JP2004299939A - Fuel reformer, and fuel battery generator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an excellently compactible fuel reformer provided with an air preheater reducing the fluid pressure loss of air for combustion, having a simple composition as the whole and having high energy efficiency, and to attain the improvement of power generation efficiency and the reduction of cost in a fuel battery generator. <P>SOLUTION: The fuel reformer comprises a reforming catalyst layer of steam-reforming hydrocarbon-based fuel, a fuel feed path for combustion and an air path for combustion, and is provided with a burner of heating the reforming catalyst by combustion exhaust gas and an air preheating part of preheating air for combustion by the combustion exhaust gas of the burner. The burner 6 comprises a hollow, cylindrical combustion tube 18, the reforming catalyst layer 3 is provided at the outside of the combustion tube so as to be cylindrical concentrically with the axial center of the combustion tube, and further, the air path (16) is provided at the inside of the combustion tube so as to be cylindrical concentrically with the axial center of the combustion tube to form the air preheating part 20 by combustion exhaust gas. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fuel reformer for steam reforming a hydrocarbon-based fuel such as methane gas, and a fuel cell power generator including the fuel reformer.
[0002]
[Prior art]
Industrial equipment and fuel cell power generators that use hydrogen as an atmospheric gas require a hydrogen generator. This hydrogen generator passes raw fuel gas such as methane gas, LNG, LPG, and methanol together with water vapor through a catalyst layer. And a reformer that generates a hydrogen-rich reformed gas.
[0003]
A fuel cell power generation device is a device that directly converts chemical energy of a fuel into electric energy without passing through mechanical energy or heat energy, and can realize high energy efficiency. As a well-known form of a fuel cell, a pair of electrodes are arranged with an electrolyte layer interposed therebetween, and a fuel gas containing hydrogen is supplied to one electrode (anode side) and oxygen gas is supplied to the other electrode (cathode side). Is supplied, and an electromotive force is obtained by utilizing an electrochemical reaction occurring between the two electrodes.
[0004]
Fuel cells are classified according to the type of electrolyte used. Among these fuel cells, polymer electrolyte fuel cells, phosphoric acid type fuel cells, molten carbonate type fuel cells, etc. are based on the properties of the electrolyte. It is possible to use an oxidizing gas or a carbon dioxide gas containing carbon dioxide. Therefore, these fuel cells usually use air as an oxidant gas, and use a hydrogen-rich gas generated by steam reforming of a hydrocarbon-based raw fuel such as natural gas as a fuel gas.
[0005]
Therefore, in a fuel cell power generation apparatus including such a fuel cell, a reformer and a carbon monoxide converter are provided. Generating gas. The following equation (1) shows the methane reforming reaction in the reformer. Note that methane is a main component of natural gas.
[0006]
CH ₄ + H ₂ O → 3H ₂ + CO (+206.14 KJ / mol: endothermic reaction) (1)
As shown in the above formula (1), since the reforming reaction of methane is an endothermic reaction, after adding steam to methane, the particulate reforming catalyst is formed by the combustion exhaust gas obtained by burning the fuel off-gas from the fuel cell. By maintaining the temperature at 600 to 700 ° C., a hydrogen-rich reformed gas is generated.
[0007]
The reformed gas exiting the reformer is supplied to a carbon monoxide converter to reduce carbon monoxide in the reformed gas, where the carbon monoxide is reduced to 1% or less, and In the case of a fuel cell (PAFC), this gas can be introduced into the fuel cell to generate power. The following equation (2) shows the conversion reaction of carbon monoxide in the carbon monoxide converter.
[0008]
CO + H ₂ O → H ₂ + CO ₂ (−41.17 KJ / mol: exothermic reaction) (2)
As shown in the formula (2), the conversion reaction of carbon monoxide is an exothermic reaction, so that cooling is required to maintain the conversion reaction temperature of 160 to 350 ° C.
[0009]
On the other hand, polymer electrolyte fuel cells (PEFCs) have a low operating temperature of 60 to 80 ° C, and if carbon monoxide is present in the reforming material, they may become catalyst poisons and degrade performance. Therefore, it is necessary to further reduce the carbon monoxide, so that the reformed gas is supplied to the carbon monoxide remover, where the carbon monoxide is reduced to 10 ppm or less. The following equation (3) shows a selective oxidation reaction of carbon monoxide in the carbon monoxide remover.
[0010]
CO + 1 / 2O ₂ → CO ₂ (−257.2 KJ / mol: exothermic reaction) (3)
As shown in the formula (3), since the selective oxidation reaction of carbon monoxide is an exothermic reaction, cooling is required to maintain the selective oxidation reaction temperature of 160 to 230 ° C.
[0011]
As described above, the polymer electrolyte fuel cell (PEFC) has a low reaction temperature, and therefore differs from the phosphoric acid fuel cell (PAFC) (reaction temperature of about 180 ° C.) in that the steam for reforming is generated by its calorific value. Since it cannot be generated, it must be generated in the reforming system equipment. Therefore, for example, a method has been proposed in which water for steam reforming is used as cooling water for a carbon monoxide remover, and this water is heated to about 100 ° C. and then put into the heat exchanger.
[0012]
FIG. 3 shows a schematic configuration diagram of an example of a polymer electrolyte fuel cell power generator equipped with a conventional fuel reformer of this type.
[0013]
In FIG. 3, the raw fuel from which the sulfur content has been removed by the desulfurizer 21 is supplied to the reformer 23 together with the steam generated by the steam generator 22, and is subjected to the steam reforming reaction shown in the equation (1). After being reformed into a hydrogen-rich gas, it is supplied to a carbon monoxide converter 24 to increase the hydrogen concentration by the carbon monoxide conversion reaction shown in the equation (2), and thereafter, the hydrogen concentration is increased together with a certain amount of air. The carbon monoxide is supplied to the carbon monoxide remover 25 and reduced to 10 ppm or less by the selective oxidation reaction of carbon monoxide shown in the formula (3), and then supplied to the fuel cell 26.
[0014]
The carbon monoxide remover 25 requires cooling. As a means for this, the reforming water supplied from the reforming water tank 27 by the reforming water supply pump 28 is provided in the selective oxidation catalyst layer. Cooling is performed by flowing through the cooling pipe 29. The reforming water heated in the cooling pipe 29 of the carbon monoxide remover 25 is supplied from the feed water preheating line 40 to the steam generator 22, where it is evaporated. Here, as a heat source of the steam generator, the burner 30 of the reformer 23 burns the fuel off-gas from the fuel cell together with the combustion air, and gives the combustion heat for the steam reaction of methane, which is an endothermic reaction. This is the combustion exhaust gas 31 after the combustion.
[0015]
In FIG. 3, reference numerals 32 and 33 denote a pressure gauge and a thermometer for measuring the pressure and the temperature of the supply water preheating line 40, respectively. Further, the system of the fuel cell power generation device employs various configurations according to the specifications of the device, and is not limited to the configuration shown in FIG.
[0016]
By the way, with respect to the configuration of the fuel reformer, various types have been proposed and put into practical use, but from the viewpoint of improving the energy efficiency of the fuel reformer itself, the combustion air supplied to the burner is reduced. It is effective to preheat with combustion exhaust gas. Since the preheat calorific value of the air is eventually reduced to the heating of the reforming catalyst via the combustion exhaust gas, it is discharged from the reformer while maintaining the proper temperature distribution of the reforming catalyst. The energy of the combustion exhaust gas can be effectively recovered.
[0017]
As described above, various configurations have also been proposed for a fuel reformer having a configuration for preheating combustion air with combustion exhaust gas (see, for example, Patent Documents 1 to 3).
[0018]
FIG. 2 shows the configuration of the fuel reformer disclosed in FIG. However, the part numbers shown in FIG. 2 are indicated by adding a suffix a to the part numbers in Patent Document 1. According to the description of Patent Document 1, the configuration of the fuel reformer shown in FIG. 2 is generally as follows. That is, "the reaction tube is composed of a reaction tube inner tube 1a and a reaction tube outer tube 2a, and a reforming catalyst 3a is provided between the reaction tube inner tube 1a and the reaction tube outer tube 2a. The combustor 6a is a fuel. A supply pipe 7a is provided and installed in a combustion gas flow path 14a constituted by a reformer inner vessel 10a and a reaction tube outer cylinder 2a, and the combustion gas flow path 14a is connected to a fuel gas discharge pipe 13a. In the upper part of the pipe, a space formed by the raw fuel supply pipe 4a and the reaction pipe inner cylinder 1a and the reaction pipe outer cylinder 2a is connected, and one end of the reaction pipe inner cylinder 1a is connected to the raw fuel discharge pipe 5a.
[0019]
Outside the reformer inner vessel 10a, a reformer outer vessel 9a is provided so as to surround the reformer inner vessel 10a, and a flow path is provided between the reformer inner vessel 10a and the reformer outer vessel 9a. A guide 11a is provided. An air supply pipe 8a is attached to an air flow path 15a composed of the outer container 9a of the reformer and the flow path guide 11a. The passage 16a is connected to the combustor 6a. A heat insulating layer 12a is provided between the outer container 9a and the atmosphere. Raw fuel such as methane to be reformed is supplied from a raw fuel supply pipe 4a after being mixed with steam, and introduced into a reaction tube.
[0020]
The raw fuel passes through the reforming catalyst 3a provided inside the reaction tube inner tube 1a and the reaction tube outer tube 2a, and at the same time, is given heat from the combustion gas flowing outside the reaction tube outer tube 2a, and the reforming reaction is an endothermic reaction. Is generated. The raw fuel that has passed through the reforming catalyst 3a flows through the inside of the reaction tube inner tube 1a and is discharged from the raw fuel discharge tube 5a to the outside of the reformer. Combustion fuel is supplied to the combustor 6a from a fuel supply pipe 7a. On the other hand, combustion air is supplied from the air supply pipe 8a into the air flow path 15a formed by the outer container 9a and the flow path guide 11a. The air flows through the air passage 15a and simultaneously cools the passage guide 11a, and the air temperature rises.
[0021]
The air that has flowed out of the air flow path 15a flows through a space formed by the flow path guide 11a and the inner container 10a, and also cools the inner container 10a. By providing these air flow paths, the temperature decreases in the order of the inner container of the reformer 10a, the flow path guide 11a, and the outer container 9a of the reformer, and the temperature of the outer container of the reformer when no air flow path is provided, That is, the thickness of the heat insulating layer can be made smaller than the thickness of the heat insulating layer with respect to the temperature of the reformer container 10a in the embodiment. In addition, it is possible to cool the reforming container 10a to improve the durability.
[0022]
The air that has passed through the flow path guide 11a and the inner container 10a of the reformer passes through the air passage 16a, is introduced into the combustor 6a, and is used as combustion air. The combustion gas generated in the combustor 6a heats the reaction tube outer cylinder 2a, flows through the combustion gas flow path 14a, and is discharged from the fuel gas discharge pipe 13a to the outside of the reformer. The heat insulation layer 12a prevents heat loss from the reformer outer container 9a to the outside air. "
"According to the above configuration, by providing the flow path guide, the air flow path covering the inner vessel of the reformer can be doubled, so that the temperature of the outer vessel of the reformer can be further lowered, The effect of reducing the heat loss is great, and the air can be preheated. "
Patent Document 2 also discloses a hydrocarbon reforming apparatus having an air preheating section, in which a combustion air supply path is folded up and down at the lower part of a burner, and heat exchange with combustion exhaust gas is performed in the folded path. A quality device is disclosed (for details, see Patent Document 2).
[0023]
Further, Patent Document 3 discloses a reformer including an air preheating unit. The configurations of the air preheating units disclosed in Patent Documents 1 and 2 each have a problem in which a return path is provided and the fluid pressure loss of air is increased (details will be described later). Although the reformer disclosed in the above has another problem which will be described later, the combustion air supply passage is disposed linearly with respect to the combustion portion of the burner, and is configured to be able to exchange heat with combustion exhaust gas ( See Patent Document 3 for details).
[0024]
[Patent Document 1]
Patent No. 2528836 (Page 2, FIG. 1)
[Patent Document 2]
JP-A-3-199105 (page 3-4, FIG. 1)
[Patent Document 3]
JP-A-2-145401 (pages 2-4, FIG. 1)
[0025]
[Problems to be solved by the invention]
By the way, the conventional fuel reformer as described above and the fuel cell power generator using the same have the following problems.
[0026]
As described above, the configurations of the air preheating units disclosed in Patent Literatures 1 and 2 each include a return path, and there is a problem that a fluid pressure loss of air is increased. In addition, the device has a complicated structure due to the return path, and furthermore, the overall compactness is poor. In a fuel cell power generator, particularly a home polymer electrolyte fuel cell power generator, it is important to reduce auxiliary power by suppressing fluid pressure loss of air, that is, to improve power generation efficiency. For example, there is a demand to further reduce the power for transporting combustion air (10 W or more) as much as possible to improve the power generation efficiency. Therefore, reducing the fluid pressure loss of combustion air in a fuel reformer has become an important issue, particularly in a fuel cell power generator.
[0027]
On the other hand, in the reformer disclosed in Patent Document 3, the combustion air supply passage is arranged linearly with respect to the combustion portion of the burner, and is configured so as to reduce the fluid pressure loss of the combustion air. However, the overall structure of the reformer has the following problems.
[0028]
In the reformer disclosed in FIG. 1 of Patent Document 3, a ceramic cylinder (13) surrounds the periphery of a triple structure conduit (12) including the combustion air supply passage, and is provided with a burner (4). It is provided at the upper end of the housing (4b). Although the above configuration is considered to be a necessary configuration depending on the temperature of each part, there is a problem that the ceramic cylinder is vulnerable to a heat cycle and is easily damaged particularly at the time of startup. In addition, there is a problem that the number of parts is large and the structure is complicated, and the outer diameter of the device is large, resulting in poor compactness.
[0029]
SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an air preheater having a reduced fluid pressure loss of combustion air, which has a simple structure and compactness as a whole. An object of the present invention is to provide a fuel reformer excellent in the above, and thereby reduce the cost of the fuel cell power generator.
[0030]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention has a reforming catalyst layer for steam reforming a hydrocarbon-based fuel, a fuel supply passage for combustion, and a combustion air passage, wherein the reforming is performed by using combustion exhaust gas. In a fuel reformer provided with a burner for heating a catalyst and an air preheating unit for preheating the combustion air with combustion exhaust gas from the burner, the burner has a hollow cylindrical combustion cylinder, The reforming catalyst layer is provided on the outer side and in a cylindrical shape concentric with the axis of the combustion cylinder via the exhaust gas discharge path, and further inside the combustion cylinder and concentric with the axis of the combustion cylinder. The air path for combustion is provided in the shape, and an air preheating section by the combustion exhaust gas is formed (the invention of claim 1).
[0031]
According to the above configuration, it is possible to reduce the fluid pressure loss of the combustion air, and it is possible to provide a simple and compact fuel reformer as a whole device.
[0032]
As an embodiment of the first aspect of the invention, the following second to fourth aspects of the invention are preferable. That is, in the fuel reformer according to claim 1, the combustion portion of the burner is provided at a substantially central portion in the axial direction within the hollow cylindrical combustion tube, and the air preheating portion is located below the combustion portion. The combustion exhaust gas is provided along the inner wall of the combustion cylinder, and the combustion exhaust gas in the combustion exhaust gas discharge path along the lower combustion cylinder outer wall performs air preheating and reforming catalyst heating simultaneously (the invention of claim 2). Further, in the fuel reformer according to claim 2, the combustion air inlet, the combustion exhaust gas outlet, the reforming fuel and the reforming steam inlet are sequentially arranged from below in the axial lower portion of the combustion cylinder. (Invention of claim 3). According to this configuration, the air preheating section is provided in parallel with the part of the reforming catalyst layer that requires the most heat transfer area through the flue gas exhaust passage, so that the air preheating unit is provided. Can be simplified and an extremely compact reformer can be provided.
[0033]
Further, the positional relationship between the respective members and the flow directions of the various gases can be reversed, as in the fourth aspect of the present invention. That is, in the fuel reformer according to claim 2 or 3, the axial position of each of the members or each of the inlets and outlets is configured such that the top and the bottom are reversed, except that all the upper and lower parts are reversed. The configuration of the invention of claim 4 is more preferable in consideration of preventing dust from accumulating on the combustion part. However, in consideration of factors other than the reformer body, for example, In some cases, the opposite is preferable, and it is desirable to use them properly depending on the application.
[0034]
Further, as in the invention of claim 5, by providing the fuel cell power generator with the fuel reformer according to any one of claims 1 to 4, the energy efficiency of the reformer is improved. Thus, the power generation efficiency can be improved. Furthermore, auxiliary power can be reduced by suppressing the fluid pressure loss of air, which can also contribute to improvement in power generation efficiency. Further, the fuel reformer becomes compact, and the cost of the fuel cell power generator can be reduced.
[0035]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0036]
FIG. 1 is a schematic configuration diagram of a fuel reformer showing an embodiment according to the present invention. Members having the same functions as those in FIG. 2 are denoted by the same reference numerals (excluding the suffix a), and are detailed. Description is omitted.
[0037]
The difference between FIG. 1 and FIG. 2 is that in FIG. 1, the burner 6 has a hollow cylindrical combustion cylinder 18, and the combustion exhaust gas is formed outside the combustion cylinder and concentrically with the axis thereof. The reforming catalyst layer 3 is provided through a discharge passage 17 of the combustion cylinder, and an air supply passage 16 for combustion is provided inside the combustion cylinder 18 and concentrically with the axis of the combustion cylinder to form a combustion exhaust gas. This is the point that the air preheating section 20 is formed.
[0038]
Further, specifically, the combustion portion of the burner 6 is provided at a substantially central portion in the axial direction in the hollow cylindrical combustion tube 18, and the air preheating portion 20 is provided over the entire axially lower portion in the combustion tube. The flue gas in the flue gas discharge passage 17 is configured to simultaneously perform air preheating and reforming catalyst heating.
[0039]
A combustion air inlet connected to the air supply passage 16 is provided below the combustion cylinder 18 in the axial direction, and a combustion exhaust gas outlet is provided thereon, and a reforming fuel and a reforming steam are further provided thereon. Are sequentially provided. In the present embodiment, the reformed gas outlet is provided at the upper part. However, a reformed gas flow path is further provided on the outer periphery of the reforming catalyst layer 3, and the flow path is turned over at the upper part of the reforming catalyst layer 3 for reforming. The gas outlet may be provided at the lower portion, and in this case, there is an advantage that the heat of the reformed gas can be given to the inner reforming catalyst.
[0040]
In FIG. 1, reference numeral 7 denotes a fuel supply pipe for combustion, which is connected to the combustion section of the burner together with combustion air. Further, the outer peripheral portion of the fuel supply pipe 7 is covered with a heat insulating material 12b, and together with the outer peripheral portion of the reforming catalyst layer 3 and the heat insulating material 12 provided on the upper surface of the reformer, the heat dissipation loss to the outside is reduced. It is configured to
[0041]
An example of the temperature of the main part in the fuel reformer shown in FIG. 1 is schematically shown as follows. According to the configuration of FIG. 1, the temperature distribution of the reforming catalyst layer is made appropriate and By preheating the air, the temperature of the combustion exhaust gas can be kept lower than before.
[0042]
-Lower temperature of the reforming catalyst layer: 200 to 250 ° C
-Upper temperature of the reforming catalyst layer: 600 to 700 ° C
・ Lower temperature of combustion air: 20 ° C
-Upper temperature of combustion air: 200 ° C
・ Temperature at the lower part of the exhaust passage of combustion exhaust gas: 150 to 200 ° C
・ Temperature at the upper part of the exhaust passage of the combustion exhaust gas: 1000 ° C
[0043]
【The invention's effect】
As described above, according to the present invention, a reforming catalyst layer for steam reforming a hydrocarbon fuel, a fuel supply passage for combustion, and a combustion air passage are provided, and the reforming catalyst is heated by combustion exhaust gas. A burner having a hollow cylindrical combustion cylinder, and an air preheating unit for preheating the combustion air with the combustion exhaust gas of the burner. The reforming catalyst layer is provided in a cylindrical shape concentric with the axis of the combustion cylinder through the discharge path of the combustion exhaust gas, and further inside the combustion cylinder and concentric with the axis of the combustion cylinder, By providing the combustion air passage and forming the air preheating section by the combustion exhaust gas, high energy efficiency of the reformer can be obtained and fluid pressure loss of the combustion air can be reduced. The whole device is simple and It is possible to provide a transfected fuel reformer.
[0044]
Further, by providing the fuel cell power generator with the fuel reformer, the fuel pressure can be reduced by suppressing the fluid pressure loss of air, the power for auxiliary equipment can be reduced, the power generation efficiency can be obtained, and the cost can be reduced. A battery power generator can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an embodiment of a fuel reformer of the present invention. FIG. 2 is a configuration diagram of an example of a conventional fuel reformer disclosed in Patent Document 1. FIG. Schematic configuration diagram of an example of a fuel cell power generation device provided with a porcelain
3: reforming catalyst layer, 6: burner, 7: fuel supply pipe, 16: air supply path, 17: exhaust gas discharge path, 18: combustion cylinder, 20: air preheating section, 21: desulfurizer, 22: steam Generator, 23: reformer, 24: carbon monoxide converter, 25: carbon monoxide remover, 26: fuel cell.

Claims (5)

A reforming catalyst layer for steam reforming a hydrocarbon-based fuel, a fuel supply passage for combustion and a combustion air passage, and a burner for heating the reforming catalyst with flue gas; In a fuel reformer having an air preheating unit for preheating with combustion exhaust gas of a burner,
The burner has a hollow cylindrical combustion cylinder, and the reforming catalyst layer is provided outside the combustion cylinder and concentrically with the axis of the combustion cylinder through a discharge path of the combustion exhaust gas. A fuel reformer, characterized in that the combustion air passage is provided inside the combustion cylinder and concentrically with the axis of the combustion cylinder to form an air preheating unit using the combustion exhaust gas. 2. The fuel reformer according to claim 1, wherein a combustion portion of the burner is provided at a substantially central portion in the axial direction in the hollow cylindrical combustion tube, and the air preheating portion is a combustion tube below the combustion portion. 3. A fuel reformer provided along an inner wall and configured to simultaneously perform air preheating and reforming catalyst heating on the flue gas in the flue gas discharge passage along the lower combustion cylinder outer wall. 3. The fuel reformer according to claim 2, wherein the combustion air inlet, the combustion exhaust gas outlet, the reforming fuel and the reforming steam are sequentially provided from below in the axial lower portion of the combustion cylinder. A fuel reformer characterized by the above. 4. The fuel reformer according to claim 2, wherein the axial position of each member or each of the inlets and outlets is configured such that the top and the bottom are reversed, except that all the upper and lower parts are reversed. 5. And a fuel reformer. A fuel cell power generator comprising the fuel reformer according to claim 1.

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