JP4245340B2 - Fuel cell reformer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
TECHNICAL FIELD The present invention relates to a reformer for a fuel cell, and more specifically, a household electric appliance that generates a hydrogen rich gas by steam reforming of a raw material hydrocarbon fuel gas such as city gas and supplies it to a fuel cell or the like. The present invention relates to a fuel cell reformer with an output of 1 kW class fuel cell system in mind.
[0002]
[Prior art]
Conventionally, a system is known in which raw material hydrocarbon fuel gas such as city gas is steam reformed to generate hydrogen rich gas, and chemical energy of the obtained hydrogen rich gas is directly converted into electric energy by a fuel cell.
[0003]
A fuel cell uses hydrogen and oxygen as fuel, and this hydrogen is produced using a hydrocarbon component such as natural gas, an alcohol such as methanol, or an organic compound having a hydrogen atom in a molecule such as naphtha as a raw material. The method of reforming with steam is widely used. Such a reforming reaction using water vapor is an endothermic reaction. For this reason, a reformer that performs steam reforming needs to provide the reforming catalyst with the amount of heat necessary for the reforming reaction and maintain it at a high temperature.
[0004]
FIG. 4 shows a conventional hydrogen generator for a fuel cell (see, for example, Patent Document 1). The fuel cell hydrogen generator 30 includes a reforming pipe 32 including a reforming catalyst 31 that reacts a raw material hydrocarbon fuel gas with water to reform the gas into a hydrogen-rich gas, and the fuel gas into the reforming pipe 32. A fuel supply unit 33 for supplying water to the reforming pipe 32, a water supply unit 34 for supplying water to the reforming pipe 32, a heating means 36 for providing a heat quantity necessary for the reforming reaction by the combustion of the combustion fuel in the combustion pipe 35, and a modification. A CO converter 37 that converts carbon monoxide contained in the reformed gas flowing out from the material pipe 32 into carbon dioxide by reacting with water, and carbon monoxide contained in the transformed gas flowing out from the CO converter 37 And 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 pipe diameter, etc.), and L is the length of the reforming catalyst layer in the gas flow direction. Show.
[0005]
The raw material hydrocarbon fuel gas is sent from the fuel supply unit 33 to the reforming pipe 32 after steam is added. The water vapor is generated when water such as cooling water flowing in the system is preheated by, for example, the heating unit 36 and heat exchanged with the exhaust heat of the fuel cell device by the water vapor generator 38. The fuel gas to which water vapor has been added comes into contact with the reforming catalyst 31 in the reforming pipe 32 and undergoes steam reforming to a gas rich in hydrogen (hydrogen-rich gas) by catalytic reaction (approximately 700 ° C., endothermic reaction). Since the produced hydrogen-rich gas contains carbon monoxide, the CO converter 37 converts carbon monoxide into carbon dioxide by reaction with excess water vapor (approximately 200 to 300 ° C., exothermic reaction). Carbon monoxide contained in the shift gas flowing out of the CO converter 37 is brought into contact with a selective oxidation catalyst (not shown) of the CO remover to react with air or oxygen (approximately 100 to 200 ° C., exothermic reaction) to form carbon dioxide. Then, reforming to a hydrogen rich gas with 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 composed of a burner 40 or the like for burning fuel for combustion such as fuel gas or unreacted hydrogen gas discharged from the fuel cell 39 is attached to the reforming pipe 32, and the reforming pipe 32 is burned by combustion in the combustion pipe 35. The amount of heat necessary for the reforming reaction is given, and the temperature of the reforming catalyst 31 is raised 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 high amount of heat necessary for a reforming reaction performed in a reformer and maintain the temperature at an appropriate high temperature to perform a reforming reaction at a high gas space velocity to cope with a high temperature. The object is to provide a reformer for a fuel cell having a high reforming rate and excellent long-term stability.
[0008]
[Means for Solving the Problems]
A reformer for a fuel cell according to claim 1 of the present invention for solving the above-described problems is a gas rich in hydrogen by reacting a city gas containing an organic compound having a hydrogen atom in its molecule or methane and water. In a reformer for a fuel cell, comprising a reforming catalyst for reforming, and a heating means for providing a heat amount 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] 7 to 38, and the reforming reaction is performed at a gas space velocity of 1000 hr ⁻¹ or less.
[0013]
In the reformer for a fuel cell, [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. High reforming that supports high temperature even when reforming reaction is performed at high gas space velocity by giving the heat necessary for reforming reaction in the reformer sufficiently by the reforming catalyst and maintaining it at an appropriate high temperature Rate is obtained. Furthermore, it also has the compactness required for a household fuel cell system with an electrical output of 1 kW.
[0014]
DETAILED DESCRIPTION OF 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 [amount of reforming catalyst (cm ³ ) / heat transfer area (cm ² )] Note that the heat transfer area means that the reforming catalyst is substantially in contact with the reforming tube. It shows the area of the part that is transferring heat through that part.
Using a reformer with a double cylindrical tube structure, the ratio of [reforming catalyst amount (cm ³ ) / heat transfer area (cm ² )] was changed to (0.3 to 1.3) to 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 (with a particle size of about 1.5 to 2.5 mm and a particle size of more than about 2.5 and 3.5 mm)
When the ratio of [reforming catalyst amount (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 quality catalyst amount (cm ³ ) / heat transfer area (cm ² )] was more than 0.5 and 1.3, a particle size exceeding about 2.5 and 3.5 mm was used.
Fuel gas: Methane reforming tube inner diameter: 40mm
Reforming catalyst layer length (L): 18 cm
[Reforming catalyst amount (cm ³ ) / heat transfer area (cm ² )]: 0.3 to 1.3
S / C: 2.5
Reformer temperature: 700 ° C. (Controlled gas outlet temperature of reformer)
However, the reforming rate was calculated by the following formula using the result of analyzing the gas composition after the reforming reaction (theoretical reforming rate under the above reforming reaction conditions is 94.8%).
[0015]
Reformation rate (%) = [(CO ₂ + CO concentration) / (CO ₂ + CO + CH ₄ concentration)] × 100
[0016]
From FIG. 1, when the gas space velocity is 500 hr ⁻¹ , the theoretical reforming rate is almost in the range of the ratio of [reforming catalyst amount (cm ³ ) / heat transfer area (cm ² )] of 0.3 to 0.8. When the gas space velocity is 1000 hr ⁻¹ , the theoretical reforming rate is almost in the range of the ratio of [reforming catalyst amount (cm ³ ) / heat transfer area (cm ² )] of 0.3 to 0.7. It can be seen that
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, 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 is reduced, and the catalyst particle size is 1.5. Even the use of ˜2.5 mm is not preferable because the catalyst filling rate decreases.
[0017]
(2) About the relationship between the reforming rate and L / S Using a reformer with a double cylindrical tube structure, the reforming catalyst amount is kept constant at 550 cm ³ and the L / S is changed to (2 to 38). 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 (with a particle size of about 1.5 to 2.5 mm and a particle size of more than about 2.5 and 3.5 mm)
[When L / S is 2 to 20, a particle size of about 1.5 to 2.5 mm is used, and when L / S exceeds 20 and 38, the particle size exceeds about 2.5. A 5 mm one was used.
Fuel gas: Methane reforming tube inner diameter: 40mm
A catalytic amount: 550cm ³
L / S: 2-38
S / C: 2.5
Reformer temperature: 700 ° C. (Controlled gas outlet temperature of reformer)
From FIG. 2, when the gas space velocity is 500 hr ⁻¹ , the theoretical reforming rate is almost obtained in the range of L / S from 7 to 38, and when the gas space velocity is 1000 hr ⁻¹ , the range of L / S is from 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, since the fuel cell system with an electrical output of 1 kw for home use was kept in mind, the catalyst amount was kept constant at 550 cm ³ , so the thickness of the catalyst layer was changed by 1 mm. Since the L / S changes greatly and the reforming pipe catalyst layer length exceeds 5 cm, it is judged that the L / S is not compact, and the upper limit value of L / S that can actually be used is up to about 38.
From the above, it can be seen that L / S is preferably 7 to 38, and more preferably 10 to 38.
[0018]
(3) Relationship between reforming rate and [reforming catalyst amount (cm ³ ) / heat transfer area (cm ² )] and L / S Reforming catalyst amount using a double cylindrical tube structure 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 of obtaining the reforming rate (%) when the gas space velocity is 1000 hr ⁻¹ under the following reforming reaction conditions.
Reforming catalyst: noble metal catalyst (with a particle size of about 1.5 to 2.5 mm and a particle size of over 2.5 mm with a particle size of about 2.5 mm)
The ratio of [reforming catalyst amount (cm ³ ) / heat transfer area (cm ² )] is 0. In the case of 4 to 0.5, a particle size of about 1.5 to 2.5 mm is used, and the ratio of [reforming catalyst amount (cm ³ ) / heat transfer area (cm ² )] is 0.5. In the case of exceeding 1.3, a particle having a particle diameter exceeding about 2.5 and 3.5 mm was used.
[When L / S is 2 to 20, a particle size of about 1.5 to 2.5 mm is used, and when L / S exceeds 20 and 38, the particle size exceeds about 2.5. A 5 mm one was used.
Fuel gas: Methane reforming pipe inner diameter: 20, 25, 30, 40, 50, 60 mm
S / C: 2.5
Reformer temperature: 700 ° C. (Controlled reformer outlet temperature)
[0019]
In FIG. 3, circles, squares, triangles, rhombuses, large circles, and large squares indicate test results for catalyst tube inner diameters of 20, 25, 30, 40, 50, and 60 mm, respectively, and black indicates theoretical reforming. The data obtained is the rate (94.8%), and the white one indicates that the theoretical modification rate (94.8%) was not obtained. In the figure, “X” indicates that the height of the reformer is too high to be miniaturized, and that it is not practical for a fuel cell system with an electrical output of 1 kW for home use, and it is not tested only by design.
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 The test of 0.3 is not performed because it is too small to be downsized and practical.
[0020]
The theoretical reforming rate can be 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. reforming catalytic amount (cm ³⁾ / heat transfer area (cm ^2)] is also in the range of 0.4 to 0.8, with L / S is not theoretical modification rate can be obtained and when it exceeds 38 The height of the reformer becomes too high to be miniaturized and is not practical.
[0021]
Although the theoretical reforming rate is obtained even when the L / D is less than 7, the catalyst layer length is actually too short, and the reforming rate is reduced by a slight variation in the amount of water vapor or variation in the amount of gas. fluctuate. Further, methane was used as the fuel gas, but since the sulfur component is contained in the actual gas, L / D is preferably 7 or more in consideration of sulfur poisoning.
1-3, [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 miniaturized, and the amount of heat required for the reforming reaction performed in the reformer can be sufficiently supplied to the reforming catalyst to maintain a high temperature in 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.
For example, [reforming catalyst amount (cm ³ ) / heat transfer area (cm ² )] of 0.3 indicates 0.25 to 0.34, and L / S of 38 indicates 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 is reduced, the catalyst filling rate is lowered, and However, if it exceeds 0.8, the heat transfer rate is limited, and a high reforming rate may not be obtained.
[0024]
When the L / S ratio is less than 7, the catalyst layer length becomes too short, and the reforming rate fluctuates due to slight fluctuations in the amount of water vapor or gas, and the amount of heat required for the reforming reaction is used as the reforming catalyst. If the L / S exceeds 38, the L / D may change greatly only by changing the thickness of the catalyst layer by 1 mm. There is a risk that the height will be too high to be miniaturized.
[0025]
The type and material of the reformer are not particularly limited. For example, the reformer may be any of a double tube structure, a flat plate structure, a multi-tube structure, etc. as shown in FIG. Good.
Any material can be used for the reformer as long as it does not interfere with the reforming reaction, such as stainless steel.
As for the heating means, the example of the heating means for giving the heat amount by the combustion of the combustion fuel in the combustion pipe is shown, but it is not limited to this.
[0026]
The description of the above embodiment is for explaining the present invention, and does not limit the invention described in the claims or reduce the scope thereof. Moreover, each part structure of this invention is not restricted to the said embodiment, A various deformation | transformation is possible within the technical scope as described in a claim.
[0027]
【The invention's effect】
A reformer for a fuel cell according to claim 1 of the present invention is a reforming catalyst that reforms a city gas containing an organic compound having hydrogen atoms in the molecule or a gas rich in hydrogen by reacting methane and water. A reformer for a fuel cell comprising heating means for providing a heat quantity 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] 7 to 38, and the reforming reaction is performed at a gas space velocity of 1000 hr ⁻¹ or less. By doing so, the structure is simple and inexpensive, and the long-term stability is improved. Even if the reforming reaction is carried out at a high gas space velocity by sufficiently giving the amount of heat necessary for the reforming reaction performed in the reformer by the reforming catalyst and maintaining it at an appropriate high temperature, the temperature can be increased. There is a remarkable effect that a corresponding high reforming rate can be obtained.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between the reforming rate and [reforming catalyst amount (cm ³ ) / heat transfer area (cm ² )].
FIG. 2 is a graph showing the relationship between the reforming rate (%) and [reforming catalyst layer length L / reforming catalyst layer cross-sectional area S].
FIG. 3 is a graph showing the 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]
30 Hydrogen generator for fuel cell 31 Reforming catalyst 32 Reforming pipe 33 Fuel supply part 34 Water supply part 35 Combustion pipe 36 Heating means 37 CO converter S Reforming catalyst layer cross-sectional area L Reforming catalyst layer length

Claims (1)

A heating means that provides a reforming catalyst that reforms a city gas containing an organic compound having a hydrogen atom in its molecule or a hydrogen-rich gas by reacting methane and water, and gives the amount of heat necessary for the reforming reaction A fuel cell reformer comprising:
[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] 7 to 38, and the reforming reaction is performed at a gas space velocity of 1000 hr ⁻¹ or less.

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