High-temperature fuel cell system based on cocurrent flow heat exchange and control method

Abstract

The invention belongs to the technical field of fuel cells, and discloses a high-temperature fuel cell system based on cocurrent flow heat exchange and a control method, the output end of a fuel gas premixing device is connected to a fuel gas reforming module, and the output end of the fuel gas reforming module is connected to the fuel gas side of a cell; the output end of the cooling and water removing module is connected to the fuel gas premixing device and the air preheating module, and the cooling and water removing module is further provided with a gas exhaust pipeline. The output end of the gas reforming module or the output end of the cooling and dewatering module is connected to a post-oxidation module; the output end of the post-oxidation module is connected to the air preheating module; the air preheating module is connected to the air side of the battery; the gas input pipeline of the air preheating module is also connected to the cooling and dewatering module through a cold air butterfly valve; and the output end of the air side of the battery is connected to the post-oxidation module. Through the system architecture that the fuel gas side and the air side of the electric pile are subjected to cocurrent flow heat exchange respectively, the risk of system cross leakage is avoided.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel cells, and in particular relates to a high-temperature fuel cell system based on recuperation and a control method. Background Art

[0002] Since high-temperature fuel cells operate at high temperatures, their systems require many thermal components to maintain stable operation of the system. At the same time, gas and air need to exchange heat and react at high temperatures, and there may be a serious fault problem of cross leakage. In addition, high-temperature fuel cells have different operating temperature ranges due to different electrolytes, which brings great trouble to the development of thermal balance systems. Therefore, the present invention comprehensively considers the system complexity, reliability, and adaptability of high-temperature fuel cells, with the aim of designing a simple and adaptable fuel cell system, and proposing corresponding startup strategies to ensure the normal operation of the system. Summary of the invention

[0003] In order to overcome the above-mentioned deficiencies of the prior art, the present invention provides a high-temperature fuel cell system and control method based on recuperation. The risk of cross leakage of the system is avoided by using a system architecture in which the fuel cell gas side and the fuel cell air side are recuperated separately.

[0004] To achieve the above-mentioned object, the first aspect of the present invention provides a high-temperature fuel cell system based on recuperation, comprising: a battery fuel side, a battery air side, a gas premixing device, a cooling and water removal module, a post-oxidation module, and an air preheating module; wherein the gas premixing device and the post-oxidation module have a gas input pipeline for introducing the gas, and the air preheating module has a gas input pipeline for introducing the air;

[0005] The output end of the gas premixing device is connected to the gas reforming module, and the output end of the gas reforming module is connected to the battery gas side; the output end of the cooling and water removal module is connected to the gas premixing device and the air preheating module respectively, and the cooling and water removal module also has a gas exhaust pipeline;

[0006] The output end of the gas reforming module, or the output end of the cooling and water removal module is connected to the post-oxidation module; the output end of the post-oxidation module is connected to the air preheating module; the air preheating module is connected to the battery air side; the gas input pipeline of the air preheating module is also connected to the cooling and water removal module via a cold air butterfly valve; the output end of the battery air side is connected to the post-oxidation module.

[0007] In some embodiments, the output end of the battery gas side is connected to the gas reforming module; the output ends of the gas reforming module are also connected to the cooling water outlet modules respectively.

[0008] In some embodiments, a steam generating device is further provided on the passage between the post-oxidation module and the air preheating module, and an output end of the steam generating device is connected to the gas reforming module.

[0009] In some embodiments, the steam generating device is installed on the inner edge of the cylinder wall of the post-oxidation device.

[0010] In some embodiments, the gas-side reforming device includes one or more of a water-gas mixing device, a heat exchanger, and an adiabatic reforming device.

[0011] In some embodiments, the gas-side reforming device includes a water-gas mixing device and a heat exchanger, the water-gas mixing device is connected to the cold side inlet of the heat exchanger through a pipeline, and the low temperature side of the heat exchanger is coated or filled with a steam reforming catalyst.

[0012] In some embodiments, the gas-side reforming device includes a water-gas mixing device, a heat exchanger and an adiabatic reforming device, the adiabatic reforming device is connected to the low-temperature side outlet of the heat exchanger through a pipeline, and the adiabatic reforming device is coated or filled with a steam reforming catalyst.

[0013] In some embodiments, the cooling and water removal device includes a cooler and a circulation pump.

[0014] In some embodiments, the system further comprises a controller connected to a controller for controlling air flow, gas flow, liquid water flow, and a circulation pump controller.

[0015] A second aspect of the present invention provides a control method for the high temperature fuel cell system based on recuperation, comprising:

[0016] Step S1: Control the circulation pump to start, and control the gas flow rate not to exceed the air side flow rate;

[0017] Step S2: a certain amount of air and fuel gas is introduced into the rear oxidation device, and the spark plug or the electric heating element is controlled to ignite and heat up through the ignition coil;

[0018] Step S3: monitoring the temperature of the pipeline from the air side of the stack to the post-oxidation module, and when it reaches above a set temperature threshold, injecting a certain flow of liquid water to perform water vapor purge;

[0019] Step S4: monitor the temperature of the pipeline from the air side of the fuel cell stack to the post-oxidation module. When it reaches the safety temperature boundary of the fuel cell stack, introduce fuel gas into the fuel gas premixing device and the post-oxidation module at the same time. While ensuring that the total fuel gas supply of the system remains unchanged, gradually reduce the flow rate introduced into the post-oxidation module until the flow rate is 0.

[0020] Step S5: Monitor the temperature of the pipeline from the air side of the stack to the post-oxidation module. When it reaches the stack operating temperature boundary, control the stack rectifier to make the stack discharge at a certain load growth rate, and generate heat to heat the supply system.

[0021] One or more of the above technical solutions avoid the risk of system cross-leakage through a system architecture with separate co-flow heat exchange on the gas side and the air side of the stack; innovatively solve the problem of the co-flow architecture being unable to start through a control method of air heating the stack and stack heating the gas reformer; and greatly simplify the system structure by integrating the water evaporation device into other structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In the drawings, the sizes and proportions do not represent the sizes and proportions of actual products. The drawings are merely illustrative, and some non-essential elements or features are omitted for clarity.

[0023] Figure 1 This is a diagram of the fuel cell system architecture of the present invention in an embodiment of the present invention;

[0024] Figure 2 It is a diagram of another fuel cell system architecture of the present invention in an embodiment of the present invention;

[0025] Figure 3 It is a schematic diagram of a gas-side reforming device in an embodiment of the present invention;

[0026] Figure 4 This is a schematic diagram of a cooling and water removal device in an embodiment of the present invention;

[0027] Figure 5 This is a schematic diagram of the installation position of the steam generating device in an embodiment of the present invention;

[0028] Figure 6 A schematic diagram of a control system according to an embodiment of the present invention;

[0029] Figure 7 This is a flow chart of the system startup control method described in the embodiment of the present invention.

[0030] In the figure, 100, a gas premixing device, 110 a gas reforming device, 120 a fuel cell stack gas side, 130 a cooling water outlet device, 111 a water-gas mixing device, 112 a heat exchanger, 113 adiabatic reforming device, 115 a first gas tail pipe, 116 a second gas tail pipe, 134 a cooler, 132 a circulating pump, 131 a gas-water separator, 133 a temperature sensor, 200 a cold air butterfly valve, 210 a steam generating device, 220 an air preheating device, 230 a post-oxidation device, 221 a first temperature sensor, 241 a second temperature sensor, 133 a third temperature sensor, 300 a control system, 310 a controller, 320 a fan controller, 330 a circulating pump controller, 340 a flow controller, 350 an air butterfly valve, and 370 an ignition coil. DETAILED DESCRIPTION

[0031] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0032] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0033] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0034] In the present invention, the directions or positional relationships indicated by terms such as "upper", "lower", "side", "bottom", etc. are based on the directions or positional relationships shown in the accompanying drawings. They are relational words determined only for the convenience of describing the structural relationships of the various parts or elements of the present invention. They do not specifically refer to any part or element in the present invention and cannot be understood as limitations on the present invention.

[0035] In the present invention, terms such as "connection" should be understood in a broad sense, indicating that the connection can be fixed, integral or detachable; it can be directly connected or indirectly connected through an intermediate medium. Those skilled in the art can determine the specific meaning of the above terms in the present invention according to specific circumstances, and they should not be understood as limiting the present invention.

[0036] In the absence of conflict, the embodiments of the present invention and the features of the embodiments may be combined with each other.

[0037] One or more embodiments of the present invention provide a high temperature fuel cell system based on recuperation. Figure 1 and Figure 2 As shown, the system includes: a battery gas side 120, a battery air side 240, a gas premixing device 100, a cooling and water removal module 130, a post-oxidation module 230, and an air preheating module 220; wherein the gas premixing device 100, the post-oxidation module 230 and the air preheating module 220 all have gas input pipelines, which are used to introduce gas A1, gas A2 and air B respectively.

[0038] The output end of the gas premixing device 100 is connected to the gas reforming module 110, and the output end of the gas reforming module 110 is connected to the battery gas side 120; the output end of the cooling and water removal module 130 is connected to the gas premixing device 100 and the air preheating module 220, respectively, and the cooling and water removal module 130 also has a gas exhaust pipeline;

[0039] The output end of the gas reforming module 110, or the output end of the cooling and water removal module 130, is connected to the post-oxidation module 230; the output end of the post-oxidation module 230 is connected to the air preheating module 220; the air preheating module 220 is connected to the battery air side 240; the gas input pipeline of the air preheating module 220 is also connected to the cooling and water removal module 130 via a cold air butterfly valve 200; the output end of the battery air side 240 is connected to the post-oxidation module 230.

[0040] The system preheats the fuel gas at the stack inlet through high-temperature exhaust gas on the fuel gas side and preheats the air at the stack inlet through high-temperature exhaust gas on the air side, eliminating the risk of cross leakage in high-temperature heat exchange between fuel gas and air, and ensuring the high-temperature reliability of the system based on the design concept.

[0041] On the system gas side, the gas A1, including but not limited to natural gas, industrial byproduct hydrogen, hydrogen-blended natural gas and hydrogen, is mixed with the stack anode tail gas from the cooling and water removal device 130 in the gas premixing device 100. The gas premixing device 100 achieves full mixing of the system inlet gas and the anode tail gas through the internal structural design, which can avoid local carbon deposition reaction in the gas reforming device 110 due to uneven concentration.

[0042] The above system provides two different implementations for the timing of connecting the anode tail gas of the stack to the post-oxidation device 230 .

[0043] One is that the gas-side reforming device 110 has four connection ports, namely, high-temperature side inlet and outlet and low-temperature side inlet and outlet, wherein the high-temperature inlet is connected to the fuel cell stack gas-side outlet 120 through a pipeline, and the high-temperature outlet is connected to the cooling and water removal device 130 and the post-oxidation device 230 through the first gas tail pipe 115 and the second gas tail pipe 116, respectively. In this method, the gas tail gas in the second gas tail pipe 116 is generally above 100°C, 200°C or even 300°C, and the advantage is that the gas tail gas has a certain high-temperature sensible heat, which improves the combustibility of the fuel.

[0044] Another is that the output end of the cooling and water removal device 130 is connected to the post-oxidation device 230. That is, the fuel cell fuel gas tail gas passes through the cooling and water removal device 130 to remove a large amount of water before entering the post-oxidation device 230. Figure 2 That is, Figure 1 The input end of the second gas tail pipe 116 is replaced by the cooling and water removal device 130 from the gas side reforming device 110. This method condenses the water vapor in the gas tail gas to increase the concentration of combustible gas in the gas, thereby improving the combustibility of the fuel cell gas tail gas.

[0045] On this basis, the output end of the battery gas side 120 is also connected to the gas reforming module 110; the output end of the gas reforming module 110 is also connected to the cooling water outlet module 130. By connecting the cold side gas outlet of the gas reforming device 110 with the inlet of the fuel cell gas side 120 through a pipeline, after the gas undergoes an electrochemical reaction on the fuel cell gas side 120, the anode tail gas generated at its outlet re-enters the high temperature side 110 of the gas reforming device, realizing recuperation.

[0046] A steam generator 201 is also provided on the passage between the post-oxidation module 230 and the air preheating module 220, and the output end of the steam generator 201 is connected to the gas reforming module 110; the steam generator 201 is provided with a liquid water input pipeline for injecting liquid water C1. At this time, the gas-side reforming device 110 should also be provided with a water vapor interface connected to the water evaporator 210. Different from the traditional heating methods that require combustion, electric heating or high-temperature air heating, the high-temperature tail gas on the gas side of the stack is self-heated to heat the gas on the inlet side of the stack, without consuming external energy and without the risk of cross leakage.

[0047] The gas-side reforming device 110 includes one or more of a water-gas mixing device 111, a heat exchanger 112, and an adiabatic reforming device 113. The water-gas mixing device 111 plays a mixing role when the system is cold started, and the water vapor from the water evaporator 210 mixes the low-temperature gas or air from 100 to achieve the purge of the downstream gas pipelines and components.

[0048] As an embodiment of the gas-side reforming device 110, the gas-side reforming device 110 only includes a water-gas mixing device 111 and a heat exchanger 112, and the water-gas mixing device 111 is connected to the cold side inlet of the heat exchanger 112 through a pipeline. The low-temperature side of the heat exchanger 112 is coated or filled with a steam reforming catalyst. After entering the heat exchanger 112, the low-temperature gas is preheated by the high-temperature anode tail gas and a reforming reaction occurs.

[0049] As another embodiment of the gas-side reforming device 110, the gas-side reforming device 110 includes a water-gas mixing device 111, a heat exchanger 112 and an adiabatic reforming device 113, and the adiabatic reforming device 113 is connected to the low-temperature side outlet of the heat exchanger 112 through a pipeline. The adiabatic reforming device 113 is coated or filled with a steam reforming catalyst. After the low-temperature gas enters the heat exchanger 112, it is preheated by the high-temperature anode tail gas to a temperature above the required temperature of the reforming reaction, and then a reforming reaction occurs in the adiabatic reforming device 113, accompanied by a temperature drop. The advantage of this embodiment is that the development difficulty of the heat exchanger 112 is reduced.

[0050] The cooling and water removal device 130 is used to cool the anode tail gas from the gas reforming device 110. Specifically, the cooling and water removal device 130 should include a cooler 134 and a circulation pump 132. In order to ensure the reliable operation of the circulation pump, the cooling and water removal device 130 can cool the anode tail gas from the gas reforming device 110 to below 200°C. Under the action of the circulation pump, the cooling and water removal device 130 can further cool the anode tail gas to below 100°C to condense and remove the water vapor in the anode tail gas. Of course, the cooling and water removal device 130 can also include a gas-water separator 131, etc., which is not specifically limited here.

[0051] The cold source of the cooling and water removal device 130 of the present invention comes from room temperature air, wherein the cold side inlet of the cooler 134 is connected to the cold air butterfly valve 200 through a pipeline. During the startup or operation of the system, based on the reading of the temperature sensor 133, the system realizes feedback adjustment of the temperature requirement before the inlet of the circulation pump 132 through the opening of the cold air butterfly valve 200. The temperature requirement before the inlet of the circulation pump 132 is jointly determined by the oxygen-carbon ratio requirement of the system and the inlet temperature of the circulation pump.

[0052] On the air side, room temperature air B is diverted to enter the cold air butterfly valve 200 and the air preheating device 220 respectively. The air heated from the cooling and water removal device 130 is mixed with the room temperature air B before entering the air preheating device 220. The cold side outlet of the air preheating device 220 is directly connected to the air side of the stack 240 through a pipeline. The hot side inlet of the air preheating device 220 is connected to the input end of the post-oxidation module 230 through a high-temperature pipeline 231. The air heated by the air preheating device 220 directly enters the air side of the stack to participate in the electrochemical reaction, and then enters the post-oxidation device 230 to undergo oxidation or combustion reaction with the anode tail gas from the first gas tail pipe 116.

[0053] A steam generator 210 is provided on the post-oxidation module 230 or the high-temperature pipeline 231. The water or water vapor in the steam generator 210 is not connected to the flue gas generated by the post-oxidation device 230, but heat exchange occurs. The function of the steam generator 210 is to heat the liquid water C1 to completely vaporize, and the vaporized water vapor enters the gas reforming device 110 to achieve purging of the gas side. As an example, Figure 5 As shown, the steam generating device can be installed on the inner edge of the cylinder wall of the post-oxidation device 230 to avoid direct contact with the high-temperature flue gas generated by the core of the post-oxidation device to increase the life of the device.

[0054] Based on the above fuel cell system, one or more embodiments of the present invention further disclose a control system 300 applied to the fuel system, such as Figure 2 , Figure 4 , Figure 6 As shown, the control system includes a controller 310, and the controller 310 is connected to a fan 320 controller participating in air B flow control, a gas flow controller 340 participating in gas A1 and A2 control, a gas circulation pump controller 330 participating in anode tail gas circulation rate control, and a water flow controller 340 participating in water C1 control through control buses such as 485 and CAN.

[0055] The control system further includes a first temperature sensor 221, a second temperature sensor 241 and a third temperature sensor 133, and the controller 310 is connected to the first temperature sensor 221, the second temperature sensor 241 and the third temperature sensor 133 through necessary I / O interfaces. Among them, the first temperature sensor 221 is arranged on the pipeline from the post-oxidation module 230 to the air preheating module 220, the second temperature sensor 241 is arranged on the pipeline from the air side 240 of the stack to the post-oxidation module 230, and the third temperature sensor 133 is arranged at the outlet of the cooler 134 in the cooling and water removal module 130. It can be understood that the above three temperature sensors are necessary components of the control system, and the control system still includes some necessary temperature sensors for monitoring temperature, such as the outlet temperature sensor of the fuel cell gas side, the outlet temperature sensor of the fuel cell air side, etc., which are not specifically limited here.

[0056] like Figure 6 As shown, the controller 330 is configured to execute a system startup control method 380, comprising the following steps:

[0057] Step S1: Basic circulation volume control on the gas side. Turn on the circulation pump 132, and make it work at a certain basic load according to the gas side circulation flow not exceeding the air side flow, and form air circulation on the gas side. During the heating process, monitor the temperature of the third temperature sensor 133. When it reaches 100°C or above 200°C, feedback control the opening of the air butterfly valve 350 to prevent the circulation pump 132 from overheating.

[0058] Step S2: Combustion starts and the temperature is raised. A certain amount of air B and fuel gas A2 are introduced into the rear oxidation device 230, and the spark plug or the electric heating element is controlled by the ignition coil 370 to ignite and raise the temperature.

[0059] Step S3: Steam purge and temperature increase. Monitor the second temperature sensor 241. When it reaches above 100°C, more generally above 200°C, and in fact above 280°C, a certain flow of liquid water is introduced through the liquid water C1 flow controller. The specific value depends on the system pipeline volume and the heating rate requirement.

[0060] Step S4: Gas switching control. Monitor the second temperature sensor 241. When it reaches the safety temperature boundary of the fuel cell stack, control the gas flow controllers of fuel cells A1 and A2 at the same time. While ensuring that the total gas supply of the system remains unchanged, gradually reduce the flow of fuel cell A2 to 0. That is, all fuels are allowed to enter the fuel cell stack first to provide the maximum power generation efficiency.

[0061] Step S5: Stack auxiliary temperature control. At this time, the flow rate of the fuel gas A2 is 0, and the second temperature sensor 241 is monitored. When it reaches the stack operating temperature boundary, the stack rectifier 350 is controlled to discharge the stack at a certain load growth rate, and the generated heat is supplied to the system for heating.

[0062] The protection scope of the present invention is limited only by the claims. With the help of the teachings of the present invention, those skilled in the art will easily recognize that alternative structures of the structures disclosed in the present invention can be used as feasible alternative embodiments, and the embodiments disclosed in the present invention can be combined to generate new embodiments, which also fall within the scope of the appended claims.

Claims

1. A high temperature fuel cell system based on recuperation, characterized in that: include: Battery fuel side, battery air side, gas premixing device, cooling and water removal module, post-oxidation module, air preheating module; wherein the gas premixing device and post-oxidation module have gas input pipelines for introducing gas, and the air preheating module has a gas input pipeline for introducing air; The output end of the gas premixing device is connected to the gas reforming module, and the output end of the gas reforming module is connected to the battery gas side; the output end of the cooling and water removal module is connected to the gas premixing device and the air preheating module respectively, and the cooling and water removal module also has a gas exhaust pipeline; The output end of the gas reforming module, or the output end of the cooling and water removal module is connected to the post-oxidation module; the output end of the post-oxidation module is connected to the air preheating module; the air preheating module is connected to the battery air side; the gas input pipeline of the air preheating module is also connected to the cooling and water removal module via a cold air butterfly valve; the output end of the battery air side is connected to the post-oxidation module.

2. The high temperature fuel cell system based on recuperation as claimed in claim 1, characterized in that: The output end of the battery gas side is connected to the gas reforming module; the output ends of the gas reforming module are also connected to the cooling water outlet modules respectively.

3. The high temperature fuel cell system based on recuperation as claimed in claim 1, characterized in that: A steam generating device is also provided on the passage between the post-oxidation module and the air preheating module, and the output end of the steam generating device is connected to the gas reforming module.

4. The high temperature fuel cell system based on recuperation as claimed in claim 3, characterized in that: The steam generating device is installed on the inner edge of the cylinder wall of the post-oxidation device.

5. The high temperature fuel cell system based on recuperation as claimed in claim 1, characterized in that: The gas-side reforming device includes one or more of a water-gas mixing device, a heat exchanger, and an adiabatic reforming device.

6. The high temperature fuel cell system based on recuperation as claimed in claim 5, characterized in that: The gas-side reforming device comprises a water-gas mixing device and a heat exchanger. The water-gas mixing device is connected to the cold-side inlet of the heat exchanger through a pipeline. The low-temperature side of the heat exchanger is coated or filled with a steam reforming catalyst.

7. The high temperature fuel cell system based on recuperation as claimed in claim 5, characterized in that: The gas-side reforming device comprises a water-gas mixing device, a heat exchanger and an adiabatic reforming device. The adiabatic reforming device is connected to the low-temperature side outlet of the heat exchanger through a pipeline. The adiabatic reforming device is coated or filled with a steam reforming catalyst.

8. The high temperature fuel cell system based on recuperation as claimed in claim 1, characterized in that: The cooling and water removal device comprises a cooler and a circulation pump.

9. The high temperature fuel cell system based on recuperation as claimed in claim 1, characterized in that: The system also includes a controller connected to the controllers for controlling air flow, fuel gas flow, liquid water flow, and a circulation pump controller.

10. A control method for a high temperature fuel cell system based on recuperation as claimed in any one of claims 1 to 9, characterized in that: include: Step S1: Control the circulation pump to start, and control the gas flow rate not to exceed the air side flow rate; Step S2: a certain amount of air and fuel gas is introduced into the rear oxidation device, and the spark plug or the electric heating element is controlled to ignite and heat up through the ignition coil; Step S3: monitoring the temperature of the pipeline from the air side of the stack to the post-oxidation module, and when it reaches above a set temperature threshold, injecting a certain flow of liquid water to perform water vapor purge; Step S4: monitor the temperature of the pipeline from the air side of the fuel cell stack to the post-oxidation module. When it reaches the safety temperature boundary of the fuel cell stack, introduce fuel gas into the fuel gas premixing device and the post-oxidation module at the same time. While ensuring that the total fuel gas supply of the system remains unchanged, gradually reduce the flow rate introduced into the post-oxidation module until the flow rate is 0. Step S5: Monitor the temperature of the pipeline from the air side of the stack to the post-oxidation module. When it reaches the stack operating temperature boundary, control the stack rectifier to make the stack discharge at a certain load growth rate, and generate heat to heat the supply system.

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