Solid oxide fuel cell system with controllable fuel reforming

Abstract

The invention relates to a solid oxide fuel cell system capable of controlling fuel reforming, which comprises a fuel supply unit, a decomposition reaction unit, a direct supply branch, an air supply unit, a combustor and an electric pile, the decomposition reaction unit comprises a plurality of reforming reaction branches, the inlets of the reforming reaction branches are communicated with the discharge port of the fuel supply unit, and the direct supply branch is communicated with the air supply unit; the reforming reaction branch is provided with a first stop valve and reforming reactors, all the reforming reactors are connected in series, and an outlet of the reforming reactor located at the most downstream is communicated with an anode inlet of the electric pile; the direct supply branch is provided with a second stop valve, an inlet of the direct supply branch is communicated with a discharge port of the fuel supply unit, an outlet of the air supply unit is communicated with a cathode inlet of the electric pile, an anode outlet and a cathode outlet of the electric pile are communicated with an air inlet of the combustor, and heat generated by the combustor is sequentially conveyed to each reforming reactor. Through the design that the reforming reactors are arranged in series and the gas inlet of each reforming reaction branch is independent, the fuel reforming degree can be flexibly regulated and controlled.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and more specifically to a solid oxide fuel cell system with controllable fuel reforming. Background Technology

[0002] SOFCs (Solid Oxide Fuel Cells) have a wide range of fuel applications, including hydrogen, natural gas, ammonia, and biomass gas. For many of these feedstock gases, to reduce the risk of performance degradation caused by anode poisoning, carbon buildup, and catalyst deactivation, pre-reforming is usually required before they enter the SOFC. This pre-reformation converts some of the large-molecule or highly reactive fuels into hydrogen and CO, which are more easily electrochemically oxidized.

[0003] Patent CN118248897A proposes a power generation system coupled with a reforming reactor and SOFC. Fuel is first fed into the reforming reactor to obtain a mixed fuel gas, which is then transported to the SOFC stack for power generation. However, current SOFC systems generally only have a single reforming reactor. Its reforming capacity is limited by factors such as reaction temperature, gas residence time, and catalyst activity. Under different operating conditions (e.g., lower temperatures during startup and higher flow rates at full power), a single reforming reactor struggles to simultaneously meet reaction kinetics and thermal management requirements, making it difficult to achieve controllable reforming levels. Insufficient reforming can lead to incompletely converted feedstock causing anode carbon buildup or chemical corrosion; excessive reforming results in energy waste and decreased system efficiency. Therefore, existing SOFC systems often fail to balance stability and efficiency under different operating conditions (e.g., temperature, flow rate) and cannot meet personalized requirements for reforming rates. Summary of the Invention

[0004] The purpose of this invention is to provide a solid oxide fuel cell system with controllable fuel reforming.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] A solid oxide fuel cell system with controllable fuel reforming is provided, comprising a fuel supply unit, a decomposition reaction unit, a direct supply branch, an air supply unit, a burner, and an SOFC stack. The decomposition reaction unit includes multiple reforming reaction branches, the inlet of each of which is connected to the outlet of the fuel supply unit. Each reforming reaction branch is equipped with a first shut-off valve and a reforming reactor. All the reforming reactors are connected in series, and the outlet of the downstream reforming reactor is connected to the anode inlet of the SOFC stack. The direct supply branch is equipped with a second shut-off valve, and its inlet is connected to the outlet of the fuel supply unit. The outlet of the air supply unit is connected to the cathode inlet of the SOFC stack. The anode outlet and cathode outlet of the SOFC stack are both connected to the air inlet of the burner. The heat generated by the burner is sequentially delivered to each of the reforming reactors to provide heat to them.

[0007] As a further embodiment of the solid oxide fuel cell system with controllable fuel reforming, the catalytic activity of the catalyst in each of the reforming reactors gradually increases along the flow direction of the fuel.

[0008] As a further embodiment of the solid oxide fuel cell system with controllable fuel reforming, the number of reforming reaction branches is three, corresponding to the number of three reforming reactors. The catalyst in the upstream reforming reactor is Ni / SiC, the catalyst in the downstream reforming reactor is Ru / CeO2, and the catalyst in the other reforming reactor is Ni / ZrO2.

[0009] As a further embodiment of the solid oxide fuel cell system with controllable fuel reforming, it also includes a first heat exchanger, wherein the direct supply branch and each of the reforming reaction branches are provided with the first heat exchanger, adjacent first heat exchangers are connected in series, the anode outlet of the SOFC stack is connected to the heat source inlet of the first heat exchanger located at the upstream end, and the heat source outlet of the first heat exchanger located at the downstream end is connected to the air inlet of the burner.

[0010] As a further embodiment of the solid oxide fuel cell system with controllable fuel reforming, a gas-water separator is also included. The heat source outlet of the first heat exchanger located at the downstream end is connected to the gas-water separator. The gas after gas-water separation is transported to the air inlet of the burner, and the liquid after gas-water separation is discharged.

[0011] As a further embodiment of the solid oxide fuel cell system with controllable fuel reforming, a second heat exchanger is also included. The second heat exchanger is disposed on the direct supply branch and is used to heat the fuel delivered by the direct supply branch. The heat generated by the burner is delivered to the downstream reforming reactor and then to the second heat exchanger.

[0012] As a further embodiment of the controllable fuel reforming solid oxide fuel cell system, a third heat exchanger is also included, which is used to heat the air supplied by the air supply unit. The cathode outlet of the SOFC stack is connected to the heat source inlet of the third heat exchanger, and the heat source outlet of the third heat exchanger is connected to the air inlet of the burner.

[0013] As a further embodiment of the solid oxide fuel cell system with controllable fuel reforming, a fourth heat exchanger is also included. The fourth heat exchanger is used to heat the air supplied by the air supply unit. The heat source inlet of the fourth heat exchanger is connected to the heat source outlet of the second heat exchanger. The air supplied by the air supply unit is heated by the fourth heat exchanger and then reheated by the third heat exchanger.

[0014] As a further embodiment of the controllable fuel reforming solid oxide fuel cell system, the air supply unit includes an air supply main pipeline, an air supply bypass, a blower, a buffer tank, a first pressure reducing valve, a third shut-off valve, and a first flow meter. The air supply main pipeline is sequentially arranged with the blower, the buffer tank, the first pressure reducing valve, the third shut-off valve, the first flow meter, the fourth heat exchanger, and the third heat exchanger along the air flow direction. The air supply main pipeline is connected to the air supply bypass via a three-way valve, which is located between the fourth heat exchanger and the flow meter. The end of the air supply bypass away from the three-way valve is connected to the air supply main pipeline, and the connection point is located between the fourth heat exchanger and the third heat exchanger. The air supply main pipeline is connected to the cathode inlet of the SOFC stack.

[0015] It also includes a condenser, the cold source inlet of which is connected to the heat source outlet of the fourth heat exchanger.

[0016] As a further embodiment of the solid oxide fuel cell system with controllable fuel reforming, the fuel supply unit includes a fuel supply pipeline, a fuel storage tank, a second pressure reducing valve, a fourth shut-off valve, and a second flow meter. Along the fuel delivery direction, the second pressure reducing valve, the fourth shut-off valve, and the second flow meter are sequentially arranged on the fuel supply pipeline. The inlet of the fuel supply pipeline is connected to the fuel storage tank, and the inlet of the direct supply branch and the inlets of all the reforming reaction branches are connected to the outlet of the fuel supply pipeline.

[0017] The beneficial effects of this invention are:

[0018] This invention flexibly adjusts the number of reactors involved in the reaction under high or low flow conditions by arranging multiple reforming reactors in series, with each reactor serving as the initiation stage. When complete fuel decomposition is required, the first shut-off valve on the reforming reaction branch containing the upstream reforming reactor is opened, while the remaining first shut-off valves and the second shut-off valve on the direct supply branch are closed. Fuel then flows sequentially through the three reforming reactors, achieving a high ammonia decomposition rate. For a lower fuel decomposition rate, the first shut-off valve on the reforming reaction branch containing the downstream reforming reactor is opened, while the remaining first shut-off valves and the second shut-off valve on the direct supply branch are closed. Fuel then flows only through the downstream reforming reactor, achieving only partial fuel decomposition. When the system can also operate in direct fuel mode, the first shut-off valve is closed, and only the second shut-off valve is opened, allowing fuel to be directly supplied to the SOFC stack. Compared with the prior art, the present invention adopts a reforming reactor structure with a series arrangement and independent gas inlet, which can flexibly adjust the number of reactors through which the fuel gas passes according to the actual working conditions, so that the residence time of the fuel gas and the catalyst contact area under different conditions can be effectively adjusted, thereby achieving controllable adjustment of the reforming rate.

[0019] This invention allows for the rational arrangement of catalysts with varying activities in different reforming reactors along the process flow, based on burner temperature and the endothermic and exothermic properties of the reforming reaction. This reduces burner-side demand and improves overall system efficiency. For example, when ammonia is used as fuel: along the flow direction of the gas exiting the burner, ammonia decomposition catalysts with progressively increasing activity are arranged in different reforming reactors. This design ensures that even at lower temperatures in the downstream reforming reactor, a higher ammonia decomposition rate can be maintained through higher catalytic activity, reducing burner-side demand and improving overall system efficiency. Furthermore, since the ammonia decomposition rate is adjustable, for SOFC stacks with good ammonia tolerance, some incompletely decomposed ammonia can be introduced to reduce the heat load and energy consumption of the ammonia reforming reactor, thereby improving the overall system efficiency. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a solid oxide fuel cell system with controllable fuel reforming in one embodiment.

[0021] In the picture:

[0022] 1. Burner; 2. SOFC stack; 3. First shut-off valve; 4. Reformer; 5. Second shut-off valve; 6. First heat exchanger; 7. Steam-water separator; 8. Second heat exchanger; 9. Third heat exchanger; 10. Fourth heat exchanger; 11. Fan; 12. Buffer tank; 13. First pressure reducing valve; 14. Third shut-off valve; 15. First flow meter; 16. Three-way valve; 17. Condenser; 18. Fuel storage tank; 19. Second pressure reducing valve; 20. Fourth shut-off valve; 21. Second flow meter. Detailed Implementation

[0023] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0024] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0025] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0026] In the description of this embodiment, the terms "upper," "lower," "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first" and "second" are used only for distinction in description and have no special meaning.

[0027] like Figure 1As shown, this embodiment provides a solid oxide fuel cell system with controllable fuel reforming, including a fuel supply unit, a decomposition reaction unit, a direct supply branch, an air supply unit, a burner 1, and an SOFC stack 2. The decomposition reaction unit includes multiple reforming reaction branches, the inlet of each reforming reaction branch is connected to the outlet of the fuel supply unit, each reforming reaction branch is equipped with a first shut-off valve 3 and a reforming reactor 4, all reforming reactors 4 are connected in series, and the outlet of the downstream reforming reactor 4 is connected to the anode inlet of the SOFC stack 2. The direct supply branch is equipped with a second shut-off valve 5, the inlet of the direct supply branch is connected to the outlet of the fuel supply unit, the outlet of the air supply unit is connected to the cathode inlet of the SOFC stack 2, and the anode outlet and cathode outlet of the SOFC stack 2 are both connected to the air inlet of the burner 1. The heat generated by the burner 1 is sequentially transported to each reforming reactor 4 to provide heat to the reforming reactor 4.

[0028] For SOFC systems employing a single reforming reactor 4, their reforming performance is limited by the matching between inlet gas flow rate, reaction temperature, and catalyst activity: when the inlet gas flow rate is high, it is often difficult to achieve a high reforming rate due to insufficient reaction residence time and limited heat and mass transfer capacity; while when the inlet gas flow rate is low, the fixed amount of catalyst is in a significant excess state, resulting in low catalyst utilization. To avoid the above contradictions, this embodiment arranges multiple reforming reactors 4 in series, and each reforming reactor 4 can serve as the reaction initiation section, thereby flexibly adjusting the number of reforming reactors 4 actually participating in the reaction under high or low flow rate conditions, and achieving controllable adjustment of the reforming rate within a wide feed range.

[0029] Specifically, in this embodiment, multiple reforming reactors 4 connected in series can progressively reform the fuel. Each reforming reaction branch is independently controlled by a first shut-off valve 3. The number of reforming reactors 4 actually participating in the reforming can be adjusted by the switching combination of the first shut-off valves 3, thereby controlling the depth of fuel reforming. Taking ammonia as fuel as an example, when complete ammonia decomposition is required, the first shut-off valve 3 of the reforming reaction branch where the upstream reforming reactor 4 is located is opened, and the remaining first shut-off valves 3 and the second shut-off valve 5 of the direct supply branch are closed. At this time, the fuel will flow through the three reforming reactors 4 in sequence to achieve a high ammonia decomposition rate. If a lower fuel decomposition rate is required, the first shut-off valve 3 of the reforming reaction branch where the downstream reforming reactor 4 is located is opened, and the remaining first shut-off valves 3 and the second shut-off valve 5 of the direct supply branch are closed. At this time, the fuel only flows through the downstream reforming reactor 4, achieving only partial fuel decomposition. The system can also operate in direct fuel mode, closing the first shut-off valves 3 and opening only the second shut-off valves 5 to directly supply fuel to the SOFC stack 2.

[0030] Compared with the prior art, the reforming controllable solid oxide fuel cell system in this embodiment, through the series arrangement of reforming reactors 4 and the independent gas inlet design, can flexibly adjust the degree of reforming and achieve controllable reforming rate: by adopting the structure of the series arrangement of reforming reactors 4 with independent gas inlet, the number of reforming reactors 4 through which the fuel gas passes can be flexibly adjusted according to the actual operating conditions, so that the residence time of the fuel gas and the catalyst contact area under different conditions can be effectively adjusted, thereby achieving controllable adjustment of the reforming rate.

[0031] Furthermore, along the fuel flow direction, the catalytic activity of the catalyst in each reforming reactor 4 gradually increases.

[0032] The reforming reactor 4 is heated by the burner 1, and the endothermic and exothermic conditions of different reforming reactions vary. In this embodiment, catalysts with different activities can be rationally arranged in different reforming reactors 4 along the flow path based on the burner 1 temperature and the endothermic and exothermic conditions of the reforming reactions, thereby reducing the demand on the burner 1 side and improving the overall system efficiency. For example, when ammonia is used as fuel, ammonia decomposition catalysts with progressively increasing activity are arranged in different reforming reactors 4 along the flow direction of the gas exiting the burner 1. This design allows a higher ammonia decomposition rate to be maintained even at a lower temperature in the downstream reforming reactor 4 through higher catalytic activity, reducing the demand on the burner 1 side and improving the overall system efficiency. Furthermore, since the ammonia decomposition rate is adjustable, for SOFC stacks 2 with good ammonia resistance, some incompletely decomposed ammonia can be introduced to reduce the heat load and energy consumption of the ammonia reforming reactor 4, improving the overall system efficiency.

[0033] Furthermore, there are three reforming reaction branches, corresponding to three reforming reactors 4. The catalyst in the upstream reforming reactor 4 is Ni / SiC, the catalyst in the downstream reforming reactor 4 is Ru / CeO2, and the catalyst in the other reforming reactor 4 is Ni / ZrO2.

[0034] In this embodiment, catalysts with different activities are arranged in the reforming reactor 4 from upstream to downstream, so complete reforming of gas can be achieved in a wide temperature range, which can be matched with SOFC stacks 2 with different operating temperatures.

[0035] Specifically, catalysts of varying prices can be rationally arranged within the different reforming reactors 4 according to their operating temperatures, thereby reducing catalyst costs while maintaining good reforming performance. For example, when ammonia is used as fuel, the upstream ammonia decomposition reactor first contacts the outlet gas of the burner 1, which is in a higher temperature range. Therefore, a low-cost Ni-based catalyst can be used to achieve good activity. The midstream and downstream reforming reactors 4, however, have relatively lower temperatures, so catalysts that maintain high activity at low temperatures are selected. For instance, a Ru-based precious metal catalyst can be added to the midstream reforming reactor 4, while a Ni / ZrO2 catalyst can be added to the downstream reforming reactor 4. This method of distributing catalysts according to temperature gradients not only maintains a high ammonia decomposition rate but also effectively reduces the amount of precious metal catalyst used, further reducing maintenance and replacement costs.

[0036] Furthermore, the solid oxide fuel cell system with controllable fuel reforming in this embodiment also includes a first heat exchanger 6. The direct supply branch and each reforming reaction branch are equipped with a first heat exchanger 6. Adjacent first heat exchangers 6 are connected in series. The anode outlet of the SOFC stack 2 is connected to the heat source inlet of the upstream first heat exchanger 6, and the heat source outlet of the downstream first heat exchanger 6 is connected to the air inlet of the burner 1.

[0037] In this embodiment, adjacent first heat exchangers 6 are connected in series, meaning that the heat source outlet of one first heat exchanger 6 is connected to the heat source inlet of another first heat exchanger 6. The anode outlet gas of the SOFC stack 2 is transported to the first heat exchanger 6 corresponding to the reforming reaction branch where the upstream reforming reactor 4 is located. Multiple first heat exchangers 6 are connected in series in the fuel supply path (direct supply branch and each reforming reaction branch) to form a "fuel preheating chain". Specifically, the flow direction of the heat source (high temperature gas at the anode outlet) is opposite to the flow direction of the cold source (fuel to be preheated) (countercurrent flow). The anode outlet gas (highest temperature) first enters the upstream first heat exchanger 6 and flows through each first heat exchanger 6 in sequence, with the temperature decreasing step by step, and finally enters the burner 1. The fuel is initially preheated from the upstream first heat exchanger 6 and is heated to a higher temperature step by step when flowing through each downstream first heat exchanger 6, thus forming a highly efficient countercurrent heat exchange system that maximizes the heat transfer temperature difference and heat recovery efficiency.

[0038] This embodiment maximizes waste heat recovery, reducing the external energy required for preheating fuel or maintaining reforming temperature (such as additional fuel consumption in burner 1), directly improving the system's net power generation efficiency and primary energy utilization rate. Simultaneously, this embodiment also improves the conversion rate and selectivity of the reforming reaction, obtaining a more ideal syngas composition (H2 / CO ratio), reducing thermal stress on the catalyst due to temperature fluctuations, extending catalyst life, and preventing carbon buildup and cracking of the fuel due to localized overheating. The solid oxide fuel cell system employing controlled fuel reforming in this embodiment can shorten system start-up time, enhance thermal stability and response smoothness under varying loads, and improve system compactness and reliability.

[0039] Furthermore, the solid oxide fuel cell system with controllable fuel reforming in this embodiment also includes a gas-water separator 7. The heat source outlet of the first heat exchanger 6 located at the downstream end is connected to the gas-water separator 7. The gas after gas-water separation is transported to the air inlet of the burner 1, and the liquid after gas-water separation is discharged.

[0040] This embodiment adds a steam-water separator 7 at the end of the series heat exchange network to condense and separate the water vapor in the anode outlet gas after the cascade cooling. On the one hand, this significantly improves the dryness and calorific value of the fuel gas entering the burner 1, reducing the additional energy consumption required to maintain the temperature of the burner 1. On the other hand, the sensible heat and latent heat of the high-temperature condensate can be recovered for use inside the system (such as preheating or steam generation), further improving the overall thermal integration and energy utilization efficiency, while avoiding the potential corrosion of downstream equipment by liquid water.

[0041] Furthermore, this embodiment also includes a second heat exchanger 8, which is disposed on the direct supply branch and is used to heat the fuel transported by the direct supply branch. The heat generated by the burner 1 is transported to the downstream reforming reactor 4 and then to the second heat exchanger 8.

[0042] By integrating the second heat exchanger 8 into the direct supply branch and utilizing the waste heat of the flue gas from the burner 1 after flowing through the downstream reforming reactor 4 as its heat source, the deep exploitation and targeted utilization of the lowest grade thermal energy of the system is achieved. This ensures that the direct-supply fuel that does not require reforming can be preheated to a suitable temperature before entering the anode of the SOFC stack 2, thereby stabilizing the stack's operating performance. At the same time, the exhaust temperature of the burner 1 is further reduced, converting the low-grade heat that might otherwise be wasted into effective preheating energy. This significantly improves the thermal integration and overall energy utilization efficiency of the entire system without increasing additional energy consumption.

[0043] Furthermore, this embodiment also includes a third heat exchanger 9, which is used to heat the air supplied by the air supply unit. The cathode outlet of the SOFC stack 2 is connected to the heat source inlet of the third heat exchanger 9, and the heat source outlet of the third heat exchanger 9 is connected to the air inlet of the burner 1.

[0044] In this embodiment, by adding a third heat exchanger 9, the waste heat of the high-temperature gas at the cathode outlet of the SOFC stack 2 can be used to preheat the air entering the SOFC stack 2, which significantly reduces the external energy consumption required for air heating. At the same time, the preheated air increases the operating temperature and reaction activity of the cathode side of the SOFC stack 2, which is beneficial to improving battery performance and reducing thermal stress. The gas at the cathode outlet after heat recovery is then fed into the burner 1, further optimizing the overall thermal integration and energy efficiency balance of the system.

[0045] Furthermore, this embodiment also includes a fourth heat exchanger 10, which is used to heat the air supplied by the air supply unit. The heat source inlet of the fourth heat exchanger 10 is connected to the heat source outlet of the second heat exchanger 8. The air supplied by the air supply unit is heated by the fourth heat exchanger 10 and then heated again by the third heat exchanger 9.

[0046] A fourth heat exchanger 10 is installed in the air supply path to preheat the air using the waste heat of the flue gas from the burner 1 after passing through the second heat exchanger 8. This, together with the third heat exchanger 9 which is heated by the gas from the cathode outlet, forms a two-stage air preheating system. This system achieves in-depth mining and tiered utilization of the thermal energy of the flue gas from the burner 1. While significantly reducing the external energy consumption for air preheating, it also ensures a stable increase in air temperature, reduces the thermal gradient and thermal stress inside the SOFC stack 2, and further improves the system's thermal integration level and overall thermal efficiency.

[0047] Furthermore, the air supply unit includes an air supply main pipeline, an air supply bypass, a fan 11, a buffer tank 12, a first pressure reducing valve 13, a third shut-off valve 14, and a first flow meter 15. The air supply main pipeline is provided with the fan 11, buffer tank 12, first pressure reducing valve 13, third shut-off valve 14, first flow meter 15, fourth heat exchanger 10, and third heat exchanger 9 in sequence along the air flow direction. The air supply main pipeline is connected to the air supply bypass through a three-way valve 16, which is located between the fourth heat exchanger 10 and the flow meter. The end of the air supply bypass away from the three-way valve 16 is connected to the air supply main pipeline, and the connection point is located between the fourth heat exchanger 10 and the third heat exchanger 9. The air supply main pipeline is connected to the cathode inlet of the SOFC stack 2. The solid oxide fuel cell system with controllable fuel reforming in this embodiment also includes a condenser 17, and the cold source inlet of the condenser 17 is connected to the heat source outlet of the fourth heat exchanger 10.

[0048] The air supply unit stabilizes the air supply pressure through the buffer tank 12 and the first pressure reducing valve 13. Combined with the three-way valve 16 and the bypass design, it enables flexible adjustment of the preheated air temperature, ensuring that the air temperature at the cathode inlet of the SOFC stack 2 is stable and controllable. Taking ammonia as fuel as an example, when the system operates in direct ammonia mode or the ammonia decomposition rate is low, since ammonia mainly undergoes an endothermic ammonia decomposition reaction in the SOFC stack 2, the air flow requirement of the SOFC stack 2 is reduced. After setting the three-way valve 16, the air can directly bypass the fourth heat exchanger 10, avoiding excessively high air temperature entering the cathode of the SOFC stack 2.

[0049] Meanwhile, a condenser 17 is installed after the fourth heat exchanger 10, which can further recover low-grade heat and latent heat in the flue gas of the burner 1, realizing full-process stepped heat recovery from high temperature to near ambient temperature, significantly improving the overall thermal efficiency and comprehensive utilization level of thermal energy of the system.

[0050] Furthermore, the fuel supply unit includes a fuel supply pipeline, a fuel storage tank 18, a second pressure reducing valve 19, a fourth shut-off valve 20, and a second flow meter 21. Along the fuel delivery direction, the second pressure reducing valve 19, the fourth shut-off valve 20, and the second flow meter 21 are sequentially installed on the fuel supply pipeline. The inlet of the fuel supply pipeline is connected to the fuel storage tank 18, and the inlet of the direct supply branch and the inlet of all reforming reaction branches are connected to the outlet of the fuel supply pipeline.

[0051] The fuel supply unit ensures stable fuel pressure through the second pressure reducing valve 19, and, in conjunction with the fourth shut-off valve 20 and the second flow meter 21, achieves precise on / off control and quantitative regulation of fuel supply, providing a stable and reliable fuel input foundation for the core reforming reaction and the electrochemical reaction of the fuel cell stack. This centralized feeding and multi-branch distribution structure not only simplifies pipeline layout and reduces leakage risk and cost, but also provides a precise flow control premise for the system to flexibly switch and allocate different fuel paths (direct supply or reforming at each stage) according to load changes, thereby improving the operational stability, regulation accuracy and safety of the entire system.

[0052] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art will be able to make various obvious changes, readjustments, and substitutions without departing from the scope of protection of the present invention. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A solid oxide fuel cell system with controllable fuel reforming, characterized in that, The system includes a fuel supply unit, a decomposition reaction unit, a direct supply branch, an air supply unit, a burner, and an SOFC stack. The decomposition reaction unit includes multiple reforming reaction branches, each with its inlet connected to the outlet of the fuel supply unit. Each reforming reaction branch is equipped with a first shut-off valve and a reforming reactor. All the reforming reactors are connected in series, with the outlet of the downstream reforming reactor connected to the anode inlet of the SOFC stack. The direct supply branch is equipped with a second shut-off valve, and its inlet is connected to the outlet of the fuel supply unit. The outlet of the air supply unit is connected to the cathode inlet of the SOFC stack. Both the anode outlet and cathode outlet of the SOFC stack are connected to the air inlet of the burner. The heat generated by the burner is sequentially supplied to each of the reforming reactors to provide heat to them.

2. The solid oxide fuel cell system with controllable fuel reforming according to claim 1, characterized in that, Along the flow direction of the fuel, the catalytic activity of the catalyst in each of the reforming reactors gradually increases.

3. The solid oxide fuel cell system with controllable fuel reforming according to claim 2, characterized in that, The number of reforming reaction branches is three, corresponding to the number of three reforming reactors. The catalyst in the upstream reforming reactor is Ni / SiC, the catalyst in the downstream reforming reactor is Ru / CeO2, and the catalyst in the other reforming reactor is Ni / ZrO2.

4. The solid oxide fuel cell system with controllable fuel reforming according to claim 1, characterized in that, It also includes a first heat exchanger, which is provided in the direct supply branch and each of the reforming reaction branches. Adjacent first heat exchangers are connected in series. The anode outlet of the SOFC stack is connected to the heat source inlet of the upstream first heat exchanger, and the heat source outlet of the downstream first heat exchanger is connected to the air inlet of the burner.

5. The solid oxide fuel cell system with controllable fuel reforming according to claim 4, characterized in that, It also includes a steam-water separator. The heat source outlet of the first heat exchanger located at the downstream end is connected to the steam-water separator. The gas after steam-water separation is transported to the air inlet of the burner, and the liquid after steam-water separation is discharged.

6. The solid oxide fuel cell system with controllable fuel reforming according to claim 4, characterized in that, It also includes a second heat exchanger, which is disposed on the direct supply branch and is used to heat the fuel transported by the direct supply branch. The heat generated by the burner is transported to the downstream reforming reactor and then to the second heat exchanger.

7. The solid oxide fuel cell system with controllable fuel reforming according to claim 6, characterized in that, It also includes a third heat exchanger, which is used to heat the air supplied by the air supply unit. The cathode outlet of the SOFC stack is connected to the heat source inlet of the third heat exchanger, and the heat source outlet of the third heat exchanger is connected to the air inlet of the burner.

8. The solid oxide fuel cell system with controllable fuel reforming according to claim 7, characterized in that, It also includes a fourth heat exchanger, which is used to heat the air supplied by the air supply unit. The heat source inlet of the fourth heat exchanger is connected to the heat source outlet of the second heat exchanger. The air supplied by the air supply unit is heated by the fourth heat exchanger and then heated again by the third heat exchanger.

9. The solid oxide fuel cell system with controllable fuel reforming according to claim 8, characterized in that, The air supply unit includes an air supply main line, an air supply bypass, a fan, a buffer tank, a first pressure reducing valve, a third shut-off valve, and a first flow meter. The air supply main line is provided with the fan, the buffer tank, the first pressure reducing valve, the third shut-off valve, the first flow meter, the fourth heat exchanger, and the third heat exchanger in sequence along the air flow direction. The air supply main line is connected to the air supply bypass through a three-way valve, which is located between the fourth heat exchanger and the flow meter. The end of the air supply bypass away from the three-way valve is connected to the air supply main line, and the connection point is located between the fourth heat exchanger and the third heat exchanger. The air supply main line is connected to the cathode inlet of the SOFC stack. It also includes a condenser, the cold source inlet of which is connected to the heat source outlet of the fourth heat exchanger.

10. The solid oxide fuel cell system with controllable fuel reforming according to any one of claims 1 to 9, characterized in that, The fuel supply unit includes a fuel supply pipeline, a fuel storage tank, a second pressure reducing valve, a fourth shut-off valve, and a second flow meter. Along the fuel delivery direction, the second pressure reducing valve, the fourth shut-off valve, and the second flow meter are sequentially arranged on the fuel supply pipeline. The inlet of the fuel supply pipeline is connected to the fuel storage tank, and the inlet of the direct supply branch and the inlets of all the reforming reaction branches are connected to the outlet of the fuel supply pipeline.

Images