利用率、例えば８０％を基にあらかじめセットされた必要燃料量に対して過剰の場合には、原燃料の供給量を減少させるが、その増加の程度を実効燃料量Ｑを基に制御し、これに合わせて水蒸気量、空気量を決定し、それらの決定量に応じてそれら各流量を制御する。図５において、それら各流量の制御はそれぞれ流量調整弁Ｖ１〜Ｖ３により行うが、以上の計算、制御は、記憶装置、入出力装置を伴う中央処理装置（ＣＰＵ）により行われる。 On the contrary, if the fuel amount corresponding to the measured current value is excessive with respect to the required fuel amount set in advance based on the fuel utilization rate, for example, 80%, the supply amount of the raw fuel is decreased. The degree of the increase is controlled based on the effective fuel amount Q, the water vapor amount and the air amount are determined in accordance with this, and the respective flow rates are controlled according to the determined amounts. In FIG. 5, the control of each flow rate is performed by the flow rate adjustment valves V1 to V3. The above calculation and control are performed by a central processing unit (CPU) with a storage device and an input / output device.

〈原燃料中の窒素等の不活性ガスの影響〉
原燃料には窒素その他の不活性ガスが含まれている可能性があるが、不活性ガスが含まれていても、燃料中の測定酸素分圧から計算、決定される水素、一酸化炭素の実効燃料量は全く影響を受けない。その理由は以下のとおりである。不活性ガスの影響を受けない点は、原燃料が炭化水素だけの場合とは限らず、一酸化炭素その他の成分を含む場合、また後述部分酸化法による改質の場合についても同様である。 <Influence of inert gas such as nitrogen in raw fuel>
The raw fuel may contain nitrogen or other inert gas. Even if inert gas is contained, hydrogen and carbon monoxide are calculated and determined from the measured oxygen partial pressure in the fuel. The effective fuel amount is not affected at all. The reason is as follows. The point of not being affected by the inert gas is not limited to the case where the raw fuel is only hydrocarbons, but also when carbon monoxide or other components are contained, or when reforming by the partial oxidation method described later.

原燃料に窒素その他の不活性ガスが混入している場合には、燃料中の個々の成分ガスの分圧を単純に低下させることになる。しかし、（９）式のシフト平衡反応に関しては、原系であるＣＯ＝１モルとＨ₂Ｏ＝１モルとの２モルのガスが、生成系であるＨ₂＝１モルとＣＯ₂＝１モルとの２モルのガスに変化する等モル反応であるので、窒素その他の不活性ガスの混入による分圧変化への影響は相殺される。 When nitrogen or other inert gas is mixed in the raw fuel, the partial pressure of each component gas in the fuel is simply reduced. However, with respect to the shift equilibrium reaction of the formula (9), 2 moles of gas of CO = 1 mol and H ₂ O = 1 mol as the original system are converted into H ₂ = 1 mol and CO ₂ = 1 as the production system. Since the reaction is an equimolar reaction that changes to 2 mol of gas, the influence on the partial pressure change due to the mixing of nitrogen and other inert gases is offset.

例えば、燃料がＨ₂＝３モル、ＣＯ＝２モル、Ｈ₂Ｏ＝４モル、ＣＯ₂＝１モル、Ｎ₂＝５モルのような組成であった場合の平衡組成を求めると、ｘモルのガスが反応して平衡に達したとすると、反応前の全体モル数は１５モル、反応後も１５モルとなる。そこで、結局、下記式（２０）を解くことになり、（２０）式のそれぞれの項で現れる分母の１５モルの部分は相殺され、窒素その他の不活性ガスが含まれていても平衡組成は変わらないことになる。

For example, when the equilibrium composition is determined when the fuel has a composition such as H ₂ = 3 mol, CO = 2 mol, H ₂ O = 4 mol, CO ₂ = 1 mol, N ₂ = 5 mol, x mol As a result, the total number of moles before the reaction is 15 moles, and after the reaction is 15 moles. Therefore, eventually, the following equation (20) is solved, and the 15 mol portion of the denominator appearing in each term of the equation (20) is canceled out, and even if nitrogen or other inert gas is contained, the equilibrium composition is It will not change.

一方、（５）式もしくは（６）式の平衡の場合は、上記と同様の条件で計算を行うと、酸素量をｍとして、下記式（２１）のとおりとなり、酸素分圧の部分に影響が出てくる。ただし、反応系全体に及ぼす影響は、やはり（９）式を通じて相殺されるので、結局、原燃料中に窒素その他の不活性ガスが含まれていても、酸素分圧から計算される水素、一酸化炭素の実効燃料量Ｑは全く影響を受けないことになる。

On the other hand, in the case of the equilibrium of the equation (5) or (6), if the calculation is performed under the same conditions as above, the oxygen amount is m, and the equation (21) is obtained, which affects the oxygen partial pressure portion. Comes out. However, since the influence on the whole reaction system is also canceled out through the equation (9), even if nitrogen or other inert gas is contained in the raw fuel, hydrogen calculated from the oxygen partial pressure, The effective fuel amount Q of carbon oxide is not affected at all.

〈原燃料中に炭化水素のほか、一酸化炭素も含まれている場合の実効燃料量Ｑの決定〉
原燃料中に炭化水素だけでなく、一酸化炭素も含まれている場合における、燃料電池の運転中における実効燃料量Ｑの算出、決定は、以下のとおりとなる。 <Determination of the effective fuel amount Q when the raw fuel contains hydrocarbons and carbon monoxide>
When the raw fuel contains not only hydrocarbon but also carbon monoxide, the calculation and determination of the effective fuel amount Q during operation of the fuel cell are as follows.

燃料電池のアノードに導入する燃料に含まれるＣ成分、Ｈ成分、ＣＯ成分及び添加するＨ₂Ｏの初期のモル量を、それぞれ、Ｃ：ｃモル、Ｈ：ａモル、ＣＯ：ｄモル、Ｈ₂Ｏ：Ｂモルとする。例えば、原燃料が１モルのＣＨ₄と１モルのＣ₂Ｈ₆と１モルのＣＯで構成され、メタン換算スチーム比Ｓ／Ｃ＝２（完全水蒸気改質に必要な水蒸気量の２倍）のＨ₂Ｏを添加するとすると、（１）式及び（２）式から、ｃ＝１＋２＝３モル、ａ＝４＋６＝１０モル、Ｂ＝（１＋２）×２＝６モルとなり、これに１モルのＣＯを含むから、ｄ＝１モルとなる。このとき、完全水蒸気改質後のガス組成は、Ｈ₂：ａ/２＋ｃ＝８モル、ＣＯ：ｃ＋ｄ＝４モル、Ｈ₂Ｏ：Ｂ−ｃ＝３モル、ＣＯ₂：０モルとなる。 The initial molar amounts of the C component, H component, CO component and H ₂ O added to the fuel introduced into the anode of the fuel cell are respectively determined as C: c mol, H: a mol, CO: d mol, H ₂ O: B mol. For example, the raw fuel is composed of 1 mole of CH ₄ , 1 mole of C ₂ H ₆ and 1 mole of CO, and the methane equivalent steam ratio S / C = 2 (twice the amount of steam required for complete steam reforming) When the addition of the H ₂ O, from (1) and (2) becomes c = 1 + 2 = 3 moles, a = 4 + 6 = 10 moles, and B = (1 + 2) × 2 = 6 moles, 1 mole to Therefore, d = 1 mol. At this time, the gas composition after complete steam reforming is H ₂ : a / 2 + c = 8 mol, CO: c + d = 4 mol, H ₂ O: Bc = 3 mol, and CO ₂ : 0 mol.

そして、（９）式のシフト反応により、組成がｘだけ変化したとすると、シフト反応後の組成は、Ｈ₂：ａ/２＋ｃ＋ｘモル、ＣＯ：ｃ＋ｄ−ｘ＝４−ｘモル、Ｈ₂Ｏ：Ｂ−ｃ−ｘ＝３−ｘモル、ＣＯ₂：ｘモルとなる。 Then, if the composition is changed by x by the shift reaction of the formula (9), the composition after the shift reaction is H ₂ : a / 2 + c + x mol, CO: c + d−x = 4-x mol, H ₂ O: B-c-x = 3- x moles, CO _2: a x mol.

そこで、上記シフト反応後の組成について、（５）式：Ｈ₂＋１/２Ｏ₂→Ｈ₂Ｏの平衡反応を考慮すると、平衡定数をＫ₁、酸素分圧をＰｏ₂として、下記式（２２）が成立する。

Therefore, considering the equilibrium reaction of the formula (5): H ₂ + 1 / 2O ₂ → H ₂ O with respect to the composition after the shift reaction, the following equation (22) is assumed where the equilibrium constant is K ₁ and the oxygen partial pressure is Po _2. ) Holds.

同じく、上記シフト反応後の組成について、（６）式：ＣＯ＋１/２Ｏ₂→ＣＯ₂の平衡反応を考慮すると、平衡定数をＫ₂、酸素分圧をＰｏ₂として、下記式（２３）が成立する。（２３）式をｘについて整理すると下記式（２４）となる。

Similarly, with regard to the composition after the shift reaction, considering the equilibrium reaction of the formula (6): CO + 1 / 2O ₂ → CO ₂ , the following formula (23) is established, assuming that the equilibrium constant is K ₂ and the oxygen partial pressure is Po _2. To do. When the equation (23) is arranged with respect to x, the following equation (24) is obtained.

そして、（２２）式に（２３）式のｘ、すなわち（２４）式を代入して整理すると下記式（２５）のとおり記述される。

Then, by substituting x in the equation (23) into the equation (22), that is, the equation (24) and arranging it, the following equation (25) is obtained.

ここで、Ｈ₂Ｏのモル量Ｂを“３条件（３点）”設定し、それぞれをＢ（１）、Ｂ（２）、Ｂ（３）とし、これらのそれぞれに対応する平衡酸素分圧をＰｏ₂（１）、Ｐｏ₂（２）、Ｐｏ₂（３）として（２５）式に代入し、ａを消去して整理すると下記式（２６）のとおり記述できる。

Here, the molar amount B of H ₂ O is set to “3 conditions (3 points)”, which are set to B (1), B (2), and B (3), respectively, and the equilibrium oxygen partial pressure corresponding to each of these is set. Is substituted as Po ₂ (1), Po ₂ (2), Po ₂ (3) in the equation (25), and a is deleted and rearranged, the following equation (26) can be obtained.

こうして、添加水蒸気量を“３条件（３点）”変えて、それぞれの条件での酸素分圧を測定し、（２６）式に代入することにより、燃料電池の運転中の実効燃料量Ｑを算出、決定することができる。 Thus, by changing the amount of added water vapor to “3 conditions (3 points)”, measuring the oxygen partial pressure under each condition, and substituting into the equation (26), the effective fuel amount Q during operation of the fuel cell can be obtained. Can be calculated and determined.

その決定操作は、図９（ｂ）のとおり、条件１の添加量の水蒸気を供給しながら所定の安定時間保持した後、酸素センサにより出力すなわち起電力Ｅをモニタし、式（１１）により酸素分圧値を計算する。次いで、条件２の添加量の水蒸気を供給しながら所定の安定時間保持した後、酸素センサにより起電力Ｅをモニタし、同じく酸素分圧値を計算する。引き続き、条件３の添加量の水蒸気を供給しながら所定の安定時間保持した後、酸素センサにより起電力Ｅをモニタし、同じく酸素分圧値を計算する。そして、それら酸素分圧値を（２６）式に代入することで実効燃料量Ｑが得られる。それら３条件（３点）への水蒸気添加量の調整は図５で言えば流量調整弁Ｖ２により行う。図５の態様の場合、流量調整弁Ｖ２により流量調整された水は加熱交換器により加熱され水蒸気として供給される。 As shown in FIG. 9 (b), the determination operation is carried out while maintaining a predetermined stable time while supplying the added amount of water vapor under the condition 1, and then monitoring the output, that is, the electromotive force E by the oxygen sensor, Calculate the partial pressure value. Next, after a predetermined stable time is maintained while supplying the added amount of water vapor of Condition 2, the electromotive force E is monitored by an oxygen sensor, and the oxygen partial pressure value is calculated in the same manner. Subsequently, after a predetermined stabilization time is maintained while supplying the added amount of water vapor of Condition 3, the electromotive force E is monitored by an oxygen sensor, and the oxygen partial pressure value is similarly calculated. The effective fuel amount Q is obtained by substituting these oxygen partial pressure values into the equation (26). Adjustment of the amount of water vapor added to these three conditions (three points) is performed by the flow rate adjusting valve V2 in FIG. In the case of the embodiment of FIG. 5, the water whose flow rate is adjusted by the flow rate adjusting valve V2 is heated by the heat exchanger and supplied as water vapor.

そして、図５のように原燃料の流量制御を燃料利用率により行う場合、例えば、電流計でモニタした電流値に相当する燃料量が燃料利用率、例えば８０％を基にあらかじめセットされた必要燃料量に対して不足する場合には、原燃料の供給量を増加させるが、その増加の程度を実効燃料量Ｑを基に制御し、これに合わせて水蒸気量、空気量を決定し、それらの決定量に応じて各流量を制御する。また、それが過剰の場合には、原燃料の供給量を減少させるが、その減少の程度を実効燃料量Ｑを基に制御し、これに合わせて水蒸気量、空気量を決定し、それらの決定量に応じて各流量を制御する。図５において、それら各流量の制御はそれぞれ流量調整弁Ｖ１〜Ｖ３により行うが、以上の計算、制御は、記憶装置、入出力装置を伴う中央処理装置（ＣＰＵ）により行われる。 When the flow control of the raw fuel is performed based on the fuel usage rate as shown in FIG. 5, for example, the fuel amount corresponding to the current value monitored by the ammeter needs to be set in advance based on the fuel usage rate, for example, 80%. When the fuel amount is insufficient, the supply amount of the raw fuel is increased. The amount of increase is controlled based on the effective fuel amount Q, and the water vapor amount and the air amount are determined in accordance with this control. Each flow rate is controlled according to the determined amount. In addition, if it is excessive, the supply amount of raw fuel is decreased, but the degree of the decrease is controlled based on the effective fuel amount Q, and the water vapor amount and air amount are determined according to this, Each flow rate is controlled according to the determined amount. In FIG. 5, the control of each flow rate is performed by the flow rate adjustment valves V1 to V3. The above calculation and control are performed by a central processing unit (CPU) with a storage device and an input / output device.

〈原燃料中に炭化水素のほか、ＣＯ（一酸化炭素）、ＣＯ₂（二酸化炭素）、あるいはＨ₂Ｏ（水蒸気）などに含まれるＯを含む場合の実効燃料量Ｑの決定〉
原燃料中に炭化水素のほか、ＣＯ、ＣＯ₂、あるいはＨ₂Ｏ（水蒸気）などに含まれるＯを含む場合の実効燃料量Ｑの算定、決定は、以下のように行うことができる。 <Determination of effective fuel quantity Q when raw fuel contains O contained in CO (carbon monoxide), CO ₂ (carbon dioxide), H ₂ O (water vapor), etc. in addition to hydrocarbons>
Calculation and determination of the effective fuel amount Q when the raw fuel contains O contained in CO, CO ₂ , H ₂ O (water vapor), etc. in addition to hydrocarbons can be performed as follows.

燃料電池のアノードに導入する燃料のうち、メタンも含めたすべてのガス中のＣ成分、Ｈ成分、Ｏ成分、ＣＯ成分及び添加するＨ₂Ｏの初期のモル量を、それぞれ、Ｃ：ｃモル、Ｈ：ａモル、Ｏ：ｍモル、Ｈ₂Ｏ：Ｂモルとする。例えば、原燃料が、１モルのＣＨ₄と１モルのＣ₂Ｈ₆と１モルのＣＯで構成され、メタン換算スチーム比Ｓ／Ｃ＝２（完全水蒸気改質に必要な水蒸気量の２倍）のＨ₂Ｏを添加するとすると、（１）及び（２）式から、ｃ＝１＋２＝３モル、ａ＝４＋６＝１０モル、Ｂ＝（１＋２）×２＝６モルとなり、これに１モルのＯを含むから、Ｏ＝１モルとなる。 Among the fuels introduced into the anode of the fuel cell, the initial molar amounts of C component, H component, O component, CO component and H ₂ O to be added in all gases including methane are respectively expressed as C: c mol. , H: a mole, O: m mole, and H ₂ O: B mole. For example, the raw fuel is composed of 1 mol of CH ₄ , 1 mol of C ₂ H ₆ and 1 mol of CO, and the methane equivalent steam ratio S / C = 2 (twice the amount of steam required for complete steam reforming) ) H ₂ O, from the formulas (1) and (2), c = 1 + 2 = 3 mol, a = 4 + 6 = 10 mol, B = (1 + 2) × 2 = 6 mol, Therefore, O = 1 mol.

このとき、完全水蒸気改質後のガス組成は、Ｈ₂：ａ/２＋ｃ−ｍモル、ＣＯ：ｃモル、Ｈ₂Ｏ：Ｂ−ｃ＋ｍモル、ＣＯ₂：０モルとなる。そして、（９）式のシフト反応により、組成がｘだけ変化したとすると、シフト反応後のガス組成は、Ｈ₂：ａ/２＋ｃ−ｍ＋ｘモル、ＣＯ：ｃ−ｘモル、Ｈ₂Ｏ：Ｂ−ｃ＋ｍ−ｘモル、ＣＯ₂：ｘモルとなる。 At this time, the gas composition after complete steam reforming is H ₂ : a / 2 + c-m mol, CO: c mol, H ₂ O: Bc + m mol, and CO ₂ : 0 mol. If the composition is changed by x by the shift reaction of formula (9), the gas composition after the shift reaction is H ₂ : a / 2 + c−m + x mole, CO: c−x mole, H ₂ O: B. -c + m-x mol, CO _2: a x mol.

ここで、実効燃料量をＱモルとすると、Ｑ＝ａ/２＋２ｃ−ｍとなる。まず、上記シフト反応後の組成について、（５）式：Ｈ₂＋１/２Ｏ₂→Ｈ₂Ｏの平衡反応を考慮すると、平衡定数をＫ₁、酸素分圧をＰｏ₂として、下記式（２７）が成立する。

Here, when the effective fuel amount is Q mol, Q = a / 2 + 2c−m. First, regarding the composition after the shift reaction, considering the equilibrium reaction of formula (5): H ₂ + 1 / 2O ₂ → H ₂ O, the equilibrium constant is K ₁ , the oxygen partial pressure is Po ₂ , and the following formula (27 ) Holds.

同じく、上記シフト反応後の組成について、（６）式：ＣＯ＋１/２Ｏ₂→ＣＯ₂の平衡反応を考慮すると、平衡定数をＫ₂、酸素分圧をＰｏ₂として、下記式（２８）が成立する。ここで（２８）式をｘについて整理すると下記式（２９）となる。

Similarly, with regard to the composition after the shift reaction, the following equation (28) is established, considering the equilibrium reaction of equation (6): CO + 1 / 2O ₂ → CO ₂ , assuming that the equilibrium constant is K ₂ and the oxygen partial pressure is Po _2. To do. Here, when formula (28) is arranged with respect to x, the following formula (29) is obtained.

そして、（２７）式に（２８）式のｘ、すなわち（３９）式を代入してｍを求め、実効燃料量：Ｑ＝ａ/２＋２ｃ−ｍに代入して整理すると下記式（３０）のとおりに簡略化できる。

Then, by substituting x in the equation (28), that is, the equation (39), into the equation (27) to obtain m, and substituting it into the effective fuel amount: Q = a / 2 + 2c−m, the following equation (30) is obtained. It can be simplified as follows.

ここで、Ｈ₂Ｏのモル量Ｂを“３条件（３点）”設定し、それぞれをＢ（１）、Ｂ（２）、Ｂ（３）とし、それぞれに対応する平衡酸素分圧をＰｏ₂（１）、Ｐｏ₂（２）、Ｐｏ₂（３）とし、（３０）式に代入してｃを求めると下記式（３１）のとおりとなる。

Here, the molar amount B of H ₂ O is set to “3 conditions (3 points)”, and each is set to B (1), B (2), and B (3), and the equilibrium oxygen partial pressure corresponding to each is Po. ₂ (1), Po ₂ (2), Po ₂ (3) and substituting into the equation (30) to obtain c, the following equation (31) is obtained.

また、（３１）式によりａを求めると下記式（３２）のとおりとなる。

Further, when a is obtained from the equation (31), the following equation (32) is obtained.

そして、（３２）式を解いて実効燃料量Ｑを求めると下記式（３３）のとおりとなる。

Then, when the effective fuel amount Q is obtained by solving the equation (32), the following equation (33) is obtained.

こうして、添加水蒸気量を“３条件（３点）”変えて、それぞれの条件での酸素分圧を測定し、（３３）式に代入することにより、メタンのほか、ＣＯ、ＣＯ₂、Ｈ₂Ｏが混入した燃料の実効燃料量Ｑを算定し、決定することができる。その決定操作は、前述“３条件（３点）”変える場合と同様であり、図９（ｂ）のように行うことができる。 Thus, by changing the amount of added water vapor to “3 conditions (3 points)” and measuring the oxygen partial pressure under each condition and substituting it into the equation (33), CO, CO ₂ , H _{2 in} addition to methane. The effective fuel amount Q of the fuel mixed with O can be calculated and determined. The determination operation is the same as that in the case of changing “3 conditions (3 points)”, and can be performed as shown in FIG.

例えば、純Ｃ₂Ｈ₆を原燃料として１モル／ｓ（ｓ＝秒）で供給し、Ｈ₂Ｏを３モル／ｓ、５モル／ｓ、７モル／ｓの３条件で供給し、それぞれの条件で酸素センサの信号により推定酸素分圧を算定すると表１のとおりとなる。表１の推定酸素分圧と供給水蒸気量を（３３）式に代入して、実効燃料量Ｑを計算するとＱ＝７となり、原燃料：Ｃ₂Ｈ₆の実効燃料量と一致する。

For example, pure C ₂ H ₆ is supplied as raw fuel at 1 mol / s (s = second), H ₂ O is supplied at 3 mol / s, 5 mol / s, and 7 mol / s, respectively, When the estimated oxygen partial pressure is calculated from the signal of the oxygen sensor under the conditions of Table 1, it is as shown in Table 1. Substituting the estimated oxygen partial pressure and the supplied water vapor amount in Table 1 into the equation (33) to calculate the effective fuel amount Q, Q = 7, which coincides with the effective fuel amount of raw fuel: C ₂ H ₆ .

また、例えば、原燃料として、ＣＨ₄が１モル／ｓ、Ｃ₂Ｈ₆が１モル／ｓ、ＣＯが１モル／ｓの燃料を供給し、且つ、混入酸素が０．５モル／ｓであるという条件で、供給水蒸気（Ｈ₂Ｏ）量を５モル／ｓ、７モル／ｓ、９モル／ｓの“３条件”変えて供給し、それぞれの条件で酸素センサの信号により推定酸素分圧を算定すると表２のとおりとなる。表２の推定酸素分圧と供給水蒸気量を（３３）式に代入して、実効燃料量Ｑを計算するとＱ＝１１となり、ＣＨ₄を１モル／ｓ、Ｃ₂Ｈ₆を１モル／ｓ、ＣＯを１モル／ｓ供給し、且つ、混入酸素（Ｏ₂）が０．５モル／ｓであるという燃料の実効燃料量と一致する。

For example, as a raw fuel, CH ₄ is supplied at 1 mol / s, C ₂ H ₆ is supplied at 1 mol / s, and CO is supplied at 1 mol / s, and the mixed oxygen is 0.5 mol / s. Under certain conditions, the amount of water vapor (H ₂ O) supplied is changed at “3 conditions” of 5 mol / s, 7 mol / s, and 9 mol / s, and the estimated oxygen content is determined by the oxygen sensor signal under each condition. The pressure is calculated as shown in Table 2. Substituting the estimated oxygen partial pressure and supply water vapor amount in Table 2 into the equation (33) and calculating the effective fuel amount Q, Q = 11, CH ₄ is 1 mol / s, and C ₂ H ₆ is 1 mol / s. , CO is supplied at 1 mol / s, and the effective fuel amount of the fuel is that the mixed oxygen (O ₂ ) is 0.5 mol / s.

《本発明の態様例２：温度が低い場合における制御態様》
本態様例２は、改質器を経た後の燃料を若干量分岐させて、分岐燃料に水蒸気を添加しながら、その分岐燃料の酸素分圧を酸素センサで測定して、実効燃料量を算出することにより供給原燃料の流量を制御する態様である。この制御は、温度が低い状態で適用でき、その制御を著しく簡略化することができる。 << Aspect Example 2 of the Present Invention: Control Aspect when Temperature is Low >>
In this embodiment example 2, the fuel after passing through the reformer is branched in a small amount, and while adding steam to the branched fuel, the oxygen partial pressure of the branched fuel is measured by an oxygen sensor to calculate the effective fuel amount. In this manner, the flow rate of the supplied raw fuel is controlled. This control can be applied at a low temperature, and the control can be greatly simplified.

本態様例２での制御の原理、メカニズム（機序）は以下のとおりである。前記（２６）式は温度が低い状態では著しく簡略化することができる。この場合、酸素センサの周りはシフト反応温度域でも、より低温域、好ましくは３００℃程度に制御されている必要がある。その理由は、（９）式のシフト平衡が右辺（生成系）に移行してＣＯは殆ど無くなり、Ｈ₂リッチのガス組成になるからである。 The control principle and mechanism (mechanism) in the second embodiment are as follows. The equation (26) can be greatly simplified when the temperature is low. In this case, the oxygen sensor needs to be controlled to a lower temperature range, preferably about 300 ° C., even in the shift reaction temperature range. The reason for this is that the shift equilibrium of the formula (9) shifts to the right side (generation system), CO is almost lost, and the gas composition is rich in H ₂ .

この場合、異なった“２条件（２点）”の水蒸気添加量条件を使用して実効燃料量Ｑを算出することができる。この態様では、実効燃料量Ｑは下記式（３４）のとおりとなる。

In this case, the effective fuel amount Q can be calculated using different “two conditions (two points)” of the water vapor addition amount conditions. In this aspect, the effective fuel amount Q is represented by the following formula (34).

したがって、（９）式のシフト平衡が殆ど右辺側に移行するような、温度が低い状態では、添加水蒸気量を“２条件（２点）”変えて、それぞれの条件での酸素分圧を測定し、（３４）式に代入することにより、実効燃料量Ｑを算出することができる。（３４）式のとおり、実効燃料量Ｑの算出式は著しく簡略化され、添加水蒸気量を“２条件（２点）”変えて酸素分圧を測定することにより実効燃料量Ｑを算出、決定することができる。 Therefore, when the temperature is low such that the shift equilibrium of equation (9) shifts almost to the right side, the amount of added water vapor is changed by “2 conditions (2 points)” and the oxygen partial pressure is measured under each condition. Then, the effective fuel amount Q can be calculated by substituting it into the equation (34). As shown in equation (34), the formula for calculating the effective fuel amount Q is remarkably simplified, and the effective fuel amount Q is calculated and determined by measuring the oxygen partial pressure while changing the amount of added water vapor by “two conditions (two points)”. can do.

図１０は本態様例２を示す図である。図１０のとおり、改質器からＳＯＦＣスタックへの改質ガス導管、すなわち燃料電池のアノードへの燃料供給管から分岐した分岐管に酸素センサを配置し、酸素センサへの分岐管の途中に水蒸気導入管を配置する。この場合、酸素センサの周りは３００℃程度に制御する。そして、分岐燃料に水蒸気を添加しながら酸素センサで分岐燃料中の酸素分圧を検知し、その酸素分圧値によりアノードに導入している実効燃料量Ｑを決定する。その決定操作は前述図９（ａ）と同様に行うことができ、またその計算は、図１０のような態様では、記憶装置、入出力装置を伴う中央処理装置（ＣＰＵ）により行われる。 FIG. 10 is a diagram showing the second embodiment example. As shown in FIG. 10, an oxygen sensor is arranged in a reformed gas conduit from the reformer to the SOFC stack, that is, a branch pipe branched from the fuel supply pipe to the anode of the fuel cell, and water vapor is placed in the middle of the branch pipe to the oxygen sensor. Arrange the introduction pipe. In this case, the area around the oxygen sensor is controlled to about 300 ° C. Then, the oxygen partial pressure in the branched fuel is detected by an oxygen sensor while adding water vapor to the branched fuel, and the effective fuel amount Q introduced into the anode is determined based on the oxygen partial pressure value. The determination operation can be performed in the same manner as in FIG. 9A, and the calculation is performed by a central processing unit (CPU) with a storage device and an input / output device in the embodiment as shown in FIG.

それと同時に、あるいはそれと前後して、ＳＯＦＣスタックで発電している電流値をモニタし、計測された電流値が実機ＳＯＦＣスタックについてあらかじめセットした許容値、例えば限界電圧、すなわち燃料利用率を利用する図３の例で言えばセル電圧０．６Ｖに対応する電流値以下であれば、原燃料の供給量を増加するよう制御し、併せてこれに対応した水蒸気量、空気量を決定し、制御する。 At the same time or before and after that, the current value generated by the SOFC stack is monitored, and the measured current value uses a preset value for the actual SOFC stack, such as a limit voltage, that is, a fuel utilization rate. For example 3, if the current value is equal to or less than the cell voltage of 0.6 V, the supply amount of raw fuel is controlled to be increased, and the water vapor amount and air amount corresponding to this are determined and controlled. .

この制御は、図１０のように、記憶装置、入出力装置を伴う中央処理装置（ＣＰＵ）により行うことができる。例えば、原燃料が例えば天然ガスとバイオガスの混合ガスの場合、その組成は未知、あるいはその組成が未知でしかも変動しているが、改質ガスすなわち燃料の組成は酸素センサによる酸素分圧値から実効燃料量Ｑが分かるので、原燃料の増減量は一義的ないしほぼ一義的に制御することができる。 This control can be performed by a central processing unit (CPU) with a storage device and an input / output device as shown in FIG. For example, when the raw fuel is, for example, a mixed gas of natural gas and biogas, the composition is unknown or the composition is unknown and fluctuates, but the reformed gas, that is, the composition of the fuel is the oxygen partial pressure value by the oxygen sensor. Since the effective fuel amount Q is known from the above, the amount of increase or decrease in the raw fuel can be controlled uniquely or almost uniquely.

《本発明の態様例３：ＰＥＦＣへの適用態様例》
図１１は本態様例２をＰＥＦＣに対して適用する例を示す図である。図１１では、酸素センサをＣＯ変成器からの出導管から分岐管に配置しているが、酸素センサをＣＯ選択酸化器からの出導管から分岐管に配置してもよい。改質器に水蒸気を加え、ＣＯ変成器あるいはＣＯ選択酸化器を経た改質ガスの酸素分圧を酸素センサで検知して、実効燃料量Ｑを決定する。ＣＯ変成器を経た改質ガスはシフト反応が進んでＣＯ成分が殆どＨ₂に変換されており、異なった“２条件（２点）”の水蒸気添加量条件を使用して前記式（３４）で実効燃料量Ｑを算出し、決定することができる。それら“２条件（２点）”への水蒸気添加量の調整は流量調整弁Ｖ２により行う。流量調整弁Ｖ２により流量調整された水は加熱交換器により加熱され水蒸気として供給される。 << Aspect Example 3: Aspects of Application to PEFC >>
FIG. 11 is a diagram illustrating an example in which the second aspect example is applied to the PEFC. In FIG. 11, the oxygen sensor is arranged in the branch pipe from the outlet pipe from the CO converter, but the oxygen sensor may be arranged in the branch pipe from the outlet pipe from the CO selective oxidizer. Water vapor is added to the reformer, and the oxygen partial pressure of the reformed gas that has passed through the CO converter or CO selective oxidizer is detected by an oxygen sensor to determine the effective fuel amount Q. The reformed gas that has passed through the CO converter has undergone a shift reaction, and most of the CO component has been converted to H ₂ , and the above formula (34) is used by using different “two conditions (two points)” steam addition amount conditions. Thus, the effective fuel amount Q can be calculated and determined. Adjustment of the added amount of water vapor to these “two conditions (two points)” is performed by the flow rate adjusting valve V2. The water whose flow rate is adjusted by the flow rate adjusting valve V2 is heated by the heat exchanger and supplied as water vapor.

実効燃料量Ｑの決定と同時に、あるいはそれと前後して、電流計によりＰＥＦＣスタックで発電している電流値をモニタし、計測された電流値が実機ＰＥＦＣスタックについてあらかじめセットした許容値、例えば限界電圧に対応する電流値以下であれば、原燃料の供給量を増加するよう制御し、併せてこれに対応した水蒸気量、空気量を決定し、制御する。図１１において、それら各流量の制御はそれぞれ流量調整弁Ｖ１〜Ｖ３により行うが、以上の計算、決定、制御は、記憶装置、入出力装置を伴う中央処理装置（ＣＰＵ）により行われる。 At the same time as or after the determination of the effective fuel amount Q, the current value generated by the PEFC stack is monitored by an ammeter, and the measured current value is an allowable value set in advance for the actual PEFC stack, for example, the limit voltage. If the current value is equal to or less than the current value, the supply amount of the raw fuel is controlled to be increased, and the water vapor amount and the air amount corresponding to this are determined and controlled. In FIG. 11, these flow rates are controlled by the flow rate adjusting valves V <b> 1 to V <b> 3, respectively. The above calculation, determination, and control are performed by a central processing unit (CPU) with a storage device and an input / output device.

ここで、原燃料が例えば天然ガスとバイオマス燃料の混合ガスのような場合、その組成は未知、あるいはその組成が未知でしかも変動する可能性があるが、改質ガスすなわち燃料の組成については酸素センサで測定される酸素分圧値から実効燃料量Ｑが分かるので、原燃料の増減量は一義的ないしほぼ一義的に制御することができる。もちろん、本態様においても原燃料の組成が既知の場合にも適用できる。 Here, when the raw fuel is, for example, a mixed gas of natural gas and biomass fuel, its composition is unknown or its composition is unknown and may vary, but the reformed gas, that is, the composition of fuel, is oxygen. Since the effective fuel amount Q is known from the oxygen partial pressure value measured by the sensor, the increase / decrease amount of the raw fuel can be uniquely or almost uniquely controlled. Of course, this embodiment can also be applied when the composition of the raw fuel is known.

《本発明の態様例４：部分酸化法による改質の場合》
炭化水素の空気による部分酸化法によるストイキメトリックな改質反応は下記反応式（３５）〜（３８）で表される。これらの反応式における生成系のＣＯ、Ｈ₂はいわゆる“反応素過程”を経て生成している。Ｃ₂〜Ｃ₄の不飽和炭化水素やＣ₅以上の炭素を含む炭化水素（飽和炭化水素のほか、不飽和炭化水素を含む）についても同様である。

<< Embodiment 4: Embodiment of Modification by Partial Oxidation Method >>
The stoichiometric reforming reaction by the partial oxidation method of hydrocarbon air is represented by the following reaction formulas (35) to (38). In these reaction formulas, CO and H ₂ in the production system are produced through a so-called “reactor process”. The same applies to C _{2 to} C ₄ unsaturated hydrocarbons and hydrocarbons containing C ₅ or more carbons (including unsaturated hydrocarbons as well as saturated hydrocarbons).

ここで、原燃料のうち、炭化水素も含めたすべてのガスの中のＣ成分及びＨ成分、並びに、添加する空気の初期のモル量を、Ｃ：ｃモル、Ｈ：ａモル、Ｏ：ｍモル、添加（＝導入）空気：Ｐモルとする。例えば、原燃料がＣＨ₄：１モルとＣ₂Ｈ₆：１モル及びＣＯ：１モルで構成されているとすると、完全部分改質に必要な酸素を添加すると定義して、ｃ＝１＋２＋１＝４モル、ａ＝４＋６＝１０モル、Ｐ＝（１＋２）/２/０．２１モル、ｍ＝１ということになる。 Here, the C component and H component in all gases including hydrocarbons in the raw fuel, and the initial molar amount of air to be added are C: c mol, H: a mol, O: m. Mole, added (= introduced) air: P mol. For example, if the raw fuel is composed of 1 mol of CH _4, 1 mol of C ₂ H ₆ and 1 mol of CO, it is defined that oxygen necessary for complete partial reforming is added, and c = 1 + 2 + 1 = 4 mol, a = 4 + 6 = 10 mol, P = (1 + 2) /2/0.21 mol, m = 1.

完全部分改質後のガス組成は、Ｈ₂：ａ/２＋ｃ−ｍ−０．４２Ｐモル、ＣＯ：ｃモル、Ｈ₂Ｏ：ｍ＋０．４２Ｐ−ｃモル、ＣＯ₂：０モル、Ｎ₂：０．７９Ｐモルである。 The gas composition after complete partial reforming was as follows: H ₂ : a / 2 + c−m−0.42 P mol, CO: c mol, H ₂ O: m + 0.42 P−c mol, CO ₂ : 0 mol, N ₂ : 0 .79 Pmol.

そして、（９）式のシフト反応により、組成がｘだけ変化したとすると、シフト反応後の平衡組成は、Ｈ₂：ａ/２＋ｃ−ｍ−０．４２Ｐ＋ｘモル、ＣＯ：ｃ−ｘモル、Ｈ₂Ｏ：ｍ＋０．４２Ｐ−ｃ−ｘモル、ＣＯ₂：ｘモル、Ｎ₂：０．７９Ｐモルとなる。（５）式及び（６）式の平衡式はそれぞれ下記式（３９）及び（４０）で表される。

If the composition is changed by x by the shift reaction of formula (9), the equilibrium composition after the shift reaction is H ₂ : a / 2 + c−m−0.42P + x mol, CO: c−x mol, H ₂ O: m + 0.42P-c-x mol, CO ₂ : x mol, N ₂ : 0.79 P mol. The balanced equations (5) and (6) are expressed by the following equations (39) and (40), respectively.

そして、（３９）及び（４０）式をｘについて解くと（４１）式のとおりとなる。

Then, when the equations (39) and (40) are solved for x, the equation (41) is obtained.

ここで、炭化水素の部分酸化による改質の場合、改質反応後の実効燃料量Ｑは、水蒸気改質の場合とは異なり、導入酸素量分だけ減少しており、（４２）式のとおりとなる。

Here, in the case of reforming by partial oxidation of hydrocarbons, the effective fuel amount Q after the reforming reaction is reduced by the amount of introduced oxygen, unlike the case of steam reforming, as shown in equation (42) It becomes.

（４１）式の結果を（４２）式に代入して整理すると（４３）式のとおりとなる。この
（４３）式のように酸素混入量が顕わに現れない式で記述される。

Substituting the result of the equation (41) into the equation (42) and rearranging the result gives the equation (43). It is described by an expression such that the amount of mixed oxygen does not appear clearly like the expression (43).

ここで、（４１）式に関して“３条件（３点）”すなわち３通りの改質用空気供給量Ｐ（１）、Ｐ（２）、Ｐ（３）を設定し、それぞれの平衡酸素分圧をＰｏ₂（１）、Ｐｏ₂（２）、Ｐｏ₂（３）とすると、下記関係式（４４）が成り立つ。

Here, “3 conditions (3 points)”, that is, three reforming air supply amounts P (1), P (2), and P (3) are set with respect to the equation (41), and the respective equilibrium oxygen partial pressures are set. Is Po ₂ (1), Po ₂ (2), Po ₂ (3), the following relational expression (44) is established.

そして、（４４）の連立式を解くと（４５）式のとおり算出される。

Then, when the simultaneous equation (44) is solved, it is calculated according to the equation (45).

このように、炭化水素の部分酸化による改質の場合も、供給空気量を“３条件（３点）”変えて、その都度酸素分圧を測定することによって、元の燃料中の実効燃料量Ｑを算出し、決定することができる。その決定操作は、前述“３条件（３点）”変える場合と同様であり、図９（ｂ）のように行うことができる。 Thus, in the case of reforming by partial oxidation of hydrocarbons, the effective fuel amount in the original fuel is obtained by changing the supply air amount by “three conditions (three points)” and measuring the oxygen partial pressure each time. Q can be calculated and determined. The determination operation is the same as that in the case of changing “3 conditions (3 points)”, and can be performed as shown in FIG.

ただし、水蒸気改質の場合とは異なり、部分酸化による改質の場合には、酸素を供給することによって実効燃料量が減少していくため、酸素供給後の実効燃料量Ｑは、最終的に供給する酸素量を決め、（４３）式を用いて算出する必要がある。このときの（４３）式中のａ及びｃの値は、３つの空気供給条件に対して測定した酸素分圧を利用し、（４５）式を用いて算出した値であり、（４３）式中の酸素分圧は、最終的に供給する酸素量をフィックスすなわち固定したときの酸素分圧である。 However, unlike the case of steam reforming, in the case of reforming by partial oxidation, the effective fuel amount Q after supplying oxygen is finally reduced because the effective fuel amount decreases by supplying oxygen. It is necessary to determine the amount of oxygen to be supplied and calculate using the equation (43). The values of a and c in equation (43) at this time are values calculated using equation (45) using oxygen partial pressures measured for three air supply conditions. The oxygen partial pressure is the oxygen partial pressure when the amount of oxygen finally supplied is fixed.

原燃料として都市ガスを用いる従来の固体酸化物形燃料電池システムを示す図Diagram showing a conventional solid oxide fuel cell system using city gas as raw fuel 燃料利用率を説明する図Diagram explaining fuel utilization 燃料利用率を利用する燃料電池の運転制御方式を説明する図The figure explaining the operation control system of the fuel cell using the fuel utilization rate 都市ガス等の組成が分かった原燃料を用いる固体酸化物形燃料電池の制御態様を示す図The figure which shows the control aspect of the solid oxide form fuel cell which uses the raw fuel whose composition such as city gas is understood 本発明の態様例１を説明する図The figure explaining the example 1 of an aspect of this invention 酸素センサの原理、構造、機能について説明する図Diagram explaining the principle, structure and function of oxygen sensor 酸素センサの構造、機能について説明する図Diagram explaining structure and function of oxygen sensor 酸素センサの構造、機能について説明する図Diagram explaining structure and function of oxygen sensor 本発明において、酸素センサによる燃料中の酸素分圧を基に実効燃料量Ｑを決定する操作態様を説明する図The figure explaining the operation aspect which determines the effective fuel amount Q based on the oxygen partial pressure in the fuel by an oxygen sensor in this invention. 本発明の態様例２を説明する図The figure explaining the example 2 of an aspect of this invention 本発明の態様例３を説明する図The figure explaining example 3 of an aspect of the present invention

Explanation of symbols

１〜３熱交換器
Ｖ１〜Ｖ４流量調整弁
1-3 Heat exchanger V1-V4 Flow control valve

Claims

A fuel cell operation control method using a fuel obtained by reforming a raw fuel, wherein an oxygen sensor is disposed in a fuel introduction portion to the anode of the fuel cell, and the fuel is a fuel obtained by reforming the raw fuel introduced to the anode. Measure the oxygen partial pressure of
A: When steam reforming raw fuel,
(A) The amount of water vapor supplied when reforming the raw fuel is changed according to each case of (b1) to (b3) below,
(B1) When the raw fuel is only hydrocarbon,
(B2) When the raw fuel contains hydrocarbon and CO,
(B3) When the raw fuel contains O contained in CO, CO ₂ or H ₂ O (water vapor) in addition to hydrocarbons,
(C) Each of the supplied water vapor amounts and (d) the oxygen partial pressure value measured by the oxygen sensor are expressed by the following equations (19), (26) and (33) according to the number of components of the raw fuel (e): ) To obtain the number of moles of the C component and H component in the fuel that is the reformed raw fuel, calculate the effective fuel amount Q from the number of moles, and based on the effective fuel amount Q In addition, the flow rate of the raw fuel is controlled so that the fuel utilization rate in the fuel cell is appropriate or optimal,
B: When reforming raw fuel by the partial oxidation method,
(A) The reforming air supply amount at the time of reforming the raw fuel is changed in three conditions, (b) each air supply amount and (c) the oxygen partial pressure value measured by the oxygen sensor (d) ) Substituting into the following formulas (43) and (45), the number of moles of the C component and the H component in the fuel that is the reformed raw fuel is obtained, and the effective fuel amount Q is calculated from the number of moles. A fuel cell operation control method, comprising: controlling a flow rate of raw fuel based on an effective fuel amount Q so that a fuel utilization rate in a fuel cell is appropriate or optimal.
However, in the formula, B (1), B (2) and B (3) are the amounts of water vapor supplied, Po ₂ (1), Po ₂ (2) and Po ₂ (3) are B (1), B ( 2), the equilibrium oxygen partial pressure corresponding to B (3), K ₁ is the equilibrium constant of the formula: H ₂ + 1 / 2O ₂ → H ₂ O, K ₂ is the equilibrium constant of the formula: CO + 1 / 2O ₂ → CO ₂ , a is the number of moles of H (hydrogen), and c is the number of moles of C (carbon).
In equations (43) and (45), p (1), p (2), and p (3) are the three conditions of reforming air supply amount, Po ₂ (1), Po ₂ (2), Po ₂ (3) is an equilibrium oxygen partial pressure corresponding to three conditions.

A fuel cell operation control method using a fuel obtained by reforming raw fuel, which measures the current value of the fuel cell and controls the flow rate of the raw fuel from the measured current value, and introduces fuel into the anode of the fuel cell. Measure the oxygen partial pressure in the fuel, which is a reformed raw fuel introduced into the anode by placing an oxygen sensor in the part,
A: When steam reforming raw fuel,
(A) The amount of water vapor supplied when reforming the raw fuel is changed according to each case of (b1) to (b3) below,
(B1) When the raw fuel is only hydrocarbon,
(B2) When the raw fuel contains hydrocarbon and CO,
(B3) When the raw fuel contains O contained in CO, CO ₂ or H ₂ O (water vapor) in addition to hydrocarbons,
(C) Each of the supplied water vapor amounts and (d) the oxygen partial pressure value measured by the oxygen sensor are expressed by the following equations (19), (26) and (33) according to the number of components of the raw fuel (e): ) To obtain the number of moles of the C component and H component in the fuel that is the reformed raw fuel, calculate the effective fuel amount Q from the number of moles, and based on the effective fuel amount Q In addition, the flow rate of the raw fuel is controlled so that the fuel utilization rate in the fuel cell is appropriate or optimal,
B: When reforming raw fuel by the partial oxidation method,
(A) The reforming air supply amount at the time of reforming the raw fuel is changed in three conditions, (b) each air supply amount and (c) the oxygen partial pressure value measured by the oxygen sensor (d) ) Substituting into the following formulas (43) and (45), the number of moles of the C component and the H component in the fuel that is the reformed raw fuel is obtained, and the effective fuel amount Q is calculated from the number of moles. A fuel cell operation control method, comprising: controlling a flow rate of raw fuel based on an effective fuel amount Q so that a fuel utilization rate in a fuel cell is appropriate or optimal.
However, in the formula, B (1), B (2) and B (3) are the amounts of water vapor supplied, Po ₂ (1), Po ₂ (2) and Po ₂ (3) are B (1), B ( 2), the equilibrium oxygen partial pressure corresponding to B (3), K ₁ is the equilibrium constant of the formula: H ₂ + 1 / 2O ₂ → H ₂ O, K ₂ is the equilibrium constant of the formula: CO + 1 / 2O ₂ → CO ₂ , a is the number of moles of H (hydrogen), and c is the number of moles of C (carbon).
In equations (43) and (45), p (1), p (2), and p (3) are the three conditions of reforming air supply amount, Po ₂ (1), Po ₂ (2), Po ₂ (3) is an equilibrium oxygen partial pressure corresponding to three conditions.

A fuel cell operation control method using fuel obtained by reforming raw fuel, wherein an oxygen sensor is disposed in a branch pipe branched from a fuel supply pipe to an anode of the fuel cell, and water is added to the branched fuel to branch fuel. Measure the oxygen partial pressure in the fuel that is a reformed raw fuel to be introduced into the anode by measuring the oxygen partial pressure, and change the amount of added water vapor by “2 conditions (2 points)”. The effective fuel amount Q is calculated by measuring the oxygen partial pressure at, and substituting it into the following equation (34), so that the fuel utilization rate in the fuel cell becomes appropriate or optimal based on the effective fuel amount Q. fuel operation control method for a battery characterized by Rukoto Gyosu control the flow rate of the raw fuel to.
However, in the formula, B (1) and B (2 ) are the amounts of added water vapor, Po ₂ (1) and Po ₂ (2 ) are the equilibrium oxygen partial pressures corresponding to B (1) and B (2 ) , K ₁ has the _{_{formula: H 2 + 1 / 2O 2}} → H 2 O equilibrium constant, K ₂ is the formula: a CO + 1 / 2O ₂ → CO equilibrium constants of _2.

The raw fuel is hydrogen, carbon monoxide, methane, ethane, ethylene, propane, butane, city gas, natural gas, petroleum gas, coal gas, generator gas, water gas, blast furnace gas, petroleum cracked gas, gasoline, light oil Kerosene, diesel oil, ethers, alcohols Biomass fuel obtained by gasification of various organic wastes such as methane fermentation and wood chips, or a mixed fuel of two or more of these fuels The operation control method of the fuel cell according to any one of 1 to 3.

5. The fuel cell according to claim 1, wherein the fuel cell is a solid oxide fuel cell, a molten carbonate fuel cell, a solid polymer fuel cell, or a phosphoric acid fuel cell. 6. A fuel cell operation control method.

A fuel cell operation control system using fuel obtained by reforming raw fuel, wherein an oxygen sensor is disposed in a fuel introduction portion to the anode of the fuel cell, and the raw fuel introduced to the anode is reformed by the oxygen sensor Measure the oxygen partial pressure in the fuel,
A: When steam reforming raw fuel,
(A) The amount of water vapor supplied when reforming the raw fuel is changed according to each case of (b1) to (b3) below,
(B1) When the raw fuel is only hydrocarbon,
(B2) When the raw fuel contains hydrocarbon and CO,
(B3) When the raw fuel contains O contained in CO, CO ₂ or H ₂ O (water vapor) in addition to hydrocarbons,
(C) Each of the supplied water vapor amounts and (d) the oxygen partial pressure value measured by the oxygen sensor are expressed by the following equations (19), (26) and (33) according to the number of components of the raw fuel (e): ) To obtain the number of moles of the C component and H component in the fuel that is the reformed raw fuel, calculate the effective fuel amount Q from the number of moles, and based on the effective fuel amount Q In addition, the flow rate of the raw fuel is controlled so that the fuel utilization rate in the fuel cell is appropriate or optimal,
B: When reforming raw fuel by the partial oxidation method,
(A) The reforming air supply amount at the time of reforming the raw fuel is changed in three conditions, (b) each air supply amount and (c) the oxygen partial pressure value measured by the oxygen sensor (d) ) Substituting into the following formulas (43) and (45), the number of moles of the C component and the H component in the fuel that is the reformed raw fuel is obtained, and the effective fuel amount Q is calculated from the number of moles. An operation control system for a fuel cell, characterized in that the flow rate of raw fuel is controlled based on the effective fuel amount Q so that the fuel utilization rate in the fuel cell is appropriate or optimal.
However, in the formula, B (1), B (2) and B (3) are the amounts of water vapor supplied, Po ₂ (1), Po ₂ (2) and Po ₂ (3) are B (1), B ( 2), the equilibrium oxygen partial pressure corresponding to B (3), K ₁ is the equilibrium constant of the formula: H ₂ + 1 / 2O ₂ → H ₂ O, K ₂ is the equilibrium constant of the formula: CO + 1 / 2O ₂ → CO ₂ , a is the number of moles of H (hydrogen), and c is the number of moles of C (carbon).
In equations (43) and (45), p (1), p (2), and p (3) are the three conditions of reforming air supply amount, Po ₂ (1), Po ₂ (2), Po ₂ (3) is an equilibrium oxygen partial pressure corresponding to three conditions.

A fuel cell operation control system using fuel obtained by reforming raw fuel, which measures the current value of the fuel cell and controls the flow rate of the raw fuel from the measured current value, and introduces fuel into the anode of the fuel cell. Measure the oxygen partial pressure in the fuel, which is a reformed raw fuel introduced into the anode by placing an oxygen sensor in the part,
A: When steam reforming raw fuel,
(A) The amount of water vapor supplied when reforming the raw fuel is changed according to each case of (b1) to (b3) below,
(B1) When the raw fuel is only hydrocarbon,
(B2) When the raw fuel contains hydrocarbon and CO,
(B3) When the raw fuel contains O contained in CO, CO ₂ or H ₂ O (water vapor) in addition to hydrocarbons,
(C) Each of the supplied water vapor amounts and (d) the oxygen partial pressure value measured by the oxygen sensor are expressed by the following equations (19), (26) and (33) according to the number of components of the raw fuel (e): ) To obtain the number of moles of the C component and H component in the fuel that is the reformed raw fuel, calculate the effective fuel amount Q from the number of moles, and based on the effective fuel amount Q In addition, the flow rate of the raw fuel is controlled so that the fuel utilization rate in the fuel cell is appropriate or optimal,
B: When reforming raw fuel by the partial oxidation method,
(A) The reforming air supply amount at the time of reforming the raw fuel is changed in three conditions, (b) each air supply amount and (c) the oxygen partial pressure value measured by the oxygen sensor (d) ) Substituting into the following formulas (43) and (45), the number of moles of the C component and the H component in the fuel that is the reformed raw fuel is obtained, and the effective fuel amount Q is calculated from the number of moles. An operation control system for a fuel cell, characterized in that the flow rate of raw fuel is controlled based on the effective fuel amount Q so that the fuel utilization rate in the fuel cell is appropriate or optimal.
However, in the formula, B (1), B (2) and B (3) are the amounts of water vapor supplied, Po ₂ (1), Po ₂ (2) and Po ₂ (3) are B (1), B ( 2), the equilibrium oxygen partial pressure corresponding to B (3), K ₁ is the equilibrium constant of the formula: H ₂ + 1 / 2O ₂ → H ₂ O, K ₂ is the equilibrium constant of the formula: CO + 1 / 2O ₂ → CO ₂ , a is the number of moles of H (hydrogen), and c is the number of moles of C (carbon).
In equations (43) and (45), p (1), p (2), and p (3) are the three conditions of reforming air supply amount, Po ₂ (1), Po ₂ (2), Po ₂ (3) is an equilibrium oxygen partial pressure corresponding to three conditions.

A fuel cell operation control system using fuel obtained by reforming raw fuel, wherein an oxygen sensor is disposed in a branch pipe branched from a fuel supply pipe to an anode of the fuel cell, and steam is added to the branched fuel to branch fuel. Measure the oxygen partial pressure in the fuel that is a reformed raw fuel to be introduced into the anode by measuring the oxygen partial pressure, and change the amount of added water vapor by “2 conditions (2 points)”. The effective fuel amount Q is calculated by measuring the oxygen partial pressure at, and substituting it into the following equation (34), so that the fuel utilization rate in the fuel cell becomes appropriate or optimal based on the effective fuel amount Q. An operation control system for a fuel cell, characterized in that the flow rate of raw fuel is controlled.
However, in the formula, B (1) and B (2 ) are the amounts of added water vapor, Po ₂ (1) and Po ₂ (2 ) are the equilibrium oxygen partial pressures corresponding to B (1) and B (2 ) , K ₁ has the _{_{formula: H 2 + 1 / 2O 2}} → H 2 O equilibrium constant, K ₂ is the formula: a CO + 1 / 2O ₂ → CO equilibrium constants of _2.

The raw fuel is hydrogen, carbon monoxide, methane, ethane, ethylene, propane, butane, city gas, natural gas, petroleum gas, coal gas, generator gas, water gas, blast furnace gas, petroleum cracked gas, gasoline, light oil Kerosene, diesel oil, ethers, alcohols Biomass fuel obtained by gasification of various organic wastes such as methane fermentation and wood chips, or a mixed fuel of two or more of these fuels The operation control system for a fuel cell according to any one of 6 to 8.

10. The fuel cell according to claim 6, wherein the fuel cell is a solid oxide fuel cell, a molten carbonate fuel cell, a solid polymer fuel cell, or a phosphoric acid fuel cell. Fuel cell operation control system.