Shutdown purging method for fuel cell

Abstract

The invention discloses a shutdown purging method for a fuel cell, which enables the shutdown purging time of the fuel cell to be reduced to 6-8 minutes and greatly shortens the purging time of the fuel cell. The method comprises the following steps that S1, after a fuel cell test is completed, the electronic load is reduced to 0.1 A / cm < 2 >, the minimum air flow is adjusted to be supplied according to the air flow with the current density of 0.3-0.6 A / cm < 2 >, and the stoichiometric ratio of a hydrogen device to air is 1: (3-4); s2, setting the back pressure of a cathode and an anode to be 0 kPa; s3, reducing the load until the current of the fuel cell is 0.01 A / cm < 2 >-0.05 A / cm < 2 >, closing air, and introducing nitrogen through a mass flow meter of an air system; s4, when the minimum single voltage reaches 0.4 V or below, humidification of the air system is closed, and meanwhile, a current load is closed; s5, closing hydrogen and humidification of the anode, and introducing nitrogen through a mass flow meter of a hydrogen system on the anode side; s6, nitrogen is introduced into the two sides of the cathode and the anode for purging for 2-4 min; and S7, the temperature of the cooling system is set to be 0 DEG C, the flow is set to be 0 SLPM, and purging is stopped.

Description

Technical Field

[0001] The invention relates to the technical field of fuel cell testing, and in particular to a fuel cell shutdown purging method. Background Art

[0002] Proton exchange membrane fuel cells are highly efficient energy conversion devices that can directly convert chemical energy stored in hydrogen fuel and oxidant into electrical energy through electrochemical reactions. They are green and environmentally friendly, have high specific energy, can start quickly at low temperatures, and can run smoothly. They are considered to be an ideal power source to replace internal combustion engines. Therefore, performance, stability, and durability tests of proton exchange membrane fuel cells are essential. The shutdown purge strategy after the test is also an important part of this.

[0003] Most of the existing shutdown purge solutions for proton exchange membrane fuel cells are to directly pass dry / wet nitrogen to the anode and cathode of the fuel cell after the test, and purge at open circuit voltage (OCV). This purge method generally takes 20 to 30 minutes, which is long and causes a certain amount of gas waste. In addition, the proton exchange membrane fuel cell will continue to be at a high OCV for a long time during the purge process, which will corrode the carbon carrier of the cathode catalyst layer and accelerate the degradation of the proton membrane to a certain extent, shortening the life of the proton exchange membrane fuel cell. Summary of the invention

[0004] In view of the above problems, the present invention provides a fuel cell shutdown purge method, which reduces the fuel cell shutdown purge time to 6 to 8 minutes, greatly shortens the fuel cell purge time, effectively reduces gas waste, and can quickly reduce the fuel cell OCV, reduce the corrosion of the proton exchange membrane fuel cell membrane electrode caused by long-term high OCV and slow down the degradation of the proton membrane.

[0005] A fuel cell shutdown purge method, the technical solution of which is as follows: a fuel cell stack test bench includes a hydrogen system, an air system, a cooling system, an electronic load, voltage acquisition, and a nitrogen system, wherein the hydrogen system inputs hydrogen to the fuel cell stack through a corresponding mass flow meter, the air system inputs air to the fuel cell stack through a corresponding mass flow meter, the nitrogen system is connected in parallel to a three-way pipeline of the hydrogen system and a three-way pipeline of the air system, and the electronic load provides a current load to the fuel cell stack, characterized in that it includes the following steps:

[0006] S1. After the fuel cell test is completed, reduce the electronic load to 0.1A / cm 2 The minimum air volume is adjusted to 0.3~0.6A / cm 2 The gas supply of current density, in which the stoichiometric ratio of hydrogen to air is 1:(3-4);

[0007] S2, the cathode and anode back pressure is set to 0 kPa;

[0008] S3, reduce the load to the fuel cell to 0.01A / cm 2 ~0.05A / cm 2 The current is set to 0.10V, the air is turned off, and nitrogen is introduced through the mass flow meter of the air system;

[0009] S4, when the lowest single voltage reaches below 0.4V, turn off the humidification of the air system and turn off the current load;

[0010] S5, shut down the hydrogen and humidification at the anode, and introduce nitrogen through the mass flow meter of the hydrogen system on the anode side;

[0011] S6. Purge nitrogen gas into both sides of the cathode and anode for 2 to 4 minutes;

[0012] S7. Set the temperature of the cooling system to 0°C, the flow rate to 0SLPM, and stop purging.

[0013] It is further characterized by:

[0014] The flow rate FL of nitrogen in step S6 氮气 Set to 1 / 2 to 7 / 8 of the full nitrogen flow rate of the test bench;

[0015] The hydrogen system and the air system are controlled by corresponding mass flow meters to control the flow of gas entering the fuel cell stack, the corresponding three-way solenoid valves are used to control the type of gas entering the fuel cell stack and whether the gas passes through the humidification tank, and the back pressure valves corresponding to the hydrogen system and the air system are used to control the back pressure of the fuel cell stack;

[0016] The temperature of the fuel cell stack is controlled by the cooling system, and finally the temperature of the stack is made to be 0°C;

[0017] The voltage acquisition monitors the battery voltage in real time to ensure efficient purging;

[0018] During purging, the volume of the gas is calculated based on the current density, reaction area, number of cells, and stoichiometric ratio. The volume flow rate of the gas is calculated as follows:

[0019] Hydrogen volume flow calculation Vhydrogen = 0.00696*iANλ;

[0020] Air volume flow calculation Vair = 0.01657*iANλ;

[0021] Where V hydrogen and V empty are in L / min, i is the current density in A / cm 2 , A is the reaction area, unit is cm 2 , N is the number of battery cells, and λ is the chemical stoichiometric ratio.

[0022] After adopting the method of the present invention, the shutdown purge time of the fuel cell is reduced to 6-8 minutes, which greatly shortens the fuel cell purge time, effectively reduces gas waste, and can quickly reduce the fuel cell OCV, reduce the corrosion of the proton exchange membrane fuel cell membrane electrode caused by long-term high OCV and slow down the degradation of the proton membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The present invention is a schematic structural diagram of a fuel cell test bench applicable to the method of the present invention. DETAILED DESCRIPTION

[0024] See Figure 1 The stack test bench includes a hydrogen system, an air system, a cooling system, an electronic load, a voltage acquisition system, and a nitrogen system. The hydrogen system inputs hydrogen to the stack through a corresponding mass flow meter, and the air system inputs air to the stack through a corresponding mass flow meter. The nitrogen system is connected in parallel to the three-way pipeline of the hydrogen system and the three-way pipeline of the air system. The electronic load provides a current load to the stack. A fuel cell shutdown purge method includes the following steps:

[0025] S1. After the fuel cell test is completed, reduce the electronic load to 0.1A / cm 2 The minimum air volume is adjusted to 0.3~0.6A / cm 2 The gas supply of current density, in which the stoichiometric ratio of hydrogen to air is 1:(3-4);

[0026] S2, the cathode and anode back pressure is set to 0 kPa;

[0027] S3, reduce the load to the fuel cell to 0.01A / cm 2 ~0.05A / cm 2 The current is set to 0.10V, the air is turned off, and nitrogen is introduced through the mass flow meter of the air system;

[0028] S4, when the lowest single voltage reaches below 0.4V, turn off the humidification of the air system and turn off the current load;

[0029] S5, shut down the hydrogen and humidification at the anode, and introduce nitrogen through the mass flow meter of the hydrogen system on the anode side;

[0030] S6, nitrogen is passed through both sides of the cathode and anode for 2 to 4 minutes, and the flow rate of nitrogen is FL 氮气 Set to 1 / 2 to 7 / 8 of the full nitrogen flow rate of the test bench;

[0031] S7. Set the temperature of the cooling system to 0°C, the flow rate to 0SLPM, and stop purging.

[0032] In specific implementation, the corresponding mass flow meters in the hydrogen system and the air system control the flow of gas entering the fuel cell stack, the corresponding three-way solenoid valves control the type of gas entering the fuel cell stack and whether the gas is humidified by the humidification tank, and the back pressure valves corresponding to the hydrogen system and the air system control the back pressure of the fuel cell stack;

[0033] The temperature of the fuel cell stack is controlled by the cooling system, and finally the temperature of the stack is made to be 0°C;

[0034] Voltage acquisition monitors the battery voltage in real time to ensure efficient purging.

[0035] During the specific operation, when purging, the volume of the gas is calculated based on the current density, reaction area, number of battery cells, and stoichiometric ratio. The volume flow rate of the gas is calculated as follows:

[0036] Hydrogen volume flow calculation (L / min): Vhydrogen = 0.00696*iANλ;

[0037] Air volume flow calculation (L / min) Vair = 0.01657*iANλ;

[0038] Where i is the current density (A / cm 2 ), A is the reaction area (cm 2 ), N is the number of battery cells, and λ is the stoichiometric ratio.

[0039] It reduces the fuel cell shutdown purge time to 6 to 8 minutes, greatly shortens the fuel cell purge time, effectively reduces gas waste, and can quickly reduce the fuel cell OCV, reduce the corrosion of the proton exchange membrane fuel cell membrane electrode caused by long-term high OCV and slow down the degradation of the proton membrane.

[0040] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0041] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A fuel cell shutdown purge method, the stack test bench includes a hydrogen system, an air system, a cooling system, an electronic load, a voltage acquisition, and a nitrogen system, wherein the hydrogen system inputs hydrogen to the stack through a corresponding mass flow meter, the air system inputs air to the stack through a corresponding mass flow meter, the nitrogen system is connected in parallel to the three-way pipeline of the hydrogen system and the three-way pipeline of the air system, and the electronic load provides a current load to the stack, characterized in that: It includes the following steps: S1. After the fuel cell test is completed, reduce the electronic load to 0.1A / cm 2 The minimum air volume is adjusted to 0.3~0.6A / cm 2 The gas supply of current density, in which the stoichiometric ratio of hydrogen to air is 1:(3-4); S2, the cathode and anode back pressure is set to 0kPa; S3, reduce the load to the fuel cell to 0.01A / cm 2 ~0.05A / cm 2 The current is set to 0.10V, the air is turned off, and nitrogen is introduced through the mass flow meter of the air system; S4, when the lowest single voltage reaches below 0.4V, turn off the humidification of the air system and turn off the current load; S5, shut down the hydrogen and humidification at the anode, and introduce nitrogen through the mass flow meter of the hydrogen system on the anode side; S6. Purge nitrogen gas into both sides of the cathode and anode for 2 to 4 minutes; S7. Set the temperature of the cooling system to 0°C, the flow rate to 0SLPM, and stop purging.

2. A fuel cell shutdown purge method according to claim 1, characterized in that: The flow rate FL of nitrogen in step S6 氮气 Set to 1 / 2 to 7 / 8 of the full nitrogen flow rate on the test bench.

3. A fuel cell shutdown purge method according to claim 1, characterized in that: The hydrogen system and the air system use corresponding mass flow meters to control the flow of gas entering the fuel cell stack, use corresponding three-way solenoid valves to control the type of gas entering the fuel cell stack and whether the gas passes through the humidification tank, and use corresponding back pressure valves in the hydrogen system and the air system to control the back pressure of the fuel cell stack.

4. A fuel cell shutdown purge method according to claim 1, characterized in that: The temperature of the fuel cell stack is controlled by the cooling system and eventually the temperature of the stack is brought to 0°C.

5. A fuel cell shutdown purge method according to claim 1, characterized in that: The voltage acquisition monitors the battery voltage in real time.

6. A fuel cell shutdown purge method according to claim 1, characterized in that: During purging, the volume of the gas is calculated based on the current density, reaction area, number of cells, and stoichiometric ratio. The volume flow rate of the gas is calculated as follows: Hydrogen volume flow calculation Vhydrogen = 0.00696*iANλ; Air volume flow calculation Vair = 0.01657*iANλ; Where V hydrogen and V empty are in L / min, i is the current density in A / cm 2 , A is the reaction area, unit is cm 2 , N is the number of battery cells, and λ is the chemical stoichiometric ratio.

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