Fuel cell system and fast start method

Abstract

The application discloses a fuel cell system and a quick starting method, and relates to the technical field of fuel cells. In the fuel cell system, a first fuel pump is used for inputting system fuel and is connected with a starting combustor through a pipeline, the starting combustor is connected with cold air input from an output pipeline of a second air branch, an output pipeline of the starting combustor is connected with a first heat exchanger, the first heat exchanger is used for heating cold air input from a third air branch, and the heated cold air is connected with a cathode inlet of a SOFC (Solid Oxide Fuel Cell) stack, and a cathode outlet of the SOFC stack is connected with an exhaust combustor. The starting combustor and the first heat exchanger are arranged, extra electric energy is not needed to heat the system, the system fuel can be used to preheat the SOFC stack of the fuel cell system, and the problems of slow starting speed and high starting energy consumption of the existing fuel cell system are solved.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and more specifically to a fuel cell system and a rapid start-up method. Background Technology

[0002] There are two main methods for heating and starting up solid oxide fuel cell (SOFC) stacks: The first method is electric furnace heating, where the outer surface is first heated to the required operating temperature inside the furnace, and the entire stack is heated to the operating temperature through heat conduction. This method has a slow start-up time and a large temperature difference between the inside and outside, which can easily lead to damage to the connections between components due to differences in the thermal expansion coefficients of the various fuel cell components. The second method is to preheat by directly heating the reducing gas on the anode side or the oxidizing gas on the cathode side.

[0003] SOFC systems typically operate at medium to high temperatures (600-800℃), resulting in relatively long start-up times (generally over 30 minutes). Among them, cathode-supported tubular solid oxide fuel cells, which offer good mechanical strength, high thermal cycling performance, and ease of assembly and management, suffer from even longer start-up times—often several hours—due to the thicker walls of the support tube. This significantly impacts their practical applications, especially when used as a backup power source, where the slow start-up time is a major obstacle. Therefore, shortening the start-up time of SOFC systems has always been a key research focus.

[0004] Existing technologies can accelerate start-up time through structural design, but their large-scale application is difficult. Using metal supports can also accelerate start-up time, but its fabrication process is difficult and costly. Solid oxide fuel cells themselves use materials such as strontium-lanthanum manganese oxide-based electrode materials, yttrium oxide-stabilized zirconium oxide electrolyte materials, or lanthanum chromate-based connector materials. Current technologies heat the material through electric heating followed by heat exchange or thermal radiation, resulting in low heat transfer efficiency and long heating and start-up times.

[0005] Therefore, it is urgent for those skilled in the art to find solutions to the problems of slow start-up speed and high start-up energy consumption in fuel cell systems. Summary of the Invention

[0006] In view of this, the present invention provides a fuel cell system and a rapid start-up method to overcome the deficiencies in the prior art. It can relatively quickly heat the solid oxide fuel cell stack to a suitable operating temperature, and at the same time preheat the reformer so that the reformer can quickly reach the reforming operating temperature.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: One aspect of this invention discloses a fuel cell system, comprising: The system comprises a first fuel pump, a starter combustor, a first heat exchanger, a reformer, an SOFC stack, a recirculation compressor, a first mixer, an exhaust combustor, a second heat exchanger, and an air intake system. The air intake system is used to provide cold air, and the output pipeline of the air intake system includes a first air branch, a second air branch and a third air branch, wherein the third air branch is divided into two paths; The anode outlet of the SOFC stack is connected to both the recirculation compressor and the exhaust gas combustor. The output line of the recirculation compressor and the output line of the first air branch are simultaneously connected to the first mixer. The output line of the first mixer is connected to the reformer. The reformer is simultaneously connected to the system fuel input line. The output line of the reformer is connected to the anode inlet of the SOFC stack. The exhaust gas burner is simultaneously connected to the output pipe of the third air branch, and the output pipe of the exhaust gas burner is connected to the second heat exchanger. The second heat exchanger is used to heat the cold air input from the third air branch and connect the heated cold air to the cathode inlet of the SOFC stack. The first fuel pump is used to input system fuel and is connected to the starter burner through a pipeline. The starter burner is also connected to the output pipeline of the second air branch. The output pipeline of the starter burner is connected to the first heat exchanger. The first heat exchanger is used to heat the cold air input from another third air branch and connect the heated cold air to the cathode inlet of the SOFC stack. The cathode outlet of the SOFC stack is connected to the exhaust gas burner.

[0008] Preferably, the air intake system includes an air compressor and an air distribution device connected to the air compressor.

[0009] Preferably, solenoid valves and flow meters are installed on the output pipes of the first air branch, the second air branch and the third air branch.

[0010] Preferably, the cold air output from the output pipe of the second air branch is used as the air required for fuel combustion in the system.

[0011] Preferably, the first heat exchanger is also connected to the reformer via an output pipeline.

[0012] Preferably, the system fuel introduced into the first fuel pump includes diesel fuel.

[0013] Another aspect of the present invention discloses a method for rapid start-up of a fuel cell system, comprising the following steps: The system fuel and cold air are simultaneously input into the starter burner for combustion; The high-temperature exhaust gas generated by the combustion of the start-up burner is input into the first heat exchanger, which heats the input cold air. The heated cold air is introduced into the cathode inlet of the SOFC stack to achieve rapid preheating of the SOFC stack.

[0014] Preferably, the above method further includes, The cold air heated by the first heat exchanger is introduced into the reformer to preheat the catalytic reaction zone inside the reformer.

[0015] As can be seen from the above technical solution, compared with the prior art, the present invention discloses a fuel cell system and a fast start-up method, which has the following beneficial effects: This invention, by setting up a start-up burner and a first heat exchanger, directly combusts the system fuel to rapidly generate high-temperature gas, eliminating the need for an additional electrical heating system. It utilizes the system fuel to preheat the SOFC stack of the fuel cell system, solving the problems of slow start-up speed and high start-up energy consumption in existing fuel cell systems that use electric heating preheating.

[0016] The starter burner designed in this invention can be used not only during system startup, but also during SOFC stack or system temperature fluctuations. It can also maintain the temperature of the fuel cell system within a reasonable range through the supplementary combustion function, thus ensuring the safe and stable operation of the fuel cell system.

[0017] This invention utilizes an air distribution device to meet the air supply needs of multiple components within the system, thereby reducing the complexity of the system. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0019] Figure 1 The attached figure is a schematic diagram of the structure provided by the present invention; In the diagram, 1-Air compressor; 2-Recirculation compressor; 3-Second fuel pump, 4-First fuel pump; 5-Reformer; 6-SOFC stack; 601-SOFC stack anode; 602-SOFC stack cathode; 7-Exhaust gas burner; 8-Start-up burner; 9-Air distribution device; 10, 11-Adjustable solenoid valves; 12, 13, 14, 15-Mass flow meters; 16-First mixer; 17-Second mixer; 18-Third mixer; 19-Fourth mixer, 20-Fifth mixer; 21-Second heat exchanger; 22-First heat exchanger; 23-Third heat exchanger. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] One embodiment of the present invention discloses a fuel cell system, such as Figure 1 As shown, it includes: The system includes a first fuel pump 4, a starter burner 8, a first heat exchanger 22, a reformer 5, an SOFC stack 6, a recirculation compressor 2, a first mixer 16, an exhaust gas burner 7, a second heat exchanger 21, and an air intake system 100. The air intake system 100 is used to provide cold air. The output pipeline of the air intake system 100 includes a first air branch, a second air branch and a third air branch, and the third air branch is divided into two paths. The anode 601 outlet of SOFC stack 6 is connected to both recirculation compressor 2 and exhaust gas burner 7. The output line of the recirculation compressor 2 and the output line of the first air branch are simultaneously connected to the first mixer 16. The output line of the first mixer 16 is connected to the reformer 5. The reformer 5 is also connected to the system fuel input line. The output line of the reformer 5 is connected to the anode 601 inlet of the SOFC stack 6. The output line of the exhaust gas burner 7 is connected to the second heat exchanger 21. The second heat exchanger 21 is used to heat the cold air input from the third air branch and connect the heated cold air to the cathode 602 inlet of the SOFC stack 6. The first fuel pump 4 is used to input system fuel and is connected to the starter burner 8 through a pipeline. The starter burner 8 is also connected to the output pipeline of the second air branch. The output pipeline of the starter burner 8 is connected to the first heat exchanger 22. The first heat exchanger 22 is used to heat the cold air input from another third air branch and connect the heated cold air to the cathode 602 inlet of the SOFC stack 6. The cathode 602 outlet of the SOFC stack 6 is connected to the exhaust gas burner 7.

[0022] Furthermore, the air intake system 100 includes an air compressor 1 and an air distribution device 9. The outlet of the air compressor 1 is connected to the air distribution device 9. The ambient air is compressed by the air compressor 1 and the resulting cold air is divided into three air branches by the air distribution device 9, namely the first air branch, the second air branch and the third air branch. The third air branch is further divided into two paths.

[0023] In the air intake system, the cold air from the first air branch is sent into the first mixer 16. At the same time, a portion of the exhaust gas from the outlet of the SOFC stack anode 601 is also sent into the first mixer 16 after being compressed and increased in pressure by the recirculation compressor 2. The increased pressure exhaust gas is mixed with the cold air from the cold air branch 1 and then sent into the reformer 5 to undergo a reforming reaction with the system fuel in the reformer 5. In this embodiment, the system uses diesel fuel. The diesel fuel is fed into the reformer 5 through the second fuel pump 3 and reformed in the reformer 5 to form reformed gas with H2 and CO as the main fuel gases.

[0024] The cold air output from the second air branch is used as the air required for fuel combustion in the start-up burner system.

[0025] The third air branch is divided into two paths. In this embodiment, the third air branch is divided into two paths through the second mixer 17. One path of cold air exchanges heat with the high-temperature exhaust gas generated after combustion of the exhaust gas burner 7 through the second heat exchanger 21. The other path of cold air exchanges heat with the high-temperature exhaust gas generated after combustion of the start-up burner 8 through the first heat exchanger 22. The cold air after the two heat exchanges are used together as the inlet gas of the cathode 602 of the SOFC stack.

[0026] Furthermore, both the first and second air branches are equipped with solenoid valves and mass flow meters, which can achieve precise control of the cold air in the first, second, and third air branches separated by the air distribution device; in addition, a mass flow meter 15 is installed at the front end of the main air intake pipe of the air intake system 100, which is used to measure the total mass flow rate of the air entering the intake system.

[0027] In one specific embodiment, an adjustable solenoid valve 10 and a mass flow meter 12 are sequentially connected to the first air branch branch of the air distribution device 9, and the output end of the mass flow meter 12 is connected to the first mixer 16. An adjustable solenoid valve 11 and a mass flow meter 13 are connected sequentially to the second air branch branch of the air distribution device 9. The output end of the mass flow meter 13 is connected to the starter burner 8. The third air branch of the air distribution device 9 is connected to the second mixer 17. The output pipeline of the second mixer 17 is divided into two paths. One path is connected to the mass flow meter 14 and the second heat exchanger 21 in sequence, and the other path is connected to the first heat exchanger 22.

[0028] In this embodiment of the invention, the exhaust gas burner 7 is connected to the second heat exchanger 21 through a pipe. It is mainly used to burn the unreacted fuel at the anode of the fuel cell to achieve heat recovery and utilization. The high-temperature exhaust gas generated by the exhaust gas burner heats one of the cold air in the third air branch to the normal operating temperature required by the SOFC stack (e.g., 650°C). During normal operation, the heated air enters the cathode of the SOFC stack to participate in the electrode reaction.

[0029] The exhaust gas from the start-up burner 8, after heat exchange in the first heat exchanger 22, merges with the exhaust gas from the exhaust gas burner 7, after heat exchange in the second heat exchanger 21, and is then discharged. A third heat exchanger 23 can be added at the downstream end of the merged exhaust gas to utilize the waste heat of the exhaust gas, thereby achieving combined heat and power generation and improving energy utilization efficiency.

[0030] In this embodiment, as Figure 1 As shown, the third mixer 18 serves as the air confluence zone after the second heat exchanger 21 and the first heat exchanger 22 heat the heated cold air is then introduced into the cathode 602 inlet of the SOFC stack 6.

[0031] During system startup, the exhaust gas from the start-up burner 8, after heat exchange in the first heat exchanger 22, enters the reformer 5 through the diversion function of the fifth mixer 20, preheating the reformer 5.

[0032] The fourth mixer 19 serves as a merging zone for the exhaust gas generated by the start-up burner 8 and the exhaust gas generated by the exhaust gas burner 7, merging the exhaust gases and discharging them from the system, or utilizing the waste heat of the exhaust gases through the third heat exchanger 23.

[0033] In this embodiment of the invention, the outlet of the fuel cell anode 601 is divided into two paths. One path connects to the exhaust gas burner 7; the other path passes through the recirculation compressor 2 (in other specific embodiments, the recirculation compressor can be designed as a hot gas compressor, blower, electric turbocharger, ejector, or pump, etc.) and mixes with the cold air in the first air branch. The mixture is then introduced into the reformer 5 to provide the reformer 5 with the air and water vapor required for reforming. When the system is operating normally, the oxygen in the air inside the reformer reacts with the system fuel (diesel) to produce hydrogen and CO. The water vapor in the exhaust gas of the SOFC stack anode 601 can increase the hydrogen production rate by undergoing water-gas shift reaction with CO, while simultaneously converting CO into CO2 and reducing the CO content in the reformed gas.

[0034] In this embodiment of the invention, the air compressor 1, the recirculation compressor 2, and the corresponding valves are preferably temperature-controlled or temperature-regulating devices.

[0035] For example, the control of air compressor 1, the solenoid valve in the first air branch, and the recirculation compressor 2 depends on the temperature of the reforming zone inside the reformer 5. The control of the recirculation compressor 2 can be precisely controlled as a function of the reforming zone temperature or as a system process parameter. The solenoid valve and air compressor 1 in the second air branch can be controlled according to the temperature at which the burner 8 is started; In this embodiment of the invention, the reformer recirculation gas system includes a portion of the exhaust gas from the outlet of the SOFC stack anode 601, which is compressed and pressurized by the recirculation compressor 2, then mixed with cold air from the first air branch and sent to the reformer 5 for reforming reaction. The recirculation ratio of the stack anode exhaust gas is determined by the recirculation compressor 2. In this embodiment, the proportion of the anode exhaust gas (mainly composed of H2, CO, N2, H2O, CO2, etc.) recirculated to the reformer accounts for a certain percentage of the total anode exhaust gas. =0.35, and in other embodiments, it can also be adjusted within a certain range according to the working condition of the reformer: for example, the ratio range is 0.2~0.5.

[0036] in

[0037] Another aspect of this invention discloses a method for rapid start-up of a fuel cell system, comprising the following steps: The system fuel and cold air are simultaneously input into the starter burner 8 for combustion; The high-temperature exhaust gas generated by the combustion of the start-up burner 8 is input into the first heat exchanger 22, and the input cold air is heated through the first heat exchanger 22. The heated cold air is introduced into the cathode 602 inlet of the SOFC stack to preheat the SOFC stack.

[0038] Preferably, the above method also includes, The cold air heated by the first heat exchanger 22 is introduced into the reformer 5 to preheat the catalytic reaction zone inside the reformer 5 and rapidly increase the temperature of the reformer.

[0039] The aforementioned rapid preheating system for starting the burner can rapidly preheat both the reformer 5 and the SOFC stack, enabling the system to quickly reach its operating temperature. At the same time, the system's energy is utilized in multiple stages, improving the energy efficiency of the battery fuel system.

[0040] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0041] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A fuel cell system, characterized in that, include: The system includes a first fuel pump (4), a starter burner (8), a first heat exchanger (22), a reformer (5), an SOFC stack (6), a recirculation compressor (2), a first mixer (16), an exhaust gas burner (7), a second heat exchanger (21), and an air intake system (100). The air intake system (100) is used to provide cold air, and the output pipeline of the air intake system includes a first air branch, a second air branch and a third air branch, wherein the third air branch is divided into two paths; The anode (601) outlet of the SOFC stack is connected to both the recirculation compressor (2) and the exhaust gas burner (7). The output line of the recirculation compressor (2) and the output line of the first air branch are simultaneously connected to the first mixer (16). The output line of the first mixer (16) is connected to the reformer (5). The reformer (5) is simultaneously connected to the system fuel input line. The output line of the reformer (5) is connected to the anode (601) inlet of the SOFC stack. The output pipe of the exhaust gas burner (7) is connected to the second heat exchanger (21), which is used to heat the cold air input from the third air branch and connect the heated cold air to the cathode (602) inlet of the SOFC stack. The first fuel pump (4) is used to input system fuel and is connected to the starter burner (8) through a pipeline. The starter burner (8) is also connected to the output pipeline of the second air branch. The output pipeline of the starter burner (8) is connected to the first heat exchanger (22). The first heat exchanger (22) is used to heat the cold air input from another third air branch and connect the heated cold air to the cathode (602) inlet of the SOFC stack. The cathode (602) outlet of the SOFC stack is connected to the exhaust gas burner (7). The first heat exchanger (22) is also connected to the reformer (5) through an output pipeline. It also includes a third mixer (18), which serves as a convergence zone for the air heated by the second heat exchanger (21) and the first heat exchanger (22). The heated cold air is then fed into the cathode (602) inlet of the SOFC stack (6). Specifically, the input end of the third mixer (18) is connected to the output end of the second heat exchanger (21) and the output end of the first heat exchanger (22), respectively, and the output end of the third mixer (18) is connected to the cathode (602) inlet of the SOFC stack (6).

2. The fuel cell system according to claim 1, characterized in that, The air intake system includes an air compressor (1) and an air distribution device (9) connected to the air compressor.

3. The fuel cell system according to claim 1, characterized in that, Solenoid valves and flow meters are installed on the output pipes of the first air branch, the second air branch and the third air branch.

4. The fuel cell system according to claim 1, characterized in that, The cold air output from the output pipe of the third air branch serves as the air required for the SOFC stack.

5. The fuel cell system according to claim 1, characterized in that, The system fuel input into the first fuel pump (4) includes diesel fuel.

6. A method for rapid start-up of a fuel cell system, characterized in that, Based on the fuel cell system according to any one of claims 1-5, the implementation includes the following steps: The system fuel and cold air are simultaneously input into the starter burner for combustion; The high-temperature exhaust gas generated by the combustion of the start-up burner is input into the first heat exchanger, which heats the input cold air. The heated cold air is introduced into the cathode of the SOFC stack to achieve rapid preheating of the SOFC stack.

7. The rapid start-up method for a fuel cell system according to claim 6, characterized in that, Also includes: The cold air heated by the first heat exchanger is introduced into the reformer to preheat the catalytic reaction zone inside the reformer.

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