Fuel cell off-gas recovery system, fuel cell system, and control method

Abstract

The application discloses a fuel cell tail gas recovery system, a fuel cell system and a control method. The fuel cell tail gas recovery system comprises a shunt, a water evaporator, an exhaust pipeline and an adjusting assembly. The shunt is used for receiving tail gas and dividing the tail gas into at least a first branch flow and a second branch flow. The water evaporator comprises a first heat exchange side and a second heat exchange side, and the first branch flow is communicated with an inlet of the first heat exchange side. One end of the exhaust pipeline is connected to an outlet of the first heat exchange side. The adjusting assembly is communicated with the exhaust pipeline and used for introducing compressed gas into the exhaust pipeline. The introduction amount of the compressed gas can be adjusted according to the operation condition of the fuel cell system, so that the temperature of the water evaporator can be effectively prevented from changing suddenly, and the long-term normal operation of the fuel cell system can be maintained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fuel cell, in particular to a fuel cell tail gas recovery system, a fuel cell system and a control method. BACKGROUND

[0002] In a fuel cell system, a module for oxidizing the anode tail gas and the cathode tail gas discharged by the stack is usually arranged, so as to avoid the pollution caused by the residual fuel in the tail gas being discharged into the environment or the combustion and explosion. After being oxidized, the anode tail gas and the cathode tail gas generate high-temperature fuel oxidation tail gas. In order to improve the thermal energy utilization efficiency of the fuel cell, the fuel oxidation tail gas is usually subjected to heat recovery, for example, the fuel oxidation tail gas is introduced into a water evaporator and exchanges heat with the liquid water in the water evaporator, so that the liquid water forms high-temperature water vapor, and the high-temperature water vapor mixes with the fuel and then returns to the anode of the stack to participate in the reaction.

[0003] When the fuel cell system rapidly increases the output power to meet the power demand, a large amount of liquid water exchanges heat with the high-temperature fuel oxidation tail gas. At this time, since the flow of the fuel oxidation tail gas is relatively constant, the rapid heat exchange reaction of a large amount of liquid water in a short time will cause the water evaporator to bear a sharp temperature change, which will cause the temperature change rate to exceed the range that can be borne by the material of the water evaporator, thereby easily causing the life and stability of the water evaporator to decrease, thereby affecting the normal operation of the fuel cell system. SUMMARY

[0004] To solve at least one of the above technical problems, the present application provides a fuel cell tail gas recovery system, a fuel cell system and a control method. By introducing compressed gas into the exhaust pipeline connected to the first heat exchange side outlet of the water evaporator, the temperature of the water evaporator can be effectively prevented from changing sharply. The technical solutions adopted are as follows.

[0005] In a first aspect, the present application provides a fuel cell tail gas recovery system, which comprises a shunt, a water evaporator, an exhaust pipeline and an adjusting assembly. The shunt is used to receive tail gas and divide the tail gas into at least a first branch and a second branch. The water evaporator comprises a first heat exchange side and a second heat exchange side. The first branch is connected to the inlet of the first heat exchange side, and the second heat exchange side is used to introduce liquid water. One end of the exhaust pipeline is connected to the outlet of the first heat exchange side. The adjusting assembly is connected to the exhaust pipeline and used to introduce compressed gas into the exhaust pipeline.

[0006] In some embodiments of the present application, the angle at which the compressed gas is introduced into the exhaust pipeline is adjustable.

[0007] In some embodiments of the present application, the exhaust pipeline is provided with a preset pressure loss part, which is used to provide a preset pressure loss to the first heat exchange side.

[0008] In some embodiments of the present application, the fuel cell tail gas recovery system further comprises a second heat exchanger, and the second branch is communicated to one of the heat exchange sides of the second heat exchanger.

[0009] In a second aspect, the present application provides a fuel cell system, comprising a fuel cell stack, a fuel oxidizer, and the fuel cell tail gas recovery system provided in the first aspect of the present application; wherein the anode outlet and the cathode outlet of the fuel cell stack are both communicated to the inlet of the fuel oxidizer, the outlet of the fuel oxidizer is connected to the flow divider, the second heat exchanger is an air heat exchanger, and the other heat exchange side of the air heat exchanger is connected to the cathode inlet of the fuel cell stack.

[0010] In some embodiments of the present application, the fuel cell system further comprises a fuel heat exchanger, the water vapor flowing out of the second heat exchange side of the water evaporator is used to mix with fuel and enter the third heat exchange side of the fuel heat exchanger, the inlet of the fourth heat exchange side of the fuel heat exchanger is communicated to the anode outlet of the fuel cell stack, the anode tail gas in the fuel cell stack is used to heat the third heat exchange side, the outlet of the third heat exchange side is communicated to the anode inlet of the fuel cell stack, and the outlet of the fourth heat exchange side is communicated to the inlet of the fuel oxidizer.

[0011] In a third aspect, the present application provides a control method of a fuel cell tail gas recovery system, which uses the fuel cell tail gas recovery system provided in the first aspect of the present application and comprises: introducing a first branch gas into the first heat exchange side of the water evaporator, and the first branch gas flows out of the outlet of the first heat exchange side and enters the exhaust pipe; supplying compressed gas to the exhaust pipe by using the adjusting assembly; adjusting the input amount of the compressed gas to change the flow rate of the first branch gas; wherein when the electric energy output of the fuel cell system increases, the input flow rate of the compressed gas is reduced; and when the electric energy output of the fuel cell system decreases, the input flow rate of the compressed gas is increased.

[0012] In some embodiments of the present application, the step of supplying compressed gas to the exhaust pipe by using the adjusting assembly comprises: adjusting the angle of the compressed gas entering the exhaust pipe by the adjusting assembly.

[0013] In some embodiments of the present application, the step of adjusting the input amount of the compressed gas to change the flow rate of the first branch gas comprises: adjusting the input flow rate of the compressed gas so that the fluid temperature at the outlet of the first heat exchange side of the water evaporator is maintained within a preset temperature range when the fuel cell system is in a full-load power generation state and when the fuel cell system is in a heat preservation state; or adjusting the input flow rate of the compressed gas so that the rate of change of the fluid temperature at the outlet of the first heat exchange side of the water evaporator does not exceed a preset value.

[0014] In some embodiments of the present application, adjusting the amount of compressed gas introduced to change the gas flow rate of the first branch includes: when the electrical power output of the fuel cell system is increased and the rate of change of the temperature of the fluid at the outlet of the first heat exchange side exceeds a preset value, if the temperature of the fluid at the outlet of the first heat exchange side rises, the rate of change of the compressed gas flow rate is slowed down; if the temperature of the fluid at the outlet of the first heat exchange side falls, the rate of change of the compressed gas flow rate is accelerated; when the electrical power output of the fuel cell system is decreased and the rate of change of the temperature of the fluid at the outlet of the first heat exchange side exceeds a preset value, if the temperature of the fluid at the outlet of the first heat exchange side rises, the rate of change of the compressed gas flow rate is accelerated; if the temperature of the fluid at the outlet of the first heat exchange side falls, the rate of change of the compressed gas flow rate is slowed down.

[0015] The embodiments of the present application have at least the following beneficial effects: by introducing compressed gas into the exhaust pipe connected to the outlet of the first heat exchange side of the water evaporator and controlling the compressed gas flow rate, the fluid flow resistance of the first heat exchange side of the water evaporator can be adjusted, thereby adjusting the pressure loss of the first heat exchange side of the water evaporator. Since the fuel oxidation tail gas is divided into at least two branches, when the pressure loss of the first heat exchange side of the water evaporator increases or decreases, the pressure loss of the first branch in communication with the first heat exchange side also increases or decreases accordingly, so that the flow rate of the fuel oxidation tail gas distributed to the first branch also decreases or increases accordingly. When the flow rate of the liquid water introduced into the water evaporator changes, the flow rate of the fuel oxidation tail gas introduced into the first branch can be matched with the flow rate of the liquid water by adjusting the flow rate of the compressed gas introduced, thereby effectively suppressing the sudden change of the temperature of the water evaporator under the premise of ensuring the heat exchange demand of the liquid water, maintaining the water evaporator in a stable working state and prolonging the service life of the water evaporator, and ensuring the long-term normal operation of the fuel cell system. BRIEF DESCRIPTION OF DRAWINGS

[0016] The present application will be further illustrated below in conjunction with the accompanying drawings and embodiments. It should be noted that the embodiments embodied in the following drawings are exemplary and are only used to explain the present application, and cannot be understood as a limitation on the present application.

[0017] Figure 1 A schematic diagram of a fuel cell tail gas recovery system provided for an embodiment of the present application;

[0018] Figure 2 A schematic diagram of a fuel cell system provided for an embodiment of the present application;

[0019] Figure 3 A schematic diagram of a fuel cell system provided for an embodiment of the present application;

[0020] Figure 4 A flowchart of a fuel cell tail gas recovery control method provided for an embodiment of the present application;

[0021] Figure 5The compressed gas of the fuel cell tail gas recovery system provided by the embodiments of the present application is injected into the exhaust pipeline at an injection angle.

[0022] The reference signs: flow divider 100, first branch flow 110, second branch flow 120, water evaporator 200, first heat exchange side inlet 210, first heat exchange side outlet 220, second heat exchange side inlet 230, second heat exchange side outlet 240, adjusting assembly 300, exhaust pipeline 400, air heat exchanger 500, hot side flow path inlet 510, hot side flow path outlet 520, cold side flow path inlet 530, cold side flow path outlet 540, stack 600, anode inlet 610, anode outlet 620, cathode inlet 630, cathode outlet 640, fuel oxidizer 700, fuel oxidizer inlet 710, 720, fuel oxidizer outlet 730, fuel heat exchanger 810, third heat exchange side inlet 811, third heat exchange side outlet 812, fourth heat exchange side inlet 813, fourth heat exchange side outlet 814, pre-reformer 820, anode tail gas flow divider 830. DETAILED DESCRIPTION

[0023] The embodiments of the present application are described in detail below with reference to the accompanying drawings, wherein the same or similar notations represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as a limitation of the present application.

[0024] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms “center”, “middle”, “longitudinal”, “transverse”, “length”, “width”, “thickness”, “upper”, “lower”, “front”, “rear”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inner”, “outer”, “axial”, “radial”, “circumferential” and the like are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the device or element indicated must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application.

[0025] In the description of the present application, if the meaning of several is more than one, the meaning of multiple is more than two, greater than, less than, more than, etc. are understood as not including the number, above, below, etc. are understood as including the number. If it is described that the first, the second is only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features or the sequence of indicated technical features.

[0026] In the description of the application, unless otherwise clearly specified and limited, the terms "set", "install", "connect", "connect" should be understood broadly, for example: can be fixedly connected, can also be detachably connected, or integrally connected; can be mechanically connected, can also be electrically connected; can be directly connected, can also be indirectly connected through an intermediate medium, can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0027] In the description of the application, if the description of the terms "as an embodiment", "an embodiment", "some examples", "some embodiments", "illustrative embodiments", "example", "specific example", "some examples" appears, it means that the specific features, structures, materials or characteristics described in combination with the embodiment or example are included in at least one embodiment or example of the application. In the specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0028] Please refer to Figure 1In a first aspect, the application provides a fuel cell tail gas recovery system, which comprises a flow divider 100, a water evaporator 200, an exhaust pipe 400 and an adjusting assembly 300. The flow divider 100 is configured to receive tail gas and divide the tail gas into at least a first branch 110 and a second branch 120. The water evaporator 200 comprises a first heat exchange side and a second heat exchange side. The first branch 110 is connected to an inlet 210 of the first heat exchange side. The second heat exchange side is configured to introduce liquid water. An outlet 220 of the first heat exchange side is connected to one end of the exhaust pipe 400. The adjusting assembly 300 is connected to the exhaust pipe 400 and configured to introduce compressed gas into the exhaust pipe 400. Specifically, the flow divider 100 is configured to receive fuel oxidation tail gas and divide the fuel oxidation tail gas. The outlet 220 of the first heat exchange side of the water evaporator 200 is configured to discharge the fuel oxidation tail gas after heat exchange reaction. The inlet 230 of the second heat exchange side of the water evaporator 200 is configured to introduce liquid water. The outlet 240 of the second heat exchange side is configured to discharge high-temperature water vapor after heat exchange reaction. By introducing compressed gas into the exhaust pipe 400, the flow resistance of the first heat exchange side of the water evaporator 200 is increased, and the pressure loss of the first heat exchange side of the water evaporator 200 is increased. Since the fuel oxidation tail gas is divided into at least two branches, when the pressure loss of the first heat exchange side of the water evaporator 200 is increased, the pressure loss of the first branch 110 connected to the first heat exchange side is also increased. At this time, more fuel oxidation tail gas will flow into the second branch 120, thereby reducing the flow of fuel oxidation tail gas distributed to the first branch 110. Therefore, the amount of compressed gas introduced can be adjusted according to the amount of liquid water introduced into the water evaporator 200, thereby controlling the pressure loss of the first heat exchange side. The flow of the first branch 110 introduced into the water evaporator 200 for heat exchange reaction can be matched with the amount of liquid water introduced, thereby slowing down the heat exchange reaction of the liquid water in the water evaporator 200, preventing the temperature of the water evaporator 200 from changing suddenly, and thereby maintaining the working stability of the water evaporator 200 and prolonging the service life of the water evaporator 200, ensuring the long-term normal operation of the fuel cell system.

[0029] Compared with the prior art which uses an active control valve to divide the fuel oxidation tail gas, the active control valve cannot withstand high temperature and has a short service life, which requires regular replacement of the valve and thus increases the operating cost of the fuel cell system. The fuel cell tail gas recovery system provided by the application adjusts the gas flow of the first branch 110 by introducing compressed gas, thereby enabling the flow divider 100 to automatically distribute the flow of each branch tail gas. Therefore, in other examples, the flow divider 100 can use passive devices, which not only can withstand high temperature, but also are inexpensive, which helps to improve the stability of the fuel cell system and reduce the operating cost.

[0030] Illustratively, the compressed gas introduced into the exhaust pipe 400 can be inert gas or air.

[0031] Optionally, the regulating assembly 300 can be an air compressor, which is in communication with the atmosphere and produces compressed air, and the produced compressed air can be directly supplied to the exhaust pipe 400; or the regulating assembly 300 can be a single or multiple compressed gas storage tank, and the compressed gas in the storage tank is delivered to the exhaust pipe 400 through a valve or a gas pump.

[0032] Optionally, the regulating assembly 300 can be arranged on the side wall of the exhaust pipe 400, and the compressed gas is introduced into the exhaust pipe 400 at an angle through the communication between the regulating assembly 300 and the exhaust pipe 400, and the specific arrangement position of the regulating assembly 300 on the side wall of the exhaust pipe 400 is not limited. In addition, the regulating assembly 300 can also be directly connected with the pipe opening of the exhaust pipe 400 away from the first heat exchange side outlet 220, and at this time, the compressed gas is introduced into the exhaust pipe 400 in a direction parallel to the exhaust pipe 400.

[0033] Optionally, in order to improve the energy utilization efficiency of the fuel cell system, the second branch flow 120 can be connected with other heat exchangers for heat exchange reaction, and the flow divider 100 can also divide the fuel oxidation exhaust gas into multiple branch flows according to the actual use demand of the fuel cell system.

[0034] Optionally, the regulating assembly 300 is further provided with a flow valve, and the flow of the compressed gas introduced into the exhaust pipe 400 can be controlled through the flow valve.

[0035] Optionally, a temperature sensor is further arranged at the first heat exchange side outlet 220, and the temperature sensor can monitor the temperature of the fluid discharged at the first heat exchange side outlet 220, and according to the monitored temperature data, the flow of the compressed gas introduced into the exhaust pipe 400 can be controlled.

[0036] In some embodiments, the inlet angle of the compressed gas into the exhaust pipe 400 is adjustable. It can be understood that when the included angle between the inlet direction of the compressed gas and the axis of the exhaust pipe 400 is large, the compressed gas will have strong turbulent flow, which will increase the pressure loss, and when the included angle between the inlet direction of the compressed gas and the axis of the exhaust pipe 400 is small, the flow of the compressed gas will be more stable, and the pressure loss caused will be smaller. By adjusting the inlet angle of the compressed gas in the exhaust pipe 400, the influence of the compressed gas on the pressure loss of the first heat exchange side can be adjusted, so that the pressure loss of the first heat exchange side can be slightly adjusted without changing the flow of the compressed gas, and then the flow of the fuel oxidation exhaust gas into the water evaporator 200 can be slightly adjusted.

[0037] Optionally, an intake valve is provided at the connection between the adjusting component 300 and the exhaust pipe 400. Adjusting the angle between the intake valve and the exhaust pipe 400 adjusts the intake angle of the compressed gas. Alternatively, a gas guide plate is provided at the connection between the adjusting component 300 and the exhaust pipe 400. Adjusting the angle of the guide plate adjusts the intake angle of the compressed gas. The adjusting component 300 can also be connected to the exhaust pipe 400 via a structure such as a tee connector. By selecting connector structures with different angle specifications, the intake angle of the adjusting component 300 can be adjusted.

[0038] In some embodiments, the exhaust pipe 400 is provided with a preset pressure loss section, which can be used to provide a preset pressure loss to the first heat exchange side. By providing a preset pressure loss section to the exhaust pipe 400, a preset flow resistance can be provided to the fluid in the exhaust pipe 400, thereby providing a preset pressure loss to the first heat exchange side, effectively reducing excessive fluctuations in the fluid on the first heat exchange side, maintaining the relative stability of the fluid on the first heat exchange side, and making the state changes of the fluid more controllable. When the fluid on the first heat exchange side maintains a relatively stable flow state, compressed gas can be introduced into the exhaust pipe 400 to increase the pressure loss on the first heat exchange side, so that the flow rate of fuel oxidation exhaust gas allocated to the first branch 110 can be reduced to a flow rate that matches the liquid water inlet flow rate, thereby slowing down the heat exchange reaction of liquid water in the water evaporator 200. Therefore, by providing a preset pressure loss section, the process of adjusting the flow rate of fuel oxidation exhaust gas using compressed gas can be made more precise.

[0039] Optionally, the pre-set pressure loss section includes a bend. The bend is formed by bending a portion of the exhaust pipe 400. When fluid at the first heat exchange side outlet 220 passes through the bend, the increased contact area between the fluid and the pipe increases the flow resistance, thereby providing a pre-set pressure loss for the first heat exchange side. The pre-set pressure loss on the first heat exchange side can be further adjusted by regulating the degree of bend or the length of the bend.

[0040] Optionally, the pre-set pressure loss section includes a contraction section. The contraction section is formed by reducing the diameter of a portion of the exhaust pipe 400. When fluid flows from the pipe with a normal diameter to the narrowed pipe, the flow resistance increases, thereby providing a pre-set pressure loss for the first heat exchange side. The pre-set pressure loss on the first heat exchange side can be further adjusted by adjusting the diameter and length of the contraction section.

[0041] Optionally, the pre-set pressure loss section is located at one end of the exhaust pipe 400 away from the first heat exchange side outlet 220, or it can be located in the middle of the exhaust pipe 400, or it can be located at one end of the exhaust pipe 400 close to the first heat exchange side outlet 220.

[0042] Optionally, the adjustment component 300 is disposed between the preset pressure loss section and the first heat exchange side outlet 220.

[0043] Optionally, the end of the exhaust pipe 400 furthest from the first heat exchanger outlet 220 can be connected to a recovery filter. The fluid discharged from the first heat exchanger outlet 220 passes through the recovery filter, where some impurities that easily cause air pollution are filtered out before being discharged into the atmosphere. Optionally, the recovery filter can also be further connected to a compressed gas recovery device, which can recover inert gases or air from the filtered fluid, thereby producing compressed gas again.

[0044] In some embodiments, the fuel cell exhaust gas recovery system further includes a second heat exchanger, with a second branch 120 connected to one of the heat exchange sides of the second heat exchanger. After passing through the splitter 100, the fuel oxidation exhaust gas is divided into a first branch 110 and a second branch 120. The first branch 110 enters a water evaporator 200 for heat exchange reaction, causing the liquid water entering the water evaporator 200 to form high-temperature steam. The second branch 120 enters one of the heat exchange sides of the second heat exchanger for heat exchange reaction, thereby further recovering and utilizing the heat in the fuel oxidation exhaust gas. Specifically, the second heat exchanger has a hot-side flow path and a cold-side flow path. The second branch 120 of the fuel oxidation exhaust gas enters the second heat exchanger through the inlet 510 of the hot-side flow path to participate in heat exchange.

[0045] Optionally, the second heat exchanger is an air heat exchanger 500. Fresh air enters the air heat exchanger 500 through the inlet 530 of the cold side flow path and undergoes a heat exchange reaction with the fuel oxidation exhaust gas that enters through the inlet 510 of the hot side flow path. The high-temperature air after heat exchange is discharged through the outlet 540 of the cold side flow path, while the cooled exhaust gas after heat exchange is discharged and recycled through the outlet 520 of the hot side flow path.

[0046] Optionally, the second heat exchanger is a coolant heat exchanger. The coolant enters the heat exchanger through the inlet 530 of the cold side flow path and undergoes a heat exchange reaction with the fuel oxidation exhaust gas that enters through the inlet 510 of the hot side flow path, thereby removing the heat from the fuel oxidation exhaust gas to maintain the thermal balance of the fuel cell system and prevent the power output efficiency from being affected due to excessively high fuel system temperature. The coolant and exhaust gas after heat exchange are discharged and recovered through the outlet 540 of the cold side flow path and the outlet 520 of the hot side flow path, respectively.

[0047] Optionally, the diverter 100 can divide the fuel oxidation exhaust gas into multiple branches, and correspondingly, multiple heat exchangers can be set up and connected to the multiple branches to recover and utilize the heat in the fuel oxidation exhaust gas of each branch.

[0048] Please see Figure 2This application provides a fuel cell system in a second aspect, including a fuel cell stack 600, a fuel oxidizer 700, and the fuel cell exhaust gas recovery system provided in the first aspect of this application. The anode outlet 620 of the fuel cell stack 600 is connected to one inlet 710 of the fuel oxidizer, and the cathode outlet 640 is connected to the other inlet 720 of the fuel oxidizer. The outlet 730 of the fuel oxidizer is connected to a splitter 100. The second heat exchanger is an air heat exchanger 500, and the other heat exchange side of the air heat exchanger 500 is connected to the cathode inlet 630 of the fuel cell stack 600. By applying the exhaust gas recovery system provided in the first aspect of this application to a fuel cell system, the fuel oxidation exhaust gas can be effectively recovered and treated while preventing the performance of the water evaporator 200 from deteriorating due to sudden temperature changes, thereby affecting the normal operation of the fuel cell system. Specifically, after the fuel cell stack 600 undergoes a redox reaction, exhaust gases are generated at the anode and cathode, respectively. Since the anode outlet 620 of the fuel cell stack 600 is connected to one inlet 710 of the fuel oxidizer, and the cathode outlet 640 is connected to the other inlet 720 of the fuel oxidizer, the exhaust gases generated by the fuel cell stack 600 can enter the fuel oxidizer. The fuel oxidizer oxidizes the residual fuel in the exhaust gases to prevent explosion hazards during subsequent emissions. The exhaust gases generated after fuel oxidation are divided into a first branch 110 and a second branch 120 by a splitter 100. The fuel oxidation exhaust gases from the first branch 110 enter the water evaporator 200, where they exchange heat with the liquid water flowing into the water evaporator 200. The cooled exhaust gases are then discharged through the outlet 220 on the first heat exchange side of the water evaporator 200. The high-temperature water vapor formed by the liquid water absorbing heat mixes with the fuel, and the mixed fuel is then transported to the anode of the fuel cell stack 600 to participate in the redox reaction. The fuel oxidation exhaust gas from the second branch 120 is fed into the air heat exchanger 500 for heat exchange. The high-temperature air generated after heat exchange can be delivered to the cathode of the fuel cell stack 600 to participate in the oxidation-reduction reaction and output electrical energy.

[0049] It is understandable that by introducing compressed gas into the exhaust pipe 400, the amount of fuel oxidation exhaust gas entering the water evaporator 200 can be reduced, while the amount of fuel oxidation exhaust gas entering the air heat exchanger 500 can be increased. This allows the flow rate of fuel oxidation exhaust gas entering the water evaporator 200 to match the flow rate of liquid water entering the water evaporator 200, thereby slowing down the thermal reaction in the water evaporator 200 and suppressing sudden temperature changes in the water evaporator 200.

[0050] Please see Figure 3In some embodiments, the fuel cell system further includes a fuel heat exchanger 810. Water vapor flowing from the second heat exchange side outlet 240 of the water evaporator 200 is mixed with fuel and introduced into the third heat exchange side of the fuel heat exchanger 810. The inlet 813 of the fourth heat exchange side of the fuel heat exchanger 810 is connected to the anode outlet 620 of the fuel stack 600. The anode exhaust gas in the fuel stack 600 is used to heat the third heat exchange side. The outlet 812 of the third heat exchange side is connected to the anode inlet 610 of the fuel stack 600. The outlet 814 of the fourth heat exchange side is connected to one of the inlets 710 of the fuel oxidizer. By providing the fuel heat exchanger 810, the fuel is preheated using the heat from the exhaust gas generated by the fuel stack 600 before it is delivered to the fuel stack 600. This not only improves the redox reaction efficiency of the fuel stack 600 but also allows for the recovery and utilization of the heat generated by the fuel stack 600, thereby improving the thermal efficiency of the fuel cell system and reducing heat loss.

[0051] Optionally, a pre-reformer 820 can be installed between the inlet 811 of the third heat exchange side of the fuel heat exchanger 810 and the outlet 240 of the second heat exchange side of the water evaporator 200. The fuel input to the fuel cell system, after mixing with the high-temperature steam generated by the water evaporator 200, is first conveyed to the pre-reformer 820. After processing in the pre-reformer 820, the fuel is then introduced into the third heat exchange side of the fuel heat exchanger 810. The pre-reformer 820 can perform a reforming reaction on the fuel, optimizing fuel performance and improving the output efficiency of the fuel cell system.

[0052] Optionally, an anode tail gas diversion component 830 may be provided between the outlet 814 of the fourth heat exchange side of the fuel heat exchanger 810 and one of the inlets 710 of the fuel oxidizer. The anode tail gas diversion component 830 can divert a portion of the anode tail gas to the fuel oxidizer 700 for reaction, while the other portion of the anode tail gas can be recovered as fuel and remixed with the high-temperature steam generated by the water evaporator 200 to be delivered to the fuel stack 600 to participate in the redox reaction.

[0053] Please see Figure 4 This application provides a control method for a fuel cell exhaust gas recovery system in a third aspect, which employs the fuel cell exhaust gas recovery system provided in the first aspect of this application, and includes:

[0054] S1000: A first branch gas 110 is introduced into the first heat exchange side of the water evaporator 200. The first branch gas 110 enters the exhaust pipe 400 from the outlet 220 of the first heat exchange side.

[0055] S2000: Compressed gas is supplied to the exhaust pipe 400 using the regulating component 300;

[0056] S3000: Adjust the flow rate of compressed gas to change the gas flow rate of the first branch 110; wherein, when the power output of the fuel cell system increases, the compressed gas input flow rate is reduced; when the power output of the fuel cell system decreases, the compressed gas input flow rate is increased.

[0057] It is understandable that, since the control method of the fuel cell exhaust gas recovery system adopts the fuel cell exhaust gas recovery system described in the first aspect above, the control method of this fuel cell exhaust gas recovery system has the beneficial effects described in the first aspect above, which is to avoid the water evaporator 200 from being subjected to drastic temperature changes, thereby maintaining the working stability of the water evaporator 200 and extending the service life of the water evaporator 200, and ensuring the long-term normal operation of the fuel cell system. This will not be elaborated further here. Specifically, when the power output of the fuel cell system increases, the system needs to generate more high-temperature water vapor to mix with the fuel to participate in the redox reaction of the stack 600, thereby outputting more power. Therefore, compared with before increasing the power output, the input flow rate of compressed gas needs to be reduced. At this time, the pressure loss on the first heat exchange side in the water evaporator 200 decreases, causing a decrease in the pressure loss of the first branch 110. More fuel oxidation exhaust gas will enter the water evaporator 200 to undergo heat exchange reaction with liquid water, thereby generating more high-temperature water vapor. Conversely, when the power output of the fuel cell system decreases, less high-temperature water vapor is needed for the reaction. Compared to before the power output decreases, the input flow rate of compressed gas needs to be increased. By increasing the pressure loss on the first heat exchange side of the water evaporator 200, the pressure loss of the first branch 110 increases. This prevents excessive fuel oxidation exhaust gas from entering the water evaporator 200, thus avoiding a sharp rise in its temperature due to accumulated heat exceeding its normal operating requirements. By adjusting the compressed gas flow rate, the pressure loss on the first heat exchange side of the water evaporator 200 can be adjusted, thereby controlling the pressure loss of the first branch 110 and achieving control over the ratio of fuel oxidation exhaust gas flow rates between the first branch 110 and other branches. Therefore, when the flow rate of liquid water entering the water evaporator 200 changes according to the actual power consumption demand, the flow rate of fuel oxidation exhaust gas entering the first branch can be matched with the flow rate of liquid water by adjusting the flow rate of compressed gas. This allows the high-temperature exhaust gas in the water evaporator 200 to undergo a heat exchange reaction with the liquid water, forming high-temperature water vapor that meets the requirements of the fuel cell system, while also preventing the water evaporator 200 from experiencing a sudden temperature change due to excessive heat accumulation or dissipation.

[0058] In some embodiments, the above step S2000 of supplying compressed gas to the exhaust pipe 400 using the regulating component 300 includes:

[0059] S2100: Adjustment component 300 adjusts the intake angle of compressed gas in exhaust pipe 400.

[0060] Please see Figure 5 Adjusting the intake angle α of the compressed gas in the exhaust pipe 400 can adjust the impact of the compressed gas on the pressure loss of the first heat exchange side. This allows for fine-tuning of the pressure loss on the first heat exchange side without changing the compressed gas flow rate, thereby enabling fine-tuning of the fuel oxidation exhaust gas flow rate entering the water evaporator 200. It is understandable that, with a constant compressed gas flow rate, the smaller the value of α, the greater the pressure loss on the first heat exchange side. The pressure loss is greatest when α is zero, i.e., when the compressed gas enters the outlet 220 of the first heat exchange side at an angle parallel to the exhaust pipe 400.

[0061] Optionally, the amount of compressed gas input and the intake angle of the compressed gas in the exhaust pipe 400 can be adjusted simultaneously according to the actual amount of fuel oxidation exhaust gas used by the water evaporator 200.

[0062] In some embodiments, step S3000, which adjusts the amount of compressed gas introduced to change the gas flow rate of the first branch 110, includes:

[0063] S3110: Adjust the compressed gas flow rate so that the fluid temperature at the outlet 220 of the first heat exchange side of the water evaporator 200 is maintained within a preset temperature range when the fuel cell system is in full-load power generation state and when the fuel cell system is in heat preservation state.

[0064] When the fuel cell system is in full-load power generation mode, the output power is at its highest. When the fuel cell system is in heat preservation mode, the output power is at its lowest. By controlling the flow rate of compressed gas, the fluid temperature at the outlet 220 of the first heat exchange side can be maintained within a preset range when the fuel cell system is in the two boundary states. This prevents the fluid temperature at the outlet 220 of the first heat exchange side from differing too much, thereby maintaining the thermal balance of the water evaporator 200. This prevents the water evaporator 200 from being damaged by an excessive temperature gradient when the fuel cell system quickly adjusts from heat preservation mode to full-load power generation mode, or vice versa.

[0065] Optionally, the fluid temperature at the outlet 220 of the first heat exchange side when the fuel cell system is in full-load power generation state is set as T1, and the fluid temperature at the outlet 220 of the first heat exchange side when the fuel cell system is in heat preservation state is set as T2, where T1 and T2 satisfy |T2-T1| / T1≤0.5.

[0066] Optionally, the temperature range of T1 is 100℃≤T1≤250℃, and the temperature range of T2 is 100℃≤T2≤250℃. Optionally, T2≈T1±50℃.

[0067] In some embodiments, step S3000, which adjusts the amount of compressed gas introduced to change the gas flow rate of the first branch 110, includes:

[0068] S3120: Adjust the compressed gas flow rate so that the fluid temperature change rate at the outlet 220 of the first heat exchange side of the water evaporator 200 does not exceed the preset value.

[0069] The fluid temperature change rate at the outlet 220 of the first heat exchange side of the water evaporator 200 refers to the temperature change value of the fluid at the outlet 220 of the first heat exchange side per unit time. By controlling the fluid temperature change rate at the outlet 220 of the first heat exchange side of the water evaporator 200 to not exceed the preset value, the water evaporator 200 can be prevented from being subjected to a temperature change value that exceeds the material's tolerance, thereby maintaining the normal operating performance of the water evaporator 200.

[0070] It is understood that a failure test can be conducted on the water evaporator 200 based on the manufacturing materials of the water evaporator 200 to determine a preset value for the temperature change rate for a specific water evaporator 200. For example, the preset value for the temperature change rate can be set to 600℃ / h.

[0071] In some embodiments, step S3000, which adjusts the amount of compressed gas introduced to change the gas flow rate of the first branch 110, includes:

[0072] S3130: When the power output of the fuel cell system increases and the fluid temperature change rate at the outlet 220 of the first heat exchange side exceeds a preset value, if the fluid temperature at the outlet 220 of the first heat exchange side rises, the rate of change of compressed gas flow rate is slowed down; if the fluid temperature at the outlet 220 of the first heat exchange side falls, the rate of change of compressed gas flow rate is accelerated.

[0073] Understandably, when the power output of the fuel cell system increases, the system requires more high-temperature water vapor to participate in the redox reaction of the stack 600 to output more power. Therefore, compared with before the power output increased, the flow rate of compressed gas needs to be reduced. However, if the rate of decrease in compressed gas flow rate is too fast, the pressure drop of the first branch 110 connected to the water evaporator 200 will drop rapidly. A large amount of high-temperature fuel oxidation exhaust gas will rush into the water evaporator 200 per unit time and undergo a violent heat exchange reaction with the liquid water. This will cause the temperature of the water evaporator 200 to rise sharply per unit time due to excessive heat supply, and the temperature of the fluid discharged from the outlet 220 on the first heat exchange side will rise, exceeding the preset temperature change rate value. Therefore, it is necessary to reduce the rate of decrease in compressed gas flow rate to allow the pressure drop of the first branch 110 connected to the water evaporator 200 to decrease slowly, thereby gradually increasing the flow rate of fuel oxidation exhaust gas entering the water evaporator 200, allowing for a stable heat exchange reaction inside the water vapor. Similarly, if the rate of decrease of the compressed gas flow is too slow, the pressure loss of the first branch 110 connected to the water evaporator 200 will not decrease significantly, resulting in insufficient high-temperature fuel oxidation exhaust gas to enter the water evaporator 200 for heat exchange per unit time. Since the heat provided by the fuel oxidation exhaust gas is insufficient to meet the heat exchange requirements of the water evaporator 200 under normal operating conditions, the temperature of the fluid discharged at the outlet 220 of the first heat exchange side drops sharply and exceeds the preset temperature change rate value. Therefore, it is necessary to accelerate the rate of decrease of the compressed gas flow so that more fuel oxidation exhaust gas can enter the water evaporator 200 to provide sufficient heat.

[0074] In some embodiments, step S3000, which adjusts the amount of compressed gas introduced to change the gas flow rate of the first branch 110, further includes:

[0075] S3140: When the power output of the fuel cell system decreases and the fluid temperature change rate at the outlet 220 of the first heat exchange side exceeds a preset value, if the fluid temperature at the outlet 220 of the first heat exchange side rises, the rate of change of compressed gas flow rate will be accelerated; if the fluid temperature at the outlet 220 of the first heat exchange side falls, the rate of change of compressed gas flow rate will be slowed down.

[0076] Understandably, when the power output of the fuel cell system decreases, less high-temperature water vapor is needed for the reaction, requiring an increase in the input flow rate of compressed gas compared to before the power output reduction. However, if the rate of increase in compressed gas flow rate is too slow, the rate of increase in pressure loss of the first branch 110 connected to the water evaporator 200 will also be too slow. This results in a large amount of high-temperature fuel oxidation exhaust gas still entering the water evaporator 200 per unit time. Due to excessive heat supply, the temperature of the water evaporator 200 rises sharply per unit time, causing the temperature change rate of the fluid discharged at the outlet 220 of the first heat exchange side to exceed the preset value. Therefore, it is necessary to accelerate the rate of increase in compressed gas flow rate to increase the pressure loss of the first heat exchange side connected to the water evaporator 200, thereby reducing the amount of fuel oxidation exhaust gas entering the water evaporator 200 and preventing a sudden increase in the temperature of the water evaporator 200. Similarly, if the rate of increase of the compressed gas flow rate is too fast, the rate of increase of the pressure loss of the first branch 110 connected to the water evaporator 200 will be too fast, resulting in insufficient amount of high-temperature fuel oxidation exhaust gas entering the water evaporator 200 for heat exchange per unit time. Since the heat provided by the fuel oxidation exhaust gas is insufficient to meet the heat exchange requirements of the water evaporator 200 under normal operating conditions, the temperature of the fluid discharged at the outlet 220 of the first heat exchange side drops sharply and exceeds the preset temperature change rate value. At this time, it is necessary to reduce the rate of increase of the compressed gas flow rate so that the rate of increase of the pressure loss of the first branch 110 connected to the water evaporator 200 is slowed down, thereby maintaining sufficient amount of high-temperature fuel oxidation exhaust gas to enter the water evaporator 200 for heat exchange and maintaining the thermal balance of the water evaporator 200.

[0077] The embodiments of this application have been described in detail above with reference to the accompanying drawings. However, this application is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of this application. Furthermore, unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other.

Claims

1. A fuel cell tail gas recovery system characterized by: The fuel cell tail gas recovery system comprises: a flow divider for receiving the tail gas and dividing the tail gas into at least a first branch and a second branch; a water evaporator comprising a first heat exchange side and a second heat exchange side, the first branch being communicated to an inlet of the first heat exchange side, and the second heat exchange side being used for passing liquid water; an exhaust pipe, one end of which is connected to an outlet of the first heat exchange side; an adjusting assembly communicated to the exhaust pipe, the adjusting assembly being used for passing compressed gas into the exhaust pipe.

2. The fuel cell off-gas recovery system of claim 1, wherein: The angle of the compressed gas passing into the exhaust pipe can be adjusted.

3. The fuel cell off-gas recovery system of claim 1, wherein: The exhaust pipe is provided with a preset pressure loss part, which can be used for providing a preset pressure loss to the first heat exchange side.

4. The fuel cell off-gas recovery system of claim 1, wherein: The fuel cell tail gas recovery system further comprises a second heat exchanger, and the second branch is communicated to one of the heat exchange sides of the second heat exchanger.

5. A fuel cell system characterized by comprising: The fuel cell system comprises an electric pile, a fuel oxidizer and the fuel cell tail gas recovery system of claim 4, the anode outlet and the cathode outlet of the electric pile are both communicated to the inlet of the fuel oxidizer, the outlet of the fuel oxidizer is connected to the flow divider, the second heat exchanger is an air heat exchanger, and the other heat exchange side of the air heat exchanger is connected to the cathode inlet of the electric pile.

6. The fuel cell system of claim 5, wherein: The fuel cell system further comprises a fuel heat exchanger, the water vapor flowing out of the second heat exchange side of the water evaporator is used for mixing with fuel and passing into a third heat exchange side of the fuel heat exchanger, the inlet of a fourth heat exchange side of the fuel heat exchanger is communicated to the anode outlet of the electric pile, the anode tail gas in the electric pile is used for heating the third heat exchange side, the outlet of the third heat exchange side is communicated to the anode inlet of the electric pile, and the outlet of the fourth heat exchange side is communicated to the inlet of the fuel oxidizer.

7. A control method of a fuel cell tail gas recovery system, characterized in that: a first branch gas is passed into a first heat exchange side of a water evaporator, and the first branch gas enters an exhaust pipe from an outlet of the first heat exchange side; compressed gas is supplied into the exhaust pipe by using an adjusting assembly; the amount of the compressed gas passing in is adjusted to change the gas flow of the first branch; when the electric energy output of the fuel cell system increases, the input flow of the compressed gas is reduced; and when the electric energy output of the fuel cell system decreases, the input flow of the compressed gas is increased.

8. The control method of the fuel cell tail gas recovery system according to claim 7, characterized by: The compressed gas is supplied into the exhaust pipe by using the adjusting assembly, which comprises: the adjusting assembly adjusts the angle of the compressed gas passing into the exhaust pipe.

9. The control method of the fuel cell tail gas recovery system according to claim 7, characterized by: The amount of the compressed gas passing in is adjusted to change the gas flow of the first branch, which comprises: the flow of the compressed gas passing in is adjusted so that the heat exchange side of the water evaporator satisfies at least one of the following conditions: the fluid temperature at the outlet of the first heat exchange side of the water evaporator is maintained within a preset temperature range when the fuel cell system is in a full-load power generation state and when the fuel cell system is in a heat preservation state; or the fluid temperature variation rate at the outlet of the first heat exchange side of the water evaporator does not exceed a preset value.

10. The control method of the fuel cell tail gas recovery system according to claim 7, characterized by: The amount of the compressed gas passing in is adjusted to change the gas flow of the first branch, which comprises: When the electric energy output of the fuel cell system is increased, and the temperature change rate of the fluid at the outlet of the first heat exchange side exceeds a preset value, if the fluid temperature at the outlet of the first heat exchange side rises, the change rate of the compressed gas flow is slowed down; if the fluid temperature at the outlet of the first heat exchange side falls, the change rate of the compressed gas flow is accelerated. When the electric energy output of the fuel cell system is decreased, and the temperature change rate of the fluid at the outlet of the first heat exchange side exceeds a preset value, if the fluid temperature at the outlet of the first heat exchange side rises, the change rate of the compressed gas flow is accelerated; if the fluid temperature at the outlet of the first heat exchange side falls, the change rate of the compressed gas flow is slowed down.

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