JP4189212B2 - Hydrogen generator and fuel cell system including the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hydrogen generator for obtaining a hydrogen-rich reformed gas supplied to a fuel cell, and a fuel cell system including the hydrogen generator.
[0002]
[Prior art]
In order to generate power in the fuel cell, it is necessary to supply a hydrogen-rich gas to the fuel cell. As a conventional example of a hydrogen generator that generates such a gas, there is an apparatus in which an evaporation chamber that generates water vapor used for a reforming reaction is configured by a coiled pipe wound in a downward gradient (for example, , See Patent Document 1). FIG. 5 is a cross-sectional view schematically showing the configuration of this conventional hydrogen generator. As shown in FIG. 5, the conventional hydrogen generator includes a cylindrical reformer 1 filled with a granular or columnar catalyst, and a burner 2 </ b> A that is a combustion section that heats the reformer 1. I have. The coiled pipe 3 described above is disposed in the combustion cylinder 2B provided above the burner 2A and inside the reformer 1, and the outlet of the coiled pipe 3 is connected to the steam supply pipe 4. Has been. The steam supply pipe 4 is connected to the raw material supply pipe 7 to become a mixed gas introduction pipe 8, and this mixed gas introduction pipe 8 is connected to a mixed gas chamber 9 provided above the combustion cylinder 2B. A reformed gas flow path 5 through which the reformed gas flows is disposed on the outer peripheral side of the reformer 1, and a combustion gas flow path 6 is disposed on the outer peripheral side of the reformed gas flow path 5. Yes.
[0003]
In the conventional hydrogen generator configured as described above, the water Y used for the reforming reaction is supplied from the upper part of the coiled pipe 3 and heated by the combustion gas while moving in the pipe. Thereby, after passing through the state of the gas-liquid two-phase flow, it is supplied to the steam supply pipe 4 as water vapor. The water vapor thus supplied to the steam supply pipe 4 is supplied to the mixed gas chamber 9 through the mixed gas introduction pipe 8 together with the raw material X flowing through the raw material supply pipe 7. The steam and the raw material X supplied to the mixed gas chamber 9 are supplied to the reformer 1 and become a reformed gas by a steam reforming reaction, and are discharged to the outside through the reformed gas channel 5. Further, the combustion gas generated in the burner 2A heats the coiled pipe 3 and the reformer 1, and then passes through the combustion gas flow path 6 and is discharged to the outside.
[0004]
[Patent Document 1]
JP 2000-281111 A
[Problems to be solved by the invention]
However, in the conventional hydrogen generator described above, since the combustion gas flow path 6 is disposed on the outermost peripheral side of the apparatus, there is a problem in that the amount of heat released to the surroundings increases and the thermal efficiency decreases.
Further, since the steam generated in the coiled pipe 3 is supplied to the reformer 1 through the steam supply pipe 4 routed in the apparatus, the heat radiation from the steam supply pipe 4 is increased, There was a problem that the thermal efficiency further decreased.
[0006]
Furthermore, since the coiled pipe 3 is heated with a high-temperature combustion gas, a so-called dry-out state in which water does not exist is generated on the inner surface of the coiled pipe 3, and as a result, a bumping state in which the water is intermittently evaporated is likely to occur. The water vapor generated by this bumping state rapidly expands by changing from the liquid phase to the gas phase. Therefore, the flow path resistance in the pipe increases rapidly. Therefore, when the bumping state is repeated, the pulsation of the supply pressure of water Y increases, and the supply amount of water Y, and hence the supply amount of water vapor, pulsates. Thus, when the amount of water vapor provided for the catalytic reaction in the reformer 1 pulsates, there has been a problem that the concentration of carbon monoxide (CO) in the reformed gas tends to fluctuate. Moreover, since the steam flowing through the steam supply pipe 4 is mixed with the raw material X and supplied to the reformer 1, the supply pressure of the raw material X pulsates due to the pulsation of the flow rate of the steam. As a result, since the flow rate of the raw material X pulsates, the flow rate of the reformed gas supplied to the fuel cell also pulsates, causing a problem that the amount of power generation in the fuel cell becomes unstable.
[0007]
The present invention has been made in view of such circumstances, and its purpose is to improve the thermal efficiency, stabilize the CO concentration in the reformed gas, and stabilize the supply amount of the reformed gas. It is to provide a generation device.
[0008]
[Means for Solving the Problems]
In order to solve the above-described problems, a hydrogen generator according to the present invention includes a combustion section that generates combustion gas, a combustion gas passage through which the combustion gas generated by the combustion section flows, and heat transfer from the combustion gas. A reformer that generates a reformed gas containing hydrogen by a steam reforming reaction from a raw material containing a compound composed of at least carbon and hydrogen and steam, and water supplied from the outside as the combustion gas An evaporation chamber for generating steam by evaporating using heat transfer from the combustion gas flowing in the flow path and supplying the steam to the reformer, and the combustion gas flow path of the reformer provided so as to cover at least a portion of the outer, the evaporating chamber is provided so as to cover at least part of the outside of the combustion gas flow passage, a first evaporation chamber having an inlet for water or steam, Within the first evaporation chamber In addition, a second evaporation chamber provided outside the combustion gas flow path and having a water vapor outlet is provided, and the first evaporation chamber and the second evaporation chamber are provided with a wall therebetween. And at least one opening formed in the wall.
Thus, since the reformer having the highest temperature is disposed on the inner side and the evaporation chamber having the lowest temperature is disposed on the outer side, the thermal efficiency can be improved as compared with the conventional case. Further, by disposing the first evaporation chamber outside the second evaporation chamber where superheated steam is generated, liquid water and saturated water vapor pass through the inside, so that the outside of the first evaporation chamber is about 100 ° C. The temperature can be lowered to the following. Therefore, the amount of heat released to the surroundings can be reduced, and the thermal efficiency can be further improved.
[0012]
Further, since the water vapor generated in the first evaporation chamber passes through the opening and quickly moves to the second evaporation chamber, an increase in pressure due to volume expansion when water vapor is generated in the first evaporation chamber can be reduced. Thereby, since the fluctuation | variation of the supply pressure of water can be made small, the amount of water vapor | steam supplied to a reformer can be stabilized. Therefore, the catalytic reaction can be stabilized, and the CO concentration and the hydrogen amount in the reformed gas can be stabilized.
[0013]
Further, in the hydrogen generator according to the invention, the evaporation chamber has a cylindrical space surrounded by an outer cylinder and an inner cylinder, and the cylindrical wall is disposed in the cylindrical space, thereby arranging the cylindrical wall. It is preferable to provide a first evaporation chamber and the second evaporation chamber.
[0014]
In the hydrogen generator according to the invention, a flow path resistance portion is formed in the circumferential direction in the first evaporation chamber, and a flow path of water or water vapor is defined by the flow path resistance portion. preferable. In this case, it is preferable that the flow path of the water or water vapor is defined in a spiral shape by the flow path resistance portion.
[0015]
If comprised in this way, since the evaporation capability of water can be improved and the amount of steam provided to the steam reforming reaction can be increased, the conversion rate of the raw material is improved and the amount of hydrogen is increased.
[0016]
In the hydrogen generator according to the invention, it is preferable that the first evaporation chamber has an inlet for the raw material.
[0017]
In the hydrogen generator according to the invention, it is preferable that a temperature detector is provided in the vicinity of the lower end of the evaporation chamber .
[0018]
Further, in the hydrogen generator according to the invention, the steam and the combustion gas are configured to be able to exchange heat in a path from the steam outlet of the second evaporation chamber to the reformer. Is preferred.
[0019]
In the hydrogen generator according to the invention, it is preferable that a combustion gas flow path is disposed outside the first evaporation chamber.
[0020]
Furthermore, it is preferable that the hydrogen generator according to the invention further includes a water preheating unit for heating water or steam supplied to the first evaporation chamber with combustion gas.
[0021]
A fuel cell system according to the present invention generates power using the hydrogen generator according to any one of claims 1 to 9 , an oxidizing gas containing oxygen, and a reformed gas supplied from the hydrogen generator. A fuel cell. Thereby, the electric power generation amount in a fuel cell can be stabilized.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.
[0023]
(Embodiment 1)
FIG. 1 is a cross-sectional view schematically showing the configuration of the hydrogen generator according to Embodiment 1 of the present invention. As shown in FIG. 1, the hydrogen generator 100 according to the present embodiment includes a burner 16 that generates combustion gas, and a cylindrical combustion chamber 17 provided above the burner 16. A cylindrical reformer 10 is provided coaxially with the combustion chamber 17 on the outer peripheral side of the combustion chamber 17. The reformer 10 accommodates a catalyst layer filled with a steam reforming catalyst, and generates a reformed gas by subjecting the raw material gas to a steam reforming reaction in the catalyst layer.
[0024]
A fuel cell 101 is provided outside the hydrogen generator 100, and the hydrogen generator 100 and the fuel cell 101 constitute the fuel cell system of the present invention. The reformed gas generated in the reformer 10 is discharged from the reformed gas outlet 27 and supplied to the fuel cell 101.
[0025]
A cylindrical reformed gas channel 11 for guiding the reformed gas generated in the reformer 10 to the reformed gas outlet 27 is provided on the outer peripheral side of the reformer 10. A cylindrical combustion gas passage 12 through which combustion gas generated in the burner 16 flows is provided coaxially with the combustion chamber 17 on the outer peripheral side of the burner 16. The combustion gas flow path 12 is composed of a flow path partitioned by a cylindrical heat insulating material 13 and a cylindrical body 14, and is configured to guide the combustion gas toward the combustion gas discharge port 15.
[0026]
Further, a cylindrical evaporation chamber 28 is provided coaxially with the combustion chamber 17 on the outer peripheral side of the combustion gas passage 12 and on the outermost periphery of the hydrogen generator 100. The evaporation chamber 28 includes a cylindrical first evaporation chamber 18 and a second evaporation chamber 22 provided with the first evaporation chamber 18 and a cylindrical partition wall 21 therebetween. Here, the second evaporation chamber 22 is located on the combustion gas flow path 12 side, and the first evaporation chamber 18 is located on the outer periphery side of the second evaporation chamber 22 via the partition wall 21, that is, on the outermost periphery of the hydrogen generator 100. ing. A raw material inlet 19 for supplying a raw material X containing a compound composed of at least carbon and hydrogen into the apparatus and a water inlet 20 for supplying water Y are formed in the upper part of the first evaporation chamber 18. ing. Examples of the compound composed of at least carbon and hydrogen include hydrocarbons such as methane, ethane, and propane, city gas, natural gas, alcohol such as methanol, kerosene, and LPG (liquefied petroleum gas). Further, a water vapor outlet 24, which is an outlet for water vapor generated in the evaporation chamber 28, is provided above the second evaporation chamber 22. The steam outlet 24 is connected to the reformer 10 via a steam supply pipe 25. Therefore, the steam discharged from the steam outlet 24 is supplied to the reformer 10 through the steam supply pipe 25.
[0027]
The first evaporation chamber 18 and the second evaporation chamber 22 communicate with each other through a plurality of openings 23 and a communication portion 26 formed in the partition wall 21. Hereinafter, this configuration will be described in detail with reference to FIG.
[0028]
FIG. 2 is a cutaway sectional view showing the configuration of the lower left end of the hydrogen generator 100 shown in FIG. As shown in FIG. 2, the partition wall 21 does not extend to the bottom wall 29 of the hydrogen generator 100, and a gap with a predetermined width extends around the entire circumference between the lower end of the partition wall 21 and the bottom wall 29. Is formed. This gap serves as a communication portion 26 that connects the first evaporation chamber 18 and the second evaporation chamber 22. A plurality of openings 23 are formed at appropriate locations of the partition wall 21. The shape of the opening 23 is not limited to a specific shape, and may be any shape such as a circle, an oval, an ellipse, or a rectangle.
[0029]
Next, operation | movement of the hydrogen generator 100 of this Embodiment comprised as mentioned above is demonstrated.
[0030]
The combustion gas generated in the burner 16 passes through the combustion gas passage 12 while sequentially heating the reformer 10, the reformed gas passage 11, and the second evaporation chamber 22, and passes from the combustion gas discharge port 15 to the outside. Discharged. Water Y to be used for the steam reforming reaction performed in the reformer 10 is supplied from the outside through the water inlet 20 and moves downward in the first evaporation chamber 18. At this time, the water Y is evaporated by the heat transfer from the combustion gas passing through the combustion gas passage 12 to become water vapor. Thus, since the water Y is evaporated using the heat transfer from the combustion gas, it is necessary to increase the amount of heat transfer from the combustion gas in order to perform the evaporation reliably. Here, in order to increase the heat transfer amount from the combustion gas, the time for the water Y to pass through the first evaporation chamber 18 may be increased. Therefore, it is desirable that the water inlet 20 is provided as high as possible above the first evaporation chamber 18.
[0031]
The water vapor generated in the first evaporation chamber 18 moves to the second evaporation chamber 22 through a plurality of openings 23 formed in the partition wall 21. The water Y that has not evaporated in the first evaporation chamber 18 accumulates at the lower end portion of the first evaporation chamber 18, passes through the connecting portion 26, and also accumulates at the lower end portion of the second evaporation chamber 22. As shown in FIG. 1, since the combustion gas flows upward from the lower side of the second evaporation chamber 22, heat transfer to the water Y accumulated at the lower ends of the first evaporation chamber 18 and the second evaporation chamber 22 is promoted. Since liquid phase water and saturated water vapor flow in the first evaporation chamber 18, the temperature of the outer peripheral surface of the hydrogen generator 100 can be lowered to about 100 ° C. or less. Therefore, since the amount of heat released to the surroundings can be reduced, the thermal efficiency of the hydrogen generator 100 is improved. Moreover, since the water vapor generated in the first evaporation chamber 18 moves quickly to the second evaporation chamber 22 by providing the opening 23, an increase in pressure in the first evaporation chamber 18 due to the volume expansion of the generated water vapor is suppressed. can do. As a result, the fluctuation in the supply pressure of the water Y can be reduced, and the amount of water vapor supplied from the water vapor outlet 24 to the reformer 10 can be stabilized, so that the catalytic reaction in the reformer 10 becomes steady and in the reformed gas. The fluctuation of the CO concentration can be reduced.
[0032]
The raw material X is supplied from the outside through the raw material inlet 19 and flows into the reformer 10 from the steam supply pipe 25 through the first evaporation chamber 18 and the second evaporation chamber 22. Thereby, in the reformer 10, a hydrogen-rich reformed gas is generated by the steam reforming reaction with the reforming catalyst. The steam reforming reaction is an endothermic reaction that occurs at a high temperature of about 700 ° C., and is performed using heat transfer from the combustion gas. The reformed gas thus generated passes through the reformed gas channel 11 and is discharged from the reformed gas outlet 27 and supplied to the fuel cell 101.
[0033]
Moreover, since the raw material X is preheated by heat transfer from the combustion gas when passing through the first evaporation chamber 18 and the second evaporation chamber 22, the thermal efficiency of the hydrogen generator 100 can be improved. In order to increase the heat transfer area, fins are provided on the first evaporation chamber 18, the first evaporation chamber 18 side of the second evaporation chamber 22, and the combustion gas flow path 12 side of the second evaporation chamber 22, respectively. It may be. By providing the fins in this way, the evaporation amount of the water Y can be increased.
[0034]
(Embodiment 2)
FIG. 3 is a cross-sectional view schematically showing the configuration of the hydrogen generator 100 according to Embodiment 2 of the present invention. As shown in FIG. 3, a round bar serving as a flow path resistance portion is spirally wound in the cylindrical first evaporation chamber 18, and thereby the spiral flow path 18 </ b> A is formed in the first evaporation chamber 18. Is formed. Further, below the first evaporation chamber 18 and the second evaporation chamber 22, temperature detection means 32 configured by a temperature sensor for detecting the temperatures of the bottoms of the first evaporation chamber 18 and the second evaporation chamber 22 is provided. ing. Further, the water vapor supply pipe 25 is provided with a heat exchange unit 33.
[0035]
In addition, about the other structure of the hydrogen generator 100 of this Embodiment, since it is the same as that of the case of Embodiment 1, it attaches | subjects the same code | symbol and abbreviate | omits description.
[0036]
Next, operation | movement of the hydrogen generator 100 of this Embodiment comprised as mentioned above is demonstrated.
[0037]
The water Y supplied from the outside through the water inlet 20 moves downward along the round bar 31 in the spiral flow path 18A. By moving the water Y along the round bar 31 wound spirally in this way, the time during which the water Y stays in the first evaporation chamber 18 becomes longer, and the water Y stays in the water Y. The distribution in the circumferential direction is made uniform. As a result, the amount of heat transferred from the combustion gas increases, so that the amount of steam provided for the steam reforming reaction can be increased. Therefore, the conversion rate of the raw material X can be increased and the amount of hydrogen in the reformed gas can be increased.
[0038]
In this way, in order to make the water Y stay in the first evaporation chamber 18 for a long time and to make the distribution of the staying water Y in the circumferential direction uniform, the water Y supplied from the outside immediately flows into the first evaporation chamber. Any structure can be used as long as it can be prevented from flowing down to the bottom. Therefore, the flow path 18A does not necessarily have a spiral shape, and it is sufficient that a flow path resistance unit for moving water or water vapor at least in the circumferential direction is provided.
[0039]
The heat exchange unit 33 performs heat exchange between the water vapor passing through the water vapor supply pipe 25 and the combustion gas. Thereby, since the heat | fever of combustion gas can be collect | recovered, the thermal efficiency of the hydrogen production | generation apparatus 100 can be improved further.
[0040]
The temperature detector 32 detects the temperatures of the bottoms of the first evaporation chamber 18 and the second evaporation chamber 22. Based on the detected temperature, it is possible to estimate whether water Y is accumulated in the bottoms of the first evaporation chamber 18 and the second evaporation chamber 22 or in an evaporated state. For example, when the detected temperature is lower than a predetermined temperature, it is estimated that water Y has accumulated at the bottoms of the first evaporation chamber 18 and the second evaporation chamber 22. When estimated in this way, evaporation in the first evaporation chamber 18 and the second evaporation chamber 22 can be reliably performed by reducing the supply amount of the water Y.
[0041]
Note that a spiral channel may be formed in the second evaporation chamber 22 in the same manner as the spiral channel 18A. In this case, since the residence time of water vapor passing through the second evaporation chamber 22 can be increased, the temperature of the water vapor can be increased.
[0042]
Further, the spiral flow path 18A can be configured by providing a spiral rib portion on the partition wall 21, and the round bar 31 is not necessarily provided.
[0043]
(Embodiment 3)
FIG. 4 is a cross-sectional view schematically showing the configuration of the hydrogen generator according to Embodiment 3 of the present invention. As shown in FIG. 4, a cylindrical combustion gas flow path 12 </ b> A is provided coaxially with the first evaporation chamber 18 on the outer peripheral side of the first evaporation chamber 18. A combustion gas discharge port 15 is formed in the lower part of the combustion gas passage 12A. In addition, a water preheating unit 41 for heating the water Y supplied to the first evaporation chamber 18 with combustion gas is provided at the upper part of the hydrogen generator 100.
[0044]
In addition, since it is the same as that of the case of Embodiment 2 about the other structure of the hydrogen generator 100 of this Embodiment, it attaches | subjects the same code | symbol and abbreviate | omits description.
[0045]
Next, operation | movement of the hydrogen generator 100 of this Embodiment comprised as mentioned above is demonstrated.
[0046]
The combustion gas flowing along the second evaporation chamber 22 flows around the water preheating portion 41 provided on the downstream side, passes through the combustion gas flow path 12A provided on the outer peripheral side of the first evaporation chamber 18, and It is discharged from the combustion gas discharge port 15. Since the water Y supplied to the water preheating unit 41 is preheated by heat transfer from the combustion gas, the thermal efficiency can be improved. Further, since the combustion gas flows through the combustion gas passage 12A, the evaporation capacity is greatly improved by the heat transfer from the combustion gas to the first evaporation chamber 18, and the temperature of the combustion gas discharged from the combustion gas discharge port 15 is lowered. Therefore, the thermal efficiency can be further improved.
[0047]
It should be noted that various hydrogen generators can be realized by appropriately combining some of the above-described embodiments in accordance with the use of the fuel cell system including the hydrogen generator of the present invention.
[0048]
【The invention's effect】
As described above, according to the hydrogen generator of the present invention, the present invention can improve the thermal efficiency, stabilize the CO concentration in the reformed gas, and stabilize the supply amount of the reformed gas. Excellent effect.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically showing a configuration of a hydrogen generator according to Embodiment 1 of the present invention.
2 is a cutaway sectional view showing a configuration of a lower left end portion of the hydrogen generator shown in FIG. 1. FIG.
FIG. 3 is a cross-sectional view schematically showing a configuration of a hydrogen generator according to Embodiment 2 of the present invention.
FIG. 4 is a cross-sectional view schematically showing a configuration of a hydrogen generator according to Embodiment 3 of the present invention.
FIG. 5 is a cross-sectional view schematically showing a configuration of a conventional hydrogen generator.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Reformer 11 Reformed gas flow path 12 Combustion gas flow path 12A Combustion gas flow path 13 Heat insulating material 14 Cylinder 15 Combustion gas discharge port 16 Burner 17 Combustion chamber 18 First evaporation chamber 18A Spiral flow path 19 Raw material inlet 20 Water inlet 21 Partition 22 Second evaporation chamber 23 Opening portion 24 Steam outlet 25 Steam supply pipe 26 Connecting portion 27 Reformed gas outlet 28 Evaporating chamber 29 Bottom wall 31 Round bar 32 Temperature detecting means 33 Heat exchanging portion 41 Water preheating portion 100 Hydrogen generator 101 Fuel cell

Claims (10)

A combustion section for generating combustion gas;
A combustion gas passage through which combustion gas generated by the combustion section flows;
A reformer for generating a reformed gas containing hydrogen by a steam reforming reaction from a raw material containing a compound composed of at least carbon and hydrogen and steam using heat transfer from the combustion gas;
An evaporation chamber for generating water vapor by evaporating water supplied from the outside using heat transfer from the combustion gas flowing through the combustion gas flow path, and supplying the water vapor to the reformer,
The combustion gas flow passage is provided so as to cover at least a portion of an outer side of the reformer, the evaporating chamber is provided so as to cover at least part of the outside of the combustion gas flow passage, water or A first evaporation chamber having a water vapor inlet; and a second evaporation chamber provided inside the first evaporation chamber and outside the combustion gas flow path and having a water vapor outlet. The hydrogen generating apparatus , wherein the evaporation chamber and the second evaporation chamber are provided with a wall therebetween, and at least one opening is formed in the wall . The evaporation chamber has a cylindrical space surrounded by an outer cylinder and an inner cylinder, and the first evaporation chamber and the second evaporation chamber are arranged by arranging the cylindrical wall in the cylindrical space. provided that the hydrogen generating apparatus according to claim 1. The hydrogen generating apparatus according to claim 2 , wherein a flow path resistance portion is formed in the circumferential direction in the first evaporation chamber, and a flow path of water or water vapor is defined by the flow path resistance portion. The hydrogen generation apparatus according to claim 3 , wherein the flow path of the water or water vapor is spirally defined by the flow path resistance unit. The first evaporation chamber, the hydrogen generating apparatus according to any one of claims 1 to 4 having an inlet for the raw material. Hydrogen generator according to any one of the evaporation chamber of claim temperature detecting portion is provided at the lower end vicinity of 1 to claim 5. In the path from the outlet of the water vapor on the second evaporation chamber has to the reformer, according to any one of claims 1 to 6 and water vapor with the combustion gases and is configured to allow heat exchange Hydrogen generator. The hydrogen generator according to claim 1 , wherein a combustion gas flow path is disposed outside the first evaporation chamber. The hydrogen generator according to claim 1 , further comprising a water preheating unit for heating water or steam supplied to the first evaporation chamber with combustion gas. A hydrogen generator according to any one of claims 1 to 9 ,
A fuel cell system comprising: an oxidizing gas containing oxygen; and a fuel cell that generates power using the reformed gas supplied from the hydrogen generator.

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