JP2016115496A - Circulation fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the efficiency of a system while simplifying the configuration, by utilizing the waste heat of fuel cell more than conventional.SOLUTION: A circulation fuel cell system 10 has a fuel processing device 14 for producing fuel gas containing hydrogen by performing steam modification of material gas, a fuel cell 11 for generating power by using fuel gas supplied from the fuel processing device 14, a steam separation membrane 16 for removing steam in the state of gas, from the off-gas discharged from the fuel cell 11 and containing fuel gas not reacting therein, and a regeneration fuel gas path 54 for supplying the regeneration fuel gas, produced by removing steam from the off-gas, to the fuel cell 11. The fuel processing device 14 modifies the material gas by using the steam removed by the steam separation membrane 16, and produces fuel gas.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a circulating 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). Moreover, a method for removing water vapor and carbon dioxide in the anode off-gas in a multi-stage stack or a single stack is disclosed (see Patent Document 2).

Japanese Patent No. 5542332 JP 2006-31989

  In order to improve the efficiency of high-temperature operating fuel cell systems such as solid oxide fuel cells and molten carbonate fuel cells, fuel circulation of fuel cell stacks has been proposed as a technique for improving the fuel utilization rate.

  If water and carbon dioxide are removed from the anode off-gas, and a regenerated fuel gas with a high concentration of fuel gas (hydrogen or carbon monoxide) contributing to the reaction can be obtained, power is generated again using this 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 the adsorption unit is used, a pressure swing or a temperature swing is required, and the system configuration and the system sequence are complicated.

  When using an electrochemical pump, 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 lower. In addition, since the electrochemical pump also uses platinum as an electrode catalyst, the facilities are generally expensive.

  In the conventional example according to Patent Document 2 described above, the method of removing water vapor from the anode off gas is condensation that cools the anode off gas to near room temperature, for example, 100 ° C. or less. In order to use it, 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 offgas with a relatively simple configuration and sequence, or inexpensive equipment, it is necessary to cool the anode offgas once, and heat energy for reheating from the temperature range to the power generation temperature. Was necessary. In addition, when condensate is recovered and used as water for reforming the raw material gas, in addition to the heat energy for heating this water to the use temperature again, heat energy for vaporizing this water is required. there were. As the heat energy source, exhaust heat of a fuel cell has been used.

  In view of the above-described facts, the present invention aims to increase the efficiency of the system while simplifying the configuration so that the exhaust heat of the fuel cell can be used more effectively than before.

  The circulating fuel cell system according to claim 1 performs power generation using a fuel processing device that generates a fuel gas containing hydrogen by steam reforming a raw material gas, and the fuel gas supplied from the fuel processing device. A fuel cell, a water vapor separation membrane for removing water vapor in a gaseous state from an off gas containing the fuel gas that has been discharged from the fuel cell and unreacted in the fuel cell, and a regenerated fuel gas from which the water vapor has been removed from the off gas A regenerated fuel gas path for supplying the fuel cell, and the fuel processing device reforms the raw material gas using the water vapor removed by the water vapor separation membrane to generate the fuel gas.

  In this circulating fuel cell system, a fuel gas containing hydrogen is generated from a raw material gas by steam reforming in a fuel processing device. 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. Thereby, the regenerated fuel gas with increased hydrogen concentration is generated. The regenerated fuel gas is supplied to the fuel cell through the regenerated fuel gas path. In the fuel cell, power generation is performed using the fuel gas supplied from the fuel processing apparatus and the regenerated fuel gas.

  Further, in this circulating fuel cell system, the water vapor in the off gas is removed from the off gas in a gaseous state by the water vapor separation membrane, so it is not necessary to cool the off gas to a temperature necessary 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, a heat exchanger or the like for heating the regenerated fuel gas can be simplified, and an additional heating device can be eliminated. In addition, 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, or the like.

  Further, in this circulating fuel cell system, the fuel processing device reforms the raw material gas using the water vapor removed by the water vapor separation membrane to generate the fuel gas, so that the system can be water self-supporting. .

  According to a second aspect of the present invention, in the circulating fuel cell system according to the first aspect, the water vapor removed by the water vapor separation membrane is used in a reforming reaction in the fuel processing apparatus as a gas.

  In this circulating fuel cell system, the water vapor removed from the off-gas is used as a gas for the reforming reaction in the fuel processing apparatus. Therefore, a water tank for storing water condensed with water vapor and a pump for sending the water toward the fuel processing device are not required.

  According to a third aspect of the present invention, in the circulating fuel cell system according to the second aspect, the water vapor removed by the water vapor separation membrane is supplied to the fuel processing apparatus or mixed into the raw material gas using a blower. The

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

  According to a fourth aspect of the present invention, in the circulating fuel cell system according to the second aspect, the raw material gas is allowed 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 into the raw material gas. Then, the fuel is supplied to the fuel processor.

  In this circulating fuel cell system, the water vapor removed by the water vapor separation membrane is directly mixed into the raw material gas flowing on the permeate side of the water vapor separation membrane and used for the reforming reaction in the fuel processing apparatus.

  According to a fifth aspect of the present invention, in the circulating fuel cell system according to any one of the first to fourth aspects, the regenerated fuel gas, the raw material gas, air, the water vapor, and the water vapor are condensed. Heat exchange between at least one of the produced water and the off gas, cooling the off gas and at least one of the regenerated fuel gas, the raw material gas, the air, the water vapor, and the water condensed with the water vapor. It has a heat exchanger that heats.

  In this circulating fuel cell system, heat exchange is performed by a heat exchanger between at least one of regenerated fuel gas, raw material gas, air, water vapor, and water condensed with the water vapor and off gas. This heat exchanger cools off-gas before reaching the water vapor separation membrane toward a temperature suitable for the water vapor separation membrane.

  According to a sixth aspect of the present invention, in the circulating fuel cell system according to the fifth aspect, in the off-gas path through which the off-gas flows, at least one of the upstream side and the downstream side of the heat exchanger is provided, and the carbon dioxide in the off-gas A carbon dioxide removal unit for removing carbon is provided, and the regenerated fuel gas is obtained by removing the water vapor and the carbon dioxide from the off gas.

  In this circulating 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 the fuel cell that is used together to generate power.

  The invention according to claim 7 is the circulating fuel cell system according to any one of claims 1 to 5, wherein the water vapor separation membrane removes the water vapor and carbon dioxide from the off-gas, The regenerated fuel gas is obtained by removing the water vapor and the carbon dioxide from the off gas.

  In this circulating fuel cell system, water vapor and carbon dioxide in the off-gas are removed by the water vapor separation membrane. Therefore, it is not necessary to separately provide a carbon dioxide removal unit.

  According to the circulation type fuel cell system of the present invention, it is possible to effectively use the exhaust heat of the fuel cell as compared with the conventional one, and it is possible to obtain an excellent effect that the configuration can be simplified and the efficiency of the system can be increased. .

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

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

[First Embodiment]
In FIG. 1, a circulating 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 as an example of a heat exchanger. An exchanger 21 and a second heat exchanger 22 are included.

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

  In addition, 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 in which water 38 obtained by condensing the water vapor removed by the water vapor separation membrane 16 is stored. In the water supply path 28, for example, a pump 32 and a vaporizer 34 are provided. The pump 32 feeds the water 38 in the water tank 26 to the water supply path 28. The vaporizer 34 is provided on the downstream side of the pump 32 and vaporizes the water 38 sent to the water supply path 28 to generate water vapor. The reformer 19 uses the water vapor supplied through the water supply path 28 to reform the raw material gas 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 the fuel gas. The fuel gas is supplied to the anode (not shown) of the fuel cell 11 through the fuel gas path 42.

  An air supply path 44 and an offgas 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. 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 the fuel gas supplied from the fuel processing device 14. The fuel cell 11 is a high-temperature fuel cell (solid oxide fuel cell, molten carbonate fuel cell) that operates at about 750 ° C., for example. Although illustration is omitted, the fuel cell 11 has an electrolyte layer and an anode and a cathode laminated on the front and back surfaces of the electrolyte layer, respectively. The anode is a fuel electrode, and the cathode is an air electrode.

  Air (oxidizing gas) is supplied to the cathode through the air supply path 44. In this cathode, oxygen, carbon dioxide (only for molten carbonate fuel cells) and electrons react electrochemically in the electrolyte layer to produce oxygen ions (for solid oxide fuel cells) and carbonate ions (melted). In the case of a carbonate fuel cell), and moves the electrolyte membrane.

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

  Then, as the electrons move from the anode to the cathode in this way, power generation is performed in the fuel cell 11. Unreacted gas at the cathode is supplied to the combustor 18 of the fuel processor 14 through the downstream air supply path 44.

  The water vapor separation membrane 16 removes water vapor in a gaseous state from off-gas discharged from the fuel cell 11 and containing unreacted fuel gas 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). As the types of the water vapor separation membrane 16, there are a polymer system, a polymer-inorganic molecule hybrid membrane, and a zeolite system. For example, as shown in Table 1, the results of performing the water vapor separation at 100 ° C. or higher have been reported. Yes.

  The regenerated fuel gas path 54 is a path for supplying the regenerated fuel gas from which the water vapor has been removed from the off-gas to the fuel cell 11, and is connected to, for example, a fuel gas path 42 positioned upstream of the fuel cell 11. Note that the regenerated fuel gas path 54 may be connected to the raw material gas path 24 located upstream of the reformer 19 in the fuel processing device 14.

  In the regenerated fuel gas path 54, for example, a blower 55 and a 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. Heating is performed again corresponding to the operating temperature of the fuel cell 11.

  On the other hand, a second heat exchanger 22 and a water tank 26 are provided on the downstream side of the water vapor separation membrane 16 in the off gas passage 52. The water vapor removed by the water vapor separation membrane 16 is cooled by the second heat exchanger 22, condensed in the water tank 26 to become water 38, and stored in the water tank 26. An off-gas path 46 is connected to the upper part of the water tank 26. A gas such as carbon dioxide that does not condense in the water tank 26 is supplied to the combustor 18 of the fuel processor 14 through the off-gas passage 46. The second heat exchanger 22 performs heat exchange between the raw material gas flowing through the raw material gas path 24 and the off gas flowing through the off gas path 52 to cool the off gas and heat the raw material gas.

  In addition, a heat exchanger that performs heat exchange between air or water vapor and off-gas may be provided. That is, the heat exchanger according to 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.

(Function)
This embodiment is configured as described above, and the operation thereof will be described below. In FIG. 1, in the circulating 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, the catalyst in the reformer 19 is heated by the combustor 18, so that the raw material gas is steam-reformed, for example, and a fuel gas containing hydrogen is generated. For reforming, steam obtained by vaporizing water 38 supplied from the water tank 26 through the water supply path 28 with 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. In the fuel cell 11, power generation is performed 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. Thereby, the regenerated fuel gas with 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, electric 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 water vapor separation membrane 16 toward a temperature suitable for the water vapor separation membrane 16, and regenerates the regenerated fuel gas before reaching the fuel cell 11. Heat again to a temperature suitable for the power generation temperature.

The water vapor removed by the water vapor separation membrane 16 flows to the downstream side of the water vapor separation membrane 16 in the off-gas path 52, is cooled by the second heat exchanger 22, and is further condensed in the water tank 26 to become the water 38. 26 is stored. When a predetermined amount or more of water 38 is stored in the water tank 26, it is drained by overflow, for example. A gas such as carbon dioxide that does not condense in the water tank 26 is supplied to the combustor 18 of the fuel processor 14 through the off-gas passage 46.
The second heat exchanger 22 performs heat exchange between the raw material gas flowing through the raw material gas path 24 and the off gas flowing through the off gas path 52 to cool the off gas and heat the raw material gas. Heating the raw material gas by the second heat exchanger 22 can effectively use the heat energy conventionally used for heating the regenerated fuel gas for the reforming reaction (endothermic reaction) in the fuel processing device 14.

  In the circulation type fuel cell system 10 according to the present embodiment, the water vapor in the off gas is removed from the off gas in a gaseous state by the water vapor separation membrane 16, so that it is necessary to cool the off gas to a temperature necessary 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 this embodiment, the regeneration fuel gas is heated from 200 ° C. to 750 ° C., so the heating width is, for example, 550 ° C. Therefore, the first heat exchanger 21 for heating the regenerated fuel gas can be simplified, and an additional heating device can be dispensed with. In addition, the heat energy conventionally used for heating the regenerated fuel gas can be effectively used for hot water supply or 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, 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 water vapor supplied through the water supply path 28 to generate a fuel gas containing hydrogen. This water vapor is the water vapor originally removed by the water vapor separation membrane 16. Thus, in this embodiment, since the fuel processing apparatus 14 reforms raw material gas using the water vapor | steam removed by the water vapor | steam separation membrane 16, the water self-supporting of a system can be achieved.

  Thus, in the circulating 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 enhanced while simplifying the configuration.

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

  As a result, 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 by the reformer 19 in the form of gas. Therefore, the water tank 26 and the pump 32 (FIG. 1) in the first embodiment are not necessary, and the system configuration is simplified.

  Since other parts are the same as those in the first embodiment, the same parts are denoted by the same reference numerals in the drawings, and the description thereof is omitted.

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

  The water vapor in the off gas passing through the off gas passage 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 to the permeation side 16B as a gas. This raw material gas and water vapor are supplied to the reformer 19 of the fuel processor 14 by the blower 25 and reformed to become fuel gas. Therefore, the water supply path 28 and the blower 33 (FIG. 2) in the second embodiment are not necessary, and the system configuration is further simplified.

  Since other parts are the same as those in the first embodiment or the second embodiment, the same parts are denoted by the same reference numerals and the description thereof is omitted.

[Fourth Embodiment]
In FIG. 4, the circulating 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 offgas path 52 through which the offgas flows, and removes carbon dioxide in the offgas. Since the off-gas before passing through the first heat exchanger 21 is a relatively high temperature of about 750 ° C., the carbon dioxide removal unit 56 that can be used at this temperature is selected. The carbon dioxide removal 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 off-gas. Specifically, the off-gas passing through the off-gas path 52 is first regenerated by removing the carbon dioxide in the carbon dioxide removing unit 56 and cooling it in the first heat exchanger 21 and then removing the water vapor in the water vapor separation membrane 16. 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 processing apparatus 14 through the off gas path 46.

  In the circulating 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 the regenerated fuel gas. Therefore, the fuel that generates power using the regenerated fuel gas. The performance of the battery 11 can be improved.

  Since other parts are the same as those in the first embodiment, the same parts are denoted by the same reference numerals in the drawings, and the description thereof is omitted.

[Fifth Embodiment]
In FIG. 5, the circulating fuel cell system 50 according to the present embodiment is configured such that the water vapor removed by the water vapor separation membrane 16 is mixed with the raw material gas as it is, as in the second embodiment. . Similarly to the fourth embodiment, a carbon dioxide removal 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.

  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, the water tank 26 and the pump 32 (FIG. 1) in the first embodiment are not necessary. Therefore, the system configuration is simplified.

  Further, not only the water vapor in the off gas is removed, but also the carbon dioxide in the off gas is removed to generate the regenerated fuel gas, so that the performance of the fuel cell 11 that generates power using the regenerated fuel gas is improved. be able to.

  Since other parts are the same as those in the first embodiment, the second embodiment, or the fourth embodiment, the same parts are denoted by the same reference numerals and the description thereof is 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, as in the third embodiment. Yes. Similarly to the fourth embodiment, a carbon dioxide removal 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.

  The water vapor in the off gas passing through the off gas path 52 is directly mixed with the raw material gas passing through the raw gas path 24 in the form of a gas. This raw material gas and water vapor are supplied to the reformer 19 of the fuel processor 14 by the blower 25 and reformed to become fuel gas. Therefore, the water supply path 28 and the blower 33 (FIG. 2) in the second embodiment are not necessary, and the system configuration is further simplified.

  Further, not only the water vapor in the off gas is removed, but also the carbon dioxide in the off gas is removed to generate the regenerated fuel gas, so that the performance of the fuel cell 11 that generates power using the regenerated fuel gas is improved. be able to.

  The other parts are the same as those in the first embodiment, the third embodiment, or the fourth embodiment, and thus the same parts are denoted by the same reference numerals and the description thereof is omitted.

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

  The position of the carbon dioxide removal unit 56 on the downstream side of the first heat exchanger 21 may be upstream or downstream of the water vapor separation membrane 16. When the carbon dioxide removal unit 56 absorbs and removes carbon dioxide, the carbon dioxide removal unit 56 can be disposed on the downstream side of the water vapor separation membrane 16.

  However, in the case where the carbon dioxide removing unit 56 is of a type that removes carbon dioxide by electrochemical separation, the carbon dioxide removing unit 56 needs to be disposed upstream of the water vapor separation membrane 16. This is because water is required for electrochemical separation, and carbon dioxide cannot be removed after the water vapor is removed.

  Here, the principle in the case where the carbon dioxide removing unit 56 is an electrochemical separation type will be briefly described. As shown in FIG. 11, the carbon dioxide removing unit 56 includes 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 source 58 is connected to the anode 62 and the cathode 66. As this power source, the fuel cell 11 can be used. An off gas path 52 is connected to the anode 62. An air supply path 68 is connected to one of the cathodes 66, and an off-gas path 46 is connected to the other. 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−

  Thus, carbon dioxide or the like removed from the off gas is purged by the air supplied from the air supply path 68 and discharged to the off gas path 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 by the first heat exchanger 21, and then carbon dioxide is removed by the carbon dioxide removing unit 56, and the water vapor separation membrane 16. In this case, the water vapor is removed to become a regenerated fuel gas.

  In the circulating 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 the regenerated fuel gas. Therefore, the regenerated fuel gas is used together with the fuel gas, The performance of the fuel cell 11 that generates power can be improved.

  Since other parts are the same as those in the first embodiment or the fourth embodiment, the same parts are denoted by the same reference numerals, and the description thereof is omitted.

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

  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, the water tank 26 and the pump 32 (FIG. 1) in the first embodiment are not necessary. Therefore, the system configuration is simplified.

  Further, not only the water vapor in the off gas is removed, but also the carbon dioxide in the off gas is removed to generate the regenerated fuel gas, so that the performance of the fuel cell 11 that generates power using the regenerated fuel gas is improved. be able to.

  The other parts are the same as those in the first embodiment, the second embodiment, the fourth embodiment, or the fifth embodiment, and therefore the same parts are denoted by the same reference numerals and the description thereof is omitted.

[Ninth Embodiment]
In FIG. 9, the circulating fuel cell system 90 according to the present embodiment is the one in which the carbon dioxide removal unit 56 is provided on the downstream side of the first heat exchanger 21 in the off-gas path 52 in the sixth embodiment.

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

  Further, not only the water vapor in the off gas is removed, but also the carbon dioxide in the off gas is removed to generate the regenerated fuel gas, so that the performance of the fuel cell 11 that generates power using the regenerated fuel gas is improved. be able to.

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

[Tenth embodiment]
10, in the circulating fuel cell system 100 according to the present embodiment, in the first embodiment, the water vapor separation membrane 16 removes water vapor 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 by the first heat exchanger 21, and then the water vapor and carbon dioxide are removed from the water vapor separation membrane 16 to become regenerated fuel gas.

  In the present embodiment, since the water vapor and 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 (fourth to ninth embodiments). For this reason, the system can be further simplified.

  Since other parts are the same as those in the first embodiment, the same parts are denoted by the same reference numerals in the drawings, and the description thereof is omitted.

[Example]
Compared to a conventional example using a condenser to remove water vapor, the heating width of the regenerated fuel gas can be reduced by using the water vapor separation membrane as in this embodiment. Assuming that only water was removed from off-gas using a water vapor separation membrane usable at 200 ° C., it was estimated that a thermal merit of 210 W would occur 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 merit of 2.23 kW would occur in a 10 kW class SOFC system.

[Other Embodiments]
As mentioned above, although an example of the present invention has been described, the embodiment of the present invention is not limited to the above, and it can be implemented with various modifications within the scope not departing from the gist of the present invention. Of course.

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

DESCRIPTION OF SYMBOLS 10 ... Circulating fuel cell system, 11 ... Fuel cell, 14 ... Fuel processing apparatus, 16 ... Steam separation membrane, 16B ... Permeation side, 20 ... Circulating fuel cell system, 21 ... 1st heat exchanger (heat exchanger) 22 ... second heat exchanger (heat exchanger), 30 ... circulating fuel cell system, 38 ... water, 40 ... circulating fuel cell system, 50 ... circulating fuel cell system, 52 ... off gas path, 56 ... dioxide Carbon removal section 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 (7)

A fuel processing apparatus for generating a fuel gas containing hydrogen by steam reforming the raw material gas;
A fuel cell that generates power using the fuel gas supplied from the fuel processor;
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;
A regenerated fuel gas path for supplying a regenerated fuel gas from which the water vapor has been removed from the off gas to the fuel cell;
The fuel processing apparatus is a circulating fuel cell system that generates the fuel gas by reforming the raw material gas using the water vapor removed by the water vapor separation membrane.   The circulating fuel cell system according to claim 1, wherein the water vapor removed by the water vapor separation membrane is used in a reforming reaction in the fuel processing apparatus as a gas.   The circulating fuel cell system according to claim 2, wherein the water vapor removed by the water vapor separation membrane is supplied to the fuel processing apparatus or mixed into the raw material gas using a blower.   The circulating fuel according to claim 2, wherein the raw material gas is allowed to flow to the permeation side of the water vapor separation membrane, and the water vapor removed by the water vapor separation membrane is directly mixed into the raw material gas and supplied to the fuel processing apparatus. Battery system.   The off-gas is cooled by performing heat exchange between at least one of the regenerated fuel gas, the raw material gas, air, the water vapor, and water condensed with the water vapor and the off gas, and the regenerated fuel gas and the raw material gas The circulating fuel cell system according to claim 1, further comprising a heat exchanger that heats at least one of the air, the water vapor, and the water condensed with the water vapor. In the off-gas path through which the off-gas flows, the carbon dioxide removing unit is provided on at least one of the upstream side and the downstream side of the heat exchanger and removes carbon dioxide in the off-gas,
The circulating fuel cell system according to claim 5, wherein the regenerated fuel gas is obtained by removing the water vapor and the carbon dioxide from the off gas. The water vapor separation membrane removes the water vapor and carbon dioxide from the off gas;
The circulating fuel cell system according to any one of claims 1 to 5, wherein the regenerated fuel gas is obtained by removing the water vapor and the carbon dioxide from the off-gas.

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