JPH07232901A - Fuel reformer - Google Patents

Abstract

PURPOSE:To provide a fuel reformer capable of surely reducing the carbon monoxide concn. in the reformed gas to such an extent that the performance of a battery is not lowered by a carbon monoxide selective oxidation catalyst and capable of being miniaturized. CONSTITUTION:A vaporization part 2, reforming part 6, first reforming part 3 and second reforming part 7 are respectively combined as a laminate, and the vaporization part 2 and first reforming part 3 are combined to form a vaporizing and reforming body 5. The heat-exchange efficiency of each part is increased by such a constitution, and the reformer itself is made extremely compact. A liq. fuel (coolant) is passed through the cooling bed 71 of the second reforming part 7 to cool the second reforming bed 72 of the part. Consequently, a carbon monoxide selective oxidation catalyst in the second reforming bed 72 is kept at 100 deg.C as the reaction temp. Accordingly, the carbon monoxide concn. in the reformed gas is surely lowered to about 100ppm which does not lower the performance of a battery.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel reformer for reforming a fossil fuel such as methanol or LNG to produce a hydrogen-rich reformed gas which is a fuel for a fuel cell.

[0002]

2. Description of the Related Art In a fuel reformer, methanol or LNG is used.
A reforming raw material composed of fossil fuel is heated and vaporized to generate a reforming raw material gas, and steam is mixed with the reforming raw material gas, so-called steam reforming is performed to generate the reformed gas.
Since the reformed gas contains a large amount of carbon monoxide that becomes a catalyst poison of the electrode catalyst of the fuel cell and shortens the battery life, the carbon monoxide concentration in the reformed gas is changed by the catalytic conversion reaction. Is used to generate a hydrogen-rich reformed gas that is the fuel of the fuel cell.

In order to further reduce the concentration of carbon monoxide in the reformed gas, a carbon monoxide selective oxidation catalyst is used. For example, in the solid polymer electrolyte fuel cell device disclosed in Japanese Patent Application Laid-Open No. 3-203165, the carbon monoxide concentration in the reformed gas generated by the reformer is determined by using the carbon monoxide selective oxidation catalyst. The carbon removal device is used to reduce the amount.

The reaction temperature of the carbon monoxide selective oxidation catalyst is a relatively low temperature of room temperature to 100 ° C. Therefore, if the operating temperature of the carbon monoxide removing device is maintained at 100 ° C. or lower, the reformed gas from the reforming device passing through the carbon monoxide removing device is
It can be directly supplied to the fuel cell without heat exchange. That is, the carbon monoxide removing device using the carbon monoxide selective oxidation catalyst is very well matched with the solid polymer electrolyte fuel cell that generates power at a temperature of about 100 ° C.

[0005]

However, in the fuel cell device of the above publication, since the carbon monoxide removing device is provided independently of the fuel reforming device, it is considerably large as a fuel supply device to the fuel cell. Will be things. Moreover, since the reaction of the carbon monoxide selective oxidation catalyst is an exothermic reaction, it is highly efficient to maintain the operating temperature of the carbon monoxide removal device at 100 ° C. or lower which is the reaction temperature of the carbon monoxide selective oxidation catalyst. A heat exchanger is required, and the size of the heat exchanger is increased by installing such a heat exchanger. Further, if the operating temperature of the carbon monoxide removing device cannot be maintained at 100 ° C. or lower, the removal rate of carbon monoxide decreases, so that the electrode catalyst in the battery is poisoned by carbon monoxide and the performance of the battery deteriorates. At the same time, its life will be shortened.

The present invention was proposed in order to solve such a problem, and the carbon monoxide concentration in the produced reformed gas is selectively oxidized to the extent that the performance of the battery is not deteriorated. An object of the present invention is to provide a fuel reformer that can be reliably reduced by a catalyst and that can be configured in a small size.

[0007]

A fuel reformer according to the present invention has the following structure.

That is, the combustion section (1) for generating the heat source gas
And a heating layer (2) through which the heat source gas from the combustion section (1) passes.
0) and the heat of the heat source gas passing through the heating layer to heat and vaporize the liquid fuel introduced through the liquid fuel manifold (22) to generate the reforming raw material gas (21).
Of the vaporization part (2), a heating layer (60) for passing the heat source gas from the combustion part (1), and heat of the heat source gas passing through the heating layer for the vaporization part (2). A reforming section (6) that forms a laminated body from a reforming layer (61) that heats the reforming raw material gas from the vaporization layer (21) and converts it into reforming gas.
And a first shift layer (3) for reducing the carbon monoxide concentration in the reformed gas introduced through the reformed gas passage (101) from the reformed layer (61) of the reforming section (6) by the shift catalyst.
0) and the first metamorphic layer is laminated with each layer of the vaporizing part (2) in a state where the first metamorphic layer is thermally bonded to the heating layer (20) of the vaporizing part (2). Complex (5)
And the residual carbon monoxide concentration in the reformed gas introduced through the reformed gas passage (100) from the first shift layer (30) of the first shift section (3). Second metamorphic layer (72) reduced by carbon monoxide selective oxidation catalyst
And a cooling layer (71) for passing a refrigerant for cooling the second metamorphic layer
And a second shift section (7) forming a laminated body, a humidifier (9) for humidifying and heating the reformed gas from the second shift section (7), and the first shift layer (30). Second metamorphic layer (7
The cooling layer (71) of the second shift conversion section (7), which is provided in a state of being thermally joined to the reformed gas passage (100) between
And a refrigerant passage (10) for guiding the refrigerant passing through to the liquid fuel manifold (22) of the vaporization section (2).

[0009]

In the fuel reformer having the above structure, the vaporization section (2),
The reforming section (6), the first shift conversion section (3), and the second shift conversion section (7) are each combined as a laminate, and the vaporization section (2) is also combined.
Since the vaporization / metamorphic section composite body (5) is formed by combining the above and the first metamorphic section (3), the efficiency of heat exchange in each section becomes high. At the same time, the device becomes very compact.

Further, the cooling layer (7) of the second shift section (7)
In order to cool the second metamorphic layer (72) of the same part by passing the refrigerant through 1), the temperature of the carbon monoxide selective oxidation catalyst in the second metamorphic layer (72) is kept at 100 ° C. or lower which is the active temperature range. To be done. Therefore, the carbon monoxide concentration in the reformed gas generated in the reforming section (6) is about 100 ppm in the first shift section (3) and the second shift section (7), which does not reduce the performance of the battery. Reduce to.

The reference numerals in parentheses are for reference to the drawings and do not limit the structure of the present invention.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an exploded perspective view showing the entire fuel reforming apparatus according to the present invention.

As shown in the figure, this fuel reforming apparatus comprises, from below, a combustion section 1, a vaporization / transformation section composite 5 consisting of a vaporization section 2 and a first shift section 3, a reforming section 6, and a second shift section. 7 are combined so as to be stacked, and humidifiers 9 are arranged side by side. The configuration of each of these parts will be described below.

The combustion section 1 generates a heat source gas. As a heat source, for example, a burner using hydrogen gas or liquid methanol as a fuel, or catalytic combustion in which hydrogen gas or methanol gas is contacted with a combustion catalyst for combustion. It is used by.

The vaporization / metamorphism section composite 5 comprising the vaporization section 2 and the first transformation section 3 constitutes a plurality of heating layers 20 and vaporization layers 21 constituting the vaporization section 2, and the first transformation section 3. It is configured by vertically arranging a plurality of first metamorphic layers 30 with the vaporization layer 21 and the first metamorphic layer 30 sandwiched between the heating layers 20. That is, the vaporization section 2 and the first shift conversion section 3 are laminated in a state where the first shift layer 30 of the first shift conversion section 3 is thermally bonded to the heating layer 20 of the vaporization section 2 to form a composite body. is doing.

In the vaporization layer 21 of the vaporization part 2, a liquid fuel (methanol / water (molar ratio) = 1/1) in which liquid methanol (CH ₃ OH) which is a reforming raw material and water (H ₂ O) are mixed.
1 to 1/4) are introduced through the liquid fuel manifold 22 of the vaporization section 2 as described later. The heat source gas from the combustion section 1 is introduced into the heating layer 20. As a result, the liquid fuel in the vaporization layer 21 is heated by the heat of the heat source gas and vaporized from the surface thereof, so that the reforming raw material gas is generated.

On the other hand, the first conversion layer 30 has a conversion catalyst supported on the inner wall thereof by impregnation, thermal spraying, electrodeposition, sputter coating, or is filled in the layer. The conversion reaction of 1 converts carbon monoxide contained in the reformed gas from the reforming section 6 described later into carbon dioxide to reduce the carbon monoxide concentration. As the above-mentioned shift catalyst, copper (C
Examples thereof include those containing at least one of u) and zinc (Zn). As for the water required for this reaction, excess water after the steam reforming reaction in the reforming section 6 described later can be used by making the water ratio of the liquid fuel excessive.

In the first shift conversion layer 30, the reformed gas that has undergone the first shift reaction (first shift gas) is stored in the first shift gas manifold 31 of the first shift section 3 and then reformed. It is introduced into the first shift gas manifold 70 of the second shift section 7 through the gas passage 100.

The reforming section 6 is a heating layer 2 of the vaporizing section 2.
It is configured by vertically arranging the reforming layer 61 between a plurality of heating layers 60 communicating with 0 and passing the heat source gas from the combustion section 1. That is, the reforming section 6 also forms a laminated body. The modified layer 61 is made of copper / zinc (C
u / Zn) or the like is carried on the inner wall of the reforming catalyst by impregnation, thermal spraying, electrodeposition, sputter coating or the like, or is filled in the layer. The vaporized reforming raw material gas is passed.

The reforming layer 61 is heated to 250 to 300 ° C. by excess heat of the vaporizing portion of the heat source gas, and the steam reforming reaction caused thereby causes the reforming raw material gas from the vaporizing portion 2 to be rich in hydrogen. Convert to reformed gas. At that time, carbon dioxide and a trace amount of carbon monoxide are generated.

The high-temperature reformed gas generated in the reformed layer 61 of the reformer 6 is reformed in the first shift converter 3 from the reformed gas manifold 62 through the reformed gas passage 101 on the rear side. Introduced into the gas manifold 32, the first shift unit 3
To the first metamorphic layer 30 of. The heat source gas that has passed through the heating layer 60 of the reforming section 6 is sent from the heat source gas manifold 63 to the humidifier 9 through a heat source gas passage (not shown).

The second shift conversion section 7 is constituted by vertically arranging the second shift conversion layer 72 between a plurality of cooling layers 71 through which the refrigerant passes. That is, the second metamorphosing part 7 also forms a laminated body. The second metamorphic layer 72 is one in which the carbon monoxide selective oxidation catalyst is attached to the inner wall by impregnation, thermal spraying, electrodeposition, sputter coating, or is filled in the layer. The high temperature first shift gas sent from the first shift gas manifold 31, the reformed gas passage 100, and the first shift gas manifold 70 together with the pressurized air from the blower (not shown) is passed through, The residual carbon monoxide concentration in the first shift gas is reduced.

The carbon monoxide selective oxidation catalyst in the second shift conversion layer 72 selectively controls the oxidation reaction with carbon monoxide by controlling the temperature without oxidizing hydrogen, that is, suppressing the reaction of water. It is a catalyst having a function of propelling to a carbon monoxide. As this carbon monoxide selective oxidation catalyst, Au / α-
Fe ₂ O ₃ / γ-Al ₂ O ₃ is exclusively used. Further, the temperature range in which this carbon monoxide selective oxidation reaction is activated is
The temperature is about room temperature to 100 ° C., and the carbon monoxide selective oxidation reaction is an exothermic reaction.

As described above, in the second shift conversion layer 72, although the temperature of the first shift conversion gas introduced is high and the temperature of the second shift conversion layer 72 rises considerably due to the heat generation of the carbon monoxide selective oxidation catalyst, Since it is cooled by the passing refrigerant, the temperature of the carbon monoxide selective oxidation catalyst in the second shift conversion layer 72 is maintained at 100 ° C. or lower which is the active temperature range.
Therefore, the residual carbon monoxide concentration in the first shift gas is set to 10
It can be reduced to about 0 ppm.

The reformed gas (second modified gas) from the second modified layer 72 is sent from the second modified gas manifold 73 to the humidifier 9.

The humidifier 9 is composed of a constant temperature bath of boiling water, and the water temperature in the bath is kept constant by the heat of the heater (not shown) and the heat source exhaust gas from the heating layer 60 of the reforming section 6. Is controlled so that That is, the heat source gas from the combustion unit 1 is used as a heat source of the humidifier 9 after passing through the heating layers 20 and 60 of the vaporization unit 2 and the reforming unit 6. The temperature of the heat source exhaust gas from the reforming section 6 is 20
It is about 0 to 300 ° C. As a result, the heater for heating the humidifier 9 can be made very small with low power consumption and can be omitted.

The second shift gas delivered from the second shift layer 72 of the second shift section 7 is bubbled into the boiling water of the humidifier 9 to be humidified, and after being heated to about 100 ° C. , Will be supplied to the fuel cell.

As described above, in this fuel reformer, the vaporization section 2, the reforming section 6, the first shift conversion section 3, and the second shift conversion section 7 are combined as a laminate, and the vaporization section 2 and the first shift conversion section are combined. Since the part 3 is combined with the vaporization / transformation part composite 5, the efficiency of heat exchange in each part is increased, and at the same time, the device is very compact.

As a configuration other than the above, as shown in FIG. 1, a refrigerant passage 10 for guiding the refrigerant passing through the cooling layer 71 of the second shift conversion section 7 to the liquid fuel manifold 22 of the vaporization section 2 is provided.

This refrigerant passage 10 has the above-mentioned first metamorphic layer 30.
And the second metamorphic layer 72 are thermally bonded to the reformed gas passage 100, for example, both passages 10 and 100 are provided in the form of a honeycomb structure. Therefore, both passages 1
In the 0,100 thermally joined part (vertical part),
The refrigerant descending in the refrigerant passage 10 and the reformed gas passage 100
The first metamorphic gas rising in the inside forms a counterflow, and the first metamorphic gas is efficiently cooled by the refrigerant.

Further, the refrigerant passage 10 is provided with the first shift converter 3 so that the first shift gas can be cooled more efficiently.
And the first and second shift gas manifolds 31, 31
The inside of 70 is also provided so as to cover the passage portion of the first shift gas and is thermally joined to the portion.

As described above, by making the temperature of the first shift gas introduced into the second shift layer 72 as low as possible, the temperature of the carbon monoxide selective oxidation catalyst in the second shift layer 72 is set to the reaction temperature. It is possible to more reliably keep the temperature below 100 ° C.

Further, the refrigerant passage 10 allows the refrigerant to naturally flow down from the upper cooling layer 71 to the lower liquid fuel manifold 22, thereby eliminating the need for providing a liquid feed pump in the refrigerant passage 10.

By the way, liquid fuel can be used as the refrigerant. That is, the liquid fuel sent from the fuel tank (not shown) by the liquid feed pump is supplied to the second shift section 7
Is introduced into the cooling layer 71 from above. In this case, the cooling layer 7
The liquid fuel (refrigerant) that descends in 1 and the first metamorphic gas that rises in the second metamorphic layer 72 form a counter flow. Then, the liquid fuel that has passed through the cooling layer 71 flows down through the refrigerant passage 10 as described above, and the liquid fuel manifold 22.
The vaporization layer 21 of the vaporization part 2
Flow into.

Further, water for producing liquid fuel may be used as the refrigerant. In this case, water flowing down the refrigerant passage 10 and liquid methanol (reforming raw material) supplied from another passage from a methanol tank (not shown) are mixed in the liquid fuel manifold 22 to obtain the liquid fuel. And is introduced into the vaporization layer 21 of the vaporization section 2.

As described above, by using the liquid fuel or the water for producing the same as the refrigerant, the temperatures of the first shift gas and the carbon monoxide selective oxidation catalyst are lowered as described above, and at the same time, the vaporization section 2 is cooled. By raising the temperature of the liquid fuel introduced into the vaporization layer 21, the vaporization energy consumed in the vaporization part 2 can be significantly reduced. Further, as a result, the combustion unit 1 can be downsized.

The refrigerant may be introduced into the cooling layer 71 from the rear surface side of the second shift conversion section 7 (two-dot chain line in FIG. 1). In this case, the refrigerant flowing from the rear surface side to the front surface side in the cooling layer 71 and the first shift gas rising in the second shift layer 72 form a cross flow.

FIG. 2 is a diagram showing the chemical reaction occurring in each part of the fuel reforming apparatus described above and the change in the carbon monoxide concentration in the reformed gas according to the gas flow. As shown
In the vaporization section 2, a vaporization reaction (endothermic reaction) occurs at a reaction temperature of 110 to 150 ° C, and in the reforming section 6, 250 to 300 ° C.
Reforming reaction (endothermic reaction) occurs at the reaction temperature of 1, the carbon monoxide conversion reaction (exothermic reaction) occurs at the reaction temperature of 150 to 200 ° C. at the first shift conversion section 3, and the room temperature to 1 at the second shift conversion section 7.
A carbon monoxide selective reaction (exothermic reaction) occurs at a reaction temperature of 00 ° C.

The carbon monoxide concentration in the reformed gas produced in the reforming section 6 is about 1% (10000 ppm), but the reformed gas that has passed through the first shift conversion section 3 (first shift gas)
The carbon monoxide concentration therein is about 1000 ppm, and the carbon monoxide concentration in the reformed gas (second shift gas) that has passed through the second shift conversion section 7 is gradually reduced to about 100 ppm. When the concentration of carbon monoxide in the reformed gas is about 100 ppm or less, it does not become a catalyst poison for the electrode catalyst of the fuel cell, and therefore does not deteriorate the performance of the cell.

The reformed gas from the second shift section 7 is sent to the fuel cell stack C after being humidified and heated by the humidifier 9 which uses the heat source exhaust gas from the reforming section 6 as a heat source.

As described above, since the carbon monoxide shift conversion reaction in the first shift converter 3 is an exothermic reaction, after the shift catalyst is once heated to the reaction temperature (150 to 200 ° C.) in the initial stage of the reaction, the reaction Since heat is naturally reinforced by heat, external heating is required only at the initial stage of the reaction.

On the other hand, since the vaporization reaction in the vaporization part 2 is an endothermic reaction, it is necessary to always heat it from the outside from the beginning of the reaction. The reaction temperature of this vaporization reaction is a liquid mixed fuel of methanol and water (methanol / water (molar ratio) = 1/1 to 1).
/ 4), which is about 90 at atmospheric pressure.
However, when the vaporization reaction is started, the vaporization layer 21 is brought into a pressurized state, and the temperature rises to about 150 ° C.

Therefore, if the vaporization section 2 and the first shift conversion section 3 are thermally bonded to each other to form the vaporization / transformation section composite 5 as in the above structure, the first shift layer 30 of the first shift section 3 is formed. Fever from
The vaporization layer 21 of the vaporization part 2 can be efficiently heated,
As a result, the fuel for generating the heat source gas in the combustion section 1 can be saved.

Moreover, the shift reaction temperature in the first shift layer 30 of the first shift section 3 is 150 to 200 ° C., and the vaporization reaction temperature in the vaporization layer 21 of the one vaporization section 2 is 110 to 150.
Since it is ℃, when both reactions proceed at the same time, the heat of reaction is exchanged between the first metamorphic layer 30 and the vaporization layer 21, and the equilibrium temperature becomes 150 to 200 ℃. This temperature range is the optimum range for both reactions. In other words, the two reactions proceed under the efficient complementary relationship of heat. As a result, the shift conversion treatment can be efficiently performed, and thermal degradation of the shift conversion catalyst can be prevented.

[0046]

As described above, according to the fuel reforming apparatus of the present invention, the temperature of the carbon monoxide selective oxidation catalyst of the second shift section is maintained at 100 ° C. or lower which is the reaction temperature thereof. Therefore, the carbon monoxide concentration in the generated reformed gas can be reliably reduced to about 100 ppm, which does not deteriorate the performance of the battery.

Moreover, since the vaporization section, the reforming section, the first shift conversion section, and the second shift conversion section are respectively combined as a laminated body, and the vaporization section and the first shift conversion section are combined to form a vaporization / transformation section composite, The efficiency of heat exchange in each part can be increased, and at the same time, the device can be made very compact.

Liquid fuel or water for producing the liquid fuel can be used as the refrigerant passing through the cooling layer of the second shift section, thereby raising the temperature of the liquid fuel and consuming it in the vaporization section. The vaporization energy that is saved can be significantly reduced. As a result, the combustion unit can be downsized.

Further, by utilizing the heat source exhaust gas from the reforming section as the heat source of the humidifier, the heater for heating the humidifier can be made very small with low power consumption, and may be omitted. It will be possible.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing an entire fuel reformer according to an embodiment of the present invention.

FIG. 2 shows chemical reactions that occur in each part of the same fuel reformer,
It is the figure which showed the change of the carbon monoxide concentration in reformed gas according to the flow of gas.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Combustion part 2 Vaporization part 20 Heating layer 21 Vaporization layer 22 Liquid fuel manifold 3 1st metamorphic part 30 1st metamorphic layer 5 Vaporization and metamorphic part complex 6 Reforming part 60 Heating layer 61 Reforming layer 7 2nd metamorphic part 71 Cooling layer 72 Second metamorphic layer 9 Humidifier 10 Refrigerant passage 100, 101 Reformed gas passage

Claims (3)

[Claims] 1. A fuel reforming apparatus for converting a liquid fuel composed of a reforming raw material and water into a hydrogen-rich reformed gas by steam reforming, and a combustion section for generating a heat source gas, and a combustion section for generating the heat source gas. Vaporization that forms a laminate of a heating layer that passes the heat source gas and a vaporization layer that heats and vaporizes the liquid fuel that is introduced through the liquid fuel manifold by the heat of the heat source gas that passes through the heating layer to generate the reforming raw material gas. Section, a heating layer for passing the heat source gas from the combustion section, and a reforming source gas for heating the reforming raw material gas from the vaporization layer of the vaporization section by the heat of the heat source gas passing through the heating layer to convert the reforming gas into reformed gas. A reforming part forming a laminated body of a layer, and a first conversion layer for reducing the carbon monoxide concentration in the reforming gas introduced from the reforming layer of the reforming part through the reforming gas passage by the conversion catalyst. And the first metamorphic layer has the vaporization section. A first shift section forming a vaporization-transformation section composite by laminating together with each layer of the vaporization section in a state of being thermally bonded to a heating layer, and a first shift layer of the first shift section through a reformed gas passage. Forming a laminate from a second metamorphic layer for reducing the residual carbon monoxide concentration in the introduced reformed gas by a carbon monoxide selective oxidation catalyst, and a cooling layer for passing a refrigerant for cooling the second metamorphic layer. The second shift section, the humidifier for humidifying and heating the reformed gas from the second shift section, and the reformed gas passage between the first shift layer and the second shift layer are provided in a state of being thermally joined. And a refrigerant passage for guiding the refrigerant passing through the cooling layer of the second shift conversion section to the liquid fuel manifold of the vaporization section. 2. The fuel reformer according to claim 1, wherein the liquid fuel or water for producing the liquid fuel is used as the refrigerant. 3. The heat source gas from the combustion section, which has passed through the heating layers of the vaporization section and the reforming section, is used as a heat source of the humidifier. Fuel reformer.