JP2000090951A - On-vehicle fuel cell power generating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an on-vehicle fuel cell power generating device having extremely high public interest and popularity. SOLUTION: This device has a reformed material storage means for storing a reformed material, a reforming means for reforming the reformed material to a hydrogen-rich reformed gas, an oxygen supply means for making the reformed gas into a mixed gas containing a small amount of oxygen, a carbon monoxide removal means for causing a mixed gas to come in contact with an oxidizing reaction catalyst in a temperature zone between -30 deg.C and 120 deg.C in a mixed gas flow passage and removing carbon monoxide contained in the reformed gas, and an electric power output means for outputting electric power upon receipt of the reforming gas reduced in carbon monoxide concentration to 10 ppm or less with the carbon monoxide removal means and an oxidant gas. Furthermore, the device has a means for controlling a gas flowrate, oxidizing reaction temperature, and cell reaction temperature for the stable performance of the above-mentioned means, and a means for controlling oxidizing reaction and cell reaction via the detection of a gas component.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an on-vehicle fuel cell power generator, and more particularly to a suitable solid polymer electrolyte fuel cell (PEFC) power generator mounted on an electric vehicle.

[0002]

2. Description of the Related Art In recent years, from the viewpoint of protecting the global environment, a gasoline engine or the like, which is a source of harmful gas, is not used as a driving source.
An electric vehicle that drives a vehicle with clean electric power has attracted attention. Assuming that it is installed in an electric vehicle, the fuel cell power generator does not use a hydrogen cylinder,
A liquid fuel such as a hydrocarbon or alcohol is used as a raw material, which is introduced into a fuel reformer to generate a hydrogen-rich reformed gas, and this reformed gas is supplied to the hydrogen electrode of the fuel cell. It is desirable to do. As a fuel cell, it is optimal to use a solid polymer electrolyte fuel cell (PEFC) having a small size and excellent energy efficiency, and there are many known proposals similar to this. Also, from the viewpoint of publicity and popularization, the characteristics of an in-vehicle fuel cell power generator should have no troubles such as replacement and repair, function stably for a long time, and depend on the region and season. It is also important that there is no change in the function with respect to the temperature change, and from the viewpoint of energy saving, it is strongly desired that the fuel cell power generation device itself be simple and lightweight.

[0003] However, the fuel cell power generator for vehicles currently proposed still has many problems that must be solved in order to satisfy the above demands. Here are some examples. PEF
The operating temperature of C is from ordinary temperature to about 130 ° C., and generally about 100 ° C. Therefore, the catalyst used for accelerating the battery reaction (in general, a Pt-based catalyst is used) also functions in a similar temperature range. However, the reformed gas used as a raw material usually contains several percent of carbon monoxide, and even if the production method of the reformed gas is devised in a complicated manner, the carbon monoxide content can be reduced to about 1%. However, it is practically the limit. Since carbon monoxide poisons the Pt catalyst, and particularly in the above-mentioned temperature range, due to the remarkable poisoning effect, the promotion of the battery reaction becomes instantly impossible, and a method for avoiding this must be taken. One possible method is to make the use temperature of the Pt catalyst extremely high. However, this is impractical from the viewpoint of the long-term heat resistance of the solid polymer electrolyte used in the PEFC.

[0004] Another example is a method in which carbon monoxide in a reformed gas is removed in advance and supplied to a fuel cell. In this case, carbon monoxide in the reformed gas needs to be 100 ppm or less, and from the viewpoint of catalyst life, it is preferably 1 ppm.
It is necessary to reduce it to 0 ppm or less. However, in order to remove carbon monoxide to such a low concentration, carbon monoxide in the reformed gas is generally selectively oxidized and removed using a noble metal-based catalyst, but this reaction also uses a temperature region exceeding 100 ° C. are doing. Therefore, the temperature of the reformed gas supplied to the oxidation reaction is required to be close to 100 ° C. or higher. In particular, in the initial drive of the fuel cell power generator in a cold region, extra operation such as preheating of the oxidation reaction zone is required. Need. In addition, the oxidation reaction and the cell reaction are exothermic reactions, and if the oxidation reaction temperature is high, the fuel cell device repeatedly stores heat and cannot maintain a suitable operating temperature, so that a complicated cooling system is sometimes required. Is done.

In short, in the prior art, the fuel cell power generator for a vehicle is generally held in a narrow temperature range as a fuel cell power generator in order to satisfy the stability and long life required for its public nature and widespread use. Need and need various heating, cooling devices and systems for such holding,
On the contrary, it can be considered that simplification and weight reduction which are other required performances are difficult.

[0006]

SUMMARY OF THE INVENTION From the viewpoint of publicity and widespread use, an on-vehicle fuel cell power generator does not require replacement, repair, and the like, functions stably for a long period of time, and has a temperature depending on the region and season. A function such as no change in function is required for the change. Further, from the viewpoint of energy saving, it is strongly desired that the fuel cell power generation device itself be simple and lightweight. An object of the present invention is to provide an on-vehicle fuel cell device that meets such a demand.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and have obtained the following findings.
The present invention has been reached. That is, the present invention provides a reforming raw material storing means for storing a reforming raw material, a reforming means for converting a reforming raw material supplied from the reforming raw material storage means into a hydrogen-rich reformed gas by a reforming reaction, An oxygen supply means for mixing a gas containing oxygen into the reformed gas to form a mixed gas containing a small amount of oxygen, and an oxidation reaction of the mixed gas in a temperature range of -30 ° C to 120 ° C in the flow path of the mixed gas. Contact with the catalyst to reduce the concentration of carbon monoxide in the reformed gas to 10
a carbon monoxide removing means for reducing the carbon monoxide concentration to 10 ppm or less, and a reformed gas and an oxidizing gas whose carbon monoxide concentration is reduced to 10 ppm or less are supplied to cause a battery reaction, thereby reducing electric power. Means for outputting, means for controlling the gas flow rate, oxidation reaction temperature, and battery reaction temperature as necessary for these means to function stably, and oxidation and battery reaction by detecting gas components as necessary. , A vehicle fuel cell power generator.

By setting the temperature zone of the oxidation reaction of the present invention,
In-vehicle fuel cell power generators are less susceptible to temperature changes due to local and climatic conditions.
By supplying the reformed gas reduced to less than ppm to the fuel cell, the durability and life of the fuel cell itself are improved, and by making full use of other components of the present invention, the on-vehicle fuel cell power generator Publicity and spreadability can be satisfied, and the entire device can be simplified and lightened, and can have excellent functions from the viewpoint of energy saving.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The cell reaction in the present invention is preferably initiated by a solid polymer electrolyte fuel cell (PEFC). The reforming raw material in the present invention refers to hydrocarbons such as methane and propane, and alcohols such as methanol. The reforming means for converting the reforming raw material into a hydrogen-rich reformed gas by a reforming reaction is generally referred to as steam reforming. In some cases, the concentration of carbon monoxide is suppressed to about 1% by volume. , A shift reaction, a shift reaction, and the like.

In the present invention, a gas containing oxygen is mixed into a hydrogen-rich reformed gas obtained by a reforming reaction to form a mixed gas containing a small amount of oxygen. In the temperature zone, the channel is brought into contact with the oxidation reaction catalyst. By setting such a wide temperature range and controlling it as necessary, it is possible to make it less susceptible to changes in temperature due to local or climatic conditions. In this case, no control is required in some cases, and a simple device as a whole can be provided. Considering the operability of PEFC, minimization of heating and cooling devices, a more preferable temperature range is -20 ° C to 90 ° C.
It is.

The oxygen-containing gas is usually pure oxygen,
Air or oxygen-enriched air is preferably used. The added amount of the gas containing oxygen is oxygen / carbon monoxide (molar ratio).
Is preferably 0.5 to 5, more preferably 0.6 to
3, most preferably 0.7-2. If this ratio is small, the removal rate of carbon monoxide will be low,
If it is large, the consumption of hydrogen becomes too large, which is not preferable.
It is effective to mix the oxygen-containing gas continuously or batchwise since the amount of addition can be reduced.

The oxidation reaction catalyst used in the present invention may be any catalyst capable of reducing the amount of carbon monoxide in the reformed gas in the above-mentioned temperature range to 10 ppm or less within a practical space treatment rate. Specifically, a catalyst mainly containing ruthenium metal is preferably used. In order to sufficiently increase the catalytic ability, it is also useful to use, as the oxidation reaction catalyst, a catalyst mainly containing ruthenium metal substantially containing no halogen. In the present invention, the phrase "substantially free of halogen" means that the amount of increase in halogen is preferably 100 ppm or less at the stage of preparing a catalyst supporting ruthenium on a carrier. More preferably, it is 50 ppm or less. Most preferably, it is 30 ppm or less. Normal,
Some industrially used carriers contain tens of ppm of halogen, but the effect of the halogen in the carrier is small.

As a more specific oxidation reaction catalyst, ruthenium metal having an adsorption amount of carbon monoxide of 1 mmol / g.ruthenium or more and an adsorption index of carbon monoxide defined below of 0.5 or more is used. The use of a catalyst as a main component gives favorable results. Adsorption index = ΔX ₁ / ΔX = ΔX ₁ / (ΔX ₁ + ΔX ₂ ) where A = introduced amount of carbon monoxide / pulse = 0.002 mmol / pulse = 0.4 mmol / g ruthenium / pulse X = per pulse of X when the adsorption amount adsorbed amount = .SIGMA.X B = reversible adsorption (X + B) /A≧0.9 and X _1, (X +
The X at the time of B) / A <0.9 and X _2.

The adsorption index of carbon monoxide defined above will be described with reference to FIG. FIG. 1 is an example in which the amount of carbon monoxide detected for each pulse is graphed. A indicates the detected amount of carbon monoxide when the catalyst is not charged, that is, the introduced amount of carbon monoxide per pulse (0.002 mmol / pulse, 0.4 mmol / g ruthenium / pulse). X indicates the amount of adsorbed carbon monoxide that changes with each pulse. B is the difference between the elution amount and A when the adsorption of carbon monoxide to the catalyst is saturated and the elution amount of carbon monoxide becomes constant, that is,
Shows the amount of reversible adsorption. The adsorption amount of carbon monoxide is represented by the sum of the adsorption amount X per pulse ΔX. Of adsorption X per pulse, (X + B) is the X ₁ when more than 0.9 A, (X + B) is When X ₂ when less than 0.9 A, the adsorption of carbon monoxide The index is expressed by the sum of X ₁ ΣX ₁ and the amount of adsorption, that is, the ratio of X to the sum ΣX. This Σ
X is the sum of the sum of X ₁ ΣX ₁ and the sum of X ₂ ΣX ₂ .

Further, the oxidation reaction catalyst used in the present invention is preferably used as a supported catalyst in which the above-mentioned ruthenium metal is supported on a carrier. The carrier may be any one that is generally used as a carrier. For example, alumina, silica alumina, silica gel, molecular sieve 3
A, ZSM-5, zeolite-X, zeolite-Y, zeolite represented by zeolite-β, mesoporous zeolite represented by MCM-41, zirconia, titania, rare earth oxide, calcium, magnesium,
Basic oxides represented by zinc oxide, activated carbon and the like are effective.

Of these carriers, alumina, silica alumina, zeolite, mesopore molecular sieve, zirconia and hafnia are preferably used. More preferably alumina, mesopore molecular sieve, zirconia, hafnia, most preferably mesopore molecular sieve, zirconia,
Hafnia is used. Zirconia and hafnia are also preferably used as a mixture thereof. Further, a carrier made of zirconia or hafnia using a precursor of zirconia or hafnia and having the surface of a carrier such as the above-mentioned alumina or mesopore molecular sieve is preferably used.

Although the shape may be anything, it is also effective to use it as a granular material such as a sphere or a column, or as a molded product represented by a honeycomb or the like. Also, the use of a mesoporous molecular sieve supports a more favorable result. The method of supporting on these carriers is performed by various methods. For example, a precipitation method such as a coprecipitation method, a sol-gel method,
An ion exchange method, an impregnation method and the like are effective. The catalyst supported by these methods reduces ruthenium to metal by a reducing agent. Hydrogen is effective as a reducing agent. Reduction with an organic compound such as formalin or hydrazine is also effective. It is effective that the reduction operation is performed in the gas phase. It is also effective to carry out the reaction in a liquid phase such as in an aqueous solution. The reduction temperature may be such that the ruthenium compound becomes a metal. However, if the temperature is too high, sintering of ruthenium occurs, which is not preferable. This temperature varies depending on the preparation method of the catalyst, but usually from room temperature to about 700 ° C. It is preferably carried out at room temperature to 500 ° C.

In order for the oxidation reaction catalyst to function sufficiently effectively from the beginning of use, the oxidation reaction catalyst is treated in a gas containing hydrogen as a main component prior to use, and then used without being brought into contact with air. That gives very favorable results. Further, in order to easily perform such a process in a fuel cell power generator for a vehicle, a reformed gas before mixing a gas containing oxygen or a hydrogen-rich gas containing no oxygen other than the reformed gas is used. It is practically effective to use an apparatus having a means for bringing it into contact with the oxidation reaction catalyst.
Because of car accidents and aging of structural materials,
If the equipment needs to be repaired or replaced, the oxidation reaction catalyst may be exposed to the atmosphere. In such a case, it is possible to avoid the trouble of treating the oxidation reaction catalyst again in a gas containing hydrogen as a main component. Because. Further, when using a means for bringing a reformed gas before mixing a gas containing oxygen, or a hydrogen-rich gas containing no oxygen other than the reformed gas into contact with an oxidation reaction catalyst, the gas may contain carbon monoxide. In the case where is contained, in order not to poison the Pt-based catalyst which is a catalyst of the battery reaction with carbon monoxide, the apparatus may be provided with a means for preventing such gas from coming into contact with the battery reaction part. It is practically effective.

In the present invention, it is effective to install a carbon monoxide removing device mainly filled with an oxidation reaction catalyst in the flow path of the mixed gas. At the time of filling, an appropriate diluent may be added to avoid pressure loss and prevent catalyst scattering. Further, in the flow path of the mixed gas, a porous diffusion layer is provided in order to disperse the mixed gas immediately before a battery reaction section. The porous diffusion layer supports the oxidation reaction catalyst, It is also effective to have means for reducing carbon monoxide.

Generally, the PEFC is composed of a membrane / electrode assembly (MEA) in which a battery reaction occurs, a battery reaction catalyst layer, and a current collector. Generally, a gas diffuser is installed so that gas is uniformly supplied to the entire surface of the electrode, and a processed carbon block is often used from the viewpoint of thermal conductivity. It is also possible to design such a diffuser to reduce the space velocity of the reformed gas. Therefore, the ability to remove carbon monoxide can be increased by providing a porous diffusion layer as a diffuser and supporting the oxidation reaction catalyst in a portion that comes into contact with the reformed gas. It is more preferable to use in combination with the above-mentioned carbon monoxide removing device. In some cases, it is possible to simplify the entire apparatus without installing the carbon monoxide removing apparatus.

In the present invention, when the content of water vapor in the mixed gas is less than the saturated water vapor pressure at the temperature of the portion where the oxidation reaction catalyst is present, the operation stability of the on-vehicle fuel cell power generator is further improved. The reformed gas produced by reforming the organic compound contains water vapor, but when the temperature of the oxidation reaction catalyst is low, such as during startup, the pressure of the water vapor in the reformed gas that comes into contact with the oxidation reaction catalyst becomes a saturated vapor pressure. In some cases, the vapor pressure may be close to or close to the saturated vapor pressure, and the water vapor may be excessively adsorbed or condensed on the catalyst, and the catalytic activity may be suppressed. The water vapor pressure in the reformed gas is conveniently less than the saturated vapor pressure of the temperature of the oxidation reaction catalyst, preferably less than 50% of the saturated vapor pressure. Therefore, it is desirable that the reformed gas produced by reforming the organic compound be brought into contact with the desiccant before coming into contact with the catalyst of the present invention.

The on-vehicle fuel cell power generator of the present invention may be used alone for power output for driving a car, etc., although the energy capacity is smaller than that of a fuel cell depending on the type of vehicle to be mounted. It can also be used as a hybrid power supply device in combination with a secondary battery having a large value.

[0023]

According to the present invention, the durability and life of the fuel cell are improved, the publicity and spreadability are satisfied, and the fuel cell is simplified, lightened, and has excellent functions from the viewpoint of energy saving. Fuel cell power generation device can be realized.

[Brief description of the drawings]

FIG. 1 is a graph showing the amount of carbon monoxide detected for each pulse.

[Explanation of symbols]

 A Amount of introduced carbon monoxide per pulse B Amount of reversible adsorption X Amount of adsorbed carbon monoxide that changes with each pulse

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01M 8/02 H01M 8/02 R 8/10 8/10 F term (Reference) 5H018 AA06 5H026 AA06 5H027 AA06 BA01 BA16 DD03 KK31 KK41 MM01

Claims (15)

[Claims] 1. A reforming material storage means for storing a reforming material, a reforming means for converting a reforming material supplied from the reforming material storage means into a hydrogen-rich reformed gas by a reforming reaction, An oxygen supply means for mixing a gas containing oxygen into the reformed gas to form a mixed gas containing a small amount of oxygen, and an oxidation reaction of the mixed gas in a temperature range of -30 ° C to 120 ° C in the flow path of the mixed gas. A carbon monoxide removing means for contacting the catalyst and reducing the concentration of carbon monoxide contained in the reformed gas to 10 ppm or less; and a reformed gas wherein the carbon monoxide concentration is reduced to 10 ppm or less by the carbon monoxide removing means. And a means for outputting electric power by causing a battery reaction when supplied with an oxidizing gas, and a gas flow rate, an oxidation reaction temperature,
An on-vehicle fuel cell power generator comprising: means for controlling a battery reaction temperature; and, if necessary, means for detecting a gas component to control an oxidation reaction and a battery reaction. 2. The on-vehicle fuel cell power generator according to claim 1, wherein the cell reaction is performed by a solid polymer electrolyte fuel cell. 3. The on-vehicle fuel cell power generator according to claim 1, wherein the oxidation reaction catalyst is a catalyst containing ruthenium metal as a main component. 4. The on-vehicle fuel cell power generator according to claim 3, wherein the oxidation reaction catalyst is mainly composed of ruthenium metal containing substantially no halogen. 5. A catalyst mainly composed of a ruthenium metal having an adsorption amount of carbon monoxide of 1 mmol / g.ruthenium or more and an adsorption index of carbon monoxide of 0.5 or more as defined below as an oxidation reaction catalyst. The on-vehicle fuel cell power generator according to claim 3 or 4, wherein: Adsorption index = ΔX ₁ / ΔX = ΔX ₁ / (ΔX ₁ + ΔX ₂ ) where A = introduced amount of carbon monoxide / pulse = 0.002 mmol / pulse = 0.4 mmol / g ruthenium / pulse X = per pulse to the X-when the adsorption amount adsorbed amount = .SIGMA.X B = reversible adsorption (X + B) the X at the time of /A≧0.9 and _{X 1 (X + B) /} a <0.9 and X ₂ 6. The on-vehicle fuel cell power generator according to claim 3, wherein the oxidation reaction catalyst is a catalyst having a mesopore molecular sieve as a carrier. 7. The on-vehicle vehicle according to claim 3, wherein the oxidation reaction catalyst is preliminarily treated in a gas containing hydrogen as a main component and then used without being brought into contact with air. For fuel cell power generator. 8. A method according to claim 1, further comprising a step of bringing a reformed gas before mixing a gas containing oxygen or a hydrogen-rich gas containing no oxygen other than the reformed gas into contact with the oxidation reaction catalyst. An in-vehicle fuel cell power generator according to any one of the above. 9. Preventing a reformed gas containing carbon monoxide before mixing with a gas containing oxygen, or a hydrogen-rich gas containing no oxygen other than the reformed gas from coming into contact with the battery reaction section. 9. The on-vehicle fuel cell power generator according to claim 8, comprising means. 10. The on-vehicle fuel cell power generator according to claim 1, wherein a carbon monoxide removing device mainly filled with an oxidation reaction catalyst is provided in a flow path of the mixed gas. apparatus. 11. A mixed gas flow path, wherein a porous diffusion layer is provided immediately before the battery reaction section to disperse the mixed gas, and an oxidation reaction catalyst is supported on the porous diffusion layer. The on-vehicle fuel cell power generator according to any one of claims 1 to 10, wherein carbon monoxide is reduced. 12. The on-vehicle fuel cell power generation according to claim 1, wherein the content of water vapor in the mixed gas is less than the saturated water vapor pressure at the temperature of the portion where the oxidation reaction catalyst is present. apparatus. 13. The on-vehicle fuel cell power generator according to claim 1, wherein the temperature zone in which the mixed gas contacts the oxidation reaction catalyst is −20 ° C. to 90 ° C. 14. The on-vehicle fuel cell power generator according to claim 1, wherein the concentration of carbon monoxide contained in the reformed gas after contact with the oxidation reaction catalyst is reduced to 2 ppm or less. apparatus. 15. The battery according to claim 1, which is used in combination with a secondary battery having a large output capacity.
5. The on-vehicle fuel cell power generator according to any one of 4.