JP2006147336A - Fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress freezing of residual moisture without deteriorating power generation efficiency and improve starting ability under a low temperature environment. <P>SOLUTION: At the starting at below zero of a fuel cell stack, hydrogen gas is heated with a fuel heating device 2 and supplied to the fuel cell stack 1 under the control of a control unit 4, and the pressure of the hydrogen gas to be supplied to the fuel cell stack 1 is set higher than the pressure of air gas to be supplied to the fuel cell stack 1 by controlling a pressure reducing valve 7 and a blower 10, and then power generation is started. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell system that suppresses freezing of moisture remaining in a fuel cell stack.

  In general, a fuel cell is a device that directly converts a chemical energy of a fuel into electric energy by electrochemically reacting a fuel gas such as hydrogen as a reaction gas with an oxidant gas such as air. The fuel cells are classified into various types depending on the difference in electrolytes, and one of them is a solid polymer electrolyte fuel cell using a solid polymer electrolyte as an electrolyte.

  The electrode reaction that proceeds in both the anode electrode serving as the fuel electrode and the cathode electrode serving as the oxidant electrode is as follows.

(Chemical formula 1)
Anode electrode: H ₂ → 2H ⁺ + 2e ⁻ (1)
Cathode electrode: 2H ⁺ + 2e ⁻ + (1/2) O ₂ → H ₂ O (2)
When the fuel is supplied to the fuel electrode, the reaction formula (1) proceeds at the fuel electrode to generate hydrogen ions. The generated hydrogen ions permeate (diffuse) the electrolyte (solid polymer electrolyte membrane in the case of a solid polymer electrolyte fuel cell) in a hydrated state to reach the oxidant electrode, and the oxygen-containing gas, For example, when air is supplied, the reaction formula (2) proceeds at the oxidizer electrode. As the electrode reactions of (1) and (2) proceed at each electrode, the fuel cell generates an electromotive force.
For example, in a polymer electrolyte fuel cell that is considered as a driving source for vehicles and the like, the moisture generated by the above reaction remains inside the fuel cell when operation is stopped, and freezes in a sub-freezing environment. Is significantly reduced.

Therefore, as a conventional technique for avoiding freezing of water remaining in the fuel cell, for example, a technique described in the following document is known (see Patent Document 1). In this document, temperature detection means for detecting the temperature of the fuel battery cell and air heating means for heating the supply air based on the temperature detected by the temperature detection means are provided, and the fuel cell is warmed up with the supply air. An invention is described in which the power generation efficiency is improved and the warm-up time for thawing the ice in the apparatus is shortened.
JP 2002-93445 A

  In the conventional fuel cell system described above, the fuel cell stack does not generate power while the air is heated. For this reason, the malfunction that power generation efficiency deteriorates significantly is caused.

  Therefore, the present invention has been made in view of the above, and an object of the present invention is to improve the startability in a low temperature environment by suppressing freezing of residual moisture without deteriorating power generation efficiency. It is to provide a battery 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 stack that generates power by a chemical reaction between a fuel gas and an oxidant gas, and is supplied to the fuel cell stack. Heating means for heating the fuel gas, pressure control means for controlling the pressure of the fuel gas and oxidant gas supplied to the fuel cell stack, and when the fuel cell stack is started at a low temperature, the fuel heating means The pressure of the oxidant gas supplied to the fuel cell stack is set higher than the pressure of the fuel gas supplied to the fuel cell stack by the pressure control means. And a control means for performing a low-temperature start-up process.

  According to the present invention, drying of the anode electrode is promoted, and the amount of water that the fuel gas removes from the anode electrode can be increased, or the amount of moisture that the oxidant gas removes from the cathode electrode can be reduced. This increases the difference between the moisture content of the cathode electrode and the moisture content of the anode electrode, promotes the back diffusion of moisture in the membrane electrode assembly, suppresses the generation of moisture at the cathode electrode, and reduces the moisture content at the cathode electrode. Freezing can be suppressed. As a result, the startability in a low temperature environment can be improved without deteriorating the power generation efficiency.

  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. The system of the first embodiment shown in FIG. 1 includes a fuel cell stack 1 that generates power by a chemical reaction between hydrogen of fuel gas and air of oxidant gas, and a fuel heating device that heats hydrogen supplied to the fuel cell stack 1. 2, a temperature sensor 3 for detecting the temperature of the fuel cell stack 1, and a control unit 4.

  The fuel cell stack 1 is a solid polymer electrolyte fuel cell, and is configured as shown in the cross-sectional view of FIG. In FIG. 2, a cell as a unit of the fuel cell stack includes an electrolyte membrane 20 made of a solid polymer membrane, and two electrodes 21 disposed on both surfaces of the electrolyte membrane 20 so as to sandwich the electrolyte membrane 20. 22 and separators 23 and 24 in which gas flow paths 27 and 28 are formed. The electrolyte membrane 20 is formed as a proton conductive membrane from a solid polymer material such as a fluororesin.

  The two electrodes 21 and 22 disposed on both surfaces of the membrane are composed of a catalyst layer (not shown) made of platinum or platinum and other metals and gas diffusion layers 25 and 26, and the surface on which the catalyst exists. It is formed so as to be in contact with the electrolyte membrane 20. The gas flow paths 27 and 28 are formed by a large number of ribs arranged on one side or both sides of a dense carbon material or the like that is impermeable to gas, and oxidant gas and fuel gas are supplied from the respective gas inlets. It is discharged from the exit.

  Returning to FIG. 1, the fuel cell stack 1 is supplied with hydrogen as a fuel gas via a fuel supply pipe 5. A fuel heating device 2 is provided in the fuel supply pipe 5, and a pressure reducing valve 7 for reducing the hydrogen pressure under the control of the control unit 4 is provided downstream of the fuel heating device 2. The fuel cell stack 1 discharges unused hydrogen in the fuel cell stack 1 to the outside of the fuel cell stack 1 through the fuel discharge pipe 9, and the pressure of hydrogen gas flowing through the fuel cell stack 1 is discharged to the fuel discharge pipe 9. A blower 10 having a function of adjusting and controlling the above is provided.

  The fuel cell stack 1 is supplied with oxidant gas air through the oxidant supply pipe 6, and unused air in the fuel cell stack 1 is discharged out of the fuel cell stack 1 through the oxidant discharge pipe 8. .

  The control unit 4 functions as a control center that controls the operation of the system, and is provided with 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, a microcomputer. Etc. The control unit functions as a control means, reads signals from each sensor (not shown) in the system including the temperature sensor 3, and based on various signals read and control logic (program) held in advance in advance, A command is sent to each component of the system including the pressure reducing valve 7 and the blower 10 to control and control all operations necessary for operation / stopping of the system including the hydrogen pressure reducing and heating operations described below. .

  Next, hydrogen decompression and heating operations performed under the control of the control unit 4 will be described with reference to the flowchart of FIG. In FIG. 3, first, the temperature Tstack of the fuel cell stack 1 is detected (step S1), and the detected temperature Tstack is a first predetermined temperature Ts1, which is preset as a temperature at which the voltage of the fuel cell stack 1 decreases due to water freezing. For example, it is determined whether the temperature is 0 ° C. or higher (step S2). If it is determined that the temperature is equal to or higher than the first predetermined temperature, the start-up operation below zero is not performed. If the temperature is equal to or lower than the first predetermined temperature Ts1, supply of hydrogen to the fuel cell stack 1 is started (step S3). Then, the hydrogen is heated and the pressure is reduced by adjusting the pressure reducing valve 7 and the blower 10 and supplied to the fuel cell stack 1 (step S4), and power generation is started (step S5).

  Next, the temperature Tstack of the fuel cell stack 1 is detected, and it is determined whether or not the detected temperature Tstack is equal to or higher than a preset first predetermined temperature Ts1, for example, 0 ° C. (step S6). If it is determined that the temperature is equal to or higher than the first predetermined temperature, heating and depressurization of hydrogen supplied to the fuel cell stack 1 are stopped (step S7), and a normal operation is started.

  By such treatment, drying of the anode is promoted by raising the temperature of hydrogen, and the amount of water removed from the anode by increasing the pressure of the air to be higher than the pressure of hydrogen increases, or the air is absorbed by the cathode. Since the amount of water removed from the electrode is reduced, the amount of water in the cathode electrode and the amount of water in the anode electrode are compared with those in the normal operation shown in FIG. The difference becomes larger. As a result, the moisture movement between the anode electrode and the cathode electrode is greater in the membrane electrode assembly constituting the cells of the fuel cell stack 1 as shown in FIG. 4 (d) than in the normal operation shown in FIG. 4 (b). Since the reverse diffusion of water is promoted, moisture generation at the cathode electrode is suppressed, and freezing of moisture at the cathode electrode can be suppressed.

  The fuel heating device 2 can easily heat hydrogen by being constituted by an electric heating means using electric power or a combustor using hydrogen.

  When starting a fuel cell system below zero, instead of depressurizing hydrogen, pressurized air may be supplied to the cathode electrode. By performing such control, a wide range of pressure control is possible. It becomes.

  When the temperature of the fuel cell stack 1 is equal to or lower than the first predetermined temperature, it is possible to determine whether or not hydrogen depressurization and heat treatment are necessary by performing hydrogen depressurization and heat treatment. It can save the energy required.

  FIG. 5 is a diagram showing a configuration of a fuel cell system according to Embodiment 2 of the present invention. The feature of the first embodiment shown in FIG. 5 is that the temperature of the hydrogen supplied to the fuel cell stack 1 provided in the pipe on the hydrogen inlet side of the fuel cell stack 1 as compared with the first embodiment shown in FIG. 1 and a resistance sensor 12 for detecting the resistance of the fuel cell stack 1 are provided.

  Next, with reference to the flowchart of FIG. 6, the decompression and heating operation of hydrogen performed under the control of the control unit 4 will be described. In FIG. 6, first, the temperature Tstack of the fuel cell stack 1 is detected, and the detected temperature Tstack is a first predetermined temperature Ts1, which is preset as a temperature at which the voltage of the fuel cell stack 1 decreases due to water freezing, for example, 0 ° C. or more. It is discriminate | determined whether it is (step S11). If it is determined that the temperature is equal to or higher than the first predetermined temperature, the start-up process below zero is not performed. On the other hand, if the temperature is equal to or lower than the first predetermined temperature Ts1, the resistance of the fuel cell stack 1 is detected (step S12).

  Next, a second predetermined temperature Ts2 is set based on the temperature and resistance of the fuel cell stack 1 (step S13). Thereafter, the supply of hydrogen to the fuel cell stack 1 is started (step S14), the hydrogen is heated by the fuel heating device 2, and the pressure is reduced by adjusting the pressure reducing valve 7 and the blower 10 to the fuel cell stack 1. Supply (step S15). Subsequently, it is determined whether or not the temperature Tf of hydrogen supplied to the fuel cell stack 1 has become higher than the second predetermined temperature Ts2 (step S16). As a result of the determination, if it becomes higher, power generation is started (step S17).

  Next, it is determined whether or not the hydrogen temperature Tf has become higher than a preset third predetermined temperature, for example, 100 ° C. (step S18). If the result of determination is not high, the heating output of the fuel heating device 2 is reduced (step S19), whereas if it is high, the temperature Tstack of the fuel cell stack 1 becomes higher than the first predetermined value Ts1. It is determined whether or not (step S20). As a result of the determination, if it is not high, the process returns to the previous step S18. If it is high, heating and depressurization of the hydrogen supplied to the fuel cell stack 1 are stopped (step S21), and normal operation is started. Transition.

  In such Example 2, in addition to being able to obtain the same effect as that obtained in the previous Example 1, it is possible to perform power generation after heating the hydrogen of the fuel to the minimum necessary, Overheating of hydrogen during operation can be prevented. Moreover, the voltage drop of the fuel cell stack 1 due to water freeze due to insufficient heating can be prevented, and damage to the membrane electrode assembly due to excessive heating of hydrogen can be suppressed.

  In the second embodiment, the second predetermined temperature is set based on the resistance value of the fuel cell stack 1 and the temperature of hydrogen at the fuel cell stack inlet. However, the second predetermined temperature is provided, and a function for detecting residual moisture in the fuel cell stack 1 is provided. Instead, the second predetermined temperature may be determined based on the residual moisture content and the resistance of the fuel cell stack 1.

  By detecting the residual moisture content inside the fuel cell stack 1 based on the resistance value of the fuel cell stack 1, the residual moisture content inside the fuel cell stack 1 can be easily detected.

  By controlling the heating of the hydrogen so that the temperature of the hydrogen supplied to the fuel cell stack 1 is lower than the third predetermined temperature, excessive heating of the hydrogen can be prevented. Thereby, energy required for heating of hydrogen can be saved, and damage to the membrane electrode assembly due to excessive heating of hydrogen can be suppressed. The third predetermined temperature is set in advance as a limit temperature that the membrane electrode assembly can withstand.

  FIG. 7 is a diagram showing a configuration of a fuel cell system according to Embodiment 3 of the present invention. The feature of the third embodiment shown in FIG. 7 is that the fuel temperature sensor 11 is omitted and the pressure difference between hydrogen and air at the outlet side of the fuel cell stack 1 is compared with the second embodiment shown in FIG. 5 is the same as FIG.

  Next, with reference to the flowchart of FIG. 8, hydrogen decompression and heating operations performed under the control of the control unit 4 will be described. In FIG. 8, first, the temperature Tstack of the fuel cell stack 1 is detected, and the detected temperature Tstack is a first predetermined temperature Ts1, which is preset as a temperature at which the voltage of the fuel cell stack 1 decreases due to water freezing, for example, 0 ° C. or more. It is discriminate | determined whether it is (step S31). As a result of the determination, if the temperature is equal to or higher than the first predetermined temperature Ts1, the sub-zero start-up process is not performed. If the temperature is equal to or lower than the first predetermined temperature Ts1, the resistance of the fuel cell stack 1 is detected (step S32).

  Next, a first predetermined pressure difference Ps1 is set based on the temperature and resistance of the fuel cell stack 1 (step S33). Thereafter, the supply of hydrogen to the fuel cell stack 1 is started (step S34), the hydrogen is heated by the fuel heating device 2, and the pressure is reduced by adjusting the pressure reducing valve 7 and the blower 10 to the fuel cell stack 1. Supply (step S35). Subsequently, it is determined whether or not the pressure difference Pf between the hydrogen discharged from the fuel cell stack 1 and air is higher than the first predetermined pressure difference Ps1 (step S36). As a result of the determination, if it becomes higher, power generation is started (step S37).

  Next, it is determined whether or not the pressure difference Pf between hydrogen and air is higher than a preset second predetermined pressure difference, for example, 100 kPa (step S38). As a result of the determination, if not high, the pressure-reducing valve 7 and the blower 10 are adjusted and controlled to reduce the pressure difference between hydrogen and air (step S39). It is determined whether or not Tstack is higher than a first predetermined value Ts1 (step S40). If the result of determination is that it is not high, the process returns to the previous step S38, whereas if it is high, heating and depressurization of the hydrogen supplied to the fuel cell stack 1 are stopped (step S41), and normal operation is started. Transition.

  In the third embodiment, the same effect as that obtained in the second embodiment can be obtained, and in addition, the difference between the hydrogen pressure and the air pressure is set to the minimum necessary pressure difference before power generation. And the difference between the hydrogen pressure and the air pressure during processing can be prevented from becoming excessive. In addition, the voltage drop of the fuel cell stack 1 due to moisture freezing due to the small difference between the hydrogen pressure and the air pressure can be prevented, and the membrane electrode assembly can be damaged by the excessive pressure difference between hydrogen and air. Can be prevented.

  In the third embodiment, the first predetermined pressure difference is set based on the resistance value of the fuel cell stack 1 and the temperature of the fuel cell stack 1. However, the fuel cell stack has a function of detecting the residual water content in the fuel cell stack 1. The first predetermined pressure difference may be determined based on the residual moisture content and the resistance of the fuel cell stack 1 instead of the temperature of 1.

  By controlling at least one of the hydrogen pressure and the air pressure so that the difference between the hydrogen pressure and the air pressure is less than a second predetermined pressure difference that is a limit pressure difference that the membrane electrode assembly can withstand, It is possible to prevent the difference between the hydrogen pressure and the air pressure from becoming excessive. Thereby, damage to the membrane electrode assembly due to an excessive pressure difference between the anode electrode and the cathode electrode can be prevented.

  FIG. 9 is a diagram showing a configuration of a fuel cell system according to Embodiment 4 of the present invention. The feature of the fourth embodiment shown in FIG. 9 is that the fuel temperature sensor 11 is provided in the same manner as in the second embodiment as compared with the third embodiment shown in FIG. A fuel drying device 14 for drying hydrogen is provided in parallel so as to be selectively switchable with the fuel supply piping 5 side by means of three-way valves 16 and 17 provided in the fuel supply piping 5. A moisture amount detection sensor 15 for detecting the moisture content of hydrogen supplied to the fuel cell stack 1 is provided upstream, and the air pressure is adjusted and controlled in the oxidant discharge pipe 8 on the air outlet side of the fuel cell stack 1. Since the pressure control valve 18 is provided, the rest is the same as in FIG.

  Next, referring to the flowchart of FIG. 10, the hydrogen decompression and heating operations performed under the control of the control unit 4 will be described. In FIG. 10, first, the temperature Tstack of the fuel cell stack 1 is detected (step S51), and the detected temperature Tstack is a first predetermined temperature Ts1, which is preset as a temperature at which the voltage of the fuel cell stack 1 decreases due to water freezing. For example, it is determined whether the temperature is 0 ° C. or higher (step S52). If the result of determination is that the temperature is equal to or higher than the first predetermined temperature Ts1, the start-up process below zero is not performed. If the temperature is equal to or lower than the first predetermined temperature Ts1, the resistance of the fuel cell stack 1 is detected (step S53).

  Next, the first predetermined pressure difference Ps1 and the second predetermined temperature Ts2 are set based on the temperature and resistance of the fuel cell stack 1 (step S54). Thereafter, supply of hydrogen to the fuel cell stack 1 is started (step S55), and the amount of water Wf contained in the hydrogen supplied to the fuel cell stack 1 is detected (step S56). Subsequently, it is determined whether or not the water content Wf of hydrogen is larger than a predetermined water content Ws set in advance (step S57). If the result of determination is that there are not, the process proceeds to step S59 to be described later. If there are more, the three-way valves 16 and 17 are switched to the fuel drying device 14 side (step S58), and hydrogen is dried by the fuel drying device 14. The hydrogen is heated by the fuel heating device 2, and the pressure is reduced by supplying the pressure to the fuel cell stack 1 by adjusting the pressure reducing valve 7 and the blower 10, and the pressure control valve 18 is further adjusted to adjust the fuel cell stack 1. The air supplied to is pressurized (step S59).

  Next, all of the pressure difference Pf between the hydrogen discharged from the fuel cell stack 1 and the air> the first predetermined pressure difference Ps1, the hydrogen temperature Tf> the second predetermined temperature Ts2, and the water content Wf <the predetermined water content Ws. It is determined whether or not the determination requirement is satisfied (step S60). As a result of determination, when all the determination requirements are satisfied, power generation is started (step S61). Thereafter, it is determined whether or not the temperature Tstack of the fuel cell stack 1 has become higher than the first predetermined temperature Ts1 (step S61). As a result of the determination, if it becomes higher, heating of hydrogen supplied to the fuel cell stack 1, depressurization, and pressurization of air are stopped (step S63), and normal operation is started.

  In the fourth embodiment, in addition to obtaining the same effect as that obtained in the third embodiment, moisture in the hydrogen supplied to the fuel cell stack 1 is removed, so that the cathode The pole can be further dried. Moreover, since the air supplied to the fuel cell stack 1 is pressurized, the amount of water in the cathode electrode can be increased. As a result, the difference in the amount of water between the anode and the cathode is further increased, so that the movement of moisture to the membrane electrode assembly is further promoted.

  The fuel drying device 14 can easily remove moisture in hydrogen by being composed of a desiccant and a water separation membrane.

It is a figure which shows the structure of the fuel cell system which concerns on Example 1 of this invention. It is a figure which shows the structure of a fuel cell stack. It is a flowchart which shows the procedure of the process which concerns on Example 1 of this invention. It is a figure which shows the mode of the moisture content of the anode electrode of a fuel cell stack, and the cathode electrode, and the water | moisture content movement between both electrodes. 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 process which concerns on Example 2 of this invention. It is a figure which shows the structure of the fuel cell system which concerns on Example 3 of this invention. It is a flowchart which shows the procedure of the process which concerns on Example 3 of this invention. It is a figure which shows the structure of the fuel cell system which concerns on Example 4 of this invention. It is a flowchart which shows the procedure of the process which concerns on Example 4 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fuel cell stack 2 ... Fuel heating device 3 ... Temperature sensor 4 ... Control unit 5 ... Fuel supply piping 6 ... Oxidant supply piping 7 ... Pressure reducing valve 8 ... Oxidant discharge piping 9 ... Fuel discharge piping 10 ... Blower 11 ... Fuel Temperature sensor 12 ... Resistance sensor 13 ... Pressure detection sensor 14 ... Fuel dryer 15 ... Water content detection sensor 16, 17 ... Three-way valve 18 ... Pressure control valve 20 ... Electrolyte membrane 21, 22 ... Electrode 23, 24 ... Separator 25, 26 ... Gas diffusion layer 27,28 ... Gas flow path

Claims (11)

In a fuel cell system including a fuel cell stack that generates power by a chemical reaction between a fuel gas and an oxidant gas,
Heating means for heating the fuel gas supplied to the fuel cell stack;
Pressure control means for controlling the pressure of the fuel gas and the oxidant gas supplied to the fuel cell stack;
When the fuel cell stack is started at a low temperature, the fuel gas is heated by the fuel heating means and supplied to the fuel cell stack, and the fuel is more than the pressure of the fuel gas supplied to the fuel cell stack by the pressure control means. A fuel cell system comprising: control means for setting a high pressure of the oxidant gas supplied to the battery stack to perform a low-temperature start-up process. 2. The fuel cell system according to claim 1, wherein the fuel heating unit includes at least one of an electric heating unit using electric power and a combustor using the fuel gas. The said control means performs one or both of supply of the decompressed fuel gas to the fuel cell stack and supply of the pressurized oxidant gas to the fuel cell stack. The fuel cell system described. Comprising temperature detecting means for detecting the temperature of the fuel cell stack;
The said control means performs the said low temperature starting process, when the temperature of the said fuel cell stack detected by the said temperature detection means is below 1st predetermined temperature, The said low temperature starting process is characterized by the above-mentioned. The fuel cell system according to any one of claims. Either one of a temperature detection means for detecting the temperature of the fuel cell stack and a moisture content detection means for detecting a residual moisture content inside the fuel cell stack;
Fuel gas temperature detection means for detecting the temperature of the fuel gas at the fuel cell stack inlet,
The control means includes the fuel gas temperature detected by the fuel gas temperature detection means, the temperature of the fuel cell stack detected by the temperature detection means, or the residual moisture of the fuel cell stack detected by the moisture amount detection means The power generation is started after the second predetermined temperature is set based on the amount and the fuel gas is heated until the second predetermined temperature is reached. The fuel cell system described. The said control means controls the heating of the said fuel heating means so that the heating temperature of fuel gas may become less than the 3rd predetermined temperature different from the said 1st, 2nd predetermined temperature. The fuel cell system described. Either one of a temperature detection means for detecting the temperature of the fuel cell stack and a moisture content detection means for detecting a residual moisture content inside the fuel cell stack;
A differential pressure detecting means for detecting a differential pressure between the pressure of the fuel gas supplied to the fuel cell stack and the pressure of the oxidant gas;
The control means sets a first predetermined pressure difference based on the temperature of the fuel cell stack detected by the temperature detection means or the residual moisture content of the fuel cell stack detected by the moisture content detection means, and an oxidant The fuel cell system according to any one of claims 1, 2, 3, and 4, wherein the power generation is started after the gas pressure is made higher than the fuel gas pressure by a first predetermined pressure difference. In the control means, the pressure difference between the pressure of the fuel gas and the pressure of the oxidant gas is less than a second predetermined pressure difference that is a limit pressure difference that a membrane electrode assembly constituting the fuel cell of the fuel cell stack can withstand. 8. The fuel cell system according to claim 7, wherein the pressure of either or both of the pressure of the fuel gas and the pressure of the oxidant is controlled. Comprising resistance detection means for detecting a resistance value of the fuel cell stack;
The fuel cell system according to any one of claims 5, 6, 7 and 8, wherein a residual moisture content inside the fuel cell stack is detected based on a resistance value detected by the resistance detection means. . Water content detection means for detecting the amount of water contained in the fuel gas;
Water removal means for removing water contained in the fuel gas,
The control means supplies the fuel gas into the fuel cell stack after removing the moisture contained in the fuel gas by the moisture removing means when the amount of moisture contained in the fuel gas is a predetermined amount or more. The fuel cell system according to any one of claims 1, 2, 3, 4, 5, 6, 7, 8, and 9. The fuel cell system according to claim 10, wherein the moisture removing unit includes a desiccant and a moisture separation membrane.

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