JP6739461B2 - Fuel cell system - Google Patents

Description

The present invention relates to a fuel cell system.

As a fuel cell system, a system in which the anode off gas discharged from the fuel cell stack is reused as a fuel for power generation has been developed. For example, Patent Document 1 discloses a configuration in which three fuel cells are connected in series and the anode off-gas discharged from the fuel cell stack in the preceding stage is supplied to the anode of the fuel cell stack in the following stage. .. In this way, when the anode off-gas is reused as the fuel for power generation, the concentration of the component that contributes to the reaction as the regenerated fuel is increased by removing water from the anode off-gas.

For example, in Patent Document 1, heat exchange is performed between the anode off gas and the regenerated fuel gas after water removal, the water vapor in the anode off gas is condensed, and water is removed from the anode off gas to obtain a regenerated fuel gas. However, since the flow rate of the regenerated fuel gas after water removal is smaller than that before water removal, it is difficult to sufficiently cool the anode off gas. On the other hand, in Patent Document 2, as in Patent Document 1, heat exchange is performed between the anode off gas and the regenerated fuel gas after water removal, and the anode off gas is cooled using condensed water separated from the anode off gas. There is. However, in order to cool the anode off-gas with condensed water, it is premised that sufficient condensation is performed, and sufficient cooling is difficult only by heat exchange with condensed water.

Patent No. 3924243 JP, 2015-138573, A

The present invention has been made in consideration of the above facts, and an object thereof is to obtain a fuel cell system capable of effectively condensing water in anode off-gas.

In the fuel cell system according to the invention of claim 1, power is generated by the fuel gas supplied to the fuel electrode and the air supplied to the air electrode, and the fuel cell in which the anode off gas is discharged from the fuel electrode and the anode off gas are A fuel regenerator that flows in, separates and stores the water in the anode offgas by condensation, and sends out the anode offgas after the water is separated as a regenerated fuel gas, the regenerated fuel gas, and the anode offgas. A first heat exchange section for exchanging heat between the fuel regenerating section and the air preheating section for exchanging heat between the air and the anode off-gas upstream of the first heat exchanging section. I have it.

A fuel cell system according to a first aspect includes a fuel cell and a fuel regeneration unit. The fuel regeneration unit separates and stores water in the inflowing anode off-gas by condensation, and sends out the anode off-gas after the water is separated as regenerated fuel gas. The regenerated fuel gas is used again for power generation or combustion.

The anode off gas is cooled by heat exchange with the regenerated fuel gas in the first heat exchange section. Further, it is cooled by heat exchange with air in the air preheating section. On the other hand, the regenerated fuel gas is heated by heat exchange with the anode off gas in the first heat exchange section, and the air toward the cathode is heated by heat exchange with the anode off gas in the air preheating section.

According to the fuel cell system of the first aspect, the anode off-gas is heat-exchanged with the regenerated fuel gas and also with the air supplied from the outside. Can be condensed. Further, since the air is heated in the air preheating section, the latent heat of water vapor can be effectively utilized in the system.

A fuel cell system according to a second aspect of the present invention performs heat exchange between a combustion unit that burns a combustible gas, air that has undergone heat exchange in the air preheating unit, and combustion exhaust gas that has been discharged from the combustion unit. 2 air preheating part, and.

According to the fuel cell system of the second aspect, the air taken in from the outside is heat-exchanged in the air preheating unit before heat exchange is performed with the combustion exhaust gas discharged from the combustion unit. The preheating part can effectively cool the anode off-gas.

In the fuel cell system according to the invention of claim 3, the fuel cell supplied with the fuel electrode and the air supplied with the air electrode generate electric power, and the anode off gas is discharged from the fuel electrode. A fuel regenerator that flows in, separates and stores the water in the anode offgas by condensation, and sends out the anode offgas after the water is separated as a regenerated fuel gas, the regenerated fuel gas, and the anode offgas. A first heat exchanging section for exchanging heat between the fuel regenerating section and the fuel preheating section for exchanging heat between the fuel gas and the anode off-gas upstream of the first heat exchanging section ; Equipped with.

A fuel cell system according to a third aspect includes a fuel cell and a fuel regeneration unit. The fuel regeneration unit separates and stores water in the inflowing anode off-gas by condensation, and sends out the anode off-gas after the water is separated as regenerated fuel gas. The regenerated fuel gas is used again for power generation or combustion.

The anode off gas is cooled by heat exchange with the regenerated fuel gas in the first heat exchange section. Further, it is cooled by heat exchange with the fuel gas in the fuel preheating section. On the other hand, the regenerated fuel gas is heated by heat exchange with the anode off gas in the first heat exchange section, and the fuel gas is heated by heat exchange with the fuel gas in the fuel preheating section.

According to the fuel cell system of the third aspect, the anode off-gas is also heat-exchanged with the fuel gas supplied from the outside in addition to the heat exchange with the regenerated fuel gas. Condensation can be performed. Further, since the fuel gas is heated in the fuel preheating section, the heat can be effectively utilized in the system.

According to a fourth aspect of the present invention, there is provided a fuel cell system in which the fuel gas supplied to the fuel electrode and the air supplied to the air electrode generate electric power, and the anode off gas is discharged from the fuel electrode. A fuel regenerator that inflows, water in the anode off-gas is separated and stored by condensation, and the anode off-gas after the water is separated is delivered as regenerated fuel gas, and a combustor that burns a combustible gas, A heat is exchanged between a first heat exchange section for exchanging heat between the regenerated fuel gas and the anode off gas, and a combustion exhaust gas discharged from the anode off gas and the combustion section on an upstream side of the fuel regeneration section. And an exhaust gas heat exchange section for performing exchange.

A fuel cell system according to a fourth aspect includes a fuel cell and a fuel regeneration unit. The fuel regeneration unit separates and stores water in the inflowing anode off-gas by condensation, and sends out the anode off-gas after the water is separated as regenerated fuel gas. The regenerated fuel gas is used again for power generation or combustion.

The anode off gas is cooled by heat exchange with the regenerated fuel gas in the first heat exchange section. Further, it is cooled by heat exchange with the combustion exhaust gas in the exhaust gas heat exchange section.

According to the fuel cell system of the fourth aspect, since the anode off-gas is heat-exchanged with the combustion exhaust gas in the system in addition to the heat exchange with the regenerated fuel gas, the temperature is further lowered and the condensation is effectively performed. It can be carried out. Further, since the combustion exhaust gas is discharged from the combustion section provided in the system, there is no need to install an external pipe, and the configuration can be simplified.

The fuel cell system according to the invention of claim 5 is provided on the upstream side of the exhaust gas heat exchange section, and has a first flow path that allows the combustion exhaust gas to flow into the exhaust gas heat exchange section, and does not flow into the exhaust gas heat exchange section. A second flow path and a branch portion that branches into a second flow path.

According to the fuel cell system of the fifth aspect, the temperature of the anode off-gas is adjusted by adjusting the flow rate of the combustion exhaust gas sent to the first flow path and the flow rate of the combustion exhaust gas sent to the second flow path. You can

A fuel cell system according to a sixth aspect of the present invention includes a cooling unit that is provided on the upstream side of the fuel regenerating unit and that performs heat exchange between the outside of the system and the anode off gas.

According to the fuel cell system of the sixth aspect, the anode off-gas can be cooled to a lower temperature by exchanging heat with the outside by the cooling unit.

The fuel cell system according to a seventh aspect of the present invention further includes a second fuel cell to which the regenerated fuel gas delivered from the fuel regeneration unit is supplied.

According to the fuel cell system of the seventh aspect, it is possible to configure a so-called multi-stage fuel cell system in which the regenerated fuel gas is used for power generation in the second fuel cell, and it is possible to improve power generation efficiency.

The fuel cell system according to the invention of claim 8 further comprises a regenerated fuel circulation path for supplying the regenerated fuel gas delivered from the fuel regeneration section to the fuel cell.

According to the fuel cell system of the eighth aspect, it is possible to configure a so-called circulation type fuel cell system in which the regenerated fuel gas is used for power generation again in the fuel cell, and it is possible to improve power generation efficiency.

Fuel cell system generates electric power by the air supplied to the fuel gas and the air electrode to be supplied to the fuel electrode, a fuel cell anode off-gas is discharged from the fuel electrode, the anode off-gas is flowed, the anode off-gas Water inside is separated and stored by condensation, and a fuel regenerator that sends out anode off gas after the water is separated as regenerated fuel gas; and the anode off gas and the air on the upstream side of the fuel regenerator. And an air preheating unit for exchanging heat with the air.

According to fuel cell systems, the anode off-gas, since the heat-exchanged with the air that is supplied to the air electrode, the temperature is lowered, can be effectively condense the water vapor. Further, since the air is heated in the air preheating section, the latent heat of water vapor can be effectively utilized in the system.

According to the fuel cell system of the present invention, the water in the anode off gas can be effectively condensed.

It is a schematic block diagram of the fuel cell system which concerns on 1st Embodiment. It is a schematic block diagram of the fuel cell system which concerns on the modification of 1st Embodiment. It is a schematic block diagram of the fuel cell system which concerns on the other modification of 1st Embodiment. It is a schematic block diagram of the fuel cell system which concerns on the other modification of 1st Embodiment. It is a schematic block diagram of the fuel cell system which concerns on 2nd Embodiment. It is a schematic block diagram of the fuel cell system which concerns on the modification of 2nd Embodiment. It is a schematic block diagram of the fuel cell system which concerns on the other modification of 2nd Embodiment. It is a schematic block diagram of the fuel cell system which concerns on the other modification of 2nd Embodiment. It is a schematic block diagram of the fuel cell system which concerns on 3rd Embodiment. It is a schematic block diagram of the fuel cell system which concerns on the modification of 3rd Embodiment. It is a schematic block diagram of the fuel cell system which concerns on the other modification of 3rd Embodiment. It is a schematic block diagram of the fuel cell system which concerns on the other modification of 3rd Embodiment. It is a schematic block diagram of the fuel cell system which concerns on the other modification of 3rd Embodiment.

[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a schematic configuration of a fuel cell system 10A according to this embodiment. The fuel cell system 10A according to the present embodiment has, as main components, a vaporizer 12, a reformer 14, a first fuel cell stack 16, a second fuel cell stack 18, a first heat exchange section 30, and a first heat exchange section 30. An air preheating unit 32, a second air preheating unit 34, a combustion unit 20, and a fuel regeneration unit 22 are provided. The fuel cell system 10A according to the present embodiment has a plurality of fuel cell cell stacks, and the gas discharged from the fuel cell cell stacks in the former stage is supplied to the fuel cell cell stacks in the latter stage to be used for power generation. Is a fuel cell system of.

One end of the raw material gas pipe P1 is connected to the vaporizer 12, and the other end of the raw material gas pipe P1 is connected to a gas source (not shown). The raw material gas pipe P1 is provided with a blower 24, and the blower 24 sends methane as a raw material gas to the vaporizer 12. Further, one end of a water supply pipe P2 is connected to the vaporizer 12, and the other end of the water supply pipe P2 is connected to a water source (not shown). A pump 26 is provided in the water supply pipe P2, and water (liquid phase) is sent to the vaporizer 12 by the pump 26. In the vaporizer 12, water is vaporized. The heat of the combustion exhaust gas from the combustion unit 20 described later is used for the vaporization.

Although methane is used as the source gas in the present embodiment, it is not particularly limited as long as it can be reformed, and a hydrocarbon fuel can be used. Examples of the hydrocarbon fuel include natural gas, LP gas (liquefied petroleum gas), coal reformed gas, and lower hydrocarbon gas. Examples of the lower hydrocarbon gas include lower hydrocarbons having 4 or less carbon atoms such as methane, ethane, ethylene, propane and butane, and methane used in the present embodiment is preferable. The hydrocarbon fuel may be a mixture of the above-mentioned lower hydrocarbon gas, and the above-mentioned lower hydrocarbon gas may be a gas such as natural gas, city gas or LP gas. Further, in the present embodiment, the fuel gas before reforming is referred to as a raw material gas, but the “fuel gas” in the present invention is directly or indirectly passed through a vaporizer, a reformer or the like to the anode of the fuel cell stack. Gas used for power generation, which is the raw material gas before reforming, the reformed gas obtained after reforming the raw material gas, and directly to the anode of the fuel cell stack without passing through the reformer for power generation. It includes all the supplied gas.

Further, in this embodiment, water is supplied for reforming the raw material gas, but other gas capable of reforming the raw material gas may be supplied. For example, carbon dioxide or oxygen can be supplied for reforming the raw material in place of or together with water.

Methane and steam are delivered from the vaporizer 12 to the reformer 14 via the pipe P3. The reformer 14 reforms methane to generate a fuel gas containing hydrogen at a temperature of about 600°C. One end of a fuel gas pipe P4 is connected to the reformer 14. The other end of the fuel gas pipe P4 is connected to the anode (fuel electrode) 16A of the first fuel cell stack 16. The fuel gas generated in the reformer 14 is supplied to the anode 16A via the fuel gas pipe P4.

The first fuel cell stack 16 is a solid oxide fuel cell stack (SOFC: Solid Oxide Fuel Cell) and has a plurality of stacked fuel cells. The operating temperature of the fuel cell stack 16 is set to about 650°C.

Each fuel cell of the fuel cell stack 16 has an electrolyte membrane, and an anode (fuel electrode) 16A and a cathode (air electrode) 16B, which are laminated on the front and back surfaces of the electrolyte membrane.

The basic structure of the second fuel cell stack 18 is similar to that of the first fuel cell stack 16, and has an anode 18A corresponding to the anode 16A and a cathode 18B corresponding to the cathode 16B.

One end of an air supply pipe P5 is connected to the cathode 16B of the first fuel cell stack 16. A blower 28 is connected to the other end of the air supply pipe P5. A first air preheating unit 32 and a second air preheating unit 34 are provided in the middle of the air supply pipe P5 in order from the upstream side. The air sent from the blower 28 is supplied to the cathode 16B by the air supply pipe P5 via the first air preheating unit 32 and the second air preheating unit 34. In the first air preheating unit 32, the air is heated by the anode off gas described later, and in the second air preheating unit 34, the air is further heated by the combustion exhaust gas from the combustion unit 20 described later.

At the cathode 16B, oxygen ions in the air react with electrons to generate oxygen ions, as shown in the following formula (1). The generated oxygen ions reach the anode 16A of the fuel cell stack 16 through the electrolyte membrane.

(Air electrode reaction)
1/2O ₂ +2e ⁻ →O ^{2 −} (1)

Cathode off-gas is discharged from the cathode 16B. A cathode offgas pipe P6 for guiding the cathode offgas discharged from the cathode 16B to the cathode 18B of the second fuel cell stack 18 is connected to the cathode 16B. In the present embodiment, the example in which the air supply pipe P5 is connected only to the cathode 16B has been described, but the air supply pipe P5 is branched and connected to the cathode 16B and the cathode 18B to supply air in parallel. You may.

On the other hand, in the anode 16A of the fuel cell stack 16, oxygen ions that have passed through the electrolyte membrane react with hydrogen and carbon monoxide in the fuel gas, as shown in equations (2) and (3) below, (Steam) and carbon dioxide and electrons are generated. Electrons generated in the anode 16A move from the anode 16A to the cathode 16B through an external circuit, so that power is generated in each fuel cell stack. Each fuel cell stack also generates heat during power generation.

(Fuel electrode reaction)
H ₂ +O ^{2 −} →H ₂ O+2e ⁻ (2)
CO+O ^{2 −} →CO ₂ +2e ⁻ (3)

One end of an anode offgas pipe P7 is connected to the anode 16A. The anode off gas is discharged from the anode 16A to the anode off gas pipe P7. The anode off-gas contains unreacted hydrogen, unreacted carbon monoxide, carbon dioxide, water vapor and the like.

The other end of the anode offgas pipe P7 is connected to the fuel regeneration unit 22 via a first heat exchange unit 30 and a first air preheating unit 32, which will be described later. One end of a regenerated fuel gas pipe P9 is connected to the outlet side of the fuel regenerator 22. The other end of the regenerated fuel gas pipe P9 is connected to the anode 18A of the second fuel cell stack 18 via a first heat exchange unit 30 described later.

In the fuel regenerator 22, water condensed by cooling by heat exchange is stored from the anode off gas. Further, the anode off gas after the water is removed is sent to the regenerated fuel gas pipe P9 as the regenerated fuel gas.

The regenerated fuel gas passes through the regenerated fuel gas pipe P9, passes through the first heat exchange section 30, and is delivered to the anode 18A of the second fuel cell stack 18 for power generation. From the anode 18A of the second fuel cell stack 18, the anode off gas is delivered to the combustion unit 20 through the anode off gas pipe P11.

One end of a cathode offgas pipe P12 is connected to the outlet side of the cathode 18B. The other end of the cathode offgas pipe P12 is connected to the combustion unit 20, and the cathode offgas is delivered to the combustion unit 20.

In the combustion section 20, the anode off gas discharged from the anode 18A of the second fuel cell stack 18 is combusted. The raw material gas pipe P1 may be branched and the raw material gas may be supplied to the combustion unit 20 as necessary. One end of the combustion exhaust gas pipe P10 is connected to the outlet side of the combustion section 20. Combustion exhaust gas is discharged from the combustion unit 20 to the combustion exhaust gas pipe P10. The combustion exhaust gas pipe P10 is opened to the outside through the second air preheating section 34 and the carburetor 12. The combustion exhaust gas undergoes heat exchange with the air heated in the first air preheating unit 32 in the second air preheating unit 34. After that, the combustion exhaust gas is sent to the vaporizer 12, and the vaporizer 12 exchanges heat with water and methane. The combustion exhaust gas is discharged to the outside (outside the fuel cell system 10A) after heat exchange is performed in the vaporizer 12.

Next, the operation of the fuel cell system 10A of this embodiment will be described.

The air delivered by the blower 28 at a predetermined air discharge amount is supplied to the cathode 16B via the first air preheating unit 32 and the second air preheating unit 34, and is used for power generation. From the cathode 16B, cathode off gas is delivered to the cathode 18B through the cathode off gas pipe P6. Then, the cathode off-gas is used for power generation at the cathode 18B, and then sent to the combustion section 20 through the cathode off-gas pipe P12.

On the other hand, the methane delivered by the blower 24 at a predetermined discharge amount is supplied to the vaporizer 12 via the raw material gas pipe P1. The water (liquid phase) delivered by the pump 26 at a predetermined discharge amount is supplied to the vaporizer 12 through the water supply pipe P2. The water and methane supplied to the vaporizer 12 are heated by heat exchange with the combustion exhaust gas. As a result, the water is vaporized, and the heated methane and steam are sent to the reformer 14 via the pipe P3. Then, it is reformed in the reformer 14, and the fuel gas is supplied from the reformer 14 to the anode 16A through the fuel gas pipe P4 and used for power generation. Anode offgas containing fuel such as unreacted hydrogen is discharged from the anode 16A and sent to the fuel regeneration unit 22 via the anode offgas pipe P7.

The anode off-gas is cooled by heat exchange in the first heat exchange section 30 and the first air preheating section 32 provided on the upstream side of the fuel regeneration section 22. That is, the anode off-gas heats the regenerated fuel gas by heat exchange with the regenerated fuel gas in the first heat exchange section 30 to remove heat from the anode off gas, and at the same time, heat is exchanged with the room temperature air in the first air preheating section 32 to generate air. Is heated to remove the heat. As a result, the anode off gas is cooled and the water in the anode off gas is condensed.

In the fuel regenerator 22, water (liquid phase) separated from the anode off gas by condensation is stored. The stored water may be sent to the vaporizer 12 for reuse or may be discarded. The regenerated fuel gas from which the water has been removed passes through the regenerated fuel gas pipe P9 from the fuel regeneration unit 22, passes through the first heat exchange unit 30, and is sent to the anode 18A of the second fuel cell stack 18 for power generation. It From the anode 18A, the anode off gas is delivered to the combustion section 20 through the anode off gas pipe P11.

In the combustion section 20, the anode off gas is used for combustion, and the reformer 14 is heated by the heat generated by the combustion. Combustion exhaust gas is sent from the combustion unit 20 to the combustion exhaust gas pipe P10, and heat is exchanged with the air in the second air preheating unit 34. The air is heated and the flue gas is cooled. The flue gas is then delivered to the vaporizer 12 for heat exchange with methane and water. Methane and water are heated and flue gas is cooled. Then, the combustion exhaust gas is discharged to the outside.

In this embodiment, the air at room temperature and the anode off gas discharged from the first anode 16A are heat-exchanged. Therefore, the temperature of the anode off-gas can be reduced as compared with the case where the heat is exchanged only by the first heat exchange unit 30 to cool the anode off-gas. Thereby, the water vapor in the anode off gas can be efficiently condensed.

Further, since the air heated by the heat exchange is supplied into the system system toward the first fuel cell stack 16, the heat of the anode off-gas is not released to the outside of the system, so that the heat radiation can be suppressed and the power generation efficiency can be reduced. Can be improved.

In the present embodiment, the first air preheating unit 32 is arranged on the downstream side of the anode offgas pipe P7 of the first heat exchange unit 30, but as shown in FIG. It may be installed on the upstream side of the anode off-gas passage of the first heat exchange unit 30.

In addition, in the present embodiment, the air sent from the blower 28 undergoes heat exchange in the first air preheating section 32, and then is sent to the second air preheating section 34 to perform heat exchange. The air may be first sent to the air preheating unit 34 to perform heat exchange with the combustion exhaust gas, and then sent to the first air preheating unit 32 to perform heat exchange. By performing the heat exchange in the first air preheating section 32 first as in the present embodiment, it is possible to effectively cool the anode off-gas in the first air preheating section 32 before the temperature of the air rises. it can.

Further, the fuel cell system 10A of the present embodiment may be further provided with a radiator 50 as shown in FIG. The radiator 50 is connected to an external cooling pipe P8 that is branched from between the first air preheating unit 32 and the fuel regeneration unit 22 of the anode offgas pipe P7. An open/close valve V1 is provided in the external cooling pipe P8, and an open/close valve V2 is provided downstream of the branch portion of the anode off-gas pipe P7 with the external cooling pipe P8. The open/close valves V1 and V2 are controlled by a control unit (not shown).

When the opening/closing valve V1 is opened and the opening/closing valve V2 is closed, the anode off-gas is cooled in the first air preheating section 32 and then sent to the radiator 50 to be further cooled and sent to the fuel regeneration section 22. .. When the opening/closing valve V2 is opened and the opening/closing valve V1 is closed, the anode off-gas is cooled in the first air preheating section 32 and then sent to the fuel regeneration section 22 without passing through the radiator 50.

By thus providing the radiator 50, when the water contained in the anode off-gas is not sufficiently condensed, the anode off-gas can be further cooled by the radiator 50 to increase the amount of water contained in the anode off-gas. it can. When the water contained in the anode off-gas is sufficiently condensed, the anode off-gas can be sent to the fuel regenerator 22 without being cooled by the radiator 50.

In the present embodiment, the radiator 50 is provided in the external cooling pipe P8 obtained by branching the anode off-gas pipe P7. However, the radiator 50 is provided in the anode off-gas pipe P7 without branching and the fan of the radiator 50 is turned on/off. By doing so, the temperature of the anode off gas may be controlled.

Further, in the present embodiment, the so-called multi-stage fuel cell system including the second fuel cell stack 18 in addition to the first fuel cell stack 16 has been described, but the present invention is shown in FIG. The fuel cell system 10B of the so-called circulation type can also be configured. In the fuel cell system 10B, the second fuel cell stack 18 is not provided, and the regenerated fuel gas pipe P9 is branched into two on the downstream side of the first heat exchange section 30. One first branch pipe P9-1 is connected to the fuel gas pipe P4 heading to the inlet side of the first anode 16A, and the other second branch pipe P9-2 is connected to the combustion unit 20. The regenerated fuel gas is supplied to the first anode 16A via the first branch pipe P9-1, and the regenerated fuel gas is supplied to the combustion unit 20 via the second branch pipe P9-2. The first branch pipe P9-1 may be connected to the reformer 14 and may supply the regenerated fuel gas to the first anode 16A via the reformer 15.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. In this embodiment, the same parts as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

As shown in FIG. 5, the fuel cell system 10C of the present embodiment has a fuel preheating unit 36 instead of the first air preheating unit 32.

The anode off-gas pipe P7 is connected to the fuel regeneration unit 22 via the fuel preheating unit 36 on the downstream side of the first heat exchange unit 30. The raw material gas pipe P1 is connected to the inlet side of the reformer 14 via the fuel preheating section 36. In the fuel preheating unit 36, heat exchange is performed between the raw material gas at room temperature and the anode off gas, the anode off gas is cooled, and the raw material gas is heated. The air sent from the blower 28 to the air supply pipe P5 is supplied to the cathode 16B via the second air preheating unit 34.

Also in this embodiment, the raw material gas at room temperature and the anode off gas discharged from the first anode 16A are heat-exchanged. Therefore, the temperature of the anode off-gas can be reduced as compared with the case where the heat is exchanged only by the first heat exchange unit 30 to cool the anode off-gas. Thereby, the water vapor in the anode off gas can be efficiently condensed.

Further, since the raw material gas heated by the heat exchange is supplied to the inside of the system system toward the first fuel cell stack 16 (such as the vaporizer 12 and the reformer 14), the heat of the anode off gas is released to the outside of the system. Therefore, the power generation efficiency can be improved.

In the present embodiment, the fuel preheating section 36 is arranged on the downstream side of the anode offgas pipe P7 of the first heat exchanging section 30, but as shown in FIG. 6, the fuel preheating section 36 is replaced by the first heat exchanging section. It may be installed on the upstream side of the anode off-gas path of 30.

Further, in the present embodiment, the fuel preheating unit 36 is provided instead of the first air preheating unit 32 of the first embodiment, but the fuel preheating unit 36 may be provided in addition to the first air preheating unit 32.

Also in this embodiment, as in the first embodiment, the fuel cell system 10C may be further provided with a radiator 50 as shown in FIG. 7. The radiator 50 is connected to an external cooling pipe P8 that is branched from between the fuel preheating unit 36 of the anode offgas pipe P7 and the fuel regeneration unit 22.

Further, in the present embodiment, the so-called multi-stage fuel cell system including the second fuel cell stack 18 in addition to the first fuel cell stack 16 has been described, but the present invention is shown in FIG. 8. The fuel cell system 10D may be configured as a so-called circulation type fuel cell system.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. In the present embodiment, the same parts as those in the first and second embodiments are designated by the same reference numerals, and detailed description thereof will be omitted.

As shown in FIG. 9, the fuel cell system 10E of the present embodiment has an exhaust gas heat exchange section 38 instead of the first air preheating section 32.

The anode off-gas pipe P7 is connected to the fuel regeneration unit 22 via the exhaust gas heat exchange unit 38 on the downstream side of the first heat exchange unit 30. The combustion exhaust gas pipe P10 is opened to the outside of the fuel cell system 10D via the second air preheating unit 34, the vaporizer 12, and the exhaust gas heat exchange unit 38 in this order. In the exhaust gas heat exchange section 38, heat is exchanged between the combustion exhaust gas cooled by the heat exchange in the second air preheating section 34 and the vaporizer 12 and the anode off gas, and the anode off gas is cooled. The combustion exhaust gas is discharged to the outside (outside the system of the fuel cell system 10E) after heat exchange is performed in the exhaust gas heat exchange section 38. The exhaust gas heat exchange section 38 is a heat exchange section immediately before the combustion exhaust gas is discharged to the outside of the fuel cell system 10E.

In the fuel cell system 10E of the present embodiment, heat exchange is performed between the cooled combustion exhaust gas flowing in the combustion exhaust gas pipe P10 in the system and the anode off gas discharged from the first anode 16A. Therefore, the temperature of the anode off-gas can be reduced as compared with the case where the heat is exchanged only by the first heat exchange unit 30 to cool the anode off-gas. Thereby, the water vapor in the anode off gas can be efficiently condensed.

Further, since the combustion exhaust gas used for heat exchange flows through the combustion exhaust gas pipe P10, it is possible to use the piping in the system system, a new external piping is not required, and an increase in the number of parts of the system can be suppressed. it can.

In the present embodiment, the exhaust gas heat exchange section 38 is arranged on the downstream side of the anode offgas pipe P7 of the first heat exchange section 30, but as shown in FIG. It may be installed on the upstream side of the anode off-gas passage of the exchange unit 30.

Further, in the present embodiment, the exhaust gas heat exchange section 38 is provided in place of the first air preheating section 32 of the first embodiment, but the exhaust gas heat exchange section 38 may be provided in addition to the first air preheating section 32. .. Further, an exhaust gas heat exchange section 38 may be provided in addition to the fuel preheating section 36 of the second embodiment. Further, all of the first air preheating unit 32, the fuel preheating unit 36 of the second embodiment, and the exhaust gas heat exchange unit 38 may be provided.

Further, as shown in FIG. 11, a flow rate adjusting unit 48 is provided on the upstream side of the exhaust gas heat exchange unit 38 of the fuel cell system 10E of the present embodiment, and a part of the combustion exhaust gas is branched to the second flow path P10B. Alternatively, the heat may be released outside without passing through the exhaust gas heat exchange section 38. In this case, the temperature of the anode off-gas can be adjusted by adjusting the amount of the combustion exhaust gas flowing from the flow rate adjusting unit 48 into the exhaust gas heat exchange unit 38 via the first flow path P10A.

Further, the fuel cell system 10E of the present embodiment may be further provided with a radiator 50 as shown in FIG. The radiator 50 is connected to an external cooling pipe P8 that branches from between the exhaust gas heat exchange portion 38 of the anode off-gas pipe P7 and the fuel regeneration portion 22.

Further, in the present embodiment, the so-called multi-stage fuel cell system including the second fuel cell stack 18 in addition to the first fuel cell stack 16 has been described, but the present invention is shown in FIG. 13. Alternatively, the so-called circulation type fuel cell system 10F may be configured.

The fuel cell of the present invention is not limited to a solid oxide fuel cell (SOFC), and may be another fuel cell such as a molten carbonate fuel cell (MCFC). May be.

Further, in the above-described first to third embodiments, the hydrocarbon fuel is used as the raw material gas and the hydrocarbon fuel is reformed in the reformer 14 to obtain the fuel gas, but pure hydrogen may be used as the fuel. Good. In this case, the vaporizer 12 and the reformer 14 are unnecessary, and pure hydrogen is directly supplied to the first anode 16A of the fuel cell stack 16.

10A, 10B, 10C, 10D, 10E, 10F Fuel cell system 16 First fuel cell stack (fuel cell)
16A 1st anode (fuel electrode)
16B First cathode (air electrode)
18 Second Fuel Cell Stack (Second Fuel Cell)
20 Combustion Section 22 Fuel Regeneration Section 30 First Heat Exchange Section 32 First Air Preheating Section (Air Preheating Section)
34 2nd air preheating part 36 Fuel preheating part 38 Exhaust gas heat exchange part 48 Flow rate adjustment part (branch part)
50 radiator (cooling unit)
P8 External cooling pipe (cooling unit)
P9-1 First branch pipe (recycled fuel circuit)
P10 Combustion exhaust gas pipe P10A First flow path P10B Second flow path

Claims (8)

A fuel cell in which power is generated by the fuel gas supplied to the fuel electrode and the air supplied to the air electrode, and the anode off gas is discharged from the fuel electrode;
A fuel regenerator that inflows the anode off-gas, separates and stores the water in the anode off-gas by condensation, and sends out the anode off-gas after the water is separated as regenerated fuel gas;
A first heat exchanging section for exchanging heat between the regenerated fuel gas and the anode off gas;
An air preheating unit for exchanging heat between the air and the anode offgas upstream of the fuel regeneration unit and the first heat exchange unit ;
Fuel cell system equipped with. A combustion unit that burns combustible gas,
A second air preheating unit that performs heat exchange between the air that has undergone heat exchange in the air preheating unit and the combustion exhaust gas that has been discharged from the combustion unit;
The fuel cell system according to claim 1, further comprising: A fuel cell in which power is generated by the fuel gas supplied to the fuel electrode and the air supplied to the air electrode, and the anode off gas is discharged from the fuel electrode;
A fuel regenerator that inflows the anode off-gas, separates and stores the water in the anode off-gas by condensation, and sends out the anode off-gas after the water is separated as regenerated fuel gas;
A first heat exchanging section for exchanging heat between the regenerated fuel gas and the anode off gas;
A fuel preheating unit for exchanging heat between the fuel gas and the anode off-gas upstream of the fuel regeneration unit and the first heat exchange unit ;
Fuel cell system equipped with. A fuel cell in which power is generated by the fuel gas supplied to the fuel electrode and the air supplied to the air electrode, and the anode off gas is discharged from the fuel electrode;
A fuel regenerator that inflows the anode off-gas, separates and stores the water in the anode off-gas by condensation, and sends out the anode off-gas after the water is separated as regenerated fuel gas;
A combustion unit that burns combustible gas,
A first heat exchanging section for exchanging heat between the regenerated fuel gas and the anode off gas;
The anode off-gas on the upstream side of the fuel regeneration section, and an exhaust gas heat exchange section for performing heat exchange between the combustion exhaust gas cooled by heat exchange after being discharged from the combustion section,
Fuel cell system equipped with. A branch portion provided on the upstream side of the exhaust gas heat exchange portion and branched into a first flow passage that allows the combustion exhaust gas to flow into the exhaust gas heat exchange portion and a second flow passage that does not flow into the exhaust gas heat exchange portion, The fuel cell system according to claim 4, further comprising: The fuel cell according to any one of claims 1 to 5, further comprising a cooling unit that is provided on an upstream side of the fuel regeneration unit and that performs heat exchange between the outside of the system and the anode off gas. system. The fuel cell system according to any one of claims 1 to 6, further comprising a second fuel cell to which the regenerated fuel gas delivered from the fuel regenerator is supplied. The fuel cell system according to claim 1, further comprising a regenerated fuel circulation path that supplies the regenerated fuel gas delivered from the fuel regenerating unit to the fuel cell.