JP2010080251A - Fuel cell system and method for controlling the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of enhancing fuel consumption efficiency in a warming device, and to provide a method for controlling the fuel cell system. <P>SOLUTION: The fuel cell system decides whether exhaust gas temperature detected with a sensor is at calculated dew-point temperature or lower or not, and when the exhaust gas temperature exceeds the dew-point temperature (S6, No), and when coolant quantity can be increased (S7, Yes), the coolant quantity is increased (S10), and when increase of the coolant quantity is not possible (S7, No), and when mixed gas quantity can be reduced (S8, Yes), the mixed gas quantity is reduced (S9). When stack temperature is at warming target temperature or higher (S11, Yes), the stack temperature is controlled at dew-point temperature or higher, and the residual water is actively exhausted to the outside (S12). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel cell system provided with a warm-up device for a fuel cell and a control method for the fuel cell system.

In the fuel cell system, in order to improve the startability of the fuel cell in a low temperature environment, a technology for mounting the catalyst combustor and warming up the fuel cell at the low temperature start has been proposed. For example, in the fuel cell system of Patent Document 1, an antifreeze liquid heated by heat exchange with combustion exhaust gas generated when fuel gas (hydrogen) and oxidant gas (oxygen) are burned is circulated between the fuel cells. A warming-up device for warming up the fuel cell has been proposed.
JP 2000-164233 (paragraph 0065, FIG. 1)

  However, when the fuel cell system is used for in-vehicle use, for example, there is a problem that the cruising distance of the vehicle is shortened when the amount of hydrogen burned by the warm-up device increases.

  The present invention solves the above-described conventional problems, and an object thereof is to provide a fuel cell system and a control method for the fuel cell system that can improve fuel consumption efficiency in a warm-up device.

  The invention according to claim 1 includes a fuel cell that generates power by reaction of a reaction gas, and a catalytic combustor that is supplied with the reaction gas and heats a refrigerant by catalytic reaction, and the fuel cell is activated when the fuel cell is started up. A fuel cell system that promotes warm-up of the fuel cell by supplying a refrigerant heated by the catalyst combustor to the fuel cell, and detects temperature of exhaust gas discharged from the catalyst combustor A dew point calculating means for calculating a dew point temperature of the exhaust gas, a dew point temperature determining means for determining whether the temperature of the exhaust gas is equal to or lower than the dew point temperature, and a temperature of the exhaust gas by the dew point determining means. Exhaust gas temperature control means for performing control so as to be equal to or lower than the dew point temperature when it is determined that it is not below.

  According to the first aspect of the present invention, the heat transfer efficiency to the fuel cell with respect to the amount of hydrogen used by actively utilizing the condensation heat generated when the water vapor contained in the exhaust gas condenses into water. As a result, fuel consumption efficiency (so-called fuel efficiency) is improved, and the amount of hydrogen used for warm-up can be reduced.

  The invention according to claim 2 has a freezing point temperature determining means for determining whether the temperature of the exhaust gas is equal to or higher than a temperature at which the exhaust gas is solidified, and the exhaust gas temperature control means is configured to solidify the exhaust gas by the freezing point temperature determining means. When it is determined that the temperature is not higher than the temperature, control is performed so that the temperature becomes higher than the temperature at which the exhaust gas is solidified.

  According to the second aspect of the invention, by controlling the temperature of the exhaust gas to be equal to or higher than the freezing point, it is possible to avoid an event in which the water vapor in the exhaust gas becomes ice and suppresses the catalytic reaction in the catalyst. It becomes possible. As a result, it becomes possible to avoid that the catalytic combustor cannot be operated.

  The invention according to claim 3 is characterized in that the exhaust gas temperature control means controls the temperature of the exhaust gas by controlling the flow rate of the refrigerant.

  According to the third aspect of the invention, by controlling the refrigerant flow rate, the temperature of the exhaust gas can be controlled without changing the flow rate of the reactive gas supplied to the catalyst. The exhaust gas temperature can be controlled in the supplied state.

  The invention according to claim 4 includes a refrigerant flow rate upper limit detection unit that detects an upper limit of the refrigerant flow rate, and the exhaust gas temperature control unit is determined to be unable to increase the refrigerant flow rate by the refrigerant flow rate upper limit detection unit. In this case, the flow rate of the reaction gas supplied to the catalytic combustor is reduced.

  According to the fourth aspect of the present invention, the exhaust gas temperature can be controlled by reducing the flow rate of the reaction gas even in a state where the flow rate of the refrigerant cannot be increased.

  The invention according to claim 5 includes fuel cell warm-up completion determination means for determining whether or not warm-up of the fuel cell is completed, and the exhaust gas temperature control means includes the fuel cell warm-up completion determination means. When it is determined that the fuel cell has been warmed up, control is performed so that the temperature of the exhaust gas becomes equal to or higher than the dew point.

  According to the invention of claim 5, by controlling the temperature of the exhaust gas to be equal to or higher than the dew point, generation of water can be suppressed and water is prevented from accumulating inside the catalytic combustor. This makes it possible to positively discharge the residual water inside. As a result, it is possible to prevent the residual water from evaporating and becoming water vapor and being adsorbed by the catalyst to reduce the activity.

The invention according to claim 6 includes a fuel cell that generates power by reaction of a reaction gas, and a catalyst combustor that is supplied with the reaction gas and heats the refrigerant by catalytic reaction, and the fuel cell is activated when the fuel cell is started up. A control method of a fuel cell system that promotes warm-up of the fuel cell by supplying a refrigerant heated by a catalyst combustor to the fuel cell, and detects a temperature of exhaust gas discharged from the catalyst combustor And calculating a dew point temperature of the exhaust gas;
Determining whether the temperature of the exhaust gas is equal to or lower than the dew point temperature, and performing a control so as to be equal to or lower than the dew point temperature when it is determined that the temperature of the exhaust gas is not lower than the dew point temperature. It is characterized by.

  According to the invention of claim 6, the heat transfer efficiency to the fuel cell with respect to the amount of hydrogen used by actively utilizing the condensation heat generated when water vapor contained in the exhaust gas condenses into water. As a result, the fuel consumption efficiency is improved and the amount of hydrogen used for warm-up can be reduced.

  According to the fuel cell system and the control method thereof of the present invention, the fuel consumption efficiency in the warm-up device can be improved.

  FIG. 1 is an overall configuration diagram showing a fuel cell system of the present embodiment, FIG. 2 is a flowchart showing warm-up control at the start of the fuel cell system of the present embodiment, and FIG. 3 is a mixed gas based on a temperature change of exhaust gas. It is a timing chart which shows control of a refrigerant. In the following, a case where the fuel cell system is applied to a vehicle such as a fuel cell vehicle will be described as an example. However, the present invention is not limited to this and may be applied to other vehicles such as ships and aircrafts. Or, it may be applied to a stationary type for home use or business use.

  As shown in FIG. 1, the fuel cell system 1 of this embodiment includes a fuel cell FC, an anode system 10, a cathode system 20, a cooling system 30, a warming system 40, a dilution system 50, a control system 60, and the like. ing.

  The fuel cell FC is a PEM (Proton Exchange Membrane) type fuel cell, which is a solid polymer type, and a membrane electrode assembly (MEA) comprising an electrolyte membrane sandwiched between an anode and a cathode, and a membrane electrode assembly (MEA). In this structure, a plurality of single cells each composed of a pair of conductive separators (not shown) provided outside the membrane electrode structure are stacked in the thickness direction. In the fuel cell FC, the separator facing the anode has a flow path a1 through which hydrogen as a fuel gas (reactive gas) flows, and the separator facing the cathode has air as an oxidant gas (reactive gas). The flow path a2 that circulates and the flow path a3 that circulates the refrigerant (heat exchange medium) for warming up and cooling the fuel cell FC are formed so as not to mix with each other. In the fuel cell FC formed as described above, hydrogen as fuel gas is supplied to the anode, and air as oxidant gas is supplied to the cathode, so that power is generated by an electrochemical reaction between hydrogen and oxygen in the air. The generated current is supplied to an external load such as a traveling motor or a high voltage battery. The high-voltage battery is composed of chargeable / dischargeable lithium ions, capacitors, and the like, and supplies power when the power of the fuel cell FC is insufficient or when power generation is stopped. When the power in the high-voltage battery is insufficient, the fuel cell FC It is comprised so that it may be charged with the generated electric power.

  The anode system 10 supplies hydrogen (fuel gas) to the anode of the fuel cell FC and discharges hydrogen (fuel off gas) from the anode. The fuel gas supply pipe 11, the fuel off gas pipe 12, and the hydrogen tank 13 and a shut-off valve 14 and the like.

  The fuel gas supply pipe 11 is a flow path for supplying hydrogen to the fuel cell FC, one end of which is connected to the hydrogen tank 13 and the other end is connected to the inlet of the anode of the fuel cell FC via the shutoff valve 14. ing. The fuel off-gas pipe 12 is a flow path for discharging hydrogen from the fuel cell FC. One end of the fuel off-gas pipe 12 is connected to the outlet of the anode, and the other end is connected to a diluter 51 of the dilution system 50 described later.

  The hydrogen tank 13 is filled with high-purity hydrogen at a high pressure.

  The shut-off valve 14 is, for example, an electromagnetically operated type, and is provided near the downstream of the hydrogen tank 13. The shutoff valve 14 may be an in-tank type that is provided integrally with the hydrogen tank 13.

  The cathode system 20 supplies air (oxidant gas) to the cathode of the fuel cell FC and discharges oxidation offgas (air, generated water, etc.) from the cathode. The pipe 22, the air compressor 23, the back pressure valve 24, and the like are included.

  The oxidizing gas supply pipe 21 is a flow path for supplying air to the cathode of the fuel cell FC, one end of which is connected to the inlet of the cathode of the fuel cell FC and the other end is connected to the air compressor 23. The oxidation off-gas pipe 22 is a flow path for discharging oxidation off-gas from the cathode, and one end thereof is connected to the cathode outlet of the fuel cell FC and the other end is connected to the diluter 51.

  The air compressor 23 is composed of a supercharger or the like driven by a motor, and supplies compressed air (outside air) to the fuel cell FC via the oxidizing gas supply pipe 21.

  The back pressure valve 24 includes a butterfly valve whose opening degree can be adjusted, and has a function of supplying air having a pressure suitable for power generation of the fuel cell FC to the cathode.

  Although not shown, the cathode system 20 is provided with a humidifier that humidifies the dry air (oxidant gas) from the air compressor 23 in the oxidizing gas supply pipe 21.

  The cooling system 30 has a function of dissipating heat generated by the fuel cell FC during power generation, and includes piping 31a, 31b, 31c, 31d, a radiator 32, a switching valve 33, a circulation pump 34, and the like.

  One end of the pipe 31a is connected to the outlet of the flow path through which the refrigerant provided in the fuel cell FC (separator) flows, and the other end is connected to the refrigerant of the catalytic combustor 47 which will be described later via the switching valve 33 and the circulation pump 34. Connected to the entrance. One end of the pipe 31b is connected to the refrigerant outlet of the catalyst combustor 47, and the other end is connected to the inlet of the flow path through which the refrigerant provided in the fuel cell FC (separator) flows. One end of the pipe 31 c is connected to the pipe 31 a between the refrigerant outlet of the fuel cell FC and the switching valve 33, and the other end is connected to the inlet of the radiator 32. One end of the pipe 31 d is connected to the outlet of the radiator 32, and the other end is connected to the switching valve 33. The refrigerant used here is water or antifreeze (ethylene glycol) generally used in vehicles.

  The radiator 32 includes pipes and fins and has a function of radiating heat from the refrigerant heated by the fuel cell FC.

  The switching valve 33 is composed of a thermostat valve or the like. When the fuel cell FC becomes hot, the switching valve 33 is switched to a valve position that passes through the radiator 32. When the fuel cell FC is warmed up, the radiator 32 is bypassed. The valve position is switched.

  The circulation pump 34 has a function of circulating a refrigerant between the fuel cell FC and the radiator 32 and between the fuel cell FC and a catalytic combustor 47 described later.

  The warm-up system 40 includes an oxidizing gas introduction pipe 41, an oxidizing gas flow rate control valve 42, a fuel gas introduction pipe 44, a hydrogen injector 45, a mixer 46, a catalytic combustor 47, and the like.

  The oxidizing gas introduction pipe 41 is a flow path for supplying dry air from the air compressor 23 to the mixer 46, one end of which is connected to the oxidizing gas supply pipe 21 upstream of the humidifier (not shown) and the other end. Is connected to the mixer 46 via the oxidizing gas flow control valve 42.

  The oxidizing gas flow rate control valve 42 is constituted by, for example, a butterfly valve. When a butterfly valve is used as the oxidizing gas flow control valve 42, it is preferable to use a shut-off valve for shutting off the air flow upstream of the oxidizing gas flow control valve 42 of the oxidizing gas introduction pipe 41. This is because, for example, when only the fuel cell FC generates power and it is not necessary to supply air to the oxidizing gas introduction pipe 41, if air flows in, the energy consumption of the air compressor 23 increases.

  The fuel gas introduction pipe 44 is a flow path for supplying hydrogen to the mixer 46 before branching from the fuel gas supply pipe 11 and supplying the fuel cell FC, and one end of the fuel gas supply pipe 44 is upstream of the shutoff valve 14. The other end of the pipe 11 is connected to the oxidizing gas introduction pipe 41 between the oxidizing gas flow rate control valve 42 and the mixer 46 via the hydrogen injector 45. The fuel gas introduction pipe 44 is provided with a shut-off valve 44 a that shuts off hydrogen supply from the hydrogen tank 13 to the hydrogen injector 45.

  The hydrogen injector 45 has a function of injecting hydrogen into the flow path of the oxidizing gas introduction pipe 41, and can control the hydrogen injection amount by the control from the control device 61. That is, by setting the injection time longer, the injection amount increases, and by setting the injection time shorter, the injection amount decreases.

  The mixer 46 is provided on the upstream side of the catalytic combustor 47 and has a space for mixing hydrogen and air to generate a mixed gas.

  The catalytic combustor 47 includes a combustion part 47a and a heat exchange part 47b. The combustion part 47a is configured by, for example, supporting a catalyst such as platinum on a base member formed in a honeycomb shape, and by circulating the mixed gas mixed in the mixer 46, hydrogen in the mixed gas is formed. The catalyst is combusted to generate high-temperature exhaust gas (a gas having a hydrogen concentration of 0). The heat exchanging part 47b has, for example, a structure in which a flow path through which the exhaust gas generated by the combustion part 47a and a flow path through which the refrigerant passes do not cross each other in a cylindrical pipe. In addition, heat exchange is performed between the exhaust gas and the refrigerant.

  The dilution system 50 includes a diluter 51, a discharge pipe 52, an exhaust gas pipe 53, and the like.

  The diluter 51 has a function of diluting hydrogen contained in the fuel off-gas discharged from the anode side of the fuel cell FC to a predetermined concentration or less. In the present embodiment, the oxidizing off gas discharged from the cathode of the fuel cell FC is used as a dilution gas when diluting the fuel off gas discharged from the anode of the fuel cell FC. The oxidizing off gas and air (oxidizing gas) before being supplied to the cathode of the fuel cell FC may be supplied to the diluter 51 to dilute the fuel off gas.

  The discharge pipe 52 is connected to the downstream side of the diluter 51 and discharges the gas diluted by the diluter 51 to the outside of the vehicle.

  The exhaust gas pipe 53 is a flow path for exhaust gas exhausted from the catalytic combustor 47 (gas after catalytic combustion), and is connected to an exhaust pipe 52 downstream of the diluter 51.

  The control system 60 includes a control device 61, temperature sensors 62, 63, 65, a flow rate sensor 64, a humidity sensor 66, a pressure sensor 67, and the like.

  The control device 61 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a peripheral circuit, an input / output interface, and the like, and includes a dew point temperature calculating unit, a dew point temperature determining unit, and an exhaust. Gas temperature control means is provided. The control device 61 also opens and closes the shut-off valve 14, the rotational speed of the motor of the air compressor 23, the opening degree of the back pressure valve 24 and the oxidizing gas flow rate control valve 42, the rotational speed of the motor of the circulation pump 34, and the injection of the hydrogen injector 45. Control each amount.

  The temperature sensor 62 is provided in the pipe 31a near the outlet of the fuel cell FC, and detects the temperature of the refrigerant discharged from the fuel cell FC.

  The temperature sensor 63 is provided in the exhaust gas pipe 53 downstream of the catalytic combustor 47 and detects the temperature of the exhaust gas discharged from the catalytic combustor 47.

  The flow sensor 64, the temperature sensor 65 and the humidity sensor 66 are provided on the upstream side (air introduction side) of the air compressor 23, and the pressure sensor 67 is provided on the exhaust gas pipe 53 on the downstream side of the catalytic combustor 47. Yes.

  The dew point temperature calculating means detects, for example, the flow rate, temperature, and relative humidity of the air that is input to the catalytic combustor 47 with the flow sensor 64, the temperature sensor 65, and the humidity sensor 66, and is input to the catalytic combustor 47. The flow rate of hydrogen is detected by the discharge amount obtained from the hydrogen injector 45, the gas pressure of the catalytic combustor 47 is detected by the pressure sensor 67, the water vapor pressure in the gas at the outlet of the catalytic combustor 47 is obtained, and the water vapor pressure Is calculated as a dew point temperature with a saturated water vapor pressure.

  Next, warm-up control of the fuel cell system of this embodiment will be described with reference to FIGS. 2 and 3 (FIG. 1 as appropriate). When the ignition switch is turned off (IG-OFF) and the operation of the fuel cell system 1 is stopped, the control device 61 closes the shut-off valves 14 and 44a and starts from the hydrogen tank 13 to the fuel cell FC. The hydrogen supply to the anode, the air compressor 23 is stopped, the air supply to the cathode of the fuel cell FC, and the circulation pump 34 is stopped to stop the refrigerant circulation.

  When detecting that the ignition switch is turned on (IG-ON), the control device 61 detects the temperature (system temperature) in the fuel cell system 1 and performs the warm-up control by the catalytic combustor 47. If it is determined whether or not the system temperature is a temperature at which it is not necessary to execute warm-up, normal start-up control is immediately performed without executing the warm-up control shown in FIG. . The normal start-up control is to open the shut-off valve 14 to supply hydrogen from the hydrogen tank 13 to the anode of the fuel cell FC, start driving the air compressor 23 and supply air to the cathode of the fuel cell FC, When the open circuit voltage (OCV) of the fuel cell FC reaches a predetermined voltage, the fuel cell FC is connected to an external load (air compressor 23, travel motor, etc.) via a contactor (not shown) to generate power. To start. As the system temperature, for example, the temperature detected by the temperature sensor 62 is used.

  On the other hand, when the controller 61 determines that the temperature needs to be warmed up, it sets the oxidizing gas flow rate control valve 42 to a predetermined opening, starts driving the air compressor 23, and Air is supplied to 46. Further, the shutoff valve 44 a is opened, hydrogen is supplied to the hydrogen injector 45, and hydrogen is supplied to the mixer 46 with a discharge amount determined from the hydrogen injector 45. Further, the circulation pump 34 is driven, and the refrigerant circulates between the fuel cell FC and the catalytic combustor 47. When the mixed gas is supplied to the catalytic combustor 47, catalytic combustion is performed in the combustion section 47a, and the catalyst temperature gradually rises. The exhaust gas discharged from the combustion unit 47a is heat exchanged with the refrigerant in the heat exchange unit 47b. The refrigerant heated and exchanged in the heat exchanging unit 47b is supplied to the fuel cell FC through the pipe 31b, the fuel cell FC is warmed up, and the refrigerant discharged from the fuel cell FC passes through the pipe 31a. The radiator 32 is circulated so as to return to the heat exchanging portion 47b, bypassing the radiator 32. Although not shown in the flow of FIG. 2, a process of increasing the temperature of the catalyst to a predetermined value is performed before normal warm-up is started (warm-up preparation and warm-up initial stage of FIG. 3). .

  In step S1, the control device 61 determines whether or not the exhaust gas temperature detected by the temperature sensor 63 is equal to or higher than the freezing point (for example, 0 ° C.) of the exhaust gas (freezing point temperature determination means). This is to prevent the water vapor in the exhaust gas from becoming ice and blocking the gas flow path of the catalytic combustor 47. If the control device 61 determines that the detected exhaust gas temperature is higher than the freezing point of the exhaust gas (Yes), the control device 61 proceeds to step S6.

  In step S6, the control device 61 determines whether or not the detected exhaust gas temperature is equal to or lower than the dew point temperature (for example, 40 ° C.) of the exhaust gas (dew point temperature determination means). As described above, the dew point temperature is calculated based on detection values detected by the various sensors 64 to 67 (dew point temperature calculating means). When it is determined that the detected exhaust gas temperature is equal to or lower than the calculated exhaust gas dew point temperature (S6, Yes), the control device 61 proceeds to step S11.

  In step S11, the control device 61 determines whether or not the stack temperature (temperature of the fuel cell FC) is equal to or higher than the warm-up target temperature (fuel cell warm-up completion determination unit). The warm-up target temperature is a temperature at which it is determined whether or not the warm-up has been completed, and is a temperature at which the warm-up by the catalytic combustor 47 is terminated. For example, the temperature detected by the temperature sensor 62 is used as the stack temperature.

  In step S11, when the control device 61 determines that the stack temperature is not equal to or higher than the warm-up target temperature, that is, the warm-up is not completed (No), the control device 61 returns to step S1 and the stack temperature is equal to or higher than the warm-up target temperature. In other words, if it is determined that the warm-up has been completed (Yes), the process proceeds to step S12 to perform control for discharging residual water. The control for discharging the residual water means that the temperature of the exhaust gas is controlled to be equal to or higher than the dew point temperature to prevent water (droplets) from generating and collecting water in the catalyst combustor 47, It is a process that promotes the vaporization of.

  In Step S1, when it is determined that the detected exhaust gas temperature is not equal to or higher than the freezing point (for example, 0 ° C.) of the exhaust gas (No), the control device 61 proceeds to Step S2 and reduces the refrigerant amount. Determine if you can. That is, the determination is made based on whether or not the refrigerant amount has reached a preset lower limit flow rate of the refrigerant. The reason why the lower limit flow rate of the refrigerant is set in this way is to prevent overheating of the fuel cell FC. By reducing the amount of refrigerant in this way, the amount of heat taken away by the refrigerant from the exhaust gas can be reduced, and the temperature of the exhaust gas discharged from the catalytic combustor 47 can be raised.

  In step S2, if it is determined that the refrigerant amount can be reduced (Yes), the control device 61 proceeds to step S5 and decreases the rotational speed of the motor of the circulation pump 34 to reduce the refrigerant amount. Note that the time for reducing the refrigerant amount is set to a predetermined time, for example.

  In Step S2, when it is determined that the amount of refrigerant cannot be reduced (No), the control device 61 proceeds to Step S3 and determines whether or not the amount of mixed gas of air and hydrogen can be increased. . By increasing the amount of the mixed gas, the temperature of the exhaust gas discharged from the catalytic combustor 47 can be raised.

  In step S3, when the control device 61 determines that the amount of mixed gas can be increased (Yes), the control device 61 proceeds to step S4, increases the discharge amount from the hydrogen injector 45, and controls the oxidizing gas flow rate control valve 42. The amount of mixed gas supplied to the catalytic combustor 47 is increased by increasing the opening. The time for increasing the amount of mixed gas is set to a predetermined time, for example.

  In step S3, when the control device 61 determines that the amount of mixed gas cannot be increased (No), the control device 61 proceeds to step S11. The case where the amount of mixed gas cannot be increased is a case where air and hydrogen are already supplied at the maximum flow rates.

  In Step S6, when it is determined that the detected exhaust gas temperature exceeds the calculated exhaust gas dew point temperature (No), the control device 61 proceeds to Step S7 and can increase the amount of refrigerant. Whether or not (refrigerant flow rate upper limit detection means). That is, it is determined whether or not the refrigerant amount has reached the upper limit flow rate.

  If the control device 61 determines in step S7 that the amount of refrigerant can be increased (Yes), the control device 61 proceeds to step S10 and increases the rotational speed of the motor of the circulation pump 34 to increase the amount of refrigerant. By increasing the amount of refrigerant, heat exchange from the exhaust gas to the refrigerant is promoted, and the exhaust gas temperature can be lowered.

  In step S7, when it is determined that the amount of refrigerant cannot be increased (No), the control device 61 proceeds to step S8 and determines whether the amount of mixed gas of air and hydrogen can be reduced.

  In step S8, when it is determined that the amount of the mixed gas can be reduced (Yes), the control device 61 proceeds to step S9 to reduce the mixed gas amount. The time for reducing the amount of mixed gas is a predetermined time set in advance. In step S9, by reducing the mixed gas, the exhaust gas temperature is lowered, and the exhaust gas temperature is lowered toward the dew point temperature. If the controller 61 determines in step S8 that the amount of mixed gas cannot be reduced (No), the controller 61 proceeds to step S11.

  When the warm-up is completed (S11, Yes) and the discharge of residual water is completed (S12), as in the normal control described above, hydrogen is supplied to the anode and air is supplied to the cathode, respectively. Raise FC to a voltage that can start power generation. Further, the exhaust gas temperature control means of the present embodiment is a process in which steps S2 to S5 are controlled to be equal to or higher than the temperature at which the exhaust gas is solidified, and steps S7 to S11 are the exhaust gas below the dew point temperature. It corresponds to the processing to be controlled.

  Further, with reference to the timing chart of FIG. 3, when the ignition switch is turned on (IG-ON) at time t0, the refrigerant temperature at the outlet of the fuel cell FC needs to be warmed up to a predetermined temperature or less. When the temperature is low (eg, minus 30 ° C.), as the warm-up preparation, the opening degree of the oxidizing gas flow rate control valve 42 is adjusted and the shutoff valve 44a is opened.

  At time t <b> 1, air is supplied from the air compressor 23 and hydrogen is supplied from the hydrogen injector 45, and a mixed gas in which hydrogen and air are mixed in the mixer 46 is supplied to the catalytic combustor 47. Thereby, oxygen in the air and hydrogen are combusted by a catalytic reaction, and the catalyst temperature of the combustion part 47a gradually increases. As the catalyst temperature rises, the exhaust gas temperature discharged from the catalyst combustor 47 (detected value of the temperature sensor 63) rises. Further, the rotational speed of the motor of the circulation pump 34 is controlled so that the refrigerant amount becomes the lower limit flow rate, so that the refrigerant is circulated between the fuel cell FC and the catalytic combustor 47. The reason for flowing the refrigerant amount at the lower limit flow rate instead of zero is to prevent a part of the fuel cell from being overheated. Further, the initial warm-up period from time t1 to t2 is a process for increasing the catalyst temperature in order to increase the reactivity of the catalyst in the catalyst combustor 47, and is executed, for example, for a predetermined time.

  At time t2, when the catalyst temperature rises to a predetermined temperature due to the initial warm-up process, the control shifts to normal control, and the rotational speed of the circulation pump 34 is increased so that the refrigerant amount is normally set during warm-up.

  At time t3, when the exhaust gas temperature exceeds the dew point temperature (S6, No), the refrigerant amount is increased to the upper limit flow rate (S10). As a result, the amount of heat deprived by the refrigerant from the exhaust gas increases, so that the exhaust gas temperature falls below the dew point temperature (S6, Yes).

  When the exhaust gas temperature again exceeds the dew point temperature at time t4 (S6, No), the refrigerant amount has already been set to the upper limit flow rate, and the refrigerant amount cannot be increased any more (S7, No). The amount of mixed gas of hydrogen is reduced (S9). By reducing the amount of the mixed gas, the reaction temperature is lowered, and the exhaust gas temperature is lowered below the dew point temperature (S6, Yes).

  At time t5, when the refrigerant temperature at the outlet of the fuel cell FC (detected value of the temperature sensor 62) reaches a predetermined temperature T2 (warm-up completion temperature), the circulation pump 34 is lowered to the rotational speed that is the lower limit flow rate. Increase the amount of gas mixture. As a result, the exhaust gas temperature rises above the dew point temperature, so that the generation of water (condensed water) is suppressed, the vaporization of the residual water is promoted, and the residual water inside the catalytic combustor 47 is discharged to the outside. . In this case as well, the refrigerant amount is set to the lower limit flow rate instead of zero to prevent partial overheating of the fuel cell FC.

  At time t6 after discharging the residual water, the shutoff valve 44a is closed to stop the supply of hydrogen to the catalytic combustor 47, and the circulation pump 34 is stopped. At this time, air is supplied to the catalytic combustor 47 to cool the catalytic combustor 47.

  At time t6, the shutoff valve 14 is opened to supply hydrogen to the anode of the fuel cell FC, and the air compressor 23 is driven to supply air to the cathode. Thereby, at time t7 when the open end voltage of the fuel cell FC increases and the open end voltage reaches a predetermined voltage, the fuel cell FC and the external load are connected by connecting a contactor (not shown), Start power generation.

  As described above, according to the fuel cell system of the present embodiment, the water vapor contained in the exhaust gas is condensed into water (droplets) by controlling the exhaust gas temperature to be the outdoor temperature or less. The heat of condensation generated at that time can be used for warming up. As a result, the efficiency of heat transfer to the fuel cell with respect to the amount of hydrogen used is improved, the fuel consumption efficiency of hydrogen is improved, and the amount of hydrogen when used for warm-up can be reduced.

  Further, according to the present embodiment, by controlling the temperature of the exhaust gas to be equal to or higher than the freezing point, it is possible to avoid an event that water vapor in the exhaust gas becomes ice and the catalytic reaction in the catalyst is impaired. It becomes possible. As a result, an event that the catalytic combustor 47 cannot be operated can be avoided.

  Further, according to the present embodiment, by controlling the amount of refrigerant, the exhaust gas temperature can be controlled without changing the flow rate of the mixed gas (reactive gas) supplied to the catalytic combustor 47. The exhaust gas temperature can be controlled in a state in which the amount of mixed gas suitable for the catalytic reaction is supplied.

  Further, according to the present embodiment, the exhaust gas temperature can be controlled by decreasing the mixed gas amount even in a state where the refrigerant amount cannot be increased due to the rotational speed limit of the circulation pump 34 or the like. In the present embodiment, the case where the refrigerant amount and the mixed gas amount are controlled has been described as an example. However, the control may be performed using only the mixed gas amount.

  In addition, according to the present embodiment, the exhaust gas temperature is controlled to be equal to or higher than the dew point temperature after the warm-up is completed, thereby preventing water (droplets) from being generated and collecting water in the catalyst combustor 47, and Residual water inside can be actively vaporized and discharged outside. As a result, it is possible to prevent the residual water from evaporating and becoming water vapor and adsorbed on the catalyst, thereby reducing the activity of the catalyst.

It is a whole lineblock diagram showing the fuel cell system of this embodiment. It is a flowchart which shows the warming-up control at the time of starting of the fuel cell system of this embodiment. It is a timing chart which shows control of the mixed gas and a refrigerant | coolant based on the temperature change of exhaust gas.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell system 10 Anode system 13 Hydrogen tank 20 Cathode system 23 Air compressor 24 Back pressure valve 30 Cooling system 32 Radiator 33 Switching valve 34 Circulation pump 40 Warm-up system 42 Oxidation gas flow rate control valve 45 Hydrogen injector 46 Mixer 47 Catalytic combustor 47a Combustion part 47b Heat exchange part 50 Dilution system 51 Diluter 60 Control system 62 Temperature sensor 63 Temperature sensor (temperature detection means)
64 Flow sensor 65 Temperature sensor 66 Humidity sensor 67 Pressure sensor 61 Control device (dew point temperature calculation means, dew point temperature determination means, exhaust gas temperature control means, freezing point temperature determination means, refrigerant flow rate upper limit detection means, fuel cell warm-up completion determination means )
FC fuel cell

Claims (6)

A fuel cell that generates electricity by reaction of the reaction gas; and
A catalytic combustor that is supplied with a reaction gas and heats the refrigerant by a catalytic reaction, and supplies the refrigerant heated by the catalytic combustor to the fuel cell when the fuel cell is started up. A fuel cell system that promotes warm-up of
Temperature detecting means for detecting the temperature of exhaust gas discharged from the catalytic combustor;
Dew point temperature calculating means for calculating a dew point temperature of the exhaust gas;
Dew point temperature determining means for determining whether the temperature of the exhaust gas is equal to or lower than the dew point temperature;
Exhaust gas temperature control means for controlling the exhaust gas temperature to be equal to or lower than the dew point temperature when the dew point temperature determination means determines that the temperature of the exhaust gas is not equal to or lower than the dew point temperature. . A freezing point temperature determining means for determining whether the temperature of the exhaust gas is equal to or higher than a temperature at which the exhaust gas is solidified;
The exhaust gas temperature control means controls the exhaust gas so as to be equal to or higher than a temperature at which the exhaust gas is solidified when it is determined by the freezing point temperature determination means that the temperature is not higher than the temperature at which the exhaust gas is solidified. The fuel cell system according to claim 1.   The fuel cell system according to claim 1 or 2, wherein the exhaust gas temperature control means controls the temperature of the exhaust gas by controlling the flow rate of the refrigerant. Refrigerant flow rate upper limit detecting means for detecting the upper limit of the flow rate of the refrigerant,
The exhaust gas temperature control means reduces the flow rate of the reaction gas supplied to the catalytic combustor when it is determined by the refrigerant flow rate upper limit detection means that the flow rate of the refrigerant cannot be increased. Item 4. The fuel cell system according to Item 3. A fuel cell warm-up completion judging means for judging whether or not the warm-up of the fuel cell is completed,
The exhaust gas temperature control means controls the exhaust gas temperature to be equal to or higher than a dew point temperature when the fuel cell warm-up completion judging means judges that the fuel cell warm-up is completed. The fuel cell system according to any one of claims 1 to 4, wherein the fuel cell system is provided. A fuel cell that generates electricity by reaction of the reaction gas; and
A catalytic combustor that is supplied with a reaction gas and heats the refrigerant by a catalytic reaction, and supplies the refrigerant heated by the catalytic combustor to the fuel cell when the fuel cell is started up. A control method for a fuel cell system that promotes warm-up of the vehicle,
Detecting the temperature of the exhaust gas discharged from the catalytic combustor;
Calculating a dew point temperature of the exhaust gas;
Determining whether the temperature of the exhaust gas is equal to or lower than the dew point temperature;
And a step of controlling the exhaust gas so as to be equal to or lower than the dew point when it is determined that the temperature of the exhaust gas is not equal to or lower than the dew point.

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