Fuel cell system, fuel cell generator set and regulation and control method of fuel cell generator set

Abstract

The invention discloses a fuel cell system, a fuel cell generator set and a regulation and control method thereof, and relates to the technical field of fuel cells. The fuel cell system comprises a first-stage electric pile group, a second-stage electric pile group, a fuel supply unit and an air supply unit, wherein a first-stage electric pile in the first-stage electric pile group comprises a first air electrode, a first fuel electrode and a first electrolyte arranged between the first air electrode and the first fuel electrode; and a second-stage electric pile in the second-stage electric pile group comprises a second air electrode, a second fuel electrode and a second electrolyte arranged between the second air electrode and the second fuel electrode. Each of the first fuel electrode and the second fuel electrode comprises an oxide material; and in the first-stage electric pile and the second-stage electric pile, the ratio of the area of the oxide material to the total area of the fuel electrode is 0.005-1. The fuel supply unit provides high-temperature fuel for the first-stage galvanic pile group and the second-stage galvanic pile group through the fuel heater, and the air supply unit provides high-temperature air for the first-stage galvanic pile group and the second-stage galvanic pile group through the air heater.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and particularly to a fuel cell system, a fuel cell power generation set and a control method thereof. Background Art

[0002] A fuel cell is a highly efficient energy conversion device that can directly convert the chemical energy stored in combustible gas into electrical energy. Since it does not require an intermediate conversion from mechanical energy to electrical energy, it has a higher energy conversion efficiency.

[0003] The high-temperature operation of high-temperature fuel cells increases the types of fuels that can be used. High-temperature fuel cells can use carbon fuels such as methane, gasoline, and diesel for power generation. The fuel electrode (anode) of a high-temperature fuel cell is composed of porous nickel metal and zirconia. The support material of the anode-supported cell is the same as the anode material, which is a mixture of nickel metal and zirconia. The thickness of the support is about 500 to 1500 micrometers. The anode functional layer with a thickness of 5 to 50 micrometers is between the support and the electrolyte, and the thickness of the electrolyte is 2 to 30 micrometers. Subsequently, the air electrode (cathode) is coated and sintered on the other side of the electrolyte.

[0004] During the electrochemical reaction process of the fuel electrode, the fuel first diffuses into the porous structure of the electrode and then undergoes an electrochemical reaction. During the operation of the cell or the stack, the upstream part of the fuel inlet usually contains more fuel and has a higher partial pressure during the diffusion to the reaction surface; in the downstream part of the fuel outlet, a large amount of fuel is consumed by the cell, and the large amount of water vapor generated reduces the diffusion partial pressure and diffusion rate of the fuel in the fuel electrode, affecting the chemical reaction of the anode. Therefore, in the actual industrial application process, generally an excessive amount of fuel is introduced to ensure the fuel diffusivity in the downstream of the fuel flow channel, resulting in a low overall fuel utilization rate of the stack. In addition, the heat generated by the electrochemical reaction of the high-temperature fuel cell under high-temperature conditions is carried into the downstream of the fuel flow channel by the fuel fluid. Usually, the downstream of the fuel flow channel has a higher reaction temperature. Water vapor has strong oxidizing properties at high temperatures, so the nickel metal inside the fuel electrode is extremely easy to be oxidized to nickel oxide. The nickel oxide agglomerates and its volume increases by about 60%. Therefore, under the condition of high fuel utilization rate, the fuel electrode is prone to expand and crack at the downstream of the fuel flow channel, resulting in the attenuation of the fuel electrode and the attenuation of the system performance.

[0005] In the prior art, a fuel circulation pump is added to a high-temperature fuel cell system to circulate a part of the tail gas at the outlet of the fuel flow channel of the stack to the inlet of the fuel flow channel. Usually, about 50% to 80% of the fuel tail gas is circulated to the inlet of the fuel flow channel, so that the fuel utilization rate inside the stack can be controlled to be 50% to 70%. There is still a large amount of unconsumed fuel near the support at the outlet of the fuel flow channel of the stack, which can increase the diffusion of fuel in the support and the functional layer. A large amount of fuel also inhibits the oxidation of nickel metal inside the support at the outlet of the fuel flow channel. At the same time, due to the presence of the fuel circulation pump, the overall fuel utilization rate of the high-temperature fuel cell system can be increased to more than 80%, greatly improving the system efficiency. However, adding a fuel circulation pump to the high-temperature fuel cell system greatly increases the complexity of the high-temperature fuel cell system. The fuel circulation pump operates under high-temperature conditions, and hydrogen and water vapor in the fuel easily corrode the blades and bearings of the fuel circulation pump, resulting in fuel leakage. Considering the long-term operation of the high-temperature fuel cell system, the use of the circulation pump increases the maintenance cost of the high-temperature fuel cell system. Summary of the Invention

[0006] The purpose of the present invention is to provide a fuel cell system, a fuel cell power generation unit and a control method thereof, which can improve the fuel utilization rate and power generation efficiency of the fuel cell system without increasing the maintenance cost.

[0007] To achieve this purpose, the present invention adopts the following technical solutions:

[0008] A fuel cell system, which includes:

[0009] A first-stage stack group, including at least one first-stage stack, and the first-stage stack includes a first air electrode, a first fuel electrode and a first electrolyte disposed between the first air electrode and the first fuel electrode;

[0010] A second-stage stack group, including at least one second-stage stack, and the second-stage stack includes a second air electrode, a second fuel electrode and a second electrolyte disposed between the second air electrode and the second fuel electrode;

[0011] Both the first fuel electrode and the second fuel electrode include an oxide material; in the first-stage stack and the second-stage stack, the ratio of the area of the oxide material to the total area of the fuel electrode is 0.005 to 1;

[0012] A fuel supply unit and an air supply unit, the fuel supply unit provides high-temperature fuel for the first-stage stack group and the second-stage stack group through a fuel heater, and the air supply unit provides high-temperature air for the first-stage stack group and the second-stage stack group through an air heater.

[0013] As an alternative to the fuel cell system, the primary stack and the secondary stack each include a plurality of single cells, and the plurality of single cells are stacked. The number of single cells in the same layer is one. The fuel electrode of one single cell includes the oxide material and the nickel-based material. The nickel-based material is disposed near the inlet of the fuel flow channel, and the oxide material is disposed near the outlet of the fuel flow channel. The ratio of the area of the oxide material to the area of the fuel electrode of the single cell is 0.005 to 1.

[0014] As an alternative to the fuel cell system, the primary stack and the secondary stack each include a plurality of single cells, and the plurality of single cells are stacked. The number of single cells in the same layer is multiple. Among the multiple single cells in the same layer, the fuel electrodes of some of the single cells are the oxide material, and the fuel electrodes of the other single cells are the nickel-based material. The single cells with the nickel-based material as the fuel electrode are disposed near the inlet of the fuel flow channel, and the single cells with the oxide material as the fuel electrode are disposed near the outlet of the fuel flow channel. The ratio of the total area of the fuel electrodes of the single cells with the oxide material as the fuel electrode to the total area of the fuel electrodes of all the single cells in this layer is 0.005 to 1.

[0015] As an alternative to the fuel cell system, both the first electrolyte and the second electrolyte are oxygen ion conductor electrolytes or proton conductor electrolytes; or, among the first electrolyte and the second electrolyte, one is an oxygen ion conductor electrolyte and the other is a proton conductor electrolyte.

[0016] As an alternative to the fuel cell system, if the electrolyte is an oxygen ion conductor electrolyte, the oxide material is a component A, a mixture of component A and component B, or a C composite. The C composite includes a composite composed of component A, component B, and a metal, and the ratio of the metal mass to the composite mass is <20%;

[0017] Among them, the component A includes one or more of cerium oxide doped with rare earth elements and transition metal elements, perovskite titanate doped with alkali metal elements, transition metal elements, and rare earth elements, perovskite chromate doped with alkali metal elements, transition metal elements, and rare earth elements, perovskite ferrate doped with alkali metal elements, transition metal elements, and rare earth elements, perovskite manganate doped with alkali metal elements, transition metal elements, and rare earth elements, perovskite nickelate doped with alkali metal elements, transition metal elements, and rare earth elements, and perovskite vanadate doped with alkali metal elements, transition metal elements, and rare earth elements;

[0018] The component B includes one or more of doped zirconia, doped cerium oxide, and doped lanthanum gallate;

[0019] The metal includes one or both of a transition metal and a noble metal.

[0020] As an alternative of the fuel cell system, if the electrolyte is a proton-conducting electrolyte, the oxide material includes a mixture of a proton-conducting oxide and an electron-conducting oxide; or,

[0021] The oxide material includes a composite composed of a proton-conducting oxide, an electron-conducting oxide, and a metal, wherein the ratio of the mass of the metal to the mass of the composite < 20%, and the metal includes one or both of a transition metal and a noble metal.

[0022] As an alternative of the fuel cell system, the fuel cell system further includes an exhaust gas heat exchanger, and the high-temperature exhaust gas after the reaction of the first stack group and the second stack group provides preheating heat to at least part of the fuel provided by the fuel supply unit and at least part of the air provided by the air supply unit through the exhaust gas heat exchanger.

[0023] As an alternative of the fuel cell system, the fuel cell system further includes a burner, the air outlets of the first air electrode and the second air electrode are both communicated with the burner, the discharge port of the first fuel electrode is communicated with the feed port of the second fuel electrode, and the discharge port of the second fuel electrode is communicated with the burner;

[0024] The high-temperature exhaust gas after the burner burns provides preheating heat to at least part of the fuel provided by the fuel supply unit and at least part of the air provided by the air supply unit through the exhaust gas heat exchanger to form preheated air and preheated fuel.

[0025] As an alternative of the fuel cell system, the exhaust gas heat exchanger includes an air exhaust gas heat exchanger and a fuel exhaust gas heat exchanger. The air exhaust gas heat exchanger is used to transfer the heat of the first air exhaust gas discharged from the first air electrode and the heat of the second air exhaust gas discharged from the second air electrode or the heat of the second air exhaust gas discharged from the second air electrode to at least part of the air provided by the air supply unit to form preheated air; the fuel exhaust gas heat exchanger is used to transfer the heat of the second fuel exhaust gas discharged from the second fuel electrode to at least part of the fuel provided by the fuel supply unit to form preheated fuel.

[0026] As an alternative of the fuel cell system, the air heater includes a first air heater and a second air heater. In the preheated air, a part of it enters the first air electrode after being heated by the first air heater, and another part enters the second air electrode after being heated by the second air heater;

[0027] The fuel heater includes a first fuel heater and a second fuel heater. The preheated fuel enters the first fuel electrode after being heated by the first fuel heater, and the low-temperature fuel supplied by the fuel supply unit enters the second fuel electrode after being heated by the second fuel heater.

[0028] As an alternative embodiment of the fuel cell system, a temperature regulator is further provided between the first fuel electrode and the second fuel heater.

[0029] As an alternative embodiment of the fuel cell system, the fuel supply unit includes a first flow control valve for controlling the low-temperature fuel supplied by the fuel supply unit to the first stack group and the second stack group.

[0030] The air supply unit includes a second flow control valve and a first flow distributor. The second flow control valve is used to control the low-temperature air supplied by the air supply unit to the first stack and the second stack, and the first flow distributor is used to distribute the preheated air supplied by the air supply unit to the first stack group and the second stack group.

[0031] As an alternative embodiment of the fuel cell system, the air supply unit further includes a mixer group configured to mix the low-temperature air and the preheated air entering the first stack group and the second stack group.

[0032] A fuel cell power generation set includes the fuel cell system according to any one of the above embodiments.

[0033] A control method for a fuel cell power generation set is applied to the fuel cell power generation set as described above. The control method for the fuel cell power generation set includes the following steps:

[0034] When the fuel cell system is started, the air supply unit provides high-temperature air to the first air electrode and the second air electrode through the air heater, and the fuel supply unit provides high-temperature fuel to the first fuel electrode and the second fuel electrode through the fuel heater, starting the first stack group and the second stack group, and controlling the total fuel utilization rate of the first stack group and the second stack group > 90% or 95%; and / or

[0035] When the fuel cell system stops running, by reducing the power of the air heater and the fuel heater, when the temperature of the first air exhaust gas discharged from the first air electrode and the temperature of the second air exhaust gas discharged from the second air electrode are reduced to be lower than the start-up temperature of the first stack group and the second stack group, control the fuel supply unit to stop supplying fuel, and reduce the current of the first stack group and the current of the second stack group to zero.

[0036] As an alternative embodiment of the regulation method of the fuel cell power generation set, the fuel cell system further includes an exhaust gas heat exchanger, the exhaust gas heat exchanger includes an air exhaust gas heat exchanger and a fuel exhaust gas heat exchanger, the air exhaust gas heat exchanger is used to transfer the heat of the first air exhaust gas discharged from the first air electrode and the heat of the second air exhaust gas discharged from the second air electrode or the heat of the second air exhaust gas discharged from the second air electrode to at least part of the air provided by the air supply unit to form preheated air; the fuel exhaust gas heat exchanger is used to transfer the heat of the second fuel exhaust gas discharged from the second fuel electrode to at least part of the fuel provided by the fuel supply unit to form preheated fuel; when the fuel cell system starts up, the air supply unit provides high-temperature air for the first air electrode and the second air electrode through the air heater, the fuel supply unit provides high-temperature fuel for the first fuel electrode and the second fuel electrode through the fuel heater, start the first stack group and the second stack group, and controlling the total fuel utilization rate of the first stack group and the second stack group > 90% or 95% includes the following steps:

[0037] After the first air exhaust gas and the second air exhaust gas enter the air exhaust gas heat exchanger to form the preheated air, and then are heated by the air heater to form the high-temperature air, and then enter the first air electrode and the second air electrode respectively;

[0038] When the temperature of the first air exhaust gas and the temperature of the second air exhaust gas are higher than the start-up temperature of the first stack group and the second stack group, the fuel supply unit provides preheated fuel, which is heated by the fuel heater to form high-temperature fuel and enters the first stack group, the first fuel exhaust gas discharged from the first fuel electrode is heated by the fuel heater and then enters the second stack group, and the second fuel exhaust gas discharged from the second fuel electrode exchanges heat through the fuel exhaust gas heat exchanger to form preheated fuel;

[0039] When fuel enters the first stack group, start the first stack group and control the fuel utilization rate of the first stack group > 60%; when fuel enters the second stack group, start the second stack group and control the fuel utilization rate of the second stack group > 90%;

[0040] By adjusting the power of the air heater and the fuel heater, as well as the inlet temperatures of the first fuel electrode and the second fuel electrode, maintain the total fuel utilization rate of the first-stage stack group and the second-stage stack group > 95% until the fuel cell system operates in a steady state.

[0041] As an alternative embodiment of the control method for the fuel cell power generation unit, when the fuel cell system operates in a steady state, maintain the total fuel utilization rate of the first-stage stack group and the second-stage stack group > 95%, control the fuel utilization rate of the first-stage stack group to be between 60% and 95%, and by adjusting the fuel utilization rate of the second-stage stack group, reduce the fuel concentration in the second fuel tail gas to 0.0001% - 5%.

[0042] As an alternative embodiment of the control method for the fuel cell power generation unit, the fuel cell system further includes an exhaust gas heat exchanger and a burner. The high-temperature exhaust gas after combustion by the burner provides preheating heat to at least part of the fuel provided by the fuel supply unit and at least part of the air provided by the air supply unit through the exhaust gas heat exchanger to form preheated air and preheated fuel. When the fuel cell system starts, the air supply unit provides high-temperature air to the first air electrode and the second air electrode through the air heater, and the fuel supply unit provides high-temperature fuel to the first fuel electrode and the second fuel electrode through the fuel heater. Starting the first-stage stack group and the second-stage stack group, controlling the total fuel utilization rate of the first-stage stack group and the second-stage stack group > 90% or 95% includes the following steps:

[0043] When the fuel cell system starts, the low-temperature air provided by the air supply unit enters the first air electrode and the second air electrode respectively and then enters the burner, and the low-temperature fuel provided by the fuel supply unit enters the burner. The high-temperature exhaust gas generated after combustion by the burner provides preheating heat to at least part of the fuel provided by the fuel supply unit and at least part of the air provided by the air supply unit through the exhaust gas heat exchanger to form preheated air and preheated fuel. The preheated air is heated by the air heater to form the high-temperature air and then enters the first air electrode and the second air electrode respectively;

[0044] When the temperature of the air exhaust gas entering the burner is higher than the first set temperature, the preheated fuel provided by the fuel supply unit enters the first-stage stack group after being heated by the fuel heater. The first fuel tail gas discharged from the first fuel electrode and the low-temperature fuel provided by the fuel supply unit enter the second-stage stack group after being heated by the fuel heater, and the second fuel tail gas discharged from the second fuel electrode enters the burner for combustion;

[0045] When the temperature of the air exhaust gas entering the burner is higher than the start-up temperature of the first stack group and the second stack group, start the first stack group and the second stack group, control the fuel utilization rate of the first stack group to be between 60% and 95%, and the temperature of the air exhaust gas entering the burner gradually rises to the steady-state operation of the fuel cell system.

[0046] As an alternative solution of the control method of the fuel cell power generation unit, when the fuel cell system operates in a steady state, maintain the fuel utilization rate of the first stack group between 60% and 95%, control the total fuel utilization rate of the first stack group and the second stack group > 95%, and reduce the fuel concentration in the second fuel exhaust gas to 0.0001% - 5% by adjusting the flow rate of the low-temperature fuel provided by the fuel supply unit to the second stack group and the fuel utilization rate of the second stack.

[0047] As an alternative solution of the control method of the fuel cell power generation unit, when the fuel cell system stops operating, by reducing the power of the air heater and the fuel heater, when the temperature of the first air exhaust gas and the second air exhaust gas is reduced to be lower than the start-up temperature of the first stack group and the second stack group, the steps of controlling the fuel supply unit to stop supplying fuel and reducing the current of the first stack group and the current of the second stack group to zero specifically include:

[0048] During the process of reducing the temperature of the first air exhaust gas and the second air exhaust gas by reducing the power of the air heater and the fuel heater, ensure that the total fuel utilization rate of the first stack group and the second stack group > 95% by gradually reducing the flow rate of the fuel entering the fuel cell system, the current of the first stack group, and the current of the second stack group.

[0049] Advantages of the present invention:

[0050] The fuel cell system provided by the present invention includes a primary stack group, a secondary stack group, a fuel supply unit, and an air supply unit. Both the first fuel electrode and the second fuel electrode include an oxide material. The fuel supply unit and the air supply unit respectively supply fuel and air to the primary stack group and the secondary stack group. The water vapor generated by the electrochemical reaction in the primary stack group and the secondary stack group has strong oxidizing properties at high temperatures. However, since the fuel electrode containing the oxide material itself has antioxidant properties and will not be oxidized, it is possible to reduce the attenuation of the first fuel electrode and the second fuel electrode caused by nickel oxide agglomeration. When the ratio of the area of the oxide material to the total area of the fuel electrode is controlled within 0.005 - 1, it can not only reduce the attenuation of the fuel electrode, improve the fuel utilization rate, but also not affect the progress of the electrochemical reaction. The air supply unit provides high-temperature air through an air heater, and the fuel supply unit provides high-temperature fuel through a fuel heater, improving the energy utilization rate. The fuel cell system provided by the present invention can not only avoid the attenuation of the first fuel electrode and the second fuel electrode, but also improve the energy utilization rate, thereby improving the fuel utilization rate.

[0051] The fuel cell power generation set provided by the present invention includes the above-mentioned fuel cell system. This fuel cell system can significantly improve the fuel utilization rate, thereby improving the power generation efficiency of the fuel cell power generation set.

[0052] The regulation method of the fuel cell power generation set provided by the present invention is applied to the above-mentioned fuel cell power generation set. When the fuel cell system is started, the air supply unit provides high-temperature air to the first air electrode and the second air electrode through the air heater, and the fuel supply unit provides high-temperature fuel to the first fuel electrode and the second fuel electrode through the fuel heater. Start the primary stack group and the secondary stack group, and control the total fuel utilization rate of the primary stack group and the secondary stack group > 90% or 95%. When the fuel cell system stops running, by reducing the power of the air heater and the fuel heater, reduce the temperature of the first air exhaust gas and the second air exhaust gas to be lower than the start-up temperature of the primary stack group and the secondary stack group, control the fuel supply unit to stop supplying fuel, and reduce the current of the primary stack group and the current of the secondary stack group to zero. This regulation method of the fuel cell power generation set significantly improves the fuel utilization rate, thereby improving the power generation efficiency. Description of the Drawings

[0053] Figure 1 is a schematic diagram of the working principle of the primary stack group and the secondary stack group in the fuel cell system provided by Embodiment 1 of the present invention Figure 1 ;

[0054] Figure 2 is a schematic diagram of the working principle of the primary stack group and the secondary stack group in the fuel cell system provided by Embodiment 1 of the present invention Figure 2 ;

[0055] Figure 3 It is a schematic diagram of the working principle of the fuel cell system provided in the first embodiment of the present invention;

[0056] Figure 4 It is a schematic diagram of the working principle of the first-stage stack group and the second-stage stack group in the fuel cell system provided in the second embodiment of the present invention Figure 1 ;

[0057] Figure 5 It is a schematic diagram of the working principle of the first-stage stack group and the second-stage stack group in the fuel cell system provided in the second embodiment of the present invention Figure 2 ;

[0058] Figure 6 It is a schematic diagram of the working principle of the fuel cell system provided in the second embodiment of the present invention.

[0059] In the figure:

[0060] 1. First-stage stack; 2. Second-stage stack; 3. Burner; 4. Tail gas heat exchanger; 5. Air heater; 6. Fuel heater; 7. Temperature regulator; 8. Temperature regulating heat exchanger; 9. First flow control valve; 10. Second flow control valve; 11. First flow distributor; 12. First mixer; 13. Second mixer; 14. Third mixer; 15. Water separator; 16. Carbon dioxide separator;

[0061] 101. First air electrode; 102. First fuel electrode; 103. First electrolyte; 201. Second air electrode; 202. Second fuel electrode; 203. Second electrolyte; 401. Air tail gas heat exchanger; 402. Fuel tail gas heat exchanger; 501. First air heater; 502. Second air heater; 601. First fuel heater; 602. Second fuel heater. Detailed implementation manners

[0062] The following details the embodiments of the present invention. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals denote the same or similar elements or elements with the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

[0063] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance. Among them, the terms "first position" and "second position" are two different positions.

[0064] Unless otherwise clearly defined and limited, the terms "installed", "connected", "communicated", "fixed" should be understood in a broad sense. For example, it can be fixedly communicated or detachably communicated; it can be mechanically communicated or electrically communicated; it can be directly connected or indirectly connected through an intermediate medium. It can be the communication inside two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0065] Unless otherwise clearly defined and limited, the first feature being "above" or "below" the second feature may include the first feature and the second feature being in direct contact, or may include the first feature and the second feature not being in direct contact but being in contact through other features therebetween. Moreover, the first feature being "above", "over" and "on" the second feature includes the first feature being directly above and obliquely above the second feature, or merely indicating that the horizontal height of the first feature is higher than that of the second feature. The first feature being "below", "under" and "beneath" the second feature includes the first feature being directly below and obliquely below the second feature, or merely indicating that the horizontal height of the first feature is less than that of the second feature.

[0066] The technical solution of the present invention will be further described below with reference to the drawings and through specific embodiments.

[0067] Embodiment 1:

[0068] As Figures 1 to 3 shown, this embodiment provides a fuel cell system, including a primary stack group, a secondary stack group, a fuel supply unit, and an air supply unit. The fuel supply unit provides high-temperature fuel for the primary stack group and the secondary stack group through a fuel heater 6, and the air supply unit provides high-temperature air for the primary stack group and the secondary stack group through an air heater 5. The high-temperature fuel and the high-temperature air undergo an electrochemical reaction in the primary stack group to generate electric energy. The first fuel tail gas discharged from the primary stack group enters the secondary stack 2 and undergoes an electrochemical reaction in the secondary stack group to generate electric energy. The fuel heater 6 and the air heater 5 can be electric heaters or heat exchangers using external heat sources.

[0069] The first - stage stack group includes at least one first - stage stack 1. The first - stage stack 1 includes a first air electrode 101, a first fuel electrode 102, and a first electrolyte 103 disposed between the first air electrode 101 and the first fuel electrode 102. The second - stage stack group includes at least one second - stage stack 2. The second - stage stack 2 includes a second air electrode 201, a second fuel electrode 202, and a second electrolyte 203 disposed between the second air electrode 201 and the second fuel electrode 202.

[0070] When there are multiple first - stage stacks 1 in a first - stage stack group, the multiple first - stage stacks 1 can be arranged in parallel, or in series. Or, the multiple first - stage stacks 1 are arranged in a series - parallel combination, that is, the multiple first - stage stacks 1 are divided into at least two groups, each group includes at least two first - stage stacks 1. After at least two first - stage stacks 1 in each group are connected in parallel, they are then connected in series with other groups. Similarly, when there are multiple first - stage stack groups in a first - stage fuel cell module, the multiple first - stage stack groups are connected in series, parallel, or in a series - parallel combination.

[0071] When there are multiple second - stage stacks 2 in a second - stage stack group, the multiple second - stage stacks 2 can be arranged in parallel, or in series. Or, the multiple second - stage stacks 2 are arranged in a series - parallel combination, that is, the multiple second - stage stacks 2 are divided into at least two groups, each group includes at least two second - stage stacks 2. After at least two second - stage stacks 2 in each group are connected in parallel, they are then connected in series with other groups. Similarly, when there are multiple second - stage stack groups in a second - stage fuel cell module 200, the multiple second - stage stack groups are connected in series, parallel, or in a series - parallel combination.

[0072] Both the first fuel electrode 102 and the second fuel electrode 202 include an oxide material; in the first - stage stack 1 and the second - stage stack 2, the ratio of the area of the oxide material to the total area of the fuel electrode is 0.005 - 1. The water vapor generated by the electrochemical reaction in the first - stage stack group and the second - stage stack group has strong oxidizing properties at high temperatures. However, since the fuel electrodes of the oxide material itself have antioxidant properties and will not be oxidized, it can reduce the attenuation of the first fuel electrode 102 and the second fuel electrode 202 caused by the aggregation of nickel oxide. By controlling the ratio of the area of the oxide material to the total area of the fuel electrode within 0.005 - 1, it can not only reduce the attenuation of the fuel electrode, improve fuel utilization, but also not affect the progress of the electrochemical reaction.

[0073] An optional solution provided in this embodiment is that both the first - stage stack 1 and the second - stage stack 2 include a plurality of single - cell batteries. The plurality of single - cell batteries are stacked. The number of single - cell batteries in the same layer is one. In a single - cell battery, the fuel electrode includes an oxide material and a nickel - based material. The nickel - based material is arranged near the inlet of the fuel flow channel, and the oxide material is arranged near the outlet of the fuel flow channel. The ratio of the area of the oxide material to the area of the fuel electrode of the single - cell battery is 0.005 - 1.

[0074] The nickel-based material is a mixture of nickel metal and yttria-doped zirconia. In a stack, fuel enters the fuel dispersion channels of the stack from the inlet of the fuel flow channel and then enters the multi-layer single cells. For the single cells in the same layer, the fuel enters from the inlet of the fuel flow channel and flows towards the outlet of the fuel flow channel. When an electrochemical reaction occurs between the fuel and air, water vapor tends to accumulate at the outlet of the fuel flow channel. The fuel electrode of the oxide material is arranged at a position close to the outlet of the fuel flow channel to avoid the attenuation of the fuel electrode caused by the agglomeration of nickel oxide due to the oxidation of the nickel-based material by water vapor under high temperature. For a stack with only one single cell in a layer, the fuel electrode of this single cell is divided into two parts. Along the direction from the inlet of the fuel flow channel to the outlet of the fuel flow channel, they are the nickel-based material and the oxide material in sequence. The ratio of the area of the oxide material to the area of the fuel electrode of this single cell is 0.005 - 1.

[0075] Another optional solution provided in this embodiment is that both the first stack 1 and the second stack 2 include a plurality of single cells, and the plurality of single cells are stacked. The number of single cells in the same layer is multiple. Among the multiple single cells in the same layer, the fuel electrodes of some single cells are made of oxide materials, and the fuel electrodes of the other single cells are made of nickel-based materials. The single cells with fuel electrodes made of nickel-based materials are arranged close to the inlet of the fuel flow channel. The ratio of the total area of the fuel electrodes of the single cells with fuel electrodes made of oxide materials to the total area of the fuel electrodes of all single cells in this layer is 0.005 - 1. For a stack with multiple single cells in the same layer, the fuel electrodes of the single cells close to the inlet of the fuel flow channel can be set as nickel-based materials, and the fuel electrodes of the single cells close to the outlet of the fuel flow channel can be set as oxide materials.

[0076] Both the first electrolyte 103 and the second electrolyte 203 are oxygen ion conductor electrolytes or proton conductor electrolytes. Or, among the first electrolyte 103 and the second electrolyte 203, one is an oxygen ion conductor electrolyte and the other is a proton conductor electrolyte. The oxygen ion conductor electrolyte is an oxygen ion conductor (O 2- ). During operation, oxygen ions are conducted from the air electrode to the fuel electrode to react with the fuel. The ratio of oxygen element to carbon element on the surface of the fuel electrode is higher than that at the inlet of the fuel flow channel, which can ensure the diffusion partial pressure and diffusion rate of the fuel at the fuel electrode and improve the fuel utilization rate. The proton conductor electrolyte is a hydrogen ion conductor (H + ). When an electrochemical reaction occurs, hydrogen ions in the proton conductor electrolyte are conducted from the fuel electrode to the air electrode to react with air to generate water vapor, and water vapor will not be generated inside the fuel electrode. Therefore, the nickel metal inside the fuel electrode will not be oxidized to nickel oxide, reducing the attenuation of the fuel electrode caused by the expansion and cracking downstream of the outlet of the fuel flow channel.

[0077] In a single cell, if the electrolyte is an oxygen ion conductor electrolyte and the fuel electrode comprises an oxide material, the oxide material is a component A, a mixture of component A and component B, or a C composite. The C composite comprises a composite of component A, component B, and a metal, and the ratio of the mass of the metal to the mass of the composite is < 20%. Component A includes cerium oxide doped with rare earth elements and transition metal elements, perovskite titanates doped with alkali metal elements, transition metal elements, and rare earth elements, perovskite chromates doped with alkali metal elements, transition metal elements, and rare earth elements, perovskite ferrites doped with alkali metal elements, transition metal elements, and rare earth elements, perovskite manganates doped with alkali metal elements, transition metal elements, and rare earth elements, perovskite nickelates doped with alkali metal elements, transition metal elements, and rare earth elements, and perovskite vanadates doped with alkali metal elements, transition metal elements, and rare earth elements, one or more of which. Component B includes one or more of doped zirconia, doped cerium oxide, and doped lanthanum gallate. The metal includes one or two of transition metals and noble metals. The transition metal may be Ni, Fe, Co, or Cu, etc. The noble metal may be Ru, Pt, Pd, Au, Rh, or Ir, etc. In this embodiment, for the transition metals in the C composite, one or more transition metals may be included. Similarly, for the noble metals in the C composite, one or more noble metals may be included.

[0078] In a single cell, if the electrolyte is a proton conductor electrolyte, the oxide material comprises a mixture of a proton conductor oxide and an electron conductor oxide; or the oxide material comprises a composite of a proton conductor oxide, an electron conductor oxide, and a metal, where the ratio of the mass of the metal to the mass of the composite is < 20%. The metal includes one or two of transition metals and noble metals.

[0079] The proton conductor oxide material is a mixture of alkali metal oxides such as BaO, SrO, CaO, and MgO, perovskite zirconate oxides doped with alkali metal elements and calcium, mixtures of perovskite cerates doped with alkali metal elements, mixtures of perovskite titanates doped with alkali metal elements, mixtures of perovskite ferrites doped with alkali metal elements, or mixtures of perovskite ferrites doped with alkali metal elements, etc. The electron conductor oxide material is cerium oxide doped with rare earth elements and transition metal elements, perovskite titanates doped with alkali metal elements, transition metal elements, and rare earth elements, perovskite chromates doped with alkali metal elements, transition metal elements, and rare earth elements, perovskite ferrites doped with alkali metal elements, transition metal elements, and rare earth elements, perovskite manganates doped with alkali metal elements, transition metal elements, and rare earth elements, perovskite nickelates doped with alkali metal elements, transition metal elements, and rare earth elements, and perovskite vanadates doped with alkali metal elements, transition metal elements, or rare earth elements, etc.

[0080] Furthermore, the fuel cell system further includes an exhaust gas heat exchanger 4. The high-temperature exhaust gas after the reaction of the first fuel cell stack group and the second fuel cell stack group provides preheating heat to at least part of the fuel supplied by the fuel supply unit and at least part of the air supplied by the air supply unit through the exhaust gas heat exchanger 4. If only the air heater 5 is used to provide high-temperature air for the first fuel cell stack group and the second fuel cell stack group, and only the fuel heater 6 is used to provide high-temperature fuel for the first fuel cell stack group and the second fuel cell stack group, if the air heater 5 and the fuel heater 6 are electric heaters, the power requirements for the electric heaters will be very high. If the air heater 5 and the fuel heater 6 are heat exchangers using external heat sources, a large amount of heat from the external heat source is also required. Since high-temperature exhaust gas is generated after the electrochemical reaction of the first fuel cell stack group and the second fuel cell stack group, the heat of the high-temperature exhaust gas is provided to at least part of the fuel supplied by the fuel supply unit and at least part of the air supplied by the air supply unit through the exhaust gas heat exchanger 4 to form preheated fuel and preheated air. In this way, the preheated fuel is further heated by the fuel heater 6 to reach the high-temperature fuel required for the reaction of the first fuel cell stack group and the second fuel cell stack group, and the preheated air is further heated by the air heater 5 to reach the high-temperature air required for the reaction of the first fuel cell stack group and the second fuel cell stack group. In this way, the power requirements for the fuel heater 6 and the air heater 5 or the heat requirements for the external heat source will be relatively low, reducing the cost.

[0081] Specifically, the fuel cell system further includes a burner 3. The air outlets of the first air electrode 101 and the second air electrode 201 are both connected to the burner 3. The discharge port of the first fuel electrode 102 is connected to the feed port of the second fuel electrode 202, and the discharge port of the second fuel electrode 202 is connected to the burner 3. The high-temperature exhaust gas after the burner 3 burns provides preheating heat to at least part of the fuel supplied by the fuel supply unit and at least part of the air supplied by the air supply unit through the exhaust gas heat exchanger 4 to form preheated air and preheated fuel. By utilizing the heat of the high-temperature exhaust gas after the burner 3 burns, preheated air and preheated fuel are provided.

[0082] Specifically, the air heater 5 includes a first air heater 501 and a second air heater 502. Among the preheated air, a part of it enters the first air electrode 101 after being heated by the first air heater 501, and the other part enters the second air electrode 201 after being heated by the second air heater 502. The fuel heater 6 includes a first fuel heater 601 and a second fuel heater 602. The preheated fuel enters the first fuel electrode 102 after being heated by the first fuel heater 601, and the low-temperature fuel supplied by the fuel supply unit enters the second fuel electrode 202 after being heated by the second fuel heater 602. An air heater 5 and a fuel heater 6 are respectively arranged in front of the first fuel cell stack group and the second fuel cell stack group to heat the air and fuel entering the first fuel cell stack group respectively, and the heating efficiency is higher.

[0083] Since the first fuel exhaust gas discharged from the first fuel electrode 102 has a relatively high temperature after the reaction of the first fuel cell stack group, and the first fuel exhaust gas contains a large amount of water and carbon dioxide, in order to improve the fuel utilization rate of the second fuel cell stack group, before the first fuel exhaust gas enters the second fuel cell stack group for reuse, the water and carbon dioxide in the first fuel exhaust gas are removed by the water separator 15 and the carbon dioxide separator 16. Before separating the water and carbon dioxide, it is necessary to first cool the first fuel exhaust gas with a relatively high temperature through the cooling unit. After the cooled first fuel exhaust gas removes most of the water and carbon dioxide, it still needs to be reheated to prevent the second fuel heater 602 from being unable to directly heat the cooled first fuel exhaust gas and the low-temperature fuel supplemented by the fuel supply unit to the temperature required for the reaction of the second fuel cell stack group.

[0084] Specifically, a temperature adjusting member is further provided between the first fuel electrode 102 and the second fuel heater 602. In this embodiment, the temperature adjusting member is a temperature adjusting heat exchanger 8, which can exchange heat with the cooling medium in the cooling unit and then raise the temperature of the first fuel exhaust gas after removing water and carbon dioxide, reducing the power of the second fuel heater 602 to reduce costs.

[0085] The fuel supply unit includes a first flow control valve 9, and the first flow control valve 9 is used to control the low-temperature fuel provided by the fuel supply unit for the first fuel cell stack group and the second fuel cell stack group. The air supply unit includes a second flow control valve 10 and a first flow distributor 11. The second flow control valve 10 is used to control the low-temperature air provided by the air supply unit for the first fuel cell 1 and the second fuel cell 2, and the first flow distributor 11 is used to distribute the preheated air provided by the air supply unit for the first fuel cell 1 and the second fuel cell stack group. By setting the first flow control valve 9 to distribute and control the low-temperature fuel entering the first fuel cell stack group and the second fuel cell stack group, so that the preheated fuel and the low-temperature fuel are evenly mixed and then heated by the first fuel heater 601 to the high-temperature fuel required for the reaction of the first fuel cell stack group, and the first fuel exhaust gas and the low-temperature fuel are mixed and then heated by the second fuel heater 602 to the high-temperature fuel required for the reaction of the second fuel cell stack group. The second flow control valve 10 distributes and controls the low-temperature fuel entering the first fuel cell stack group and the second fuel cell stack group, and the first flow distributor 11 is used to distribute the preheated air entering the first fuel cell stack group and the second fuel cell 2.

[0086] Further, the air supply unit further includes a mixer group configured to mix the low-temperature air and the preheated air entering the first-stage stack 1 and the second-stage stack 2. After the low-temperature air and the preheated air entering the first-stage stack 1 are evenly mixed by the mixer group, they are heated by the first air heater 501 into the high-temperature air required for the reaction of the first-stage stack 1 to ensure the uniformity of the temperature of the high-temperature air entering the first-stage stack 1. At the same time, the low-temperature air and the preheated air entering the second-stage stack 2 are evenly mixed and then heated by the second air heater 502 into the high-temperature air required for the reaction of the second-stage stack 2 to ensure the uniformity of the temperature of the high-temperature air entering the second-stage stack 2.

[0087] In this embodiment, the flow control valve can not only control the flow rate but also distribute the flow rate. When used at low temperatures, the flow control valve can not only control the flow rate but also distribute the flow rate. However, when used at high temperatures, the quality requirements for the flow control valve are relatively high. Therefore, a flow distributor is used to distribute the flow rate at high temperatures, reducing the cost.

[0088] Specifically, the mixer group includes a first mixer 12 and a second mixer 13. The first mixer 12 is used to mix the low-temperature air and the preheated air provided by the air supply unit for the first-stage stack 1; the second mixer 13 is used to mix the low-temperature air and the preheated air provided by the air supply unit for the second-stage stack 2. Further, the air supply unit further includes a third mixer 14, and the third mixer 14 is used to mix the air mixed by the second mixer 13 and the first air tail gas discharged from the first-stage stack 1 and then supply it to the second-stage stack 2. The first mixer 12 realizes the mixing of the low-temperature air and the preheated air entering the first-stage stack 1, and then is heated by the first air heater 501 into the high-temperature air required for the reaction of the first-stage stack 1. The second mixer 13 realizes the mixing of the low-temperature air and the preheated air provided by the air supply unit for the second-stage stack 2, and the third mixer 14 realizes the mixing of the first air tail gas and the air mixed by the second mixer 13, and then is heated by the second air heater 502 into the high-temperature air required for the reaction of the second-stage stack 2.

[0089] This embodiment also provides a fuel cell power generation set, including the above fuel cell system. This fuel cell system can greatly improve the fuel utilization rate, thereby improving the power generation efficiency of the fuel cell power generation set.

[0090] This embodiment also provides a regulation method for a fuel cell power generation set, which is applied to the above fuel cell power generation set. The regulation method for the fuel cell power generation set includes the following steps:

[0091] When the fuel cell system starts up, the air supply unit supplies high-temperature air to the first air electrode 101 and the second air electrode 201 through the air heater 5, and the fuel supply unit supplies high-temperature fuel to the first fuel electrode 102 and the second fuel electrode 202 through the fuel heater 6, starting the first-stage stack group and the second-stage stack group, and controlling the total fuel utilization rate of the first-stage stack group and the second-stage stack group to be > 90% or 95%.

[0092] Specifically, it includes the following steps:

[0093] (1) When the fuel cell system starts up, the low-temperature air supplied by the air supply unit enters the first air electrode 101 and the second air electrode 201 respectively and then enters the burner 3. The low-temperature fuel supplied by the fuel supply unit enters the burner 3. The high-temperature exhaust gas generated after the burner 3 burns provides preheating heat to at least part of the fuel supplied by the fuel supply unit and at least part of the air supplied by the air supply unit through the exhaust gas heat exchanger 4 to form preheated air and preheated fuel. The preheated air is heated by the air heater 5 to form high-temperature air and then enters the first air electrode 101 and the second air electrode 201 respectively.

[0094] When the fuel cell system starts up, first close the first air heater 501 and the second air heater 502. The air supply unit supplies low-temperature air to the first air electrode 101 and the second air electrode 201 respectively. The first air exhaust gas discharged from the first air electrode 101 and the second air exhaust gas discharged from the second air electrode 201 enter the burner 3. The fuel supply unit supplies low-temperature fuel to the burner 3 through an external pipeline. The low-temperature fuel enters the burner 3 and burns with the air. The high-temperature exhaust gas after the burner 3 burns enters the exhaust gas heat exchanger 4 to transfer heat to at least part of the low-temperature air supplied by the air supply unit and at least part of the low-temperature fuel supplied by the fuel supply unit to form preheated air and preheated fuel.

[0095] (2) When the temperature of the air exhaust gas entering the burner 3 is higher than the first set temperature, the preheated fuel supplied by the fuel supply unit is heated by the fuel heater 6 and then enters the first-stage stack group. The first fuel exhaust gas and the low-temperature fuel supplied by the fuel supply unit are heated by the fuel heater 6 and then enter the second-stage stack group. The second fuel exhaust gas enters the burner 3 to burn.

[0096] In this embodiment, the first set temperature is 200 °C. The preheated air is divided into two parts by the first flow distributor 11, and the low-temperature air is divided into two parts by the second flow control valve 10. One part of the preheated air and one part of the low-temperature air are mixed evenly by the first mixer 12 and then heated by the first air heater 501 and then enter the first-stage stack 1. The other part of the preheated air and the other part of the low-temperature air are mixed evenly by the second mixer 13 and then enter the third mixer 14 and are mixed evenly with the first air tail gas, and then enter the second-stage stack 2 after being heated by the second air heater 502. The low-temperature fuel is divided into two parts by the first flow control valve 9. The preheated fuel or the preheated fuel and a part of the low-temperature fuel enter the first fuel heater 601 for heating and then enter the first-stage stack 1. The first fuel tail gas is passed through the water separator 15 and the carbon dioxide separator 16 to remove water and carbon dioxide, and then enters the second fuel heater 602 for heating after being heated up by the temperature-regulating heat exchanger 8 and then enters the second-stage stack 2 together with the other part of the low-temperature fuel.

[0097] (3) When the temperature of the air tail gas entering the burner 3 is higher than the start-up temperature of the first-stage stack group and the second-stage stack group, start the first-stage stack group and the second-stage stack group, and control the fuel utilization rate of the first-stage stack group to be between 60% and 95%. The temperature of the air tail gas entering the burner 3 gradually rises to the steady-state operation of the fuel cell system.

[0098] In this embodiment, the start-up temperature of the first-stage stack group and the second-stage stack group is 400 °C. After starting the first-stage stack group and the second-stage stack group, gradually increase the current of the first-stage stack 1 and the second-stage stack 2, adjust the flow rate of the preheated fuel entering the first-stage stack 1 and the flow rate of the low-temperature fuel entering the second-stage stack 2, and control the fuel utilization rate of the first-stage stack group to be between 60% and 95%, so that the temperature of the air tail gas entering the burner 3 gradually rises to the steady-state operation condition of the fuel cell system.

[0099] Further, gradually increase the total fuel utilization rate of the first-stage stack group and the second-stage stack group to > 90%. At this time, the burner 3 will go out due to too low fuel concentration. By increasing the power of the first air heater 501, the second air heater 502, the first fuel heater 601 and the second fuel heater 602, compensate for the heat loss caused by the extinction of the burner 3.

[0100] When the fuel cell system operates in a steady state, the fuel utilization rate of the first stack group is maintained between 60% and 95%, and the total fuel utilization rate of the first stack group and the second stack group is controlled to be > 95%. By adjusting the flow rate of the low-temperature fuel supplied by the fuel supply unit to the second stack group and the fuel utilization rate of the second stack 2, the fuel concentration in the second fuel tail gas is reduced to 0.0001% - 5%. After the second fuel tail gas and the air tail gas entering the burner 3 are burned in the burner 3, the heat of the high-temperature tail gas is supplied to the low-temperature fuel and the second air through the tail gas heat exchanger 4 and then discharged from the fuel cell system, ensuring that the fuel concentration in the low-temperature fuel tail gas discharged from the fuel cell system is within the explosion limit of the combustible gas and avoiding explosion when the low-temperature fuel tail gas is discharged into the air.

[0101] When the fuel cell system stops operating, by reducing the power of the air heater 5 and the fuel heater 6, when the temperatures of the first air tail gas and the second air tail gas are reduced to below the start-up temperature of the first stack group and the second stack group, the fuel supply unit is controlled to stop supplying fuel, and the currents of the first stack group and the second stack group are reduced to zero. Specifically, in the process of reducing the temperatures of the first air tail gas and the second air tail gas by reducing the power of the air heater 5 and the fuel heater 6, by gradually reducing the flow rate of the fuel entering the fuel cell system, the currents of the first stack group and the second stack group, it is ensured that the total fuel utilization rate of the first stack group and the second stack group is > 95%.

[0102] By reducing the power of the first air heater 501, the second air heater 502, the first fuel heater 601 and the second fuel heater 602, the temperatures of the first air tail gas and the second air tail gas are gradually reduced to below 400 °C. In this process, the flow rate of the fuel entering the fuel cell system, the currents of the first stack group and the second stack group are gradually reduced, ensuring that the total fuel utilization rate of the first stack group and the second stack group is > 95%. When the temperature of the air entering the burner 3 is lower than 400 °C, the fuel supply to the fuel cell system is stopped, and the currents of the first stack group and the second stack group are reduced to zero.

[0103] The regulation method of this fuel cell power generation unit greatly improves the fuel utilization rate, and thus improves the power generation efficiency.

[0104] Embodiment 2:

[0105] This embodiment provides a fuel cell system, which is basically the same as the structure of the fuel cell system provided in Embodiment 1. The same structure will not be described in detail here. The difference is that as Figures 4 to 6As shown in the figure, the fuel cell system provided in this embodiment does not have a burner 3. The exhaust gas heat exchanger 4 includes an air exhaust gas heat exchanger 401 and a fuel exhaust gas heat exchanger 402. The air exhaust gas heat exchanger 401 is used to transfer the heat of the first air exhaust discharged from the first air electrode 101 and the heat of the second air exhaust discharged from the second air electrode 201 or the heat of the second air exhaust discharged from the second air electrode 201 to at least part of the air provided by the air supply unit to form preheated air; the fuel exhaust gas heat exchanger 402 is used to transfer the heat of the second fuel exhaust discharged from the second fuel electrode 202 to at least part of the fuel provided by the fuel supply unit to form preheated fuel. The heat of the first air exhaust and the heat of the second air exhaust or the heat of the second air exhaust are directly transferred to the low-temperature air through the air exhaust gas heat exchanger 401 to form preheated air, and the heat of the second fuel exhaust is directly transferred to the low-temperature fuel through the fuel exhaust gas heat exchanger 402 to form preheated fuel.

[0106] This embodiment also provides a fuel cell power generation set, including the fuel cell system provided in this embodiment. This fuel cell system can greatly improve the fuel utilization rate, and thus improve the power generation efficiency of the fuel cell power generation set.

[0107] This embodiment also provides a control method for a fuel cell power generation set, which is applied to the fuel cell power generation set provided in this embodiment. This control method for the fuel cell power generation set includes the following steps:

[0108] When the fuel cell system is started, the air supply unit provides high-temperature air for the first air electrode 101 and the second air electrode 201 through the air heater 5, and the fuel supply unit provides high-temperature fuel for the first fuel electrode 102 and the second fuel electrode 202 through the fuel heater 6. The first-stage stack group and the second-stage stack group are started, and the total fuel utilization rate of the first-stage stack group and the second-stage stack group is controlled to be > 90% or 95%.

[0109] Specifically, it includes the following steps:

[0110] (1) After the first air exhaust and the second air exhaust enter the air exhaust gas heat exchanger 401 to form preheated air, and then are heated by the air heater 5 to form high-temperature air, they respectively enter the first air electrode 101 and the second air electrode 201.

[0111] (2) When the temperatures of the first air exhaust and the second air exhaust are higher than the start-up temperatures of the first-stage stack group and the second-stage stack group, the fuel supply unit provides preheated fuel, which is heated by the fuel heater 6 to form high-temperature fuel and enters the first-stage stack group. The first fuel exhaust discharged from the first fuel electrode 102 is heated by the fuel heater 6 and enters the second-stage stack group. The second fuel exhaust discharged from the second fuel electrode 202 is heat-exchanged by the fuel exhaust gas heat exchanger 402 to form preheated fuel.

[0112] When the temperature of the first air exhaust gas discharged from the first air electrode 101 and the temperature of the second air exhaust gas discharged from the second air electrode 201 are > 400 °C, fuel is introduced into the fuel cell system. The fuel passes through the first fuel heater 601 and enters the first fuel electrode 102, and the temperature of the first fuel exhaust gas generated by the first fuel electrode 102 is very high.

[0113] In this embodiment, the temperature regulating member provided between the first fuel electrode 102 and the second fuel heater 602 is a temperature regulator 7. The temperature regulator 7 regulates the temperature of the first fuel exhaust gas, reduces the temperature of the first fuel exhaust gas, and then enters the second fuel heater 602 with low-temperature fuel to be heated to the high-temperature fuel required for the reaction of the second-stage stack group. By reducing the temperature of the first fuel exhaust gas through the temperature regulator 7 and then heating it, it is avoided that the temperature of the first fuel exhaust gas is too high. When the low-temperature fuel enters the first fuel heater 601, the first fuel heater 601 stops heating because it recognizes that the temperature of the first fuel exhaust gas has reached the temperature of the high-temperature fuel, resulting in some low-temperature fuel entering the second-stage stack group without reaching the temperature of the high-temperature fuel, causing uneven fuel temperature entering the second-stage stack group and affecting the progress of the electrochemical reaction.

[0114] (3) When the fuel enters the first-stage stack group, start the first-stage stack group and control the fuel utilization rate of the first-stage stack group > 60%; when the fuel enters the second-stage stack group, start the second-stage stack group and control the fuel utilization rate of the second-stage stack group > 90%.

[0115] When the first-stage stack group starts to generate electricity through electrochemical reaction, adjust the flow rate of the fuel entering the first-stage stack group and the current of the first-stage stack group, and control the fuel utilization rate of the first-stage stack group > 60%.

[0116] When the second-stage stack group starts to generate electricity through electrochemical reaction, adjust the flow rate of the fuel entering the second-stage stack group and the current of the second-stage stack group, and control the fuel utilization rate of the first-stage stack group > 90%.

[0117] By adjusting the power of the air heater 5 and the fuel heater 6, as well as the inlet temperature of the first fuel electrode 102 and the inlet temperature of the second fuel electrode 202, maintain the total fuel utilization rate of the first-stage stack group and the second-stage stack group > 95% until the fuel cell system operates stably. Specifically, adjust the power of the first air heater 501, the second air heater 502, the first fuel heater 601 and the second fuel heater 602, as well as the inlet temperature of the first fuel electrode 102 and the inlet temperature of the second fuel electrode 202.

[0118] When the fuel cell system operates in a steady state, the total fuel utilization rate of the first stack group and the second stack group is maintained at > 95%, the fuel utilization rate of the first stack group is controlled between 60% and 95%, and by adjusting the fuel utilization rate of the second stack group, the fuel concentration in the second fuel tail gas is reduced to 0.0001% - 5%. The second fuel tail gas transfers heat to the low-temperature fuel through the fuel tail gas heat exchanger 402 and then is discharged from the fuel cell system, ensuring that the fuel concentration of the low-temperature fuel tail gas discharged from the fuel cell system is within the explosion limit of the combustible gas to avoid explosion.

[0119] When the fuel cell system stops operating, by reducing the power of the air heater 5 and the fuel heater 6, when the temperatures of the first air tail gas and the second air tail gas are reduced to below the start-up temperatures of the first stack group and the second stack group, the fuel supply unit is controlled to stop supplying fuel, and the currents of the first stack group and the second stack group are reduced to zero. Specifically, during the process of reducing the temperatures of the first air tail gas and the second air tail gas by reducing the power of the air heater 5 and the fuel heater 6, by gradually reducing the flow rate of the fuel entering the fuel cell system, the currents of the first stack group and the second stack group, it is ensured that the total fuel utilization rate of the first stack group and the second stack group is > 95%.

[0120] By reducing the power of the first air heater 501, the second air heater 502, the first fuel heater 601 and the second fuel heater 602, the temperatures of the first air tail gas and the second air tail gas are gradually reduced to below 400°C. During this process, the flow rate of the fuel entering the fuel cell system, the currents of the first stack group and the second stack group are gradually reduced, ensuring that the total fuel utilization rate of the first stack group and the second stack group is > 95%. When the temperature of the air entering the burner 3 is lower than 400°C, the fuel supply to the fuel cell system is stopped, and the currents of the first stack group and the second stack group are reduced to zero.

[0121] The regulation method of this fuel cell generator set greatly improves the fuel utilization rate, and thus improves the power generation efficiency.

[0122] The above content is only the preferred embodiment of the present invention. For those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. The content of this specification should not be construed as a limitation to the present invention.

Claims

1. A fuel cell system, characterized in that: include: A primary stack group, comprising at least one primary stack (1), wherein the primary stack (1) comprises a first air electrode (101), a first fuel electrode (102), and a first electrolyte (103) disposed between the first air electrode (101) and the first fuel electrode (102); A two-stage battery stack group, comprising at least one two-stage battery stack (2), wherein the two-stage battery stack (2) comprises a second air electrode (201), a second fuel electrode (202), and a second electrolyte (203) disposed between the second air electrode (201) and the second fuel electrode (202); The first fuel electrode (102) and the second fuel electrode (202) both comprise oxide materials; in the first-stage fuel cell stack (1) and the second-stage fuel cell stack (2), the ratio of the area of ​​the oxide material to the total area of ​​the fuel electrodes is 0.005 to 1; A fuel supply unit and an air supply unit, wherein the fuel supply unit provides high-temperature fuel to the primary stack group and the secondary stack group through a fuel heater (6), and the air supply unit provides high-temperature air to the primary stack group and the secondary stack group through an air heater (5).

2. The fuel cell system according to claim 1, characterized in that: The primary stack (1) and the secondary stack (2) both include a plurality of single cells, the plurality of single cells are stacked, the number of single cells located in the same layer is one, the fuel electrode in one single cell includes the oxide material and the nickel-based material, the nickel-based material is arranged near the feed inlet of the fuel flow channel, the oxide material is arranged near the discharge outlet of the fuel flow channel, and the ratio of the area of ​​the oxide material to the area of ​​the fuel electrode of the single cell is 0.005 to 1.

3. The fuel cell system according to claim 1, characterized in that: The first-stage battery stack (1) and the second-stage battery stack (2) both include a plurality of single cells, which are stacked in layers. The number of single cells located in the same layer is plural. Among the single cells located in the same layer, the fuel electrodes of some of the single cells are made of the oxide material, and the fuel electrodes of another portion of the single cells are made of nickel-based materials. The single cells whose fuel electrodes are made of the nickel-based materials are arranged near the feed inlet of the fuel flow channel, and the single cells whose fuel electrodes are made of the oxide material are arranged near the discharge outlet of the fuel flow channel. The ratio of the total area of ​​the fuel electrodes of the single cells whose fuel electrodes are made of the oxide material to the total area of ​​the fuel electrodes of all the single cells in the layer is 0.005 to 1.

4. The fuel cell system according to claim 1, characterized in that: The first electrolyte (103) and the second electrolyte (203) are both oxygen ion conductor electrolytes or proton conductor electrolytes; or, one of the first electrolyte (103) and the second electrolyte (203) is an oxygen ion conductor electrolyte and the other is a proton conductor electrolyte.

5. The fuel cell system according to claim 4, characterized in that: If the electrolyte is an oxygen ion conductor electrolyte, the oxide material is component A, a mixture of component A and component B, or a C complex, wherein the C complex includes a complex composed of component A, component B and a metal, and the ratio of the metal mass to the composite mass is less than 20%; Wherein, the A component includes one or more of cerium oxide doped with rare earth elements and transition metal elements, perovskite titanates doped with alkali metal elements, transition metal elements and rare earth elements, perovskite chromates doped with alkali metal elements, transition metal elements and rare earth elements, perovskite ferrites doped with alkali metal elements, transition metal elements and rare earth elements, perovskite manganates doped with alkali metal elements, transition metal elements and rare earth elements, perovskite nickelates doped with alkali metal elements, transition metal elements and rare earth elements, and perovskite vanadates doped with alkali metal elements, transition metal elements and rare earth elements; The B component includes one or more of doped zirconium dioxide, doped cerium oxide, and doped lanthanum gallate; The metal includes one or both of a transition metal and a noble metal.

6. The fuel cell system according to claim 4, characterized in that: If the electrolyte is a proton conductor electrolyte, the oxide material comprises a mixture of a proton conductor oxide and an electron conductor oxide; or, The oxide material comprises a composite of a proton conductor oxide, an electron conductor oxide and a metal, wherein the ratio of the metal mass to the composite mass is less than 20%, and the metal comprises one or both of a transition metal and a noble metal.

7. The fuel cell system according to claim 1, characterized in that: The fuel cell system further comprises an exhaust gas heat exchanger (4), through which high-temperature exhaust gas after the reaction of the primary fuel cell stack and the secondary fuel cell stack provides preheating heat to at least part of the fuel provided by the fuel supply unit and at least part of the air provided by the air supply unit.

8. The fuel cell system according to claim 7, characterized in that: The fuel cell system further comprises a burner (3), the gas outlet of the first air electrode (101) and the gas outlet of the second air electrode (201) are both in communication with the burner (3), the material outlet of the first fuel electrode (102) is in communication with the material inlet of the second fuel electrode (202), and the material outlet of the second fuel electrode (202) is in communication with the burner (3); The high-temperature exhaust gas after combustion in the burner (3) provides preheating heat to at least part of the fuel provided by the fuel supply unit and at least part of the air provided by the air supply unit through the exhaust gas heat exchanger (4), so as to form preheated air and preheated fuel.

9. The fuel cell system according to claim 7, characterized in that: The exhaust gas heat exchanger (4) comprises an air exhaust gas heat exchanger (401) and a fuel exhaust gas heat exchanger (402), wherein the air exhaust gas heat exchanger (401) is used to transfer the heat of the first air exhaust gas discharged by the first air electrode (101) and the heat of the second air exhaust gas discharged by the second air electrode (201) or the heat of the second air exhaust gas discharged by the second air electrode (201) to at least part of the air provided by the air supply unit to form preheated air; and the fuel exhaust gas heat exchanger (402) is used to transfer the heat of the second fuel exhaust gas discharged by the second fuel electrode (202) to at least part of the fuel provided by the fuel supply unit to form preheated fuel.

10. The fuel cell system according to claim 8 or 9, characterized in that: The air heater (5) comprises a first air heater (501) and a second air heater (502); a portion of the preheated air is heated by the first air heater (501) and then enters the first air electrode (101), and another portion of the preheated air is heated by the second air heater (502) and then enters the second air electrode (201); The fuel heater (6) includes a first fuel heater (601) and a second fuel heater (602); the preheating fuel is heated by the first fuel heater (601) and then enters the first fuel electrode (102); the low-temperature fuel supplied by the fuel supply unit is heated by the second fuel heater (602) and then enters the second fuel electrode (202).

11. The fuel cell system according to claim 10, characterized in that: A temperature regulating element is also provided between the first fuel electrode (102) and the second fuel heater (602).

12. The fuel cell system according to claim 10, characterized in that: The fuel supply unit comprises a first flow control valve (9), and the first flow control valve (9) is used to control the low-temperature fuel provided by the fuel supply unit to the primary fuel cell group and the secondary fuel cell group; The air supply unit comprises a second flow control valve (10) and a first flow distributor (11), wherein the second flow control valve (10) is used to control the low-temperature air provided by the air supply unit to the first-stage fuel cell stack (1) and the second-stage fuel cell stack (2), and the first flow distributor (11) is used to distribute the preheated air provided by the air supply unit to the first-stage fuel cell stack group and the second-stage fuel cell stack group.

13. The fuel cell system according to claim 1, characterized in that: The air supply unit further includes a mixer group configured to mix low-temperature air and preheated air entering the primary fuel cell stack group and the secondary fuel cell stack group.

14. A fuel cell generator set, characterized in that: Comprising the fuel cell system according to any one of claims 1 to 13.

15. A control method for a fuel cell generator set, characterized in that: Applied to the fuel cell generator set according to claim 14, the control method of the fuel cell generator set comprises the following steps: When the fuel cell system is started, the air supply unit provides high-temperature air to the first air electrode (101) and the second air electrode (201) through the air heater (5), and the fuel supply unit provides high-temperature fuel to the first fuel electrode (102) and the second fuel electrode (202) through the fuel heater (6), starts the first-stage stack group and the second-stage stack group, and controls the total fuel utilization rate of the first-stage stack group and the second-stage stack group to be greater than 90% or 95%; and / or, When the fuel cell system stops operating, the power of the air heater (5) and the fuel heater (6) are reduced to reduce the temperature of the first air exhaust gas discharged from the first air electrode (101) and the second air exhaust gas discharged from the second air electrode (201) to a temperature lower than the starting temperature of the first-stage stack group and the second-stage stack group, and the fuel supply unit is controlled to stop supplying fuel, and the current of the first-stage stack group and the current of the second-stage stack group are reduced to zero.

16. The control method of the fuel cell generator set according to claim 15, characterized in that: The fuel cell system further comprises an exhaust gas heat exchanger (4), wherein the exhaust gas heat exchanger (4) comprises an air exhaust gas heat exchanger (401) and a fuel exhaust gas heat exchanger (402), wherein the air exhaust gas heat exchanger (401) is used to transfer the heat of the first air exhaust gas discharged by the first air electrode (101) and the heat of the second air exhaust gas discharged by the second air electrode (201) or the heat of the second air exhaust gas discharged by the second air electrode (201) to at least part of the air provided by the air supply unit to form preheated air; and the fuel exhaust gas heat exchanger (402) is used to transfer the heat of the second air exhaust gas discharged by the second fuel electrode (202) to at least part of the air provided by the air supply unit to form preheated air. The heat of the secondary fuel tail gas is transferred to at least part of the fuel provided by the fuel supply unit to form preheated fuel; when the fuel cell system is started, the air supply unit provides high-temperature air to the first air electrode (101) and the second air electrode (201) through the air heater (5), and the fuel supply unit provides high-temperature fuel to the first fuel electrode (102) and the second fuel electrode (202) through the fuel heater (6), and the primary stack group and the secondary stack group are started, and the total fuel utilization rate of the primary stack group and the secondary stack group is controlled to be greater than 90% or 95%, which includes the following steps: The first exhaust air and the second exhaust air enter the exhaust air heat exchanger (401) to form the preheated air, which is then heated by the air heater (5) to form the high-temperature air, and then enter the first air electrode (101) and the second air electrode (201) respectively; When the temperature of the first air exhaust gas and the temperature of the second air exhaust gas are higher than the start-up temperature of the primary stack group and the secondary stack group, the fuel supply unit provides preheated fuel which is heated by the fuel heater (6) to form the high-temperature fuel and enters the primary stack group, the first fuel exhaust gas discharged by the first fuel electrode (102) is heated by the fuel heater (6) and enters the secondary stack group, and the second fuel exhaust gas discharged by the second fuel electrode (202) is heat exchanged by the fuel exhaust gas heat exchanger (402) to form the preheated fuel; When the fuel enters the primary stack group, the primary stack group is started, and the fuel utilization rate of the primary stack group is controlled to be greater than 60%; when the fuel enters the secondary stack group, the secondary stack group is started, and the fuel utilization rate of the secondary stack group is controlled to be greater than 90%; By adjusting the power of the air heater (5) and the fuel heater (6), as well as the feed port temperature of the first fuel electrode (102) and the feed port temperature of the second fuel electrode (202), the total fuel utilization of the first-stage stack group and the second-stage stack group is maintained at >95% until the fuel cell system operates in a steady state.

17. The control method of the fuel cell generator set according to claim 16, characterized in that: When the fuel cell system is in steady-state operation, the total fuel utilization of the primary stack group and the secondary stack group is maintained at >95%, the fuel utilization of the primary stack group is controlled between 60% and 95%, and the fuel concentration in the second fuel exhaust gas is reduced to 0.0001% to 5% by adjusting the fuel utilization of the secondary stack group.

18. The control method of a fuel cell generator set according to claim 15, characterized in that: The fuel cell system further comprises an exhaust gas heat exchanger (4) and a burner (3), wherein the high-temperature exhaust gas after combustion by the burner (3) provides preheating heat to at least part of the fuel provided by the fuel supply unit and at least part of the air provided by the air supply unit through the exhaust gas heat exchanger (4), so as to form preheated air and preheated fuel; when the fuel cell system is started, the air supply unit provides high-temperature air to the first air electrode (101) and the second air electrode (201) through the air heater (5), and the fuel supply unit provides high-temperature fuel to the first fuel electrode (102) and the second fuel electrode (202) through the fuel heater (6), and the first-level stack group and the second-level stack group are started, and the total fuel utilization rate of the first-level stack group and the second-level stack group is controlled to be greater than 90% or 95%, which comprises the following steps: When the fuel cell system is started, the low-temperature air provided by the air supply unit enters the first air electrode (101) and the second air electrode (201) respectively and then enters the burner (3); the low-temperature fuel provided by the fuel supply unit enters the burner (3); the high-temperature exhaust gas generated after combustion in the burner (3) provides preheating heat to at least part of the fuel provided by the fuel supply unit and at least part of the air provided by the air supply unit through the exhaust gas heat exchanger (4), so as to form preheated air and preheated fuel; the preheated air is heated by the air heater (5) to form the high-temperature air and then enters the first air electrode (101) and the second air electrode (201) respectively; When the temperature of the air tail gas entering the burner (3) is higher than the first set temperature, the preheated fuel provided by the fuel supply unit is heated by the fuel heater (6) and then enters the primary stack group, the first fuel tail gas discharged by the first fuel electrode (102) and the low-temperature fuel provided by the fuel supply unit are heated by the fuel heater (6) and then enter the secondary stack group, and the second fuel tail gas discharged by the second fuel electrode (202) enters the burner (3) for combustion; When the temperature of the exhaust air entering the burner (3) is higher than the start-up temperature of the primary fuel cell stack and the secondary fuel cell stack, the primary fuel cell stack and the secondary fuel cell stack are started, the fuel utilization rate of the primary fuel cell stack is controlled to be between 60% and 95%, and the temperature of the exhaust air entering the burner (3) gradually rises to the point where the fuel cell system is in steady state operation.

19. The control method of a fuel cell generator set according to claim 18, characterized in that: When the fuel cell system is in steady-state operation, the fuel utilization rate of the primary stack group is maintained between 60% and 95%, and the total fuel utilization rate of the primary stack group and the secondary stack group is controlled to be greater than 95%. By adjusting the flow rate of the low-temperature fuel provided by the fuel supply unit to the secondary stack group and the fuel utilization rate of the secondary stack (2), the fuel concentration in the second fuel exhaust gas is reduced to 0.0001% to 5%.

20. The control method of a fuel cell generator set according to claim 15, characterized in that: When the fuel cell system stops running, by reducing the power of the air heater (5) and the fuel heater (6), the temperature of the first air exhaust gas and the second air exhaust gas is reduced to a temperature lower than the start-up temperature of the primary stack group and the secondary stack group, and the steps of controlling the fuel supply unit to stop supplying fuel and reducing the current of the primary stack group and the current of the secondary stack group to zero specifically include: By reducing the power of the air heater (5) and the fuel heater (6), in the process of reducing the temperature of the first air exhaust gas and the second air exhaust gas, by gradually reducing the flow rate of fuel entering the fuel cell system, the current of the first-stage stack group and the current of the second-stage stack group, it is ensured that the total fuel utilization rate of the first-stage stack group and the second-stage stack group is greater than 95%.

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