Proton exchange membrane fuel cell system low-temperature starting method, system and cell

Abstract

The invention discloses a low-temperature starting method and system of a proton exchange membrane fuel cell system and a cell, and the starting method comprises the following steps: step A, under a low-temperature condition, starting a galvanic pile, supplying a gas condition meeting an initial operation requirement to the galvanic pile, and loading the output current density from 0A cm <-2 > to a starting state by starting a loading slope; step B, monitoring a time-high-frequency impedance value curve, setting the starting time of the cooling system according to the increment of the inclination angle of the curve within 10s, and meanwhile, turning on a PTC heater on a small circulation path for heating; step C, monitoring the out-of-pile temperature of the cooling liquid, and on the premise that the out-of-pile temperature stably rises and does not exceed a normal operation temperature interval, turning on the PTC heater on the small circulation path for heating; operating conditions are matched in different pile outlet temperature intervals; and D, when the temperature of the cooling liquid out of the electric pile is stabilized to the operating temperature, supplying a gas condition meeting normal operation, and completing the low-temperature starting process. According to the invention, the start-up time can be shortened, so that quick, safe and effective cold start is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel cells, and in particular relates to a low-temperature starting method, system and battery for a proton exchange membrane fuel cell system. Background Art

[0002] With the rapid development of the hydrogen energy industry, proton exchange membrane fuel cells (PEMFC) are being used in more and more low-temperature scenarios, which places high demands on the rapid start-up capability of PEMFC in low-temperature environments. At present, the self-heating is usually achieved by controlling the output characteristics of the stack, that is, by controlling the load to operate at a constant current or constant voltage at a low temperature to generate heat for internal heating of the fuel cell. At low temperatures, if there is too much residual water in the stack or too much water generated in the catalyst layer, it will freeze in the pores of the porous material, cover the surface of the platinum catalyst particles or hinder the transmission of the reaction gas, resulting in reduced battery output performance. Before the catalyst layer is completely covered with ice, if the temperature of the stack does not rise above 0°C, the electrochemical reaction of the battery stops and the cold start fails. Therefore, the process of the cold start process is essentially a competition between the freezing rate and the heating rate of the stack.

[0003] In order to speed up the heating speed, the coolant can be turned off in the early stage of startup to reduce the thermal melt of the fuel cell system, but the timing of the subsequent coolant flow is not easy to control. In the prior art, the timing of passing the coolant is usually determined by monitoring the temperature of the air out of the fuel cell stack or the temperature of the coolant out of the fuel cell stack to reach a certain value. The accuracy of this judgment method is poor and the response time required is long, which may cause a large temperature difference between the inlet and outlet of the fuel cell stack, which can easily cause uneven temperature on the membrane electrode surface in the fuel cell stack, generate local hot spots, cause leakage of the membrane electrode, and cause safety accidents.

[0004] Therefore, in view of the above technical problems, it is necessary to provide a low-temperature start-up method, system and battery for a proton exchange membrane fuel cell system.

[0005] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0006] The object of the present invention is to provide a low-temperature starting method, system and battery for a proton exchange membrane fuel cell system.

[0007] In order to achieve the above object, a technical solution provided by a specific embodiment of the present invention is as follows:

[0008] A low temperature start-up method for a proton exchange membrane fuel cell system, comprising:

[0009] Step A: Under low temperature conditions, start the stack and supply it with gas conditions that meet the initial operation requirements to start the loading slope and increase the output current density from 0 A cm -2 Load to startup state;

[0010] Step B, monitor the time-high frequency impedance value curve, set the start time of the cooling system according to the increase of the inclination angle of the curve within 10 seconds, and turn on the PTC heater on the small circulation path for heating:

[0011] Step C, monitoring the discharge temperature of the coolant, and matching the operating conditions in different discharge temperature ranges under the premise that the discharge temperature rises steadily and does not exceed the normal operating temperature range, the operating conditions including the gas conditions that meet the operation at the limited output current density, the input parameters of the coolant, and the circulation state setting of the coolant;

[0012] Step D: When the temperature of the coolant stack stabilizes to the operating temperature, the gas conditions that meet normal operation are supplied and the low-temperature startup process is completed.

[0013] In one or more embodiments of the present invention, the setting of the start-up time of the cooling system in step B satisfies:

[0014] If the curve increases inclination angle from 0 to 30° within 10 seconds, the cooling system will be started after 5 seconds;

[0015] If the curve increases inclination angle to 30-45° within 10 seconds, the cooling system will be started after 3 seconds;

[0016] If the inclination angle of the curve increases to 45-60° within 10 seconds, the cooling system will be started immediately.

[0017] In one or more embodiments of the present invention, the matching of the operating conditions based on the discharge temperature range in step C includes the following process:

[0018] When the temperature of the coolant stack rises to 20-30°C, the temperature should be 0.7-0.9A cm -2 The gas supply to the fuel cell stack is carried out under the gas condition of operation, and the output current density is increased from 0.2-0.3A cm at a loading slope of 8-10A / s. -2 Load to 0.6-0.8A cm -2 ;

[0019] When the temperature of the coolant leaving the stack reaches 40-45°C, control the thermostat opening at 5%-10%; after the temperature of the coolant leaving the stack continues to rise by 5-10°C, control the thermostat opening according to the temperature difference between the coolant entering and leaving the stack, and gradually intervene in the large circulation of the stack cooling system.

[0020] Preferably, the thermostat opening is controlled according to the temperature difference between the coolant entering and leaving the stack: when the temperature difference between the coolant entering and leaving the stack is greater than 10°C, the thermostat opening is reduced; when the temperature difference between the coolant entering and leaving the stack is less than 10°C, the thermostat opening is increased, and the thermostat is gradually fully opened.

[0021] In one or more embodiments of the present invention, after the thermostat opening reaches 60-100%, the cathode stoichiometric ratio is reduced by 0.1-0.5 to increase the heat generation of the stack.

[0022] In one or more embodiments of the present invention, when the temperature of the coolant stack is stabilized at 60-65°C in step D, the temperature is controlled to meet the requirements of 1.0-1.2A cm -2 The gas supply to the fuel cell stack is carried out under the gas condition of operation, and the output current density is increased from 0.6 to 0.8 A cm at a loading slope of 15 to 20 A / s. -2 Load to 1.0-1.2A cm -2 Stable operation, low temperature startup process is completed.

[0023] In one or more embodiments of the present invention, in step A: after the stack is turned on, the temperature is kept at 0.3-0.5A cm -2 The gas supply to the fuel cell stack is carried out under the gas condition of operation, and the output current density is increased from 0A cm to 3A / s at a loading slope of 1-3A / s. -2 Load to 0.2-0.3A cm -2 .

[0024] In one or more embodiments of the present invention, the gas conditions in step A are: the flow rates of cathode gas and anode gas are 3000-5000NLPM and 900-1500NLPM, respectively, and the pressures of cathode gas and anode gas are 60-80KPa and 70-90KPa, respectively.

[0025] In one or more embodiments of the present invention, the low temperature condition of step A satisfies: not higher than 5°C.

[0026] In one or more embodiments of the present invention, a low temperature start-up system is used to execute a low temperature start-up method for a proton exchange membrane fuel cell system.

[0027] In one or more embodiments of the present invention, a battery includes a fuel cell body and a cold start system connected to the body.

[0028] Compared with the prior art, the low-temperature start-up method, system and battery of the proton exchange membrane fuel cell system of the present invention can quickly judge the heat generation state inside the stack by monitoring the increase rate of the high-frequency impedance value in the time-high-frequency impedance value curve of the stack, so as to control the timing of passing cooling water. The response time required is very short, so that the temperature distribution within the membrane electrode surface of the stack is uniform, and the durability of the stack is improved. Controlling the intervention timing and intervention strategy of the large cycle in the small cycle operation during the low-temperature loading process can effectively avoid the drastic fluctuation of the internal temperature of the stack. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 A schematic diagram of a process of a cold start method for a fuel cell according to an embodiment of the present invention;

[0031] Figure 2 This is a table of polarization conditions during the cold start of a fuel cell in one embodiment of the present invention;

[0032] Figure 3 Schematic diagram of the large and small circulation of the cooling liquid circuit of the low-temperature starting system in one embodiment of the present invention. DETAILED DESCRIPTION

[0033] In order 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 in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0034] The low temperature startup method of the proton exchange membrane fuel cell system of the present invention may specifically include the following steps:

[0035] Step (1), turn on the battery stack and apply 0.3-0.5A cm according to the polarization condition table. -2 The output current density was increased from 0A cm to 3A / s under the gas condition with a loading slope of 1-3A / s. -2 Load to 0.2-0.3A cm -2 ;

[0036] Step (2), when the curve in the time-high frequency impedance value curve of the waiting battery stack increases, if the increasing inclination angle of the curve within 10 seconds is 0-30°, then the water pump is started after 5 seconds; if the increasing inclination angle of the curve within 10 seconds is 30-45°, then the water pump is started after 3 seconds; if the increasing inclination angle of the curve within 10 seconds is 45-60°, then the water pump is started immediately, and the PTC heater on the small circulation path is turned on for heating;

[0037] Step (3), when the temperature of the coolant stack rises to 20-30°C, give 0.7-0.9Acm according to the polarization condition table. -2 Under the gas condition, the output current density is increased from 0.2-0.3A cm with a loading slope of 8-10A / s. -2 Load to 0.6-0.8A cm -2 ;

[0038] Step (4), when the temperature of the coolant out of the stack reaches 40-45°C, the thermostat is opened at the minimum opening, and the thermostat opening is controlled at 5%-10%; after the temperature of the coolant out of the stack rises by 5-10°C, the thermostat opening is controlled according to the temperature difference between the coolant in and out of the stack, and the large circulation of the stack cooling system is gradually involved;

[0039] Step (5), after the thermostat opening reaches 60-100%, reducing the cathode stoichiometric ratio by 0.1-0.5 to increase the heat generation of the stack;

[0040] Step (6), when the temperature of the coolant stack is stable at 60-65°C, give 1.0-1.2Acm according to the polarization condition table. -2 Under the gas condition, the output current density is increased from 0.6 to 0.8 A cm at a loading slope of 15 to 20 A / s. -2 Load to 1.0-1.2A cm -2 , the low temperature start-up process is completed.

[0041] In one or more embodiments of the present invention, before the cold start of the fuel cell stack, it is determined whether the ambient temperature is <5°C. If so, a low-temperature cold start process is performed, and parts such as the water pump, circulation pump, drain valve, nitrogen exhaust valve, air compressor, back pressure valve, hydrogen main valve, and proportional valve are opened and closed to confirm whether they can operate normally. Otherwise, it is determined that some parts are damaged and the start is canceled. If so, the fuel cell stack cold start steps are executed.

[0042] In one or more embodiments of the present invention, the gas condition of 0.3-0.5A cm-2 in step (1) is that dry or humidified hydrogen and air are respectively introduced into the anode and cathode of the battery, the flow rates of the cathode and cathode gases are 3000-5000NLPM and 900-1500NLPM, respectively, and the pressures of the cathode and cathode gases are 60-80 and 70-90KPa, respectively;

[0043] In one or more embodiments of the present invention, as described in step (2), an AC impedance meter is used to measure the time-high frequency impedance value curve of the entire stack, and an AC impedance meter can also be used to measure the time-high frequency impedance value curve of 10-20 membrane electrodes in the middle of the stack.

[0044] In one or more embodiments of the present invention, the coolant circulation system includes a coolant outlet, a coolant inlet, a PTC heater, a thermostat, a water pump, a main radiator and an expansion water tank, wherein the coolant outlet, the PTC heater, the thermostat, the water pump and the coolant inlet form a small cycle, and the coolant outlet, the thermostat, the main radiator, the expansion water tank, the water pump and the coolant inlet form a large cycle;

[0045] In one or more embodiments of the present invention, as described in step (2), when the water pump is running, the thermostat is used to control only a small circulation of the stack cooling system.

[0046] In one or more embodiments of the present invention, the cooling liquid is an ethylene glycol solution.

[0047] Example 1

[0048] 500 sections with an active area of ​​350cm 2 The fuel cell system of the fuel cell stack (water-cooled fuel cell stack, the same below) is filled with ethylene glycol antifreeze and placed in a low-temperature environment of -20℃, with the ambient temperature <5℃, for low-temperature cold start operation. First, open and close the water pump, circulation pump, drain valve, nitrogen exhaust valve, air compressor, back pressure valve, hydrogen main valve, proportional valve and other components. The above components can operate normally, and then perform the cold start steps of the fuel cell stack. Turn on the fuel cell stack and follow the Figure 2 The polarization conditions shown in the table are 0.3A cm -2 The gas conditions were as follows: dry hydrogen and air were introduced into the anode and cathode of the battery respectively. The flow rates of the cathode and cathode gases were 3340 NLPM and 915 NLPM respectively, and the pressures of the cathode and cathode gases were 60 KPa and 70 KPa respectively. Then, the output current density was increased from 0 A cm to 1000 A cm with a loading slope of 3 A / s. -2 Load to 0.2A cm -2 The time-high frequency impedance curve of the entire stack was measured using an AC impedance meter. The curve first decreased rapidly, then slowly and steadily increased. The slope angle of the curve increased by 40° within 10 seconds. After waiting for 3 seconds, the water pump was started and the PTC heater on the small circulation path was turned on for heating. Wait for the coolant to rise to 20°C at the stack outlet. According to the polarization condition table, 0.7A cm -2The gas conditions were as follows: the flow rates of the cathode and anode gases were 4907 NLPM and 1592 NLPM, respectively; the pressures of the cathode and anode gases were 100 KPa and 110 KPa, respectively. Then, the output current density was increased from 0.2 A cm to 1.5 A cm with a loading slope of 8 A / s. -2 Loaded to 0.6A cm -2 . When the temperature of the coolant leaving the stack reaches 40°C, open the thermostat at a minimum opening of 1%, and control the thermostat opening at 5%-10%. After the temperature of the coolant leaving the stack rises by 10°C, the temperature difference between the coolant entering and leaving the stack reaches 15°C, reduce the thermostat opening, and then the temperature difference between the coolant entering and leaving the stack is less than 10°C. At this time, increase the thermostat opening and gradually intervene in the large cycle of the stack cooling system. After the thermostat opening reaches 60%, reduce the cathode stoichiometric ratio of 2.5 by 0.5 to increase the heat generation of the stack. When the temperature of the coolant leaving the stack stabilizes at 60°C, give 1.0A cm according to the polarization condition table. -2 Under the gas condition, the output current density was increased from 0.6A cm -2 Load to 1.0Acm -2 The cold start process is completed. The entire cold start process takes only 2 minutes to pull the fuel cell system at -20 degrees Celsius to 1.0A cm -2 .

[0049] Example 2

[0050] 500 sections with an active area of ​​350cm 2 The fuel cell system of the fuel cell stack (water-cooled fuel cell stack, the same below) is filled with ethylene glycol antifreeze and placed in a low-temperature environment of -20℃, with the ambient temperature <5℃, for low-temperature cold start operation. First, open and close the water pump, circulation pump, drain valve, nitrogen exhaust valve, air compressor, back pressure valve, hydrogen main valve, proportional valve and other components. The above components can operate normally, and then perform the cold start steps of the fuel cell stack. Turn on the fuel cell stack and follow the Figure 2 The polarization conditions shown in the table are 0.3A cm -2 The gas conditions were as follows: dry hydrogen and air were introduced into the anode and cathode of the battery respectively. The flow rates of the cathode and cathode gases were 3340 NLPM and 915 NLPM respectively, and the pressures of the cathode and cathode gases were 60 KPa and 70 KPa respectively. Then, the output current density was increased from 0 A cm to 1000 A cm with a loading slope of 3 A / s. -2 Load to 0.2A cm -2The time-high frequency impedance curve of the entire stack was measured using an AC impedance meter. The curve first decreased rapidly, then slowly and steadily increased. The slope angle of the curve increased by 20° within 10 seconds. After waiting for 5 seconds, the water pump was started and the PTC heater on the small circulation path was turned on for heating. Wait for the coolant to rise to 20°C at the stack outlet. According to the polarization condition table, 0.7A cm -2 The gas conditions were as follows: the flow rates of the cathode and anode gases were 4907 NLPM and 1592 NLPM, respectively; the pressures of the cathode and anode gases were 100 KPa and 110 KPa, respectively. Then, the output current density was increased from 0.2 A cm to 1.5 A cm with a loading slope of 8 A / s. -2 Loaded to 0.6A cm -2 . When the temperature of the coolant leaving the stack reaches 40°C, open the thermostat at a minimum opening of 1%, and control the thermostat opening at 5%-10%. After the temperature of the coolant leaving the stack rises by 10°C, the temperature difference between the coolant entering and leaving the stack reaches 15°C, reduce the thermostat opening, and then the temperature difference between the coolant entering and leaving the stack is less than 10°C. At this time, increase the thermostat opening and gradually intervene in the large cycle of the stack cooling system. After the thermostat opening reaches 60%, reduce the cathode stoichiometric ratio of 2.5 by 0.5 to increase the heat generation of the stack. When the temperature of the coolant leaving the stack stabilizes at 60°C, give 1.0A cm according to the polarization condition table. -2 Under the gas condition, the output current density was increased from 0.6A cm -2 Load to 1.0Acm -2 The cold start process is completed. The entire cold start process takes only 2 minutes to pull the fuel cell system at -20 degrees Celsius to 1.0A cm -2 .

[0051] Example 3

[0052] 500 sections with an active area of ​​350cm 2 The fuel cell system of the fuel cell stack (water-cooled fuel cell stack, the same below) is filled with ethylene glycol antifreeze and placed in a low-temperature environment of -20℃, with the ambient temperature <5℃, for low-temperature cold start operation. First, open and close the water pump, circulation pump, drain valve, nitrogen exhaust valve, air compressor, back pressure valve, hydrogen main valve, proportional valve and other components. The above components can operate normally, and then perform the cold start steps of the fuel cell stack. Turn on the fuel cell stack and follow the Figure 2 The polarization conditions shown in the table are 0.3A cm -2 The gas conditions were as follows: dry hydrogen and air were introduced into the anode and cathode of the battery respectively. The flow rates of the cathode and cathode gases were 3340 NLPM and 915 NLPM respectively, and the pressures of the cathode and cathode gases were 60 KPa and 70 KPa respectively. Then, the output current density was increased from 0 A cm to 1000 A cm with a loading slope of 3 A / s. -2Load to 0.2A cm -2 The time-high frequency impedance curve of the entire stack was measured using an AC impedance meter. The curve first decreased rapidly, then slowly and steadily increased. The slope angle of the curve increased by 50° within 10 seconds. The water pump was immediately started, and the PTC heater on the small circulation path was turned on for heating. Wait for the coolant to rise to 20°C at the stack temperature, and give 0.7A cm -2 The gas conditions were as follows: the flow rates of the cathode and anode gases were 4907 NLPM and 1592 NLPM, respectively; the pressures of the cathode and anode gases were 100 KPa and 110 KPa, respectively. Then, the output current density was increased from 0.2 A cm to 1.5 A cm with a loading slope of 8 A / s. -2 Loaded to 0.6A cm -2 . When the temperature of the coolant leaving the stack reaches 40°C, open the thermostat at a minimum opening of 1%, and control the thermostat opening at 5%-10%. After the temperature of the coolant leaving the stack rises by 10°C, the temperature difference between the coolant entering and leaving the stack reaches 15°C, reduce the thermostat opening, and then the temperature difference between the coolant entering and leaving the stack is less than 10°C. At this time, increase the thermostat opening and gradually intervene in the large cycle of the stack cooling system. After the thermostat opening reaches 60%, reduce the cathode stoichiometric ratio of 2.5 by 0.5 to increase the heat generation of the stack. When the temperature of the coolant leaving the stack stabilizes at 60°C, give 1.0A cm according to the polarization condition table. -2 Under the gas condition, the output current density was increased from 0.6A cm -2 Load to 1.0A cm -2 The cold start process is completed. The entire cold start process takes only 2 minutes to pull the fuel cell system at -20 degrees Celsius to 1.0A cm -2 .

[0053] Example 4

[0054] 500 sections with an active area of ​​350cm 2 The fuel cell system of the fuel cell stack (water-cooled fuel cell stack, the same below) is filled with ethylene glycol antifreeze and placed in a low-temperature environment of -20℃, with the ambient temperature <5℃, for low-temperature cold start operation. First, open and close the water pump, circulation pump, drain valve, nitrogen exhaust valve, air compressor, back pressure valve, hydrogen main valve, proportional valve and other components. The above components can operate normally, and then perform the cold start steps of the fuel cell stack. Turn on the fuel cell stack and follow the Figure 2 The polarization conditions shown in the table are 0.3A cm -2 The gas conditions were as follows: dry hydrogen and air were introduced into the anode and cathode of the battery respectively. The flow rates of the cathode and cathode gases were 3340 NLPM and 915 NLPM respectively, and the pressures of the cathode and cathode gases were 60 KPa and 70 KPa respectively. Then, the output current density was increased from 0 A cm to 1000 A cm with a loading slope of 3 A / s.-2 Load to 0.2A cm -2 The time-high frequency impedance curve of the entire stack was measured using an AC impedance meter. The curve first decreased rapidly, then slowly and steadily increased. The slope angle of the curve increased by 30° within 10 seconds. After waiting for 3 seconds, the water pump was started and the PTC heater on the small circulation path was turned on for heating. Wait for the coolant to rise to 20°C at the stack outlet. According to the polarization condition table, 0.7A cm -2 The gas conditions were as follows: the flow rates of the cathode and anode gases were 4907 NLPM and 1592 NLPM, respectively; the pressures of the cathode and anode gases were 100 KPa and 110 KPa, respectively. Then, the output current density was increased from 0.2 A cm to 1.5 A cm with a loading slope of 8 A / s. -2 Loaded to 0.6A cm -2 . When the temperature of the coolant leaving the stack reaches 40°C, open the thermostat at a minimum opening of 1%, and control the thermostat opening at 5%-10%. After the temperature of the coolant leaving the stack rises by 10°C, the temperature difference between the coolant entering and leaving the stack reaches 15°C, reduce the thermostat opening, and then the temperature difference between the coolant entering and leaving the stack is less than 10°C. At this time, increase the thermostat opening and gradually intervene in the large cycle of the stack cooling system. After the thermostat opening reaches 60%, reduce the cathode stoichiometric ratio of 2.5 by 0.5 to increase the heat generation of the stack. When the temperature of the coolant leaving the stack stabilizes at 60°C, give 1.0A cm according to the polarization condition table. -2 Under the gas condition, the output current density was increased from 0.6A cm -2 Load to 1.0Acm -2 The cold start process is completed. The entire cold start process takes only 2 minutes to pull the fuel cell system at -20 degrees Celsius to 1.0A cm -2 .

[0055] Example 5

[0056] 500 sections with an active area of ​​350cm 2 The fuel cell system of the fuel cell stack (water-cooled fuel cell stack, the same below) is filled with ethylene glycol antifreeze and placed in a low-temperature environment of -20℃, with the ambient temperature <5℃, for low-temperature cold start operation. First, open and close the water pump, circulation pump, drain valve, nitrogen exhaust valve, air compressor, back pressure valve, hydrogen main valve, proportional valve and other components. The above components can operate normally, and then perform the cold start steps of the fuel cell stack. Turn on the fuel cell stack and follow the Figure 2 The polarization conditions shown in the table are 0.4A cm -2The gas conditions were as follows: dry hydrogen and air were introduced into the anode and cathode of the battery respectively. The flow rates of the cathode and cathode gases were 4204NLPM and 1226NLPM respectively, and the pressures of the cathode and cathode gases were 70KPa and 80KPa respectively. Then, the output current density was increased from 0A cm to 100A cm with a loading slope of 1A / s. -2 Load to 0.25A cm -2 The time-high frequency impedance curve of the entire stack was measured using an AC impedance meter. The curve first decreased rapidly, then slowly and steadily increased. The slope angle of the curve increased to 0° within 10 seconds. After waiting for 5 seconds, the water pump was started and the PTC heater on the small circulation path was turned on for heating. Wait for the coolant to rise to 20°C at the stack outlet. According to the polarization condition table, 0.7A cm -2 The gas conditions were as follows: the flow rates of the cathode and anode gases were 4907 NLPM and 1592 NLPM, respectively; the pressures of the cathode and anode gases were 100 KPa and 110 KPa, respectively. Then, the output current density was increased from 0.2 A cm to 1.5 A cm with a loading slope of 8 A / s. -2 Loaded to 0.6A cm -2 . When the temperature of the coolant leaving the stack reaches 40°C, open the thermostat at a minimum opening of 1%, and control the thermostat opening at 5%-10%. After the temperature of the coolant leaving the stack rises by 10°C, the temperature difference between the coolant entering and leaving the stack reaches 15°C, reduce the thermostat opening, and then the temperature difference between the coolant entering and leaving the stack is less than 10°C. At this time, increase the thermostat opening and gradually intervene in the large cycle of the stack cooling system. After the thermostat opening reaches 60%, reduce the cathode stoichiometric ratio of 2.5 by 0.5 to increase the heat generation of the stack. When the temperature of the coolant leaving the stack stabilizes at 60°C, give 1.0A cm according to the polarization condition table. -2 Under the gas condition, the output current density was increased from 0.6A cm -2 Load to 1.0Acm -2 The cold start process is completed. The entire cold start process takes only 2.5 minutes to pull the fuel cell system at -20 degrees Celsius to 1.0A cm -2 .

[0057] Example 6

[0058] 500 sections with an active area of ​​350cm 2 The fuel cell system of the fuel cell stack (water-cooled fuel cell stack, the same below) is filled with ethylene glycol antifreeze and placed in a low-temperature environment of -30°C, with the ambient temperature <5°C, for low-temperature cold start operation. First, open and close the water pump, circulation pump, drain valve, nitrogen exhaust valve, air compressor, back pressure valve, hydrogen main valve, proportional valve and other components. The above components can operate normally, and then perform the cold start steps of the fuel cell stack. Turn on the fuel cell stack and follow the Figure 2The polarization conditions shown in the table are 0.5 A cm -2 The gas conditions were such that dry hydrogen and air were introduced into the anode and cathode of the battery respectively. Then the output current density was increased from 0A cm to 10A cm at a loading slope of 2A / s. -2 Load to 0.3A cm -2 The time-high frequency impedance curve of the entire stack was measured using an AC impedance meter. The curve first decreased rapidly, then slowly and steadily increased. The slope angle of the curve increased by 20° within 10 seconds. After waiting for 5 seconds, the water pump was started and the PTC heater on the small circulation path was turned on for heating. Wait for the coolant to rise to 25°C at the stack outlet. According to the polarization condition table, 0.8A cm -2 Then the output current density was increased from 0.25Acm with a loading slope of 10A / s. -2 Loaded to 0.7A cm -2 . When the temperature of the coolant leaving the stack reaches 40°C, the thermostat is opened at a minimum opening of 1%, and the thermostat opening is controlled to 5%. After the temperature of the coolant leaving the stack rises by 5°C, the temperature difference between the coolant entering and leaving the stack reaches 15°C, and the thermostat opening is reduced. After the temperature difference between the coolant entering and leaving the stack is less than 10°C, the thermostat opening is increased at this time, and the large circulation of the stack cooling system is gradually involved. After the thermostat opening reaches 80%, the cathode stoichiometric ratio of 2.5 is reduced by 0.1 to increase the heat generation of the stack. When the temperature of the coolant leaving the stack stabilizes at 63°C, give 1.1A cm according to the polarization condition table. -2 Under the gas condition, the output current density was increased from 0.7A cm -2 Load to 1.1A cm -2 The cold start process is completed. The entire cold start process takes only 3 minutes to pull the fuel cell system at minus 30 degrees Celsius to 1.1A cm -2 .

[0059] Example 7

[0060] 500 sections with an active area of ​​350cm 2 The fuel cell system of the fuel cell stack (water-cooled fuel cell stack, the same below) is filled with ethylene glycol antifreeze and placed in a low-temperature environment of -40°C, with the ambient temperature <5°C, for low-temperature cold start operation. First, open and close the water pump, circulation pump, drain valve, nitrogen exhaust valve, air compressor, back pressure valve, hydrogen main valve, proportional valve and other components. The above components can operate normally, and then perform the cold start steps of the fuel cell stack. Turn on the fuel cell stack and follow the Figure 2 The polarization conditions shown in the table are 0.3A cm -2 The gas conditions were such that dry hydrogen and air were introduced into the anode and cathode of the battery respectively. Then the output current density was increased from 0A cm to 10A cm at a loading slope of 3A / s.-2 Load to 0.2A cm -2 The time-high frequency impedance curve of the entire stack was measured using an AC impedance meter. The curve first decreased rapidly, then slowly and steadily increased. The slope angle of the curve increased by 40° within 10 seconds. After waiting for 3 seconds, the water pump was started and the PTC heater on the small circulation path was turned on for heating. Wait for the coolant to rise to 30°C at the stack outlet. According to the polarization condition table, 0.9A cm -2 Then the output current density was increased from 0.3Acm to 9A / s with a loading slope of 9A / s. -2 Loaded to 0.8A cm -2 . When the temperature of the coolant leaving the stack reaches 40°C, the thermostat opens at a minimum opening of 1%, and the thermostat opening is controlled to 10%. After the temperature of the coolant leaving the stack rises by 8°C, the temperature difference between the coolant entering and leaving the stack reaches 15°C, and the thermostat opening is reduced. After the temperature difference between the coolant entering and leaving the stack is less than 10°C, the thermostat opening is increased at this time, and the large circulation of the stack cooling system is gradually involved. After the thermostat opening reaches 100%, reduce the cathode stoichiometric ratio of 2.5 by 0.3 to increase the heat generation of the stack. When the temperature of the coolant leaving the stack stabilizes at 65°C, give 1.2A cm according to the polarization condition table. -2 Under the gas condition, the output current density was increased from 0.8A cm -2 Loaded to 1.2A cm -2 The cold start process is completed. The entire cold start process takes only 5 minutes to pull the fuel cell system at -40 degrees Celsius to 1.2A cm -2 .

[0061] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

[0062] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A low temperature start-up method for a proton exchange membrane fuel cell system, comprising: Step A: Under low temperature conditions, start the stack and supply it with gas conditions that meet the initial operation requirements to increase the output current density from 0 A cm -2 Load to startup state; Step B, monitor the time-high frequency impedance value curve, set the start time of the cooling system according to the increase of the inclination angle of the curve within 10 seconds, and turn on the PTC heater on the small circulation path for heating: Step C, monitoring the discharge temperature of the coolant, and matching the operating conditions in different discharge temperature ranges under the premise that the discharge temperature rises steadily and does not exceed the normal operating temperature range, wherein the operating conditions include gas conditions that meet the conditions for operation at a limited output current density, input parameters of the coolant, and circulation state settings of the coolant; Step D: When the temperature of the coolant stack stabilizes to the operating temperature, the gas conditions that meet normal operation are supplied and the low-temperature startup process is completed.

2. The low temperature start-up method of a proton exchange membrane fuel cell system according to claim 1, characterized in that: The setting of the start-up time of the cooling system in step B satisfies: If the curve increases inclination angle from 0 to 30° within 10 seconds, the cooling system will be started after 5 seconds; If the curve increases inclination angle to 30-45° within 10 seconds, the cooling system will be started after 3 seconds; If the inclination angle of the curve increases to 45-60° within 10 seconds, the cooling system will be started immediately.

3. The low temperature startup method of a proton exchange membrane fuel cell system according to claim 1, characterized in that: The matching of the operating conditions based on the temperature range of the stack in step C includes the following process: When the temperature of the coolant stack rises to 20-30°C, the temperature should be 0.7-0.9A cm -2 The gas supply to the fuel cell stack is carried out under the gas condition of operation, and the output current density is increased from 0.2-0.3A cm at a loading slope of 8-10A / s. -2 Load to 0.6-0.8A cm -2 ; When the temperature of the coolant leaving the stack reaches 40-45°C, control the thermostat opening at 5%-10%; after the temperature of the coolant leaving the stack continues to rise by 5-10°C, control the thermostat opening according to the temperature difference between the coolant entering and leaving the stack, and gradually intervene in the large circulation of the stack cooling system.

4. The low temperature startup method of a proton exchange membrane fuel cell system according to claim 3, characterized in that: After the thermostat opening reaches 60-100%, the cathode stoichiometric ratio is reduced by 0.1-0.5 to increase the heat generation of the stack.

5. The low temperature startup method of a proton exchange membrane fuel cell system according to claim 1, characterized in that: In step D, when the temperature of the coolant stack is stable at 60-65°C, the temperature is adjusted to meet the requirements of 1.0-1.2A cm -2 The gas supply to the fuel cell stack is carried out under the gas condition of operation, and the output current density is increased from 0.6 to 0.8 A cm at a loading slope of 15 to 20 A / s. -2 Load to 1.0-1.2A cm -2 Stable operation, low temperature startup process is completed.

6. The low temperature startup method of a proton exchange membrane fuel cell system according to claim 1, characterized in that: In step A: After turning on the stack, follow the conditions to meet 0.3-0.5A cm -2 The gas condition under which the fuel cell stack is operated is supplied with gas, and the output current density is increased from 0A cm-3 at a loading slope of 1-3A / s. -2 Load to 0.2-0.3A cm -2 .

7. The low temperature startup method of a proton exchange membrane fuel cell system according to claim 6, characterized in that: The gas conditions in step A are: the flow rates of cathode gas and anode gas are 3000-5000 NLPM and 900-1500 NLPM respectively, and the pressures of cathode gas and anode gas are 60-80 KPa and 70-90 KPa respectively.

8. The low temperature startup method of a proton exchange membrane fuel cell system according to claim 1, characterized in that: The low temperature condition in step A satisfies: not higher than 5°C.

9. A low-temperature start-up system for running the low-temperature start-up method for a proton exchange membrane fuel cell system according to any one of claims 1 to 8.

10. A battery comprising a fuel cell body and the cold starting system according to claim 1 connected to the body.

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