JP2005158434A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system properly performing draining of a demineralized water circulatory system. <P>SOLUTION: The fuel cell system comprises piping 15 circulating demineralized water, a water storage tank 11 storing the demineralized water, and a demineralized water pump 12 circulating the demineralized water, as a demineralized water circulatory system 3. The system comprises an ion remover 13 adjusting the conductivity of the demineralized water, in advance of humidification or cooling. The system also comprises: an atmosphere release valve 21 atmospherically releasing selectively the upstream side of the ion remover 13 in the circulation direction of the demineralized water during normal operation; a passage shut-off valve 22 shutting off selectively the piping 15 in the downstream side of the ion remover 13. In addition; and further an air shut-off valve 23 for selecting whether compressed air is introduced between the ion remover 13 and the passage shut-off valve 22. The system performs draining of the demineralized water circulatory system 3, by opening and shutting in a predetermined order the atmosphere release valve 21, the passage shut-off valve 22, and the air shut-off valve 23 when the demineralized water may be frozen. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel cell system. In particular, the present invention relates to a fuel cell system having a pure water circulation system in the system.

  In a fuel cell system equipped with a pure water circulation system, the pure water freezes and expands when left in a low temperature environment for a long time, which may damage the fuel cell system, including the pure water circulation system. is there. In order to prevent such damage, the following are known as conventional fuel cell systems.

When the operation of the fuel cell device is terminated and the freeze prevention button is pressed, it is determined by the temperature sensor whether or not the outside air temperature is below the freezing temperature (below freezing point). When affirmative, the solenoid valves A and B are opened, and the circulation pump is driven for a certain time. By opening the electromagnetic valve A, the main tank communicates with the atmosphere, and water is discharged from the electromagnetic valve B provided at the bottom of the main tank. Further, the circulation pump is driven, and the water remaining in the water supply pipe, the fuel cell module, and the drain pipe is returned to the main tank. That is, since water in the water circulation system in the fuel cell device is discharged to the outside through the main tank, there is no water to be frozen and the device is not damaged (see, for example, Patent Document 1). .
JP-A-11-273704

  The method of pumping water in the system as presented in the background art is very effective when there are no large resistance elements in the system. However, in the case of a system that circulates and uses pure water, it is equipped with elements that provide resistance to drainage, such as ion removal means for keeping the conductivity of pure water low. Therefore, in the conventional system, it is difficult to sufficiently drain water, and there is a problem that damage due to freezing of water may occur in a low temperature environment.

  In view of the above problems, an object of the present invention is to provide a fuel cell system that can appropriately perform drainage of a pure water circulation system.

  The present invention provides a fuel cell system including a fuel cell that is humidified or cooled by pure water, wherein the pure water circulation system includes a pure water channel that circulates pure water, and pure water that flows through the pure water channel. Water storage means for storing, and circulation means for taking out pure water from the water storage means and circulating it in the pure water flow path. Prior to humidification or cooling, an ion removing unit that adjusts the conductivity of pure water and an atmosphere that selectively opens the upstream side of the ion removing unit with respect to the flow direction of the pure water during normal operation. And an opening means. Further, a flow path blocking means for selectively blocking the pure water flow path downstream of the ion removal means in the flow direction of pure water during normal operation, and between the ion removal means and the flow path blocking means And a compressed gas shut-off means for selectively introducing the compressed gas. When there is a possibility that pure water is frozen when the fuel cell is stopped, the pure water circulation system is opened and closed by opening and closing the air release means, the flow path blocking means, and the compressed gas blocking means in a predetermined order. Drain the water.

   There is an air release means for selectively releasing the inside of the pure water circulation system upstream of the ion removal means, and a compressed gas blocking means for selectively introducing compressed gas is provided on the downstream side, so that the compressed gas is ion-removed. It can be distributed from the downstream side of the means toward the upstream side. Thereby, the water of the ion removal means in which water tends to stay can be appropriately removed from the configuration, and the drainage of the pure water circulation system can be appropriately performed.

  The configuration of the fuel cell system used in the first embodiment is shown in FIG.

  A fuel cell 2 that generates power using a fuel gas that is a hydrogen-containing gas and an oxidant gas that is an oxygen-containing gas is provided. For example, hydrogen gas is used as the fuel gas, and air is used as the oxidant gas. The fuel cell 2 is a solid polymer fuel cell using a solid polymer electrolyte membrane as an electrolyte.

  In addition, air supply means 1 for supplying air to the fuel cell 2 is provided. The air supply means 1 is provided with piping, a compressor, etc. which distribute | circulate air. Although not shown here, a fuel supply means for supplying hydrogen gas to the fuel cell 2 is provided.

  Further, a pure water circulation system 3 for circulating pure water for cooling or humidifying the fuel cell 2 is provided. Here, the wet state of the reaction gas in the fuel cell 2, and thus the solid polymer electrolyte membrane, is adjusted by circulating pure water through the pure water flow path in the fuel cell 2.

  The pure water circulation system 3 includes a pipe 15 for circulating pure water, a water storage tank 11 for storing pure water, a pure water pump 12 for circulating pure water, an ion remover 13 for removing ions in pure water, and pure water. Conductivity detecting means 14 for detecting the conductivity of. The pure water taken out from the water storage tank 11 circulates in the order of the pure water pump 12, the ion remover 13, the conductivity detecting means 14, and the fuel cell 2, and is collected again in the water storage tank 11.

  In addition, an atmosphere release valve 21 is provided for selecting whether to open the pure water circulation system 3 to the atmosphere. The air release valve 21 branches from between the pure water pump 12 and the ion remover 13 and is provided in a pipe whose end is open to the atmosphere. When viewed from the pure water circulation direction during normal operation, the air release valve 21 is disposed downstream of the pure water pump 12, but as will be described later, when viewed from the gas flow direction during drainage, ion removal is performed. It is arranged downstream of the vessel 13.

  Further, a flow path cutoff valve 22 that selectively shuts off at least a part of the pipe 15 is provided. The flow path shut-off valve 22 is disposed on the downstream side of the ion remover 13 when viewed from the direction of circulation of pure water during normal operation. In particular, here, the flow path shutoff valve 22 is disposed on the downstream side of the fuel cell 2 and on the upstream side of the water storage tank 11. Furthermore, an air shutoff valve 23 is provided for selecting whether or not the compressed air is branched from the air supply means 1 and supplied to the pure water circulation system 3. Here, the compressed air discharged from the fuel cell 2 is selectively supplied to the pure water supply system 3 by opening and closing the air shut-off valve 23. At this time, the configuration is such that the compressed air is introduced at a position downstream of the ion remover 13 and upstream of the flow path shut-off valve 23 when viewed from the direction of circulation of pure water during normal operation. In particular, here, the configuration is such that compressed air is introduced between the fuel cell 2 and the flow path shut-off valve 23.

  In addition, a water storage amount detection unit 24 that detects a water storage amount in the water storage tank 11 and a pressure detection unit 25 that detects a pressure in the pure water circulation system 3 are provided. The pressure detection means 25 detects the pressure on the downstream side of the ion remover 13. Here, the pressure of the fluid flowing through the pure water pipe 15 between the ion remover 13 and the conductivity detecting means 14 is detected. Further, a controller 30 that controls such a fuel cell system is provided. The controller 30 opens and closes the atmosphere release valve 21, the flow passage cutoff valve 22, and the air cutoff valve 23 in a preset order and timing.

  Next, a state during normal operation of such a fuel cell system will be described.

  Air is supplied to the fuel cell 2 from the air supply system 1 and fuel gas is supplied from a fuel supply system (not shown). At this time, in order to maintain the efficiency of the fuel cell 2, it is necessary to maintain the solid polymer electrolyte membrane used in the fuel cell 2 in a wet state. Therefore, the wet state of the solid polymer electrolyte membrane is adjusted by circulating pure water in the pure water circulation system 3 into the fuel cell 2.

  In the pure water circulation system 3, during normal operation, the air release valve 21 and the air cutoff valve 23 are closed, and the flow path cutoff valve 22 is opened. By operating the pure water pump 12, pure water is taken out from the water storage tank 11 and introduced into the ion remover 13. The ion remover 13 removes ions in the pure water to the extent that it does not cause deterioration of the fuel cell 2. Here, for example, the degree of deterioration of the ion removing means 13 can be known according to the output of the conductivity detecting means 14 for detecting the conductivity of pure water discharged from the ion remover 13.

  The pure water whose conductivity is adjusted in this way is introduced into the fuel cell 2. For example, the reaction gas flow path in the fuel cell 2 is constituted by a groove formed in a porous material plate, and a pure water flow path is provided on the back surface thereof. The porous material plate contains water such as generated water, and the solid polymer film is humidified by evaporating it in the dry state. Further, in a portion where water is excessive and condensed water is generated, the condensed water is absorbed by the porous material, thereby suppressing flooding. At this time, the pure water flowing through the pure water flow path formed on the back surface of the reaction gas flow path moves into the porous material, thereby adjusting the excess or deficiency of the water contained in the porous material. As a result, the humidity of the reaction gas is appropriately maintained, and consequently the wet state of the solid polymer electrolyte membrane is appropriately maintained.

  After being used to adjust the wetness of the solid polymer electrolyte membrane in this way, pure water is discharged from the fuel cell 2 and is collected again in the water storage tank 11 via the flow path shutoff valve 22.

  Next, the state when the fuel cell 2 is stopped will be described.

  If such a fuel cell system is left in a low temperature environment when the fuel cell 2 is stopped, the pure water in the pure water circulation system 3 is frozen, and the fuel cell 2, the conductivity detecting means 14, the ion remover. 13 and the piping 15 may be destroyed. Therefore, when it is determined that the fuel cell system may be exposed to a low temperature environment at the time of stoppage, the pure water circulation system 3 is drained.

  The drainage control when the fuel cell system is stopped will be described with reference to the timing chart of FIG. For example, when the fuel cell 2 is stopped and the temperature detecting means (not shown) determines that the fuel cell 2 or the outside air temperature has become a predetermined value or less, the drainage control is started.

  Simultaneously with the start of draining (time T0), the flow path shutoff valve 22 is closed. Next, the air shutoff valve 23 is opened. Thereby, supply of the compressed air from the air supply means 1 to the pure water circulation system 3 is started. Pure water in the pure water circulation system 3 moves in the direction of the fuel cell 2, the conductivity detector 14, the ion remover 13, and the pure water pump 12 and is collected in the water storage tank 11.

  Next, the atmosphere release valve 21 is opened. Here, when the time required from the start of draining until the water in the pure water circulation system 3 is collected is T1, and the time from the start of draining to the opening of the air release valve 21 is T2, T2 The time T2 is set so that> T1. For example, if the air release valve 21 is opened while a large amount of water remains in the pure water circulation system 3, the water is discharged from the pure water circulation system 3 to the atmosphere, and there is a possibility that the water will be insufficient at the next start-up. There is. Therefore, in order to prevent this water shortage, after the time T1 has elapsed and most of the water in the pure water circulation system 3 has been collected, the atmosphere release valve 21 is opened to open the pure water circulation system 3 to the atmosphere. The time T2 is set to

  Next, the state where the pure water circulation system 3 is opened to the atmosphere is maintained for a predetermined time. Here, a predetermined time for keeping the atmosphere open is T3.

  While the air release is maintained, the compressed air from the air supply means 1 unilaterally flows in the direction of the fuel cell 2, the conductivity detection means 14, and the ion remover 13. Therefore, since the packing is stored and high-pressure air can flow directly to the ion remover 13 with poor drainage, it is advantageous for draining the ion remover 13. Here, with respect to the flow direction of pure water during normal operation, compressed air circulates in the ion remover 13 from the downstream side to the upstream side, and is discharged to the outside through the atmosphere release valve 21. Compressed air removes moisture that is retained when it flows through the ion remover 13, and is discharged to the outside through the atmosphere release valve 21 while containing moisture.

  Therefore, the time T3 for maintaining the air release is set to a time sufficient for draining the ion remover 13 in the pure water circulation system 3 where water is likely to remain, with the air being open. During the time T3, the air release valve 21 is kept open, and after the time T3 has elapsed, the air release valve 21 is closed to end the air release.

  Next, the flow path shutoff valve 22 is opened. Here, assuming that the time from the start of draining to the opening of the flow path shutoff valve 22 is T4, the time T4 is set to be longer than the time T2 + T3 from the start of draining to the end of air release. That is, T4> T2 + T3. When the flow path shut-off valve 22 is opened, the compressed air introduced into the pure water circulation system 3 through the air shut-off valve 23 flows to the water storage tank 11 side with a small pressure loss. At this time, if the air release valve 21 is open, the water in the water storage tank 11 flows out to the pure water pump 12 side by the compressed air, and as a result, the pure water pump 12 and the pure water pipe 15 are purified. There is a possibility that problems such as water remaining and freezing will occur. Therefore, after the atmosphere release valve 21 is closed and the atmosphere release is finished, the time T4 is set so that the flow path shutoff valve 22 is opened, thereby preventing the above-described problem.

  In this way, by opening the flow passage shut-off valve 22 while the air release valve 21 is closed and the air shut-off valve 23 is open, the purity of the pipe 15 between the flow shut-off valve 22 and the water storage tank 11 is reduced. Water is collected in the water storage tank 11 by compressed air.

  Next, the air shutoff valve 23 is closed to stop the introduction of compressed air. Here, when the time from the start of draining to the closing of the air shut-off valve 23 is T5, T5> T4 is set. That is, as described above, in order to recover the pure water in the pipe 15 between the flow path shut-off valve 22 and the water storage tank 11, after the flow path shut-off valve 22 is opened with the introduction of compressed air, The air shutoff valve 23 is closed and the introduction of the compressed air is finished. The time T5 is set so that the time difference between T4 and T5 (= T5−T4) is a time during which the pure water in the pipe 15 between the flow path shutoff valve 22 and the water storage tank 11 can be sufficiently collected. preferable.

  Next, the flow path shutoff valve 22 is closed. Here, the flow path shut-off valve 22 is closed at the start of draining, and the time from when it is once opened until it is closed again is T6. At this time, the time T6 is set to be longer than the time T5 from the start of draining to the end of the introduction of compressed air (T5 <T6). When the introduction of air is completed after the flow path shut-off valve 22 is closed, the pressure on the upstream side of the flow path shut-off valve 22 is left high, so the fuel cell 2, the conductivity detecting means 14, ion removal The durability of the vessel 13 may be reduced. In order to avoid this, the air shut-off valve 23 is closed and then the flow passage shut-off valve 22 is closed again (T5 <T6). As a result, the pressure on both sides of the flow path shut-off valve 22 can be made uniform. Especially when a part of the upper end portion of the water storage tank 11 communicates with the outside air, the inside of the pure water circulation system 3 is maintained. Atmospheric pressure can be achieved. Time T6 corresponds to the time from the start of draining to the end of draining.

   The times T1 to T6 can be set in advance. For example, the volume of the pure water circulation system 3 including the volumes of the pure water pump 12, the ion remover 13, the conductivity detecting means 14, the pure water passage of the fuel cell 2 and the like is measured in advance. From this volume and the amount of air supplied via the air shut-off valve 23, a time T1 required for collecting the water in the pure water circulation system 3 into the water storage tank 11 can be set in advance. If there is a time difference between the start of draining and the opening of the air shut-off valve 23, it is preferable to add this time difference. Further, T3 indicating the time for maintaining the atmosphere open can also be set in advance from the amount of air supplied via the air shutoff valve 23 and the volume of the pure water circulation system 3. Using these times T1 and T3, T2 and T4 to T6 can be set in advance. Alternatively, the times T1 to T6 may be set in advance by experiments or the like.

Alternatively, the atmosphere release valve 21 may be controlled according to the output of the pressure detection means 25. The output of the pressure detection means 25 provided between the ion remover 13 and the conductivity detection means 14 is as shown in FIG. Thus, a portion of the pure water circulatory system 3 that is opened to the atmosphere, when it changes abruptly to a low pressure (atmospheric pressure) from the high pressure, the output of the pressure detecting means 25 at this time is smaller than a predetermined value P _A ions It can also be determined that the water in the remover 13 has been discharged, and the air release can be terminated. That is, the time T2 + T3 for closing the atmosphere release valve 21 can be determined according to the output of the pressure detection means 25.

  Next, the effect of this embodiment will be described.

  In a fuel cell system including a fuel cell 2 that is humidified or cooled by pure water, a pure water circulation system 3 includes a pipe 15 that circulates pure water and a water storage tank 11 that stores the pure water flowing through the pipe 15. Prepare. Further, a pure water pump 12 that takes out pure water from the water storage tank 11 and circulates through the pure water passage (pipe 15), and an ion remover 13 that adjusts the conductivity of pure water prior to humidification or cooling are provided. . In addition, an air release valve 21 that selectively opens the upstream side of the ion remover 13 with respect to the flow direction of pure water during normal operation, and a downstream of the ion remover 13 with respect to the flow direction of pure water during normal operation. A flow path cutoff valve 22 that selectively shuts off the pipe 15 on the side is provided. Furthermore, an air shut-off valve 23 for selectively introducing compressed air (compressed gas) by opening and closing is provided between the ion remover 13 and the flow passage shut-off valve 22. When there is a possibility that the pure water may freeze when the fuel cell 2 is stopped, the pure water circulation system 3 is opened and closed by opening and closing the air release valve 21, the flow passage cutoff valve 22, and the air cutoff valve 23 in a predetermined order. Drain the water. As described above, the air release valve 21 that opens the pure water circulation system 3 to the atmosphere is provided on the upstream side of the ion remover 13, and the air shut-off valve 23 that selects whether or not to supply compressed air is provided on the downstream side. Therefore, at the time of draining, compressed air can be circulated from the downstream side to the upstream side of the ion remover 13. Thereby, the water of the ion remover 13 in which water tends to stay can be appropriately removed, and the drainage of the pure water circulation system 3 can be appropriately performed. Moreover, the water in the pure water circulation system 3 can be appropriately removed by opening and closing the atmosphere release valve 21, the flow passage cutoff valve 11, and the air cutoff valve 23 in a predetermined order.

  Compressed air is used as the compressed gas. Here, the compressed air is introduced into the pure water circulation system 3 by branching from the air supply means 1 for supplying air to the fuel cell 2. As a result, the compressed gas can be introduced into the pure water circulation system 3 with a simple configuration. Moreover, the pure water in the pure water circulation system 3 can be more efficiently removed by using the compressed air. Further, compressed air is used as the compressed gas, and the air release valve 21 is opened with the air shut-off valve 23 opened. As a result, the inside of the ion remover 13 can be rapidly changed from a high pressure to a low pressure (atmospheric pressure), and the water in the ion remover 13 can be discharged to the low pressure portion (atmosphere). Water can be removed.

  Further, the pure water whose conductivity is adjusted by the ion remover 13 is configured to flow directly to the fuel cell 2. The flow path shutoff valve 22 is provided so as to shut off the pipe 22 on the downstream side of the fuel cell 2 in the flow direction of pure water during normal operation. Further, the air shut-off valve 23 is provided on the downstream side of the fuel cell 2 and the upstream side of the flow passage shut-off valve 22 so as to select whether or not to supply compressed air. Thereby, the compressed air introduced through the air shutoff valve 23 is introduced into the ion remover 13 after flowing through the fuel cell 2, so that the water removal performance in the fuel cell 2 can also be improved. Further, damage to the fuel cell 2 due to freezing of pure water can be further suppressed.

  If there is a possibility that pure water may freeze when the fuel cell 2 is stopped, the flow passage shut-off valve 22 is closed, the air shut-off valve 23 is opened, the air release valve 21 is opened, the air release valve 21 is closed, The passage cutoff valve 22 is opened, the air cutoff valve 23 is closed, and the flow passage cutoff valve 22 is closed. Thereby, the inside of the pure water circulation system 3 can be drained appropriately.

  In addition, when there is a possibility that pure water is frozen when the fuel cell is stopped, the atmosphere release valve 21, the flow passage shut-off valve 22, and the air shut-off valve 23 are opened and closed in a predetermined order at a predetermined timing. . By setting a predetermined order and a predetermined timing in advance so that water does not stay in the pure water circulation system 3, water can be easily drained without requiring special control.

  If there is a possibility that the pure water is frozen when the fuel cell 2 is stopped, the time T2 from the start of draining to the opening of the air release valve 21 is set to the internal volume of the pipe 15 and the air shutoff valve 23. It is assumed that the time is longer than the time T1 which is obtained in advance from the compressed air flow selectively supplied through the main water of the pure water circulation system 3 and is collected. The timing (T2) for opening the air release valve 21 is set after the time T1 at which main water in the pure water circulation system 3 is recovered, which is determined in advance by calculation or experiment. Most of the pure water can be collected in the water storage tank 11, and water shortage can be prevented during the next operation.

  Further, when there is a possibility that the pure water is frozen when the fuel cell 2 is stopped, the air flow shut-off valve 22 is opened after the air release valve 21 is closed while the air shut-off valve 23 is open. Thus, in order to set the timing (T4) for opening the flow path shut-off valve 22 after the timing (T2 + T3) for closing the atmosphere release valve 21, the water storage tank 11 is driven by the pressure of the air supplied from the air supply means 1. It is possible to prevent the inside water from entering the pure water circulation system 3 on the pure water tank 12 side again.

  If there is a possibility that pure water may freeze when the fuel cell 2 is stopped, the air shut-off valve 23 is opened after the air shut-off valve 23 is open, the air shut-off valve 23 is closed, and the compressed air Stop supplying. Since the timing (T5) for closing the air shut-off valve 23 is after the timing (T4) for opening the flow shut-off valve 22, water between the flow shut-off valve 22 and the water storage tank 11 is also collected in the water storage tank 11. can do.

  If there is a possibility that the pure water may freeze when the fuel cell 2 is stopped, the air shutoff valve 23 is closed and the supply of compressed air is stopped, and then the flow passage shutoff valve 22 is closed again. Since the timing (T6) when the flow path shut-off valve 22 is closed for the second time is after the timing (T5) when the air shut-off valve 23 is closed, the pressure is locally increased in the pure water circulation system 3 after draining. It can suppress that a high part arises.

Furthermore, a pressure detection means 25 for detecting the pressure in the pipe 15 on the downstream side of the ion remover 13 in the flow direction of pure water during normal operation is provided, and after opening the atmosphere release valve 21, the pressure detection means the output of 25 is, if a value below the predetermined value P _a set in advance, the atmosphere opening valve 21 is closed. Here, the provided pressure detecting means 25 during the ion removal device 13 and the conductivity detector 14, the air release valve 21 is closed when the output of the pressure detecting means 25 is below a predetermined value P _A. As a result, the air release can be maintained until the water in the ion remover 13 is reliably discharged. In addition, it is possible to avoid keeping the atmosphere open unnecessarily for a long time, and draining can be completed in the minimum necessary time.

  Next, a second embodiment will be described. Here, the description will focus on parts that are different from the first embodiment.

  A timing chart of the water drain control is shown in FIG. Here, the timing is measured according to the amount of pure water in the water storage tank 11 detected by the water storage amount detection means 24.

  For example, as shown in FIG. 5, when ΔD / ΔT falls below a predetermined value due to the change rate of the increase ΔD in the storage amount of the water storage tank 11 per unit time ΔT, the pure water circulation system 3 It is determined that pure water has been collected in the water storage tank 11, and this time can be set as time T1. Similarly, when ΔD / ΔT falls below a predetermined value after the flow passage shut-off valve 22 is opened in a state where the supply of air via the air shut-off valve 23 is continued at time T4, the flow passage It is determined that the water between the shutoff valve 22 and the water storage tank 11 has been recovered, and this time can be set as time T5.

   Here, the case where the timing of T1 and T5 is measured based on the output of the water storage amount detection means 24 has been described, but other than that, T2 also depends on the amount of pure water in the water storage tank 11 detected by the water storage amount detection means 24. Can be set. Alternatively, the timings of T2, T3, T4, and T6 may be determined by presetting the time differences between T1 and T5, respectively.

  Next, the effect of this embodiment will be described. Only the effects different from those of the first embodiment will be described below.

  Water storage amount detection means 24 for detecting the amount of pure water in the water storage tank 11 is provided. When there is a possibility that pure water may freeze when the fuel cell 2 is stopped, the air release valve 21, the flow passage shutoff valve 22, and the air shutoff valve 23 are opened and closed in a predetermined order according to the output of the water storage amount detection means 24. By doing so, the pure water circulation system 3 is drained. As a result, the timing of draining can be controlled without variation due to changes in system or disturbance over time. As a result, it is possible to discharge the water in the pure water circulation system 3 more reliably and without wasteful time.

  If there is a possibility that pure water may freeze when the fuel cell 2 is stopped, after the start of draining, when the rate of increase ΔD / ΔT of the output of the stored water amount detecting means 24 falls below a predetermined value, the pure water circulation It is judged that the main pure water of system 3 has been recovered. Thereby, it is possible to detect the time T1 until the pure water is completely collected in the water storage tank 11 more accurately. Further, the air release valve 21 is then opened. As a result, after the water in the pure water circulation system 3 has surely returned to the water storage tank 11, the air release valve 21 can be quickly opened, and the time for draining can be shortened.

  If there is a possibility that the pure water may freeze when the fuel cell 2 is stopped, drainage is started and the atmosphere is released, and the flow passage shut-off valve 22 is opened. The air shutoff valve 23 is closed after the rate of increase ΔD / ΔT falls below a predetermined value. That is, the timing (T5) at which the air shut-off valve 23 is closed is when the amount of increase in the detected value per unit time of the stored water amount detecting means 24 becomes the predetermined value or less for the second time in the sequence. Accordingly, the pure water in the pure water circulation system 3 is completely collected in the water storage tank 11, and at the same time, the air shutoff valve 23 can be closed, and the water draining time can be shortened. Moreover, the fuel consumption in the air supply means 1 can be improved by shortening the introduction time of the compressed air.

  Here, pure water is directly circulated to the fuel cell 2 to be used for humidifying the solid polymer membrane, but this is not restrictive. For example, the present invention can be similarly applied when pure water circulating directly through the fuel cell 2 is involved only in cooling. Further, the present invention can be similarly applied when pure water is supplied to a humidifying means provided outside the fuel cell 2 and used for humidifying the reaction gas supplied to the fuel cell 2.

  Thus, the present invention is not limited to the best mode for carrying out the invention, and it goes without saying that various modifications can be made within the scope of the technical idea described in the claims. .

  The present invention can be applied to a fuel cell system having a pure water circulation system. In particular, the present invention can be applied to a fuel cell system mounted on a mobile body that may be exposed to a low temperature environment.

It is a schematic block diagram of the fuel cell system used for 1st Embodiment. It is a timing chart of draining control used for a 1st embodiment. It is a figure which shows the relationship between a pure water circulation system pressure and the maintenance time (T3) of atmospheric release. It is a timing chart of drainage control used for a 2nd embodiment. It is explanatory drawing of the raise rate of the amount of stored water used for 2nd Embodiment.

Explanation of symbols

2 Fuel cell 3 Pure water circulation system 11 Water storage tank (water storage means)
12 Pure water pump (circulation means)
13 Ion remover (ion removal means)
15 Piping (pure water flow path)
21 Air release valve (atmosphere release means)
22 Channel shutoff valve (channel shutoff means)
23 Air shut-off valve (Compressed gas shut-off means)
24 Water storage amount detection means 25 Pressure detection means

Claims (13)

In a fuel cell system including a fuel cell that is humidified or cooled with pure water,
As the pure water circulation system,
A pure water flow path for circulating pure water;
Water storage means for storing pure water flowing through the pure water flow path;
A circulation means for taking out pure water from the water storage means and circulating it in the pure water flow path;
Prior to humidification or cooling, ion removal means for adjusting the conductivity of pure water;
Atmospheric release means for selectively releasing the upstream side of the ion removing means with respect to the flow direction of pure water during normal operation;
A flow path blocking means for selectively blocking the pure water flow path downstream of the ion removing means with respect to the flow direction of the pure water during normal operation;
A compressed gas blocking means for selectively introducing a compressed gas between the ion removing means and the flow path blocking means,
When there is a possibility that pure water may freeze when the fuel cell is stopped, the pure water circulation system is opened and closed by opening and closing the air release means, the flow path blocking means, and the compressed gas blocking means in a predetermined order. A fuel cell system for draining water. As the compressed gas, compressed air is used,
2. The fuel cell system according to claim 1, wherein the air release means is opened while the compressed gas shut-off means is open. The pure water whose conductivity is adjusted by the ion removing means is configured to circulate directly to the fuel cell,
The flow path blocking means is provided so as to block the pure water flow path on the downstream side of the fuel cell with respect to the flow direction of pure water during normal operation,
Whether or not to supply compressed gas to the downstream side of the fuel cell and the upstream side of the flow path blocking unit for the compressed gas blocking unit in the flow direction of pure water during normal operation is selected. The fuel cell system according to claim 1 or 2 provided. If there is a possibility that pure water may freeze when the fuel cell stops,
4. The fuel cell system according to claim 1, wherein, after the compressed gas blocking unit is open, the flow path blocking unit is opened after the air release unit is closed. 5. If there is a possibility that pure water may freeze when the fuel cell stops,
4. The supply of compressed gas according to claim 1, wherein after the compressed gas blocking means is open and the flow path blocking means is opened, the compressed gas blocking means is closed to stop the supply of compressed gas. 5. Fuel cell system. If there is a possibility that pure water may freeze when the fuel cell stops,
The fuel cell system according to any one of claims 1 to 3, wherein after the compressed gas blocking means is closed and the supply of compressed gas is stopped, the flow path blocking means is closed again. If there is a possibility that pure water may freeze when the fuel cell stops,
Close the flow path blocking means, open the compressed gas blocking means, open the atmosphere opening means, close the air opening means, open the flow path blocking means, close the compressed gas blocking means, block the flow path The fuel cell system according to any one of claims 1 to 3, wherein the means are operated in the order of closing.   When there is a possibility that pure water may freeze when the fuel cell is stopped, the air release means, the flow path shut-off means, and the compressed gas shut-off means are opened and closed in a predetermined order at a predetermined timing. The fuel cell system according to any one of claims 1 to 7. If there is a possibility that pure water may freeze when the fuel cell stops,
The time from the start of draining to the opening of the air release means,
The time is longer than the time during which main pure water in the pure water circulation system is recovered, which is obtained in advance from the internal volume of the pure water flow path and the compressed gas flow rate selectively supplied by the compressed gas shut-off means. The fuel cell system according to claim 8. A water storage amount detection means for detecting the amount of pure water in the water storage means,
If there is a possibility that pure water may freeze when the fuel cell is stopped, the air release means, the flow path shut-off means, and the compressed gas shut-off means are set in a predetermined order according to the output of the water storage amount detection means. The fuel cell system according to any one of claims 1 to 7, wherein the pure water circulation system is drained by opening and closing. If there is a possibility that pure water may freeze when the fuel cell stops,
11. The fuel cell according to claim 10, wherein after starting draining, when the rate of increase in the output of the water storage amount detection means falls below a predetermined value, it is determined that main pure water in the pure water circulation system has been recovered. system. If there is a possibility that pure water may freeze when the fuel cell stops,
After the drainage is started and the atmosphere is released, and the flow passage blocking means is opened, the compressed gas blocking means is closed after the rate of increase in the output of the water storage amount detecting means falls below a predetermined value. The fuel cell system according to claim 10. A pressure detecting means for detecting the pressure in the pure water flow path downstream of the ion removing means in the flow direction of the pure water during normal operation;
8. The air release means according to claim 1, wherein after the atmosphere release means is opened, the atmosphere release means is closed when an output of the pressure detection means falls below a predetermined value set in advance. 9. Fuel cell system.

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