JP2005213133A - Reformer and fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve high thermal efficiency by making a reformer and a fuel cell system compact.
A reformer having a reaction tube containing a reforming catalyst and a burner for heating the reaction tube from the outside for reforming a raw material for hydrogen production to produce a hydrogen-containing gas containing hydrogen. The reaction tube is a double tube whose one end is closed, and the reforming catalyst is accommodated in the outer tube part, and a fin is provided on the outer wall of the reaction tube, and the position of the fin is the length of the reaction tube from the inlet of the reaction tube. It is at least part of the range up to half the height. A fuel cell system provided with this reformer.
[Selection] Figure 1

Description

  The present invention relates to a reformer for producing hydrogen by reforming raw materials such as kerosene. In particular, the present invention relates to a reformer that can be suitably used in a fuel cell system. The present invention also relates to a fuel cell system having such a reformer.

  Development of fuel cells has been actively promoted as a power generation system with high energy utilization efficiency. Among them, the polymer electrolyte fuel cell is particularly attracting attention because of its high power density and ease of handling.

  Since a fuel cell generates power by an electrochemical reaction between hydrogen and oxygen, it is essential to establish a hydrogen supply means. As one of the methods, there is a method of producing hydrogen by reforming a raw material for hydrogen production such as a hydrocarbon fuel, and a method using pure hydrogen in that a hydrocarbon fuel supply system has already been socially established. More advantageous.

  Examples of the hydrocarbon fuel include city gas, gasoline, kerosene, and light oil. Liquid fuels such as gasoline, kerosene, and light oil are attracting attention as fuel cells because they are easy to handle, store and transport, and are inexpensive. In order to use these hydrocarbon fuels in fuel cells, it is necessary to produce hydrogen from hydrocarbons. For this purpose, hydrocarbons are reacted with water in a reformer, mainly into carbon monoxide and hydrogen. In the shift reactor, where most of the carbon monoxide reacts with water to convert it to hydrogen and carbon dioxide, and finally in the selective oxidation reactor, a small amount of residual carbon monoxide reacts with oxygen to form carbon dioxide. Things have been done. Further, since sulfur becomes a poisoning substance such as a reforming catalyst, a desulfurizer for removing sulfur in the hydrocarbon fuel is often provided.

As a reformer used for a fuel cell, Patent Document 1 discloses a reformer having a plurality of reforming reaction tubes (catalyst tubes). A fuel cell system having a reformer is disclosed in, for example, Patent Document 2.
Special table 2002-529895 gazette JP 2003-187832 A

  A reformer that performs a steam reforming reaction is widely used as a reformer. Since the steam reforming reaction is an endothermic reaction, a reaction tube for performing the steam reforming reaction is heated by a burner from the outside of the reaction tube. That is, the heat held by the combustion gas of the burner is exchanged through the tube wall of the reaction tube and supplied to the reforming catalyst layer provided inside the reaction tube.

  However, it cannot be said that the efficiency of this heat exchange is high in the conventional reformer, and as a result, the length of the reaction tube has to be relatively long, so that the compactness of the reformer is hindered. Was in the situation.

  An object of the present invention is to improve the heat exchange efficiency of transferring the combustion heat of the burner to the reforming reaction region in the reformer.

  Another object of the present invention is to provide a reformer that can be made more compact, and to provide a reformer with high thermal efficiency.

  Another object of the present invention is to provide a fuel cell system that is more compact and more thermally efficient.

According to the present invention, a reformer for producing a hydrogen-containing gas containing hydrogen by reforming a raw material for hydrogen production, having a reaction tube containing a reforming catalyst and a burner for heating the reaction tube from the outside. In
The reaction tube is a double tube with one end closed, and the reforming catalyst is accommodated in the outer tube,
A fin on the outer wall of the reaction tube;
The reformer is provided in which the position of the fin is at least a part of a range from the inlet of the reaction tube to half of the length of the reaction tube.

  The reformer preferably further includes a combustion catalyst downstream of the burner in the combustion gas flow direction of the burner.

  In the reformer, it is preferable that fins are provided on the outer wall of the reaction tube in a region downstream of the combustion catalyst in the combustion gas flow direction of the burner.

  In the reformer, the burner is preferably a surface combustion burner.

According to the present invention, a reformer for producing a hydrogen-containing gas containing hydrogen by reforming a raw material for hydrogen production, comprising a reaction tube containing a reforming catalyst and a burner for heating the reaction tube from the outside. And a fuel cell system using the hydrogen-containing gas as a fuel,
The reaction tube is a double tube with one end closed, and the reforming catalyst is accommodated in the outer tube,
A fin on the outer wall of the reaction tube;
The position of the fin is at least a part of a range from the inlet of the reaction tube to half the length of the reaction tube. A fuel cell system is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the heat exchange efficiency which transmits the combustion heat of a burner to a reforming reaction area | region can be improved in a reformer. Therefore, a reformer that can be made more compact is provided, and a reformer with high thermal efficiency is provided.

  A fuel cell system including such an excellent reformer has high thermal efficiency and can be made compact.

  Hereinafter, the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto.

  FIG. 1 is a schematic cross-sectional view showing a schematic configuration of an embodiment of the reformer of the present invention. In this reformer, a reforming reaction tube 10 and a burner 2 forming a reforming reaction section are provided in a cylindrical sealable container 1. The reforming reaction tube is a double tube with its lower end closed, and its outer tube portion 10a is filled with a reforming catalyst to form a reforming catalyst layer 10c, and the inner tube portion 10b is hollow.

  For example, the raw material for hydrogen production and steam necessary for reforming are supplied from the raw material supply port 11 to the outer tube portion 10a of the reforming reaction tube, cause a reforming reaction in the presence of the reforming catalyst, and obtained reforming. The gas is discharged from the reformed gas discharge port 12 through the inner pipe portion 10b.

  In the burner 2, the combustion fuel is burned by air, the combustion gas A comes into contact with the reaction tube, and the reaction tube is heated.

  The temperature of the catalyst layer tends to be highest at the location closest to the burner, that is, the highest upstream side in the flow direction of the combustion gas A, and lowest at the downstream side in the flow direction of the combustion gas A. From the viewpoint of promoting the reforming reaction, it is preferable that the temperature of the catalyst layer is high. Therefore, from the viewpoint of increasing the temperature of the catalyst layer by increasing the heat exchange rate of the portion where the temperature tends to be low, the downstream of the combustion gas A flow direction The fin 20 is provided on the side. In order to promote the reforming reaction at the reaction tube inlet portion where the temperature tends to be low, the fin is installed in a range from the reaction tube inlet to half the length of the reaction tube (in the form shown in FIG. 1). It is preferable to install a fin at a position from the upper end of the reaction tube 10 to the center in the length direction of the reaction tube. Fins may be provided over the entire length of the reaction tube in this range, or fins may be provided in a part thereof. When fins are installed over the entire length of the reaction tube, the temperature distribution of the catalyst layer becomes larger, and the temperature of the catalyst layer in the vicinity of the reaction tube inlet decreases. Therefore, it is better not to provide fins in a portion exceeding 1/2 of the reaction tube length in the longitudinal direction from the reaction tube inlet.

  Regarding the gas flow, in order to minimize damage to the reforming catalyst and coking, the combustion gas and reformed gas (reformed gas flowing in the outer tube) are counter-current heat exchanged in the double-tube type reaction tube. The method is preferred. In the counter-current system, the high-temperature combustion gas and the high-temperature reformed gas exchange heat, so the temperature difference between them is small, and damage to the catalyst and the reforming tube itself is reduced. Since the gas exchanges heat, the large temperature difference is disadvantageous in that it may impair the durability of the catalyst and the tube material.

  In FIG. 1, one end (upper end) of the fin is aligned with the downstream end (upper end of the reaction tube) of the reaction tube in the combustion gas A flow direction.

  FIG. 2 shows the arrangement of fins in the cross section of the reaction tube. A plurality (eight in the figure) of fins are provided on the outer wall of the reaction tube 10 at equal intervals along the outer periphery thereof.

  The shape, size, number, etc. of the fins can be appropriately designed according to the desired temperature distribution of the catalyst layer. Examples of the fin shape include a flat plate shape and a spiral shape.

  In the present invention, a double tube type reaction tube is used from the viewpoint of temperature distribution and thermal efficiency. In FIG. 1, only one reaction tube is shown, but a plurality of reaction tubes may be provided. The arrangement of the burner can also be selected as appropriate. For example, a plurality of reaction tubes can be arranged at equal intervals on one circumference, and a burner can be arranged at the center. At this time, the burner is installed downward (a flame is formed downward), a partition is provided between the burner and the reaction tube, and an opening is provided at the bottom of the partition, or the partition is placed on the bottom surface of the reformer vessel. It can be assumed that the combustion gas of the burner goes around the partition wall, contacts the lower part of the reaction tube, and flows upward along the reaction tube.

  The kind of burner can also be selected as appropriate, and not only a general diffusion combustion burner but also a surface combustion burner can be used.

  Further, a catalyst assisted combustor can be used as the burner. As the catalyst assisted combustor, for example, a combustion catalyst is provided inside the burner body, a fuel supply nozzle for supplying fuel to the upstream side of the combustion catalyst, a fuel for combustion from the fuel supply nozzle, Combustion oxygen-containing gas is supplied from the upstream side, and the combustion oxygen-containing gas and combustion fuel are mixed to form an air-fuel mixture, and a part of the air-fuel mixture is combusted by the combustion catalyst, and downstream of the combustion catalyst. Thus, it is possible to use a catalytic combustion type burner that autonomously flame-combusts an unburned mixture. In this catalytic combustion type burner, it has an evaporative mixing cylinder which is a cylindrical member provided with a heater for promoting the evaporation of the fuel and the mixing downstream of the fuel supply nozzle and upstream of the combustion catalyst, A flame holder is disposed immediately downstream of the combustion catalyst in the burner body, and an ignition device for igniting and forcibly burning an unburned mixture existing downstream of the flame holder, A first combustion section including a flame detector for confirming ignition and confirming continuation of combustion after a predetermined time of operation of the ignition device, and an alarm device for issuing an alarm when no flame is detected by the flame detector; A combustion cylinder that is covered from the outer periphery of the flame holder to the upper side with a gap, and a fuel electrode off-gas supply nozzle that ejects the fuel electrode off-gas of the fuel cell. Burn off-gas Preferably it has a second combustion section.

  Although not shown, a known ignition can be appropriately provided in the burner for ignition.

  FIG. 3 shows an embodiment in which combustion for reaction tube heating is performed in two stages using a surface combustion burner and further using catalytic combustion. In this reformer, a catalytic combustor 3 and an auxiliary supply port 7 forming a catalytic combustion section are added to the configuration of the reformer shown in FIG. Further, in place of the burner 2, a surface combustion burner 2 ′, an air supply port 4, a fuel supply port 5, and a gap 6 forming a premixing portion are provided. The first combustion is performed by the surface combustion burner, and the second combustion is performed by using the combustion catalyst downstream in the exhaust gas flow direction.

  For combustion in the surface combustion burner, combustion air is supplied from the air supply port 4, combustion fuel is supplied from the fuel supply port 5, premixes in the gap 6, and burns in the surface combustion burner 2 ′. Combustion gas A generated by the surface combustion burner contacts the reaction tube, and the reaction tube is heated. On the other hand, the combustion gas A is cooled by the reaction tube. Further, fuel (hereinafter referred to as auxiliary fuel) is supplied from the auxiliary supply port 7, a combustion reaction occurs in the catalytic combustor 3, and the combustion gas B heats the reaction tube downstream thereof. That is, in the form shown in FIG. 1, the amount of heat for heating the reaction tube is all generated by the burner 2, but in the form shown here, only a part is generated by the surface combustion burner and the remaining part is the catalyst. It is generated by a combustor.

  Combustion by the surface combustion burner is planar combustion, and it is suppressed that the flame becomes locally high temperature, and thus generation of thermal NOx is suppressed. In addition, the reaction tube can be efficiently heated by the radiant heat of the surface combustion burner. Furthermore, since the surface combustion burner only needs to supply a part of the heat necessary for reforming, the combustion temperature can be lowered compared with the case where combustion is performed in one stage, and the generation of thermal NOx is suppressed. . Here, the fuel supplied to the burner 2 ′ is reduced compared with the fuel supplied to the burner 2 in the form of FIG. 1, and the shortage of the calorific value is compensated by catalytic combustion of the auxiliary fuel in the subsequent stage. Therefore, even if the total air ratio is constant, the air ratio can be increased in the combustion in the surface combustion burner, and a reduction in NOx can be realized. In the catalytic combustor, auxiliary fuel is burned by oxygen contained in the combustion gas A. Although the temperature of the combustion gas A is reduced by heat exchange with the reaction tube before reaching the catalytic combustor, since the catalytic combustion can be performed at a low temperature, good combustion can be performed.

  By performing catalytic combustion in this way, the combustion gas A whose temperature has been lowered by heat exchange with the downstream portion of the reaction tube (the lower portion of the reaction tube 10 in the figure) is heated again to become the combustion gas B whose temperature has risen, and upstream of the reaction tube The temperature of the reforming catalyst in the section (upper part of the reaction tube 10 in the figure) can be increased. Thereby, the upstream portion of the reaction tube also rises to a temperature at which the reforming reaction occurs favorably. Therefore, there is an effect of leveling the temperature of the reforming catalyst layer, and the reforming catalyst can be used effectively.

  It is also possible to control the catalytic combustion temperature by appropriately setting the temperature of the auxiliary fuel supplied from the auxiliary supply port.

  The case where the surface combustion burner performs combustion at a relatively large air ratio has been shown above, but there may be a case where the air ratio in the surface combustion burner is reduced. In this case, the surface combustion burner burns under partial oxidation conditions. Air is supplied from the auxiliary supply port 7 instead of auxiliary fuel. At this time, the combustion gas A contains combustible components such as carbon monoxide and hydrogen, which are catalytically combusted. In this case, since so-called incomplete combustion occurs in the surface combustion burner, the combustion can be performed at a relatively low temperature, and low NOx can be realized. Since the catalytic combustion can be performed at a low temperature as in the case described above, the NOx reduction can be realized here, the temperature of the catalyst layer can be leveled, and the temperature range where the reforming reaction can be satisfactorily increased. In addition, the advantages of the surface combustion burner, such as the ability to prevent local high temperatures and efficient heating by radiant heat, can be utilized as in the case described above.

  As the partial oxidation condition, an air ratio of 0.65 or more is preferable from the viewpoint of preventing soot generation, and an air ratio of less than 0.90 is preferable from the viewpoint of preventing backfire.

  By combining surface combustion and catalytic combustion in this way, combustion can be performed at a low temperature even at a low air ratio, and both low NOx and high energy efficiency can be achieved at a high level.

  The combustion heat generated in the surface combustion burner is 10% or more from the viewpoint of heating the reaction tube to a high temperature of 700 ° C. or higher with respect to the total of the heat generated in the surface combustion burner and the combustion heat generated in the catalytic combustion section Preferably, it is 50% or more, more preferably 60% or more. Further, this ratio is preferably 90% or less, more preferably 80% or less, and further preferably 70% or less from the viewpoint of reducing NOx.

  In the embodiment shown in FIG. 3, a diffusion combustion burner can be used instead of the surface combustion burner. That is, there is a form in which a catalytic combustor is added to the form shown in FIG. Even in such a form, by performing combustion in two stages, the temperature of the catalyst layer can be leveled, and the temperature range where the reforming reaction occurs favorably can be increased.

[Surface burner]
As the surface combustion burner, the structure of a known surface combustion burner can be used as appropriate, and for example, it can be composed of a burner mat and a burner mat holding member for holding the burner mat and partitioning the container together with the burner mat.

  The burner mat used for the surface combustion burner includes a sintered non-woven fabric or woven fabric of metal fibers, and a non-woven fabric or woven fabric of fibers made of ceramics such as cordierite, titania, mullite, alumina, silica, and alumina-silica. Can be used. A metal fiber mat is preferable as the burner mat from the viewpoint of heat uniformity and prevention of backfire.

  The average porosity of the burner mat is preferably from 60% to 98%, more preferably from 70% to 95%, from the viewpoint of pressure loss.

  Further, when the fuel combusted by the surface combustion burner is liquid, vaporization means for appropriately vaporizing the liquid fuel can be provided outside or inside the reformer.

  When the surface combustion burner is provided with a combustion catalyst, it is preferable in that the NOx can be further reduced. This is because the presence of the combustion catalyst enables combustion even at a lower temperature. For this purpose, the combustion catalyst can be carried on the surface combustion burner. As the combustion catalyst, a known combustion catalyst can be appropriately used. For example, active metals such as rhodium, ruthenium, palladium and platinum can be used. In addition, nickel is also preferable because it is inexpensive.

[Catalyst combustion section]
As the catalytic combustion section, a known catalytic combustor structure can be used as appropriate, and for example, it can be constituted by a combustion catalyst and a combustion catalyst holding member that holds the combustion catalyst and partitions the inside of the container together with the combustion catalyst.

  There may be a form in which the granular catalyst is filled on a porous plate or a dispersion plate such as punching metal, or a combustion catalyst is supported on a honeycomb-shaped ceramic.

  As the components of the combustion catalyst, known combustion catalysts can be used as appropriate, and active metals such as rhodium, ruthenium, palladium and platinum can be used. In addition, nickel is also preferable because it is inexpensive.

〔container〕
The reformer container 1 may be, for example, a cylindrical shape, and the cross-sectional shape thereof may be any shape such as a circle or a square. To match.

When a surface combustion burner is used, the cross-sectional area of the container is a factor that determines the area of the surface combustion burner, and the burner mat area and the container cross-sectional area are appropriately determined according to the surface load. If the surface load is small relative to the burner mat area, it is disadvantageous in that the area of the mat portion becomes large. If the surface load is large, a large load is applied to the burner mat, which tends to cause damage to the mat and increase in NOx. This is disadvantageous. From this viewpoint, preferably 100kW / m ² ~3000kW / m ² for a surface ^{load, 400kW / m 2 ~2000kW / m} 2 is more preferable.

[Fuel for combustion, etc.]
As the fuel to be burned in the burner and the catalytic combustion section, a known fuel can be appropriately selected and used. If the raw material for hydrogen production is also used as a fuel for combustion, its storage means and supply line can be shared, which is preferable.

  When a surface combustion burner or a catalyst combustion part is provided, gas fuel can be vaporized as it is, and liquid fuel can be vaporized and supplied to the surface combustion burner or catalyst combustion part.

  In the fuel cell system, anode off-gas (gas discharged from the fuel cell anode chamber) can also be used as a combustion fuel. In particular, an anode off gas is preferably used as the auxiliary fuel. This is because even if the anode offgas is low in calories, it can be burned well by catalytic combustion, and the anode offgas can be used effectively. It is also possible to use an anode off gas added with another fuel (for example, the same fuel as the combustion fuel used in the burner).

  In the above-described embodiment, air is used for combustion, and the use of air is preferable from the viewpoint of availability. However, any gas containing oxygen can be used for combustion as appropriate, as long as it contains oxygen. For example, it is possible to use a cathode off gas discharged from the cathode chamber of the fuel cell as an oxygen-containing gas for combustion.

[Reformer]
In the reformer, a hydrogen-containing reformed gas is produced by reacting a raw material for hydrogen production with water (steam) and, in some cases, oxygen in addition to these. In this apparatus, the raw material for hydrogen production is mainly decomposed into hydrogen and carbon monoxide. Usually, carbon dioxide and methane are also contained in the cracked gas. Examples of the reforming reaction include a steam reforming reaction and an autothermal reforming reaction.

The steam reforming reaction is a reaction between steam and a raw material for producing hydrogen. However, since it involves a large endotherm, heating from the outside is usually required. Usually, the reaction is carried out in the presence of a metal catalyst typified by a Group VIII metal such as nickel, cobalt, iron, ruthenium, rhodium, iridium and platinum. The reaction temperature can be 450 ° C to 900 ° C, preferably 500 ° C to 850 ° C, more preferably 550 ° C to 800 ° C. The amount of steam introduced into the reaction system is defined as the ratio of the number of moles of water molecules to the number of moles of carbon atoms contained in the raw material for hydrogen production (steam / carbon ratio), and this value is preferably 0.5-10. Preferably it is 1-7, More preferably, it is 2-5. When the raw material for hydrogen production is liquid, the space velocity (LHSV) at this time is A / B when the flow rate in the liquid state of the raw material for hydrogen production is A (L / h) and the volume of the catalyst layer is B (L). This value is preferably set in the range of 0.05 to 20 h ⁻¹ , more preferably 0.1 to 10 h ⁻¹ , and still more preferably 0.2 to 5 h ⁻¹ .

  Autothermal reforming reaction is a method of reforming while balancing the reaction heat by advancing the steam reforming reaction with the heat generated at this time while oxidizing part of the raw material for hydrogen production, Since it has a relatively short start-up time and is easy to control, it has recently attracted attention as a hydrogen production method for fuel cells. When the heat required for steam reforming cannot be covered by the oxidation reaction heat, the reaction tube is heated from the outside. Also in this case, the reaction is usually carried out in the presence of a metal catalyst, typically a Group VIII metal such as nickel, cobalt, iron, ruthenium, rhodium, iridium and platinum. The amount of steam introduced into the reaction system is preferably 0.3 to 10, more preferably 0.5 to 5, and still more preferably 1 to 3 as a steam / carbon ratio.

  In autothermal reforming, oxygen is added to the raw material in addition to steam. The oxygen source may be pure oxygen, but in many cases air is used. Usually, oxygen is added to such an extent that it can generate an amount of heat that can balance the endothermic reaction associated with the steam reforming reaction, but the amount added is appropriately determined in relation to heat loss and external heating. The amount is preferably from 0.05 to 1, more preferably from 0.1 to 0.75, even more preferably as the ratio of the number of moles of oxygen molecules to the number of moles of carbon atoms contained in the raw material for hydrogen production (oxygen / carbon ratio). Is set to 0.2 to 0.6. The reaction temperature of the autothermal reforming reaction is set in the range of 450 ° C. to 900 ° C., preferably 500 ° C. to 850 ° C., more preferably 550 ° C. to 800 ° C., as in the case of the steam reforming reaction. When the raw material for hydrogen production is liquid, the space velocity (LHSV) at this time is preferably selected in the range of 0.1 to 30, more preferably 0.5 to 20, and still more preferably 1 to 10.

[Raw materials for hydrogen production]
As a raw material for hydrogen production, any substance that can obtain a reformed gas containing hydrogen by the above reforming reaction can be used. For example, compounds having carbon and hydrogen in the molecule such as hydrocarbons, alcohols and ethers can be used. Preferable examples that can be obtained inexpensively for industrial use or consumer use include methanol, ethanol, dimethyl ether, city gas, LPG (liquefied petroleum gas), gasoline, kerosene and the like. Of these, kerosene is preferable because it is easily available for industrial use and consumer use, and is easy to handle.

[Shift reactor]
Although the hydrogen-containing gas produced by the reformer may be supplied to the fuel cell with the same composition, for example, the performance of a solid polymer fuel cell may be deteriorated by carbon monoxide. In the fuel cell system, it is preferable to provide a CO shift reactor downstream of the reformer.

  The gas generated in the reformer contains, for example, carbon monoxide, carbon dioxide, methane, and steam in addition to hydrogen. Further, nitrogen is also contained when air is used as an oxygen source in the autothermal reforming. Among these, the shift reactor performs a shift reaction in which carbon monoxide is reacted with water and converted into hydrogen and carbon dioxide. Usually, the reaction proceeds in the presence of a catalyst, and a catalyst containing a noble metal such as a mixed oxide of Fe—Cr, a mixed oxide of Zn—Cu, platinum, ruthenium, and iridium is used. Mol%) is preferably reduced to 2% or less, more preferably 1% or less, and even more preferably 0.5% or less. The shift reaction can also be carried out in two stages, in which case a high temperature shift reactor and a low temperature shift reactor are used.

[Selective oxidation reactor]
For example, in the polymer electrolyte fuel cell system, it is preferable to further reduce the carbon monoxide concentration. For this purpose, it is preferable to treat the outlet gas of the CO shift reactor with a selective oxidation reaction. In this step, a catalyst containing iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, platinum, copper, silver, gold, etc. is used, preferably 0.5 to the number of moles of carbon monoxide remaining. The carbon monoxide concentration is preferably increased by selectively converting carbon monoxide to carbon dioxide by adding 10 moles, more preferably 0.7-5 moles, and even more preferably 1-3 moles of oxygen. Is reduced to 10 ppm (on a molar basis of the dry base) or less. In this case, the carbon monoxide concentration can be reduced by reacting with the coexisting hydrogen simultaneously with the oxidation of carbon monoxide to generate methane. The selective oxidation reaction can also be performed in two stages.

[Composition of hydrogen-containing gas]
When the steam reforming reaction is used in the reformer, the composition of the gas that has passed through the reformer (mol% in dry base) is typically, for example, 63 to 73% hydrogen, 0.1 to 5% methane, 5 to 5 carbon dioxide. 20%, carbon monoxide 5-20%. On the other hand, the composition when using the autothermal reforming reaction (mol% in dry base) is usually 23 to 37% hydrogen, 0.1 to 5% methane, 5 to 25% carbon dioxide, 5 carbon monoxide, for example. -25%, nitrogen 30-60%.

  When the steam reforming reaction is used in the reformer, the composition of the gas that has passed through the reformer and the shift reactor (mol% or mol ppm in dry base) is usually, for example, 65 to 75% hydrogen, 0.1 to methane 0.1 5%, carbon dioxide 20-30%, carbon monoxide 1000 ppm-10000 ppm. On the other hand, the composition when using the autothermal reforming reaction (mol% or mol ppm of dry base) is usually 25 to 40% hydrogen, 0.1 to 5% methane, 20 to 40% carbon dioxide, one Carbon oxide is 1000 ppm to 10000 ppm and nitrogen is 30 to 54%.

  The composition of the gas that has passed through the reformer, shift reactor, and selective oxidation reactor (mol% of the dry base) is usually, for example, 65 to 75% hydrogen, 0. 1 to 5%, carbon dioxide 20 to 30%, nitrogen 1 to 10%. On the other hand, the composition (dry base mol%) when using the autothermal reforming reaction is usually, for example, 25 to 40% hydrogen, 0.1 to 5% methane, 20 to 40% carbon dioxide, and 30 to 54 nitrogen. %.

(Catalyst shape)
In any of the reforming catalyst, the combustion catalyst, the shift catalyst, and the selective oxidation catalyst, the shape of the catalyst is appropriately selected. Typically, it is granular, but in some cases, it may have a honeycomb shape.

〔Fuel cell〕
As the fuel cell, a fuel cell of a type in which hydrogen is a reactant of the electrode reaction in the fuel electrode can be appropriately employed. For example, a fuel cell of a solid polymer type, a phosphoric acid type, a molten carbonate type, or a solid oxide type can be employed. Hereinafter, the configuration of the polymer electrolyte fuel cell will be described.

  The fuel cell electrode is composed of an anode (fuel electrode) and a cathode (air electrode) and a solid polymer electrolyte sandwiched between them. The hydrogen-containing gas produced by the hydrogen production apparatus is on the anode side, and the air is on the cathode side. These oxygen-containing gases are introduced after appropriate humidification treatment if necessary.

  At this time, a reaction in which hydrogen gas becomes protons and emits electrons proceeds at the anode, and a reaction in which oxygen gas obtains electrons and protons to become water proceeds at the cathode. In order to promote these reactions, platinum black and Pt catalyst or Pt-Ru alloy catalyst supported on activated carbon are used for the anode, and platinum black and Pt catalyst supported on activated carbon are used for the cathode. Usually, both the anode and cathode catalysts are formed into a porous catalyst layer together with Teflon, a low molecular weight polymer electrolyte membrane material, activated carbon or the like as necessary.

  As solid polymer electrolytes, Nafion (Nafion, manufactured by DuPont), Gore (Gore, manufactured by Gore), Flemion (Flemion, manufactured by Asahi Glass), Aciplex (Aciplex, manufactured by Asahi Kasei), etc. A molecular electrolyte membrane is usually used, and the porous catalyst layer is laminated on both sides thereof to form an MEA (Membrane Electrode Assembly). Further, the fuel cell is assembled by sandwiching the MEA with a separator having a gas supply function, a current collecting function, particularly an important drainage function in the cathode, and the like made of a metal material, graphite, carbon composite and the like. The electric load is electrically connected to the anode and the cathode.

[Other equipment]
In addition to the above devices, known components of the reformer and known components of the fuel cell system can be appropriately provided as necessary. Specific examples include a desulfurizer that reduces the concentration of sulfur in the raw material for hydrogen production before supplying the reformer, a means for supplying an oxygen-containing gas such as air to the cathode of the fuel cell, and a fuel cell. Steam generator for generating steam for humidifying gas, cooling system for cooling various devices such as fuel cells, pumps for pressurizing various fluids, pressurizing means such as compressors and blowers, fluid flow rate For adjusting the flow rate, or for controlling or shutting off the flow of fluid, such as a flow rate control means such as a valve, a flow path shutoff / switching means, a heat exchanger for performing heat exchange or heat recovery, a vaporizer for vaporizing liquid, and a gas Condensers that condense, heating / heat-retaining means that externally heat various devices with steam, various fluid storage means, instrumentation air and electrical systems, control signal systems, control devices, output and power electricity System.

[Example 1]
Steam reforming was performed using a reformer having the configuration shown in FIG. As steam reforming conditions, JIS No. 1 kerosene 1.75 kg / h and water were added to the reforming catalyst so that the steam / carbon ratio was 3.25. The combustion conditions were set so that the burner fuel input was 1.0 kg / h and the air ratio was 1.6. The double tube reaction tube had an outer diameter (diameter) of 43 mm and a length of 600 mm. Fifteen fins having a width of 8 mm and a length of 250 mm were provided on the outer wall of the reaction tube. At that time, one end (upper end) of the fin was aligned with the downstream end portion (upper end of the reaction tube) in the combustion gas A flow direction of the reaction tube.

  The burner combustion amount and the air ratio were adjusted so that the most upstream temperature (this temperature is T) in the flow direction of the combustion gas A in the catalyst layer was 850 ° C.

  When the temperature of the catalyst layer was measured, the temperature gradually decreased along the flow direction of the combustion gas A. The highest temperature was the temperature T, and the lowest temperature was observed most downstream in the combustion gas A direction. In the catalyst layer, the volume ratio of the region at 550 ° C. or higher was about 62%.

[Example 2]
The upper end of the combustion catalyst layer (Pt / Al ₂ O ₃ ) is 250 mm below the upstream end (reaction tube upper end) in the combustion gas A flow direction of the reaction tube (upstream with respect to the combustion gas flow direction). (Catalyst layer length is 100 mm). The combustion catalyst layer was formed by filling a catalyst between the reaction tube 10 and the container 1 as shown in FIG. The burner combustion conditions were set to be 0.6 kg / h of kerosene and an air ratio of 1.6 (conditions in which the anode off gas was counted as fuel in addition to kerosene to an air ratio of 1.6). As the fuel for the combustion catalyst, anode off-gas (H ₂ : 33%, CO ₂ : 53%, N ₂ : 14% (all dry mole%)) from the fuel cell was supplied immediately upstream of the catalyst combustion layer. Conditions were set so that the total amount of combustion was the same as in Example 1. Other than this, the modification was performed in the same manner as in Example 1.

  When the temperature of the catalyst layer was measured, the temperature gradually decreased along the flow direction of the combustion gas A, and then the temperature started to increase in the vicinity of the combustion catalyst layer and gradually decreased again. The maximum temperature was the temperature T, and the minimum temperature was observed most downstream in the direction of the combustion gas A, but the temperature T was about 50 ° C. lower than that of Example 1, and the minimum temperature was about 80 ° C. higher than that of Example 1. . In the catalyst layer, the volume ratio of the region at 550 ° C. or higher was about 85%.

[Comparative Example 1]
Modification was performed in the same manner as in Example 1 except that no fin was provided.

  When the temperature of the catalyst layer was measured, the temperature gradually decreased along the flow direction of the combustion gas A. When the volume ratio of the area | region which becomes 550 degreeC or more among catalyst layers was calculated | required, it was about 38%. The highest temperature was the temperature T, and the lowest temperature was observed most downstream in the combustion gas A direction. The maximum temperature was about the same as in Example 1, but the minimum temperature was about 50 ° C. lower than Example 1.

[Comparative Example 2]
The reforming was performed in the same manner as in Example 1 except that the fins were installed over the entire longitudinal direction of the reforming tube.

  When the temperature of the catalyst layer is measured, the temperature distribution is such that the temperature stays at a high temperature of 750 ° C. or more along the flow direction of the combustion gas A, and the temperature gradually decreases from 150 mm along the flow direction. became. When the volume ratio of the region of the catalyst layer at 550 ° C. or higher was determined, it was about 37%. The highest temperature was the temperature T, and the lowest temperature was observed most downstream in the combustion gas A direction. The maximum temperature was about the same as in Example 1, but the minimum temperature was about 70 ° C. lower than Example 1.

  Table 1 shows the reforming conversion rate and the like in the above examples. In the table, the reforming conversion rate is the ratio of the amount of hydrogen production raw material converted (number of moles) to the amount of hydrogen production raw material charged (number of moles), and the raw material is C2 (number of carbons) such as butane or kerosene. 2) In the case of the above hydrocarbon fuel, it is defined by the following formula. In the formula, the number of moles of unconverted raw material means the number of moles of hydrocarbon components having 2 or more carbon atoms discharged from the reformer.

  In the table, the concentration of hydrocarbons with 2 or more carbon atoms in the reformed gas is shown in ppm on a dry mole basis, and the heat exchange rate is the amount of heat transferred to the reformer for the combustion heat (burner combustion and anode off-gas combustion). The percentage is shown as a percentage.

  Compared with the comparative example, the region where Example 1 was 550 ° C. or higher was wider. This means that Example 1 had a higher heat exchange rate, and that the region where the reforming reaction proceeded excellently was wider. Table 1 also shows that the heat exchange rate of Example 1 was higher than that of Comparative Example 1, and the reforming was performed well. Therefore, in order to perform the same level of reforming, a smaller reforming catalyst layer is required when the fins are provided, and the reaction tube can be shortened and the like can be made compact. Alternatively, if a reforming catalyst layer having the same size is used, the life of the reformer can be extended. This is because, in general, the catalyst layer gradually deteriorates from the inlet, and the region where most of the reforming reaction proceeds gradually shifts to the downstream side, but compared with the narrow region where the reforming reaction proceeds excellently. This is because the entire region deteriorates in a short time, whereas if the region where the reforming reaction proceeds excellently is wide, the time until the entire region deteriorates becomes relatively long.

  Moreover, in Example 2 using a combustion catalyst, the maximum temperature of the catalyst layer could be reduced. This contributes to extending the life of the catalyst and the reaction tube. In addition, the minimum temperature could be increased compared to Example 1. As a result, the region where the reforming reaction proceeds excellently is wider than that in Example 1. Also from Table 1, it can be seen that the heat exchange rate of Example 2 was higher than that of Comparative Example 1 as compared with Example 1.

  The reformer of the present invention can be used in a hydrogen production apparatus, for example, a hydrogen production apparatus used in a hydrogen station, a fuel cell system, or the like. The fuel cell system of the present invention can be used for a power generator for a moving body such as an automobile, a fixed power generation system, a cogeneration system, and the like.

It is a typical sectional side view which shows one form of the reformer of this invention. It is a typical sectional view of a reaction tube and a fin. It is typical sectional drawing which shows another form of the reformer of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Container 2 Burner 2 'Surface combustion burner 3 Catalytic combustor 4 Combustion air supply port 5 Combustion fuel supply port 6 Air gap (premixing part)
7 Auxiliary supply port 8 Combustion gas discharge port 10 Reforming reaction section 11 Raw material supply port 12 Reformed gas discharge port A Burner combustion gas flow B Catalytic combustor combustion gas flow

Claims (5)

In a reformer for producing a hydrogen-containing gas containing hydrogen by reforming a raw material for hydrogen production, comprising a reaction tube containing a reforming catalyst and a burner for heating the reaction tube from the outside,
The reaction tube is a double tube with one end closed, and the reforming catalyst is accommodated in the outer tube,
A fin on the outer wall of the reaction tube;
The reformer characterized in that the position of the fin is at least part of a range from the inlet of the reaction tube to half of the length of the reaction tube.   The reformer according to claim 1, further comprising a combustion catalyst downstream of the burner in the combustion gas flow direction of the burner.   The reformer according to claim 2, wherein fins are provided on the outer wall of the reaction tube in a region downstream of the combustion catalyst in the combustion gas flow direction of the burner.   The reformer according to any one of claims 1 to 3, wherein the burner is a surface combustion burner. A reformer for producing a hydrogen-containing gas containing hydrogen by reforming a raw material for hydrogen production, comprising a reaction tube containing a reforming catalyst and a burner for heating the reaction tube from the outside; In a fuel cell system comprising a fuel cell using a contained gas as fuel,
The reaction tube is a double tube with one end closed, and the reforming catalyst is accommodated in the outer tube,
A fin on the outer wall of the reaction tube;
The position of the fin is at least a part of a range from the inlet of the reaction tube to half of the length of the reaction tube.

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