Rapid recovery method for fuel cell system

Abstract

The invention discloses a quick recovery method for a fuel cell system. The method comprises the following steps: S1, detecting whether power attenuation of a fuel cell stack reaches a starting condition or not; if yes, running a recovery program, and entering the step S2; s2, judging whether a backflow throttle valve is opened or not according to the performance state of the fuel cell stack; if so, entering step S3; s3, the angle of a backflow throttle valve is adjusted to be 20-90 degrees, and air backflow is conducted; meanwhile, the hydrogen concentration of a tail exhaust pipeline is monitored, and if the tail exhaust concentration is larger than a concentration threshold value, the angle of a backflow throttle valve is reduced; s4, the rotating speed of a cooling loop fan is increased, and the temperature of a cooling inlet is reduced to 50-60 DEG C; the cooling loop flow is increased, and the cooling inlet and outlet temperature difference is 5-10 DEG C; s5, judging whether the average single-chip voltage of the fuel cell is smaller than a closing threshold value or not; if yes, the backflow throttle valve is closed after operation is conducted for 2-5 s, and the step S6 is executed; s6, the current average voltage of the fuel cell stack is judged, and if the current average voltage is larger than the voltage before recovery, the step S7 is executed; and S7, judging whether a cycle stopping condition is met or not, if so, stopping cycle, and completing rapid recovery of the fuel cell system. Otherwise, returning to the step S3. According to the innovative recovery method provided by the invention, by intelligently regulating and controlling the oxygen concentration, on the premise of ensuring normal operation of the fuel cell stack, efficient reduction of the catalyst and effective removal of the vulcanized film are realized, and the limitation of the prior art on performance recovery is solved; and powerful technical support is provided for long-term stable operation of fuel cell automobiles and other application fields.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular to a rapid recovery method for a fuel cell system. Background Art

[0002] The present invention continues to deepen the exploration in the field of fuel cell engine system technology, focusing on providing an innovative fuel cell recovery method, aiming to solve the problem of fuel cell stack performance degradation caused by start-stop conditions, load cycles and dynamic operating environments, especially in the challenges of chemical degradation such as catalyst modification and sulfide contamination.

[0003] Fuel cell stacks will suffer physical and chemical damage in long-term operation, especially when facing frequent starts and stops, load changes and extreme operating conditions. Physical damage comes from frequent fluctuations in pressure, temperature and humidity, which lead to wear of materials and structures. At the chemical level, voltage fluctuations caused by dynamic load changes accelerate the degradation of catalyst performance, such as the dissolution and agglomeration of platinum catalysts, and the degradation of polymer electrolytes. In particular, during starting, stopping, idling and high-potential cycling, the accumulation of oxidation intermediates (such as Pt-Ox (-OH, -O)) under the action of potential cycling hinders normal electrochemical reactions, which is directly manifested as a decrease in stack performance. .

[0004] The solutions provided in the prior art include: Constant current recovery method: A method of reducing the cathode catalyst by increasing the operating current to below 0.6V. This method is limited by the system design margin and cost, and is prone to uneven distribution of the stack. In addition, the sulfide film (such as Pt-SO3-) formed by sulfide pollution in the air is difficult to desorb naturally during normal operation. After accumulation, it seriously damages the performance of the fuel cell and ultimately affects the vehicle's operating ability. Therefore, an efficient recovery strategy is needed that can both achieve catalyst reduction and effectively remove the sulfide film.

[0005] In view of the above challenges, the present invention proposes an innovative recovery strategy, which aims to simultaneously achieve the target voltage of catalyst reduction and sulfide membrane desorption by controlling the oxygen concentration under conventional current conditions, so as to restore and maintain the high performance of the fuel cell stack. Summary of the invention

[0006] The object of the present invention is to provide a fuel cell system rapid recovery method to overcome the deficiencies in the prior art.

[0007] To achieve the above object, the present invention provides the following technical solutions: The present application discloses a method for rapid recovery of a fuel cell system, comprising an air circuit and a cooling circuit of the fuel cell system, wherein the air circuit of the fuel cell system is provided with an air filter, an air compressor, an intercooler, a humidifier, a fuel cell stack and a tail exhaust pipeline in sequence from the air inlet end; a return pipeline is provided on the tail exhaust pipeline, and the other end of the return pipeline is connected to the air inlet end of the air filter; a return throttle is provided on the circuit pipeline; The method comprises the following steps: S1, detecting whether the power attenuation of the fuel cell stack reaches the start-up condition; if so, running the recovery program and entering step S2; otherwise, looping step S1; S2, judging whether to open the reflux throttle valve according to the performance status of the fuel cell stack; if it is opened, proceed to step S3; otherwise, loop step S2; S3. Adjust the angle of the reflux throttle valve to 20°~90° to perform air reflux. Meanwhile, monitor the hydrogen concentration in the tail exhaust pipeline. If the tail exhaust concentration is greater than the concentration threshold, reduce the angle of the reflux throttle valve. S4. Increase the speed of the cooling circuit fan and reduce the cooling inlet temperature to 50°C~60°C; increase the cooling circuit flow rate to meet the cooling inlet and outlet temperature difference of 5°C~10°C; S5, judging whether the average single-chip voltage of the fuel cell is less than the shutdown threshold; if so, closing the reflow throttle after running for 2 to 5 seconds and entering step S6; otherwise, looping step S5; S6, determining the current average voltage of the fuel cell stack, if the current average voltage is greater than the voltage before recovery, restarting the recovery process and entering step S7; S7, judging whether the stopping circulation condition is met, if so, stopping the circulation to complete the rapid recovery of the fuel cell system; otherwise, returning to step S3.

[0008] Preferably, the starting condition in step S1 is: determine whether the power of the current fuel cell stack is greater than the attenuation of the single-chip voltage in the previous unit time than the attenuation threshold; if so, enter step S2, otherwise, loop step S1.

[0009] Preferably, the previous unit time is the previous 50 to 100 hours; and the attenuation threshold is 5 mV.

[0010] Preferably, step S2 specifically includes the following operations: determining whether the electrical density of the fuel cell stack reaches the electrical density threshold value; if so, opening the reflux throttle valve and entering step S3; otherwise, looping step S2.

[0011] Preferably, the electric density threshold is 800-1200 mA / cm 2 .

[0012] Preferably, the concentration threshold value in step S3 is 1%VOL.

[0013] Preferably, the closing threshold value in step S5 is 0.2V.

[0014] Preferably, the condition for stopping the circulation in step S5 is as follows: the increment between the average voltage of the fuel cell stack and the average voltage at the last recovery is less than 2 mV.

[0015] Beneficial effects of the present invention: 1. Efficient catalyst recovery: There is no need to significantly increase the operating current. Efficient catalyst reduction can be achieved under normal operating conditions by intelligently controlling the oxygen concentration, reducing the difficulty and cost of system design.

[0016] 2. Effective removal of sulfide film: Using a low oxygen concentration environment can not only achieve the purpose of catalyst reduction, but also effectively remove the constraints of the sulfide film on the catalytic layer and restore the activity of the fuel cell without damaging the fuel cell.

[0017] 3. Improved performance stability and durability: This strategy not only improves the immediate performance of the fuel cell stack, but also effectively extends the service life of the fuel cell system, reduces maintenance requirements, and improves overall economy and reliability.

[0018] The features and advantages of the present invention will be described in detail through embodiments in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic structural diagram of the air circuit of the fuel cell system of the present invention; Figure 2 It is a schematic flow chart of a method for rapid recovery of a fuel cell system of the present invention; DETAILED DESCRIPTION In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below through the accompanying drawings and embodiments. However, it should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the scope of the present invention. In addition, in the following description, the description of known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0020] See also Figure 1The embodiment of the present invention provides a method for rapid recovery of a fuel cell system, including an air circuit and a cooling circuit of a fuel cell system, wherein the air circuit of the fuel cell system is provided with an air filter, an air compressor, an intercooler, a humidifier, a fuel cell stack and a tail exhaust pipe in sequence from the air inlet end; a return pipe is provided on the tail exhaust pipe, and the other end of the return pipe is connected to the air inlet end of the air filter; a return throttle is provided on the circuit pipe; a structure of a controllable inlet oxygen concentration of the cathode is realized through the return pipe, so as to achieve a lower voltage under low current, thereby reducing and desorbing oxidation and sulfidation on the surface of the catalyst to achieve a recovery effect, specifically including: S1, detecting whether the power attenuation of the fuel cell stack reaches the start-up condition; if so, running the recovery program and entering step S2; otherwise, looping step S1; Specifically: determine whether the power of the current fuel cell stack is greater than the attenuation of the single-chip voltage in the previous unit time than the attenuation threshold; if greater, enter step S2, otherwise, loop step S1; wherein the previous unit time is the previous 50~100h; the attenuation threshold is 5mV.

[0021] S2, judging whether to open the reflux throttle valve according to the performance status of the fuel cell stack; if it is opened, proceed to step S3; otherwise, loop step S2; Specifically, the following operations are included: determining whether the electric density of the fuel cell stack reaches the electric density threshold, if so, opening the reflux throttle and entering step S3; otherwise, looping step S2; wherein the electric density threshold is 800~1200mA / cm 2 ; S3. Adjust the reflux throttle angle to 20°~90° to perform air reflux with low oxygen concentration at the cathode; at the same time, monitor the hydrogen concentration in the tail exhaust pipeline. If the tail exhaust concentration is greater than the concentration threshold, reduce the reflux throttle angle, increase the tail exhaust air flow, and reduce the tail exhaust hydrogen concentration; the concentration threshold is 1%VOL.

[0022] S4. Increase the speed of the cooling circuit fan, reduce the cooling inlet temperature to 50℃~60℃, and increase the intake humidity, which is conducive to performance recovery; increase the cooling circuit flow to meet the cooling inlet and outlet temperature difference of 5℃~10℃; when the cathode intake oxygen concentration is low, the reduction in average voltage will cause the heat generation of the battery stack to increase significantly. It is necessary to increase the speed of the water pump to even out the internal temperature to prevent excessive temperature difference from causing local overheating inside and causing secondary damage to the battery stack; S5. As the hypoxic concentration increases, determine whether the average single-chip voltage of the fuel cell is less than the shutdown threshold; if so, close the reflow throttle after running for 2 to 5 seconds and enter step S6; otherwise, loop step S5; wherein the shutdown threshold is 0.2V; S6, as the oxygen concentration at the cathode inlet increases instantaneously after the reflux throttle is closed, the fuel cell voltage rises instantaneously, forming a rapid voltage pulse, which is beneficial to the performance recovery effect. When the average voltage rises to a value greater than the voltage before recovery, after running for 1 minute, the reflux throttle is opened again for a secondary recovery process, and then enters step S7; S7. The recovery steps of steps S3 to S6 are cycled for 5 to 10 times. When it is detected that the increment between the average voltage and the last recovery is less than 2 mV, the cycle is stopped.

[0023] The present invention is an effective strategy to restore fuel cell performance by intelligently controlling the low oxygen concentration air at the cathode outlet to flow back to the cathode inlet, adjusting the voltage and utilizing the principle of chemical kinetics. It is particularly suitable for solving performance degradation caused by catalyst surface oxidation and sulfidation.

[0024] The innovative recovery method proposed in the present invention, through intelligent regulation of oxygen concentration, achieves efficient reduction of the catalyst and effective removal of the sulfide film while ensuring the normal operation of the fuel cell stack, thereby solving the limitations of the prior art in performance recovery and providing strong technical support for the long-term stable operation of fuel cell vehicles and other application fields.

[0025] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent substitution or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for rapid recovery of a fuel cell system, comprising an air circuit and a cooling circuit of the fuel cell system, characterized in that: The fuel cell system air circuit is provided with an air filter, an air compressor, an intercooler, a humidifier, a fuel cell stack and a tail exhaust pipeline in sequence from the air inlet end; a return pipeline is provided on the tail exhaust pipeline, and the other end of the return pipeline is connected to the air inlet end of the air filter; a return throttle valve is provided on the loop pipeline; The method comprises the following steps: S1, detecting whether the power attenuation of the fuel cell stack reaches the start-up condition; if so, running the recovery program and entering step S2; otherwise, looping step S1; S2. judging whether to open the reflux throttle valve according to the performance status of the fuel cell stack; If it is on, go to step S3; Otherwise, loop step S2; S3. Adjust the angle of the reflux throttle valve to 20°~90° to perform air reflux. Meanwhile, monitor the hydrogen concentration in the tail exhaust pipeline. If the tail exhaust concentration is greater than the concentration threshold, reduce the angle of the reflux throttle valve. S4. Increase the speed of the cooling circuit fan and reduce the cooling inlet temperature to 50°C~60°C; increase the cooling circuit flow rate to meet the cooling inlet and outlet temperature difference of 5°C~10°C; S5, judging whether the average single-chip voltage of the fuel cell is less than the shutdown threshold; if so, closing the reflow throttle after running for 2 to 5 seconds and entering step S6; otherwise, looping step S5; S6, determining the current average voltage of the fuel cell stack, if the current average voltage is greater than the voltage before recovery, restarting the recovery process and entering step S7; S7, judging whether the stopping circulation condition is met, if so, stopping the circulation to complete the rapid recovery of the fuel cell system; otherwise, returning to step S3.

2. A fuel cell system rapid recovery method as claimed in claim 1, comprising a fuel cell system air circuit, characterized in that: The starting condition in step S1 is: determine whether the power of the current fuel cell stack is greater than the attenuation of the single-chip voltage in the previous unit time than the attenuation threshold; if greater, enter step S2, otherwise, loop step S1.

3. A fuel cell system rapid recovery method as claimed in claim 2, comprising a fuel cell system air circuit, characterized in that: The previous unit time is the previous 50-100 hours; the attenuation threshold is 5mV.

4. A fuel cell system rapid recovery method as claimed in claim 1, comprising a fuel cell system air circuit, characterized in that: Step S2 specifically includes the following operations: determining whether the electrical tightness of the fuel cell stack reaches the electrical tightness threshold, if so, opening the reflux throttle and entering step S3; otherwise, looping step S2.

5. A fuel cell system rapid recovery method as claimed in claim 4, comprising a fuel cell system air circuit, characterized in that: The electric density threshold is 800~1200mA / cm 2 .

6. A fuel cell system rapid recovery method as claimed in claim 1, comprising a fuel cell system air circuit, characterized in that: The concentration threshold value in step S3 is 1%VOL.

7. A fuel cell system rapid recovery method as claimed in claim 1, comprising a fuel cell system air circuit, characterized in that: In step S5, the closing threshold value is 0.2V.

8. A fuel cell system rapid recovery method as claimed in claim 1, comprising a fuel cell system air circuit, characterized in that: The stopping condition in step S7 is as follows: the increment between the average voltage of the fuel cell stack and the average voltage at the last recovery is less than 2 mV.

9. A fuel cell system rapid recovery method as claimed in claim 1, comprising a fuel cell system air circuit, characterized in that: The air filter comprises a physical filter and a chemical filter, the air outlet end of the physical filter is connected to the air inlet end of the chemical filter, and the other end of the return line is connected to the air outlet end of the physical filter.

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