SOFC (Solid Oxide Fuel Cell) system with high-temperature anode tail gas circulation and operation method

Abstract

The invention provides an SOFC (solid oxide fuel cell) system with high-temperature anode tail gas circulation and an operation method, and belongs to the field of fixed oxide fuel cells. The system comprises a mixing cavity, a reformer, a burner, a heat exchanger and a galvanic pile, the galvanic pile comprises an anode end and a cathode end, the anode end is connected with the burner and the mixing cavity, one part of anode tail gas enters the burner to burn and heat, and the other part of the anode tail gas enters the mixing cavity to be mixed with fuel gas and then enters the galvanic pile through the reformer to be subjected to electrochemical reaction. By adopting the SOFC system with high-temperature anode tail gas circulation and the operation method provided by the embodiment of the invention, the problem of low utilization rate of fuel in the prior art can be solved.

Description

Technical Field

[0001] The present invention relates to the field of solid oxide fuel cells, and particularly to a SOFC system with high-temperature anode exhaust gas circulation and an operation method thereof. Background Art

[0002] For solid oxide fuel cells, since the fuel utilization rate of the stack cannot reach 100%, and combustible gases cannot be directly discharged into the atmosphere, the treatment of the unreacted fuel gas at the anode outlet of the stack is crucial.

[0003] In the prior art, usually all the anode exhaust gas is introduced into a burner for combustion, and the heat energy generated in the burner maintains the high-temperature reaction environment required by the equipment in the SOFC system, so as to make full use of the fuel gas introduced into the SOFC system. However, in some cases, when the high-temperature environment required by the SOFC has been reached, excessive anode exhaust gas is introduced into the burner for combustion, which may result in a low combustion utilization rate of the anode exhaust gas.

[0004] In the prior art, the method of recycling the anode exhaust gas directly introduces all the anode exhaust gas into the burner for combustion heating. When the temperature of the SOFC system has reached a certain high temperature, all the anode exhaust gas is still continuously introduced into the burner for combustion heating, resulting in a low fuel utilization rate. Summary of the Invention

[0005] Embodiments of the present invention provide a SOFC system with high-temperature anode exhaust gas circulation and an operation method thereof, which can solve the problem of low fuel utilization rate in the prior art. The technical solutions are as follows:

[0006] In a first aspect, a SOFC system with high-temperature anode exhaust gas circulation includes: a mixing chamber, a reformer, a burner, a heat exchanger, and a stack.

[0007] The stack includes an anode end and a cathode end. The mixing chamber is connected to the reformer, the reformer is connected to the anode end, and the heat exchanger is connected to the cathode end.

[0008] One side of the anode end is used to connect to a fuel gas supply end, and the other end is respectively connected to the burner and the mixing chamber. One side of the cathode end is used to connect to an air supply end, and the other side is connected to the burner.

[0009] Optionally, a first inlet of the mixing chamber, a second inlet of the mixing chamber, and a first outlet of the mixing chamber are provided on the mixing chamber. The reformer includes a reaction end and a heating end. A reformer reaction end inlet, a reformer reaction end outlet, a reformer heating end inlet, and a reformer heating end outlet are provided on the reformer. A first inlet of the burner, a second inlet of the burner, and a first outlet of the burner are provided on the burner. The heat exchanger includes a hot fluid end and a cold fluid end. A heat exchanger hot fluid end inlet, a heat exchanger hot fluid end outlet, a heat exchanger cold fluid end inlet, and a heat exchanger cold fluid end outlet are provided on the heat exchanger. The fuel cell stack includes an anode end and a cathode end. The first inlet of the mixing chamber is used to connect to a gas source. The first outlet of the mixing chamber is connected to the reformer reaction end inlet. The reformer reaction end outlet is connected to the anode end. The anode end is respectively connected to the first inlet of the burner and the second inlet of the mixing chamber. The heat exchanger cold fluid end inlet is used to connect to an air source. The heat exchanger cold fluid end outlet is connected to the cathode end. The cathode end is connected to the second inlet of the burner. The first outlet of the burner is connected to the reformer heating end inlet. The reformer heating end outlet is connected to the heat exchanger hot fluid end inlet. The heat exchanger hot fluid end outlet is used to connect to the outside. A circulation pump is provided between the anode end and the second inlet of the mixing chamber.

[0010] Optionally, a temperature sensor is provided at the first outlet of the burner. The temperature sensor is in signal connection with the circulation pump.

[0011] Optionally, a hydrogen concentration sensor is provided at the second inlet of the burner. The hydrogen concentration sensor is in signal connection with the circulation pump.

[0012] Optionally, a water evaporator is further included. A first inlet of the water evaporator reaction end, a second inlet of the water evaporator reaction end, and an outlet of the water evaporator reaction end are provided on the water evaporator. The first inlet of the water evaporator reaction end is used to connect to a gas source. The outlet of the water evaporator reaction end is connected to the first inlet of the mixing chamber. The second inlet of the water evaporator reaction end is used to connect to a water source.

[0013] Optionally, a water evaporator heating end inlet and a water evaporator heating end outlet are further provided on the water evaporator. The water evaporator heating end inlet is connected to the heat exchanger hot fluid end outlet. The water evaporator heating end outlet is used to connect to the outside.

[0014] Optionally, a third inlet of the burner is further provided on the burner. The third inlet of the burner is used to connect to a gas source.

[0015] Optionally, a regulating valve is provided between the anode end and the second inlet of the mixing chamber.

[0016] Optionally, an air purifier is provided at the front end of the heat exchanger cold fluid end inlet.

[0017] In a second aspect, a method for operating an SOFC system with high-temperature anode exhaust gas circulation includes the aforementioned SOFC system with high-temperature anode exhaust gas circulation, and further includes the following steps:

[0018] Step 1: Introduce fuel gas into the mixing chamber. The fuel gas passes through the mixing chamber, the reformer, and the anode end to reach the burner. Introduce air into the heat exchanger. The air passes through the heat exchanger and the cathode end to reach the burner, and ignite the mixed gas in the burner.

[0019] Step 2: The high-temperature combustion exhaust gas generated in the burner is discharged after passing through the reformer and the heat exchanger. The high-temperature combustion exhaust gas heats the reformer and the heat exchanger. Subsequently, the air entering the heat exchanger is heated and then introduced into the stack to heat the cathode end, and the fuel gas introduced into the stack from the reformer heats the anode end.

[0020] Step 3: After the stack reaches the reaction temperature, the stack starts to undergo an electrochemical reaction, generating anode exhaust gas at the anode end. The anode exhaust gas is unreacted fuel gas. Part of the anode exhaust gas enters the burner for combustion to supply heat, and the other part enters the mixing chamber to mix with the fuel gas and continue the electrochemical reaction.

[0021] The beneficial effects brought by the technical solution provided in the embodiments of the present invention at least include:

[0022] For an SOFC system and an operating method with high-temperature anode exhaust gas circulation provided in the embodiments of the present invention, after the fuel gas and air introduced into the stack undergo an electrochemical reaction at the stack, the remaining anode exhaust gas that has not undergone the reaction still contains fuel gas. Part of the anode exhaust gas is connected to the burner through the first inlet of the burner, so that the fuel gas enters the burner for combustion to generate heat and supply heat to the reformer and the stack; the other part enters the mixing chamber through the second inlet of the mixing chamber and mixes with the newly introduced fuel gas in the mixing chamber, and is used again as the gas raw material for the reaction at the anode of the stack to re-enter the electrochemical reaction. Through this setting, in the SOFC system, part of the anode exhaust gas can be introduced into the burner for combustion to supply heat to the system, and the other part of the anode exhaust gas can be returned to the stack through the mixing chamber for electrochemical reaction, which can effectively solve the problem of low fuel utilization rate in the prior art. Description of the Drawings

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0024] Figure 1 It is a schematic diagram of the system principle provided by the embodiment of the present invention;

[0025] Figure 2 It is a schematic diagram of signal transmission provided by the embodiment of the present invention;

[0026] Figure 3 It is a flowchart of the method provided by the embodiment of the present invention.

[0027] In the figure: 1 - mixing chamber; 11 - first inlet of the mixing chamber; 12 - second inlet of the mixing chamber; 13 - first outlet of the mixing chamber; 2 - reformer; 21 - inlet of the reaction end of the reformer; 22 - outlet of the reaction end of the reformer; 23 - inlet of the heating end of the reformer; 24 - outlet of the heating end of the reformer; 3 - burner; 31 - first inlet of the burner; 32 - second inlet of the burner; 33 - first outlet of the burner; 34 - third inlet of the burner; 4 - heat exchanger; 41 - inlet of the hot fluid end of the heat exchanger; 42 - outlet of the hot fluid end of the heat exchanger; 43 - inlet of the cold fluid end of the heat exchanger; 44 - outlet of the cold end of the heat exchanger; 5 - fuel cell stack; 51 - anode end; 52 - cathode end; 61 - circulation pump; 62 - regulating valve; 71 - temperature sensor; 72 - hydrogen concentration sensor; 8 - water evaporator; 81 - first inlet of the reaction end of the water evaporator; 82 - second inlet of the reaction end of the water evaporator; 83 - outlet of the reaction end of the water evaporator; 84 - inlet of the heating end of the water evaporator; 85 - outlet of the heating end of the water evaporator; 9 - air purifier. Specific Embodiments

[0028] To make the objectives, technical solutions and advantages of the present invention clearer, the following will further describe the embodiments of the present invention in detail with reference to the drawings.

[0029] Figure 1 It is a schematic diagram of the system principle provided by the embodiment of the present invention; Figure 2 It is a schematic diagram of signal transmission provided by the embodiment of the present invention; Figure 3 It is a flowchart of the method provided by the embodiment of the present invention. As Figures 1 to 3An SOFC system with high-temperature anode exhaust gas recycling is shown, including: a mixing chamber 1, a reformer 2, a burner 3, a heat exchanger 4, and an electric stack 5. The electric stack 5 includes an anode end 51 and a cathode end 52. The mixing chamber 1 is connected to the reformer 1, the reformer 2 is connected to the anode end 51, the heat exchanger 4 is connected to the cathode end 52. One side of the anode end 51 is used to connect to a fuel gas supply end, and the other end is respectively connected to the burner 3 and the mixing chamber 1. One side of the cathode end 52 is used to connect to an air supply end, and the other side is connected to the burner 3.

[0030] Exemplarily, in the embodiment of the present invention, in the initial ignition step, fuel gas is continuously introduced into the mixing chamber through the first inlet 11 of the mixing chamber, and then passes through the first outlet 13 of the mixing chamber, the reformer reaction end inlet 21, the reformer reaction end outlet 22, the anode end 51, and the first inlet 31 of the burner to reach the burner 3. Air is continuously introduced into the cold flow end inlet 43 of the heat exchanger. The air passes through the cold flow end outlet 44 of the heat exchanger, the cathode end 52, and the second inlet 32 of the burner to reach the burner 3. At this time, the fuel gas and air meet in the burner 3 to ignite the burner. The high-temperature exhaust gas generated by the combustion of the burner 3 is discharged after passing through the first outlet 33 of the burner, the reformer heating end inlet 23, the reformer heating end outlet 24, the hot flow end inlet 41 of the heat exchanger, and the hot flow end outlet 42 of the heat exchanger. The high-temperature combustion exhaust gas heats the reformer 2 and the heat exchanger 4. Subsequently, the air entering from the cold flow end inlet 43 of the heat exchanger is heated by the heat exchanger 4 and then heats the electric stack 5. After the fuel gas is heated in the reformer 2, it is also introduced into the electric stack 5 to heat the electric stack 5, and finally the electric stack 5 gradually reaches the reaction temperature of the electrochemical reaction. When the electric stack 5 reaches the reaction temperature, when the fuel gas and air pass through the electric stack 5, an electrochemical reaction will occur to generate electric energy. After the reaction is completed, some of the reaction gases will not participate in the reaction. At this time, the anode exhaust gas coming out of the anode end 51 still contains fuel gas. Part of the anode exhaust gas enters the burner 3 through the first inlet 31 of the burner for combustion heat supply, continuously heating the reformer 2 and the heat exchanger 4 to make the reformer 2 and the electric stack 5 reach the reaction temperature; another part of the anode exhaust gas enters the mixing chamber 1 through the second inlet 12 of the mixing chamber and is mixed with the fuel gas continuously introduced into the mixing chamber 1, and then the mixed gas is sent to the electric stack 5 through the reformer 2 and continues to be used as the reaction gas for the electrochemical reaction. Through this setting, the anode exhaust gas can be divided into two parts for utilization. One part of the anode exhaust gas is introduced into the burner 3 for combustion to supply heat to the system, and the other part of the anode exhaust gas is returned to the electric stack 5 through the mixing chamber 1 for electrochemical reaction, so as to make full use of the fuel gas part in the anode exhaust gas.

[0031] An SOFC system with high-temperature anode exhaust gas circulation and an operation method provided by an embodiment of the present invention. After the fuel gas and air introduced into the fuel cell stack 5 undergo an electrochemical reaction at the fuel cell stack 5, the remaining anode exhaust gas that has not undergone the reaction still contains fuel gas. A part of the anode exhaust gas is connected to the burner 3 through the first inlet 31 of the burner, so that the fuel gas enters the burner 3 to burn and generate heat, and provides heat for the reformer 2 and the fuel cell stack 5; another part enters the mixing chamber 1 through the second inlet 12 of the mixing chamber, and is mixed with the newly introduced fuel gas into the mixing chamber 1, and is used again as the gas raw material for the reaction at the anode of the fuel cell stack 5 to re-perform the electrochemical reaction. Through this setting, in the SOFC system, a part of the anode exhaust gas can be introduced into the burner 3 for combustion to provide heat for the system, and another part of the anode exhaust gas can be returned to the fuel cell stack 5 through the mixing chamber 1 for electrochemical reaction, which can effectively solve the problem of low fuel utilization rate in the prior art.

[0032] Optionally, the mixing chamber 1 is provided with a first inlet 11, a second inlet 12 and a first outlet 13 of the mixing chamber. The reformer 2 includes a reaction end and a heating end. The reformer 2 is provided with a reformer reaction end inlet 21, a reformer reaction end outlet 22, a reformer heating end inlet 23 and a reformer heating end outlet 24. The burner 3 is provided with a first inlet 31, a second inlet 32 and a first outlet 33 of the burner. The heat exchanger 4 includes a hot flow end and a cold flow end. The heat exchanger 4 is provided with a heat exchanger hot flow end inlet 41, a heat exchanger hot flow end outlet 42, a heat exchanger cold flow end inlet 43 and a heat exchanger cold flow end outlet 44. The fuel cell stack 5 includes an anode end 51 and a cathode end 52. The first inlet 11 of the mixing chamber is used to connect with the fuel gas source. The first outlet 13 of the mixing chamber is connected to the reformer reaction end inlet 21. The reformer reaction end outlet 22 is connected to the anode end 51. The anode end 51 is respectively connected to the first inlet 31 of the burner and the second inlet 12 of the mixing chamber. The heat exchanger cold flow end inlet 43 is used to connect with the air source. The heat exchanger cold flow end outlet 44 is connected to the cathode end 52. The cathode end 52 is connected to the second inlet 32 of the burner. The first outlet 33 of the burner is connected to the reformer heating end inlet 23. The reformer heating end outlet 24 is connected to the heat exchanger hot flow end inlet 41. The heat exchanger hot flow end outlet 42 is used to connect with the outside. A circulation pump 61 is provided between the anode end 51 and the second inlet 12 of the mixing chamber.

[0033] Exemplarily, in an embodiment of the present invention, by providing a circulation pump 61, the distribution ratio of the anode tail gas can be adjusted. When the temperature of the burner 3 has reached a relatively high temperature, the power of the circulation pump 61 is increased, so that more anode tail gas is introduced into the mixing chamber 1 for mixing, so that more of the fuel part in the anode tail gas participates in the electrochemical reaction for power generation. When the temperature of the burner 3 drops to a certain level and may no longer be able to maintain the reaction temperature of the system, the power of the circulation pump 61 is reduced at this time, so that more anode tail gas is introduced into the burner 3 for combustion and heat generation, thereby maintaining the reaction temperature of the system. By providing the circulation pump 61, the distribution of the anode tail gas can be regulated according to the current temperature of the system, so that the gas part in the anode tail gas can be further fully utilized, and the gas utilization rate of the present system is further improved.

[0034] Optionally, a temperature sensor 71 is provided at the first outlet 33 of the burner, and the temperature sensor 71 is in signal connection with the circulation pump 61.

[0035] Exemplarily, in an embodiment of the present invention, by providing a temperature sensor 71 at the first outlet 33 of the burner, the temperature of the high-temperature tail gas coming out of the burner 3 can be measured. Under normal circumstances, in order to maintain the temperature of 650 °C required by the stack 5, the required temperature of the high-temperature tail gas coming out of the burner 3 is 780 - 820 °C. When the temperature sensor 71 detects that the temperature of the high-temperature tail gas is within the temperature target value range of 780 - 820 °C, there is no need to change the circulation power of the circulation pump 61. When the temperature sensor 71 detects that the temperature is higher than this range, a signal is transmitted to the circulation pump 61, so that the power of the circulation pump 61 becomes larger, so that more anode tail gas is introduced into the mixing chamber 1 for subsequent electrochemical reactions. When the temperature sensor 71 detects that the temperature is lower than this range, a signal is transmitted to the circulation pump 61, so that the power of the circulation pump 61 becomes smaller, so that more anode tail gas is introduced into the burner 3 for combustion, thereby maintaining the target temperature range. By providing the temperature sensor 71, automatic control of the circulation pump 61 can be realized, so as to more accurately distribute the gas in the anode tail gas, thereby further improving the gas utilization rate of the present system.

[0036] Optionally, a hydrogen concentration sensor 72 is provided at the second inlet 32 of the burner, and the hydrogen concentration sensor 72 is in signal connection with the circulation pump 61.

[0037] Exemplarily, in the embodiment of the present invention, in the anode tail gas, most of the fuel gas for combustion is hydrogen. By providing a hydrogen concentration sensor 72 at the second inlet 32 of the burner, the hydrogen concentration entering the burner 3 can be detected. Since there is a concentration range for hydrogen to maintain combustion, below this value, combustion will not occur and the flame will go out. When the hydrogen concentration sensor 72 detects a low concentration, a signal is transmitted to the circulation pump 61 to reduce the power, so that more anode tail gas is introduced into the burner 3 for combustion heating, thereby stably maintaining the reaction temperature of the system.

[0038] Optionally, it further includes a water evaporator 8. The water evaporator 8 is provided with a first inlet 81 of the reaction end of the water evaporator, a second inlet 82 of the reaction end of the water evaporator, and an outlet 83 of the reaction end of the water evaporator. The first inlet 81 of the reaction end of the water evaporator is used to connect to a fuel gas source, the outlet 83 of the reaction end of the water evaporator is connected to the first inlet 11 of the mixing chamber, and the second inlet 82 of the reaction end of the water evaporator is used to connect to a water source.

[0039] Exemplarily, in the embodiment of the present invention, by providing the water evaporator 8, steam reforming can be adopted in the system. The anode tail gas also includes water vapor generated by the electrochemical reaction in the fuel cell stack 5. By adopting the steam reforming technology, the water vapor part in the anode tail gas can be fully utilized, thereby making more full use of the anode tail gas. When the fuel cell stack 5 is just started, the electrochemical reaction has not occurred yet. At this time, it is necessary to replenish water through an external water source to enable the fuel gas introduced to undergo a steam reforming reaction in the reformer 2. During the startup stage, since the anode end 51 of the fuel cell stack 5 was exposed to the air before startup and contains some oxygen, it will cause the noble metal catalyst at the anode end 51 to undergo an oxidation reaction at high temperature, resulting in the failure of the fuel cell stack 5. By using the water vapor introduced from the second inlet 82 of the reaction end of the water evaporator to purge the anode end 51 of the fuel cell stack 5, the noble metal catalyst at the anode end 51 is prevented from being oxidized by air. Compared with the prior art that uses nitrogen purging, the external nitrogen cylinder is cancelled, thus simplifying the overall system configuration and reducing the production cost.

[0040] Optionally, the water evaporator 8 is further provided with a heating end inlet 84 and a heating end outlet 85 of the water evaporator. The heating end inlet 84 of the water evaporator is connected to the outlet 42 of the heat flow end of the heat exchanger, and the heating end outlet 85 of the water evaporator is used to connect to the outside.

[0041] Exemplarily, in the embodiment of the present invention, by providing the inlet 84 of the heating end of the water evaporator and the outlet 85 of the heating end of the water evaporator, the high-temperature tail gas coming out of the outlet 42 of the heat flow end of the heat exchanger can heat the water evaporator 8. When it is necessary to introduce water vapor into the water evaporator 8, it can be changed to introduce deionized water into the water evaporator 8. When the high-temperature tail gas passes through the water evaporator 8, it heats the deionized water, causing the deionized water to become water vapor. In the external environment, water vapor is more difficult to store and collect than liquid water. Therefore, compared with directly introducing water vapor from the outside, this setting can make more full use of the heat in the high-temperature tail gas, thereby simplifying the process in this system.

[0042] Optionally, a third inlet 34 of the burner is further provided on the burner 3, and the third inlet 34 of the burner is used to connect to a gas source.

[0043] Exemplarily, in the embodiment of the present invention, by providing the third inlet 34 of the burner, gas can be provided for the burner 3 alone. During the startup phase, gas can be directly introduced into the burner 3 through the third inlet 34 of the burner, so that there is no need to make the gas circulate in the system structure and then enter the burner 3. Therefore, the startup time of this system can be reduced. On the other hand, during the subsequent power generation cycle reaction, when the fuel in the burner 3 is too low or the temperature is too low, gas can be introduced into the burner 3 through an additional separate line, thereby stably maintaining the reaction temperature of the entire system, and thus improving the stability of this system.

[0044] Optionally, a regulating valve 62 is provided between the positive electrode end 51 and the second inlet 12 of the mixing chamber.

[0045] Exemplarily, in the embodiment of the present invention, by providing a regulating valve 62 between the positive electrode end 51 and the second inlet 12 of the mixing chamber, in extreme cases, by closing the regulating valve 62, all the anode tail gas can enter the burner 3 for combustion and heat supply to ensure the reaction temperature of the entire system. In the SOFC system, the reaction temperature is the basis for the electrochemical reaction. In extreme cases, in order to maintain the reaction temperature, the regulating valve 62 can be closed, thereby further improving the stability of this system.

[0046] Optionally, an air purifier 9 is provided at the front end of the cold flow end inlet 43 of the heat exchanger.

[0047] Exemplarily, in the embodiment of the present invention, the air usually contains many impurities, which may affect the electrochemical reaction of the stack 5. By providing the air purifier 9, the impurities in the sucked air can be removed, thereby ensuring the purity of the reaction gas and further improving the stability of this system.

[0048] An operating method for a SOFC system with high-temperature anode exhaust gas circulation, including the aforementioned SOFC system with high-temperature anode exhaust gas circulation, further includes the following steps:

[0049] S1: Introduce fuel gas into the mixing chamber 1. The fuel gas passes through the mixing chamber 1, reformer 2, and anode end 51 and reaches the burner 3. Introduce air into the heat exchanger 4. The air passes through the heat exchanger 4 and cathode end 52 and reaches the burner 3, and ignite the mixed gas in the burner 3;

[0050] S2: The high-temperature combustion exhaust gas generated in the burner 3 is discharged after passing through the reformer 2 and heat exchanger 4. The high-temperature combustion exhaust gas heats the reformer 2 and heat exchanger 4. Subsequently, the air entering the heat exchanger 4 is heated and then introduced into the stack 5 to heat the cathode end 52, and the fuel gas introduced into the stack 5 from the reformer 2 heats the anode end 51;

[0051] S3: After the stack 5 reaches the reaction temperature, the stack 5 starts to undergo an electrochemical reaction, generating anode exhaust gas at the anode end 51. The anode exhaust gas is unreacted fuel gas. Part of the anode exhaust gas enters the burner 3 for combustion heating, and the other part enters the mixing chamber 1 to mix with the fuel gas and continue the electrochemical reaction.

[0052] Specifically, in the embodiment of the present invention, the first stage is the start-up heating stage. The channel for introducing fuel gas into the first inlet 81 at the reaction end of the water evaporator is closed, and the channel for introducing liquid water into the second inlet 82 at the reaction end of the water evaporator is closed. The third inlet 34 of the burner is opened, and fuel gas is introduced from an external fuel gas source. The fuel gas enters the burner 3. At the same time, the cold-side inlet 43 of the heat exchanger is opened, and air is introduced from an external air source. The air flows through the air purifier 9, then through the heat exchanger 4 and the cathode end 52 and finally reaches the burner 3. At this time, since the system temperature is at room temperature, the inflow of air into the system will not cause the oxidation problem of the catalyst of the fuel cell stack 5. The fuel gas is ignited in the burner 3 by an ignition device, so that the burner 3 is quickly heated up. After reaching a certain temperature, the ignition device can be turned off, and the fuel gas and air burn freely to increase the temperature. The high-temperature exhaust gas is respectively introduced into the reformer 2, the heat exchanger 4 and the water evaporator 8 through the first outlet 33 of the burner, so that the reformer 2, the heat exchanger 4 and the water evaporator 8 are quickly heated up. During this process, the clean air passing through the heat exchanger 4 and the fuel gas heated by the reformer 2 are introduced into the fuel cell stack 5, so that the fuel cell stack 5 gradually reaches the temperature required for power generation. The second stage is the purging stage. The channel for introducing fuel gas into the first inlet 81 at the reaction end of the water evaporator is closed, the channel for introducing liquid water into the second inlet 82 at the reaction end of the water evaporator is opened, the third inlet 34 of the burner is opened, and fuel gas is introduced from an external fuel gas source. The cold-side inlet 43 of the heat exchanger is opened, and air is introduced from an external air source. During the start-up heating, due to the continuous heating of the fuel cell stack 5 by the hot air flowing through the cathode end 52 of the fuel cell stack 5, the temperature of the anode end 51 of the fuel cell stack 5 will also gradually increase. When reaching a certain specific high temperature value, due to the oxygen contained in the air exposed before starting in the anode of the fuel cell stack 5, the noble metal of the anode catalyst will undergo an oxidation reaction at high temperature, resulting in the failure of the fuel cell stack 5. At this time, it is necessary to open the second inlet 82 at the reaction end of the water evaporator to introduce deionized water. The high-temperature exhaust gas flowing into the water evaporator 8 through the hot-side outlet 42 of the heat exchanger evaporates the liquid water to generate water vapor, and the water vapor purges the air existing in the anode end 51 of the fuel cell stack 5 and the front and rear pipelines, so as to prevent the fuel cell stack 5 from being oxidized during the start-up heating stage.The third stage is the power generation stage. When the fuel cell stack 5 reaches the high-temperature environment required for power generation, the third inlet 34 of the burner is closed, the second inlet 82 of the reaction end of the water evaporator is closed, and the first inlet 81 of the reaction end of the water evaporator is opened. The inlet 43 of the cold flow end of the heat exchanger remains open. The first inlet 81 of the reaction end of the water evaporator continuously supplies the fuel gas required for power generation, and the inlet 43 of the cold flow end of the heat exchanger continuously supplies the air required for power generation. The circulation pump 61 is turned on, and through a specific anode exhaust gas circulation ratio, a part of the anode exhaust gas flows into the mixing chamber 1 through the circulation pump 61 for reuse, and the other part of the anode exhaust gas flows into the burner 3 for combustion to ensure the exhaust gas temperature at the first outlet 33 of the burner, and then the high-temperature environment required by the system is maintained through the multiple heat exchange structures. At this time, the system reaches a stable and efficient power generation state, and the system itself can maintain the balance of temperature and reformed water vapor. Moreover, the power of the circulation pump 61 can be adjusted through the temperature sensor and the hydrogen concentration sensor, so that the distribution of the anode exhaust gas is more reasonable, and the fuel utilization rate is improved as much as possible.

[0053] The solid oxide fuel cell system with high-temperature anode exhaust gas circulation and its operation method provided by this design directly circulate the anode exhaust gas of the fuel cell stack 5 to the mixing chamber 1 at the front end of the reformer 2, and reuse the unreacted fuel gas. The recycling of the fuel gas significantly improves the fuel utilization rate and power generation efficiency of the SOFC system, and the circulation of the high-temperature gas also provides the heat required for steam reforming and power generation, improving the thermal efficiency of the system; the circulated exhaust gas also contains the water vapor which is the electrochemical reaction product of the fuel cell stack 5, which makes it no longer necessary to additionally introduce deionized water or steam to be condensed and then evaporated to meet steam reforming during the stable power generation stage of the system, which also reduces the complexity of the system, the makeup water volume and the volume of the makeup water tank.

[0054] In this system, it is not necessary to generate exhaust gas and high-temperature steam through an additional first group of fuel cell stacks for the start-up of the second group of fuel cell stacks, which greatly reduces the manufacturing cost and overall volume of the system, and is more conducive to the mass production and application of SOFC. During the start-up stage, the high-temperature exhaust gas is used to evaporate the liquid water, and then the water vapor required for steam reforming is satisfied, without the need to increase additional electric heating equipment, reducing the power consumption during start-up and the cost of the external power supply. During the start-up stage, the generated water vapor can also be used to purge the anode of the fuel cell stack to avoid the oxidation of the noble metal catalyst at the anode by air. Compared with the mainstream technology that uses nitrogen for purging, the external nitrogen cylinder and the cost of using nitrogen are eliminated. By controlling the specific ratio of the anode exhaust gas circulation through the circulation pump, it is easier to achieve the coupled control of the system in terms of the recycling of the exhaust gas and the combustion of the exhaust gas to maintain the high-temperature environment required for system power generation. Moreover, the reformer technology with integrated heat exchange function also reduces the use of heat exchangers, reducing the overall volume and cost of the system.

[0055] Unless otherwise defined, technical terms or scientific terms used herein shall have the ordinary meanings as understood by those of ordinary skill in the art to which this invention pertains. The terms "first", "second" and similar terms used in the description and claims of this patent application for invention do not denote any order, quantity or importance, but are only used to distinguish different components. Similarly, terms such as "a" or "an" do not denote a limitation of quantity, but rather indicate the presence of at least one. The terms "comprising" or "including" and similar terms mean that the elements or items appearing before "comprising" or "including" cover the elements or items listed after "comprising" or "including" and their equivalents, and do not exclude other elements or items. The terms "connected" or "coupled" and similar terms are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The terms "upper", "lower", "left", "right" etc. are only used to indicate relative positional relationships, and when the absolute position of the object being described changes, the relative positional relationships may also change accordingly.

[0056] The foregoing are only optional embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A SOFC system with high-temperature anode exhaust gas recycling, characterized in that, Comprising: A mixing chamber (1), a reformer (2), a burner (3), a heat exchanger (4) and an electrolyzer stack (5), The electrolyzer stack (5) includes an anodic end (51) and a cathodic end (52). The mixing chamber (1) is connected to the reformer (1), the reformer (2) is connected to the anodic end (51), and the heat exchanger (4) is connected to the cathodic end (52). One side of the anodic end (51) is used for connection to a gas supply end, and the other end is respectively connected to the burner (3) and the mixing chamber (1). One side of the cathodic end (52) is used for connection to an air supply end, and the other side is connected to the burner (3).

2. The SOFC system with high-temperature anode exhaust gas circulation according to claim 1, characterized in that The mixing chamber (1) is provided with a first mixing chamber inlet (11), a second mixing chamber inlet (12) and a first mixing chamber outlet (13). The reformer (2) includes a reaction end and a heating end. The reformer (2) is provided with a reformer reaction end inlet (21), a reformer reaction end outlet (22), a reformer heating end inlet (23) and a reformer heating end outlet (24). The burner (3) is provided with a first burner inlet (31), a second burner inlet (32) and a first burner outlet (33). The heat exchanger (4) includes a heat flow end and a cold flow end. The heat exchanger (4) is provided with a heat exchanger heat flow end inlet (41), a heat exchanger heat flow end outlet (42), a heat exchanger cold flow end inlet (43) and a heat exchanger cold flow end outlet (44). The electrolyzer stack (5) includes an anodic end (51) and a cathodic end (52). The first mixing chamber inlet (11) is used for connection to a gas source. The first mixing chamber outlet (13) is connected to the reformer reaction end inlet (21). The reformer reaction end outlet (22) is connected to the anodic end (51). The anodic end (51) is respectively connected to the first burner inlet (31) and the second mixing chamber inlet (12). The heat exchanger cold flow end inlet (43) is used for connection to an air source. The heat exchanger cold flow end outlet (44) is connected to the cathodic end (52). The cathodic end (52) is connected to the second burner inlet (32). The first burner outlet (33) is connected to the reformer heating end inlet (23). The reformer heating end outlet (24) is connected to the heat exchanger heat flow end inlet (41). The heat exchanger heat flow end outlet (42) is used for connection to the outside. A circulation pump (61) is provided between the anodic end (51) and the second mixing chamber inlet (12).

3. The SOFC system with high-temperature anode exhaust gas circulation according to claim 2, characterized in that, A temperature sensor (71) is provided at the first burner outlet (33). The temperature sensor (71) is in signal connection with the circulation pump (61).

4. A SOFC system with high-temperature anode exhaust gas circulation according to claim 3, characterized in that, A hydrogen concentration sensor (72) is provided at the second burner inlet (32). The hydrogen concentration sensor (72) is in signal connection with the circulation pump (61).

5. A SOFC system with high-temperature anode exhaust gas circulation according to claim 2, characterized in that, It further includes a water evaporator (8). A first inlet (81) of the reaction end of the water evaporator, a second inlet (82) of the reaction end of the water evaporator, and an outlet (83) of the reaction end of the water evaporator are arranged on the water evaporator (8). The first inlet (81) of the reaction end of the water evaporator is used for connecting with a gas source. The outlet (83) of the reaction end of the water evaporator is connected to the first inlet (11) of the mixing chamber. The second inlet (82) of the reaction end of the water evaporator is used for connecting with a water source.

6. The SOFC system with high-temperature anode exhaust gas circulation according to claim 5, characterized in that, A heating end inlet (84) and a heating end outlet (85) of the water evaporator are further arranged on the water evaporator (8). The heating end inlet (84) of the water evaporator is connected to the outlet (42) of the heat flow end of the heat exchanger. The heating end outlet (85) of the water evaporator is used for connecting with the outside.

7. A SOFC system with high-temperature anode exhaust gas circulation according to claim 2, characterized in that, A third inlet (34) of the burner is further arranged on the burner (3). The third inlet (34) of the burner is used for connecting with a gas source.

8. A SOFC system with high-temperature anode off-gas circulation according to claim 2, characterized in that A regulating valve (62) is arranged between the positive electrode end (51) and the second inlet (12) of the mixing chamber.

9. A SOFC system with high-temperature anode exhaust gas recycling according to claim 2, characterized in that An air purifier (9) is arranged at the front end of the cold flow end inlet (43) of the heat exchanger.

10. A method for operating an SOFC system with high-temperature anode exhaust gas circulation, including an SOFC system with high-temperature anode exhaust gas circulation as described in claims 1 to 9, characterized in that, It further includes the following steps: Step 1: Introduce gas into the mixing chamber (1). The gas passes through the mixing chamber (1), the reformer (2), and the positive electrode end (51) to reach the burner (3). Introduce air into the heat exchanger (4). The air passes through the heat exchanger (4) and the negative electrode end (52) to reach the burner (3), and ignite the mixed gas in the burner (3). Step 2: The high-temperature combustion exhaust gas generated in the burner (3) is discharged after passing through the reformer (2) and the heat exchanger (4). The high-temperature combustion exhaust gas heats the reformer (2) and the heat exchanger (4). Subsequently, the air entering the heat exchanger (4) is heated and then introduced into the fuel cell stack (5) to heat the negative electrode end (52). The gas introduced from the reformer (2) into the fuel cell stack (5) heats the positive electrode end (51). Step 3: After the fuel cell stack (5) reaches the reaction temperature, the fuel cell stack (5) starts an electrochemical reaction. Anode exhaust gas is generated at the positive electrode end (51). The anode exhaust gas is unreacted gas. Part of the anode exhaust gas enters the burner (3) for combustion heating, and the other part enters the mixing chamber (1) to be mixed with the gas and continue the electrochemical reaction.

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