JP2008016320A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system capable of preventing thermal deterioration of a purifier, of realizing a long lifetime, and of suppressing the rise in the electrical conductivity of water, to cool a fuel cell at a low cost using a simple constitution. <P>SOLUTION: The fuel cell system is provided with the fuel cell 1, a purified water tank 23 for storing water used for cooling the fuel cell 1, a recovered water tank 7 for storing water recovered from the fuel cell 1; a water supply passage 18 for connecting the recovered water tank 7 and the purified water tank 23; a purifying device 9 for purifying water to flow in the water supply passage 18; a purified water returning route 17 for returning the water of the purified water tank 23 to the recovered water tank 7; and a controller 10, in which the controller 10 executes a water-purifying operation mode. The system reduces the water-circulating volume in the water-purifying operation mode, when the temperature related to the water temperature of the recovered water tank 7 has a value not lower than the prescribed threshold, as compared with the case in which the temperature related to the water temperature of the recovered water tank 7 has a value lower than the prescribed threshold. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel cell system, and more particularly to a fuel cell system that generates electricity while maintaining the conductivity of water for cooling the fuel cell below a threshold value.

  In the fuel cell system, power is generated by an electrochemical reaction between a fuel gas and an oxidant gas (these are called reaction gases) supplied from the outside to the fuel cell. At this time, heat is generated by the reaction of the reaction gas. For this reason, the cooling water is supplied to the fuel cell in order to keep the generated fuel cell at a constant temperature. The cooling water supplied into the fuel cell exchanges heat in the fuel cell, is heated, and is discharged from the fuel cell. The discharged cooling water is cooled by exchanging heat with a heat exchanger and supplied again to the fuel cell.

  In such a fuel cell system that circulates cooling water, when the water quality of the cooling water deteriorates (conductivity increases), electric leakage occurs in the fuel cell and the voltage drops. In the worst case, there is a risk of stopping power generation. Yes, it is necessary to maintain the conductivity below a predetermined value. For this reason, a fuel cell system that maintains a conductivity below a predetermined value by providing a purifier filled with an ion exchange resin and adsorbing conductive ions in cooling water is known (for example, Patent Document 1). .

Specifically, the water in the recovered water tank that stores the recovered water condensed from the moisture in the exhaust gas of the fuel cell is supplied to the purifier, and the ionic impurities are removed by the ion exchange resin, and the water whose conductivity is lowered. Is supplied to the cooling water tank, and water exceeding the specified water level in the cooling water tank is supplied to the recovery water tank from the overflow pipe, and water circulates between the cooling water tank and the recovery water tank. While performing the purification operation for maintaining the water quality of the cooling water. Further, as a preferable mode of the circulation operation for maintaining the water quality of the cooling water, it has been proposed to implement it during the stop operation of the fuel cell system.
JP 2002-141095 A

  In addition, when performing the purification operation for maintaining the water quality during the stop operation as described in the above-mentioned Patent Document 1, it has a relatively high temperature of about 60-70 ° C. immediately after the operation of the fuel cell is stopped. The cooling water is mixed with the recovered water having a temperature lower than that of the cooling water, so that water having a temperature lower than the heat-resistant temperature (50-60 ° C.) of the ion exchange resin is normally supplied to the purifier. However, the temperature of the recovered water tank is easily affected by the atmospheric temperature, and in summer when the atmospheric temperature is high, even if overflowed cooling water is supplied to the recovered water tank, the temperature is not sufficiently reduced. There was a possibility that water having a temperature higher than the heat-resistant temperature was supplied to the purifier and the thermal deterioration of the ion exchange resin was promoted.

  The present invention has been made in view of the above problems, and a purification operation for maintaining the water quality of cooling water is performed so that thermal deterioration of the ion exchange resin in the purifier is not promoted even under a high atmospheric temperature. An object is to provide a possible fuel cell system.

  In order to solve such a problem, a fuel cell system of the present invention includes a fuel cell that generates power using a fuel gas and an oxidant gas, a purified water tank that stores water used for cooling the fuel cell, A recovered water tank for storing water recovered from at least one of exhaust fuel gas and exhaust oxidant gas discharged from the fuel cell; a water supply path connecting the recovered water tank and the purified water tank; A purifier for purifying water flowing through the water supply path, a pump for flowing water from the recovered water tank to the purified water tank through the water supply path, and water from the purified water tank to the recovered water tank A purified water return path for returning, and a controller, wherein the controller operates the pump to circulate water between the purified water tank and the recovered water tank. And when the temperature related to the water temperature of the recovered water tank is equal to or higher than a predetermined threshold, the pump is controlled and the water circulation amount in the water purification operation mode is related to the water temperature of the recovered water tank. Decrease than when the temperature is below a predetermined threshold.

  As a result, when the temperature related to the water temperature of the recovered water tank is high in the water purification operation mode, it is purified by the heat capacity of the water in the recovered water tank, the water supply path, and the purifier by reducing the amount of water flowing to the purifier. Since it is possible to prevent the temperature inside the vessel from rising rapidly, thermal degradation of the purifier can be prevented.

  The purified water tank may be a cooling water tank that stores cooling water for cooling the fuel cell.

  The temperature related to the water temperature of the recovered water tank is the water temperature in the recovered water tank, and the controller controls the pump when the water temperature is equal to or higher than a first threshold value, and performs the water purification operation. The water circulation amount in the mode may be reduced as compared with the case where the water temperature is lower than the first threshold.

  As a result, in the water purification operation mode, when the temperature of the recovered water is high (above the first threshold value), the amount of water flow to the purifier is reduced, so that the inside of the recovered water tank, the water supply path, and the purifier Since the temperature inside the purifier can be prevented from rapidly rising due to the heat capacity of the water, it is possible to prevent thermal deterioration of the ion exchange resin in the purifier.

  The temperature related to the water temperature of the recovered water tank is an atmospheric temperature, and the controller controls the pump when the atmospheric temperature is equal to or higher than a second threshold, and the water circulation amount in the water purification operation mode May be reduced as compared with the case where the atmospheric temperature is lower than the second threshold value.

  Thereby, when the atmospheric temperature is equal to or higher than the second threshold, it is estimated that the recovered water temperature is equal to or higher than the first threshold, and by reducing the amount of water flow to the purifier, the recovered water tank, the water supply path, and Since it is possible to prevent the temperature in the purifier from rapidly rising due to the heat capacity of the water in the purifier, it is possible to prevent thermal deterioration of the ion exchange resin in the purifier.

  The controller makes the operation period of the pump shorter than the case where the operation period is less than the predetermined threshold value, so that the water circulation amount in the water purification operation mode is a temperature related to the water temperature of the recovered water tank. It may be reduced as compared with the case of less.

  The controller makes the output of the pump smaller than when it is less than the predetermined threshold, so that the water circulation amount in the water purification operation mode is less than the predetermined threshold. It may be reduced as compared with the case of.

  When the temperature related to the water temperature of the recovered water tank is equal to or higher than a predetermined threshold, the controller has a smaller amount of water circulation than when the temperature related to the water temperature of the recovered water tank is lower than the predetermined threshold. After stopping the operation of the pump, when the water temperature in the cooling water tank becomes lower than the third threshold value, the operation of the pump may be resumed.

  As a result, even if the purification of the cooling water is insufficient due to the short water purification operation mode, the temperature of the water entering the purifier is reduced by restarting the pump operation after the cooling water temperature has decreased. It becomes possible to maintain the conductivity of the cooling water below a predetermined value while keeping it below the heat-resistant temperature of the ion exchange resin.

  When the temperature related to the water temperature of the recovered water tank is equal to or higher than a predetermined threshold, the controller has a smaller amount of water circulation than when the temperature related to the water temperature of the recovered water tank is lower than the predetermined threshold. After the operation of the pump is stopped, the operation of the pump may be resumed when a predetermined time elapses after the system stop operation is started.

  Thereby, even if the purification of the cooling water is insufficient because the water purification operation mode is short, the operation of the pump is resumed after a predetermined time estimated that the cooling water temperature has decreased. Thus, it is possible to keep the conductivity of the cooling water below a predetermined value while keeping the temperature of water entering the purifier below the heat resistant temperature of the ion exchange resin.

  The controller may start the water purification operation mode after starting a system stop operation of the fuel cell system.

  The purified water tank includes the cooling water tank that stores cooling water that is circulated so as to cool the fuel cell, and the makeup water tank that stores water flowing in from the water supply path, and the water in the makeup water tank is the water The purified water return path is configured to be able to supply to the cooling water tank, and the purified water return path returns water from the cooling water tank to the recovered water tank. In the water purification operation mode, the makeup water tank, the cooling water Water may circulate through the tank and the recovered water tank.

  According to the fuel cell system of the present invention, it is possible to perform a purification operation for maintaining the water quality of the cooling water so as not to promote the thermal deterioration of the ion exchange resin in the purifier even under a high atmospheric temperature.

  Further, according to the fuel cell system of the present invention, the water purification operation mode is resumed after the temperature of the cooling water is lowered, so that the conductivity can be reliably maintained at a predetermined value or less.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
(Embodiment 1)
FIG. 1 is a block diagram schematically showing the configuration of the fuel cell system according to Embodiment 1 of the present invention.

  First, the configuration of the fuel cell system according to Embodiment 1 will be described.

  As shown in FIG. 1, the fuel cell system according to Embodiment 1 includes a fuel cell 1, a fuel gas supplier 2, an oxidant gas supplier 3, a heat exchanger 4, a cooling water tank 5, and a first pump 6. , A recovered water tank 7, a second pump 8, a purifier 9 and a controller 10.

  One end of a fuel gas supply channel 11 is connected to the fuel cell 1, and a fuel gas supply device 2 is connected to the other end of the fuel gas supply channel 11. The fuel gas supply device 2 supplies fuel gas to the anode (not shown) of the fuel cell 1 through the fuel gas supply channel 11. Here, the fuel gas supply device 2 includes a plunger pump (not shown) for sending natural gas (raw material gas) supplied from the natural gas supply infrastructure to a fuel processor (not shown), and its delivery amount. It has a flow rate adjusting device (not shown) that can be adjusted, and a fuel processor that reforms the delivered natural gas into a hydrogen-rich fuel gas. In the fuel processor, natural gas and steam are subjected to a reforming reaction to generate a reformed gas, and carbon monoxide contained in the reformed gas is reduced to about 1 ppm to generate a fuel gas. At this time, the fuel gas contains a certain amount of water vapor provided for the reforming reaction, but may be configured to further humidify a certain amount of water vapor. In addition, one end of a fuel gas discharge channel 12 is connected to the fuel cell 1, and a fuel processor of the fuel gas supply device 2 is connected to the other end of the fuel gas discharge channel 12.

  Further, one end of an oxidant gas supply channel 13 is connected to the fuel cell 1, and the oxidant gas supply unit 3 is connected to the other end of the oxidant gas supply channel 13. The oxidant gas supply unit 3 supplies humidified oxidant gas to the cathode (not shown) of the fuel cell 1 through the oxidant gas supply channel 13. Here, the oxidant gas supply device 3 includes a blower (not shown) whose suction port is open to the atmosphere and a humidifier (not shown) for humidifying the sucked air or the sucked air with a certain amount of water vapor. It consists of The oxidant gas supply unit 3 may be configured to use fans such as a sirocco fan.

  Further, an oxidant gas discharge channel 14 is connected to the fuel cell 1 to discharge unreacted oxidant gas (hereinafter referred to as exhaust oxidant gas) out of the system.

  In the fuel cell 1, the fuel gas containing hydrogen supplied from the fuel gas supply device 2 and the oxidant gas containing oxygen supplied from the oxidant gas supply device 3 react electrochemically to generate water. Generates heat and electricity. At this time, water vapor contained in the unreacted reaction gas (hereinafter referred to as exhaust reaction gas) is separated from the exhaust reaction gas by an appropriate method and condensed into water. Of the exhausted reaction gas, unreacted fuel gas (hereinafter referred to as “exhaust fuel gas”) passes through the fuel gas discharge channel 12 and is a fuel processor of the fuel gas supply device 2 (more precisely, a heating section of the fuel processor). ) As off-gas. Further, the water separated from the discharged reaction gas and the water generated by the reaction of the reaction gas are supplied to the recovered water tank 7 via the recovered water channel 15 connected to the fuel cell 1. Here, the water vapor is recovered from the exhaust fuel gas and the exhaust oxidant gas, but the water vapor may be recovered from one of the exhaust reaction gases.

  The fuel cell 1 is connected to the cooling water tank 5 by a cooling water circulation path 16, and the cooling water circulation path 16 is provided with a first pump 6 capable of adjusting the flow rate. The cooling water circulation path 16 has a cooling water forward path 16A and a cooling water return path 16B. The upstream end of the heat medium forward path 16 </ b> A is connected to the cooling water tank 5, and the downstream end thereof is connected to the inlet of the cooling water flow path of the fuel cell 1. Further, the upstream end of the cooling water return path 16B is connected to the outlet of a cooling water flow path (not shown) of the fuel cell 1, and the downstream end thereof is connected to the cooling water tank 5 in the middle of the cooling water return path 16B. Is provided with a heat exchanger 4. Thereby, the cooling water supplied to the fuel cell 1 can recover the heat generated when the reaction gas is reacted, and the inside of the fuel cell 1 can be maintained at an appropriate temperature. Here, the first pump 6 uses a pump capable of adjusting the flow rate. However, the first pump 6 is not limited to this, and the flow rate of the cooling water is adjusted using a flow rate regulator such as a pump and a flow rate control valve. Also good.

  The cooling water tank 5 is connected to the recovered water tank 7 through a cooling water return path 17, and when the cooling water stored in the cooling water tank 5 overflows from the cooling water tank 5, the cooling water tank 5 passes through the cooling water return path 17. The recovered water tank 7 is supplied. The recovered water tank 7 is connected to the cooling water tank 5 by a water supply path 18, and in the middle of the water supply path 18, a second pump 8 capable of adjusting the flow rate and a purifier 9 having an ion exchange resin. Is provided. Thereby, the water recovered from the fuel cell 1 and the cooling water supplied from the cooling water tank 5 are mixed in the recovered water tank 7. Then, these mixed waters (hereinafter, these waters are referred to as recovered water) are passed through the purifier 9 by the second pump 8, and the conductive ions dissolved in the water are ion-exchanged by the purifier 9. The water adsorbed by the tree and passed through the purifier 9 is supplied to the cooling water tank 5. Thereby, the conductivity of the water stored in the cooling water tank 5 is kept below a predetermined value at which no leakage occurs in the fuel cell 1.

  Further, the cooling water tank 5 is provided with a cooling water temperature detector 19 for detecting the temperature of the cooling water stored in the cooling water tank 5. Similarly, the recovered water tank 7 is provided with a recovered water temperature detector 20. The cooling water temperature detector 19 and the recovered water temperature detector 20 are composed of, for example, a thermistor or a thermocouple. The recovered water tank 7 is provided with a stored water amount detector (not shown) for detecting the amount of recovered water stored, and when the stored water amount is smaller than the predetermined stored water amount, a predetermined amount of city water is supplied. It is comprised so that.

  Next, the controller 10 constituting the fuel cell system according to Embodiment 1 will be described.

  FIG. 2 is a block diagram schematically showing the configuration of the controller 10 shown in FIG.

  As shown in FIG. 2, the controller 10 is configured by a computer such as a microcomputer, and operates an arithmetic processing unit 41 including a CPU, a storage unit 42 including a memory, a display unit 43 such as a monitor, and a keyboard operation. An input unit 44 and a clock unit 45 having a calendar function are provided. The arithmetic processing unit 41 reads out a predetermined control program stored in the storage unit 42 and executes it to perform various controls relating to the fuel cell system. In addition, the arithmetic processing unit 41 processes data stored in the storage unit 42 and data input from the operation input unit 44. In particular, the arithmetic processing unit 41 has a water purification operation mode for purifying the cooling water through the purifier by continuously circulating the water in the cooling water tank between the recovered water tanks for a predetermined time as described above. When carrying out, based on the temperature information detected by the recovered water temperature detector 20 as the temperature related to the temperature of the recovered water of the present invention, the amount of water circulated, that is, the water flowing through the purifier 9 Adjust the flow rate. The water purification operation mode will be described later.

  Here, in this specification, the controller means not only a single controller but also a controller group in which a plurality of controllers cooperate to execute control of the fuel cell system. For this reason, the controller 10 does not need to be composed of a single controller, and a plurality of controllers may be arranged in a distributed manner so that they cooperate to control the fuel cell system.

  Next, the operation of the fuel cell system according to Embodiment 1 will be described.

  The fuel cell system is started when a control signal for starting operation is output from the arithmetic processing unit 41 of the controller 10. Specifically, fuel gas and oxidant gas are respectively supplied from the fuel gas supply device 2 and the oxidant gas supply device 3 to the fuel cell 1, and in the fuel cell 1, these supplied gases react to generate electricity and Heat is generated. For this reason, the arithmetic processing unit 41 issues an operation command to the first pump 6 to circulate the cooling water between the cooling water tank 5 and the fuel cell 1 so as to keep the inside of the fuel cell 1 at a temperature suitable for the reaction. To control. Further, the water vapor is separated from the exhaust reaction gas discharged from the fuel cell 1 and condensed into water, and this condensed water is supplied to the recovered water tank 7 together with the water generated in the fuel cell 1. Then, the operation stop control signal is output from the arithmetic processing unit 41 of the controller 10 to perform the stop operation. When the stop operation is completed, the fuel cell system stops.

  The arithmetic processing unit 41 of the controller 10 sets a time for the second pump 8 to operate as the water purification operation mode based on the recovered water temperature detector 20, and the cooling water tank 5 A water purification operation mode for circulating water between the recovered water tank 7 is performed.

  The water purification operation mode is from when the system stop operation of the fuel cell system is started (when the arithmetic processing unit 41 of the controller 10 outputs a control signal for stopping operation) until the system operation is completely stopped. It may be performed during the stop operation period, may be performed during the stop period after the system is completely stopped, or when the fuel cell 1 starts power generation (calculation processing of the controller 10). When the fuel cell 1 stops generating power (when the controller 41 outputs a command signal for starting power generation by the fuel cell 1) (the arithmetic processing unit 41 of the controller 10 outputs a command signal for stopping power generation by the fuel cell 1) May be carried out during the system operation period until Further, when the water purification operation mode is performed during the system operation period, the operation start time may be stored in the storage unit 42 in advance, and the water purification operation mode may be performed at a predetermined time. It is good also as a structure which starts after the data which start water purification operation mode are input.

  Next, the water purification operation mode of the fuel cell system according to Embodiment 1 will be described.

  FIG. 3 is a flowchart schematically showing the contents of the water purification operation mode program stored in the storage unit 42 of the controller 10.

  First, the arithmetic processing unit 41 of the controller 10 issues an operation command to the second pump 8 as a start command for the water purification operation mode (step S1). And the arithmetic processing part 41 acquires the information regarding the water temperature of the recovered water (here, the water temperature of the recovered water) from the recovered water temperature detector 20 (step S2), and stores the first information stored in the storage unit 42. The threshold value is compared with the acquired temperature of the collected water (step S3).

  Here, the first threshold is the recovered water that may cause the recovered water mixed with the cooling water to exceed the heat resistance temperature of the ion exchange resin when the water purification operation is performed with the water circulation amount in the normal water purification operation mode. For example, the water circulation amount in the normal water purification operation mode is W1 [L], the temperature of the cooling water at the start of the water purification operation mode is T1 [° C.], and the temperature of the recovered water tank is T2 [° C. ], Assuming that the amount of water in the recovered water tank is W2 [L] and the heat-resistant temperature of the ion exchange resin constituting the purifier 9 is T3 [° C.], W1, T1, and T3 can be set as predetermined constants, respectively. , W2 is normally controlled so that the water in the tank is at a predetermined water level, and can be set as a constant. Therefore, the first threshold value is determined as the value on the right side of the equation (1b) and is collected. Whether the temperature T2 of the water tank satisfies the formula (1b) There is performed in step S2.

T3 ≦ (W1 × T1 + W2 × T2) / (W1 + W2) (1a)
Therefore,
T2 ≧ T3-W1 / W2 × (T1-T3) (1b)
In the above equation, it is assumed that an amount of cooling water equivalent to the water circulation amount W1 overflows and is supplied to the recovered water tank 7. Further, in the above formula, the heat capacity and heat release amount of the cooling water return path 17, the recovered water tank 7, and the water supply path 18 are not considered, but the first threshold value may be set in consideration of these. I do not care.

  At this time, when the temperature of the recovered water is lower than the first threshold, the arithmetic processing unit 41 reads out the water circulation time (normal circulation time) in the normal water purification operation mode from the storage unit 42, and uses this. The set time t1 is set (step S4), the operation of the second pump 8 is started, and the water purification operation is started (step S5). And the arithmetic processing part 41 acquires time information from the clock part 45 (step S6), and determines whether the time after starting operation | movement of the 2nd pump 8 became more than the said setting time t1 ( Step S7). If it is less than the set time t1, the process returns to step S5, and steps S6 to S7 are repeated. On the other hand, if the set time t1 or longer, the arithmetic processing unit 41 issues a stop command to the second pump 8, stops the operation of the second pump 8 (step S8), and ends the water purification operation.

  The set time t1 is necessary to cause the recovered water to flow through the purifier 9 by operating the second pump 8, and to reduce the conductivity of the cooling water in the cooling water tank 5 to a predetermined value or less. It is the operation time of the second pump 8, and the amount of water circulation in the water purification operation and the second pump 8 in the water purification operation necessary for lowering the conductivity of the cooling water in the cooling water tank to a predetermined value or less. For example, it is set as the time required for all the cooling water in the cooling water tank 5 to be replaced with the recovered water flowing through the purifier 9.

  On the other hand, when the temperature of the recovered water is higher than the first threshold value, the calculation processing unit 41 is shorter than the water circulation time in the normal water purification operation from the storage unit 42 and serves as a water purification operation mode at a high temperature. The water circulation time is read out and set as the set time t2 (step S9), the operation of the second pump 8 is started, and the water purification operation is started (step S10). Then, the arithmetic control unit 41 acquires time information from the clock unit 45 (step S11), and determines whether or not the time since the start of the operation of the second pump 8 has become the set time t2 or more ( Step S12). If it is less than the set time t2, the process returns to step S11, and steps S11 to S12 are repeated. On the other hand, if it is longer than the set time, the arithmetic processing unit 41 issues a stop command to the second pump 8, stops the operation of the second pump 8, and stops the water purification operation (step S13). The set time t2 may be a time shorter than the set time t1, and is set as a time necessary for, for example, half of the cooling water in the cooling water tank to be replaced with the recovered water that has flowed through the purifier 9. The

  Next, the arithmetic processing unit 41 acquires the temperature information of the cooling water from the cooling water temperature detector 19 as time elapses after the water purification operation is stopped (step S14). And the arithmetic processing part 41 compares the temperature of the cooling water acquired by step S13 with the 3rd threshold value memorize | stored in the memory | storage part 42, and is the temperature of a cooling water less than a 3rd threshold value? It is determined whether or not (step S15). When the temperature of the cooling water is equal to or higher than the third threshold value, the process returns to step S14, and steps S14 to S15 are repeated. On the other hand, when the temperature of the cooling water is lower than the third threshold value, the arithmetic processing unit 41 determines that the temperature of the recovered water flowing through the purifier 9 is equal to or higher than the heat resistance temperature of the ion exchange resin that constitutes the purifier 9. The water circulation time when the water purification operation is resumed is read from the storage unit 42 and set as the set time t3 (step S16). And the arithmetic processing part 41 restarts the operation | movement of the 2nd pump 8, and restarts water purification driving | operation (step S17).

  Next, the arithmetic processing unit 41 obtains time information from the clock unit 45 (step S18), and determines whether or not the time after restarting the operation of the second pump 8 is equal to or longer than the set time t3. (Step S19). If it is less than the set time t3, the process returns to step S18, and steps S18 to S19 are repeated. On the other hand, if the set time t3 or longer, the arithmetic processing unit 41 issues a stop command to the second pump 8, stops the operation of the second pump 8 (step S20), and ends the water purification operation.

  Here, the third threshold value is that there is no possibility that the recovered water mixed with the cooling water exceeds the heat resistant temperature of the ion exchange resin even if the water purification operation is performed with the water circulation amount between step S17 and step S20. For example, if the temperature of the recovered water and the water circulation amount in the restarted water purification operation mode is W3 [L], the third threshold value is determined as the value on the right side of the equation (2b), and the cooling water tank Whether or not the temperature T1 of the above satisfies the equation (2b) is executed in step S12.

T3> (W3 × T1 + W2 × T2) / (W3 + W2) (2a)
Therefore,
T1 <T3-W2 / W3 × (T3-T2) (2b)
Here, as in the case of the formulas (1a) and (1b), it is assumed that the amount of cooling water equivalent to the water circulation amount W3 overflows and is supplied to the recovered water tank in the above formula. Further, in this formula, the heat capacity and the heat radiation amount of the cooling water return path 17, the recovered water tank 7, and the water supply path 18 are not considered, but the third threshold value may be set in consideration of these. Absent.

  The set time t3 is, for example, the remaining half of the cooling water in the cooling water tank 5 that has not been replaced with the recovered water that has flowed through the purifier 9 in the first water purification operation at a high temperature (step S10 to step S13). It is set as the time required for the water to replace the recovered water that has flowed through the purifier 9.

  In step S12, whether or not to restart the water purification operation is determined depending on whether or not the temperature detected by the cooling water temperature detector 19 is less than the third threshold value. If it is a period after the stop operation of the system, the fuel cell 1 stops generating power, and a predetermined time sufficient to estimate that the water temperature in the cooling water tank 5 becomes lower than the third threshold due to natural heat radiation is generated by the fuel cell 1 It is possible to determine whether or not a certain period of time has elapsed since the fuel cell system was stopped (may be after a fuel cell system stop command is output), and to restart the water purification operation if it is determined that a predetermined time has elapsed. Absent.

  By executing the water purification operation mode program described above, the purification operation for maintaining the water quality of the cooling water is performed so as not to promote the thermal deterioration of the ion exchange resin in the purifier 9 even under a high atmospheric temperature. It becomes possible, and it becomes possible to suppress the electric leakage in the fuel cell 1.

  In the present embodiment, when the water purification operation mode is performed when the temperature of the recovered water is a high temperature equal to or higher than the first threshold, the output of the second pump 8 is not changed with respect to the normal time, and the pump The amount of water circulation was reduced by shortening the operation time of the pump, but the pump operation time was not changed, and the output of the pump was reduced to reduce the amount of water circulation in the water purification operation when the recovered water was hot. In addition, the method is not limited to the above-described method as long as the water circulation amount in the water purification operation at the time when the temperature of the recovered water is higher than the first threshold value can be reduced as compared with the normal time.

  Next, a modification of the fuel cell system according to Embodiment 1 will be described.

[Modification 1]
FIG. 4 is a block diagram schematically showing the configuration of the fuel cell stem according to the first modification of the first embodiment. In the following description, the same or corresponding parts as in FIG.

  As shown in FIG. 4, the first modification includes an atmospheric temperature detector 21 instead of the recovered water temperature detector 20. The atmospheric temperature detector 21 detects the temperature of the outside air (atmosphere), and the detected temperature information is transmitted to the arithmetic processing unit 41 of the controller 10 as a temperature related to the water temperature of the recovered water of the present invention. Then, the arithmetic processing unit 41 compares the transmitted temperature information with the second threshold stored in the storage unit 42, and when the transmitted temperature information is lower than the second threshold, 2 A command to operate the pump 8 is issued. Here, since the temperature of the outside air (atmosphere) where the recovery water tank 7 is installed correlates with the temperature of the recovery water stored in the recovery water tank 7, the second threshold value is obtained in advance through experiments or the like. The temperature of the atmosphere corresponding to (estimated) the first threshold value.

  As a result, the temperature of the recovered water stored in the recovered water tank 7 is indirectly detected as an atmospheric temperature, and the temperature of the water passed through the purifier 9 in the water purification operation mode is the ion exchange resin of the purifier 9. It is possible to control the temperature so as not to exceed the heat resistance temperature, to prevent thermal deterioration of the ion exchange resin and to extend the life. Thereby, the conductivity of the cooling water stored in the cooling water tank 5 can be stably kept below a predetermined value.

[Modification 2]
In this modification, the configuration of the fuel cell system is the same as that in the first embodiment, and the controller 10 performs the water purification operation mode as follows.

  FIG. 5 is a flowchart schematically showing the contents of the water purification operation mode program stored in the storage unit 42 of the controller 10 shown in FIG. Since steps S1 to S7 are the same as those in FIG. 3, detailed description thereof is omitted.

  First, the arithmetic processing unit 41 issues a command for starting the water purification operation mode after a stop command for operation of the fuel cell system (step S1). Then, the information about the temperature of the recovered water (here, the temperature of the recovered water) is acquired from the recovered water temperature detector 20 (step S2), and the first threshold value stored in the storage unit 42 and the acquired recovered water are acquired. Are compared with each other (step S3). At this time, if it is lower than the first threshold value, the process proceeds to step S4. On the other hand, if it is greater than or equal to the first threshold, the process proceeds to step S21.

  In step S <b> 21, the arithmetic processing unit 41 acquires cooling water temperature information from the cooling water temperature detector 19 as time elapses. And the arithmetic process part 41 compares the temperature of the cooling water acquired by step S21, and the 4th threshold value memorize | stored in the memory | storage part 42, and determines whether it is less than a 4th threshold value ( Step S22). If it is greater than or equal to the fourth threshold, the process returns to step S21, and steps S21 to S22 are repeated. On the other hand, when it is less than the fourth threshold value, the process proceeds to step S4 to perform a normal water purification operation.

  Here, the fourth threshold value is that there is no possibility that the recovered water mixed with the cooling water exceeds the heat-resistant temperature of the ion exchange resin even if the water purification operation is performed with the water circulation amount W1 in the normal water purification operation. The temperature of the cooling water, for example, the fourth threshold value is determined as the value on the right side of the equation (3b), and it is determined in step S21 whether the temperature T1 of the cooling water tank satisfies the equation (3b). Is done.

T3> (W1 × T1 + W2 × T2) / (W1 + W2) (3a)
Therefore,
T1 <T3-W2 / W1 × (T3-T2) (3b)
In this case as well, as in the case of the formulas (1a) and (1b), it is assumed that an amount of cooling water equivalent to the water circulation amount W1 overflows and is supplied to the recovered water tank 7 in the above formula. . In this formula, the heat capacity and the heat radiation amount of the cooling water return path 17, the recovered water tank 7, and the water supply path 18 are not considered, but the fourth threshold value may be set in consideration of these. Absent.

  In step S21, it is determined whether or not to restart the water purification operation depending on whether or not the temperature detected by the cooling water temperature detector 19 is less than the fourth threshold value. However, the fuel cell 1 stops generating power. It may be after a predetermined period of time that the water temperature of the cooling water tank 5 is estimated to be lower than the fourth threshold due to natural heat radiation after the power generation of the fuel cell 1 is stopped (a stop command for the fuel cell system is output). It is determined whether or not a certain period of time has elapsed. If it is determined that a predetermined time or more has elapsed, a normal water purification operation may be performed.

  Thus, in this modification, since the water purification operation mode is performed after the operation of the fuel cell system is stopped, it is suitable when performing so-called DSS (Daily Start-up & Shut-down) operation.

[Modification 3]
FIG. 6 is a block diagram schematically showing the configuration of the fuel cell system of Modification 3 of Embodiment 1. As shown in FIG. FIG. 7 is a schematic diagram showing the configuration of the purified water tank 23 shown in FIG. In the following description, the same or corresponding parts as in FIG.
As shown in FIG. 6, in this modification, a makeup water tank 22 is provided between the purifier 9 and the cooling water tank 5 in the water supply path 18 that connects the recovered water tank 7 and the cooling water tank 5. Yes. Then, the purified water tank 23 is constituted by the cooling water tank 5 and the makeup water tank 22, the water flowing through the purifier 9 is supplied to the makeup water tank 22, and the water having low conductivity is supplied from the makeup water tank 22 to the cooling water. It is supplied to the tank 5.

  In addition, as shown in FIG. 7, you may comprise the purified water tank 23 with one tank. Hereinafter, a configuration when the purified water tank 23 is integrated will be described.

  As shown in FIG. 7, the purified water tank 23 is provided with a partition plate 24. The lower end of the partition plate 24 is connected to the bottom wall of the purified water tank 23, while the upper end of the partition plate 24 is the ceiling of the purified water tank 23 so that the cooling water tank 5 and the makeup water tank 22 communicate with each other. Accordingly, the purified water tank 23 is partitioned into the cooling water tank 5 and the makeup water tank 22 by the partition plate 24, and the purifier 9. The low-conductivity water that has flowed through is supplied to the makeup water tank 22. When the water level of the make-up water tank 22 exceeds the height of the partition plate 24, the low conductivity water stored in the make-up water tank 22 overflows the partition plate 24 and is supplied to the cooling water tank 5. The

  In the fuel cell power generation system of the present invention, when the water purification operation mode is performed when the recovered water temperature is high or the atmospheric temperature is high, the increase in the incoming water temperature is suppressed by reducing the amount of water flow to the purifier. Thereby, the heat deterioration of the purifier can be prevented and the life can be extended with a simple structure at a low cost, which is useful for a fuel cell system used for home use or the like.

1 is a block diagram schematically showing a fuel cell system according to Embodiment 1. FIG. It is a schematic diagram which shows the structure of the controller of the fuel cell system shown in FIG. It is a flowchart which shows roughly the content of the water purification operation mode program stored in the memory | storage part of the controller shown in FIG. It is a block diagram which shows typically the modification of the fuel cell system shown in FIG. It is a flowchart which shows roughly the content of the modification of the water purification operation mode program stored in the memory | storage part of the controller shown in FIG. It is a block diagram which shows typically the modification of the fuel cell system shown in FIG. It is a schematic diagram which shows the structure of the purification tank shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell 2 Fuel gas supply device 3 Oxidant gas supply device 4 Heat exchanger 5 Cooling water tank 6 1st pump 7 Recovery water tank 8 2nd pump 9 Purifier 10 Controller 11 Fuel gas supply flow path 12 Fuel gas discharge Flow path 13 Oxidant gas supply flow path 14 Oxidant gas discharge flow path 15 Recovery water flow path 16 Cooling water circulation path 16A Cooling water forward path 16B Cooling water return path 17 Cooling water return path 18 Water supply path 19 Cooling water temperature detector 20 Recovered water Temperature detector 21 Atmospheric temperature detector 22 Supply water tank 23 Purified water tank 24 Partition plate

Claims (10)

A fuel cell that generates power using fuel gas and oxidant gas;
A purified water tank for storing water used for cooling the fuel cell;
A recovered water tank for storing water recovered from at least one of exhaust fuel gas and exhaust oxidant gas discharged from the fuel cell;
A water supply path connecting the recovered water tank and the purified water tank;
A purifier for purifying water flowing through the water supply path;
A pump for flowing water from the recovered water tank to the purified water tank through the water supply path;
A purified water return path for returning the water of the purified water tank to the recovered water tank;
A controller, and
The controller performs a water purification operation mode in which water is circulated between the purified water tank and the recovered water tank by operating the pump, and a temperature related to the water temperature of the recovered water tank is a predetermined value. A fuel cell system that controls the pump to reduce the amount of water circulation in the water purification operation mode when the temperature is greater than or equal to a threshold value than when the temperature related to the water temperature of the recovered water tank is less than a predetermined threshold value.   The fuel cell system according to claim 1, wherein the purified water tank is a cooling water tank that stores cooling water for cooling the fuel cell. The temperature related to the water temperature of the recovered water tank is the water temperature in the recovered water tank,
The controller controls the pump when the water temperature is equal to or higher than a first threshold, and reduces the amount of water circulation in the water purification operation mode than when the water temperature is lower than the first threshold. Item 4. The fuel cell system according to Item 1. The temperature related to the water temperature of the recovered water tank is an atmospheric temperature,
The controller controls the pump when the atmospheric temperature is equal to or higher than a second threshold, and reduces the amount of water circulation in the water purification operation mode than when the atmospheric temperature is less than the second threshold. The fuel cell system according to claim 1.   The controller makes the operation period of the pump shorter than the case where the operation period is less than the predetermined threshold value, so that the water circulation amount in the water purification operation mode is a temperature related to the water temperature of the recovered water tank. The fuel cell system according to claim 1, wherein the fuel cell system is reduced as compared with a case where the ratio is less than.   The controller makes the output of the pump smaller than when it is less than the predetermined threshold, so that the water circulation amount in the water purification operation mode is less than the predetermined threshold. The fuel cell system according to claim 1, wherein the fuel cell system is reduced as compared with the case of.   When the temperature related to the water temperature of the recovered water tank is equal to or higher than a predetermined threshold, the controller has a smaller amount of water circulation than when the temperature related to the water temperature of the recovered water tank is lower than the predetermined threshold. 2. The fuel cell system according to claim 1, wherein after stopping the operation of the pump, when the water temperature in the cooling water tank becomes lower than a third threshold value, the operation of the pump is resumed.   When the temperature related to the water temperature of the recovered water tank is equal to or higher than a predetermined threshold, the controller has a smaller amount of water circulation than when the temperature related to the water temperature of the recovered water tank is lower than the predetermined threshold. 2. The fuel cell system according to claim 1, wherein after stopping the operation of the pump, the operation of the pump is resumed when a predetermined time elapses after the system stop operation is started.   2. The fuel cell system according to claim 1, wherein the controller starts the water purification operation mode after starting a system stop operation of the fuel cell system. The purified water tank includes the cooling water tank that stores cooling water that is circulated so as to cool the fuel cell, and the makeup water tank that stores water flowing in from the water supply path,
The water of the makeup water tank is configured to be able to be supplied to the cooling water tank, and the purified water return path is configured to return the water of the cooling water tank to the recovered water tank, and the water purification operation The fuel cell system according to claim 1, wherein water circulates through the makeup water tank, the cooling water tank, and the recovered water tank in a mode.

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