Nitrogen recycling device for fuel cell system in closed environment

Abstract

The present invention discloses a nitrogen recycling device for a fuel cell system in a closed environment, comprising a fuel cell power generation unit, a primary tail gas treatment unit, a secondary tail gas treatment unit, a nitrogen recovery storage unit and a connecting pipeline. The device can address the problem that the cabin pressure increases due to nitrogen discharge during the operation of the fuel cell system in the closed environment, thereby affecting the safety of personnel and equipment. The tail gas generated by the fuel cell power generation unit is sequentially processed through the primary tail gas treatment unit and the secondary tail gas treatment unit, and hydrogen and oxygen in the tail gas are removed to obtain nitrogen with higher purity. The nitrogen is then recovered and circulated to the fuel cell power generation unit for reuse. In this way, the tail gas is continuously recycled and recycled after being treated, so that the fuel cell system no longer discharges nitrogen into the closed cabin, thereby effectively ensuring the stability of the cabin pressure in the closed cabin during the operation of the fuel cell, as well as the safety of personnel and equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular to a nitrogen circulation utilization device for a fuel cell system in a closed environment. Background Art

[0002] A closed environment is a special type of environmental condition. Its main characteristics are that it is relatively isolated from the outside world and has no or limited air inside. It is commonly found in aerospace, deep-sea equipment and other fields. In recent years, with the continuous deepening of human commercial exploration of space and deep sea, the demand for efficient, silent and reliable closed space development technology at home and abroad has become more urgent. However, due to the lack of air, conventional technologies such as thermal engine power generation cannot be used in closed spaces, so fuel cells are considered to be the main research and development direction of closed space power generation technology.

[0003] At present, most fuel cell systems used in confined spaces use hydrogen-oxygen fuel cell systems, that is, hydrogen from a hydrogen storage device and oxygen from an oxygen storage device react electrochemically directly inside the fuel cell module to generate electricity for use by external loads. In order to ensure the health of personnel in a closed environment and the normal operation of instruments and equipment, most closed environments have strict requirements on the upper limit of cabin pressure, that is, the equipment in the closed cabin is required not to discharge or discharge less gas into the cabin during operation to keep the cabin pressure stable. However, according to the characteristics of the fuel cell system, during its operation, a certain amount of nitrogen will inevitably be discharged into the cabin during startup, shutdown and storage. The above nitrogen discharge will cause the cabin pressure to increase, threatening the safety of personnel and affecting the normal operation of instruments and equipment. In response to the above problems, the current solutions mainly include two aspects: one is to reduce the number of times the fuel cell is turned on and off by optimizing the fuel cell operation strategy; the other is to reduce the nitrogen consumption of a single start and shutdown of the fuel cell. However, in actual engineering applications, in order to meet the complex external power consumption conditions, the number of times the fuel cell can be turned on and off is limited by simply optimizing the operation strategy; in addition, blindly reducing the nitrogen consumption of a single start and shutdown will make the nitrogen purge process in the fuel cell stack incomplete, which is not conducive to the cycle life of the fuel cell. In general, the existing solutions to the bottleneck problem of increased cabin pressure caused by nitrogen emissions from fuel cells in a closed environment have great limitations. Summary of the invention

[0004] In view of this, the present invention provides a nitrogen recycling device for a fuel cell system in a closed environment to solve the technical problem that nitrogen discharge causes increased cabin pressure and affects the safety of personnel and equipment when using a fuel cell in a closed environment.

[0005] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0006] A nitrogen recycling device for a fuel cell system in a closed environment comprises a fuel cell power generation unit, a tail gas primary treatment unit, a tail gas secondary treatment unit, a nitrogen recovery storage unit and a connecting pipeline, wherein:

[0007] The tail gas primary treatment unit comprises a first hydrogen-oxygen catalytic reactor.

[0008] The tail gas secondary treatment unit comprises a second hydrogen-oxygen catalytic reactor and a gas mixing tank.

[0009] The connecting pipeline includes a primary tail gas delivery pipeline, a secondary tail gas delivery pipeline, a tail gas recovery circulation pipeline, a nitrogen recovery pipeline and a hydrogen and oxygen content adjustment pipeline.

[0010] The two ends of the primary tail gas delivery pipeline are respectively connected to the fuel cell power generation unit and the first hydrogen-oxygen catalytic reactor.

[0011] The two ends of the secondary tail gas delivery pipeline are respectively connected to the first hydrogen-oxygen catalytic reactor and the gas mixing tank, and the gas mixing tank is provided with two outlet ends.

[0012] One end of the tail gas recovery circulation pipeline is connected to one of the outlet ends of the gas mixing tank, and the other end is connected to the inlet end of the second hydrogen-oxygen catalytic reactor, and the outlet end of the second hydrogen-oxygen catalytic reactor is further connected to the gas mixing tank through the tail gas recovery circulation pipeline.

[0013] One end of the nitrogen recovery pipeline is connected to the other outlet end of the gas mixing tank, and the other end is connected to the nitrogen recovery storage unit, and the outlet end of the nitrogen recovery storage unit is further connected to the fuel cell power generation unit through the nitrogen recovery pipeline.

[0014] The two ends of the hydrogen and oxygen content regulating pipeline are respectively connected to the gas mixing tank and the fuel cell power generation unit to adjust the molar content ratio of hydrogen and oxygen in the gas mixing tank.

[0015] In one of the preferred embodiments, the fuel cell power generation unit includes a hydrogen supply device, an oxygen supply device and a stack reaction device, the hydrogen supply device and the oxygen supply device are respectively connected to the hydrogen side inlet and the oxygen side inlet of the stack reaction device, and a first hydrogen supply valve is provided on the pipeline connecting the hydrogen supply device and the stack reaction device, and a first oxygen supply valve is provided on the pipeline connecting the oxygen supply device and the stack reaction device.

[0016] In one of the preferred embodiments, the primary exhaust gas delivery pipeline includes a hydrogen side exhaust gas delivery pipeline and an oxygen side exhaust gas delivery pipeline, and the two ends of the hydrogen side exhaust gas delivery pipeline are respectively connected to the hydrogen side outlet of the fuel cell reactor and the first hydrogen-oxygen catalytic reactor, and the two ends of the oxygen side exhaust gas delivery pipeline are respectively connected to the oxygen side outlet of the fuel cell reactor and the first hydrogen-oxygen catalytic reactor.

[0017] In one of the preferred embodiments, a hydrogen side tail exhaust valve and a hydrogen side water separator are sequentially arranged on the side of the hydrogen side tail gas delivery pipeline close to the fuel cell reactor, and an oxygen side tail exhaust valve and an oxygen side water separator are sequentially arranged on the side of the oxygen side tail gas delivery pipeline close to the fuel cell reactor.

[0018] In a preferred embodiment, the exhaust gas primary treatment unit further includes a first water tank, and the first water tank is connected to the first hydrogen-oxygen catalytic reactor, the hydrogen-side water separator and the oxygen-side water separator through a first drain valve, respectively.

[0019] In a preferred embodiment, the tail gas secondary treatment unit further includes a second water tank, and the second water tank is connected to the second hydrogen-oxygen catalytic reactor via a second drain valve.

[0020] In a preferred embodiment, a circulation pump is provided on the tail gas recovery circulation pipeline and between the gas mixing tank and the second hydrogen-oxygen catalytic reactor.

[0021] In one preferred embodiment, the hydrogen and oxygen content regulating pipeline includes a hydrogen content regulating pipeline and an oxygen content regulating pipeline, the two ends of the hydrogen content regulating pipeline are respectively connected to the hydrogen supply device and the gas mixing tank, the two ends of the oxygen content regulating pipeline are respectively connected to the oxygen supply device and the gas mixing tank, and a second hydrogen supply valve and a hydrogen flow controller are sequentially arranged on the side of the hydrogen content regulating pipeline close to the hydrogen supply device, and a second oxygen supply valve and an oxygen flow controller are sequentially arranged on the side of the oxygen content regulating pipeline close to the oxygen supply device.

[0022] In a preferred embodiment, the nitrogen recovery pipeline includes a nitrogen recovery main pipeline, a hydrogen-side nitrogen recovery branch pipeline, and an oxygen-side nitrogen recovery branch pipeline, the inlet end of the nitrogen recovery main pipeline is connected to an outlet end of the gas mixing tank, and the nitrogen recovery storage unit is arranged on the nitrogen recovery main pipeline, wherein:

[0023] The nitrogen recovery and storage unit includes a low-pressure intake valve, a drying tank, a compressor, a high-pressure intake valve, a nitrogen storage tank and a regulating valve which are sequentially connected to the inlet end of the nitrogen recovery main pipeline; one end of the hydrogen-side nitrogen recovery branch pipeline and the oxygen-side nitrogen recovery branch pipeline are respectively connected to the nitrogen storage tank and the regulating valve through the hydrogen-side nitrogen supply valve and the oxygen-side nitrogen supply valve; the other ends of the hydrogen-side nitrogen recovery branch pipeline and the oxygen-side nitrogen recovery branch pipeline are respectively connected to the hydrogen-side inlet and the oxygen-side inlet of the fuel cell reactor.

[0024] In a preferred embodiment, the gas mixing tank is further provided with a hydrogen concentration sensor and an oxygen concentration sensor for detecting the molar contents of hydrogen and oxygen in the gas mixing tank, respectively.

[0025] Compared with the prior art, the beneficial effects of the present invention mainly include:

[0026] The present invention provides a nitrogen recycling device for a fuel cell system in a closed environment, which mainly includes a fuel cell power generation unit, a tail gas primary treatment unit, a tail gas secondary treatment unit, a nitrogen recovery storage unit, and a connecting pipeline connecting each unit. The tail gas generated by the fuel cell power generation unit is sequentially processed by the tail gas primary treatment unit and the tail gas secondary treatment unit to remove hydrogen and oxygen in the tail gas to obtain nitrogen with higher purity, and then the nitrogen is recovered and circulated to the fuel cell power generation unit for reuse. In this way, the tail gas is continuously recycled and recycled after being treated, so that the fuel cell system no longer discharges nitrogen into the closed cabin, thereby effectively ensuring the stability of the cabin pressure of the closed cabin during the operation of the fuel cell, as well as the safety of personnel and equipment. The present invention makes it possible for the fuel cell system to operate for a long time in a closed environment, and has broad application prospects and huge potential value in the fields of deep-sea scientific research, resource exploration, oil and gas development, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the structural composition of the nitrogen recycling device of the present invention.

[0028] As shown in the figure:

[0029] 100 - fuel cell power generation unit, 110 - hydrogen supply device, 120 - oxygen supply device, 130 - stack reaction device, 140 - first hydrogen supply valve, 150 - first oxygen supply valve;

[0030] 200- tail gas primary treatment unit, 210- first hydrogen-oxygen catalytic reactor, 220- first water tank, 230- hydrogen side water separator, 240- oxygen side water separator, 250- hydrogen side tail drain valve, 260- oxygen side tail drain valve, 270- first drain valve;

[0031] 300- tail gas secondary treatment unit, 310- second hydrogen-oxygen catalytic reactor, 320- second water tank, 330- gas mixing tank, 331- hydrogen concentration sensor, 332- oxygen concentration sensor, 340- circulation pump, 350- second drain valve;

[0032] 400-nitrogen recovery storage unit, 410-low-pressure air intake valve, 420-drying tank, 430-compressor, 440-high-pressure air intake valve, 450-nitrogen storage tank, 460-regulating valve, 470-hydrogen side nitrogen supply valve, 480-oxygen side nitrogen supply valve;

[0033] 500-connecting pipeline, 510-primary exhaust gas delivery pipeline, 511-hydrogen side exhaust gas delivery pipeline, 512-oxygen side exhaust gas delivery pipeline, 520-secondary exhaust gas delivery pipeline, 530-exhaust gas recovery circulation pipeline, 540-nitrogen recovery pipeline, 541-nitrogen recovery main pipeline, 542-hydrogen side nitrogen recovery branch pipeline, 543-oxygen side nitrogen recovery branch pipeline, 550-hydrogen and oxygen content regulating pipeline, 551-hydrogen content regulating pipeline, 5511-second hydrogen supply valve, 5512-hydrogen flow controller, 552-oxygen content regulating pipeline, 5521-second oxygen supply valve, 5522-oxygen flow controller. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0035] Figure 1 The schematic diagram of the structure of the nitrogen recycling device of the present invention is shown. Figure 1As shown, the present invention provides a nitrogen recycling device for a fuel cell system in a closed environment, including a fuel cell power generation unit 100, a tail gas primary treatment unit 200, a tail gas secondary treatment unit 300, a nitrogen recovery storage unit 400 and a connecting pipeline 500 connecting the above-mentioned units. With such arrangement, the high-nitrogen exhaust gas generated by the fuel cell power generation unit 100 first undergoes a hydrogen-oxygen catalytic reaction in the exhaust gas primary treatment unit 200 to remove part of the hydrogen and oxygen, and then enters the exhaust gas secondary treatment unit 300. The exhaust gas secondary treatment unit 300 uses the pure hydrogen and pure oxygen provided by the fuel cell power generation unit 100 to adjust the molar content ratio of hydrogen and oxygen in the exhaust gas, and then combines the hydrogen-oxygen cycle catalytic reaction to achieve the gradual removal of hydrogen and oxygen in the exhaust gas, and finally obtains high-purity nitrogen. Finally, the high-purity nitrogen is dried and compressed, and then recovered and stored in the nitrogen recovery storage unit 400 and returned to the fuel cell power generation unit 100 to provide nitrogen for its nitrogen purge process. Such a cycle prevents the fuel cell from emitting nitrogen into the closed cabin, thereby effectively ensuring the stability of the cabin pressure in the closed cabin during the operation of the fuel cell and the safety of personnel and equipment.

[0036] The various components of the nitrogen recycling device of the present invention will be described in detail below.

[0037] The fuel cell power generation unit 100 is the main body of nitrogen use and is also the source of high nitrogen tail gas. In addition, it can also provide pure hydrogen and pure oxygen supply for the tail gas secondary treatment unit 300. In one embodiment, the fuel cell power generation unit 100 includes a hydrogen supply device 110, an oxygen supply device 120 and an electric stack reaction device 130, and the hydrogen supply device 110 and the oxygen supply device 120 are respectively connected to the hydrogen side inlet and the oxygen side inlet of the electric stack reaction device 130, and the pipeline connecting the hydrogen supply device 110 and the electric stack reaction device 130 is provided with a first hydrogen supply valve 140, and the pipeline connecting the oxygen supply device 120 and the electric stack reaction device 130 is provided with a first oxygen supply valve 150, then the hydrogen from the hydrogen supply device 110 is transported to the hydrogen side inlet of the electric stack reaction device 130 through the control of the first hydrogen supply valve 140; the oxygen from the oxygen supply device 120 is transported to the oxygen side inlet of the electric stack reaction device 130 through the control of the first oxygen supply valve 150, and provides hydrogen and oxygen for the electric stack reaction.

[0038] Optionally, the hydrogen supply device 110 may use high-pressure hydrogen storage, alloy hydrogen storage, liquid hydrogen or on-site hydrogen production, and the oxygen supply device 120 may use high-pressure oxygen storage, liquid oxygen, or on-site oxygen production.

[0039] During the use of the above-mentioned fuel cell power generation unit 100, due to insufficient reaction and nitrogen purge process, the stack reaction device 130 will produce high nitrogen tail gas containing hydrogen and oxygen, and the purpose of the nitrogen recycling device of the present invention is to prevent the above-mentioned high nitrogen tail gas from being discharged into the cabin. Specifically, the high nitrogen tail gas is transported to the tail gas primary treatment unit 200 and the tail gas secondary treatment unit 300 through the connecting pipeline 500 for treatment to obtain high-purity nitrogen stored in the nitrogen recovery storage unit 400, and then the high-purity nitrogen obtained after treatment is circulated to the fuel cell power generation unit 100. Among them, the connecting pipeline 500 includes a primary tail gas delivery pipeline 510, a secondary tail gas delivery pipeline 520, a tail gas recovery circulation pipeline 530, a nitrogen recovery pipeline 540 and a hydrogen and oxygen content adjustment pipeline 550.

[0040] In one of the embodiments, the high-nitrogen tail gas generated by the fuel cell power generation unit 100 is transmitted to the tail gas primary treatment unit 200 through the primary tail gas delivery pipeline 510. The main function of the tail gas primary treatment unit 200 is to pre-treat the high-nitrogen tail gas from the fuel cell power generation unit 100, eliminate part of the hydrogen and oxygen in the high-nitrogen tail gas through hydrogen and oxygen catalysis, and remove the liquid water in the high-nitrogen tail gas. Furthermore, the primary tail gas delivery pipeline 510 includes a hydrogen-side tail gas delivery pipeline 511 and an oxygen-side tail gas delivery pipeline 512, and the tail gas primary treatment unit 200 includes a first hydrogen-oxygen catalytic reactor 210, a first water tank 220, a hydrogen-side water separator 230, an oxygen-side water separator 240, a hydrogen-side tail exhaust valve 250, an oxygen-side tail exhaust valve 260 and a first drain valve 270. The high-nitrogen tail gas from the hydrogen side of the stack reaction device 130 is delivered through the hydrogen-side tail gas delivery pipeline 511. The high nitrogen exhaust gas from the oxygen side of the fuel cell reactor 130 is also transported to the first hydrogen-oxygen catalytic reactor 210 through the oxygen side exhaust gas transport pipeline 512 for hydrogen-oxygen catalytic reaction to remove part of the hydrogen and oxygen, while the unreacted high nitrogen exhaust gas is transported to the exhaust gas secondary treatment unit 300 through the secondary exhaust gas transport pipeline 520 via the exhaust valve for secondary treatment. At the same time, the generated water enters the first water tank 220 through the first drain valve 270.

[0041] Optionally, the hydrogen side tail drain valve 250 and the hydrogen side water separator 230 are arranged on the hydrogen side tail gas delivery pipeline 511, which are used to control the amount of hydrogen and remove moisture in the hydrogen; and the hydrogen side water separator 230 is connected to the first water tank 220 through the first drain valve 270, and the removed moisture can be transferred to the first water tank 220.

[0042] Optionally, the oxygen side tail drain valve 260 and the oxygen side water separator 240 are arranged on the oxygen side tail gas delivery pipeline 512, which are used to control the amount of oxygen and remove moisture from the oxygen; and the oxygen side water separator 240 is connected to the first water tank 220 through the first drain valve 270, and the removed moisture can be transferred to the first water tank 220.

[0043] In one embodiment, the high-nitrogen tail gas treated by the primary tail gas treatment unit 200 is transmitted to the secondary tail gas treatment unit 300 through the secondary tail gas delivery pipeline 520. The main function of the secondary tail gas treatment unit 300 is to adjust the hydrogen and oxygen concentration ratio of the high-nitrogen tail gas from the primary tail gas treatment unit 200 using the hydrogen and oxygen provided by the fuel cell power generation unit 100, and then use hydrogen and oxygen cycle catalysis to gradually react the hydrogen and oxygen therein, and finally make the hydrogen and oxygen concentrations reach zero or a relatively low level to obtain high-purity nitrogen. Furthermore, the exhaust gas secondary treatment unit 300 includes a second hydrogen-oxygen catalytic reactor 310, a second water tank 320, a gas mixing tank 330, a circulation pump 340 and a second drain valve 350. The gas mixing tank 330, the circulation pump 340 and the second hydrogen-oxygen catalytic reactor 310 are sequentially connected to the exhaust gas recovery circulation pipeline 530 to form a high-nitrogen exhaust gas circulation loop. The high-nitrogen exhaust gas from the exhaust gas primary treatment unit 200 first enters the gas mixing tank 330, and then enters the second hydrogen-oxygen catalytic reactor 310 through the circulation pump 340 to undergo a hydrogen-oxygen catalytic reaction to generate water. The generated water is discharged into the second water tank 320 through the second drain valve 350, and the unreacted high-nitrogen exhaust gas returns to the gas mixing tank 330 through the exhaust gas recovery circulation pipeline 530. This cycle is repeated until the hydrogen and oxygen in the high-nitrogen exhaust gas are considered to be completely removed.

[0044] In one embodiment, the tail gas secondary treatment unit 300 is connected to the nitrogen recovery storage unit 400 through a nitrogen recovery pipeline 540. The main function of the nitrogen recovery storage unit 400 is to dry and compress the high-purity nitrogen from the tail gas secondary treatment unit 300 and store it, and provide nitrogen to the fuel cell power generation unit 100 as required. Further, the nitrogen recovery pipeline 540 includes a nitrogen recovery main pipeline 541, a hydrogen-side nitrogen recovery branch pipeline 542, and an oxygen-side nitrogen recovery branch pipeline 543. The inlet end of the nitrogen recovery main pipeline 541 is connected to an outlet end of the gas mixing tank 330, and the nitrogen recovery storage unit 400 is arranged on the nitrogen recovery main pipeline 541.

[0045] The nitrogen recovery and storage unit 400 includes a low-pressure intake valve 410, a drying tank 420, a compressor 430, a high-pressure intake valve 440, a nitrogen storage tank 450 and a regulating valve 460 which are sequentially connected to the inlet end of the nitrogen recovery main pipeline 541, one end of the hydrogen side nitrogen recovery branch pipeline 542 and the oxygen side nitrogen recovery branch pipeline 543 are respectively connected to the nitrogen storage tank 450 and the regulating valve 460 through the hydrogen side nitrogen supply valve 470 and the oxygen side nitrogen supply valve 480, and the other ends of the hydrogen side nitrogen recovery branch pipeline 542 and the oxygen side nitrogen recovery branch pipeline 543 are respectively connected to the hydrogen side inlet and the oxygen side inlet of the fuel cell reactor 130, so that the high-purity nitrogen in the nitrogen recovery and storage unit 400 can be respectively transported to the hydrogen side inlet and the oxygen side inlet of the fuel cell reactor 130 to provide high-purity nitrogen for the nitrogen purge process.

[0046] Optionally, the drying tank 420 is filled with a dehydrating agent for removing moisture from the high-purity nitrogen. In this embodiment, a molecular sieve is used as the dehydrating agent. The function of the compressor 430 is to pressurize the high-purity nitrogen to meet the subsequent storage and use requirements. In this embodiment, the outlet nitrogen pressure of the compressor 430 is set to 15MPa. The function of the nitrogen storage tank 450 is to store high-purity nitrogen. In this embodiment, the volume of the nitrogen storage tank 450 is 200L.

[0047] In one embodiment, the hydrogen and oxygen content regulating pipeline 550 includes a hydrogen content regulating pipeline 551 and an oxygen content regulating pipeline 552, the two ends of the hydrogen content regulating pipeline 551 are respectively connected to the hydrogen supply device 110 and the gas mixing tank 330, the two ends of the oxygen content regulating pipeline 552 are respectively connected to the oxygen supply device 120 and the gas mixing tank 330, and a second hydrogen supply valve 5511 and a hydrogen flow controller 5512 are sequentially arranged on the side of the hydrogen content regulating pipeline 551 close to the hydrogen supply device 110, and a second oxygen supply valve 5521 and an oxygen flow controller 5522 are sequentially arranged on the side of the oxygen content regulating pipeline 552 close to the oxygen supply device 120.

[0048] The hydrogen supply device 110 and the oxygen supply device 120 are connected to the gas mixing tank 330 respectively for the purpose of adjusting the molar content ratio of hydrogen and oxygen in the gas mixing tank 330. When in use, a hydrogen concentration sensor 331 and an oxygen concentration sensor 332 for detecting the molar content of hydrogen and oxygen in the gas mixing tank 330 are also provided in the gas mixing tank 330. The hydrogen concentration sensor 331 and the oxygen concentration sensor 332 are required to be linked with the second hydrogen supply valve 5511, the hydrogen flow controller 5512, the second oxygen supply valve 5521, the oxygen flow controller 5522, the circulation pump 340 and the nitrogen recovery storage unit 400. In this way, a molar ratio of hydrogen to oxygen is set. When the hydrogen to oxygen concentration ratio measured by the hydrogen concentration sensor 331 and the oxygen concentration sensor 332 is higher than the set value, the second oxygen supply valve 5521 and the oxygen flow controller 5522 are started; when the measured hydrogen to oxygen concentration ... When the concentration ratio is lower than the set value, the second hydrogen supply valve 5511 and the hydrogen flow controller 5512 are started; when the concentration of at least one of the hydrogen concentration and the oxygen concentration reaches zero (that is, the reading of the hydrogen concentration sensor 331 or the oxygen concentration sensor 332 is zero, the same below), and the concentration of the other component is lower than the set value, it means that there is a very small amount of hydrogen or oxygen in the gas mixing tank 330 at this time, and it is considered that the mixed gas in the gas mixing tank 330 is high-purity nitrogen, then the second hydrogen supply valve 5511, the hydrogen flow controller 5512, the second oxygen supply valve 5521 and the oxygen flow controller 5522 are closed, and the circulation pump 340 is closed, and the nitrogen recovery storage unit 400 is operated at the same time to circulate the high-purity nitrogen to the fuel cell power generation unit 100, otherwise the nitrogen recovery storage unit 400 is stopped, and the circulation pump 340 and the second hydrogen supply valve 5511, the hydrogen flow controller 5512, the second oxygen supply valve 5521 and the oxygen flow controller 5522 are opened.

[0049] The nitrogen recycling device of the present invention will be described in further detail below through specific examples.

[0050] In this embodiment, it is assumed that the purity of hydrogen and oxygen provided by the hydrogen supply device 110 and the oxygen supply device 120 is 99.999%, and the impurity content therein can be ignored. In addition, since the nitrogen emission of the fuel cell is mainly concentrated in the startup or shutdown process, the nitrogen emission during normal and stable operation can be almost ignored. Therefore, this embodiment mainly focuses on the processing of nitrogen emission during the startup and shutdown process.

[0051] First, the hydrogen from the hydrogen supply device 110 enters the hydrogen side inlet of the stack reactor 130 through the first hydrogen supply valve 140, and the oxygen from the oxygen supply device 120 enters the oxygen side inlet of the stack reactor 130 through the first oxygen supply valve 150. The hydrogen and oxygen react electrochemically inside the stack reactor 130 to generate water while generating electricity. In this embodiment, it is assumed that the power of the stack reactor 130 is 30 kilowatts, the volume of the gaseous space on the hydrogen side is 2L, and the volume of the gaseous space on the oxygen side is also 2L. The nitrogen consumption for a single startup or shutdown is assumed to be 100L, of which 50L is on the hydrogen side and 50L is on the oxygen side. For this reason, for a single startup or shutdown, the tail exhaust components of the hydrogen side of the stack reactor 130 are 50L nitrogen + 2L hydrogen, and the tail exhaust components of the oxygen side are 50L nitrogen + 2L oxygen. In summary, in this embodiment, the single tail exhaust volume and gas composition of the fuel cell power generation unit 100 are: the high nitrogen tail exhaust composition on the hydrogen side is 50L nitrogen + 2L hydrogen, and the high nitrogen tail exhaust composition on the oxygen side is 50L nitrogen + 2L oxygen, and the above tail exhausts all enter the exhaust gas primary treatment unit 200.

[0052] Secondly, the high nitrogen tail gas entering the tail gas primary treatment unit 200 undergoes a hydrogen-oxygen catalytic reaction in the first hydrogen-oxygen catalytic reactor 210. Specifically, a catalyst for the catalytic reaction of hydrogen and oxygen is provided in the first hydrogen-oxygen catalytic reactor 210. In this embodiment, a noble metal Pd-based catalyst is selected as the catalyst, and the mechanism of the catalytic reaction of hydrogen and oxygen is:

[0053]

[0054] It is known that the high nitrogen tail gas composition on the hydrogen side is 50L nitrogen + 2L hydrogen, and the high nitrogen tail gas composition on the oxygen side is 50L nitrogen + 2L oxygen. Assuming that the reaction efficiency of the hydrogen-oxygen catalytic reaction in the first hydrogen-oxygen catalytic reactor 210 is 95%, the high nitrogen tail gas composition at the gas outlet of the first hydrogen-oxygen catalytic reactor 210 is: 0.1L hydrogen, 1.05L oxygen and 100L nitrogen, and the generated 1.53g water enters the first water tank 220 through the first drain valve 270. So far, after being processed by the exhaust primary treatment unit 200, a total of 0.1L hydrogen, 1.05L oxygen and 100L nitrogen high nitrogen tail gas enters the gas mixing tank 330 of the exhaust secondary treatment unit 300.

[0055] Next is the process of secondary treatment of high nitrogen tail gas in the tail gas secondary treatment unit 300, and the second hydrogen-oxygen catalytic reactor 310 is also provided with a catalyst. In this embodiment, a noble metal Pd-based catalyst is selected, and the hydrogen and oxygen catalytic reaction mechanism is the same as the hydrogen and oxygen catalytic reaction mechanism in the first hydrogen-oxygen catalytic reactor 210, which is not repeated here. The difference is that the tail gas secondary treatment unit 300 includes a tail gas recovery circulation pipeline 530, which can repeatedly circulate the unreacted mixed gas back to the second hydrogen-oxygen catalytic reactor 310 for catalytic reaction until the hydrogen and oxygen in the mixed gas are considered to be non-existent. At the same time, in this process, the amount of hydrogen and oxygen in the gas mixing tank 330 is detected in real time by the hydrogen concentration sensor 331 and the oxygen concentration sensor 332, and the second hydrogen supply valve 5511 and the hydrogen flow controller 5512 and the second oxygen supply valve 5521 and the oxygen flow controller 5522 are controlled by linkage to add hydrogen or oxygen respectively to adjust the hydrogen and oxygen and molar ratio in the gas mixing tank 330.

[0056] In this embodiment, the setting value of the molar content ratio of hydrogen and oxygen is 2, and the concentration of at least one component reaches zero and the setting value of the concentration of the other component is 1ppm. Then, a mixed gas of 0.1L hydrogen, 1.05L oxygen and 100L nitrogen from the primary exhaust gas treatment unit 200 enters the gas mixing tank 330 of the secondary exhaust gas treatment unit 300. At this time, the molar content ratio of hydrogen and oxygen in the gas mixing tank 330 is 0.095, which is lower than the set value 2. Therefore, the second hydrogen supply valve 5511 and the hydrogen flow controller 5512 are started to increase the molar content of hydrogen in the gas mixing tank 330 to meet the stoichiometric ratio of the hydrogen and oxygen catalytic reaction. The hydrogen supply flow can be controlled by the hydrogen flow controller 5512 so that the molar content ratio of hydrogen and oxygen in the gas mixing tank 330 finally reaches the set value 2; the high nitrogen exhaust gas with adjusted hydrogen and oxygen molar content ratio enters the second hydrogen-oxygen catalytic reactor 310 through the circulation pump 340, and the hydrogen and oxygen in the high nitrogen exhaust gas are catalytically reacted in the second hydrogen-oxygen catalytic reactor 310 to generate water, and the unreacted high nitrogen exhaust gas returns to the gas mixing tank 330 through the exhaust gas recovery circulation pipeline 530. After a period of time (assuming 5 minutes) of circulating hydrogen-oxygen catalytic reaction, the system detects the molar content ratio of hydrogen and oxygen in the gas mixing tank 330 again, and operates according to the above procedure according to the detected hydrogen and oxygen concentrations and molar content ratios, until at least one of the hydrogen and oxygen concentrations reaches zero, and the concentration of the other component is lower than the set value (in this embodiment, the set value is 1ppm), at this time, it is considered that the hydrogen and oxygen in the high-nitrogen tail gas are basically eliminated, and the circulation pump 340 is turned off. In summary, after this process is processed by the tail gas secondary treatment unit 300, at least one of the hydrogen and oxygen concentrations in the high-nitrogen tail gas reaches zero, and the content of the other component is lower than 1ppm, that is, the high-nitrogen tail gas is converted into high-purity nitrogen.

[0057] Finally, the high-purity nitrogen is stored in the nitrogen recovery storage unit 400 for reuse. Further, the nitrogen recovery storage unit 400 is linked with the hydrogen concentration sensor 331 and the oxygen concentration sensor 332. When the concentration of at least one of the hydrogen concentration and the oxygen concentration reaches zero and the concentration of the other component is lower than the set value (in this embodiment, the set value is 1 ppm), the nitrogen recovery storage unit 400 operates, that is, the low-pressure intake valve 410 and the high-pressure intake valve 440 are opened, and the drying tank 420 and the compressor 430 operate; otherwise, the nitrogen recovery storage unit 400 stops, that is, the low-pressure intake valve 410 and the high-pressure intake valve 440 are closed, and the drying tank 420 and the compressor 430 are shut down.

[0058] In addition, according to the operation requirements of the fuel cell power generation unit 100 , the nitrogen recovery storage unit 400 can open the regulating valve 460 , the hydrogen side gas supply valve 470 and the oxygen side gas supply valve 480 to provide nitrogen supply to the fuel cell reactor 130 .

[0059] Through the above-mentioned nitrogen recycling device of the fuel cell system in a closed environment, the recycling of nitrogen is achieved, the discharge of nitrogen into the closed cabin is avoided, and the elimination of hydrogen and oxygen in the fuel cell exhaust gas is completed, thereby ensuring the stability of the cabin pressure in the closed environment cabin and the safety of personnel and equipment.

[0060] Compared with the prior art, the present invention has the following advantageous features:

[0061] (1) The recycling of nitrogen is achieved, ensuring the pressure stability of the closed environment cabin during long-term operation. The existing technology mainly reduces nitrogen emissions by optimizing operation strategies and reducing single nitrogen consumption. However, due to the limited reduction, the cumulative nitrogen emissions are still high when the operation time is long. The present invention achieves full recovery and recycling of nitrogen in the tail gas by secondary treatment of high-nitrogen tail gas, completely solving the bottleneck problem of nitrogen emission into the closed cabin.

[0062] (2) The nitrogen recycling process does not interfere with the normal operation of the fuel cell, which is beneficial to the performance and cycle life of the fuel cell. In order to reduce the nitrogen emissions of the fuel cell, the existing technical solution will adjust and optimize the fuel cell operation strategy, and this optimization measure will have an adverse effect on the performance or life of the fuel cell. The entire processing process of the present invention does not interfere with the fuel cell operation strategy or operating conditions, does not limit the number of times the fuel cell system is turned on and off or the single nitrogen consumption, and the fuel cell can operate under its optimal strategy or operating conditions, which is beneficial to improving the performance of the fuel cell and extending the cycle life.

[0063] (3) While recycling nitrogen, the simultaneous elimination of hydrogen and oxygen in the exhaust gas of the fuel cell is achieved, with outstanding comprehensive benefits and application prospects. The existing technical solutions simply reduce the nitrogen emissions in the exhaust gas of the fuel cell, without treating the hydrogen and oxygen in the exhaust gas. The present invention, while recycling nitrogen, achieves the simultaneous elimination of hydrogen and oxygen in the exhaust gas of the fuel cell, while ensuring the stability of the cabin pressure in the closed environment cabin, ensuring the safety of the cabin personnel and equipment, with outstanding comprehensive benefits and application prospects.

[0064] The specific implementation of the present invention described above does not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A nitrogen recycling device for a fuel cell system in a closed environment, characterized in that: It includes a fuel cell power generation unit, a tail gas primary treatment unit, a tail gas secondary treatment unit, a nitrogen recovery storage unit and connecting pipelines, wherein: The tail gas primary treatment unit comprises a first hydrogen-oxygen catalytic reactor; The tail gas secondary treatment unit includes a second hydrogen-oxygen catalytic reactor and a gas mixing tank; The connecting pipeline includes a primary tail gas delivery pipeline, a secondary tail gas delivery pipeline, a tail gas recovery circulation pipeline, a nitrogen recovery pipeline and a hydrogen and oxygen content adjustment pipeline; The two ends of the primary tail gas delivery pipeline are respectively connected to the fuel cell power generation unit and the first hydrogen-oxygen catalytic reactor. The two ends of the secondary tail gas delivery pipeline are respectively connected to the first hydrogen-oxygen catalytic reactor and the gas mixing tank, and the outlet end of the gas mixing tank is provided with two, One end of the tail gas recovery circulation pipeline is connected to one of the outlet ends of the gas mixing tank, and the other end is connected to the inlet end of the second hydrogen-oxygen catalytic reactor, and the outlet end of the second hydrogen-oxygen catalytic reactor is further connected to the gas mixing tank through the tail gas recovery circulation pipeline. One end of the nitrogen recovery pipeline is connected to the other outlet end of the gas mixing tank, and the other end is connected to the nitrogen recovery storage unit, and the outlet end of the nitrogen recovery storage unit is further connected to the fuel cell power generation unit through the nitrogen recovery pipeline. The two ends of the hydrogen and oxygen content regulating pipeline are respectively connected to the gas mixing tank and the fuel cell power generation unit to adjust the molar content ratio of hydrogen and oxygen in the gas mixing tank; The fuel cell power generation unit comprises a hydrogen supply device, an oxygen supply device and a stack reaction device, wherein the hydrogen supply device and the oxygen supply device are respectively connected to the hydrogen side inlet and the oxygen side inlet of the stack reaction device, and a first hydrogen supply valve is provided on the pipeline connecting the hydrogen supply device and the stack reaction device, and a first oxygen supply valve is provided on the pipeline connecting the oxygen supply device and the stack reaction device; The hydrogen and oxygen content regulating pipeline comprises a hydrogen content regulating pipeline and an oxygen content regulating pipeline, the two ends of the hydrogen content regulating pipeline are respectively connected to the hydrogen supply device and the gas mixing tank, the two ends of the oxygen content regulating pipeline are respectively connected to the oxygen supply device and the gas mixing tank, and a second hydrogen supply valve and a hydrogen flow controller are sequentially arranged on the side of the hydrogen content regulating pipeline close to the hydrogen supply device, and a second oxygen supply valve and an oxygen flow controller are sequentially arranged on the side of the oxygen content regulating pipeline close to the oxygen supply device; The nitrogen recovery pipeline comprises a nitrogen recovery main pipeline, a hydrogen-side nitrogen recovery branch pipeline and an oxygen-side nitrogen recovery branch pipeline, the inlet end of the nitrogen recovery main pipeline is connected to an outlet end of the gas mixing tank, and the nitrogen recovery storage unit is arranged on the nitrogen recovery main pipeline, wherein: The nitrogen recovery and storage unit includes a low-pressure intake valve, a drying tank, a compressor, a high-pressure intake valve, a nitrogen storage tank and a regulating valve which are sequentially connected to the inlet end of the nitrogen recovery main pipeline; one end of the hydrogen-side nitrogen recovery branch pipeline and the oxygen-side nitrogen recovery branch pipeline are respectively connected to the nitrogen storage tank and the regulating valve through the hydrogen-side nitrogen supply valve and the oxygen-side nitrogen supply valve; the other ends of the hydrogen-side nitrogen recovery branch pipeline and the oxygen-side nitrogen recovery branch pipeline are respectively connected to the hydrogen-side inlet and the oxygen-side inlet of the fuel cell reactor.

2. The nitrogen recycling device for a fuel cell system in a closed environment according to claim 1, characterized in that: The primary exhaust gas delivery pipeline includes a hydrogen side exhaust gas delivery pipeline and an oxygen side exhaust gas delivery pipeline. The two ends of the hydrogen side exhaust gas delivery pipeline are respectively connected to the hydrogen side outlet of the fuel cell reactor and the first hydrogen-oxygen catalytic reactor, and the two ends of the oxygen side exhaust gas delivery pipeline are respectively connected to the oxygen side outlet of the fuel cell reactor and the first hydrogen-oxygen catalytic reactor.

3. The nitrogen recycling device for a fuel cell system in a closed environment according to claim 2, characterized in that: A hydrogen side tail exhaust valve and a hydrogen side water separator are sequentially arranged on the side of the hydrogen side tail gas delivery pipeline close to the fuel cell reactor, and an oxygen side tail exhaust valve and an oxygen side water separator are sequentially arranged on the side of the oxygen side tail gas delivery pipeline close to the fuel cell reactor.

4. The nitrogen recycling device for a fuel cell system in a closed environment according to claim 3, characterized in that: The exhaust gas primary treatment unit also includes a first water tank, which is connected to the first hydrogen-oxygen catalytic reactor, the hydrogen-side water separator and the oxygen-side water separator through a first drain valve.

5. The nitrogen recycling device for a fuel cell system in a closed environment according to claim 1, characterized in that: The tail gas secondary treatment unit further includes a second water tank, and the second water tank is connected to the second hydrogen-oxygen catalytic reactor via a second drain valve.

6. The nitrogen recycling device for a fuel cell system in a closed environment according to claim 1, characterized in that: A circulation pump is provided on the tail gas recovery circulation pipeline and between the gas mixing tank and the second hydrogen-oxygen catalytic reactor.

7. The nitrogen recycling device for a fuel cell system in a closed environment according to claim 1, characterized in that: The gas mixing tank is also provided with a hydrogen concentration sensor and an oxygen concentration sensor for detecting the molar contents of hydrogen and oxygen in the gas mixing tank respectively.

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