JP7720271B2 - fuel cell system - Google Patents

Description

The present invention relates to a fuel cell system.

Fuel cell systems are sometimes installed in environments where the air contains a large amount of impurities. If air containing impurities is continuously supplied to the cathode of the fuel cell stack for power generation, deterioration such as catalyst poisoning and corrosion of component parts in the fuel cell stack will accelerate, potentially leading to system failure or a shortened lifespan.

Patent Document 1 discloses a technology for removing impurities by bubbling air through reforming water, dissolving the impurities in the air into condensed water, and supplying the purified air to the air electrode. According to the technology in Patent Document 1, water-soluble impurities can be easily removed from air using reforming water.

Japanese Patent Application Laid-Open No. 2000-331703

However, if the reformed water tank is sealed and bubbled, as in Patent Document 1, it is possible that air may flow back into the condenser or other piping.

The present invention was developed in consideration of the above, and aims to easily purify the air supplied to the air electrode of a fuel cell while suppressing backflow of air.

The fuel cell system of claim 1 includes a reforming unit that reforms a feed gas to produce fuel gas containing hydrogen gas; a fuel cell that generates electricity using the fuel gas supplied to an anode and air supplied to an cathode; a condensing unit that condenses water in off-gas discharged from the fuel cell; an inlet through which the water condensed in the condensing unit flows; a water storage chamber that stores the water that flows in from the inlet; an air inlet provided at the bottom of the water storage chamber for flowing air into the water storage chamber; a post-bubbling air storage unit at the top of the water storage chamber that stores the air that flows in from the air inlet; and an isolation unit that isolates the inlet from the post-bubbling air storage unit; a post-bubbling air supply path that supplies the air stored in the post-bubbling air storage unit to the cathode; and a reforming water supply path that supplies reforming water from the water storage chamber to the reforming unit.

In the fuel cell system of claim 1, the reforming water tank has a water storage chamber. Condensed water, which is water in the off-gas condensed in the condenser, flows into the water storage chamber from an inlet and is stored therein. An air inlet is provided at the bottom of the water storage chamber to allow air to flow into the water storage chamber. When air flows in from the air inlet, water-soluble impurities in the air are dissolved in the water in the water storage chamber and removed from the air. The air from which impurities have been removed is stored in a post-bubbling air storage chamber at the top of the bubbling water storage chamber. The air stored in the post-bubbling air storage chamber is supplied to the air electrode via a post-bubbling air supply channel. The condensed water stored in the water storage chamber is supplied to the reformer via a reforming water supply channel as reforming water.

In the fuel cell system of claim 1, the inlet and the post-bubbling air storage section are separated by the isolation section, which prevents air from entering the inlet from the post-bubbling air storage section and flowing back.

In the fuel cell system according to claim 2, the isolation section is composed of a partition wall that extends from the top surface of the reforming water tank to a position lower than the water level in the water storage chamber and separates the post-bubbling air storage section.

In the fuel cell system according to claim 2, by providing a partition wall from the top surface to a position lower than the water level in the water storage section, the inlet and the post-bubbling air storage section can be separated with a simple structure.

The fuel cell system according to claim 3 has a discharge path that allows water to overflow and discharge from the water storage chamber at a predetermined water level.

The fuel cell system according to claim 3 makes it easy to maintain the water level in the water storage chamber.

In the fuel cell system according to claim 4, the water storage chamber includes a condensed water storage chamber into which water flows in from the inlet, and a bubbling water storage chamber isolated from the condensed water storage chamber and connected to the air inlet, the reforming water supply passage is connected to the condensed water storage chamber, and the post-bubbling air storage section is formed in the bubbling water storage chamber.

In the fuel cell system of claim 4, the water storage chamber is divided into a condensed water storage chamber and a bubbling water storage chamber, so the water in the bubbling water storage chamber, which contains dissolved water-soluble impurities in the air, does not move to the condensed water storage chamber. Therefore, water with fewer impurities can be supplied to the reforming section as reforming water.

The fuel cell system according to the present invention can easily purify the air supplied to the fuel cell's air electrode and suppress backflow of air.

1 is a configuration diagram of a fuel cell system according to a first embodiment. FIG. 10 is a configuration diagram of a fuel cell system according to a second embodiment. FIG. 10 is a configuration diagram of a fuel cell system according to a third embodiment.

First Embodiment
A first embodiment of the present invention will be described with reference to the drawings.

The fuel cell system 10A is a power generation system installed in a user's home, an apartment building, a factory, etc. Figure 1 shows an outline of the main components of the fuel cell system 10A according to an embodiment of the present invention. The main components of the fuel cell system 10A according to an embodiment of the present invention include a fuel cell stack 12, a reformer 14, a combustor 16, a condenser 18, a reforming water tank 30, and an ion exchange resin 22.

A raw material gas supply pipe P1 is connected to the reformer 14, and raw material gas is supplied from the raw material gas supply pipe P1 to the reformer 14 by a raw material gas supply blower B1. The raw material gas is not particularly limited as long as it can be reformed, and hydrocarbon fuels can be used. Examples of hydrocarbon fuels include methane, city gas, natural gas, LP gas (liquefied petroleum gas), coal-reformed gas, and lower hydrocarbon gases. Biogas may also be used.

The reformer 14 reforms the raw material gas to produce fuel gas containing hydrogen. The reformer 14 is connected to the fuel electrode 12A of the fuel cell stack 12. The fuel gas produced in the reformer 14 is supplied to the fuel electrode 12A of the fuel cell stack 12 via the fuel gas pipe P2.

The fuel cell stack 12 is a cell stack having multiple stacked fuel cells. The fuel cell stack 12 is an example of a fuel cell in the present invention, and each fuel cell has an electrolyte layer (not shown) and a fuel electrode 12A and an air electrode 12B stacked on the front and back surfaces of the electrolyte layer, respectively. Various fuel cells can be used as the fuel cell stack 12, including solid oxide fuel cells (SOFCs), molten carbonate fuel cells (MCFCs), and polymer electrolyte fuel cells (PEFCs). In this embodiment, a PEFC will be used as an example.

One end of a clean air supply channel P6 is connected to the air electrode 12B of the fuel cell stack 12, and a clean air supply blower B3 is connected to the clean air supply channel P6. The upstream end of the clean air supply channel P6 is connected to a clean air outlet 33 of the reforming water tank 30, which will be described later. External air that has passed through an air electrode filter 24 and a bubbling section 34B, which will be described later, is supplied to the air electrode 12B by the clean air supply blower B3. Details of the air electrode filter 24 and the bubbling section 34B will be described later.

In the fuel cell stack 12, electricity is generated through a power generation reaction at the fuel electrode 12A and the air electrode 12B, and the electricity is output to a circuit (not shown).

Anode offgas is discharged from the anode 12A to the anode offgas channel P3, and cathode offgas is discharged from the cathode 12B to the cathode offgas channel P7. The anode offgas contains fuel gas that has not reacted in the power generation reaction, and is supplied from the anode offgas channel P3 to the combustor 16 for combustion. The cathode offgas contains oxygen that has not reacted in the power generation reaction, water produced in the power generation reaction, and other substances. The cathode offgas is sent to the condenser 18 from the cathode offgas channel P7.

The combustor 16 is located adjacent to the reformer 14 and heats the reformer 14 with the heat of combustion. Anode off-gas is supplied to the combustor 16 from the anode off-gas passage P3, and combustible components in the anode off-gas are combusted by reaction with oxygen contained in air supplied from an air supply pipe (not shown).

A combustion exhaust gas passage P4 is connected to the outlet side of the combustor 16. Combustion exhaust gas is discharged from the combustor 16 to the outside via the combustion exhaust gas passage P4. Note that while this embodiment describes an example in which combustion exhaust gas is discharged to the outside, the combustion exhaust gas passage P4 may also be connected to a condenser 18, and water in the combustion exhaust gas may also be condensed and reused.

The other end of the cathode off-gas passage P7 is connected to the condenser 18, where the gas-phase water in the cathode off-gas is condensed and separated into gas and liquid. The liquid water is sent to the reforming water tank 30 via passage P8. A check valve V1 is provided in passage P8. The cathode off-gas from which the water has been removed is discharged through discharge passage P9.

The reformed water tank 30 comprises a condensed water storage chamber 32 and a bubbling water storage chamber 34. The condensed water storage chamber 32 and the bubbling water storage chamber 34 form the water storage chamber of the present invention. The condensed water storage chamber 32 comprises an inflow water storage section 32B in which water is stored, and a gas storage section 32A in which gas is stored above the water surface in the inflow water storage section 32B. The bubbling water storage chamber 34 comprises a bubbling section 34B in which water is stored, and a post-bubbling air storage section 34A in which gas is stored above the water surface in the bubbling section 34B. An air chamber partition wall 38 is provided between the condensed water storage chamber 32 and the bubbling water storage chamber 34. The air chamber partition wall 38 separates the gas storage section 32A and the post-bubbling air storage section 34A to prevent gas from moving between them, and hangs down from the ceiling surface of the reforming water tank 30 to below the water surface in the bubbling section 34B. The lower end of the air chamber partition wall 38 is spaced apart from the floor, and is positioned so that the inflow water storage section 32B and the bubbling section 34B are connected at their lower ends. The lower end of the air chamber partition wall 38 is positioned so that air supplied from the air inflow section 35 (described below) does not flow over the air chamber partition wall 38 from the bubbling section 34B to the condensed water storage chamber 32 side.

A condensed water inlet 31 is provided at the top of the gas storage section 32A of the condensed water storage chamber 32. The downstream end of flow path P8 is connected to the condensed water inlet 31, and water condensed in the condenser 18 flows from the condensed water inlet 31 into the condensed water storage chamber 32 and is stored in the influent water storage section 32B. A reforming water outlet 37 is provided at the bottom of the influent water storage section 32B of the condensed water storage chamber 32.

A clean air outlet 33 is provided above the post-bubbling air storage section 34A of the bubbling water storage chamber 34. The upstream end of the clean air supply path P6 is connected to the clean air outlet 33.

Condensed water flows into the bubbling water storage chamber 34 from the condensed water storage chamber 32 through the communication portion below the air chamber partition wall 38.

An air inlet 35 is provided at the bottom of the side wall of the bubbling section 34B of the bubbling water storage chamber 34. One end of an air supply pipe P5 is connected to the air inlet 35, and an air supply blower B2 is connected to the air supply pipe P5. An air electrode filter 24 is provided on the air supply pipe P5 upstream of the air supply blower B2. External air that has passed through the air electrode filter 24 is supplied from the air inlet 35 to the bubbling section 34B by the air supply blower B2. Foreign matter is physically removed from the external air by the air electrode filter 24, and water-soluble impurities are dissolved and removed in the water stored in the bubbling section 34B. After bubbling, the external air is stored in the air storage section 34A.

A water discharge channel P11 is provided on the side wall of the condensed water storage chamber 32. The water discharge channel P11 is installed so that water is drained by overflow when the water level in the condensed water storage chamber 32 reaches a predetermined level.

One end of the reforming water supply channel P10 is connected to the reforming water outlet 37 located at the bottom of the condensed water storage chamber 32. The reforming water supply channel P10 is provided with a pump 21 and an ion exchange resin 22. The other end of the reforming water supply channel P10 is connected to the reformer 14, and the water stored in the condensed water storage chamber 32 is supplied to the reformer 14 as reforming water via the ion exchange resin 22 when driven by the pump 21. The ion exchange resin 22 removes impurities from the water passing through it by ion exchange.

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

In the fuel cell system 10A, air stored in the post-bubbling air storage section 34A is supplied to the air electrode 12B of the fuel cell stack 12 by the clean air supply blower B3 through the clean air supply path P6. The air stored in the post-bubbling air storage section 34A is supplied from the air inlet section 35 to the bubbling section 34B and bubbled, so water-soluble impurities are dissolved in the water stored in the bubbling section 34B and removed. Therefore, purified air can be supplied to the air electrode 12B.

In addition, the air electrode off-gas discharged from the air electrode 12B is sent to the condenser 18 through the air electrode off-gas passage P7, where the water contained in the air electrode off-gas is condensed and stored in the condensed water storage chamber 32 and bubbling water storage chamber 34 of the reforming water tank 30. This eliminates the need to prepare a separate bubbling tank and enables impurities to be removed from the air supplied to the air electrode 12B with a simple configuration.

In addition, the gas storage section 32A is separated from the post-bubbling air storage section 34A by the air chamber partition wall 38, which prevents air from flowing from the post-bubbling air storage section 34A into the condensed water inlet 31.

In addition, the water stored in the condensed water storage chamber 32 and the bubbling water storage chamber 34 is discharged through the water discharge passage P11 by overflow, making it easy to manage the water level in the reforming water tank 30.

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.

The fuel cell system 10B of this embodiment has a water partition wall 36 in addition to the air chamber partition wall 38 of the fuel cell system 10A of the first embodiment. Furthermore, instead of the water discharge channel P11, a bubbling water discharge port 39, a bubbling water discharge channel P12, and a solenoid valve V2 are provided. Other than these, the configuration is the same as that of the fuel cell system 10A of the first embodiment shown in FIG. 1.

As shown in FIG. 2, the fuel cell system 10B has a water partition wall 36 provided in the reforming water tank 30. The water partition wall 36 is provided at a distance from the air chamber partition wall 38, closer to the condensed water storage chamber 32 than the air chamber partition wall 38. The upper end of the water partition wall 36 is set at a position lower than the air chamber partition wall 38, so that water on the condensed water storage chamber 32 side overflows over the water partition wall 36 and flows into the bubbling water storage chamber 34 side.

A water seal section 40 is formed between the water partition wall 36 and the air chamber partition wall 38. The water level in the water seal section 40 is the same height as the bubbling section 34B, allowing water to overflow from the condensed water storage chamber 32 to the bubbling water storage chamber 34, but it is sealed with water to prevent gas from moving between the gas storage section 32A and the post-bubbling air storage section 34A.

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

In this embodiment, as in the first embodiment, impurities can be removed from the air supplied to the air electrode 12B with a simple configuration, and air inflow from the post-bubbling air reservoir 34A to the condensed water inlet 31 can be suppressed.

Furthermore, in this embodiment, the inflow water storage section 32B is separated from the bubbling section 34B by the water partition wall 36, preventing water from moving from the bubbling section 34B, so condensed water without dissolved impurities can be supplied to the reformer 14 as reforming water.

In addition, in this embodiment, the condensed water inlet 31 can be isolated from the post-bubbling air reservoir 34A with a simple structure by sealing with water stored in the bubbling section 34B.

Third Embodiment
Next, a third embodiment of the present invention will be described. In this 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.

The fuel cell system 10C of this embodiment does not have the bubbling water outlet 39, bubbling water discharge channel P12, or solenoid valve V2 of the fuel cell system 10B of the second embodiment, but instead has the water discharge channel P11 of the fuel cell system 10A of the first embodiment. Other than these, the configuration is the same as that of the fuel cell system 10B of the second embodiment shown in FIG. 2.

As shown in FIG. 3, in the fuel cell system 10C, the water discharge channel P11 is positioned vertically higher than the upper end of the water partition wall 36. When the water level in the condensed water storage chamber 32 exceeds the upper end of the water partition wall 36, water overflows from the condensed water storage chamber 32 to the bubbling water storage chamber 34. When the water level exceeds the outlet of the water discharge channel P11, water is drained by overflow from the water discharge channel P11. The gas storage section 32A is open to the atmosphere.

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

In this embodiment, as in the first embodiment, impurities can be removed from the air supplied to the air electrode 12B with a simple configuration, and air inflow from the post-bubbling air reservoir 34A to the condensed water inlet 31 can be suppressed.

Furthermore, as in the second embodiment, the inflow water storage section 32B is separated from the bubbling section 34B by the water partition wall 36, preventing water from moving from the bubbling section 34B, so that condensed water without dissolved impurities can be supplied to the reformer 14 as reforming water.

Furthermore, the water stored in the condensed water storage chamber 32 and the bubbling water storage chamber 34 is discharged through the water discharge passage P11 by overflow, making it easy to manage the water level in the reforming water tank 30.

The above describes an embodiment of the present invention, but the present invention is not limited to the above, and it goes without saying that various modifications and variations are possible within the scope of the present invention.

10A, 10B, 10C Fuel cell system 12 Fuel cell stack (fuel cell)
12A fuel electrode 12B air electrode 14 reformer (reforming section)
18 Condenser (condensation section)
30 Reformed water tank 31 Condensed water inlet (inlet)
32 Condensate storage chamber (water storage chamber)
34 Bubbling water storage chamber 34A Post-bubbling air storage section (water storage chamber)
35 Air inlet section 36 Water partition wall (check mechanism)
38 Air chamber partition wall (isolation section)
40 Water sealing section (water sealing structure)
P6 Clean air supply path (post-bubbling air supply path)
P10 Reformed water supply path P11 Water discharge path (discharge path)

Claims (4)

a reforming unit that reforms the raw material gas to generate a fuel gas containing hydrogen gas;
a fuel cell that generates electricity using the fuel gas supplied to the fuel electrode and air supplied to the air electrode;
a condensation unit that condenses water in the off-gas discharged from the fuel cell;
a reforming water tank having an inlet through which water condensed in the condenser flows, a water storage chamber for storing the water that has flowed in from the inlet, an air inlet provided in a lower portion of the water storage chamber for allowing air to flow into the water storage chamber, a post-bubbling air storage section provided in an upper portion of the water storage chamber for storing the air that has flowed in from the air inlet section, and an isolation section for isolating the inlet from the post-bubbling air storage section;
a post-bubbling air supply path that supplies the air stored in the post-bubbling air storage section to the air electrode;
a reforming water supply passage that supplies reforming water from the water storage chamber to the reforming unit;
A fuel cell system comprising: the isolation section is configured as a partition wall extending from the top surface of the reforming water tank to a position lower than the water level of the water storage chamber and partitioning the post-bubbling air storage section.
The fuel cell system according to claim 1 . The fuel cell system of claim 1 or 2, further comprising a drainage channel that allows water to overflow and drain from the water storage chamber at a predetermined water level. the water storage chamber includes a condensed water storage chamber into which water flows in from the inlet, and a bubbling water storage chamber isolated from the condensed water storage chamber and connected to the air inlet portion;
the reforming water supply passage is connected to the condensed water storage chamber, and the post-bubbling air storage section is formed in the bubbling water storage chamber;
3. The fuel cell system according to claim 1 or 2.