JP2007026893A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a freeze by removing remaining water in an anode system of a fuel cell without increasing the size of a structure nor complicating it. <P>SOLUTION: This fuel cell system is so structured that, in stopping the fuel cell system, liquid water accumulated in a gas-liquid separation means 105 for separating moisture included in an off-gas discharged from the anode electrode side of the fuel cell is discharged, through a second liquid water discharge means 108b, to a liquid water storage means 106 without running a reaction gas in starting and operating this fuel cell system; and hence the operation of the fuel cell system is stopped without leaving the liquid water in the gas-liquid separation means 105. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel cell system having an improved function of removing water remaining in an anode system of a fuel cell.

  Conventionally, as this type of technology, for example, those described in the following documents are known (see Patent Documents 1 to 3). As described above, as a technique for preventing moisture freezing by removing moisture remaining in the anode system in which the fuel gas supplied to the fuel cell circulates in the system, for example, the fuel cell system may be left in a low temperature environment. When it can be predicted, a fuel gas such as hydrogen gas is circulated to the anode system of the fuel cell when the fuel cell system is stopped, and the collected moisture is separated from the fuel gas by the gas-liquid separator, and the separated moisture is removed. A method of draining outside the system is known.

In such a method, in order to drain all the liquid water in the gas-liquid separator and not to release the fuel gas having a concentration higher than the predetermined value outside the fuel cell system, In order to dilute the fuel gas to be released and reduce the concentration, it is necessary to install a high-capacity dilution means in the system.
JP2002-313376 JP 2004-95384 A JP2004-172030

  However, in a system that does not include the above-described dilution means or a sensor that detects the liquid water amount of the gas-liquid separator with high accuracy, the fuel gas is not released outside the system together with moisture. It was necessary to stop the fuel cell system with liquid water remaining. For this reason, moisture remaining in the gas-liquid separator may freeze in a low-temperature environment, and if the remaining moisture freezes, there is a possibility that the system cannot be restarted.

  In order to avoid such problems, it is necessary to thaw the frozen water by heating the frozen portion with a heating means such as an electric heater before starting the fuel cell system. In this case, this heating and thawing process takes time, and the time required for starting the system becomes long.

  Further, when using an electric heater or the like that uses electric energy as means for heating and thawing the frozen portion, the electric power for thawing consumed by the electric heater before starting the fuel cell system is required. For this reason, the system configuration must be able to receive this electric power from outside the fuel cell system, but in such a configuration, the system configuration is complicated. On the other hand, in the configuration in which the power for thawing cannot be received from the outside of the system, there is a problem that it is extremely difficult to start the fuel cell system.

  On the other hand, it is conceivable to supply thawing power from the secondary battery installed in the fuel cell system. In this case, the open-circuit voltage of the secondary battery is reduced in a low temperature environment. There is a possibility that the total voltage of the secondary battery is lowered and the electric power necessary for starting the fuel cell system cannot be taken out.

  Therefore, the present invention has been made in view of the above, and the object of the present invention is to prevent freezing by removing residual moisture in the anode system of the fuel cell without increasing the size and complexity of the configuration. An object of the present invention is to provide a fuel cell system.

  In order to achieve the above object, means for solving the problems of the present invention is a fuel cell system including a fuel cell that generates power by an electrochemical reaction of a reaction gas between a fuel gas and an oxidant gas. Gas-liquid separation means for separating water contained in the off-gas discharged from the anode electrode side, and temporarily storing the obtained liquid water; liquid water stored in the gas-liquid separation means flows into the liquid Water is stored, and liquid water storage means in which no reaction gas flows when the fuel cell system is started and operated, and liquid water stored in the gas-liquid separation means is selectively drained to the liquid water storage means. Second liquid water discharge means and control for draining all liquid water stored in the gas-liquid separation means via the second liquid water discharge means to the liquid water storage means when the operation of the fuel cell system is stopped Having means The features.

  According to the present invention, when the operation of the system is stopped, the liquid water accumulated in the gas-liquid separation means can be drained to the liquid-water separation means so that no liquid water remains in the gas-liquid separation means. It is possible to prevent the liquid water in the gas-liquid separation means from freezing under the environment, and to improve the startability of the system under the low temperature environment.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS The best embodiment for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram showing a configuration of a fuel cell system according to Embodiment 1 of the present invention. In FIG. 1, a fuel cell system includes a fuel cell 100 that generates power, a fuel gas distribution system (anode system) in which a fuel gas (for example, hydrogen or hydrogen-rich gas) supplied to the fuel cell 100 circulates in the system, It has an oxidant gas distribution system in which an oxidant gas (for example, air containing oxygen) supplied to the fuel cell 100 circulates in the system.

  The fuel cell 100 has a multi-stage power generation cell in which a hydrogen electrode (anode electrode) to which hydrogen gas is supplied and an air electrode (cathode electrode) to which oxygen (air) is supplied are stacked with an electrolyte / electrode catalyst composite interposed therebetween. A power generation unit that is stacked and converts chemical energy into electrical energy by an electrochemical reaction between hydrogen gas and oxygen is configured.

  At the hydrogen electrode of the fuel cell 100, when hydrogen gas is supplied, it is dissociated into hydrogen ions and electrons, the hydrogen ions pass through the electrolyte, the electrons generate electric power through an external circuit, and move to the air electrode. At the air electrode, oxygen in the supplied air reacts with the hydrogen ions and electrons to generate water, which is discharged to the outside.

  In the fuel gas distribution system, hydrogen gas discharged from the high-pressure fuel gas supply device 101 that is a fuel gas supply source is supplied to the hydrogen electrode of the fuel cell 100. At this time, the pressure of the supplied hydrogen gas is adjusted so that the pressure in the hydrogen electrode and the hydrogen electrode passage of the fuel cell 100 becomes a pressure corresponding to the load.

  In the fuel cell 100, not all of the supplied hydrogen gas is consumed. The hydrogen off-gas discharged from the fuel cell 100 without being consumed passes through the hydrogen circulation pipe 102 and is constituted by a hydrogen circulation pump or the like. It is circulated by the gas pressurizing means 103, mixed with the hydrogen gas newly supplied from the high-pressure fuel gas supply apparatus 101 side by the ejector 104, and supplied again to the hydrogen electrode of the fuel cell 100. Thereby, the stoichiometric ratio (SR: supply flow rate / consumption flow rate) of hydrogen can be made 1 or more, and the cell voltage is stabilized.

  As described above, in the system having the configuration for circulating the hydrogen gas, in the first embodiment, the gas-liquid separation means 105, the liquid water storage means 106, the electric heater 107, the first liquid water discharge means 108a, and the second liquid water. A discharge means 108b, a third liquid water discharge means 108c, and a controller 109 are provided.

  The gas-liquid separation unit 105 is a unit that receives the hydrogen off-gas discharged from the fuel cell 100 and separates the water contained in the hydrogen off-gas from the hydrogen off-gas, and includes, for example, a condenser. The water separated by the gas-liquid separation means 105 temporarily accumulates in the gas-liquid separation means 105, while the hydrogen off gas is introduced into the hydrogen circulation pipe 102.

  The gas-liquid separation means 105 is provided with a first liquid-water amount detection means 110 that detects the amount of liquid water accumulated in the gas-liquid separation means 105 and gives the detected liquid water amount to the controller 109.

  The liquid water storage means 106 is introduced with the liquid water accumulated in the gas-liquid separation means 105 and temporarily stores the introduced liquid water. The liquid water storage means 106 is provided with second liquid water amount detection means 111 that detects the amount of liquid water stored in the liquid water storage means 106 and supplies the detected liquid water amount to the controller 109. The liquid water storage means 106 is provided with a temperature sensor 112 that detects the temperature in the liquid water storage means 106 and supplies the detected temperature to the controller 109. The liquid water storage means 106 is connected to the liquid water storage means 106 and the gas / liquid separation means 105, and when the liquid water is discharged from the gas / liquid separation means 105 to the liquid water storage means 106, the liquid water storage means 106 Air venting means 113 for leading the gas component in 106 to the gas-liquid separation means 105 is provided.

  The electric heater 107 is provided in the liquid water storage means 106, is supplied with electric power obtained by power generation after the system is started, and is adjusted in output under the control of the controller 109. The frozen liquid water stored in the water storage means 106 is thawed.

  The first liquid water discharge means 108a is provided in the gas-liquid separation means 105, is controlled to flow / shut off under the control of the controller 109, and controls discharge of liquid water accumulated in the gas-liquid separation means 105 outside the system. The second liquid water discharge means 108 b is provided between the gas-liquid separation means 105 and the liquid water storage means, and is controlled to flow / shut off under the control of the controller 109, so that the liquid water collected in the gas-liquid separation means 105 The liquid water storage means 106 controls the drainage. The third liquid water discharge means 108c is provided in the liquid water storage means 106, and is controlled to flow / shut off under the control of the controller 109, and controls discharge of the liquid water stored in the liquid water storage means 106 outside the system.

  The controller 109 functions as a control center that controls the operation of the fuel cell system, and includes resources such as a CPU, a storage device, and an input / output device necessary for a computer that controls various operation processes based on a program, for example. It is realized by a computer or the like. The controller 109 receives the above-described sensors in the fuel cell system and sensors (not shown) that collect information necessary for operation of the system, such as other pressures, temperatures, voltages, and currents that cannot be obtained by these sensors. A signal is read, and a command is sent to each component of the fuel cell system based on the read various signals and a control logic (program) stored in advance, and remains in the anode system of the fuel cell system described below. All operations necessary for operation / stop of the fuel cell system including water removal processing are managed and controlled.

  In such a configuration, the processing operation is performed according to the flowchart shown in FIG. Referring to FIG. 2, first, when the fuel cell system receives a fuel cell system activation signal instructing system activation (step S21), the system is activated to generate electric power (step S22). The water is thawed / drainage control is performed (step S23). When this processing control is finished and the system receives a fuel cell system stop signal for commanding the fuel cell system to stop operating (step S24), the power generation is stopped and then hydrogen gas is circulated through the hydrogen circulation pipe 102. Then, the water remaining in the fuel gas circulation system is circulated through the gas-liquid separation means 105 together with the hydrogen gas, the water is separated by the gas-liquid separation means 105, and the separated water is temporarily stored in the gas-liquid separation means 105.

  Thereafter, liquid water discharge processing control for discharging water accumulated in the gas-liquid separation means 105 is performed (step S25). When the liquid water discharge process control ends, the operation of the fuel cell system is stopped (step S26).

  The thawing / drainage processing control performed in step S23 shown in FIG. 2 is executed according to the flowchart of FIG. Referring to FIG. 3, first, based on a signal detected by temperature sensor 112 provided in liquid water storage means 106, controller 109 obtains temperature T1 of liquid water stored in liquid water storage means 106 (step). S31). Subsequently, it is determined whether or not the temperature T1 of the liquid water is equal to or lower than a first predetermined value set in advance (step S32), and it is estimated whether or not the stored liquid water is frozen. Therefore, the first predetermined value is set to about 0 ° C.

  As a result of the determination, if it is above, the process of step S35 to be described later is executed. If it is below, the electric heater 107 is fed and controlled to drive the electric heater 107 (step S33). The liquid water storage means 106 is heated by the electric heater 107, and thawing of the frozen liquid water in the liquid water storage means 106 is started. Thereafter, it is determined whether or not the temperature of the liquid water storage means 106 detected by the temperature sensor 112 is equal to or higher than the first predetermined value (step S34).

  As a result of the determination, if it is as follows, it is determined that the thawing is insufficient, the process of the previous step S33 is performed and the thawing process is continued. On the other hand, if it is above, it is determined that the liquid has been thawed, the third liquid water discharge means 108c is opened (step S35), and the liquid water stored in the liquid water storage means 106 is discharged outside the system. Start processing. Thereafter, it is determined whether or not the liquid water amount of the liquid water storage means 106 detected by the second liquid water amount detection means 111 is equal to or less than a second predetermined value (step S36). Here, as will be described later, when the liquid water is discharged from the liquid water storage means 106, the second predetermined value is that hydrogen gas existing in the liquid water storage means 106 is released from the liquid water storage means 106 to the outside of the system. The liquid volume is set so as not to be used.

  If the result of determination is not below, the liquid water discharging process is continued through the third liquid water discharging means 108c. On the other hand, if the result is below, the third liquid water discharging means 108c is shut off and drained. Is stopped (step S37).

  Here, the second predetermined value will be described with reference to FIG. 4 showing the relationship between the time after the third liquid water discharge means 108c is opened and the amount of liquid water in the liquid water storage means 106. First, the response time of the second liquid water amount detection unit 111 is set to T1 (sec), and the time until the controller 109 receives the signal of the second liquid water amount detection unit 111 and gives a shutoff command to the third liquid water discharge unit 108c is determined. When T2 (sec) is set, and the response time until the third liquid water discharge means 108c receives the cutoff command and the third liquid water discharge means 108c is cut off is T3 (sec), the sum of these times (T1 + T2 + T3) Is the response time Ts of the third liquid water discharging means 108c. T1, T2, and T3 are obtained in advance through experiments and the like.

  Further, when the liquid water is discharged from the liquid water storage means 106 via the third liquid water discharge means 108c, the fuel gas present in the liquid water storage means 106 is stored in the liquid water storage means via the third liquid water discharge means 108c. In order to prevent discharge from the fuel cell system from the means 106, a certain amount of liquid water remains in the liquid water storage means 106. At this time, the liquid water amount Hlimit remaining in the liquid water storage means 106 is obtained in advance by experiments. Furthermore, as shown in FIG. 4, the amount and time of the liquid water in the liquid water storage means 106 after the third liquid water discharge means 108c is opened from the shut-off state and the discharge of liquid water from the liquid water storage means 106 is started. This relationship is obtained in advance by experiments.

  As described above, in order to prevent the hydrogen gas from being discharged from the liquid water storage means 106 to the outside of the fuel cell system when draining through the third liquid water discharge means 108c, the liquid water storage means 106 has Hlimit or more. The amount of liquid water is required. Therefore, referring to the relationship between the response time Ts of the third liquid water discharge means 108c obtained above and FIG. 4, after the drainage from the liquid water storage means 106 is started, the amount of liquid water in the liquid water storage means 106 becomes Hlimit. A liquid water amount Hclose corresponding to a time Tclose (= Tlimit−Ts) obtained by subtracting the response time Ts from the time Tlimit is obtained.

  Therefore, when the liquid water amount in the liquid water storage means 106 reaches the liquid water amount Hclose, the controller 109 gives a command to switch the third liquid water discharge means 108c from the open state to the third liquid water discharge means 108c. In this case, when the discharge operation is finished, the liquid water storage means 106 has the liquid water amount Hlimit remaining. Thereby, the drainage operation of the liquid water storage means 106 can be performed without discharging the fuel gas from the liquid water storage means 106 to the outside of the system. Therefore, the second predetermined value is set to the value of Hclose.

  Next, the liquid water drainage process shown in step S25 of FIG. 2 will be described using the flowchart of FIG. With reference to FIG. 5, first, the detection signal of the first liquid water amount detection means 110 is read into the controller 109, and the liquid water quantity accumulated in the gas-liquid separation means 105 is obtained (step S51). Subsequently, the detection signal of the second liquid water amount detection unit 111 is read into the controller 109, and the amount of liquid water remaining in the liquid water storage unit 106 is obtained. Thereafter, based on the obtained liquid water amount and the storage capacity of the liquid water storage unit 106, the liquid water amount (storage allowable amount) that can be stored in the current liquid water storage unit 106 is calculated (step S52).

  Subsequently, it is determined whether or not the amount of liquid water in the gas-liquid separation means 105 is equal to or less than the storage allowable amount (step S53). As a result of the determination, if the following is true, the second liquid water discharge means 108b is opened, and all the liquid water collected in the gas-liquid separation means 105 through the second liquid water discharge means 108b is stored in the liquid water storage means 106. (Step S54), and the gas-liquid separation means 105 is made empty with no liquid water remaining.

  When all the liquid water accumulated in the gas-liquid separation means 105 is discharged to the liquid water storage means 106 via the second liquid water discharge means 108b, a gas corresponding to the volume of liquid water flowing into the liquid water storage means 106 The component flows from the liquid water storage means 106 into the gas-liquid separation means 105 through the air vent means 113. Here, if the air venting means 113 is constituted by a sufficiently thick and short pipe, the pressure in the gas-liquid separation means 105 and the pressure in the liquid water storage means 106 are approximately the same value (= the outlet of the fuel cell 100). Hydrogen gas pressure). In such a state, when the second liquid water discharge means 108b is opened and liquid water flows from the gas-liquid separation means 105 into the liquid water storage means 106, the force into which the liquid water flows is expressed as follows. .

(Equation 1)
P + mg
Here, P is the pressure in the gas-liquid separation means 105, m is the mass of liquid water in the gas-liquid separation means 105, and g is the gravitational acceleration.

  As described above, since the air pressure in the liquid water storage means 106 is almost the same value (P) as the air pressure in the gas liquid separation means 105, the liquid water is supplied from the gas liquid separation means 105 to the liquid water storage means by the force of mg. 106. Due to the inflow force of the liquid water, a gaseous component containing hydrogen gas corresponding to the volume of the inflowing liquid water is led out from the liquid water storage means 106 to the gas-liquid separation means 105 via the air vent means 113. Therefore, even if hydrogen gas present in the gas-liquid separation means 105 flows into the liquid water storage means 106 via the second liquid water discharge means 108b, it is returned to the gas-liquid separation means 105 as described above. Gas is prevented from being released out of the system.

  On the other hand, if the result of the determination process in step S53 is not the following, if all of the liquid water accumulated in the gas-liquid separation means 105 in this state is to be discharged to the liquid water storage means 106, the liquid water is discharged to the liquid water storage means 106. I can't understand. Therefore, first, the first liquid water discharge means 108a is opened (step S55), and the liquid water in the gas-liquid separation means 105 is discharged outside the system. When this discharge operation is started, the detection signal of the first liquid water amount detection means 110 is read into the controller 109, and the liquid water amount remaining in the gas-liquid separation means 105 is obtained (step S56). Thereafter, it is determined whether or not the amount of liquid water in the gas-liquid separation means 105 is less than or equal to the allowable storage amount (step S57). If the result of determination is not below, the processing shown in steps S56 and S57 is executed. On the other hand, if the result is below, the first liquid water discharging means 108a is shut off and the first liquid water discharging means 108a. After the drainage process from the liquid is finished (step S58), the process shown in the previous step S54 is executed to store all the liquid water remaining in the gas-liquid separation means 105 via the second liquid water discharge means 108b. The gas is discharged to the means 106 (step S54), and the gas-liquid separation means 105 is made empty with no liquid water remaining.

  Thus, in the first embodiment, all the liquid water is drained from the gas-liquid separation means 105 to the liquid water storage means 106 by controlling the second liquid water discharge means 108b when the fuel cell system is stopped. Thus, even if the fuel cell system is stopped in a low temperature environment, no liquid water remains in the gas-liquid separation means 105, so that the liquid water remaining in the gas-liquid separation means 105 can be prevented from freezing. . As a result, it is possible to prevent the liquid cell remaining in the gas-liquid separation means 105 from freezing and thus preventing the fuel cell system from being restarted. Moreover, hydrogen gas can be prevented from being released to the outside of the fuel cell system by setting the first liquid water discharging means 108a and the third liquid water discharging means 108c to the cutoff state.

  In order to prevent the liquid water in the liquid water storage means 106 from overflowing with the liquid water drained from the gas-liquid separation means 105 via the second liquid water discharge means 108b, the liquid water in the gas-liquid separation means 105 is preliminarily liquid water. In order to reduce the amount of liquid water that can be stored in the storage means 106, the first liquid water discharge means 108 a discharges it outside the fuel cell system, and then all the liquid water remaining in the gas-liquid separation means 105 is transferred to the liquid water storage means 106. Since the fuel cell system is stopped by draining, it is possible to prevent liquid water from remaining in the gas-liquid separation means 105 without overflowing the liquid water in the liquid water storage means 106.

  By controlling the third liquid water discharge means 108c so that the liquid water amount in the liquid water storage means 106 is always equal to or less than the liquid water quantity that can be stored in the liquid water storage means 106, the liquid water overflows from the liquid water storage means 106. Can be prevented.

  By providing the third liquid water discharge means 108c for discharging the liquid water in the liquid water storage means 106, the upper limit of the amount of liquid water that can be stored in the liquid water storage means 106 can be reduced. The size can be made compact (size capable of storing a single amount of liquid water flowing from the gas-liquid separation means 105 when the fuel cell system is stopped), and the fuel cell system can be reduced in weight.

  Further, the third liquid water discharge means 108c is controlled from the liquid water storage means 106 by controlling the third liquid water discharge means 108c so that the amount of liquid water stored in the liquid water storage means 106 is not always below a predetermined value. It is possible to prevent the fuel gas from being discharged outside the fuel cell system.

  When it is estimated that the liquid water is frozen in the liquid water storage means 106 based on the temperature measured by the temperature sensor 112, the liquid water storage means 106 passes through the third liquid water discharge means 108 c. Liquid water cannot be discharged out of the fuel cell system. As a result, when the fuel cell system is stopped while the liquid water in the liquid water storage means 106 is frozen, it is drained from the gas-liquid separation means 105 to the liquid water storage means 106 via the second liquid water discharge means 108b. Liquid water may overflow from the liquid water storage means 106 and liquid water may remain in the gas-liquid separation means 105.

  Therefore, when the liquid water storage means 106 determines that the liquid water is frozen, the electric heater 107 is driven so that the liquid water can be discharged from the liquid water storage means 106 to the outside of the fuel cell system. By thawing the frozen liquid water, the liquid water can be prevented from remaining in the gas-liquid separation means 105. Further, even if the liquid water in the liquid water storage means 106 is frozen, it does not affect the startability of the fuel cell system, so the frozen liquid water in the liquid water storage means 106 is thawed before the system is started. Since it is not necessary, the startup time of the fuel cell system can be shortened.

  The temperature sensor 112 determines whether or not the liquid water in the liquid water storage means 106 is frozen, and before the liquid water is frozen in the liquid water storage means 106, the electric heater 107 is driven to drive the liquid water storage means. Freezing of 106 can be prevented. In addition, when the temperature in the liquid water storage means 106 is lower than a predetermined value when the vehicle equipped with this system is started, the electric heater 107 is driven to defrost liquid water remaining in the liquid water storage means 106, In addition, freezing can be prevented.

  The electric water heater 107 is provided in the liquid water storage means 106 as a means for thawing the frozen liquid water in the liquid water storage means 106, so that it can be in any state during the fuel cell system activation control or after the fuel cell system activation. By adjusting the output of the electric heater 107, the thawing time of the liquid water storage means 106 can be shortened.

  In addition, when the electric heater 107 is driven after the fuel cell system is started, the electric power generated by the fuel cell 100 is thawed out of the liquid water without using the power of the secondary battery or the like remaining before the fuel cell system is started. Since it can be used as the energy of the fuel cell system, the power consumption of the secondary battery used when starting the fuel cell system can be reduced, the startup performance of the system can be secured, and the energy for thawing from outside the fuel cell system No need to procure.

  FIG. 6 is a diagram showing a configuration of a fuel cell system according to Embodiment 2 of the present invention. In FIG. 6, the feature of the second embodiment is that a fuel cell installed in a normal fuel cell system is used instead of the electric heater 107 described in the first embodiment, as compared with the first embodiment. 1 is that the frozen liquid water in the liquid water storage means 106 is thawed using the heat obtained by the cooling means for cooling the fuel cell that has generated heat due to 100 power generation. This is the same as the embodiment shown.

  The cooling means includes a cooling device 600 that supplies and circulates cooling water for cooling the fuel cell 100 to the fuel cell 100, and a cooling water pipe 601 that serves as a cooling water flow passage. A part of the cooling water pipe 601 is installed in contact with the liquid water storage means 106, and the cooling water discharged from the cooling device 600 is supplied to the fuel cell 100 via the cooling water pipe 601 and generates heat by power generation. The fuel cell 100 is cooled and heat exchanged. Cooling water that has been subjected to heat exchange by cooling the fuel cell 100 is heated and warmed, and the warmed cooling water flows through the cooling water pipe 601 in contact with the liquid water storage means 106 and returns to the cooling device 600. Has been circulating. At this time, the heated cooling water and the liquid water storage means 106 are heat-exchanged, thereby thawing the liquid water frozen in the liquid water storage means 106.

  In the second embodiment, the thawing / drainage processing control performed in step S23 shown in FIG. 2 is executed according to the flowchart shown in FIG. Referring to FIG. 7, first, based on a signal detected by temperature sensor 112 provided in liquid water storage means 106, controller 109 obtains temperature T1 of liquid water stored in liquid water storage means 106 (step). S71). Subsequently, it is determined whether or not the temperature T1 of the liquid water is equal to or lower than a first predetermined value set to the same value as described above (step S72), and it is estimated whether or not the stored liquid water is frozen. To do.

  As a result of the determination, if the following is true, it is estimated that the liquid water is frozen, and the heat generated by the power generation of the fuel cell 100 is performed with the third liquid water discharge means 108c shut off (step S73). The liquid water storage means 106 is heated with the heated cooling water to raise the temperature, and the thawing process of the frozen water is started, and the determination process in step S72 is executed.

  If the result of the determination process in step S72 is the above, it is determined that the liquid water in the liquid water storage means 106 is not frozen, and the third liquid water discharge means 108c is opened (step S74). The process of discharging the liquid water stored in the water storage means 106 to the outside of the system is started. Thereafter, it is determined whether or not the amount of liquid water in the liquid water storage means 106 detected by the second liquid water amount detection means 111 is equal to or less than a second predetermined value (step S75). Here, the second predetermined value is set to the same value as in the first embodiment.

  If the result of determination is not below, the liquid water discharging process is continued through the third liquid water discharging means 108c. On the other hand, if the result is below, the third liquid water discharging means 108c is shut off and drained. Is stopped (step S76).

  As described above, in the second embodiment, in addition to obtaining the same effect as in the first embodiment, the cooling water used during the operation of the fuel cell system is used as the liquid water thawing means. Since the high-temperature cooling water heat-exchanged with each part of the fuel cell system after the start-up adopts a configuration in which heat is exchanged with the frozen water in the liquid water storage means 106, electric power is not required for thawing the frozen water, and the fuel cell system Power consumption can be reduced.

  Next, a fuel cell system according to Example 3 of the present invention will be described. Compared with the configuration shown in FIG. 1, the feature of the third embodiment is that the thawing means for thawing the frozen liquid water in the liquid water storage means 106 instead of the electric heater 107 described in the first embodiment. As described above, the high-temperature liquid water discharged from the anode electrode side outlet of the fuel cell 100 to the gas-liquid separation unit 105 and separated by the gas-liquid separation unit 105 at the time of power generation of the fuel cell 100 is used. The same as in the first embodiment.

  In the third embodiment, the thawing / drainage processing control performed in step S23 shown in FIG. 2 is executed according to the flowchart shown in FIG. Referring to FIG. 8, first, based on a signal detected by temperature sensor 112 provided in liquid water storage means 106, controller 109 obtains temperature T1 of liquid water stored in liquid water storage means 106 (step). S81). Subsequently, it is determined whether or not the temperature T1 of the liquid water is equal to or lower than a first predetermined value set to the same value as described above (step S82), and it is estimated whether or not the stored liquid water is frozen. To do.

  As a result of the determination, if it is the following, it is estimated that the liquid water is frozen, and the second liquid water discharge means 108b is opened (step S83). As a result, during the power generation of the fuel cell 100, the high-temperature liquid water that is discharged from the anode electrode side outlet of the fuel cell 100 to the gas-liquid separation means 105 and separated by the gas-liquid separation means 105 is discharged to the second liquid water discharge. The gas-liquid separation means 105 is discharged to the liquid water storage means 106 via the means 108b. As a result, the thawing process of the liquid water frozen in the liquid water storage means 106 with the high-temperature liquid water discharged from the gas-liquid separation means 105 is started, and the discrimination process of the previous step S82 is executed.

  If the result of the determination processing in the previous step S82 is the above, it is determined that the liquid water in the liquid water storage means 106 is not frozen, and the liquid water storage detected by the second liquid water amount detection means 111 is determined. It is determined whether or not the liquid water amount of the means 106 is equal to or smaller than a second predetermined value (step S84). Here, the second predetermined value is set to the same value as in the first embodiment.

  If the result of determination is not below, the third liquid water discharge means 108c is opened (step S85), and the liquid stored in the liquid water storage means 106 outside the system via the opened third liquid water discharge means 108c. When the water is discharged and the following condition is reached, the third liquid water discharging means 108c is shut off and the drainage is stopped (step S86).

  As described above, in the third embodiment, the high-temperature liquid water discharged from the outlet on the anode electrode side of the fuel cell 100 and separated by the gas-liquid separation means 105 is used as the thawing means for liquid water. The same effects as those of the second embodiment can be obtained.

  In each of the first to third embodiments, when it is determined that the liquid water in the liquid water storage means 106 is frozen after the system is started, a process for thawing the frozen water after the system is started is executed. However, when the system operation is stopped after the system is started, it is determined whether or not the system is frozen.If it is determined that the system is frozen, the system is operated after the frozen water is thawed. You may make it stop.

  If the liquid water is frozen in the liquid water storage means 106 when the fuel cell system is stopped, there is a possibility that the liquid water cannot be discharged from the liquid water storage means 106, and all the liquid water is discharged from the gas-liquid separation means 105. There was a risk that the fuel cell system would stop without any failure. For this reason, by thawing the frozen water in the liquid water storage means 106 by operating the liquid water thawing means, it is possible to discharge all liquid water from the gas-liquid separation means 105 and stop the system.

  As a result, since liquid water does not remain in the gas-liquid separation means 105 even if left in a low temperature environment after the fuel cell system is stopped, the gas-liquid separation means 105 can be prevented from freezing. It can be prevented that the fuel cell system cannot be restarted due to the separation means 105 being frozen.

It is a figure which shows the structure of the fuel cell system which concerns on Example 1 of this invention. It is a flowchart which shows the procedure of the control processing which concerns on Example 1 of this invention. It is a flowchart which shows the procedure of one process shown in FIG. It is a figure which shows the relationship between the time after opening of a 3rd liquid water discharge means, and the amount of liquid water of a liquid water storage means. It is a flowchart which shows the procedure of one process shown in FIG. It is a figure which shows the structure of the fuel cell system which concerns on Example 2 of this invention. It is a flowchart which shows the procedure of the control processing which concerns on Example 2 of this invention. It is a flowchart which shows the procedure of the control processing which concerns on Example 3 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Fuel cell 101 ... High pressure fuel gas supply apparatus 102 ... Hydrogen circulation piping 103 ... Fuel gas pressurization means 104 ... Ejector 105 ... Gas-liquid separation means 106 ... Liquid water storage means 107 ... Electric heater 108a ... 1st liquid water discharge means 108b ... second liquid water discharging means 108c ... third liquid water discharging means 109 ... controller 110 ... first liquid water amount detecting means 111 ... second liquid water amount detecting means 112 ... temperature sensor 113 ... air venting means 600 ... cooling device 601 ... Cooling water piping

Claims (9)

In a fuel cell system including a fuel cell that generates power by an electrochemical reaction of a reaction gas between a fuel gas and an oxidant gas,
Gas-liquid separation means for separating the water contained in the off-gas discharged from the anode side of the fuel cell and temporarily storing the obtained liquid water;
Liquid water stored in the gas-liquid separation means flows in, stores the liquid water that has flowed in, and liquid water storage means in which no reaction gas flows during startup and operation of the fuel cell system,
Second liquid water discharge means for selectively controlling drainage of the liquid water stored in the gas-liquid separation means to the liquid water storage means;
And control means for controlling the drainage of the liquid water stored in the gas-liquid separation means to the liquid water storage means via the second liquid water discharge means when the operation of the fuel cell system is stopped. Fuel cell system. First liquid water discharge means for selectively controlling drainage of liquid water stored in the gas-liquid separation means to the outside of the fuel cell system;
First liquid water amount detection means for detecting the amount of liquid water stored in the gas-liquid separation means;
A second liquid water amount detection means for detecting the liquid water amount stored in the liquid water storage means,
The control means includes an amount of liquid water stored in the gas-liquid separation means detected by the first liquid water amount detection means, and a liquid stored in the liquid water storage means detected by the second liquid water amount detection means. 2. The fuel cell system according to claim 1, wherein drainage of the first liquid water discharge unit and the second liquid water discharge unit is controlled based on a water amount. A third liquid water discharging means for selectively controlling drainage of the liquid water stored in the liquid water storage means outside the fuel cell system;
The control means controls the drainage of the third liquid water discharge means based on the liquid water amount stored in the liquid water storage means detected by the second liquid water amount detection means, and the liquid water storage means 3. The fuel cell system according to claim 2, wherein the amount of liquid water stored is set to a predetermined amount of liquid water. Freezing judgment means for judging whether or not the liquid water stored in the liquid water storage means is frozen,
Thawing means for thawing frozen liquid water in the liquid water storage means,
When the control means judges that the liquid water stored in the liquid water storage means is frozen by the freezing judgment means, the liquid water frozen by the thawing means after starting the fuel cell system is thawed. The fuel cell system according to any one of claims 1, 2, and 3, wherein: The freezing judgment means is composed of a temperature sensor installed in the liquid water storage means,
5. The fuel cell according to claim 4, wherein when the temperature detected by the temperature sensor is equal to or less than a predetermined value, it is determined that the liquid water stored in the liquid water storage means is frozen. system. The thawing means is composed of an electric heater installed in the liquid water storage means,
If the freezing determination means determines that the liquid water stored in the liquid water storage means is frozen, the control means drives the electric heater after the fuel cell system is started to 6. The fuel cell system according to claim 4, wherein the frozen water is thawed by heating the water storage means. The thawing means is constituted by a cooling means for cooling the fuel cell,
The cooling means includes a cooling device that supplies cooling water to be cooled by exchanging heat with the fuel cell to the fuel cell;
Cooling water supplied to the fuel cell circulates, and a part of the piping is configured with cooling water piping arranged in contact with the liquid water storage means,
5. The cooling water heat-exchanged with the fuel cell flows through the cooling water pipe and exchanges heat with the liquid water storage means, and thaws the liquid water frozen by the cooling water heat. 6. The fuel cell system according to 5. The thawing means is liquid water discharged from the anode electrode outlet side of the fuel cell and separated by the gas-liquid separation means,
6. The liquid water of the thawing means is drained to the liquid water storage means via the second liquid water discharging means, and the frozen liquid water is thawed by the heat of the drained liquid water. The fuel cell system described in 1. When the control unit determines that the liquid water stored in the liquid water storage unit is frozen by the freezing determination unit when the fuel cell system is stopped, the control unit freezes by the thawing unit. The fuel cell system according to any one of claims 4, 5, 6, 7 and 8, wherein the liquid water is thawed.

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