JP2009292706A - Fuel reforming module and its operation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel reforming module which can stably run continuously for a long period, and its operation method. <P>SOLUTION: This fuel reforming module 10 generates a reformed gas containing a hydrogen gas by using a fuel gas and an oxygen-containing gas, and is equipped with an outer pipe 30 having a hollow part and an inner pipe 20 disposed in the hollow part and extending in the longitudinal direction of the outer pipe 30; the inner pipe 20 has a tubular oxygen-permeating membrane 2, a hollow part 6 to be a flow path of the oxygen-containing gas formed at the oxygen-permeating membrane 2, and a catalyst layer 4 covering at least a part of an outer wall of the oxygen-permeating membrane; and a gap part 8 to be a flow path of the fuel gas and the reformed gas is provided between the outer wall of the inner pipe 20 and the inner wall of the outer pipe 30 facing to the outer wall. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel reforming module and an operation method thereof.

  Hydrogen is a key raw material of the chemical industry used for petroleum refining, ammonia synthesis, methanol synthesis and the like. In recent years, a fuel cell using hydrogen gas as a fuel has attracted attention from the viewpoint of energy saving and environmental protection because it has high energy use efficiency and emits almost no harmful substances. Therefore, the demand for hydrogen is increasing year by year, and methods for efficiently producing hydrogen gas are being studied in order to meet such demands.

  As one method for producing hydrogen gas, a partial oxidation reforming reaction in which hydrogen gas is generated by partially oxidizing a hydrocarbon (for example, methane in natural gas) as a fuel is known. Since this method is an exothermic reaction and has the advantages of high energy efficiency and short start-up time, it can be said that it is an efficient method for generating hydrogen gas. However, in this partial oxidation reforming reaction, it is necessary to use high-purity oxygen in order to obtain a high-concentration hydrogen gas. Therefore, a complicated process for preparing high-purity oxygen is necessary, and there is room for improvement in the stage of preparing oxygen, for example, the cost increases.

  In recent years, a method using an oxygen permeable membrane is known as a method for supplying high-purity oxygen. The oxygen permeable membrane can transmit only oxygen from an air-fuel mixture (for example, air). If this oxygen permeable membrane is used, high-purity oxygen can be supplied relatively easily. The oxygen permeable membrane is usually used in the form of a flat plate or a tube. Of these, the flat plate needs to be combined with other members such as a separator and a high-temperature sealant when modularized. The structure tends to be complicated. On the other hand, since the tubular oxygen permeable membrane can be used as it is as a module by flowing air outside and fuel gas inside, for example, the number of members to be combined is small, and the structure of the module is easy to simplify.

  In such a module, oxygen separated by the oxygen permeable membrane undergoes a partial oxidation reforming reaction with a fuel gas mainly composed of hydrocarbon gas, thereby generating a reformed gas containing hydrogen gas and carbon monoxide gas. To do. Hydrogen gas and carbon monoxide gas contained in the reformed gas are used as fuel cell materials.

By the way, as a method for efficiently generating a reformed gas by a partial oxidation reforming reaction, a technique of arranging a catalyst (reforming catalyst) on the fuel side of an oxygen permeable membrane is known. As a specific structure of the fuel reforming module using such a technique, a tubular oxygen permeable membrane and a tubular structure in which a hollow region inside the tube is filled with a catalyst are known (for example, (See Non-Patent Document 1)
W. Jin et al., Journal of Membrane Science, 166 (2000), 13-22.

  However, the tubular fuel reforming module in which the catalyst is filled in the tubular oxygen permeable membrane as in the above prior art, carbon used as a by-product by the partial oxidation reforming reaction is blocked inside the tube when used for a long period of time. As a result, it was found that the gas pressure tends to increase and the oxygen permeable membrane tends to break. If the oxygen permeable membrane is destroyed, the oxygen-containing gas such as air cannot be separated from the fuel gas, making it difficult to produce hydrogen and possibly leading to fuel gas leakage.

  In order to remedy such problems, the present inventors have arranged a catalyst layer so as to cover the inner wall of the tubular oxygen permeable membrane and provided a hollow portion at the center, thereby allowing oxygen permeation due to tube blockage. We investigated the prevention of film breakage. By adopting such a structure, it is possible to sufficiently suppress an increase in pressure due to carbon deposition and blockage, and it is possible to extend the operation period of the fuel reforming module.

  However, even if the structure as described above is, for example, a structure in which a plurality of tubular oxygen permeable membranes are arranged in parallel, since the carbon deposition state differs for each fuel reforming module, the flow rate of the fuel gas varies, It may be difficult to continue stable operation. In addition, when the operation is continued for a longer period, the oxygen permeable membrane may be destroyed.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a fuel reforming module capable of continuously performing stable operation for a long period of time and an operation method thereof.

  In order to achieve the above object, in the present invention, a fuel reforming module that generates a reformed gas containing hydrogen gas using a fuel gas and an oxygen-containing gas, the outer tube having a hollow portion, and a hollow portion An inner tube extending in the longitudinal direction of the outer tube, the inner tube comprising a tubular oxygen permeable membrane, a hollow portion formed of the oxygen permeable membrane and serving as a flow path for the oxygen-containing gas, and an oxygen permeable membrane And a catalyst layer that covers at least a part of the outer wall of the fuel, and a fuel reforming module having a gap portion serving as a flow path for the fuel gas and the reformed gas between the inner tube and the outer tube.

  When such a fuel reforming module is used to generate hydrogen gas and carbon monoxide gas from a fuel gas and an oxygen-containing gas by a partial oxidation reforming reaction or the like, a sufficiently high conversion of the partial oxidation reforming reaction is achieved. It is possible to continue operation for a sufficiently long period while maintaining the rate and the selectivity of hydrogen gas and carbon monoxide gas. The reason why such an effect is obtained is as follows. However, the reason is not limited to the following points.

  In the fuel reforming module of the present invention, since the catalyst layer is provided so as to cover the outer wall of the tubular oxygen permeable membrane, the oxygen-containing gas is introduced into the hollow portion of the inner tube formed of the oxygen permeable membrane. It becomes possible to circulate the raw material fuel gas and the reformed gas as a product in a gap provided between the outer wall and the outer wall of the outer pipe. Here, the partial oxidation reforming reaction proceeds mainly in the catalyst layer, but it is considered that carbon deposition occurs with time in or around the catalyst layer due to side reactions. In a conventional fuel reforming module that fills the hollow part of a tube with a catalyst layer, the hollow part is blocked by the deposition of carbon, and the fuel gas pressure rises and the oxygen permeable membrane is damaged. I could not. However, in the fuel reforming module of the present invention, a catalyst layer in which carbon deposition occurs is provided so as to cover the outer wall of the tubular oxygen permeable membrane, and a gap is formed between the outer wall of the inner tube and the inner wall of the outer tube. Therefore, the cross-sectional areas of the flow paths of the fuel gas and the reformed gas can be maintained sufficiently large while reducing the amount of catalyst used. For this reason, even if carbon deposition progresses, the time-dependent increase in the gas pressure in the oxygen-containing gas flow path is sufficiently suppressed, and stable operation can be continued for a long period of time.

  The partial oxidation reforming reaction proceeds by partially oxidizing the fuel gas with oxygen. When this reaction proceeds, the oxygen concentration gradient between the inner side and the outer side of the tubular oxygen permeable membrane. Occurs. That is, the oxygen permeable membrane on the surface side where the fuel gas is supplied has a lower oxygen concentration and a higher reducing gas concentration such as hydrogen gas or carbon monoxide gas. For this reason, it is considered that stress is generated in the oxygen permeable membrane due to reductive expansion in which the surface side having a higher reducing gas concentration expands. In the fuel reforming module of the present invention, since the outer side of the tubular oxygen permeable membrane is in contact with a gas having a higher reducing gas concentration, the tubular oxygen permeable membrane is reductively expanded on the outer side, that is, on the outer peripheral portion than the inner side. It becomes. For this reason, compressive stress is generated inside the tubular oxygen permeable membrane. Usually, an oxygen permeable membrane made of a solid electrolyte material has a higher strength against compressive stress than tensile stress. Therefore, compared to conventional fuel reforming modules in which tensile stress is generated outside the tubular oxygen permeable membrane, the occurrence of cracks in the oxide permeable membrane is sufficiently suppressed, and stable operation can be continued for a long period of time. Become.

  The fuel reforming module of the present invention preferably includes a plurality of inner pipes in the hollow portion of the outer pipe, and has a gap portion serving as a flow path for the fuel gas and the reformed gas between the plurality of inner pipes. . Thus, by providing a plurality of inner pipes in the hollow part of one outer pipe, it becomes possible to produce reformed gas efficiently. In addition, since the gap between the inner pipes serves as a flow path for the fuel gas and the reformed gas, the cross-sectional area of the flow path for the fuel gas and the reformed gas can be maintained sufficiently large. . For this reason, even if carbon deposition progresses, the time-dependent increase in the gas pressure in the oxygen-containing gas flow path is sufficiently suppressed, and stable operation can be continued for a long period of time.

  The catalyst layer of the fuel reforming module of the present invention preferably has ceramic paper and a catalyst supported on the ceramic paper. This makes it possible to efficiently bring oxygen, fuel gas, and catalyst into contact with each other while sufficiently reducing the amount of expensive catalyst. Therefore, the conversion rate of the partial oxidation reforming reaction and the selectivity of hydrogen gas and carbon monoxide gas can be sufficiently increased.

  Further, in the present invention, a step of supplying an oxygen-containing gas to a hollow portion of an inner tube having a tubular oxygen permeable membrane, and at least a part of oxygen contained in the oxygen-containing gas diffuses inside the oxygen permeable membrane; In the catalyst layer covering at least a part of the outer wall of the oxygen permeable membrane, the oxygen diffused inside the oxygen permeable membrane is supplied to the gap between the inner tube and the outer tube provided around the inner tube. A method for operating a fuel reforming module is provided that includes a step of subjecting a fuel gas to a partial oxidation reforming reaction to generate a reformed gas containing hydrogen gas.

  By this operation method, it is possible to sufficiently suppress the gas pressure increase with time on the fuel gas flow path side and sufficiently suppress the breakage due to the stress accompanying the reduction expansion of the oxygen permeable membrane. Therefore, stable operation of the fuel reforming module can be continuously performed for a long time.

  The catalyst layer in the operation method of the fuel reforming module of the present invention includes ceramic paper and a catalyst supported on the ceramic paper, and it is preferable that oxygen and fuel gas undergo partial oxidation reforming reaction in the catalyst. .

  This makes it possible to efficiently bring oxygen, fuel gas, and catalyst into contact with each other while sufficiently reducing the amount of expensive catalyst. Therefore, it becomes possible to operate with a sufficiently high conversion rate of the partial oxidation reforming reaction and selectivity of hydrogen gas and carbon monoxide.

  ADVANTAGE OF THE INVENTION According to this invention, the fuel reforming module which can perform a stable driving | operation continuously for a long period of time, and its operating method can be provided. By using the fuel reforming module of the present invention, it is possible to stably continue the operation for realizing a sufficiently high partial oxidation reforming reaction conversion rate and hydrogen gas and carbon monoxide gas selectivity over a long period of time. Thus, the reformed gas containing hydrogen gas can be generated efficiently.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings. In the description of the drawings, the same or equivalent elements will be denoted by the same reference numerals, and redundant description will be omitted depending on the case.

(First embodiment)
FIG. 1 is an axial sectional view schematically showing a first embodiment of a fuel reforming module of the present invention. FIG. 2 is a radial cross-sectional view schematically showing a cross-sectional structure taken along the line II-II of the fuel reforming module shown in FIG.

  As shown in FIGS. 1 and 2, the fuel reforming module 10 includes a tubular outer tube 30 and one inner tube 20 provided in a hollow portion of the outer tube 30. That is, the fuel reforming module 10 includes a double tube structure including an inner tube 20 and an outer tube 30 provided around the inner tube 20. The outer wall of the inner tube 20 and the outer wall of the outer tube 30 are provided to face each other, and the inner tube 20 is inserted into the outer tube 30. The inner tube 20 has a tubular oxygen permeable membrane 2 and a catalyst layer 4 formed so as to cover at least a part of the outer wall of the oxygen permeable membrane 2. The inner tube 20 has a hollow portion 6 penetrating in the longitudinal direction, and the inner tube 20 and the outer tube 30 have a tube-type structure as a whole.

The oxygen permeable membrane 2 in the fuel reforming module 10 is a conductor capable of conducting oxygen ions and electrons. The material thereof includes a single-phase perovskite structure oxide, an oxygen ion conductor and an electron conductor. A composite type mixed conductor composed of a mixed composition may be mentioned. Among these, the latter composite-type mixed conductor can be configured by individually selecting an oxygen ion conductor and an electron conductor, so that the range of material selection is wide and the mixed conductivity can be easily controlled. To preferred. An example of a suitable composite-type mixed conductor is a mixed conductor having CeO ₂ —Sm ₂ O ₃ as an oxygen ion conductor and MnFe ₂ O ₄ as an electron conductor.

  The thickness of the oxygen permeable membrane 2 is preferably 100 to 500 μm, and more preferably 150 to 250 μm. When the oxygen permeable membrane 2 has such a thickness, both sufficient oxygen permeability and sufficient strength can be achieved. When this thickness is thin, high oxygen permeability can be obtained. However, when the thickness is too thin, it becomes difficult to form the oxygen permeable membrane 2, and the strength is insufficient, so that it is difficult to secure a sufficient gas flow rate. There is a tendency. On the other hand, if it is too thick, oxygen permeability may not be obtained sufficiently, and the compressive stress generated with reductive expansion will be excessive, and the oxygen permeable membrane 2 may be easily broken by long-term use. .

  When the oxygen permeable membrane 2 is a porous support membrane, the thickness of the oxygen permeable membrane 2 is preferably 1 to 100 μm, more preferably 10 to 50 μm. It is easy to make it thinner than the material. By thinning in this way, high oxygen transmission characteristics can be obtained.

  The catalyst layer 4 is formed so as to be in close contact with the outer wall surface of the oxygen permeable membrane 2, and the oxygen permeable membrane 2 and the catalyst layer 4 are integrally formed.

  The aspect of the catalyst layer 4 is not particularly limited, and examples thereof include an aspect in which the catalyst is attached to the surface of the support made of an inorganic compound, an aspect in which the catalyst is attached in the pores of the porous support. As the catalyst layer 4, ceramic paper is used as a carrier from the viewpoint of improving a sufficient conversion rate and hydrogen gas selectivity, and from the viewpoint of ease of forming the tubular fuel reforming module 10, and the catalyst is applied to the ceramic paper. It is preferable that the structure be adhered. However, the present invention is not limited to such a configuration. For example, the catalyst layer 4 may be formed by directly attaching a catalyst to the outer wall surface of the oxygen permeable membrane 2 without using a carrier.

  Examples of the ceramic paper constituting the catalyst layer 4 include those having a laminated structure in which a mesoporous carrier layer is formed on a macroporous support layer. As the support layer, a honeycomb-shaped support layer is preferable, and for example, a layer composed of ceramic fibers is preferable. The porosity is preferably 5 to 95%, and more preferably 30 to 90%.

Examples of the support layer include inorganic oxides such as mesoporous alumina, silica, ceria, zirconia, and titania, and composite oxides combining these. Among these, when the support layer is made of mesoporous silica, the carbon deposition due to the partial oxidation reforming reaction tends to be reduced. The suitable surface area of the carrier layer is preferably 5 to 1000 m ² / g, more preferably 50 to 500 m ² / g.

  The catalyst contained in the catalyst layer 4 can be used without particular limitation as long as it is a metal that can promote the partial oxidation reforming reaction. For example, the main component is Ni, which is modified with a noble metal such as Ru, Rh, Pt, Ir, or Pd.

  Among these, a catalyst mainly composed of Ni and containing at least one noble metal of Ru, Ir and Pd as a subcomponent is suitable. Such a catalyst can satisfactorily suppress a side reaction that precipitates carbon in the partial oxidation reforming reaction. In addition, as a noble metal which is a subcomponent, you may combine 2 or more types among Ru, Ir, and Pd.

  In such a suitable catalyst, the content of Ni as a main component is preferably 0.1 to 90% by mass, more preferably 1 to 30% by mass with respect to the entire catalyst, More preferably, it is 15 mass%. Moreover, it is preferable that it is 0.01-10 mass% with respect to the whole catalyst, and, as for content of a noble metal (Ru, Ir, or Pd), it is more preferable that it is 0.1-5 mass%. If the noble metal content is less than 0.01% by mass, the catalytic effect of the partial oxidation reforming reaction by Ni may not be sufficiently promoted. On the other hand, when it exceeds 10 mass%, since it contains many expensive noble metals, it exists in the tendency for cost to increase.

  It is preferable that the metal which comprises a catalyst exists separately for every metal seed | species, and it is preferable not to comprise the alloy etc. Further, each of these metals is preferably contained as a single metal, but a part thereof may be contained in the form of a compound such as a metal salt. Further, these metals can be attached to the above-mentioned carrier, for example, in the form of particles. In this case, for example, the particle diameter of Ni is preferably about 5 to 50 nm, and the particle diameter of other noble metals is more preferably about 1 to 10 nm.

The catalyst layer 4 may further contain a component that functions as a promoter such as Ce, La, or Pr in addition to the above-described catalyst. This tends to further enhance the effect of promoting the partial oxidation reforming reaction by the catalyst. Especially, it is preferable to contain a cerium oxide (specifically, Ce ₂ O ₃ ) as a cocatalyst. By further containing cerium oxide in addition to the catalyst, it is possible to further reduce the carbon deposition during the partial oxidation reaction.

  The thickness of the catalyst layer 4 is preferably about 1/1000 to 30 times that of the oxygen permeable membrane 2, and more preferably about 1/100 to 20 times. If the catalyst layer 4 is too thin relative to the oxygen permeable membrane 2, the catalyst layer 4 may not sufficiently exert the effect of promoting the partial oxidation reforming reaction. On the other hand, even if it is too thick as compared with the oxygen permeable membrane 2, the rate of occurrence of side reactions increases and the selectivity of hydrogen gas in the partial oxidation reforming reaction may be lowered.

  The outer diameter of the inner tube 20 is preferably 1 to 6.5 mm, and more preferably 2 to 4 mm. If the outer diameter is less than 1 mm, the hollow region inside the inner tube 20 becomes narrow, the internal pressure due to the oxygen-containing gas introduced into the inside becomes excessively high, and the burden on the oxygen permeable membrane 2 tends to increase. It is in. In addition, manufacturing inconveniences such as difficulty in forming a tubular oxygen permeable membrane tend to occur. On the other hand, when the outer diameter exceeds 6.5 mm, the oxygen permeation amount per volume decreases, and thus the oxygen permeation efficiency tends to decrease. Further, there is a possibility that the fuel reforming module 10 cannot be sufficiently downsized.

  The outer tube 30 is provided outside the inner tube 20 and has a function of blocking the fuel gas and the reformed gas generated by the partial oxidation reforming reaction from the external atmosphere. The material of the outer tube 30 is not particularly limited as long as it does not allow a large amount of fuel gas or reformed gas to permeate. Specifically, a commercially available glass, ceramic or metal material is used, and a metal material is preferably used from the viewpoint of manufacturing cost and safety.

  The fuel reforming module 10 serves as a flow path for fuel gas and / or reformed gas in a region between the inner wall of the outer tube 30 and the outer wall of the inner tube 20 so as to surround the outer periphery of the inner tube 20. It has a gap 8. The fuel reforming module 10 can sufficiently suppress an increase in gas pressure even if the catalyst layer 4 is somewhat clogged due to carbon deposition during operation, by having the gap 8. For this reason, it becomes possible to continue stable operation for a long time.

  The thickness of the gap 8 in the radial direction is preferably 1 mm or more. When the thickness is less than 1 mm, when the operation is continued for a long time, it tends to be difficult to sufficiently suppress the increase in gas pressure.

  The outer diameter of the outer tube 30 is not particularly limited, and can be appropriately set according to the size of the inner tube, for example.

  In the catalyst reforming module 10 having the above-described configuration, the fuel gas is introduced from the fuel gas introduction portion 16 into the gap portion 8 provided between the outer wall of the inner tube 20 and the inner wall of the outer tube 20. At the same time, a gas containing oxygen (oxygen-containing gas) is supplied from the oxygen-containing gas introduction portion 12 to the hollow portion 6 inside the inner tube 20.

Examples of the fuel gas include hydrocarbon fuels such as natural gas, LPG gas, naphtha, gasoline, kerosene, and light oil, alcohol fuels such as methanol and ethanol, and ether fuels such as dimethyl ether and diethyl ether. Can be mentioned. As the oxygen-containing gas, air or oxygen is preferable. Hereinafter, the operation method of the fuel reforming module 10 when methane gas (CH _{4 in the} figure) is used as the fuel gas and air (Air in the figure) is used as the oxygen-containing gas will be described below.

  The fuel reforming module 10 is operated by supplying air to the hollow portion 6 of the inner tube 20 having the tubular oxygen permeable membrane 2 so that at least part of oxygen contained in the air passes through the oxygen permeable membrane 2 from the inside to the outside. In the first step of diffusing toward the outer surface, in the catalyst layer 4 covering the outer wall of the oxygen permeable membrane 2, oxygen diffused in the oxygen permeable membrane 2, and the outer tube 30 provided around the inner tube 20 and the inner tube 20 And a second step of generating a reformed gas containing hydrogen gas and carbon monoxide gas by subjecting the fuel gas supplied to the gap 8 between them to a partial oxidation reforming reaction.

  In the first step, air is introduced from the introduction part 12 to the hollow part 6, and methane gas is introduced from the introduction part 16 to the gap part 8. Due to the difference in oxygen concentration in the gas flowing inside and outside the inner tube 20 (oxygen permeable membrane 2), only oxygen diffuses from the air in the hollow portion 6 through the oxygen permeable membrane 2 and is supplied to the outer wall surface of the oxygen permeable membrane 2. Is done.

In the second step, oxygen supplied to the outer wall surface of the oxygen permeable membrane 2 comes into contact with methane gas supplied to the gap 8. Then, at the interface between the catalyst layer 4 and the oxygen permeable membrane 2, methane gas and oxygen undergo a partial oxidation reforming reaction (the following formula (1)) to generate a reformed gas containing carbon monoxide gas and hydrogen gas. To do.
CH ₄ + 1 / 2O ₂ → CO + 2H ₂ (1)

In the second step, a complete oxidation reaction between methane and oxygen as represented by the following chemical formula (2) occurs depending on the type of catalyst used and the temperature of the catalyst. In this case, the water and carbon dioxide generated by the complete oxidation reaction further undergo a reaction (reforming reaction) with methane as represented by the following chemical formulas (3) and (4), and hydrogen and monoxide To produce carbon. That is, in this case, the partial oxidation reforming reaction occurs as a whole.
CH ₄ + 2O ₂ → 2H ₂ O + CO ₂ (2)
CH ₄ + H ₂ O → 3H ₂ + CO (3)
CH ₄ + CO ₂ → 2H ₂ + 2CO (4)

  In addition to the reactions (1) to (4), a side reaction such as a disproportionation reaction may occur, and carbon may precipitate in the catalyst layer and in the vicinity of the catalyst layer. Since the fuel reforming module 10 has the gap 8 between the inner tube 20 having the catalyst layer 4 and the outer tube 30, the flow of the fuel gas and the reformed gas is hardly obstructed, and the gas pressure is reduced. The rise can be sufficiently suppressed. Further, since the partial oxidation reforming reaction and reforming reaction described above mainly occur near the interface between the catalyst layer 4 and the oxygen permeable membrane 2, the conversion rate and hydrogen due to the partial oxidation reforming reaction are increased during the operation period. The selectivity of gas and carbon monoxide can be maintained at a high level. Therefore, the fuel reforming module 10 can be continuously operated stably over a long period of time. Furthermore, since the catalyst layer 4 is disposed only on the outer wall of the oxygen permeable membrane 2, the catalyst can be effectively used. For example, the catalyst layer 4 is formed over the entire region between the outer wall of the inner tube 20 and the inner wall of the outer tube 30. Compared with the case of filling the catalyst, the amount of the catalyst used can be sufficiently reduced.

  The reformed gas containing hydrogen gas generated by the fuel reforming module 10 is discharged to the outside together with unreacted methane gas from the mixed gas discharge unit 18 of the fuel reforming module. Then, by separating hydrogen gas and carbon monoxide gas from methane gas, carbon dioxide gas, and the like by a gas separation device (not shown) provided on the downstream side of the fuel reforming module 10, a fuel cell, etc. It is possible to efficiently produce hydrogen gas and carbon monoxide gas used in the production.

  Next, a preferred method for manufacturing the fuel reforming module 10 having the above-described configuration will be described. First, the oxygen permeable membrane 2 having a tubular shape can be formed by press molding, extrusion molding, injection molding or the like. Of these, extrusion molding is preferred because a uniform film having a uniform thickness and the like can be obtained.

  In the case of extrusion molding, for example, first, powder of a material constituting the oxygen permeable membrane (for example, oxygen ion conductor or electronic conductor) is mixed with an organic binder or organic solvent and dispersed, and then extruded. Extrusion into a tube using a molding machine to obtain a green tube. The green tube thus obtained is heat-treated at a certain temperature to remove the organic binder and organic solvent contained therein, and then baked at about 1000 to 1600 ° C. to thereby form an oxygen having a tubular shape. A permeable membrane 2 is obtained.

  In forming the catalyst layer 4, first, a catalyst sheet for forming the catalyst layer 4 is prepared. When the catalyst layer 4 having a structure in which the catalyst is attached to the carrier as described above is used, examples of the catalyst sheet include those having a structure in which the catalyst is attached to the ceramic paper that is a sheet-like carrier. Such a catalyst sheet can be obtained by an impregnation method, a slurry method, a spray method, a coating method, a solid phase mixing method, or the like. Among these methods, the impregnation method is preferable because the catalyst can be uniformly dispersed in the ceramic paper and the loading amount can be easily adjusted.

  When Ni is attached to the support by the impregnation method, for example, nitrates, hydrochlorides, acetates, etc. are used as Ni raw materials, and after impregnating the support with a solution containing these Ni salts, the raw materials are added by ammonia vapor or the like. It is converted into highly active metallic Ni by hydroxylation and further by thermal decomposition and hydrogen reduction. Thereby, a catalyst sheet in which Ni is supported on the carrier is obtained. Further, when Ni is modified with a noble metal as described above, or when a cocatalyst is used, it is preferable that these noble metal and cocatalyst are also supported on the support by an impregnation method in the same manner as Ni.

  When the catalyst sheet is thus prepared, the catalyst layer 4 is formed on the outer wall surface of the tubular oxygen permeable membrane 2 using the catalyst sheet. Specifically, the catalyst layer 4 covering the outer wall of the tubular oxygen permeable membrane 2 is obtained by cutting the catalyst sheet in accordance with the outer diameter of the tube made of the oxygen permeable membrane 2 and disposing it on the outer wall surface of the tube. Can be formed. In order to form the catalyst layer 4 having a desired thickness, a plurality of catalyst sheets may be stacked on the outer wall surface of the oxygen permeable membrane 2. The manufacturing method of the present embodiment in which the catalyst layer 4 is formed so as to cover the outer wall surface of the oxygen permeable membrane 2 has a fuel reforming module as compared with the case where the catalyst layer is formed inside the tubular oxygen permeable membrane 2. It becomes possible to manufacture very easily.

  By arranging the catalyst sheet on the outer wall surface of the tubular oxygen permeable membrane 2, the inner tube 20 including the oxygen permeable membrane 2 and the catalyst layer 4 is formed. Then, the outer tube 30 is prepared according to the size of the formed inner tube 20. A commercially available quartz glass tube can be used as the outer tube 30. The inner tube 20 is disposed inside the outer tube 30 so as to have a predetermined gap (gap portion 8). Thereby, the fuel reforming module 10 is obtained.

  Note that a plurality of fuel reforming modules 10 may be arranged in parallel to form a fuel reforming module having a plurality of double pipe structures. This makes it possible to efficiently produce a reformed gas containing hydrogen gas.

  As described above, the fuel reforming module 10 includes the inner tube 20 in which the fuel reforming module 10 is hollow in the axial direction and the outer tube 30 provided so as to have a predetermined gap along the outer peripheral portion of the inner tube 20. Having a double tube structure. For this reason, the fuel gas and the oxygen-containing gas in the fuel reforming module 10 can be sufficiently distributed, and the amount of catalyst used can be reduced as compared with the structure in which the catalyst layer is filled. Even if the partial oxidation reforming reaction is performed for a long period of time, carbon deposition occurs and the catalyst layer 4 is clogged. As a result, the pressure of the fuel gas hardly increases. Destruction is extremely unlikely. Further, even when a plurality of fuel reforming modules 10 are used in parallel, the flow rate variation between the fuel reforming modules 10 can be sufficiently suppressed, so that the conversion rate of partial oxidation reforming reaction and hydrogen gas can be reduced. In addition, it becomes possible to continue the operation while maintaining the selectivity of the carbon monoxide gas sufficiently high.

  Since the fuel reforming module 10 operates by circulating fuel gas outside the oxygen permeable membrane 2 and oxygen-containing gas inside the inner tube 20, oxygen reduction is performed by reductive expansion of the oxygen permeable membrane 2. Compressive stress is generated in the permeable membrane 2, and the oxygen permeable membrane 2 can be sufficiently prevented from being broken as compared with the conventional structure in which tensile stress is generated. As a result, a fuel reforming module having extremely excellent durability can be obtained.

(Second Embodiment)
FIG. 3 is a radial cross-sectional view schematically showing a second embodiment of the fuel reforming module of the present invention.

  As shown in FIG. 3, the fuel reforming module 50 includes a tubular outer tube 32 and four inner tubes 20 provided in the hollow portion of the outer tube 32 and extending in the longitudinal direction of the outer tube 32. That is, the four inner tubes 20 are inserted into the hollow portion of the outer tube 32. The inner tube 20 has a tubular oxygen permeable membrane 2 and a catalyst layer 4 formed so as to cover at least a part of the outer wall of the oxygen permeable membrane 2. The inner tube 20 has a hollow portion 6 penetrating in the longitudinal direction, and the inner tube 20 and the outer tube 32 have a tube-type structure as a whole.

  In the fuel reforming module 50 of the present embodiment, one inner tube 20 is provided in the hollow portion of the outer tube 30 in that four inner tubes 20 are provided in the hollow portion of the outer tube 32. This is different from the fuel reforming module 10 of the first embodiment. The materials and methods for forming the oxygen permeable membrane 2 and the catalyst layer 4 constituting the outer tube 32 and the inner tube 20 of the fuel reforming module 50 are the same as in the first embodiment.

  The fuel reforming module 50 has a gap 8 serving as a flow path for fuel gas and reformed gas between the outer wall of the inner tube 20 and the inner wall of the outer tube 32 facing the outer wall and between the inner tubes 20. is doing. Thereby, the cross-sectional areas of the flow paths of the fuel gas and the reformed gas can be sufficiently increased. Further, the fuel gas can be efficiently brought into contact with the outer wall of the inner pipe 20, and the stable operation can be continuously performed for a long time.

  Since the fuel reforming module 50 includes four inner tubes 20 inside one outer tube 32, the amount of reformed gas generated can be increased compared to the fuel reforming module 10. For this reason, the size of the whole fuel reforming module can be made compact. The number of the inner tubes 20 provided in the hollow portion of the outer tube 32 is not particularly limited, and it is possible to provide five or more inner tubes. However, if the number of inner pipes is increased too much, the cross-sectional area of the gap 8, that is, the flow path of the fuel gas and reformed gas, becomes small, and the gas pressure in the gap 8 tends to increase during operation. .

  The inner pipes are preferably arranged so that the inner pipes do not come into contact with each other, and it is more preferable that the distance between the inner pipes and the distance between the inner pipe and the outer pipe be the same in the hollow portion of the outer pipe. This makes it possible to efficiently advance the partial reforming oxidation reaction while sufficiently suppressing clogging due to carbon deposition.

  The outer diameter of the inner tube 20 is preferably 1 to 6.5 mm, and more preferably 2 to 4 mm. If the outer diameter is less than 1 mm, the hollow region inside the inner tube 20 becomes narrow, the internal pressure due to the oxygen-containing gas introduced into the inside becomes excessively high, and the burden on the oxygen permeable membrane 2 tends to increase. It is in. In addition, manufacturing inconveniences such as difficulty in forming a tubular oxygen permeable membrane tend to occur. On the other hand, when the outer diameter exceeds 6.5 mm, the oxygen permeation amount per volume decreases, and thus the oxygen permeation efficiency tends to decrease. Further, there is a possibility that the fuel reforming module 50 cannot be sufficiently downsized.

  The outer tube 32 has the same function as the outer tube 30 of the first embodiment, and can be made of the same material as the outer tube 30. The outer diameter of the outer tube 30 is not particularly limited, and can be appropriately set depending on the size and number of inner tubes.

  The catalyst reforming module 50 having the above-described configuration is similar to the fuel reforming module 10 of the first embodiment, in which the fuel gas is introduced from the fuel gas introduction unit into the gap 8 and the oxygen-containing gas. A gas containing oxygen (oxygen-containing gas) is supplied from the introduction portion to the hollow portion 6 inside the inner tube 20. The reformed gas can be generated by operating in the same manner as the fuel reforming module 10.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments. For example, in each of the above-described embodiments, the fuel reforming modules are exemplified by those having a circular cross section, but a hollow portion inside the inner tube and a gap between the inner tube and the outer tube are provided. If it is such a structure, the cross-sectional shape will not be specifically limited.

  EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example and a comparative example, this invention is not limited to a following example at all.

[Production of catalyst sheet]
(Production of oxygen permeable membrane tube)
A mixed powder of an oxygen ion conductor powder of Ce _0.85 Sm _0.15 O ₂ and an electron conductor powder of MnFe ₂ O ₄ was prepared. This mixed powder was dispersed in an organic binder and an organic solvent, and then formed into a tubular shape by an extrusion method to obtain a green tube. This green tube is heat-treated in air to remove the organic binder and organic solvent, and then fired at 1000-1600 ° C. to form an oxygen tube having an outer diameter of 3.0 mm, an inner diameter of 2.6 mm, and a thickness of 200 μm. An oxygen permeable membrane tube made of a permeable membrane was obtained.

(Preparation of catalyst sheet 1)
The organic binder contained therein was removed by firing a sheet-like ceramic fiber having a thickness of 0.5 mm (made by ITM Co., Ltd., paper 320, porosity of about 80%) at 550 ° C. in the air. Next, this was impregnated with colloidal silica (containing 30% by mass of SiO ₂ , produced by Catalyst Chemical Industry Co., Ltd.), and ammonia treatment, drying and firing were performed. As a result, a support in which a mesoporous silica support (20% by mass) as a support layer was coated on a macroporous catalyst support made of ceramic fibers was obtained.

The obtained support was impregnated with an iridium (IV) chloride aqueous solution, followed by ammonia treatment, drying, and firing in a reducing air stream containing hydrogen, thereby supporting 1.1 mass% of Ir on the support. It was. Further, by impregnating a mixed aqueous solution of nickel nitrate and lanthanum nitrate (III), followed by ammonia treatment, drying, and firing in a reducing air stream containing hydrogen, 10% by mass of Ni on the carrier, and 5. 6% by mass of La ₂ O ₃ was further supported. In this way, a plurality of catalyst sheets 1 (having a composition of Ir—Ni—La ₂ O ₃ / SiO ₂ ) having a thickness of 0.5 mm were manufactured.

(Preparation of catalyst sheet 2)
By using praseodymium nitrate (III) instead of lanthanum nitrate, instead of supporting 5.6% by mass of La ₂ O ₃ on the support, 5.7% by mass of Pr ₂ O ₃ was supported, A plurality of catalyst sheets 2 (having a composition of Ir—Ni—Pr ₂ O ₃ / SiO ₂ ) were produced in the same manner as the catalyst sheet 1.

(Preparation of catalyst sheet 3)
By using cerium (III) nitrate instead of lanthanum nitrate, a catalyst sheet except that 5.6% by mass of CeO ₂ was supported instead of 5.6% by mass of La ₂ O ₃ on the support. In the same manner as in Example ₁ , a plurality of catalyst sheets 3 (having a composition of Ir—Ni—CeO ₂ / SiO ₂ ) were produced.

[Examples 1 to 4, 7 to 10]
(Production of fuel reforming module)
The catalyst sheets 1 to 3 produced as described above were cut into a predetermined size and wound so as to be in close contact with the outer wall of the oxygen permeable membrane tube to produce an inner tube having a catalyst layer and an oxygen permeable membrane tube. The type of catalyst sheet used, the length in the longitudinal direction of the catalyst layer, and the volume of the catalyst layer were as shown in Table 1.

  A fuel having a double tube structure by inserting the produced inner tube into a commercially available quartz glass tube (wall thickness: 1 mm, outer diameter: 12 mm) and fixing the positions of the inner tube and the outer tube (quartz glass tube). A modified module was produced. The distance between the outer wall of the inner tube and the inner wall of the outer tube was 3 mm in the portion where the catalyst layer was disposed. A plurality of such fuel reforming modules were produced.

(Driving evaluation)
Supplying air to the hollow part of the inner pipe of the produced fuel reforming module and supplying commercially available methane gas to the gap between the inner pipe and the outer pipe at the flow rates shown in Table 1 to perform a partial reforming reaction The performance of the fuel reforming module was evaluated. The evaluation results are as shown in Table 1.

[Comparative Examples 1-2]
(Production of fuel reforming module)
Instead of providing the catalyst sheets 1 to 3 prepared as described above on the outer wall of the oxygen permeable membrane tube, the hollow portion formed by the oxygen permeable membrane tube is filled, and the oxygen permeable membrane tube and the oxygen permeable membrane tube A fuel reforming module was produced in the same manner as in Examples 1 to 4, except that an inner tube having a catalyst layer in the hollow portion was used.

(Driving evaluation)
The fuel reforming module is operated by supplying commercially available methane gas to the hollow portion of the inner tube of the produced fuel reforming module and supplying air to the gap between the inner tube and the outer tube at the flow rates shown in Table 1, respectively. The performance evaluation was performed. The evaluation results are as shown in Table 1.

[Examples 5 and 6]
As shown in FIG. 3, fuel reforming modules were produced in the same manner as in Examples 1 to 4, except that four inner tubes were inserted into the hollow portion of one outer tube and arranged uniformly. As the outer tube, the inner tube produced as described above is inserted into a commercially available quartz glass tube (thickness: 1 mm, outer diameter: 30 mm) to fix the positions of the inner tube and the outer tube (quartz glass tube). A fuel reforming module including an outer tube and four inner tubes inserted into the outer tube was produced. The distance between the outer wall of the inner tube and the inner wall of the outer tube was about 6.5 mm at the portion where the catalyst layer was disposed. Moreover, the space | interval of the outer wall of one inner pipe and the outer wall of another inner pipe was about 5.3 mm in the part which has arrange | positioned the catalyst layer. A plurality of such fuel reforming modules were produced.

  Table 1 shows the types of catalyst sheets used, the total length of the catalyst layers for the four inner tubes in the longitudinal direction, and the total volume of the catalyst layers. Using the produced fuel reforming module, the operation was evaluated in the same manner as in Examples 1 to 4. The flow rates of methane gas and air were as shown in Table 1. The evaluation results are as shown in Table 1.

[Comparative Example 3]
Instead of providing the catalyst sheets 1 to 3 prepared as described above on the outer wall of the oxygen permeable membrane tube, the hollow portion formed by the oxygen permeable membrane tube is filled, and the oxygen permeable membrane tube and the oxygen permeable membrane tube A fuel reforming module was produced in the same manner as in Examples 5 and 6, except that an inner tube having a catalyst layer in the hollow portion was used.

  Table 1 shows the types of catalyst sheets used, the total length of the catalyst layers for the four inner tubes in the longitudinal direction, and the total volume of the catalyst layers. Operation evaluation was performed in the same manner as in Comparative Examples 1 and 2 using the produced fuel reforming module. The flow rates of methane gas and air were as shown in Table 1. The evaluation results are as shown in Table 1.

In Table 1, the “oxygen permeation amount” of the oxygen permeable membrane was calculated by subtracting the discharge amount from the supply amount and dividing it by the unit area of the oxygen permeable membrane. The “reformed gas generation amount” is the total flow rate of hydrogen gas and carbon monoxide gas calculated from the flow rate of the exhaust gas from the fuel reforming module and the composition analysis result, and the “conversion rate” is [( H ₂ + H ₂ O) / (2CH ₄ + H ₂ + H ₂ O)], “hydrogen selectivity” is [H ₂ / (H ₂ + H ₂ O)], and “CO selectivity” is [CO / (CO + CO ₂ ). ] Is expressed as a percentage (calculated from the flow rate of each gas). The “reformed gas generation amount”, “conversion rate”, “hydrogen selectivity” and “CO selectivity” are obtained by performing the operation continuously for 1 to 4 hours and obtaining average values.

  In Table 1, “pressure” and “carbon deposition amount” are the pressure on the fuel gas side when the operation is performed for 5 hours and the mass ratio of carbon to the mass of catalyst deposited on the catalyst layer. The carbon mass was determined by collecting the catalyst layer from each fuel reforming module after operation and performing thermogravimetric analysis in an air stream. In thermogravimetric analysis, the carbon mass was determined based on the mass loss in the temperature range from room temperature to 800 ° C.

  In Table 1, “heat cycle resistance” refers to the step of heating from room temperature to 1000 ° C. and then cooling to near room temperature as one cycle. (° C./hour and 600 ° C./hour) were measured respectively.

  As shown in Table 1, a catalyst layer is formed so as to cover the outer wall of the tube-shaped oxygen permeable membrane, air is supplied to the hollow portion of the oxygen permeable membrane, and fuel gas is supplied to the outer side (void portion with the outer tube). It was found that the supplied fuel reforming modules of Examples 1 to 10 can be stably operated over a long period of time while maintaining a high conversion rate and a high selectivity of hydrogen gas and carbon monoxide.

  On the other hand, in the structure in which the catalyst layer is filled in the hollow portion inside the tubular oxygen permeable membrane as in Comparative Examples 1 to 3, carbon deposition proceeds toward the inside of the catalyst layer to which oxygen is not supplied, and the gas pressure Was confirmed to rise. It was also confirmed that the thermal shock resistance was poor.

1 is an axial sectional view schematically showing a first embodiment of a fuel reforming module of the present invention. It is radial direction sectional drawing which shows typically the cross-section which follows the II-II line of the fuel reforming module shown in FIG. It is radial direction sectional drawing which shows 2nd Embodiment of the fuel reforming module of this invention typically.

Explanation of symbols

  2 ... oxygen permeable membrane, 4 ... catalyst layer, 6 ... hollow part, 8 ... gap part, 10, 50 ... fuel reforming module, 12 ... oxygen-containing gas introduction part (introduction part), 14 ... discharge part, 16 ... fuel Gas introduction part (introduction part), 18 ... Mixed gas discharge part, 20 ... Inner pipe, 30, 32 ... Outer pipe.

Claims (5)

A fuel reforming module that generates a reformed gas containing hydrogen gas using a fuel gas and an oxygen-containing gas,
An outer tube having a hollow portion;
An inner tube provided in the hollow portion and extending in a longitudinal direction of the outer tube,
The inner tube has a tubular oxygen permeable membrane, a hollow portion formed of the oxygen permeable membrane and serving as a flow path for the oxygen-containing gas, and a catalyst layer that covers at least a part of the outer wall of the oxygen permeable membrane. And a fuel reforming module having a gap between the inner tube and the outer tube that serves as a flow path for the fuel gas and the reformed gas. A plurality of inner tubes are provided in the hollow portion of the outer tube;
The fuel reforming module according to claim 1, wherein a gap portion serving as a flow path for the fuel gas and the reformed gas is provided between the plurality of inner pipes.   The fuel reforming module according to claim 1, wherein the catalyst layer has ceramic paper and a catalyst supported on the ceramic paper. Supplying an oxygen-containing gas to a hollow portion of an inner tube having a tubular oxygen-permeable membrane, and diffusing at least part of the oxygen contained in the oxygen-containing gas inside the oxygen-permeable membrane;
In the catalyst layer covering at least a part of the outer wall of the oxygen permeable membrane, in the gap between the oxygen diffused inside the oxygen permeable membrane and the outer tube provided around the inner tube and the inner tube And a step of generating a reformed gas containing hydrogen gas by subjecting the supplied fuel gas to a partial oxidation reforming reaction.   The fuel reforming module according to claim 4, wherein the catalyst layer includes a ceramic paper and a catalyst supported on the ceramic paper, and the oxygen and the fuel gas are subjected to a partial oxidation reforming reaction in the catalyst. Driving method.

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