Fuel cell system with gas collection function and working method thereof

Abstract

The invention relates to a fuel cell system with a gas collection function and a working method thereof.The fuel cell system comprises an electric pile, an oxygen supply subsystem, a hydrogen supply subsystem and a gas collection subsystem, and the gas collection subsystem is connected with the oxygen supply subsystem and the hydrogen supply subsystem; the gas collection subsystem is used for collecting stack outlet gas of a stack cathode; the membrane tube oxygen separator is arranged at the rear and is used for extracting nitrogen and oxygen in high-temperature cathode heap outlet gas, and the optimal separation temperature of the oxygen separator is achieved without increasing the air temperature through external heat exchange; and the membrane tube oxygen separator is only started in a gas collection state, and the use frequency is relatively low, so that the service life of the membrane tube oxygen separator is prolonged, and adverse effects on the service life and the cost of a fuel cell system caused by frequent replacement are avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular to a fuel cell system with a gas collection function and a working method thereof. Background Art

[0002] In existing fuel cell technology, oxygen separators are usually used to separate nitrogen from the air entering the stack, thereby increasing the oxygen concentration of the air entering the stack and improving the electrochemical efficiency of the stack. The application of oxygen separators at the front end of the stack greatly increases the flow resistance of the oxygen supply subsystem and the power consumption of the air compressor. At the same time, the adsorption of nitrogen causes the expander to be unable to collect the energy contained in the nitrogen in the exhaust gas, which greatly increases the auxiliary energy consumption of the system. The increase in oxygen concentration has limited effect on improving battery efficiency, which is often not worth the cost. The use of membrane oxygen separators is expensive, and as an oxygen-rich material in stable operation, it greatly increases the operating cost of the system; when molecular sieves are used as adsorption materials, the molecular sieves have the problem of limited adsorption capacity. When the molecular sieve reaches the upper limit of adsorption, it will fail and need to be shut down for desorption before it can continue to be used, which limits the use of fuel cell systems.

[0003] For the shutdown purge process, purge with load can easily cause the battery to be under-empty, resulting in local hot spots, which has an adverse effect on the battery life. It also increases the hydrogen consumption during the purge process, reducing the efficiency of the fuel cell system. After the purge is completed, water will be re-generated inside the battery, increasing the difficulty of cold starting the battery. In addition, there is still hydrogen in the battery stack. Since the system cannot ensure complete sealing, air will infiltrate the system after a long period of shutdown to produce a hydrogen-air interface, causing great durability damage.

[0004] For the startup state, in order to meet the fuel cell operating conditions, it is usually necessary to add an additional external power supply to assist the fuel cell startup process, which increases the system complexity and system cost.

[0005] Therefore, it is urgent to design a fuel cell system with a gas collection function and a working method thereof to solve the problems existing in the above-mentioned prior art. Summary of the invention

[0006] In view of this, the present invention provides a fuel cell system with a gas collection function and a working method thereof, the purpose of which is to optimize the structure of the fuel cell system, make full use of the oxygen separator to separate and collect the cathode outflow gas, and effectively utilize the above-mentioned collected gas to improve the durability of the fuel cell system.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A fuel cell system with a gas collection function, the fuel cell system comprising a stack, an oxygen supply subsystem, a hydrogen supply subsystem and a gas collection subsystem, the gas collection subsystem being connected to the oxygen supply subsystem and the hydrogen supply subsystem respectively, and the gas collection subsystem being used to collect gas discharged from the cathode of the stack;

[0009] The oxygen supply subsystem comprises: an air filter, a turbo expansion air compressor, an intercooler, a first solenoid valve and a second solenoid valve; the air filter is sequentially connected to the air compressor part of the turbo expansion air compressor, the intercooler, the first solenoid valve and the cathode inlet of the stack; the cathode outlet of the stack is sequentially connected to the expander part of the turbo expansion air compressor, the outlet of the expander part is provided with a T-shaped pipe, and a second solenoid valve is provided on one branch of the T-shaped pipe;

[0010] The gas collection subsystem includes a third solenoid valve, a membrane tube oxygen separator, a first air pump, a nitrogen collector, a fourth solenoid valve, a second air pump and an oxygen collector. The inlet of the third solenoid valve is connected to the other branch of the T-shaped pipe at the outlet of the expander, the outlet of the third solenoid valve is connected to the T-shaped pipe, one branch of the T-shaped pipe is connected to the membrane tube oxygen separator, the nitrogen outlet of the membrane tube oxygen separator is connected to the first air pump and the nitrogen collector in sequence, the oxygen outlet of the membrane tube oxygen separator is connected to the second air pump and the oxygen collector in sequence, the first outlet of the nitrogen collector is connected to the other branch of the T-shaped pipe at the outlet of the third solenoid valve through a pipe, and a fourth solenoid valve is also arranged on this pipe.

[0011] Furthermore, the compressor shaft of the compressor part of the turboexpansion air compressor is coaxially connected to the turbine shaft of the expander part.

[0012] Furthermore, the hydrogen supply subsystem includes: a hydrogen source, a high-pressure component, an ejector, a hydrogen valve, a gas-liquid separator and a hydrogen tail exhaust valve. The hydrogen source is connected to the high-pressure component, the ejector, the hydrogen valve and the anode inlet of the fuel cell stack in sequence, the anode outlet of the fuel cell stack is connected to the gas-liquid separator, the gas outlet of the gas-liquid separator is connected to the ejector, and the liquid outlet of the gas-liquid separator is connected to the hydrogen tail exhaust valve.

[0013] Furthermore, the second outlet of the nitrogen collector is connected to the anode inlet of the fuel cell stack through a pipeline, and a fifth solenoid valve is arranged on the pipeline; the gas outlet of the oxygen collector is connected to the cathode inlet of the fuel cell stack through a pipeline, and a third air pump is arranged on the pipeline.

[0014] Furthermore, a humidity sensor is provided at the outlet of the expander part of the turboexpansion air compressor for measuring the gas humidity in the oxygen supply subsystem; a first pressure sensor is provided in the nitrogen collector for measuring the pressure in the nitrogen collector; and a second pressure sensor is provided in the oxygen collector for measuring the pressure in the oxygen collector.

[0015] The present invention also provides a working method of the fuel cell system with gas collection function based on the above-mentioned fuel cell system, wherein the fuel cell system includes four working states: startup, collection, steady state, and shutdown;

[0016] In the startup state, oxygen is supplied through the oxygen collector;

[0017] In the collection state, the gas discharged from the cathode of the stack is separated by a membrane tube oxygen separator, and the separated oxygen is collected by an oxygen collector; the remaining nitrogen is collected by a nitrogen collector;

[0018] In steady state, the expander part of the turboexpansion air compressor uses the cathode gas to drive the turbine shaft to rotate, thereby providing part of the energy for the air compressor and realizing energy recovery;

[0019] In shutdown state, nitrogen is supplied through a nitrogen collector to purge the anode.

[0020] Furthermore, the startup state is as follows:

[0021] The hydrogen provided by the hydrogen source passes through the high-voltage component, the ejector, and the hydrogen valve in sequence, and enters the fuel cell from the anode inlet to participate in the reaction. The unreacted hydrogen flows out from the anode outlet of the fuel cell and enters the gas-liquid separator. The separated hydrogen enters the ejector again for recycling; the separated liquid water is discharged through the hydrogen tail valve;

[0022] At the same time, open the second solenoid valve, close the remaining solenoid valves, start the third air pump, pump out the oxygen in the oxygen collector, enter the fuel cell stack from the cathode inlet of the fuel cell stack, participate in the reaction to start the power stack, and the cathode gas out of the stack is discharged through the second solenoid valve; after the fuel cell is successfully started, start the turbo expansion air compressor, open the first solenoid valve, and close the third air pump.

[0023] Furthermore, the collection status is as follows:

[0024] The operation method of the hydrogen supply subsystem is consistent with that of the startup state;

[0025] Close the second solenoid valve, keep the first solenoid valve open, and open the third solenoid valve; the air is filtered to remove harmful gases and impurities through the air filter, and after being pressurized by the air compressor part of the turboexpansion air compressor, it enters the intercooler for cooling, passes through the first solenoid valve, enters the fuel cell stack from the cathode inlet to participate in the reaction, and the cathode gas is recovered by the expander part of the turboexpansion air compressor, and then enters the membrane tube oxygen separator through the third solenoid valve; the membrane tube oxygen separator separates oxygen and nitrogen, and the nitrogen enters the nitrogen collector for storage under the action of the first air pump; the oxygen enters the oxygen collector for storage under the action of the second air pump; when the pressure of the nitrogen collector and the oxygen collector reaches the set standard, stop gas collection, close the third solenoid valve, and open the second solenoid valve; then open the fourth solenoid valve to circulate the gas in the nitrogen collector in the fourth solenoid valve, the membrane tube oxygen separator, the air pump, and the nitrogen collector until the pressure in the nitrogen collector is stable and without fluctuations, close the fourth solenoid valve, close the first air pump and the second air pump, and complete the gas collection.

[0026] Further, the steady state is as follows:

[0027] The operation method of the hydrogen supply subsystem is consistent with that of the startup state;

[0028] Continue to keep the first solenoid valve and the second solenoid valve open, and keep the other solenoid valves closed; the air is filtered out of harmful gases and impurities through the air filter, pressurized by the air compressor part of the turboexpansion air compressor, cooled in the intercooler, and then passes through the first solenoid valve and enters the fuel cell stack from the cathode inlet to participate in the reaction. The cathode gas is discharged through the second solenoid valve after recovering energy through the expander part of the turboexpansion air compressor.

[0029] Furthermore, the shutdown state is as follows:

[0030] First, close the hydrogen valve, open the fifth solenoid valve and the hydrogen tail valve respectively, and the nitrogen in the nitrogen collector passes through the fifth solenoid valve and enters the stack from the anode inlet of the stack to perform anode purge. When the voltage drops to zero, close the fifth solenoid valve and the hydrogen tail valve;

[0031] Continue to keep the first solenoid valve and the second solenoid valve open, and keep the other solenoid valves closed. The air passes through the air filter, turbo expansion air compressor, intercooler, and the first solenoid valve at one time, and enters the fuel cell stack from the cathode inlet for cathode purging. When the humidity measured by the humidity sensor is less than or equal to 40%, turn off the turbo expansion air compressor and close all solenoid valves to complete the shutdown.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) By placing the membrane tube oxygen separator at the rear, it is used to extract nitrogen and oxygen from the high-temperature cathode gas leaving the stack, without the need for external heat exchange to increase the air temperature so as to reach the optimal separation temperature of the oxygen separator; and the membrane tube oxygen separator is only started in the gas collection state, and the frequency of use is low, thereby increasing the service life of the membrane tube oxygen separator and avoiding the adverse effects of frequent replacement on the life and cost of the fuel cell system.

[0034] (2) The nitrogen separated by the membrane tube oxygen separator is stored in the nitrogen collector and used as the anode purge gas during shutdown to ensure that there is no hydrogen in the stack after shutdown and to avoid the formation of hydrogen-air interface due to oxygen penetration, thereby increasing the service life of the fuel cell; the oxygen separated by the membrane tube oxygen separator is stored in the oxygen collector, and the high-oxygen content gas is used as the starting gas of the fuel cell system. No external auxiliary power supply is required, which reduces the complexity of the system and avoids the influence of nitrogen in the external low-temperature air on the temperature inside the stack during the cold start process, thereby improving the heating efficiency of the fuel cell and increasing the cold start performance of the fuel cell.

[0035] (3) During the nitrogen collection process, the nitrogen is purified using a nitrogen circulation purification method to ensure that there is no oxygen in the purge nitrogen entering the anode of the fuel cell; in addition, the fuel cell system also utilizes a turboexpansion air compressor, and the cathode outflow gas enters the expander part of the turboexpansion air compressor. The high-temperature gas pushes the blades, and the turbine rotates accordingly. Since the turbine shaft and the air compressor shaft are coaxially arranged, it is equivalent to pushing the air compressor to rotate, realizing energy recovery and improving energy utilization.

[0036] Other features and advantages of the present invention will be described in the following description, and partly become obvious from the description, or be understood by implementing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0038] Figure 1 A schematic structural diagram of a fuel cell system with a gas collection function according to an embodiment of the present invention is shown.

[0039] In the figure: 1. air filter; 2. turbo expansion air compressor; 3. intercooler; 4. first solenoid valve 4; 5. fuel cell stack; 6. humidity sensor; 7. second solenoid valve; 8. third solenoid valve; 9. fourth solenoid valve; 10. membrane tube oxygen separator; 11. first air pump; 12. nitrogen collector; 13. first pressure sensor; 14. second air pump; 15. oxygen collector; 16. second pressure sensor; 17. third air pump; 18. fifth solenoid valve; 19. hydrogen valve; 20. ejector; 21. high pressure assembly; 22. hydrogen source; 23. gas-liquid separator; 24. hydrogen tail valve. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are 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 are within the scope of protection of the present invention.

[0041] The embodiment of the present invention provides a fuel cell system with a gas collection function, as shown in the attached Figure 1 As shown, the fuel cell system includes a stack 5, an oxygen supply subsystem, a hydrogen supply subsystem and a gas collection subsystem, wherein the gas collection subsystem is connected to the oxygen supply subsystem and the hydrogen supply subsystem respectively, and the gas collection subsystem is used to collect the gas discharged from the cathode of the stack 5;

[0042] The oxygen supply subsystem comprises: an air filter 1, a turboexpansion air compressor 2, an intercooler 3, a first solenoid valve 4 and a second solenoid valve 7; the air filter 1 is sequentially connected to the air compressor part of the turboexpansion air compressor 2, the intercooler 3, the first solenoid valve 4 and the cathode inlet of the stack 5; the cathode outlet of the stack 5 is sequentially connected to the expander part of the turboexpansion air compressor 2, the outlet of the expander part is provided with a T-shaped pipe, and a second solenoid valve 7 is provided on one branch of the T-shaped pipe;

[0043] The compressor shaft of the compressor part of the turboexpansion air compressor 2 is coaxially connected with the turbine shaft of the expander part;

[0044] The gas collection subsystem includes a third solenoid valve 8, a membrane tube oxygen separator 10, a first air pump 11, a nitrogen collector 12, a fourth solenoid valve 9, a second air pump 14 and an oxygen collector 15. The inlet of the third solenoid valve 8 is connected to the other branch of the T-shaped pipe at the outlet of the expander, the outlet of the third solenoid valve 8 is connected to the T-shaped pipe, one branch of the T-shaped pipe is connected to the membrane tube oxygen separator 10, the nitrogen outlet of the membrane tube oxygen separator 10 is connected to the first air pump 11 and the nitrogen collector 12 in sequence, the oxygen outlet of the membrane tube oxygen separator 10 is connected to the second air pump 14 and the oxygen collector 15 in sequence, the first outlet of the nitrogen collector 12 is connected to the other branch of the T-shaped pipe at the outlet of the third solenoid valve 8 through a pipeline, and the fourth solenoid valve 9 is also arranged on this pipeline.

[0045] The hydrogen supply subsystem includes: a hydrogen source 22, a high-pressure component 21, an ejector 20, a hydrogen valve 19, a gas-liquid separator 23 and a hydrogen tail exhaust valve 24. The hydrogen source 22 is connected to the high-pressure component 21, the ejector 20, the hydrogen valve 19 and the anode inlet of the fuel cell stack 5 in sequence, the anode outlet of the fuel cell stack 5 is connected to the gas-liquid separator 23, the gas outlet of the gas-liquid separator 23 is connected to the ejector 20, and the liquid outlet of the gas-liquid separator 23 is connected to the hydrogen tail exhaust valve 24.

[0046] The second outlet of the nitrogen collector 12 is connected to the anode inlet of the fuel cell stack 5 through a pipeline, and a fifth solenoid valve 18 is arranged on the pipeline; the gas outlet of the oxygen collector 15 is connected to the cathode inlet of the fuel cell stack 5 through a pipeline, and a third air pump 17 is arranged on the pipeline.

[0047] A humidity sensor 6 is provided at the outlet of the expander part of the turboexpansion air compressor 2 for measuring the gas humidity in the oxygen supply subsystem; a first pressure sensor 13 is provided in the nitrogen collector 12 for measuring the pressure in the nitrogen collector 12; a second pressure sensor 16 is provided in the oxygen collector 15 for measuring the pressure in the oxygen collector 15.

[0048] The embodiment of the present invention further proposes a working method based on the above-mentioned fuel cell system with gas collection function, which is specifically as follows:

[0049] The fuel cell system includes four working states: startup, collection, steady state, and shutdown;

[0050] In the startup state, oxygen is supplied through the oxygen collector 15;

[0051] In the collection state, the gas discharged from the cathode of the stack 5 is separated by the membrane tube oxygen separator 10, and the separated oxygen is collected by the oxygen collector 15; the remaining nitrogen is collected by the nitrogen collector 12;

[0052] In the steady state, the expander part of the turboexpansion air compressor 2 uses the cathode gas to drive the turbine shaft to rotate, thereby providing part of the energy for the air compressor and realizing energy recovery;

[0053] In shutdown state, nitrogen is supplied through the nitrogen collector 12 to purge the anode.

[0054] Specifically, the startup state is as follows:

[0055] The hydrogen provided by the hydrogen source 22 passes through the high-voltage component 22, the ejector 20, and the hydrogen valve 19 in sequence, and enters the fuel cell 5 from the anode inlet of the fuel cell 5 to participate in the reaction. The unreacted hydrogen flows out from the anode outlet of the fuel cell 5 and enters the gas-liquid separator 23. The separated hydrogen enters the ejector 20 again for recycling; the separated liquid water is discharged through the hydrogen tail valve 24;

[0056] At the same time, open the second solenoid valve 7, close the remaining solenoid valves, start the third air pump 17, pump out the oxygen in the oxygen collector 15, enter the fuel cell from the cathode inlet of the fuel cell 5, participate in the reaction to start the power stack, and the cathode gas out of the stack is discharged through the second solenoid valve 7; after the fuel cell is successfully started, that is, when it is loaded to the idle condition, start the turbo expansion air compressor 2, open the first solenoid valve 4, and close the third air pump 17.

[0057] Specifically, the collection status is as follows:

[0058] The operation method of the hydrogen supply subsystem is consistent with that of the startup state;

[0059] Close the second solenoid valve 7, keep the first solenoid valve 4 open, and open the third solenoid valve 8; the air is filtered out of harmful gases and impurities through the air filter 1, and after being pressurized by the air compressor part of the turboexpansion air compressor 2, it enters the intercooler 3 for cooling, passes through the first solenoid valve 4, and enters the fuel cell stack from the cathode inlet of the fuel cell stack 5 to participate in the reaction. The cathode gas is recovered by the expander part of the turboexpansion air compressor 2, and then enters the membrane tube oxygen separator 10 through the third solenoid valve 8; the membrane tube oxygen separator 10 separates oxygen and nitrogen, and the nitrogen enters the nitrogen collector 12 for storage under the action of the first air pump 11; the oxygen is The gas enters the oxygen collector 15 for storage; when the pressures of the nitrogen collector 12 and the oxygen collector 15 reach the set standard, the gas collection is stopped, the third solenoid valve 8 is closed, and the second solenoid valve 7 is opened; then the fourth solenoid valve 9 is opened to allow the gas in the nitrogen collector 12 to circulate in the fourth solenoid valve 9, the membrane tube oxygen separator 10, the air pump 11, and the nitrogen collector 12 until the pressure in the nitrogen collector 12 is stable and has no fluctuations, then the fourth solenoid valve 7 is closed, the first air pump 11 and the second air pump 14 are closed, and the gas collection is completed. At this time, the gas in the nitrogen collector 12 is pure nitrogen, and the gas in the oxygen collector 15 is high-purity oxygen.

[0060] Specifically, the steady state is as follows:

[0061] The operation method of the hydrogen supply subsystem is consistent with that of the startup state;

[0062] Continue to keep the first solenoid valve 4 and the second solenoid valve 7 open, and keep the other solenoid valves closed; the air is filtered out of harmful gases and impurities through the air filter 1, and is pressurized by the air compressor part of the turboexpansion air compressor 2, enters the intercooler 3 for cooling, passes through the first solenoid valve 4, and enters the fuel cell stack from the cathode inlet of the fuel cell stack 5 to participate in the reaction. The cathode gas is discharged through the second solenoid valve 7 after recovering energy through the expander part of the turboexpansion air compressor 2.

[0063] Specifically, the shutdown state is as follows:

[0064] First, the hydrogen valve 19 is closed, and the fifth solenoid valve 18 and the hydrogen tail valve 24 are opened respectively. The nitrogen in the nitrogen collector 12 passes through the fifth solenoid valve 18 and enters the stack from the anode inlet of the stack 5 for anode purge. When the voltage drops to zero, the fifth solenoid valve 18 and the hydrogen tail valve 24 are closed;

[0065] Continue to keep the first solenoid valve 4 and the second solenoid valve 7 open, and keep the other solenoid valves closed. The air passes through the air filter 1, the turboexpansion air compressor 2, the intercooler 3, and the first solenoid valve 4 at one time, and enters the battery stack from the cathode inlet of the battery stack 5 for cathode purge. When the humidity measured by the humidity sensor 6 is less than or equal to 40%, turn off the turboexpansion air compressor 2 and close all the solenoid valves to complete the shutdown.

[0066] By placing the membrane tube oxygen separator at the rear to extract nitrogen and oxygen from the high-temperature cathode gas out of the stack, there is no need for external heat exchange to increase the air temperature and thus reach the optimal separation temperature of the oxygen separator; and the membrane tube oxygen separator is only started in the gas collection state, and the frequency of use is low, thereby increasing the service life of the membrane tube oxygen separator and avoiding the adverse effects of frequent replacement on the life and cost of the fuel cell system.

[0067] The nitrogen separated by the membrane tube oxygen separator is stored in the nitrogen collector and used as the anode purge gas during shutdown to ensure that there is no hydrogen in the stack after shutdown and to avoid the formation of hydrogen-air interface due to oxygen penetration, thereby increasing the service life of the fuel cell; the oxygen separated by the membrane tube oxygen separator is stored in the oxygen collector, and the high-oxygen content gas is used as the starting gas of the fuel cell system. No external auxiliary power supply is required, which reduces the complexity of the system and avoids the influence of nitrogen in the external low-temperature air on the temperature inside the stack during the cold start process, thereby improving the heating efficiency of the fuel cell and increasing the cold start performance of the fuel cell.

[0068] During the nitrogen collection process, the nitrogen is purified using the nitrogen circulation purification method to ensure that there is no oxygen in the purge nitrogen entering the fuel cell anode; in addition, the fuel cell system also utilizes a turboexpansion air compressor, and the cathode outflow gas enters the expander part of the turboexpansion air compressor. The high-temperature gas pushes the blades, and the turbine rotates accordingly. Since the turbine shaft and the air compressor shaft are coaxially arranged, it is equivalent to pushing the air compressor to rotate, realizing energy recovery and improving energy utilization.

[0069] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent substitutions for some of the technical features therein; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A fuel cell system with a gas collection function, characterized in that: The fuel cell system comprises a fuel cell stack, an oxygen supply subsystem, a hydrogen supply subsystem and a gas collection subsystem, wherein the gas collection subsystem is connected to the oxygen supply subsystem and the hydrogen supply subsystem respectively, and the gas collection subsystem is used to collect gas discharged from the cathode of the fuel cell stack; The oxygen supply subsystem includes: an air filter, a turbo expansion air compressor, an intercooler, a first solenoid valve and a second solenoid valve; The air filter is connected to the air compressor part of the turbo expansion air compressor, the intercooler, the first solenoid valve and the cathode inlet of the fuel cell stack in sequence; the cathode outlet of the fuel cell stack is connected to the expander part of the turbo expansion air compressor in sequence, the outlet of the expander part is provided with a T-shaped pipe, and a second solenoid valve is provided on one branch of the T-shaped pipe; The gas collection subsystem includes a third solenoid valve, a membrane tube oxygen separator, a first air pump, a nitrogen collector, a fourth solenoid valve, a second air pump and an oxygen collector. The inlet of the third solenoid valve is connected to the other branch of the T-shaped pipe at the outlet of the expander, the outlet of the third solenoid valve is connected to the T-shaped pipe, one branch of the T-shaped pipe is connected to the membrane tube oxygen separator, the nitrogen outlet of the membrane tube oxygen separator is connected to the first air pump and the nitrogen collector in sequence, the oxygen outlet of the membrane tube oxygen separator is connected to the second air pump and the oxygen collector in sequence, the first outlet of the nitrogen collector is connected to the other branch of the T-shaped pipe at the outlet of the third solenoid valve through a pipe, and a fourth solenoid valve is also arranged on this pipe.

2. The fuel cell system with gas collection function according to claim 1, characterized in that: The compressor shaft of the compressor part of the turboexpansion air compressor is coaxially connected with the turbine shaft of the expander part.

3. The fuel cell system with gas collection function as claimed in claim 2, characterized in that: The hydrogen supply subsystem includes: a hydrogen source, a high-pressure component, an ejector, a hydrogen valve, a gas-liquid separator and a hydrogen tail exhaust valve. The hydrogen source is connected to the high-pressure component, the ejector, the hydrogen valve and the anode inlet of the fuel cell stack in sequence, the anode outlet of the fuel cell stack is connected to the gas-liquid separator, the gas outlet of the gas-liquid separator is connected to the ejector, and the liquid outlet of the gas-liquid separator is connected to the hydrogen tail exhaust valve.

4. The fuel cell system with gas collection function as claimed in claim 3, characterized in that: The second outlet of the nitrogen collector is connected to the anode inlet of the fuel cell stack through a pipeline, and a fifth solenoid valve is arranged on the pipeline; the gas outlet of the oxygen collector is connected to the cathode inlet of the fuel cell stack through a pipeline, and a third air pump is arranged on the pipeline.

5. The fuel cell system with gas collection function as claimed in claim 1, characterized in that: A humidity sensor is provided at the outlet of the expander part of the turboexpansion air compressor for measuring the gas humidity in the oxygen supply subsystem; a first pressure sensor is provided in the nitrogen collector for measuring the pressure in the nitrogen collector; a second pressure sensor is provided in the oxygen collector for measuring the pressure in the oxygen collector.

6. A method for operating a fuel cell system with a gas collection function based on any one of claims 1 to 5, characterized in that: The fuel cell system includes four working states: startup, collection, steady state, and shutdown; In the startup state, oxygen is supplied through the oxygen collector; In the collection state, the gas discharged from the cathode of the stack is separated by a membrane tube oxygen separator, and the separated oxygen is collected by an oxygen collector; the remaining nitrogen is collected by a nitrogen collector; In steady state, the expander part of the turboexpansion air compressor uses the cathode gas to drive the turbine shaft to rotate, thereby providing part of the energy for the air compressor and realizing energy recovery; In shutdown state, nitrogen is supplied through a nitrogen collector to purge the anode.

7. The operating method of the fuel cell system with gas collection function as claimed in claim 6, characterized in that: The startup status is as follows: The hydrogen provided by the hydrogen source passes through the high-voltage component, the ejector, and the hydrogen valve in sequence, and enters the fuel cell from the anode inlet to participate in the reaction. The unreacted hydrogen flows out from the anode outlet of the fuel cell and enters the gas-liquid separator. The separated hydrogen enters the ejector again for recycling; the separated liquid water is discharged through the hydrogen tail valve; At the same time, open the second solenoid valve, close the remaining solenoid valves, start the third air pump, pump out the oxygen in the oxygen collector, enter the fuel cell stack from the cathode inlet of the fuel cell stack, participate in the reaction to start the power stack, and the cathode gas out of the stack is discharged through the second solenoid valve; after the fuel cell is successfully started, start the turbo expansion air compressor, open the first solenoid valve, and close the third air pump.

8. The operating method of the fuel cell system with gas collection function as claimed in claim 7, characterized in that: The collection status is as follows: The operation method of the hydrogen supply subsystem is consistent with that of the startup state; Close the second solenoid valve, keep the first solenoid valve open, and open the third solenoid valve; the air is filtered out of harmful gases and impurities through the air filter, and after being pressurized by the air compressor part of the turboexpansion air compressor, it enters the intercooler for cooling, passes through the first solenoid valve, and enters the fuel cell stack from the cathode inlet to participate in the reaction. The cathode gas is recovered by the expander part of the turboexpansion air compressor, and then enters the membrane tube oxygen separator through the third solenoid valve; the membrane tube oxygen separator separates oxygen and nitrogen, and the nitrogen enters the nitrogen collector for storage under the action of the first air pump; the oxygen enters the oxygen collector for storage under the action of the second air pump; when the pressure of the nitrogen collector and the oxygen collector reaches the set standard, stop gas collection, close the third solenoid valve, and open the second solenoid valve; Then open the fourth solenoid valve to allow the gas in the nitrogen collector to circulate in the fourth solenoid valve, membrane tube oxygen separator, air pump and nitrogen collector until the pressure in the nitrogen collector is stable and without fluctuation. Then close the fourth solenoid valve, turn off the first air pump and the second air pump to complete gas collection.

9. The operating method of the fuel cell system with gas collection function as claimed in claim 8, characterized in that: The steady state is as follows: The operation method of the hydrogen supply subsystem is consistent with that of the startup state; Continue to keep the first solenoid valve and the second solenoid valve open, and keep the other solenoid valves closed; the air is filtered out of harmful gases and impurities through the air filter, pressurized by the air compressor part of the turboexpansion air compressor, cooled in the intercooler, and then passes through the first solenoid valve and enters the fuel cell stack from the cathode inlet to participate in the reaction. The cathode gas is discharged through the second solenoid valve after recovering energy through the expander part of the turboexpansion air compressor.

10. The operating method of the fuel cell system with gas collection function according to claim 9, characterized in that: The shutdown status is as follows: First, close the hydrogen valve, open the fifth solenoid valve and the hydrogen tail valve respectively, and the nitrogen in the nitrogen collector passes through the fifth solenoid valve and enters the stack from the anode inlet of the stack to perform anode purge. When the voltage drops to zero, close the fifth solenoid valve and the hydrogen tail valve; Continue to keep the first solenoid valve and the second solenoid valve open, and keep the other solenoid valves closed. The air passes through the air filter, turbo expansion air compressor, intercooler, and the first solenoid valve at one time, and enters the fuel cell stack from the cathode inlet for cathode purging. When the humidity measured by the humidity sensor is less than or equal to 40%, turn off the turbo expansion air compressor and close all solenoid valves to complete the shutdown.

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