JP4799827B2 - Fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell system including a fuel cell, and more particularly to temperature control at the time of starting the fuel cell.

  The fuel cell system includes a fuel cell 10 that is supplied with fuel and air to a fuel electrode and an air electrode, respectively, and generates heat by a chemical reaction thereof, and a heat medium in which a heat medium that exchanges heat between the fuel cell 10 circulates. A circulation circuit 20; a pump 24 provided on the heat medium circulation circuit 20 for circulating the heat medium; and a temperature adjusting means for adjusting the temperature of the heat medium circulating in the heat medium circulation circuit 20 (radiator 21, temperature control valve). 23, a flow path control valve 31, and a heater 32) are known (Patent Document 1).

In the fuel cell system described in Patent Document 1, moisture is generated inside the fuel cell with power generation. In addition, the fuel cell humidifies the reformed gas and air supplied to the fuel cell in order to ensure the function of the electrolyte interposed between the fuel electrode and the air electrode. In a low temperature environment, there is a problem that the moisture freezes and the fuel cell does not start or the output decreases, and in order to cope with this, a part of the fuel cell is heated intensively with an electric heater or the like. Some start-up methods have been implemented in which power generation is possible in some of them, and the remaining portions are heated using self-heating generated by the partial power generation. Specifically, when the fuel cell temperature Tfc is lower than the operable temperature (fuel cell bypass temperature Tfb), it is heated by the electric heater 32. Is further heated by self-heating by the power generation and heating by the electric heater 32, and when the temperature exceeds the radiator bypass temperature Trb, it is determined that the entire fuel cell can generate power, and control during steady operation is performed. Yes.
Japanese Patent Laying-Open No. 2003-249251 (page 7-9, FIGS. 1 and 3) JP 2002-42841 A

  In the fuel cell system described above, water is generated when power generation is started in a portion where power generation is possible, and thus flooding occurs and stabilizes in other portions where the water balance exceeds zero and other temperatures are low. Cannot be started. In particular, in a low-pressure operation system such as a stationary fuel cell system, if flooding occurs in the fuel cell, it is difficult to discharge the condensed water, and stable start-up and power generation are impossible.

  The present invention has been made to solve the above-described problems. When the fuel cell is started at a low temperature, the fuel cell is started in consideration of the water balance in the fuel cell, thereby enabling stable start-up and power generation. An object of the present invention is to provide a simple fuel cell system.

In order to solve the above-mentioned problem, the structural feature of the invention according to claim 1 is that the fuel is supplied to the fuel electrode, the oxidant gas is supplied to the oxidant electrode, and electric power is generated by their chemical reaction. A fuel cell that is a type that generates generated water, a heat medium circulation circuit that circulates a heat medium that exchanges heat with the fuel cell, and a pump that is provided on the heat medium circulation circuit and circulates the heat medium And a temperature control means for adjusting the temperature of the heat medium circulating in the heat medium circuit, the oxidant gas introduced into the oxidant electrode of the fuel cell is steam saturated or dry air, and is oxidized When the oxidant off-gas discharged from the oxidant electrode is saturated with water vapor, the amount of water introduced into the oxidant electrode and the amount of water discharged from the oxidant electrode calculated from the temperatures at the inlet and outlet of the oxidant electrode Created using The oxidant electrode is the difference between the calculated amount of water introduced into the oxidant electrode and the amount of water generated in the fuel cell and the amount of water discharged from the calculated oxidant electrode with respect to the generated current value of the fuel cell. Storage means for storing a calculation formula or map for determining the temperature of the heat medium at which the water balance becomes zero, and a power generation start current of the fuel cell that is a predetermined amount of current that can be output from the fuel cell The reading means for reading the value, and the temperature of the heat medium at which the water balance becomes zero at the power generation start current value read by the reading means is calculated from an arithmetic expression or a map, and the calculated temperature of the heating medium is the specified warm-up temperature. and the warm-up specified temperature calculating means you, a temperature sensor for detecting the temperature of the heat medium flowing through the heat medium circulation circuit, after starting the start-up of the fuel cell system to a heat medium temperature reaches a warm-up provisions temperature , For temperature control A temperature raising means for raising the temperature of the heat medium, a power generation start means for starting the power generation of the fuel cell after the heat medium temperature reaches the warm-up specified temperature and before reaching the steady operation temperature, A temperature maintaining means for maintaining the temperature of the heat medium at a steady operation temperature when the temperature of the heat medium reaches a steady operation temperature by raising the temperature of the fuel cell by self-heating due to the power generation of the battery; .

In the invention according to claim 1 configured as described above, the warm-up specified temperature calculation means calculates a power generation start current value of the fuel cell that is a predetermined amount of current that can be output from the fuel cell. The temperature of the heat medium at which the water balance becomes zero at the power generation start current value read by the reading means to be read is calculated from an arithmetic expression or a map, the calculated temperature of the heat medium is set as the warm-up specified temperature , and the temperature raising means From the start of the fuel cell system until the heat medium temperature reaches the specified warm-up temperature, the temperature of the heat medium is raised by the temperature control means, and the power generation start means reaches the specified heat-up temperature. Later, before reaching the steady operation temperature, power generation of the fuel cell is started, and the temperature maintaining means raises the temperature of the fuel cell by self-heating due to power generation of the fuel cell, so that the heat medium temperature is reduced. Achieving steady operating temperature Then, to maintain the heat medium temperature in the steady state operating temperature. As a result, when the fuel cell system is started, the power generation of the fuel cell is started before the start of the fuel cell system and the heating medium temperature is equal to or higher than the warm-up specified temperature and reaches the steady operation temperature. Heating is started. At this time, the warm-up regulation temperature is set so as to be the temperature of the heat medium at which the water balance in the oxidant electrode of the fuel cell becomes zero with respect to the generated current value of the fuel cell. No flooding occurs in the oxidizer electrode. Therefore, it is possible to provide a fuel cell system capable of stable start-up and power generation.
Furthermore, the water balance is the difference between the amount of water introduced into the oxidant electrode of the fuel cell and the amount of water produced by the fuel cell and the amount of water discharged from the oxidant electrode, so that heat with respect to the power generation start current value can be reliably and easily An arithmetic expression or map indicating the warm-up regulation temperature that is the temperature of the medium can be created.

  Hereinafter, an 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 containing hydrogen gas necessary for the fuel cell 10.

  The fuel cell 10 includes a fuel electrode 11, an air electrode 12, which is an oxidant electrode, and an electrolyte 13 interposed between the electrodes 11, 12. The reformed gas supplied to the fuel electrode 11 and the air electrode 12 Electric power is generated using air (cathode air) which is the supplied oxidant gas. A supply pipe 61 that supplies air and a discharge pipe 62 that discharges cathode off-gas are connected to the air electrode 12 of the fuel cell 10. Air is humidified in the middle of the supply pipe 61 and the discharge pipe 62. A humidifier 14 is provided. The humidifier 14 is of a water vapor exchange type and dehumidifies water vapor in the gas discharged from the discharge pipe 62, that is, from the air electrode 12, and supplies the water vapor into the supply pipe 61, that is, air supplied to the air electrode 12. And humidify. Note that air-enriched gas may be supplied instead of air.

  The reformer 20 steam-reforms fuel such as natural gas, LP gas, kerosene, methanol, etc., and supplies hydrogen-rich reformed gas to the fuel cell 10. 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 burner 21 is supplied with combustion fuel and combustion air from the outside during start-up, or anode off-gas (reformed gas discharged to the fuel cell and not used) from the fuel electrode 11 of the fuel cell 10 during steady operation. Is supplied, the supplied gas is combusted, and the combustion gas is led out to the reforming unit 22. This combustion gas heats the reforming section 22 (so that it becomes the activation temperature range of the catalyst of the reforming section 22), and then the water vapor contained in the combustion gas is condensed through the combustion gas condenser 34. And exhausted to the outside.

  The reforming unit 22 reforms a mixed gas obtained by mixing the fuel supplied from the outside with the water vapor (reformed water) from the evaporator 25 by using a catalyst charged in the reforming unit 22 to generate hydrogen gas and carbon monoxide. Gas is generated (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 with CO purification air further supplied from the outside using a catalyst filled therein. . 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. The reforming water supply pipe 68 is provided with a reforming water pump 53. 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, the combustion gas discharged from the burner 21, the heat of the reforming unit 22, the CO shift unit 23, and the like, thereby steaming the reformed water fed under pressure.

  A condenser 30 is provided in the middle of a pipe 64 that connects the CO selective oxidation unit 24 of the reformer 20 and the fuel electrode 11 of the fuel cell 10. The condenser 30 is an integral structure in which a reformed gas condenser 31, an anode off gas condenser 32, a cathode off gas condenser 33, and a combustion gas condenser 34 are integrally connected. 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 pipe 64. The anode off-gas condenser 32 is provided in the middle of a pipe 65 that communicates the fuel electrode 11 of the fuel cell 10 and the burner 21 of the reformer 20, and the fuel electrode 11 of the fuel cell 10 that flows in the pipe 65. Water vapor in the anode off-gas discharged from is condensed. The cathode offgas condenser 33 is provided downstream of the humidifier 14 in the discharge pipe 62, and condenses the water vapor in the cathode offgas discharged from the air electrode 12 of the fuel cell 10 flowing in the discharge pipe 62.

  The above-described condensers 31 to 34 communicate with the deionizer 40 via the pipe 66 so that the condensed water condensed in each of the condensers 31 to 34 is led out to the deionizer 40 and collected. It has become. The deionizer 40 converts the condensed water supplied from the condenser 30 and the combustion gas condenser 34, that is, the recovered water into pure water using a built-in ion exchange resin, and the purified water is converted into the water reservoir 50. Is derived. 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.

  The fuel cell system includes a first heat exchanger 71, a heat medium circulation circuit 72 provided between the first heat exchanger 71 and the fuel cell 10, in which a heat medium is circulated, and a heat medium circulation circuit 72. A first pump 73 for circulating the heat medium is provided. Thereby, when the heat medium passes through the fuel cell 10, heat exchange is performed between the heat medium and the fuel cell 10. A temperature sensor 85 for detecting the temperature of the heat medium is provided in the vicinity of the outlet of the fuel cell 10 of the heat medium circuit 72.

  Also, a hot water storage tank 74 that is a hot water storage tank for storing hot water is provided, and a hot water circulation circuit 75 in which hot water as a heat medium is circulated between the first heat exchanger 71 and the hot water storage tank 74, and hot water A second pump 76 that circulates hot water on the circulation circuit 75 is provided. Thus, in the first heat exchanger 71, heat exchange is performed between the heat medium passing through the heat medium circulation circuit 72 and the hot water passing through the hot water circulation circuit 75. One end and the other end of the hot water circulation circuit 75 are connected to an upper part and a lower part of the hot water tank 74, and one end is connected to the other end side of the hot water circulation circuit 75, that is, a lower side part of the hot water tank 74. The other end of the connected pipe 77 is connected. The pipe 77 is provided with a first valve 78. A second valve 79 is provided in the hot water circulation circuit 75 between the connection portion with the pipe 77 and the hot water storage tank 74. Accordingly, when the first and second valves 78 and 79 are opened and closed, respectively, and the second pump 76 is driven, hot water having a high temperature in the upper part of the hot water tank 74 is supplied to the first heat exchanger 71. When the first and second valves 78 and 79 are closed and opened, and the second pump 76 is driven, hot water having a low temperature below the hot water tank 74 is supplied to the first heat exchanger 71.

  The piping 77 is provided with an additional cooking burner 81, and the additional cooking burner 81 further heats the hot water led out from the upper part of the hot water tank 74.

  A second heat exchanger 82 is provided on the hot water circulation circuit 75. A condenser heat medium circulation circuit 83 for circulating the condenser heat medium is provided between the second heat exchanger 82 and the condenser 30. A third pump 84 for circulating the condenser heat medium is provided on the condenser heat medium circulation circuit 83. Accordingly, in the second heat exchanger 82, heat exchange is performed between the condenser heat medium passing through the condenser heat medium circulation circuit 83 and the hot water passing through the hot water circulation circuit 75, and the The hot water is heated by the high-temperature condenser heat medium.

  In the present embodiment, temperature control means for adjusting the temperature of the heat medium circulating in the heat medium circulation circuit 72 from the hot water tank 74, the hot water circulation circuit 75, the first heat exchanger 71, and the second pump 76. Is configured.

The temperature sensor 85, the first to third pumps 73, 76, 83, and the first and second valves 78, 79 are connected to the control device 90 (see FIG. 2). The control device 90 is connected to the storage unit 91. Storage unit 91, operation indicating the temperature at which the warm-up specified temperature Ta of the heat medium water balance is zero empty Kikyokunai of the fuel cell 10 to the generator current I of the fuel cell 10 shown in FIG. 3 Remembers an expression or map.

This arithmetic expression or map can be obtained as follows. As shown in FIG. 4, when the output current value of the fuel cell 10 is constant (for example, I2) and the temperature of the cooling water (heat medium) of the fuel cell is changed in a predetermined temperature range, the water balance with respect to that temperature is changed. Is calculated or measured. Then, the temperature at which the water balance becomes 0 (for example, T2) is derived as the warm-up specified temperature Ta with respect to the output current value I2. Then, by varying the output current value within a predetermined range and deriving the warm-up specified temperature for the output current value in the same manner as described above, the relationship between the derived warm-up specified temperature and the output current value is shown. There is an arithmetic expression or a map showing a temperature at which the warm-up specified temperature Ta of the heat medium water balance is zero empty Kikyokunai of the fuel cell 10 to the generator current I in FIG.

Incidentally, the water balance is defined by the difference between the amount of water discharged from water quantity and the fuel cell 10 of the water and the fuel cell 10 is introduced into the air electrode 1 in 2 of the fuel cell 10. The amount of water to be introduced and the amount of water to be discharged can be derived from the temperatures at the inlet and outlet of the air electrode 12, respectively, assuming that the cathode air and the cathode off-gas are saturated with water vapor. In addition, when the air introduced is dry air, the amount of water introduced is almost zero. The amount of generated water is derived from the output current of the fuel cell 10.

  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 of FIG. 4 to calculate the warm-up specified temperature Ta corresponding to the set power generation start current I, and executes the program corresponding to the flowchart of FIG. The system startup control is executed. 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 FIGS. The control device 90 reads the power generation start current value I of the fuel cell 10 input and stored in advance by an operator, and calculates the warm-up specified temperature Ta for the power generation start current value I from the arithmetic expression or map shown in FIG. (Steps 102 and 104). For example, when the power generation start current value I is I2, the warm-up regulation temperature Ta for the power generation current I2 is T2. The derived warm-up specified temperature Ta is preferably stored in the storage unit 91 or the control device 90.

  Then, the control device 90 executes the program shown in FIG. 6 when a start switch (not shown) is turned on. In step 202, activation of the fuel cell system is started. Specifically, combustion fuel and combustion air are supplied to the burner 21 and burned. When the reforming unit 22 reaches a predetermined temperature by heating the combustion gas, fuel and reforming water are supplied to the reforming unit 22. Further, oxidation air is supplied to the CO selective oxidation unit 24. However, the reformed gas derived from the reformer 20 is not supplied to the fuel cell 10.

  Further, the control device 90 detects the coolant temperature Th of the fuel cell with the temperature sensor 85, and raises the temperature of the coolant based on the temperature (steps 204 and 206). Specifically, the temperature of the cooling water is raised using the hot water in the hot water tank 71. That is, the first and second valves are opened and closed, respectively, and the second pump 76 is driven to send hot water to the first heat exchanger 71. Further, the first pump 73 is driven to send the cooling water (heat medium) in the fuel cell 10 to the first heat exchanger 71. As a result, the cooling water (heat medium) is heated by the hot water in the first exchanger 71 (temperature raising means).

  And after the time (time t1 in FIG. 7) when the coolant temperature Th of the fuel cell reaches the warm-up specified temperature Ta (T2 in this embodiment), the warm-up of the reformer 20 is completed. At the time (time t2 in FIG. 7), the power generation of the fuel cell 10 is started (steps 208 to 210). In step 208, it is determined whether or not the coolant temperature Th has reached the warm-up specified temperature Ta, and the processing of steps 204 to 208 is repeatedly executed until it reaches, and if it reaches, the program proceeds to step 209. In step 209, it is determined whether or not the amount of hydrogen and the concentration of carbon monoxide in the reformed gas derived from the reformer 20 have reached specified values, and the processing in steps 204 to 209 is repeated until it reaches the specified value. Execute and, if reached, advance the program to step 210.

  In step 210, the controller 90 supplies the reformed gas derived from the reformer 20 to the fuel cell 10 and starts power generation of the fuel cell 10. The power generation current I at this time, that is, the power generation start current value is predetermined I2, while the cooling water temperature Th at the time of power generation start (time t2) is higher by ΔT than the cooling water temperature T2 corresponding to the power generation start current value I2. Because of the temperature, the water balance is less than zero, i.e., it feels dry, so no flooding occurs in the fuel cell 10.

  Further, in addition to the heating by the temperature raising means described above, the temperature of the fuel cell 10 is raised by self-heating by the power generation of the fuel cell 10, and the temperature of the cooling water is also raised thereby. The control device 90 detects the coolant temperature Th of the fuel cell by the temperature sensor 85, and when the coolant temperature Th of the fuel cell reaches the steady operation temperature Tb (specifically, 60 to 80 ° C.) (time in FIG. 7). After that, the cooling water temperature Th is adjusted to be maintained at the steady operation temperature Tb until the system is stopped (steps 212 to 216). Specifically, the control device 90 opens and closes the first and second valves 78 and 79, drives the second pump 76, and sends hot water to the first heat exchanger 71. Further, the first pump 73 is driven to send the cooling water (heat medium) in the fuel cell 10 to the first heat exchanger 71. As a result, the cooling water (heat medium) is heated by the first exchanger 71 with the hot water. Further, the first and second valves 78 and 79 are closed and opened, respectively, and the second pump 76 is driven to send warm water having a low temperature to the first heat exchanger 71. Further, the first pump 73 is driven to send the cooling water (heat medium) in the fuel cell 10 to the first heat exchanger 71. As a result, the cooling water (heat medium) is lowered by the first exchanger 71 with the hot water.

As can be understood from the above description, in this embodiment, the warm-up specified temperature calculation means (steps 102 and 104) calculates the warm-up specified temperature Ta, which is the temperature of the heat medium relative to the power generation start current value, or Calculation is performed based on the map, and the temperature raising means (steps 204 to 208) raises the heat medium by the temperature adjusting means until the heat medium temperature reaches at least the warm-up specified temperature Ta after the start of startup of the fuel cell system. The power generation start means (step 210) starts the power generation of the fuel cell after the heat medium temperature reaches the warm-up specified temperature Ta and before reaching the steady operation temperature Tb, and the temperature maintenance means ( step 212-216) is by the fuel cell 10 is heated by self-heating caused by the power generation of the fuel cell 10, the heat medium temperature reaches a steady operating temperature Tb, the heat medium Degrees to maintain a steady operating temperature Tb. As a result, when the fuel cell system is started, power generation of the fuel cell 10 is started before the start of the fuel cell system and the heat medium temperature is equal to or higher than the warm-up specified temperature Ta and reaches the steady operation temperature Tb. Is heated by self-heating. At this time, the warm-up specified temperature Ta is set to be the temperature of the heat medium at which the water balance in the air electrode 12 of the fuel cell 10 becomes zero with respect to the generated current value I of the fuel cell 10. Therefore, no flooding occurs in the air electrode 12 of the fuel cell 10. Therefore, it is possible to provide a fuel cell system capable of stable start-up and power generation.

Further, by the water balance is the difference between the water discharged from the produced water and the fuel cell 10 of the water and the fuel cell 10 is introduced into the air electrode 1 2 of the fuel cell 10, reliably and easily generator starting current An arithmetic expression or a map indicating the warm-up regulation temperature that is the temperature of the heat medium with respect to the value can be created.

  In the above-described embodiment, when the cooling water temperature Th is equal to or higher than the warm-up specified temperature Ta and the warm-up of the reformer 20 is completed, the fuel cell 10 starts power generation. The present invention is also applied to a case where the warming-up of the reformer 20 is completed before the cooling water temperature Th becomes equal to or higher than the warm-up specified temperature Ta, or a case where no reformer is provided in the fuel cell system. be able to. In these cases, the flowchart shown in FIG. 8 may be executed instead of the flowchart shown in FIG. The flowchart of FIG. 8 is obtained by deleting step 209 from the flowchart of FIG.

  The case where no reformer is provided and hydrogen gas is used as the fuel will be described. When the control device 90 executes the flowchart shown in FIG. 8, the fuel cell system is controlled as shown in the time chart of FIG. That is, in step 202, the controller 90 starts the fuel cell system, detects the coolant temperature Th of the fuel cell with the temperature sensor 85, and raises the temperature of the coolant based on the temperature. (Steps 204 and 206). When the coolant temperature Th of the fuel cell reaches the warm-up specified temperature Ta (T2 in the present embodiment) (time t4 in FIG. 9), power generation of the fuel cell 10 is started (steps 208 and 210). That is, the humidified hydrogen gas is supplied to the fuel cell 10. The power generation current I, that is, the power generation start current value at this time is I2 corresponding to the cooling water temperature T2, and the water balance is zero at the cooling water temperature T2, so that no flooding occurs in the fuel cell 10. Further, in addition to the heating by the temperature raising means described above, the temperature of the fuel cell 10 is raised by self-heating due to the power generation of the fuel cell 10, thereby raising the temperature of the cooling water. The control device 90 detects the coolant temperature Th of the fuel cell by the temperature sensor 85, and when the coolant temperature Th of the fuel cell reaches the steady operation temperature Tb (specifically, 60 to 80 ° C.) (time in FIG. 9). After that, the cooling water temperature Th is adjusted to be maintained at the steady operation temperature Tb until the system is stopped (steps 212 to 216).

  In each of the above-described embodiments, the temperature control means for adjusting the temperature of the heat medium circulating in the heat medium circuit 72 is the hot water tank 74, the hot water circuit 75, the first heat exchanger 71, and the second pump. However, the present invention is not limited to this, and other temperature control means (for example, a temperature heater) for adjusting the temperature of the heat medium circulating in the heat medium circuit 72 may be used.

  Moreover, in embodiment mentioned above, as shown in FIG. 10, it is good also as a structure using the warm water of the hot water tank 74. As shown in FIG. Specifically, the other end of a pipe 77 having one end connected to the upper portion of the hot water tank 74 is connected to one end side of the hot water circulation circuit 75, that is, the upper side portion of the hot water tank 74. The pipe 77 is provided with a first valve 78. In addition, a supplementary cooking burner 81 is provided in the pipe 77. A second valve 79 is provided in the hot water circulation circuit 75 between the connection portion with the pipe 77 and the hot water storage tank 74. Further, the hot water circulation circuit 75 is provided with a fourth pump 92 that discharges in the direction opposite to the second pump 76. As a result, when the fourth pump 92 is driven with the first and second valves 78 and 79 closed and open, respectively, hot water having a high temperature at the top of the hot water tank 74 is supplied to the first heat exchanger 71. When the first and second valves 78 and 79 are closed and opened, and the second pump 76 is driven, hot water having a low temperature below the hot water tank 74 is supplied to the first heat exchanger 71. When the fourth pump 92 is driven with the first and second valves 78 and 79 opened and closed, respectively, the hot water having a high temperature at the top of the hot water tank 74 is heated by the reheating burner 81 and the first heat is generated. It is supplied to the exchanger 71. The same members as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted.

  Moreover, in embodiment mentioned above, as shown in FIG. 11, it is good also as a structure using the hot water of the hot water tank 74. FIG. Specifically, a three-way valve 93 is provided at the other end side of the hot water circulation circuit 75, that is, a connection side portion with the lower part of the hot water tank 74, and a pipe 94 that connects the three-way valve 93 and the upper part of the hot water tank 74 is provided. . The three-way valve 93 is a valve capable of switching between a state in which the lower part and the upper part of the hot water tank 74 are communicated with each other and a state in which the upper part of the hot water tank 74 is communicated with each other via a pipe 94. An electric heater 95 is provided in the upper part of the hot water tank 74. As a result, when the second pump 76 is driven by switching the three-way valve 93 to a state in which the upper portions of the hot water tank 74 communicate with each other via the pipe 94, the hot water having a high temperature at the upper portion of the hot water tank 74 is converted into the first heat exchanger 71. To be supplied. At this time, when the electric heater 95 is operated, hot water heated by the electric heater 95 is supplied to the first heat exchanger 71. Further, when the second pump 76 is driven by switching the three-way valve 93 to a state in which the lower part and the upper part of the hot water tank 74 are communicated with each other, hot water having a lower temperature in the lower part of the hot water tank 74 is supplied to the first heat exchanger 71. The same members as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted.

  Moreover, in embodiment mentioned above, as shown in FIG. 12, it is good also as a structure using the warm water of the hot water tank 74. As shown in FIG. Specifically, the three-way valve 93 and the pipe 94 may be eliminated from the configuration shown in FIG. 11 and a fifth pump 96 that discharges in the direction opposite to the second pump 76 may be provided in the hot water circulation circuit 75. Accordingly, when only the fifth pump 96 is driven, hot water having a high temperature at the upper part of the hot water tank 74 is supplied to the first heat exchanger 71, and when only the second pump 76 is driven, hot water having a low temperature at the lower part of the hot water tank 74. Is supplied to the first heat exchanger 71.

1 is a schematic diagram showing an outline of an embodiment of a fuel cell system according to the present invention. It is a block diagram which shows the fuel cell system shown in FIG. It is an arithmetic expression or a map which shows the temperature of the heat carrier in which the water balance in the air electrode of the fuel cell becomes zero with respect to the generated current value of the fuel cell. It is explanatory drawing of the method of calculating | requiring the computing equation or map shown in FIG. It is a flowchart of the control program performed with the control apparatus shown in FIG. It is a flowchart of the control program performed with the control apparatus shown in FIG. It is a time chart which shows operation | movement of embodiment of the fuel cell system by this invention. It is a flowchart of the other control program performed with the control apparatus shown in FIG. It is a time chart which shows the other operation | movement of embodiment of the fuel cell system by this invention. It is a schematic diagram which shows the outline | summary of other embodiment of the fuel cell system by this invention. It is a schematic diagram which shows the outline | summary of other embodiment of the fuel cell system by this invention. It is a schematic diagram which shows the outline | summary of other embodiment of the fuel cell system by this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Fuel cell, 11 ... Fuel electrode, 12 ... Air electrode, 20 ... Reformer, 21 ... Burner, 22 ... Reformer, 23 ... Carbon monoxide shift reaction part (CO shift part), 24 ... Carbon monoxide Selective oxidation reaction section (CO selective oxidation section), 25 ... evaporator, 30 ... condenser, 31 ... reformer gas condenser, 32 ... anode off-gas condenser, 33 ... cathode off-gas condenser, 34 ... combustion gas Condenser, 40 ... pure water device, 50 ... water reservoir, 53 ... reforming water pump, 61-66 ... piping, 68 ... reforming water supply pipe, 71 ... first heat exchanger, 72 ... heat medium circulation circuit 73 ... 1st pump, 74 ... Hot water storage tank, 75 ... Hot water circulation circuit, 76 ... 2nd pump, 77 ... Pipe, 78 ... 1st valve, 79 ... 2nd valve, 81 ... Additional cooking burner, 82 ... 2nd Heat exchanger, 83 ... Condenser heat medium circulation circuit, 84 ... Third pump, 85 ... Temperature Capacitors, 90 ... controller.

Claims (1)

A fuel cell is a type in which fuel is supplied to the fuel electrode, oxidant gas is supplied to the oxidant electrode, and electric power is generated by their chemical reaction and generated water is generated at the oxidant electrode, and heat is generated between the fuel cell. A heat medium circuit that circulates the heat medium to be replaced, a pump that is provided on the heat medium circuit and circulates the heat medium, and a temperature controller that adjusts the temperature of the heat medium that circulates through the heat medium circuit A fuel cell system comprising:
When the oxidant gas introduced into the oxidant electrode of the fuel cell is steam saturated or dry air, and the oxidant off-gas discharged from the oxidant electrode is steam saturated, the inlet of the oxidant electrode and It is created using the amount of water introduced into the oxidant electrode calculated from the temperature of the outlet and the amount of water discharged from the oxidant electrode, and is calculated with respect to the generated current value of the fuel cell. The temperature of the heat medium at which the water balance in the oxidant electrode, which is the difference between the amount of water introduced into the oxidant electrode and the amount of water generated by the fuel cell and the calculated amount of water discharged from the oxidant electrode, becomes zero Storage means for storing an arithmetic expression or a map for obtaining
Reading means for reading out the power generation start current value of the fuel cell, which is the amount of current that can be output from the fuel cell, and is stored in advance.
The temperature of the heat medium at which the water balance becomes zero at the power generation start current value read by the reading means is calculated from the arithmetic expression or the map, and the calculated temperature of the heat medium is defined as a warm-up specified temperature . Warm-up regulation temperature calculation means,
A temperature sensor for detecting a temperature of the heat medium flowing through the heat medium circuit;
From the start of the start of the fuel cell system until the heat medium temperature reaches the specified warm-up temperature, the temperature raising means for raising the temperature of the heat medium by the temperature adjustment means,
Power generation start means for starting power generation of the fuel cell after the heat medium temperature reaches the warm-up specified temperature and before reaching the steady operation temperature;
Temperature maintaining means for maintaining the temperature of the heat medium at the steady operation temperature when the temperature of the heat medium reaches the steady operation temperature by the temperature of the fuel cell being raised by self-heat generation accompanying the power generation of the fuel cell; A fuel cell system comprising:

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