JP2006318798A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system of which stability, accuracy, and responsiveness of humidification control are improved without bringing about lowering of thermal efficiency of a total system, and the size and cost are reduced while keeping a sufficient humidifying property. <P>SOLUTION: The fuel cell system is provided with a humidifier 14 humidifying cathode air and supplying it to an oxidant electrode 12. The humidifier 14 is constituted by a first humidifier 14a humidifying cathode air by exchanging vapor between cathode off-gas exhausted from the oxidant electrode 12 and cathode air; and a second humidifier 14b arranged on a condensed coolant circulation circuit 75 in which a heat medium (a condensed coolant) as liquid containing water in which waste heat exhausted from the fuel cell 10 and/or waste heat generated at a reformer 20 is recovered, is made to circulate, humidifying cathode air by evaporating the heat media by utilizing the recovered heat. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell system including a fuel cell that generates electric power using fuel and an oxidant gas supplied to a fuel electrode and an oxidant electrode, respectively, and a humidifier that humidifies the oxidant gas and supplies the oxidant gas to the oxidant electrode. About.

  The fuel cell system includes a fuel cell that generates power using fuel and oxidant gas supplied to the fuel electrode and the oxidant electrode, respectively, and a humidifier that humidifies the oxidant gas and supplies the oxidant electrode to the oxidant electrode. Is well known.

  As one type of such a fuel cell system, one shown in Patent Document 1 “Humidification system for fuel cell” is known. As shown in FIG. 1 of Patent Document 1, the fuel cell humidification system includes a moisture permeable humidifier 6 that humidifies the reaction gas used for the reaction with moisture in the off-gas discharged after the reaction. The humidification amount is controlled according to the required humidification amount of the fuel cell 1. A dew point meter 19 for measuring the dew point of the dry air supplied into the fuel cell 1 is provided between the humidifier 6 and the gas inlet 2 of the fuel cell 1 in the reaction gas supply path 3. Further, a reaction gas bypass passage 21 that bypasses the humidification device 6 is provided in the reaction gas supply passage 3 that reaches the fuel cell 1 through the humidification device 6. Here, a flow rate adjustment valve 22 capable of adjusting the bypass flow rate of the reaction gas is attached to the reaction gas bypass passage 21, and the flow rate adjustment valve 22, the dew point meter 19, and the voltmeter 20 are connected via the control device 23. It is connected. By adjusting the amount of dry air flowing through the reaction gas bypass passage 21 based on the dew point measured by the dew point meter 19, the amount of dry air flowing through the humidifier 6 is increased or decreased, so that the optimum dew point (required dew point) is always obtained. The fuel cell 1 operates in an optimum state so that condensation is not generated in the fuel cell 1 and the power generation capacity is not reduced.

Further, as another type, one disclosed in Patent Document 2 “Fuel cell operation control system and method” is known. As shown in FIG. 6 of Patent Document 2, the fuel cell operation control system supplies a fuel cell 12 having a solid electrolyte fuel cell and a fuel gas 12 to the fuel electrode of the fuel cell of the fuel cell 11. A fuel gas supply line L ₁ , a fuel gas discharge line L ₂ for discharging fuel exhaust gas 13 discharged from the fuel cell 11, an air supply line L ₃ for supplying air 14 to the fuel cell 11 from the outside, and the fuel An air discharge line L ₄ that discharges exhaust air 15 from the battery 11, and an air preheat that is interposed in the air supply line L ₃ and the air discharge line L ₄ and preheats the supplied air 14 with the exhaust heat of the exhaust air 15. A bypass line L ₅ that branches off from the air supply line 16 and the air supply line L ₃ , bypasses the air preheater 16 and supplies air without preheating, and the bypass line L ₅ joins Fuel electricity A thermometer 17 for measuring the temperature of the feed air before supply to 11, a temperature controller 18 to adjust the valve B ₃ interposed in the bypass line L ₅ by the temperature information of the temperature meter 17, the air supply line It is provided with a flow controller 20 to adjust the valve B ₁ by the flow meter 19 and flow meter 19 information for measuring the flow rate of the interposed by the main supply air to L _3. In this system, the temperature of the air supplied to the fuel cell 11 is adjusted by monitoring the thermometer 17 as necessary.

Further, as another type, one disclosed in Patent Document 3 “Solid Polymer Fuel Cell System” is known. As shown in FIG. 1 of Patent Document 3, in the polymer electrolyte fuel cell system, the wet heat exchange type humidifier 2 connected to the battery module 1 sandwiches the wet heat exchange element 6 as a basic configuration. Thus, the off gas flow path 3, the reaction gas flow path 4, and the battery cooling water humidification flow path 5 are stacked. Further, the battery module 1 branches to a battery cooling water main circuit 7 and a battery cooling water humidification circuit 8 in the vicinity of the cooling water outlet, and a flow rate control means 9 is provided at the branch location. Furthermore, sensors 10 to 12 are appropriately provided at various points in the system, and the flow rate of the battery cooling water to the battery cooling water humidification circuit 8 is controlled by a signal from the sensor.
JP 2001-216984 A (page 3-4, FIG. 1) JP 2001-202981 A (first page, FIG. 6) JP 2004-31073 A (page 2-9, FIG. 1)

  In the fuel cell humidification system described in Patent Document 1 described above, the reaction gas used for the reaction is humidified by the moisture in the off-gas discharged after the reaction, that is, the off-gas is the humidification source. However, since the humidification capacity is determined by the water vapor partial pressure of the off-gas, which is a gas, if the water vapor partial pressure of the off gas fluctuates, the humidification capacity also fluctuates. There was a possibility that the sex would deteriorate. Further, in order to adjust the amount of dry air flowing through the reaction gas bypass passage 21 based on the dew point measured by the dew point meter 19 and to bring the inside of the fuel cell 1 into the optimum humidified state, after humidification derived from the humidifier 6. It is desirable that the reaction gas is saturated (water vapor saturation). In order to realize this, it is conceivable to sufficiently increase the surface area of the hollow fiber membrane through which the water of the humidifying device 6 permeates. In this case, the inside of the fuel cell 1 can be brought into an optimum humidified state, but there has been a problem that the humidifier 6 is increased in size and cost, and the entire fuel cell system is increased in size and cost. The fuel cell operation control system described in Patent Document 2 described above has a similar problem.

  In the polymer electrolyte fuel cell system described in Patent Document 3 described above, the problems described above can be greatly improved. However, the reaction gas is humidified by removing heat from the cooling water of the battery module 1. As a result, the temperature of the cooling water decreases accordingly. When recovering the heat generated by the power generation of the battery module 1 to the hot water storage via the cooling water, when the temperature of the cooling water decreases, the amount of heat recovered in the hot water and the temperature of the hot water returning to the hot water (recovery) There was a problem that the water temperature was decreased. In addition, the battery module 1 cannot be controlled to an appropriate temperature, and there is a risk that power generation cannot be performed appropriately. Furthermore, since the heat of the off-gas that is not used in the heat exchanger type humidifier 2 is discharged as it is, a large amount of heat is discharged when the heat exchanger type humidifier 2 uses less. As a result, the thermal efficiency of off-gas deteriorates, and the thermal efficiency of the entire system deteriorates.

  The present invention has been made to solve the above-described problems. In a fuel cell system, the stability, accuracy, and responsiveness of humidification control are improved without causing a decrease in the thermal efficiency of the entire system. The objective is to reduce the size and cost of the system while maintaining a high humidification capability.

  In order to solve the above-mentioned problem, the structural feature of the invention according to claim 1 is that a fuel cell that generates electric power using the fuel and oxidant gas respectively supplied to the fuel electrode and the oxidant electrode, and humidifying the oxidant gas. And a humidifier that supplies the oxidant electrode to the oxidant electrode, the humidifier exchanges water vapor between the oxidant off-gas discharged from the oxidant electrode and the oxidant gas to exchange the oxidant gas. A first humidifier that humidifies and a heat medium circulating circuit that circulates a heat medium that is a liquid containing at least recovered heat exhausted from the fuel cell is circulated. It is comprised from the 2nd humidifier which humidifies oxidant gas by steaming.

  Further, the structural feature of the invention according to claim 2 is that in claim 1, the oxidant off-gas exhaust heat for recovering the exhaust heat of the oxidant off-gas after passing through the first humidifier is disposed on the heat medium circulation circuit. The collection means is arranged.

  The structural feature of the invention according to claim 3 is that, in claim 2, the second humidifier is disposed downstream of the oxidant off-gas exhaust heat recovery means.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, the oxidant gas is circulated in the order of the first humidifier and the second humidifier, and then the oxidant. Is to be supplied to the pole.

  According to a fifth aspect of the present invention, the humidifier according to any one of the first to fourth aspects includes a flow path through which the oxidant gas, the oxidant off-gas, and the heat medium flow. It is an integral structure.

  Further, the structural feature of the invention according to claim 6 is that, in claim 5, the flow path through which the oxidant gas flows is adjacent to the flow path through which the oxidant off-gas and the heat medium flow, respectively, so that water vapor can be exchanged. In addition, the flow paths through which the oxidant off-gas and the heat medium respectively flow are not arranged adjacent to each other so as to exchange water vapor.

  According to a seventh aspect of the present invention, the structural feature of the invention according to any one of the first to sixth aspects further includes a circulation means provided on the heat medium circulation circuit for circulating the heat medium. By controlling the delivery amount, the temperature of the oxidant gas flowing into the oxidant electrode of the fuel cell is adjusted to the target temperature, or the temperature of the heat medium after the circulation of the second humidifier is adjusted to the target temperature. .

  Further, the structural feature of the invention according to claim 8 is that in any one of claims 1 to 7, the condensed water recovered from at least off gas discharged from the fuel cell as the heat medium of the heat medium circuit. Is to use.

  A structural feature of the invention according to claim 9 is that, in any one of claims 1 to 8, a bypass path provided on the heat medium circuit and bypassing the second humidifier, and a second humidification And a flow rate adjusting means for adjusting the flow rate of the heat medium flowing through the vessel and the flow rate of the heat medium flowing through the bypass path by bypassing the second humidifier.

  The structural feature of the invention according to claim 10 is that in any one of claims 1 to 9, further comprising a reformer that generates fuel to be supplied to the fuel cell, wherein the second humidifier comprises: Waste heat discharged from the fuel cell and / or waste heat generated in the reformer is provided on a heat medium circuit where a heat medium that is a liquid containing at least recovered water is circulated, and the recovered heat is used. Thus, the oxidizing medium is humidified by steaming the heat medium.

  According to an eleventh aspect of the present invention, there is provided a structural feature of the invention according to the tenth aspect, in which the off-gas discharged from the fuel cell, the fuel generated by the reformer, and the reformer combustion are used as the heat medium of the heat medium circulation circuit. The condensed water recovered from at least one gas of the combustion exhaust gas discharged from the vessel is used.

  In the invention according to claim 1 configured as described above, the humidifier humidifies the oxidant gas with the oxidant off-gas in the first humidifier, and the exhaust gas discharged from the fuel cell in the second humidifier. The oxidant gas is humidified by a heat medium that is a liquid containing water from which heat is at least recovered. As a result, the fuel cell can be controlled to an appropriate temperature without generating heat from the fuel cell heat medium that has recovered the exhaust heat generated by the power generation of the fuel cell, and without deteriorating the heat recovery efficiency. In addition, the oxidizing gas can be humidified to the optimum humidified state.

  In addition, since the heat medium that is a liquid containing water serves as a humidification source, the water vapor partial pressure can be kept extremely high as compared with the case where the humidification source is only off-gas as in the past, so The area can be reduced and the apparatus can be miniaturized. Further, since the water vapor partial pressure can be kept high and constant, it is possible to improve the accuracy of the humidifying performance, improve the stability of the humidifying ability, and improve the responsiveness.

  In the invention according to claim 2 configured as described above, in the invention according to claim 1, the oxidation for recovering the exhaust heat of the oxidant off-gas after passing through the first humidifier on the heat medium circulation circuit. Since the oxidant off-gas exhaust heat recovery means is disposed, the exhaust heat of the oxidant off-gas that has been recovered by the first humidifier and remains unused is converted into a heat medium by the oxidant off-gas exhaust heat recovery means. It can be recovered and used. Therefore, since the exhaust heat of the oxidant off-gas can be recovered without waste and used without waste, the heat recovery efficiency can be improved and the heat recovery efficiency of the entire system can be maintained high.

  In the invention according to claim 3 configured as described above, in the invention according to claim 2, the second humidifier is disposed downstream of the oxidant off-gas exhaust heat recovery means, thereby oxidant off-gas exhaust heat. Since the heat recovered in the heat medium by the recovery means can be used when the oxidant gas is humidified by the second humidifier, the heat recovered by the oxidant off-gas exhaust heat recovery means can be used without waste. Can do.

  In the invention according to Claim 4 configured as described above, in the invention according to any one of Claims 1 to 3, the oxidizing gas flows in the order of the first humidifier and the second humidifier. After being supplied to the oxidant electrode, even if the oxidant gas is not in the optimum humidified state by the first humidifier, it is further humidified by the second humidifier to be in the optimum humidified state. It is possible to ensure that the oxidizing gas to be brought into the optimum humidified state. In addition, by setting the oxidant gas supplied to the oxidant electrode to a water vapor saturation state with respect to the temperature, it becomes possible to grasp the humidified state based on the temperature, improving controllability, and reliability by using a general-purpose temperature sensor High maintenance and cost reduction can be achieved.

  In the invention according to Claim 5 configured as described above, in the invention according to any one of Claims 1 to 4, the humidifier is a flow in which the oxidant gas, the oxidant off-gas, and the heat medium respectively flow. Since it is an integral structure provided with a path, it becomes possible to achieve compactness.

  In the invention according to claim 6 configured as described above, in the invention according to claim 5, the flow path through which the oxidant gas flows is adjacent to the flow path through which the oxidant off-gas and the heat medium respectively flow so that water vapor can be exchanged. And the flow paths through which the oxidant off-gas and the heat medium respectively flow are not arranged adjacent to each other so that water vapor exchange is possible, so that the heat medium does not waste the oxidant off-gas unnecessarily, and Since the oxidant gas humidifies the heat medium and the oxidant off-gas, the humidification controllability can be improved.

  In the invention according to claim 7 configured as described above, the invention according to any one of claims 1 to 6 further includes a circulation means provided on the heat medium circulation circuit for circulating the heat medium. Then, the amount of the circulated means is controlled to adjust the temperature of the oxidant gas flowing into the oxidant electrode of the fuel cell to the target temperature, or the temperature of the heat medium after the circulation of the second humidifier is adjusted to the target temperature. Therefore, the humidity can be adjusted accurately and accurately, the influence of disturbances such as fluctuations in the ambient temperature can be reduced, and flooding can be reliably prevented.

  In the invention according to claim 8 configured as described above, in the invention according to any one of claims 1 to 7, at least from the off-gas discharged from the fuel cell as the heat medium of the heat medium circuit. Since the condensed water is used as humidified water by using the collected condensed water, it is possible to cover the amount of water used for humidification with the amount of water condensed from off-gas. Humidification is possible.

  In the invention according to claim 9 configured as described above, in the invention according to any one of claims 1 to 8, a bypass path provided on the heat medium circuit and bypassing the second humidifier, Since it further comprises a flow rate adjusting means for adjusting the flow rate of the heat medium flowing through the second humidifier and the flow rate of the heat medium flowing through the bypass path by bypassing the second humidifier, it corresponds to a heat amount necessary and sufficient for humidification. Since the heat medium can be supplied to the second humidifier so as to achieve a flow rate of the oxidant gas, the oxidant gas can be optimally humidified. Also, since the heat medium is not supplied to the second humidifier more than necessary, the heat medium temperature is kept at a high temperature by suppressing the temperature of the heat medium from being unnecessarily high, and the heat recovery efficiency of the fuel cell system is kept high. can do.

  In the invention according to claim 10 configured as described above, when the fuel cell system is provided with a reformer, the second humidifier serves as exhaust heat exhausted from the fuel cell and / or reformer. Is provided on a heat medium circuit in which a heat medium, which is a liquid containing water, at least recovering the exhaust heat generated in this way, and humidifies the oxidant gas by steaming the heat medium using the recovered heat . Thus, the fuel cell system including the reformer can also obtain the effects of the above-described inventions.

  In the invention according to claim 11 configured as described above, in the invention according to claim 10, as the heat medium of the heat medium circuit, the off-gas discharged from the fuel cell, the fuel generated by the reformer, Since the condensed water recovered from at least one gas of the flue gas discharged from the combustor of the gasifier is used, the amount of water used for humidification can be covered by the amount of water condensed from the water vapor in each gas. Humidification is possible without adding a large amount of water.

1) First Embodiment Hereinafter, a first embodiment of a fuel cell system according to the present invention will be described. FIG. 1 is a schematic diagram showing an outline of this fuel cell system. The fuel cell system includes a fuel cell 10 and a reformer 20 that generates a reformed gas (fuel gas) containing hydrogen gas necessary for the fuel cell 10.

  The fuel cell 10 includes a fuel electrode 11, an air electrode 12 that is an oxidizer electrode, and an electrolyte 13 (polymer electrolyte membrane in the present embodiment) interposed between both electrodes 11 and 12, and is supplied to the fuel electrode 11. Electric power is generated using the fuel gas (reformed gas) that is the remaining fuel and the air (cathode air) that is the oxidant gas supplied to the air electrode 12. Note that air-enriched gas may be supplied instead of air.

  The reformer 20 steam-reforms the reforming fuel and supplies a hydrogen-rich reformed gas to the fuel cell 10. The reformer 20 is a burner (combustion unit) 21, a reforming unit 22, which is a combustor. It is composed of a carbon oxide shift reaction part (hereinafter referred to as a CO shift part) 23 and a carbon monoxide selective oxidation reaction part (hereinafter referred to as a CO selective oxidation part) 24. The reforming fuel includes natural gas, LPG, kerosene, gasoline, methanol, and the like. In the present embodiment, description will be made on natural gas.

  The burner 21 generates combustion gas for heating the reforming unit 22 and supplying heat necessary for the steam reforming reaction. The burner 21 burns combustion fuel supplied from the outside with combustion air until the start of supply of the reforming fuel after being started, and from the start of supply of the reforming fuel to the start of steady operation. , The reformed gas directly supplied from the CO selective oxidation unit 24 is burned with combustion air, and the anode off-gas supplied from the fuel electrode 11 of the fuel cell 10 during steady operation (not supplied to the fuel cell and used) The reformed gas discharged into the combustion chamber is burned with combustion air, and the combustion gas is led out to the reforming section 22. Note that the shortage of heat in the reformed gas or anode off gas is supplemented with combustion fuel. The combustion gas heats the reforming section 22 (so as to be within the catalyst activation temperature range of the reforming section 22), and then is discharged to the outside through the exhaust pipe 63.

  The reforming unit 22 reforms a mixed gas obtained by mixing the reforming fuel supplied from the outside with water vapor (reformed water) from the evaporator 25 by using a catalyst charged in the reforming unit 22 to generate hydrogen gas. Carbon monoxide gas is produced (so-called steam reforming reaction). At the same time, carbon monoxide and steam generated by the steam reforming reaction are converted into hydrogen gas and carbon dioxide (so-called carbon monoxide shift reaction). These generated gases (so-called reformed gas) are led to the CO shift unit 23.

  The CO shift unit 23 is converted into hydrogen gas and carbon dioxide gas by reacting carbon monoxide and water vapor contained in the reformed gas with a catalyst filled therein. Thus, the reformed gas is led to the CO selective oxidation unit 24 with the carbon monoxide concentration reduced.

  The CO selective oxidation unit 24 generates carbon dioxide by reacting carbon monoxide remaining in the reformed gas and CO oxidation air (air) further supplied from the outside with a catalyst filled therein. is doing. Thereby, the reformed gas is led to the fuel electrode 11 of the fuel cell 10 with the carbon monoxide concentration further reduced (10 ppm or less).

  The evaporator 25 is disposed in the middle of the reforming water supply pipe 68 having one end disposed in the water reservoir 50 and the other end connected to the reforming unit 22. A reforming water pump 53 is provided in the reforming water supply pipe 68. The pump 53 is controlled by a control device 90 and pumps recovered water used as reforming water in the water reservoir 50 to the evaporator 25. The evaporator 25 is heated by, for example, combustion gas discharged from the burner 21 (or exhaust heat from the reforming unit 22, the CO shift unit 23, etc.), and the reformed water thus pumped is steamed.

  A CO selective oxidation unit 24 is connected to the inlet of the fuel electrode 11 of the fuel cell 10 via a reformed gas supply pipe 64 so that the reformed gas is supplied to the fuel electrode 11. A burner 21 is connected to the outlet of the fuel electrode 11 via an off-gas supply pipe 65, and anode off-gas discharged from the fuel cell 10 is supplied to the burner 21. A bypass pipe (not shown) that bypasses the fuel cell 10 and directly connects the reformed gas supply pipe 64 and the offgas supply pipe 65 is provided between the reformed gas supply pipe 64 and the offgas supply pipe 65. In order to avoid the reformed gas having a high carbon monoxide concentration from the reformer 20 being supplied to the fuel cell 10 during the start-up operation, the bypass gas is circulated, and from the CO selective oxidation unit 24 during the steady operation. The reformed gas is supplied directly to the fuel cell 10.

  An air supply pipe 61 is connected to the inlet of the air electrode 12 of the fuel cell 10 so that air (cathode air) is supplied into the air electrode 12. An exhaust pipe 62 is connected to the outlet of the air electrode 12 of the fuel cell 10 so that air (cathode off-gas) from the air electrode 12 is discharged to the outside.

  Further, in the middle of the air supply pipe 61 and the exhaust pipe 62, there are first humidifiers 14a that humidify the cathode air supplied to the air electrode 12 by the cathode off gas that is the oxidant gas off gas discharged from the air electrode 12. It is provided so as to straddle the tubes 61 and 62. The first humidifier 14 a is a water vapor exchange type that humidifies the cathode air by exchanging water vapor between the cathode off-gas discharged from the air electrode 12 and the cathode air, and is discharged from the air electrode 12 in the exhaust pipe 62. The water vapor in the gas is supplied into the air supply pipe 61, that is, into the air supplied to the air electrode 12, and humidified. That is, the first humidifier 14a has a humidification source gas (cathode off-gas) and a gas (cathode air) to be humidified with a membrane 14a1 (for example, a water permeable membrane such as a hollow fiber membrane or an ion exchange membrane) permeable only to water vapor. ) And the water vapor in the source gas passes through the membrane 14a1 and humidifies the gas to be humidified.

  Further, the air supply pipe 61 is provided with a second humidifier 14b (described later) between the inlet of the air electrode 12 and the first humidifier 14a. Further, the air supply pipe 61 is provided with a temperature sensor 61a for detecting the cathode air temperature T1 of the fuel cell 10 between the inlet of the air electrode 12 and the second humidifier 14b. To be sent to.

  Further, in the middle of the reformed gas supply pipe 64, the off gas supply pipe 65, the exhaust pipe 62, and the exhaust pipe 63, the reformed gas condenser 31, the anode off gas condenser 32, the cathode off gas condenser 33, and the combustion, respectively. A gas condenser 34 is provided. Although these condensers 31 to 34 are separated in the drawing, they constitute a condenser 30 that is an integrally connected structure. The reformed gas condenser 31 condenses water vapor in the reformed gas supplied to the fuel electrode 11 of the fuel cell 10 flowing in the reformed gas supply pipe 64. The anode offgas condenser 32 is provided in the middle of an offgas supply pipe 65 that communicates the fuel electrode 11 of the fuel cell 10 and the burner 21 of the reformer 20, and the fuel cell 10 that flows in the offgas supply pipe 65. The water vapor in the anode off-gas discharged from the fuel electrode 11 is condensed. The cathode offgas condenser 33 is an oxidant offgas exhaust heat recovery means for recovering exhaust heat of the oxidant offgas that is the cathode offgas after passing through the first humidifier 14a. The cathode off-gas condenser 33 is provided in the exhaust pipe 62, and condenses the water vapor in the cathode off-gas discharged from the air electrode 12 of the fuel cell 10 flowing in the exhaust pipe 62 into a condensed refrigerant. The exhaust heat of the cathode off gas is recovered. The combustion gas condenser 34 is provided in the exhaust pipe 63, and condenses water vapor in the combustion exhaust gas discharged from the reforming unit 22 flowing in the exhaust pipe 63.

  These condensers 31 to 34 communicate with the deionizer 40 via the pipe 66, and the condensed water condensed in each of the condensers 31 to 34 is led out to the deionizer 40 and collected. ing. The deionizer 40 converts the condensed water supplied from the condenser 30, that is, the recovered water into pure water using a built-in ion exchange resin, and leads the purified water to the water reservoir 50. The water reservoir 50 temporarily stores the recovered water derived from the pure water device 40 as reformed water. Further, a pipe for introducing makeup water (tap water) supplied from a tap water supply source (for example, a water pipe) is connected to the deionizer 40, and the amount of water stored in the deionizer 40 is below the lower limit water level. And tap water is supplied.

  Further, the fuel cell system includes a hot water tank 71 for storing hot water, a hot water circulation circuit 72 that is provided independently of the condensing refrigerant circulation circuit 75, and a hot water circulation circuit 72 through which the hot water is circulated. FC cooling water circulation circuit 73 that is a fuel cell heat medium circulation circuit in which FC cooling water that is a medium circulates, first heat exchanger 74 that performs heat exchange between the hot water and the fuel cell heat medium, and a fuel cell A condensed refrigerant circulation circuit 75 which is a heat medium circulation circuit in which a heat medium (condensed refrigerant) that is a liquid containing water at least recovering exhaust heat exhausted from the exhaust gas and / or exhaust heat generated in the reformer 20 is circulated. And a second heat exchanger 76 that exchanges heat between the hot water and the condensed refrigerant. As a result, the exhaust heat (thermal energy) generated by the power generation of the fuel cell 10 is recovered in the FC cooling water, recovered in the hot water via the first heat exchanger 74, and as a result, the hot water is heated ( Temperature). Further, the exhaust heat (thermal energy) of the off gas (anode off gas and cathode off gas) discharged from the fuel cell 10 and the exhaust heat (thermal energy) generated in the reformer 20 are converted into condensed refrigerant via the condenser 30. It collect | recovers and is collect | recovered by the hot water storage via the 2nd heat exchanger 76, As a result, hot water storage is heated (temperature rising). The exhaust heat generated in the reformer 20 includes exhaust heat of the reformed gas, exhaust heat of the combustion exhaust gas from the burner 21, and exhaust heat exchanged with the reformer 20 (exhaust heat of the reformer itself). It is included. In the present specification and the accompanying drawings, “FC” is described as an abbreviation for “fuel cell”.

  The hot water storage tank 71 is provided with one columnar container, and the hot water is stored in a layered manner inside thereof, that is, the temperature of the upper part is the highest and the temperature is lowered as it goes to the lower part, and the temperature of the lower part is the lowest. It has become so. Water (low-temperature water) such as tap water is supplied to the lower part of the columnar container of the hot water tank 71, and hot hot water stored in the hot water tank 71 is led out from the upper part of the columnar container of the hot water tank 71. ing. The hot water storage tank 71 is of a sealed type, and the pressure of tap water is directly applied to the inside, and consequently to the hot water storage water circulation circuit 72.

  One end and the other end of the hot water circulating circuit 72 are connected to the lower part and the upper part of the hot water tank 71. On the hot water circulating circuit 72, a hot water circulating pump 72a, a second heat exchanger 76, and a first heat exchanger 74, which are hot water circulating means, are arranged in order from one end to the other end. The hot water circulating pump 72a sucks in hot water stored in the lower part of the hot water tank 71, causes the hot water circulating circuit 72 to flow through it, and discharges it to the upper part of the hot water tank 71. ) Is controlled. Thus, the hot water is circulated through the second heat exchanger 76 and the first heat exchanger 74 in that order, and the heat from the condensed refrigerant is recovered by the second heat exchanger 76 to the first heat exchanger 74. To recover heat from FC cooling water.

  An FC cooling water circulation pump 73a, which is an FC cooling water circulation means, is disposed on the FC cooling water circulation circuit 73, and this FC cooling water circulation pump 73a is controlled by the control device 90 to control its flow rate (delivery amount). It has come to be. Further, temperature sensors 73b and 73c are disposed on the FC cooling water circulation circuit 73, and the temperature sensors 73b and 73c detect the FC cooling water inlet temperature T4 and the FC cooling water outlet temperature T5 of the fuel cell 10, respectively. These detection results are output to the control device 90. Further, a first heat exchanger 74 is disposed on the FC cooling water circulation circuit 73. Thereby, the FC cooling water is circulated to the fuel cell 10, recovers the heat generated in the fuel cell 10 and raises the temperature, and the heat is recovered in the hot water storage by the first heat exchanger 74, and the fuel is cooled again. The battery 10 is distributed.

  On the condensing refrigerant circulation circuit 75, a condensing refrigerant circulation pump 75a as a condensed refrigerant circulation means is disposed. The condensing refrigerant circulation pump 75a is configured to flow the condensing refrigerant in the direction of the arrow, and is controlled by the control device 90 to control the flow rate (delivery amount). A second heat exchanger 76 is disposed on the condensed refrigerant circulation circuit 75. Further, on the condensing refrigerant circulation circuit 75, a radiator 77, a condensing refrigerant circulation pump 75 a, an anode off-gas condenser 32, a combustion gas condenser 34, and a cathode off-gas condenser are sequentially arranged downstream from the second heat exchanger 76. 33, a reformed gas condenser 31, a temperature sensor 75b, a flow rate regulator 79, a second humidifier 14b, and a temperature sensor 75c are provided.

  In addition, arrangement | positioning of each condenser 31-34 is not restricted to the order mentioned above, Moreover, each condenser 31-34 is not restricted to the case where it arrange | positions in series with one piping, and branches the condensed refrigerant | coolant circulation circuit 75 into plurality. And you may make it arrange | position in parallel at each branch path. Further, at least the cathode offgas condenser 33 is arranged on the condensing refrigerant circulation circuit 75.

  The radiator 77 is a cooling means for cooling the condensed refrigerant, and is controlled to be turned on / off by a command from the control device 90. The radiator 77 cools the condensed refrigerant in the on state and does not cool it in the off state. The temperature sensor 75 b detects the condensed refrigerant outlet temperature T 2 of the reformed gas condenser 31 and outputs the detection result to the control device 90.

  The second humidifier 14b circulates a water-containing liquid (for example, pure water) and a gas to be humidified through a membrane 14b1 (for example, a water-permeable film such as a hollow fiber membrane or an ion exchange membrane) that transmits only water vapor. This is a membrane permeable humidifier that humidifies a gas using a liquid containing a gas as a humidification source. In the present embodiment, the humidification source is pure water which is a condensed refrigerant, and the gas to be humidified is cathode air (oxidant gas). Thus, since the heat medium which is a liquid containing water serves as a humidification source, the water vapor partial pressure can be kept extremely high and constant as compared with the case where the humidification source is off-gas as in the past. Thereby, the 2nd humidifier 14b humidifies cathode air by vaporizing a heat medium using the collect | recovered heat. The second humidifier 14 b is disposed downstream of the cathode offgas condenser 33 and the reformed gas condenser 31 and upstream of the second heat exchanger 76.

  Further, the condensing refrigerant circulation circuit 75 is provided with a bypass path 78 that bypasses the second humidifier 14b, and also bypasses the flow path of the heat medium flowing through the second humidifier 14b and the second humidifier 14b. A flow rate regulator 79 (flow rate adjusting means) is provided for adjusting the flow rate of the heat medium flowing through the. On the condensing refrigerant circulation circuit 75 from the branch point of the bypass passage 78 to the junction, an electromagnetic valve, the second humidifier 14b, and the temperature sensor 75c, which are the flow rate regulator 79, are arranged in order from the upstream. The flow rate regulator (electromagnetic valve) 79 opens and closes the condensed refrigerant circulation circuit 75 and adjusts the flow rate of the heat medium according to a command from the control device 90. The flow rate regulator 79 is not a gas valve such as an air valve but a water valve. The temperature sensor 75c detects the condensed refrigerant outlet temperature T3 of the second humidifier 14b and outputs the detection result to the control device 90.

  Thereby, the condensed refrigerant flows through each condenser 32, 24, 33, 31 and exchanges heat with each gas flowing through each condenser 32, 24, 33, 31 in each condenser 32, 24, 33, 31. Then, the sensible heat and latent heat of each gas are collected and the temperature is raised. Thereafter, the condensed refrigerant is divided into the condensed refrigerant circulation circuit 75 and the bypass path 78 in which the second humidifier 14b is disposed. Note that the flow rate of both flow paths is adjusted by a flow rate regulator 79. The condensed refrigerant flowing through the condensed refrigerant circulation circuit 75 flows through the second humidifier 14b, humidifies the cathode air by steam / heat exchange in the second humidifier 14b, and lowers the temperature. Then, after the condensed refrigerant merges with the condensed refrigerant flowing through the bypass passage 78, the heat recovered through the second heat exchanger 76 is recovered into the hot water storage by the second heat exchanger 76, and the temperature is lowered. The condensers 32, 24, 33 and 31 are circulated again. If sufficient heat recovery is not performed by the second heat exchanger 76, such as when the inside of the hot water tank 71 is full of temperature, the radiator 77 is turned on, and the condensed refrigerant is supplied by the radiator 77. The temperature is lowered.

  The exhaust heat discharged from the fuel cell 10 includes not only exhaust heat of off-gas (anode and cathode off-gas) discharged from the fuel cell 10 but also exhaust heat generated by power generation of the fuel cell 10. The exhaust heat generated by the power generation of the fuel cell 10 is exhaust heat via the FC cooling water of the fuel cell 10. The exhaust heat generated in the reformer 20 includes exhaust heat of the reformed gas, exhaust heat of the combustion exhaust gas from the burner 21, and exhaust heat exchanged with the reformer 20 (exhaust heat of the reformer itself). Heat).

  The condensed refrigerant circulation circuit 75 circulates (uses) pure water as the condensed refrigerant. A replenisher 75 d is disposed on the condensed refrigerant circulation circuit 75. The replenisher 75d automatically replenishes the pure water in the water reservoir 50 to the condensed refrigerant circulation circuit 75 via the water supply pipe 67. For example, the replenisher 75d is similar to a radiator cap provided in a radiator of an automobile engine. It has a simple structure. Thereby, even if the pure water in the condensed refrigerant circulation circuit 75 is reduced by humidification, the pure water can be automatically replenished.

  The humidifier 14 is composed of the first and second humidifiers 14a and 14b described above. As shown in FIG. 2, the flow path 14c through which cathode air flows, the flow 14d through which cathode off-gas flows, and the flow path through which condensed refrigerant flows. 14e is an integral structure. The flow path 14c through which the cathode air flows is disposed adjacent to the flow path 14d through which the cathode off gas flows and the flow path 14e through which the condensed refrigerant flows through the membranes 14a1 and 14b1, respectively. Furthermore, the channel 14d through which the cathode off-gas flows and the channel 14e through which the condensed refrigerant flows are not arranged adjacent to each other via the membrane 14a1 or 14b1.

  Moreover, each temperature sensor 61a, 73b, 73c, 75b, 75c mentioned above, each pump 53, 72a, 73a, 75a, and the flow volume regulator 79 are connected to the control apparatus 90 (refer FIG. 3). The control device 90 has a microcomputer (not shown), and the microcomputer includes an input / output interface, a CPU, a RAM, and a ROM (all not shown) connected via a bus. The CPU executes a program corresponding to the flowchart shown in FIG. 4 and controls the pumps 72a, 73a, 75a and the flow rate regulator 79 based on the temperatures detected by the temperature sensors 61a, 73b, 73c, 75b, 75c. By controlling, the temperature and humidity of the fuel cell 10 are appropriately controlled. The RAM temporarily stores variables necessary for executing the program, and the ROM stores the program.

  Next, the operation of the above-described fuel cell system will be described with reference to the flowchart shown in FIG. When a start switch (not shown) is turned on, the control device 90 repeatedly executes a program corresponding to the above flowchart every predetermined short time. Each time the control device 90 starts executing the program in step 100 of FIG. 4, the condensing refrigerant outlet temperature T2 of the reforming gas condenser 31 (or the reforming gas outlet temperature of the reforming gas condenser 31). Is detected by the temperature sensor 75b (step 102), and the detected condensing refrigerant outlet temperature T2 of the reformed gas condenser 31 (or the reformed gas outlet temperature of the reformed gas condenser 31) is the target temperature T2 * (for example, The flow rate of the condensing refrigerant circulation pump 75a is controlled to be 50 to 60 ° C. (step 104). The higher the condensing refrigerant outlet temperature T2 of the reformed gas condenser 31 is, the better the efficiency of collecting and recovering the amount of hot water stored in the second heat exchanger 76. Therefore, it is desirable to set the target temperature T2 * higher. On the other hand, when the condensed refrigerant outlet temperature T2 of the reformed gas condenser 31 increases, the temperature of the reformed gas that exchanges heat with the condensed refrigerant in the reformed gas condenser 31, that is, the FC inlet temperature of the reformed gas increases. Flooding occurs in the fuel electrode 11 of the fuel cell 10. Accordingly, the target temperature T2 * is set to a temperature at which the recovery efficiency of the condensation recovery heat amount is as good as possible within a range in which no flooding occurs.

  The control device 90 detects the cathode air inlet temperature T1 of the fuel cell 10 (the air electrode 12 thereof) with the temperature sensor 61a (step 106), and the detected cathode air inlet temperature T1 of the fuel cell 10 becomes the target temperature T1 *. Thus, the flow rate regulator 79 is controlled to adjust the flow rate of the cathode air flowing through the second humidifier 14b (step 108). The target temperature T1 * corresponds to a humidification amount determined in consideration of the output current of the fuel cell 10, the cathode air flow rate, and the cathode offgas outlet temperature (water vapor amount) so that the cathode air is optimally humidified. Is set. Note that the FC temperature (for example, the FC cooling water inlet temperature T4 and the FC cooling water outlet temperature T5 of the fuel cell 10) can be used as a substitute for the cathode offgas outlet temperature (water vapor amount). As a result, the condensed refrigerant can be supplied to the second humidifier 14b so as to have a flow rate corresponding to the heat quantity necessary and sufficient for humidification, so that the cathode air can be optimally humidified.

  Instead of detecting the cathode air inlet temperature T1 of the fuel cell 10 and controlling the flow rate regulator 79 so that the temperature T1 becomes the target temperature T1 *, the condensed refrigerant outlet temperature T3 (or the second humidifier 14b) (or The temperature of the second humidifier 14b (condensed refrigerant inlet temperature) is detected by the temperature sensor 75c, and the detected temperature of the second humidifier 14b condensed refrigerant outlet temperature T3 (or the second humidifier 14b condensed refrigerant inlet temperature) is the target temperature T3 *. The flow rate regulator 79 may be controlled so that The target temperature T3 * is set similarly to the target temperature T1 *.

  The control device 90 detects the FC cooling water inlet temperature T4 and the FC cooling water outlet temperature T5 of the fuel cell 10 by the fourth and fifth temperature sensors 73a and 73b, respectively (step 110), and the detected FC cooling of the fuel cell 10 is performed. The flow rate of the hot water circulating pump 72a is controlled so that the water inlet temperature T4 (or the FC cooling water outlet temperature T5 of the fuel cell 10) becomes the target temperature T4 * (or T5 *) (step 112). The target temperatures T4 * and T5 * are optimum operating temperatures of the fuel cell 10.

  Then, the control device 90 calculates a difference ΔT between the FC cooling water inlet temperature T4 and the FC cooling water outlet temperature T5 of the fuel cell 10 (step 114), and the difference ΔT is a predetermined temperature difference ΔT * (for example, 3 to 5 ° C.). ) To control the flow rate of the FC cooling water circulation pump P3 (step 116). The predetermined temperature difference ΔT * is set so that the water vapor in the reformed gas flow path or the air flow path of the fuel cell 10 can be maintained under optimum humidification conditions. Thereafter, the program proceeds to step 118 and is temporarily terminated.

  As is apparent from the above description, in this embodiment, the humidifier 14 humidifies the oxidant gas (cathode air) with the oxidant off-gas (cathode off-gas) in the first humidifier 14a and the second humidifier 14a. Humidifier 14b humidifies the oxidant gas with a heat medium (condensed refrigerant) that is a liquid that contains at least the exhaust heat exhausted from fuel cell 10 and / or exhaust heat generated in reformer 20 that has been recovered. . As a result, the fuel cell 10 can be controlled to an appropriate temperature without depriving the heat from the fuel cell heat medium (FC cooling water) that has recovered the exhaust heat generated by the power generation of the fuel cell 10 and without causing a decrease in heat recovery efficiency. In addition to being able to generate electricity appropriately, the oxidant gas can be humidified to an optimum humidified state. In addition, since the heat medium (condensation refrigerant) that is a liquid containing water serves as a humidification source, the water vapor partial pressure can be maintained extremely high as compared with the conventional case where the humidification source is only off-gas. The area of the part to be converted can be reduced, and the apparatus can be reduced in size. Further, since the water vapor partial pressure can be kept high and constant, it is possible to improve the accuracy of the humidifying performance, improve the stability of the humidifying ability, and improve the responsiveness.

  Further, as the flow rate regulator 79, a water type valve can be used instead of a gas type valve such as an air valve, that is, as compared with a case where a gas type valve having a high flow rate is used as in the prior art. Since a small and low-cost water-based valve that requires a small flow rate can be used, the fuel cell system can be reduced in size and cost. In addition, from the viewpoint of miniaturization, there is an idea of downsizing the gas-based valve, but doing so is not preferable in a fuel cell system in which pressure loss increases and high power generation efficiency is required. Therefore, there is an advantage of using a water system valve from the viewpoint of high power generation efficiency.

  Further, the exhaust heat exhausted from the fuel cell 10 and / or the exhaust heat generated in the reformer 20 is converted into off gas exhausted from the fuel cell 10, fuel gas generated by the reformer 20, reformer 20. Since the heat of condensation is generated when water vapor in at least one gas of the combustion exhaust gas discharged from the burner 21 is condensed, a simple configuration and reliability can be achieved without increasing the size by effectively utilizing the conventional configuration. In addition, the heat medium (condensed refrigerant) can be steamed using the heat of condensation.

  An oxidant off-gas exhaust heat recovery means (cathode off-gas) for recovering exhaust heat of the oxidant off-gas (cathode off-gas) after passing through the first humidifier 14a is placed on the heat medium circulation circuit (condensed refrigerant circulation circuit) 75. Since the condenser 33) is disposed, the exhaust heat of the oxidant off-gas that has been recovered by the first humidifier 14a and remains unused is used by the oxidant off-gas exhaust heat recovery means as a heat medium ( (Condensed refrigerant). The heat can be used for steam heat exchange in the second humidifier 14b and the second heat exchanger 76 located downstream of the cathode offgas condenser 33, respectively, or for increasing the temperature of the stored hot water. It can be used. Therefore, since the exhaust heat of the oxidant off-gas can be recovered without waste and used without waste, the heat recovery efficiency can be improved and the heat recovery efficiency of the entire system can be maintained high.

  Further, the second humidifier 14b is disposed downstream of the oxidant off-gas exhaust heat recovery means (cathode off-gas condenser 33), so that the oxidant off-gas exhaust heat recovery means recovers the heat medium (condensed refrigerant). This heat can be used when the oxidant gas (cathode air) is humidified by the second humidifier 14b, so that the heat recovered by the oxidant off-gas exhaust heat recovery means can be used without waste.

  Further, the oxidant gas (cathode air) is supplied to the oxidant electrode (air electrode) 12 after passing through the first humidifier 14a and the second humidifier 14b in this order, and is oxidized by the first humidifier 14a. Even when the agent gas is not in the optimum humidified state, it is further humidified by the second humidifier 14b to be in the optimum humidified state, so that the oxidant gas supplied to the oxidant electrode 12 can be surely brought into the optimum humidified state. Further, by setting the oxidant gas supplied to the oxidant electrode 12 to a water vapor saturation state with respect to the temperature, the humidified state can be grasped by the temperature, the controllability is improved, and the reliability by using the general-purpose temperature sensor. Maintenance and cost reduction can be achieved.

  Further, the humidifier 14 is an integrated structure including flow paths 14c, 14d, and 14e through which an oxidant gas (cathode air), an oxidant offgas (cathode offgas), and a heat medium (condensed refrigerant) flow, respectively. Can be achieved.

  Further, the flow path 14c through which the oxidant gas (cathode air) flows can exchange water vapor through the films 14a1 and 14b1 to the flow paths 14d and 14e through which the oxidant offgas (cathode offgas) and the heat medium (condensed refrigerant) flow, respectively. Since the flow paths 14d and 14e through which the oxidant off-gas and the heat medium respectively flow are not arranged adjacent to each other through a membrane that allows only water vapor to pass through, they are not arranged adjacent to each other. Since the heat medium does not unnecessarily humidify the oxidant off-gas and the oxidant gas humidifies the heat medium and the oxidant off-gas, the humidification controllability can be improved.

  Further, as a heat medium of the heat medium circulation circuit (condensed refrigerant circulation circuit) 75, off-gas discharged from the fuel cell 10, fuel gas generated by the reformer 20, and combustion discharged from the burner 21 of the reformer 20 By using the condensed water recovered from at least one gas of the exhaust gas, the condensed water is used as humidified water, so the amount of water used for humidification can be covered by the amount of water condensed from the water vapor in each gas. Therefore, humidification is possible without adding a large amount of water.

  Also, a bypass path 78 provided on the heat medium circulation circuit (condensation refrigerant circulation circuit) 75 to bypass the second humidifier 14b, the flow rate of the heat medium (condensation refrigerant) flowing through the second humidifier 14b, and the second humidifier Since it further includes a flow rate adjusting means (flow rate adjuster) 79 that adjusts the flow rate of the heat medium (condensed refrigerant) that bypasses 14b and flows through the bypass path 78, the flow rate corresponds to a heat amount necessary and sufficient for humidification. Thus, since the heat medium can be supplied to the second humidifier 14b, the oxidant gas (cathode air) can be optimally humidified. In addition, since the heat medium (condensed refrigerant) is not supplied to the second humidifier 14b more than necessary, the temperature of the heat medium is prevented from being cooled more than necessary, and the heat medium temperature is maintained at a high temperature. The recovery efficiency can be kept high.

  In the first embodiment described above, the heat recovery efficiency of the condenser 30 is improved by controlling the delivery amount of the condensing refrigerant circulation pump 75a and adjusting the temperature T2 of the heat medium to the target temperature T2 *. And by controlling the flow rate regulator 79 to control the flow rate of the condensed refrigerant to the second humidifier 14b and adjusting the cathode air outlet temperature T1 of the second humidifier 14b to the target temperature T1 *, The humidification of the cathode air can be optimally controlled.

  In the first embodiment described above, the condensed water collected by the condenser 30 is used as the condensing refrigerant. However, the present invention is not limited to this, and pure water used in the fuel cell system may be used. Good.

  In the first embodiment described above, pure water purified by the deionizer 40 is used as the condensing refrigerant. However, the present invention is not limited to this, and the condensed water collected by the condenser 30 is directly used. It may be.

  Further, in the first embodiment described above, the bypass path 78 and the flow rate regulator 79 may not be provided. In this case, oxidation is performed by adjusting the cathode air outlet temperature T1 to the target temperature T1 * by controlling the delivery amount of the condensing refrigerant circulation pump 75a which is provided on the condensing refrigerant circulation circuit 75 and circulates the heat medium. The agent gas (cathode air) is set to a desired humidity. That is, the cathode air outlet temperature T1 of the second humidifier 14b is detected by the first temperature sensor 61a, and the condensed refrigerant circulation pump 75a is set so that the detected cathode air outlet temperature T1 of the second humidifier 14b becomes the target temperature T1 *. The flow rate is controlled. Instead of detecting the cathode air inlet temperature T1 of the fuel cell 10 and controlling the flow rate of the condensing refrigerant circulation pump 75a so that the temperature T1 becomes the target temperature T1 *, the condensing refrigerant outlet temperature T3 of the second humidifier 14b is used. (Or the condensed refrigerant inlet temperature of the second humidifier 14b) is detected by the temperature sensor 75c, and the detected condensed refrigerant outlet temperature T3 of the second humidifier 14b (or the condensed refrigerant inlet temperature of the second humidifier 14b) is the target temperature. The flow rate of the condensed refrigerant circulation pump 75a may be controlled so as to be T3 *.

  This also controls the fuel cell 10 to an appropriate temperature without depriving the heat from the fuel cell heat medium (FC cooling water) that has recovered the exhaust heat generated by the power generation of the fuel cell 10 and without causing a decrease in heat recovery efficiency. It is possible to generate electric power appropriately, and it is possible to humidify the oxidant gas to an optimum humidified state. Therefore, the humidity can be adjusted accurately and accurately, the influence of disturbances such as fluctuations in the atmospheric temperature can be reduced, and flooding can be reliably prevented. In addition, since the liquid heat medium (condensation refrigerant) serves as a humidification source, the water vapor partial pressure can be maintained extremely high compared to the case where the humidification source is only off-gas as in the prior art. Can be reduced, and the apparatus can be miniaturized. Further, since the water vapor partial pressure can be kept high and constant, it is possible to improve the accuracy of the humidifying performance, improve the stability of the humidifying ability, and improve the responsiveness. In addition, since the exhaust heat of the oxidant off-gas can be recovered without waste and used without waste, the heat recovery efficiency can be improved and the heat recovery efficiency of the entire system can be maintained high.

  Further, in the first embodiment described above, the flow rate regulator 79 may be configured with a three-way valve capable of controlling the flow rate ratio instead of an electromagnetic valve. In this case, the flow rate regulator 79 is provided at the branch point of the bypass path 78.

2) Second Embodiment Next, a second embodiment of the fuel cell system according to the present invention will be described with reference to FIG. FIG. 5 is a schematic diagram showing an outline of the fuel cell system according to the second embodiment. In the first embodiment described above, the hot water circulation circuit 72 and the condensed refrigerant circulation circuit 75 are provided independently. However, in the second embodiment, as shown in FIG. One heat medium circulation circuit (hot water circulation circuit 72) is provided. In this case, the second heat exchanger 76 and the condensing refrigerant circulation pump 75a are deleted, and on the hot water circulation circuit 72, the hot water circulation pump 72a, the radiator 77, the replenisher 75d, Each condenser 32, 34, 33, 31, a first heat exchanger 74, a temperature sensor 75b, a second humidifier 14b, and a temperature sensor 75c are disposed. Further, in this case, the hot water storage circuit 72 is provided with a bypass path 78 that bypasses the second humidifier 14b, and the bypass medium 78 is bypassed by bypassing the flow rate of the heat medium flowing through the second humidifier 14b and the second humidifier 14b. A flow rate regulator 79 for adjusting the flow rate of the flowing heat medium is provided. As the flow rate regulator 79, a three-way valve 79 capable of controlling the flow rate ratio is provided at the branch point of the bypass path 78. In addition, the same code | symbol is attached | subjected about the structural member same as 1st Embodiment, and the description is abbreviate | omitted. The temperature sensor 75c detects the stored hot water temperature T3 after passing through the second humidifier 14b.

  In this case, the control device 90 determines that the FC cooling water inlet temperature T4 of the fuel cell 10 (or the FC cooling water outlet temperature T5 of the fuel cell 10) detected by the temperature sensor 73b (or the temperature sensor 73c) is the target temperature T4 * (or The flow rate of the hot water circulating pump 72a is controlled so that T5 *). Further, the control device 90 calculates a difference ΔT between the FC cooling water inlet temperature T4 and the FC cooling water outlet temperature T5 of the fuel cell 10 so that the difference ΔT becomes a predetermined temperature difference ΔT * (for example, 3 to 5 ° C.). The flow rate of the FC cooling water circulation pump 73a is controlled.

  Further, the control device 90 controls the flow rate regulator 79 so that the cathode air outlet temperature T1 of the second humidifier 14b becomes the target temperature T1 * to control the flow rate of the hot water stored in the second humidifier 14b. Yes. As a result, the hot water can be supplied to the second humidifier 14b so as to have a flow rate corresponding to the amount of heat necessary and sufficient for humidification, so that the cathode air can be optimally humidified. It should be noted that the flow rate regulator 79 is controlled so that the other temperature considered to be correlated with the cathode air outlet temperature T1 of the second humidifier 14b, for example, the temperature T3 of the heat medium (hot water storage water) becomes the target temperature T3 *. Thus, the flow rate of the hot water stored in the second humidifier 14b may be controlled.

  According to this, the humidifier 14 humidifies the oxidant gas (cathode air) with the oxidant offgas (cathode offgas) in the first humidifier 14a, and is discharged from the fuel cell 10 in the second humidifier 14b. The oxidant gas is humidified by a heat medium (hot water) that is a liquid that collects at least the exhaust heat generated and / or the exhaust heat generated in the reformer 20. As a result, the fuel cell 10 can be controlled to an appropriate temperature without depriving the heat from the fuel cell heat medium (FC cooling water) that has recovered the exhaust heat generated by the power generation of the fuel cell 10 and without causing a decrease in heat recovery efficiency. In addition to being able to generate electricity appropriately, the oxidant gas can be humidified to an optimum humidified state. In addition, since the liquid heat medium (hot water) serves as a humidification source, the water vapor partial pressure can be maintained at a very high level compared to the conventional case where the humidification source is only off-gas. Can be reduced, and the apparatus can be miniaturized. Further, since the water vapor partial pressure can be kept high and constant, it is possible to improve the accuracy of the humidifying performance, improve the stability of the humidifying ability, and improve the responsiveness.

  Further, an oxidant off-gas exhaust heat recovery means (cathode) that recovers exhaust heat of the oxidant off-gas (cathode off-gas) after passing through the first humidifier 14a is disposed on the heat medium circulation circuit (hot water coolant circulation circuit) 72. Since the off-gas condenser 33) is provided, the exhaust heat of the oxidant off-gas, which is recovered by the first humidifier 14a and remains unused, is heated by the oxidant off-gas exhaust heat recovery means. It is collected in (hot water). The heat can be used for steam heat exchange in the second humidifier 14b located downstream of the cathode offgas condenser 33. Therefore, since the exhaust heat of the oxidant off-gas can be recovered without waste and used without waste, the heat recovery efficiency can be improved and the heat recovery efficiency of the entire system can be maintained high.

  In addition, a first heat exchanger 74 is provided on the hot water circulating circuit 72, which is a heat medium circulating circuit, in which heat is exchanged between the fuel cell cooling water that exchanges heat with the fuel cell 10 and the heat medium (hot water). Therefore, the heat medium that recovers at least the exhaust heat discharged from the fuel cell 10 and / or the exhaust heat generated in the reformer 20 further recovers the exhaust heat generated by the power generation of the fuel cell 10, so that the higher temperature heat This medium becomes a medium, and this high-temperature heat medium can be used in the second humidifier 14b. For this reason, a humidification control range can be expanded more and controllability can be improved more. Note that the location of the first heat exchanger 74 may be downstream of the second humidifier 14b.

  Further, in each of the above-described embodiments, the present invention is applied to the fuel cell system including the reformer 20, but the fuel that supplies the fuel gas to the fuel cell 10 without the reformer 20 is provided. It is possible to apply to a battery system. The fuel cell system includes a hydrogen storage unit that stores hydrogen gas as a fuel gas, a system that supplies hydrogen gas from the hydrogen storage unit to the fuel cell 10, and a methanol storage unit that stores methanol as a fuel. And a system for supplying methanol to the fuel cell 10 from the methanol reservoir.

  In this case, the humidifier 14 humidifies the oxidant gas (cathode air) with the oxidant off-gas (cathode off-gas) in the first humidifier 14a, and the exhaust gas discharged from the fuel cell 10 in the second humidifier 14b. The oxidant gas is humidified by a heat medium (condensed refrigerant) that is at least a liquid from which heat has been recovered. As a result, the fuel cell 10 can be controlled to an appropriate temperature without depriving the heat from the fuel cell heat medium (FC cooling water) that has recovered the exhaust heat generated by the power generation of the fuel cell 10 and without causing a decrease in heat recovery efficiency. In addition to being able to generate electricity appropriately, the oxidant gas can be humidified to an optimum humidified state. In addition, since the liquid heat medium (condensation refrigerant) serves as a humidification source, the water vapor partial pressure can be maintained extremely high compared to the case where the humidification source is only off-gas as in the prior art. Can be reduced, and the apparatus can be miniaturized. Further, since the water vapor partial pressure can be kept high and constant, it is possible to improve the accuracy of the humidifying performance, improve the stability of the humidifying ability, and improve the responsiveness.

  Further, at least condensed water recovered from off-gas discharged from the fuel cell 10 is used as a heat medium of the heat medium circulation circuit (condensed refrigerant circulation circuit) 75. As a result, since condensed water is used as humidified water, the amount of water used in humidification can be covered by the amount of water condensed from the water vapor in the offgas, so humidification is possible without adding a large amount of water from the outside. .

1 is a schematic diagram showing an outline of a first embodiment of a fuel cell system according to the present invention. It is a schematic diagram which shows the humidifier used with the fuel cell system shown in FIG. It is a block diagram which shows the fuel cell system shown in FIG. 4 is a flowchart of a control program executed by the control device shown in FIG. 3. It is a schematic diagram which shows the outline | summary of 2nd Embodiment of the fuel cell system by this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Fuel cell, 11 ... Fuel electrode, 12 ... Air electrode, 13 ... Electrolyte, 14 ... Humidifier, 14a ... 1st humidifier, 14b ... 2nd humidifier, 20 ... Reformer, 21 ... Burner, 22 ... Reforming unit, 23 ... carbon monoxide shift reaction unit (CO shift unit), 24 ... carbon monoxide selective oxidation reaction unit (CO selective oxidation unit), 25 ... evaporator, 30 ... condenser, 31 ... for reformed gas Condenser, 32 ... Condenser for anode off gas, 33 ... Condenser for cathode off gas, 34 ... Condenser for combustion gas, 40 ... Pure water device, 50 ... Reservoir, 53 ... Reformed water pump, 61 ... Air supply pipe 62, 63 ... exhaust pipe, 64 ... reformed gas supply pipe, 65 ... off-gas supply pipe, 66 ... piping, 67 ... water supply pipe, 68 ... reformed water supply pipe, 71 ... hot water tank, 72 ... hot water circulation circuit, 73 ... FC cooling water circulation circuit, 74 ... first heat exchanger, 75 ... condensed refrigerant circulation Path, 75c ... replenisher, 76 ... second heat exchanger, 77 ... radiator, 78 ... bypass path, 79 ... flow regulator (electromagnetic valve, three-way valve), 72a, 73a, 75a ... pump, 61a, 75b, 75c 73b, 73c ... temperature sensors, 90 ... control devices.

Claims (11)

A fuel cell that generates electricity by using fuel and oxidant gas respectively supplied to the fuel electrode and the oxidant electrode;
A humidifier for humidifying the oxidant gas and supplying the oxidant gas to the oxidant electrode;
The humidifier is a first humidifier that humidifies the oxidant gas by exchanging water vapor between the oxidant off-gas discharged from the oxidant electrode and the oxidant gas.
Provided on a heat medium circuit in which a heat medium, which is a liquid containing water at least recovering exhaust heat discharged from the fuel cell, circulates, and steaming the heat medium using the recovered heat A fuel cell system comprising a second humidifier for humidifying an oxidant gas.   2. The oxidant off-gas exhaust heat recovery means for recovering exhaust heat of the oxidant off-gas after passing through the first humidifier is disposed on the heat medium circulation circuit. A fuel cell system.   3. The fuel cell system according to claim 2, wherein the second humidifier is arranged downstream of the oxidant off-gas exhaust heat recovery means.   The fuel according to any one of claims 1 to 3, wherein the oxidant gas is supplied to the oxidant electrode after flowing in the order of the first humidifier and the second humidifier. Battery system.   5. The humidifier according to claim 1, wherein the humidifier is an integral structure including flow paths through which the oxidant gas, the oxidant off-gas, and the heat medium flow. Fuel cell system.   6. The flow path through which the oxidant gas flows is disposed adjacent to the flow path through which the oxidant off gas and the heat medium respectively flow so that water vapor can be exchanged, and the oxidant off gas and the heat medium. The fuel cell system is characterized in that the flow paths through which the gas flows are not arranged adjacent to each other so as to exchange water vapor. In any one of Claims 1 thru | or 6,
A circulation means provided on the heat medium circulation circuit for circulating the heat medium;
The amount of the circulating means is controlled to adjust the temperature of the oxidant gas flowing into the oxidant electrode of the fuel cell to a target temperature, or the temperature of the heat medium after circulation through the second humidifier is adjusted. A fuel cell system that adjusts to a target temperature.   8. The fuel cell system according to claim 1, wherein condensed water recovered from at least off gas discharged from the fuel cell is used as a heat medium of the heat medium circulation circuit. 9. In any one of Claims 1 thru | or 8,
A bypass path provided on the heat medium circulation circuit and bypassing the second humidifier;
The fuel cell further comprising: a flow rate adjusting unit configured to adjust a flow rate of the heat medium flowing through the second humidifier and a flow rate of the heat medium flowing through the bypass path while bypassing the second humidifier. system. In any one of Claims 1 to 9,
A reformer that generates the fuel to be supplied to the fuel cell;
The second humidifier is disposed on a heat medium circulation circuit in which a heat medium that is a liquid containing at least recovered heat exhausted from the fuel cell and / or exhaust heat generated in the reformer circulates. A fuel cell system, wherein the oxidant gas is humidified by steaming the heat medium using the recovered heat. 11. The heat medium of claim 10, wherein at least one of off-gas discharged from the fuel cell, fuel generated by the reformer, and combustion exhaust gas discharged from the combustor of the reformer is used as the heat medium of the heat medium circulation circuit. A fuel cell system using condensed water recovered from two gases.

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