Fuel cell anode drainage and humidification system

Abstract

The utility model discloses a fuel cell anode drainage and humidification system which comprises a fuel cell stack, a gas-water separator, a water ejector for anode humidification and a water storage tank, the gas-water separator is connected with an anode outlet of the fuel cell stack, and the water ejector is arranged on a hydrogen conveying pipeline of the fuel cell stack. The upper end of the water storage tank is connected with a water outlet of the gas-water separator, the water storage tank is connected with the water ejector through a water pump, the bottom of the water storage tank is connected with a drain valve, and a liquid level sensor is arranged in the water storage tank and is in control connection with the drain valve and the water pump. The anode pressure fluctuation in the anode drainage process can be eliminated, water is not stored in the gas-water separator, the water separation effect of the gas-water separator is improved, the collected drainage water is used for controlling the system anode humidity, a humidifier commonly used at present is replaced, and the cost can be remarkably reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of fuel cells, in particular to a fuel cell anode drainage and humidification system. Background Technique

[0002] When the fuel cell system operates, water will be carried at the anode outlet position. If it directly enters the stack, it will not only increase the power consumption of the hydrogen circulation pump, but also seriously affect the performance of the fuel cell stack. Therefore, a water separation device and a drainage device need to be set at the anode outlet position. There are two drainage strategies for the conventional fuel cell anode drainage system. One is based on a position sensor. When the water level in the water separation device reaches the high threshold, the drain valve opens, and when it drops to the low threshold, it closes. This strategy and structure can effectively prevent hydrogen from being discharged and reduce the anode pressure fluctuation. Another switch control strategy is based on periodicity. The drain valve enters a switch cycle with different duty ratios according to different working conditions. The problem with this strategy is that once the duty ratio is set unreasonably and the duty ratio is too small, the accumulated water cannot be drained in time and completely, which may cause waterlogging in the anode and increase the risk of drain valve freezing; if the duty ratio is too large, hydrogen will be discharged, resulting in a large decrease in overall economy.

[0003] For example, a fuel cell anode drainage method disclosed in Chinese Patent CN 115632143A includes the following steps: setting the calibrated closing time of the drain valve as Toff, the calibrated opening drainage time as Twtr, and the calibrated opening exhaust time as TN2. Then the total opening time of the drain valve is Twtr + TN2, and the operating cycle of the drain valve is Toff + Twtr + TN2. During the operating cycle of the drain valve, when the drain valve is open, the gas pressure change is monitored. The time from the opening of the drain valve to the start of the gas pressure drop is the actual drainage time Twtr-act. By comparing the actual drainage time Twtr-act with the calibrated opening drainage time Twtr, the operating cycle and / or drainage volume of the drain valve are dynamically adjusted.

[0004] When a fuel cell operates, water is generated at the cathode. Due to the existence of a water concentration gradient, the water at the cathode will transfer to the anode through the proton exchange membrane. However, due to the reason of electro-migration, hydrogen ions will carry water and transfer to the cathode. Generally speaking, the anode is short of water. Because of the lack of water, the battery cannot work properly. Therefore, to maintain the continuous and stable normal operation of the fuel cell, it is necessary to maintain the water balance in the battery. Humidification is a very effective measure to maintain the water balance. To achieve the purpose of humidification, a humidification system is mostly set up now, but this setting will make the battery complex and the cost will increase significantly. What needs to be solved for the realization of the self-humidification technology is how to effectively transfer the water generated at the oxygen electrode to the hydrogen electrode. At present, this self-humidification technology is divided into three categories: one is to try to accelerate the diffusion rate of the water generated at the oxygen electrode to the hydrogen electrode, which requires forming a high water concentration gradient or a large diffusion coefficient, and this has the defect of great technical difficulty; the second is to chemically react to generate water in the proton exchange membrane through a catalytic reaction, and the disadvantage of this technology is large internal resistance and the inability to match the water shortage and the water supply; the third is to achieve the purpose of self-humidification by improving the battery structure; so far, no better structure has been found to achieve the purpose of this self-humidification, and how to effectively achieve self-humidification is a technical problem that needs to be solved currently. Utility Model Content

[0005] Aiming at the deficiencies of the prior art, the present utility model provides a fuel cell anode drainage and humidification system, which can eliminate the anode pressure fluctuation during the anode drainage process and can accurately control the anode humidity of the system.

[0006] In order to solve the above technical problems, the technical solution adopted by the present utility model is as follows:

[0007] The fuel cell anode drainage and humidification system includes a fuel cell stack, a gas-water separator, and a water injector for anode humidification. The gas-water separator is connected to the anode outlet of the fuel cell stack. The water injector is arranged on the hydrogen delivery pipeline of the fuel cell stack. It also includes a water storage tank. The upper end of the water storage tank is connected to the water outlet of the gas-water separator. The water storage tank is connected to the water injector through a water pump, and a drain valve is connected to the bottom of the water storage tank. A liquid level sensor is arranged in the water storage tank, and the liquid level sensor is connected to control the drain valve and the water pump.

[0008] Further:

[0009] An ejector and a mixing chamber are arranged on the hydrogen delivery pipeline. The ejector is connected to the hydrogen outlet of the gas-water separator through a hydrogen circulation pump, and the water injector is arranged corresponding to the mixing chamber.

[0010] The water storage tank is arranged below the gas-water separator.

[0011] A nitrogen discharge valve is connected to the upper end of the gas-water separator. The nitrogen discharge valve is connected to a tail discharge pipeline, and a muffler is arranged on the tail discharge pipeline.

[0012] The bottom of the water storage tank is provided with two outlets arranged side by side. One outlet is connected to a drain valve, and the other outlet is connected to a water pump.

[0013] The drain valve is an electromagnetic drain valve, and the water pump is a high-pressure vortex pump.

[0014] A hydrogen pressure sensor is provided at the hydrogen inlet of the hydrogen path of the fuel cell stack on the hydrogen delivery pipeline.

[0015] Compared with the prior art, the present utility model has the following advantages:

[0016] The fuel cell anode drainage and humidification system is reasonably designed, eliminating the anode pressure fluctuation during the anode drainage process, preventing water accumulation in the gas-liquid separator, enhancing the water separation effect of the gas-liquid separator, and replacing the currently commonly used humidifier by using the collected drainage water to humidify the anode of the system, which can significantly reduce costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The following briefly describes the content expressed by each drawing of this specification and the marks in the drawings:

[0018] Figure 1 It is a schematic diagram of the drainage and humidification system of the present utility model.

[0019] In the figure:

[0020] 1 - stop valve; 2 - proportional valve; 3 - ejector; 4 - water injector; 5 - high-pressure vortex pump; 6 - drain valve; 7 - hydrogen pressure sensor I; 8 - hydrogen circulation pump; 9 - water storage tank; 10 - gas-liquid separator; 11 - liquid level sensor; 12 - silencer; 13 - nitrogen discharge valve; 14 - back pressure valve; 15 - hydrogen pressure sensor II; 16 - fuel cell stack; 17 - electrochemical impedance spectrometer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] The following further describes in detail the specific embodiments of the present utility model with reference to the accompanying drawings and through the description of the embodiments.

[0022] As Figure 1 shown, the fuel cell anode drainage and humidification system includes a fuel cell stack 16, a gas-liquid separator 10, a water storage tank 9, and a water injector 4 for anode humidification; the gas-liquid separator 10 is connected to the anode outlet of the fuel cell stack, the water injector is arranged on the hydrogen delivery pipeline of the fuel cell stack, the upper end of the water storage tank is connected to the water outlet of the gas-liquid separator, the water storage tank is connected to the water injector through a water pump, and a drain valve is connected to the bottom of the water storage tank. A liquid level sensor 11 is arranged in the water storage tank, and the liquid level sensor is connected to control the drain valve and the water pump.

[0023] This system will not affect the anode hydrogen pressure while ensuring the anode drainage capacity. The water tank is connected to the water ejector to achieve anode self-humidification. The humidifier can also be removed, reducing costs while making the system layout more flexible and compact.

[0024] An ejector 3 and a mixing chamber are provided on the hydrogen delivery pipeline. A shut-off valve 1 and a proportional valve 2 are provided in front of the ejector on the hydrogen delivery pipeline. The ejector is connected to the hydrogen outlet of the gas-water separator through a hydrogen circulation pump 8. A water ejector 4 is provided corresponding to the mixing chamber. The preferred water ejector is a high-pressure atomizer, which has a better humidification and mixing effect.

[0025] The upper end of the gas-water separator 10 is connected to a nitrogen exhaust valve 13 , which is connected to a tail exhaust pipeline on which a muffler 12 is provided; and the tail exhaust pipeline is connected to the fuel cell stack through a back pressure valve 14 and a hydrogen pressure sensor II 15 .

[0026] The water storage tank 9 is arranged below the gas-water separator. Preferably, the gas-water separator at the anode outlet is connected to the water storage tank through a 3mm drain pipe, and two outlets are arranged side by side at the bottom of the water storage tank, one connected to the electromagnetic drain valve 6 and the other connected to the high-pressure vortex pump 5, and the water storage tank is monitored based on a liquid level sensor.

[0027] The gas-water separator is connected to the water storage tank through a 3mm drain pipe, so when the hydrogen circulates through the water, it has a good water separation effect and does not evaporate the water in the water storage tank for humidification.

[0028] A hydrogen pressure sensor Ⅰ7 is provided at the hydrogen path inlet of the fuel cell stack on the hydrogen transmission pipeline, and the operation is stable and reliable.

[0029] This system connects an air-water separator to an external water tank, which is monitored by a liquid level sensor. It stores water, exhausts gas, and realizes self-humidification of the anode without affecting the anode pressure. It drains water when the anode humidity is too high and the liquid level in the water tank is high. When the anode humidity is insufficient, the wet gas discharged from the anode outlet of the fuel cell stack is used to store water in the water tank, and the water in the wet gas is used to accurately humidify the anode through the ejector through the membrane tube inside the humidifier, thereby realizing precise control of the anode humidity of fuel cell systems of various powers under all-weather and all-operating conditions.

[0030] Preferred specific embodiments are:

[0031] When this fuel cell system operates, the hydrogen pipeline cut-off valve is opened, and the hydrogen inlet pressure of the fuel cell anode is controlled by the hydrogen pipeline proportional valve. After being pressurized at the secondary flow inlet in the ejector body, it is mixed with the recycled hydrogen at the hydrogen return port of the hydrogen circulation pump. By arranging a mixing chamber between the ejector and the fuel cell stack inlet, before the dry hydrogen enters the stack, high-pressure atomized water is first injected by a water injector. The atomized water and hydrogen are fully mixed in the mixing chamber and then evaporated to form water vapor, which enters the stack together. The anode outlet is connected to a gas-water separator. A nitrogen discharge valve is connected to the gas-water separator, and the nitrogen discharge valve is connected to the tail discharge pipeline; a water storage tank is connected below the gas-water separator through a 3mm pipeline. A liquid level sensor is placed in the water storage tank to monitor the liquid level in the water storage tank. A drain valve is connected below the water storage tank, and the drain valve is connected to the tail discharge pipe. Another pipeline below the water storage tank is connected to a high-pressure vortex pump. The high-pressure vortex water pump is connected to the water injector, and the water injector is connected to the rear end of the ejector to humidify the mixed hydrogen.

[0032] The gas-water separator is externally connected to the water storage tank through a 3mm drain pipe. Therefore, when hydrogen is circulated through water, it has a good water separation effect and will not evaporate the water in the water storage tank to humidify the recycled hydrogen, increasing the water separation effect of the gas-water separator.

[0033] The liquid level in the water storage tank is monitored by a liquid level sensor, and the liquid level thresholds are set as X1, X2, and X3 respectively. When the liquid level reaches the lowest threshold X1, if the anode needs to be humidified, the water in the water storage tank is connected to the water injector for self-humidification. By arranging a mixing chamber between the fuel cell stack and the ejector, before the hydrogen enters the stack, high-pressure atomized water is first injected by the water injector. The atomized water and the hydrogen ejected by the ejector are fully mixed in the mixing chamber and then enter the stack together. If the humidity is sufficient and humidification is not required, the water injector is not opened. By arranging a mixing chamber between the fuel cell stack and the ejector, before the hydrogen enters the stack, high-pressure atomized water is first injected by the water injector. The atomized water and the hydrogen ejected by the ejector are fully mixed in the mixing chamber and then enter the stack together. The high-pressure vortex pump extracts water from the water tank and compresses it to serve as the pressure source for the water injector to ensure good atomization effect during water injection.

[0034] When the water collected in the water tank is more than the water consumed by the water injector, the liquid level in the water tank will gradually rise. When it reaches the highest threshold X3, the electromagnetic drain valve at the bottom of the water tank can be opened to drain some water to prevent the water tank from being full and causing blockage of the gas-water separator. When the liquid level in the water storage tank monitored by the liquid level sensor drops to X2, the electromagnetic drain valve is closed. If the water consumption for anode humidification is more than the water provided by the gas-water separator to the water tank and the liquid level drops to X1, humidification is stopped to ensure that there is always some water in the water storage tank and the anode hydrogen pressure will not fluctuate violently due to emptying.

[0035] When the liquid level in the water storage tank is greater than X1, the water injection volume of the water injector is adjusted and controlled by the injection pulse width time. The required water injection volume is determined in the following two ways under different conditions. First, under dynamic conditions, according to the collected ambient temperature T env , ambient pressure P env , and ambient relative humidity R Henv , calculate the mass flow rate of water vapor m vap.env in the current air flow. Then, according to the collected inlet temperature T in , inlet pressure P in , and the designed target relative humidity R Hin of the reactor inlet, calculate the target required mass flow rate of water vapor m vap.in . The difference m vap.in-mvap.env between the two is the injection volume of the water injector. Using this open-loop control strategy under dynamic conditions can enable the system to reach the target humidity faster and improve the response speed. Under steady-state conditions, the impedance data collected by the electrochemical impedance spectrometer is used to judge the humidity state of the membrane and accurately adjust the water injection volume to achieve closed-loop control. In addition, the two control strategies can be supplemented when one of them fails or malfunctions to ensure the normal function and stable operation of the system.

[0036] The high-pressure vortex pump extracts water from the water tank and compresses it to serve as the pressure source of the water injector, ensuring good atomization effect during water injection.

[0037] The above is only a description of the preferred embodiments of the present invention. The above technical features can be arbitrarily combined to form multiple embodiment schemes of the present invention.

[0038] The present invention has been described exemplarily above in conjunction with the accompanying drawings. Obviously, the specific implementation of the present invention is not limited by the above methods. As long as various non-substantive improvements are made by adopting the concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A fuel cell anode drainage and humidification system, comprising a fuel cell stack, a gas-water separator, and a water injector for anode humidification. The gas-water separator is connected to the anode outlet of the fuel cell stack, and the water injector is arranged on the hydrogen delivery pipeline of the fuel cell stack. It is characterized in that: It further includes a water storage tank. The upper end of the water storage tank is connected to the water outlet of the gas-water separator. The water storage tank is connected to the water injector through a water pump, and a drain valve is connected to the bottom of the water storage tank. A liquid level sensor is provided in the water storage tank, and the liquid level sensor is connected to the drain valve and the water pump for control.

2. The fuel cell anode drainage and humidification system according to claim 1, wherein: An ejector and a mixing chamber are provided on the hydrogen delivery pipeline. The ejector is connected to the hydrogen outlet of the gas-water separator through a hydrogen circulation pump, and the water injector is arranged corresponding to the mixing chamber.

3. The fuel cell anode drainage and humidification system according to claim 1, characterized in that: The water storage tank is arranged below the gas-water separator.

4. The fuel cell anode drainage and humidification system according to claim 1, wherein: A nitrogen discharge valve is connected to the upper end of the gas-water separator, and the nitrogen discharge valve is connected to a tail discharge pipeline, and a muffler is provided on the tail discharge pipeline.

5. The fuel cell anode drainage and humidification system according to claim 1, wherein: Two outlets are arranged side by side at the bottom of the water storage tank. One outlet is connected to the drain valve, and the other outlet is connected to the water pump.

6. The fuel cell anode drainage and humidification system according to claim 1, wherein: The drain valve is an electromagnetic drain valve, and the water pump is a high-pressure vortex pump.

7. The fuel cell anode drainage and humidification system according to claim 2, characterized in that: A hydrogen pressure sensor is provided at the hydrogen inlet of the fuel cell stack on the hydrogen pipeline of the hydrogen delivery pipeline.

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