A fuel cell system quick recovery method

Abstract

The application discloses a kind of fuel cell system quick recovery method, comprising the following steps: S1, detect whether the power attenuation of fuel cell stack reaches starting condition;If reach, run recovery program, enter step S2;S2, according to the performance state of fuel cell stack, judge whether to open backflow throttle;If open, enter step S3;S3, adjust backflow throttle angle to 20°~90° to carry out air backflow;While monitoring tail exhaust pipeline hydrogen concentration, if tail exhaust concentration is greater than concentration threshold, then reduce backflow throttle angle;S4, improve cooling circuit fan speed, reduce cooling inlet temperature to 50℃~60℃;Increase cooling circuit flow, meet cooling import and export temperature difference 5℃~10℃;S5, judge whether the average single piece voltage of fuel cell is less than closing threshold;If less than, then after running 2~5s, close backflow throttle, enter step S6;S6, judge the current average voltage of fuel cell stack, if current average voltage is greater than voltage before recovery, enter step S7;S7, judge whether to reach stop cycle condition, if reach, then stop cycle, complete the quick recovery of fuel cell system;Otherwise, return to step S3.The innovative recovery method proposed in the application realizes efficient reduction of catalyst and effective removal of sulfidation film under the premise of guaranteeing normal operation of fuel cell stack by intelligent control of oxygen concentration, solves the limitation of prior art in performance recovery, and provides strong technical support for long-term stable operation of fuel cell vehicle and other application fields.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fuel cell technology, particularly to a fuel cell system rapid recovery method. BACKGROUND

[0002] The present application 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 stack performance degradation caused by start-stop operating conditions, load cycling and dynamic operating environment, especially the challenges in chemical degradation such as catalyst modification and sulfide contamination.

[0003] In the long-term operation of fuel cell stacks, especially in the face of frequent start-stop, load variation and extreme operating conditions, both physical and chemical losses will occur. Physical damage is caused by frequent fluctuations in pressure, temperature and humidity, leading to wear and tear of materials and structures. On 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 start-up, shutdown, 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, directly manifested as a decrease in stack performance.

[0004] The existing solutions to this problem are:

[0005] 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 system design margins and cost, and is prone to cause uneven distribution of the stack. In addition, the sulfur film (such as Pt-SO3-) formed by the contamination of sulfur in the air is difficult to desorb naturally during normal operation, and after accumulation, it seriously damages the performance of the fuel cell, ultimately affecting the vehicle's operating ability. Therefore, a high-efficiency recovery strategy that can both reduce the catalyst and effectively remove the sulfur film is needed.

[0006] In view of the above challenges, the present application proposes an innovative recovery strategy aimed at achieving the target voltage for catalyst reduction and sulfur film desorption simultaneously by controlling the oxygen concentration under normal current conditions, in order to restore and maintain the high performance of the fuel cell stack. SUMMARY

[0007] The present application aims to provide a fuel cell system rapid recovery method to overcome the shortcomings of the prior art.

[0008] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0009] The application discloses a fuel cell system quick recovery method, comprising a fuel cell system air loop and a cooling loop, wherein the fuel cell system air loop is sequentially provided with an air filter, an air compressor, an intercooler, a humidifier, a fuel cell stack and a tail exhaust pipeline from an air inlet end; a backflow pipeline is arranged on the tail exhaust pipeline, and the other end of the backflow pipeline is connected to an air inlet end of the air filter; a backflow throttle valve is arranged on the backflow pipeline.

[0010] The method comprises the following steps:

[0011] S1, detecting whether the power attenuation of the fuel cell stack reaches a starting condition; if yes, a recovery program is run, and step S2 is entered; otherwise, step S1 is recycled;

[0012] S2, judging whether the current density of the fuel cell stack reaches a current density threshold value; if yes, the backflow throttle valve is opened, and step S3 is entered; otherwise, step S2 is recycled;

[0013] S3, adjusting the angle of the backflow throttle valve to 20°-90° to perform air backflow; meanwhile, the hydrogen concentration of the tail exhaust pipeline is monitored; if the hydrogen concentration of the tail exhaust pipeline is greater than a concentration threshold value, the angle of the backflow throttle valve is reduced;

[0014] S4, increasing the rotating speed of the cooling loop fan to reduce the cooling inlet temperature to 50-60°C; increasing the cooling loop flow to meet the cooling inlet and outlet temperature difference of 5-10°C;

[0015] S5, judging whether the average single piece voltage of the fuel cell is less than a shutdown threshold value; if yes, the backflow throttle valve is closed after 2-5s of running, and step S6 is entered; otherwise, step S5 is recycled;

[0016] S6, judging the current average voltage of the fuel cell stack; if the current average voltage is greater than the voltage before recovery, the recovery flow is opened again, and step S7 is entered;

[0017] S7, judging whether a stop cycle condition is reached; if yes, the cycle is stopped, and the quick recovery of the fuel cell system is completed; otherwise, step S3 is returned.

[0018] Preferably, the starting condition in step S1 is that whether the current fuel cell stack power is greater than the single piece voltage attenuation amount of the previous unit time by an attenuation threshold value; if yes, step S2 is entered; otherwise, step S1 is recycled.

[0019] Preferably, the previous unit time is 50-100h; and the attenuation threshold value is 5mV.

[0020] Preferably, the current density threshold value is 800-1200mA / cm 2 .

[0021] As a preferred, the concentration threshold value in step S3 is 1% VOL.

[0022] As a preferred, the closing threshold value in step S5 is 0.2V.

[0023] As a preferred, the stopping cycle condition in step S5 is as follows: the increment of the average voltage of the fuel cell stack from the last recovery is less than 2mV.

[0024] The beneficial effects of the present application are:

[0025] 1. High-efficiency catalyst recovery: without significantly increasing the operating current, the intelligent control of oxygen concentration can achieve high-efficiency reduction of the catalyst under normal operating conditions, reducing the system design difficulty and cost.

[0026] 2. Effective removal of sulfidation film: using a low-oxygen concentration environment, not only achieves catalyst reduction, but also effectively removes the sulfidation film from the catalyst layer without damaging the stack, restoring the stack activity.

[0027] 3. Performance stability and durability improvement: this strategy not only improves the immediate performance of the stack, but also effectively extends the service life of the fuel cell system, reduces maintenance requirements, and improves overall economic efficiency and reliability.

[0028] The features and advantages of the present application will be described in detail with reference to the embodiments combined with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a structural schematic diagram of the fuel cell system air circuit of the present application;

[0030] Figure 2 is a flowchart of a fuel cell system rapid recovery method of the present application; DETAILED DESCRIPTION

[0031] To make the purpose, technical solutions and advantages of the present application clearer and more explicit, the following describes the present application in further detail with reference to the accompanying drawings and embodiments. However, it should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the scope of the present application. 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 application.

[0032] Reference is made to Figure 1The embodiment of the present application provides a kind of fuel cell system quick recovery method, including fuel cell system air loop and cooling loop, the fuel cell system air loop is sequentially provided with air filter, air compressor, intercooler, humidifier, fuel cell stack and tail exhaust pipeline from air inlet end;The tail exhaust pipeline is provided with backflow pipeline, the other end of the backflow pipeline is connected with the air inlet end of air filter;Backflow throttle is provided on the backflow pipeline;The structure of cathode controllable inlet oxygen concentration is realized by backflow pipeline, reach lower voltage under low current, so as to restore effect of reducing and desorbing catalyst surface oxidation and sulfidation, specifically includes:

[0033] S1, detect whether the power attenuation of fuel cell stack reaches starting condition;If it reaches, run recovery program, enter step S2;Otherwise, cycle step S1;

[0034] Specifically: judge whether the power of current fuel cell stack is greater than the decay threshold compared with the single piece voltage decay amount of previous unit time;If it is greater than, enter step S2, otherwise, cycle step S1;Wherein, the previous unit time takes 50~100h;The decay threshold takes 5mV.

[0035] S2, judge whether the current density of fuel cell stack reaches current density threshold, if it reaches, open backflow throttle, enter step S3;Otherwise, cycle step S2;

[0036] Specifically, it includes the following operations: judge whether the current density of fuel cell stack reaches current density threshold, if it reaches, open backflow throttle, enter step S3;Otherwise, cycle step S2;Wherein, the current density threshold takes 800~1200mA / cm 2 ;

[0037] S3, adjust backflow throttle angle to 20°~90°, carry out cathode low oxygen concentration air backflow;Meanwhile, monitor the hydrogen concentration of tail exhaust pipeline, if the hydrogen concentration of tail exhaust pipeline is greater than concentration threshold, reduce backflow throttle angle, improve tail exhaust air flow, reduce tail exhaust hydrogen concentration;Wherein, the concentration threshold takes 1%VOL.

[0038] S4, improve cooling loop fan speed, reduce cooling inlet temperature to 50℃~60℃, improve air inlet humidity, which is conducive to performance recovery;Increase cooling loop flow to meet the cooling inlet and outlet temperature difference 5℃~10℃;When the oxygen concentration of cathode inlet air is low, the decrease of average voltage will cause the heat generation of stack to increase significantly, and it is necessary to increase the speed of water pump to uniform internal temperature, prevent excessive temperature difference from causing local overheating in internal part to cause secondary damage of stack;

[0039] S5, with the increase of the low oxygen concentration, determine whether the average single piece voltage of the fuel cell is less than the closing threshold value; if less, close the backflow throttle after running 2-5s, enter step S6; otherwise, cycle step S5; wherein, the closing threshold value is 0.2V;

[0040] S6, with the increase of the low oxygen concentration, determine whether the average single piece voltage of the fuel cell is less than the closing threshold value; if less, close the backflow throttle after running 2-5s, enter step S6; otherwise, cycle step S5; wherein, the closing threshold value is 0.2V;

[0041] S7, according to the recovery steps of steps S3-S6, cycle 5-10 times, when the average voltage increment is less than 2mV compared with the last recovery, stop the cycle.

[0042] The application recovers the performance of the fuel cell by intelligently controlling the low oxygen concentration air backflow from the cathode outlet to the cathode inlet, adjusting the voltage and using the chemical kinetics principle, and is particularly suitable for solving the performance degradation caused by the oxidation and sulfuration of the catalyst surface.

[0043] The innovative recovery method provided by the application realizes the efficient reduction of the catalyst and the effective removal of the sulfuration film under the premise of ensuring the normal operation of the fuel cell stack by intelligently controlling the oxygen concentration, solves the limitations of the prior art in performance recovery, and provides strong technical support for the long-term stable operation of the fuel cell vehicle and other application fields.

[0044] The above only describes the preferred embodiments of the application and is not used to limit the application, and any modification, equivalent replacement or improvement made within the spirit and principle of the application should be included in the protection scope of the application.

Claims

1. A rapid recovery method for a fuel cell system, comprising an air circuit and a cooling circuit of the fuel cell system, characterized in that: 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 an exhaust pipe in sequence from the air inlet end; the exhaust pipe is provided with a return pipe, the other end of which is connected to the air inlet end of the air filter; the return pipe is provided with a return throttle valve. The method includes the following steps: S1. Detect whether the power decay of the fuel cell stack has reached the start-up condition; if it has, run the recovery program and proceed to step S2; otherwise, repeat step S1. S2. Determine whether the current density of the fuel cell stack has reached the current density threshold. If it has, open the reflux throttle valve and proceed to step S3; otherwise, repeat step S2. S3. Adjust the recirculation throttle angle to 20°~90° to perform air recirculation; at the same time, monitor the hydrogen concentration in the exhaust pipe. If the hydrogen concentration in the exhaust pipe is greater than the concentration threshold, reduce the recirculation throttle angle. S4. Increase the cooling circuit fan speed to reduce the cooling inlet temperature to 50℃~60℃; increase the cooling circuit flow rate to meet the cooling inlet and outlet temperature difference of 5℃~10℃. S5. Determine whether the average single cell voltage of the fuel cell is less than the shut-off threshold; if it is less, close the return throttle valve after running for 2~5 seconds and proceed to step S6. Conversely, repeat step S5; S6. Determine the current average single cell voltage of the fuel cell stack. If the current average single cell voltage is greater than or equal to 2mV compared to the voltage increment at the time of the last recovery, return to step S3; otherwise, proceed to step S7. S7. If the current average single-chip voltage increment is less than 2mV compared to the voltage before the last recovery, then stop the loop.

2. A rapid recovery method for a fuel cell system as described in claim 1, comprising an air circuit for the fuel cell system, characterized in that: The start condition in step S1 is: determine whether the power of the current fuel cell stack decreases by more than the voltage decay of a single cell in the previous unit time than the decay threshold; if it does, proceed to step S2; otherwise, repeat step S1.

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

4. A rapid recovery method for a fuel cell system as described in claim 1, comprising an air circuit for the fuel cell system, characterized in that, The current density threshold is set to 800~1200mA / cm2.

5. A rapid recovery method for a fuel cell system as described in claim 1, comprising an air circuit of the fuel cell system, characterized in that, In step S3, the concentration threshold is set to 1%VOL.

6. A rapid recovery method for a fuel cell system as described in claim 1, comprising an air circuit for the fuel cell system, characterized in that, In step S5, the threshold value is set to 0.2V.

7. A rapid recovery method for a fuel cell system as described in claim 1, comprising an air circuit for the fuel cell system, characterized in that, The air filter includes a physical filter and a chemical filter. The outlet of the physical filter is connected to the inlet of the chemical filter, and the other end of the return pipe is connected to the outlet of the physical filter.

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