JP2011249234A - Fuel cell system and method of operating fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell system which is easy to use, and a method of operating the fuel cell system.SOLUTION: A reservoir device 6 reserves reformed gas generated by a reformer 12, and supplies the reserved reformed gas to a power generation module. Consequently, a hydrogen cylinder which is used before is not necessary, so the trouble to replace it is saved to lower the cost and also to improve usability.

Description

  The present invention relates to a fuel cell system that generates electric power using a fuel gas and an oxidant gas.

  In recent years, fuel cells have attracted attention because of their high efficiency regardless of the size. A fuel cell is a battery that uses a chemical reaction between an oxidant gas such as oxygen and a fuel gas such as hydrogen. A fuel cell is composed of a single cell with an electrolyte layer sandwiched between an anode called an air electrode and a cathode called a fuel electrode. A stack structure in which a plurality of layers are stacked in parallel or in series is used. The electric voltage obtained in one set of cells (single cells) is about 1 V, but a desired voltage can be supplied by using a plurality of single cells in an overlapping manner. An example of the configuration of a system that generates power using such a fuel cell is shown in FIG.

  The power generation system shown in FIG. 6 includes two power generation modules 100, a load 110 to which power generated by the power generation module 100 is supplied, a fuel line 120 that supplies fuel gas to each power generation module 100, and each power generation system. A nitrogen cylinder 130 for supplying nitrogen to the module 100 and a hydrogen cylinder 140 for supplying hydrogen gas to each power generation module 100 are provided.

  Here, the power generation module 100 includes a heat insulating container 101 that prevents internal heat from conducting to the outside, a reformer 102 provided inside the heat insulating container 101, and a stack 103 provided inside the heat insulating container 101. A heating device (not shown) provided inside the heat insulating container 101 is provided. The reformer 102 reforms a fuel gas such as a hydrocarbon supplied from the fuel line 120 and takes out hydrogen from the fuel gas. The stack 103 includes a plurality of single cells, and a separator that holds each single cell separately from other single cells and supplies an oxidant gas and a fuel gas to the single cell. Have.

  When operating such a power generation system, fuel gas such as nitrogen carbide is supplied from the fuel line 120 to the power generation module 100. Then, the power generation module 100 reforms the fuel gas into hydrogen by the reformer 102 and supplies the hydrogen to the stack 103. The stack 103 supplies a reformed gas (hydrogen) supplied from the reformer 102 and an oxidant gas such as air supplied from a compressor or the like (not shown) to each single cell. Thus, when hydrogen and oxidant gas are supplied to a single cell at a predetermined operating temperature, an electrochemical reaction occurs between the fuel electrode and the air electrode. In this state, when the separator at the upper end and the separator at the lower end of the stack 103 are connected to the load 110 as terminals, electric power is supplied to this load.

  In such a power generation system, when the stack 103 is heated up to the operating temperature at the time of starting or is lowered from the operating temperature at the time of stopping, the stack 103 needs to be in a reducing atmosphere in order to prevent deterioration (reoxidation) of the single cell. There is. For this reason, conventionally, when the power generation system is started and stopped, a gas in which a small amount of hydrogen is mixed with nitrogen is supplied from the nitrogen cylinder 130 and the hydrogen cylinder 140 to the stack 103 as a purge gas, thereby reducing the stack 103 to a reducing atmosphere. (For example, refer nonpatent literature 1.).

Hiroaki Tagawa, “Solid Oxide Fuel Cell and Global Environment”, Agne Jofusha, pp. 283-286, issued in June 1998

  However, in the conventional fuel cell system, it is necessary to replace the hydrogen cylinder 140 every time the hydrogen cylinder 140 becomes empty. Since hydrogen is expensive and requires careful handling, replacement of the hydrogen cylinder 140 is costly and laborious, and a fuel cell system that eliminates the need to replace the hydrogen cylinder has been desired.

  Accordingly, an object of the present invention is to provide a fuel cell system that is easy to use and a method for operating the fuel cell system.

  In order to solve the above-described problems, a fuel cell system according to the present invention includes at least one single cell including an electrolyte, a fuel electrode, and an air electrode, and a reformer that extracts hydrogen from a hydrocarbon gas. And at least one power generation module that generates power by supplying hydrogen taken out by the reformer to a single cell at a predetermined temperature, and a storage device that stores hydrogen and supplies the stored hydrogen to the power generation module. It is characterized by having.

  In the fuel cell system, the reformer may supply hydrogen to the single cell, and the storage device may store hydrogen that was not used for power generation in the single cell.

  In the fuel cell system, the reformer includes a first reformer that extracts hydrogen from the hydrocarbon gas and supplies the hydrogen to the single cell, and a second reformer that extracts hydrogen from the hydrocarbon gas and supplies the hydrogen to the storage device. You may make it comprise from a reformer.

  The fuel cell system may include a plurality of power generation modules, and the storage device may store hydrogen generated by each power generation module and supply hydrogen to each power generation module.

  The fuel cell system may further include a nitrogen supply device that supplies nitrogen gas to the power generation module.

  The operating method of the fuel cell system according to the present invention includes an extraction step for extracting hydrogen from a hydrocarbon gas, and a single cell composed of an electrolyte, a fuel electrode, and an air electrode using the hydrogen extracted by the extraction step. A power generation step of generating power with the power generation module; a storage step of storing hydrogen; and a supply step of supplying hydrogen stored in the storage step to the single cell when the power generation module is started or stopped Is.

  In the operation method of the fuel cell system, the storage step may store hydrogen that was not used for power generation of the single cell in the power generation step.

  In the operation method of the fuel cell system, the storage step may store hydrogen extracted in the extraction step.

  Further, in the operation method of the fuel cell system, when any power generation module is stopped during power generation by a plurality of power generation modules, the fuel usage rate for the power generation module during power generation is lowered and stored in the storage step. Hydrogen may be supplied to the power generation module that is generating power.

  According to the present invention, since the hydrogen taken out by the reformer is stored and the storage device for supplying the stored hydrogen to the power generation module is provided, it is not necessary to replace the hydrogen cylinder.

FIG. 1 is a diagram schematically showing a configuration of a fuel cell system according to the present invention. FIG. 2 is a diagram schematically showing the configuration of another fuel cell system according to the present invention. FIG. 3 is a diagram schematically showing the configuration of another fuel cell system according to the present invention. FIG. 4 is a graph showing the fuel utilization rate of a single cell in a flat plate solid oxide fuel cell. FIG. 5 is a diagram schematically showing the configuration of another fuel cell system according to the present invention. FIG. 6 is a diagram schematically showing a configuration of a conventional fuel cell system.

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

[First Embodiment]
First, a first embodiment according to the present invention will be described.

<Configuration of fuel cell system>
As shown in FIG. 1, the fuel cell system according to the present embodiment includes a power generation module 1, a load 2 to which power generated by the power generation module 1 is supplied, and a fuel that supplies fuel gas to the power generation module 1. A line 3, a nitrogen cylinder 4 that supplies nitrogen to the power generation module 1, a water condenser 5 that removes moisture from the unreacted reformed gas in the power generation module 1, and a modification in which moisture has been removed by the water condenser 5. And a storage device 6 for storing the quality gas.

  The power generation module 1 includes a heat insulating container 11 that prevents internal heat from conducting to the outside, a reformer 12 provided inside the heat insulating container 11, a stack 13 provided inside the heat insulating container 11, a heat insulating container 11 is provided with a heating device (not shown) provided inside, and has a heat self-supporting function. Here, the reformer 12 uses the heat generated when the stack 13 generates power to reform the fuel gas such as hydrocarbons supplied from the fuel line 3 and takes out hydrogen from the fuel gas. The extracted hydrogen (reformed gas) is supplied to the stack 13. The stack 13 includes a plurality of single cells, and a separator that holds each single cell separately from other single cells and supplies an oxidant gas and a fuel gas to the single cell. Have.

  The water condenser 5 is composed of a known condenser, and removes moisture from the unreacted reformed gas supplied from the stack 13. The reformed gas (hydrogen) from which moisture has been removed is sent to the storage device 6.

  The storage device 6 includes a well-known gas tank, and stores hydrogen sent from the water condenser 5. The stored hydrogen is supplied to the stack 13 through the water condenser 5 and the reformer 12, and is used as a pre-purge gas when starting or stopping the fuel cell system. Hydrogen cylinders used in conventional power generation systems are not supplied with hydrogen from the outside, and must be replaced when empty. On the other hand, since the storage device 6 is supplied with hydrogen from the power generation module 1 via the water condenser 5, it does not need to be replaced like a conventional hydrogen cylinder.

<Operation of fuel cell system>
Next, the operation of the fuel cell system according to the present embodiment will be described.

  When starting up the power generation system, first, the temperature of the power generation module 1 is raised by the heating device. At this time, a gas obtained by mixing a small amount of hydrogen with nitrogen from the nitrogen cylinder 4 and the storage device 6 is supplied to the stack 13 as a purge gas. . Thereby, since the stack 13 is in a reducing atmosphere, deterioration (re-oxidation) of the single cell can be prevented. When starting up the power generation system for the first time, hydrogen may be stored in the storage device 6 in advance and used as a purge gas.

  When the power generation module 1 reaches a predetermined temperature, a fuel gas such as nitrogen carbide is supplied from the fuel line 3 to the power generation module 1. The power generation module 1 reforms the fuel gas into hydrogen by the reformer 12 and supplies the hydrogen to the stack 13. The stack 13 supplies a reformed gas (hydrogen) supplied from the reformer 12 and an oxidant gas such as air supplied from a compressor or the like (not shown) to each single cell. Thus, when hydrogen and oxidant gas are supplied to a single cell at a predetermined operating temperature, an electrochemical reaction occurs between the fuel electrode and the air electrode. In such a state, when the upper end separator and the lower end separator of the stack 13 are connected to the load 2 as terminals, power is supplied to the load.

  During power generation in this way, out of the reformed gas supplied from the reformer 12 to the stack 13, the unreacted reformed gas in the stack 13 is sent from the stack 13 to the water condenser 5. The reformed gas (hydrogen) from which water has been removed by the water condenser 5 is sent to the storage device 6 and stored in the storage device 6. The hydrogen stored in the storage device 6 is used as a purge gas at the time of start-up described above or at a stop described later. This eliminates the trouble of periodically replacing the hydrogen tank as in the case of a conventionally used hydrogen tank, so that it is easy to use.

  When power generation is stopped, the heating device is stopped and the supply of fuel gas is stopped. At this time, a gas obtained by mixing a small amount of hydrogen with nitrogen from the nitrogen cylinder 4 and the storage device 6 is supplied to the stack 13 as a purge gas. . Thereby, since the stack 13 is in a reducing atmosphere, deterioration (re-oxidation) of the single cell can be prevented.

  As described above, according to the present embodiment, hydrogen gas is stored by providing the storage device 6 that stores the reformed gas generated by the reformer 12 and supplies the stored reformed gas to the power generation module. A cylinder can be dispensed with. As described above, since the replacement of the hydrogen cylinder is unnecessary, the cost can be reduced and the usability can be improved.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. The fuel cell system according to the present embodiment is provided with two reformers in the power generation module shown in the first embodiment, and the configuration other than the power generation module is the same as in the first embodiment. It is equivalent to the form. Therefore, in this embodiment, the same name and code | symbol are attached | subjected to the component equivalent to 1st Embodiment, and description is abbreviate | omitted suitably.

  As shown in FIG. 2, the fuel cell system according to the present embodiment includes a power generation module 1 ′ having a thermal autonomous function, a load 2 to which power generated by the power generation module 1 ′ is supplied, and the power generation module 1. A fuel line 3 for supplying fuel gas to ', a nitrogen cylinder 4 for supplying nitrogen to the power generation module 1', a water condenser 5 for removing moisture from the unreacted reformed gas in the power generation module 1 ', and this water And a storage device 6 for storing the reformed gas from which moisture has been removed by the condenser 5.

  The power generation module 1 ′ is provided in a heat insulating container 11 that prevents internal heat from conducting to the outside, a reformer 12 a and a reformer 12 b provided in the heat insulating container 11, and a heat insulating container 11. A stack 13 and a heating device (not shown) provided inside the heat insulating container 11 are provided.

  Here, the reformers 12a and 12b use the heat generated when the stack 13 generates power to reform the fuel gas such as hydrocarbons supplied from the fuel line 3 to form a reformed gas made of hydrogen. Is generated. The reformed gas generated by the reformer 12 a is supplied to the stack 13. On the other hand, the reformed gas generated by the reformer 12 b is supplied to the water condenser 5. The reformed gas from which moisture has been removed by the water condenser 5 is sent to the storage device 6 and stored.

  Thus, in the present embodiment, the reformer gas can be reliably stored by the storage device 6 by providing the two reformers 12a and 12b. Further, since the reformed gas is sent to the storage device 6 without passing through the stack 13, it is possible to prevent reaction products of the reformed gas in the stack 13 from entering the storage device 6, and impurities other than hydrogen Can be stored in the storage device 6.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. In addition, the fuel cell system according to the present embodiment is provided with ten power generation modules shown in the first embodiment, and other configurations are the same as those in the first embodiment. Therefore, in this embodiment, the same name and code | symbol are attached | subjected to the component equivalent to 1st Embodiment, and description is abbreviate | omitted suitably.

  As shown in FIG. 3, the fuel cell system according to the present embodiment includes ten power generation modules 1 a to 1 j that are electrically connected in parallel to each other and have the same configuration, and the power generation modules 1 a to 1 j generate power. A load 2 to which the generated power is supplied, a fuel line 3 that supplies fuel gas to each of the power generation modules 1a to 1j, a nitrogen cylinder 4 that supplies nitrogen to each of the power generation modules 1a to 1n, and the power generation modules 1a to 1j A water condenser 5 that removes moisture from the unreacted reformed gas and a storage device 6 that stores the reformed gas from which moisture has been removed by the water condenser 5 are provided.

  Thus, even when a plurality of power generation modules are provided, it is possible to achieve the same effects as those of the first embodiment described above.

  In addition, by providing a plurality of power generation modules 1a to 1j, even if a power generation module has to be replaced due to a failure during operation or inspection, it is possible to generate power other than this power generation module. The power supplied to the load 2 by the module can be maintained. This principle will be described with reference to FIG.

  FIG. 4 is a measurement result of the fuel utilization rate of a single cell in a flat plate type solid oxide fuel cell. Here, the fuel utilization rate indicates the ratio of the amount of fuel used for the actual power generation reaction in the supplied amount of fuel. As can be seen from FIG. 4, when the fuel utilization rate is lowered from 85% to 34%, the output of the single cell can be increased to 1.11 times. When the fuel utilization rate of the battery module is lowered in this way, the power generation output increases. Therefore, by adding the gas stored in the storage device 6 to increase the fuel supply and lower the fuel utilization rate per cell, the power to the load can be reduced. Can keep the supply. For example, even if one power generation module out of 10 fuel cell systems that are normally operating at a fuel utilization rate of 85% goes down, the remaining nine power generation modules are stored using the gas stored in the storage device 6. By temporarily reducing the fuel utilization rate to 34%, the power supplied to the load 2 can be maintained without increasing the fuel gas consumption flow rate.

  Thus, according to the present embodiment, by connecting a plurality of power generation modules 1a to 1j in parallel, even if one power generation module stops operating, the supply of fuel gas does not increase, that is, the system The output of the entire system can be temporarily maintained without reducing the efficiency. Thereby, it is not necessary to provide an extra power generation module or secondary battery in preparation for a failure.

  The fuel utilization rate of 34% shown in FIG. 4 is within the feasible control range obtained from the experimental results. If the number of power generation modules is increased further, it becomes difficult to maintain the output only by controlling the fuel utilization rate. Therefore, the number of power generation modules is desirably 10 or less.

  In the present embodiment, the output scale of one power generation module is desirably 1.5 kW or more in consideration of the heat insulation performance of the heat insulation container 11 and the necessity of the combustor. That is, when a power generation operation test was performed by covering a 1.5 kW class power generation module (not provided with a reforming function) with a heat insulating container, the temperature in the stack at a rated 800 ° C. became 880 ° C. As described above, when the output scale of the power generation module increases, the heat necessary for gas reforming can be supplemented by its own heat generation, and when the output scale increases further, the heat for reforming the gas exceeding its own power generation capacity. Therefore, the output scale of one power generation module is preferably 1.5 kW or more.

  In the present embodiment, the case where the power generation modules 1a to 1j have the same configuration as that of the power generation module 1 described in the first embodiment has been described as an example. Needless to say, the power generation module 1 ′ described in the embodiment may have the same configuration.

  Further, in the present embodiment and the first and second embodiments described above, the reformed gas may contain not only hydrogen but also carbon monoxide and water, and such reformed gas is stored in the storage device. 6 may be stored. Therefore, as shown in FIG. 5, a PSA (Pressure Swing Absorption) for removing carbon monoxide from the fuel cell system according to the present embodiment shown in FIG. ) 7 may be further provided. As a result, only pure hydrogen is stored in the storage device 6. Since this pure hydrogen has a higher hydrogen concentration than the reformed gas, a higher output than the stored gas can be obtained when supplied to the stack. Therefore, when the PSA 7 is provided, an output equivalent to or higher than that when the PSA 7 is not provided can be realized even if the storage amount in the storage device 6 is reduced compared to the case where the PSA 7 is not provided.

  The present invention can be used in a fuel cell system.

  1, 1 ', 1a-1j ... power generation module, 2 ... load, 3 ... fuel line, 4 ... nitrogen cylinder, 5 ... water condenser, 6 ... storage device, 7 ... PSA, 11 ... heat insulation container, 12, 12a, 12b ... reformer, 13 ... stack.

Claims (9)

And at least one single cell including an electrolyte, a fuel electrode, and an air electrode, and a reformer that extracts hydrogen from a hydrocarbon gas. The single cell that is extracted by the reformer at a predetermined temperature At least one power generation module that generates power by supplying to
A fuel cell system comprising: a storage device that stores the hydrogen and supplies the stored hydrogen to the power generation module. The reformer supplies the hydrogen to the single cell,
The fuel cell system according to claim 1, wherein the storage device stores the hydrogen that has not been used for power generation in the single cell. The reformer is
A first reformer that extracts the hydrogen from the hydrocarbon gas and supplies the hydrogen to the single cell;
The fuel cell system according to claim 1, further comprising: a second reformer that extracts the hydrogen from the hydrocarbon gas and supplies the hydrogen to the storage device. A plurality of the power generation modules;
4. The fuel cell according to claim 1, wherein the storage device stores the hydrogen generated in each power generation module and supplies the hydrogen to each power generation module. 5. system. The fuel cell system according to any one of claims 1 to 4, further comprising a nitrogen supply device that supplies nitrogen gas to the power generation module. An extraction step for extracting hydrogen from the hydrocarbon gas;
Using the hydrogen extracted in this extraction step, a power generation step of generating power with a power generation module including a single cell comprising an electrolyte, a fuel electrode, and an air electrode;
A storage step for storing the hydrogen;
A supply step of supplying the hydrogen stored in the storage step to the single cell when the power generation module is started or stopped. A method for operating a fuel cell system, comprising: The operation method of the fuel cell system according to claim 6, wherein the storage step stores the hydrogen that was not used for the power generation of the single cell in the power generation step. The operation method of the fuel cell system according to claim 6, wherein the storage step stores the hydrogen extracted in the extraction step. The power generation step includes
When any of the power generation modules is stopped during power generation by a plurality of the power generation modules, the fuel usage rate for the power generation module during power generation is lowered, and the hydrogen stored in the storage step is supplied to the power generation module during power generation The method for operating a fuel cell system according to any one of claims 6 to 8, wherein:

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