A system and method for hydrogen supply and circulation for fuel cells

Abstract

The present invention relates to a system and method for supplying and circulating hydrogen for a fuel cell, wherein a hydrogen source, a pressure reducing valve, an ejector, an ejector and a hydrogen inlet solenoid valve are sequentially connected at the hydrogen inlet of the fuel cell, the ejector is provided with a feed port, a discharge port, a circulation port a and a circulation port b, the feed port is connected to the ejector, the discharge port is connected to the hydrogen inlet solenoid valve, a three-way valve is connected at the hydrogen outlet of the fuel cell, one outlet of the three-way valve is connected to a tail gas treatment unit through a hydrogen discharge pipeline, the other outlet of the three-way valve is connected to a water vapor separator, the bottom of the water vapor separator is connected to the hydrogen discharge pipeline, and the top of the water vapor separator is respectively connected to the circulation port a and the circulation port b. The present invention reduces the overall power consumption of the system, improves the recovery rate of hydrogen, reduces the system volume, improves the controllability of the hydrogen supply, shortens the control time, and saves the system cost through the combination of the ejector and the ejector.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular to a system and method for supplying and circulating hydrogen in fuel cells. Background Art

[0002] Fuel cell technology is a new energy industry with good prospects for application in the future automotive industry.

[0003] In the hydrogen system of a fuel cell system subsystem, proportional valves and circulation pumps are commonly used to supply and circulate hydrogen. However, this has certain drawbacks. The proportional valve controls the hydrogen flow through PID control, matching the flow rate and duty cycle based on the pressure drop. This makes the hydrogen flow supply less precise and the control response time longer.

[0004] However, the circulating pump consumes a certain amount of power while circulating hydrogen. As the system power increases and the amount of hydrogen circulated increases, the circulating pump's speed also increases. This increases the overall power consumption of the circulating pump, which in turn increases the power consumption of the entire system. This also increases the number of piping connections throughout the system, making the system larger. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above-mentioned defects of the prior art and provide a continuous, stable, simple and easy-to-control hydrogen supply and circulation system.

[0006] The purpose of this application is also to provide a hydrogen supply and circulation method using the above system.

[0007] In order to achieve the purpose of the present invention, this application provides the following technical solutions.

[0008] In the first aspect, the present application provides a system for hydrogen supply and circulation of fuel cells, the system comprising a fuel cell, wherein a hydrogen source, a pressure reducing valve, an injector, an ejector and a hydrogen inlet solenoid valve are sequentially connected at the hydrogen inlet of the fuel cell, the ejector is provided with a feed port, a discharge port, a circulation port a and a circulation port b, the feed port is connected to the injector, the discharge port is connected to the hydrogen inlet solenoid valve, a three-way valve is connected at the hydrogen outlet of the fuel cell, one outlet of the three-way valve is connected to the tail gas treatment unit through a hydrogen discharge pipeline, the other outlet of the three-way valve is connected to a water vapor separator, the bottom of the water vapor separator is connected to the hydrogen discharge pipeline, the top of the water vapor separator is respectively connected to the circulation port a and the circulation port b, and a circulation solenoid valve is provided on the connecting pipeline between the water vapor separator and the circulation port b. The present application adopts an ejector to control the injection amount of hydrogen, calculates the required hydrogen flow rate according to the loading current demand and the current change rate, and thus uses the ejector to provide the required hydrogen amount, which changes the traditional use of the proportional valve duty cycle control flow, shortens the control time, responds quickly, and can adapt to any rapid conversion of large and small power. At the same time, since the metering ratio of the supplied hydrogen is greater than 1 (metering ratio = (injector injection amount + water vapor separator circulating hydrogen amount) / injector injection amount), the remaining hydrogen is injected back to the fuel cell through the ejector after passing through the water vapor separator from the fuel cell outlet. The injection of hydrogen back to the fuel cell is divided into two routes. When the power is low, circulation port a is used for circulation. When the power is high, circulation port a and circulation port b are used to operate together. The combination of the ejector and the ejector reduces the overall power consumption of the system, improves the recovery rate of hydrogen, reduces the size of the system, improves the controllability of the hydrogen supply, shortens the control time, saves system costs, reduces the length of the system pipeline, and improves the overall airtightness.

[0009] In one embodiment of the first aspect, one outlet of the three-way valve is connected to the exhaust gas treatment unit through a hydrogen exhaust pipeline, and a hydrogen exhaust solenoid valve is provided on the hydrogen exhaust pipeline; a water drainage solenoid valve is provided between the bottom of the water vapor separator and the hydrogen exhaust pipeline.

[0010] In one embodiment of the first aspect, a temperature sensor and a pressure sensor are provided at both the hydrogen inlet and the hydrogen outlet of the fuel cell. These temperature and pressure sensors are used to monitor the temperature and pressure at the fuel cell's hydrogen inlet and outlet, preventing excessive hydrogen pressure and temperature imbalance entering the fuel cell, thereby improving fuel cell power generation performance and facilitating strategy control and adjustment.

[0011] In one embodiment of the first aspect, a pressure relief branch is provided between the hydrogen inlet and the hydrogen outlet of the fuel cell, and a pressure relief valve is provided on the pressure relief branch. Generally, when the pressure at the hydrogen outlet of the fuel cell reaches 1.7 bar, the pressure relief valve is opened to relieve pressure.

[0012] In one embodiment of the first aspect, the system is provided with a purge unit, the purge unit comprising a nitrogen source, the nitrogen source and the hydrogen source are arranged in parallel, the nitrogen source is connected to the pressure reducing valve, and a one-way valve is provided on the connecting pipeline.

[0013] In a second aspect, the present application further provides a method for supplying and circulating hydrogen for a fuel cell using the above system, the method comprising the following steps:

[0014] (1) Control the amount of hydrogen injected and the inlet pressure of the injector, obtain the relationship LP between the inlet pressure and the outlet flow rate of the injector, and then install the injector in the system; that is, control the injector to inject hydrogen according to the hydrogen flow demand value, which can accurately control the pressure and flow rate. This control method avoids the PID control based on the pressure feedback at the rear end of the proportional valve;

[0015] (2) Start the fuel cell, adjust the injection amount of the injector, monitor the injector inlet pressure P1 in real time, and monitor the output current I1 of the fuel cell in real time;

[0016] (3) According to LP, the ejector outlet flow rate L1 is obtained using the ejector inlet pressure P1;

[0017] (4) Calculating the power of the fuel cell in real time based on the output current I1 of the fuel cell: W = U * I1 * N, where U is the output voltage of each cell in the fuel cell and N is the number of cells in the fuel cell;

[0018] (5) When the power of the fuel cell is low, the circulation solenoid valve is closed so that the water vapor separator is connected only to the circulation port a. When the power of the fuel cell is high, the circulation solenoid valve is opened so that the water vapor separator is connected to both the circulation port a and the circulation port b.

[0019] (6) When the power of the fuel cell reaches the rated power and remains constant, the injection amount of the injector is kept constant.

[0020] In this application, the flow rate is regulated by controlling the pressure. Pressure and flow are directly proportional, so the corresponding values ​​of the pressure and flow of the injector need to be measured in advance. In actual testing, the pressure value corresponding to the required flow rate is found, thereby controlling the pressure.

[0021] When the amount of hydrogen gas in the fuel cell is different, the output current of the fuel cell is different. The specific calculation formula is as follows:

[0022] Hydrogen flow rate = (6.96*I1*N)*stoichiometric ratio / 1000;

[0023] Stoichiometric ratio = (injector injection amount + water vapor separator circulating hydrogen amount) / injector injection amount. The stoichiometric ratio is generally set at 1.2 to 1.6 and is adjusted according to actual conditions.

[0024] The 6.96 is calculated as follows:

[0025] (1) According to Faraday's law, 1 mol of a substance contains a charge of 96500C;

[0026] (2) According to Coulomb's law, 1 ampere = 1 coulomb per second;

[0027] (3) 1 / 96500 mol of hydrogen is required to produce 1 ampere of current, and the molar volume of the gas is 22400 ml / mol;

[0028] (4) Therefore, the required hydrogen flow rate is 1 / 96500*22400 / 2*60=6.96L / min

[0029] The flow rate is calculated from the current using the above formula.

[0030] At the same time, the power of the fuel cell is W=U*I1*N, so there is a correspondence between power, current and flow. Combined with the relationship between the injector pressure and flow, the corresponding point is found, and the relationship between power, current and pressure is obtained. Therefore, the pressure value of the pressure sensor can be used to stabilize the pressure required for different powers, that is, as long as the pressure value of the target power is reached, a fuel cell of this power can be obtained.

[0031] In one embodiment of the second aspect, the dividing point between high power and low power is 50 kW. Because the air intake of each ejector circulation port has a certain upper limit, and the greater the hydrogen flow rate, the greater the output power of the fuel cell, when the fuel cell power reaches a certain value, one circulation port can no longer pass sufficient hydrogen, and therefore a second circulation port is opened. Actual measurements have shown that this dividing point is around 50 kW.

[0032] In one embodiment of the second aspect, when the fuel cell is flooded, the fuel cell is drained, the hydrogen injection amount of the injector is reduced, and then the injection amount of the injector is gradually restored.

[0033] In one embodiment of the second aspect, a pressure relief branch is provided between the hydrogen inlet and the hydrogen outlet of the fuel cell, and a pressure relief valve is provided on the pressure relief branch; when the pressure at the hydrogen inlet and the hydrogen outlet of the fuel cell is too high, the pressure relief valve is opened to relieve the pressure to protect the fuel cell stack from being damaged by high-load pressure shock.

[0034] In one embodiment of the second aspect, the system is provided with a purge unit, the purge unit including a nitrogen source, the nitrogen source and the hydrogen source being arranged in parallel, the nitrogen source being connected to a pressure reducing valve, and a one-way valve being provided on the connecting pipeline; when the fuel cell finishes working, the hydrogen source is closed, the one-way valve and the nitrogen source are opened, and the system is purged with nitrogen.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] The combination of hydrogen spray and ejector reduces the overall power consumption of the system, improves the recovery rate of hydrogen, reduces the system volume, improves the controllability of hydrogen supply, shortens the control time, saves system costs, reduces the length of system pipelines, and improves the overall air tightness. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a structural diagram of the application system.

[0038] In the accompanying drawings, 1 is a hydrogen cylinder, 2 is a hydrogen cylinder pressure reducing valve, 3 is a pressure reducing valve, 4 is a third pressure sensor, 5 is an ejector, 6 is an ejector, 7 is a hydrogen inlet solenoid valve, 8 is a first temperature sensor, 9 is a first pressure sensor, 10 is a pressure relief valve, 11 is a fuel cell, 12 is a second pressure sensor, 13 is a second temperature sensor, 14 is a drain solenoid valve, 15 is a hydrogen discharge solenoid valve, 16 is a water vapor separator, 17 is a circulation solenoid valve, 18 is a circulation port a, 19 is a circulation port b, 20 is a nitrogen cylinder, 21 is a nitrogen cylinder pressure reducing valve, and 22 is a one-way valve. DETAILED DESCRIPTION

[0039] Unless otherwise defined, technical or scientific terms used in this specification and claims shall have the ordinary meaning as understood by persons having ordinary skill in the art to which this invention belongs. All numerical values ​​listed herein, from the lowest value to the highest value, refer to all numerical values ​​obtained by incrementing the lowest value to the highest value by one unit when the difference between the lowest value and the highest value is two units or more.

[0040] The following describes specific embodiments of the present invention. It should be noted that, in the context of describing these embodiments, for the sake of brevity and clarity, this specification does not exhaustively describe all features of the actual embodiments. Those skilled in the art may modify and substitute the embodiments of the present invention without departing from the spirit and scope of the present invention, and the resulting embodiments are also within the scope of protection of the present invention.

[0041] This patent provides a fuel cell hydrogen supply and circulation system. The pressure reducer, ejector, ejector, and hydrogen inlet solenoid valve are all located at the fuel cell inlet end. The steam separator, hydrogen inlet stainless steel pipe, hydrogen outlet stainless steel pipe, and hydrogen inlet solenoid valve are all located at the fuel cell outlet end and connected to the hydrogen inlet pipeline. The steam separator outlet is connected to the ejector circulation port and the exhaust port, respectively. Meanwhile, the tail exhaust is connected to the pressure relief valve, and the water discharge solenoid valve is connected to the hydrogen discharge pipeline.

[0042] When the system is in the low-power range, the amount of hydrogen obtained is calculated to adjust the flow rate of the injector and the hydrogen outlet pressure at the rear end of the injector, and then enter the fuel cell stack through the ejector. The remaining hydrogen then passes through the water vapor separator and is ejected back to the fuel cell stack through the circulation port using the ejector to continue the reaction. The generated water is released by the solenoid valve of the water vapor separator. When the system is in the high-power range, the amount of hydrogen supplied by the injector is adjusted in time, and at the same time, it enters the fuel cell stack through the ejector. The remaining hydrogen passes through the water vapor separator and returns to the ejector circulation port and circulation port respectively. The two circulation ports re-converge the flow and send it to the fuel cell stack again.

[0043] The hydrogen injector can adjust the hydrogen flow rate and hydrogen inlet pressure to achieve fast response and steady-state hydrogen supply.

[0044] An ejector is used to realize the circulation of high power section and low power section through two circulation ports.

[0045] When the pressure exceeds a certain value, the pressure relief valve of the fuel cell stack automatically opens to protect the fuel cell stack from being damaged by high-load pressure shock.

[0046] When the system is shut down, open the nitrogen inlet valve for purging.

[0047] The source of hydrogen is the hydrogen cylinder. The gas comes out through the pressure reducing valve and enters the injector, which is then regulated by the injector to increase the stability of the hydrogen and the required hydrogen pressure.

[0048] Temperature sensors and pressure sensors are installed at the outlet of the fuel cell stack to monitor the temperature and pressure at the outlet of the fuel cell stack in real time, and use the values ​​as a basis for the control system.

[0049] Example

[0050] The embodiments of the present invention will be described in detail below. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0051] Example 1

[0052] A system for supplying and circulating hydrogen to a fuel cell, the structure of which is as follows Figure 1 As shown, it includes a fuel cell 11, which has a hydrogen inlet and a hydrogen outlet. A hydrogen inlet pipeline is provided at the hydrogen inlet, and a hydrogen outlet pipeline is provided at the hydrogen outlet. The hydrogen inlet pipeline includes, in sequence, a hydrogen cylinder 1, a hydrogen cylinder pressure reducing valve 2, a pressure reducing valve 3, a third pressure sensor 4, an ejector 5, an ejector 6, a hydrogen inlet solenoid valve 7, a first temperature sensor 8, and a first pressure sensor 9. The hydrogen outlet pipeline is provided with a second pressure sensor 12 and a second temperature sensor 13, and then splits into two paths. The first path is provided with a hydrogen outlet solenoid valve 15, and the second path is provided with a water vapor separator 16. The bottom of the water vapor separator 16 is provided with a water discharge solenoid valve 14, which merges with the hydrogen outlet pipeline after the hydrogen outlet solenoid valve 15. The top of the water vapor separator 16 is connected to the circulation port a18 and the circulation port b19 of the ejector 6, respectively. A circulation solenoid valve 17 is provided on the pipeline connected to the circulation port b19.

[0053] A pressure relief branch is provided between the hydrogen inlet and the hydrogen outlet, and a pressure relief valve 10 is provided on the pressure relief branch. The system also includes a purge unit, which in sequence includes a nitrogen cylinder 20, a nitrogen cylinder pressure reducing valve 21, and a one-way valve 22, the outlet of the one-way valve 22 being connected to the inlet of the pressure reducing valve 3.

[0054] The working process of the above system is as follows:

[0055] (1) Obtaining the relationship LP between the inlet pressure of the injector 5 and the amount of hydrogen injected;

[0056] (2) starting the fuel cell 11, adjusting the injection amount of the injector 5, monitoring the inlet pressure P1 of the injector 5 in real time, and monitoring the output current I1 of the fuel cell 11 in real time;

[0057] (3) According to LP, the outlet flow rate L1 of the ejector 5 is obtained using the inlet pressure P1 of the ejector 5;

[0058] (4) Based on the output current I1 of the fuel cell 11, the power W of the fuel cell 11 is calculated in real time as W = U * I1 * N, where U is the output voltage of each single cell in the fuel cell 11. In this embodiment, the voltage of the single cell is 0.65 V. This voltage is determined by the structure of the single cell itself and has nothing to do with the amount of hydrogen. N is the number of single cells in the fuel cell 11. In this embodiment, the number of single cells is 240.

[0059] (5) When the power of the fuel cell 11 is less than 50 kW, the circulation solenoid valve 17 is closed so that the water vapor separator 16 is connected only to the circulation port a18. When the power of the fuel cell 11 is greater than 50 kW and less than 60 kW (the rated output power of the fuel cell in this embodiment is 60 kW), the circulation solenoid valve 17 is opened so that the water vapor separator 16 is connected to both the circulation port a18 and the circulation port b19. During this process, the metering ratio is 1.5.

[0060] (6) When the power of the fuel cell 11 reaches the rated power (60 kW) and remains constant, the injection amount of the injector 5 is kept constant;

[0061] (7) When the fuel cell 11 is flooded, the fuel cell 11 is drained, the hydrogen injection amount of the injector 5 is reduced, and then the injection amount of the injector 5 is gradually restored.

[0062] (8) When the pressure at the hydrogen inlet and the hydrogen outlet of the fuel cell 11 is greater than 1.7 bar, the pressure relief valve 10 is opened to relieve the pressure.

[0063] (9) When the fuel cell 11 finishes working, the hydrogen source is turned off, the one-way valve 22 and the nitrogen source are opened, and the system is purged with nitrogen.

[0064] Through actual operation, when the rated power of the above system is 60kw, the stack power is about 75Kw (system power = stack power | - power consumed by components), the air flow rate is 802L / min, and the circulation flow rate is 401L / min. At this time, the intake volume only needs to be adjusted to 802L / min, because the remaining 0.5 times the amount of circulation is constantly circulating in the pipeline, and the adjustment time is about 10 minutes. When the rated power of the existing hydrogen intake system is 60kw, the stack power is about 73Kw (system power = stack power | - power consumed by components). The system of this application has reduced the power consumption of the circulation pump by about 2kw. The air flow rate is 781L / min, and the circulation flow rate is 319L / min. At this time, the intake volume only needs to be adjusted to 781L / min, because the remaining 0.5 times the amount of circulation is constantly circulating in the pipeline, and the entire adjustment time is about 12 minutes. It can be seen that the system and method of the present application can reduce the overall power consumption of the system, improve the recovery and utilization rate of hydrogen, improve the controllability of the hydrogen supply, shorten the control time, and save system costs.

[0065] The above description of the embodiments is intended to facilitate understanding and application of the present application by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without expending any creative effort. Therefore, the present application is not limited to the embodiments described herein, and improvements and modifications made by those skilled in the art based on the disclosure of this application without departing from the scope and spirit of this application are within the scope of this application.

Claims

1. A method for supplying and circulating hydrogen for a fuel cell, the method utilizing a system comprising a fuel cell, wherein a hydrogen source, a pressure reducing valve, an injector, an ejector and a hydrogen inlet solenoid valve are sequentially connected at the hydrogen inlet of the fuel cell, the ejector is provided with a feed port, a discharge port, a circulation port a and a circulation port b, the feed port is connected to the injector, the discharge port is connected to the hydrogen inlet solenoid valve, a three-way valve is connected at the hydrogen outlet of the fuel cell, one outlet of the three-way valve is connected to a tail gas treatment unit via a hydrogen discharge pipeline, the other outlet of the three-way valve is connected to a water vapor separator, the bottom of the water vapor separator is connected to a hydrogen discharge pipeline, the top of the water vapor separator is respectively connected to the circulation port a and the circulation port b, and a circulation solenoid valve is provided on the connecting pipeline between the water vapor separator and the circulation port b, characterized in that The method comprises the following steps: (1) Controlling the injected hydrogen amount and inlet pressure of the injector to obtain the relationship LP between the inlet pressure and the outlet flow rate of the injector, and then installing the injector in the system; (2) Start the fuel cell, adjust the injection amount of the injector, monitor the injector inlet pressure P1 in real time, and monitor the output current I1 of the fuel cell in real time; (3) According to LP, the ejector outlet flow rate L1 is obtained using the ejector inlet pressure P1; (4) Calculate the power W=U* I1*N of the fuel cell in real time according to the output current I1 of the fuel cell, where U is the output voltage of each single cell in the fuel cell, and N is the number of single cells in the fuel cell; (5) When the power of the fuel cell is low, the circulation solenoid valve is closed so that the water vapor separator is connected only to the circulation port a. When the power of the fuel cell is high, the circulation solenoid valve is opened so that the water vapor separator is connected to both the circulation port a and the circulation port b. (6) When the power of the fuel cell reaches the rated power and remains constant, the injection amount of the injector is kept constant.

2. The method for supplying and circulating hydrogen for a fuel cell according to claim 1, characterized in that: The dividing point between high power and low power is 50kw.

3. The method for supplying and circulating hydrogen for a fuel cell according to claim 1, characterized in that: When the fuel cell is flooded, the fuel cell is drained, the hydrogen injection amount of the injector is reduced, and then the injection amount of the injector is gradually restored.

4. The method for supplying and circulating hydrogen for a fuel cell according to claim 1, characterized in that: A pressure relief branch is provided between the hydrogen inlet and the hydrogen outlet of the fuel cell, and a pressure relief valve is provided on the pressure relief branch; when the pressure at the hydrogen inlet and the hydrogen outlet of the fuel cell is too high, the pressure relief valve is opened to relieve the pressure.

5. The method for supplying and circulating hydrogen for a fuel cell according to claim 1, characterized in that: The system is provided with a purge unit, which includes a nitrogen source, which is arranged in parallel with a hydrogen source, and the nitrogen source is connected to a pressure reducing valve, and a one-way valve is arranged on the connecting pipeline; when the fuel cell finishes working, the hydrogen source is closed, the one-way valve and the nitrogen source are opened, and the system is purged with nitrogen.

6. The method for supplying and circulating hydrogen for a fuel cell according to claim 1, characterized in that: One outlet of the three-way valve is connected to the tail gas treatment unit through a hydrogen discharge pipeline, and a hydrogen discharge solenoid valve is provided on the hydrogen discharge pipeline; A drainage solenoid valve is arranged between the bottom of the water vapor separator and the hydrogen discharge pipeline.

7. The method for supplying and circulating hydrogen for a fuel cell according to claim 1, characterized in that: A temperature sensor and a pressure sensor are provided at the hydrogen inlet and the hydrogen outlet of the fuel cell.

8. The method for supplying and circulating hydrogen for a fuel cell according to claim 1, characterized in that: A pressure relief branch is provided between the hydrogen inlet and the hydrogen outlet of the fuel cell, and a pressure relief valve is provided on the pressure relief branch.

9. The method for supplying and circulating hydrogen for a fuel cell according to claim 1, characterized in that: The system is provided with a purge unit, which includes a nitrogen source, the nitrogen source and the hydrogen source are arranged in parallel, the nitrogen source is connected to the pressure reducing valve, and a one-way valve is arranged on the connecting pipeline.

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