JPH0757758A - Fuel cell system - Google Patents

Abstract

PURPOSE:To increase the hydrogen concentration in a fuel gas, and to improve the efficiency of a fuel cell by purifying the fuel gas by a hydrogen gas separator and by feeding the gas to the fuel cell, and by removing carbon monoxide which is the catalytic poison to the electrode of the fuel cell. CONSTITUTION:A material fuel is fed from a material fuel feeder 1 to a reformer 4 through a feeding valve 1a and a carburetor 3, and the fuel gas rich in hydrogen gas thus provided is purified by a hydrogen purifier 14, and the amount of carbon monoxide is reduced to no more than 1000ppm. Steam is separated from the mixed gas by a heat exchanger 10 and a moisture separator 12, and the steam is fed to the reformer 4 by a recycle line 21 provided with a circulation blower 20. The gases separated from the steam by the hydrogen separator 12, namely, carbon monoxide, the hydrogen carbide not yet reacted, and the hydrogen not yet processed, are fed to a heating furnace 6 by a line 23 through a blower 22, and is combusted therein. The hydrogen gas purified by the hydrogen purifier 14 is fed to the negative electrode 16a of a fuel cell 16, as a fuel. The air is fed to an air electrode 16b from an air line 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell power generation system having a fuel cell using hydrogen gas as a fuel and oxygen gas or oxygen in the air as an oxidant. Purification by the body before feeding to fuel cells.

[0002]

2. Description of the Related Art A fuel cell is a type of device that electrochemically converts the chemical energy of fuel directly into electrical energy without burning it. Although a compound that can be reduced can be used as the fuel, a fuel cell in which hydrogen is used as the fuel in the negative electrode and oxygen in the air is used as the positive electrode is drawing attention. In this fuel cell, hydrogen is oxidized by oxygen to produce water, so unlike fossil fuels such as petroleum and coal, it does not generate hydrocarbons, nitrogen oxides, sulfur oxides, etc. and does not cause air pollution. , Because it becomes a clean energy source. In addition, so-called on-site power generation, which supplies electric power using this fuel cell in a place that consumes electric power, is also a technical target, and its application to power generation systems and electric vehicles is a challenge. Further, a fuel cell that uses hydrogen gas as a fuel and oxygen in the air as an oxidant (hereinafter, simply referred to as “fuel cell”) has better power generation efficiency than a cell that uses another fuel.

Fuel cells can be classified according to the type of electrolyte sandwiched between the positive electrode and the negative electrode. There are electrolytes using an aqueous phosphoric acid solution, ion exchange membranes, that is, those using a solid polymer. In the former phosphoric acid type, a porous matrix for holding an electrolytic solution is used between a negative electrode which is a fuel electrode and a positive electrode which is an air electrode. In the latter ion-exchange membrane type, the ion-exchange membrane is sandwiched by conductive foil-shaped or mesh-shaped electrodes from both sides. Platinum is used as a catalyst for the electrode regardless of whether it is a phosphoric acid type or an ion exchange membrane type. For example,
Finely divided platinum particles for increasing the surface area are supported on a carrier such as activated carbon. In the case of the phosphoric acid type, the surface of an electrode substrate made of a carbon material such as graphite or a carbon sheet is coated with the catalyst composition containing platinum and a carrier to form a catalyst layer. The ion exchange membrane fuel cell has a structure in which gas diffusion electrodes are integrally joined to both surfaces of a hydrous perfluorocarbon sulfonic acid membrane which is a solid electrolyte. The perfluorocarbon sulfonic acid film is-(CF
_{2) n} - in the main chain ^- be those _{[SO 3 CF 2 CF 2 O-} ] group or the like is introduced, for example, can be suitably used trade name NAFION like from Du Pont Company. In the ion exchange membrane type, it is important to remove water from the positive electrode side and supply water to the negative electrode side.

Hydrogen used as fuel for the fuel cell is natural gas,
Hydrocarbons such as naphtha or alcohols such as methanol are reformed and used as fuel gas rich in hydrogen gas. Natural gas is mainly composed of methane (about 90%), and the rest is lower hydrocarbons such as ethane, propane and butane. These saturated hydrocarbons are, for example, at a temperature of 650 to 800 ° C., 1 to 10 kg by a nickel catalyst or a rhodium catalyst.
It can be converted into hydrogen by the following reaction at a pressure of f / cm ² . Steam reforming reaction: CH ₄ + H ₂ O → CO + 3H ₂ (1) Shift reaction: CO + H ₂ O → CO ₂ + H ₂ (2) When hydrocarbons such as natural gas are used as raw fuel, A steam reforming reaction (1) is carried out in a pouch to obtain a reformed gas containing carbon monoxide and hydrogen. Usually, in order to increase the reaction rate, excess water vapor is made, and excess water vapor is recovered from the latter stage of the fuel cell system. At this time, the shift reaction may slightly progress. Then, the carbon monoxide contained in this reformed gas is subjected to a shift reaction in a carbon monoxide shift converter (2).
Is converted to carbon dioxide and hydrogen. Further, the carbon monoxide shifter is usually in two stages, and the reformed gas obtained in the reformer has a high operating temperature, for example, about 40 degrees.
It is directed to a 0 ° C. high temperature carbon monoxide transformer and then to a low operating temperature, eg, 200 ° C. low temperature carbon monoxide transformer.

When methanol is used as a raw fuel, methanol is prepared by using, for example, a Cu--Zn--Al system catalyst.
It can be converted into hydrogen by the following reaction at a temperature of 200 to 300 ° C. and a pressure of 10 kgf / cm ² or less. Decomposition reaction: CH ₃ OH → CO + 2H ₂ (3) Shift reaction: CO + H ₂ O → CO ₂ + H ₂ (4) In alcohol, it is common to carry out both these reactions in one reformer. is there. A polymer electrolyte fuel cell using methanol as a raw fuel is drawing attention as a power source for electric vehicles.

[0006]

No matter which hydrogen generation source is used, carbon monoxide is involved in the hydrogen generation reaction, and the fuel gas supplied to the anode of the fuel cell contains not only hydrogen but also a trace amount. It contains carbon monoxide as an impurity. However, carbon monoxide becomes a catalyst poison of the platinum catalyst of the electrode used in the fuel cell, and a small amount of carbon monoxide reduces the power generation efficiency of the fuel cell. For example, in a phosphoric acid fuel cell, when the operating temperature is 190 ° C. or lower, the concentration of carbon monoxide is 1%, and when the operating temperature is 190 ° C. or higher, 2-3%.
Due to the carbon monoxide concentration, the platinum catalyst is poisoned and the power generation efficiency decreases.
It is shown on page 41. Furthermore, Los Ay Lemons,
Journal of Power Sources (J. Power Source
s) 29 (1990) 251-264, page 261, a solid polymer electrolyte fuel cell, a few p in hydrogen gas.
It is described that the power generation efficiency of the fuel cell decreases even when pm carbon monoxide is contained. In FIG. 8, 500
20% of angstrom platinum particles, using the PEM08 electrode of Prototech, which is supported on a carbon carrier, when the hydrogen pressure on the negative electrode side is 24 psig and the air pressure on the positive electrode side is 60 psig, in the hydrogen gas of the negative electrode, When carbon monoxide is not contained and when carbon monoxide is 5, 10, 20, 50 and 1
The relationship between the current density and the electromotive force of the battery is shown when the content is 00 ppm. The current density is 600 to 700 m even when 5 ppm of carbon monoxide is contained in hydrogen gas.
It can be seen that when A / cm ² or more, the battery electromotive force is remarkably reduced. Furthermore, if gas other than hydrogen gas such as carbon dioxide and water vapor is mixed in the fuel gas, the power generation efficiency of the fuel cell may be reduced. Therefore, an object of the present invention is to improve the hydrogen gas concentration in the fuel gas by removing impurities such as carbon monoxide contained in the fuel gas supplied to the negative electrode of the fuel cell. As described above, this effect is particularly exerted in the polymer electrolyte fuel cell using the ion exchange membrane as the electrolyte.

[0007]

According to the present invention, there are provided a fuel reaction device for converting a raw fuel into a fuel gas rich in hydrogen gas by a catalytic reaction, and a fuel cell for supplying power to the negative electrode to generate electric power. In the fuel cell system having the fuel gas, the fuel gas permeates the hydrogen gas separator and is purified to be purified hydrogen gas, which is supplied to the negative electrode. The hydrogen gas separator is a porous support through which gas molecules can enter. And a gas separation membrane covering the support, wherein the gas separation membrane is capable of dissolving hydrogen gas and is composed of an alloy containing palladium. It

In the present invention, the negative electrode preferably contains platinum as a catalyst for the negative electrode reaction for converting hydrogen into hydrogen ions. Further, it is preferable that the hydrogen gas separator is disposed inside a hydrogen purifier, and the hydrogen purifier separates the fuel gas into the purified hydrogen gas and a second gas other than the purified hydrogen gas. Further, the raw fuel is a hydrocarbon, and the fuel reactor has a reformer that produces a reformed gas containing hydrogen and carbon monoxide from the hydrocarbon, and the reformed gas is the hydrogen gas. It is preferably fed to the separator. At this time, the second gas separated by the hydrogen purifier can be used as fuel for heating the reformer after removing the steam. Further, the raw fuel is a hydrocarbon, and the fuel reactor is supplied with a reformer that produces a reformed gas containing hydrogen and carbon monoxide from the hydrocarbon, and the reformed gas is supplied to the reformer. And a carbon monoxide shifter for converting the carbon monoxide of the natural gas by shift reaction into hydrogen gas and carbon dioxide to generate a shift gas, and the shift gas is supplied to the hydrogen gas separator. It is preferable. Further, the raw fuel is an alcohol that is a liquid at room temperature, the fuel reactor has a reformer for producing a reformed gas containing hydrogen gas, carbon monoxide and carbon dioxide from alcohol, Reforming gas is preferably supplied to the hydrogen gas separator. Furthermore, the fuel reactor has a reformer for producing a reformed gas containing at least hydrogen gas and carbon monoxide from the raw fuel, and the hydrogen gas separator is provided inside the reformer. Are preferably arranged. Further, carbon monoxide may be generated together with hydrogen gas by the catalytic reaction, and the concentration of carbon monoxide contained in the purified hydrogen gas may be 1000 ppm or less of the capacity of the purified hydrogen gas. Furthermore, it is preferable that the fuel cell uses an ion exchange membrane as an electrolyte.

[0009]

According to the fuel cell system of the present invention, since the hydrogen gas separator is provided between the fuel reaction device and the fuel cell, the fuel gas rich in hydrogen gas obtained in the fuel reaction device is generated. The hydrogen gas is permeated through the hydrogen gas separator to be purified, and the hydrogen gas is purified, that is, impurities such as carbon monoxide are removed, and then the hydrogen gas is supplied to the negative electrode of the fuel cell. It becomes a catalyst poison of the platinum catalyst of the electrode and a small amount of carbon monoxide contained in the fuel gas can be removed, and the power generation efficiency of the fuel cell is improved. Further, since the purity of hydrogen gas in the fuel gas is increased, the power generation efficiency of the fuel cell is improved.

[0010]

EXAMPLE FIG. 4 shows the basic configuration of a fuel cell system with an AC load. The fuel cell system includes a fuel reaction device 32 that converts a raw fuel 31 such as hydrocarbon or alcohol into a fuel gas 33 rich in hydrogen gas, and a hydrogen gas contained in the fuel gas 33 and an oxygen gas or oxygen in the air. A fuel cell 34 that chemically reacts to generate DC power 35, and an orthogonal converter 36 that converts the DC power 35 into AC power 37.
And a control device 38 for controlling the fuel reaction device 32, the fuel cell 34, and the orthogonal transformation device 36. The DC power 35 from the fuel cell is converted into AC power 3 by the orthogonal converter 36.
Since it is converted into 7 and supplied to the load, it is possible to absorb a sudden change in the output voltage on the load side and keep the AC output voltage constant. On the other hand, in the case of a DC load, DC power can be directly supplied to the load without using the orthogonal transformation device 36. Next, as elements corresponding to the fuel reactor 32 and the fuel cell 34 of FIG. 4, when a hydrocarbon-based raw fuel such as natural gas, liquefied natural gas (LPG) or naphtha is used, and when alcohol such as methanol is used. It will be explained separately at times.

FIG. 1 is a system diagram showing an embodiment of the fuel cell system of the present invention when using a hydrocarbon-based raw fuel. In this example, a fuel reactor for converting a raw fuel into a fuel gas rich in hydrogen gas by a catalytic reaction is
The reformer 4, the heating furnace 6, the heat exchanger 10, the water separator 12, and the hydrogen purifier 14 are provided as elements. The reformer 4 converts the raw fuel of hydrocarbon by the steam reforming reaction (1).
Reforming into a reformed gas containing carbon monoxide and hydrogen. This steam reforming reaction is performed inside the reforming reaction tube 4a provided inside the reformer 4, and has a catalyst layer that catalyzes the steam reforming reaction (1) inside the reaction tube 4a. Reaction tube 4a
Is heated by the heating furnace 6, and the reaction heat necessary for the reaction (1) is supplied. The reaction tube 4a is preferably connected to the temperature sensor 4b so that the temperature of the reaction tube can be monitored. Usually, the water vapor is in excess of the hydrocarbon.

The raw fuel such as natural gas in a storage tank (not shown) is a raw fuel supply device 1 for supplying the raw fuel.
Is connected to the inside of the reforming reaction tube 4a provided inside the reformer 4 via the supply valve 1a. Further, the steam supply device 2 for supplying steam is connected to the inside of the reforming reaction pipe 4a via the supply valve 2a. When the raw fuel contains sulfur, it is preferable to remove the sulfur in the desulfurization reactor and then supply it to the reformer 4. When the raw fuel is not gas but liquid or solid, it can be supplied to the reformer 4 after being made into gas by the vaporizer.

The heating furnace 6 is equipped with a burner, in which the residual hydrogen contained in the exhaust gas of the negative electrode of the fuel cell is supplied through the fuel supply line 25 and becomes a fuel. Further, when starting the fuel cell system, a part of the raw fuel can be used as the fuel for the burner. Air taken in by an air blower (not shown) is supplied from the air supply line 7. Although not shown, the exhaust gas burned in the heating furnace 6 and the exhaust gas from the air electrode 16b can join together and be released into the atmosphere from the exhaust tower.

The hydrogen gas-rich fuel gas obtained in the reformer 4 is purified by a hydrogen purifier 14 having a hydrogen gas separator inside. The hydrogen purity of the fuel gas is, for example, 99
It can be made to be not less than volume% and the monoxide concentration of the fuel gas can be made to be 1000 ppm (volume) or less. Further, the hydrogen purity of the fuel gas can be made 99.5% by volume or more. The concentration of carbon monoxide that may be contained in this purified hydrogen gas depends on the type of electrolyte and the electrode of the fuel cell. For example, when the fuel cell is an ion exchange membrane type, the concentration of carbon monoxide contained in the purified hydrogen gas is preferably 100 ppm or less, more preferably 50 ppm or less. The hydrogen purifier will be described later. The hydrogen gas separator has a carbon monoxide concentration of 100 ppm or less, or
It is known that the content can be 10 ppm or less. The hydrogen gas separator will be described later.

On the other hand, the gases removed in the hydrogen purifier 14 include steam, carbon monoxide, unreacted hydrocarbons in the steam reforming reaction (1), untreated hydrogen in the hydrogen gas separator, and the like.
From these mixed gases, the heat exchanger 10 and the water separator 1
2, the water vapor is condensed and separated. Water separator 1
The steam separated into 2 can be supplied to the reformer 4 through a recycle line 21 equipped with a circulation blower 20. On the other hand, gases other than water vapor separated in the hydrogen separator 12, that is, carbon monoxide, unreacted hydrocarbons, untreated hydrogen, etc., are supplied to the heating furnace 6 by a line 23 equipped with a blower 22. ,
Carbon monoxide, hydrocarbons, and hydrogen can be used as fuel for the heating furnace. At this time, it is preferable to use a catalyst for a reaction in which carbon monoxide is oxidized.

The fuel gas rich in hydrogen gas purified by the hydrogen purifier 14, that is, the purified hydrogen gas, is fed through the purified hydrogen gas line 15 to the fuel electrode 16a which is the negative electrode of the fuel cell 16.
As fuel. When the reaction temperature in the hydrogen purifier 14 is high and the operating temperature of the fuel cell 16 is lower than this, a heat exchanger can be provided in the purified hydrogen gas line 15. On the other hand, the air electrode 1 which is the positive electrode of the fuel cell 16
Air taken in by an air blower (not shown) is supplied to 6b from an air supply line 17. Fuel pole 1
A part of the exhaust fuel gas discharged from 6a is recirculated to the inlet of the fuel electrode through the fuel electrode circulation blower 18, and the remaining exhaust fuel gas is provided in the heating furnace 6 by the fuel supply line 25. Used as combustion fuel for burners. From the outlet of the air electrode, water vapor produced by the electrochemical reaction can be cooled and recovered by the anode outlet gas cooler 24 and supplied to the reformer 4 by a line 27 equipped with a blower 26. Except for water vapor, it can be discharged as an exhaust gas to the outside of the fuel cell system.

The fuel cell 16 is provided with a matrix serving as an electrolyte sandwiched between the positive electrode 16b and the negative electrode 16a, but the matrix is omitted in FIG. When the matrix is phosphoric acid, the operating temperature of the fuel cell is 170 to 220 ° C., so that the fuel gas supplied to the fuel electrode 16a is also preferably in this temperature range.
Further, in order to maintain the operating temperature of the fuel cell 16, it is preferable that the fuel cell 16 be provided with a cooling system. The fuel cell system is provided with a nitrogen gas system (not shown) in order to replace the fuel gas with nitrogen gas when the fuel cell system is stopped. In this fuel cell system, the fuel gas in the reforming pipe 4a of the reformer 4 is, for example, about 600 ° C., and in the hydrogen purifier 14, the fuel gas is within the operating temperature range of the hydrogen gas separator 500. ~ 600 ℃
become. There is no need to adjust the temperature between the reformer 4 and the hydrogen purifier 14 using a heat exchanger or the like. The hydrogen purifier 14
It is preferable that, if necessary, a compressor is provided so that the pressure can be increased to a pressure necessary for the hydrogen purification reaction, for example, 5 to 10 atm. Hydrogen purifier 14
A heat exchanger between the fuel cell and the fuel cell
The temperature of the purified hydrogen gas supplied to the fuel cell 16 is adjusted to the operating temperature of the fuel cell.

FIG. 2 is a system diagram showing an embodiment of the fuel cell system of the present invention when carbon monoxide generated in the reformer is treated by using the shift converter 8. This system system diagram is basically the same as that of FIG. 1, and the elements having basically the same effect as the elements shown in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. The reformed gas obtained in the reformer 4 is connected to the carbon monoxide shift converter 8 to convert carbon monoxide into hydrogen by the above shift reaction (2) to increase the hydrogen gas concentration of the fuel gas, It is supplied to the hydrogen purifier 14.

The fuel gas refined by the hydrogen purifier 14 is
The purified hydrogen gas line 15 supplies the fuel to the fuel electrode 16a, which is the negative electrode of the fuel cell 16, as fuel. On the other hand, the gas removed in the hydrogen purifier 14 is, for example, steam, carbon monoxide that has not reacted in the shift reaction (2), and the shift reaction (2).
Although there are carbon dioxide generated in step 1 and untreated hydrogen in the hydrogen gas separator, unreacted water vapor is condensed and separated from these gases by the heat exchanger 10 and the water separator 12. The steam obtained in the water separator 12 is used as the circulation blower 2
It can be supplied to the reformer 4 in a recycle line 21 equipped with zero. On the other hand, in the hydrogen separator 12, a small amount of carbon monoxide, carbon dioxide, etc. other than water vapor can be supplied to the shift converter 8 through a line 23 equipped with a blower 22, for example. These may be supplied to the reformer 4 instead of the transformer 8.
It may also be released outside the fuel cell system. Particularly, it is preferable to release carbon dioxide to the outside of the system.

FIG. 3 is a system diagram showing an embodiment of the fuel cell system of the present invention when alcohol such as methanol is used as a raw fuel. In this embodiment, the fuel reactor for converting the raw fuel into the fuel gas rich in hydrogen gas by the catalytic reaction is a vaporizer 3, a reformer 4, and a heating furnace 6.
, Heat exchanger 10, moisture separator 12, and hydrogen purifier 1
4 and. This system system diagram is basically the same as that of FIG. 1, and portions that exhibit basically the same effect as the technique shown in FIG. 1 are designated by the same reference numerals and description thereof will be omitted. The blower 26 and the line 27 are connected to the vaporization chamber 3a of the vaporizer 3 from the air electrode 16b of the fuel cell 16, but they are omitted because they are complicated.

A vaporizer 3 for vaporizing a mixture of water and alcohol as a raw fuel may be provided before the reformer 4. Since this mixture is generally a liquid, the gas in the mixture improves the reactivity in the reformer 4. However, the vaporizer 3 is not always an essential element, and this mixture can be directly supplied to the reformer 4. The vaporizer 3 is a heat exchanger divided into two chambers, and the mixed liquid is supplied to the vaporization chamber 3a which is one chamber, and the vaporization chamber 3a
The vaporized gas is guided to the reformer 4 from the outlet of a. The other refrigerant chamber 3b cools the fuel cell 16 and is connected to a refrigerant system 29 having a pump 28.

The gas vaporized by the vaporizer 3 is introduced into a reformer 4 for reforming into a gas rich in hydrogen gas. The reformer 4 is
In the reaction tube 4a therein, the alcohol decomposition reaction (3) and the shift reaction (4) simultaneously proceed. Therefore, after the reformer 5, no shift converter for the shift reaction is generally required.

In any of the embodiments shown in FIGS. 1 to 3, as the hydrogen purifier 14, for example, Japanese Patent Application No.
The hydrogen gas separation device described in 34407 can be used. FIG. 5 shows a sectional view of the hydrogen purifier according to FIG. 5, and FIG. 6 shows a partially enlarged view thereof. A plurality of cylindrical hydrogen gas separators 41 are housed in the high-pressure container 40. Each of the hydrogen gas separators 41 is attached to the flange 42 with the hydrogen gas separator 41.
Through a through hole 42a having a diameter slightly larger than the outer diameter of
The inside of the hydrogen gas separator is supported so as to communicate with the upper space of the flange 42. On the other hand, each hydrogen gas separator 41 has a hole 43a that does not penetrate the flange 43.
Due to this, the end portion is sealed and supported. The hydrogen gas separator 41 is made of an inorganic adhesive such as cement and used for the flange 4
Bond with 2, 43. In the hydrogen gas separator, a tubular support is covered with a gas separation membrane.

The flanges 48 and 49 correspond to the support plate 4
7, the flange 42 is fixed by the support plate 47 and the member 46, and the hydrogen gas separator 41 and the flange 43 are suspended. Fuel gas to be purified is supplied into the high-pressure vessel 40 from the first pipe 50 connected to the reformer 4 of FIG. 1, the shift converter 8 of FIG. 2 or the reformer 4 of FIG. After passing through the cylindrical hydrogen gas separator 41, the purified hydrogen gas moves to the inside of the cylinder, and the purified hydrogen gas is
It is guided to the third pipe 52 connected to the purified hydrogen gas line 15. On the other hand, the unrefined fuel gas flows out from the second pipe 51 connected to the heat exchanger 10. The fuel gas to be purified is, for example, at a temperature of 400 to 600 ° C.
It is preferably 10 atm.

In any of the embodiments shown in FIGS. 1, 2 and 3, the hydrogen purifier 14 includes a heat exchanger 10 and a water separator 1.
It is arranged in the upper two rows. However, the heat exchanger 10 and the water separator 12 may be arranged between the hydrogen purifier 14 and the fuel cell 16. That is, in FIG. 1 and FIG. 3, the reformed gas generated in the reformer 4 has steam removed by the heat exchanger 10 and the water separator 12, and then the hydrogen purifier 14
May be further purified and sent to the fuel electrode 16a of the fuel cell 16. In FIG. 2, the fuel gas generated in the shift converter 8 has its water vapor removed in the heat exchanger 10 and the water separator 12, and the hydrogen purifier 14 having a hydrogen gas separator inside is removed.
May be further purified and sent to the fuel electrode 16a of the fuel cell 16.

In the above embodiments, the hydrogen purifier provided with the hydrogen gas separator is one element incorporated in the fuel cell system. However, in the present invention, the hydrogen gas separator includes the reformer 4, the carbon monoxide shift converter 8, and the heat exchanger 10.
Also, it may be used by being incorporated in an element of a system for supplying fuel gas to the fuel cell such as the water separator 12. Reformer 4
Alternatively, a hydrogen gas separator may be arranged inside the carbon monoxide shift converter 8. Thereby, the reaction formulas (1), (2),
The hydrogen gas generated on the right side of (3) or (4) is released from these reactors via the hydrogen gas separator, and is outside the system composed of the generation system on the right side and the reaction system on the left side in these reaction equations. Removed from. Therefore, chemical reaction (1)
The equilibrium of (4) moves to the right side, and the production of hydrogen gas is promoted like a membrane reactor. Further, a hydrogen gas separator may be provided inside the moisture separator, and purified hydrogen gas purified by the hydrogen gas separator may be supplied from the moisture separator to the fuel cell. Further, the present invention may incorporate hydrogen gas separators in the pipes that mechanically connect these elements.

In the present invention, the hydrogen gas separator has a porous support through which gas molecules can penetrate, and a gas separation membrane covering the support, and the gas separation membrane has hydrogen gas dissolved therein. It can be composed of an alloy containing palladium. As the palladium or palladium alloy forming the gas separation membrane, a known one that solid-dissolves and permeates hydrogen gas is used. Japanese Membrane Science, 56 (1991) 315-32
5: "Hydrogen Permeable Palladium-Silver Alloy Mem
brane Supported on Porous Ceramics "and JP-A-63-
As described in JP-A-295402, the content of metals other than palladium is preferably 10 to 30% by weight. The main purpose of alloying palladium is to prevent hydrogen embrittlement of palladium and to improve separation efficiency at high temperatures.
Further, it is preferable to contain silver as a metal other than palladium in order to prevent hydrogen embrittlement of palladium.

Further, as described in JP-A-3-146122, in a thin film containing palladium and silver, the concentration of silver components is relatively evenly distributed in the thickness direction of the thin film. Any thing can be used. Japanese Patent Laid-Open No. 3-14
No. 6122 discloses that a palladium thin film is formed on the surface of a heat resistant porous support by a chemical plating method, a silver thin film is formed on the palladium thin film by a chemical plating method, and then,
Disclosed is a method of manufacturing a hydrogen gas separator that is heat-treated. In this manufacturing method, palladium and silver are uniformly distributed in the palladium alloy thin film by heat treatment. The thickness of the gas separation membrane is preferably 50 μm or less, more preferably 20 μm or less. When the thickness is more than 50 μm, the time required for the fuel gas to diffuse through the gas separation membrane during gas separation by the gas separator becomes long, which is not preferable because the processing time becomes long. When the support has a tubular shape, the surface covered with the gas separation membrane may be the outside, the inside, or both of the inside of the tube.

The support of the hydrogen gas separator supports the palladium thin film because the palladium thin film alone has a weak mechanical strength. The support is porous so that gas molecules can penetrate therein, and has, for example, a large number of minute pores that are three-dimensionally continuous. The pore size is preferably 0.003 to 20 μm, more preferably 0.005 to 5 μm, and
0.01 to 1 μm is preferable. This is because when the pore size is less than 0.003 μm, the resistance when the gas passes increases. On the other hand, if the pore size exceeds 20 μm, pinholes are likely to occur in the gas separation membrane, which is not preferable. Such a porous support is disclosed, for example, in JP-A-62-173030.
It can be obtained by the method described in the publication. The material forming the support is preferably one in which fuel gas does not react, and specifically, alumina, silica,
In addition to ceramics such as silica-alumina, mullite, cordierite and zirconia, ceramics such as carbon and porous glass can be used. Also,
The material forming the support is not limited to ceramics, and a metal that does not react with the fuel gas and palladium and is porous can be used.

Further, Japanese Patent Application No. 5-73 filed by the present applicant.
No. 449 discloses a hydrogen gas separator in which a gas separation membrane made of a palladium alloy fills and closes the inside of small holes that are open on the surface of a support. In this hydrogen gas separator, the raw material gas leaks to the purified hydrogen gas from the hole penetrating the gas separation membrane, and it is difficult to deteriorate the purity of the purified hydrogen gas. 10
It can be 0 ppm or less, and can be even 10 ppm or less. Therefore, when the hydrogen gas separator that fills / blocks the inside of this small hole is used in the above-mentioned hydrogen purifier or shift converter, it is difficult for gas to leak through the seal between the hydrogen purifier or shift converter and the hydrogen gas separator. Thus, the concentration of carbon monoxide in the purified hydrogen gas can be 100 ppm or less, and even 10 ppm or less.

FIG. 7 is a sectional view for explaining the structure of the electrolyte and the electrodes in the solid polymer electrolyte fuel cell. Electrodes are bonded to both sides of the ion exchange membrane 71 which is an electrolyte,
In FIG. 7, only one electrode is shown. The electrode is a carbon support 7
2 and a catalyst layer covering the surface of the carbon support 72, the catalyst layer comprising platinum particles 74 acting as a catalyst,
Polymer film 73 capable of conducting hydrogen ions
Consists of. As the material of the ion exchange membrane 71 and the material of the polymer film 73, for example, the above-mentioned perfluorocarbon sulfonic acid membrane can be used. The platinum particles 74 can come into contact with the gas supplied to the electrodes due to the gap between the opposing polymer films 73. The gas supplied to the electrodes through this gap can contact the surface of the ion exchange membrane 71. Moreover, the platinum particles 74 can conduct hydrogen ions through the platinum ion exchange membrane 71 and the hydrogen ion conductive polymer film 73.

[0032]

In the fuel cell system of the present invention, the fuel gas is purified by the hydrogen gas separator before it is supplied to the fuel cell, so that the hydrogen concentration of the fuel gas is increased and the catalyst poison of the electrode of the fuel cell is increased. The carbon monoxide is removed to improve the power generation efficiency of the fuel cell.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of a fuel cell system of the present invention.

FIG. 2 is a system diagram showing an embodiment of the fuel cell system of the present invention.

FIG. 3 is a system diagram showing an embodiment of the fuel cell system of the present invention.

FIG. 4 is a system diagram showing the basic configuration of a fuel cell system.

FIG. 5 is a cross-sectional view illustrating a hydrogen purifier that can be used in the fuel cell system of the present invention.

FIG. 6 is a cross-sectional view illustrating a part of FIG. 5 in an enlarged manner.

FIG. 7 is a cross-sectional view illustrating the configurations of an electrolyte and electrodes in a solid polymer electrolyte fuel cell.

FIG. 8 is a diagram showing a relationship between current density and cell electromotive force when carbon monoxide in hydrogen gas supplied to a solid polymer electrolyte fuel cell changes.

[Explanation of symbols]

1 ... Raw fuel supply device, 1a ... Supply valve, 2 ... Steam supply device, 2a ... Supply valve, 3 ... Vaporizer, 3a ... Vaporization chamber, 3b ... Refrigerant Chamber, 4 ... reformer, 4a ... reforming reaction tube, 4b ... temperature sensor, 6 ... heating furnace, 8 ... carbon monoxide shifter, 10 ... exchanger, 12 ... Water separator, 14 ...
-Hydrogen refiner, 15 ... Purified hydrogen line, 16 ... Fuel cell, 16a ... Fuel electrode, 16b ... Air electrode, 16c ... Cooling chamber, 17 ... Air supply line, 18 ... Fuel electrode circulation blower, 20 ... Circulation blower, 21 ... Recycle line, 2
2 ... Blower, 23 ... Line, 24 ... Anode outlet gas cooler, 25 ... Fuel supply line, 26 ... Blower, 27 ...
・ Line, 28 ... Pump, 29 ... Refrigerant system, 31 ... Raw fuel, 32 ... Fuel reactor, 33 ... Fuel gas, 34 ...
Fuel cell, 35 ... DC power, 36 ... Orthogonal converter, 3
7 ... AC power, 38 ... Control device, 40 ... High-pressure container, 41 ... Hydrogen gas separator 42, 43 ... Flange,
42a ... Through hole, 43a ... Hole, 48, 49 ... Flange, 50 ... First pipe, 51 ... Second pipe, 52 ...
Third pipe, 71 ... Ion exchange membrane, 72 ... Carbon support,
73 ... Polymer film, 74 ... Platinum particles

Claims (8)

[Claims] 1. A fuel cell system comprising a fuel reaction device for converting a raw fuel into a fuel gas rich in hydrogen gas by a catalytic reaction, and a fuel cell in which the fuel gas is supplied to a negative electrode to generate electricity. Is permeated through the hydrogen gas separator to be purified, and is supplied to the negative electrode as purified hydrogen gas, and the hydrogen gas separator is a porous support through which gas molecules can penetrate and the support. A fuel cell system comprising: a gas separation membrane for coating; the gas separation membrane being capable of dissolving hydrogen gas, and being composed of an alloy containing palladium. 2. The fuel cell system according to claim 1, wherein the negative electrode contains platinum as a catalyst for a negative electrode reaction for converting hydrogen into hydrogen ions. 3. The hydrogen gas separator is arranged inside a hydrogen purifier, and the hydrogen purifier separates the fuel gas into the purified hydrogen gas and a second gas other than the purified hydrogen gas. The fuel cell system according to claim 1. 4. The raw fuel is a hydrocarbon, and the fuel reactor has a reformer for producing a reformed gas containing hydrogen and carbon monoxide from the hydrocarbon. Gas is supplied to the said gas separator, The fuel cell system of Claim 1, 2 or 3 characterized by the above-mentioned. 5. The raw fuel is a hydrocarbon, and the fuel reactor includes a reformer for producing a reformed gas containing hydrogen and carbon monoxide from the hydrocarbon, and the reformed gas is And a carbon monoxide shift converter which is supplied to convert the carbon monoxide of the reformed gas into hydrogen gas and carbon dioxide by a shift reaction to generate a shift gas, wherein the shift gas is The fuel cell system according to claim 1, 2 or 3, wherein the fuel cell system is supplied to a hydrogen gas separator. 6. The reformer in which the raw fuel is an alcohol which is a liquid at room temperature, and the fuel reaction device produces a reformed gas containing hydrogen gas, carbon monoxide and carbon dioxide from the alcohol. The fuel cell system according to claim 1, wherein the reformed gas is supplied to the hydrogen gas separator. 7. The fuel reactor includes a reformer for producing a reformed gas containing at least hydrogen gas and carbon monoxide from the raw fuel, and the hydrogen gas is provided inside the reformer. The fuel cell system according to claim 1 or 2, wherein a separator is arranged. 8. The fuel cell system according to claim 1, wherein the fuel cell is a polymer electrolyte fuel cell.