Anhydrous fuel cell system and starting control method thereof

Abstract

The invention provides an anhydrous fuel cell system and a start control method thereof, and belongs to the technical field of fuel cell design. Comprising an electric pile, an air blower, a mass flow controller, a hydrogen supply device and an anode tail gas circulating device, wherein the air blower is sequentially communicated with the ejector, the first heat exchanger, the stack cathode inlet and the combustor to form a cathode air supply passage; the mass flow controller and the hydrogen supply device are arranged in parallel, the mass flow controller is communicated with the galvanic pile anode inlet through the second heat exchanger, the galvanic pile anode outlet is communicated with the combustor and the anode tail gas circulating device, and the anode tail gas circulating device is connected back to the galvanic pile anode inlet through the second heat exchanger to form a fuel gas supply channel; the combustor exchanges heat through the first heat exchanger and the second heat exchanger in sequence, and a waste gas heat exchange channel is formed. According to the invention, the simplified design of the fuel cell system under a water-free structure is realized on the basis of ensuring the reliability in a mode of matching anode circulation with internal reforming.

Description

Technical Field

[0001] This invention belongs to the field of fuel cell design technology, and particularly relates to an anhydrous fuel cell system and its start-up control method. Background Technology

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

[0003] Solid-state fuel cells (SOFCs) are clean and efficient power generation devices that convert the chemical energy in fuel into electrical energy through electrochemical reactions. They have a wide range of applications, covering power levels from hundreds of watts to megawatts. SOFCs can use gaseous hydrocarbon fuels (natural gas, propane, etc.) as their power generation fuel. They generate electricity by reforming water vapor and gaseous hydrocarbon fuels into syngas, which is then fed into the SOFC stack.

[0004] Existing SOFC systems mostly combine external and internal reforming. By configuring a reformer and a reforming water system, the fuel gas is partially reformed outside the stack to increase the hydrogen concentration at the stack inlet. Then, an anode tail gas recirculation system is configured to improve the system's fuel utilization rate. Such systems require additional configuration of an external reformer and a reforming water supply system, which not only has the disadvantages of complex structure and high cost, but is also prone to reliability issues such as reformer catalyst shedding. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention provides a waterless fuel cell system and its start-up control method. By combining anode circulation with internal reforming, a simplified design of the fuel cell system in a waterless structure is achieved while ensuring reliability.

[0006] To achieve the above objectives, one or more embodiments of the present invention provide the following technical solutions: The first aspect of the present invention provides a waterless fuel cell system.

[0007] A waterless fuel cell system includes: a fuel cell stack, a blower, a mass flow controller, a hydrogen supply device, and an anode exhaust gas recirculation device; The outlet end of the blower is connected to the ejector, the output end of the ejector is connected to the cathode inlet of the fuel cell stack via the first heat exchanger, and the cathode outlet of the fuel cell stack is connected to the first inlet of the burner, forming a cathode air supply passage. The mass flow controller and the hydrogen supply device are arranged in parallel. The mass flow controller is connected to the anode inlet of the fuel cell stack via the second heat exchanger. The anode outlet of the fuel cell stack is connected to the second inlet of the burner and the input end of the anode exhaust gas circulation device. The output end of the anode exhaust gas circulation device is connected back to the anode inlet of the fuel cell stack via the second heat exchanger, forming a gas supply path. The outlet of the burner passes through the first heat exchanger and the second heat exchanger in sequence to exchange heat, forming a heat exchange path for the exhaust gas.

[0008] Furthermore, the anode exhaust gas recirculation device includes a recirculation pump and a flow control valve for regulating the exhaust gas flow rate circulating to the anode side of the fuel cell stack.

[0009] Furthermore, an anhydrous fuel cell system also includes a control unit for executing the start-up and operation control strategy of the anhydrous fuel cell system, namely: controlling the hydrogen supply device to supply hydrogen during the start-up phase and simultaneously starting the anode tail gas recirculation device; subsequently, determining the hydrogen flow rate and number of times based on the stack voltage; applying the load current after the stack reaches a predetermined temperature and controlling the anode tail gas recirculation flow rate based on the target AOGR rate; and shutting off the hydrogen supply device after the anhydrous fuel cell system is operating stably.

[0010] Furthermore, the hydrogen supply device adopts a portable hydrogen cylinder or hydrogen generator.

[0011] Furthermore, the control unit is also used to calculate the actual anode tail gas flow rate and composition based on the demand current, stack fuel utilization rate, actual current and fuel flow rate of the anhydrous fuel cell system, and to calculate the required AOGR rate based on the target O:C ratio.

[0012] Furthermore, the first heat exchanger is used to realize heat exchange between the exhaust gas from the burner and the air delivered by the blower, and the second heat exchanger is used to realize heat exchange between the exhaust gas from the burner and the fuel gas; wherein, the fuel gas includes hydrogen and anode circulating gas.

[0013] Furthermore, the stack is a solid oxide fuel cell (SOFC) stack, which has an internal reforming function and can use water vapor transported by the anode tail gas recirculation device to carry out an internal reforming reaction on the fuel gas.

[0014] A second aspect of the present invention provides a start-up control method for a waterless fuel cell system as described in the first aspect.

[0015] A startup control method, comprising: The anhydrous fuel cell system and anode exhaust gas recirculation device are started simultaneously, and the heating rate of the anode side of the fuel cell stack is controlled. When the fuel cell stack outlet temperature reaches the preset first target temperature, a fixed amount of hydrogen is introduced into the gas side multiple times. The hydrogen flow rate and number of times are determined by monitoring the fuel cell stack voltage. The air flow rate and gas flow rate are kept constant so that the fuel cell stack continues to heat up. When the fuel cell stack gas outlet temperature reaches the preset second target temperature, a small current is applied to control the fuel cell stack voltage to be no lower than the set threshold, and the anode tail gas circulation flow rate is controlled according to the target AOGR rate. Once the O:C ratio and stack temperature of the anhydrous fuel cell system reach the set requirements, the load current is started, and the anhydrous fuel cell system completes the startup process. After the anhydrous fuel cell system is running stably, the hydrogen supply device stops working, and the anhydrous fuel cell system enters an anhydrous, non-reforming steady-state operation mode.

[0016] Furthermore, when the anhydrous fuel cell system enters the anhydrous and reforming-free steady-state operation mode, the actual anode tail gas flow rate and composition are calculated based on the current demand of the anhydrous fuel cell system and the fuel utilization rate of the stack, combined with the real-time current and fuel flow rate; the required AOGR rate is calculated based on the target O:C ratio; and the anhydrous fuel cell system is kept in stable operation at the target AOGR rate by adjusting the flow control device of the anode tail gas recirculation device.

[0017] Furthermore, the value of the microcurrent is set within the safe range of the fuel cell's rated current to achieve a smooth transition in temperature rise and avoid damage to the fuel cell caused by large current surges.

[0018] The above one or more technical solutions have the following beneficial effects: This invention arranges the mass flow controller and hydrogen supply device in parallel, connecting them to the anode inlet of the fuel cell stack via a second heat exchanger. The anode outlet of the fuel cell stack is connected to the second inlet of the burner and the input of the anode exhaust gas recirculation device. The output of the anode exhaust gas recirculation device is connected back to the anode inlet of the fuel cell stack via the second heat exchanger, forming a fuel gas supply path. This invention eliminates the external water supply system and reformer, replacing the reforming water system with a hydrogen supply device. This simplifies the overall architectural design complexity and reduces costs, while also avoiding problems such as reformer catalyst shedding, ensuring overall reliability.

[0019] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0020] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0021] Figure 1 This is a structural diagram of a waterless fuel cell system according to Embodiment 1 of the present invention.

[0022] Figure 2 This is a flowchart of the startup control process in Embodiment 1 of the present invention.

[0023] In the diagram: 1. Fuel cell stack; 2. Blower; 3. Mass flow controller; 4. Hydrogen supply device; 5. Anode tail gas recirculation device; 6. Ejector; 7. First heat exchanger; 8. Burner; 9. Second heat exchanger; 10. Hydrogen source. Detailed Implementation

[0024] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0025] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations of the present invention.

[0026] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0027] The overall concept proposed in this invention is as follows: This invention proposes a waterless fuel cell system. The system architecture adopts an anode cycle combined with internal reforming, eliminating the external water supply system and reformer. A hydrogen supply device is used to replace the reforming water system to achieve system startup. While ensuring high reliability, the system structure is greatly simplified, which can greatly enhance product competitiveness.

[0028] Example 1 This embodiment discloses a waterless fuel cell system.

[0029] like Figure 1 As shown, a waterless fuel cell system includes: a stack 1, a blower 2, a mass flow controller 3, a hydrogen supply device 4, and an anode tail gas recirculation device 5. The outlet end of the blower 2 is connected to the ejector 6, the output end of the ejector 6 is connected to the cathode inlet of the fuel cell stack via the first heat exchanger 7, and the cathode outlet of the fuel cell stack is connected to the first inlet of the burner 8, forming a cathode air supply passage. The mass flow controller 3 and the hydrogen supply device 4 are arranged in parallel and are connected to the anode inlet of the fuel cell stack via the second heat exchanger 9. The anode outlet of the fuel cell stack is connected to the second inlet of the burner 8 and the input end of the anode exhaust gas circulation device 5, respectively. The output end of the anode exhaust gas circulation device 5 is connected back to the anode inlet of the fuel cell stack via the second heat exchanger 9, forming a gas supply path. The outlet of the burner passes through the first heat exchanger and the second heat exchanger in sequence to exchange heat, forming a heat exchange path for the exhaust gas.

[0030] Based on the above structured design, this invention achieves a simplified design of a fuel cell system in an anhydrous structure by combining anode circulation with internal reforming, while ensuring reliability. To facilitate understanding of the technical solution of this invention, the specific implementation methods are further explained and described below.

[0031] The present invention provides an anhydrous fuel cell system that uses a dedicated hydrogen source to replace the existing reforming water supply system during the system startup phase. This anhydrous fuel cell system combines an anode tail gas recirculation system (i.e., an anode tail gas recirculation device) with internal reforming. The anode tail gas recirculation provides the water vapor required for internal reforming and maintains the hydrogen concentration inside the fuel cell stack. The hydrogen supply device can use a hydrogen cylinder or a hydrogen generator as a hydrogen source 10, and is configured in a portable form, used only during startup, allowing different systems to share a single hydrogen supply system.

[0032] The anhydrous fuel cell system includes a control unit for executing the startup and operation control strategy of the anhydrous fuel cell system, namely: during the startup phase, controlling the hydrogen supply device to supply hydrogen and simultaneously starting the anode tail gas recirculation device; subsequently, determining the hydrogen flow rate and number of times based on the stack voltage; after the stack reaches the predetermined temperature, applying the load current and controlling the anode tail gas recirculation flow rate based on the target AOGR rate; and shutting off the hydrogen supply device after the anhydrous fuel cell system is operating stably.

[0033] The control unit is also used to calculate the actual anode tail gas flow rate and composition based on the demand current of the anhydrous fuel cell system, the stack fuel utilization rate, the actual current and the fuel flow rate, and to calculate the required AOGR rate based on the target O:C ratio.

[0034] like Figure 2 As shown, the overall start-up control process of a waterless fuel cell system includes: The system issues a start-up signal, activating the blower. Once the blower starts successfully, fuel is supplied to the TGB MFC, and the system ignites. Simultaneously, the starting circulation pump is activated and operates at the target speed, initiating system heating. As the system temperature rises, the system enters the next stage once the stack temperature reaches the target requirement. At this stage, air and fuel gas flow rates and temperatures are maintained, while hydrogen is repeatedly and metered into the fuel gas side, with the amount and frequency of hydrogen injection determined by changes in the stack voltage. When the stack voltage, stack temperature, and system O:C reach the required levels, the system enters the micro-current ramp-up stage. During this micro-current ramp-up, the system continues to heat up. Once the stack temperature and system O:C reach the power generation requirements, the system enters the power generation stage. In the power generation stage, the system ramps up the current according to the target demand, simultaneously controlling the MFC to supply a metered amount of fuel, the blower to supply a metered amount of air, and the circulation pump to maintain the AOGR rate. The system continues to heat up, and once the current and stack temperature reach the required levels, the system successfully starts up.

[0035] After successful ignition and startup of the anhydrous fuel cell system, the anode circulation pump (i.e., the anode exhaust gas circulation system) is started simultaneously, and the anode side heating rate is controlled. When the stack outlet temperature reaches the target value t1, a fixed amount of hydrogen is introduced into the gas side multiple times, and the flow rate and number of hydrogen introductions are determined by the stack voltage. At the same time, the air flow rate and gas flow rate are kept constant, and the stack continues to heat up. When the stack gas outlet temperature reaches the target value t2, a small current is applied, while the stack voltage is controlled to be no lower than the system requirements. Subsequently, the circulation flow rate is controlled according to the target value of AOGR rate. When the system O:C ratio and stack temperature reach the system requirements, the system starts to apply current, and the system starts successfully.

[0036] After the system is successfully started, the required current and fuel utilization rate of the fuel cell stack are set according to the actual operating conditions. The actual AOG flow rate and composition are calculated by combining the actual current and fuel flow rate. The AOGR rate is calculated based on the O:C requirement value. The AOG flow rate is controlled by the AOGR pump speed. At this time, the system is running stably and the hydrogen supply system no longer participates in the work.

[0037] Example 2 This embodiment discloses a startup control method.

[0038] A startup control method, comprising: The anhydrous fuel cell system and anode exhaust gas recirculation device are started simultaneously, and the heating rate of the anode side of the fuel cell stack is controlled. When the fuel cell stack outlet temperature reaches the preset first target temperature, a fixed amount of hydrogen is introduced into the gas side multiple times. The hydrogen flow rate and number of times are determined by monitoring the fuel cell stack voltage. The air flow rate and gas flow rate are kept constant so that the fuel cell stack continues to heat up. When the fuel cell stack gas outlet temperature reaches the preset second target temperature, a small current is applied to control the fuel cell stack voltage to be no lower than the set threshold, and the anode tail gas circulation flow rate is controlled according to the target AOGR rate. Once the O:C ratio and stack temperature of the anhydrous fuel cell system reach the set requirements, the load current is started, and the anhydrous fuel cell system completes the startup process. After the anhydrous fuel cell system is running stably, the hydrogen supply device stops working, and the anhydrous fuel cell system enters an anhydrous, non-reforming steady-state operation mode.

[0039] Furthermore, when the anhydrous fuel cell system enters the anhydrous and reforming-free steady-state operation mode, the actual anode tail gas flow rate and composition are calculated based on the current demand of the anhydrous fuel cell system and the fuel utilization rate of the stack, combined with the real-time current and fuel flow rate; the required AOGR rate is calculated based on the target O:C ratio; and the anhydrous fuel cell system is kept in stable operation at the target AOGR rate by adjusting the flow control device of the anode tail gas recirculation device.

[0040] Furthermore, the value of the microcurrent is set within the safe range of the rated current of the fuel cell stack, for example, 5%-15% of the rated current of the fuel cell stack, so as to achieve a smooth transition in temperature rise of the fuel cell stack and avoid damage to the fuel cell stack caused by large current surges.

[0041] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A waterless fuel cell system, characterized in that, include: Fuel cell stack, blower, mass flow controller, hydrogen supply device and anode tail gas recirculation device; The outlet end of the blower is connected to the ejector, the output end of the ejector is connected to the cathode inlet of the fuel cell stack via the first heat exchanger, and the cathode outlet of the fuel cell stack is connected to the first inlet of the burner, forming a cathode air supply passage. The mass flow controller and the hydrogen supply device are arranged in parallel. The mass flow controller is connected to the anode inlet of the fuel cell stack via the second heat exchanger. The anode outlet of the fuel cell stack is connected to the second inlet of the burner and the input end of the anode exhaust gas circulation device. The output end of the anode exhaust gas circulation device is connected back to the anode inlet of the fuel cell stack via the second heat exchanger, forming a gas supply path. The outlet of the burner passes through the first heat exchanger and the second heat exchanger in sequence to exchange heat, forming a heat exchange path for the exhaust gas.

2. The waterless fuel cell system as described in claim 1, characterized in that, The anode exhaust gas recirculation device includes a recirculation pump and a flow control valve for regulating the exhaust gas flow rate circulating to the anode side of the fuel cell stack.

3. The waterless fuel cell system as described in claim 1, characterized in that, It also includes a control unit for executing the start-up and operation control strategy of the waterless fuel cell system, namely: controlling the hydrogen supply device to supply hydrogen during the start-up phase and simultaneously starting the anode tail gas recirculation device. Subsequently, the hydrogen flow rate and number of cycles are determined based on the stack voltage; after the stack reaches the predetermined temperature, the load current is applied, and the anode tail gas circulation flow rate is controlled based on the target AOGR rate. The hydrogen supply device is shut off after the waterless fuel cell system is operating stably.

4. The waterless fuel cell system as described in claim 3, characterized in that, The hydrogen supply device uses a portable hydrogen cylinder or a hydrogen generator.

5. The waterless fuel cell system as described in claim 3, characterized in that, The control unit is also used to calculate the actual anode tail gas flow rate and composition based on the demand current, stack fuel utilization rate, actual current and fuel flow rate of the anhydrous fuel cell system, and to calculate the required AOGR rate based on the target O:C ratio.

6. The waterless fuel cell system as described in claim 1, characterized in that, The first heat exchanger is used to realize the heat exchange between the exhaust gas from the burner and the air delivered by the blower, and the second heat exchanger is used to realize the heat exchange between the exhaust gas from the burner and the fuel gas; wherein, the fuel gas includes hydrogen and anode circulating gas.

7. The waterless fuel cell system as described in claim 1, characterized in that, The stack is a solid oxide fuel cell (SOFC) stack, which has an internal reforming function and can use water vapor supplied by the anode tail gas recirculation device to carry out internal reforming reaction of the fuel gas.

8. A start-up control method for an anhydrous fuel cell system as described in any one of claims 1-7, characterized in that, include: The anhydrous fuel cell system and anode exhaust gas recirculation device are started simultaneously, and the heating rate of the anode side of the fuel cell stack is controlled. When the fuel cell stack outlet temperature reaches the preset first target temperature, a fixed amount of hydrogen is introduced into the gas side multiple times. The hydrogen flow rate and number of times are determined by monitoring the fuel cell stack voltage. The air flow rate and gas flow rate are kept constant so that the fuel cell stack continues to heat up. When the fuel cell stack gas outlet temperature reaches the preset second target temperature, a small current is applied to control the fuel cell stack voltage to be no lower than the set threshold, and the anode tail gas circulation flow rate is controlled according to the target AOGR rate. Once the O:C ratio and stack temperature of the anhydrous fuel cell system reach the set requirements, the load current is started, and the anhydrous fuel cell system completes the startup process. After the anhydrous fuel cell system is running stably, the hydrogen supply device stops working, and the anhydrous fuel cell system enters an anhydrous, non-reforming steady-state operation mode.

9. The start-up control method as described in claim 8, characterized in that, When the anhydrous fuel cell system enters the anhydrous and reforming-free steady-state operation mode, the actual anode tail gas flow rate and composition are calculated based on the current demand of the anhydrous fuel cell system and the fuel utilization rate of the stack, combined with the real-time current and fuel flow rate; the required AOGR rate is calculated based on the target O:C ratio; and the anhydrous fuel cell system is kept in stable operation at the target AOGR rate by adjusting the flow control device of the anode tail gas recirculation device.

10. The start-up control method as described in claim 8, characterized in that, The value of the microcurrent is set within the safe range of the fuel cell's rated current to achieve a smooth transition in temperature rise and avoid damage to the fuel cell caused by large current surges.

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