JP6629167B2 - Recirculating fuel cell system - Google Patents

Description

  The present invention relates to a circulation type fuel cell system.

  As a fuel recycling technique for a high temperature operation type fuel cell, a fuel cell system for recycling anode exhaust has been disclosed (see Patent Document 1). Further, a method for removing water vapor and carbon dioxide in an anode off-gas in a multi-stage stack or a single stack has been disclosed (see Patent Document 2).

Japanese Patent No. 5542332 JP 2006-31989 A

  Fuel circulation of a fuel cell stack has been proposed as a technique for improving the fuel utilization rate for improving the efficiency of a high-temperature operating fuel cell system such as a solid oxide fuel cell or a molten carbonate fuel cell.

  If water vapor and carbon dioxide are removed from the anode off-gas and a regenerated fuel gas having a higher concentration of a fuel gas (hydrogen or carbon monoxide) contributing to the reaction can be obtained, power is generated again using the regenerated fuel gas. It is possible.

  In the conventional example according to Patent Document 1 described above, a partial pressure swing adsorption unit, a temperature swing adsorption unit, and an electrochemical pump are proposed for removing water vapor and carbon dioxide. However, when using an adsorption unit, a pressure swing or a temperature swing is required, and the system configuration and the system sequence are complicated.

  When an electrochemical pump is used, it is not necessary to perform a pressure swing or a temperature swing, but it is necessary to lower the fuel off-gas to 200 ° C. or less. In addition, since the electrochemical pump also uses platinum as an electrode catalyst, equipment is generally expensive.

  In the conventional example according to Patent Literature 2 described above, since the method of removing water vapor from the anode off-gas is condensation by cooling the anode off-gas to near room temperature of, for example, 100 ° C. or less, the regenerated fuel gas is removed by removing the water vapor from the anode off-gas. In order to use the regenerated fuel gas, it is necessary to reheat the regenerated fuel gas to the power generation temperature of the fuel cell stack.

  That is, in order to remove water vapor from the anode off-gas with a relatively simple configuration and sequence, or with inexpensive equipment, the anode off-gas needs to be cooled once, and heat energy for reheating from that temperature range to the power generation temperature is required. Was needed. Further, when condensed water is recovered and used as water for reforming a raw material gas, heat energy for vaporizing the water is required in addition to heat energy for heating the water to a use temperature again. there were. As the heat energy source, exhaust heat of a fuel cell and the like have been used.

  SUMMARY OF THE INVENTION The present invention has been made in consideration of the above circumstances, and has an object to improve the efficiency of a system while simplifying a configuration by making it possible to more effectively use exhaust heat of a fuel cell than before.

As an example, a circulating fuel cell system includes a fuel processing device that generates a fuel gas containing hydrogen by steam reforming a raw material gas, and a fuel cell that performs power generation using the fuel gas supplied from the fuel processing device. A water vapor separation membrane that removes water vapor in a gaseous state from an off gas containing the fuel gas that has been discharged from the fuel cell and has not reacted in the fuel cell; and a regenerated fuel gas in which the water vapor has been removed from the off gas. A regeneration fuel gas path for supplying to the battery, wherein the fuel processing device reforms the source gas using the steam removed by the steam separation membrane to generate the fuel gas.

  In this circulation type fuel cell system, a fuel gas containing hydrogen is generated from a raw material gas by steam reforming in a fuel processor. This fuel gas is supplied to the fuel cell. In a fuel cell, power generation is performed using fuel gas. The off-gas discharged from the fuel cell contains unreacted fuel gas, water vapor, and the like. The water vapor is removed from the off-gas in a gaseous state by the water vapor separation membrane. As a result, a regenerated fuel gas having an increased hydrogen concentration is generated. The regenerated fuel gas is supplied to the fuel cell through the regenerated fuel gas path. In a fuel cell, power generation is performed using a fuel gas supplied from a fuel processor and a regenerated fuel gas.

  Further, in this circulation type fuel cell system, since the water vapor in the off-gas is removed from the off-gas in a gaseous state by the water vapor separation membrane, there is no need to cool the off-gas to a temperature required for water condensation. Therefore, the heating width when heating the regenerated fuel gas to the power generation temperature suitable for the fuel cell is reduced. Therefore, the heat exchanger and the like for heating the regenerated fuel gas can be simplified, and an additional heating device can be eliminated. Further, the heat energy conventionally used for heating the regenerated fuel gas can be effectively used for hot water supply, a reforming reaction (endothermic reaction) in a heat treatment apparatus, and the like.

  Further, in this circulation type fuel cell system, the fuel processing apparatus reforms the raw material gas using the water vapor removed by the water vapor separation membrane to generate the fuel gas, so that the water of the system can be made independent. .

In the above-described circulation type fuel cell system, the water vapor removed by the water vapor separation membrane may be used as a gas for a reforming reaction in the fuel processor.

  In this circulation type fuel cell system, the steam removed from the off-gas is used as a gas for the reforming reaction in the fuel processor. Therefore, a water tank for storing water in which water vapor is condensed and a pump for sending out the water to the fuel processor are not required.

Incidentally, in the above circuit of the fuel cell system, the water vapor is removed by the water vapor separation membrane, using a blower, it can also be mixed into feed or the feed gas to the fuel processor.

  In this circulation type fuel cell system, water vapor removed from off-gas is sent as a gas by a blower, supplied to a fuel processor or mixed with a raw material gas, and used for a reforming reaction in the fuel processor.

In the above-described circulation type fuel cell system, the raw material gas is caused to flow on the permeation side of the water vapor separation membrane, and the water vapor removed by the water vapor separation membrane is mixed with the raw material gas and supplied to the fuel processing device. You can also .

  In this circulation type fuel cell system, the water vapor removed by the water vapor separation membrane is directly mixed into the raw material gas flowing on the permeation side of the water vapor separation membrane, and used for the reforming reaction in the fuel processor.

Note that, in the above-described circulating fuel cell system, heat exchange is performed between the off-gas and at least one of the regenerated fuel gas, the source gas, air, the water vapor, and water obtained by condensing the water vapor, and the off-gas is discharged. A heat exchanger for cooling and heating at least one of the regenerated fuel gas, the raw material gas, the air, the steam, and the water condensed with the steam may be provided .

  In this circulation type fuel cell system, heat exchange is performed by a heat exchanger between at least one of a regenerated fuel gas, a raw material gas, air, water vapor, and water obtained by condensing the water vapor and an off-gas. This heat exchanger cools off-gas before reaching the steam separation membrane to a temperature suitable for the steam separation membrane.

Note that, in the above-described circulating fuel cell system, in the offgas path through which the offgas flows, a carbon dioxide removal unit that is provided on at least one of the upstream side and the downstream side of the heat exchanger and removes carbon dioxide in the offgas is provided. has the reproduction fuel gas may I der obtained by removing the water vapor and the carbon dioxide from the off-gas.

  In this circulation type fuel cell system, not only the water vapor in the off-gas is removed, but also the carbon dioxide in the off-gas is removed by the carbon dioxide removing unit to generate the regenerated fuel gas. It is possible to improve the performance of a fuel cell that generates electric power by using it together.

Incidentally, the water vapor separation membrane the aforementioned, which removes the water vapor and carbon dioxide from the off-gas, the regeneration fuel gas may I der obtained by removing the water vapor and the carbon dioxide from the off-gas .

In this multi-stage fuel cell system, water vapor and carbon dioxide in off-gas are removed by the water vapor separation membrane. Therefore, there is no need to separately provide a carbon dioxide removing unit.
The circulation type fuel cell system according to claim 1, wherein a fuel cell that generates power using a fuel gas containing hydrogen, and an off-gas containing the fuel gas that is discharged from the fuel cell and is unreacted in the fuel cell, from water vapor and A water vapor separation membrane for removing carbon dioxide in a gaseous state, a regenerated fuel gas path for supplying a regenerated fuel gas in which the water vapor and carbon dioxide are removed from the off gas to the fuel cell, and a part of the off gas is supplied. A combustor for burning the off-gas, wherein the steam separated from the off-gas removed from the off-gas by the steam separation membrane and separated from the regenerated fuel gas is condensed on the downstream side of the fuel cell to remove the steam. The regenerated fuel gas after separation is supplied to the combustor.
The circulation type fuel cell system according to claim 2 has a water tank for storing water obtained by condensing the steam separated by the steam separation membrane.
Circuit of the fuel cell system according to claim 3, air, the steam, and performs heat exchange between at least one said off gas condensed water the water vapor, the regeneration fuel gas to cool the off-gas A heat exchanger for heating at least one of the raw material gas, the air, the water vapor, and the water condensed with the water vapor.
The circulation fuel cell system according to claim 4, wherein a fuel cell that generates power using a fuel gas containing hydrogen, and water vapor that is discharged from the fuel cell and contains off-gas containing the fuel gas that has not reacted in the fuel cell. and removing the regeneration fuel gas regeneration fuel gas path for supplying to the fuel cell, performs heat exchange between the regeneration fuel gas before Symbol offgas before merging the raw material gas, the regeneration cools the off-gas having a fuel gas and pressurized heat heat exchanger, a.
The recirculation type fuel cell system according to claim 5, wherein in the offgas path through which the offgas flows, at least one of an upstream side and a downstream side of the heat exchanger, and a carbon dioxide removing unit that removes carbon dioxide in the offgas. Wherein the regenerated fuel gas is obtained by removing the water vapor and the carbon dioxide from the off-gas.

  ADVANTAGE OF THE INVENTION According to the circulation type fuel cell system which concerns on this invention, the outstanding effect that the waste heat of a fuel cell can be used more effectively than before, and the system efficiency can be improved while simplifying a structure is obtained. .

FIG. 1 is a block diagram schematically illustrating a circulation fuel cell system according to a first embodiment. It is a block diagram showing typically the circulation type fuel cell system concerning a 2nd embodiment. It is a block diagram showing typically the circulation type fuel cell system concerning a 3rd embodiment. It is a block diagram showing typically the circulation type fuel cell system concerning a 4th embodiment. It is a block diagram showing typically the circulation type fuel cell system concerning a 5th embodiment. It is a block diagram showing typically the circulation type fuel cell system concerning a 6th embodiment. It is a block diagram showing typically the circulation type fuel cell system concerning a 7th embodiment. It is a block diagram showing typically the circulation type fuel cell system concerning an 8th embodiment. It is a block diagram showing typically the circulation type fuel cell system concerning a 9th embodiment. It is a block diagram showing typically the circulation type fuel cell system concerning a 10th embodiment. It is a block diagram which shows the principle of a carbon dioxide removal part typically.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

[First Embodiment]
In FIG. 1, the circulation type fuel cell system 10 according to the present embodiment includes a fuel processor 14, a fuel cell 11, a water vapor separation membrane 16, a regenerated fuel gas path 54, and a first heat exchanger as an example of a heat exchanger. It has an exchanger 21 and a second heat exchanger 22.

  The fuel processing device 14 is an FPS (Fuel Processing System) that generates a fuel gas containing hydrogen from a source gas such as methane, and includes a catalyst (not shown) for producing hydrogen from the source gas and a combustor for heating the catalyst. 18. The catalyst is a reforming catalyst, and is provided in the reformer 19. A source gas path 24 is connected to the reformer 19, and the source gas is supplied through the source gas path 24. The source gas path 24 is provided with a blower 25 for sending the source gas. In addition, a second heat exchanger 22 described below is provided between the blower 25 and the reformer 19 in the source gas path 24 so that the source gas is heated by the second heat exchanger 22. Has become.

  Further, a water supply path 28 is connected to the reformer 19, and the water supply path 28 is connected to a water tank 26. The water tank 26 is a container for storing water 38 obtained by condensing the water vapor removed by the water vapor separation membrane 16. In the water supply path 28, for example, a pump 32 and a vaporizer 34 are provided. The pump 32 sends out water 38 in the water tank 26 to the water supply path 28. The vaporizer 34 is provided downstream of the pump 32 and vaporizes water 38 sent to the water supply path 28 to generate steam. The reformer 19 reforms the raw material gas by using the steam supplied through the water supply path 28 to generate a fuel gas containing hydrogen. That is, the fuel processing device 14 reforms the raw material gas using the water vapor removed by the water vapor separation membrane 16 to generate a fuel gas. The fuel gas is supplied to an anode (not shown) of the fuel cell 11 through the fuel gas path 42.

  An air supply path 44 and an off-gas path 46 are connected to the combustor 18 of the fuel processor 14. The combustor 18 burns a mixed gas of air supplied through the air supply path 44 and burner gas (off gas described later) supplied through the off gas path 46, and heats the catalyst in the reformer 19. The exhaust gas from the combustor 18 is exhausted through an exhaust path 48.

  The fuel cell 11 is, for example, a fuel cell stack that generates power using fuel gas supplied from the fuel processor 14. The fuel cell 11 is, for example, a high-temperature fuel cell (solid oxide fuel cell, molten carbonate fuel cell) operating at about 750 ° C. Although not shown, the fuel cell 11 has an electrolyte layer, and an anode and a cathode which are respectively laminated on the front and back surfaces of the electrolyte layer. The anode is a fuel electrode and the cathode is an air electrode.

  Air (oxidizing gas) is supplied to the cathode through an air supply path 44. At the cathode, oxygen, carbon dioxide gas (only in the case of a molten carbonate fuel cell) and electrons are electrochemically reacted in the electrolyte layer to form oxygen ions (in the case of a solid oxide fuel cell) and carbonate ions (in the case of a molten oxide fuel cell). (In the case of a carbonate fuel cell), and the electrolyte membrane is moved.

  On the other hand, fuel gas is supplied from the fuel processor 14 to the anode through the fuel gas path 42. At this anode, hydrogen reacts with carbonate ions and oxygen ions that have moved through the electrolyte layer, and water and carbon dioxide gas (electrons are generated only in the case of a molten carbonate fuel cell. The electrons generated at the anode are: Move to the cathode through an external circuit.

  Then, as the electrons move from the anode to the cathode in this manner, power is generated in the fuel cell 11. The unreacted gas at the cathode is supplied to the combustor 18 of the fuel processor 14 through the air supply path 44 on the downstream side.

  The water vapor separation membrane 16 removes water vapor in a gaseous state from off-gas containing fuel gas which is discharged from the fuel cell 11 and not reacted in the fuel cell 11. The water vapor separation membrane 16 is provided in the off gas path 52, and can remove water vapor from the off gas at a temperature higher than the condensation point of water (for example, 100 ° C. or higher). Examples of the type of the steam separation membrane 16 include a polymer system, a polymer-inorganic molecule hybrid membrane, and a zeolite system. For example, as shown in Table 1, the results of performing steam separation at 100 ° C. or higher have been reported. I have.

  The regenerated fuel gas path 54 is a path for supplying the regenerated fuel gas obtained by removing water vapor from the off gas to the fuel cell 11, and is connected to, for example, the fuel gas path 42 located on the upstream side of the fuel cell 11. The regenerated fuel gas path 54 may be connected to the raw material gas path 24 located on the upstream side of the reformer 19 in the fuel processor 14.

  In the regenerated fuel gas path 54, for example, a blower 55 and the first heat exchanger 21 are provided. The first heat exchanger 21 exchanges heat between the off gas flowing through the off gas path 52 and the regenerated fuel gas flowing through the regenerated fuel gas path 54 to cool the off gas to, for example, about 200 ° C. The heating is performed again according to the operating temperature of the fuel cell 11.

  On the other hand, the second heat exchanger 22 and the water tank 26 are provided downstream of the steam separation membrane 16 in the off-gas path 52. The water vapor removed by the water vapor separation membrane 16 is cooled in the second heat exchanger 22, condensed in the water tank 26 to become water 38, and stored in the water tank 26. An offgas path 46 is connected to an upper part of the water tank 26. Gas such as carbon dioxide that is not condensed in the water tank 26 is supplied to the combustor 18 of the fuel processing device 14 through the off-gas path 46. The second heat exchanger 22 exchanges heat between the source gas flowing through the source gas path 24 and the off gas flowing through the off gas path 52, thereby cooling the off gas and heating the source gas.

  In addition, a heat exchanger that performs heat exchange between air or steam and the off-gas may be provided. That is, the heat exchanger in the present embodiment performs heat exchange between at least one of the regenerated fuel gas, the raw material gas, the air, the water vapor, and the water 38 condensed with the water vapor and the off-gas.

(Action)
The present embodiment is configured as described above, and its operation will be described below. In FIG. 1, in a circulation type fuel cell system 10 according to the present embodiment, a fuel gas containing hydrogen is generated from a raw material gas in a fuel processing device 14. Specifically, in the fuel processor 14, by heating the catalyst in the reformer 19 with the combustor 18, the raw material gas is reformed, for example, by steam, and a fuel gas containing hydrogen is generated. For the reforming, steam obtained by vaporizing water 38 supplied from the water tank 26 through the water supply path 28 by the vaporizer 34 can be used.

  The fuel gas generated by the fuel processor 14 is supplied to the fuel cell 11 through the fuel gas path 42. The fuel cell 11 generates power using fuel gas. The off-gas discharged from the fuel cell 11 contains unreacted fuel gas, water vapor, and the like. The water vapor is removed from the off-gas in a gaseous state by the water vapor separation membrane 16. As a result, a regenerated fuel gas having an increased hydrogen concentration is generated. The regenerated fuel gas is joined to the fuel gas path 42 by the blower 55 through the regenerated fuel gas path 54 and supplied to the first fuel cell 11 together with the fuel gas. In the first fuel cell 11, power is generated using the regenerated fuel gas together with the fuel gas.

  Note that heat exchange by the first heat exchanger 21 is performed between the off gas flowing through the off gas path 52 and the regenerated fuel gas flowing through the regenerated fuel gas path 54. The first heat exchanger 21 cools off-gas before reaching the steam separation membrane 16 to a temperature suitable for the steam separation membrane 16, and also converts regenerated fuel gas before reaching the fuel cell 11 into the fuel cell 11. Is heated again to a temperature suitable for the power generation temperature.

The water vapor removed by the water vapor separation membrane 16 flows downstream of the water vapor separation membrane 16 in the off-gas path 52, is cooled by the second heat exchanger 22, is further condensed in the water tank 26 to become water 38, 26. When a predetermined amount or more of water 38 is stored in the water tank 26, drainage drainage is caused by overflow, for example. Gas such as carbon dioxide that is not condensed in the water tank 26 is supplied to the combustor 18 of the fuel processor 14 through the off-gas path 46.
The second heat exchanger 22 exchanges heat between the source gas flowing through the source gas path 24 and the off gas flowing through the off gas path 52, thereby cooling the off gas and heating the source gas. By heating the raw material gas by the second heat exchanger 22, the thermal energy conventionally used for heating the regenerated fuel gas can be effectively used for the reforming reaction (endothermic reaction) in the fuel processor 14.

  In the circulation type fuel cell system 10 according to the present embodiment, since the water vapor in the off gas is removed from the off gas in a gaseous state by the water vapor separation membrane 16, it is necessary to cool the off gas to a temperature required for water condensation. There is no. Therefore, the heating width when the regenerated fuel gas is heated again to the power generation temperature suitable for the fuel cell 11 is reduced. In the case of the present embodiment, since the temperature of the regenerated fuel gas is raised from 200 ° C. to 750 ° C., the heating width is, for example, 550 ° C. Therefore, the first heat exchanger 21 for heating the regenerated fuel gas and the like can be simplified, and an additional heating device can be eliminated. Further, the thermal energy conventionally used for heating the regenerated fuel gas can be effectively used for hot water supply and the like.

  The water 38 in the water tank 26 is sent out to the water supply path 28 by the pump 32, is vaporized by the vaporizer 34 and becomes steam, and is supplied to the reformer 19 of the fuel processor 14. The reformer 19 can reform the raw material gas using the steam supplied through the water supply path 28 to generate a fuel gas containing hydrogen. This water vapor is water vapor originally removed by the water vapor separation membrane 16. As described above, in the present embodiment, since the fuel processing apparatus 14 reforms the raw material gas using the steam removed by the steam separation membrane 16, the system can be made water independent.

  As described above, in the circulation type fuel cell system 10 according to the present embodiment, the exhaust heat of the fuel cell can be used more effectively than before, and the efficiency of the system can be increased while simplifying the configuration.

[Second embodiment]
2, the circulation type fuel cell system 20 according to the present embodiment has a configuration in which the steam removed by the steam separation membrane 16 is used as a gas for the reforming reaction in the fuel processor 14. Specifically, the downstream side of the steam separation membrane 16 in the off-gas path 52 is directly connected to, for example, the reformer 19 of the fuel processor 14 through the water supply path 28. A blower 33 is provided in the water supply path 28. The steam removed by the steam separation membrane 16 is supplied to the reformer 19 of the fuel processor 14 using the blower 33. Since the second heat exchanger 22 (FIG. 1) in the first embodiment is not provided in the water supply path 28, the raw material gas is directly supplied to the reformer 19 of the fuel processing device 14. Note that the water supply path 28 may be connected to the source gas path 24 to mix the water vapor with the source gas.

  Thus, the steam removed from the off-gas by the steam separation membrane 16 is reformed by being mixed with the raw material gas in the reformer 19 as a gas. Therefore, since the water tank 26 and the pump 32 (FIG. 1) in the first embodiment are not required, the configuration of the system is simplified.

  The other parts are the same as in the first embodiment, so the same parts are denoted by the same reference numerals in the drawings, and description thereof will be omitted.

[Third embodiment]
In FIG. 3, in the circulation type fuel cell system 30 according to the present embodiment, similarly to the second embodiment, the water vapor removed by the water vapor separation membrane 16 is mixed with the raw material gas as it is. . Specifically, the off-gas path 52 is disposed on the feed side 16A of the steam separation membrane 16, and the raw gas path 24 is passed through the permeation side 16B of the steam separation membrane 16.

  The water vapor in the off gas passing through the off gas path 52 passes through the water vapor separation membrane 16 from the feed side 16A to the permeation side 16B in the direction of arrow A, and is directly mixed with the raw material gas flowing through the permeation side 16B as a gas. The raw material gas and the steam are supplied to the reformer 19 of the fuel processing device 14 by the blower 25 and reformed to become a fuel gas. Accordingly, since the water supply path 28 and the blower 33 (FIG. 2) in the second embodiment are not required, the configuration of the system is further simplified.

  The other parts are the same as those of the first embodiment or the second embodiment. Therefore, the same parts are denoted by the same reference numerals in the drawings, and description thereof will be omitted.

[Fourth embodiment]
In FIG. 4, the circulation type fuel cell system 40 according to the present embodiment is configured by adding a carbon dioxide removing unit 56 to the first embodiment. The carbon dioxide removing unit 56 is provided on the upstream side (high-temperature part) of the first heat exchanger 21 in the off-gas path 52 through which the off-gas flows, and removes carbon dioxide in the off-gas. Since the off-gas before passing through the first heat exchanger 21 has a relatively high temperature of about 750 ° C., a carbon dioxide removal unit 56 that can be used at this temperature is selected. The carbon dioxide removing unit 56 is connected to the off-gas path 46.

  The regenerated fuel gas returned to the fuel cell 11 is obtained by removing carbon dioxide and water vapor from the off-gas. Specifically, the off-gas passing through the off-gas path 52 is first subjected to removal of carbon dioxide in the carbon dioxide removal unit 56, cooled in the first heat exchanger 21, and then removed in the steam separation membrane 16 to be regenerated. It becomes fuel gas.

  The carbon dioxide removed from the off-gas by the carbon dioxide removing unit 56 is supplied to the combustor 18 of the fuel processor 14 through the off-gas path 46.

  In this circulation type fuel cell system 40, not only the water vapor in the off-gas is removed, but also the carbon dioxide in the off-gas is removed to generate a regenerated fuel gas. The performance of the battery 11 can be improved.

  The other parts are the same as in the first embodiment, so the same parts are denoted by the same reference numerals in the drawings, and description thereof will be omitted.

[Fifth Embodiment]
In FIG. 5, the circulation type fuel cell system 50 according to the present embodiment has a configuration in which the water vapor removed by the water vapor separation membrane 16 is mixed with the raw material gas as it is, similarly to the second embodiment. . Further, as in the fourth embodiment, a carbon dioxide removing unit 56 is provided on the upstream side (high-temperature portion) of the first heat exchanger 21 in the off-gas path 52 through which the off-gas flows.

  Since the water vapor removed from the off-gas by the water vapor separation membrane 16 is reformed by being mixed with the raw material gas in the reformer 19 as a gas, the water tank 26 and the pump 32 (FIG. 1) in the first embodiment are unnecessary. Therefore, the configuration of the system is simplified.

  In addition, not only the water vapor in the off-gas is removed, but also the carbon dioxide in the off-gas is removed to generate a regenerated fuel gas, so that the performance of the fuel cell 11 that performs power generation using the regenerated fuel gas is improved. be able to.

  Other parts are the same as those of the first embodiment, the second embodiment, or the fourth embodiment. Therefore, the same parts are denoted by the same reference numerals in the drawings, and description thereof will be omitted.

[Sixth embodiment]
In FIG. 6, the circulating fuel cell system 60 according to the present embodiment has a configuration in which the water vapor removed by the water vapor separation membrane 16 is directly mixed with the raw material gas as it is, similarly to the third embodiment. I have. Further, as in the fourth embodiment, a carbon dioxide removing unit 56 is provided on the upstream side (high-temperature portion) of the first heat exchanger 21 in the off-gas path 52 through which the off-gas flows.

  The water vapor in the off gas passing through the off gas path 52 is directly mixed with the source gas passing through the source gas path 24 as a gas. The raw material gas and the steam are supplied to the reformer 19 of the fuel processing device 14 by the blower 25 and reformed to become a fuel gas. Accordingly, since the water supply path 28 and the blower 33 (FIG. 2) in the second embodiment are not required, the configuration of the system is further simplified.

  In addition, not only the water vapor in the off-gas is removed, but also the carbon dioxide in the off-gas is removed to generate a regenerated fuel gas, so that the performance of the fuel cell 11 that performs power generation using the regenerated fuel gas is improved. be able to.

  Other parts are the same as those of the first embodiment, the third embodiment, or the fourth embodiment, and therefore, the same parts are denoted by the same reference numerals in the drawings, and description thereof will be omitted.

[Seventh embodiment]
7, a circulating fuel cell system 70 according to the present embodiment is different from the fourth embodiment in that the carbon dioxide removing unit 56 is provided on the off-gas path 52 downstream of the first heat exchanger 21. Since the off-gas that has passed through the first heat exchanger 21 is at a relatively low temperature of about 200 ° C., a carbon dioxide removing unit 56 that can be used at this temperature is selected.

  The position of the carbon dioxide removing unit 56 on the downstream side of the first heat exchanger 21 may be on the upstream side or on the downstream side of the steam separation membrane 16. When the carbon dioxide removing unit 56 is of a type that absorbs and removes carbon dioxide, the carbon dioxide removing unit 56 can be disposed downstream of the steam separation membrane 16.

  However, when the carbon dioxide removing unit 56 is of a type that removes carbon dioxide by electrochemical separation, it is necessary to arrange the carbon dioxide removing unit 56 on the upstream side of the steam separation membrane 16. This is because water is required for electrochemical separation, and carbon dioxide cannot be removed after water vapor has been removed.

  Here, the principle when the carbon dioxide removing unit 56 is of the electrochemical separation type will be briefly described. As shown in FIG. 11, the carbon dioxide removing unit 56 has an anode 62, an electrolyte membrane 64, and a cathode 66, and the electrolyte membrane 64 is sandwiched between the anode 62 and the cathode 66. A power supply 58 is connected to the anode 62 and the cathode 66. As this power source, a fuel cell 11 can be used. An off-gas path 52 is connected to the anode 62. One of the cathodes 66 is connected to an air supply path 68, and the other is connected to the off-gas path 46. When a voltage is applied to the anode 62 and the cathode 66, the following reactions occur at the anode 62 and the cathode 66, respectively, and carbon dioxide is removed.

Anode 62: 2H20 → 2H2 + 02 02 + 2C02 + 2e− → CO3-2
Cathode 66: CO3-2 → 02 + 2C02 + 2e−

  As a result, the carbon dioxide and the like removed from the off-gas are purged by the air supplied from the air supply passage 68 and discharged to the off-gas passage 46.

  In the circulating fuel cell system 70 according to the present embodiment, the off-gas passing through the off-gas path 52 is first cooled in the first heat exchanger 21, and then carbon dioxide is removed in the carbon dioxide removing unit 56. At which the water vapor is removed to become a regenerated fuel gas.

  In this circulation type fuel cell system 70, not only the water vapor in the off-gas is removed but also the carbon dioxide in the off-gas is removed to generate a regenerated fuel gas. The performance of the fuel cell 11 that performs power generation can be improved.

  The other parts are the same as in the first embodiment or the fourth embodiment, and therefore, the same parts are denoted by the same reference numerals in the drawings, and description thereof will be omitted.

[Eighth Embodiment]
In FIG. 8, in the circulation type fuel cell system 80 according to the present embodiment, in the fifth embodiment, the carbon dioxide removing unit 56 is provided on the downstream side of the first heat exchanger 21 (low temperature part) in the off-gas path 52. Things.

  Since the steam removed from the off-gas by the steam separation membrane 16 is reformed by being mixed with the raw material gas in the reformer 19 as a gas, the water tank 26 and the pump 32 (FIG. 1) in the first embodiment are unnecessary. Therefore, the configuration of the system is simplified.

  In addition, not only the water vapor in the off-gas is removed, but also the carbon dioxide in the off-gas is removed to generate a regenerated fuel gas, so that the performance of the fuel cell 11 that performs power generation using the regenerated fuel gas is improved. be able to.

  Other parts are the same as those of the first, second, fourth, or fifth embodiment, and therefore, the same parts are denoted by the same reference numerals in the drawings, and description thereof will be omitted.

[Ninth embodiment]
9, a circulating fuel cell system 90 according to the present embodiment is different from the sixth embodiment in that the carbon dioxide removing unit 56 is provided on the off-gas path 52 downstream of the first heat exchanger 21.

  The water vapor in the off gas passing through the off gas path 52 is directly mixed with the source gas passing through the source gas path 24 as a gas. The raw material gas and the steam are supplied to the reformer 19 of the fuel processing device 14 by the blower 25 and reformed to become a fuel gas. Therefore, since the water supply path 28 and the pump 32 (FIG. 2) in the second embodiment are not required, the configuration of the system is further simplified.

  In addition, since not only the water vapor in the off-gas is removed but also the carbon dioxide in the off-gas is removed to generate a regenerated fuel gas, the performance of the fuel cell 11 that generates electric power using the regenerated fuel gas is improved. be able to.

  Other parts are the same as those of the first, third, fourth, or sixth embodiment, and therefore, the same parts are denoted by the same reference numerals in the drawings, and description thereof will be omitted.

[Tenth embodiment]
In FIG. 10, in the circulating fuel cell system 100 according to the present embodiment, in the first embodiment, the steam separation membrane 16 removes steam and carbon dioxide from off-gas. As the water vapor separation membrane 16, a membrane described in "Zi Tong et al.," Water vapor and CO2 transport through amine-containing facilitated transport membranes ", Reactive & Functional Polymers (2014) can be used.

  The off-gas passing through the off-gas path 52 is first cooled in the first heat exchanger 21, and then the steam and carbon dioxide are removed in the steam separation membrane 16 to become a regenerated fuel gas.

  In the present embodiment, since the water vapor and the carbon dioxide in the off-gas are removed by the water vapor separation membrane 16, it is not necessary to separately provide the carbon dioxide removing unit 56 (the fourth to ninth embodiments). For this reason, the system can be further simplified.

  The other parts are the same as in the first embodiment, so the same parts are denoted by the same reference numerals in the drawings, and description thereof will be omitted.

[Example]
By using the steam separation membrane as in the present embodiment, the heating width of the regenerated fuel gas can be reduced as compared with a conventional example using a condenser for removing steam. Assuming that only water was removed from the off-gas using a steam separation membrane usable at 200 ° C., it was estimated that 210 W of thermal advantage would be generated in a 10 kW class SOFC system. Further, assuming that the recovered water was not condensed and supplied to the fuel processor for reforming as steam, it was estimated that a thermal advantage of 2.23 kW would be generated in a 10 kW-class SOFC system.

[Other embodiments]
As described above, an example of the present invention has been described. However, the embodiments of the present invention are not limited to the above, and other than the above, various modifications can be made without departing from the gist of the present invention. Of course.

  Although the fuel processing apparatus 14 reforms the source gas using the steam removed by the steam separation membrane 16, the reforming may be performed using steam supplied from another source.

DESCRIPTION OF SYMBOLS 10 ... Circulation type fuel cell system, 11 ... Fuel cell, 14 ... Fuel processing apparatus, 16 ... Steam separation membrane, 16B ... Permeation side, 20 ... Circulation type fuel cell system, 21 ... First heat exchanger (heat exchanger) , 22 ... second heat exchanger (heat exchanger), 30 ... circulation type fuel cell system, 38 ... water, 40 ... circulation type fuel cell system, 50 ... circulation type fuel cell system, 52 ... off gas path, 56 ... dioxide Carbon removal unit, 60: circulating fuel cell system, 70: circulating fuel cell system, 80: circulating fuel cell system, 90: circulating fuel cell system, 100: circulating fuel cell system

Claims (5)

A fuel cell that generates power using fuel gas containing hydrogen,
A water vapor separation membrane that removes water vapor and carbon dioxide in a gaseous state from an off gas containing the fuel gas that has been discharged from the fuel cell and has not reacted in the fuel cell;
A regenerated fuel gas path for supplying the regenerated fuel gas obtained by removing the water vapor and carbon dioxide from the off gas to the fuel cell,
A combustor to which a part of the off-gas is supplied and burns the off-gas,
Has,
For the gas removed from the off-gas by the steam separation membrane and separated from the regenerated fuel gas, steam is condensed on the downstream side of the fuel cell, and the gas separated from the regenerated fuel gas after the steam is removed is separated from the regenerated fuel gas. Supplying to the combustor,
Recirculating fuel cell system. A water tank for storing water obtained by condensing water vapor separated by the water vapor separation membrane,
The circulation fuel cell system according to claim 1, comprising: A heat exchange is performed between at least one of the air, the water vapor, and the water condensed with the water vapor and the off-gas to cool the off-gas and at least one of the air, the water vapor, and the water condensed with the water vapor. A heat exchanger for heating one
The circulation fuel cell system according to claim 1 or 2, further comprising: A fuel cell that generates power using fuel gas containing hydrogen,
A regenerated fuel gas path for supplying a regenerated fuel gas from which water vapor has been removed from the off gas containing the fuel gas unreacted in the fuel cell and discharged from the fuel cell to the fuel cell,
Exchanges heat between the regeneration fuel gas before Symbol offgas before merging the raw material gas, a heat exchanger for heating the regeneration fuel gas to cool the off-gas,
A circulation type fuel cell system having: In the offgas path through which the offgas flows, provided on at least one of the upstream side and the downstream side of the heat exchanger, and having a carbon dioxide removal unit for removing carbon dioxide in the offgas,
The circulation fuel cell system according to claim 4 , wherein the regenerated fuel gas is obtained by removing the water vapor and the carbon dioxide from the off-gas.