fuel cell system

Abstract

To simply purify air supplied to an air electrode of a fuel cell stack and also to suppress mixture of impurities into modified water.SOLUTION: A fuel cell system 10A includes: a condenser 18 which condenses water in off-gas discharged from a fuel cell stack 12; a modified water tank 30 including a condensate storage chamber 32 which stores condensate from the condenser 18 therein, a bubbling water storage chamber 34 which stores water flowing in from the condensate storage chamber 32 therein and in which the movement of water into the condensate storage chamber 32 is blocked, an air inflow part 35 allowing air to flow into the bubbling water storage chamber 34 from a lower part of the bubbling water storage chamber 34, and a storage part 34A for air after bubbling which stores the air flowing from the air inflow part 35 at an upper part of the bubbling water storage chamber 34; a supply passage P6 for air after bubbling, which supplies, to an air electrode 12B, the air stored in the storage part 34A for air after bubbling; and a modified water supply passage P10 which supplies modified water from the condensate storage chamber 32 to a reformer 14.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a fuel cell system. [Background technology]

[0002] Fuel cell systems are often 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.

[0003] Therefore, Patent Document 1 discloses a technique for removing impurities by bubbling air through reforming water to dissolve the impurities in the air in condensed water, and then supplying the purified air to the air electrode. According to the technique in Patent Document 1, water-soluble impurities can be easily removed from the air using reforming water. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-331703 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when impurities in the air are removed by dissolving them in the reformed water, the impurities end up being mixed into the reformed water. As in Patent Document 1, impurities can be removed by performing a desalination process, but this increases the frequency of membrane replacement for the desalination process, which increases costs and labor.

[0006] The present invention has been made in consideration of the above circumstances, and aims to easily purify the air supplied to the air electrode of a fuel cell stack and to suppress the incorporation of impurities into the reforming water. [Means for solving the problem]

[0007] The fuel cell system according to claim 1 includes a reforming section that reforms a raw material gas to generate a 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 section that condenses water in off-gas discharged from the fuel cell, a condensed water storage chamber into which condensed water flows from the condensing section and into which the condensed water is stored, a bubbling water storage chamber that is separated from the condensed water storage chamber and stores the water that flows in from the condensed water storage chamber, and a bubbling water storage chamber that stores the water that flows in from the bubbling water storage chamber. The reforming water tank has a check mechanism that prevents water from moving into the water storage chamber, an air inlet section that is provided at the bottom of the bubbling water storage chamber and allows air to flow into the bubbling water storage chamber, and a post-bubbling air storage section that is provided at the top of the bubbling water storage chamber and stores the air that has flowed in from the air inlet section, a post-bubbling air supply path that supplies the air stored in the post-bubbling air storage section to the air electrode, and a reforming water supply path that supplies reforming water from the condensed water storage chamber to the reforming section.

[0008] In the fuel cell system according to claim 1, the reforming water tank has a condensed water storage chamber and a bubbling water storage chamber. Condensed water, which is water in the off-gas condensed in the condenser, flows into the condensed water storage chamber and is stored therein. The bubbling water storage chamber is separated from the condensed water storage chamber and stores water flowing in from the condensed water storage chamber. The bubbling water storage chamber has a check mechanism that prevents water from moving from the bubbling water storage chamber to the condensed water storage chamber, so that condensed water is prevented from flowing back into the condensed water storage chamber after moving from the condensed water storage chamber to the bubbling water storage chamber.

[0009] An air inlet is provided at the bottom of the bubbling water storage chamber to allow air to flow into the bubbling water storage chamber. When air flows in through the air inlet, water-soluble impurities in the air are dissolved in the water in the bubbling water storage chamber, removing them from the air. The air from which impurities have been removed is stored in the post-bubbling air storage section at the top of the bubbling water storage chamber.

[0010] The air stored in the post-bubbling air storage section is supplied to the air electrode through a post-bubbling air supply passage, and the condensed water stored in the condensed water storage chamber is supplied to the reforming section as reforming water through a reforming water supply passage.

[0011] In the fuel cell system according to claim 1, the check mechanism allows condensed water to move only from the condensed water storage chamber to the bubbling water storage chamber, so the water in the bubbling water storage chamber, in which water-soluble impurities from the air are dissolved, does not move to the condensed water storage chamber, making it possible to supply water with fewer impurities as reforming water to the reforming section.

[0012] In the fuel cell system according to claim 2, the check mechanism is an overflow mechanism that allows water to overflow from the condensed water storage chamber into the bubbling water storage chamber.

[0013] According to the fuel cell system of claim 2, the overflow mechanism can be used to prevent water from moving from the bubbling water storage chamber to the condensed water storage chamber with a simple configuration.

[0014] The fuel cell system according to claim 3 includes an isolation section that isolates an inlet through which the condensed water flows into the condensed water storage chamber from the post-bubbling air storage section.

[0015] According to the fuel cell system of claim 3, the inlet into which the condensed water flows is isolated from the post-bubbling air storage section by the isolation section, so that backflow of air from the inlet to the condensation section can be suppressed.

[0016] In the fuel cell system according to claim 4, the isolation section is formed to include a water sealing structure using water stored in the bubbling water storage chamber.

[0017] According to the fuel cell system of claim 4, the inlet can be easily isolated from the post-bubbling air reservoir by a water-sealing structure using water stored in the bubbling water reservoir. [Effects of the Invention]

[0018] The fuel cell system according to the present invention can easily purify the air supplied to the air electrode of the fuel cell stack and can also suppress the inclusion of impurities in the reforming water. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a configuration diagram of a fuel cell system according to a first embodiment. [Figure 2] FIG. 10 is a configuration diagram of a fuel cell system according to a second embodiment. [Figure 3] FIG. 10 is a configuration diagram of a fuel cell system according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0020] First Embodiment A first embodiment of the present invention will be described with reference to the drawings.

[0021] The fuel cell system 10A is a power generation system installed in a user's home, an apartment building, a factory, etc. Fig. 1 shows an outline of the main components of the fuel cell system 10A according to an embodiment of the present invention. The fuel cell system 10A according to an embodiment of the present invention includes, as its main components, 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.

[0022] 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.

[0023] The reformer 14 reforms the raw material gas to generate a fuel gas containing hydrogen. The reformer 14 is connected to the fuel electrode 12A of the fuel cell stack 12. The fuel gas generated in the reformer 14 is supplied to the fuel electrode 12A of the fuel cell stack 12 via a fuel gas pipe P2.

[0024] The fuel cell stack 12 is a cell stack having a plurality of 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. Note that various fuel cells can be used as the fuel cell stack 12, such as a solid oxide fuel cell (SOFC), a molten carbonate fuel cell (MCFC), and a polymer electrolyte fuel cell (PEFC). In this embodiment, a PEFC will be described as an example.

[0025] One end of a clean air supply passage 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 passage P6. The upstream end of the clean air supply passage P6 is connected to a clean air outlet 33 of a reforming water tank 30, which will be described later. External air that has passed through a air electrode filter 24 and a bubbling unit 34B, which will be described later, is supplied to the air electrode 12B by the clean air supply blower B3. The air electrode filter 24 and the bubbling unit 34B will be described in detail later.

[0026] In the fuel cell stack 12, power is generated by a power generation reaction at the fuel electrode 12A and the air electrode 12B, and the power is output to a circuit (not shown).

[0027] Anode offgas is discharged from the anode 12A to anode offgas channel P3, and cathode offgas is discharged from the cathode 12B to anode offgas channel P7. The anode offgas contains fuel gas that has not reacted in the power generation reaction, and this anode offgas 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 the like. The cathode offgas is sent to the condenser 18 from the cathode offgas channel P7.

[0028] Combustor 16 is provided adjacent to reformer 14 and heats reformer 14 with the heat of combustion. Anode off-gas is supplied to combustor 16 from 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).

[0029] A combustion exhaust gas passage P4 is connected to the outlet side of the combustor 16. The combustion exhaust gas is discharged from the combustor 16 to the outside through the combustion exhaust gas passage P4. In this embodiment, an example in which the combustion exhaust gas is discharged to the outside will be described, but the combustion exhaust gas passage P4 may be connected to a condenser 18 so that water in the combustion exhaust gas can also be condensed and reused.

[0030] The other end of the cathode off-gas passage P7 is connected to the condenser 18, where 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 a passage P8. A check valve V1 is provided in the passage P8. The cathode off-gas from which the water has been removed is discharged through a discharge passage P9.

[0031] The reformed water tank 30 includes a condensed water storage chamber 32 and a bubbling water storage chamber 34. The condensed water storage chamber 32 includes an inflow water storage section 32B for storing water, and a gas storage section 32A for storing gas above the water surface in the inflow water storage section 32B. The bubbling water storage chamber 34 includes a bubbling section 34B for storing water, and a post-bubbling air storage section 34A for storing gas above the water surface in the bubbling section 34B. A water partition wall 36 is provided between the condensed water storage chamber 32 and the bubbling water storage chamber 34, separating the inflow water storage section 32B from the bubbling section 34B. The upper end position of the water partition wall 36 is set so that the gas storage section 32A and the post-bubbling air storage section 34A are connected at the top.

[0032] A condensed water inlet 31 is provided at an upper part of the gas storage section 32A of the condensed water storage chamber 32. The downstream end of the 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 inflow water storage section 32B. A reforming water delivery outlet 37 is provided at a lower part of the inflow water storage section 32B of the condensed water storage chamber 32.

[0033] A clean air outlet 33 is provided above the post-bubbling air reservoir 34A of the bubbling water reservoir 34. The upstream end of the clean air supply passage P6 is connected to the clean air outlet 33.

[0034] When the water level of the condensed water stored in the condensed water storage chamber 32 exceeds the water partition wall 36, the condensed water overflows into the bubbling water storage chamber 34. A bubbling water outlet 39 is provided at the bottom of the bubbling section 34B of the bubbling water storage chamber 34. A bubbling water outlet 39 is connected to a bubbling water outlet path P12 that discharges water from the bubbling section 34B. A solenoid valve V2 is provided in the bubbling water outlet path P12. The water level in the bubbling section 34B is detected by a water level sensor (not shown), and when the water level exceeds a predetermined level, the solenoid valve V2 is opened to maintain the water level lower than the water partition wall 36. Therefore, water is prevented from moving from the bubbling water storage chamber 34 to the condensed water storage chamber 32.

[0035] An air inlet section 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 section 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 section 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, and the air is stored in the air storage section 34A after bubbling.

[0036] One end of a reforming water supply passage P10 is connected to a reforming water outlet 37 provided at the bottom of the condensed water storage chamber 32. A pump 21 and an ion exchange resin 22 are provided in the reforming water supply passage P10. The other end of the reforming water supply passage P10 is connected to the reformer 14, and the water stored in the condensed water storage chamber 32 is supplied as reforming water to the reformer 14 via the ion exchange resin 22 by driving the pump 21. The ion exchange resin 22 removes impurities from the water passing through it by ion exchange.

[0037] Next, the operation of the fuel cell system 10A of this embodiment will be described.

[0038] In the fuel cell system 10A, air stored in a post-bubbling air storage section 34A is supplied to the air electrode 12B of the fuel cell stack 12 by a clean air supply blower B3 through a clean air supply passage 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 that 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.

[0039] Furthermore, the air electrode off-gas discharged from the air electrode 12B is sent from the air electrode off-gas passage P7 to the condenser 18, where the water contained in the air electrode off-gas is condensed and sent to the condensed water storage chamber 32 of the reforming water tank 30. The condensed water is transferred by overflow from the condensed water storage chamber 32 to the bubbling water storage chamber 34 and used for bubbling, so there is no need to provide a separate tank for bubbling, and impurities can be removed from the air supplied to the air electrode 12B with a simple configuration.

[0040] In addition, the inflow water storage section 32B is partitioned from the bubbling section 34B, and the movement of water from the bubbling section 34B is prevented, so that condensed water in which impurities are not dissolved can be supplied to the reformer 14 as reforming water.

[0041] Second Embodiment Next, a second embodiment of the present invention will be described. In this embodiment, the same parts as in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

[0042] The fuel cell system 10B of this embodiment has an air chamber partition wall 38 in addition to the water partition wall 36 of the fuel cell system 10A of the first embodiment. The configuration other than the air chamber partition wall 38 is the same as that of the fuel cell system 10A of the first embodiment shown in FIG.

[0043] 2, the fuel cell system 10B has an air chamber partition wall 38 provided in the reforming water tank 30. The air chamber partition wall 38 is provided closer to the bubbling water storage chamber 34 than the water partition wall 36 and is spaced apart from the water partition wall 36. The air chamber partition wall 38 separates the gas storage section 32A and the post-bubbling air storage section 34A so as 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 surface, allowing water to flow.

[0044] A water sealing section 40 is formed between the water partition wall 36 and the air chamber partition wall 38. The water level in the water sealing section 40 is the same height as the bubbling section 34B, and although water is permitted to overflow from the condensed water storage chamber 32 to the bubbling water storage chamber 34, the water sealing section 40 is sealed with water to prevent gas from moving between the gas storage section 32A and the post-bubbling air storage section 34A.

[0045] Next, the operation of the fuel cell system 10B of this embodiment will be described.

[0046] 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 condensed water in which impurities are not dissolved can be supplied to the reformer 14 as reforming water.

[0047] Furthermore, in this embodiment, the gas storage section 32A and the post-bubbling air storage section 34A are partitioned by the air chamber partition wall 38 so that gas does not move between them. Therefore, the condensed water inlet 31 is isolated from the post-bubbling air storage section 34A, and backflow of air from the condensed water inlet 31 to the condenser 18 can be suppressed.

[0048] Furthermore, 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 portion 34B.

[0049] <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 denoted by the same reference numerals, and detailed description thereof will be omitted.

[0050] The fuel cell system 10C of this embodiment does not have the bubbling water outlet 39, bubbling water discharge channel P12, and solenoid valve V2 of the fuel cell system 10B of the second embodiment, but has a water discharge channel P11. Other than these, the configuration is the same as that of the fuel cell system 10B of the second embodiment shown in FIG.

[0051] As shown in FIG. 3, in the fuel cell system 10C, 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 discharged by overflow when the water level in the condensed water storage chamber 32 reaches a predetermined level. The outlet of 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, and when the water level exceeds the outlet of the water discharge channel P11, water is discharged by overflow from the water discharge channel P11. The gas storage section 32A is open to the atmosphere.

[0052] Next, the operation of the fuel cell system 10C of this embodiment will be described.

[0053] 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 the inflow of air from the post-bubbling air storage section 34A to the condensed water inlet 31 can be suppressed.

[0054] 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, and the movement of water from the bubbling section 34B is prevented, so that condensed water in which impurities are not dissolved can be supplied to the reformer 14 as reforming water.

[0055] Furthermore, since the water stored in the condensed water storage chamber 32 and the bubbling water storage chamber 34 is discharged from the water discharge passage P11 by overflow, the water level in the reforming water tank 30 can be easily managed.

[0056] 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 the present invention can be implemented in various modified forms within the scope of the gist of the present invention. [Explanation of symbols]

[0057] 10A, 10B, 10C fuel cell systems 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 Condensate inlet (inlet) 32 Condensate storage chamber 34 Bubbling water storage chamber 34A Post-bubbling air reservoir 35 Air inlet 36 Water partition wall (check mechanism, overflow mechanism) 38 Air chamber partition wall (isolation section) 40 Water sealing section (water sealing structure) P6 Clean air supply line (post-bubbling air supply line) P10 Reformed water supply channel P12 Bubbling water discharge channel (check mechanism) V2 solenoid valve (check mechanism)

Claims

[Claim 1] 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 including: a condensed water storage chamber into which condensed water flows from the condensation section and stores the condensed water; a bubbling water storage chamber partitioned from the condensed water storage chamber and storing the water that flows in from the condensed water storage chamber; a check mechanism that prevents water from moving from the bubbling water storage chamber to the condensed water storage chamber; an air inlet section that is provided at a lower part of the bubbling water storage chamber and that allows air to flow into the bubbling water storage chamber; and a post-bubbling air storage section that is provided at an upper part of the bubbling water storage chamber and stores the air that flows in from the air inlet 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 condensed water storage chamber to the reforming section; an isolation section that isolates an inlet through which the condensed water flows into the condensed water storage chamber from the post-bubbling air storage section; Equipped with the check mechanism is an overflow mechanism that allows water to overflow from the condensed water storage chamber to the bubbling water storage chamber at an upper portion of a water partition wall that separates the condensed water storage chamber from the bubbling water storage chamber, The isolation section is formed to include a water sealing structure using water stored in the bubbling water storage chamber, and is provided on the bubbling water storage chamber side of the water partition wall and spaced apart from the water partition wall. Fuel cell system.

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