JP2004182522A - Reformer for fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reformer for a fuel cell in which a structure that gives high reforming efficiency responding to high temperature even when the reforming reaction is carried out at a high gas space velocity while keeping properly high temperature by adding calories necessary for the reforming reaction in the reformer to the reforming catalyst can be easily obtained at a low cost, which is excellent in long-term stability, and which can be made small in size. <P>SOLUTION: The reformer for a fuel cell is equipped with a reforming catalyst which allows a fuel containing an organic compound having hydrogen atoms in the molecule to react with water to reform the fuel into hydrogen-rich gas, and equipped with a heating means to give calories required for the reforming reaction. The ratio of [reforming catalyst amount (cm<SP>3</SP>)/heat conducting area (cm<SP>2</SP>)] is specified to 0.3 to 0.8. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a reformer for a fuel cell, and more particularly, to a household electric power generator for producing a hydrogen-rich gas by steam reforming of a raw hydrocarbon fuel gas such as city gas and supplying the gas to a fuel cell or the like. The present invention relates to a fuel cell reformer with a 1 kW class fuel cell system in mind.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, there is known a system in which a raw hydrocarbon fuel gas such as city gas is steam-reformed to generate a hydrogen-rich gas, and the chemical energy of the obtained hydrogen-rich gas is directly converted into electric energy by a fuel cell.
[0003]
Fuel cells use hydrogen and oxygen as fuels. Hydrogen is produced using hydrocarbon components such as natural gas, alcohols such as methanol, or organic compounds containing hydrogen atoms in molecules such as naphtha. The method of reforming with steam is widely used. Such a reforming reaction using steam is an endothermic reaction. For this reason, the reformer that performs steam reforming needs to provide the amount of heat required for the reforming reaction to the reforming catalyst and maintain the temperature at a high temperature.
[0004]
FIG. 4 shows a conventional hydrogen generator for a fuel cell (for example, see Patent Document 1). The fuel cell hydrogen generator 30 includes a reforming tube 32 having a reforming catalyst 31 for reacting a raw hydrocarbon fuel gas with water to reform the gas into a hydrogen-rich gas; A water supply unit 34 for supplying water to the reforming pipe 32; a heating means 36 for supplying heat required for the reforming reaction by burning combustion fuel in the combustion pipe 35; A CO converter 37 that converts carbon monoxide contained in the reformed gas flowing out of the reforming tube 32 with water to convert it into carbon dioxide, and a carbon monoxide contained in the reformed gas flowing out of the CO converter 37 A CO remover (not shown) provided with a selective oxidation catalyst that reacts with air or oxygen to form carbon dioxide.
In the figure, S is the cross-sectional area of the reforming catalyst layer (for example, the cross-sectional area in the gas flow direction of the reforming catalyst layer derived from the tube diameter or the like), and L is the length of the reforming catalyst layer in the gas flow direction. Show.
[0005]
The raw hydrocarbon fuel gas is sent from the fuel supply unit 33 to the reforming pipe 32 after the steam is added. The steam is generated by water such as cooling water flowing through the system by the steam generator 38, for example, being preheated by the heating means 36 and exchanged with the exhaust heat of the fuel cell device. The fuel gas to which the steam has been added comes into contact with the reforming catalyst 31 in the reforming tube 32 and is steam reformed into a hydrogen-rich gas (hydrogen-rich gas) by a catalytic reaction (about 700 ° C., endothermic reaction). Since the generated hydrogen-rich gas contains carbon monoxide, the CO converter 37 converts carbon monoxide into carbon dioxide by a reaction with excess water vapor (about 200 to 300 ° C., exothermic reaction). The carbon monoxide contained in the shift gas flowing out of the CO shift converter 37 is brought into contact with a selective oxidation catalyst of a CO remover (not shown) to react with air or oxygen (about 100 to 200 ° C., exothermic reaction) to form carbon dioxide. To reform into a hydrogen-rich gas having a low carbon monoxide concentration. The hydrogen-rich gas obtained as described above is continuously supplied to the hydrogen electrode 39a of the fuel cell 39, and generates a battery reaction with the air supplied to the air electrode 39b to generate power. A heating means 36 including a burner 40 for burning a fuel for combustion such as fuel gas or unreacted hydrogen gas discharged from a fuel cell 39 is attached to the reforming pipe 32. The amount of heat necessary for the reforming reaction in step (1) is given to raise the temperature of the reforming catalyst 31 to enhance the catalytic action.
[0006]
[Patent Document 1]
JP 2000-281313 A
[Problems to be solved by the invention]
An object of the present invention is to provide a reforming catalyst with an amount of heat necessary for a reforming reaction performed in a reformer to maintain a proper high temperature and perform a reforming reaction at a high gas space velocity so as to correspond to a high temperature. An object of the present invention is to provide a reformer for a fuel cell, which has a high reforming rate and is excellent in long-term stability.
[0008]
[Means for Solving the Problems]
The fuel cell reformer according to claim 1 of the present invention for solving the above-mentioned problem reforms a fuel containing an organic compound having a hydrogen atom in a molecule with water and reforms it into a hydrogen-rich gas. A fuel cell reformer comprising a reforming catalyst and a heating means for providing a calorie necessary for the reforming reaction,
[Reforming catalyst amount (cm ³ ) / heat transfer area (cm ² )] is set to 0.3 to 0.8.
[0009]
The fuel cell reformer of the present invention has a simple structure, is inexpensive, can be miniaturized, and has a [reforming catalyst amount (cm ³ ) / heat transfer area (cm ² )] of 0.3 to 0.1. By setting it to 8, the amount of heat required for the reforming reaction performed in the reformer is given to the reforming catalyst to maintain an appropriate high temperature, and even if the reforming reaction is performed at a high gas space velocity, it can cope with a high temperature. A high reforming rate is obtained.
[0010]
The reformer for a fuel cell according to claim 2 of the present invention includes a reforming catalyst for reforming a fuel containing an organic compound having a hydrogen atom in a molecule with water and reforming it into a hydrogen-rich gas. In a fuel cell reformer provided with a heating means for giving a calorie necessary for the reforming reaction,
[Length L of reforming catalyst layer / Section area S of reforming catalyst layer] is 7 to 38.
[0011]
In the reformer for a fuel cell, the reforming is performed by setting [length L of reforming catalyst layer / cross-sectional area S of reforming catalyst layer] (hereinafter sometimes referred to as L / S) to 7 to 38. Even if the reforming reaction is carried out at a high gas space velocity by supplying the amount of heat necessary for the reforming reaction performed in the reactor to the reforming catalyst and maintaining the temperature at an appropriate high temperature, a high reforming rate corresponding to the high temperature can be obtained.
[0012]
The fuel cell reformer according to claim 3 of the present invention includes a reforming catalyst for reforming a fuel containing an organic compound having a hydrogen atom in a molecule with water and reforming it into a hydrogen-rich gas. In a fuel cell reformer provided with a heating means for giving a calorie necessary for the reforming reaction,
[Reforming catalyst amount (cm ³ ) / heat transfer area (cm ² )] is set to 0.3 to 0.8, and [reforming catalyst layer length L / reforming catalyst layer cross-sectional area S]. Is set to 7 to 38.
[0013]
In the fuel cell reformer, the [reforming catalyst amount (cm ³ ) / heat transfer area (cm ² )] is set to 0.3 to 0.8 and L / S is set to 7 to 38. , The amount of heat required for the reforming reaction in the reformer is sufficiently provided by the reforming catalyst to maintain a suitable high temperature, and high reforming that can handle high temperatures even when the reforming reaction is performed at a high gas space velocity Rate is obtained. Furthermore, the compactness required for a household fuel cell system having an electric output of 1 kW class is also provided.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(1) Regarding the relationship between the reforming rate and [reforming catalyst amount (cm ³ ) / heat transfer area (cm ² )] The heat transfer area means that the reforming catalyst substantially contacts the reforming tube. It shows the area of the part where heat is transferred through that part.
The ratio of [reforming catalyst amount (cm ³ ) / heat transfer area (cm ² )] was changed to (0.3 to 1.3) using a reformer having a double cylindrical tube structure, and the following modification was performed. gas hourly space velocity in the quality reaction conditions (GHSV = gas volume ^(cm 3 / hr) / catalyst weight ^{(cm 3))} 500 hr -1, for the case of 1000 hr ^-1 reforming conversion ratio results was determined (%) in FIG. 1 Show.
Reforming catalyst: noble metal-based catalyst (a catalyst having a particle size of about 1.5 to 2.5 mm and a catalyst having a particle size of about 2.5 to 3.5 mm were used.)
When the ratio of [amount of reforming catalyst (cm ³ ) / heat transfer area (cm ² )] is 0.3 to 0.5, a catalyst having a particle size of about 1.5 to 2.5 mm is used. When the ratio of the amount of catalyst for quality (cm ³ ) / heat transfer area (cm ² )] is more than 0.5 and 1.3, the one having a particle size of more than 2.5 and 3.5 mm was used.
Fuel gas: Methane reforming tube inner diameter: 40 mm
Reforming catalyst layer length (L): 18 cm
[Amount of reforming catalyst (cm ³ ) / heat transfer area (cm ² )]: 0.3 to 1.3
S / C: 2.5
Reformer temperature: 700 ° C (the gas outlet temperature of the reformer was controlled)
However, the reforming rate was calculated by the following equation using the result of analyzing the gas composition after the reforming reaction (the theoretical reforming rate under the above-mentioned reforming reaction conditions is 94.8%).
[0015]
Reforming rate (%) = [(CO ₂ + CO concentration) / (CO ₂ + CO + CH ₄ concentration)] × 100
[0016]
From FIG. 1, when the gas hourly space velocity is 500 hr ⁻¹ , the ratio of [reforming catalyst amount (cm ³ ) / heat transfer area (cm ² )] is in the range of 0.3 to 0.8, and the theoretical reforming rate is almost equal. At a gas hourly space velocity of 1000 hr ^-1 , the ratio of [reforming catalyst amount (cm ³ ) / heat transfer area (cm ² )] is in the range of 0.3 to 0.7. Is obtained.
From the above, it can be seen that the ratio of [reforming catalyst amount (cm ³ ) / heat transfer area (cm ² )] is preferably 0.3 to 0.8, and more preferably 0.3 to 0.7.
Here, when the ratio of [reforming catalyst amount (cm ³ ) / heat transfer area (cm ² )] is less than 0.3, the catalyst layer thickness of the reforming tube is reduced, and the catalyst particle diameter is 1.5. It is not preferable to use a catalyst having a thickness of up to 2.5 mm because the catalyst filling rate is reduced.
[0017]
(2) Regarding the relationship between the reforming rate and L / S The L / S was changed to (2-38) while the reforming catalyst amount was kept constant at 550 cm ³ using a reformer having a double cylindrical tube structure. following the reforming reaction conditions gas space velocity ^{500 hr} -1, the results obtained reforming ratio (%) for the case of 1000 hr ^-1 shown in Fig.
Reforming catalyst: noble metal-based catalyst (a catalyst having a particle size of about 1.5 to 2.5 mm and a catalyst having a particle size of about 2.5 to 3.5 mm were used.)
[If L / S is 2 to 20, use a particle size of about 1.5 to 2.5 mm; if L / S is more than 20 and 38, use a particle size of about 2.5 to more than 2.5. The thing of 5 mm was used.
Fuel gas: Methane reforming tube inner diameter: 40 mm
Catalyst amount: 550 cm ³
L / S: 2-38
S / C: 2.5
Reformer temperature: 700 ° C (the gas outlet temperature of the reformer was controlled)
From FIG. 2, it can be seen that when the gas hourly space velocity is 500 hr ^-1 , the L / S is almost in the range of 7 to 38, and when the gas hourly space velocity is 1000 hr ^-1 , the L / S is in the range of 10 to 38. It can be seen that almost the theoretical reforming rate can be obtained.
Here, when L / S exceeds 38, in this test, a fuel cell system having a household electric output of 1 kW was taken into consideration, and the amount of the catalyst was fixed at 550 cm ^3. Therefore, the thickness of the catalyst layer was changed only by 1 mm. Since the L / S greatly changed and the length of the reforming tube catalyst layer exceeded 5 cm, it was determined that the compactness was lacking, and the upper limit of the actually usable L / S was up to about 38.
From the above, it can be seen that L / S is preferably in the range of 7 to 38, preferably 10 to 38.
[0018]
(3) Relationship between Reforming Rate, [Reforming Catalyst Amount (cm ³ ) / Heat Transfer Area (cm ² )] and L / S Using a Double Cylindrical Tube Reformer 550 cm ³ and then fixed, by changing the L / S to (2-38), the reforming catalyst amount ^(cm 3) / heat transfer area ^(cm 2)] in (0.4 to 1.3) FIG. 3 shows the results obtained by changing the reforming rate (%) for the gas space velocity of 1000 hr ^-1 under the following reforming reaction conditions.
Reforming catalyst: noble metal catalyst (using a particle size of about 1.5 to 2.5 mm and a particle size of about 2.5 to 3.5 mm)
When the ratio of [amount of reforming catalyst (cm ³ ) / heat transfer area (cm ² )] is 0.3 to 0.5, a catalyst having a particle size of about 1.5 to 2.5 mm is used. When the ratio of the amount of catalyst for quality (cm ³ ) / heat transfer area (cm ² )] is more than 0.5 and 1.3, the one having a particle size of more than 2.5 and 3.5 mm was used.
[If L / S is 2 to 20, use a particle size of about 1.5 to 2.5 mm; if L / S is more than 20 and 38, use a particle size of about 2.5 to more than 2.5. The thing of 5 mm was used.
Fuel gas: Methane reforming tube inner diameter: 20, 25, 30, 40, 50, 60 mm
S / C: 2.5
Reformer temperature: 700 ° C (the outlet temperature of the reformer was controlled)
[0019]
In FIG. 3, circles, squares, triangles, rhombuses, large circles, and large squares indicate test results when the catalyst tube inner diameter is 20, 25, 30, 40, 50, and 60 mm, respectively, and black indicates theoretical reforming. The data at which the ratio (94.8%) was obtained are shown, and the white ones indicate that the theoretical modification ratio (94.8%) was not obtained. In the figure, x indicates that the height of the reformer was too high to be miniaturized, that it was considered impractical for a household fuel cell system with an electric output of 1 kW, and that it was not designed and tested.
In this study (and the reforming catalyst quantity 550 cm ³ constant), [reforming catalytic amount ^(cm 3) / heat transfer area ^(cm 2)] is higher height of the reformer is 0.4 or less Since it was too small to be miniaturized and not practical, the test of 0.3 was not performed.
[0020]
The theoretical reforming rate is obtained when the [reforming catalyst amount (cm ³ ) / heat transfer area (cm ² )] is in the range of 0.4 to 0.8 and L / S is in the range of 7 to 38. Even if the amount of reforming catalyst (cm ³ ) / heat transfer area (cm ² ) is in the range of 0.4 to 0.8, if L / S exceeds 38, the theoretical reforming rate cannot be obtained and The height of the reformer is too high to reduce the size, and is not practical.
[0021]
Although the theoretical reforming rate is obtained even under the condition that the L / D is less than 7, the catalyst layer length is actually too short, and the reforming rate can be reduced by a slight change in the amount of water vapor or gas. fluctuate. Further, the test was conducted using methane as a fuel gas. However, since the actual gas contains a sulfur component, the L / D is preferably 7 or more in consideration of sulfur poisoning.
From FIGS. 1 to 3, [reforming catalyst amount (cm ³ ) / heat transfer area (cm ² )] is in the range of 0.3 to 0.8, and L / S is in the range of 7 to 38. Therefore, the structure can be simplified and the size can be reduced, and the amount of heat required for the reforming reaction in the reformer is sufficiently given to the reforming catalyst to maintain an appropriate high temperature to maintain a high gas space. Even if the reforming reaction is performed at a high speed, a high reforming rate corresponding to a high temperature can be obtained.
In addition, for example, [the amount of reforming catalyst (cm ³ ) / heat transfer area (cm ² )] is 0.3 to indicate 0.25 to 0.34, and L / S is 38 is 37.5 to 38. .4.
[0022]
In order to enhance the long-term stability and improve the compactness, the [reforming catalyst amount (cm ³ ) / heat transfer area (cm ² )] is in the range of 0.4 to 0.7 and L / S is preferably in the range of 10 to 38.
[0023]
If the ratio of [reforming catalyst amount (cm ³ ) / heat transfer area (cm ² )] is less than 0.3, the catalyst layer thickness of the reforming tube decreases, the catalyst filling rate decreases, and the If the ratio exceeds 0.8, heat transfer is rate-determined and a high reforming rate may not be obtained.
[0024]
If the L / S ratio is less than 7, the length of the catalyst layer becomes too short, and the reforming rate fluctuates due to slight fluctuations in the amount of steam or gas, and the amount of heat required for the reforming reaction is transferred to the reforming catalyst. When the L / S exceeds 38, the L / D greatly changes only by changing the thickness of the catalyst layer by 1 mm, and the L / D of the reformer may not be obtained. The height may be too high to reduce the size.
[0025]
The type and material of the reformer are not particularly limited. For example, the type may be any of a double tube structure, a flat plate structure, and a multi-tube structure as shown in FIG. Good.
As the material of the reformer, any material such as stainless steel which does not hinder the reforming reaction can be used.
As the heating means, an example of the heating means for providing heat by burning the combustion fuel in the combustion tube has been described, but the heating means is not limited to this.
[0026]
The description of the above embodiments is for describing the present invention, and does not limit the invention described in the claims or reduce the scope thereof. Further, the configuration of each part of the present invention is not limited to the above embodiment, and various modifications can be made within the technical scope described in the claims.
[0027]
【The invention's effect】
The fuel cell reformer according to claim 1 of the present invention includes a reforming catalyst for reacting a fuel containing an organic compound having a hydrogen atom in a molecule with water and reforming it into a hydrogen-rich gas. In a reformer for a fuel cell provided with a heating means for providing heat required for the reforming reaction, [amount of reforming catalyst (cm ³ ) / heat transfer area (cm ² )] is set to 0.3 to 0.1. 8, which has a simple structure, is inexpensive, has excellent long-term stability, can be miniaturized, and has a capacity of [reforming catalyst (cm ³ ) / heat transfer area (cm ² )]. Is set to 0.3 to 0.8, the amount of heat required for the reforming reaction performed in the reformer is given to the reforming catalyst, and the reforming reaction is performed at a high gas space velocity while maintaining a proper high temperature. However, there is a remarkable effect that a high reforming rate corresponding to a high temperature can be obtained.
[0028]
The reformer for a fuel cell according to claim 2 of the present invention includes a reforming catalyst for reforming a fuel containing an organic compound having a hydrogen atom in a molecule with water and reforming it into a hydrogen-rich gas. In the reformer for a fuel cell provided with a heating means for giving a calorie necessary for the reforming reaction, [length L of reforming catalyst layer / cross-sectional area S of reforming catalyst layer] is 7 to 38. It has a simple structure, is inexpensive, has excellent long-term stability, can be miniaturized, and has a [reforming catalyst layer length L / reforming catalyst layer cross-sectional area S] of 7 to 38. By providing the amount of heat necessary for the reforming reaction performed in the reformer to the reforming catalyst and maintaining a suitable high temperature, even if the reforming reaction is performed at a high gas space velocity, a high temperature corresponding to the high temperature can be obtained. It has a remarkable effect that a reforming rate can be obtained.
[0029]
The fuel cell reformer according to claim 3 of the present invention includes a reforming catalyst for reforming a fuel containing an organic compound having a hydrogen atom in a molecule with water and reforming it into a hydrogen-rich gas. In a reformer for a fuel cell provided with a heating means for providing heat required for the reforming reaction, [amount of reforming catalyst (cm ³ ) / heat transfer area (cm ² )] is set to 0.3 to 0.1. 8, and [the length L of the reforming catalyst layer / the cross-sectional area S of the reforming catalyst layer] is 7 to 38, whereby the structure is simplified. It is inexpensive, has better long-term stability, can be made more compact, and provides a sufficient amount of heat required for the reforming reaction performed in the reformer by the reforming catalyst to maintain an appropriate high temperature to achieve a high gas space velocity. This has a remarkable effect that a high reforming rate corresponding to a high temperature can be obtained even when the reforming reaction is performed.
[Brief description of the drawings]
FIG. 1 is a graph showing a relationship between a reforming rate and [amount of reforming catalyst (cm ³ ) / heat transfer area (cm ² )].
FIG. 2 is a graph showing a relationship between a reforming rate (%) and [reforming catalyst layer length L / reforming catalyst layer cross-sectional area S].
FIG. 3 is a graph showing a relationship between [reforming catalyst amount (cm ³ ) / heat transfer area (cm ² )] and [reforming catalyst layer length L / reforming catalyst layer cross-sectional area S]. is there.
FIG. 4 is an explanatory view showing a conventional hydrogen generator for a fuel cell.
[Explanation of symbols]
Reference Signs List 30 hydrogen generator for fuel cell 31 reforming catalyst 32 reforming pipe 33 fuel supply section 34 water supply section 35 combustion pipe 36 heating means 37 CO transformer S reforming catalyst layer cross-sectional area L reforming catalyst layer length

Claims (3)

A reforming catalyst for reforming a fuel containing an organic compound having a hydrogen atom in the molecule with water and reforming it into a hydrogen-rich gas; and a heating means for providing a calorie necessary for the reforming reaction. In a fuel cell reformer,
A reformer for a fuel cell, wherein [amount of reforming catalyst (cm ³ ) / heat transfer area (cm ² )] is 0.3 to 0.8. A reforming catalyst for reforming a fuel containing an organic compound having a hydrogen atom in the molecule with water and reforming it into a hydrogen-rich gas; and a heating means for providing a calorie necessary for the reforming reaction. In a fuel cell reformer,
A reformer for a fuel cell, wherein [length L of reforming catalyst layer / cross-sectional area S of reforming catalyst layer] is 7 to 38. A reforming catalyst for reforming a fuel containing an organic compound having a hydrogen atom in the molecule with water and reforming it into a hydrogen-rich gas; and a heating means for providing a calorie necessary for the reforming reaction. In a fuel cell reformer,
[Reforming catalyst amount (cm ³ ) / heat transfer area (cm ² )] is set to 0.3 to 0.8, and [reforming catalyst layer length L / reforming catalyst layer cross-sectional area S]. Is 7 to 38. A reformer for a fuel cell.

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