A minimalist fuel cell system and control method

Abstract

The present invention discloses a minimalist fuel cell system and control method, wherein the fuel cell system includes a stack, the stack includes a fuel side and an air side, the fuel side is connected to a fuel channel, and the air side is connected to an air channel; the air channel includes an air preheater, a burner and an evaporator; the fuel channel includes a fuel tank, a four-way valve, a circulating autothermal reformer along the fuel transmission direction, the stack fuel side, a three-way valve, a burner and an evaporator, the second output end of the evaporator is connected to the third port of the four-way valve; the third port of the three-way valve is connected to the circulating autothermal reformer, the second output end of the circulating autothermal reformer is connected to a circulating pump, and the output end of the circulating pump is connected to the fourth port of the four-way valve; the evaporator is provided with a liquid water supply inlet; the air preheater is provided with a combustion exhaust gas outlet. The present invention reduces the manufacturing cost by arranging a single-way fuel supply and coupling a burner.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel cells, and in particular relates to a minimalist fuel cell system and a control method. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] When the high-temperature fuel cell system is started, the raw gas needs to be heated up, and in order to meet important parameters such as oxygen-carbon ratio and air-fuel ratio and improve the safety performance of the system, the system has gradually become more complex. When the system is initially started, the air and fuel in the fuel side pipeline of the fuel stack are mixed, which poses a certain safety risk. Therefore, water vapor or inert gas is usually used for purging, which increases the complexity of the system purging process.

[0004] In order to be compatible with the problem of load regulation ratio and steady-state lean combustion of hydrogen-containing fuel, the startup fuel supply and the fuel supply on the fuel side of the stack can be isolated. For example, patent document CN117577877A discloses an integrated fuel cell system and a fuel cell system. The system includes a flame burner and a catalytic burner. During the system startup process, the flame burner is used for premixed flame combustion. When the system is in steady-state operation, the catalytic burner is used to treat the exhaust gas. This is a solution for two-way fuel supply burner. The purging of the fuel side pipeline of the stack is achieved by water vapor. This method increases the difficulty of burner design, requires the separate design of combustion channels for the two fuels, increases system redundancy, and increases costs. However, the existing single-way fuel supply solution has problems such as conventional burner flameout, which causes the system to fail to start. Summary of the invention

[0005] In order to overcome the above-mentioned deficiencies of the prior art, the present invention provides a minimalist fuel cell system and control method. By setting a single fuel supply and coupling burner, the safety and simplification requirements of the fuel cell system are met, and the manufacturing cost is reduced.

[0006] To achieve the above-mentioned object, a first aspect of the present invention provides a minimalist fuel cell system, comprising a fuel cell stack, wherein the fuel cell stack comprises a fuel side and an air side, wherein the fuel side is connected to a fuel channel, and the air side is connected to an air channel; the air channel comprises an air preheater, a burner and an evaporator;

[0007] The fuel channel includes a fuel tank, a four-way valve, a circulating autothermal reformer, the fuel side of the stack, a three-way valve, a burner and an evaporator along the fuel transmission direction, the second output end of the evaporator is connected to the third port of the four-way valve; the third port of the three-way valve is connected to the circulating autothermal reformer, the second output end of the circulating autothermal reformer is connected to a circulation pump, and the output end of the circulation pump is connected to the fourth port of the four-way valve; the evaporator is provided with a liquid water supply inlet; the air preheater is provided with a combustion exhaust gas outlet.

[0008] In some embodiments, the air channel includes an air preheater, the air side of the fuel cell stack, a burner and an evaporator along the gas transmission direction, and the first output end of the evaporator is connected to the air preheater; a fan is also provided on one side of the air preheater.

[0009] A third aspect of the present invention provides a safe startup method for the minimalist fuel cell system, comprising:

[0010] Control the fan and air preheater to start, and the cold air enters the air side of the stack after being heated by the air preheater. After the battery stack consumes oxygen, it burns with the tail gas on the fuel side of the stack in the burner to generate high-temperature flue gas. The high-temperature flue gas passes through the evaporator and returns to the air preheater to heat the cold air. The other way reaches the circulating autothermal reformer through the four-way valve;

[0011] The evaporator is controlled to start, and the injected liquid water is evaporated at high temperature. The water vapor, fuel, and tail gas on the fuel side of the fuel stack pressurized by the circulating pump are mixed at the four-way point, and then enter the circulating autothermal reformer. The obtained reformed gas enters the fuel stack and is converted into electrical energy, which is burned in the burner to release heat.

[0012] In some embodiments, when the battery is operating in a steady state, liquid water is no longer injected.

[0013] A third aspect of the present invention provides a control method applied to the minimalist fuel cell system, which is applied to a fuel cell system controller, wherein a temperature sensor is provided at the inlet of the fuel side of the stack, and the method comprises:

[0014] If the temperature is higher than the preset high temperature threshold and the downtime exceeds the set duration, the required air flow is calculated based on the fuel-to-air ratio that meets safety requirements and the required fuel flow;

[0015] The fan is controlled to start, and after the air flow reaches the required air flow, the fuel tank valve is controlled to open and fuel begins to be introduced; after a first set time, the fuel tank valve is controlled to close;

[0016] Control the circulation pump to start according to the set circulation rate and turn on the ignition.

[0017] In some embodiments, after the ignition is turned on, the fuel tank valve is controlled to open again after a second set time has passed.

[0018] In some embodiments, the required air flow rate is calculated as follows:

[0019]

[0020] Wherein, X represents the required air concentration, Y represents the required fuel concentration, Z represents the fuel explosion limit concentration corresponding to the maximum operating temperature of the fuel cell system, and P is a percentage.

[0021] In some embodiments, if the temperature is lower than a preset low temperature threshold, the fuel cell is controlled to start.

[0022] In some embodiments, if the temperature is higher than a preset high temperature threshold and the downtime is short, the fan is controlled to start, and after a set air flow is introduced, the ignition is turned on, and the fuel tank valve is controlled to open and a set fuel flow is introduced.

[0023] In some embodiments, the first set time is the time it takes for the fuel to flow from the fuel cell system inlet through the fuel channel so that the concentration at the fuel inlet entering the burner is the set concentration; the second set time is the time it takes for the concentration at the fuel inlet entering the burner to reach the set concentration again.

[0024] One or more of the above technical solutions retain necessary components such as the fuel cell stack, evaporator, air preheater, circulating autothermal reformer, etc., and set up a single fuel supply and coupled burner, which meets the safety and simplified startup requirements of the fuel cell system and reduces manufacturing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0026] Figure 1 This is a framework diagram of a minimalist fuel cell system in an embodiment of the present invention. DETAILED DESCRIPTION

[0027] The embodiments of the present application will be described in more detail below with reference to the accompanying drawings. Although certain embodiments of the present application are shown in the accompanying drawings, it should be understood that the present application can be implemented in various forms and should not be construed as being limited to the embodiments described herein. Instead, these embodiments are provided to provide a more thorough and complete understanding of the present application. It should be understood that the drawings and embodiments of the present application are only for exemplary purposes and are not intended to limit the scope of protection of the present application.

[0028] In the description of the embodiments of the present application, the term “including” and similar terms should be understood as open inclusion, that is, “including but not limited to.” The term “based on” should be understood as “based at least in part on.”

[0029] As described in the background technology, in order to be compatible with the load regulation ratio and the steady-state lean combustion of hydrogen-containing fuel, the startup fuel supply and the fuel supply on the fuel stack fuel side can be isolated, but this will lead to increased difficulty in burner design and processing costs. In order to solve this problem, one or more embodiments of the present invention provide a fuel cell system that simplifies the fuel channel of the existing fuel cell system and adopts a coupled burner with a single fuel supply, which can significantly reduce system redundancy and manufacturing costs.

[0030] It should be noted that the "coupled burner" described in one or more embodiments of the present application is a single-channel fuel supply. Since the fuel changes from a high calorific value state to a low calorific value state, the conventional flame combustion method is prone to flameout. Any scheme such as "electric heating preheating + catalytic burner", "flame + catalytic burner", "flame + catalytic burner", single flame burner, etc. can be adopted, again without limitation.

[0031] Specifically, Figure 1 As shown, the fuel cell system includes a fan, an air preheater, an evaporator, a four-way valve, a circulation pump, a circulating autothermal reformer, a stack, a three-way valve, and a burner. The stack includes a fuel side and an air side, the fuel side is connected to the fuel channel, and the air side is connected to the air channel;

[0032] The air channel includes an air preheater, the air side of the stack, a burner and an evaporator along the gas transmission direction, and the first output end of the evaporator is connected to the air preheater; a fan is also provided on one side of the air preheater;

[0033] The fuel channel includes a fuel tank, a four-way valve, a circulating autothermal reformer, the fuel side of the stack, a three-way valve, a burner and an evaporator along the fuel transmission direction, the second output end of the evaporator is connected to the third port of the four-way valve; the third port of the three-way valve is connected to the circulating autothermal reformer, the second output end of the circulating autothermal reformer is connected to a circulation pump, and the output end of the circulation pump is connected to the fourth port of the four-way valve; the evaporator is provided with a liquid water supply inlet; the air preheater is provided with a combustion exhaust gas outlet.

[0034] By setting a four-way valve, the two-way fuel channels of the catalytic burner and the flame burner are combined into one channel, which simplifies the system structure and reduces the cost.

[0035] Air channel: After the cold air is pressurized by the fan, it is heated by the air preheater and enters the air side of the fuel cell stack. After the fuel cell stack consumes oxygen, it is burned in the burner with the exhaust gas from the fuel side of the fuel cell stack to produce high-temperature flue gas. The high-temperature flue gas is heated by the air preheater for the cold air.

[0036] Fuel Channel:

[0037] A) During the startup process, liquid water is heated and evaporated by high-temperature flue gas. Water vapor, fuel, and tail gas on the fuel side of the stack pressurized by the circulating pump are mixed at the four-way point, and then enter the circulating autothermal reformer to decompose the fuel from high-carbon to low-carbon and hydrogen reformed gas. The reformed gas enters the stack and is converted into electricity and then burned in the burner to release heat. The liquid water introduced during the startup process, the water vapor generated by high-temperature evaporation can prevent the fuel from forming carbon deposits in the stack, and the amount of water vapor used is relatively small. Compared with the water reformer in most fuel cell systems, the cumulative water vapor consumption is low.

[0038] B) During steady-state operation, liquid water does not need to be supplied. The fuel is mixed with the fuel side tail gas of the fuel stack pressurized by the circulating pump at the four-way. The oxygen-carbon ratio of the mixed gas can meet the needs of the fuel stack, and the oxygen-carbon ratio can be controlled at 2.0-4.0.

[0039] The dual-channel design of the burner is that the fuel is supplied to the burner separately during the startup process, and the tail gas on the fuel side of the stack is passed into the burner. In the entire fuel cell system, the fuel supply channel includes two channels. After the dual-channel fuel channel is merged into a single channel, when starting, it is necessary to first turn on the burner to form water vapor, and the water vapor will purge the system; the source of water vapor heat is ignited by the burner. If the burner is not started, there will be no water vapor, and the air in the anode side pipeline cannot be expelled. In order to ensure the absolute safety of the anode side pipeline when supplying fuel to the burner, the normal startup of the burner must be guaranteed.

[0040] However, since there is only one fuel supply channel, there is air in the fuel channel during cold start. The fuel enters the four-way valve from the fuel tank, and then enters the circulating autothermal reformer and the fuel cell stack. Finally, part of it circulates to the four-way valve through the three-way valve, and part of it enters the burner. At this time, the fuel channel is a mixture of fuel and air. If the burner is ignited at this time, due to the large proportion of air in the fuel-air mixture, it is difficult to ignite the premixed fuel. Continuous ignition failures will cause a large amount of combustible and explosive atmosphere to accumulate in the burner cavity and the pipeline behind the burner. After the fuel discharges the air in the fuel channel in front of the fuel stack, the sudden ignition of the burner will cause the entire pipeline behind the burner to detonate. Therefore, in order to avoid the increase in cumulative water purge consumption caused by water purge, increase the complexity of the water system, and reduce the risk of fuel explosion, one or more embodiments of the present invention are based on the above-mentioned minimalist fuel cell system, and provide a control method applied to the fuel cell system, which is applied to the fuel cell system controller. A temperature sensor is provided at the inlet of the fuel side of the fuel cell stack. The method includes:

[0041] In response to a fuel cell startup instruction, the temperature data monitored by the temperature sensor is acquired; and subsequent operations are performed according to the temperature.

[0042] If the temperature is lower than the preset low temperature threshold, the fuel cell system is considered to be in a low temperature state, that is, a completely cooled state, and the fuel flow rate is not controlled. If the fuel cell has been completely cooled, it means that the system has been stationary for a long time, and the air will diffuse into the fuel channel to replace the fuel. At this time, due to the low temperature, there is no ignition source such as high temperature or electric sparks, and the mixture of fuel and air has no risk of explosion. Therefore, if the temperature is lower than the preset low temperature threshold, the fuel cell is directly controlled to start;

[0043] If the temperature is higher than the preset high temperature threshold, when the temperature is high, if it has been static for a certain period of time, air will diffuse in the fuel side pipeline. At this time, when starting again, it is necessary to first purge and discharge the air in the combustion side pipeline. Based on this, if the temperature is higher than the preset high temperature threshold, air is first introduced to cool the pipeline, and then fuel is slowly introduced, and the mixing degree of fuel and air is controlled within the explosion line. Specifically, the following control is performed:

[0044] (1) Calculate the required air flow rate based on the fuel-air ratio that meets safety requirements and the required fuel flow rate; control the fan to start, and when the incoming air flow rate reaches the required air flow rate, it is considered that the fuel can be passed, and execute step (2);

[0045] The fan is started, and the air flow rate is set to X mol to complete the purge of the fuel stack, burner and related air channels. Among them, X depends on the fuel flow rate Y mol entering the fuel cell system, and the concentration of fuel and air mixed in the burner is lower than the P% of the fuel explosion limit Z corresponding to the maximum operating temperature of the system. The Z value depends on the setting of the system safety margin. That is:

[0046]

[0047] Taking methane as an example, the explosion limit of methane at room temperature is 5%. Assuming that the explosion limit Z of methane at the highest operating temperature of the system is 3%, and the P value is set to 50, then the concentration after mixing in the burner should be lower than 1.5%. According to the fuel-air ratio and the fuel flow rate entering the system, it is easy to calculate the required flow rate X of the fan.

[0048] (2) The fuel tank valve is controlled to open and fuel begins to flow in. After a first set time t1, it is considered that the fuel flow reaches the required flow rate, and the fuel tank valve is controlled to close.

[0049] Open the fuel tank valve, the fuel flow is Y mol, the fuel passes through the four-way, enters the circulating autothermal reformer, the fuel side of the fuel stack, and then enters the burner. t1 is the time required for the required fuel flow to reach the burner, which can be estimated based on the size parameters of the pipeline to be purged and the required fuel flow.

[0050] The circulation pump must be turned on during the purging process. However, since fuel is being supplied at this time, the circulation rate of the circulation pump is too high, which may blow in external air and discharge internal gas. Therefore, the circulation pump must be controlled to ensure that the amount of air and fuel entering does not exceed the preset range. Based on this, step (3) is further executed.

[0051] (3) Control the circulation pump to start according to the set circulation rate and start the ignition; after the second set time t2, control the fuel tank valve to open again.

[0052] After time t1, the circulation pump is turned on, and the circulation rate of the circulation pump is set to Q. The ignition is turned on and the air flow rate is reduced to R mol after time t2. The fuel flow rate Y value depends on the burner power required by the fuel cell system. Time t1 depends on the time when the fuel flows from the inlet of the fuel cell system through the fuel channel so that the concentration of the fuel inlet entering the burner is S%. t1 can be determined experimentally in the fuel system, and S is the concentration that ensures that the burner can be stably ignited multiple times under an air flow rate of X mol. The range of the circulation rate Q is 0% to 100%. During the startup process, the value of the circulation rate Q is controlled as much as possible within (0%, 50%] to avoid excessive suction flow causing some air to mix into the fuel channel. After the circulation pump is turned on, the air in the fuel circulation channel will be diluted again to enter the burner fuel. Therefore, the time t2 depends on the time when the concentration of the fuel inlet entering the burner is S% again. t2 can be determined experimentally in the fuel system. The size of t2 is related to the length of the fuel cycle. Since the value of t2 is small, it is recommended to start ignition with an electric spark after turning on the circulation pump, and gradually reduce the air flow from X mol to Rmol to complete the ignition. The value of R is related to the required temperature of the burner and the internal structure design of the burner.

[0053] If the system is shut down for a short period of time and the fuel in the fuel channel is still fuel, there is no need to go through processes (2) and (3) and jump to process (5).

[0054] (5) The fan is started, the air flow rate is set to X mol, the ignition is turned on, the fuel tank valve is opened, the fuel flow rate is Y mol, and after time t2, the air flow rate is reduced to R mol to achieve stable startup of the burner and the system.

[0055] The extremely simplified fuel cell system in one or more of the above embodiments retains only necessary components and adopts a single-path fuel supply, thereby reducing the complexity of the fuel supply system and lowering the system cost. The system has strong robustness.

[0056] The minimalist fuel cell system is based on fuel lean purge and safety threshold time control to complete the purge of the fuel channel of the stack system. There is no need for water vapor or other inert gas purge, and there will be no pipeline explosion due to multiple ignition failures. In addition, by using fuel to purge the fuel pipeline, due to the short purge time, it is believed that the fuel consumption at this stage is only for the long-term operation system, and the consumption of the purge is considered to be within an acceptable range.

[0057] Although the subject matter has been described in language specific to structural features and / or methodological logical actions, it should be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or actions described above. On the contrary, the specific features and actions described above are merely example forms of implementing the claims.

Claims

1. A minimalist fuel cell system, characterized in that: The stack includes a fuel side and an air side, wherein the fuel side is connected to a fuel channel, and the air side is connected to an air channel; the air channel includes an air preheater, a burner, and an evaporator; The fuel channel includes a fuel tank, a four-way valve, a circulating autothermal reformer, the fuel side of the stack, a three-way valve, a burner and an evaporator along the fuel transmission direction, the second output end of the evaporator is connected to the third port of the four-way valve; the third port of the three-way valve is connected to the circulating autothermal reformer, the second output end of the circulating autothermal reformer is connected to a circulation pump, and the output end of the circulation pump is connected to the fourth port of the four-way valve; the evaporator is provided with a liquid water supply inlet; the air preheater is provided with a combustion exhaust gas outlet.

2. A minimalist fuel cell system as claimed in claim 1, characterized in that: The air channel includes an air preheater, the air side of the fuel cell stack, a burner and an evaporator along the gas transmission direction. The first output end of the evaporator is connected to the air preheater. A fan is also provided on one side of the air preheater.

3. A safe startup method for a minimalist fuel cell system as claimed in claim 1 or 2, characterized in that: include: Control the fan and air preheater to start, and the cold air enters the air side of the stack after being heated by the air preheater. After the battery stack consumes oxygen, it burns with the tail gas on the fuel side of the stack in the burner to generate high-temperature flue gas. The high-temperature flue gas passes through the evaporator and returns to the air preheater to heat the cold air. The other way reaches the circulating autothermal reformer through the four-way valve; The evaporator is controlled to start, and the injected liquid water is evaporated at high temperature. The water vapor, fuel, and tail gas on the fuel side of the fuel stack pressurized by the circulating pump are mixed at the four-way point, and then enter the circulating autothermal reformer. The obtained reformed gas enters the fuel stack and is converted into electrical energy, which is burned in the burner to release heat.

4. The safe startup method of the minimalist fuel cell system according to claim 3, characterized in that: When the battery is operating in steady state, no liquid water is injected.

5. A control method for a minimalist fuel cell system as claimed in claim 1 or 2, applied to a fuel cell system controller, wherein a temperature sensor is provided at the inlet of the fuel side of the stack, and the method comprises: If the temperature is higher than the preset high temperature threshold and the downtime exceeds the set duration, the required air flow is calculated based on the fuel-to-air ratio that meets safety requirements and the required fuel flow; The fan is controlled to start, and when the incoming air flow reaches the required air flow, the fuel tank valve is controlled to open and fuel begins to be introduced; After a first set time, the fuel tank valve is controlled to close; Control the circulation pump to start according to the set circulation rate and turn on the ignition.

6. The control method according to claim 5, characterized in that: After the ignition is turned on, after the second set time, the fuel tank valve is controlled to open again.

7. The control method according to claim 5, characterized in that: The required air flow rate is calculated as: Wherein, X represents the required air concentration, Y represents the required fuel concentration, Z represents the fuel explosion limit concentration corresponding to the maximum operating temperature of the fuel cell system, and P is a percentage.

8. The control method according to claim 5, characterized in that: If the temperature is lower than the preset low temperature threshold, the fuel cell is controlled to start.

9. The control method according to claim 5, characterized in that: If the temperature is higher than the preset high temperature threshold and the shutdown time is short, the fan is controlled to start, and after the set air flow is introduced, the ignition is turned on, and the fuel tank valve is controlled to open and the set fuel flow is introduced.

10. The control method according to any one of claims 5 to 9, characterized in that: The first set time is the time when the fuel flows from the fuel cell system inlet through the fuel channel so that the concentration at the fuel inlet entering the burner reaches the set concentration; the second set time is the time when the concentration at the fuel inlet entering the burner reaches the set concentration again.

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