JP2000095506A - Fuel reformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel reformer capable of reducing the difference in temp. within a CO selective oxidation reaction section to uniformize the temp., and performing CO selective oxidation reaction at a temp. within the optimum temp. range to reduce the CO concn. in a reformed fuel. SOLUTION: This reformer is provided with: a reforming reaction section for reforming a raw fuel by steam reforming reaction to form a reformed gas consisting essentially of hydrogen; a shift reaction section for subjecting CO in the reformed gas to water-gas shift reaction to reduce the CO content in the reformed gas; and a CO selective oxidation reaction section 3 which has, in a vessel 7, a CO oxidation catalyst 6 for oxidizing CO remaining in the resulting reformed gas to further reduce the CO content in the reformed gas, wherein the CO selective oxidation reaction section 3 also has a liquid phase heating medium 8 in contact with the outer surface of the vessel 7 and also a gas phase heating medium 9 which is formed by vaporizing the liquid phase heating medium 8 and is in contact with the liquid phase heating medium 8. Thus, the heat of reaction, that is generated in the vessel 7 of the CO selective oxidation reaction section 3, is absorbed by the liquid phase heating medium 8 and consumed as the heat of vaporization of the heating medium 8, to prevent any local rise in temp. of the CO oxidation catalyst 6 from being caused and to enable uniformization of the temp. of the catalyst 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel reformer that uses an alcohol-based or hydrocarbon-based fuel as a raw fuel and generates a reformed gas containing hydrogen as a main component from the raw fuel.

[0002]

2. Description of the Related Art Conventionally, a raw fuel such as an alcohol fuel such as methanol or a hydrocarbon fuel such as methane, propane or butane is subjected to a steam reforming reaction to generate a reformed gas containing hydrogen as a main component. A fuel reformer is provided. A typical use of the reformed gas obtained by the fuel reformer is as a power generation material for a fuel cell.

[0003] In a reformed gas obtained by performing a steam reforming reaction in a fuel reformer, CO is usually produced and contained as one of the by-products. It becomes a catalyst poison of the battery and causes a decrease in the power generation capacity of the fuel cell. Therefore, a fuel reformer as shown in FIG. 4 is used.

[0004] In this apparatus, a reforming reaction section 1 for reforming a raw fuel by a steam reforming reaction to generate a reformed gas, and CO in the reformed gas generated in the reforming reaction section 1 are subjected to an aqueous shift. The shift reaction unit 2 that is reduced by the reaction and the CO selective oxidation reaction unit 3 that oxidizes and further reduces CO in the reformed gas treated in the shift reaction unit 2 are sequentially connected in series and arranged. The reforming reaction section 1, shift reaction section 2, and CO selective oxidation reaction section 3 can be heated by the combustion section 5. The reforming reaction section 1, shift reaction section 2, and CO selective oxidation reaction section 3 are each formed by filling a predetermined catalyst in a container, and form these reaction sections 1, 2, 3 respectively. The container is formed in a tubular shape such as a circular tube long in the gas flow direction in order to bring the gas into sufficient contact with the catalyst to improve the reaction efficiency.

Here, a reforming reaction section 1, a shift reaction section 2,
Each of the CO selective oxidation reaction sections 3 has a temperature range required for maintaining the reaction, and among these temperature ranges, there is an optimum temperature range for maintaining a better reaction state. The optimum temperature range varies depending on the type of the raw fuel and the catalyst. For example, when butane is used as the raw fuel, the optimum temperature range of the reforming reaction section 1 is 550 to 650 ° C. When a zinc-based catalyst is used, the optimum temperature range of the shift reaction section 2 is 220 to 260 ° C., and when a ruthenium-based catalyst is used for selective CO oxidation, the optimum temperature range of the CO selective oxidation reaction section 3 is 120 to 260 ° C. 1
40 ° C. The reaction heat required in each of the reaction units 1, 2, 3 is supplied using the combustion unit 5 as a heat source, and the amount of heat transferred from the combustion unit 5 to each of the reaction units 1, 2, 3 By adjusting the temperature, each reaction section 1, 2, 3
Within the required temperature range to generate reformed gas and C
A reaction for reducing O is performed.

[0006]

However, since each of the reforming reaction section 1, shift reaction section 2, and CO selective oxidation reaction section 3 has a structure that is long in the gas flow direction as described above, each reaction The catalyst temperature of the parts 1, 2, 3 causes a temperature difference between the gas inlet side and the gas outlet side. That is, since the reforming reaction in the reforming reaction section 1 is an endothermic reaction, the catalyst temperature on the gas outlet side tends to be lower than the catalyst temperature on the inlet side, and the shift reaction in the shift reaction section 2 The CO selective oxidation reaction in the CO selective oxidation reaction section 3 is an exothermic reaction, and conversely, the catalyst temperature on the gas outlet side tends to be higher than the catalyst temperature on the inlet side.

As described above, when a temperature difference occurs between the catalyst temperature at the gas inlet side and the gas outlet side in each of the reaction sections 1, 2, and 3 and partially deviates from the optimum temperature range, a desired good The reaction will be hindered. In particular, in the CO selective oxidation reaction section where the optimum temperature is relatively narrow, there is a problem that the temperature tends to partially deviate from the optimum temperature range, and the CO concentration in the reformed gas may not be sufficiently reduced.

The present invention has been made in view of the above points, and has been made to reduce the temperature difference in the CO selective oxidation reaction section to make it uniform, and to perform the CO selective oxidation reaction in an optimum reaction temperature range to reduce the CO concentration. It is an object of the present invention to provide a fuel reformer that can be reduced.

[0009]

A fuel reforming apparatus according to the present invention comprises a reforming reaction section 1 for reforming a raw fuel by a steam reforming reaction to generate a reformed gas containing hydrogen as a main component. A shift reaction section 2 for reducing the CO contained in the reformed gas generated in the reforming reaction section 1 by an aqueous shift reaction, and oxidizing CO in the reformed gas treated in the shift reaction section 2 to further reduce the CO In a fuel reformer formed with a CO selective oxidation reaction section 3 having a CO oxidation catalyst 6 to be formed inside a container 7, a liquid phase heat medium 8 in contact with the outer surface of the container 7 of the CO selective oxidation reaction section 3 And a liquid-phase heat medium 8 which is vaporized into a gaseous phase is provided in contact with the liquid-phase heat medium 8.

A second aspect of the present invention is characterized in that a heat exchanger 10 is provided so as to be connected to the gaseous heat medium 9.

[0011] The invention according to claim 3 provides the heat exchanger 1 as described above.
0 is externally cooled.

Further, the invention of claim 4 is characterized in that water is used as the heat medium 8 in the liquid phase.

Further, the invention of claim 5 is characterized in that a means for heating the liquid-phase heat medium 8 is provided.

[0014]

Embodiments of the present invention will be described below.

FIG. 4 shows the overall configuration of a fuel reforming apparatus, which is formed by connecting a reforming reaction section 1, a shift reaction section 2, and a CO selective oxidation reaction section 3 in series. 1,
2 and 3 can be heated by the combustion section 5, respectively. Each of the reforming reaction section 1, shift reaction section 2, and CO selective oxidation reaction section 3 is formed by filling a catalyst into a tubular container such as a circular tube long in the gas flow direction. These catalysts include, for example, the reforming reaction section 1
Is a reforming catalyst such as a nickel-based, ruthenium-based or rhodium-based reforming catalyst for a steam reforming reaction, and a shift reaction unit 2 is a copper-zinc-based shift catalyst for an aqueous shift reaction.
Platinum for CO selective oxidation reaction is provided in the selective oxidation reaction section 3,
A CO oxidation catalyst such as ruthenium is used.
Further, the combustion unit 5 includes combustion means such as a burner and a combustion catalyst. The combustion unit 5 burns the fuel and supplies the combustion heat, so that the reforming reaction unit 1, the shift reaction unit 2, the CO selective oxidation reaction unit 3 Can be heated individually. Each of these reaction sections 1, 2, 3 is connected to the combustion section 5 in order of increasing heating capacity.

As the raw fuel, an alcohol fuel such as methanol or a hydrocarbon fuel such as methane, propane or butane can be used. And a steam reforming reaction of the raw fuel by the action of the reforming catalyst to generate a reformed gas mainly composed of hydrogen. Since this reformed gas contains CO, the reformed gas generated in the reforming reaction section 1 is supplied to the shift reaction section 2, and the CO in the reformed gas is subjected to the aqueous shift reaction by the action of the shift catalyst. Let it be reduced. Shift reaction unit 2
, The amount of CO in the reformed gas is reduced, but the trace amount still remains. Therefore, the reformed gas processed in the shift reaction unit 2 is supplied to the CO oxidation selective reaction unit 3. At the same time, air is also supplied to the CO oxidation selective reaction section 3, and the CO in the reformed gas is oxidized by the action of the CO oxidation catalyst to further reduce it. The hydrogen-rich reformed gas having a low CO concentration in this manner is supplied to a fuel cell or the like.

FIG. 1 shows the CO selective oxidation reaction section 3 of the fuel reformer formed as described above. The CO selective oxidation reaction section 3 contains a C gas in a tubular container 7 long in the gas flow direction.
It is formed by filling the O oxidation catalyst 6. A heating medium container 12 is provided on the outer periphery of the tubular container 7 so as to surround the entire container 7 and the entire CO oxidation catalyst 6. Fins 13 are provided. The heat medium container 12 is in a closed state, and the heat medium 8 in a liquid phase is sealed in the heat medium container 12. The container 7 is located below the heat medium container 12, and the liquid-phase heat medium 8 is contained in the container 7 with a volume that is about half the volume of the heat medium container 12. Therefore, the container 7 is the heat medium container 1
2 so as to be immersed in the heat medium 8 in the liquid phase.
A liquid-phase heat medium 8 is in contact with the entire outer surface of the container 7 of the O selective oxidation reaction section 3. In the space above the liquid surface of the liquid-phase heat medium 8 in the heat medium container 12, there is a gas-phase heat medium 9 in which the liquid-phase heat medium 8 is vaporized. Numeral 9 is in contact with liquid-phase heat medium 8 at its liquid level.

In the CO selective oxidation reaction section 3 formed as described above, first, before the operation of the fuel reformer is started, the combustion section 5 is burned and the heat thereof is used to heat the fins 13 of the heat medium container 12. To heat the liquid-phase heat medium 8 in the heat medium container 12 from the fins 13 through the heat medium container 12, and further heat the CO oxidation catalyst 6 in the CO selective oxidation reaction section 3 with the heat medium 8. Heat to the optimal temperature. Thus, CO
After the oxidation catalyst 6 is heated to a predetermined optimum temperature, the operation of the fuel reformer is started, and thereafter the fin 1
The heating of 3 is stopped.

The reformed gas generated in the reforming reaction section 1 and processed in the shift reaction section 2 flows in from the gas inlet 7a at one end of the vessel 7 and comes into contact with the CO oxidation catalyst 6. After undergoing the CO selective oxidation reaction, the gas is discharged from the gas outlet 7b at the other end of the container 7. Here, as described above, C
The CO selective oxidation reaction in the O selective oxidation reaction section 3 is an exothermic reaction, and the temperature of the CO oxidation catalyst 6 on the gas outlet 7b side tends to be higher than the temperature of the CO oxidation catalyst 6 on the gas inlet 7a side. However, this reaction heat is absorbed as heat of vaporization by the liquid-phase heat medium 8 via the container 7. The gas phase heat medium 9 in which the liquid phase heat medium 8 is vaporized is cooled and condensed by the radiating action of the fins 13 and returns to the liquid phase heat medium 8 again. As described above, the heat of reaction of the CO selective oxidation reaction section 3 is the heat medium 8 in the liquid phase.
CO selective oxidation reaction part 3
It is possible to prevent the temperature of the CO oxidation catalyst 6 from becoming partially high, thereby making the catalyst temperature uniform, and to prevent the CO oxidation catalyst 6 from being partially out of the optimum temperature range. Therefore, CO in the CO selective oxidation reaction section 3
The selective oxidation reaction can be performed in an optimum reaction temperature range, and it becomes easy to reduce the CO concentration in the reformed gas.

Here, when a ruthenium-based catalyst is used as the CO selective oxidation catalyst, the optimum reaction temperature of the CO selective oxidation reaction section 3 is 120 to 140 ° C. as described above. Therefore, in this case, the heat medium 8 is 120 to 14
A substance in which a liquid phase and a gaseous phase coexist at a pressure near the atmospheric pressure at 0 ° C.,
That is, those having a boiling point near this temperature are preferable. For example, water can be used as the heat medium 8. Since water has a large heat of vaporization and can efficiently absorb the heat of reaction,
In this regard, it is preferable to use water as the heat medium 8.

FIG. 2 shows another embodiment of the present invention, in which a heat exchanger 10 is provided in connection with a heat medium 9 in a gas phase. The heat exchanger 10 is mounted on an upper part of a heat medium container 12 and has a heat medium container 1 in which a gaseous heat medium 9 exists.
It is connected with the upper part of 2 by a communication pipe 14. Other configurations are the same as those in FIG. 1 (the fins 13 are not shown in FIG. 2). In this case, when the heat medium 8 in the liquid phase is heated by the reaction heat of the CO selective oxidation reaction unit 3 and is vaporized to become the heat medium 9 in the gas phase, the heat medium 9 in the gas phase is transmitted from the communicating pain tube 14 through the pain tube 14. It enters the heat exchanger 10 and is cooled and condensed by the heat radiating action of the heat exchanger 10 to become the liquid-phase heat medium 8. The liquid-phase heat medium 8 condensed in the heat exchanger 10 is returned to the heat medium container 12 through the communication pipe 14. As described above, since the heat medium 9 in the liquid phase can be cooled by the heat exchanger 10 because the heat medium 9 in the liquid phase is vaporized and becomes a gas phase.
The heat of vaporization can be efficiently released to the outside, and the effect of absorbing the heat of reaction of the CO selective oxidation reaction section 3 and making the temperature of the CO oxidation catalyst 6 uniform can be highly obtained.

In this case, the fan 15 is connected to the heat exchanger 10.
For example, means for cooling the heat exchanger 10 from outside may be provided. In this way, the heat exchanger 10 can be forcibly cooled and the heat of vaporization can be more efficiently discharged to the outside. The reaction heat of the CO selective oxidation reaction section 3 is absorbed and the CO oxidation catalyst is absorbed. 6, the effect of making the temperature uniform can be further enhanced.

FIG. 3 shows still another embodiment of the present invention. In this embodiment, a heating means such as an electric heater 16 is provided in a heating medium container 12 so as to be immersed in a heating medium 8 in a liquid phase. It is provided. Other configurations are the same as those in FIG. 2 (the fins 13 are not shown in FIG. 3). In this case, the liquid heating medium 8 can be heated by the heater 16 to maintain the temperature of the liquid heating medium 8 at a predetermined temperature. It becomes easy to control the temperature to a predetermined temperature, so that the CO selective oxidation
This facilitates the selective oxidation reaction.

[0024]

As described above, the present invention provides a reforming reaction section for reforming raw fuel by a steam reforming reaction to generate a reformed gas containing hydrogen as a main component, and a reforming reaction section formed by the reforming reaction section. A shift reaction section for reducing CO contained in the reformed gas by an aqueous shift reaction, and a CO oxidation catalyst for oxidizing and further reducing CO in the reformed gas treated in the shift reaction section. In a fuel reformer formed with a selective oxidation reaction section, a liquid phase heat medium in contact with the outer surface of the vessel of the CO selective oxidation reaction section is provided, and the liquid phase heat medium is vaporized to form a gas phase. Because the heat medium that has become the heat medium in the liquid phase is provided in contact with the heat medium in the liquid phase, the heat of reaction of the CO selective oxidation reaction section is absorbed by the heat medium in the liquid phase as heat of vaporization. That the temperature of the CO oxidation catalyst partially increases In addition, the catalyst temperature can be made uniform and the CO oxidation catalyst can be partially prevented from deviating from the optimum temperature range. The density can be reduced.

According to the second aspect of the present invention, since the heat exchanger is provided by connecting to the above-described heat medium in the gas phase, the heat medium in the gas phase which has been vaporized from the heat medium in the liquid phase is converted into the heat medium. It can be cooled by an exchanger, can efficiently release heat of vaporization to the outside, and can enhance the effect of absorbing the reaction heat of the CO selective oxidation reaction section to make the temperature of the CO oxidation catalyst uniform. Is what you can do.

Further, since the invention of claim 3 includes means for cooling the heat exchanger from the outside, the heat exchanger can be forcibly cooled and the heat of vaporization can be more efficiently discharged to the outside. The effect of absorbing the reaction heat of the CO selective oxidation reaction section and making the temperature of the CO oxidation catalyst uniform can be further enhanced.

According to the invention of claim 4, since water is used as the heat medium of the liquid phase, the water has a large heat of vaporization, and can efficiently absorb the reaction heat of the CO selective oxidation reaction section. It is possible to obtain a high effect of making the temperature of the CO oxidation catalyst uniform.

According to a fifth aspect of the present invention, since the means for heating the liquid phase heat medium is provided, the temperature of the liquid phase heat medium can be maintained at a predetermined temperature. In addition, it is easy to control the temperature of the CO selective oxidation reaction section to a predetermined temperature, and it is easy to perform the CO selective oxidation reaction in the optimum temperature range.

[Brief description of the drawings]

FIG. 1 is a sectional view of a CO selective oxidation reaction section according to an example of an embodiment of the present invention.

FIG. 2 is a sectional view of a CO selective oxidation reaction section according to another example of the embodiment of the present invention.

FIG. 3 is a cross-sectional view of a CO selective oxidation reaction section according to another example of the embodiment of the present invention.

FIG. 4 is a schematic configuration diagram illustrating an example of a fuel reforming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reforming reaction part 2 Shift reaction part 3 CO selective oxidation reaction part 6 CO oxidation catalyst 7 Container 8 Liquid phase heat medium 9 Gas phase heat medium 10 Heat exchanger

Claims (5)

[Claims] 1. A reforming reaction section for reforming a raw fuel by a steam reforming reaction to generate a reformed gas containing hydrogen as a main component, and the reformed gas generated in the reforming reaction section is included in the reforming reaction section. A shift reaction section for reducing CO by an aqueous shift reaction, and a CO selective oxidation reaction section having a CO oxidation catalyst for oxidizing and further reducing CO in the reformed gas treated in the shift reaction section. In the fuel reforming apparatus formed by the above method, a liquid-phase heat medium is provided in contact with the outer surface of the vessel of the CO selective oxidation reaction section, and the heat medium in the liquid phase is vaporized to become a gas phase. A fuel reformer characterized by being provided in contact with the heat medium of (1). 2. The fuel reformer according to claim 1, further comprising a heat exchanger connected to the gaseous heat medium. 3. The fuel reformer according to claim 2, further comprising means for externally cooling the heat exchanger. 4. The fuel reformer according to claim 1, wherein water is used as the heat medium in the liquid phase. 5. The fuel reformer according to claim 1, further comprising means for heating the heat medium in the liquid phase.