JP2006076802A - Hydrogen production apparatus and fuel cell system equipped with the same, and method for producing hydrogen - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydrogen production apparatus capable of keeping catalytic activity of a reforming catalyst over long period of time, by making concentration of sulfur content contained in a raw material gas to sufficiently low level by virtue of a simple constitution, and to provide a fuel cell system equipped with the apparatus. <P>SOLUTION: This hydrogen production apparatus 101 is equipped with a reformer 5 in which a first reforming catalytic body 23 is filled for producing a reformed gas containing hydrogen by a reforming reaction of the raw material gas including a sulfur compound. In the upstream of the first reforming catalytic body 23, desulfurization layers 21 and 22 are provided which comprise the reforming catalyst and a hydrogen sulfide adsorbent. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a hydrogen generator, a fuel cell system equipped with the hydrogen generator, and a hydrogen generation method, and in particular, the sulfur component contained in the raw material gas is set to a sufficiently low concentration level over a long period of time with a simple configuration. The present invention relates to a hydrogen generator capable of maintaining the catalytic activity of a reforming catalyst, a fuel cell system including the hydrogen generator, and a hydrogen generation method.

  A fuel cell system capable of high-efficiency and small-scale power generation is suitable as a distributed power generation system because it is easy to construct a system that uses thermal energy generated during power generation and can achieve high energy use efficiency.

  A fuel cell system has a fuel cell as its power generation main body. When this fuel cell is classified according to a power generation mechanism, for example, a polymer electrolyte fuel cell (hereinafter referred to as PEFC) or a phosphoric acid fuel cell (hereinafter referred to as PEFC). , Called PAFC).

  By the way, since these PEFCs and PAFCs require hydrogen gas as power generation fuel, a fuel cell system equipped with PEFC or the like usually has a fuel reformer (hydrogen generation device) that generates hydrogen gas as power generation fuel. Is provided. The fuel cell generates power by consuming hydrogen-rich reformed gas (hydrogen gas) and air (oxygen gas) sent from the hydrogen generator at the anode and the cathode, respectively.

  Here, in the hydrogen generator, a steam reforming method in which a mixed gas composed of a hydrocarbon-based source gas (hereinafter simply referred to as source gas) and steam is reformed to generate hydrogen gas, and the hydrocarbon source gas is oxidized with air. Thus, hydrogen gas is generated from the source gas by a desired hydrogen generation method such as a partial oxidation method for generating hydrogen gas and an autothermal method in which both are combined. Examples of the source gas include methane, ethane, propane, butane, city gas, and LP gas (including source gas in which two or more of these gases are mixed).

  Hereinafter, the hydrogen gas generation process in the hydrogen generator will be outlined. Here, the reformed gas generation process will be described taking the steam reforming method as an example of the hydrogen generation method.

  The steam reforming reaction of the mixed gas composed of the raw material gas and steam led to the reformer of the hydrogen generator is maintained by heating the reforming catalyst such as Ni-based or Ru-based to about 600 ° C to 700 ° C. To make progress.

  In the reformed gas sent out from the reformer during the reforming reaction, carbon monoxide gas (hereinafter referred to as CO gas) in addition to unreacted raw material gas (for example, methane gas), unreacted water vapor and carbon dioxide gas. ) As a by-product. In addition, although the content rate of these by-products depends on the performance of the reforming catalyst and the operating temperature of the hydrogen generator, it is usually 8 to 15% by volume.

  If the CO gas concentration in the reformed gas supplied to the PEFC exceeds about 50 ppm, the power generation performance of the fuel cell is significantly deteriorated. For this reason, before the reformed gas is supplied to the PEFC, the reformed gas sent from the reformer is sent in advance to a transformer for reducing the CO gas concentration arranged downstream thereof.

  In this transformer, the CO gas in the reformed gas sent from the reformer is converted into carbon dioxide gas by the shift reaction with water shown in the following formula (1), whereby the CO gas in the reformed gas is converted. The gas concentration is reduced to about 0.5% by volume. In the shift reaction, hydrogen gas is also generated together with carbon dioxide gas.

CO + H ₂ O → CO ₂ + H ₂ (1)
Subsequently, the reformed gas sent out from the transformer is guided to a selective oxidizer disposed downstream of the reformer to further reduce the CO gas concentration to a lower concentration. The gas concentration is at a level that does not cause deterioration of the power generation performance of the fuel cell.

  In this selective oxidizer, the CO gas in the reformed gas sent from the transformer is converted into carbon dioxide by the oxidation reaction of the CO gas and oxygen gas shown in (2) below. The CO gas concentration in the quality gas is reduced to 50 ppm or less, desirably 10 ppm or less.

2CO + O ₂ → 2CO ₂ (2)
Thus, the hydrogen-rich reformed gas that has undergone the steam reforming reaction, shift reaction, and CO gas oxidation reaction in the hydrogen generator is supplied from the hydrogen generator toward the anode of the PEFC or PAFC.

  By the way, the fuel raw material gas supplied to the hydrogen generator described above may contain a sulfur compound. Specifically, odorants containing sulfur compounds such as sulfides and mercaptans are added to city gas and LP gas for the purpose of leakage detection.

  On the other hand, the effect of such sulfur compounds on the reforming reaction differs depending on the type of reforming catalyst and cannot be generally stated, but with Ni-based and Ru-based reforming catalysts frequently used in steam reforming reactions, It is known that the activity decrease is progressed even at an extremely low concentration of sulfur.

  For this reason, the source gas such as city gas and LP gas is appropriately subjected to desulfurization treatment in advance before being supplied to the hydrogen generator. However, in the adsorptive desulfurization treatment of a zeolite adsorbent that has been frequently performed conventionally, the lower limit of the sulfur concentration contained in the raw material gas after the desulfurization treatment is about 1 to 10 ppb. It has been found that it is difficult to expect the catalytic activity of the reforming catalyst to be maintained when the Ni-based or Ru-based reforming catalyst is used for a long time with the raw material gas at this sulfur concentration level.

In response to such a problem, a technique called hydrodesulfurization that can reduce the concentration of sulfur contained in the raw material gas to 0.1 to 1 ppb has been proposed (see Patent Document 1 as a conventional example).
Japanese Patent No. 3242514

  The influence of the sulfur component on the reforming catalyst can be concluded as follows.

  Odorants (sulfur compounds) such as sulfides and mercaptans added to city gas and LP gas are converted to hydrogen sulfide under steam reforming conditions, and this hydrogen sulfide poisons the active metal of the reforming catalyst. As a result, the raw material gas conversion rate is lowered. In particular, Ni-based and Ru-based reforming catalysts have high activity and are suitable for steam reforming reactions, but these catalysts are easily sulfur poisoned and subjected to room temperature adsorption desulfurization (zeolite-based absorption desulfurization treatment). Even if source gas is used, an appropriate reforming reaction cannot be maintained over a long period of time.

  In addition, when a Pt, Rh, and Pd-based reforming catalyst is used, although it is excellent in resistance to sulfur poisoning, the activity for the steam reforming reaction is not sufficient and the cost is increased. That is, any of the above reforming catalysts has advantages and disadvantages with respect to measures against sulfur poisoning.

  Certainly, according to the hydrodesulfurization method described in the conventional example, such a problem can be technically dealt with. However, if this hydrodesulfurization method is adopted as it is, an apparatus for adding hydrogen gas to the raw material gas is used. It is necessary to provide it separately. For this reason, in the apparatus using the method described in the conventional example, there is a problem that the entire configuration of the desulfurization apparatus is complicated and enlarged.

  The present invention has been made in order to solve such problems, and has a simple structure to reduce the concentration of the sulfur component contained in the raw material gas to a sufficiently low concentration level over a long period of time. An object of the present invention is to provide a hydrogen generator capable of maintaining the catalytic activity of the above and a fuel cell system including the same.

  Another object of the present invention is to provide a hydrogen generation method for producing hydrogen gas by setting the concentration of the sulfur component contained in the raw material gas to a sufficiently low concentration level by a simple desulfurization method.

    A hydrogen generation apparatus according to the present invention is a hydrogen generation apparatus including a reformer filled with a first reforming catalyst body that generates a reformed gas containing hydrogen gas by a reforming reaction from a raw material gas having a sulfur compound. The apparatus includes a desulfurization layer including a reforming catalyst and a hydrogen sulfide adsorbent upstream of the first reforming catalyst body.

  Here, the hydrogen sulfide adsorbent may be at least one metal of Mn, Co, Cu, Zn, Ce, Zr and Fe or an oxide of the metal.

  Thus, a part of the hydrogen gas generated by the reforming reaction of the reforming catalyst is diverted to convert the sulfur compound contained in the raw material gas into hydrogen sulfide, and then the converted hydrogen sulfide Is reliably adsorbed and absorbed by the desulfurization layer. For this reason, the concentration of the sulfur component contained in the raw material gas can be made sufficiently low to maintain the catalytic activity of the first reforming catalyst body over a long period of time.

  An example of the desulfurization layer has a second reforming catalyst body made of the reforming catalyst, and the hydrogen sulfide adsorbent is formed between the first reforming catalyst body and the second reforming catalyst body. It may be arranged between them.

  Then, by diverting a part of the hydrogen gas generated by the reforming reaction of the second reforming catalyst body to convert the sulfur compound contained in the raw material gas into hydrogen sulfide, The converted hydrogen sulfide is reliably adsorbed and absorbed by the hydrogen sulfide adsorbent downstream of the second reforming catalyst body.

  Another example of the desulfurization layer is a layer configured by mixing the reforming catalyst and the hydrogen sulfide adsorbent.

  Thus, by diverting a part of the hydrogen gas generated by the reforming reaction of the reforming catalyst, the sulfur compound contained in the raw material gas is converted into hydrogen sulfide, and the converted hydrogen sulfide is converted into hydrogen sulfide. Adsorption and absorption are ensured by the hydrogen sulfide adsorbent contained in the desulfurization layer.

  Thus, hydrogen gas is generated by the reforming reaction of the reforming catalyst, and the sulfur compound contained in the raw material gas is converted into hydrogen sulfide by the hydrogen gas, and the hydrogen sulfide is contained in the desulfurization layer. It is removed from the source gas by a metal or an oxide of the metal.

  Here, the first reforming catalyst body includes at least one metal of Pt, Pd, Rh, Ru, and Ni, and the second reforming catalyst body is formed of Pt, Rh, and Pd. It may contain at least one metal.

  The Pt-based, Rh-based, and Pd-based reforming catalysts have excellent resistance to sulfur poisoning, and the second reforming catalyst generates hydrogen gas for converting the sulfur compound contained in the raw material gas into hydrogen sulfide. Suitable as a medium.

  Ru-based and Ni-based reforming catalysts have high catalytic activity, and are suitable as the first reforming catalyst body that performs a reforming reaction for generating reformed gas from desulfurized raw material gas in earnest. is there. Of course, even Pt, Pd, and Rh based reforming catalysts that have inferior catalytic activity compared to Ru based and Ni based reforming catalysts can be used as the first reforming catalyst body. is there.

  It is desirable to maintain the temperature of the desulfurization layer at 650 ° C. or lower.

  When the operating temperature of the metal (hydrogen sulfide adsorbent) or the oxide of the metal (hydrogen sulfide adsorbent) exceeds 650 ° C., the sintering of the desulfurizing agent exposed to a high temperature proceeds and the reaction surface area decreases. May inhibit the reaction.

  The fuel cell system according to the present invention includes the hydrogen generator and the fuel cell described above, and supplies the reformed gas flowing out from the hydrogen generator to the fuel cell.

The hydrogen generation method according to the present invention includes a step of generating hydrogen gas from a raw material gas containing a sulfur compound by a reforming reaction based on a first reforming catalyst, and the sulfur compound reacts with the hydrogen gas. Removing the converted hydrogen sulfide from the source gas; generating a reformed gas containing hydrogen gas from the gas from which the hydrogen sulfide has been removed by a reforming reaction based on a second reforming catalyst; It is a method including.
It is.

  Further, this hydrogen generation method removes the hydrogen sulfide from the source gas by a desulfurization layer containing at least one metal of Mn, Co, Cu, Zn, Ce, Zr and Fe or an oxide of the metal. It may be a method to do.

  According to this method, a part of the hydrogen gas generated by the reforming reaction of the first reforming catalyst is diverted to convert the sulfur compound contained in the raw material gas into hydrogen sulfide. The hydrogen sulfide thus obtained is surely adsorbed and absorbed by the desulfurization layer.

  The desulfurization layer includes the first reforming catalyst, and the hydrogen generation method is a method in which the hydrogen gas is generated in the desulfurization layer and the hydrogen sulfide is removed from the source gas. good.

  According to the present invention, a hydrogen generator capable of removing a small amount of sulfur component contained in a raw material gas with a simple configuration and maintaining the catalytic activity of a reforming catalyst over a long period of time, and The provided fuel cell system is obtained.

  In addition, according to the present invention, there can be obtained a hydrogen generation method for producing hydrogen gas while removing sulfur components contained in the raw material gas to a sufficiently low concentration level by a simple desulfurization method.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram schematically showing a configuration of a fuel cell system according to an embodiment of the present invention.

  The main part of the fuel cell system 100 according to the present embodiment includes a hydrogen generator 101 and a fuel cell 9 as will be described in detail later.

  The hydrogen generator 101 generates a hydrogen-rich reformed gas using a raw material gas for fuel desulfurized to about 1 to 10 ppb and vaporized water vapor.

  The fuel cell 9 uses the reformed gas produced by the hydrogen generator 101 and led to the anode (not shown) and the air led to the cathode (not shown) to output electric power. The predetermined power generation operation is executed.

  Initially, the structure of the gas supply system regarding the source gas and water vapor | steam guide | induced to this hydrogen production | generation apparatus 101 is demonstrated with reference to FIG.

  In order to supply the raw material for fuel desulfurized to the hydrogen generator 101, the fuel cell system 100 includes a raw material supply device 1 and a raw material desulfurization device 2. Examples of the raw material gas supplied to the raw material desulfurization device 2 by the raw material supply device 1 include natural gas, methanol, and gasoline.

  In this embodiment in which natural gas is used as the raw material gas, a booster (not shown) for boosting the natural gas sent from the infrastructure (not shown) that allows the natural gas to be always supplied to the raw material supply apparatus 1 is provided. It has been. As shown in FIG. 1, the infrastructure and the raw material supply apparatus 1 are connected by a pipe a, and the natural gas supplied from the infrastructure is guided to the raw material supply apparatus 1 through the pipe a.

  The raw material desulfurization apparatus 2 has a zeolite-based adsorbent for adsorbing sulfur compounds. And the raw material supply apparatus 1 and the raw material desulfurization apparatus 2 are connected by the piping b, and natural gas is guide | induced to the raw material desulfurization apparatus 2 from the raw material supply apparatus 1 via this piping b.

  The raw material desulfurizer 2 and the hydrogen generator 101 are connected by a pipe c, and the raw material gas desulfurized to a predetermined sulfur concentration level by the raw material desulfurizer 2 is introduced to the hydrogen generator 101 through the pipe c. It is burned.

  On the other hand, after the reformed water subjected to purification treatment such as deionization is vaporized and supplied to the hydrogen generator 101, the reformed water is supplied in the middle of the pipe between the water tank 15 and the hydrogen generator 101. A device 3 and an evaporator 4 are arranged. The reforming water supply device 3 is a plunger pump (not shown) for pumping the reforming water from the water tank 15 to the evaporation device 4, and the evaporation device 4 is a heater for evaporating the reforming water. (Not shown) are built in each.

  Although detailed illustration of the inside of the evaporator 4 is omitted, the heat generated in the reformer 5 may be supplied to the heater of the evaporator 4 to heat the reforming water.

  Here, the water tank 15 and the reforming water supply device 3 are connected by a pipe n, and the reforming water stored in the water tank 15 is guided to the reforming water supply apparatus 3 through the pipe n. It is burned.

  The reforming water supply device 3 and the evaporator 4 are connected by a pipe o, and the reforming water passing through the pipe o is pressure-fed and supplied from the reforming water supply device 3 to the evaporator 4.

  The evaporator 4 and a predetermined position in the middle of the pipe c are connected by a pipe p. That is, the pipe p extends from the middle of the pipe c so as to reach the evaporator 4. And the water vapor | steam vaporized by the evaporator 4 is mixed with the desulfurized source gas which flows through the inside of the piping c through this piping p in this branch location. The mixed gas in which the raw material gas and the water vapor are mixed in this manner flows downstream of the branch point in the pipe c and is guided into the hydrogen generator 101 (reformer 5).

  Next, the internal configuration of the hydrogen generator 101 will be described with reference to FIG.

  The hydrogen generator 101 includes a reformer 5 that generates a reformed gas by a steam reforming reaction, a reforming heater 17 that supplies heat necessary for the steam reforming reaction to the reformer 5, and a reformer. A shifter 6 for proceeding with a shift reaction for reducing the CO gas concentration in the reformed gas flowing out from the reformer 5, and for further reducing the CO gas concentration in the reformed gas flowing out from the shifter 6 The selective oxidizer 7 that causes the oxidation reaction to proceed and the first air supply device 8 (blower) that can continuously supply the air necessary for the oxidation reaction to the selective oxidizer 7 are configured.

  Here, the internal space of the reformer 5 (described in detail later) is filled with a reforming catalyst body for catalyzing the steam reforming reaction. Here, as the reforming catalyst, a reforming catalyst supporting Pt and a reforming catalyst similarly supporting Ru are used on alumina which is a heat-resistant carrier.

  The inner space of the transformer 6 is filled with a shift catalyst body for catalyzing a shift reaction. Here, as the shift catalyst, a shift catalyst in which Pt is supported on a ceria-zirconia carrier is used.

  The internal space of the selective oxidizer 7 is filled with a CO gas oxidation catalyst body for catalyzing an oxidation reaction that oxidizes CO gas. Here, a CO gas oxidation catalyst in which Pt is supported on alumina is used as the CO gas oxidation catalyst.

  The reforming heater 17 is a burner 29 (see FIG. 2) in which mainly dehumidified reformed gas (hereinafter referred to as off-gas) that has been discharged from the condenser 13 (described later) and was not consumed by power generation is combusted. Built-in. The reforming catalyst body of the reformer 5 is heated and kept at a predetermined temperature necessary for the steam reforming reaction by heat exchange with the combustion gas generated by the off-gas combustion in the burner 29.

  Next, the piping configuration inside the hydrogen generator 101 will be described with reference to FIG.

  The reformer 5 and the transformer 6 are connected by a pipe d, and the reformed gas generated by the reformer 5 is supplied to the transformer 6 through the pipe d.

  The transformer 6 and the selective oxidizer 7 are connected by a pipe e, and the reformed gas whose CO gas concentration is reduced by the shift reaction of the transformer 6 is supplied to the selective oxidizer 7 through the pipe e. Is done.

  A pipe g branched and extended from the middle of the pipe e is connected to the downstream side of the air flow of the first air supply device 8 and a pipe f connected to an air intake (not shown) communicating with the atmosphere is: The first air supply device 8 is connected to the upstream side of the air flow. That is, the first air supply device 8 blows the air introduced into the inside thereof through the pipe f to the pipe g by the blower, and can thereby supply air to the branch position of the pipe e. A mixed gas obtained by mixing the reformed gas flowing out from 6 and air at the branch position is supplied to the selective oxidizer 7.

  A pipe h extends from the selective oxidizer 7 to the anode inlet of the fuel cell 9, and the hydrogen-rich reformed gas produced and purified by the hydrogen generator 101 through the pipe h is the anode of the fuel cell 9. To be supplied.

Here, the reforming heater 17 and the condensing device 13 are connected by a pipe u, and the anode outlet of the fuel cell 9 and the condensing device 13 are connected by a pipe i. The off gas that has not been consumed by power generation inside the fuel cell 9 is supplied from the anode outlet of the fuel cell 9 to the condensing device 13 via i, dehumidified there, and then the degassed degassed via the pipe u is condensed. The catalyst 13 is supplied from the apparatus 13 to the reforming heater 17 and combusted there. The catalyst charged in the shift converter 6 and the selective oxidizer 7 is a Pt-based catalyst that is widely used in a hydrogen generator as already described. However, instead of this, a Cu—Zn-based catalyst or Fe—Cr-based catalyst may be used as the shift catalyst, a Ru-based catalyst or the like may be used as the CO gas oxidation catalyst, and other catalysts having similar functions may be used. use You may do it.

  Next, the piping configuration connected to the fuel cell 9 will be described with reference to FIG.

  The reformed gas is supplied from the hydrogen generator 101 to the anode of the fuel cell 9 through the pipe h, and air from the second air supply apparatus 16 is supplied to the cathode through the pipes j, k, and l. In the fuel cell 9, power generation is performed to consume these supply gases and output electric power.

  As an example of the fuel cell 9, PEFC using a solid polymer electrolyte membrane as an electrolyte is employed, but detailed description of its configuration is omitted.

  Note that the fuel cell 9 that generates heat in accordance with the power generation operation is appropriately cooled by the cooling water supplied from the water tank 15 and configured to exhibit a predetermined power generation performance.

  Next, the cooling configuration of the fuel cell 9 in the fuel cell system 100 will be described with reference to FIG.

  The cooling configuration of the fuel cell 9 (and its peripheral configuration) mainly includes a cooling water circulation device 10 that supplies cooling water used for cooling the fuel cell 9 and a cooling that detects the temperature of the cooling water flowing inside the fuel cell 9. A water temperature detector 12, a heat exchanger 11 for dissipating heat present in the cooling water heated after cooling the fuel cell 9 by heat exchange, and humidifying air supplied to the cathode of the fuel cell 9, And a second air supply device 16 for supplying air necessary for power generation to the fuel cell 9.

  Here, the cooling water circulation device 10 has a plunger pump (not shown) that can supply cooling water from the water tank 15 to the fuel cell 9, and the heat exchanger 11 is a perfluorosulfonic acid resin membrane (not shown). The second air supply device 16 has a blower (not shown) capable of continuously supplying air. An example of the coolant temperature detector 12 is a thermistor.

  The cooling water circulation device 10 and the inlet of a cooling water channel (not shown) formed inside the fuel cell 9 are connected by a pipe r, and between the cooling water circulation device 10 and the water tank 15. , The cooling water supplied from the water tank 15 is sent to the cooling water circulation device 10 via the piping q, and then the cooling water circulates via the piping r. The apparatus 10 is pumped and supplied to the inlet of the cooling water channel of the fuel cell 9.

  The outlet (drainage port) of the cooling water channel of the fuel cell 9 and the heat exchanger 11 are connected by a pipe s, thereby being discharged from the cooling water channel of the fuel cell 9 and exchanging heat with the fuel cell 9. The cooling water whose temperature has been increased by the above is supplied to the heat exchanger 11 through this pipe s.

  The heat exchanger 11 and the water tank 15 are connected by a pipe t, thereby cooling water cooled by heat exchange with air blown from the second air supply device 16 in the heat exchanger 11. Is returned to the water tank 15 via the pipe t.

  A pipe j for introducing air is connected to the second air supply device 16, and the second air supply device 16 and the heat exchanger 11 are connected by a pipe k. The heat exchanger 11 and the fuel cell are connected to each other. 9 is connected by a pipe l. Thereby, as already described, the air guided from the atmosphere to the second air supply device 16 via the pipe j is pumped to the heat exchanger 11 via the pipe k by the second air supply device 16. Then, after being humidified to a predetermined humidity, it is supplied to the cathode of the fuel cell 9 via the pipe l.

  Next, the structure of the treatment of water (water and water vapor) used in the fuel cell system 100 will be described with reference to FIG.

  The water treatment system of the fuel cell system 100 mainly purifies the condensing device 13 that dehumidifies by condensing off-gas and air discharged from the fuel cell 9 and not consumed by power generation, and the condensed water flowing out from the condensing device 13. The water purifier 14 and the water tank 15 for storing the water purified by the water purifier 14 are configured.

  Here, in the condensing device 13, the off-gas and air in a dry state are obtained by condensing off-gas and water vapor contained in the air by an appropriate condensing mechanism. The condensing device 13 and the fuel cell 9 are connected by a pipe m, whereby the air discharged from the fuel cell 9 and not consumed by power generation is supplied to the condensing device 13 through the pipe m. .

  The dry off-gas is discharged from the condenser 13 to the reforming heater 17 via the pipe u, and the dry air is discharged into the atmosphere.

  The purification device 14 is configured by using an ion exchange resin containing a styrene-based strongly acidic cation exchange resin having a sulfonic acid group and a weakly basic anion exchange resin, thereby removing ion components in water.

  The condenser 13 and the water purifier 14 are connected by a pipe v, and the water purifier 14 and the water tank 15 are connected by a pipe w so that the condensed water accumulated in the condenser 13 is connected to this pipe. It is sent to the purifier 14 via v, where impurities such as ionic components are removed and then supplied to the water tank 15 via the pipe w.

  In addition, although illustration is abbreviate | omitted here, there exists a control apparatus which controls operation | movement of each component of the fuel cell system 100, and predetermined | prescribed electric power generation operation | movement is performed while controlling operation | movement of a fuel cell system suitably by this control apparatus. It is running.

  Hereinafter, the configuration of the reformer 5 and the reforming heater 17 incorporated in the hydrogen generator 101 will be described in detail with reference to the drawings.

  FIG. 2 is a cross-sectional view schematically showing a configuration of a reformer and a reforming heater according to an embodiment of the present invention (a peripheral configuration of the reformer).

  The peripheral structure of the reformer 5 is a cylinder in which the upper part in the axial direction is closed except for the mixed gas supply port 20 a and the reformed gas discharge port 20 b and the lower part in the axial direction is closed except for the region of the cylindrical combustion cylinder 28. The outer casing 24 is disposed inside the outer casing 24 with a first cylindrical space 25 therebetween, and the upper part in the axial direction is closed except for the mixed gas supply port 20a, and the entire area in the lower part in the axial direction is covered. A high-temperature combustion gas is produced by mixing and burning the open cylindrical inner casing 26, off-gas introduced from the pipe u (see FIG. 1), and air supplied by a blower (not shown). The burner 29 to be generated and the lower lid of the outer casing 24 extend through the inner casing 26 so as to move the hot combustion gas up and down in the axial direction across the second cylindrical space 27. A combustion in which the upper part in the axial direction is closed and the lower part is connected to the burner 29 28 and the pipe c so as to guide a mixed gas of the raw material gas desulfurized to a predetermined sulfur concentration level by the raw material desulfurization apparatus 2 (see FIG. 1) and the water vapor evaporated by the evaporation apparatus 4 (see FIG. 1). A supply port 20a formed in the upper lid of the inner casing 26 so as to pass through the upper lid of the outer casing 24 and the reformed gas generated by the reforming reaction of this mixed gas downstream (transformer 6) ) And is connected to the pipe d (see FIG. 1) so as to flow out into the second cylindrical space 27 upstream of the mixed gas flow and the discharge port 20b formed in the upper lid of the outer casing 24. The annular Pt-based reforming catalyst body 21 (second reforming catalyst body) and the Pt-based reforming catalyst body 21 are arranged in the second cylindrical space 27 downstream of the mixed gas flow. Cyclic ceria-zirconia oxide 22 (hydrogen sulfide adsorbent; And the annular Ru-based reforming catalyst disposed in the second cylindrical space 27 downstream of the mixed gas flow with respect to the ceria-zirconia-based oxide 22. Medium 23 (first reforming catalyst body). Here, the desulfurization layer is composed of a Pt-based reforming catalyst body 21 composed of a Pt-based reforming catalyst and a hydrogen sulfide adsorbent composed of a ceria-zirconia-based oxide 22.

  That is, the Pt-based reforming catalyst body 21, the Ru-based reforming catalyst body 23, and the ceria-zirconia-based oxide 22 having different material systems are all present in the second cylindrical space 27 inside the inner housing 26. is doing.

  More specifically, the second cylindrical shape between the inner casing 26 and the combustion cylinder 28 in a state in which the Pt-based reforming catalyst body 21 and the Ru-based reforming catalyst body 23 are separated into two layers and separated from each other. A ceria-zirconia-based oxide 22 disposed in the space 27 and sandwiched between the Pt-based reforming catalyst body 21 and the Ru-based reforming catalyst body 23 is also disposed in the second cylindrical space 27.

  The reforming catalyst bodies 21 and 23 and the oxide 22 are supported so as to be positioned in the second cylindrical space 27 by an appropriate fixing means.

  Here, the reformer 5 includes an outer casing 24, an inner casing 26, a supply port 20a, a discharge port 20b, a Pt-based reforming catalyst body 21, a ceria-zirconia-based oxide 22, The reforming heater 17 is composed of a burner 29 and a combustion cylinder 28.

  The Pt-based reforming catalyst body 21 is disposed at the upstream side of the gas flow while maintaining the temperature at 300 ° C. or higher, and the sulfur compound remaining in the raw material gas that has not been completely removed by the raw material desulfurizer 2 is converted into hydrogen sulfide. It plays a role of generating hydrogen gas for conversion by reforming reaction.

  The Ru-based reforming catalyst body 23 is disposed on the downstream side of the gas flow with an inlet temperature of about 500 ° C., an outlet temperature of 650 ° C. or more, and a predetermined temperature gradient in the axial direction. It plays a role of generating a reformed gas from a mixed gas by a steam reforming reaction so as to achieve a conversion rate. Here, the conversion rate is defined by the following equation (3) and used as an index of the catalytic activity of the reforming catalyst.

Conversion rate (%) = ((CO ₂ + CO) / (CO ₂ + CO + CH ₄ )) × 100 (3)
The ceria-zirconia-based oxide 22 is disposed between the Pt-based reforming catalyst body 21 and the Ru-based reforming catalyst body 23 after the desirable temperature range is set to 200 ° C. or more and 600 ° C. or less, It plays a role of adsorbing and absorbing hydrogen sulfide converted from sulfur compounds by the Pt-based reforming catalyst body 21.

  That is, in order to appropriately adsorb and absorb hydrogen sulfide by the ceria-zirconia-based oxide 22, it is necessary to heat the ceria-zirconia-based oxide 22 to about 200 ° C.

  Further, when the ceria-zirconia-based oxide 22 is heated at a temperature exceeding 600 ° C., as will be described later, the ceria-zirconia-based oxide 22 is sintered, and the adsorption and absorption are reduced by reducing the reaction surface area. The reaction will be inhibited.

  The Pt-based reforming catalyst body 21 and the Ru-based reforming catalyst are exchanged by exchanging heat with the high-temperature combustion gas while the high-temperature combustion gas generated by the burner 29 rises and falls in the axial direction of the combustion cylinder 28. The medium 23 and the ceria-zirconia-based oxide 22 are each appropriately heated to the above temperature.

  Here, a lower annular gap 30d is formed between the lower end in the axial direction of the inner casing 26 and the lower lid of the outer casing 24, and between the upper end in the axial direction of the inner casing 26 and the upper lid of the outer casing 24. The axial positional relationship between the two is set so that the upper annular gap 30u is formed in the upper part, so that the reformed gas flowing out from the Ru-based reforming catalyst body 23 is appropriately downstream through the first cylindrical space. Configured to be sent to.

  Next, the power generation operation of the fuel cell system 100 according to the present embodiment will be described with reference to FIG. 1 and FIG. Here, the operation related to the raw material gas desulfurization process inside the reformer 5 will be mainly described, and the operation of the fuel cell system 100 not directly related thereto will be described in a simplified manner.

  Examples of the raw material gas supplied to the reformer 5 include natural gas, methanol, or gasoline. Examples of the raw material gas reforming method include reforming using a steam reforming method using steam or air. There is a partial reforming method.

  Hereinafter, the operation of the fuel cell system 100 will be described on the premise of a steam reforming method using natural gas as a raw material gas. However, the operation and effect obtained by the present embodiment are of course not limited thereto.

  In order to remove sulfur compounds contained in natural gas to a predetermined sulfur concentration level (about 1 to 10 ppb), natural gas flowing out from the raw material supply device 1 is introduced into the raw material desulfurization device 2, and this raw material desulfurization device 2. The sulfur component contained in the natural gas is selectively adsorbed and absorbed by the desulfurizing agent by the desulfurization treatment.

  Further, water necessary for the steam reforming reaction in the reformer 5 is supplied from the water tank 15 to the evaporation device 4 by the reforming water supply device 3. Then, the water supplied from the reforming water supply device 3 is heated by the evaporation device 4 to become steam. The water vapor generated by the evaporator 4 is mixed at the joining position of the natural gas desulfurized by the raw material desulfurization apparatus 2 described above and the pipe p and the pipe c.

  When the mixed gas of the desulfurized natural gas and water vapor is supplied to the supply port 20a of the reformer 5 of the hydrogen generator 101, the gas is changed while passing through the path indicated by the thin solid arrow in FIG. Then, the reformed gas flows out from the outlet 20 b of the reformer 5.

  That is, the mixed gas containing natural gas and water vapor flowing through the pipe c (see FIG. 1) and flowing into the supply port 20a spreads in the radial direction along the upper lid of the inner housing 26 from the supply port 20a. The flow is changed by 90 [deg.] By the side wall and flows downward in the second cylindrical space 27. And while this mixed gas flows down along the 2nd cylindrical space 27 through the reforming catalyst bodies 21 and 23 and the oxide 22 which are arrange | positioned in the 2nd cylindrical space 27, combustion gas It is reformed by a steam reforming reaction while exchanging heat with it and converted to a reformed gas, and after desulfurization treatment as will be described in detail later, this reformed gas flows through the lower lid of the outer casing 24. The angle is again changed by 90 ° and spreads radially through the lower annular gap 30d along the lower lid.

  Subsequently, the reformed gas changes its flow again by 90 ° by the side wall of the outer casing 24, flows into the first cylindrical space 25, and rises along the first cylindrical space 25. Further, the reformed gas is changed by 90 ° again by the upper lid of the outer casing 24, passes through the upper annular gap 30u, and then gathers along the upper lid so as to gather at the discharge port 20b arranged in the upper lid. Then, it moves in the radial direction and flows downstream from the discharge port 20b.

  In this way, the natural gas that could not be removed by the raw material desulfurization apparatus 2 using the hydrogen gas generated by the steam reforming reaction based on the Pt-based reforming catalyst body 21 excellent in resistance to sulfur poisoning on the upstream side of the mixed gas stream. A small amount of sulfur compound remaining therein is converted into hydrogen sulfide, and the hydrogen sulfide can be efficiently adsorbed and absorbed by the ceria-zirconia oxide 22 downstream thereof, so that the sulfur component in the natural gas is sufficient. It becomes a low concentration level (about 0.1 to 1 ppb).

  Based on this Ru-based reforming catalyst body 23, the gas from which hydrogen sulfide has been removed is caused to flow through the Ru-based reforming catalyst body 23 having excellent reforming catalyst activity on the downstream side of the mixed gas stream. A high conversion rate of natural gas can be ensured by the steam reforming reaction.

  The reformed gas produced by the reformer 5 contains 8 to 15% by volume of unreacted natural gas, hydrogen gas, water vapor, carbon dioxide gas, and CO gas as by-products.

  For example, in this reformed gas, although it changes depending on the temperature of the reforming catalyst bodies 21 and 23, as an average value of the content ratio of each by-product excluding water vapor, hydrogen gas is about 80%. The carbon dioxide gas and the CO gas are each contained about 10%.

  Therefore, the CO gas concentration in the reformed gas generated by the reformer 5 is reduced to about 0.5% by a shift reaction in the transformer 6 installed downstream of the reformer 5, The concentration of CO gas contained in the reformed gas is 10 ppm by a chemical reaction between oxygen gas (contained in the air supplied from the first air supply device 8) and CO gas in the selective oxidizer 7 installed downstream of the gas generator 6. Reduce to: In this way, the reformed gas is purified into a high-quality reformed gas that does not deteriorate even when supplied to the PEFC.

  The refined reformed gas is supplied to the anode of the fuel cell 9. On the other hand, the air humidified by the second air supply device 16 and the heat exchanger 11 is supplied to the cathode of the fuel cell 9. As a result, the reformed gas and air are consumed inside the fuel cell 9 to generate power for outputting predetermined power. Since heat is generated inside the fuel cell 9 at the same time as the power generation of the fuel cell 9, the temperature of the fuel cell 9 caused by this heat is caused by flowing the cooling water supplied by the cooling water circulation device 10 into the fuel cell 9. The fuel cell 9 is cooled so as to be within a predetermined temperature range while preventing the rise.

  That is, the temperature of the cooling water flowing inside the fuel cell 9 is detected by the cooling water temperature detector 12, and the cooling water circulation is performed so that the temperature of the cooling water detected by the cooling water temperature detector 12 is substantially constant. The increase / decrease in the circulation amount of the cooling water by the device 10 is controlled by a control device (not shown), and as a result, the temperature of the fuel cell 9 is controlled to be within a predetermined temperature range.

  During the power generation of the fuel cell 9, the offgas and air discharged from the fuel cell 9 and not consumed by the power generation are guided to the condensing device 13, where water vapor contained in the offgas and air by a predetermined condensing mechanism. Is condensed, thereby properly dehumidifying off-gas and air. The degassed off gas is supplied to the reforming heater 17 of the hydrogen generator 101, and the dehumidified air is released into the atmosphere.

  The condensed water in the condenser 13 is purified by the ion exchange resin present in the water purifier 14 and then returned to the water tank 15. The condensed water returned to the water tank 15 is supplied again to the evaporation device 4 by the reforming water supply device 3.

  According to the fuel cell system 100 described above, poisoning of the reforming catalyst proceeds with time due to a small amount of sulfur compound remaining in the source gas that could not be removed by the raw material desulfurization apparatus 2, and It is possible to appropriately cope with the problem of gradually reducing the catalyst activity. That is, the inner casing 26 of the reformer 5 is filled with a Pt-based reforming catalyst body 21 with excellent sulfur poisoning resistance upstream of the mixed gas flow, and the mixed gas of the Pt-based reforming catalyst body 21 A ceria-zirconia-based oxide 22 is packed downstream of the flow, and a Ru-based reforming catalyst body 23 with high reforming activity is packed downstream of the mixed gas flow of the ceria-zirconia-based oxide 22.

  With such a configuration, a part of the hydrogen gas generated by the reforming reaction of the Pt-based reforming catalyst body 21 is diverted to convert the sulfur compound contained in the raw material gas into hydrogen sulfide. The converted hydrogen sulfide is reliably adsorbed and absorbed by the ceria-zirconia oxide 22 present in the inner casing 26.

  Further, in order to convert the sulfur compound contained in the raw material gas into hydrogen sulfide using hydrogen gas, it is necessary to expose the sulfur compound to a predetermined temperature or higher. It can be said that the sulfur compound can be easily heated.

  It has been found that even when such a fuel cell system 100 is operated for about 3000 hours, the raw material gas conversion rate in the steam reforming reaction can be maintained at 90% or more.

  As a comparison, when a reformer in which the Ru-based reforming catalyst body 23 is uniformly filled in the inner casing 26 is used, when the fuel cell system is operated for about 3000 hours, the conversion rate is 85. % Result was obtained.

  Due to the difference in conversion rate, in the fuel cell system 100 according to this embodiment, the sulfur compound contained in the raw material gas is converted into hydrogen sulfide by the Pt-based reforming catalyst body 21 on the upstream side of the mixed gas flow. Since the hydrogen sulfide converted by the ceria-zirconia-based oxide can be adsorbed and absorbed, the Ru-based reforming catalyst body 23 on the downstream side of the mixed gas stream is not poisoned with sulfur, and its high catalytic activity Is presumed to be maintained.

  Using a simple atmospheric pressure gas flow type reaction experimental device (hereinafter referred to as an atmospheric pressure flow type reaction device), the principle of maintaining a high conversion rate obtained by the catalyst configuration shown in FIG. 2 is confirmed. The contents of the basic experiment are described below. In addition, examples based on various catalyst configurations (measurement of methane gas conversion rate) and comparative examples thereof using this atmospheric pressure flow reactor will be described.

(Basic experiment)
First, the basic experiment using the first atmospheric pressure flow reactor will be described.

  FIG. 3 is a diagram schematically showing the configuration of the first normal-pressure flow reactor.

  The first normal-pressure flow reactor 102 includes a water tank 32 that stores a predetermined amount of water, a water supply device 33 that supplies the water stored in the water tank 32 to the evaporation device 34 under pressure, and a water supply. From an evaporator 34 that vaporizes supply water supplied by the apparatus 33 into steam, a gas supply source 31 that stores a reaction gas corresponding to a raw material gas for generating reformed gas, and a mixed gas obtained by mixing reaction gas and steam A reforming catalyst body 35 in which reforming catalyst pieces in the form of pellets (3 mm to 5 mm in spherical shape) that generate reformed gas by a steam reforming reaction are assembled, and the reforming catalyst body 35 is surrounded so as to surround the steam reforming reaction. And an electric furnace 36 for heating the reforming catalyst body 35 to a temperature level necessary for the above.

  Here, as shown in FIG. 3, the water tank 32 and the water supply device 33 and the water supply device 33 and the evaporation device 34 are connected by a predetermined pipe.

  Further, the pipe extending from the evaporator 34 toward the reforming catalyst body 35 and the pipe extending from the gas supply device 31 toward the reforming catalyst body 35 are unified at a predetermined pipe joint position JC. The pipe is connected to the reforming catalyst body 35.

  That is, these pipes are arranged so that a mixed gas composed of water vapor and reaction gas is generated at the pipe joint position JC, and this mixed gas can be supplied to the reforming catalyst body 35.

  Here, using the first atmospheric pressure flow reactor 102 shown in FIG. 3, the influence of the sulfur compound on the catalyst activity was evaluated under the following experimental conditions using the material of the reforming catalyst as a parameter.

Methane gas as a reaction gas is at a rate of 100 mL / min, and argon gas containing 0.1% of (CH ₃ ) ₃ CSH as a sulfur compound is at a rate of 1 mL / min from the gas supply source 31 to the pipe joint JC. Supplied towards.

  At the same time, the supply water supplied from the water tank 32 by the water supply device 33 has its ion component removed by ion exchange treatment, and the supply water from which the ion component has been removed has a steam / carbon ratio (S / C) of 3. After being adjusted to be supplied to the evaporator 34 and vaporized into water vapor, the water vapor is supplied toward the pipe joint position JC.

  Also, Pt-based catalyst A, Rh-based catalyst B, Pd-based catalyst C, Ru-based reforming catalyst body D (comparative example), and Ni-based catalyst E (comparative example) are used as materials for reforming catalyst body 35. Each of the catalysts A, B, C, D, and E is processed into pellets and filled in an area surrounded by an electric furnace 36 with 10 mL.

  Further, 50 hours after the reforming catalyst body 35 is heated by the electric furnace 36 so that the temperature of the reforming catalyst body 35 becomes 650 ° C., and the mixed gas composed of water vapor and the reaction gas is led to the reforming catalyst body 35. The methane gas conversion rate was evaluated. A list of the evaluation results is shown in FIG.

  As shown in FIG. 4, the Pt-based catalyst A, the Rh-based catalyst B, and the Pd-based catalyst C maintain a higher conversion rate with respect to the reaction gas containing the sulfur compound than the Ru-based reforming catalyst D and the Ni-based catalyst E. It has been found. That is, as understood from FIG. 4, it was confirmed that the Pt-based catalyst A, the Ru-based catalyst B, and the Pd-based catalyst C are superior in sulfur poisoning resistance to the Ru-based catalyst D and the Ni-based catalyst.

When Pt-based catalyst A, Rh-based catalyst B, and Pd-based catalyst C are used, hydrogen sulfide is contained in the gas after the reaction, and sulfur compound (CH ₃ ) ₃ CSH is appropriately sulfided. It was also confirmed that it was converted to hydrogen.

  Next, using the first normal pressure flow reactor 102 shown in FIG. 3, the influence of the desulfurization agent that adsorbs and absorbs hydrogen sulfide on the reforming reaction was verified under the following conditions. However, here, the reforming catalyst body 35 shown in FIG. 3 is changed to a desulfurizing agent 35 shown below.

  Methane gas as the reaction gas is supplied from the gas supply source 31 toward the pipe joint position JC at a rate of 100 mL per minute.

  At the same time, the supply water supplied from the water tank 32 by the water supply device 33 has its ion component removed by ion exchange treatment, and the supply water from which the ion component has been removed has a steam / carbon ratio (S / C) of 3. After being adjusted to be supplied to the evaporator 34 and vaporized into water vapor, the water vapor is supplied toward the pipe joint position JC.

Further, 10 mL of a desulfurizing agent 35 that adsorbs and absorbs hydrogen sulfide is filled in an area surrounded by the electric furnace 36. More specifically, at least one metal of Mn, Co, Cu, Zn, Ce, Zr, and Fe (FIG. 5 illustrates Mn, Co, and Fe) or an oxide of these metals (FIG. 5). Was exemplified by CuO, ZnO, Ce ₂ O ₃ , ZrO ₂ and ZrCe composite oxides).

  Then, various desulfurization agents 35 were heated by the electric furnace 36 so that the temperature of the desulfurization agent 35 that adsorbs and absorbs hydrogen sulfide was 650 ° C., and hydrogen gas reduction treatment was performed, and then the methane gas conversion rate was evaluated. . A list of the evaluation results is shown in FIG.

  According to FIG. 5, it was confirmed that none of the desulfurizing agents 35 containing the metal or metal oxide shown here and adsorbing and absorbing hydrogen sulfide function as methane conversion as a reforming catalyst.

  Next, the hydrogen sulfide removal performance of the desulfurization agent that absorbs and adsorbs hydrogen sulfide under the following conditions was verified using the first atmospheric pressure flow reactor 102 shown in FIG. Here, however, the reforming catalyst body 35 shown in FIG. 3 is changed to a desulfurizing agent 35 shown below.

  Hydrogen gas at a rate of 80 mL / min, CO gas at a rate of 10 mL / min, carbon dioxide gas at a rate of 10 mL / min, and nitrogen gas containing 50 ppm of hydrogen sulfide at a rate of 10 mL / min Supplied from the supply source 31.

  At the same time, the supply water supplied from the water tank 32 by the water supply device 33 has its ionic components removed by ion exchange treatment, and the supply water from which the ionic components have been removed is adjusted to have a dew point of 90 ° C while being evaporated. After being supplied to 34 and vaporized into water vapor, this water vapor is supplied toward the pipe joint position JC.

Further, 10 mL of pellet-shaped desulfurization agent 35 that absorbs and adsorbs hydrogen sulfide is filled in an area surrounded by the electric furnace 36. More specifically, at least one metal oxide of Mn, Co, Cu, Zn, Ce, Zr and Fe (FIG. 6 shows MnO ₂ , CoO, CuO, ZnO, Ce ₂ O ₃ , ZrO ₂ , A desulfurizing agent 35 made of Fe ₂ O ₃ and ZrCe composite oxide was formed into pellets, and heated by an electric furnace 36 so that the desulfurizing agent 35 was 400 to 800 ° C.

  FIG. 6 is a list of evaluation results for confirming the hydrogen sulfide removal performance of the desulfurization agent that adsorbs and absorbs hydrogen sulfide using the heating temperature of the desulfurization agent as a parameter, from the time when hydrogen sulfide was passed through the desulfurization agent. It is the figure by which time until hydrogen sulfide was detected with the hydrogen sulfide detector (not shown) in the downstream of a desulfurization agent was shown.

In this evaluation experiment, the desulfurizing agent 35 is formed into a pellet, but the desulfurizing agent 35 may be formed into a honeycomb and is supported on a predetermined carrier (for example, Al ₂ O ₃ ). The hydrogen sulfide removal performance of the desulfurizing agent 35 does not change due to the difference in these forms. However, when the desulfurizing agent 35 is supported on the carrier, the amount of the desulfurizing agent 35 can be reduced.

  As understood from FIG. 6, as the use temperature of the desulfurization agent 35 (the temperature of the internal atmosphere of the inner casing 26) is increased, the hydrogen sulfide detection time is shortened, and as the temperature of the desulfurization agent 35 increases, The hydrogen sulfide removal performance is degraded. This phenomenon is presumed to be caused by advancing sintering of the desulfurizing agent 35 exposed to a high temperature and inhibiting the reaction by reducing the reaction surface area. In addition, for example, when the ZnO material is heated to about 800 ° C., it is considered that the ZnO material is volatilized and cannot be used.

  Therefore, the operating temperature of the desulfurizing agent 35 that absorbs and adsorbs hydrogen sulfide needs to be adjusted to 700 ° C. or lower, preferably 650 ° C. or lower.

  The reforming reaction temperature of the reforming catalyst is also 700 ° C. or lower, and the desired use temperature of the desulfurizing agent 35 is consistent with this temperature.

  Further, according to FIG. 6, the ZrCe composite oxide (ceria-zirconia-based oxide) exhibits extremely high hydrogen sulfide removal performance as compared with other oxidants over the entire use temperature range. The material is the best material for the desulfurization agent. In particular, the ZrCe composite oxide is suitable because it can stably secure hydrogen sulfide removal performance even in a high temperature range (for example, a temperature range exceeding 700 ° C.).

Note that, here, at least one metal oxide of Mn, Co, Cu, Zn, Ce, Zr and Fe is described as a material to be filled first, but these materials are reduced along with the desulfurization treatment. It is gradually converted to metal. That is, the hydrogen sulfide detection time described in FIG. 6 may be regarded as data in a state where a metal oxide (MnO ₂ or the like) and a corresponding metal (Mn) coexist. And it was confirmed that at least one metal oxide of Mn, Co, Cu, Zn, Ce, Zr and Fe and the metal corresponding to them have the same effect as a desulfurization agent for hydrogen sulfide. ing.

(Example 1)
Based on the results of the basic experiment described above, Pt-based catalyst A is selected as a typical catalyst for converting a sulfur compound to hydrogen sulfide, ceria-zirconia-based oxide is selected as a typical desulfurizing agent, and steam reforming is performed. The Ru-based catalyst D is selected as a typical reforming catalyst that promotes the quality reaction, and the atmospheric pressure flow reactor is used to achieve a methane gas conversion rate based on the difference in the catalyst configuration surrounded by the electric furnace 36. The impact was evaluated.

  Of course, the same effect can be obtained even if such a catalyst is used as long as it has a performance equivalent to those of these materials. For example, Rh-based catalyst B or Pd-based catalyst C may be used instead of Pt-based catalyst A, and Ni-based catalyst E may be used instead of Ru-based catalyst D.

  Furthermore, although the Pt-based catalyst, Rh-based catalyst, and Pd-based catalyst are inferior in activity for the reforming reaction, it is possible to use these catalysts instead of the Ru-based catalyst D.

  FIG. 7 is a diagram schematically showing the configuration of the second normal pressure flow reactor according to Example 1 of the present invention.

  The configuration of the second normal-pressure flow reactor 103 is the same as that of the first normal-flow reactor 102 shown in FIG. 3 except for the catalyst material and the desulfurization agent surrounded by the electric furnace 36. A description of the configuration common to both is omitted.

  Using the second atmospheric pressure flow reactor 103 shown in FIG. 7, the methane gas conversion rate was measured under the following experimental conditions.

  A reforming catalyst body 35 a and a desulfurization agent 35 b that absorbs and adsorbs hydrogen sulfide downstream of the gas flow with respect to the reforming catalyst body 35 a are filled in a region surrounded by the electric furnace 36. More specifically, the reforming catalyst body 35a is configured by charging 10 mL of the Pt-based catalyst A, and the desulfurizing agent 35b by charging 5 mL of ceria-zirconia-based oxide.

Methane gas as a reaction gas is supplied at a rate of 100 mL / min, and argon gas containing 1% of (CH ₃ ) ₃ CSH as a sulfur compound is supplied at a rate of 1 mL / min from the gas supply source 31 toward the pipe joint position P. Supplied.

  At the same time, the supply water supplied from the water tank 32 by the water supply device 33 has the ionic component removed by ion exchange treatment, and the supply water from which the ionic component has been removed has a steam / carbon ratio (S / C) of 3. After being supplied to the evaporator 34 and vaporized into water vapor while being adjusted as described above, the water vapor is supplied toward the pipe joint position JC.

  The reforming catalyst body 35a and the desulfurization agent 35b are heated by the electric furnace 36, whereby the reforming catalyst body 35a has an inlet temperature of 500 ° C., an outlet temperature of 550 ° C., and a desulfurization agent 35b that absorbs and adsorbs hydrogen sulfide. The temperature was maintained at 550 ° C.

As a result of the experiment based on these conditions, even after 100 hours from the start of the experiment, the methane gas conversion rate is maintained at 50% or more, and hydrogen sulfide and a sulfur compound (CH ₃ ) ₃ are contained in the gas that has passed through the desulfurization agent 35b. None of the CSH was detected.

Therefore, in addition to the Pt-based catalyst A being excellent in resistance to sulfur poisoning, the sulfur compound (CH ₃ ) ₃ CSH is appropriately produced by the hydrogen gas generated based on the steam reforming reaction of the Pt-based catalyst A. It was confirmed that the hydrogen sulfide was adsorbed and absorbed by the ceria-zirconia oxide while being converted to hydrogen sulfide.

(Example 2)
FIG. 8 is a diagram schematically showing a configuration of a third normal pressure flow reactor according to Example 2 of the present invention.

  The configuration of the third normal pressure flow reactor 104 is the same as that of the first normal pressure flow reactor 102 shown in FIG. 3 except for the catalyst material and the desulfurization agent surrounded by the electric furnace 36. A description of the configuration common to both is omitted.

  Using the third normal pressure flow reactor 104 shown in FIG. 8, the methane gas conversion rate was measured under the following experimental conditions.

  A mixed layer 37 in which the reforming catalyst body 35 a and the desulfurizing agent 35 b that absorbs and adsorbs hydrogen sulfide are mixed is filled in a region surrounded by the electric furnace 36. More specifically, the mixed layer 37 is a mixture of 10 mL of Pt-based catalyst A (reforming catalyst) and 5 mL of ceria-zirconia-based oxide (desulfurization agent that adsorbs and absorbs hydrogen sulfide).

  That is, the desulfurization layer as the mixed layer 37 is a layer configured by mixing a reforming catalyst (Pt-based catalyst A) and a hydrogen sulfide absorption desulfurizing agent (ceria-zirconia oxide).

Methane gas as a reaction gas is at a rate of 100 mL / min, and argon gas containing 1% of (CH ₃ ) ₃ CSH as a sulfur compound is at a rate of 1 mL / min from the gas supply source 31 toward the pipe joint position JC. Supplied.

  At the same time, the supply water supplied from the water tank 32 by the water supply device 33 has its ion component removed by ion exchange treatment, and the supply water from which the ion component has been removed has a steam / carbon ratio (S / C) of 3. After being supplied to the evaporator 34 while being adjusted to be vaporized into water vapor, the water vapor is supplied toward the pipe joint position JC.

  The mixed layer 37 was heated by the electric furnace 36, whereby the inlet temperature of the mixed layer 37 was maintained at 450 ° C. and the outlet temperature thereof was maintained at 550 ° C.

As a result of the experiment based on these conditions, even after 100 hours from the start of the experiment, the methane gas conversion rate is maintained at 50% or more, and hydrogen sulfide and a sulfur compound (CH ₃ ) ₃ are contained in the gas that has passed through the desulfurization agent 35b. None of the CSH was detected.

Therefore, in addition to the Pt-based catalyst A being excellent in resistance to sulfur poisoning, the steam reforming of the Pt-based catalyst A is similarly applied to a mixed layer in which the Pt-based catalyst A and the ceria-zirconia oxide are mixed. The sulfur gas (CH ₃ ) ₃ CSH is appropriately converted to hydrogen sulfide by the hydrogen gas generated based on the quality reaction, and the hydrogen sulfide is adsorbed and absorbed by the ceria-zirconia oxide. .

(Example 3)
FIG. 9 is a diagram schematically showing the configuration of a fourth normal pressure flow reactor according to Example 3 of the present invention.

  The configuration of the fourth normal pressure flow reactor 105 is the same as that of the first normal pressure flow reactor 102 shown in FIG. 3 except for the catalyst material and the desulfurization agent surrounded by the electric furnace 36. A description of the configuration common to both is omitted.

  Using the fourth atmospheric pressure flow reactor 105 shown in FIG. 9, the methane gas conversion rate was measured under the following experimental conditions.

  A second reforming catalyst body 35a, a desulfurization agent 35b that absorbs and adsorbs hydrogen sulfide downstream of the gas flow with respect to the second reforming catalyst body 35a, and a gas flow with respect to the desulfurization agent 35b. A region surrounded by the electric furnace 36 is filled with the first reforming catalyst body 35 c located downstream. More specifically, the second reforming catalyst body 35a includes 10 mL of Pt-based catalyst A, the desulfurizing agent 35b includes 5 mL of ceria-zirconia-based oxide, and the first reforming catalyst body 35c includes Ru-based catalyst E. 10 mL each.

The reaction gas is methane gas at a rate of 100 mL / min, and argon gas containing 1% of (CH ₃ ) ₃ CSH as a sulfur compound is 1 mL / min from the gas supply source 31 to the pipe joint JC. Supplied.

  At the same time, the supply water supplied from the water tank 32 by the water supply device 33 has its ion component removed by ion exchange treatment, and the supply water from which the ion component has been removed has a steam / carbon ratio (S / C) of 3. After being supplied to the evaporator 34 while being adjusted to be vaporized into water vapor, the water vapor is supplied toward the pipe joint position JC.

  The second reforming catalyst body 35a, the first reforming catalyst body 35c, and the desulfurization agent 35b are heated by the electric furnace 36, whereby the inlet temperature of the second reforming catalyst body 35a is desulfurized to 500 ° C. The temperature of the agent 35b was maintained at 550 ° C., and the outlet temperature of the first reforming catalyst body 35c was maintained at 650 ° C.

  As a result of the experiment, the methane gas conversion rate was maintained at 81% even after 100 hours from the start of the experiment.

(Comparative Example 1)
Here, as a comparative experiment with respect to Example 3, as the second reforming catalyst body 35 a, 10 mL of the Ru-based catalyst E is filled in a region surrounded by the electric furnace 36.

  The apparatus configuration and experimental conditions according to Comparative Example 1 other than the second reforming catalyst body 35a are the same as those shown in Example 3, and the description thereof is omitted here.

  As a result of the experiment, the methane gas conversion rate decreased to 56% after 100 hours from the start of the experiment.

  From the comparison of the experimental results of Example 3 and Comparative Example 1, the following findings were obtained.

  In the catalyst configuration shown in the third embodiment, the Pt-based reforming catalyst body (second reforming catalyst body 35a in the third embodiment) on the upstream side of the mixed gas flow is difficult to be poisoned with sulfur. The sulfur compound contained in the reaction gas is effectively converted to hydrogen sulfide by the porous catalyst body, and the hydrogen sulfide converted by the ceria-zirconia oxide (desulfurization agent 35b of Example 3) is appropriately adsorbed and absorbed. Therefore, the Ru-based reforming catalyst body (the first reforming catalyst body 35c of Example 3) on the downstream side of the mixed gas flow is not poisoned with sulfur, and a high methane gas conversion rate is maintained.

  On the other hand, in the catalyst configuration shown in Comparative Example 1, the Ru-based reforming catalyst body (second reforming catalyst body 35a of Comparative Example 1) upstream of the mixed gas flow itself absorbs hydrogen sulfide. It is gradually poisoned by sulfur. And after the poisoning of the Ru-based reforming catalyst body upstream of the mixed gas flow, the Ru-based reforming catalyst body can no longer effectively convert the sulfur compound into hydrogen sulfide, and the ceria-zirconia-based oxidation Hydrogen sulfide cannot be adequately adsorbed and absorbed by the product (desulfurization agent 35b of Comparative Example 1). For this reason, the Ru-based reforming catalyst body (the first reforming catalyst body 35c of Comparative Example 1) downstream of the mixed gas flow is also poisoned with sulfur, and the methane gas conversion rate is greatly reduced.

(Example 4)
FIG. 10 is a diagram schematically showing the configuration of the fifth normal pressure flow reactor according to Example 4 of the present invention.

  The configuration of the fifth normal-pressure flow reactor 106 is the same as that of the first normal-flow reactor 102 shown in FIG. 3 except for the catalyst material and the desulfurization agent surrounded by the electric furnace 36. A description of the configuration common to both is omitted.

  Using the fourth atmospheric-pressure flow reactor 106 shown in FIG. 10, the methane gas conversion rate was measured under the following experimental conditions.

  A mixed layer 37 in which a second reforming catalyst body 35a and a desulfurizing agent 35b that absorbs and adsorbs hydrogen sulfide are mixed, and a first reforming catalyst body 35c downstream of the mixed layer 37 in the gas flow direction; Is filled in a region surrounded by the electric furnace 36. More specifically, the mixed layer 37 is prepared by mixing 10 mL of Pt-based catalyst A as a material of the second reforming catalyst body 35a and 5 mL of ceria-zirconia-based oxide as a desulfurizing agent 35b that absorbs and adsorbs hydrogen sulfide. Filled.

  That is, the desulfurization layer as the mixed layer 37 is a layer configured by mixing a reforming catalyst (Pt-based catalyst A) and a hydrogen sulfide absorption desulfurizing agent (ceria-zirconia oxide).

  The first reforming catalyst body 35c is filled with 10 mL of Ru-based catalyst E.

Methane gas as a reaction gas is at a rate of 100 mL / min, and argon gas containing 1% of (CH ₃ ) ₃ CSH as a sulfur compound is at a rate of 1 mL / min from the gas supply source 31 to the pipe joint position JC. Supplied.

  At the same time, the supply water supplied from the water tank 32 by the water supply device 33 has the ionic component removed by ion exchange treatment, and the supply water from which the ionic component has been removed has a steam / carbon ratio (S / C) of 3. After being supplied to the evaporator 34 while being adjusted and vaporized into water vapor, the water vapor is supplied toward the pipe joint position JC.

  The mixed layer 37 and the first reforming catalyst body 35c are heated by the electric furnace 36, whereby the inlet temperature of the mixed layer 37 is maintained at 500 ° C. and the outlet temperature of the first reforming catalyst body 35c is maintained at 650 ° C. It was done.

  As a result of the experiment, the methane gas conversion rate was maintained at 80% even after 100 hours from the start of the experiment.

(Comparative Example 2)
Here, as a comparative experiment with respect to Example 4, the mixed layer 37 was mixed with 10 mL of Ru-based catalyst E as the material of the second reforming catalyst body 35a and 5 mL of ceria-zirconia-based oxide as the desulfurizing agent 35b. Filled.

  The apparatus configuration and experimental conditions other than the mixed layer 37 are the same as those shown in the third embodiment, and the description thereof is omitted here.

  As a result of the experiment, the methane gas conversion rate decreased to 54% after 100 hours from the start of the experiment.

  From the comparison of the experimental results of Example 4 and Comparative Example 2, the following findings were obtained.

  Similar to Example 3, in the catalyst configuration shown in Example 4, the Pt-based reforming catalyst body (second reforming catalyst body 35a of Example 4) upstream of the mixed gas flow is not easily poisoned by sulfur. Therefore, the sulfur compound contained in the reaction gas is effectively converted into hydrogen sulfide by the Pt-based reforming catalyst body and is also converted by the ceria-zirconia oxide (desulfurization agent 35b of Example 4). Since hydrogen sulfide can be adsorbed and absorbed appropriately, the Ru-based reforming catalyst body (the first reforming catalyst body 35c of Example 4) on the downstream side of the mixed gas stream is not poisoned with sulfur, and high methane gas conversion is achieved. The rate is maintained.

  On the other hand, as in Comparative Example 1, in the catalyst configuration shown in Comparative Example 2, the Ru-based reforming catalyst body (second reforming catalyst body 35a of Comparative Example 2) upstream of the mixed gas flow itself Absorbs hydrogen sulfide and is gradually poisoned by sulfur. And after poisoning of the Ru-type reforming catalyst body upstream of the mixed gas flow, this Ru-type reforming catalyst body can no longer effectively convert the sulfur compound into hydrogen sulfide, and the ceria-zirconia system Hydrogen sulfide cannot be adsorbed and absorbed properly by the oxide (desulfurization agent 35b of Comparative Example 2). For this reason, the Ru-based reforming catalyst body (the first reforming catalyst body 35c of Comparative Example 2) downstream of the mixed gas flow is also poisoned with sulfur, and the methane gas conversion rate is greatly reduced.

  Up to this point, the configuration and operation capable of appropriately removing sulfide compounds such as sulfides and mercaptans have been described on the assumption that sulfide compounds such as sulfides and mercaptans are contained in the raw material gas. Based on the fuel cell system 100 according to the invention, even when a sulfide compound is mixed in the water used in the steam reforming reaction, the sulfide compound in the water can be appropriately removed.

  According to the fuel cell system of the present invention, it is possible to remove a very small amount of sulfur component contained in the raw material gas by a simple configuration without providing additional equipment and by a reliable desulfurization method over a long period of time. The catalytic activity of the reforming catalyst can be maintained, and for example, it is useful as a household fuel cell system.

1 is a block diagram schematically showing a configuration of a fuel cell system according to an embodiment of the present invention. It is sectional drawing which shows typically the structure of the reformer by embodiment of this invention. It is a block diagram which shows typically the structure of a 1st normal pressure flow type reactor. It is the list figure which showed the activity evaluation result (methane gas conversion rate) which summarized the influence which it has on the various reforming catalysts brought about by a sulfur compound. It is the list figure which showed the activity evaluation result (methane gas conversion rate) with respect to the reforming reaction by the various desulfurization agents which absorb and adsorb hydrogen sulfide. It is the list figure which showed the result of having summarized the hydrogen sulfide removal effect by the various desulfurization agents which absorb and adsorb hydrogen sulfide. It is a block diagram which shows typically the structure of a 2nd atmospheric pressure flow-type reaction apparatus. It is a block diagram which shows typically the structure of a 3rd atmospheric pressure flow-type reaction apparatus. It is a block diagram which shows typically the structure of a 4th atmospheric pressure flow-type reaction apparatus. It is a block diagram which shows typically the structure of a 5th normal pressure flow type | mold reaction apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Raw material supply apparatus 2 Raw material desulfurization apparatus 3 Reformed water supply apparatus 4 Evaporator 5 Reformer 6 Transformer 7 Selective oxidizer 8 First air supply apparatus 9 Fuel cell 10 Cooling water circulation apparatus 11 Heat exchanger 12 Cooling water temperature Detector 13 Condensing device 14 Water purification device 15 Water tank 16 Second air supply device 17 Reforming heater 20a Supply port 20b Discharge port 21, 35a Second reforming catalyst body 22 Desulfurization agent 23 for absorbing and adsorbing hydrogen sulfide , 35c First reforming catalyst body 24 Outer casing 25 First cylindrical space 26 Inner casing 27 Second cylindrical space 28 Combustion cylinder 29 Burner 30u Upper annular gap 30d Lower annular gap 31 Gas supply source 32 Water Tank 33 Water supply device 34 Evaporation device 35 Reforming catalyst body (or desulfurization agent)
35b Desulfurizing agent 36 Electric furnace 37 Mixed layer 100 Fuel cell system 101 Hydrogen generator 102-106 Normal pressure flow reactor

Claims (12)

  A hydrogen generator comprising a reformer filled with a first reforming catalyst body that generates a reformed gas containing hydrogen gas from a raw material gas having a sulfur compound by a reforming reaction, wherein the first reforming is performed A hydrogen generator comprising a desulfurization layer including a reforming catalyst and a hydrogen sulfide adsorbent upstream of a catalyst body.   The hydrogen generator according to claim 1, wherein the hydrogen sulfide adsorbent is at least one metal of Mn, Co, Cu, Zn, Ce, Zr and Fe or an oxide of the metal.   The hydrogen generation apparatus according to claim 2, wherein the desulfurization layer is a layer configured by mixing the reforming catalyst and the hydrogen sulfide adsorbent. The desulfurization layer has a second reforming catalyst body made of the reforming catalyst,
The hydrogen generator according to claim 2, wherein the hydrogen sulfide adsorbent is disposed between the first reforming catalyst body and the second reforming catalyst body.   The hydrogen generator according to claim 2, wherein hydrogen gas is generated by a reforming reaction of the reforming catalyst, and a sulfur compound contained in the raw material gas is converted into hydrogen sulfide by the hydrogen gas.   The hydrogen generator according to claim 5, wherein the hydrogen sulfide is removed from the source gas by the metal or the metal oxide contained in the desulfurization layer.   The first reforming catalyst body includes at least one metal of Pt, Rh, Pd, Ru, and Ni, and the second reforming catalyst body includes at least one of Pt, Rh, and Pd. The hydrogen generator of Claim 3 or 4 containing a metal.   The hydrogen generator according to claim 1, wherein the temperature of the desulfurization layer is maintained at 650 ° C. or lower.   A fuel cell system comprising the hydrogen generator according to claim 1 and a fuel cell, wherein the reformed gas flowing out of the hydrogen generator is supplied to the fuel cell. Generating hydrogen gas from a raw material gas containing a sulfur compound by a reforming reaction based on a first reforming catalyst;
Removing hydrogen sulfide converted by reacting the sulfur compound with the hydrogen gas from the source gas;
Generating a reformed gas containing hydrogen gas from the gas from which the hydrogen sulfide has been removed by a reforming reaction based on a second reforming catalyst.   The hydrogen sulfide is removed from the source gas by a desulfurization layer containing at least one metal of Mn, Co, Cu, Zn, Ce, Zr and Fe or an oxide of the metal. 11. The method for producing hydrogen according to 10.   The hydrogen generation method according to claim 11, wherein the desulfurization layer includes the first reforming catalyst, and the hydrogen gas is generated and the hydrogen sulfide is removed from the raw material gas in the desulfurization layer.

Images