A method for pressure control during low temperature start-up of a fuel cell

Abstract

The present application relates to a kind of fuel cell starting method, specifically relates to a kind of pressure control method when fuel cell low temperature starts, the fuel cell includes connected electric pile, oxidant system, fuel agent system and cooling circulation system, including the following processes: detecting cooling liquid inlet T1, when T1 is lower than T 10 , open PTC heating and detect cooling liquid outlet T2;Respectively into oxidant and fuel, and control oxidant inlet for P O1 , control fuel inlet for P F1 ;Open cooling circulation system, control cooling liquid inlet for P C1 ;When T1 reaches T 10 And T2 reaches T 20 , stop PTC heating, connect load;Continuously load current to oxidant outlet T3 reaches T 30 ;Wherein, P F1 >P O1 ≥P C1 Compared with prior art, the present application solves the problem that deviation is too large due to pressure control failure or delay in prior art, electric pile reliability decreases, affects use reliability and safety.

Description

TECHNICAL FIELD

[0001] The present application relates to a fuel cell starting method, in particular to a pressure control method during low-temperature starting of a fuel cell. BACKGROUND

[0002] In order to enable the fuel cell to continuously work in a high-efficiency and safe range, the reliability and safety of each component in the fuel cell system are particularly important. The fuel cell will be subjected to various operating conditions during use, including complex low-temperature operating conditions.

[0003] During low-temperature (lower than 5℃) starting and operation of the fuel cell, in order to quickly raise the temperature of the stack, the commonly used low-temperature starting methods are: 1. starting by PTC external heating; 2. self-starting of the stack. In the low-temperature starting process, in order to avoid the unreliability caused by heat distribution, the cooling circulation system needs to be started in the initial operation stage. Especially in the starting process by PTC external heating, PTC is used for auxiliary heating during cold starting, which is a common control method in actual vehicle operation. Since the heating speed is slow, the cooling circulation needs to be started during the heating process. At this time, due to the significant increase in the viscosity of the cooling liquid at low temperature, the pressure in the cooling cavity will increase sharply, which will cause a long-term large pressure difference between the gas cavity and the cooling cavity, thereby increasing the risk of failure of the polar plate and the stack seal, and reducing the reliability of the stack. That is, due to the failure or delay of pressure control during low-temperature starting, the pressure control deviation of the fuel cell may be too large, and repeated occurrence of this situation during long-term use will lead to a decrease in the reliability of the stack, affecting the use reliability and safety.

[0004] For example, Chinese patent CN202110855893.8 discloses a fuel cell system and a low-temperature starting control method thereof. In the low-temperature starting process, the stack voltage is controlled by the electronic load in stages, and the output current of the stack is controlled in stages, which is beneficial to the absorption of generated water by the dry membrane, and the performance of the stack is improved, and then the stack is heated by controlling the stack voltage to increase the heat generation of the stack, and the pore space of the catalyst layer and the diffusion layer is fully utilized. In addition, the generated electric energy directly heats the cooling liquid by PTC, in order to prevent the PTC from overheating, the water pump is intermittently started, the opening degree of the thermostat is controlled to make the fuel cell system work in a small cycle, and the PTC directly heats the cooling liquid. Although it provides a control method for low-temperature starting, it only considers the influence of temperature and ignores the influence of pressure, and the situation of too large pressure difference may still occur, which will affect the reliability and safety of the stack during long-term use.

[0005] Therefore, it is necessary to balance the control strategy of the stack design requirement and the BoP capability from the overall point of view, and then improve the reliability of the fuel cell. SUMMARY

[0006] The present application aims to solve at least one of the above problems by providing a pressure control method for a fuel cell during low-temperature startup, so as to solve the problem of excessive deviation of pressure control of the fuel cell, which leads to a decrease in reliability of the stack and affects the use reliability and safety, caused by the failure or delay of pressure control during startup by PTC external heating in the prior art.

[0007] The object of the present application is achieved by the following technical solutions.

[0008] A pressure control method for a fuel cell during low-temperature startup, the fuel cell comprising a stack and an oxidant system, a fuel system and a cooling circulation system connected to the stack respectively, the pressure control method comprising the following processes:

[0009] S1: detecting a cooling liquid inlet temperature T1, when T1 is lower than an inlet target temperature T 10 , starting PTC heating, and detecting a cooling liquid outlet temperature T2;

[0010] S2: passing the oxidant and the fuel into the stack through the oxidant system and the fuel system respectively, and controlling the oxidant inlet pressure to be P O1 and the fuel inlet pressure to be P F1 ;

[0011] S3: starting the cooling circulation system, and controlling the cooling liquid inlet pressure to be P C1 ;

[0012] S4: when T1 reaches the inlet target temperature T 10 and T2 reaches the outlet target temperature T 20 , stopping the PTC heating, and connecting a load to make the stack start low-current loading work;

[0013] S5: continuing to load the current until the oxidant outlet temperature T3 reaches a set temperature T 30 , and completing the low-temperature startup;

[0014] Wherein, P F1 >P O1 ≥P C1 .

[0015] Preferably, the oxidant comprises air; the fuel comprises hydrogen; and the cooling liquid comprises one or both of ethylene glycol and deionized water.

[0016] Preferably, T 10 ≤5℃; T 20 ≥5℃; and T 30 ≥20℃.

[0017] Preferably, T 3020-30℃.

[0018] Preferably, the P F1 20-250kPag; the P O1 20-250kPag; the P C1 20-200kPag.

[0019] Preferably, the P F1 20-150kPag; the P O1 20-150kPag; the P C1 20-100kPag.

[0020] Preferably, the cooling circulating system pressurizes the cooling liquid by a cooling circulating pump; the cooling circulating pump is intermittent or continuous.

[0021] Preferably, the oxidant system is purged before the oxidant is introduced into the stack; the fuel agent system is purged before the fuel is introduced into the stack.

[0022] Preferably, the purging time is not less than 10s.

[0023] Preferably, the current range in the low current loading operation is 30-500A.

[0024] The working principle of the present application is as follows:

[0025] During the operation of the fuel cell, the operation pressure of hydrogen needs to be greater than that of air, which can protect the stack from safety and stability.

[0026] Safety: In the stack, if hydrogen permeates to the air side, it can be quickly diluted and discharged; hydrogen close to the catalytic layer is quickly reacted to ensure that the hydrogen concentration is lower than the explosion concentration. Since P F1 >P O1 , the hydrogen consumption is much greater than the air consumption, so even if a leak occurs, hydrogen will permeate to the air side and be quickly diluted and discharged, avoiding the safety risk of hydrogen reaching the explosion limit.

[0027] Stability: The gas flow and pressure difference between the inlet and outlet in the anode side gas chamber are small, and the drainage capacity is limited, which can be inhibited by forming a pressure difference between the cooling chamber to suppress excessive cooling liquid from permeating to the anode, reducing the probability of flooding.

[0028] Compared with the prior art, the present application has the following beneficial effects:

[0029] 1. During the operation of the fuel cell, the operation pressure of hydrogen needs to be greater than that of air, which can protect the stack from safety and stability.

[0030] Safety: In the stack, if hydrogen permeates to the air side, it can be quickly diluted and discharged; hydrogen near the catalytic layer is quickly reacted to ensure that the hydrogen concentration is below the explosive concentration.

[0031] Stability: The gas flow and pressure difference between the inlet and outlet in the gas cavity on the anode side are relatively small, and the liquid discharge capacity is limited. The pressure difference between the cooling cavity can be formed to inhibit excessive cooling liquid from permeating to the anode and reduce the probability of flooding.

[0032] 2. Under the action of the assembly force of the stack, the gas cavity flow passages on the polar plate are tightly compressed together. Under the condition of ensuring the pressure difference between the hydrogen and air sides, the gas cavity can withstand a relatively large pressure. Relatively speaking, the cooling cavity distributes the pressure to the entire surface through its own strength and indirect contact, so fewer fulcrums are formed. Therefore, during operation, the pressure of the gas cavity is as high as possible to avoid the pressure of the cooling liquid being greater than that of the gas cavity, prevent the leakage of the cooling liquid, and be conducive to the overall reliability. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 A structure diagram of a stack part in a fuel cell is shown.

[0034] In the figure: 1 - stack; 2 - fuel inlet; 3 - fuel outlet; 4 - oxidant inlet; 5 - oxidant outlet; 6 - cooling liquid inlet; 7 - cooling liquid outlet. DETAILED DESCRIPTION

[0035] The present application will be described in detail below in conjunction with the drawings and specific examples.

[0036] Example 1

[0037] Figure 1 A structure diagram of a stack 1 part in a fuel cell is shown.

[0038] The fuel cell system of the present embodiment can be a fuel cell system in the prior art, which at least includes: an air compressor, a hydrogen source, a humidifier, a fuel cell stack 1, a hydrogen discharge device, a thermostat, a radiator, a plurality of electromagnetic valves, etc. The connection relationship of each component in the fuel cell system is the same as that of each component in the fuel cell system in the prior art, and is not the research object of the present embodiment, which will not be described in detail in the present embodiment.

[0039] In the present embodiment, hydrogen is selected as the fuel, air is selected as the oxidant, and a mixture of ethylene glycol and deionized water is selected as the cooling liquid.

[0040] The structure of the stack 1 of the present embodiment is as follows: Figure 1As shown in the figure, the fuel inlet 2 is located at the upper left, and the fuel outlet 3 is located at the lower right; the oxidant inlet 4 is located at the upper right, and the oxidant outlet 5 is located at the lower left; the coolant inlet 6 is located at the middle right, and the coolant outlet 7 is located at the middle left.

[0041] When the temperature of the coolant inlet 6 of the stack 1 is detected to be less than 5°C (T 10 ), implement the cold start operation strategy, which specifically includes the following steps:

[0042] (1) Adjust the hydrogen pressure reducing valve and continuously add 60kPag (P F1 ) of hydrogen for 10s anode purge; after the purge, continue to add hydrogen to keep the gas chamber pressure on the anode side at 60kPag (P F1 );

[0043] (2) Adjust the air compressor and pressure reducing valve, and continuously add 50kPag (P O1 ) of air for 10s cathode purge; after the purge is completed, continue to add air to keep the gas chamber pressure on the cathode side at 50kPag (P O1 );

[0044] (3) Turn on PTC heating and at the same time turn on the cooling circulation pump of the cooling circulation system, which can be intermittent or continuous, and control the pressure of the coolant inlet 6 to be no higher than 50kPag (P C1 );

[0045] (4) Wait for PTC heating to raise the temperature of the coolant inlet 6 and coolant outlet 7 to 5°C (T 10 、T 20 )above;

[0046] (5) Through the load controller, set the loading current rate to 15A / s to load the stack 1, and load until the temperature of the oxidant outlet 5 reaches 20°C (T 30 ), startup successful.

[0047] Example 2

[0048] The overall steps are the same as in Example 1, except that:

[0049] T 10 0℃, T 20 is 10℃; T 30 25℃;

[0050] Hydrogen pressure (P F1 ) is 100kPag, air pressure (P O1 ) is 80kPag, control the coolant pressure not to exceed 80kPag;

[0051] The loading current is 80A.

[0052] Example 3

[0053] The overall procedure was the same as Example 1, except that:

[0054] T 10 was -10°C, T 20 was 5°C; and T 30 was 25°C;

[0055] The hydrogen pressure (P F1 ) was 150 kPag, the air pressure (P O1 ) was 120 kPag, and the controlled coolant pressure was not higher than 90 kPag;

[0056] The charging current was 325 A.

[0057] Example 4

[0058] The overall procedure was the same as Example 1, except that:

[0059] T 10 was -5°C, T 20 was 5°C; and T 30 was 30°C;

[0060] The hydrogen pressure (P F1 ) was 250 kPag, the air pressure (P O1 ) was 200 kPag, and the controlled coolant pressure was not higher than 180 kPag;

[0061] The charging current was 500 A.

[0062] The above description of the examples is to enable one of ordinary skill in the art to understand and use the invention. Various modifications to these examples, obvious to those skilled in the art, can be made without departing from the spirit of the invention. Therefore, the invention is not limited to the above examples, and improvements and modifications made by those skilled in the art based on the disclosure of the invention without departing from the scope of the invention should be within the scope of the invention.

Claims

1. A method for controlling pressure during low-temperature startup of a fuel cell, wherein the fuel cell comprises a fuel cell stack and an oxidant system, a fuel system, and a cooling circulation system respectively connected to the fuel cell stack, characterized in that: The pressure control method includes the following steps: S1: Detect the coolant inlet temperature T1. When T1 is lower than the inlet target temperature T 10 When , turn on PTC heating and detect the coolant outlet temperature T2; S2: Oxidant and fuel are introduced into the stack through the oxidant system and fuel system respectively, and the oxidant inlet pressure is controlled to P O1 , control the fuel inlet pressure to P F1 ; S3: Start the cooling circulation system and control the coolant inlet pressure to P C1 ; S4: When T1 reaches the inlet target temperature T 10 And T2 reaches the outlet target temperature T 20 When the PTC is turned off, the PTC heating is stopped and the load is connected to start the stack to work with low current loading. S5: Continue to load current until the oxidant outlet temperature T3 reaches the set temperature T 30 , complete low temperature start-up; Among them, -10℃≤T 10 ≤5℃; 5℃ <T 20 ≤10℃; 20℃≤T 30 ≤30℃; P F1 >P O1 ≥P C1 , and the P F1 is 20-250kPag; the P O1 is 20-250kPag; the P C1 20-200kPag.

2. The method for controlling the pressure of a fuel cell during low-temperature startup according to claim 1, characterized in that: The oxidant includes air; the fuel includes hydrogen; and the coolant includes one or two of ethylene glycol and deionized water.

3. The method for controlling the pressure of a fuel cell during low-temperature startup according to claim 1, wherein: The P F1 20-150kPag; the P O1 20-150kPag; the P C1 20-100kPag.

4. The method for controlling the pressure of a fuel cell during low-temperature startup according to claim 1, wherein: In the cooling circulation system, the coolant is pressurized by a cooling circulation pump; the cooling circulation pump is intermittent or continuous.

5. The method for controlling the pressure of a fuel cell during low-temperature startup according to claim 1, characterized in that: Before the oxidant is introduced into the fuel cell stack, the oxidant system is purged first; before the fuel is introduced into the fuel cell stack, the fuel system is purged first.

6. The method for controlling the pressure of a fuel cell during low-temperature startup according to claim 5, characterized in that: The purging time is no less than 10 seconds.

7. The method for controlling the pressure of a fuel cell during low-temperature startup according to claim 1, characterized in that: The current range in the low current loading operation is 30-500A.

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