Fuel cell low temperature shutdown purging method, apparatus and system

Abstract

The application discloses a kind of fuel cell low-temperature shutdown purging method, device and system, wherein purging method includes the following steps: whether the outlet temperature of cooling liquid of electric pile meets low-temperature purging condition, purging flow is as follows: step (1), fuel cell is set at 0.15-0.18 standard current density condition and operates, during which dry hydrogen and air are respectively introduced into the anode and cathode of battery;Step (2), fuel cell is set at 0.15-0.18 standard current density condition and operates;Step (3), fuel cell is set at 0.10-0.12 standard current density condition and operates;Step (4), fuel cell is set at 0.05-0.08 standard current density condition and operates;Step (5), fuel cell is set at 0.03-0.04 standard current density condition and operates;Step (6), 0.03-0.04 standard current density is carried with load.The application can effectively reduce the initial water content of electric pile, improve the success rate of electric pile cold start, improve the durability of electric pile, and slow down performance degradation.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of fuel cells, and particularly relates to a fuel cell low-temperature shutdown purging method, device and system. BACKGROUND

[0002] With the rapid development of hydrogen energy, proton exchange membrane fuel cells (PEMFC) are widely applied and promoted, but the low-temperature cold start problem of PEMFC has not been completely solved. The low-temperature purging process is closely related to the cold start process, and whether the PEMFC cold start can be successful depends largely on whether the low-temperature purging process makes the water content of the membrane electrode reach a suitable value. If the initial water content is too much before the low-temperature start, the reaction will be hindered by ice during the low-temperature start process, resulting in the failure of the stack start. The gas purging during the shutdown process can effectively reduce the initial water content of the stack.

[0003] Currently, a small current load purging method in air blowing purging is usually adopted. The core requirement of purging is that the purging process has no high potential and is completely purged. However, the purging method currently adopted usually makes the stack stay at a high potential for a long time, which will cause carbon corrosion and affect the durability of the stack. Therefore, an accurate shutdown purging strategy must be proposed to meet the requirement of the low-temperature cold start for the initial water content of the stack and reduce the time of the stack staying at a high potential, thereby improving the durability of the stack.

[0004] Therefore, in view of the above technical problems, it is necessary to provide a fuel cell low-temperature shutdown purging method, device and system.

[0005] The information disclosed in this BACKGROUND section is only intended to increase an understanding of the general context in which the present application can be practiced. It is not admitted that any of the information provided in this BACKGROUND section is prior art or is relevant to the patentability of the application. SUMMARY

[0006] The purpose of the present application is to provide a fuel cell low-temperature shutdown purging method, device and system.

[0007] In order to achieve the above-mentioned purpose, a technical solution provided by an embodiment of the present application is as follows:

[0008] The fuel cell low-temperature shutdown purging method comprises the following steps:

[0009] The outlet temperature of the stack cooling liquid is judged whether it meets the low-temperature purging condition, if not, the temperature rising process is entered, and if yes, the load is gradually reduced to the idle speed working point, and then the stack purging process is entered, and the purging process is as follows:

[0010] Step (1), the fuel cell is set to operate at 0.15-0.18 standard current density, dry hydrogen and air are supplied to the anode and cathode of the cell respectively, the flow rate of the anode and cathode gas corresponds to the flow rate at 1.2-1.4 standard current density, the outlet temperature of the stack cooling liquid is controlled to maintain at 60-65℃, and the purge time is set to 10-20 seconds;

[0011] Step (2), the fuel cell is set to operate at 0.15-0.18 standard current density, the flow rate of the anode and cathode gas corresponds to the flow rate at 0.8-1.0 standard current density, and the purge time is set to 10-20 seconds;

[0012] Step (3), the fuel cell is set to operate at 0.10-0.12 standard current density, the flow rate of the anode and cathode gas corresponds to the flow rate at 0.8-1.0 standard current density, and the purge time is set to 10-20 seconds;

[0013] Step (4), the fuel cell is set to operate at 0.05-0.08 standard current density, the flow rate of the anode and cathode gas corresponds to the flow rate at 0.5-0.8 standard current density, and the purge time is set to 10-20 seconds;

[0014] Step (5), the fuel cell is set to operate at 0.03-0.04 standard current density, the flow rate of the anode and cathode gas corresponds to the flow rate at 0.5-0.8 standard current density, and the purge time is set to 5-10 seconds;

[0015] Step (6), the load is set to 0.03-0.04 standard current density, the gas flow rate is set to 0.05-0.3 standard current density, the supply of air is stopped, the residual oxygen in the cathode is consumed, and when the average voltage is <0.15-0.35 V, the load current is stopped, and the supply of hydrogen is stopped;

[0016] In the steps (1)-(6), at least any one of the following conditions is met: the pressure of the anode and cathode gas is 30-40 kPa and 35-45 kPa respectively. The standard current density refers to the current density of the stack during operation, which is 1 A / cm 2 .

[0017] In one or more embodiments of the present application, the low-temperature purging condition is that when the electric pile is pulled to 1 standard current density, it is determined whether the electric pile coolant outlet temperature is greater than or equal to 60-70℃, yes, then enter the temperature raising process to continue normal loading, otherwise, gradually reduce the load to the idling operating point, and after the reduction is completed, enter the electric pile purging process. The purpose of this scheme is to determine whether the current working condition is a low-temperature environment in winter according to the coolant outlet temperature. When it is less than this temperature, it is in a low-temperature environment and needs to be purged at low temperature.

[0018] In one or more embodiments of the present application, the hydrogen and / or air in steps (1)-(6) is preheated.

[0019] In one or more embodiments of the present application, the preheated hydrogen and / or air temperature ranges from 25-65℃.

[0020] In one or more embodiments of the present application, the idling operating point is that the current density of the electric pile is reduced to 0.4-0.5 standard current density.

[0021] In one or more embodiments of the present application, the electric pile is operated at the idling operating point for 120-240 seconds before entering the electric pile purging process.

[0022] In one or more embodiments of the present application, steps (1)-(6) meet that the pressure of the gas of the anode is the same, and the pressure of the gas of the cathode is the same.

[0023] In one or more embodiments of the present application, after the air supply is closed in step (6), the time for the average voltage of the fuel cell to decrease from the purging voltage to an average voltage <0.15-0.35V is 5 to 20s.

[0024] In one or more embodiments of the present application, the purging device implements the fuel cell low-temperature shutdown purging method.

[0025] In one or more embodiments of the present application, the purging system comprises a main body and a plurality of purging devices arranged on the main body.

[0026] Compared with the prior art, the fuel cell low-temperature shutdown purging method, device and system of the present application can effectively reduce the initial water content of the electric pile, improve the cold start success rate of the electric pile, reduce the time of the electric pile at high potential, and improve the durability of the electric pile. After purging, using auxiliary load discharge to consume the oxygen in the cathode can effectively slow down the performance degradation of the fuel cell after frequent start-stop. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to make the technical solution in the embodiments of the present application or the prior art clearer, the accompanying drawings needed in the embodiments or the prior art description will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments described in the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0028] Figure 1 The figure of the change of the high-frequency impedance of the proton exchange membrane with time in the water-removing purging process in the embodiment 1 of the present application;

[0029] Figure 2 The change of the average voltage of the stack with time in the water-removing purging process in the embodiment 1 of the present application;

[0030] Figure 3 The photos of the cross-section of the catalytic layer taken by the scanning electron microscope before and after the low-temperature purging test in the embodiment 1 of the present application, wherein the left photo is before the test and the right photo is after the test;

[0031] Figure 4 The photos of the surface of the cathode catalytic layer taken by the scanning electron microscope before and after the low-temperature purging test in the embodiment 1 of the present application, wherein the left photo is before the test and the right photo is after the test;

[0032] Figure 5 The photos of the surface of the anode catalytic layer taken by the scanning electron microscope before and after the low-temperature purging test in the embodiment 1 of the present application, wherein the left photo is before the test and the right photo is after the test;

[0033] Figure 6 The purging gas flow corresponding to different current densities in the embodiment 1 of the present application. DETAILED DESCRIPTION

[0034] In order to make the technical solution in the embodiments of the present application or the prior art clearer, the accompanying drawings needed in the embodiments or the prior art description will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments described in the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0035] The method for fuel cell comprises the following steps:

[0036] The purging condition identification module judges whether the low-temperature purging condition is met according to the outlet temperature of the cooling liquid of the fuel cell stack, if not, the temperature rising process is entered, if yes, the load is gradually reduced to the idle working point, and then the stack purging process is entered;

[0037] Step (1), the fuel cell is set to operate at 0.15-0.18 standard current density, dry hydrogen and air are supplied to the anode and cathode of the cell respectively, the flow rate of the anode and cathode gas corresponds to the flow rate at 1.2-1.4 standard current density, the pressure of the anode and cathode gas is 40 and 45 kPa respectively, the outlet temperature of the stack cooling liquid is controlled to be 60-65°C, and the purging time is set to 10-20 seconds;

[0038] Step (2), the fuel cell is set to operate at 0.15-0.18 standard current density, the flow rate of the anode and cathode gas corresponds to the flow rate at 0.8-1.0 standard current density, and the purging time is set to 10-20 seconds;

[0039] Step (3), the fuel cell is set to operate at 0.10-0.12 standard current density, the flow rate of the anode and cathode gas corresponds to the flow rate at 0.8-1.0 standard current density, and the purging time is set to 10-20 seconds;

[0040] Step (4), the fuel cell is set to operate at 0.05-0.08 standard current density, the flow rate of the anode and cathode gas corresponds to the flow rate at 0.5-0.8 standard current density, and the purging time is set to 10-20 seconds;

[0041] Step (5), the fuel cell is set to operate at 0.03-0.04 standard current density, the flow rate of the anode and cathode gas corresponds to the flow rate at 0.5-0.8 standard current density, and the purging time is set to 5-10 seconds;

[0042] Step (6), the load is set to 0.03-0.04 standard current density, and the gas flow rate is set to 0.05-0.3 standard current density. The supply of air is stopped, and the residual oxygen in the cathode is consumed. When the average voltage is less than 0.15-0.35 V, the load current is turned off, and the supply of hydrogen is stopped.

[0043] As a preferred solution, in step (1), the low-temperature purging condition is determined by whether the outlet temperature of the stack cooling liquid is greater than or equal to 60-70°C when the stack is loaded to 1 standard current density. If yes, the temperature rising process is entered for continuing normal loading, otherwise, the load is gradually reduced to the idle operating point of 0.5 standard current density, and after the load reduction is completed, the stack purging process is entered.

[0044] As a preferred solution, the operating conditions of different current densities in step (1) to step (6) are the optimal operating conditions table obtained from the sensitivity experiment, and the conditions of the sensitivity experiment include different current densities, anode and cathode gas pressure, cooling liquid pressure, anode and cathode gas flow, cooling liquid flow, anode and cathode gas temperature, cooling liquid temperature, anode and cathode gas metering ratio, anode and cathode gas humidity, etc.

[0045] As a preferred solution, in step (6), the time for the average voltage of the fuel cell to decrease from the purge voltage to an average voltage < 0.15-0.35 V is between 5 to 20 s, that is, the time interval from the air being turned off to the voltage decreasing to an average voltage < 0.15-0.35 V.

[0046] As a preferred solution, an alternating current impedance meter is used to monitor the water content in the stack to calculate the internal resistance value of the stack, including the wet-state internal resistance under idling operation of the stack, the internal resistance during the stack purging process, and the internal resistance after waiting for the water balance in the proton exchange membrane.

[0047] As a preferred solution, after the stack is purged, the maximum resistance value during the purging process is 5-15 times the wet-state internal resistance, and the internal resistance after waiting for 0.1-1 h after the end of the purging process, that is, after waiting for the water balance in the proton exchange membrane, is 2-5 times the wet-state internal resistance.

[0048] Example 1

[0049] 500 active area 350 cm 2The stack (water-cooled fuel cell stack, same below) is pulled to 1 standard current density, the stack cooling liquid outlet temperature is 55°C, meeting the low temperature purging condition, gradually reduced to idle speed operating point 0.5 standard current density, running 120 seconds after entering the stack purging process. The fuel cell is set to run at 0.15 standard current density, during which dry and unheated hydrogen and air are respectively introduced into the anode and cathode of the cell, the flow of the anode and cathode gas corresponds to the gas flow under 1.2 standard current density, the pressure of the anode and cathode gas is 40 and 45 kPa respectively (the same gas supply pressure is used in the following stages, same below), while the stack cooling liquid outlet temperature is controlled to maintain at 65°C, the purging time is set to 10 seconds; the fuel cell is set to run at 0.15 standard current density, the flow of the anode and cathode gas is set to 0.8 standard current density, the purging time is set to 20 seconds; the fuel cell is set to run at 0.10 standard current density, the flow of the anode and cathode gas corresponds to the gas flow under 0.8 standard current density, the purging time is set to 10 seconds; the fuel cell is set to run at 0.05 standard current density, the flow of the anode and cathode gas corresponds to the gas flow under 0.5 standard current density, the purging time is set to 15 seconds; the fuel cell is set to run at 0.03 standard current density, the flow of the anode and cathode gas corresponds to the gas flow under 0.5 standard current density, the purging time is set to 5 seconds; under 0.03 standard current density, the gas flow is set to 0.05 standard current density. Then the air supply is turned off, the residual oxygen in the cathode is consumed, when the average voltage is <0.2V, the load current is turned off, and the hydrogen supply is turned off.

[0050] During purging, AC impedance is used to monitor the water content in the stack to calculate the internal resistance of the stack, including the wet-state internal resistance under idle speed operation of the stack, the internal resistance during the stack purging process, and the internal resistance after waiting for the proton exchange membrane internal water balance. After the stack is purged, the maximum resistance value reached during the purging process is 15 times the wet-state internal resistance, and the internal resistance after waiting for the proton exchange membrane internal water balance, i.e. after 10 minutes of purging, does not change, which is 3.2 times the wet-state internal resistance.

[0051] After purging, the stack can be successfully cold started at -20°C. And the purged stack is subjected to 10-40-60°C freezing / thawing cycle tests, as shown in Figure 3 , the scanning electron microscope photograph of the cross-section of the catalyst layer after the test shows that there is no separation between the catalyst layer and the proton exchange membrane. As shown in Figure 4 and 5 , the surface crack of the cathode catalyst layer changes little, while the surface crack of the anode catalyst layer increases slightly due to the repeated expansion and contraction of the MEA caused by the repeated changes of the water content in the relatively thin anode catalyst layer. As shown in Figure 2The load current is controlled in the method of the embodiment to precisely control the battery voltage during the discharging process, i.e. the voltage drop of the battery can be prevented from being too fast to cause uneven voltage distribution and battery reverse polarity, and the long-time high potential of the stack can be avoided.

[0052] Example 2

[0053] A stack of 300 cells with an active area of 300 cm 2 was loaded to 1 standard current density, and the stack coolant outlet temperature was 55°C, satisfying the low-temperature purging condition. The load was gradually reduced to the idling operating point of 0.5 standard current density, and the stack purging process was entered after 120 seconds of operation. The fuel cell was set to operate at 0.15 standard current density, during which dry and unheated hydrogen and air were supplied to the anode and cathode of the cell respectively, and the flow rates of the anode and cathode gases corresponded to those at 1.2 standard current density. The anode and cathode gas pressures were 40 and 45 kPa respectively (the same gas supply pressures were used in the following stages). The stack coolant outlet temperature was controlled to be maintained at 65°C, and the purging time was set to 20 seconds. Then the fuel cell was set to operate at 0.15 standard current density, and the flow rates of the anode and cathode gases were set to those at 0.8 standard current density, and the purging time was set to 10 seconds. The fuel cell was set to operate at 0.10 standard current density, and the flow rates of the anode and cathode gases corresponded to those at 0.8 standard current density, and the purging time was set to 20 seconds. The fuel cell was set to operate at 0.05 standard current density, and the flow rates of the anode and cathode gases corresponded to those at 0.5 standard current density, and the purging time was set to 20 seconds. The fuel cell was set to operate at 0.03 standard current density, and the flow rates of the anode and cathode gases corresponded to those at 0.5 standard current density, and the purging time was set to 10 seconds. The flow rates of the anode and cathode gases were set to those at 0.05 standard current density while the load was kept at 0.03 standard current density. Then the air supply was turned off to consume the residual oxygen in the cathode, and the load current was turned off when the average voltage was less than 0.2 V, and the hydrogen supply was turned off.

[0054] After the stack was purged, the maximum resistance reached during the purging process was 12 times the wet-state internal resistance, and the internal resistance did not change after the stack was left for 10 minutes after the purging process was completed, i.e. the internal resistance was 2.5 times the wet-state internal resistance. After the purging process, the stack would not be damaged at -20°C and could be successfully cold-started.

[0055] Example 3

[0056] A stack of 300 cells with an active area of 300 cm 2The stack cooling liquid outlet temperature is 55°C when the stack is pulled to 1 standard current density, satisfying the low temperature purging condition, and is gradually reduced to the idle speed operating point of 0.5 standard current density, and after running for 120 seconds, the stack purging process is entered. The fuel cell is set to run at 0.15 standard current density, during which dry hydrogen and air heated to 25°C are respectively introduced into the anode and cathode of the cell, and the flow rates of the anode and cathode gases correspond to the gas flow rates under 1.2 standard current density, and the anode and cathode gas pressures are 40 and 45 kPa respectively, while the stack cooling liquid outlet temperature is controlled to maintain 65°C, and the purging time is set to 20 seconds; the fuel cell is set to run at 0.15 standard current density, and the flow rates of the anode and cathode gases are set to the gas flow rates under 0.8 standard current density, and the purging time is set to 10 seconds; the fuel cell is set to run at 0.10 standard current density, and the flow rates of the anode and cathode gases correspond to the gas flow rates under 0.8 standard current density, and the purging time is set to 20 seconds; the fuel cell is set to run at 0.05 standard current density, and the flow rates of the anode and cathode gases correspond to the gas flow rates under 0.5 standard current density, and the purging time is set to 20 seconds; the fuel cell is set to run at 0.03 standard current density, and the flow rates of the anode and cathode gases correspond to the gas flow rates under 0.5 standard current density, and the purging time is set to 10 seconds; under a load of 0.03 standard current density, the gas flow rate is set to 0.05 standard current density. Then the air supply is turned off, the residual oxygen remaining in the cathode is consumed, and when the average voltage is <0.2V, the load current is turned off and the hydrogen supply is turned off.

[0057] After the stack is purged, the maximum resistance reached during the purging process is 13 times the wet state resistance, and after waiting for the proton exchange membrane to reach equilibrium, the resistance does not change after 10 minutes of purging and waiting, which is 2.5 times the wet state resistance. After purging, the stack will not be damaged at -20°C and can successfully perform a cold start.

[0058] Example 4

[0059] 300 active area 300 cm 2The stack cooling liquid outlet temperature is 55°C when the stack is pulled to 1 standard current density, satisfying the low temperature purging condition, and gradually reduced to the idle speed operating point of 0.5 standard current density, and after running for 120 seconds, the stack purging process is entered. The fuel cell is set to run at 0.15 standard current density, during which dry hydrogen and air heated to 65°C are respectively introduced into the anode and cathode of the cell, and the flow rates of the anode and cathode gases correspond to the gas flow rates at 1.2 standard current density, and the anode and cathode gas pressures are 40 and 45 kPa respectively, while the stack cooling liquid outlet temperature is controlled to maintain 65°C, and the purging time is set to 20 seconds; the fuel cell is set to run at 0.15 standard current density, and the flow rates of the anode and cathode gases are set to the gas flow rates at 0.8 standard current density, and the purging time is set to 10 seconds; the fuel cell is set to run at 0.10 standard current density, and the flow rates of the anode and cathode gases correspond to the gas flow rates at 0.8 standard current density, and the purging time is set to 20 seconds; the fuel cell is set to run at 0.05 standard current density, and the flow rates of the anode and cathode gases correspond to the gas flow rates at 0.5 standard current density, and the purging time is set to 20 seconds; the fuel cell is set to run at 0.03 standard current density, and the flow rates of the anode and cathode gases correspond to the gas flow rates at 0.5 standard current density, and the purging time is set to 10 seconds; under a load of 0.03 standard current density, the gas flow rate is set to 0.05 standard current density. Then the air supply is turned off, the residual oxygen remaining in the cathode is consumed, and when the average voltage is <0.2V, the load current is turned off and the hydrogen supply is turned off.

[0060] After the stack is purged, the maximum resistance reached during the purging process is 15 times the wet state resistance, and after waiting for the proton exchange membrane to reach equilibrium, the resistance does not change after 10 minutes of purging and waiting, which is 3.0 times the wet state resistance. After purging, the stack will not be damaged at -20°C and can successfully perform a cold start.

[0061] Example 5

[0062] 300 active area 300 cm 2The stack cooling liquid outlet temperature is 55°C when the stack is pulled to 1 standard current density, satisfying the low temperature purging condition, and gradually reduced to the idle speed operating point of 0.5 standard current density, and after running for 120 seconds, the stack purging process is entered. The fuel cell is set to run at 0.15 standard current density, during which dry hydrogen and air heated to 45°C are respectively introduced into the anode and cathode of the cell, and the flow rates of the anode and cathode gases correspond to the gas flow rates at 1.2 standard current density, and the anode and cathode gas pressures are 40 and 45 kPa respectively, while the stack cooling liquid outlet temperature is controlled to maintain 65°C, and the purging time is set to 20 seconds; the fuel cell is set to run at 0.15 standard current density, and the flow rates of the anode and cathode gases are set to the gas flow rates at 0.8 standard current density, and the purging time is set to 10 seconds; the fuel cell is set to run at 0.10 standard current density, and the flow rates of the anode and cathode gases correspond to the gas flow rates at 0.8 standard current density, and the purging time is set to 20 seconds; the fuel cell is set to run at 0.05 standard current density, and the flow rates of the anode and cathode gases correspond to the gas flow rates at 0.5 standard current density, and the purging time is set to 20 seconds; the fuel cell is set to run at 0.03 standard current density, and the flow rates of the anode and cathode gases correspond to the gas flow rates at 0.5 standard current density, and the purging time is set to 10 seconds; under a load of 0.03 standard current density, the gas flow rate is set to 0.05 standard current density. Then the air supply is turned off, the residual oxygen remaining in the cathode is consumed, and when the average voltage is <0.2V, the load current is turned off and the hydrogen supply is turned off.

[0063] After the stack is purged, the maximum resistance reached during the purging process is 14 times the wet state resistance, and after waiting for the proton exchange membrane to reach equilibrium, the resistance does not change after 10 minutes of purging and waiting, which is 2.8 times the wet state resistance. After purging, the stack will not be damaged at -20°C and can successfully perform a cold start.

[0064] Example 6

[0065] 300 active area 300 cm 2The stack cooling liquid outlet temperature is 55°C when the stack is pulled to 1 standard current density, satisfying the low temperature purging condition, and gradually reduced to the idle speed operating point 0.4 standard current density, and after running for 240 seconds, the stack purging process is entered. The fuel cell is set to run at 0.18 standard current density, during which dry and unheated hydrogen and air are respectively introduced into the anode and cathode of the cell. The flow rates of the anode and cathode gases correspond to the gas flow rates at 1.4 standard current density, and the anode and cathode gas pressures are 35 and 35 kPa, respectively. The stack cooling liquid outlet temperature is controlled to maintain 60°C, and the purging time is set to 10 seconds. Then the fuel cell is set to run at 0.16 standard current density, and the flow rates of the anode and cathode gases are set to the gas flow rates at 0.9 standard current density, and the purging time is set to 20 seconds. The fuel cell is set to run at 0.11 standard current density, and the flow rates of the anode and cathode gases correspond to the gas flow rates at 0.9 standard current density, and the purging time is set to 10 seconds. The fuel cell is set to run at 0.06 standard current density, and the flow rates of the anode and cathode gases correspond to the gas flow rates at 0.7 standard current density, and the purging time is set to 10 seconds. The fuel cell is set to run at 0.035 standard current density, and the flow rates of the anode and cathode gases correspond to the gas flow rates at 0.7 standard current density, and the purging time is set to 7 seconds. Then the gas flow rate is set to 0.15 standard current density under a load of 0.035 standard current density. Then the air supply is turned off, the residual oxygen remaining in the cathode is consumed, and when the average voltage is <0.15V, the load current is turned off and the hydrogen supply is turned off.

[0066] After the stack is purged, the maximum resistance reached during the purging process is 15 times the wet state resistance, and after waiting for the proton exchange membrane water balance, the resistance does not change after 10 minutes of purging and waiting, which is 3.1 times the wet state resistance. After purging, the stack will not be damaged at -20°C and can successfully perform a cold start.

[0067] Example 7

[0068] 300 active area 300 cm 2The stack cooling liquid outlet temperature is 55°C when the stack is pulled to 1 standard current density, satisfying the low temperature purging condition, and gradually reduced to the idle speed operating point 0.45 standard current density, and after running for 200 seconds, the stack purging process is entered. The fuel cell is set to run at 0.16 standard current density, during which dry and unheated hydrogen and air are respectively introduced into the anode and cathode of the cell. The flow rates of the anode and cathode gases correspond to the gas flow rates at 1.3 standard current density, and the anode and cathode gas pressures are 30 and 40 kPa, respectively. The stack cooling liquid outlet temperature is controlled to maintain 63°C, and the purging time is set to 15 seconds. Then the fuel cell is set to run at 0.18 standard current density, and the flow rates of the anode and cathode gases are set to the gas flow rates at 1.0 standard current density, and the purging time is set to 15 seconds. The fuel cell is set to run at 0.12 standard current density, and the flow rates of the anode and cathode gases correspond to the gas flow rates at 0.9 standard current density, and the purging time is set to 15 seconds. The fuel cell is set to run at 0.08 standard current density, and the flow rates of the anode and cathode gases correspond to the gas flow rates at 0.8 standard current density, and the purging time is set to 15 seconds. The fuel cell is set to run at 0.04 standard current density, and the flow rates of the anode and cathode gases correspond to the gas flow rates at 0.8 standard current density, and the purging time is set to 5 seconds. With a load of 0.04 standard current density, the gas flow rate is set to 0.03 standard current density. Then the air supply is turned off, the residual oxygen remaining in the cathode is consumed, and when the average voltage is <0.35V, the load current is turned off and the hydrogen supply is turned off.

[0069] After the stack is purged, the maximum resistance reached during the purging process is 14 times the wet state resistance, and after waiting for the proton exchange membrane to reach equilibrium, the resistance does not change after 10 minutes of purging and waiting, which is 2.7 times the wet state resistance. After purging, the stack will not be damaged at -20°C and can successfully perform a cold start.

[0070] Example 8

[0071] 300 active area 300 cm 2The stack is cooled to 55°C at 1 standard current density, and the stack cooling liquid outlet temperature meets the low-temperature purging condition. The load is gradually reduced to the idle operating point of 0.45 standard current density, and the stack purging process is entered after 200 seconds of operation. The fuel cell is set to operate at 0.16 standard current density, and dry and unheated hydrogen and air are supplied to the anode and cathode of the cell, respectively. The flow rates of the anode and cathode gases correspond to the flow rates of the gases at 1.3 standard current density, and the pressures of the anode and cathode gases are 40 and 40 kPa, respectively. The stack cooling liquid outlet temperature is controlled to maintain 63°C, and the purging time is set to 15 seconds. The fuel cell is set to operate at 0.15 standard current density, and the flow rates of the anode and cathode gases are set to the flow rates of the gases at 0.8 standard current density. The pressures of the anode and cathode gases are 40 and 40 kPa, respectively, and the purging time is set to 10 seconds. The fuel cell is set to operate at 0.10 standard current density, and the flow rates of the anode and cathode gases correspond to the flow rates of the gases at 0.8 standard current density. The pressures of the anode and cathode gases are 30 and 35 kPa, respectively, and the purging time is set to 20 seconds. The fuel cell is set to operate at 0.05 standard current density, and the flow rates of the anode and cathode gases correspond to the flow rates of the gases at 0.5 standard current density. The pressures of the anode and cathode gases are 30 and 35 kPa, respectively, and the purging time is set to 20 seconds. The fuel cell is set to operate at 0.03 standard current density, and the flow rates of the anode and cathode gases correspond to the flow rates of the gases at 0.5 standard current density. The pressures of the anode and cathode gases are 35 and 45 kPa, respectively, and the purging time is set to 10 seconds. The fuel cell is set to operate at 0.03 standard current density, and the flow rates of the anode and cathode gases are set to the flow rates of the gases at 0.05 standard current density. The pressures of the anode and cathode gases are 35 and 45 kPa, respectively. Then, the supply of air is stopped, the residual oxygen remaining in the cathode is consumed, and when the average voltage is <0.2V, the load current is turned off, and the supply of hydrogen is stopped.

[0072] After the stack is purged, the maximum resistance reached during the purging process is 12 times the wet-state internal resistance, and the internal resistance does not change after the purging process ends and the proton exchange membrane internal balance is waited for 10 minutes, which is 2.6 times the wet-state internal resistance. After purging, the stack will not be damaged at -20°C and can be successfully cold-started.

[0073] Comparative Example 1

[0074] 500 active area 350 cm 2The stack cooling liquid outlet temperature is 55℃ when the stack is pulled to 1 standard current density, which meets the low-temperature purging condition, and is gradually pulled to the idle speed working point of 0.5 standard current density, and after running for 120 seconds, the stack purging process is entered. The fuel cell is set to run at 0.15 standard current density, during which dry and unheated hydrogen and air are respectively supplied to the anode and cathode of the cell, the flow rates of the anode and cathode gases correspond to the flow rates of the gases at 1.2 standard current density, the pressures of the anode and cathode gases are 40 and 45 kPa respectively, and the stack cooling liquid outlet temperature is controlled to be maintained at 65℃, and the purging time is set to 2 min; then the load is lowered to 0.03 standard current density, and the gas flow rate is set to 0.05 standard current density. Then the air supply is turned off, the residual oxygen in the cathode is consumed, and when the average voltage is <0.2V, the load current is turned off, and the hydrogen supply is turned off.

[0075] After the stack is purged, the maximum resistance reached during the purging process is only 8 times the wet-state resistance, and after the end of the purging process and waiting for 10 minutes, the resistance no longer changes and is 2 times the wet-state resistance. The results prove that this constant-flow purging method cannot achieve the ideal purging effect, which further affects the low-temperature starting performance of the fuel cell stack. If this method is used for purging to achieve the ideal resistance value, at least 5 min of purging time is required, which consumes a large amount of electrical energy and gas.

[0076] It is apparent for those skilled in the art that the present application is not limited to the details of the foregoing exemplary embodiments, and the present application can be implemented in other concrete forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be considered in all aspects as illustrative and not restrictive, and the scope of the present application is defined by the appended claims rather than the foregoing description, and it is intended to encompass all changes falling within the meaning and range of equivalents of the elements of the claims.

[0077] In addition, it should be understood that although the present specification is described in terms of embodiments, not every embodiment contains only one independent technical solution, and the description of the specification is only for the sake of clarity, and those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that those skilled in the art can understand.

Claims

1. A fuel cell low temperature shutdown purging method, comprising the following steps: Judging whether the stack coolant outlet temperature meets the low temperature purging condition, the low temperature purging condition being that when the stack is pulled to 1 standard current density, judging whether the stack coolant outlet temperature is greater than or equal to 60-70℃, if yes, entering the temperature rising process to continue normal loading, otherwise, gradually reducing the load to an idle operating point, after the load reduction is completed, entering the stack purging process, the purging process being as follows: Step (1), the fuel cell is set to operate at 0.15-0.18 standard current density, during which dry hydrogen and air are respectively introduced into the anode and cathode of the cell, the flow rates of the anode and cathode gases corresponding to the gas flow rates at 1.2-1.4 standard current density, the stack coolant outlet temperature is controlled to be maintained at 60-65℃, and the purging time is set to 10-20 seconds; Step (2), the fuel cell is set to operate at 0.15-0.18 standard current density, the flow rates of the anode and cathode gases corresponding to the gas flow rates at 0.8-1.0 standard current density, and the purging time is set to 10-20 seconds; Step (3), the fuel cell is set to operate at 0.10-0.12 standard current density, the flow rates of the anode and cathode gases corresponding to the gas flow rates at 0.8-1.0 standard current density, and the purging time is set to 10-20 seconds; Step (4), the fuel cell is set to operate at 0.05-0.08 standard current density, the flow rates of the anode and cathode gases corresponding to the gas flow rates at 0.5-0.8 standard current density, and the purging time is set to 10-20 seconds; Step (5), the fuel cell is set to operate at 0.03-0.04 standard current density, the flow rates of the anode and cathode gases corresponding to the gas flow rates at 0.5-0.8 standard current density, and the purging time is set to 5-10 seconds; Step (6), with a load of 0.03-0.04 standard current density, the gas flow rate is set to 0.05-0.3 standard current density, the air supply of the fuel cell is turned off, the residual oxygen remaining in the cathode is consumed, and when the average voltage is <0.15-0.35V, the load current is turned off, and the hydrogen supply is turned off; wherein At least any one of steps (1)-(6) meets that the gas supply pressures of the anode and cathode are 30-40 kPa and 35-45 kPa, respectively.

2. The fuel cell subfreezing shutdown purge method of claim 1, wherein, The hydrogen and / or air in steps (1)-(6) is preheated.

3. The fuel cell subfreezing shutdown purge method of claim 2, wherein, The preheated hydrogen and / or air has a temperature in the range of 25-65℃.

4. The fuel cell subfreezing shutdown purge method of claim 1 wherein, The idle operating point is that the current density of the stack is reduced to 0.4-0.5 standard current density.

5. The method of claim 1, wherein, The stack is operated at the idle operating point for 120-240 seconds before entering the stack purging process.

6. The fuel cell subfreezing shutdown purge method of claim 1 wherein, In steps (1)-(6), the gas supply pressures of the anode and cathode in each step are the same.

7. The method of claim 1, wherein, After the air supply is turned off in step (6), the time for the average voltage of the fuel cell to decrease from the purging voltage to <0.15-0.35V is 5 to 20 seconds.

8. A purge apparatus for performing the fuel cell low temperature shutdown purge method according to any one of claims 1 to 7.

9. A purge system comprising a main body and a plurality of purge apparatuses according to claim 8 disposed in the main body.

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