JP5687147B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system.

  As a conventional fuel cell system, a hydrogen generation unit that generates a hydrogen-containing gas using a hydrocarbon-based fuel, a cell stack that generates power using the hydrogen-containing gas, and an upstream of the hydrogen generation unit are arranged by a desulfurization catalyst. The thing provided with the desulfurization part which carries out the adsorption desulfurization of the hydrocarbon-type fuel is known (for example, refer patent document 1). As such a desulfurization section, the desulfurization section is filled with a catalyst amount suitable for the catalyst life, and the desulfurization catalyst is used up to the catalyst life, and the cartridge is filled with the desulfurization catalyst, and the cartridge is replaced when the catalyst life is completed. The type is known.

JP 2008-218308 A

  Here, when moisture is contained in the hydrocarbon-based fuel (that is, when a high-dew point hydrocarbon-based fuel is used), the desulfurization catalyst may adsorb moisture, which may hinder the adsorption of sulfur compounds. . Therefore, there is a problem that the life of the desulfurization section is shortened due to the shortened life of the desulfurization catalyst, and the replacement frequency of the cartridge is greatly increased. Moreover, in order to ensure the lifetime of the conventional desulfurization part, or in order to make the replacement frequency of a cartridge into the conventional one, it will be necessary to increase the filling amount of a desulfurization catalyst significantly. This causes problems such as an increase in system size and cost.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a fuel cell system that can suppress a decrease in the life of a desulfurization catalyst in a desulfurization section.

  Here, as a result of intensive research, the present inventors have conducted a regeneration process of the desulfurization catalyst (a process for desorbing moisture adsorbed from the desulfurization catalyst) by heating the desulfurization catalyst to a temperature within a predetermined range. I found it possible. That is, in the temperature range where only moisture is desorbed and sulfur compounds are not desorbed, the desulfurization catalyst can desorb the adsorbed moisture, while maintaining the adsorbed state without desorbing the sulfur compound. Based on such a viewpoint, the present inventors have found a fuel cell system capable of suppressing a decrease in the lifetime of the desulfurization catalyst.

  A fuel cell system according to the present invention includes a hydrogen generation unit that generates a hydrogen-containing gas using a hydrocarbon-based fuel, a cell stack that generates power using the hydrogen-containing gas, and a hydrocarbon-based fuel supplied to the hydrogen generation unit The fuel cell system includes a fuel supply unit that is disposed upstream of the hydrogen generation unit, and a desulfurization unit that adsorbs and desulfurizes hydrocarbon-based fuel using a desulfurization catalyst, and desorbs only moisture and desorbs sulfur compounds. It is characterized by comprising a heating section that heats to a temperature that does not.

  The fuel cell system according to the present invention includes a heating unit that heats to a temperature at which only moisture is desorbed and sulfur compounds are not desorbed. When the desulfurization catalyst adsorbs moisture due to the moisture contained in the hydrocarbon-based fuel, the heating unit heats the desulfurization catalyst to raise the temperature so that only moisture is desorbed and sulfur compounds are not desorbed. Thereby, moisture adsorbed on the desulfurization catalyst is desorbed from the desulfurization catalyst and removed. In addition, the sulfur compound adsorbed on the desulfurization catalyst maintains the state adsorbed on the desulfurization catalyst without desorption. Such regeneration treatment restores the life of the desulfurization catalyst. As described above, it is possible to suppress the life reduction of the desulfurization catalyst in the desulfurization section.

  Further, as a result of further intensive studies, the present inventors have found that the temperature at which only moisture is desorbed and the sulfur compound is not desorbed is preferably, for example, 100 ° C. or higher and 250 ° C. or lower. Therefore, it is preferable that the heating unit heats the desulfurization catalyst to a temperature of 100 ° C. or higher and 250 ° C. or lower.

  The desulfurization unit includes a first reaction unit and a second reaction unit, and the heating unit includes a first heating unit that heats the desulfurization catalyst of the first reaction unit, and a desulfurization catalyst of the second reaction unit. It is preferable that when one of the first heating unit and the second heating unit is heating, the other stops heating. As a result, the desulfurization catalyst related to one reaction part becomes a regeneration treatment (treatment that desorbs moisture adsorbed from the desulfurization catalyst) when the temperature becomes high, and the desulfurization catalyst related to the other reaction part becomes desulfurization due to a low temperature. It becomes possible. Thus, moisture is desorbed and removed from the desulfurization catalyst in one reaction part, and the sulfur compound of the hydrocarbon fuel can be removed by the desulfurization catalyst in the other reaction part. Next, by replacing the heating side and the heating stop side, moisture is desorbed and removed from the desulfurization catalyst in the other reaction part, and the sulfur compound of the hydrocarbon fuel can be removed by the desulfurization catalyst in one reaction part. it can. As a result, it is possible to surely remove the sulfur compound of the hydrocarbon-based fuel heading toward the hydrogen generating part, and to remove the moisture of the desulfurization catalyst over the entire region of the desulfurization part. Moreover, since the desulfurization catalyst can be regenerated while the hydrocarbon fuel can be desulfurized, the desulfurization catalyst can be regenerated while the fuel cell system is continuously operated.

  In the fuel cell system, the first reaction unit and the second reaction unit may be arranged in series, or the first reaction unit and the second reaction unit may be arranged in parallel. In any arrangement, the desulfurization catalyst can be regenerated while the fuel cell system is continuously operated.

  In the fuel cell system, it is preferable to supply a fluid (moisture desorption fluid) for desorbing the moisture adsorbed on the desulfurization catalyst and sending it out of the desulfurization unit to the desulfurization unit when the heating unit is operated. By supplying a fluid to the desulfurization unit during the operation of the heating unit, moisture desorbed from the desulfurization catalyst is surely removed from the desulfurization unit. As a result, it is possible to reliably prevent the moisture once desorbed from being adsorbed by the desulfurization catalyst again.

  It is preferable to supply a hydrocarbon fuel or an oxidant as the fluid. Fluid can be supplied by sharing existing equipment in the fuel cell system. Thereby, the whole fuel cell system can be made compact. For example, by using a hydrocarbon-based fuel as a fluid, the fuel supply unit can function as a fluid supply unit. Alternatively, by using an oxidant as a fluid, an oxidant supply unit that supplies an oxidant to the cell stack can function as a fluid supply unit.

  On the other hand, in order to supply the fluid, an existing device in the fuel cell system may not be shared as the fluid supply unit, and a fluid supply unit for regeneration processing may be further provided. Thereby, it is possible to suppress the complicated switching control and flow rate control of the fuel and oxidant supply lines that occur when the fuel supply unit and the oxidant supply unit are shared.

  Moreover, as a desulfurization catalyst, a catalyst in which a metal is supported on zeolite can be preferably used.

  In the fuel cell system, the hydrocarbon fuel may contain moisture. Even when such a hydrocarbon fuel is applied, a decrease in the life of the desulfurization catalyst is suppressed. Therefore, the fuel cell system can exhibit sufficient performance regardless of the state of the hydrocarbon fuel.

  In the fuel cell system, the hydrocarbon-based fuel is preferably a hydrocarbon having 1 to 4 carbon atoms. By applying such a hydrocarbon fuel, desulfurization and generation of hydrogen can be easily performed, and the fuel cell system can exhibit sufficient performance.

  ADVANTAGE OF THE INVENTION According to this invention, the fall of the lifetime of the desulfurization catalyst of a desulfurization part can be suppressed.

FIG. 1 is a block configuration diagram showing the configuration of the fuel cell system according to the first embodiment of the present invention. FIG. 2 is a block configuration diagram showing a configuration near the desulfurization unit of the fuel cell system according to the first embodiment. FIG. 3 is a flowchart showing the contents of the control process of the fuel cell system according to the first embodiment. FIG. 4 is a block configuration diagram showing the configuration near the desulfurization unit of the fuel cell system according to the second embodiment. FIG. 5 is a flowchart showing the contents of the control process of the fuel cell system according to the second embodiment. FIG. 6 is a block configuration diagram showing the configuration near the desulfurization unit of the fuel cell system according to the third embodiment. FIG. 7 is a graph showing experimental results for deriving the regeneration temperature of the desulfurization catalyst. FIG. 8 is a graph showing experimental results for deriving the regeneration temperature of the desulfurization catalyst.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the same or an equivalent part, and the overlapping description is abbreviate | omitted.

[First embodiment]
As shown in FIG. 1, the fuel cell system 1 includes a desulfurization unit 2, a water vaporization unit 3, a hydrogen generation unit 4, a cell stack 5, an off-gas combustion unit 6, a fuel supply unit 7, and a water supply. Unit 8, oxidant supply unit 9, power conditioner 10, and control unit 11. The fuel cell system 1 generates power in the cell stack 5 using a hydrocarbon fuel and an oxidant. The type of the cell stack 5 in the fuel cell system 1 is not particularly limited, and examples thereof include a polymer electrolyte fuel cell (PEFC), a solid oxide fuel cell (SOFC), and phosphoric acid. A type fuel cell (PAFC: Phosphoric Acid Fuel Cell), a molten carbonate type fuel cell (MCFC), and other types can be adopted. The components shown in FIG. 1 may be omitted as appropriate according to the type of cell stack 5, the type of hydrocarbon fuel, the reforming method, and the like.

  As the hydrocarbon fuel, a compound containing carbon and hydrogen in the molecule (may contain other elements such as oxygen) or a mixture thereof is used. Examples of hydrocarbon fuels include hydrocarbons, alcohols, ethers, and biofuels. These hydrocarbon fuels are derived from conventional fossil fuels such as petroleum and coal, and synthetic systems such as synthesis gas. Those derived from fuel and those derived from biomass can be used as appropriate. Specific examples of hydrocarbons include methane, ethane, propane, butane, natural gas, LPG (liquefied petroleum gas), city gas, town gas, gasoline, naphtha, kerosene, and light oil. Examples of alcohols include methanol and ethanol. Examples of ethers include dimethyl ether. Examples of biofuels include biogas, bioethanol, biodiesel, and biojet. In the present embodiment, a gas containing methane as a main component (for example, city gas, town gas, natural gas, biogas, etc.) or LPG supplied through a pipeline is used. It can be preferably used.

  In the present embodiment, the hydrocarbon fuel preferably contains a hydrocarbon compound having 4 or less carbon atoms. Specific examples of the hydrocarbon compound having 4 or less carbon atoms include saturated aliphatic hydrocarbons such as methane, ethane, propane, and butane, and unsaturated aliphatic hydrocarbons such as ethylene, propylene, and butene. The hydrocarbon-based fuel is preferably a gas containing a hydrocarbon compound having 4 or less carbon atoms, that is, a gas containing one or more of methane, ethane, ethylene, propane, propylene, butane and butene. Moreover, as gas containing a C4 or less hydrocarbon compound, the gas containing 80 volume% or more of methane is preferable, and the gas containing 85 volume% or more of methane is more preferable.

The hydrocarbon fuel generally contains a sulfur compound. Examples of the sulfur compound include sulfur compounds originally contained in hydrocarbons and the like and compounds contained in odorants for detecting gas leaks. The sulfur compounds originally contained in the hydrocarbon are hydrogen sulfide (H ₂ S), carbonyl sulfide (COS), carbon disulfide (CS ₂ ) and the like. As the odorant, alkyl sulfide, mercaptan alone or a mixture thereof is used. For example, diethyl sulfide (DES), dimethyl sulfide (DMS), ethyl methyl sulfide (EMS), tetrahydrothiophene (THT), tert-butyl mercaptan (TBM). ), Isopropyl mercaptan, dimethyl disulfide (DMDS), diethyl disulfide (DEDS) and the like. The sulfur compound is contained in an amount of 0.1 to 10 mass ppm in terms of sulfur atom based on the total amount of hydrocarbon fuel.

  As the oxidizing agent, for example, air, pure oxygen gas (which may contain impurities that are difficult to remove by a normal removal method), or oxygen-enriched air is used.

  The desulfurization unit 2 performs desulfurization of the hydrocarbon fuel supplied to the hydrogen generation unit 4. The desulfurization part 2 has a desulfurization catalyst for removing sulfur compounds contained in the hydrocarbon fuel. As the desulfurization method of the desulfurization unit 2, for example, an adsorptive desulfurization method that adsorbs and removes sulfur compounds is employed. The desulfurization unit 2 supplies the desulfurized hydrocarbon fuel to the hydrogen generation unit 4.

  The water vaporization unit 3 generates water vapor supplied to the hydrogen generation unit 4 by heating and vaporizing water. Heating of the water in the water vaporization unit 3 may use, for example, heat generated in the fuel cell system 1 such as recovering the heat of the hydrogen generation unit 4, the heat of the off-gas combustion unit 6, or the heat of the exhaust gas. . Moreover, you may heat water using other heat sources, such as a heater and a burner separately. In FIG. 1, only heat supplied from the off-gas combustion unit 6 to the hydrogen generation unit 4 is described as an example, but the present invention is not limited to this. The water vaporization unit 3 supplies the generated water vapor to the hydrogen generation unit 4.

  The hydrogen generation unit 4 generates a hydrogen rich gas using the hydrocarbon fuel from the desulfurization unit 2. The hydrogen generator 4 has a reformer that reforms the hydrocarbon fuel with a reforming catalyst. The reforming method in the hydrogen generating unit 4 is not particularly limited, and for example, steam reforming, partial oxidation reforming, autothermal reforming, and other reforming methods can be employed. The hydrogen generator 4 may have a configuration for adjusting the properties in addition to the reformer reformed by the reforming catalyst depending on the properties of the hydrogen rich gas required for the cell stack 5. For example, when the type of the cell stack 5 is a polymer electrolyte fuel cell (PEFC) or a phosphoric acid fuel cell (PAFC), the hydrogen generation unit 4 is configured to remove carbon monoxide in the hydrogen-rich gas. (For example, a shift reaction part and a selective oxidation reaction part). The hydrogen generation unit 4 supplies a hydrogen rich gas to the anode 12 of the cell stack 5.

  The cell stack 5 generates power using the hydrogen rich gas from the hydrogen generation unit 4 and the oxidant from the oxidant supply unit 9. The cell stack 5 includes an anode 12 to which a hydrogen-rich gas is supplied, a cathode 13 to which an oxidant is supplied, and an electrolyte 14 disposed between the anode 12 and the cathode 13. The cell stack 5 supplies power to the outside via the power conditioner 10. The cell stack 5 supplies the hydrogen rich gas and the oxidant, which have not been used for power generation, to the off gas combustion unit 6 as off gas. Note that a combustion section (for example, a combustor that heats the reformer) provided in the hydrogen generation section 4 may be shared with the off-gas combustion section 6.

  The off gas combustion unit 6 burns off gas supplied from the cell stack 5. The heat generated by the off-gas combustion unit 6 is supplied to the hydrogen generation unit 4 and used for generation of a hydrogen rich gas in the hydrogen generation unit 4.

  The fuel supply unit 7 supplies hydrocarbon fuel to the desulfurization unit 2. The water supply unit 8 supplies water to the water vaporization unit 3. The oxidant supply unit 9 supplies an oxidant to the cathode 13 of the cell stack 5. The fuel supply unit 7, the water supply unit 8, and the oxidant supply unit 9 are configured by a pump, for example, and are driven based on a control signal from the control unit 11.

  The power conditioner 10 adjusts the power from the cell stack 5 according to the external power usage state. For example, the power conditioner 10 performs a process of converting a voltage and a process of converting DC power into AC power.

  The control unit 11 performs control processing for the entire fuel cell system 1. The control unit 11 is configured by, for example, a device including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and an input / output interface. The control unit 11 is electrically connected to a fuel supply unit 7, a water supply unit 8, an oxidant supply unit 9, a power conditioner 10, and other sensors and auxiliary equipment (not shown). The control unit 11 acquires various signals generated in the fuel cell system 1 and outputs a control signal to each device in the fuel cell system 1.

  A hydrocarbon fuel having a high dew point, that is, a hydrocarbon fuel containing moisture, may be applied as the hydrocarbon fuel supplied to the desulfurization unit 2. The water contained in the hydrocarbon-based fuel is, for example, the one mixed during the production of the hydrocarbon-based fuel, the one mixed in due to damage to the pipeline, or the like in the distribution path until the hydrocarbon-based fuel is supplied to the desulfurization section 2. The mixed thing etc. are mentioned. When a hydrocarbon-based fuel containing moisture is supplied, the desulfurization catalyst 2a adsorbs moisture together with the sulfur compound. Therefore, there is a concern that the adsorption of the sulfur compound may be hindered, and there is a concern about an adverse effect on the catalyst life. The fuel cell system 1 according to the present invention has a function of removing moisture adsorbed on the desulfurization catalyst 2a of the desulfurization section 2 and regenerating the desulfurization catalyst 2a. The fuel cell system 1 can use a hydrocarbon fuel containing 0 to 2.5% by volume of water (volume ratio of water in the entire hydrocarbon fuel). As shown in FIGS. 1 and 2, the fuel cell system 1 includes a heating unit 21, a fluid supply unit 22, and a temperature sensor 23. The control unit 11 includes a supply control unit 101, a heating control unit 102, a temperature detection unit 103, and a determination unit 104.

  The heating unit 21 has a function of heating the desulfurization catalyst 2a. As the heating unit 21, for example, a heating wire, a siliconite heater, a carbon heater, or the like can be applied. When using a heating wire, the heating part 21 can be comprised by winding a heating wire around the casing of the desulfurization part 2, for example. The heating unit 21 is electrically connected to the control unit 11, and heating on / off and adjustment of the heating temperature are performed by the control unit 11. The heating unit 21 heats the desulfurization catalyst 2a to a temperature (for example, preferably 100 ° C. or more and 250 ° C. or less) at which only moisture is desorbed and sulfur compounds are not desorbed. By being heated to such a temperature, the desulfurization catalyst 2a can desorb the adsorbed moisture while maintaining the sulfur compound adsorbed state. Hereinafter, such a temperature will be referred to as a regeneration temperature. The lower limit of the regeneration temperature is 100 ° C or higher, preferably 130 ° C or higher, more preferably 150 ° C or higher, while the upper limit of the regeneration temperature is 250 ° C or lower, preferably 240 ° C or lower, more preferably 230 ° C or lower. Heat.

  The fluid supply unit 22 supplies a fluid to the desulfurization unit 2. The fluid supply unit 22 removes moisture from the desulfurization unit 2 by flowing the moisture desorbed from the desulfurization catalyst 2a together with the fluid to the hydrogen generation unit 4 side. As the fluid, for example, an oxidant, a hydrocarbon fuel, or the like can be applied. The fluid supply unit 22 is configured by a pump, for example, and is driven based on a control signal from the control unit 11. In this embodiment, the fluid supply unit 22 for supplying a fluid to the desulfurization unit 2 is provided. However, when an oxidant is used as the fluid, the oxidant supply unit 9 and the fluid supply unit 22 may be shared. In that case, the flow path is branched from the oxidant supply unit 9 so that the oxidant is supplied upstream of the desulfurization unit 2. Moreover, when using a hydrocarbon-type fuel as a fluid, you may share the fuel supply part 7 and the fluid supply part 22. FIG. The timing at which the fluid supply unit 22 supplies the fluid is not particularly limited as long as it can remove the moisture desorbed from the desulfurization catalyst 2a. It is preferable that the fluid supply unit 22 supplies the fluid when the desulfurization catalyst 2a is at the regeneration temperature so that the water once desorbed is not adsorbed again by the desulfurization catalyst 2a.

  In the present embodiment, moisture is removed by supplying a fluid from the fluid supply unit 22 when the fuel cell system 1 is stopped. In this embodiment, the desulfurization catalyst 2a cannot be continuously regenerated. The fluid used for moisture removal is exhausted from the desulfurization unit 2 to the atmosphere or combusted in the off-gas combustion unit 6 and then exhausted to the atmosphere. The supply destination of exhaust gas from the desulfurization section 2 in the case of desulfurization treatment of hydrocarbon fuel is set to the hydrogen generation section 4, and the supply destination of exhaust gas from the desulfurization section 2 in the case of regeneration treatment of the desulfurization catalyst 2a is exhaust. The system and the off-gas combustion unit 6 are switched. The switching control can be performed by valve opening / closing control or the like.

  The temperature sensor 23 detects the temperature at a predetermined location of the desulfurization unit 2. The position of the temperature sensor 23 is not particularly limited, and may be disposed at a position where the temperature of the desulfurization catalyst 2a can be directly detected, such as a casing of the desulfurization unit 2, and disposed at a position where the temperature of the desulfurization catalyst 2a can be indirectly detected. May be. Moreover, the temperature sensor 23 may be installed in multiple places with respect to the desulfurization part 2. FIG. The temperature sensor 23 is electrically connected to the control unit 11 and outputs a detection result to the control unit 11.

  The supply control unit 101 of the control unit 11 has a function of controlling the fuel supply unit 7, the water supply unit 8, the oxidant supply unit 9, and the fluid supply unit 22. The supply control unit 101 outputs a control signal to these supply units, and controls supply start, supply amount, supply stop, and the like.

  The heating control unit 102 of the control unit 11 has a function of controlling the heating state of the desulfurization catalyst 2 a by the heating unit 21. The heating control unit 102 has functions of turning on / off the heating unit 21 and adjusting the heating temperature. The heating control unit 102 has a function of increasing the temperature of the desulfurization catalyst 2a to the regeneration temperature by starting heating by the heating unit 21 in the regeneration process of the desulfurization catalyst 2a. Further, the heating control unit 102 has a function of adjusting the heating state of the heating unit 21 so as to maintain the regeneration temperature when the desulfurization catalyst 2a reaches the regeneration temperature. The method for adjusting the heating state of the heating unit 21 is not particularly limited, and the heating control unit 102 may maintain the temperature of the desulfurization catalyst 2a by keeping the temperature of the heating unit 21 constant at a predetermined temperature. The temperature of the desulfurization catalyst 2a may be maintained by repeating on / off of 21. In addition to the regeneration process of the desulfurization catalyst 2a (during normal operation of the fuel cell system 1), the heating control unit 102 stops the heating unit 21.

  The temperature detection unit 103 of the control unit 11 has a function of acquiring information related to the temperature of the desulfurization catalyst 2 a based on the detection result of the temperature sensor 23. The temperature detection unit 103 may acquire a value that directly indicates the temperature of the desulfurization catalyst 2a, or may acquire a value corresponding to the temperature of the desulfurization catalyst 2a (such as the temperature of the casing of the desulfurization unit 2). For example, when the temperature sensor 23 is not disposed at a location where the temperature of the desulfurization catalyst 2a can be directly measured, the temperature detection unit 103 uses the detection result of the temperature sensor 23 to perform arithmetic processing or inquiry processing with previously prepared data. Thus, the temperature of the desulfurization catalyst 2a may be estimated. Or the temperature detection part 103 may use the detection result from the temperature sensor 23 for control as it is by adjusting the threshold value used by the determination part 104. FIG.

  The determination unit 104 of the control unit 11 has a function of determining whether or not the desulfurization catalyst 2 a is within the regeneration temperature range based on the detection result of the temperature detection unit 103. When the regeneration process of the desulfurization catalyst 2a is completed and the normal operation of the fuel cell system 1 is resumed, the determination unit 104 has a function of determining whether or not the temperature of the desulfurization catalyst 2a is in the range of 0 to 60 ° C. have. For example, the determination unit 104 performs determination by setting a threshold value in advance and comparing the threshold value with the temperature acquired by the temperature detection unit 103.

<Desulfurization catalyst>
Preferred examples of the desulfurization catalyst 2a include a catalyst in which a metal is supported on zeolite.

  As zeolite, various zeolites such as A type and faujasite type can be used, and among them, X type zeolite and Y type zeolite can be preferably used.

As the X-type zeolite, for example, one having a SiO ₂ / Al ₂ O ₃ ratio of 2 to 3, preferably 2.2 to 3, more preferably 2.3 to 3 can be used. When the ratio is less than 2, the life of the resulting catalyst as a desulfurization catalyst tends to be reduced. When the ratio is greater than 3, the amount of active metal supported is reduced, and sufficient desulfurization performance is achieved. There is a tendency that it cannot be obtained.

As the Y-type zeolite, for example, those having a SiO ₂ / Al ₂ O ₃ ratio of 3 to 10, preferably 3.5 to 8, and more preferably 4 to 7 can be used. When the ratio is less than 3 or greater than 10, the life of the obtained catalyst as a desulfurization catalyst tends to be reduced, and sufficient desulfurization performance cannot be obtained.

  As the metal supported on the zeolite, silver, copper and zinc can be preferably mentioned, and silver and / or copper are more preferable.

  In the case of supporting silver, the range of the supported amount of silver is preferably 10 to 30% by mass and more preferably 15 to 25% by mass on the basis of zeolite from the viewpoint of improving the desulfurization performance. As a method for supporting silver, an ion exchange method is preferably used. As the zeolite used for ion exchange, various types such as sodium type, ammonium type and proton type can be used, and the sodium type is most preferably used. On the other hand, silver is usually prepared as a cation dissolved in water. Specific examples thereof include an aqueous solution of silver nitrate and silver perchlorate, an aqueous solution of silver ammine complex ion, and the like, and an aqueous silver nitrate solution is most preferably used. The density | concentration of the aqueous solution containing silver ion is 0.5-10 mass% normally as a density | concentration of silver, Preferably it is the range of 1-5 mass%.

  In the case of supporting copper, the range of the amount of copper supported is preferably 3 to 20% by mass, more preferably 5 to 15% by mass on the basis of zeolite from the viewpoint of improving the desulfurization performance. As a method for supporting copper, an ion exchange method is preferably used. As the zeolite used for ion exchange, various types such as sodium type, ammonium type and proton type can be used, and the sodium type is most preferably used. On the other hand, copper is usually prepared as a cation dissolved in water. Specific examples thereof include aqueous solutions of copper sulfate, copper nitrate, copper chloride, and copper acetate, and aqueous solutions of copper complex ions such as copper ammine complex ions. The density | concentration of the aqueous solution containing a copper ion is 0.1-10 mass% normally as a copper density | concentration, Preferably it is the range of 0.5-5 mass%.

  The ion exchange method is not particularly limited, but the above-mentioned zeolite is usually added to the above solution containing cationic silver or copper, and the temperature is usually 0 to 90 ° C., preferably 20 to 70 ° C. The ion exchange treatment is performed for a period of time to several hours, preferably with stirring. Next, the solid matter is separated by means such as filtration and washed with water, and then dried at a temperature of 50 to 200 ° C., preferably 80 to 150 ° C. This ion exchange treatment can be repeated. Next, if necessary, it may be fired at 200 to 600 ° C., preferably 250 to 400 ° C. for about several hours. By such a method, the target silver ion exchange zeolite (silver supported zeolite) or copper ion exchange zeolite (copper supported zeolite) can be obtained.

  Zeolite supporting silver or copper produced by the above method is made by extrusion molding, tableting molding, rolling molding, using alumina, silica, clay mineral, etc. or a precursor thereof such as boehmite as an appropriate binder. It can be molded and used in a conventional manner, such as by granulation, spray drying, and firing as necessary.

  Under the desulfurization conditions when the above catalyst is used, it is usually preferable that the fuel is in a vaporized state. The desulfurization temperature is preferably 100 ° C. or less, for example, in the range of −50 ° C. to 100 ° C., more preferably in the range of −20 ° C. to 80 ° C., further preferably in the range of 0 to 60 ° C., and still more preferably in the range of 10 to 50. It is selected in the range of ° C.

When using a fuel that is a gas at normal temperature (25 ° C.) / Normal pressure (gauge pressure 0 MPa), such as city gas, GHSV is selected between 10 and 20000 h ⁻¹ , preferably between 10 and 7000 h ⁻¹ . When GHSV is lower than 10 h ⁻¹ , the desulfurization performance is sufficient, but since a desulfurization catalyst is used more than necessary, the desulfurizer becomes excessive, which is not preferable. On the other hand, if GHSV is larger than 20000 h ⁻¹ , sufficient desulfurization performance cannot be obtained. In addition, liquid fuel can also be used as fuel, and in that case, a range of 0.01 to 100 h ⁻¹ can be selected as LHSV.

  The pressure conditions are usually selected in the range of normal pressure to 1 MPa (gauge pressure, the same shall apply hereinafter), preferably normal pressure to 0.5 MPa, and more preferably normal pressure to 0.2 MPa. Most preferred.

<Control processing>
Next, an example of the control process of the fuel cell system 1 according to the present embodiment will be described with reference to FIG. The process shown in FIG. 3 is repeatedly executed at a predetermined timing in the control unit 11 during the regeneration process of the desulfurization catalyst 2a. The regeneration process of the desulfurization catalyst 2a is performed, for example, at the time of stopping the fuel cell system 1 by periodic inspection or the like.

  As shown in FIG. 3, the supply control unit 101 outputs a control signal to the fuel supply unit 7 and stops the supply of hydrocarbon fuel (step S10). The heating control unit 102 starts heating the desulfurization catalyst 2a by activating the heating unit 21 (step S20). As a result, the temperature of the desulfurization catalyst 2a increases. The temperature detector 103 detects the temperature T of the desulfurization catalyst 2a (or a temperature T indirectly indicating the temperature of the desulfurization catalyst 2a) based on the detection result of the temperature sensor 23 (step S30).

  The determination unit 104 determines whether or not the temperature T detected in S30 is equal to or higher than a preset threshold value X1 (step S40). By this processing, the determination unit 104 determines whether or not the temperature of the desulfurization catalyst 2a is within the regeneration temperature range. The threshold value X1 is not particularly limited as long as it can be determined that the temperature of the desulfurization catalyst 2a is within the regeneration temperature range. For example, when a value directly indicating the temperature of the desulfurization catalyst 2a is used as the temperature T, the threshold value X1 is set to any value of 100 ° C. or more and 250 ° C. or less which is the regeneration temperature range. In addition, when a value indirectly indicating the temperature of the desulfurization catalyst 2a (for example, the temperature of the casing of the desulfurization unit 2) is used as the temperature T, the threshold value X1 depends on the measurement location of the temperature of the desulfurization unit 2. Is set to a value that satisfies the condition of 100 ° C. or more and 250 ° C. or less. When the determination unit 104 determines that the temperature T is lower than the threshold value X1 in S40, the processes of S30 and S40 are executed again.

  If it is determined in S40 that the temperature T is equal to or higher than the threshold value X1, the determination unit 104 determines that the desulfurization catalyst 2a has reached the regeneration temperature. In this state, the desulfurization catalyst 2a is regenerated by desorbing the adsorbed moisture. The heating control unit 102 adjusts the heating state by the heating unit 21 so that the state is maintained (step S50). For example, the optimum temperature most suitable for the regeneration treatment of the desulfurization catalyst 2a among the regeneration temperatures may be set, and the temperature T may be maintained at the optimum temperature by the heating control unit 102 controlling the heating unit 21. Alternatively, the upper limit value and the lower limit value of the temperature T are set, and the heating control unit 102 turns off the heating unit 21 (or suppresses the output) when the temperature T reaches the upper limit value, and the temperature T reaches the lower limit value. The heating unit 21 may be turned on (or the output is increased).

  Moreover, the supply control part 101 outputs a control signal to the fluid supply part 22, and supplies a fluid to the desulfurization part 2 (step S60). As a result, moisture desorbed from the desulfurization catalyst 2a is removed from the desulfurization section 2. The determination unit 104 determines whether or not the regeneration process for the desulfurization catalyst 2a has been completed (step S70). The judgment condition for completion of the reproduction process is not particularly limited. For example, the determination unit 104 may determine that the reproduction process is complete when a predetermined time has elapsed. Or when the sensor is arrange | positioned in the downstream of the desulfurization part 2, the determination part 104 may determine with completion | finish of a regeneration process, when a water | moisture content is no longer detected in a fluid. If the determination unit 104 determines in S70 that the reproduction process has not been completed, the processes in S50, S60, and 70 are executed again. The fluid supply may be performed continuously during the regeneration process or may be performed at predetermined timings.

  When the determination unit 104 determines that the regeneration process is completed in S70, the heating control unit 102 stops heating the desulfurization catalyst 2a by the heating unit 21 (step S80). As a result, the temperature of the desulfurization catalyst 2a decreases. The temperature detector 103 detects the temperature T of the desulfurization catalyst 2a (or a temperature T indirectly indicating the temperature of the desulfurization catalyst 2a) based on the detection result of the temperature sensor 23 (step S90).

  The determination unit 104 determines whether or not the temperature T detected in S90 is equal to or lower than a preset threshold value X2 (step S100). With this process, the determination unit 104 determines whether the temperature of the desulfurization catalyst 2a is within a range where the hydrocarbon-based fuel can be efficiently desulfurized. The threshold value X2 is not particularly limited as long as it can be determined that the temperature of the desulfurization catalyst 2a is 60 ° C. or less. For example, when a value directly indicating the temperature of the desulfurization catalyst 2a is used as the temperature T, the threshold value X2 is set to any value of 60 ° C. or less. In addition, when a value indirectly indicating the temperature of the desulfurization catalyst 2a (for example, the temperature of the casing of the desulfurization unit 2) is used as the temperature T, the threshold value X2 depends on the measurement location of the temperature of the desulfurization unit 2. The temperature is set to a value that satisfies the condition of 60 ° C. or less. When the determination unit 104 determines in S100 that the temperature T is higher than the threshold value X2, the processes of S90 and S100 are executed again. When the determination unit 104 determines in S100 that the temperature T is equal to or less than the threshold value X2, the control process illustrated in FIG. 3 ends. Thereby, the desulfurization preparation of the hydrocarbon fuel by the desulfurization catalyst 2a is completed. Thereafter, the fuel cell system 1 shifts to normal operation, and the process is started again from S10 at the timing of the next regeneration process.

<Action and effect>
In the fuel cell system 1 according to the present embodiment, the heating control unit 102 of the control unit 11 controls the heating unit 21 so that the desulfurization catalyst 2a only desorbs moisture and does not desorb sulfur compounds (for example, 100 ° C. or higher and 250 ° C. or lower). When the desulfurization catalyst 2a adsorbs moisture due to moisture contained in the hydrocarbon-based fuel, the heating unit 21 heats the desulfurization catalyst 2a, so that the temperature of the desulfurization catalyst 2a is desorbed only by moisture and the sulfur compound is removed. The temperature is raised to a temperature that does not desorb (for example, 100 ° C. or more and 250 ° C. or less). Further, the fluid supply unit 22 supplies a fluid to the desulfurization unit 2. As a result, the moisture adsorbed on the desulfurization catalyst 2a is desorbed from the desulfurization catalyst 2a and is removed from the desulfurization section 2 together with the fluid. Further, the sulfur compound adsorbed on the desulfurization catalyst 2a is maintained in the state of being adsorbed on the desulfurization catalyst 2a without being desorbed and flowing to the hydrogen generation unit 4 side. By such regeneration treatment, the life of the desulfurization catalyst 2a is restored. As described above, it is possible to suppress the life reduction of the desulfurization catalyst 2a of the desulfurization section 2.

[Second Embodiment]
As shown in FIG. 4, in the fuel cell system 1 according to the second embodiment, the desulfurization unit 2 includes a first reaction unit 2A on the upstream side and a second reaction unit 2B on the downstream side. The first reaction unit 2A and the second reaction unit 2B are connected in series. The method of dividing the reaction parts 2A and 2B is not particularly limited. For example, two casings filled with the desulfurization catalyst 2a are arranged on the upstream side and the downstream side, and the upstream casing is defined as the first reaction part 2A. The downstream casing may be used as the second reaction section. Alternatively, in one casing, the upstream region may be the first reaction unit 2A, and the downstream region may be the second reaction unit 2B. The fuel cell system 1 according to the second embodiment includes a first heating unit 21A that heats the desulfurization catalyst 2a of the first reaction unit 2A, and a first temperature that detects the temperature of the desulfurization catalyst 2a of the first reaction unit 2A. Temperature sensor 23A, a second heating unit 21B for heating the desulfurization catalyst 2a of the second reaction unit 2B, a second temperature sensor 23B for detecting the temperature of the desulfurization catalyst 2a of the second reaction unit 2B, Is further provided. In the fuel cell system 1 according to the second embodiment, the hydrocarbon-based fuel supplied from the fuel supply unit 7 functions as a fluid that removes moisture desorbed from the desulfurization catalyst 2a. The fuel supply unit 7 functions as the fluid supply unit 22.

<Control processing>
With reference to FIG. 5, an example of the control process of the fuel cell system 1 according to the second embodiment will be described. The process shown in FIG. 5 is repeatedly executed at a predetermined timing in the control unit 11 during the regeneration process of the desulfurization catalyst 2a.

  As shown in FIG. 5, the supply control unit 101 outputs a control signal to the fuel supply unit 7 to supply hydrocarbon fuel (step S110). When the fuel supply unit 7 has already been driven since the normal operation, the supply state is continued. The heating control unit 102 activates the first heating unit 21A and maintains the stopped state of the second heating unit 21B (step S120). As a result, the temperature of the desulfurization catalyst 2a of the first reaction unit 2A is increased, and the temperature of the desulfurization catalyst 2a of the second reaction unit 2B is maintained at a low temperature. The temperature detection unit 103 detects the temperature T1 of the desulfurization catalyst 2a of the first reaction unit 2A (or a temperature T1 that indirectly indicates the temperature of the desulfurization catalyst 2a) based on the detection result of the first temperature sensor 23A. (Step S130).

  The determination unit 104 determines whether or not the temperature T1 detected in S130 is equal to or higher than a preset threshold value X1 (step S140). By this processing, the determination unit 104 determines whether or not the temperature of the desulfurization catalyst 2a of the first reaction unit 2A is within the regeneration temperature range. If the determination unit 104 determines that the temperature T1 is lower than the threshold value X1 in S140, the processes of S130 and S140 are executed again.

  When it is determined in S140 that the temperature T1 is equal to or higher than the threshold value X1, the determination unit 104 determines that the desulfurization catalyst 2a of the first reaction unit 2A has reached the regeneration temperature. In this state, the desulfurization catalyst 2a of the first reaction unit 2A is regenerated by desorbing the adsorbed moisture. The heating control unit 102 adjusts the heating state by the first heating unit 21A so that the state is maintained (step S150). At this time, the supply control unit 101 supplies the hydrocarbon fuel to the desulfurization unit 2 by the fuel supply unit 7. Thereby, the moisture desorbed from the desulfurization catalyst 2a of the first reaction unit 2A is removed from the desulfurization unit 2. On the other hand, since the desulfurization catalyst 2a of the second reaction unit 2B is not heated, the sulfur compound of the hydrocarbon fuel is removed.

  The determination unit 104 determines whether or not the regeneration process of the desulfurization catalyst 2a of the first reaction unit 2A has been completed (step S160). If the determination unit 104 determines in S160 that the reproduction process has not been completed, the processes in S150 and S160 are executed again. The fluid supply may be performed continuously during the regeneration process or may be performed at predetermined timings.

  When the determination unit 104 determines that the regeneration process is complete in S160, the heating control unit 102 stops the heating of the desulfurization catalyst 2a of the first reaction unit 2A by the first heating unit 21A (step S170). As a result, the temperature of the desulfurization catalyst 2a of the first reaction section 2A is lowered. The temperature detection unit 103 detects the temperature T1 of the desulfurization catalyst 2a of the first reaction unit 2A (or a temperature T1 that indirectly indicates the temperature of the desulfurization catalyst 2a) based on the detection result of the first temperature sensor 23A. (Step S180).

  The determination unit 104 determines whether or not the temperature T1 detected in S180 is equal to or lower than a preset threshold value X2 (step S190). By this processing, the determination unit 104 determines whether the temperature of the desulfurization catalyst 2a of the first reaction unit 2A is within a range where the hydrocarbon fuel can be efficiently desulfurized. When the determination unit 104 determines in S190 that the temperature T1 is greater than the threshold value X2, the processes in S180 and S190 are executed again. When the determination unit 104 determines that the temperature T1 is equal to or lower than the threshold value X2 in S190, the heating control unit 102 maintains the stopped state of the first heating unit 21A and activates the second heating unit 21B (step S200). ). As a result, the temperature of the desulfurization catalyst 2a of the second reaction unit 2B is increased, and the temperature of the desulfurization catalyst 2a of the first reaction unit 2A is maintained at a low temperature. The temperature detection unit 103 detects the temperature T2 of the desulfurization catalyst 2a of the second reaction unit 2B (or a temperature T2 that indirectly indicates the temperature of the desulfurization catalyst 2a) based on the detection result of the second temperature sensor 23B. (Step S210).

  The determination unit 104 determines whether or not the temperature T2 detected in S210 is equal to or higher than a preset threshold value X1 (step S220). With this process, the determination unit 104 determines whether the temperature of the desulfurization catalyst 2a of the second reaction unit 2B is within the regeneration temperature range. If the determination unit 104 determines in S220 that the temperature T2 is lower than the threshold value X1, the processes in S210 and S220 are executed again.

  If it is determined in S220 that the temperature T2 is equal to or higher than the threshold value X1, the determination unit 104 determines that the desulfurization catalyst 2a of the second reaction unit 2B has reached the regeneration temperature. In this state, the desulfurization catalyst 2a of the second reaction unit 2B is regenerated by desorbing the adsorbed moisture. The heating control unit 102 adjusts the heating state by the second heating unit 21B so that the state is maintained (step S230). At this time, the supply control unit 101 supplies the hydrocarbon fuel to the desulfurization unit 2 by the fuel supply unit 7. As a result, moisture desorbed from the desulfurization catalyst 2a of the second reaction unit 2B is removed from the desulfurization unit 2. On the other hand, since the desulfurization catalyst 2a of the first reaction unit 2A is not heated, the sulfur compound of the hydrocarbon fuel is removed.

  The determination unit 104 determines whether or not the regeneration process of the desulfurization catalyst 2a of the second reaction unit 2B has been completed (step S240). If the determination unit 104 determines in S240 that the reproduction process has not been completed, the processes in S230 and S240 are executed again. The fluid supply may be performed continuously during the regeneration process or may be performed at predetermined timings.

  When the determination unit 104 determines that the regeneration process is completed in S240, the heating control unit 102 stops the heating of the desulfurization catalyst 2a of the second reaction unit 2B by the second heating unit 21B (step S250). As a result, the temperature of the desulfurization catalyst 2a of the second reaction section 2B decreases. The temperature detection unit 103 detects the temperature T2 of the desulfurization catalyst 2a of the second reaction unit 2B (or a temperature T2 that indirectly indicates the temperature of the desulfurization catalyst 2a) based on the detection result of the second temperature sensor 23B. (Step S260).

  The determination unit 104 determines whether or not the temperature T2 detected in S260 is equal to or lower than a preset threshold value X2 (step S270). By this processing, the determination unit 104 determines whether or not the temperature of the desulfurization catalyst 2a of the second reaction unit 2B is within a range where the hydrocarbon fuel can be efficiently desulfurized. If the determination unit 104 determines in S270 that the temperature T2 is greater than the threshold value X2, the processes of S260 and S270 are executed again. When the determination unit 104 determines in S270 that the temperature T2 is equal to or lower than the threshold value X2, the control process illustrated in FIG. 5 ends. Thereby, the desulfurization preparation of the hydrocarbon fuel by the desulfurization catalyst 2a is completed. Thereafter, the fuel cell system 1 shifts to normal operation, and the process is started again from S110 at the timing of the next regeneration process. However, since at least the first reaction unit 2B is in a desulfurizable state, S260 and S270 may be omitted and the normal operation may be performed. Moreover, although switching of the 1st heating part 21A and the 2nd heating part 21B is performed only once, you may repeat several times. Moreover, you may heat from the 2nd heating part 21B previously. However, since the water from the first reaction unit 2A passes through the second reaction unit 2B when the first heating unit 21A is heated, it is preferable to heat in the order from the upstream side to the downstream side.

<Action and effect>
As described above, in the fuel cell system 1 according to the second embodiment, the desulfurization unit 2 includes the first reaction unit 2A and the second reaction unit 2B, and the heating unit 21 includes the first reaction unit 2A. It has the 1st heating part 21A which heats the desulfurization catalyst 2a, and the 2nd heating part 21B which heats the desulfurization catalyst 2a of the 2nd reaction part 2B. The first reaction unit 2A and the second reaction unit 2B are connected in series. When one of the first heating unit 21A and the second heating unit 21B is heating, the other stops heating. The fuel supply unit 7 that functions as a fluid supply unit supplies hydrocarbon fuel to the desulfurization unit 2 as a fluid. As a result, the desulfurization catalyst 2a related to the first reaction section 2A becomes a regeneration treatment state when the temperature becomes high, and the desulfurization catalyst 2a related to the second reaction section 2B becomes a state capable of desulfurization when the temperature becomes low. When hydrocarbon fuel is supplied to the desulfurization unit 2 in this state, the hydrocarbon fuel removes moisture desorbed from the desulfurization catalyst 2a in the first reaction unit 2A, and in the second reaction unit 2B. The sulfur compound is removed by the desulfurization catalyst 2a. Next, by switching the heating side and the heating stop side in the heating units 21A and 21B, the hydrocarbon-based fuel removes moisture desorbed from the desulfurization catalyst 2a in the second reaction unit 2B, and the first reaction unit In 2A, the sulfur compound is removed by the desulfurization catalyst 2a. When using a hydrocarbon-based fuel as the fluid, it is preferable to remove sulfur compounds in the fluid upstream of the hydrogen generator 4, but the desulfurization catalyst 2 a that has reached a high temperature has reduced desulfurization efficiency. According to the fuel cell system 1 according to the second embodiment, even when a hydrocarbon-based fuel is used as the fluid, the sulfur compound toward the hydrogen generating unit 4 side is surely removed, and all of the desulfurizing unit 2 is removed. Moisture of the desulfurization catalyst over the region can be removed. In the fuel cell system 1 according to the second embodiment, during the continuous operation of the fuel cell system, the reaction units 2A and 2B are alternately heated to remove moisture from the desulfurization catalyst 2a while removing sulfur compounds from the hydrocarbon fuel. And can be discharged together with the hydrocarbon-based fuel to the hydrogen generator 4. In this embodiment, since the sulfur compound of the hydrocarbon fuel is removed in any one of the reaction units 2A and 2B, the desulfurization catalyst 2a can be continuously regenerated. Since the hydrocarbon fuel can be used as a fluid for removing moisture and the sulfur compound of the hydrocarbon fuel can be removed, the hydrocarbon fuel may be sent to the hydrogen generation unit 4. It is possible to omit the fluid supply unit 22 and the like.

[Third embodiment]
As shown in FIG. 6, in the fuel cell system 1 according to the third embodiment, the desulfurization unit 2 includes a first reaction unit 2A and a second reaction unit 2B, and the first reaction unit 2A and the second reaction unit 2B. Reaction parts 2B are connected in parallel. That is, the fuel supply unit 7, the fluid supply unit 22, and the hydrogen generation unit 4 are connected to both the first reaction unit 2A and the second reaction unit 2B. The method of dividing the reaction parts 2A and 2B is not particularly limited. For example, two casings filled with the desulfurization catalyst 2a are arranged in parallel, one casing is used as the first reaction part 2A, and the other casing is used as the first casing. It is good also as 2 reaction parts. Alternatively, in one casing, one region may be the first reaction unit 2A and the other region may be the second reaction unit 2B.

  In the fuel cell system 1 according to the third embodiment, the reaction units 2A and 2B can be alternately heated during the continuous operation of the fuel cell system. Water is removed from the desulfurization catalyst 2a in one heated reaction section and fluid is removed from the fluid supply section 22 so that the exhaust gas is discharged to the atmosphere or burned in the off-gas combustion section 6. After exhausting to the atmosphere. As the fluid, a hydrocarbon-based fuel or an oxidant (air) can be used. In this case, the fluid supply unit 22 is shared with the fuel supply unit 7 or the oxidant supply unit 9, thereby the fluid supply unit. 22 can be omitted. The other unheated reaction section is desulfurized by supplying a hydrocarbon fuel from the fuel supply section 7, and the hydrocarbon fuel from which the sulfur compound has been removed is supplied to the hydrogen generation section 4. As a control example, similar to the control process in the second embodiment, the temperature T1, T2 of each reaction unit 2A, 2B is monitored and the heating control is performed, so that the regeneration process and the desulfurization process can be switched. . It should be noted that the supply destination of hydrocarbon fuel from the fuel supply section 7, the supply destination of fluid from the fluid supply section 22, the exhaust gas from the reaction sections 2 A and 2 B (desulfurized hydrocarbon fuel, or The switching of the discharge destination of the fluid from which moisture has been removed can be controlled by opening and closing a valve provided in a pipe or the like.

<Action and effect>
As described above, in the fuel cell system 1 according to the third embodiment, the desulfurization unit 2 includes the first reaction unit 2A and the second reaction unit 2B, and the heating unit 21 includes the first reaction unit 2A. It has the 1st heating part 21A which heats the desulfurization catalyst 2a, and the 2nd heating part 21B which heats the desulfurization catalyst 2a of the 2nd reaction part 2B. The first reaction unit 2A and the second reaction unit 2B are connected in parallel. When one of the first heating unit 21A and the second heating unit 21B is heating, the other stops heating. As a result, the desulfurization catalyst 2a related to the first reaction section 2A becomes a regeneration treatment state when the temperature becomes high, and the desulfurization catalyst 2a related to the second reaction section 2B becomes a state capable of desulfurization when the temperature becomes low. In this state, by supplying the fluid from the fluid supply unit 22 to the first reaction unit 2A, the moisture desorbed from the desulfurization catalyst 2a is removed in the first reaction unit 2A, and the second reaction is performed from the fuel supply unit 7. By supplying the hydrocarbon fuel to the part 2B, the sulfur compound of the hydrocarbon fuel is removed by the desulfurization catalyst 2a in the second reaction part 2B. Next, in the heating units 21A and 21B, the heating side and the heating stop side are switched, and the fluid supply destination of the fluid supply unit 22 and the hydrocarbon-based fuel supply destination of the fuel supply unit 7 are switched, so that the second reaction is performed. In part 2B, water desorbed from the desulfurization catalyst 2a is removed, and in the first reaction part 2A, sulfur compounds of hydrocarbon fuel are removed by the desulfurization catalyst 2a. In the fuel cell system 1 according to the third embodiment, during the continuous operation of the fuel cell system, the reaction units 2A and 2B are alternately heated, and the hydrocarbon fuel from which the sulfur compounds have been removed is discharged to the hydrogen generation unit 4 to obtain moisture. The fluid from which the gas is removed can be exhausted or burned in the off-gas combustion unit 6 to be exhausted. In this embodiment, since the sulfur compound of the hydrocarbon fuel is removed in any one of the reaction units 2A and 2B, the desulfurization catalyst 2a can be continuously regenerated.

  As mentioned above, although preferred embodiment of this invention was described, the fuel cell system which concerns on this invention is not limited to the said fuel cell system 1 which concerns on embodiment. For example, in the second embodiment and the third embodiment, the desulfurization unit 2 has two reaction units, but may have three or more.

<Experimental example 1>
Next, an experimental example for deriving the regeneration temperature of the desulfurization catalyst 2a will be described. First, in a fixed bed flow type reaction tube filled with 6 ml of desulfurization catalyst 1 as desulfurization section 2, a city gas having a composition shown in Table 1 as a hydrocarbon fuel (4.0 mass ppm of DMS (dimethyl sulfide) as a sulfur content) is used. Content and water content of 1% by volume) were circulated at GHSV = 5000 h ⁻¹ at normal pressure and 30 ° C. The sulfur atom equivalent concentration is measured by SCD (sulfur Chemiluminescence Detector) gas chromatography based on the total amount of hydrocarbon fuel at the outlet of the reaction tube. After the experiment is started, the hydrocarbon fuel is supplied until the concentration in terms of sulfur atom is 0.05 ppm by volume or more based on the total amount of the hydrocarbon fuel in the outlet gas.

Desulfurization catalyst 1: AgX (silver supported X-type zeolite)
Hydrocarbon fuel: having the composition shown in Table 1 and 4.0 mass of DMS (dimethyl sulfide)
Contains ppm (sulfur atom equivalent concentration based on the total amount of hydrocarbon fuel)
City gas The volume ratio of moisture in the entire hydrocarbon fuel: 1% by volume

(Preparation method of desulfurization catalyst 1)
A silver nitrate aqueous solution was prepared by adding 600 ml of distilled water to 19 g of silver nitrate. Next, the mixture was mixed with 50 g of commercially available NaX-type zeolite powder with SiO ₂ / Al ₂ O ₃ (molar ratio) = 2.5 while stirring, and ion exchange was performed. Then, it was washed with distilled water so as not to leave nitrate radicals. After washing, it was dried overnight at 180 ° C. in air. 5 g of an alumina binder was mixed with 30 g of the powdered silver exchanged zeolite after drying, and extrusion molding was performed at 1 mmφ to prepare a desulfurization catalyst 1. The amount of Ag supported in the desulfurization catalyst 1 was 25% by mass based on the zeolite.

Next, the desulfurization catalyst after the sulfur atom equivalent concentration based on the total amount of the hydrocarbon-based fuel of the outlet gas reaches 0.05 ppm by volume is heated to raise the temperature. The weight reduction rate of the desulfurization catalyst at each temperature is measured, and the detection intensity of the substance desorbed from the desulfurization catalyst is measured. The experimental results are shown in FIG. In FIG. 7, the weight reduction rate of the desulfurization catalyst is shown by a graph of TG, the detection strength of moisture is shown by a graph of H ₂ O, and the detection strength of sulfur compounds is MeS (methyl mercaptan) and DMS (dimethyl sulfide). Shown in the graph. For TG, refer to the scale (weight reduction rate) on the left vertical axis, and for H ₂ O, MeS, and DMS, refer to the scale (detection intensity) on the right vertical axis. The weight reduction rate is 100% when the weight of the desulfurization catalyst including all the adsorbing substances is desorbed, and the value decreases as the entire weight decreases. The stronger the detection intensity, the greater the desorption amount of the adsorbed substance at that temperature. The TG measurement was performed using a model number R / TG-DTA2010SA / G manufactured by Bruker axs in a He atmosphere at a heating rate of 5 ° C./min.

  As understood from FIG. 7, the weight reduction rate of the desulfurization catalyst gradually decreases from 100% as the temperature of the desulfurization catalyst increases. From this, it is understood that the adsorbed substance of the desulfurization catalyst is desorbed with heating. Examining the breakdown of the adsorbed substances that have been desorbed, it is understood that the amount of desorbed water greatly increases in the vicinity of 100 ° C to 230 ° C. In particular, up to 200 ° C., the desorption amount of water shows a large value. The desorption of sulfur compounds has not been detected up to around 280 ° C. Desorption of sulfur compounds is detected in the range of 280 ° C to 330 ° C. Therefore, it is understood that in the range of 100 ° C. or higher and 250 ° C. or lower, the desulfurization catalyst efficiently desorbs moisture, while the sulfur compound is reliably maintained without desorption.

<Experimental example 2>
An experiment similar to Example 1 was performed except that the following desulfurization catalyst 2 was used as the desulfurization catalyst 2 instead of the desulfurization catalyst 1.

Desulfurization catalyst 2: CuY (copper-supported Y-type zeolite)

(Preparation method of desulfurization catalyst 2)
To 40 g of copper sulfate pentahydrate, 600 ml of distilled water was added to prepare an aqueous copper sulfate solution. Next, the mixture was mixed with 50 g of commercially available NaY-type zeolite powder having a SiO ₂ / Al ₂ O ₃ (molar ratio) = 4.5 with stirring to perform ion exchange. Then, it washed with distilled water so that a sulfate radical might not remain. After washing, it was dried overnight at 180 ° C. in an air stream. 5 g of an alumina binder was mixed with 30 g of the powdered copper-exchanged zeolite after drying, and extrusion molding was performed at 1 mmφ to obtain a desulfurization catalyst 2. The amount of copper supported in the desulfurization catalyst 2 was 10% by mass based on the carrier.

  FIG. 8 is a graph showing the results of an experimental example in which the desulfurization catalyst 2a is changed from the experimental example shown in FIG. The desulfurization catalyst 2 was applied as the desulfurization catalyst 2a, and an experiment similar to the experiment of FIG. 7 was performed.

Next, the desulfurization catalyst after the sulfur atom equivalent concentration based on the total amount of the hydrocarbon-based fuel of the outlet gas reaches 0.05 ppm by volume is heated to raise the temperature. The weight reduction rate of the desulfurization catalyst at each temperature is measured, and the detection intensity of the substance desorbed from the desulfurization catalyst is measured. The experimental results are shown in FIG. In FIG. 8, the weight reduction rate of the desulfurization catalyst is indicated by a TG graph, the moisture detection intensity is indicated by a H ₂ O graph, and the sulfur compound detection intensity is indicated by a MeS (methyl mercaptan) graph. For TG, refer to the scale on the left vertical axis, and for H ₂ O and MeS, refer to the scale on the right vertical axis. The weight reduction rate is 100% when the weight of the desulfurization catalyst including all the adsorbing substances is desorbed, and the value decreases as the entire weight decreases. The stronger the detection intensity, the greater the desorption amount of the adsorbed substance at that temperature.

  As understood from FIG. 8, the weight reduction rate of the desulfurization catalyst gradually decreases from 100% as the temperature of the desulfurization catalyst increases. From this, it is understood that the adsorbed substance of the desulfurization catalyst is desorbed with heating. Examining the breakdown of the desorbed adsorbed material, it is understood that the amount of desorbed water greatly increases from 100 ° C. and remains high up to around 320 ° C. In particular, up to 220 ° C., the desorption amount of water shows a large value. Desorption of sulfur compounds is hardly detected up to 290 ° C. The desorption of the sulfur compound is detected in the range from around 290 ° C. to 400 ° C. Therefore, it is understood that in the range of 100 ° C. or higher and 250 ° C. or lower, the desulfurization catalyst efficiently desorbs moisture, while the sulfur compound is reliably maintained without desorption. If it is 250 degrees C or less, it will be understood that a sulfur compound is hardly detected and it is more preferable.

DESCRIPTION OF SYMBOLS 1 ... Fuel cell system, 2 ... Desulfurization part, 2a ... Desulfurization catalyst, 2A ... 1st reaction part, 2B ... 2nd reaction part, 4 ... Hydrogen generation part, 5 ... Cell stack, 11 ... Control part, 21 ... Heating unit, 21A ... first heating unit, 21B ... second heating unit, 22 ... fluid supply unit, 23 ... temperature sensor, 23A ... first temperature sensor, 23B ... second temperature sensor, 101 ... supply control Part (fluid supply part), 102 ... heating control part (heating part), 103 ... temperature detection part, 104 ... determination part.

Claims (11)

A hydrogen generation unit that generates a hydrogen-containing gas using a hydrocarbon-based fuel;
A cell stack for generating power using the hydrogen-containing gas;
A fuel supply section for supplying the hydrocarbon-based fuel to the hydrogen generation section;
A desulfurization unit that is disposed upstream of the hydrogen generation unit and that adsorbs and desulfurizes the hydrocarbon fuel with a desulfurization catalyst;
A heating unit for heating the desulfurization catalyst to a temperature at which only moisture is desorbed and sulfur compounds are not desorbed ;
The heating unit heats the desulfurization catalyst to the temperature during the regeneration process for desorbing moisture adsorbed from the desulfurization catalyst, and stops heating during the desulfurization process for adsorbing and desulfurizing the hydrocarbon fuel with the desulfurization catalyst. A fuel cell system.   The fuel cell system according to claim 1, wherein the heating unit heats the desulfurization catalyst to a temperature of 100 ° C. or more and 250 ° C. or less. The desulfurization part has a first reaction part and a second reaction part,
The heating unit includes a first heating unit that heats the desulfurization catalyst of the first reaction unit, and a second heating unit that heats the desulfurization catalyst of the second reaction unit,
3. The fuel cell system according to claim 1, wherein when one of the first heating unit and the second heating unit is heating, the other stops heating. 4.   The fuel cell system according to claim 3, wherein the first reaction unit and the second reaction unit are arranged in series.   The fuel cell system according to claim 3, wherein the first reaction unit and the second reaction unit are arranged in parallel.   6. The fuel cell system according to claim 1, wherein a fluid is supplied to the desulfurization unit when the heating unit is operated.   The fuel cell system according to claim 6, wherein the fluid is the hydrocarbon fuel or an oxidant.   The fuel cell system according to any one of claims 1 to 7, further comprising a fluid supply unit that supplies a fluid to the desulfurization unit.   The fuel cell system according to any one of claims 1 to 8, wherein the desulfurization catalyst is a catalyst in which a metal is supported on zeolite.   The fuel cell system according to any one of claims 1 to 9, wherein the hydrocarbon-based fuel contains water.   The fuel cell system according to any one of claims 1 to 10, wherein the hydrocarbon fuel includes a hydrocarbon compound having 4 or less carbon atoms.

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