JP4754242B2 - Hydrogen production apparatus and fuel cell system - Google Patents

Description

  The present invention relates to a hydrogen production apparatus for producing hydrogen by reforming raw materials such as liquefied petroleum gas (LPG). Moreover, it is related with a fuel cell system provided with a hydrogen production apparatus.

  2. Description of the Related Art In a fuel cell system, particularly a polymer electrolyte fuel cell (PEFC) system that has been developed in recent years, a hydrogen production apparatus for obtaining hydrogen by reforming raw fuel for hydrogen production such as LPG is used.

  For example, in a polymer electrolyte fuel cell, carbon monoxide may adversely affect cell performance. Therefore, a shift reactor is provided downstream of the reformer in order to reduce the CO concentration in the fuel supplied to the fuel electrode.

  In the shift reactor, the concentration of carbon monoxide is reduced by a shift reaction in which carbon monoxide and water react to produce carbon dioxide and hydrogen in the presence of a catalyst.

Performing the shift reaction after the reforming reaction is described in Patent Document 1, for example. As for the reformer, a reformer having a substantially cylindrical outer shape is described in Patent Document 2, for example.
JP 2002-274807 A Japanese Patent Laid-Open No. 11-292502

  The shift reaction that reduces the carbon monoxide concentration is an exothermic reaction, but there is a lower limit (reaction start temperature) that depends on the catalyst used, the reactor, and the reaction conditions. In order to perform proper CO conversion, it is important to reach the temperature of the catalyst layer at this temperature. However, if the amount of heat applied to the catalyst layer increases, the catalyst deterioration is accelerated beyond the upper limit of the catalyst's preferred temperature, and if the shift catalyst temperature rises until it does not reach, In many cases, it was not preferable because it led to a decrease in hydrogen production efficiency, such as an increase in the amount of heat released.

  In other words, there is a need for a technology that can provide an appropriate amount of heat to the shift reaction catalyst layer in order to advance the shift reaction, and that can efficiently remove the reaction heat so as not to impair the durability and hydrogen production efficiency of the catalyst. It has been.

  The object of the present invention is to efficiently start the reaction from the inlet of the shift reaction catalyst layer and to prevent the temperature of the shift reaction catalyst layer from rising due to the reaction heat of the shift reaction, thereby suppressing the thermal deterioration of the shift reaction catalyst. Another object of the present invention is to provide a hydrogen production apparatus capable of improving the long-term reliability of the hydrogen production apparatus.

  Another object of the present invention is to provide a fuel cell system which has an excellent hydrogen production apparatus as described above and which is efficient and excellent in long-term reliability.

  The present invention is as follows.

1) It has a reforming section for obtaining a reformed gas containing hydrogen by steam reforming a raw material for hydrogen production, and a shift reaction section for reducing the carbon monoxide concentration in the reformed gas by a shift reaction,
The reforming part has a cylindrical part in the outer shape,
The shift reaction portion has an annular portion for accommodating a shift reaction catalyst layer filled with a shift reaction catalyst;
A cylindrical part of the reforming part is arranged on the inner peripheral side of the annular part of the shift reaction part,
An annular gas flow path through which gas can flow is provided in contact with an inner peripheral side or an outer peripheral side of the annular portion of the shift reaction part via a partition wall,
The reforming section, the annular gas flow path, and the shift reaction section are connected in this order so that the reformed gas can flow from the reforming section through the annular gas flow path and flow into the shift reaction section by reversing the flow direction. ,
A hydrogen production apparatus further comprising a cooling means for cooling the reformed gas downstream of the reforming section and upstream of the annular gas flow path .

2) the cooling means, the supply line of the water used in the steam reforming is connected heat exchanger 1) device according.

3 ) Further, a high-temperature or medium-temperature shift reaction catalyst is provided in the heat exchanger or in the preceding stage,
The apparatus according to 2 ), wherein the shift reaction catalyst layer accommodated in the annular portion of the shift reaction section is filled with a low temperature shift reaction catalyst.

4 ) The apparatus according to any one of 1) to 3 ), wherein the annular gas flow path is disposed in contact with the inner peripheral side of the annular portion of the shift reaction section.

5 ) The apparatus according to 4 ), wherein the cylindrical portion of the reforming section and the annular gas flow path are in contact with each other via a heat insulating layer.

6 ) The apparatus according to 4 ) or 5 ), further comprising heat exchange means for cooling and / or heating the annular part on the outer peripheral side of the annular part of the shift reaction part.

7) said heat exchange means is a heat exchanger supply line for water is connected to be used for steam reforming 6) Apparatus according.

8 ) Further, the reforming section has a heating means for heating water used for steam reforming,
It said heat exchange means comprises a supply line of water heated by the heating means, and a supply line of water used for steam reforming, a heat exchanger which is connected via a line switching means 6) Apparatus according .

9 ) The apparatus according to 4 ) or 5 ), further comprising an electric heater on the outer peripheral side of the annular portion of the shift reaction section.

10 ) Hydrogen production having a reforming section for obtaining a reformed gas containing hydrogen by steam reforming a raw material for hydrogen production, and a shift reaction section for reducing the carbon monoxide concentration in the reformed gas by a shift reaction A fuel cell system comprising a device and a fuel cell using hydrogen obtained from the hydrogen production device as fuel,
The reforming part has a cylindrical part in the outer shape,
The shift reaction portion has an annular portion for accommodating a shift reaction catalyst layer filled with a shift reaction catalyst;
A cylindrical part of the reforming part is arranged on the inner peripheral side of the annular part of the shift reaction part,
An annular gas flow path through which gas can flow is provided in contact with an inner peripheral side or an outer peripheral side of the annular portion of the shift reaction part via a partition wall,
The reforming section, the annular gas flow path, and the shift reaction section are connected in this order so that the reformed gas can flow from the reforming section through the annular gas flow path and flow into the shift reaction section by reversing the flow direction. ,
The fuel cell system further comprising cooling means for cooling the reformed gas downstream of the reforming section and upstream of the annular gas flow path .

  In the present invention, by using the heat generated in the shift reaction catalyst layer, the gas temperature supplied to the shift reaction unit is efficiently started from the inlet of the catalyst layer by increasing the gas temperature at the shift reaction unit inlet. By removing the heat of the shift reaction catalyst layer by itself, the shift reaction catalyst temperature is prevented from rising due to the reaction heat of the shift reaction, thereby suppressing the thermal deterioration of the shift reaction catalyst and improving the long-term reliability of the hydrogen production equipment. Can be improved.

  Thus, according to the present invention, the reaction can be efficiently started from the inlet of the shift reaction catalyst layer, and the temperature of the shift reaction catalyst layer is suppressed from rising due to the reaction heat of the shift reaction. Provided is a hydrogen production apparatus that can suppress thermal degradation and improve the long-term reliability of the hydrogen production apparatus.

  Moreover, in a fuel cell system provided with a hydrogen production apparatus, the use of the hydrogen production apparatus provides a fuel cell system that is efficient and excellent in long-term reliability.

[Hydrogen production equipment]
The hydrogen production apparatus includes a reforming unit that obtains a reformed gas that is a gas containing hydrogen from a raw material for hydrogen production by a steam reforming reaction. The hydrogen production apparatus further includes a shift reaction unit in order to reduce the CO concentration in the reformed gas obtained in the reforming unit. A CO selective oxidation reactor for further reducing the CO concentration of the hydrogen-containing gas that has undergone the shift reaction may be provided downstream of the shift reaction unit. In addition, peripheral accessories for operating these, supply means for raw materials and water vapor, and the like are provided as appropriate.

  In the present invention, the reforming portion has a cylindrical portion, and the shift reaction portion has an annular portion that accommodates the shift reaction catalyst layer filled with the shift reaction catalyst. An annular gas flow path is provided in contact with the outer peripheral side via a partition wall. The reforming part preferably has a substantially cylindrical outer shape. The shift reaction part and the annular gas channel are preferably substantially annular. With such a configuration, a multi-cylindrical structure can be formed by the reforming unit, the shift reaction unit, and the annular gas channel. This structure is excellent in terms of compactness of the hydrogen production apparatus and suppression of heat loss.

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

  FIG. 1A is a side sectional view of a structure in which a reforming section, a shift reaction section, an annular gas flow path, and the like are integrated, and FIG. It is an arrow view. FIG. 2 shows a schematic flow of the hydrogen production apparatus including the raw material and water supply lines.

  The reformer 1 has a substantially cylindrical outer shape. In particular, the side surface is a cylindrical peripheral surface. An annular heat insulating layer 5 is provided on the outer peripheral side in contact with the entire side surface of the reforming section, and an annular gas flow path 2 through which gas can flow is provided in contact with the outer peripheral side of the heat insulating layer. An annular shift reaction unit 3 is provided in contact with the outer peripheral side of the annular gas channel 2 via a partition wall 7. A shift reaction catalyst layer 3a is accommodated in the annular shift reaction portion. The reforming unit 1, the annular gas channel 2, the shift reaction unit 3, and the heat insulating layer 5 are integrated. A shift reaction catalyst layer can be formed by filling at least a part of the shift reaction catalyst with the shift reaction catalyst. A shift reaction catalyst layer may be formed.

  Annular means, for example, the shape of a region formed by two concentric cylindrical surfaces, but is not necessarily limited thereto. For example, one or both of the two cylindrical surfaces may be conical surfaces or may be stepped.

  In addition, regarding this integrated structure, the upper side of the drawing coincides with the upper side in the vertical direction.

  The annular gas flow path 2 may be provided on the outer peripheral side of the shift reaction section. However, if necessary, the gas can dissipate heat released from the high-temperature reforming section located at the center of the reaction vessel to the outside in the radial direction through a heat insulating material layer or the like. From the viewpoint of recovery, it is more preferable that the reforming section, the annular gas flow path, and the shift catalyst layer are arranged in this order from the inside of the multiple cylindrical structure as shown in FIG. In this case, it is preferable to provide a heat insulating layer between the reforming part and the annular gas channel for the purpose of keeping the high temperature reforming part warm. A heat insulation layer can be comprised with a well-known heat insulating material. For example, by wrapping the heat insulating material fiber around the reforming part, filling the powdery heat insulating material between the reforming part and the annular gas flow path, or inserting the integrally formed heat insulating material into the part. An insulating layer can be provided.

  Since this heat insulating layer has a function of preventing heat dissipation from the high temperature reforming portion and keeping the reforming portion at a temperature necessary for the reforming reaction, it is preferable that the heat insulating efficiency of the heat insulating layer is high. Specifically, when the reforming part is held at a constant temperature, it is preferable that the amount of heat released to the outside through the heat insulating layer is small, that is, the outer surface temperature of the heat insulating layer is kept low. However, in an actual hydrogen production apparatus, the type and volume of the heat insulating material that can be used are limited, and it is difficult to completely suppress the heat radiation from the reforming unit. By forming a flow path through which the gas flowing into the shift reaction part flows outside the heat insulation layer, the heat release from the reforming part that could not be suppressed is recovered in the form of a temperature rise of the gas supplied to the shift reaction part, Moreover, the shift inlet gas temperature can be raised to the temperature required for the start of the shift reaction.

The annular gas flow path 2 and the shift reaction unit 3 have a structure in which the inside of one annular container is partitioned. More specifically, the inside of one annular container is divided into two annular regions communicating with each other near the bottom of the container by a partition wall forming a cylindrical peripheral surface, and a gas inlet 8 communicating with the inner peripheral region; A gas outlet 9 communicating with the outer peripheral region is provided. The reformed gas passes from the gas inlet through the inner peripheral region, reverses the flow direction, passes through the outer peripheral region, and is discharged from the gas outlet. The shift reaction catalyst layer is formed by filling at least a part of the outer peripheral region with the shift reaction catalyst. The inner peripheral region can be an annular gas flow path, and the outer region can be a shift reaction part.

The reformer 1 is provided with a burner 1a, and a flame is formed during combustion. Both the upward and downward direction of the burner can be used. When a gaseous fuel such as city gas or LPG is used as the fuel for the burner, the upward direction is usually upward, but the liquid such as naphtha or kerosene is used as the burner fuel. When using fuel, a downward burner may be used from the viewpoint of preventing dripping. Hereinafter, the case where an upward burner is used in the present invention will be described.

  The combustion cylinder 1b is provided to a certain height from the connection part with the burner so as to surround the flame forming part of the burner. The combustion gas of the burner rises in the combustion cylinder, turns back at the upper end of the combustion cylinder, falls while touching the inside of the reforming pipe 1c, and further rises while touching the bottom of the reforming section and touching the outside of the reforming pipe 1c. To do. The reforming pipe 1c has a double-pipe structure whose lower end is closed and provided concentrically with the outer peripheral surface of the reforming section 1. The steam reforming catalyst is filled in the annular inner tube portion of the reforming tube. A mixed gas containing the raw material for hydrogen production and steam is supplied to the inner tube side of the reforming tube, the steam reforming reaction proceeds, and the reformed gas is discharged through the annular outer tube portion of the reforming tube. The reforming tube and the bottom surface of the reforming part are spaced apart.

  The raw material is supplied from the line 100 and the steam is supplied from the line 102 and mixed, and the mixed gas containing these is supplied from the line 103 to the reforming section 1, particularly the reforming pipe 1c.

  The reformed gas discharged from the reforming section can be cooled by the cooling means. For example, the cooler 10 which is a heat exchanger to which a water supply line 101 used for steam reforming is connected is provided. The reformed gas (line 104) is cooled by the cooler 10 using water from the line 101 as a cooling medium, and then supplied from the line 105 to the annular gas flow path 2.

  The reformed gas containing hydrogen obtained by the reforming reaction has a high temperature as it is, and the heat amount of the gas is recovered by some heat exchanging means, and the gas temperature is lowered, and then supplied to the shift reaction unit in the subsequent stage. Is preferred. From the viewpoint of the efficiency of the hydrogen production apparatus, it is preferable to recover as much heat as possible from the high-temperature reformed gas and lower the gas temperature. Specifically, the temperature of the gas supplied to the shift reaction unit depends on the cooling medium of the heat exchanger used in the cooler 10, the structure of the shift unit connected to the subsequent stage, and the catalyst type. From the viewpoint of durability, it is preferably 300 ° C. or lower, more preferably 250 ° C. or lower, and further preferably 200 ° C. or lower.

  On the other hand, the water supplied to the cooler 10 is heated by the reformed gas to become steam (line 102). If the entire water does not become steam only by heat exchange with the reformed gas, the entire water can be made steam by, for example, providing a heat exchanger in the line 102. In addition, a super heater can be installed in the line 104. As these heat sources, the heat recovered in the hydrogen production apparatus or the fuel cell system can be used as appropriate, or the heat generated by combustion means provided separately can be used if necessary.

  The reformed gas supplied from the reformed gas inlet 8 to the upper part of the annular gas channel 2 cools the shift reaction part 3, particularly the shift reaction catalyst layer 3a while flowing downward, and the temperature of the gas itself rises. To do. This gas turns back below the annular gas flow path, enters the shift reaction section 3 from the bottom of the shift reaction section, and the shift reaction proceeds in the shift reaction catalyst layer 3a. The heat generated during the shift reaction is recovered by the reformed gas flowing through the adjacent annular gas flow path 2, and a rapid temperature rise due to the shift reaction is suppressed. The reformed gas 106 extracted from the reformed gas outlet 9 and having a reduced CO concentration is treated such that the CO concentration is further reduced by a CO removal reaction section such as a CO selective oxidation reaction provided as necessary. After that, the fuel cell 11 is supplied to the fuel electrode, particularly the fuel electrode.

  Note that the gas flow direction in the annular gas flow path and the shift reaction section may be opposite to the above. That is, the reformed gas is introduced from the lower part of the annular gas flow path 2 and rises, turns back at the upper part of the annular gas flow path, falls into the upper part of the shift reaction part 3, and is discharged from the lower part of the shift reaction part. You may do it.

  Furthermore, heat exchange means for cooling and / or heating the annular part can be provided on the outer peripheral side of the annular part of the shift reaction part. As this heat exchange means, there may be a case where a tube wall having a substantially cylindrical surface is further provided on the outside of the shift reaction section, and cooling is performed by flowing water or the like between the shift catalyst layer. The case where the heat exchanger 4 having a rotated structure is provided is shown.

  By supplying water used for steam reforming from the line 201 to the heat exchanger 4 via the three-way valve 12 and the line 202, the shift reaction unit 3 can be cooled. The water supplied for cooling recovers the heat of the shift reaction section, is mixed with the raw material for hydrogen production via the line 203, the three-way valve 13, and the line 204, and is supplied for reforming. If all the water from the line 202 does not become steam only by heat exchange with the shift reaction unit, all the water can be made steam by providing a heat exchanger in the lines 203 and 204. In addition, a super heater can be installed in the line 204.

  As described above, the water used as the cooling medium recovers heat from the reformed gas and the shift reaction section. Therefore, from the viewpoint of effectively using the heat energy, the water used for steam reforming is used. Preferably used as a source.

  By the way, when the hydrogen production apparatus is started, the temperature of the reforming section and the shift reaction section is raised from, for example, room temperature. At this time, the reforming unit 1 can raise the temperature by burning the burner 1a. About a shift reaction part, the heating means which heats the water used for steam reforming can be provided in a reforming part, and it can heat up using the said heat exchange means.

  This heating means can use the combustion heat of the burner 1a as a heat source. For example, a heat exchanger that uses the combustion gas as a heat transfer fluid can be provided in a region where the combustion gas of the burner 1a in the reforming section flows to serve as a heating means. As a specific example, a heat exchanger 14 having a structure in which a tube is wound around the bottom of the reforming section in a coil shape or a bellows shape can be used as the heating means.

  When starting up, water is supplied from the line 201 to the heat exchanger 14 via the three-way valve 12 and the line 211, and the steam generated here is supplied from the line 212 to the heat exchanger 4. The steam and / or its condensed water discharged from the heat exchanger 4 may be discharged via the line 203, the three-way valve 13 and the line 213.

  The three-way valves 12 and 13 are a kind of line switching means for switching lines. Not only the three-way valve but also a plurality of stop valves can be combined to constitute the line switching means.

  In addition, an electric heater may be provided on the outer peripheral side of the shift reaction catalyst layer in order to raise the temperature of the shift reaction unit when the hydrogen production apparatus is started. The electric heater can be appropriately selected from known electric heaters.

  FIG. 1 shows a simplified structure for explanation. A structure for gas exchange and distribution, for example, a manifold structure is appropriately provided.

  About the temperature of the water supplied from the lines 101 and 201, normal temperature water can be used, without heating especially, or it can be set to 5-60 degreeC, for example. The pressure can be set as appropriate, but in the case of a household fuel cell, it is usually used between normal pressure and 500 kPa.

  In order to supply the steam necessary for steam reforming, and the steam (lines 102 and 204) generated to supply the steam used for suppressing carbon deposition, for example, a saturated steam pressure corresponding to the pressure may be used. This can be superheated to, for example, 250-450 ° C. Superheating the steam is preferable from the viewpoint of stable operation.

[Raw materials for hydrogen production]
As a raw material for hydrogen production, a known substance capable of obtaining a hydrogen-containing gas by a reforming reaction can be used. For example, hydrocarbon fuels such as natural gas or city gas, LPG (liquefied petroleum gas), naphtha, and kerosene can be used. When liquid fuel such as naphtha or kerosene is used, it can be appropriately vaporized from the viewpoint of feed supply stability.

[Desulfurization]
Since sulfur has the effect of inactivating the steam reforming catalyst, the sulfur concentration in the raw material for hydrogen production supplied to the reforming unit (the mass of sulfur atoms per unit mass of the fluid containing sulfur. The same) is preferably 1 ppm or less, more preferably 0.5 ppm or less, and even more preferably 0.1 ppm or less. For this reason, if necessary, the raw material for hydrogen production can be desulfurized before steam reforming. The raw material for hydrogen production that has been desulfurized before being supplied to the hydrogen production apparatus of the present invention may be used, or a desulfurizer may be provided in the hydrogen production apparatus. When providing a desulfurizer, the raw material for hydrogen production supplied to the desulfurizer can be used as long as it can be desulfurized, for example, to the sulfur concentration in the desulfurizer.

  As a desulfurization method, a method of adsorbing sulfur in the presence of an adsorption-type desulfurization catalyst is preferable from the viewpoint of simplification of the system, ease of control method, and ease of catalyst pretreatment. The adsorption-type desulfurization catalyst removes sulfur by adsorption and / or absorption. For example, from the viewpoint of sulfur adsorption capacity, a metal-based desulfurization catalyst containing Zn / ZnO, Cu / CuO, Ni / NiO, etc. Desulfurizing agents are preferred. Moreover, these can also be used in combination of 2 or more types.

  When using an adsorption-type desulfurization catalyst, the desulfurization temperature is preferably normal temperature or higher and 350 ° C. or lower from the viewpoint of causing the desulfurization catalyst to function well.

[Reformer]
As long as it has a portion whose outer shape is cylindrical as described above, a known steam reformer configuration can be appropriately used for the configuration of the reforming unit. In the reforming section that performs the steam reforming reaction, the hydrogen-producing raw material and water react to obtain a reformed gas containing hydrogen. This reaction is accompanied by a large endotherm. For this reason, for example, a reaction tube for performing a steam reforming reaction is provided, and a burner for heating the reaction tube from the outside is provided. The reforming pipe is heated from the outside by the combustion heat of the burner, and heat for advancing the steam reforming reaction is supplied. The reaction tube is filled with a granular steam reforming catalyst or a monolith (molded body) type catalyst is inserted, and a raw material for hydrogen production and steam are supplied.

  The steam reforming reaction can be performed in the presence of a metal catalyst, typically a Group VIII metal such as nickel, cobalt, iron, ruthenium, rhodium, iridium and platinum.

  The reaction temperature is 350 ° C to 900 ° C, preferably 400 ° C to 850 ° C, more preferably 450 ° C to 800 ° C. As described above, since the reforming reaction is a significant endothermic reaction, a temperature distribution is often formed along the fluid flow direction. For this reason, a specific position of the reaction part, for example, a high temperature part after the reaction part is often used as the control temperature. The control temperature of the reforming reaction is preferably 450 ° C. or higher, more preferably 500 ° C. or higher, further preferably 550 ° C. or higher, preferably 900 ° C. or lower, more preferably 900 ° C. or lower, from the viewpoint of preventing carbon deposition (coking). Is in the range of 850 ° C. or lower, more preferably 800 ° C. or lower.

  The pressure of the reforming reaction can be appropriately set, but is preferably in the range of atmospheric pressure to 1 MPa, more preferably atmospheric pressure to 0.5 MPa, and still more preferably atmospheric pressure to 0.2 MPa.

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 1.5-10. Preferably it is 2.0-7, More preferably, it is 2.5-5. The liquid space velocity (LHSV) at this time is A / B when the flow rate in the liquid state is A (L / h) and the catalyst layer volume is B (L) when the hydrocarbon fuel to be used is liquid. 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 . Further, when the fuel to be used is gas at normal temperature and normal pressure, it is defined as GHSV using a gas-state flow rate as the flow rate A (GHSV represents a gas space velocity in terms of 15 ° C. and 0.101 MPa. The same applies hereinafter). In this case, the range is usually 50 to 5000 h ⁻¹ , preferably 100 to 4000 h ⁻¹ , more preferably 150 to 3000 h ⁻¹ . The gas space velocity of the reforming fuel varies significantly depending on the type of fuel used. For example, when the GHSV range is limited to LPG, it is usually 50 to 2000 h ⁻¹ , preferably 100 to 1500 h ⁻¹ , more preferably It is in the range of 150 to 1000 h ⁻¹ .

  The form of the reforming tube is preferably a double tube reactor from the viewpoint of heat balance. In the double tube reactor, the reforming catalyst is filled in the inner ring portion of the double tube, and the catalyst is not filled in the outer tube portion, and can be used as a return line of the obtained reformed gas. The reforming raw material is introduced into the inner ring, undergoes a steam reforming reaction when passing through the catalyst layer, turns back at the end opposite to the introduced side, and passes through the outer tube to introduce the raw material. Discharged from the end of the side.

  As the fuel supplied for burning the burner, combustible materials can be used as appropriate. It is preferable to use the raw material for hydrogen production also for combustion from the viewpoint of simplifying the hydrogen production apparatus or its incidental facilities. When the hydrogen production apparatus is used in a fuel cell system, anode offgas discharged from the anode (fuel electrode) of the fuel cell can be used as burner fuel, or a hydrogen production raw material is mixed with the anode offgas to burner. From the viewpoint of energy efficiency, it can be used as a fuel, or it is preferable to feed them simultaneously to a single burner for co-firing. For this reason, a mixed burner capable of burning both the raw material for hydrogen production and the anode off-gas of the fuel cell can be used as the burner.

  The maximum combustion temperature of the burner is preferably 800 to 1000 ° C. from the viewpoint of the heat resistance temperature of the reformed pipe material.

[Shift reaction section]
The reformed gas obtained from the reforming section contains carbon monoxide, carbon dioxide, methane, and water vapor in addition to hydrogen. From the viewpoint of producing gas to be supplied to the anode of the fuel cell, carbon monoxide may be a catalyst poison for the polymer electrolyte fuel cell electrode, so to reduce the carbon monoxide concentration and to increase the hydrogen concentration, The shift reaction unit converts carbon monoxide with water to convert it into hydrogen and carbon dioxide. Fe-Cr mixed oxide, Zn-Cu mixed oxide, platinum, palladium, iridium and other noble metal-containing catalysts are used, and the carbon monoxide content (mol% in dry base) is preferably 2% or less, more Preferably it can be reduced to 1% or less, more preferably 0.75% or less.

Shift reaction is preferably 400～20000H ^-1 gas hourly space velocity GHSV, more preferably 500~10000h ^-1, more preferably performed at 600~5000h ^-1.

  The shift reaction can also be performed in two stages. In this case, a low temperature shift reaction catalyst is used for the catalyst layer 3a of the shift reaction portion, and a high temperature or medium temperature shift reaction catalyst is used in the cooler 10 or in the previous stage. With such a configuration, the space velocity can be increased in CO conversion at high temperature, and the CO concentration can be reduced to a sufficient equilibrium composition by low temperature shift.

[Selective oxidizer]
For example, in the polymer electrolyte fuel cell system, it is preferable to further reduce the carbon monoxide concentration, and for this purpose, the outlet gas of the shift reactor can be treated with a selective oxidizer. In the selective oxidizer, CO is selectively oxidized to carbon dioxide.

  For this reaction, a catalyst containing iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, platinum, copper, silver, gold, etc. is used, and preferably 0.5 mol relative to the remaining number of moles of carbon monoxide. The carbon monoxide concentration is reduced by selectively converting carbon monoxide to carbon dioxide by adding 10 to 10 times mol, more preferably 0.7 to 5 times mol, and still more preferably 1 to 3 times mol. Preferably, it is reduced to 10 mass ppm 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. For example, air can be used as the oxygen source.

The selective oxidation can be performed using a selective oxidation catalyst having a suitable use temperature of 100 to 200 ° C. The molar ratio of oxygen to be supplied and CO (O ₂ / CO ratio) is preferably 1.0 to 3.0, and preferably 2000 to 10,000 h ^{−1 in} GHSV.

[Fuel cell system]
The fuel cell system of the present invention includes the above-described hydrogen production apparatus and a fuel cell using a hydrogen-containing gas obtained from the hydrogen production apparatus as a fuel electrode supply gas. In addition, other devices such as means for supplying oxygen-containing gas such as air to the cathode, means for taking out electricity from the fuel cell, instrumentation control devices, etc., as conventionally provided devices for fuel cell systems, etc. Can be provided as appropriate.

  The anode off gas of the fuel cell can be burned by the burner when the reforming unit of the hydrogen production apparatus is provided with a mixed combustion burner. For this reason, the fuel cell system can have a line for guiding the anode off gas to the mixed burner. This line can be appropriately formed by piping or valves.

  With such a configuration, for example, combustion fuel such as a raw material for hydrogen production is combusted when the fuel cell system is started, but only anode off-gas is combusted during rated operation, and consumption of the fuel for combustion can be suppressed.

  The hydrogen production apparatus of the present invention can be used for producing a hydrogen-containing gas to be used for a fuel cell system and to be supplied to the fuel cell, and to be used for producing a hydrogen-containing gas stored or produced in a hydrogen station. Can do.

  The fuel cell system of the present invention can be used for a power generation system or a cogeneration system for a moving object such as an automobile, industrial use, or consumer use.

It is a schematic diagram for demonstrating a reforming part, a shift reaction part, and a cyclic | annular gas flow path about one form of the hydrogen production apparatus of this invention. It is a flowchart which shows one form of the hydrogen production apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reforming part 1a Burner 1b Combustion cylinder 1c Reforming pipe 2 Annular gas flow path 3 Shift reaction part 3a Shift catalyst layer 4 Shift reaction part cooling / heating heat exchanger 5 Heat insulation layer 7 Partition wall 8 Reformed gas inlet 9 Reformation Gas outlet (after shift reaction)
DESCRIPTION OF SYMBOLS 10 Cooler 11 Fuel cell 12 Three-way valve 13 Three-way valve 14 Heat exchanger (heating means)

Claims (10)

A reforming section for obtaining a reformed gas containing hydrogen by steam reforming the raw material for hydrogen production, and a shift reaction section for reducing the carbon monoxide concentration in the reformed gas by a shift reaction,
The reforming part has a cylindrical part in the outer shape,
The shift reaction portion has an annular portion for accommodating a shift reaction catalyst layer filled with a shift reaction catalyst;
A cylindrical part of the reforming part is arranged on the inner peripheral side of the annular part of the shift reaction part,
An annular gas flow path through which gas can flow is provided in contact with an inner peripheral side or an outer peripheral side of the annular portion of the shift reaction part via a partition wall,
The reforming section, the annular gas flow path, and the shift reaction section are connected in this order so that the reformed gas can flow from the reforming section through the annular gas flow path and flow into the shift reaction section by reversing the flow direction. ,
A hydrogen production apparatus further comprising a cooling means for cooling the reformed gas downstream of the reforming section and upstream of the annular gas flow path . It said cooling means, The apparatus of claim 1, wherein the heat exchanger supply line for water is connected to be used for steam reforming. Further, in the heat exchanger or in the previous stage, there is a high temperature or medium temperature shift reaction catalyst,
The apparatus according to claim 2, wherein the shift reaction catalyst layer accommodated in the annular portion of the shift reaction section is filled with a low temperature shift reaction catalyst. The apparatus according to any one of claims 1 to 3 , wherein the annular gas flow path is disposed in contact with an inner peripheral side of an annular portion of the shift reaction portion. The apparatus according to claim 4 , wherein the cylindrical portion of the reforming portion and the annular gas flow path are in contact with each other via a heat insulating layer. Furthermore, the apparatus of Claim 4 or 5 which has a heat exchange means for cooling and / or heating this annular part on the outer peripheral side of the annular part of the said shift reaction part. The apparatus according to claim 6 , wherein the heat exchange means is a heat exchanger to which a supply line of water used for steam reforming is connected. Furthermore, the reforming unit has a heating means for heating water used for steam reforming,
It said heat exchange means comprises a supply line of water heated by the heating means, and a supply line of water used in the steam reforming, according to claim 6, wherein the heat exchanger is connected via a line switching means apparatus. Furthermore, the apparatus of Claim 4 or 5 which has an electric heater in the outer peripheral side of the annular part of the said shift reaction part. A hydrogen production apparatus comprising: a reforming unit that obtains a reformed gas containing hydrogen by steam reforming a raw material for hydrogen production; and a shift reaction unit that reduces a carbon monoxide concentration in the reformed gas by a shift reaction; A fuel cell system comprising a fuel cell using hydrogen obtained from the hydrogen production apparatus as a fuel,
The reforming part has a cylindrical part in the outer shape,
The shift reaction portion has an annular portion for accommodating a shift reaction catalyst layer filled with a shift reaction catalyst;
A cylindrical part of the reforming part is arranged on the inner peripheral side of the annular part of the shift reaction part,
An annular gas flow path through which gas can flow is provided in contact with an inner peripheral side or an outer peripheral side of the annular portion of the shift reaction part via a partition wall,
The reforming section, the annular gas flow path, and the shift reaction section are connected in this order so that the reformed gas can flow from the reforming section through the annular gas flow path and flow into the shift reaction section by reversing the flow direction. ,
The fuel cell system further comprising cooling means for cooling the reformed gas downstream of the reforming section and upstream of the annular gas flow path .

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