A hydrogen fuel cell stack maintenance system and method

Abstract

The present application relates to hydrogen fuel cell stack maintenance technical field, especially to a kind of for hydrogen fuel cell stack maintenance system, by hydrogen fuel cell stack is connected into system, maintenance cleaning is carried out, the import side of hydrogen fuel cell stack is equipped with anode flow passage import anode flow passage export, and the export side is equipped with cathode flow passage import and cathode flow passage export, system includes: nitrogen supply unit, cleaning unit, rinsing unit, waste water collection unit and control unit, unified control by control unit, pipe path switching is carried out according to preset program by tangential valve assembly, can automatically complete to hydrogen fuel cell stack purging, rinsing, cleaning and drying maintenance process, effectively remove the impurity ion accumulated in the stack, restore stack performance, cleaning effect is good, and cleaning cost is low.The present application also correspondingly discloses a kind of for hydrogen fuel cell stack maintenance method.

Description

Technical Field

[0001] This invention relates to the field of hydrogen fuel cell stack maintenance technology, and in particular to a hydrogen fuel cell stack maintenance system and method. Background Technology

[0002] With the rapid development of the hydrogen energy industry, hydrogen fuel cell technology has been widely applied in various fields such as land, sea, and air. Among them, marine hydrogen fuel cell systems and portable hydrogen production fuel cell systems are currently research hotspots. However, these two types of fuel cell systems generally face a common problem in practical use: significant performance degradation of the fuel cell stack and limited service life.

[0003] For marine hydrogen fuel cell systems, marine salt spray environments are a key factor leading to stack degradation. Chloride ions (Cl-) in the salt spray... - ) and sodium ions (Na + A small amount of the substance can enter the fuel cell stack through the air system and gradually accumulate on the surface of the proton exchange membrane and catalyst layer, causing catalyst poisoning and damage to the membrane electrode structure.

[0004] For portable hydrogen fuel cell systems that produce hydrogen on-site, the main reason for performance degradation lies in the instability of the gas source quality. These systems typically use on-site hydrogen production, but the purity of the produced hydrogen is difficult to match that of industrially produced high-purity hydrogen, and may contain trace amounts of alkaline vapors, impurities, etc. Simultaneously, the air quality in the operating environment is difficult to guarantee; impurities from highly polluted air or high-salt-spray environments can enter the fuel cell stack with the airflow. Although gas source filtration systems are installed on the pipelines, trace amounts or small quantities of impurities inevitably enter the fuel cell stack during long-term operation.

[0005] Studies have shown that the main impurities entering the fuel cell stack include: alkaline vapor and potassium (K). + Na + Mg 2+ Ca 2+ Cl - SO4 2- These impurities accumulate during long-term operation of the fuel cell stack: on the one hand, ionic impurities contaminate the proton exchange membrane, reducing proton conductivity and increasing ohmic resistance; on the other hand, some impurities adsorb onto the catalyst surface, covering active sites and reducing catalytic efficiency. These combined effects gradually cause irreversible performance degradation in the hydrogen fuel cell stack.

[0006] Currently, there is a lack of effective online or offline maintenance methods to address the performance degradation caused by the accumulation of such impurities. If hydrogen fuel cell stacks are not maintained and serviced in a timely manner, irreversible degradation of the stack's electrical performance can occur in severe cases, significantly shortening its lifespan. Traditional maintenance methods often require disassembling the stack for chemical cleaning, which is complex, costly, and the disassembly and reassembly process itself may cause secondary damage to the stack. Summary of the Invention

[0007] To address at least one of the aforementioned technical problems, this invention proposes a maintenance system and method for hydrogen fuel cell stacks.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: The first aspect of this invention provides a maintenance system for a hydrogen fuel cell stack. This system connects the hydrogen fuel cell stack to the system for maintenance and cleaning. The hydrogen fuel cell stack has an anode flow channel inlet and an anode flow channel outlet on its inlet side, and a cathode flow channel inlet and a cathode flow channel outlet on its outlet side. The system includes: A nitrogen supply unit is used to provide nitrogen required for the maintenance of the hydrogen fuel cell stack in purging mode and drying mode. The nitrogen supply unit is located on the inlet side of the hydrogen fuel cell stack. A cleaning unit is provided in cleaning mode to provide cleaning fluid required for the maintenance of the hydrogen fuel cell stack. The cleaning unit is located on the outlet side of the hydrogen fuel cell stack. A rinsing unit is used to provide rinsing fluid required for the maintenance of the hydrogen fuel cell stack in rinsing mode. The rinsing unit is located on the outlet side of the hydrogen fuel cell stack. A wastewater collection unit is used to collect wastewater after purging, drying, cleaning and rinsing. The wastewater collection unit is located on the inlet side and the outlet side, respectively. The inlet-side pipeline has one end connected to the inlet of the anode flow channel and the inlet of the cathode flow channel, respectively, and the other end connected to the nitrogen supply unit and the inlet-side wastewater collection unit, respectively. The outlet-side pipeline has one end connected to the outlet of the anode flow channel and the outlet of the cathode flow channel, and the other end connected to the cleaning unit, the rinsing unit and the wastewater collection unit on the outlet side. A tangential valve assembly is installed on the inlet-side pipeline and the outlet-side pipeline, and is used to switch between different modes by switching the pipeline path; The control unit is electrically connected to the nitrogen supply unit, cleaning unit, rinsing unit, wastewater collection unit, and tangential valve assembly. It is used to control the tangential valve assembly to switch between purging mode, drying mode, cleaning mode, and rinsing mode under maintenance parameter conditions, so as to realize the maintenance and cleaning of the hydrogen fuel cell stack.

[0009] Preferably, the tangential valve assembly includes: The first directional valve has a P1 port that is connected to the anode flow channel inlet and the cathode flow channel inlet of the fuel cell, respectively, and a C port and a D port that are connected to the wastewater collection unit and the nitrogen supply unit, respectively. The second tangential valve has a P2 port that is connected to the cathode flow channel outlet and the cathode flow channel outlet of the fuel cell respectively, and an A port that is connected to the wastewater collection unit. The third tangential valve has a P3 port that communicates with the B port of the second tangential valve, and an E port and a F port that communicate with the cleaning unit and the rinsing unit respectively. A water pump is provided on the pipeline between the B port of the second tangential valve and the P3 port of the third tangential valve.

[0010] Preferably, the nitrogen supply unit includes a nitrogen tank and a pressure reducing valve and a second solenoid valve arranged sequentially on the nitrogen tank outlet pipeline. The second solenoid valve is connected to port C of the first tangential valve. Under the control of the control unit, the nitrogen supply unit performs pulse purging in a pulse manner. The pressure holding time of the pulse purging is 5-60 seconds, the pressure release time is 1-10 seconds, and the purging pressure is 20-50 kPa.

[0011] Preferably, the wastewater collection unit includes a conductivity meter and a first wastewater tank connected in sequence to port D of the first tangential valve, and a first solenoid valve and a second wastewater tank connected in sequence to port A of the second tangential valve; the conductivity meter is used to monitor the conductivity of deionized water flowing to the first wastewater tank in the cleaning mode, and the control unit is configured to stop the cleaning mode when the monitored value of the conductivity meter is in the range of 1-20 μs / cm.

[0012] Preferably, the rinsing unit includes a rinsing water tank and a first thermometer for measuring the temperature of the rinsing solution in the rinsing water tank. The rinsing solution is a mixed solution of dilute acid and deionized water with a concentration of 0.05-1 mol / L and a temperature of 20-35°C.

[0013] Preferably, the cleaning unit includes a cleaning water tank and a second thermometer for measuring the temperature of the cleaning fluid in the cleaning water tank. The cleaning fluid is deionized water with a conductivity of 0.0625-0.2 μs / cm. The control unit is configured to simultaneously shut down the first solenoid valve and the water pump when the temperature monitored by the first or second thermometer is greater than 35°C or less than 15°C, or when the temperature monitored by the second thermometer is greater than 35°C or less than 15°C.

[0014] Preferably, the maintenance system further includes a first pressure sensor and a second pressure sensor. The first pressure sensor is disposed on the inlet side pipeline and connected to the P1 port of the first tangential valve, and is used to measure the gas or liquid pressure at the P1 port of the first tangential valve. The second pressure sensor is disposed on the main pipeline on the outlet side and connected to the P2 port of the second tangential valve, and is used to measure the gas or liquid pressure at the P2 port of the second tangential valve. The control unit is configured to perform pressure relief when the pressure value of the first pressure sensor and / or the second pressure sensor is greater than 80 kPa or the pressure difference between the first pressure sensor and the second pressure sensor is greater than 25 kPa.

[0015] Preferably, the control unit includes a system controller, a display connected to the system controller, and a power supply and a relay connected in sequence to the system controller.

[0016] A second aspect of the present invention provides a method for maintaining a hydrogen fuel cell stack, applied to a hydrogen fuel cell stack maintenance system as described in the first aspect, comprising the following steps: S1: Connect the hydrogen fuel cell stack to be maintained to the maintenance system, and connect its anode flow channel inlet, anode flow channel outlet, cathode flow channel inlet and cathode flow channel outlet to the nitrogen supply unit, cleaning unit, rinsing unit and wastewater collection unit through the inlet side pipeline and the outlet side tangential pipeline, respectively. S2: Control the tangential valve assembly through the control unit to switch to the purging mode, start the nitrogen supply unit, and perform nitrogen pulse purging on the internal flow channel of the hydrogen fuel cell stack in a pulse manner; S3: Control the tangential valve assembly through the control unit to switch to the rinsing mode, start the rinsing unit, and let the rinsing liquid flow through the internal flow channel of the hydrogen fuel cell stack for cyclic rinsing; S4: Repeat steps S2 and S3 to perform cyclic purging and rinsing on the hydrogen fuel cell stack, and finally end the cycle in purging mode. S5: Control the tangential valve assembly through the control unit to switch to the cleaning mode, start the cleaning unit, and allow deionized water to flow through the internal flow channel of the hydrogen fuel cell stack for circulating cleaning; S6: Repeat steps S5 and S2 to perform cyclic purging and cleaning on the hydrogen fuel cell stack; monitor the conductivity of the waste liquid after cleaning in real time using the conductivity meter; when the monitored conductivity value reaches a preset range, the control unit stops the cleaning mode. S7: The control unit controls the tangential valve assembly to switch to the drying mode and perform nitrogen purging and drying treatment on the hydrogen fuel cell stack.

[0017] Preferably, pure hydrogen tests are performed before and after maintenance of the hydrogen fuel cell stack to calibrate the performance of the fuel cell stack before and after maintenance.

[0018] Compared with the prior art, the present invention has the following beneficial effects: This invention organically combines a nitrogen supply unit, a rinsing unit, a cleaning unit, a wastewater collection unit, and a tangential valve assembly. Under unified control by a control unit, the tangential valve assembly switches pipeline paths according to a preset program, automatically completing the purging, rinsing, cleaning, and drying maintenance process of the hydrogen fuel cell stack. This effectively removes accumulated impurity ions from the stack, restoring its performance. The cleaning effect is excellent, and the cleaning cost is low. The system features fully automatic monitoring and automatic protection logic. During maintenance and cleaning, when abnormalities in key parameters are detected, the protection strategy is automatically activated, maximizing the protection of the fuel cell stack during the maintenance and cleaning process. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a structure for a hydrogen fuel cell stack maintenance system (purge mode medium flow direction); Figure 2 This is a schematic diagram of the structure of a hydrogen fuel cell stack maintenance system (medium flow direction in rinsing and cleaning modes); Figure 3 A flowchart of a method for maintaining a hydrogen fuel cell stack; Figure 4 Performance curves of hydrogen fuel cell stacks before and after maintenance; In the diagram: 1. Hydrogen fuel cell stack; 2. Anode flow channel outlet; 3. Anode flow channel inlet; 4. Cathode flow channel inlet; 5. Cathode flow channel outlet; 6. Cleaning water tank; 7. Water pump; 8. First tangential valve; 9. First pressure sensor; 10. Second pressure sensor; 11. Second tangential valve; 12. First wastewater tank; 13. Conductivity meter; 14. Nitrogen cylinder; 15. First solenoid valve; 16. Second solenoid valve; 17. Second wastewater tank; 18. Power supply; 19. Relay; 20. System controller; 21. Display; 22. Pressure reducing valve; 23. Rinse water tank; 24. Third tangential valve; 25. First thermometer; 26. Second thermometer. Detailed Implementation

[0020] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments of the present invention.

[0021] Example 1

[0022] Please refer to Figure 1 and Figure 2 As shown, a maintenance system for a hydrogen fuel cell stack 1 is provided. The hydrogen fuel cell stack 1 is connected to the system for maintenance and cleaning. The hydrogen fuel cell stack 1 has an anode flow channel inlet 3 and an anode flow channel outlet 2 on the inlet side, and a cathode flow channel inlet 4 and a cathode flow channel outlet 5 on the outlet side. The system mainly includes a nitrogen supply unit, a cleaning unit, a rinsing unit, a wastewater collection unit, and a control unit, as well as an inlet-side tangential pipeline and an outlet-side pipeline connecting the system and the hydrogen fuel cell stack 1.

[0023] Specifically, in this embodiment, a first tangential valve 8 is provided on the inlet-side pipeline. The first tangential valve 8 has a P1 port, a C port, and a D port. Among them, the P1 port, after passing through the second pressure sensor 10, sequentially passes through the inlet-side main pipeline and two inlet-side branch pipelines connected to the inlet-side main pipeline, and is connected to the anode flow channel inlet 3 and the cathode flow channel inlet 4 of the fuel cell, respectively. The C port and the D port are connected to the first wastewater tank 12 and the nitrogen supply unit, respectively, through pipelines.

[0024] It should be noted that, in this embodiment, the nitrogen supply unit includes a nitrogen tank and a pressure reducing valve 22 and a second solenoid valve 16 sequentially arranged on the nitrogen tank outlet pipeline. The second solenoid valve 16 is connected to port C of the first tangential valve 8. The pipeline between the first wastewater tank 12 and port D is equipped with a device for monitoring the conductivity of the deionized water flowing into the first wastewater tank 12 during the cleaning mode.

[0025] The outlet-side pipeline is equipped with a second tangential valve 11 and a third tangential valve 24 in sequence. The second tangential valve 11 has ports P2, A, and B, and the third tangential valve 24 has ports P3, E, and F. Port P2, after passing through the first pressure sensor 9, connects sequentially to the main outlet-side pipeline and two outlet-side branches connected to the main outlet-side pipeline, respectively, to the anode inlet 3 and the cathode inlet 4 of the fuel cell. Port B of the second tangential valve 11 is connected to port P3 of the third tangential valve 24 via a water pump 7. Port A of the second tangential valve 11 is connected to the second wastewater tank 17 via a first solenoid valve 15. Ports E and F of the third tangential valve 24 are connected to the cleaning unit and the rinsing unit, respectively.

[0026] It should be noted that, in this embodiment, the cleaning unit includes a cleaning water tank 6 and a second thermometer 26 for measuring the temperature of the cleaning fluid in the cleaning water tank 6. The cleaning fluid is deionized water with a conductivity of 0.0625-0.2 μs / cm.

[0027] The rinsing unit includes a rinsing water tank 23 and a first thermometer 25 for measuring the temperature of the rinsing solution in the rinsing water tank 23. The rinsing solution is a mixed solution of dilute acid and deionized water with a concentration of 0.05-1 mol / L and a temperature of 20-35℃.

[0028] Meanwhile, in this embodiment, the control unit is configured to stop the cleaning mode when the monitored value of the conductivity meter 13 is within the range of 1-20 μs / cm. When the monitored temperature of the first thermometer 25 or the second thermometer 26 is greater than 35°C or less than 15°C, the first solenoid valve 15 and the water pump 7 are simultaneously shut off. When the pressure value of the first pressure sensor 9 and / or the second pressure sensor 10 is greater than 80 kPa or the pressure difference between the first pressure sensor 9 and the second pressure sensor 10 is greater than 25 kPa, pressure relief is performed.

[0029] It should be noted that the control unit in this embodiment includes at least a system controller 20, a display 21 connected to the system controller 20, and a power supply 18 and a relay 19 sequentially connected to the system controller 20. The display 21 is a touch-screen human-machine interface display 21, which can set parameters for various maintenance and cleaning modes according to the type, size, and potential severity of contamination of the fuel cell stack. It also displays the working mode status and key parameter values ​​in real time, and provides audio and visual prompts upon completion of maintenance and cleaning. It is understood that the control principle of the control unit in this embodiment is prior art, and will not be elaborated upon here.

[0030] This embodiment provides a maintenance system for hydrogen fuel cell stack 1. Each unit of the system is controlled by a control unit. The tangential valve assembly switches pipeline paths according to a preset program, which can automatically complete the purging, rinsing, cleaning and drying maintenance process of hydrogen fuel cell stack 1, effectively removing impurity ions accumulated inside the stack and restoring the stack performance.

[0031] Specifically, the nitrogen supply unit, rinsing unit, cleaning unit, and wastewater collection unit form a multi-stage synergistic cleaning chain of "pulse impact - chemical dissolution - pure water rinsing - gas drying" through automatic switching of the tangential valve assembly. Specifically, the tangential valve assembly achieves seamless switching between the gas and liquid paths, allowing the fuel cell stack to handle multiple media within the same piping system without disassembly. The control unit receives real-time data from pressure sensors, thermometers, and conductivity meters 13, dynamically adjusting operating parameters to form a closed-loop control of "monitoring-judgment-execution." The alternation of nitrogen pulse purging and liquid rinsing utilizes the synergistic effect of gas-liquid two-phase flow, first using high-pressure gas to loosen impurities, then using chemical solution to dissolve ionic contaminants; this alternating process significantly improves cleaning efficiency.

[0032] Example 2

[0033] Please refer to Figure 3 As shown, this embodiment provides a maintenance method for a hydrogen fuel cell stack 1, which mainly performs maintenance and cleaning of the hydrogen fuel cell stack 1 through purging mode, rinsing mode, cleaning mode, and drying mode. It includes the following steps: S1: Connect the hydrogen fuel cell stack 1 to be maintained to the maintenance system, and connect its anode flow channel inlet 3, anode flow channel outlet 2, cathode flow channel inlet 4 and cathode flow channel outlet 5 to the nitrogen supply unit, cleaning unit, rinsing unit and wastewater collection unit through the inlet side tangential pipeline and the outlet side tangential pipeline, respectively.

[0034] It should be noted that the connection method of each unit of the system has been described in detail in Embodiment 1, and will not be repeated here.

[0035] S2: Control the tangential valve assembly through the control unit to switch to the purging mode, start the nitrogen supply unit, and perform nitrogen pulse purging on the internal flow channel of the hydrogen fuel cell stack 1 in a pulse manner.

[0036] It should be noted that, as Figure 1 As shown, in purging mode, the system control unit activates the nitrogen supply unit. Nitrogen flows out of the nitrogen tank, passes through the pressure reducing valve 22 to regulate the pressure (operating pressure range 20-50 kPa), then through the second solenoid valve 16, and enters port C of the first tangential valve 8. Through the internal path switching of the first tangential valve 8, nitrogen flows out from its P1 port and enters the anode flow channel inlet 3 and the cathode flow channel inlet 4 of the fuel cell stack through the inlet side pipeline.

[0037] After nitrogen enters the fuel cell stack, it flows along the flow channels, carrying away residual free water and some loose impurities. Subsequently, the nitrogen and impurities flow out from the anode flow channel outlet 2 and cathode flow channel outlet 5 on the fuel cell stack outlet side, and enter the P2 port of the second tangential valve 11 through the outlet side pipeline. Through the internal path switching of the second tangential valve 11, the gas flow exits from its A port and enters the second wastewater tank 17.

[0038] To achieve the best purging effect, the control unit controls the nitrogen gas to work in a pulse mode. Specifically, in this embodiment, the purging is carried out in a cycle of holding pressure for 5-60 seconds and releasing pressure for 1-10 seconds, with a single purging lasting 2-15 minutes.

[0039] In purging mode, the cooperation between pressure reducing valve 22 and second solenoid valve 16 enables control of nitrogen pressure and on / off state. The pulse timing of the control unit allows nitrogen to accumulate pressure during the pressure holding phase and generate instantaneous impacts during the pressure release phase. This "energy storage-release" pulse effect effectively breaks down and removes stubborn impurities adhering to the flow channel walls. Synchronous switching between the first tangential valve 8 and the second tangential valve 11 ensures smooth airflow path switching while directing waste gas and wastewater into the second wastewater tank 17 to avoid cross-contamination. Pressure sensors monitor the pressure at both ends of the fuel cell stack in real time during this process. When a pulse impact causes an instantaneous pressure anomaly, the control unit responds immediately, achieving a coordinated balance between "efficient purging" and "safety protection."

[0040] S3: Control the tangential valve assembly through the control unit to switch to the rinsing mode, start the rinsing unit, and let the rinsing liquid flow through the internal flow channel of the hydrogen fuel cell stack 1 for cyclic rinsing.

[0041] It should be noted that, as Figure 2 The rinsing mode shown is used to dissolve alkaline impurities (such as potassium, sodium, and calcium ions) accumulated inside the fuel cell stack. The rinsing tank 23 contains a mixed solution of dilute acid and deionized water with a concentration of 0.05-1 mol / L, and the temperature is controlled at 20-35℃.

[0042] In rinsing mode, the control unit starts water pump 7 and controls the third directional valve 24 to connect its P3 port and F port. The rinsing solution flows out of the rinsing tank 23, enters through port F of the third directional valve 24, exits through port P3, and then is pressurized by water pump 7 before entering port B of the second directional valve 11. Through internal path switching of the second directional valve 11, the rinsing solution flows out from port P2 of the second directional valve 11, passes through the outlet side pipeline, and enters the fuel cell stack in reverse direction from the anode flow channel outlet 2 and cathode flow channel outlet 5 on the fuel cell stack outlet side.

[0043] The rinsing solution flows counter-currently inside the fuel cell stack (compared to the flow direction of nitrogen gas), making full contact with and neutralizing the impurities adhering to the flow channel walls. The rinsing solution, now carrying impurities, flows out from the anode flow channel inlet 3 and cathode flow channel inlet 4 on the fuel cell stack inlet side, and enters the P1 port of the first tangential valve 8 through the inlet-side pipeline. Through internal path switching within the first tangential valve 8, the rinsing solution flows out from its D port, passes through the first solenoid valve 15, and enters the first wastewater tank 12.

[0044] It should be noted that during the rinsing process, the rinsing fluid flow rate is controlled at 1-20L / min, the pressure difference before and after the fuel cell stack is maintained at 2-20kPa, and each rinsing session lasts 2-15 minutes.

[0045] Understandably, in this embodiment, the first thermometer 25 in the rinsing tank 23 works in conjunction with the heating / cooling device to maintain the rinsing solution within the optimal reaction temperature range of 20-35°C. Excessive temperature can damage the proton exchange membrane, while excessively low temperature reduces the chemical reaction rate, thus ensuring the effectiveness of the chemical cleaning. The coordinated operation of the water pump 7 and the tangential valve assembly allows the rinsing solution to enter the fuel cell stack in a reverse flow, alternating with the forward purging flow, preventing impurities from being repeatedly pushed in the same direction and clogging the flow channels. The control unit dynamically adjusts the speed of the water pump 7 based on the pressure difference value fed back by the pressure sensor, ensuring that the rinsing solution flow rate is always maintained at the optimal rinsing force, guaranteeing effective rinsing of the flow channel walls while preventing excessive pressure differential from damaging the internal structure of the fuel cell stack.

[0046] S4: Repeat steps S2 and S3 to perform cyclic purging and rinsing of the hydrogen fuel cell stack 1, and finally end the cycle in purging mode.

[0047] It should be noted that the alternating cycle of rinsing and purging has the following effects: After the rinsing solution wets and dissolves ionic impurities, the residual liquid in the flow channel may cause the dissolved impurities to be deposited again in dead corners. At this time, nitrogen pulse purging is inserted, and the high-speed airflow can blow out these residual droplets along with the impurities, realizing a complete cleaning cycle of "dissolving-discharging". At the same time, nitrogen purging changes the humidification state in the flow channel, allowing the next rinse solution to better contact the new wall area and avoid cleaning blind spots caused by liquid film coverage. Furthermore, the two-phase flow effect generated by the alternation of gas and liquid creates a slug-like flow pattern within the flow channel, where gas and liquid plugs alternately pass through. This results in a much higher shear force on the wall surface compared to a single liquid-phase flow, enabling more effective removal of attached impurities. In this embodiment, rinsing and purging cycles are performed 2-10 times. The specific number of cycles can be selected according to actual needs.

[0048] S5: Control the tangential valve assembly through the control unit to switch to the cleaning mode, start the cleaning unit, and allow deionized water to flow through the internal flow channel of the hydrogen fuel cell stack 1 for circulation cleaning.

[0049] It should be noted that, as Figure 2 As shown, the cleaning mode uses high-purity deionized water to rinse away residual rinsing fluid and dissolved impurity ions inside the fuel cell stack. The conductivity of the deionized water in cleaning tank 6 is controlled at 0.0625-0.2 μs / cm, and the temperature is 20-35℃.

[0050] In cleaning mode, the control unit starts water pump 7 and controls the third directional valve 24 to connect its P3 port and E port. Deionized water flows out from the cleaning water tank 6, enters through the E port of the third directional valve 24, flows out from its P3 port, is pressurized by water pump 7, and enters the B port of the second directional valve 11. Through the internal path switching of the second directional valve 11, deionized water flows out from its P2 port, passes through the outlet side pipeline, and enters the fuel cell stack in reverse from the anode flow channel outlet 2 and the cathode flow channel outlet 5 on the fuel cell stack outlet side.

[0051] Deionized water flows inside the fuel cell stack, diluting and carrying away residual rinsing solution and impurity ions. Subsequently, the water flows out from the anode inlet 3 and cathode inlet 4 on the fuel cell stack inlet side, and enters the P1 port of the first tangential valve 8 through the inlet-side pipeline. Through internal path switching within the first tangential valve 8, the deionized water flows out from its D port, passes through the first solenoid valve 15, and finally enters the first wastewater tank 12. Before entering the first wastewater tank 12, the water flow passes through a conductivity meter 13 for real-time monitoring of conductivity values.

[0052] During the cleaning process, the deionized water flow rate is controlled at 1-20L / min, the pressure difference before and after the fuel cell stack is maintained at 2-20kPa, and each cleaning session lasts 2-10 minutes.

[0053] Understandably, at the start of cleaning, the initial conductivity of the deionized water in the cleaning tank 6 is approximately 0.0625-0.2 μs / cm. After the cleaning fluid passes through the hydrogen fuel cell stack 1, the cleaning fluid carrying impurities will increase the value monitored by the conductivity meter 13 at the outlet. When the conductivity value monitored by the conductivity meter 13 is at the cleaning stop threshold (1-20 μs / cm) preset by the control unit, the control unit stops the cleaning mode, thereby ensuring that the cleaning endpoint is determined based on evidence and avoiding over-cleaning or under-cleaning.

[0054] Meanwhile, the switching of the third tangential valve 24 between port E (cleaning) and port F (rinsing) enables the cleaning unit and the rinsing unit to share the same pumping and piping system, reducing system complexity and manufacturing costs.

[0055] S6: Repeat steps S5 and S2 to perform cyclic purging and cleaning of the hydrogen fuel cell stack 1; monitor the conductivity of the waste liquid after cleaning in real time using a conductivity meter 13; when the monitored conductivity value reaches the preset range, the control unit stops the cleaning mode.

[0056] It should be noted that after one cleaning cycle is completed, the system automatically switches to purging mode and executes one purging cycle. This "cleaning-purging" cycle is repeated 2-10 times. During the drainage process after each cleaning cycle, the conductivity meter 13 continuously monitors the conductivity of the deionized water flowing into the first wastewater tank 12. When the monitored conductivity value drops to the range of 1-20 μs / cm, it indicates that the impurities inside the fuel cell stack have been basically removed, and the control unit automatically stops the cleaning mode.

[0057] Understandably, the alternating cycle of cleaning and purging continues the "gas-liquid alternation synergistic effect" mechanism of the rinsing stage, further enhancing the thoroughness of cleaning. The closed-loop feedback formed by the conductivity meter 13 and the control unit eliminates reliance on manual experience in the cleaning process, achieving consistency and repeatability of cleaning results. Simultaneously, the conductivity meter 13, located at the front end of the drain pipe rather than inside the water tank, can reflect the purity of the waste liquid flowing directly from the fuel cell stack in real time, avoiding interference from mixing and dilution within the water tank and ensuring the timeliness and accuracy of the feedback signal.

[0058] S7: Control the tangential valve assembly through the control unit to switch to the drying mode and perform nitrogen purging and drying treatment on the hydrogen fuel cell stack 1.

[0059] It should be noted that after the cleaning mode is completed, the system enters the drying mode. This mode follows the same path as the purging mode, but the parameters are adjusted. Specifically, the control unit activates the nitrogen supply unit, and nitrogen is continuously (non-pulsed) purging the system, with the purging pressure increased to 30-80 kPa for 3-15 minutes. After the drying mode is completed, the internal flow channels of the fuel cell stack are thoroughly dried, and the maintenance and cleaning process is complete.

[0060] Understandably, the drying mode and purging mode share the same set of gas path components and pipelines. By adjusting the set value of the pressure reducing valve 22 and the on / off timing of the second solenoid valve 16 through the control unit, the same hardware implements the two differentiated functions of "pulse impact" and "continuous drying". Simultaneously, the higher purging pressure (30-80 kPa) and longer duration (3-15 minutes) ensure that residual moisture in the microchannels and diffusion layer pores inside the fuel cell stack is thoroughly removed, preventing residual liquid water from affecting the performance of the fuel cell stack after it is put back into service. After drying, the inside of the fuel cell stack is in a dry nitrogen environment, effectively preventing oxidative damage to the membrane electrode caused by air ingress.

[0061] Throughout the maintenance process, the control unit monitors key maintenance parameters in real time. Specifically, the first pressure sensor 9, located on the inlet side pipeline (at the first tangential valve 8P1 port), and the second pressure sensor 10, located on the outlet side pipeline (at the second tangential valve 11P2 port), continuously monitor the pressure values ​​before and after the fuel cell stack. When either pressure value exceeds 80 kPa, or the pressure difference before and after exceeds 25 kPa, the control unit immediately activates the pressure relief protection, closes the relevant solenoid valves, and opens the pressure relief passage.

[0062] Meanwhile, the first thermometer 25 in the rinsing water tank 23 and the second thermometer 26 in the cleaning water tank 6 monitor the liquid temperature in real time. When the monitored temperature is higher than 35℃ or lower than 15℃, the control unit immediately stops the water pump 7 and closes the first solenoid valve 15, and reports an alarm message on the display 21. It can only continue to operate after the abnormality is resolved.

[0063] In addition, during system maintenance, pure hydrogen tests are performed before and after maintenance of the hydrogen fuel cell stack 1 to calibrate the performance of the fuel cell stack before and after maintenance.

[0064] To verify the maintenance effect, pure hydrogen tests were conducted under the same operating conditions before and after the fuel cell stack maintenance. By comparing the stack performance curves (such as voltage-current density curves) before and after maintenance, the cleaning effect can be visually evaluated. Practical application shows that after maintenance and cleaning by this system, the performance of hydrogen fuel cell stack 1 can be restored to near its initial state, significantly extending the stack's service life in harsh gas sources or polluted environments.

[0065] Specifically, the pre- and post-maintenance pure hydrogen testing is not a mandatory function of this system, but rather an external verification method for the cleaning effect. Through standardized testing procedures, the cleaning effect is transformed into quantifiable and comparable performance data, providing an objective basis for continuous system optimization. For example... Figure 4The performance curves shown are compared. It is clear from the black curve before cleaning and the red curve after cleaning that the power density of hydrogen fuel cell stack 1 is significantly improved after cleaning, indicating that the stack has higher power generation capacity and efficiency. This demonstrates that the maintenance and cleaning of this system effectively removes impurities from the stack.

[0066] The above description is a specific implementation of the embodiments of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A maintenance system for a hydrogen fuel cell stack, comprising maintaining and cleaning a hydrogen fuel cell stack (1) by connecting it to the system, wherein the hydrogen fuel cell stack (1) has an anode flow channel inlet (3) and an anode flow channel outlet (2) on its inlet side, and a cathode flow channel inlet (4) and a cathode flow channel outlet (5) on its outlet side, characterized in that, include: A nitrogen supply unit is provided for supplying nitrogen required for the maintenance of the hydrogen fuel cell stack (1) in purging mode and drying mode. The nitrogen supply unit is located on the inlet side of the hydrogen fuel cell stack (1). A cleaning unit is provided in cleaning mode to provide cleaning fluid required for the maintenance of the hydrogen fuel cell stack (1). The cleaning unit is located on the outlet side of the hydrogen fuel cell stack (1). A rinsing unit is used to provide rinsing fluid required for the maintenance of the hydrogen fuel cell stack (1) in rinsing mode. The rinsing unit is located on the outlet side of the hydrogen fuel cell stack (1). A wastewater collection unit is used to collect wastewater after purging, drying, cleaning and rinsing. The wastewater collection unit is located on the inlet side and the outlet side, respectively. The inlet side pipeline is connected at one end to the anode flow channel inlet (3) and the cathode flow channel inlet (4) respectively, and at the other end to the nitrogen supply unit and the inlet side wastewater collection unit respectively; The outlet side pipeline is connected at one end to the anode flow channel outlet (2) and the cathode flow channel outlet (5) respectively, and at the other end to the cleaning unit, the rinsing unit and the wastewater collection unit on the outlet side respectively. A tangential valve assembly is installed on the inlet-side pipeline and the outlet-side pipeline, and is used to switch between different modes by switching the pipeline path; The control unit is electrically connected to the nitrogen supply unit, cleaning unit, rinsing unit, wastewater collection unit and the tangential valve assembly, and is used to control the tangential valve assembly to switch between purging mode, drying mode, cleaning mode and rinsing mode under maintenance parameter conditions, so as to realize the maintenance and cleaning of the hydrogen fuel cell stack (1).

2. The maintenance system for hydrogen fuel cell stacks according to claim 1, characterized in that, The tangential valve assembly includes: The first directional valve (8) has a P1 port that is connected to the anode flow channel inlet (3) and the cathode flow channel inlet (4) of the fuel cell, respectively, and a C port and a D port that are connected to the wastewater collection unit and the nitrogen supply unit, respectively. The second tangential valve (11) has a P2 port that is connected to the cathode flow channel outlet (5) of the fuel cell and the cathode flow channel outlet (5) respectively, and an A port that is connected to the wastewater collection unit. The third tangential valve (24) has a P3 port that communicates with the B port of the second tangential valve (11), and an E port and an F port that communicate with the cleaning unit and the rinsing unit respectively. A water pump (7) is provided on the pipeline between the B port of the second tangential valve (11) and the P3 port of the third tangential valve (24).

3. The maintenance system for hydrogen fuel cell stacks according to claim 2, characterized in that, The nitrogen supply unit includes a nitrogen tank and a pressure reducing valve (22) and a second solenoid valve (16) sequentially arranged on the nitrogen tank outlet pipeline. The second solenoid valve (16) is connected to port C of the first tangential valve (8). Under the control of the control unit, the nitrogen supply unit performs pulse purging in a pulse manner. The pressure holding time of the pulse purging is 5-60 seconds, the pressure release time is 1-10 seconds, and the purging pressure is 20-50 kPa.

4. The maintenance system for hydrogen fuel cell stacks according to claim 2, characterized in that, The wastewater collection unit includes a conductivity meter (13) and a first wastewater tank (12) connected in sequence to port D of the first tangential valve (8), and a first solenoid valve (15) and a second wastewater tank (17) connected in sequence to port A of the second tangential valve (11). The conductivity meter (13) is used to monitor the conductivity of deionized water flowing to the first wastewater tank (12) in the cleaning mode. The control unit is configured to stop the cleaning mode when the monitored value of the conductivity meter (13) is in the range of 1-20 μs / cm.

5. The maintenance system for a hydrogen fuel cell stack according to claim 4, characterized in that, The rinsing unit includes a rinsing tank (23) and a first thermometer (25) for measuring the temperature of the rinsing solution in the rinsing tank (23). The rinsing solution is a mixed solution of dilute acid and deionized water with a concentration of 0.05-1 mol / L and a temperature of 20-35°C.

6. The maintenance system for a hydrogen fuel cell stack according to claim 5, characterized in that, The cleaning unit includes a cleaning water tank (6) and a second thermometer (26) for measuring the temperature of the cleaning fluid in the cleaning water tank (6). The cleaning fluid is deionized water with a conductivity of 0.0625-0.2 μs / cm. The control unit is configured to simultaneously close the first solenoid valve (15) and the water pump (7) when the temperature monitored by the first thermometer (25) is greater than 35°C or less than 15°C, or the temperature monitored by the second thermometer (26) is greater than 35°C or less than 15°C.

7. The maintenance system for hydrogen fuel cell stacks according to claim 4, characterized in that, The maintenance system also includes a first pressure sensor (9) and a second pressure sensor (10). The first pressure sensor (9) is installed on the inlet side pipeline and connected to the P1 port of the first tangential valve (8) for measuring the gas or liquid pressure at the P1 port of the first tangential valve (8). The second pressure sensor (10) is installed on the main pipeline on the outlet side and connected to the P2 port of the second tangential valve (11) for measuring the gas or liquid pressure at the P2 port of the second tangential valve (11). The control unit is configured to perform pressure relief when the pressure value of the first pressure sensor (9) and / or the second pressure sensor (10) is greater than 80 kPa or the pressure difference between the first pressure sensor (9) and the second pressure sensor (10) is greater than 25 kPa.

8. The maintenance system for a hydrogen fuel cell stack according to any one of claims 4-7, characterized in that, The control unit includes a system controller (20), a display (21) connected to the system controller (20), and a power supply (18) and a relay (19) connected in sequence to the system controller (20).

9. A method for maintaining a hydrogen fuel cell stack, applied to the hydrogen fuel cell stack maintenance system as described in any one of claims 4-8, characterized in that, Includes the following steps: S1: Connect the hydrogen fuel cell stack (1) to be maintained to the maintenance system, and connect its anode flow channel inlet (3), anode flow channel outlet (2), cathode flow channel inlet (4) and cathode flow channel outlet (5) to the nitrogen supply unit, cleaning unit, rinsing unit and wastewater collection unit through the inlet side pipeline and the outlet side tangential pipeline, respectively. S2: Control the tangential valve assembly through the control unit, switch to the purging mode, start the nitrogen supply unit, and perform nitrogen pulse purging on the internal flow channel of the hydrogen fuel cell stack (1) in a pulse manner; S3: Control the tangential valve assembly through the control unit to switch to the rinsing mode, start the rinsing unit, and make the rinsing liquid flow through the internal flow channel of the hydrogen fuel cell stack (1) for cyclic rinsing; S4: Repeat steps S2 and S3 to perform cyclic purging and rinsing on the hydrogen fuel cell stack (1), and finally end the cycle in purging mode. S5: Control the tangential valve assembly through the control unit to switch to the cleaning mode, start the cleaning unit, and make deionized water flow through the internal flow channel of the hydrogen fuel cell stack (1) for circulation cleaning; S6: Repeat steps S5 and S2 to perform cyclic purging and cleaning on the hydrogen fuel cell stack (1); monitor the conductivity of the waste liquid after cleaning in real time through the conductivity meter (13), and stop the cleaning mode by the control unit when the monitored conductivity value reaches the preset range; S7: Control the tangential valve assembly through the control unit to switch to the drying mode and perform nitrogen purging and drying treatment on the hydrogen fuel cell stack (1).

10. The hydrogen fuel cell stack maintenance method according to claim 9, characterized in that, Pure hydrogen tests were performed on the hydrogen fuel cell stack (1) before and after maintenance to calibrate the performance of the fuel cell stack before and after maintenance.

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